Method for producing a steel component

Patent metadata

Field	Value
Publication number	US-2016201157-A1
Application number	US-201414913592-A
Country	US
Kind code	A1
Filing date	Aug 18, 2014
Priority date	Aug 22, 2013
Publication date	Jul 14, 2016
Grant date	—

Abstract

A complexly formed steel component may have a tensile strength Rm of greater than 1200 MPa and an elongation at break A50 of greater than 6%. Example methods for producing such components comprise providing a flat steel product, which in addition to iron and unavoidable impurities, contains in percent by weight 0.10-0.60% C, 0.4-2.5% Si, up to 3.0% Al, 0.4-3.0% Mn, up to 1% Ni, up to 2.0% Cu, up to 0.4% Mo, up to 2% Cr, up to 1.5% Co, up to 0.2% Ti, up to 0.2% Nb, and up to 0.5% V. At least 10% by volume of a microstructure of the flat steel product may consist of residual austenite comprising globular residual austenite islands with a grain size of at least 1 μm. Before being cooled, the flat steel product may be heated to a forming temperature of 150-400° C. and formed into a component with a degree of forming that is at most equal to uniform elongation Ag.

First claim

1 .- 10 . (canceled)

11 . A method for producing a steel component having a tensile strength Rm of more than 1200 MPa and an elongation at break A50 of more than 6%, the method comprising:
providing a flat steel product that contains iron, unavoidable impurities, 0.10-0.60% by weight C, 0.4-2.5% by weight Si, up to 3.0% by weight Al, 0.4-3.0% by weight Mn, up to 1% by weight Ni, up to 2.0% by weight Cu, up to 0.4% by weight Mo, up to 2% by weight Cr, up to 1.5% by weight Co, up to 0.2% by weight Ti, up to 0.2% by weight Nb, and up to 0.5% by weight V, wherein at least 10% by volume of a microstructure of the flat steel product consists of residual austenite comprising globular residual austenite islands with a grain size of at least 1 μm; heating the flat steel product to a forming temperature of 150-400 degrees Celsius; forming the flat steel product heated to the forming temperature into a component with a degree of forming that is at most uniform elongation Ag; and cooling the flat steel product.

12 . The method of claim 11 wherein the flat steel product is provided with a metallic protective coating.

13 . The method of claim 11 wherein the flat steel product is a hot-rolled steel strip or steel sheet.

14 . The method of claim 13 wherein the microstructure of the flat steel product contains at least 60% by volume bainite, at least 10% by volume residual austenite, up to 5% by volume ferrite, up to 10% by volume ferrite, and up to 10% by volume martensite, wherein at least part of the residual austenite is in block form and at least 98% of blocks of the residual austenite that have a block form have an average diameter of less than 5 μm.

15 . The method of claim 14 wherein amounts of Mn, Cr, Ni, Cu, and C in the flat steel product follow
1<0.5% Mn+0.167% Cr+0.125% Ni+0.125% Cu+1.334% C<2,
wherein % Mn is an amount of Mn content in % by weight,
wherein % Cr is an amount of Cr content in % by weight,
wherein % Ni is an amount of Ni content in % by weight,
wherein % Cu is an amount of Cu content in % by weight, and
wherein % C is an amount of C content in % by weight.

16 . The method of claim 11 wherein the flat steel product that is provided is a cold-rolled steel strip or steel sheet.

17 . The method of claim 16 wherein a microstructure of the cold-rolled steel strip or steel sheet contains at least 20% by volume bainite, 10-35% by volume residual austenite, and at least 10% by volume martensite.

18 . The method of claim 17 wherein the cold-rolled steel strip or steel sheet contains at least 50% by volume bainite.

19 . The method of claim 11 wherein a sum content of Al and Si of the provided flat steel product is at least 1.5% by weight.

20 . The method of claim 11 wherein the cooling of the flat steel product occurs in still air.

Assignees

• Thyssenkrupp Steel Europe Ag

Inventors

• Hammer Brigitte
• Heller Thomas
• Hisker Frank
• Kawalla Rudolf
• Korpala Grzegorz

Classifications

• C21D8/02

  during manufacturing of plates or strips (C21D8/12 takes precedence) · CPC title

• C22C38/16

  containing copper · CPC title

• C22C38/42

  with copper · CPC title

• C22C38/06

  containing aluminium · CPC title

• C21D6/005

  containing Mn · CPC title