Production method for hot press molded articles, press molded article, die mold, and mold set

Patent metadata

Field	Value
Publication number	US-12179246-B2
Application number	US-201917044194-A
Country	US
Kind code	B2
Filing date	Apr 9, 2019
Priority date	Apr 13, 2018
Publication date	Dec 31, 2024
Grant date	Dec 31, 2024

Abstract

A method of producing a hot press-formed product includes subjecting an Al-plated steel sheet having a zinc compound layer or a metallic zinc layer, as an outermost layer, provided on an Al plating layer to hot press forming using a die. The die includes a hard layer having a skewness (Rsk), as measured in a direction from the outside of a die hole toward the inside of the die hole, of 1.3 or less and a hardness Hv_Die of HV 2,000 or more, over the entirety of a region of a steel sheet contact surface that is adjacent to a die shoulder portion. The steel sheet contact surface is a surface located outside of the die hole and configured to contact the Al-plated steel sheet that is to be subjected to the hot press forming.

First claim

The invention claimed is:

1. A method of producing a hot press-formed product, the method comprising:
subjecting an Al-plated steel sheet to hot press forming using a die, the Al-plated steel sheet having a zinc compound layer or a metallic zinc layer, as an outermost surface layer, provided on an Al plating layer,
wherein the die comprises a hard layer having a skewness (Rsk), as measured in a direction from an outside of a die hole toward an inside of the die hole, of 1.3 or less and a hardness Hv_Die of HV 2,000 or more, over an entirety of a region of a steel sheet contact surface that is adjacent to a die shoulder portion, the steel sheet contact surface being located outside of the die hole and configured to contact with the Al-plated steel sheet that is to be subjected to the hot press forming.

2. The method of producing a hot press-formed product according to claim 1 , wherein the skewness (Rsk) of the hard layer is −5.0 or more.

3. The method of producing a hot press-formed product according to claim 1 , wherein the hard layer comprises: a nitride layer; and a hard coating layer provided on a surface of the nitride layer.

4. The method of producing a hot press-formed product according to claim 3 , wherein the hard coating layer has a hardness Hv_Die of HV 3,200 or less.

5. The method of producing a hot press-formed product according to claim 4 , wherein the hard coating layer comprises Cr.

6. The method of producing a hot press-formed product according to claim 3 , wherein the hard coating layer comprises Ti and has a hardness Hv_Die of HV 3,160 or less.

7. The method of producing a hot press-formed product according to claim 3 , wherein the hard coating layer has a hardness Hv_Die of from HV 2,500 to HV 3,000.

8. A die, comprising a hard layer having a skewness (Rsk), as measured in a direction from an outside of a die hole toward an inside of the die hole, of 1.3 or less and a hardness Hv_Die of HV 2,000 or more, over an entirety of a region of a die shoulder adjacent surface that is adjacent to a die shoulder portion, the die shoulder adjacent surface being located outside of the die hole and adjacent to the die shoulder portion.

9. The die according to claim 8 , wherein the skewness (Rsk) of the hard layer is −5.0 or more.

10. The die according to claim 8 , wherein the hard layer comprises: a nitride layer; and a hard coating layer provided on a surface of the nitride layer.

11. The die according to claim 10 , wherein the hard coating layer has a hardness Hv_Die of 3,200 or less.

12. The die according to claim 11 , wherein the hard coating layer comprises Cr.

13. The die according to claim 10 , wherein the hard coating layer comprises Ti and has a hardness Hv_Die of HV 3,160 or less.

14. The die according to claim 10 , wherein the hard coating layer has a hardness Hv_Die of from HV 2,500 to HV 3,000.

15. A die set, comprising:
the die according to claim 8 ; and
a steel blank holder;
wherein the steel blank holder comprises a second hard layer having a skewness (Rsk), as measured in a direction from an outside of a punch-insertion portion toward an inside of the punch-insertion portion, of 1.3 or less and a hardness Hv_Die of HV 2,000 or more, over an entirety of a region of a facing surface that faces the region of the die provided with the hard layer, the facing surface facing the die shoulder adjacent surface of the die.

16. The die set according to claim 15 , wherein the skewness (Rsk) of the second hard layer is −5.0 or more.

17. The die set according to claim 15 , wherein the second hard layer comprises: a second nitride layer; and a second hard coating layer provided on a surface of the second nitride layer.

18. The die set according to claim 17 , wherein the second hard coating layer has a hardness Hv_Die of HV 3,200 or less.

19. The die set according to claim 18 , wherein the second hard coating layer comprises Cr.

20. The die set according to claim 17 , wherein the second hard coating layer comprises Ti and has a hardness Hv_Die of HV 3,160 or less.

21. The die set according to claim 17 , wherein the second hard coating layer has a hardness Hv_Die of from HV 2,500 to HV 3,000.

22. A die set, comprising:
the die according to claim 8 ; and
a punch;
wherein the punch comprises a second hard layer having a skewness (Rsk), as measured in a direction from an outside of a punch portion toward an inside of the punch portion, of 1.3 or less and a hardness Hv_Die of HV 2,000 or more, over an entirety of a region of a facing surface that faces the region of the die provided with the hard layer, the facing surface facing the die shoulder adjacent surface of the die.

23. The die set according to claim 22 , wherein the skewness (Rsk) of the second hard layer is −5.0 or more.

24. The die set according to claim 22 , wherein the second hard layer comprises: a second nitride layer; and a second hard coating layer provided on a surface of the second nitride layer.

25. The die set according to claim 24 , wherein the second hard coating layer has a hardness Hv_Die of HV 3,200 or less.

26. The die set according to claim 25 , wherein the second hard coating layer comprises Cr.

27. The die set according to claim 24 , wherein the second hard coating layer comprises Ti and has a hardness Hv_Die of HV 3,160 or less.

28. The die set according to claim 24 , wherein the second hard coating layer has a hardness Hv_Die of from HV 2,500 to HV 3,000.

Assignees

• Nippon Steel Corp

Inventors

• Kubo Masahiro
• Fujita Soshi
• Nakazawa Yoshiaki
• Irikawa Hideaki
• Fuda Masahiro

Classifications

• C21D8/00 Primary

  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

• C23C2/28

  Thermal after-treatment, e.g. treatment in oil bath · CPC title

• C23C2/29

  Cooling or quenching · CPC title

• C23C2/26

  After-treatment (C23C2/14 takes precedence) · CPC title

• C22C38/14

  containing titanium or zirconium · CPC title