# US 11,992,892 B2 · Resistance spot welding method and method for producing resistance spot welded joint

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- Number: US 11,992,892 B2
- Document ID: US11992892B2
- Status: Granted
- Kind: B2
- Application number: 16/967,193
- Filed: 2019-02-05
- Published: 2021-11-25
- Granted: 2024-05-28
- Earliest claimed: 2018-02-09
- Assignees: Jfe Steel Corporation
- Applicants: JFE Steel Corporation
- Inventors: Reiko Endo; Muneo Matsushita; Koichi Taniguchi; Hiroshi Matsuda; Rinsei Ikeda
- Web page: https://patentgrep.com/patent/US11992892B2

## CPC

- B23K 11/115: {by means of two electrodes placed opposite one another on both sides of the welded parts}
- B23K 11/16: taking account of the properties of the material to be welded
- B23K 11/24: Electric supply or control circuits therefor
- C21D 6/004: {containing Cr and Ni}
- C21D 9/50: for welded joints
- C22C 38/002: {containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60}
- C22C 38/02: containing silicon
- C22C 38/04: containing manganese
- C22C 38/06: containing aluminium
- C22C 38/42: with copper
- C22C 38/44: with molybdenum or tungsten
- C22C 38/46: with vanadium
- C22C 38/48: with niobium or tantalum
- C22C 38/50: with titanium or zirconium
- C22C 38/54: with boron
- B23K 2101/006: {Vehicles}
- B23K 2101/18: Sheet panels
- B23K 2103/04: Steel {or steel} alloys
- B23K: SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- C21D: MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B)
- C22C: ALLOYS (treatment of alloys C21D, C22F)

## Abstract

The present invention provides a resistance spot welding method. A resistance spot welding method according to the present invention in which a sheet combination of two or more overlapping steel sheets is sandwiched between a pair of electrodes and joined together by applying current while applying pressure, the method including a main current application step in which current application is performed with a current Iw (kA), and subsequently, a post-tempering heat treatment step in which after cooling is performed for a cooling time tct (ms) shown in formula (1) below, current application is performed with a current It (kA) shown in formula (2) below for a current application time tt (ms) shown in formula (3) below: 800≤tct . . . formula (1), 0.5×Iw≤It≤Iw . . . formula (2), and 500≤tt . . . formula (3).

## Claims

### Claim 1

A resistance spot welding method in which a sheet combination of two or more overlapping steel sheets is sandwiched between a pair of electrodes and joined together by applying current while applying pressure, the method comprising:
a main current application step in which current application is performed with a current Iw (kA); and
subsequently, a post-tempering heat treatment step in which after cooling is performed for a cooling time tct (ms) shown in formula (1) below, current application is performed with a current It (kA) shown in formula (2) below for a current application time tt (ms) shown in formula (3) below, and
between the main current application step and the post-tempering heat treatment step, a post-segregation reduction heat treatment step in which after cooling is performed for a cooling time tco (ms) shown in formula (4) below, current application is performed with a current Io (kA) shown in formula (5) below for a current application time to (ms) shown in formula (6) below,
wherein at least one steel sheet in the sheet combination has a composition containing 0.08≤C≤0.3 (% by mass), 0.1≤Si≤0.8 (% by mass), 2.5≤Mn≤10.0 (% by mass), and P≤0.1 (% by mass), with the balance being Fe and unavoidable impurities:
800≤tct formula(1),
0.5×Iw≤It≤Iw formula (2),
500≤tt formula (3),
10≤tcp formula (4),
0.6×Iw≤Ip≤0.99×Iw formula (5), and
400≤tp formula (6).

### Claim 2 (depends on 1)

The resistance spot welding method according to claim 1, wherein at least one steel sheet in the sheet combination has the composition further contains, at least one selected from Cu≤3 (% by mass), Ni≤3 (% by mass), Mo≤1.0 (% by mass), Cr≤1.0 (% by mass), Nb≤0.2 (% by mass), V≤0.5 (% by mass), Ti≤0.2 (% by mass), B≤0.005 (% by mass), Al≤2 (% by mass), Ca≤0.010 (% by mass).

### Claim 3 (depends on 1)

The resistance spot welding method according to claim 1, wherein at least one steel sheet in the sheet combination has a tensile strength of 780 MPa or more.

### Claim 4 (depends on 2)

The resistance spot welding method according to claim 2, wherein at least one steel sheet in the sheet combination has a tensile strength of 780 MPa or more.

### Claim 5 (depends on 1)

A method for producing a resistance spot welded joint by using the resistance spot welding method according to claim 1.

### Claim 6 (depends on 2)

A method for producing a resistance spot welded joint by using the resistance spot welding method according to claim 2.

### Claim 7 (depends on 3)

A method for producing a resistance spot welded joint by using the resistance spot welding method according to claim 3.

### Claim 8 (depends on 4)

A method for producing a resistance spot welded joint by using the resistance spot welding method according to claim 4.