Method for producing workpieces from lightweight steel having material properties that are adjustable across the wall thickness

Patent metadata

Field	Value
Publication number	US-9593392-B2
Application number	US-201113634980-A
Country	US
Kind code	B2
Filing date	Feb 10, 2011
Priority date	Mar 16, 2010
Publication date	Mar 14, 2017
Grant date	Mar 14, 2017

Abstract

A method for producing a workpiece having properties which are adjustable across a wall thickness or strip thickness of the workpiece, includes the steps of subjecting the workpiece to a decarburizing annealing treatment under an oxidizing atmosphere and to an accelerated cooling and/or a cold forming for generating a property gradient of the workpiece, wherein the workpiece is made of an austenitic lightweight steel which has an alloy composition which includes by weight percent 0.2% to 1% carbon, 0.05% to<15% aluminum, 0.05% to 6.0% silicon, 9% to<30% manganese, and at least one element selected from the group consisting of chromium, copper, boron, titanium, zirconium, vanadium and niobium, wherein chromium=4.0%; titanium+zirconium=0.7%; niobium+vanadium=0.5%, boron=1%, the remainder iron including common steel companion elements.

First claim

What is claimed is:

1. A Method for producing a workpiece having properties which are adjustable across a wall thickness or strip thickness of the workpiece, said workpiece being made of an austenitic lightweight steel which has an alloy composition comprising by weight percent
0.2% to 1% carbon,
0.05% to <15% aluminum,
0.05% to 6.0% silicon,
9% to <30% manganese,
and at least one element selected from the group consisting of chromium, copper, boron, titanium, zirconium, vanadium and niobium, chromium≦6.5%; titanium+zirconium≦0.7%; niobium+vanadium≦0.5%, boron≦1%, the remainder iron including common steel companion elements,
said method comprising the steps of:
subjecting the workpiece to a decarburizing annealing treatment under an oxidizing atmosphere thereby causing a ferritic or meta-stable austenitic structure to form in a surface proximate region of the workpiece; and
subjecting the workpiece to an accelerated cooling and/or a cold forming for generating an increased hardness in the surface proximate region and a property gradient of the workpiece, wherein a layer thickness and properties of the austenitic structure are adjustable via variation of at least one annealing parameter selected from the group consisting of temperature and holding time and via variation of at least one of a gas composition and a partial pressure of the atmosphere.

2. The method of claim 1 , further comprising forming the workpiece before, during or after the annealing treatment.

3. The method of claim 2 , wherein the forming is a hot or cold forming.

4. The method of claim 3 , wherein the forming is a hot or cold rolling.

5. The method of claim 4 , further comprising after the rolling process, subjecting the workpiece to an annealing process under a reducing or inert atmosphere to adjust a depth and a degree of a decarburization generated in the workpiece by the annealing treatment before and/or after individual rolling passes of the hot rolling.

6. The method of claim 4 , further comprising adjusting a depth and a degree of a decarburization caused by the decarburizing annealing treatment in a targeted manner by reheating the workpiece between individual rolling passes of the hot rolling.

7. The method of claim 3 , wherein the forming is a hydroforming.

8. The method of claim 3 , wherein the forming is a deep drawing.

9. The method of claim 3 , wherein the forming is a pressing.

10. The method of claim 3 , wherein the forming is a press hardening.

11. The method of claim 2 , wherein the forming is performed after the annealing treatment, and wherein the accelerated cooling is performed during the forming.

12. The method of claim 1 , wherein the accelerated cooling is a quenching.

13. The method of claim 1 , wherein the oxidizing annealing atmosphere is ambient air.

14. The method of claim 3 , wherein oxygen or oxygen containing gases are added to the ambient air.

Assignees

• John Daniela
• Otto Manuel
• Schmidt-Jürgensen Rune
• Evertz Thomas
• Georgeou Zacharias
• Springub Bianca
• Salzgitter Flachstahl Gmbh

Inventors

• John Daniela
• Otto Manuel
• Schmidt-Jürgensen Rune
• Evertz Thomas
• Georgeou Zacharias
• Springub Bianca

Classifications

• C21D6/005 Primary

  containing Mn · CPC title

• C22C38/06

  containing aluminium · CPC title

• C22C38/02

  containing silicon · CPC title

• C21D9/46

  for sheet metals · CPC title

• C21D9/42

  for armour plate · CPC title