Can vacuum furnace be used for CuproBraze?
The furnaces are CAB-furnaces (Controlled Atmosphere Brazing Furnaces). Nitrogen is used as inert atmosphere. The reason why vacuum furnaces cannot be used is that in vacuum zinc starts evaporating out of brasses at elevated temperatures. Why some people talk about vacuum furnaces in conjunction of CuproBraze, is understanable but misleading. In the beginning of the furnace cycle air (oxygen) is evacuated normally by flushing with nitrogen or, alternatively, the air can by removed by creating vacuum and then backfilling with nitrogen, before heating up and brazing. The heating and brazing never takes place in vacuum.
