Pressing and welding a bearing cage - GIF

[hemmjo]

That was not welding, for one thing there were no sparks. Looks more like soldering possible brazing. Needless to say a nice operation and a great bearing.

Brazing and soldering both require a metal different than the base metal added to the joint. That is not present in this operation.

As mentioned above, resistance welding does not produce sparks when done correctly.

One other possibility is pressure “deforming” like riveting. But my vote is resistance heating with pressure deformation similar to hot rivets.