Gases used for brazing copper tubes used in refrigeration systems

The gases normally used for welding are the mixture of oxygen with acetylene, ie a flame feed gas and a combustible gas.
Acetylene gas is highly combustible, and produces a high temperature flame (over 3000 ° C) in the presence of oxygen.

combustible gas with oxygen flame temperature:

acetylene 3480 ° c
butane 2925 ° c