On Nov 8, 6:56*pm, "Martin H. Eastburn"
wrote:

N_Cook wrote:
I wonder how they "weld" these 2 materials
together.

Explosive welding.
Simple as that.

This might be the correct answer, but there are fill-metal/reducing
atmosphere/heat solutions that might do a kind of brazing for lower
cost
if you get the materials right. Explosive welding is used for US
coins
because it was possible to mimic the electromagnetic properties of
silver well enough to keep lots of vending machines in service.
I've gotta believe the requirements for a thermostat bimetal system
are loose enough to allow for alloys that don't require explosive
welds.