A method for the manufacture of a coated steel sheet

Patent metadata

Field	Value
Publication number	US-2020277693-A1
Application number	US-201816753739-A
Country	US
Kind code	A1
Filing date	Oct 19, 2018
Priority date	Oct 24, 2017
Publication date	Sep 3, 2020
Grant date	—

Abstract

Method for the manufacture of a coated steel sheet including the following step of A) the provision of a pre-coated steel sheet coating with a first coating including iron and nickel, B) the thermal treatment of such pre-coated steel sheet at a temperature between 600 and 1000° C., and C) the coating of the steel sheet obtained in step B) with a second coating based on zinc.

First claim

What is claimed is:

1 - 30 . (canceled)

31 . A method for the manufacture of a coated steel sheet comprising the following steps:
providing a pre-coated steel sheet coated with a first coating including iron and nickel; thermally treating the pre-coated steel sheet at a temperature between 600 and 1000° C.; and coating the pre-coated steel sheet obtained after the thermally treating step with a second coating based on zinc.

32 . The method as recited in claim 31 wherein the first coating includes from 10% to 75% by weight of iron.

33 . The method as recited in claim 32 wherein the first coating includes from 25 to 65% by weight of iron.

34 . The method as recited in claim 33 wherein the first coating includes from 40 to 60% of weight of iron.

35 . The method as recited in claim 31 wherein the first coating includes from 25 to 90% by weight of nickel.

36 . The method as recited in claim 35 wherein the first coating includes from 35 to 75% by weight of nickel.

37 . The method as recited in claim 36 wherein the first coating includes from 40 to 60% by weight of nickel.

38 . The method as recited in claim 31 wherein the first coating consists of iron and nickel.

39 . The method as recited in claim 31 wherein the first coating has a thickness equal or above 0.5 μm.

40 . The method as recited in claim 39 wherein the first coating has a thickness between 0.8 and 5.0 μm.

41 . The method as recited in claim 40 wherein the first coating has a thickness between 1.0 and 2.0 μm.

42 . The method as recited in claim 31 wherein a steel substrate of the pre-coated steel sheet has a steel sheet composition comprising by weight:
0.10<C<0.40%,
1.5<Mn<3.0%,
0.7<Si<2.0%,
0.05<Al<1.0%
0.75<(Si+Al)<3.0%

and on a purely optional basis, one or more elements including:
Nb≤0.5%,
B≤0.005%,
Cr≤1.0%,
Mo≤0.50%,
Ni≤1.0%
Ti≤0.5%,

a remainder of the composition being made up of iron and inevitable impurities resulting from processing.

43 . The method as recited in claim 31 wherein the second layer includes above 50% by weight of zinc.

44 . The method as recited in claim 43 wherein the second layer includes above 75% by weight of zinc.

45 . The method as recited in claim 44 wherein the second layer includes above 90% by weight of zinc.

46 . The method as recited in claim 45 wherein the second layer consists of zinc.

47 . The method as recited in claim 31 wherein the thermally treating step is a continuous annealing.

48 . The method as recited in claim 44 wherein the thermally treating step is performed in an atmosphere including from 1 to 30% of H 2 at a dew point between −10 and −60° C.

49 . A steel sheet obtainable from the method as recited in claim 31 , the steel sheet comprising: a steel substrate coated with a diffused alloy layer comprising iron and nickel, the diffused alloy layer being directly topped by a zinc based layer.

50 . The steel sheet as recited in claim 49 wherein a steel microstructure of the steel substrate includes from 1 to 50% of residual austenite, from 1 to 60% of martensite and optionally at least one element chosen from: bainite, ferrite, cementite and pearlite.

51 . The steel sheet as recited in claim 50 wherein the microstructure includes from 5 to 25% of residual austenite.

52 . The steel sheet as recited in claim 50 wherein the microstructure includes from 1 to 60% of tempered martensite.

53 . The steel sheet as recited in claim 50 wherein the microstructure includes from 10 to 40% of bainite.

54 . The steel sheet as recited in claim 50 wherein the microstructure includes from 1 to 25% of ferrite.

55 . The steel sheet as recited in claim 50 wherein the microstructure includes from 1 to 15% of untempered martensite.

56 . A spot welded joint comprising:
at least two metal sheets, at least one of the metal sheets being the steel sheet as recited in claim 49 , the joint containing less than 3 cracks having a size above 100 μm and wherein the longest crack has a length below 500 μm.

57 . The spot welded joint as recited in claim 56 wherein the second metal sheet is a steel sheet or an aluminum sheet.

58 . The spot welded joint as recited in claim 57 wherein the second metal sheet is a second steel sheet including a second steel substrate coated with a second diffused alloy layer including iron and nickel, the second diffused alloy layer being directly topped by a second zinc based layer.

59 . The spot welded joint as recited in claim 56 wherein the at least two metal sheets include a third metal sheet being a steel sheet or an aluminum sheet.

60 . A spot welded joint comprising:
at least two metal sheets, at least one of the metal sheets being a steel sheet obtained by the method as recited in claim 31 , the joint containing less than 3 cracks having a size above 100 μm and wherein the longest crack has a length below 500 μm.

61 . An automobile vehicle part comprising the steel sheet as recited in claim 49 .

62 . An automobile vehicle part comprising a steel sheet obtained by the method as recited in claim 31 .

Assignees

• Arcelormittal

Inventors

• Chakraborty Anirban
• Ghassemi-Armaki Hassan

Classifications

• C23C2/022

  by heating · CPC title

• C23C2/02 Primary

  Pretreatment of the material to be coated, e.g. for coating on selected surface areas (C23C2/30 takes precedence) · CPC title

• C23C28/025

  with at least one zinc-based layer · CPC title

• C21D6/008

  containing Si · CPC title

• B32B15/015

  the said other metal being copper or nickel or an alloy thereof · CPC title