# US 11,298,773 B2 · Resistance spot welding method

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- Number: US 11,298,773 B2
- Document ID: US11298773B2
- Status: Granted
- Kind: B2
- Application number: 16/488,703
- Filed: 2018-03-01
- Published: 2020-07-23
- Granted: 2022-04-12
- Earliest claimed: 2017-03-01
- Assignees: Jfe Steel Corporation
- Applicants: JFE Steel Corporation
- Inventors: Koichi Taniguchi; Chikaumi Sawanishi; Katsutoshi Takashima; Hiroshi Matsuda; Rinsei Ikeda
- Web page: https://patentgrep.com/patent/US11298773B2

## CPC

- B23K 11/11: Spot welding
- B23K 11/115: {by means of two electrodes placed opposite one another on both sides of the welded parts}
- B23K 11/0026: {Welding of thin articles}
- B23K 11/163: {Welding of coated materials}
- B23K 11/166: {of galvanized or tinned materials}
- B23K 11/24: Electric supply or control circuits therefor
- 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

## Abstract

Provided is a resistance spot welding method. The resistance spot welding method for joining a sheet set including a plurality of lapped steel sheets includes: holding the sheet set between a pair of electrodes; and energizing the sheet set under application of electrode force to thereby join the steel sheets together. At least one of the plurality of lapped steel sheets is a surface-treated steel sheet including a metal coating layer on a surface thereof. The energizing includes: a primary energizing step of performing energization to form a nugget portion; a non-energizing step in which, after the primary energizing step, the energization is suspended for an energization suspension time Tc (cycles); and a secondary energizing step of, after the non-energizing step, performing energization for reheating while the nugget portion is prevented from growing. During the energizing, the relations of a particular formula are satisfied.

## Claims

### Claim 1

A resistance spot welding method for joining a sheet set including a plurality of lapped steel sheets, the method comprising: holding the sheet set between a pair of electrodes; and energizing the sheet set under application of electrode force to thereby join the steel sheets together,
wherein at least one of the plurality of lapped steel sheets is a surface-treated steel sheet including a metal coating layer on a surface thereof,
wherein the energizing comprises
a primary energizing step of performing energization to form a nugget portion,
a non-energizing step in which, after the primary energizing step, the energization is suspended for an energization suspension time Tc (cycles), and
a secondary energizing step of, after the non-energizing step, performing energization for reheating while the nugget portion is prevented from growing, and
wherein, during the energizing, the relations of the following formula (I) are satisfied:
(22+A)·B/100<Ip/Im<C when 0<A<3,
(17+A)·B/80<Ip/Im<C when 3≤A<7, and
(11+A)·B/60<Ip/Im<C when 7≤A<15, formula (I)
where A is an electrode misalignment angle (degrees) of the electrodes, Im is a current value (kA) in the primary energizing step, Ip is a current value (kA) in the secondary energizing step, B is a variable defined as 1+0.1·Tc, and C is a variable defined as 1+0.2·Tc.

### Claim 2 (depends on 1)

The resistance spot welding method according to claim 1,
wherein, in the non-energizing step, the relations of the following formula (II) are satisfied:
0<Tc<(103−A)·t/D when 0<A<3,
0<Tc<5·(23−A)·t/D when 3≤A<7, and
0<Tc<8·(17−A)·t/D when 7≤A<15, formula (II)
where t is the total thickness (mm) of the plurality of lapped steel sheets, and D is the tip diameter (mm) of the electrodes.

### Claim 3 (depends on 1)

The resistance spot welding method according to claim 1,
wherein, after the primary energizing step, the non-energizing step and the secondary energizing step are repeated in this order at least twice.

### Claim 4 (depends on 1)

The resistance spot welding method according to claim 1,
wherein at least one of the plurality of lapped steel sheets has a tensile strength of 590 MPa or more.

### Claim 5 (depends on 2)

The resistance spot welding method according to claim 2,
wherein, after the primary energizing step, the non-energizing step and the secondary energizing step are repeated in this order at least twice.

### Claim 6 (depends on 2)

The resistance spot welding method according to claim 2,
wherein at least one of the plurality of lapped steel sheets has a tensile strength of 590 MPa or more.

### Claim 7 (depends on 3)

The resistance spot welding method according to claim 3,
wherein at least one of the plurality of lapped steel sheets has a tensile strength of 590 MPa or more.

### Claim 8 (depends on 5)

The resistance spot welding method according to claim 5,
wherein at least one of the plurality of lapped steel sheets has a tensile strength of 590 MPa or more.