Zinc-coated hot formed steel component with tailored property

Patent metadata

Field	Value
Publication number	US-10619223-B2
Application number	US-201615141248-A
Country	US
Kind code	B2
Filing date	Apr 28, 2016
Priority date	Apr 28, 2016
Publication date	Apr 14, 2020
Grant date	Apr 14, 2020

Abstract

Methods of selectively cooling and quenching surface regions of high-strength transformation induced plasticity (TRIP) steel are provided. The method may comprise selectively cooling at least one region of an exposed surface of a hot-formed press-hardened component comprising a high-strength steel. Prior to selective cooling, the component has a microstructure comprising ≥about 5% by volume retained austenite in a matrix of martensite. The selective cooling is conducted at a temperature of ≤about −40° C. and forms at least one quenched region comprising ≤about 2% by volume austenite. The TRIP steel may be zinc-coated and having a surface coating comprising zinc and substantially free of liquid metal embrittlement (LME). Zinc-coated hot-formed press-hardened components, including automotive components, formed from such methods are also provided.

First claim

What is claimed is:

1. A method of selectively quenching at least one region of a steel component, the method comprising:
selectively cooling at least one region of a hot-formed press-hardened component comprising a transformation induced plasticity (TRIP) steel selected from the group consisting of:
a Mn-TRIP steel comprising:
manganese (Mn) at greater than or equal to about 4% by weight of the total steel composition, and
carbon (C) at greater than or equal to about 0.1% by weight to less than or equal to about 0.4% by weight; and

a delta-TRIP steel comprising:
aluminum (Al) at greater than or equal to about 3% by weight to less than or equal to about 6% by weight of the total steel composition;
manganese at greater than or equal to about 0.1% by weight to less than or equal to about 1% by weight of the total steel composition; and
carbon at greater than or equal to about 0.3% by weight to less than or equal to about 0.5% by weight,

wherein the hot-formed press-hardened component has a microstructure comprising greater than or equal to about 5% by volume retained austenite in a matrix of martensite, wherein the selectively cooling quenches and cools the at least one region to a temperature of less than or equal to about −40° C. and forms at least one quenched region comprising less than or equal to about 1% by volume austenite.

2. The method of claim 1 , wherein the selectively cooling comprises submerging the at least one region of the component in a cooling medium.

3. The method of claim 2 , wherein the cooling medium is selected from the group consisting of: water, liquid nitrogen, solid carbon dioxide, and combinations thereof.

4. The method of claim 1 , wherein the selectively cooling comprises spraying the at least one region with a cooling medium.

5. The method of claim 4 , wherein the cooling medium is selected from the group consisting of: air, water, liquid nitrogen, solid carbon dioxide, and combinations thereof.

6. The method of claim 4 , wherein the cooling medium has a temperature of less than or equal to about −60° C.

7. The method of claim 1 , wherein the transformation induced plasticity (TRIP) steel is:
(i) a Mn-TRIP steel comprising:
manganese (Mn) at greater than or equal to about 4% by weight to less than or equal to about 12% by weight of the total steel composition, and
carbon (C) at greater than or equal to about 0.1% by weight to less than or equal to about 0.4% by weight of the total steel composition;
silicon (Si) at greater than or equal to about 0.1% by weight to less than or equal to about 0.5% by weight of the total steel composition;
chromium (Cr) at less than or equal to about 1% by weight of the total steel composition;
titanium (Ti) at less than or equal to about 0.2% by weight of the total steel composition;
aluminum (Al) at less than or equal to about 0.1% by weight of the total steel composition;
phosphorus (P) at less than or equal to about 0.2% by weight of the total steel composition;
sulfur (S) at less than or equal to about 0.05% by weight of the total steel composition;
one or more impurities cumulatively present at less than or equal to about 0.5% by weight of the total steel composition; and
a balance iron; or

(ii) a delta-TRIP steel comprising:
aluminum (Al) at greater than or equal to about 3% by weight to less than or equal to about 6% by weight of the total steel composition;
manganese at greater than or equal to about 0.1% by weight to less than or equal to about 1% by weight of the total steel composition;
carbon at greater than or equal to about 0.3% by weight to less than or equal to about 0.5% by weight of the total steel composition;
silicon (Si) at greater than or equal to about 0.1% by weight to less than or equal to about 0.5% by weight of the total steel composition;
chromium (Cr) at less than or equal to about 1% by weight of the total steel composition;
titanium (Ti) at less than or equal to about 0.2% by weight of the total steel composition;
phosphorus (P) at less than or equal to about 0.2% by weight of the total steel composition;
sulfur (S) at less than or equal to about 0.05% by weight of the total steel composition;
one or more impurities cumulatively present at less than or equal to about 0.5% by weight of the total steel composition; and
a balance iron.

8. The method of claim 1 , prior to the selectively cooling further comprising: heating a blank to a temperature of less than or equal to about 782° C. for austenization; and press hardening the blank in at least one die to press and quench the blank to form the hot-formed press-hardened component.

9. The method of claim 1 , wherein the at least one quenched region comprises less than 0.5% by volume austenite.

10. A method of selectively quenching at least one region of a steel component, the method comprising:
selectively cooling at least one region of a zinc-coated hot-formed press-hardened component comprising a transformation induced plasticity (TRIP) steel having a surface coating comprising zinc, the steel selected from the group consisting of:
(i) a Mn-TRIP steel comprising:
manganese (Mn) at greater than or equal to about 4% by weight of the total steel composition, and
carbon (C) at greater than or equal to about 0.1% by weight to less than or equal to about 0.4% by weight, and

(ii) a delta-TRIP steel comprising:
aluminum (Al) at greater than or equal to about 3% by weight to less than or equal to about 6% by weight of the total steel composition;
manganese at greater than or equal to about 0.1% by weight to less than or equal to about 1% by weight of the total steel composition; and
carbon at greater than or equal to about 0.3% by weight to less than or equal to about 0.5% by weight,

wherein the zinc-coated hot-formed press-hardened component has a microstructure comprising greater than or equal to about 5% by volume retained austenite in a matrix of martensite, wherein the selectively cooling quenches and cools the at least one region to a temperature of less than or equal to about −40° C. and forms at least one quenched region comprising less than or equal to about 1% by volume austenite.

11. The method of claim 10 , wherein the selectively cooling comprises submerging the at least one region of the component in a cooling medium.

12. The method of claim 11 , wherein the cooling medium is selected from the group consisting of: water, liquid nitrogen, solid carbon dioxide, and combinations thereof.

13. The method of claim 10 , wherein the selectively cooling comprises spraying the at least one region with a cooling medium.

14. The method of claim 13 , wherein the cooling medium is selected from the group consisting of: air, water, liquid nitrogen, solid carbon dioxide, and combinations thereof.

15. The method of claim 13 , wherein the cooling medium has a temperature of less than or equal to about −60° C.

16. The method of claim 10 , wherein the high strength transformation induced plasticity (TRIP) steel is:
(i) a Mn-TRIP steel comprising:
manganese (Mn) at greater than or equal to about 4% by weight to less than or equal to about 12% by weight of the total steel composition, and
carbon (C) at greater than or equal to about 0.1% by weight to less than or equal to about 0.4% by weight of the total steel composition;
silicon (Si) at greater than or equal to about 0.1% by weight to less than or equal to about 0.5% by weight of the total steel composition;
chromium (Cr) at less than or equal to about 1% by weight of the total steel composition;
titanium (Ti) at less than or equal to about 0.2% by weigh

Assignees

• Gm Global Tech Operations Llc

Inventors

• Wang Jianfeng

Classifications

• C22C38/06

  containing aluminium · CPC title

• C21D6/04

  Hardening by cooling below 0 degrees Celsius · CPC title

• C21D1/06

  Surface hardening · CPC title

• C21D1/613

  Gases; Liquefied or solidified normally gaseous material · CPC title

• C21D1/56

  characterised by the quenching agents · CPC title