BlueScope Steel Limited v Dongkuk Steel Mill Co., Ltd (No 2)
[2019] FCA 2117
•17 December 2019
FEDERAL COURT OF AUSTRALIA
BlueScope Steel Limited v Dongkuk Steel Mill Co., Ltd (No 2) [2019] FCA 2117
File number: VID 1429 of 2016 Judge: BEACH J Date of judgment: 17 December 2019 Catchwords: PATENTS – alloy-coated steel strip products – alloy coatings of aluminium, zinc, silicon and magnesium – hot dip coating methods – asserted grounds of invalidity – lack of clarity and definition – lack of fair basis – lack of sufficiency – failure to disclose best method – false suggestion – novelty – inventive step – construction of patent claims – application to amend the specification – application of ss 102 and 105 of the Patents Act 1990 (Cth) – asserted infringement – measurement protocol – experimental proof of infringement – infringement not established – some grounds of invalidity upheld Legislation: Intellectual Property Laws Amendment (Raising the Bar) Act 2012 (Cth) Sch 1
Patents Act 1990 (Cth) ss 7, 18, 29, 30, 40, 65, 102, 105, 138
Cases cited: Albany Molecular Research Inc v Alphapharm Pty Ltd (2011) 90 IPR 457
Apotex Pty Ltd v Sanofi-Aventis (2009) 82 IPR 416
Apotex Pty Ltd v Warner-Lambert Company LLC (No 2) (2016) 122 IPR 17
Apotex Pty Ltd (formerly GenRx Pty Ltd) v Sanofi-Aventis (2008) 78 IPR 485
Arrow Pharmaceuticals Ltd v Merck & Co Inc (2004) 213 ALR 182
AstraZeneca AB v Apotex Pty Ltd (2014) 226 FCR 324
Bayer Pharma Aktiengesellschaft v Generic Health Pty Ltd (2012) 99 IPR 59
Bristol-Myers Squibb Company v F H Faulding & Co Limited (2000) 97 FCR 524
CSL Ltd v Novo Nordisk Pharmaceuticals Pty Ltd (No 2) (2010) 190 FCR 522
David Kahn Inc v Conway Stewart & Co Ltd (1974) 91 RPC 279
DSI Australia (Holdings) Pty Ltd v Garford Pty Ltd (2013) 100 IPR 19
Electric & Musical Industries Ld v Lissen Ld (1939) 56 RPC 23
Eli Lilly and Co v Pfizer Overseas Pharmaceuticals (2005) 218 ALR 408
Foster’s Australia Ltd v Cash’s (Australia) Pty Ltd (2013) 219 FCR 529
General Tire & Rubber Co v Firestone Tyre and Rubber Co Ltd (1971) 1A IPR 121
Gilead Sciences Pty Ltd v Idenix Pharmaceuticals LLC (2016) 117 IPR 252
GlaxoSmithKline Consumer Healthcare Investments (Ireland) (No 2) Ltd v Apotex Pty Ltd (2016) 119 IPR 1; [2016] FCA 608
GlaxoSmithKline Consumer Healthcare Investments (Ireland) (No 2) Ltd v Generic Partners Pty Ltd (2018) 131 IPR 384
ICI Chemicals & Polymers Ltd v Lubrizol Corp Inc (1999) 45 IPR 577
Idenix Pharmaceuticals LLC v Gilead Sciences Pty Ltd (2017) 134 IPR 1
Kauzal v Lee (1936) 58 CLR 670
Kimberly-ClarkAustralia Pty Ltd v Arico Trading International Pty Ltd (2001) 207 CLR 1
Les Laboratoires Servier v Apotex Pty Ltd (2010) 273 ALR 630
Les Laboratoires Servier v Apotex Pty Ltd (2016) 247 FCR 61; [2016] FCAFC 27
Lockwood Security Products Pty Ltd v Doric Products Pty Ltd (2004) 217 CLR 274
Lockwood Security Products Pty Ltd v Doric Products Pty Ltd (No 2) (2007) 235 CLR 173
Martin v Scribal Pty Ltd (1954) 92 CLR 17
Meat & Livestock Australia Limited v Cargill, Inc (No 2) (2019) 139 IPR 47; [2019] FCA 33
Meat & Livestock Australia Ltd v Cargill, Inc (2018) 354 ALR 95; [2018] FCA 51
Meyers Taylor Pty Ltd v Vicarr Industries Ltd (1977) 137 CLR 228
Minnesota Mining and Manufacturing Co v Beiersdorf (Aust) Ltd (1980) 144 CLR 253
Neurim Pharmaceuticals (1991) Ltd v Generic Partners Pty Ltd [2018] FCA 1082
Norton and Gregory Ld v Jacobs (1937) 54 RPC 271
Novartis AG v Bausch & Lomb (Australia) Pty Ltd (2004) 62 IPR 71
Olin Corporationv Super Cartridge Co Pty Ltd (1977) 180 CLR 236
Pfizer Overseas Pharmaceuticals v Eli Lilly & Co (2005) 225 ALR 416
Prestige Group (Australia) Pty Ltd v Dart Industries Inc (1990) 26 FCR 197
Ranbaxy Australia Pty Ltd v Warner-Lambert Co LLC (2008) 77 IPR 449
Rescare Ltd v Anaesthetic Supplies Pty Ltd (1992) 111 ALR 205
Sachtler GmbH and Co KG (formerly Sachtler AG) v RE Miller Pty Ltd (2005) 221 ALR 373
Sartas No 1 Pty Ltd v Koukourou & Partners Pty Ltd (1994) 30 IPR 479
Sequenom Inc v Ariosa Diagnostics Inc (2019) 143 IPR 24; [2019] FCA 1011
Sigma Pharmaceuticals (Australia) Pty Ltd v Wyeth (2011) 119 IPR 194
Smith Kline & French Laboratories Ltd v Evans Medical Limited [1989] 1 FSR 561
SNF (Australia) Pty Ltd v Ciba Speciality Chemicals Water Treatments Ltd (2011) 92 IPR 46
Warner-Lambert Co LLC v Apotex Pty Ltd (No 2) (2018) 355 ALR 44
Welch Perrin & Co Pty Ltd v Worrel (1961) 106 CLR 588
Date of hearing: 15 to 19, 22 to 24 October, 18 and 19 December 2018 Date of last submissions: 24 December 2018 Registry: Victoria Division: General Division National Practice Area: Intellectual Property Sub-area: Patents and Associated Statutes Category: Catchwords Number of paragraphs: 1517 Counsel for the Applicant and Cross-Respondent: Mr BN Caine QC and Ms C Cunliffe Solicitor for the Applicant and Cross-Respondent: King & Wood Mallesons Counsel for the Respondent and Cross-Claimant: Mr A Ryan SC and Mr JS Cooke Solicitor for the Respondent and Cross-Claimant: Bird & Bird ORDERS
VID 1429 of 2016 BETWEEN: BLUESCOPE STEEL LIMITED (ACN 000 011 058)
Applicant
AND: DONGKUK STEEL MILL CO., LTD
Respondent
AND BETWEEN: DONGKUK STEEL MILL CO., LTD
Cross-Claimant
AND: BLUESCOPE STEEL LIMITED (ACN 000 011 058)
Cross-Respondent
JUDGE:
BEACH J
DATE OF ORDER:
17 December 2019
THE COURT ORDERS THAT:
1.Each of the parties file and serve by 3 February 2020 minutes of orders and short submissions (limited to 3 pages) to give effect to these reasons.
2.Costs reserved.
3.Liberty to apply.
Note: Entry of orders is dealt with in Rule 39.32 of the Federal Court Rules 2011.
REASONS FOR JUDGMENT
BEACH J:
BlueScope Steel Limited (BlueScope) contends that Dongkuk Steel Mill Co Ltd (Dongkuk) has infringed various claims of Australian Patent No. 2009225257 (the 257 Patent) and Australian Patent No. 2009225258 (the 258 Patent). BlueScope is the registered proprietor of both Patents, the applications for which were filed on 13 March 2009.
BlueScope carries on business, inter-alia, as a manufacturer and supplier of alloy-coated steel strip products which are sold in Australia and elsewhere. Dongkuk carries on business outside Australia, inter-alia, as a manufacturer and supplier of alloy-coated steel strip products which are sold by third parties in Australia and elsewhere.
The invention the subject of the 257 Patent relates to a hot dip coating method for coating steel strips with an alloy coating of aluminium, zinc, silicon and magnesium (Al-Zn-Si-Mg) where variations in the thickness of the coating are controlled such that there is only a small proportion of Mg2Si particles or substantially no Mg2Si particles in the surface of the coating. The invention also relates to a coated steel strip formed by that method.
The invention the subject of the 258 Patent relates to an Al-Zn-Si-Mg alloy-coated steel strip where the distribution of Mg2Si particles is such that there is no more than 10% by weight of Mg2Si particles in a surface region of the coating. The invention also relates to a hot dip coating method for forming such a coated steel strip.
BlueScope says that Dongkuk without the licence or authority of BlueScope has imported and authorised other persons to offer for sale, sell and supply in Australia an Al-Zn-Si-Mg alloy-coated steel strip product (the GLX product) that infringes both Patents because it is a product which:
(a)results from the use of the method claimed in claims 1, 3, 4, 5, 6, 8, 9, 11, 12 and 13 of the 257 Patent;
(b)falls within the scope of claims 14 and 15 of the 257 Patent; and
(c)falls within the scope of claims 2, 5, 6, 11 and 12 of the 258 Patent.
Now although BlueScope originally pleaded infringement of claim 7 of the 257 Patent, it does not now press that claim. Further, although it originally pleaded infringement of claims 1 and 17 to 25 of the 258 Patent, it no longer presses those claims.
Dongkuk has denied infringement and has alleged that BlueScope has made unjustified threats in respect of the alleged infringing conduct asserted by BlueScope. Dongkuk has also cross-claimed seeking orders revoking both the 257 Patent and the 258 Patent in so far as they relate to various claims.
Dongkuk has alleged that claims 1, 3 to 6, 8, 9 and 11 to 15 of the 257 Patent are invalid upon the grounds that:
(a)the invention is not novel;
(b)the invention does not involve an inventive step;
(c)the specification does not disclose the best method of performing the invention;
(d)the specification does not describe the invention fully;
(e)the claims do not define the invention or are not clear;
(f)the claims are not fairly based; and
(g)the Patent was obtained by false suggestion or misrepresentation.
Further, Dongkuk has alleged that claims 1, 2, 5, 6, 11, 12, 17, 18 and 20 to 25 of the 258 Patent are invalid upon similar grounds.
Now as I have said, the applications for the Patents were filed on 13 March 2009. But although ss 7 and 40 of the Patents Act 1990 (Cth) (the Act) were amended by the Intellectual Property Laws Amendment (Raising the Bar) Act 2012 (Cth) (the Raising the Bar Act), the amendments brought about do not affect the present case.
Further, each of the 257 Patent and the 258 Patent claim priority from two convention applications being AU2008901223 and AU2008901224 filed on 13 March 2008 (the priority date). There is no issue concerning the priority date.
I should note one other preliminary matter. By an interlocutory application dated 13 April 2017, BlueScope has applied to amend the 257 Patent. The amendments sought relate to the description in the body of the 257 Patent, but not the claims.
In summary and for the reasons that I have explained in more detail later, I have rejected BlueScope’s infringement case even assuming the asserted claims of the 257 Patent and the 258 Patent to be valid. But in any event, the asserted claims of the 257 Patent and some of the asserted claims of the 258 Patent are invalid by reason of the specifications failing to disclose the best method known to BlueScope at the relevant time. Further, I have rejected BlueScope’s amendment application relating to the 257 Patent.
It is convenient to divide my reasons into the following sections:
(a)The 257 Patent – [17] to [81].
(b)The 258 Patent – [82] to [120].
(c)The measurement protocol – [121] to [134].
(d)BlueScope’s application of the protocol – [135] to [232].
(e)Deficiencies in the experimental evidence – [233] to [415].
(f)Infringement of the 257 Patent – [416] to [602].
(g)Infringement of the 258 Patent – [603] to [679].
(h)Invalidity – general – [680] to [702].
(i)Lack of clarity and lack of definition – [703] to [747].
(j)Lack of fair basis – [748] to [799].
(k)Lack of sufficiency – [800] to [826].
(l)Lack of disclosure of best method – [827] to [960].
(m)False suggestion – [961] to [1013].
(n)Lack of novelty – [1014] to [1219].
(o)Lack of inventive step – [1220] to [1323].
(p)Amendment application – [1324] to [1513].
(q)Conclusion – [1514] to [1517].
I should say at the outset that I have been much assisted by the technical presentations of all counsel. Their cases were presented with notable efficiency.
Let me begin with identifying and describing some of the key features of the 257 Patent and the 258 Patent. I will then turn to questions of infringement before dealing with questions of invalidity. It is convenient to take this course, albeit that this may seem counter-intuitive, in order to achieve some comprehensible flow to the technical issues.
THE 257 PATENT
The Patents relate to the field of alloy-coated steel strips, where the alloy coating provides corrosion resistance. The work in this field was undertaken by materials scientists and engineers with a focus on corrosion resistance. In the present case, the person skilled in the art is a team of materials scientists and engineers working in the coatings field, with a particular interest in Al-Zn coatings, who were involved in a research project to identify an improved coating at the priority date. The team would have expertise in hot dip coatings, including galvalume, that is, alloy coatings having 55 wt. % aluminium, 43 wt. % zinc and approximately 1.5 to 2 wt. % silicon. They would have a practical interest in the subject matter of the invention but be presumed to be unimaginative and non-inventive.
The invention the subject of the specification of the 257 Patent is described in the following terms (p 1 lines 3 to 36):
The present invention relates to strip, typically steel strip, which has a corrosion-resistant metal alloy coating.
The present invention relates particularly to a corrosion-resistant metal alloy coating that contains aluminium-zinc-silicon-magnesium as the main elements in the alloy, and is hereinafter referred to as an “Al-Zn-Si-Mg alloy” on this basis. The alloy coating may contain other elements that are present as deliberate alloying additions or as unavoidable impurities. Hence, the phrase “Al-Zn-Si-Mg alloy” is understood to cover alloys that contain such other elements and the other elements may be deliberate alloying additions or as unavoidable impurities.
The present invention relates particularly but not exclusively to steel strip that is coated with the above-described Al-Zn-Si-Mg alloy and can be cold formed (e.g. by roll forming) into an end-use product, such as roofing products.
Typically, the Al-Zn-Si-Mg alloy comprises the following ranges in % by weight of the elements aluminium, zinc, silicon, and magnesium:
Aluminium: 40 to 60 %
Zinc: 40 to 60 %
Silicon: 0.3 to 3%
Magnesium 0.3 to 10 %
Typically, the corrosion-resistant metal alloy coating is formed on steel strip by a hot dip coating method.
In terms of the addition of silicon and magnesium, the following was said (p 3 line 4 to p 4 line 7):
It is known to add silicon to the coating alloy composition to prevent excessive alloying between the steel substrate and the molten coating in the hot-dip coating method. A portion of the silicon takes part in a quaternary alloy layer formation but the majority of the silicon precipitates as needle-like, pure silicon particles during solidification. These needle-like silicon particles are also present in the inter-dendritic regions of the coating.
It has been found by the applicant that when Mg is included in a 55%Al-Zn-Si alloy coating composition, Mg brings about certain beneficial effects on product performance, such as improved cut-edge protection, by changing the nature of corrosion products formed.
However, it has also been found by the applicant that Mg reacts with Si to form a Mg2Si phase and that the formation of the Mg2Si phase compromises the above-mentioned beneficial effects of Mg in a number of ways.
One particular way, which is the focus of the present invention is a surface defect called “mottling”. The applicant has found that mottling can occur in Al-Zn-Si-Mg alloy coatings under certain solidification conditions. Mottling is related to the presence of the Mg2Si phase on the coating surface.
More particularly, mottling is a defect where a large number of coarse Mg2Si particles cluster together on the surface of the coating, resulting in a blotchy surface appearance that is not acceptable from an aesthetic viewpoint. More particularly, the clustered Mg2Si particles form darker regions approximately 1-5 mm in size and introduce non-uniformity in the appearance of the coating which makes the coated product unsuitable for applications where a uniform appearance is important.
The above description is not to be taken as an admission of the common general knowledge in Australia or elsewhere.
Then there is a statement of the invention as follows (p 4 lines 9 to 14):
The present invention is an Al-Zn-Si-Mg alloy coated strip that has Mg2Si particles in the coating with the distribution of Mg2Si particles being such that a surface of the coating has only a small proportion of Mg2Si particles or is at least substantially free of any Mg2Si particles.
As to this statement, what does “small proportion” mean? Almost nothing? And does the phrase “only a small proportion” mean the same thing as “at least substantially free”? And does the latter phrase mean immaterially small?
Further, it was then explained (p 4 lines 16 to 27):
The applicant has found that the above-described distribution of Mg2Si particles in the coating microstructure provides significant advantages and can be achieved by any one or more of:
(a) strontium additions in the coating alloy,
(b)selection of the cooling rate during solidification of coated strip for a given coating mass (i.e. coating thickness) exiting a coating bath; and
(c) minimising variations in coating thickness.
There are two issues to note concerning this passage. Does “can” in the phrase “can be achieved” mean may or must? Further, what is the significance of “any one or more of”? Does this mean that the promise can be achieved with one only?
The addition of strontium (Sr) is then explained (p 4 line 29 to p 5 line 12):
The applicant has found that Sr additions described in more detail below control the distribution characteristics of the Mg2Si phase in the thickness direction of an Al-Zn-Si-Mg alloy coating so that the surface of the coating has only a small proportion of Mg2Si particles or is at least substantially free of Mg2Si particles, whereby there is a considerably lower risk of Mg2Si mottling.
The applicant has found that when at least 250 ppm Sr, preferably 250-3000 ppm Sr, is added to a coating bath containing an Al-Zn-Si-Mg alloy the distribution characteristics of the Mg2Si phase in the coating thickness direction are completely changed by this addition of Sr from the distribution that is present when there is no Sr in the coating bath. Specifically, the applicant has found that these additions of Sr promote the formation of a surface of the coating that has only a small proportion of Mg2Si particles or is free of any Mg2Si particles and consequently a considerably lower risk of mottling on the surface.
The reference to “below” (p 4 line 30) appears to be a reference to p 7. Further, are these passages saying that Sr is the cause (i.e. on its own)?
In an apparently self-contained passage referring to the subject matter in (b) (p 4 line 23), the following is said (p 5 lines 14 to 23):
The applicant has also found that selecting the cooling rate during solidification of a coated strip exiting a coating bath to be below a [threshold] cooling rate, typically below 80℃/sec for coating masses less than 100 grams per square metre of strip surface per side, controls the distribution characteristics of the Mg2Si phase so that the surface has only a small proportion of Mg2Si particles or is at least substantially free of Mg2Si particles, whereby there is a considerably lower risk of Mg2Si mottling.
In a yet further apparently self-contained passage referring to the subject matter in (c) (p 4 line 27), the following is said (p 5 lines 25 to 34):
The applicant has also found that minimising coating thickness variations controls the distribution characteristics of the Mg2Si phase so that the surface has only a small proportion of Mg2Si particles or is at least substantially free of Mg2Si particles, whereby there is a considerably lower risk of Mg2Si mottling. As is the case with Sr addition and selection of cooling rate during solidification, the resultant coating microstructure is advantageous in terms of appearance, enhanced corrosion resistance and improved coating ductility.
Then the invention is described (p 5 line 36 to p 6 line 4):
The claims define the invention in terms of minimising coating thickness variations to control the distribution characteristics of the Mg2Si phase so that the surface has only a small proportion of Mg2Si particles or is at least substantially free of Mg2Si particles, whereby there is a considerably lower risk of Mg2Si mottling.
Then there are listed consistory clauses (p 6 line 6 to p 9 line 5).
The advantages are then described as follows (p 9 lines 6 to 21):
The advantages of the invention include the following advantages.
•Elimination of mottling defect and improved first-time-prime production rate. The risk of the mottling defect is at least substantially eliminated and the surface of the resultant coating maintains a beautiful, silvery metallic appearance. As a result, first-time-prime production rate is improved and profitability is boosted.
•Prevention of mottling defect by the addition of Sr allows the use of higher cooling rates, reducing the length of cooling equipment required after the pot.
In terms of line trials the following was said (p 11 line 3 to p 13 line 25):
The applicant has also carried out line trials on 55%Al-Zn-1.5%Si-2.0%Mg alloy composition (not containing Sr) coated on steel substrates.
The purpose of these trials was to investigate the impact of cooling rates and coating masses on mottling in the surface of the coatings.
The trials covered a range of coating masses from 60 to 100 grams per square metre surface per side of strip, with cooling rates up to 90℃/sec.
The applicant found two factors that affected the coating microstructure, particularly the distribution of Mg2Si particles in the coatings, in the trials.
The first factor is the effect of the cooling rate of the strip exiting the coating bath before completing the coating solidification. The applicant found that controlling the cooling rate makes it possible to avoid mottling.
By way of example, the applicant found that for a AZ150 class coating (or 75 grams of coating per square 25 metre surface per side of strip – refer to Australia Standard AS1397-2001), if the cooling rate is greater than 80℃/sec, Mg2Si particles formed on the surface of the coating. In particular, when the cooling rate was greater than 100℃/sec, mottling occurred.
The applicant also found that for the same coating it is not desirable that the cooling rate be too low, particularly below 11℃/sec, as in this case the coating develops a defective “bamboo” structure, whereby the zinc-rich phases forms a vertically straight corrosion path from the coating surface to the steel interface, which compromises the corrosion performance of the coating.
Therefore, for a AZ150 class coating, under the experimental conditions tested, the cooling rate should be controlled to be in a range of 11-80℃/sec to avoid mottling on the surface.
On the other hand, the applicant also found that for a AZ200 class coating, if the cooling rate was greater than 50℃/sec, Mg2Si particles formed on the surface of the coating and mottling occurred.
Therefore, for a AZ200 class coating, under the experimental conditions tested, a cooling rate in a range of 11-50℃/sec is desirable.
The second important factor found by the applicant is the uniformness of coating thickness across the strip surface.
The applicant found that the coating on the strip surface normally had thickness variations that are (a) long range (across the entire strip width, measured by the “weight-strip-weight” method on a 50mm diameter disc) and (b) short range (across every 25 mm length in the strip width direction, measured in the cross-section of the coating under a microscope with 500x magnification). In a production situation, the long range thickness variation is normally regulated to meet the minimum coating mass requirements as defined in relevant national standards. In a production situation, as far is the applicant is aware, there is no regulation for short range thickness variation, as long as the minimum coating mass requirements as defined in relevant national standards are met.
However, the applicant found that short range coating thickness variations could be very high, and special operational measures had to be applied to keep the variations under control. It was not uncommon in the experimental work for the coating thickness to change by a factor of two or more over a distance as short as 5 mm, even when the product perfectly met the minimum coating mass requirements as defined in relevant national standards. This short range coating thickness variation had a pronounced impact on the Mg2Si particles in the surface of coatings.
By way of example, the applicant found that for a AZ150 class coating even in the desirable cooling rate ranges as described above, if the short range coating thickness variation was greater than 40% above the nominal coating thickness within a distance of 5 mm across the strip surface, Mg2Si particles formed on the surface of the coating and thereby increased the risk of mottling.
Therefore, under the experimental conditions tested, the short range coating thickness variation should be controlled to no greater than 40% above the nominal coating thickness within a distance of 5mm across the strip surface to avoid mottling.
I will return later to the significance of the phrase “special operational measures” (p 13 line 3).
I should also set out some other passages (p 16 line 23 to p 18 line 3):
Practically, the applicant has found that, to achieve the distribution of Mg2Si particles of the present invention, i.e. to avoid mottling defect on the surface of a coated strip, the cooling rate for coated strip exiting the coating bath has to be in a range of 11-80℃/sec for coating masses up to 75 grams per square metre of strip surface per side and in a range 11-50℃/sec for coating masses of 75-100 grams per square metre of strip surface per side. The short range coating thickness variation also has to be controlled to be no greater than 40% above the nominal coating thickness within a distance of 5 mm across the strip surface to achieve the distribution of Mg2Si particles of the present invention.
The applicant has also found that, when Sr is present in a coating bath, the above described kinetics of Mg2Si nucleation can be significantly influenced. At certain Sr concentration levels, Sr strongly segregates into the quaternary alloy layer (i.e. changes the chemistry of the quaternary alloy phase). Sr also changes the characteristics of surface oxidation of the molten coating, resulting in a thinner surface oxide on the coating surface. Such changes alter significantly the preferential nucleation sites for the Mg2Si phase and, as a result, the distribution pattern of the Mg2Si phase in the coating thickness direction. In particular, the applicant has found that, Sr at concentrations 250-3000ppm in the coating bath makes it virtually impossible for the Mg2Si phase to nucleate on the quaternary alloy layer or on the surface oxide, presumably due to the very high level of increase in system free energy would otherwise be generated. Instead, the Mg2Si phase can only nucleate at the central region of the coating in the thickness direction, resulting in a coating structure that is substantially free of Mg2Si at both the coating outer surface region and the region near the steel surface. Therefore, Sr additions in the range 250-3000ppm are proposed as one of the effective means to achieve a desired distribution of Mg2Si particles in a coating.
Many modifications may be made to the present invention as described above without departing from the spirit and scope of the invention.
In this context, whilst the above description of the present invention focuses on (a) the addition of Sr to Al-Zn-Si-Mg coating alloys, (b) cooling rates (for a given coating mass) and (c) control of short range coating thickness variation as means for achieving a desired distribution of Mg2Si particles in coatings, i.e. at least substantially no Mg2Si particles in the surface of a coating, the present invention is not so limited and extends to the use of any suitable means to achieve the desired distribution of Mg2Si particles in the coating.
The following claims, inter-alia, are then made (pp 19 to 21):
1. A hot-dip coating method for forming a coating of a corrosion-resistant Al-Zn-Si-Mg alloy on a steel strip comprising passing the steel strip through a hot dip coating bath that contains Al, Zn, Si, and Mg and optionally other elements and forming an alloy coating on the strip with a variation in thickness of the coating of no more than 40% in any given 5 mm diameter section so that the distribution of Mg2Si particles in the coating microstructure is such that there is only a small proportion of Mg2Si particles or substantially no Mg2Si particles in the surface of the coating.
…
3. The method defined in any one of the preceding claims wherein the small proportion of Mg2Si particles in the surface of the coating is no more than 10wt.% of the Mg2Si particles.
4. The method defined in any one of the preceding claims wherein the coating thickness variation is no more than 30% in any given 5 mm diameter section of the coating.
5. The method defined in any one of the preceding claims wherein, for a coating thickness of 22μm, the maximum thickness in any region of the coating greater than 1mm in diameter is 27μm.
6. The method defined in any one of the preceding claims comprising selecting the cooling rate during solidification of coated strip exiting the coating bath to be less than a threshold cooling rate.
…
8. The method defined any one of claims 1 to 6 comprising selecting the cooling rate for coated strip exiting the coating bath to be less than 50℃/sec for coating masses of 75-100 grams per square metre of strip surface per side.
9. The method defined in any one of the preceding claims wherein the coating comprises the following ranges in % by weight of the elements aluminium, zinc, silicon, and magnesium:
Aluminium: 40 to 60 %
Zinc: 40 to 60 %
Silicon: 0.3 to 3%
Magnesium 0.3 to 10 %.
…
11. The method defined in any one of the preceding claims wherein the coating contains less than 3000 ppm Sr.
12. The method defined in any one of the preceding claims comprising forming the coating to have a thickness of less than 30μm.
13. The method defined in any one of the preceding claims comprising forming the coating to have a thickness 35 of greater than 7μm.
14. A steel strip having a coating of a corrosion-resistant Al-Zn-Si-Mg alloy formed by the method defined in any one of the preceding claims.
15. An Al-Zn-Si-Mg alloy coated strip that has Mg2Si particles in the coating with the distribution of Mg2Si particles being such that a surface of the coating has only a small proportion of Mg2Si particles or is at least substantially free of any Mg2Si particles formed by the method defined in any one of the preceding claims.
It will be apparent that claim 1 is the only truly independent claim.
Let me summarise some of the aspects of the specification.
The specification explains that the invention relates to strip, typically steel strip, which has a corrosion-resistant metal alloy coating and more particularly a corrosion-resistant metal alloy coating that contains as its main elements aluminium, zinc, silicon and magnesium being an Al-Zn-Si-Mg alloy.
The specification observes that the alloy coating may contain other elements that are present as deliberate alloying additions or unavoidable impurities. The specification explains that the expression “an Al-Zn-Si-Mg alloy” is to be understood as covering an Al-Zn-Si-Mg alloy which also includes other elements.
The specification explains that the present invention relates to steel strip that is coated with the Al-Zn-Si-Mg alloy and can be cold formed into an end-use product such as roofing products.
The specification explains that typically the Al-Zn-Si-Mg alloy comprises 40 to 60% weight of Al, 40 to 60% weight Zn, 0.3 to 3% Si and 0.3 to 10% Mg and that typically the metal alloy coating is formed by a hot dip coating method.
After explaining the conventional hot dip coating method, the specification explains that a 55%Al-Zn alloy coating that is sold under the name “galvalume” is a well known metal alloy coating for steel strip, and that after solidification, such a coating normally consists of Al dendrites that are a characteristic tree-like structure of Al crystals, and a Zn phase in the inter-dendritic regions that is the region or space between the Al dendrites. The specification explains that it is known to add Si to prevent excessive alloying between the steel substrate and the molten coating. But only a portion of Si takes part in the quaternary alloy layer formation. The majority of Si precipitates as needle-like pure Si particles. The needle-like Si particles are also present in the inter-dendritic regions of the coating.
At this point I note that a 55% Al-Zn alloy coating was a coating originally developed by Bethlehem Steel in the United States in the 1960s and known there as “galvalume” and in Australia as “galvalume” or “zincalume”. BlueScope and its predecessors produced that product in Australia under licence for many years before the priority date.
As I have already indicated, the specification states that the applicant has found that when Mg is included in a 55%Al-Zn-Si alloy coating composition, it brings about certain beneficial effects on product performance, such as improved cut-edge protection, by changing the nature of the corrosion products formed. However, it was also found that the Mg reacts with Si to form an Mg2Si phase which compromises the beneficial effects of Mg in a number of ways.
One of the consequences of the Mg2Si phase being formed is a surface defect called “mottling”. This can occur in Al-Zn-Si-Mg alloy coatings under certain solidification conditions and is related to the presence of an Mg2Si phase on the surface of the coating. The specification explains that mottling occurs where a large number of coarse Mg2Si particles cluster together on the surface of the coating, resulting in a blotchy and aesthetically unacceptable surface. The clustered Mg2Si particles form darker regions from 1 to 5 mm in size and introduce non-uniformity in the appearance of the coating.
The specification identifies the present invention as an Al-Zn-Si-Mg alloy coated strip that has Mg2Si particles in the coating with the distribution of Mg2Si particles being such that a surface of the coating has only a small proportion of Mg2Si or is at least substantially free of Mg2Si particles.
The specification explains that the applicant has found that such a distribution of Mg2Si particles in the coating microstructure provides significant advantages in terms of appearance, enhanced corrosion resistance and improved coating ductility (p 5 lines 33 to 34). As I have indicated, it states (p 4 lines 16 to 28) that those advantages can be achieved by any one or more of:
(a)adding Sr in the coating alloy;
(b)selection of the cooling rate for the coated strip for a given coating mass as it exits the coating bath; and
(c)minimising variations in coating thickness.
BlueScope submits that the use of the word “can” is permissive, when read in context. So, it means “may” rather than “will”. I agree.
Further, BlueScope says that the proper construction of the phrase “any one or more” does not mean that if a skilled addressee practices one of the trilogy of matters set out in (a), (b) or (c) above in isolation, it will inevitably give rise to the requisite distribution of Mg2Si. It says that the specification makes it plain that where the claimed cooling rate is used, it is also necessary to control coating thickness variation. Generally speaking I agree with BlueScope’s construction. Its construction is supported by various passages of the specification some of which I have set out earlier. It is convenient to identify them as follows:
By way of example, the applicant found that for a AZ150 class coating even in the desirable cooling rate ranges as described above, if the short range coating thickness variation was greater than 40% above the nominal coating thickness within a distance of 5mm across the strip surface, Mg2Si particles formed on the surface of the coating and thereby increased the risk of mottling. (page 13 lines 13 to 19)
…
In particular, the applicant has found that for a set coating thickness, the cooling rate should be regulated to a particular range, and more particularly not to exceed a threshold temperature, to avoid the risk for the Mg2Si phase to nucleate in region A. (page 16 lines 1 to 5)
…
Practically, the applicant has found that, to achieve the distribution of Mg2Si particles of the present invention, i.e. to avoid mottling defect on the surface of a coated strip, the cooling rate for coated strip exiting the coating bath has to be in a range of 11-80°C/sec for coating masses up to 75 grams per square metre of strip surface per side and in a range 11-50°C/sec for coating masses of 75-100 grams per square metre of strip surface per side. The short range coating thickness variation also has to be controlled to be no greater than 40% above the nominal coating thickness within a distance of 5mm across the strip surface to achieve the distribution of Mg2Si particles of the present invention. (page 16 lines 23 to 35)
In relation to the addition of Sr, BlueScope refers to p 17 lines 1 to 17 of the specification and says that this passage says that Sr can also have an effect, but not that it can occur in isolation. Again, generally speaking I agree with BlueScope’s construction.
Further, it seems to me that the relevant passages indicate that it may be necessary to combine the trilogy to achieve the desired distribution of Mg2Si particles resulting in a product that is mottle-defect free.
It seems to me, as BlueScope correctly submitted, that the three methods referred to above control the distribution characteristics of the Mg2Si phase so that the surface has only a small proportion of Mg2Si particles or is at least substantially free of Mg2Si particles, resulting in a considerably lower risk of Mg2Si mottling.
Let me proceed further with the specification. As I have set out earlier, the specification goes on (at p 5 lines 1 to 3) to describe the addition of Sr and notes that the applicant has found that the desired distribution of Mg2Si is obtained when at least 250 ppm Sr is added to the coating bath.
The specification then explains how keeping the cooling rate below a certain threshold for a given coating mass can control the Mg2Si distribution.
The specification then describes that the applicant has found that minimising coating thickness variations also controls the distribution characteristics of the Mg2Si phase.
As I have indicated earlier, the specification then states (at p 5 lines 36 to 37 and p 6 lines 1 to 4) that “[t]he claims define the invention in terms of minimising coating thickness variations” to obtain the desired distribution of Mg2Si. Then there is a consistory clause corresponding to claim 1 followed by consistory clauses broadly corresponding to dependent claims. All of the claims involve minimising coating thickness variations and certain of the dependent claims also involve either Sr additions or selection of cooling rate.
The specification then recites the aspect of the invention which is the subject of claim 1 (p 6 lines 6 to 17). The specification then recites preferred aspects of the method which are reflected in dependent claims 2 to 14 (p 6 line 19 to p 8 line 25). The specification goes on to explain that the invention also relates to a steel strip which is formed by the earlier described method of the invention.
The specification then outlines the advantages of the invention, which include the following as I have already indicated (p 9 lines 9 to 22).
First, it is said that one advantage is that the risk of the mottling defect is at least substantially eliminated and the surface of the coating retains a beautiful, silvery metallic appearance, improving first-time-prime production rate and profitability.
Second, it is said that another advantage is that the addition of Sr to prevent mottling allows the use of higher cooling rates, reducing the length of cooling equipment required after the pot.
The specification then discloses laboratory experiments on a series of 55% Al, 1.5% Si, 2.0% Mg with the remainder Zn alloy compositions, being an alloy composition including 41.5% Zn, having up to 3000 ppm Sr. The purpose of the experiments was to investigate the impact of Sr on mottling (p 9 lines 30 to 32). The specification states that alloys without Sr have Mg2Si particles distributed throughout, whereas alloys with 250 ppm to 3000 ppm Sr have upper and lower regions at the coating surface and at the interface of the steel substrate that are free of Mg2Si (p 9 line 25 to p 10 line 35).
Reference is also made to figure 1 which shows photomicrographs of a coating without Sr and a coating with Sr and it is noted that the alloy to which 500 ppm of Sr was added demonstrates “[a] complete absence of mottling”.
At p 10 lines 32 to 35 it is said:
The laboratory experiments found that the microstructure shown in the right hand side of the Figure were formed with Sr additions in the range of 250-3000 ppm.
Dongkuk notes that there is no suggestion that Sr additions below 250 ppm had any beneficial effect on Mg2Si distribution.
As I have indicated earlier, the specification describes line trials of 55% Al, 1.5% Si, 2.0% Mg with the remainder Zn alloy compositions that did not contain Sr. The specification reports that the applicant found there to be two factors that particularly affected the distribution of Mg2Si (p 11 lines 1 to 15). The first factor is cooling rate (p 11 lines 16 to 21). The second factor is the uniformity of the coating thickness across the surface of the strip (p 12 lines 18 to 20).
Dongkuk says that this first factor is consistent with the three alternative methods of achieving the desired distribution of Mg2Si set out at p 4 lines 16 to 27 and set out above.
According to Dongkuk, the specification then goes on to say, at p 11 lines 23 to 36 and p 12 lines 1 to 2, which I have set out earlier:
By way of example, the applicant found that for a AZ150 class coating (or 75 grams of coating per square metre surface per side of strip – refer to Australia Standard AS1397-2001), if the cooling rate is greater than 80°C/sec, Mg2Si particles formed on the surface of the coating. In particular, when the cooling rate was greater than 100°C/sec, mottling occurred.
The applicant also found that for the same coating it is not desirable that the cooling rate be too low, particularly below 11°C/sec, as in this case the coating develops a defective “bamboo” structure, whereby the zinc-rich phases forms a vertically straight corrosion path from the coating surface to the steel interface, which compromises the corrosion performance of the coating.
The patentee is telling the person skilled in the art that for an AZ150 class coating (i.e. up to 75 grams per square metre of strip surface per side) if the cooling rate is kept at a rate below 80°C per second, Mg2Si particles will not form on the surface of the coating. The patentee is also telling the person skilled in the art not to use a cooling rate below 11°C per second for different reasons.
The specification then goes on at p 12 to make similar observations in respect of AZ200 class coating, that is, 100 grams per square metre of strip surface per side, and indicates that the cooling rate should be kept at a rate between 11 to 50°C per second. So, the thicker the coating the lower the cooling rate.
The specification then describes the second factor affecting Mg2Si distribution (at p 12 lines 18 to 20):
The second important factor found by the applicant is the uniformness of coating thickness across the strip surface.
The specification describes the uniformity of the coating thickness across the strip surface. The specification explains that the coating had long range thickness variations across the entire strip width and short range thickness variations (p 12 lines 22 to 28). The specification explains that in a production situation short range thickness variation was not regulated so long as minimum coating mass requirements were met as defined in national standards (p 12 lines 32 to 36). However, short range coating thickness variations could be very high (p 13 lines 1 to 2). It was not uncommon in the experimental work for the coating thickness to change by a factor of two or more over a distance as short as 5 mm, even where it met minimum coating mass requirements (p 13 lines 4 to 9). This variation had a pronounced impact on Mg2Si particles (p 13 lines 9 and 10). But unlike short range thickness variations, long range thickness variations were measured by the weigh-strip-weigh method (p 12 lines 24 and 25); I will use “weigh-strip-weigh” rather than “weight-strip-weight”. The specification explains (p 13 lines 13 to 25):
By way of example, the applicant found that for a AZ150 class coating even in the desirable cooling rate ranges as described above, if the short range coating thickness variation was greater than 40% above the nominal coating thickness within a distance of 5 mm across the strip surface, Mg2Si particles formed on the surface of the coating and thereby increased the risk of mottling.
Therefore, under the experimental conditions tested, the short range coating thickness variation should be controlled to no greater than 40% above the nominal coating thickness within a distance of 5mm across the strip surface to avoid mottling.
The specification says that it was found that short range coating thickness variations could be very high and special operational measures had to be applied to keep the variations under control. It is said (at p 13 lines 1 to 11):
However, the applicant found that short range coating thickness variations could be very high, and special operational measures had to be applied to keep the variations under control. It was not uncommon in the experimental work for the coating thickness to change by a factor of two or more over a distance as short as 5 mm, even when the product perfectly met the minimum coating mass requirements as defined in relevant national standards. This short range coating thickness variation had a pronounced impact on the Mg2Si particles in the surface of coatings.
It is then said (at p 13 lines 13 to 19):
By way of example, the applicant found that for a AZ150 class coating even in the desirable cooling rate ranges as described above, if short range coating thickness variation was greater than 40% above the nominal coating thickness within a distance of 5 mm across the strip surface, Mg2Si particles formed on the surface of the coating and thereby increased the risk of mottling.
Dongkuk says that there is an inconsistency between the above paragraph and the assertion that is made on p 4 line 23 that “selection of the cooling rate during solidification of coated strip for a given coating mass (i.e. coating thickness) exiting a coating bath” alone can achieve the desired distribution of Mg2Si particles. One way to resolve this inconsistency is to understand the expression “even in the desirable cooling rate ranges as described above” not to mean the whole extent of the ranges described above, but, rather, the end of those ranges. Thus, for an AZ150 class coating, if the cooling rate approaches the 80°C per second point, there may be a need to control thickness variation.
Dongkuk says that the specification then advances a theory as to why cooling rates for certain thicknesses can influence the distribution of Mg2Si. In substance the theory is that Mg2Si particles tend to move from the surface of the alloy coating to the centre of the alloy coating before they begin to solidify, but if the cooling rate is too high for the distance which needs to be travelled, those particles will solidify at or near the surface before they can reach the centre.
The specification then says at p 16 lines 23 to 35:
Practically, the applicant has found that, to achieve the distribution of Mg2Si particles of the present invention, i.e. to avoid mottling defect on the surface of a coated strip, the cooling rate for coated strip exiting the coating bath has to be in a range of 11-80°C/sec for coating masses up to 75 grams per square metre of strip surface per side and in a range 11-50°C/sec for coating masses of 75-100 grams per square metre of strip surface per side. The short range coating thickness variation also has to be controlled to be no greater than 40% above the nominal coating thickness within a distance of 5 mm across the strip surface to achieve the distribution of Mg2Si particles of the present invention.
Again Dongkuk says that there is an inconsistency between this passage and the passage at p 4 lines 16 to 27.
The specification then goes on to describe how Sr achieves the desired Mg2Si distribution. In substance Sr brings about a chemical effect which makes it less desirable for Mg2Si to nucleate at the surface of the alloy coating.
In summary, the specification explains that it has been found that to achieve a distribution of Mg2Si particles that substantially eliminates mottling, various things are important.
First, the cooling rate for the coated strip exiting the coating bath has to be in the range of 11 to 80°C/sec for coating masses up to 75 grams per square metre of strip surface per side. Further, the cooling rate has to be in the range of 11 to 50°C/sec for coating masses of 75 to 100 grams per square metre of strip surface per side.
Second, the short range coating thickness variation has to be controlled so that it is no greater than 40% above the nominal coating thickness within a distance of 5 mm across the strip surface to achieve the distribution of Mg2Si particles of the present invention. The specification describes minimising coating thickness variations. Specifically, the specification describes a variation in thickness of the coating of no more than 40% in any given 5mm diameter section or no more than 30% in any given 5mm diameter section. In any given situation the selection of an appropriate thickness variation will be related to the coating thickness or coating mass.
Third, as to the addition of Sr, the specification describes the addition of 250 to 3000 ppm of Sr. The specification explains that the inclusion of Sr in the coating bath can affect the kinetics of Mg2Si nucleation because Sr changes the chemistry of the quaternary alloy layer and the characteristics of surface oxidation. But the specification does not suggest that the inclusion of Sr affects coating thickness variation.
THE 258 PATENT
The 258 Patent deals with both product claims (claims 1 to 12) and method claims (claims 13 to 25). The first two and a half pages of the specification are similar to the 257 Patent specification, but then there are some differences.
The specification does not address mottling. Rather, it is said (p 3 line 25 to p 14 line 15):
By way of example, the Mg2Si phase forms as large particles in relation to typical coating thicknesses and can provide a path for rapid corrosion where particles extend from a coating surface to an alloy layer adjacent the steel strip.
By way of further example, the Mg2Si particles tend to be brittle and sharp particles and provide both an initiation and propagation path for cracks that form on bending of coated products formed from coated strip. Increased cracking compared to Mg-free coatings can result in more rapid corrosion of the coatings.
The above description is not to be taken as an admission of the common general knowledge in Australia or elsewhere.
The present invention is an Al-Zn-Si-Mg alloy coated strip that has Mg2Si particles in the coating microstructure with the distribution of Mg2Si particles being such that a surface region of the coating has only a small proportion of Mg2Si particles or is at least substantially free of any Mg2Si particles.
The term “surface region” is understood herein to mean a region that extends inwardly from the exposed surface of a coating.
So, ductility rather than the problem with mottling seems to be the issue.
The statement of the invention (at p 4 line 5) is also slightly different to that of the 257 Patent. It is said:
The present invention is an Al-Zn-Si-Mg alloy coated strip that has Mg2Si particles in the coating microstructure with the distribution of Mg2Si particles being such that a surface region of the coating has only a small proportion of Mg2Si particles or is at least substantially free of any Mg2Si particles.
The specification goes on:
The term “surface region” is understood herein to mean a region that extends inwardly from the exposed surface of a coating.
The specification then repeats the passage of the 257 Patent set out earlier (p 4 lines 16 to 27). It says that the desired distribution of Mg2Si can be achieved by Sr additions, selection of cooling rate, and minimising variations in coating thickness.
The specification then provides a consistory clause in the terms of claim 1. It says:
According to the present invention there is provided an Al-Zn-Si-Mg alloy coated steel strip that comprises a coating of an Al-Zn-Si-Mg alloy on a steel strip with the alloy comprising in % by weight 40 to 60% Al, 40 to 60% Zn, 0.3 to 3% Si, and 0.3 to 10% Mg and unavoidable impurities, with the microstructure of the coating comprising Mg2Si particles, and with the distribution of the Mg2Si particles being such that there is no more than 10% by weight of Mg2Si particles in a surface region of the coating that has a thickness that is less than 30% of the total thickness of the coating.
So, the invention is said to be a coated steel strip with an alloy coating having the same components in the same ranges as claim 9 of the 257 Patent but the difference is that the distribution of Mg2Si particles is such that the surface region, that is the region below the surface itself, is “substantially free” of Mg2Si particles.
Consistently with the above there are also separate consistory clauses for each means whereby the desired distribution of Mg2Si particles is achieved.
The specification sets out the advantages of the invention (p 9 line 16 to p 10 line 23). The first advantage is said to be:
Enhanced corrosion resistance. The Mg2Si distribution of the present invention eliminates direct corrosion channels from the coating surface to steel strip that occurs with a conventional Mg2Si distribution. As a result, the corrosion resistance of the coating is markedly enhanced.
The next advantage is said to be improved coating ductility.
The third advantage is said to be as follows:
The addition of Sr allows the use of higher cooling rates, reducing the length of cooling equipment required after the pot.
The Sr addition experiments are identical to those described in the 257 Patent. They illustrate the effect on Mg2Si distribution with the addition of Sr.
Further, there is a discussion of line trials. So at p 12 lines 1 to 27 the following was said:
The applicant has also carried out line trials on 55%Al-Zn-1.5%Si-2.0%Mg alloy composition (not containing Sr) coated on steel strip.
The purpose of these trials was to investigate the impact of cooling rates and coating masses on the distribution of Mg2Si particles in the coatings.
The experiments covered a range of coating masses from 60 to 100 grams per square metre surface per side of strip, with cooling rates up to 90℃/sec.
The applicant found two factors that affected the coating microstructure, particularly the distribution of Mg2Si particles in the coatings.
The first factor is the effect of the cooling rate of the strip exiting the coating bath before completing the coating solidification. The applicant found that controlling the cooling rate is important.
By way of example, the applicant found that for a AZ150 class coating (or 75 grams of coating per square metre surface per side of strip – refer to Australia Standard AS1397-2001), if the cooling rate is greater than 80℃/sec, Mg2Si particles formed in the surface region of the coating.
There is no reference to mottling.
It is also said:
The applicant also found that for the same coating it is not desirable that the cooling rate be too low, particularly below 11°C/sec, as in this case the coating develops a defective “bamboo” structure, whereby the zinc-rich phases forms a vertically straight corrosion path from the coating surface to the steel interface, which compromises the corrosion performance of the coating.
The specification is saying that for an AZ150 class coating, that is, up to 75 grams per square metre of strip surface per side, if the cooling rate is kept at a rate below 80°C per second, Mg2Si particles will not form in the surface region. The specification is saying not to use a cooling rate below 11°C per second for different reasons. The specification then goes on to make similar observations in respect of AZ200 class coating (i.e. 75 to 100 grams per square metre of strip surface per side), and indicates that the cooling rate should be kept at a rate between 11 and 50°C per second.
Page 12 and the first half of p 13 are relevantly the same as for the 257 Patent, but p 13, line 15 of the 258 Patent does not discuss “the second factor”, thickness variation, as the 257 Patent does. Rather, at this point it discusses the BlueScope research work in substantially the same terms as the 257 Patent.
Later it is said (p 16 line 8 to p 17 line 24):
Practically, the applicant has found that, to achieve the distribution of Mg2Si particles of the present invention, i.e. to avoid nucleation of the Mg2Si phase in region A, the cooling rate for coated strip exiting the coating bath has to be in a range of 11-80℃/sec for coating masses up to 75 grams per square metre of strip surface per side and in a range 11-50℃/sec for coating masses of 75-100 grams per square metre of strip surface per side. The short range coating thickness variation also has to be controlled to be no greater than 40% above the nominal coating thickness within a distance of 5 mm across the strip surface to achieve the distribution of Mg2Si particles of the present invention.
The applicant has also found that, when Sr is present in a coating bath, the above described kinetics of Mg2Si nucleation can be significantly influenced. At certain Sr concentration levels, Sr strongly segregates into the quaternary alloy layer (i.e. changes the chemistry of the quaternary alloy phase). Sr also changes the characteristics of surface oxidation of the molten coating, resulting in a thinner surface oxide on the coating surface. Such changes alter significantly the preferential nucleation sites for the Mg2Si phase and, as a result, the distribution pattern of the Mg2Si phase in the coating thickness direction. In particular, the applicant has found that, Sr at concentrations 250-3000ppm in the coating bath makes it virtually impossible for the Mg2Si phase to nucleate on the quaternary alloy layer or on the surface oxide, presumably due to the very high level of increase in system free energy would otherwise be generated. Instead, the Mg2Si phase can only nucleate at the central region of the coating in the thickness direction, resulting in a coating structure that is substantially free of Mg2Si at both the coating outer surface region and the region near the steel surface. Therefore, Sr additions in the range 250-3000ppm are proposed as one of the effective means to achieve a desired distribution of Mg2Si particles in a coating.
Many modifications may be made to the present invention as described above without departing from the spirit and scope of the invention.
In this context, whilst the above description of the present invention focuses on (a) the addition of Sr to Al-Zn-Si-Mg coating alloys, (b) regulating cooling rates (for a given coating mass) and (c) minimising variations in coating thickness as means for achieving a desired distribution of Mg2Si particles in coatings, i.e. at least substantially no Mg2Si particles in the surface of a coating, the present invention is not so limited and extends to the use of any suitable means to achieve the desired distribution of Mg2Si particles in the coating.
The passage at p 16 lines 8 to 20 is equivalent to that set out earlier for the 257 Patent (p 16 lines 23 to 35).
The specification ends with 25 claims. All claims are dependent upon claim 1. Claims 1 to 12 are product claims and claims 13 to 25 are method claims.
I should set out some of the claims:
1. An Al-Zn-Si-Mg alloy coated steel strip that comprises a coating of an Al-Zn-Si-Mg alloy on a steel strip with the alloy comprising in % by weight 40 to 60% Al, 40 to 60% Zn, 0.3 to 3% Si, and 0.3 to 10% Mg and unavoidable impurities, with the microstructure of the coating comprising Mg2Si particles, and with the distribution of the Mg2Si particles being such that there is no more than 10% by weight of Mg2Si particles in a surface region of the coating that has a thickness that is less than 30% of the total thickness of the coating.
2. The alloy coated steel strip defined in claim 1 wherein the surface region has a thickness that is at least 5% of the total thickness of the coating.
…
5. The alloy coated steel strip defined in any one of the preceding claims wherein the coating thickness is less than 30μm.
6. The alloy coated steel strip defined in any one of the preceding claims wherein the coating thickness is greater than 7μm.
…
11. The alloy coated steel strip defined in any one of the preceding claims wherein the coating contains less than 3000 ppm Sr.
12. The alloy coated steel strip defined in any one of the preceding claims wherein there are minimal coating thickness variations.
…
17. A hot-dip coating method for forming a coating of a corrosion-resistant Al-Zn-Si-Mg alloy on a steel strip as defined in any one of claims 1 to 12 that is characterised by passing the steel strip through a hot dip coating bath that contains Al, Zn, Si, and Mg and optionally other elements and forming an alloy coating on the strip, and cooling coated strip exiting the coating bath during solidification of the coating at a rate that is controlled so that the distribution of Mg2Si particles in the coating microstructure is such that there is no more than 10% by weight of Mg2Si particles in a surface region of the coating that has a thickness that is less than 30% of the total thickness of the coating.
18. The method defined in claim 17 comprises selecting the cooling rate for coated strip exiting the coating bath to be at less than a threshold cooling rate.
…
20. The method defined in any one of claims 17 to 19 comprises selecting the cooling rate for coated strip exiting the coating bath to be less than 50℃/sec for coating masses 75-100 grams per square metre of strip surface per side.
21. The method defined in any one of claims 17 to 20 comprises selecting the cooling rate for coated strip exiting the coating bath to at least 11℃/sec.
22. A hot-dip coating method for forming a coating of a corrosion-resistant Al-Zn-Si-Mg alloy on a steel strip as defined in any one of claims 1 to 12 that is characterised by passing the steel strip through a hot dip coating bath that contains Al, Zn, Si, and Mg and optionally other elements and forming an alloy coating on the strip with minimal variation in the thickness of the coating so that the distribution of Mg2Si particles in the coating microstructure is such that there is no more than 10% by weight of Mg2Si particles in a surface region of the coating that has a thickness that is less than 30% of the total thickness of the coating.
23. The method defined in claim 22 wherein the coating thickness variation is no more than 40% in any given 5 mm diameter section of the coating.
24. The method defined in claim 22 or claim 23 wherein the coating thickness variation is no more than 30% in any given 5 mm diameter section of the coating.
25. The method defined in any one of claims 22 to 24 comprises selecting the cooling rate during solidification of coated strip exiting the coating bath to be less than a threshold cooling rate.
Again, let me summarise some key themes.
The field of technology to which the specification relates is also a strip, typically steel strip, which has a corrosion-resistant metal alloy coating, and particularly a corrosion-resistant metal alloy coating that contains Al, Zn, Si and Mg as its main elements being an Al-Zn-Si-Mg alloy.
The specification describes the background to the invention in the same terms as the 257 Patent specification. But whereas the 257 Patent specification focuses on the surface defect “mottling”, the 258 Patent specification focuses on improved corrosion resistance performance and overcoming formability problems.
The specification is directed to keeping Mg2Si particles away from a “surface region” of the coating and within the central part of the coating. It explains the detrimental effects of Mg2Si particles on the corrosion resistance and formability of coated strip products.
The specification explains that with typical coating thicknesses, the Mg2Si phase forms as large particles which can provide a path for rapid corrosion where the particles extend from the surface of the coating to an alloy layer adjacent the steel strip. Further, the Mg2Si particles tend to be brittle and sharp particles, and provide both an initiation site and propagation path for cracks that form on the bending of coated products formed from coated strip. Moreover, increased cracking compared to Mg-free coatings can result in more rapid corrosion of the coatings.
The specification explains that the invention is an Al-Zn-Si-Mg alloy coated strip that has Mg2Si particles in the coating microstructure with the distribution of Mg2Si particles being such that a surface region of the coating has only a small proportion of Mg2Si particles or is at least substantially free of any Mg2Si particles. It explains that the term “surface region” should be understood to mean a region that extends inwardly from the exposed surface of a coating.
The specification states that the coated steel strip of the invention has a distribution of Mg2Si particles such that there is no more than 10% by weight of Mg2Si particles in the surface region of the coating. The surface region of the coating is to have a thickness which is at least 5% and less than 30% of the total thickness of the coating.
The specification explains that the applicant has found that such a distribution of Mg2Si particles in the coating microstructure provides significant advantages. Further, those advantages can be achieved by the three techniques described.
The specification lists other preferred aspects of the invention.
The specification states that there is also provided a hot dip coating method for forming a coating of a corrosion-resistant Al-Zn-Si-Mg alloy on a steel strip as defined in any one of claims 1 to 12 that is characterised by passing the steel strip through a hot dip coating bath that contains Al, Zn, Si, Mg, and more than 250 ppm Sr and optionally other elements, and forming an alloy coating on the strip that has Mg2Si particles in the coating microstructure with the distribution of the Mg2Si particles being such that there is no more than 10% by weight of Mg2Si particles in a surface region of the coating that has a thickness that is less than 30% of the total thickness of the coating.
Further, after listing other preferred aspects of the invention, the specification states that the Al-Zn-Si-Mg-Sr alloy coating may contain other elements as deliberate additions or as unavoidable impurities.
Further, after detailing possible coating thickness variations, the specification explains that in any given situation, the selection of an appropriate thickness variation is related to the coating thickness or coating mass.
The specification identifies various advantages (p 10 lines 1 to 23) as I have indicated earlier.
The specification describes laboratory experiments which showed that the addition of 500 ppm Sr to the alloy had the result that Mg2Si was confined to a central band of the coating. The specification later explains that Sr at concentrations in the range 250 to 3000ppm in the coating bath significantly influences nucleation of Mg2Si and makes it “virtually impossible” for the Mg2Si phase to nucleate on the quaternary alloy layer or on the surface oxide.
The specification also details the same line trials as described in the 257 Patent specification, which showed that the cooling rate of the strip, which should be from 11 to 80°C/sec for AZ150 class coatings and 11 to 50°C/sec for AZ200 class coatings, affects the microstructure.
The specification concludes by saying that to achieve the distribution of Mg2Si particles of the invention, specified cooling rates must be used and the short range coating thickness variation must be controlled to be no greater than 40% above the nominal coating thickness within a distance of 5 mm across the strip surface. Moreover, the specification states that the inclusion of Sr can influence the kinetics of Mg2Si by changing the chemistry of the quaternary alloy layer and characteristics of surface oxidation, and thereby the distribution pattern of the Mg2Si phase, particularly at concentrations of 250 ppm to 3000 ppm.
Let me now turn to the infringement question. As I have said, it is convenient to deal with this before invalidity questions.
MEASUREMENT PROTOCOL
It is appropriate to set out as the starting point for the analysis concerning infringement the measurement protocol used by BlueScope which was applied to the GLX product. Parts of two A4 size samples of the GLX product which had been provided to BlueScope by Dongkuk in March 2016 were used.
The facts that were sought to be proved by applying the protocol to parts of the March 2016 samples were:
(a)the proportion of the surface area of the March 2016 samples that comprised exposed Mg2Si particles;
(b)the proportion by weight of Mg2Si particles in the coating microstructure of the March 2016 samples that were exposed at the surface of the coating;
(c)the proportion by weight of Mg2Si particles in the coating microstructure of the March 2016 samples that were present in the top 5% of the thickness of the coating;
(d)the average, minimum and maximum coating thickness of the March 2016 samples; and
(e)the average, minimum and maximum coating thickness of 5mm diameter sections of the March 2016 samples.
The protocol reproduced images of portions of the March 2016 samples that remained following other testing that BlueScope had conducted on the samples as set out in Figure 1. The discs and cross-sections which are noted in red in Figure 1 are the approximate locations of where the discs were to be punched and the cross-sections sheared in accordance with the protocol.
Figure 1: Location of discs and cross sections from the March 2016 samples.
The protocol used the notation of “sample A” and “sample B” to refer to the samples of the March 2016 samples marked as such in Figure 1.
Stage 1 being sample preparation involved the following steps:
(a)Using a scribe, a 50mm diameter circle was to be marked near the centre of samples A and B as depicted in Figure 1 being the intended punch locations.
(b)Using a scribe, each 50mm diameter circle was to be marked with the sample name (either sample A or sample B) and the side (either top or reverse), as depicted in Figure 1.
(c)After the samples had been labelled, the labelled 50mm diameter circles were to be punched from each sample.
(d)Each disc was to be sheared in half as indicated by the red, dotted, horizontal line in Figure 1, maintaining the labels on each half. The sample was to be trimmed, if necessary, to ensure the sample was properly located on the Electron Probe Microanalyzer (EPMA) to be used at the relevant stage. All burs were to be removed.
(e)One 10mm slice was to be sheared across the full strip width of samples A and B, and cut into 30mm lengths (for 40mm diameter mounts) as indicated in Figure 1 in preparation for metallographic mounting and polishing of the 30mm long edge.
(f)Each 30×10mm section was to be placed into a separate contamination free plastic bag and the section location was to be recorded on each bag.
Stage 2 being to assess the Mg2Si surface presence or elemental surface mapping involved the following steps:
(a)A Jeol JXA-8530FPlus HyperProbe Electron Probe Microanalyzer (FE-EPMA) was to be used.
(b)For each half (top and reverse) of the two 50mm diameter discs, four separate areas were to be mapped, selected randomly but spaced at least 10mm apart.
(c)Each area mapped was to be 500x500µm, at a resolution of 1µm per pixel, using a beam dwell time of 50 milliseconds [the original protocol incorrectly referred to mm rather than µm].
(d)The maps were to be generated using electron beam settings of 5kV for the accelerating voltage and a beam current setting of 50 nanoAmps. This accelerating voltage and beam current setting were to be used throughout the experiment for all FE-EPMA analysis to ensure that the FE-EPMA analysis was not affected by using different parameters. The parameters used for each FE-EPMA analysis were to be recorded.
(e)The elemental maps for Mg, Si, Zn were to be measured by wavelength dispersive spectroscopy and captured as separate grey scale images.
(f)The characteristic x-rays and spectrometer crystals to be used for each element were: Mg: Kα on TAPH crystal, Zn: Lα on TAPH crystal and Si: Kα on TAP crystal.
(g)A professional grade photo editing software tool, such as COREL Paint Shop Pro, was to be used to convert each grey scale elemental map to a colour and each map was to be saved as a separate file.
(h)The following colours and settings were to be applied to the individual elemental x-ray map of the specified element:
(i)Mg x-ray map = Red (gamma setting: 4, grey scale offset: -4).
(ii)Si x-ray map = Green (gamma setting: 4, grey scale offset: -4).
(iii)Zn x-ray map = Blue (gamma setting: 3, grey scale offset: -0).
(i)To identify Mg2Si particles on the surface, a professional grade photo editing software tool, such as COREL Paint Shop Pro, was to be used to create a composite image of the red, green and blue coloured elemental x-ray maps. Mg2Si particles would appear as a yellow/orange coloured particles in the composite image.
(j)The surface area fraction of all identified Mg2Si was to be measured using standard image analysis software and techniques. The surface area of the Mg2Si was to be reported as a % of the total surface area imaged.
Stage 3 being the coating thickness measurement involved the following steps.
As to the sample preparation steps:
(a)Each 10mmx30mm length of samples A and B was to be mounted in a cold mount resin (such as Epofix) to allow preparation and viewing of the cross-section of the 30mm edge of each length. A 30mm length would be chosen by example as being appropriate for a 40mm diameter mount, where three to four lengths could be put into each mount.
(b)The strip was to be polished to a 1-3μm diamond finish using standard metallographic grinding and polishing techniques, specifically avoiding edge rounding or staining/corrosion of the Mg2Si or the metal coating. An alcohol based diamond polishing lubricant such as Struers “DP-Lubricant Yellow” and absolute ethanol for cleaning would be used for the final stages of polishing to assist with the prevention of corrosion and staining.
As to the image capture methodology:
(a)The metal coating thickness of one side of the strip would be measured at intervals of 0.5mm along each 30mm (a total of 60 measurements per 30mm cross-section) polished metallographic cross-section using an optical microscope at a magnification of 1000x, and the results recorded.
(b)The metal coating thickness measurement would be repeated on the reverse side of each cross-section.
(c)Cross-section images of the coating at 1000x magnification would be captured and saved for each side of each cross-section.
(d)The microscope images would be calibrated using a certified calibration slide.
As to calculating average metal coating thickness, for each cross-section image, the average metal coating thickness (AMCT) would be calculated as follows:
(a)One would threshold each image to highlight the area from the steel/alloy layer interface to the external metal coating surface.
(b)One would measure the highlighted area in square microns.
(c)One would measure the width of the image in microns.
(d)One would calculate the AMCT by dividing the highlighted area by the width of the image.
As to the metal coating thickness variation measurement:
(a)A 5mm width of cross-section (10 consecutive images long) would be randomly selected (see Figure 2 below).
(b)The maximum AMCT measurement from the 10 consecutive image measurements, denoted as AMCTmax, would be identified and recorded. The minimum AMCT measurement from the 10 consecutive image measurements, denoted as AMCTmin, would be identified and recorded.
(c)The average 5mm width metal coating thickness (A5MCT) would be calculated using the following formula:
(d)Thickness variation would be calculated according to the following formula:
Thickness Variation = (AMCTmax – AMCTmin) / A5MCT
Figure 2: 5mm width cross-sections (10 consecutive images long)
As to the full width metal coating thickness measurement, one would separately calculate the top and reverse full width average metal coating thickness (FWAMCT) according to the following formula:
Where S = Total number of consecutive 30mm mounted sections covering full width of strip.
Stage 4 being an assessment of the proportion of Mg2Si in the cross-sections involved the following steps:
(a)The metallographic cross-sections previously prepared for optical thickness measurements were to be used for this stage.
(b)The first and last cross-sections from each of samples A and B (four cross-sections in total) would be selected for analysis.
(c)FE-EPMA would be used to create elemental maps.
(d)Elemental maps for Mg, Si, Zn of the top and bottom metallic coated surfaces of the four selected cross-sections would be measured by FE-EPMA/WDS.
(e)Two 150μm wide areas, five millimetres apart, on each selected metallic coated cross-section would be mapped (see Figure 3), at a resolution of 0.2µm per pixel, using a beam dwell time of 50 milliseconds. Each cross-section map would include the full thickness of the coating.
Figure 3: Image of one selected 30mm cross-sections showing the two 150μm wide mapped areas
(f)The maps would be generated using electron beam settings of 5kV for the accelerating voltage and a beam current setting of 50 nanoAmps (i.e., the same parameters used in Stage 2, step (d) that I have set out earlier).
(g)The elemental maps for Mg, Si, Zn would be measured by WDS and captured as separate grey scale images.
(h)The characteristic x-rays and spectrometer crystals to be used for each element were: Mg: Kα on TAPH crystal, Zn: Lα on TAPH crystal and Si: Kα on TAP crystal.
(i)A professional grade photo editing software tool, such as COREL Paint Shop Pro, would be used to convert each grey scale elemental map to a colour and each map would be saved as a separate file.
(j)The following colours and settings would be applied to the individual elemental x-ray map of the specified element:
(i)Mg x-ray map = Red (gamma setting: 4, grey scale offset: -4).
(ii)Si x-ray map = Green (gamma setting: 4, grey scale offset: -4).
(iii)Zn x-ray map = Blue (gamma setting: 3, grey scale offset: -0).
(k)To identify Mg2Si particles on the surface and in the cross-section, a professional grade photo editing software tool, such as COREL Paint Shop Pro, would be used to create a composite image of the red, green and blue coloured elemental x-ray maps. Mg2Si particles would appear as a yellow/orange coloured particles in the composite image.
(l)The cross-sectional area of all identified Mg2Si particles within each 150μm wide mapped area would be measured using standard image analysis techniques available in proprietary image analysis software tools, such as Olympus’ analySIS Pro.
(m)The cross-sectional area of all identified Mg2Si particles within each 150μm wide mapped area that were in contact with the external surface of the metal coating would be isolated and measured as depicted in Figure 4 below.
(n)To calculate the proportion of Mg2Si particles in the surface in respect of each mapped area, the cross-sectional area of the Mg2Si particles determined to be in the surface would be divided by the cross-sectional area of all Mg2Si particles.
Figure 4: 150μm wide mapped area identifying the Mg2Si particles in the surface and not in the surface
(o)To calculate the proportion of Mg2Si particles in the top 5% of the AMCT (258 Patent, claim 2):
(i)one would, using the steel substrate/alloy layer interface as the reference line, measure the cross-sectional area of Mg2Si that resided above 95% of the AMCT (see Figure 5 below);
(ii)one would calculate the proportion of Mg2Si in the 5% thickness surface region by dividing the cross-sectional area of Mg2Si residing above 95% of the AMCT by the total cross-sectional area of Mg2Si in the mapped area.
Figure 5: 150μm wide mapped area identifying Mg2Si particles residing above 95% of the AMCT
(p)All measurements and calculations were to be recorded.
Now although Dongkuk attempted to demonstrate that the implementation of air flotation stabilisers was a process attended with difficulty, BlueScope says that the evidence does not support that proposition.
Mr Lopez explained that BlueScope’s research and development between 2008 and 2012 was largely driven by the practical constraints associated with a difficult working environment above a molten metal bath, rather than the principles involved in implementing wiping jets in conjunction with a stabiliser. Mr Lopez explained that although it was necessary to learn how to operate the stabiliser with the new coating, the relevant difficulties were able to be overcome without changing the design markedly.
Mr Renshaw explained that some of the trial and error resulted from the fact that BlueScope made its own product, rather than buying from a supplier. Mr Renshaw explained that BlueScope knew that the stabilisers would work, but that it was more a matter of the difficulty BlueScope would have in retrofitting. He explained that BlueScope decided not to purchase from an external supplier for cost reasons and because it had the internal know-how. But it needed to fit the stabiliser into the existing (decades old) line, which required careful consideration.
Mr Lopez’s evidence was that the air flotation stabiliser was settled around the end of 2008 or 2009, but that the project was put on hold in the wake of the global financial crisis until 2012. Mr Renshaw also gave evidence that the design of the air flotation stabiliser had been settled by November 2009, but that the global financial crisis delayed the project.
In relation to the system that was built in 2012, Mr Lopez explained to me the following:
HIS HONOUR: Sorry, just before you go on, Mr Lopez. Am I to understand this was the first proposal for the detailed engineering as opposed to what I would describe as a concept? Is this the first work for this type of air flotation stabiliser that could be described as something more than just a concept?
MR LOPEZ: Your Honour, you could describe it that way, but previously we had fully detailed earlier versions of the [Air Flotation Stabiliser] that had to be engineered with compromises to fit the existing equipment. So we weren’t replacing the air knives. We knew there were limitations there like the distance above the air knife was too great – a number of different things. So we had fully designed the system before but under specific or within specific constraints. This was now reflecting on everything we had learned and not only adding AFS but re-engineering that whole system with the air knife and AFS built in to give us more optimal geometry.
I accept much of BlueScope’s evidence as to the above matters. But the fact is that BlueScope’s failure to disclose in the unamended specification the best method known to it of performing the invention at the filing date has meant that it has obtained an unfair advantage to the detriment of the public such that I ought to exercise my discretion to refuse the amendment application.
An unfair advantage that BlueScope obtained was the inability for others to experiment or improve on the invention. It has sought to protect its invalid monopoly. The public has been disadvantaged by BlueScope’s conduct because for the last 10 years it has been deprived of the knowledge of what is the best method of performing the invention. A failure to disclose the best method of performing an invention impedes persons from lawfully exploiting a patent during its term such as acts for experimental purposes (s 119C). The failure also impedes persons from conducting research in other ways that do not constitute exploitation of the invention. It also impedes persons from legitimately seeking to exploit commercially what the patentee has learned whilst avoiding the forbidden territory of the claims. Further, I agree with Dongkuk that it does not have to demonstrate that a member of the public has in fact suffered detriment by BlueScope’s failure to disclose the best method. This can be inferred from its failure to comply with its obligations under s 40(2)(a) and the consequential loss of rights available to persons under s 119C. In any event, BlueScope carries the onus of establishing why I should exercise my discretion to allow the proposed amendments.
Further, another unfair advantage that BlueScope obtained was the secret use of the invention. The necessity for BlueScope to elect between preservation of its trade secrets and obtaining patent protection with its disclosure obligations was thereby avoided. It would seem that whilst withholding information from the public, BlueScope applied and optimised the best method known to it of performing the invention during the period 2009 to 2013. And it used that best method commercially from 2013. Mr Renshaw gave the following evidence:
Business conditions between the end of 2007 and March 2009 meant that further line trials for Project EDGE were put on hold. This meant that I did not complete the task of optimising the precise parameters for adjusting stripping jets to control short range coating thickness variations and introducing a stabiliser, as I had originally planned. [This] task was not completed on all metal coating lines until February 2012, with further adjustments continuing to be made later in 2012 and 2013 prior to commercial launch of BlueScope’s AM product.
On 30 June 2008, the Project EDGE Manufacturing Team circulated a process development forward work plan (Work Plan). The Work Plan stated that the next line trials would take place on MCL5 (metal coating line 5) and MCL4 (metal coating line 4) in March and June 2009 (under “Potential Future Trials”). The Work Plan also stated the relationship between cooling rate, coating thickness, impact pressure and mottle had been determined (under the heading After Pot Cooling (Mottle)).
The Work Plan also noted an issue in relation to jet stripping equipment and conditions. Namely, that the addition of magnesium may change jet stripping conditions to a set of new, unfamiliar operating conditions (under the heading Issue: Jet Stripping Equipment and Conditions). It was apparent from the work we had already done (and our conclusion that the jet stripping distances would need to be smaller) that it might be necessary to optimise the jet stripping equipment for AM coating lines, including by introducing stabilisers. However, this work did not need to be done until all of the other manufacturing issues identified in the Work Plan had been resolved. The task of optimising jet stripping conditions was therefore a low priority unless a commercially viable AM coated steel could be developed.
The Work Plan identified the next steps to be taken by the Project EDGE team, including monitoring the steel strips for mottle in the next line trials (under the heading After Pot Cooling (Mottle). However, we did not propose to take any active steps to reduce mottle in these next trials, given the more significant issues identified in the Work Plan that needed to be solved.
…
The need to modify coating air knives (jet stripping apparatus) was reflected in the Project EDGE – PSDG (Product Steering and Development Group) Update dated December 2008, which was created by Project EDGE team leader Rob Scott (under the heading “Manufacturing areas of focus”). The jet stripping apparatus used for AZ coating lines was in any event old and would need to be replaced. The update also noted that manufacturing changes, including the coating mass control project, were subject to capital review (under the heading “Project Interaction – Updates in Orange”).
…
A further line trial was conducted in March 2009 on MCL5 (the March 2009 Trial). The purpose of this trial was to conduct an extended production run of approximately two weeks duration in order to test potential process capability solutions and confirm line upgrade requirements, and to identify if there were any additional manufacturing issues, which were not apparent in the shorter, line trials. Although the task brief identified the need to examine jet stripping parameters, the focus was on reducing pock marks (a different surface defect), by observing the effect of jet stripping parameters on pock marks…
The March 2009 Trial was conducted at speeds and cooling rates that would not be suitable for commercial production. Due to the configuration of the line and the lower solidification temperature of the AM coating, unless slower speeds were used the coating would not have solidified by the time it reached the Turn-Around Roll.
At the cooling rates which were used, the Project EDGE team did not expect that mottle would result (since, as set out above, the appearance of mottle results in part from the use of higher cooling rates), and we did not observe mottle. Therefore, we did not introduce any measures to address mottle including arrangements to reduce short range coating thickness variations (that is, we did not alter the arrangements of the jets or introduce a stabiliser)…
No stabiliser was used in the March 2009 Trial.
No further line trial was conducted until November 2009 on MCL4 (the November 2009 Trial). The November 2009 Trial addressed manufacturing issues associated with the manufacture of low coating mass and to diagnose and design a solution for a surface defect, streaking. In this line trial the jets were moved closer to the metal strip for the first time, on an experimental basis, and an air flotation stabiliser was used…One of the aims of the trial was to assess the effectiveness of “Air Floatation Stabilisers” in minimising the jet to strip distance in the jet stripping zone…
Like the March 2009 Trial, the November 2009 Trial was run at reduced production speeds (of 175 metres per minute) due to equipment limitations. Therefore, the Project EDGE team did not expect that the process conditions would produce mottle. Consistent with this prediction, no mottle was observed. However, it was not possible to produce a commercially viable product using the reduced production speeds, because production volume was significantly reduced.
…
Following the November 2009 Trial, the Project EDGE team produced a Project EDGE Manufacturing Update in December 2009. That update said that the best AM product to date had been produced when the line was stabilised with an Air Floatation Stabiliser (AFS) allowed successful jet stripping at 15mm jet to jet distance (which is a jet to strip distance of 7.5mm), and that initial indications suggested the AFS reduced strip vibration by a factor of 4. The update focused on other defects. It did not mention mottle…
On 24 December 2009, I created a document analysing the effect of the AFS on strip position and stability, based on the results of the November 2009. I concluded that the effect of the AFS on strip stability is significant even at pressures of approximately 2 kPa. The magnitude of the improvement seemed dependant on the level of instability with the AFS off.
…
In 2011 the Project EDGE team ran an eight week line trial on MCL4 at speeds between 80% and 100% of normal commercial speeds, depending on the thickness of the strip. In this trial the first commercial air flotation stabiliser was used and the position of the jets were modified…
It was still necessary to modify the upleg cooling equipment (to allow production of the full range of strip thicknesses at commercial speeds) and arrive at the commercial specifications for the jet equipment (to prevent excessive short range coating thickness variations). These modifications were made in 2012…
In 2012 the Project EDGE team ran two further line trials on MCL1. The first line trial in February 2012 was to test the implementation of the solution to surface streaks and to confirm successful operation of the final jet modifications. These modifications consisted of an air floatation stabiliser that was integrated with the jet support system and a new narrow bodied jet barrel design. These jet modifications enabled a reduction in the jet height above the bath and a reduction in the jet to strip distance. The updated jet stripping equipment was designed and constructed by Hatch Engineering to BlueScope specifications.
In October 2012, further modifications to MCL1 were made. These modifications included an extra cooling zone in the upleg cooling section to increase the overall cooling capacity and redesign of the cooling control system to allow for the restrictions in cooling rate identified in the earlier work on mottle. The modifications to the upleg cooler design and control systems were undertaken by BlueScope engineering personnel.
The second line trial in December 2012 related to issues with chemical passivation and was to confirm successful operation of the upleg cooler modifications which had been made in October 2012. In both of these trials an integrated air flotation stabiliser was used (which was an updated version of the air flotation stabiliser used in the 2011 trial on MCL4) and the position of the jets were further modified…
In 2013 the Project EDGE team conducted a final line trial on MCL4 to confirm production capability for AM coated steel. This included use of final modifications to the upleg cooler and modified jet stripping conditions…
Following the successful completion of the 2013 line trial, AM coated steel was launched by BlueScope in 2013.
Finally, I agree with Dongkuk that BlueScope sought to obtain an unfair advantage by threatening Dongkuk during the period June to December 2016 with infringement proceedings on the unamended 257 Patent. At that time, BlueScope knew or ought to have known that it had not disclosed the best method and that for at least that reason the 257 Patent was invalid. BlueScope sought to obtain a further unfair advantage by commencing infringement proceedings on the unamended 257 Patent some four months before it filed the amendment application.
Fifth, in my view there has been unreasonable delay in seeking the amendment.
BlueScope says that it has moved expeditiously in making its application to amend the 257 Patent and that there has been no unreasonable delay. Let me elaborate on its submissions.
BlueScope says that it acted expeditiously to include what it considered to be the best method known to it of performing the invention as soon as it was alerted by its solicitors and counsel to the prospect that it might be necessary to amend the 257 Patent.
Further, it says that it was reasonable for it not to amend the 257 Patent despite the fact that the APO raised the issue of best method in its Second Examination Report in September 2014. In light of Mr Munt’s response, no amendment was required by the APO. Mr Munt considered that the issue had been dealt with and therefore did not recommend amendment. And the 257 Patent proceeded to grant.
Further, it says that it was also reasonable for it not to amend the 257 Patent despite the adverse reports in China, South Korea, Japan and the United States. Following BlueScope’s responses to the adverse reports in China, South Korea and the first office action in Japan the objections were resolved. No Patent Office required an amendment to be made. Further, although BlueScope did not press its divisional application in Japan, it had filed another patent. Further, it says that the adverse report from the United States Patent Office related to whether the claimed invention was anticipated, not sufficiency or enablement.
Further, it says that when it was first alerted by its solicitors and counsel on 5 October 2016 that it might be necessary to amend the 257 Patent, it undertook extensive investigations to identify the state of BlueScope’s knowledge at the date of filing, whether amendment was necessary, and ultimately the appropriate form of the amendment required.
Now unreasonable delay is a compelling reason for refusing an application to amend a patent. In Smith Kline & French Laboratories Ltd v Evans Medical Limited [1989] 1 FSR 561, Aldous J stated at 568:
[I]n a case where a patentee who is aware of the facts and either decides not to amend or takes no action, but later changes his mind, the court will refuse to exercise its discretion in his favour unless there is a good and proper reason for his failure to seek amendment promptly.
This encompasses a situation where a patentee is aware that there is a significant risk of invalidity if it maintains the patent in its unamended form. Constructive knowledge of the patentee may also be relevant. Indeed, the Full Court in Servier 2016 also held that constructive knowledge of the need to amend the patent is sufficient for establishing unreasonable delay. In particular, the Full Court at [243] held that:
…
•Unreasonable delay is a circumstance likely to lead to refusal of the amendment.
…
•In assessing delay, the time when the patentee was unaware and reasonably did not know of the need for amendment is not taken into account. The relevant delay is from when the patentee knows of the likely invalidity, or has its attention drawn to a defect in the patent, or is advised to strengthen the patent by amendment. That is, amendment will not be permitted in cases where a patentee knows or ought to know that amendment should be sought and fails to do so for a substantial period of time. Thus the reasonableness of the conduct of the patentee is a relevant consideration when assessing delay.
In my view BlueScope has unreasonably delayed in seeking amendments to the 257 Patent.
It is not in dispute that BlueScope knew of the best method of performing the alleged invention before the filing date notwithstanding that it had not in fact applied those “special operational measures”.
Further, BlueScope applied and optimised the best method known to it of performing the alleged invention during the period 2009 to 2013 and used that best method commercially from 2013.
Further, during at least the period 2012 to 2014, through the prosecution of foreign equivalent patents to the 257 Patent in at least China, the United States and South Korea, BlueScope was made aware or ought reasonably to have been aware that the specification of the 257 Patent did not disclose any method, let alone the best method known to BlueScope, of achieving minimal variation in the short range coating thickness to achieve the described distribution of Mg2Si particles in the surface of the coating. This is evident from various documented comments made to BlueScope by the Patent Offices in those jurisdictions. I have set some of these out earlier.
Further, on 4 September 2014, in the second examination report in respect of the 257 Patent, the examiner expressly raised a failure to disclose the best method. The examiner said:
I am not currently satisfied that the present specification provides an enabling disclosure of how to provide a strip with a variation in thickness of the coating of now [sic] more than 40% in any 5 mm diameter section and / or a best method of achieving this particular result…
Reviewing the specification as a whole, I can find no disclosure of what those special conditions are so as to provide the defined thickness variation…I am not satisfied that the subject matter claimed is provided with a best method of performance… even if a manner of performing the invention is self-evident, applicants are nevertheless required to set out the best method of performing the invention known to them.
Notwithstanding that express notification, BlueScope did not amend the 257 Patent specification. Instead on 5 September 2014 it advocated a position to the office in the following terms:
The skilled person in the field is a person who has experience in operating metal alloy coating lines and therefore understands the parameters that can be varied to control the line and, in particular, would understand the “special operational measures” mentioned in the…specification that could be applied to achieve the necessary control. The term “special” is intended to be understood in this context that they are not the usual measures employed to control a metal alloy coating line…
By way of example, the skilled person would understand that control of the gas stripping equipment that controls coating thickness is one of a number of measures that have an impact on controlling short range thickness variations of coatings. One particular control measure for the skilled person is to adjust the height of the stripping knife above the coating bath…
Further, on 8 January 2015, the 257 Patent in its unamended form was granted.
Further, on 16 February 2015, in response to a US office action, BlueScope referred to the special operational measures that had to be applied to keep the variation under control as a basis for an amendment to one of the claims.
Further, on 3 March 2015, the US Patent Office responded in relation to application no. 12/811,213:
Applicant cites Page 14-Page 15 of the specification, arguing that the [“]special operational measures had to be applied to keep variation under control” and that one skilled in the art understands that parameters can be varied to control the line and these special operational measures are not the usual measures employed to control a metal alloy line. This is not persuasive because the claims are substantially broader then argued and the applicant has failed to establish with specificity the special measures that are controlled for the entire breadth of the claim.
Further, on 18 March 2016, in response to US Patent Office action #6, BlueScope said:
…The specification makes it clear that the key findings of the line trials led to the subject invention. The purpose of the line trials was to investigate the impact of cooling rates and coating masses on mottling in the surface of coatings… In fact, whilst not described explicitly in the specification, the production line included gas wiping technology to control the thickness of coatings on steel strip emerging from the coating bath of the production line…
Further, on 6 June 2016, BlueScope sent a letter of demand to Dongkuk threatening infringement proceedings in relation to the unamended 257 Patent.
Further, on 21 June 2016, the Japanese Patent Office notified BlueScope in relation to a divisional patent based on JP application no. 5850619 that:
…it is not categorically described in the specification what conditions may be adjusted in the hot-dip coating method in order to satisfy the feature that “an alloy coating is formed on the strip with a variation no more than 40% in any given 5 mm diameter section of the coating”. Therefore, a large amount of trials and errors are needed to find the specific condition of the hot-dip coating method from all adjustable experimental conditions even if considering common general technical knowledge at the time of filing the present application, and it is not recognized that a person with ordinary skill in the art can carry out the inventions of Claims even if considering common general technical knowledge at the time of filing the present application in the whole specification.
Further, on 29 July 2016, a third party filed an opposition in respect of Japanese patent no. 5850619 alleging that the “special operational measures” are neither described nor suggested in the detailed description of the invention.
Further, on 13 December 2016 BlueScope commenced infringement proceedings against Dongkuk in relation to the unamended 257 Patent.
Finally, and belatedly, BlueScope filed the amendment application on 13 April 2017.
In summary, it would seem from the evidence that BlueScope’s lawyers and attorneys had to explain, by reference to matters beyond what was apparent from the specification, to Patent Offices in Australia, South Korea, Japan and the US, what was meant by “special operational measures” in order to try to overcome objections to applications for patents in those countries for the invention in suit. Clearly, BlueScope was on notice of the need to explain that expression in the specification. As Jessup J explained in CSL Ltd v Novo Nordisk Pharmaceuticals Pty Ltd (No 2) (2010) 190 FCR 522 at [76] with his customary pellucidity:
…a patentee who has been exposed to facts from which it was, or reasonably ought to have been, apparent to him or her that a claim might well be invalid unless amended, and who later seeks the favourable exercise of the Court’s discretion under s 105 is, in my opinion, in no position to say that there was, on the earlier occasion, no “need” to amend simply because it had not then been conclusively established that the claim was in fact invalid…
At the least BlueScope had constructive knowledge of the need to amend the specification well before it did so and simply made a calculated decision to take its chances with the disclosure it had made, whilst simultaneously benefiting commercially from the best method to the detriment of the public. I agree with Dongkuk that BlueScope should be held to that choice by my refusing the amendment.
(f) Summary
Taking into account the foregoing matters and also the other considerations raised in the parties’ submissions, in the exercise of my discretion I would refuse the amendment.
CONCLUSION
BlueScope has failed on its infringement case.
Dongkuk has partly succeeded on its invalidity case concerning the failure by BlueScope to disclose the best method known to it at the relevant time. Otherwise its invalidity case has failed on all other grounds.
BlueScope has failed on its amendment application.
I will hear further from the parties concerning the orders to give effect to these reasons, the resolution of any outstanding issues, and on costs.
I certify that the preceding one thousand, five hundred and seventeen (1517) numbered paragraphs are a true copy of the Reasons for Judgment herein of the Honourable Justice Beach. Associate:
Dated: 17 December 2019
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