Automotive member having resistance weld

Patent metadata

Field	Value
Publication number	US-10940556-B2
Application number	US-201716323570-A
Country	US
Kind code	B2
Filing date	Aug 21, 2017
Priority date	Aug 22, 2016
Publication date	Mar 9, 2021
Grant date	Mar 9, 2021

Abstract

Provided is an automotive member, or particularly, a steel sheet having a tensile strength exceeding 900 MPa. The automotive member has a resistance weld for fixing two or more steel sheets containing a predetermined composition, in which a maximum hardness (HVBM) in a heat-affected zone of the resistance weld is at least 1.1 times hardness (HVW) of a nugget in the resistance weld formed in a softest steel sheet of a sheet set during resistance welding, and furthermore, an average grain size of a steel sheet structure of the heat-affected zone within 2 mm in a direction at a right angle to a sheet thickness from an end part of the nugget of the high-strength steel sheet is 3 μm or less, and a minimum hardness (HVmin) in the heat-affected zone is at least 90% of hardness (HVα) of the high-strength steel sheet before the resistance welding.

First claim

The invention claimed is:

1. An automotive member having a resistance weld for fixing two or more steel sheets including at least one high-strength steel sheet, the high-strength steel sheet including a composition containing, in mass %,
C: 0.08 to 0.25%,
Si: 0.01 to 2.50%,
Mn: 3.89 to 8.1%,
Al: 0.01 to 1.50%,
N: 0.010% or less,
each of one or two of Ti: 0.010 to 0.10% and Nb: 0.010 to 0.10%,
the balance being Fe and unavoidable impurities, wherein
a maximum hardness (HV BM ) in a heat-affected zone of the resistance weld is at least 1.1 times hardness (HV W ) of a nugget in the resistance weld formed in a softest steel sheet of a sheet set during resistance welding,
an average grain size of a steel sheet structure of the heat-affected zone within 2 mm in a direction at a right angle to a sheet thickness from an end part of the nugget of the high-strength steel sheet is 3 μm or less, and
a minimum hardness (HV min ) in the heat-affected zone is at least 90% of hardness (HV α ) of the high-strength steel sheet before the resistance welding.

2. The automotive member having a resistance weld according to claim 1 , wherein the composition further contains, in mass %, one or more selected from the group of
V: 0.05% or less,
B: 0.010% or less,
Cu: 0.50% or less,
Ni: 0.50% or less,
Cr: 0.50% or less,
Mo: 0.50% or less,
Ca: 0.0050% or less, and
REM: 0.0050% or less.

3. The automotive member having a resistance weld according to claim 1 , wherein the high-strength steel sheet has a structure containing, in terms of an area ratio, 20 to 50% of retained austenite.

4. The automotive member having a resistance weld according to claim 1 , the high-strength steel sheet includes a coating layer formed on a surface thereof.

5. The automotive member having a resistance weld according to claim 4 , wherein the coating layer is a galvanized layer.

6. The automotive member having a resistance weld according to claim 4 , wherein the coating layer is a galvannealed layer.

7. The automotive member having a resistance weld according to claim 2 , wherein the high-strength steel sheet has a structure containing, in terms of an area ratio, 20 to 50% of retained austenite.

8. The automotive member having a resistance weld according to claim 2 , the high-strength steel sheet includes a coating layer formed on a surface thereof.

9. The automotive member having a resistance weld according to claim 3 , the high-strength steel sheet includes a coating layer formed on a surface thereof.

10. The automotive member having a resistance weld according to claim 7 , the high-strength steel sheet includes a coating layer formed on a surface thereof.

11. The automotive member having a resistance weld according to claim 8 , wherein the coating layer is a galvanized layer.

12. The automotive member having a resistance weld according to claim 9 , wherein the coating layer is a galvanized layer.

13. The automotive member having a resistance weld according to claim 10 , wherein the coating layer is a galvanized layer.

14. The automotive member having a resistance weld according to claim 8 , wherein the coating layer is a galvannealed layer.

15. The automotive member having a resistance weld according to claim 9 , wherein the coating layer is a galvannealed layer.

16. The automotive member having a resistance weld according to claim 10 , wherein the coating layer is a galvannealed layer.

Assignees

• Jfe Steel Corp

Inventors

• Takashima Katsutoshi
• Matsuda Hiroshi
• Ikeda Rinsei
• Kawasaki Yoshiyasu

Classifications

• C21D8/02

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

• C22C38/14

  containing titanium or zirconium · CPC title

• B23K11/0026

  Welding of thin articles · CPC title

• B23K11/115

  by means of two electrodes placed opposite one another on both sides of the welded parts · CPC title

• C22C38/26

  with niobium or tantalum · CPC title