Method for producing hot-formed and press-hardened automobile column

Patent metadata

Field	Value
Publication number	US-9637174-B2
Application number	US-201314031772-A
Country	US
Kind code	B2
Filing date	Sep 19, 2013
Priority date	Oct 15, 2010
Publication date	May 2, 2017
Grant date	May 2, 2017

Abstract

A method for producing an automobile column is disclosed. The automobile column has a region of a first type and a region of a second type which have mutually different strengths. A transition region having a width of less than 50 mm is formed between the two regions. The automobile column has in the region of the first type a bainitic structure and in the region of the second type a martensitic structure.

First claim

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims and includes equivalents of the elements recited therein:

1. A method for producing a hot-formed and press-hardened automobile column having at least two regions of different hardness, said method comprising the steps of:
providing a hardenable metal plate or semi-finished product and heating the hardenable metal plate or semi-finished product to at least an austenizing temperature,
intermediately cooling a first region of the metal plate or semi-finished product with a cooldown speed selected to be greater than a lower critical cooldown speed of a material of the metal plate or semi-finished product, and
hot-forming and press-hardening the metal plate or semi-finished product in a press-hardening tool to form the automobile column
wherein the first region has a stretchability A50 between 10% and 30%,
wherein a yield strength or a tensile strength decreases or increases in a transition region between the first region and the second region with a gradient of more than 200 N/mm 2 per 10 mm, and
wherein the first region contains a mixed structure of martensite, bainite and at least one of ferrite and perlite and wherein a bainite content of the first region is more than 50%.

2. The method of claim 1 , wherein a second region is held above the austenizing temperature until the second region is transported into the press-hardening tool.

3. The method of claim 1 , wherein the cooldown speed during intermediate cooling of the first region is selected such that a bainitic structure is obtained.

4. The method of claim 3 , wherein the first region is cooled to a cooling temperature between 600 and 400° C.

5. The method of claim 4 , wherein the first region is cooled to a cooling temperature of about 500° C.

6. The method of claim 3 , wherein the first region is held at the cooling temperature for a predetermined time.

7. The method of claim 3 , wherein the first region is held at the cooling temperature isothermally.

8. The method of claim 1 , wherein the mixed structure of the first region is obtained by quenching the first region in the press-hardening tool from a bainitic structure transformation stage.

9. The method of claim 1 , further comprising the step of holding the first region isothermally so as to form a substantially pure bainitic structure by press-hardening.

10. The method of claim 1 , wherein the cooldown speed of the intermediate cooling is selected to be greater than an upper critical cooling-down speed.

11. The method of claim 1 , wherein the intermediate cooling of the region of first region is performed in the press-hardening tool.

12. The method of claim 11 , wherein the intermediate cooling of first region is performed by using cooling plates arranged in the press-hardening tool.

13. The method of claim 1 , wherein the metal plate is pre-formed into a semi-finished product while cold before being heated to at least the austenizing temperature.

14. The method of claim 1 , wherein the first region has a tensile strength between 500 and 1000 N/mm 2 .

15. The method of claim 2 , wherein a transition region between the first region and the second region smaller than 80 mm.

16. The method of claim 2 , wherein at least portions of the first region are enclosed by the region of the second type.

17. The method of claim 2 , wherein the first region is completely enclosed by the region of the second type.

18. The method of claim 1 , wherein the first region is spot-shaped with a diameter of less than 40 mm.

19. The method of claim 1 , further comprising constructing the first region as a flange, a connecting flange or an outside edge of the automobile column, or a combination thereof.

20. The method of claim 1 , wherein the first region is formed in regions of the automobile column which are subject to strong deformations in a crash or which are configured to dissipate crash energy through deformations.

21. The method of claim 2 , wherein the first region has an increased wall thickness in relation to the second region.

22. The method of claim 1 , further comprising forming a passage or an edge, or both, in the first region after the hot-forming.

23. The method of claim 1 , wherein a yield strength or a tensile strength decreases or increases in a transition region between the first region and the second region with a gradient of more than 400 N/mm 2 per 10 mm.

24. The method of claim 2 , wherein the second region has a strength of more than 1000 N/mm 2 .

25. The method of claim 2 , wherein the second region has a strength of more than 1200 N/mm 2 .

26. The method of claim 2 , wherein the second region has a strength of more than 1400 N/mm 2 .

27. The method of claim 1 , wherein first region has a yield strength between 200 and 800 N/mm 2 .

28. The method of claim 1 , further comprising manufacturing the automobile column from a Tailor Welded Blank or a Tailor Rolled Blank.

Assignees

• Benteler Automobiltechnik Gmbh

Inventors

• Zimmermann Andreas
• Dingemans Jan
• Pellmann Markus
• Böke Johannes

Classifications

• C21D8/02

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

• C21D8/00

  Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment (hardening articles or materials formed by forging or rolling with no further heating beyond that required for the formation C21D1/02) · CPC title

• B62D25/08

  Front or rear portions {(sub-frames for mounting engine or suspensions B62D21/11)} · CPC title

• C22C38/02

  containing silicon · CPC title

• C21D1/673

  for die quenching · CPC title