Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
  • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
  • C23C2/12—Aluminium or alloys based thereon
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
  • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
  • C23C2/06—Zinc or cadmium or alloys based thereon
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
  • C23C2/26—After-treatment
  • C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
  • C23C2/26—After-treatment
  • C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
  • C23C2/29—Cooling or quenching
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
  • C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
  • C23C2/36—Elongated material
  • C23C2/40—Plates; Strips

Definitions

• 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.
• Al-Zn-Si-Mg alloy is understood to cover alloys that contain such other elements as deliberate alloying additions or as unavoidable impurities.
• the metal -coated strip may be sold as an end product itself or may have a paint coating applied to one or both surfaces and be sold as a painted end product.
• the present invention relates particularly but not exclusively to a method of enhancing the ductility of an Al-Zn-Si-Mg coating on steel strip.
• the present invention relates particularly but not exclusively to steel strip that is coated with the above-described Al-Zn-Si-Mg alloy and is optionally coated with a paint and thereafter is cold formed (e.g. by roll forming) into an end-use product, such as building products (e.g. profiled wall and roofing sheets.
• end-use product such as building products (e.g. profiled wall and roofing sheets.
• the ductility of coatings, particularly in areas (e.g. tension bends) that are directly subjected to cold forming, is an important issue for such end-use products (painted and un- painted) .
• the Al-Zn-Si-Mg alloy of the present invention comprises the following ranges in % by weight of the elements aluminium, zinc, silicon, and magnesium:
• Zinc 40 to 60 %
• the corrosion-resistant metal alloy coating of the present invention is formed on steel strip by a hot-dip coating method.
• steel strip In the conventional hot-dip metal coating method, steel strip generally passes through one or more heat treatment furnaces and thereafter into and through a bath of molten metal alloy held in a coating pot.
• the heat treatment furnace that is adjacent a coating pot has an outlet snout that extends downwardly to a location close to an upper surface of the bath.
• the metal alloy is usually maintained molten in the coating pot by the use of heating inductors.
• the strip usually exits the heat treatment furnaces via an outlet end section in the form of an elongated furnace exit chute or snout that dips into the bath. Within the bath the strip passes around one or more sink rolls and is taken upwardly out of the bath and is coated with the metal alloy as it passes through the bath.
• the metal alloy coated strip After leaving the coating bath the metal alloy coated strip passes through a coating thickness control station, such as a gas knife or gas wiping station, at which its coated surfaces are subjected to jets of wiping gas to control the thickness of the coating.
• a coating thickness control station such as a gas knife or gas wiping station
• the metal alloy coated strip then passes through a cooling section and is subjected to forced cooling.
• the cooled metal alloy coated strip may thereafter be optionally conditioned by passing the coated strip successively through a skin pass rolling section (also known as a temper rolling section) and a tension levelling section.
• the conditioned strip is coiled at a coiling station.
• the metal - coated strip may be painted, for example with a polymeric paint, on one or both surfaces of the strip.
• the profiled sheets are usually manufactured by cold forming painted, metal alloy coated strip. Typically, the profiled sheets are manufactured by roll-forming the painted strip.
• the applicant is aware that following solidification of a 55%A1-Zn-1.5%Si metallic coating, an age hardening reaction occurs wherein excess Zn dissolved in the Al-rich phase in the coating precipitates as a metastable phase. This causes an increase in strength of the Al-rich phase, and consequently increases the effectiveness of any potential crack initiation sites.
• This age hardening reaction results in a significant increase in coating hardness within 2-4 weeks of coating solidification, and if cold forming (e.g. roll forming) of tight bends in the metal alloy coated steel (including painted metal-coated steel) is not carried out soon after coating solidification, increased bend cracking can result. In some situations this can be a significant problem.
• the present invention is a coating of an Al-Zn-
• Si-Mg alloy on a steel strip that is applied by a hot dip process and is subsequently heat treated to improve the ductility of the coating.
• the resultant coating can be cold formed with a reduced level of cracking on tension bends compared to coatings that are not heat treated.
• the applicant has also found that the benefit obtained during the heat treatment can be long lasting. Specifically, improved ductility can be retained for a period of 12 months or more.
• the present invention provides an Al-Zn-Si-Mg alloy coated steel strip produced by hot dip coating the steel strip with the alloy and then heat treating the coated strip.
• a corrosion- resistant Al-Zn-Si-Mg alloy on a steel strip that comprises:
• the method comprises heat treating the coated strip at a hold temperature of at least 150 0 C.
• w hold temperature is understood herein to mean a maximum temperature to which a coated strip is heated to and held at during the course of a heat treatment cycle. More preferably the method comprises heat treating the coated strip at a hold temperature of at least 200 0 C.
• the method comprises heat treating the coated strip at a hold temperature of at least 225°C.
• the method comprises heat treating the coated strip at a hold temperature of less than 300 0 C.
• the method comprises heat treating the coated strip at a hold temperature of less than 275°C.
• the method comprises holding the coated strip at the hold temperature for up to 45 minutes.
• the method comprises holding the coated strip at the hold temperature for up to 30 minutes.
• the method comprises slow cooling the heat treated coated strip from the hold temperature to a temperature of 100 0 C or less.
• the cooling rate of heat treated coated strip affects the durability of the softening effect, i.e. the improved ductility, obtained by the heat treatment and that it is preferable that the cooling rate be a "slow" cooling rate.
• the method comprises slow cooling the heat treated coated strip from the hold temperature to a temperature of 80 0 C or less.
• the cooling rate is 40°C/hr or less. More preferably the cooling rate is 30°C/hr or less.
• the heat treatment step of the method may be carried out on a batch or a continuous basis.
• the Al-Zn-Si-Mg alloy of the present invention comprises the following ranges in % by weight of the elements aluminium, zinc, silicon, and magnesium:
• Zinc 40 to 60 %
• the magnesium concentration is less than 8 wt.%.
• the magnesium concentration is less than 3 wt.%.
• the magnesium concentration is at least 0.5 wt.%.
• the magnesium concentration is between the magnesium concentration and the magnesium concentration.
• the magnesium concentration is between 1.5 wt . % and 2.5 wt . % .
• the silicon concentration is less than 3.0 wt.%.
• the silicon concentration is less than 1.6 wt.%. Preferably the silicon concentration is less than 1.2 wt.%.
• the silicon concentration is less than 0.6 wt . % .
• the aluminium concentration is at least 45 wt.%.
• the aluminium concentration is at least 50 wt.%.
• the Al-Zn-Si-Mg alloy does not contain deliberate additions, i.e. additions above concentration levels that would be regarded as impurity levels, of chromium and/or manganese.
• the Al-Zn-Si-Mg alloy may contain other elements as impurities or as deliberate additions.
• the coating on the strip is no more than 30 microns.
• the metal coated steel strip is cold formed into an end-use product, such as building products (e.g. profiled wall and roofing sheets).
• building products e.g. profiled wall and roofing sheets.
• a method of forming a painted, metal coated steel strip that comprises:
• the Al-Zn-Si-Mg alloy and the heat treatment step are as described above.
• the metal coated steel strip is cold formed into an end-use product, such as building products (e.g. profiled wall and roofing sheets).
• building products e.g. profiled wall and roofing sheets.
• the present invention is based on experimental work carried out by the applicant.
• the experimental work was carried out on samples of steel strip that were coated with a 55%Al-Zn-1.5%Si- 2%Mg alloy with a coating density of 150g/m 2 (i.e. 75g/m 2 of each surface of the strip samples) and then heat treated by heating the samples to a range of different hold temperatures and holding the samples at the temperatures for a pre-determined period of 30 minutes and then cooling the heat treated samples to ambient temperature.
• the experimental work also included a paint bake cycle (PBC) heat treatment simulation for some of the samples.
• the PBC treatment comprised heating samples to a peak metal temperature of 230 0 C at ⁇ 7°C/s, followed by water quenching .
• Figure 1 shows the critical bend strain (CBS) , i.e. the strain in a coating that is required to initiate cracking, for samples having the 55%Al-Zn-1.5%Si-2%Mg (150g/m 2 coating density) coating held at different temperatures for the above predetermined time of 30 minutes and then cooled to 80 0 C at a rate of 0.5°C/min.
• CBS critical bend strain
• Figure 1 shows that the CBS increased from 5.3% for the as-received coated sample (i.e. the sample point at ambient temperature) to a maximum of 8.3% for a coated samples that were heat treated at hold temperatures in the range of 225-25O 0 C. This constitutes a 56% increase in coating ductility - a significant improvement.
• CSR Crack Severity Rating
• Figure 2 shows the CSR for samples having heat- treated 55%Al-Zn-1.5%Si-2%Mg (150g/m 2 ) coatings as a function of hold temperature. It is evident from the Figure that 225 0 C is the optimum hold temperature in this experiment. Also, it is evident from the Figure that the CSR started to improve at a hold temperature of 150 0 C.
• Figure 3 shows the ageing behaviour of (a) samples having coatings of 55%A1-Zn-1.5%Si-2%Mg alloy that were heat treated at the above-established optimum hold temperature of 225 0 C for the above predetermined time of 30 minutes that were aged for up to three months, (b) samples as described in item (a) that were then subjected to a paint bake cycle treatment, (c) samples having as- received coatings of 55%Al-Zn-1.5%Si-2%Mg alloy, and (d) samples having coatings of 55%A1-Zn-1.5%Si-2%Mg alloy that were subjected to a paint bake cycle treatment only.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Thermal Sciences (AREA)
• Coating With Molten Metal (AREA)

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• 2009
  • 2009-02-06 KR KR1020157019849A patent/KR101749923B1/ko active IP Right Grant
  • 2009-02-06 CN CN2009801016184A patent/CN101910445B/zh active Active
  • 2009-02-06 US US12/811,214 patent/US20100316805A1/en not_active Abandoned
  • 2009-02-06 KR KR1020107014567A patent/KR20100108543A/ko not_active Application Discontinuation
  • 2009-02-06 WO PCT/AU2009/000145 patent/WO2009097663A1/en active Application Filing
  • 2009-02-06 AU AU2009212109A patent/AU2009212109B2/en active Active
  • 2009-02-06 EP EP09708502.1A patent/EP2238273B1/en active Active
  • 2009-02-06 JP JP2010545330A patent/JP5815947B2/ja active Active
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  • 2009-02-06 BR BRPI0907450A patent/BRPI0907450A2/pt not_active Application Discontinuation
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• 2018
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