US 12,440,917 B2
Resistance spot welding method and weld member production method
Chikaumi Sawanishi, Tokyo (JP); Yasuaki Okita, Tokyo (JP); and Hiroshi Matsuda, Tokyo (JP)
Assigned to JFE STEEL CORPORATION, Tokyo (JP)
Appl. No. 17/754,480
Filed by JFE STEEL CORPORATION, Tokyo (JP)
PCT Filed Oct. 6, 2020, PCT No. PCT/JP2020/037915
§ 371(c)(1), (2) Date Apr. 4, 2022,
PCT Pub. No. WO2021/070835, PCT Pub. Date Apr. 15, 2021.
Claims priority of application No. 2019-186404 (JP), filed on Oct. 9, 2019.
Prior Publication US 2023/0121205 A1, Apr. 20, 2023
Int. Cl. B23K 11/11 (2006.01); B23K 11/16 (2006.01); B23K 11/25 (2006.01)
CPC B23K 11/115 (2013.01) [B23K 11/16 (2013.01); B23K 11/257 (2013.01)] 8 Claims
OG exemplary drawing
 
1. A resistance spot welding method for joining parts to be welded, the parts to be welded comprising a plurality of overlapping metal sheets, the method comprising:
squeezing the parts to be welded by a pair of electrodes;
passing a welding current through the parts to be welded while applying an electrode force thereto, wherein said passing the welding current comprises a main current passage, the main current passage including a first electrode force application step and a second electrode force application step following the first electrode force application step, wherein an electrode force F1 applied during the first electrode force application step and an electrode force F2 applied during the second electrode force application step satisfy a relationship F1<F2; and
dynamically determining and setting an electrode force switching point Tf for transitioning from the first electrode force application step to the second electrode force application step during the main current passage, said step of dynamically determining and setting Tf comprising:
(i) obtaining a reference electrode force switching point T0, a total welding time Tm for the main current passage, a first time integration value RA representing a time integration of a resistance between the electrodes from a start of the main current passage up to the reference electrode force switching point T0 for a current weld, and a second time integration value R0 representing a time integration of a resistance between the electrodes from the start of the main current passage up to the reference electrode force switching point T0 when current passage is performed under a same welding condition as the main current passage for the current weld but when the parts to be welded are substantially free of disturbance;
(ii) determining a time TA at which a time integration value of the resistance between the electrodes in the main current passage for the current weld reaches the second time integration value R0; and
(iii) setting the electrode force switching point Tf based upon comparing TA to T0 or RA to R0 as follows:
(1) if TA≤0.8×T0, then setting Tf such that TA≤Tf<T0;
(2) if 0.8×T0<TA≤T0 or 0.9×R0≤RA≤R0, then setting Tf such that 0.9×T0<Tf<1.1×T0; or
(3) if RA<0.9×R0, then setting Tf such that T0<Tf≤T0+2×(R0−RA)/R0×Tm.