To achieve an energy conservation and to perform excellent vacuum characteristics by surrounding a heating chamber by a pressure resistant furnace shell, and providing an exhaust port and a seasoning gas inlet at the shell.
Before vacuum heating a material to be treated, a seasoning atmospheric gas is introduced from an atmospheric gas stand 21 into a furnace shell 5 through an inlet 20, and the air in the shell is exhausted from an exhaust port 18. A heater 3 is heated by supplying a current to heat a heating chamber therein to a high temperature to thereby convect the gas in the shell. A moisture, air or the like contained in a heat insulation wall 1 is wiped by beating with the gas by means of the convection, and exhausted together with the gas from the port 18. Thus, since the residue of impurities in the furnace can be suppressed to a minimum limit by a vacuum treatment to be subsequently executed, an environment in the furnace is held in a highly clean state, thereby guaranteeing a quality of a treated material 4. A swinging door 16 is closed during the heat treating.
SATO KENJIRO
AKUTSU KOICHI
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