Method of resistance spot welding and resistance spot welding apparatus

Patent metadata

Field	Value
Publication number	US-12023752-B2
Application number	US-202117368042-A
Country	US
Kind code	B2
Filing date	Jul 6, 2021
Priority date	Jul 8, 2020
Publication date	Jul 2, 2024
Grant date	Jul 2, 2024

Abstract

The present disclose provides a method of resistance spot welding that can inhibit Liquid Metal Embrittlement-induced cracking in zinc-coated steel plates irrespective of the plate thicknesses. One aspect of the present disclosure provides a method of resistance spot welding that includes welding a workpiece with a resistance spot welding apparatus. The workpiece includes two or more steel plates in an overlapping state. The two or more steel plates include at least one steel plate coated with zinc. The welding includes causing a cooling rate of a high-tensile steel plate among the two or more steel plates to be higher than a cooling rate of an other steel plate among the two or more steel plates. The high-tensile steel plate has a tensile strength higher than a tensile strength of the other steel plate.

First claim

What is claimed is:

1. A method of resistance spot welding, the method comprising welding a workpiece, including two or more steel plates in an overlapping state, with a resistance spot welding apparatus including a first electrode and a second electrode, the first electrode being configured to be in contact with a high-tensile steel plate of the two or more steel plates, the second electrode being configured to be in contact with an other steel plate of the two or more steel plates,
the welding comprising:
causing a cooling rate of the high-tensile steel plate to be higher than a cooling rate of the other steel plate, the high-tensile steel plate having a tensile strength higher than a tensile strength of the other steel plate; and
cooling the first electrode by circulation of a first coolant inside the first electrode and cooling the second electrode by circulation of a second coolant inside the second electrode,

wherein the first coolant configured to circulate in the first electrode has a thermal absorptivity higher than a thermal absorptivity of the second coolant configured to circulate in the second electrode, and
wherein at least one of the high-tensile steel plate or the other steel plate is coated with zinc.

2. The method of resistance spot welding according to claim 1 ,
wherein an area of contact between the first electrode and the high-tensile steel plate is larger than an area of contact between the second electrode and the other steel plate.

3. A resistance spot welding apparatus configured to weld a workpiece including two or more steel plates in an overlapping state, with a steel plate of the two or more steel plates being a high-tensile steel plate, the resistance spot welding apparatus including a first electrode and a second electrode, the first electrode being configured to be in contact with the high-tensile steel plate, the second electrode being configured to be in contact with an other steel plate of the two or more steel plates,
the resistance spot welding apparatus being configured to cause a cooling rate of the high-tensile steel plate to be higher than a cooling rate of the other steel plate, the high-tensile steel plate having a tensile strength higher than a tensile strength of the other steel plate, and the cooling rate of the high-tensile steel plate and the cooling rate of the other steel plate being cooling rates at a time of welding,
wherein the first electrode is cooled by circulation of a first coolant inside the first electrode and the second electrode is cooled by circulation of a second coolant inside the second electrode,
wherein the first coolant configured to circulate in the first electrode has a thermal absorptivity higher than a thermal absorptivity of the second coolant configured to circulate in the second electrode, and
wherein at least one of the high-tensile steel plate or the other steel plate is coated with zinc.

4. The resistance spot welding apparatus according to claim 3 ,
wherein an area of contact between the first electrode and the high-tensile steel plate is larger than an area of contact between the second electrode and the other steel plate.

5. The method of resistance spot welding according to claim 1 ,
wherein the welding includes forming a final solidification portion in a nugget away from a surface of the high-tensile steel plate by causing the cooling rate of the high-tensile steel plate to be higher than the cooling rate of the other steel plate.

6. The resistance spot welding apparatus according to claim 3 ,
wherein the resistance spot welding apparatus is configured such that a final solidification portion of a weld of the workpiece is a nugget is formed away from a surface of the high-tensile steel plate caused by the cooling rate of the high-tensile steel plate during the welding being higher than the cooling rate of the other steel plate during the welding.

7. The method of resistance spot welding according to claim 1 ,
wherein a thickness of a contact portion, at a leading end of the first electrode, touching the high-tensile steel plate is larger than a thickness of a contact portion, at a leading end of the second electrode, touching the other steel plate.

8. The resistance spot welding apparatus according to claim 3 ,
wherein a thickness of a contact portion, at a leading end of the first electrode, touching the high-tensile steel plate is larger than a thickness of a contact portion, at a leading end of the second electrode, touching the other steel plate.

Assignees

• Futaba Ind Co Ltd

Inventors

• Yasuda Keigo

Classifications

• B23K11/163

  Welding of coated materials · CPC title

• B23K11/30

  Features relating to electrodes · CPC title

• B23K2103/04

  Steel {or steel} alloys · CPC title

• B23K11/318

  Supporting devices for electrode holders · CPC title

• B23K11/3018

  Cooled pressure electrodes · CPC title