Control of gas carburising at low pressures - involves pumping gas out of vacuum furnace and replacing it after it has decomposed by specific amt.

摘要

After evacuating a furnace, a gas which evolves carbon is fed into the furnace until a constant, specific and predetermined pressure is obtd. When the gas decomposes to a constant, predetermined level, the gas is pumped out of the furnace and replaced; and when the fresh gas decomposes to level, the pumping out and replacement is repeated. This replacement procedure is continued until a prescribed depth of carburisation is obtd. The predetermined level pref. corresponds with 5-40% decompsn. of the gas and is pref. detected by monitoring the pressure of the gas in the furnace. Optimum carburising of the entire surfaces of the workpieces can be achieved without the formation of soot and without requiring long carburising times.