Patent ID: 11904404
Assignee: JFE STEEL CORPORATION
Field: Machine tools (Mechanical engineering)
Classification: CPC B | IPC B

Claim 0:
1. A resistance spot welding method of squeezing, by a pair of electrodes, parts to be welded which are a plurality of overlapping metal sheets, and passing a current while applying an electrode force to join the parts to be welded, the resistance spot welding method comprising:
performing test welding; and
performing actual welding after the test welding,
wherein
(a) in the test welding, main current passage for nugget formation and subsequent current passage for subsequent heat treatment are performed,
in the main current passage in the test welding, a time variation curve of an instantaneous amount of heat generated per unit volume and a cumulative amount of heat generated per unit volume that are calculated from an electrical property between the electrodes in forming an appropriate nugget by performing current passage by constant current control are stored, and
in the subsequent current passage in the test welding, current passage is performed by constant current control under a condition:
0.2≤Vtp/Vtm≤1.5,
where Vtm is an average value of a voltage between the electrodes in the main current passage in the test welding and Vtp is an average value of a voltage between the electrodes in the subsequent current passage in the test welding, and a time variation curve of an instantaneous amount of heat generated per unit volume and a cumulative amount of heat generated per unit volume that are calculated from an electrical property between the electrodes in the current passage performed under the condition are stored, and
(b) thereafter, in the actual welding, main current passage for nugget formation and subsequent current passage for subsequent heat treatment are performed, and
in the main current passage and the subsequent current passage in the actual welding, the time variation curve of the instantaneous amount of heat generated per unit volume and the cumulative amount of heat generated per unit volume that are stored in the main current passage in the test welding and the time variation curve of the instantaneous amount of heat generated per unit volume and the cumulative amount of heat generated per unit volume that are stored in the subsequent current passage in the test welding are respectively set as a target, and adaptive control welding is performed to control a current passage amount according to the target.