A method for the manufacture of a coated steel sheet

Patent metadata

Field	Value
Publication number	US-2020340124-A1
Application number	US-201816754538-A
Country	US
Kind code	A1
Filing date	Oct 19, 2018
Priority date	Oct 24, 2017
Publication date	Oct 29, 2020
Grant date	—

Abstract

Method for the manufacture of a coated steel sheet including the following successive steps A. the provision of an annealed steel sheet having the following chemical composition in 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 such as Nb≤0.5%, B≤0.005%, Cr≤1.0%, Mo≤0.50%, Ni≤1.0%, Ti≤0.5%, the remainder of the composition making up of iron and inevitable impurities resulting from the elaboration, such steel sheet being annealed at a temperature between 600 to 1200° C., B. the coating of the steel sheet obtained in step A) with a first coating including nickel, such first coating not including iron, and having a thickness equal or above 0.5 μm and C. the coating of the steel sheet obtained in step B) with a second coating based on zinc. A steel sheet, a spot welded joint and further uses of the steel sheet are also provided.

First claim

What is claimed is:

1 - 27 . (canceled)

28 . A method for the manufacture of a coated steel sheet comprising the following successive steps:
providing an annealed steel substrate having the following chemical composition in 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 such as
Nb≤0.5%,
B≤0.005%,
Cr≤1.0%,
Mo≤0.50%,
Ni≤1.0%,
Ti≤0.5%,
remainder of the composition making up of iron and inevitable impurities resulting from processing, the steel sheet being annealed at a temperature between 600 to 1200° C.; coating of the annealed steel substrate with a first coating including nickel but not including iron, and having a thickness equal or above 0.5 μm; and coating, with a second coating based on zinc, the annealed steel substrate coated with the first coating.

29 . The method as recited in claim 28 wherein the steel substrate is annealed in a continuous annealing.

30 . The method as recited in claim 28 wherein the annealing is performed in an atmosphere comprising from 1 to 30% of H 2 at a dew point between −10 and −60° C.

31 . The method as recited in claim 28 wherein the first coating includes above 80% by weight of nickel.

32 . The method as recited in claim 31 wherein the first coating includes above 90% by weight of nickel.

33 . The method as recited in claim 32 wherein the first coating consists of nickel.

34 . The method as recited in claim 28 wherein the first coating does not include phosphorus, nickel hydroxide or sulfur compounds.

35 . The method as recited in claim 28 wherein the first coating has a thickness equal or above 1.0 μm.

36 . The method as recited in claim 35 wherein the first coating has a thickness equal or above 1.6 μm.

37 . The method as recited in claim 36 wherein the first coating has a thickness between 1.8 to 7.0 μm.

38 . The method as recited in claim 28 wherein the second coating includes above 50% of zinc.

39 . The method as recited in claim 38 wherein the second coating includes above 75% of zinc.

40 . The method as recited in claim 39 wherein the second coating includes above 90% of zinc.

41 . The method as recited in claim 28 wherein the second coating does not comprise nickel.

42 . The method as recited in claim 40 wherein the second coating consists of zinc.

43 . A steel sheet obtainable from the method as recited in claim 28 , the steel sheet comprising a steel substrate coated with a first coating comprising nickel and having a thickness equal or above 0.5 μm, the first coating being directly topped by a zinc based layer.

44 . The steel sheet as recited in claim 43 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.

45 . The steel sheet as recited in claim 44 wherein the microstructure comprises from 5 to 25% of residual austenite.

46 . The steel sheet as recited in claim 44 wherein the microstructure comprises from 1 to 60% of tempered martensite.

47 . The steel sheet as recited in claim 44 wherein the microstructure comprises from 10 to 40% of bainite.

48 . The steel sheet as recited in claim 44 wherein the microstructure comprises from 1 to 25% of ferrite.

49 . The steel sheet as recited in claim 44 wherein the microstructure comprises from 1 to 15% of untempered martensite.

50 . A spot welded joint comprising:
at least two metal sheets including a first metal sheet being the steel sheet as recited in claim 43 , the joint containing less than 3 cracks having a size above 100 μm and wherein the longest crack has a length below 300 μm.

51 . The spot welded joint as recited in claim 50 wherein a second metal sheet of the metal sheets is a steel sheet or an aluminum sheet.

52 . The spot welded joint as recited in claim 50 wherein a second metal sheet of the metal sheets is a second steel sheet including an annealed second steel substrate with a first coating including nickel but not including iron, and having a thickness equal or above 0.5 μm; and with a second coating based on zinc.

53 . The spot welded joint as recited in claim 50 wherein the at least two metal sheets include a third metal sheet being a steel sheet or an aluminum sheet.

54 . A spot welded joint comprising:
at least two metal sheets including a first metal sheet being a steel sheet obtained by the method as recited in claim 28 , the joint containing less than 3 cracks having a size above 100 μm and wherein the longest crack has a length below 300 μm.

55 . An automotive vehicle part comprising the steel sheet as recited in claim 43 .

56 . An automotive vehicle part comprising a steel sheet obtained by the method as recited in claim 28 .

Assignees

• Arcelormittal

Inventors

• Bertho Pascal
• Chakraborty Anirban
• Ghassemi-Armaki Hassan
• Allely Christian
• Machado Amorim Tiago
• Chaleix Daniel

Classifications

• C23C2/06 Primary

  Zinc or cadmium or alloys based thereon · CPC title

• C23C2/026

  Deposition of sublayers, e.g. adhesion layers or pre-applied alloying elements or corrosion protection · CPC title

• C23C2/0224

  Two or more thermal pretreatments · CPC title

• C23C2/0222

  in a reactive atmosphere, e.g. oxidising or reducing atmosphere (C23C2/024 takes precedence) · CPC title

• C21D2211/005

  Ferrite · CPC title