Furnace Brazing Protective Atmosphere

For furnace brazing you need a protective gas atmosphere, otherwise the parts oxidize and the filler metal doesn't wet cleanly. Nitrogen is the standard, it just displaces the air. If you want really clean results, use a reducing gas like hydrogen or a mixture, it even attacks the oxide layer. Argon also works, but it's more expensive and offers no real advantage in brazing. It's important that enough gas flows in so that no oxygen gets in from outside, and that you only load the furnace once the atmosphere is established.