Low density press-hardening steel having enhanced mechanical properties

Patent metadata

Field	Value
Publication number	US-11951522-B2
Application number	US-202318123592-A
Country	US
Kind code	B2
Filing date	Mar 20, 2023
Priority date	Jun 19, 2018
Publication date	Apr 9, 2024
Grant date	Apr 9, 2024

Abstract

A method of forming a shaped steel object is provided. The method includes cutting a blank from an alloy composition including 0.05-0.5 wt. % carbon, 4-12 wt. % manganese, 1-8 wt. % aluminum, 0-0.4 wt. % vanadium, and a remainder balance of iron. The method also includes heating the blank until the blank is austenitized to form a heated blank, transferring the heated blank to a press, forming the heating blank into a predetermined shape to form a stamped object, and decreasing the temperature of the stamped object to a temperature between a martensite start (Ms) temperature of the alloy composition and a martensite final (Mf) temperature of the alloy composition to form a shaped steel object comprising martensite and retained austenite.

First claim

What is claimed is:

1. An alloy composition comprising:
carbon (C) at a concentration of greater than or equal to about 0.05 wt. % to less than or equal to about 0.5 wt. % of the alloy composition,
manganese (Mn) at a concentration of greater than or equal to about 4 wt. % to less than or equal to 5.4 wt. % of the alloy composition,
aluminum (Al) at a concentration of greater than or equal to about 2 wt. % to less than or equal to about 8 wt. % of the alloy composition,
vanadium (V) at a concentration of greater than 0 wt. % to less than or equal to about 0.4 wt. % of the alloy composition,
nitrogen (N) at a concentration of greater than 0 wt. % to less than 0.001 wt. % of the alloy composition, and
a balance of the alloy composition being iron (Fe).

2. The alloy composition according to claim 1 , wherein the alloy composition comprises:
zirconium (Zr) at a concentration of greater than 0 wt. % to less than or equal to about 0.5 wt. % of the alloy composition.

3. The alloy composition according to claim 1 , wherein the alloy composition comprises ZrN.

4. The alloy composition according to claim 2 , wherein the alloy composition comprises at least one of:
nickel (Ni) at a concentration of greater than 0 wt. % to less than or equal to about 5 wt. % of the alloy composition,
molybdenum (Mo) at a concentration of greater than 0 wt. % to less than or equal to about 0.5 wt. % of the alloy composition,
niobium (Nb) at a concentration of greater than 0 wt. % to less than or equal to about 0.2 wt. % of the alloy composition,
copper (Cu) at a concentration of greater than 0 wt. % to less than or equal to about 3 wt. % of the alloy composition,
titanium (Ti) at a concentration of greater than 0 wt. % to less than or equal to about 0.1 wt. % of the alloy composition,
and
boron (B) at a concentration of greater than 0 wt. % to less than or equal to about 0.005 wt. % of the alloy composition.

5. The alloy composition according to claim 1 , wherein the Al is at a concentration of greater than or equal to 2 wt. % to less than or equal to about 5 wt. %.

6. The alloy composition according to claim 1 , wherein the C is at a concentration of greater than or equal to about 0.1 wt. % to less than or equal to about 0.45 wt. %.

7. The alloy composition according to claim 1 , wherein the alloy composition has a higher strength and lower weight after press hardening relative to an equivalent 22MnB5 steel after press hardening.

8. The alloy composition according to claim 1 , wherein after press hardening, the alloy composition comprises greater than or equal to about 80 wt. % to less than or equal to about 95 wt. % martensite and greater than or equal to about 5 wt. % to less than or equal to about 20 wt. % retained austenite.

9. The alloy composition according to claim 1 , wherein after press hardening, the alloy composition has a martensite:retained austenite ratio that increases when a load is applied to the alloy composition.

10. The alloy composition according to claim 1 , wherein the C is at a concentration of about 0.5 wt. % of the alloy composition.

11. The alloy composition according to claim 10 , wherein the alloy composition has a martensite start (Ms) temperature less than ambient temperature.

12. The alloy composition according to claim 1 , wherein the C is at a concentration of about 0.05 wt. % of the alloy composition and the Mn is at a concentration of about 4 wt. %.

13. The alloy composition according to claim 12 , wherein the alloy composition has a martensite final (Mf) temperature greater than ambient temperature.

14. The alloy composition according to claim 1 , wherein the alloy composition has a critical transformation temperature (A c3 ) of greater than or equal to about 880° C. to less than or equal to about 1000° C.

15. An automobile part comprising the alloy composition according to claim 1 , wherein the automobile part is a pillar, a bumper, a roof rail, a rocker rail, a tunnel, a beam, or a reinforcement.

16. A method of forming a shaped steel object, the method comprising:
heating a blank to a temperature of greater than or equal to about 900° C. to less than or equal to about 950° C. for a time period of greater than or equal to about 1 minute to less than or equal to about 60 minutes to generate a heated blank, the blank being composed of an alloy composition comprising:
carbon (C) at a concentration of greater than or equal to about 0.05 wt. % to less than or equal to about 0.5 wt. % of the alloy composition,
manganese (Mn) at a concentration of greater than or equal to about 4 wt. % to less than or equal to 5.4 wt. % of the alloy composition,
aluminum (Al) at a concentration of greater than or equal to 2 wt. % to less than or equal to about 8 wt. % of the alloy composition,
vanadium (V) at a concentration of greater than 0 wt. % to less than or equal to about 0.4 wt. % of the alloy composition,
zirconium (Zr) at a concentration of greater than 0 wt. % to less than or equal to about 0.5 wt. % of the alloy composition,
nitrogen (N) at a concentration of greater than 0 wt. % to less than 0.001 wt. % of the alloy composition, and
a balance of the alloy composition being iron (Fe);
forming the heated blank into a predetermined shape to generate a stamped object;
quenching the stamped object by decreasing the temperature of the stamped object to about ambient temperature to form a shaped steel object comprising martensite and retained austenite; and
tempering the shaped steel object by heating the shaped steel object to greater than or equal to about 150° C. to less than or equal to about 300° C. for a time period of greater than or equal to about 1 minute to less than or equal to about 120 minutes and then decreasing the temperature of the shaped steel object to ambient temperature.

17. The method according to claim 16 , further comprising:
transferring the heated blank to a press,
wherein the heated blank is formed into the predetermined shape defined by the press to generate the stamped object.

18. The method according to claim 16 , wherein the shaped steel object is an automobile part selected from the group consisting of a pillar, a bumper, a roof rail, a rocker rail, a tunnel, a beam, and a reinforcement.

Assignees

• Gm Global Tech Operations Llc

Inventors

• Pang Jiachen
• Lu Qi
• Wang Jianfeng

Classifications

• C22C38/14 Primary

  containing titanium or zirconium · CPC title

• C22C38/12

  containing tungsten, tantalum, molybdenum, vanadium, or niobium · CPC title

• C22C38/06

  containing aluminium · CPC title

• C22C38/04

  containing manganese · CPC title

• C21D2211/008

  Martensite · CPC title