To prevent vapor or gas leaked into an inner furnace space from adhering to a heat insulation member or a side wall thus avoiding the contamination of the inside of the furnace by covering a gap defined between a die and a punch with a cover, discharging gas present in this inner space to the outside of the furnace directly, and providing means for introducing a carrier gas into the inner furnace space.
A material to be treated W is filled in a treatment space S1, a cover 4 and push rod 12 are set at given positions, and a furnace 1 is closed. A main gas discharge system 7 and an inner gas discharge system 5 are operated. When the degree of vacuum in an inner furnace space S3 and the treatment space S1 reaches a given degree of vacuum, a valve 72 of the main gas discharge system 7 is closed. While continuing the operation of the inner gas discharge system 5, the valve 62 of a gas introduction system is opened to introduce a carrier gas X into the inner furnace space S3 outside the cover 4. While applying a pressing force by way of a push rod 12, electricity is supplied to a heater 10 to start the heat treatment of the material W to be treated. Upon completion of the above-mentioned degassing process, the valve 62 is closed to stop the introduction of the gas, the main gas discharge system 7 is operated, and the supply amount of electricity to the heater 10 is increased to fire the material W to be treated.
YAMAUCHI IPPEI
TAKEDA MASAO