Metal-coated steel strip

Patent metadata

Field	Value
Publication number	US-2023100917-A1
Application number	US-202217901419-A
Country	US
Kind code	A1
Filing date	Sep 1, 2022
Priority date	Aug 29, 2006
Publication date	Mar 30, 2023
Grant date	—

Abstract

A steel strip having a coating of a metal alloy on at least one surface of the strip is disclosed. The metal alloy contains aluminium, zinc, silicon, and magnesium as the major elements. The metal alloy also contains strontium and/or calcium and unavoidable impurities and optionally other elements that are present as deliberate alloying elements. The concentration of magnesium is at least 1 wt. % and the concentration of (i) strontium or (ii) calcium or (iii) strontium and calcium is greater than 50 ppm.

First claim

1 . A steel strip having a coating of a metal alloy on at least one surface of the strip, wherein the metal alloy contains aluminium, zinc, silicon, and magnesium as the major elements and also contains strontium and/or calcium and unavoidable impurities and optionally other elements that are present as deliberate alloying elements, and wherein the concentration of aluminium is 40 to 60 wt. %, the concentration of zinc is 40 to 60 wt. %, the concentration of silicon is 0.3 to 3 wt. %, the concentration of magnesium is at least 1 wt. % and the concentration of (i) strontium or (ii) calcium or (iii) strontium and calcium together is greater than 50 ppm.

2 . The steel strip defined in claim 1 wherein the concentration of (i) strontium or (ii) calcium or (iii) strontium and calcium together is less than X, where X is selected from 0.2 wt. %, 150 ppm, and 100 ppm.

3 .- 4 . (canceled)

5 . The steel strip defined in claim 1 wherein the magnesium concentration is less than X, where X is selected from 10 wt. %, 5 wt. %, 3 wt. %, and 0.5 wt. %.

6 .- 8 . (canceled)

9 . The steel strip defined in claim 1 wherein the magnesium concentration is between X and Y, where X is selected from 1 wt. % and 1.5 wt. % and Y is selected from 5 wt. % and 3 wt. %.

10 . (canceled)

11 . The steel strip defined in claim 1 wherein the aluminium, zinc, silicon, and magnesium alloy is a titanium diboride-modified alloy as defined herein.

12 . The steel strip defined in claim 1 wherein the aluminium, zinc, silicon, and magnesium alloy contains any one or more of indium, tin, beryllium, titanium, copper, nickel, cobalt, and manganese.

13 . The steel strip defined in claim 1 wherein the aluminium, zinc, silicon, and magnesium alloy does not contain vanadium and/or chromium as deliberate alloy elements—as opposed to being present in trace amounts for example due to contamination in the molten bath.

14 . The steel strip defined in claim 1 wherein the concentration of iron is less than 1 wt. %.

15 . The steel strip defined in claim 1 wherein the coating has small spangles as defined herein.

16 . The steel strip defined in claim 1 wherein the strip is coated on one or both sides thereof.

17 . The steel strip defined in claim 1 wherein the coating has a coating mass of less than 80 g/m 2 of metal alloy on the or each side of the strip.

18 . The steel strip defined in claim 1 wherein the coating has an average coating thickness of less than 20 micrometers on the or each side of the strip.

19 . A method of forming a corrosion-resistant coating of a metal alloy on at least one surface of a steel strip, wherein the metal alloy coating contains aluminium, zinc, silicon, and magnesium as the major elements and also contains strontium, or calcium, or strontium and calcium, and unavoidable impurities, and optionally other elements that are present as deliberate alloying elements, wherein
the concentration of aluminium is about 55 wt. %, the concentration of silicon is about 1.5 wt. %, the concentration of magnesium is greater than 1.5 wt. % and less than 3 wt. % and the concentration of (i) strontium, or (ii) calcium, or (iii) strontium and calcium together is greater than 50 ppm and less than 150 ppm, and the balance is zinc;
the method includes the steps of successively passing the steel strip through a heat treatment furnace and a molten bath that contains the metal alloy by
(a) heat treating the steel strip in the heat treatment furnace; and
(b) hot-dip coating the strip in the molten bath and forming a coating of the metal alloy on the steel strip;

wherein the metal alloy coating provides galvanic protection to the steel strip.

20 .- 21 . (canceled)

22 . The method defined claim 19 wherein step (b) includes forming the coating with a coating mass of less than 80 g/m 2 of metallic coating on the or each side of the strip, and/or forming the coating with an average coating thickness of less than 20 micrometers on the or each side of the strip.

23 . (canceled)

24 . The method defined in claim 19 wherein step (b) includes forming the coating with small spangles less than 0.5 mm, measured using the intercept distance method as described in the Australian Standard AS1733.

25 . Cold formed products made from the metal alloy coated steel strip defined in claim 1 .

26 .- 27 . (canceled)

28 . The method defined in claim 19 , wherein the metal alloy coating contains as deliberate alloying elements any one or more of indium, tin, beryllium, titanium, copper, nickel, cobalt and manganese.

29 . The method defined in claim 19 , wherein the metal alloy coating does not contain vanadium or chromium as deliberate alloying elements.

30 . (canceled)

31 . The method defined in claim 19 wherein the coating contains strontium at a concentration of greater than 50 ppm and less than 150 ppm.

32 .- 33 . (canceled)

34 . The method defined in claim 19 wherein the coating contains calcium at a concentration of greater than 50 ppm and less than 150 ppm.

35 .- 36 . (canceled)

Assignees

• Bluescope Steel Ltd

Inventors

• Liu Qiyang
• Renshaw Wayne
• Williams Joe

Classifications

• C23C2/06 Primary

  Zinc or cadmium or alloys based thereon · CPC title

• C23C2/12

  Aluminium or alloys based thereon · CPC title

• Y10T428/12757

  Fe · CPC title