Method for producing a flat steel product which can be readily formed, flat steel product and method for producing a component from such a flat steel product

Patent metadata

Field	Value
Publication number	US-9234253-B2
Application number	US-201013513682-A
Country	US
Kind code	B2
Filing date	Dec 3, 2010
Priority date	Dec 10, 2009
Publication date	Jan 12, 2016
Grant date	Jan 12, 2016

Abstract

A readily formable flat steel product has a ductile edge layer that is from 10 to 200 μm thick and has a ductility greater than a ductility of an inner core layer of the flat steel product. The readily formable flat steel product is produced by annealing a flat steel product having a C content of from 0.1 to 0.4% by weight in a continuous furnace. The annealing is carried out under an annealing atmosphere that contains from 0.1 to 25% by vol. of H 2 and H 2 O, with the balance being N 2 and technically unavoidable impurities. A dew point is between −20° C. and +60° C., and a ratio of H 2 O/H 2 is a maximum of 0.957. In the course of the annealing, the flat steel product is heated to a holding temperature of from 600 to 1100° C. and for a holding time of from 10 to 360 seconds.

First claim

The invention claimed is:

1. A method for producing a readily formable flat steel product that has an inner core layer and a ductile edge layer at a free surface of the flat steel product, wherein the ductile edge layer covers the inner core layer, wherein the ductile edge layer is from 10 to 200 μm thick, and wherein a ductility of the ductile edge layer is greater than a ductility of the inner core layer, the method comprising the steps of:
annealing a flat steel product having a C content of from 0.1 to 0.4% by weight in a continuous furnace, wherein the step of annealing is carried out under an annealing atmosphere that contains from 0.1 to 25% by vol. of a total amount of H 2 and H 2 O, with the balance being N 2 and technically unavoidable impurities, wherein a dew point of the annealing atmosphere is between −20° C. and +60° C., and wherein a volume ratio of H 2 O/H 2 of the annealing atmosphere is a maximum of 0.957; and
in the course of the annealing, heating the flat steel product to a holding temperature of from 600 to 1100° C. and for a holding time of from 10 to 360 seconds.

2. The method according to claim 1 , wherein the flat steel product is coated with a metal protective layer after the step of annealing.

3. The method according to claim 2 , wherein the flat steel product is hot-dip-coated in a continuous operating sequence after the step of annealing.

4. The method according to claim 2 , wherein the flat steel product is hot-coated after the step of annealing.

5. The method according to claim 4 , wherein oxidation of the surface of the flat steel product is carried out before the flat steel product is hot-coated.

6. The method according to claim 2 , wherein the flat steel product is coated with a metal/organic coating.

7. The method according to claim 3 , wherein the flat steel product is coated with a metal/organic coating.

8. The method according to claim 2 , wherein the flat steel product is coated with a metal/inorganic coating.

9. The method according to claim 3 , wherein the flat steel product is coated with a metal/inorganic coating.

10. The method according to claim 1 , wherein the C content of the flat steel product is less than 0.38% by weight.

11. A flat steel product having a C content of from 0.1 to 0.4% by weight and having an inner core layer and a ductile edge layer at a free surface of the flat steel product, wherein the ductile edge layer covers the inner core layer, wherein the ductile edge layer is from 10 to 200 μm thick, and wherein a ductility of the ductile edge layer is greater than a ductility of the inner core layer.

12. The flat steel product according to claim 11 , wherein the ductile edge layer includes a ferritic structure.

13. The flat steel product according to claim 11 , wherein the C content of the flat steel product is a maximum of 0.38% by weight.

14. The flat steel product according to claim 12 , wherein the C content of the flat steel product is a maximum of 0.38% by weight.

15. The flat steel product according to claim 11 , wherein a hardness (HV) of the ductile edge layer is a maximum of 75% of a hardness (HV) of the inner core layer of the flat steel product.

16. A method for producing a component from a flat steel product of claim 11 , wherein the flat steel product is subjected to hot forming, in which the flat steel product is initially heated to a heating temperature above its Ac1 temperature and subsequently hot-formed to form the component.

17. The method according to claim 16 , wherein the heating temperature is at least equal to the Ac3 temperature of the flat steel product.

18. A method for producing a component from a flat steel product of claim 11 , wherein the flat steel product is cold-formed to form the component.

Assignees

• Warnecke Wilhelm
• Meurer Manfred
• Kondratiuk Jens
• Blumenau Marc
• Norden Martin
• Wuttke Thiemo
• Thyssenkrupp Steel Europe Ag

Inventors

• Warnecke Wilhelm
• Meurer Manfred
• Kondratiuk Jens
• Blumenau Marc
• Norden Martin
• Wuttke Thiemo

Classifications

• C21D9/46

  for sheet metals · CPC title

• C22C38/38

  with more than 1.5% by weight of manganese · CPC title

• C22C38/04

  containing manganese · CPC title

• C21D1/76 Primary

  Adjusting the composition of the atmosphere · CPC title

• B21D31/00

  Other methods for working sheet metal, metal tubes, metal profiles (deforming one surface of tubes helically by rolling B21H3/00; upsetting B21J5/08; working metal by removing material therefrom B23; embossing B44B) · CPC title