To obtain a heating furnace operating in an inert atmosphere at a carbon vapor pressure in a specific system or above in which damage in the system is suppressed during operation by surrounding the innermost layer of the furnace with a graphite plate having a specific bulk weight within a specified range.
A heating furnace is operated in an inert atmosphere and carbon vapor pressure in the system is at 10-8 atm or above. An innermost layer 1 on the high temperature side facing an article to be heated is surrounded by a graphite plate having a specific bulk weight of 1.0-2.2 g/cm3, preferably 1.5-2.0 g/cm3. Since a graphite plate exists as an innermost layer 1 between a space for placing an article to be heated and a heat insulating material 4, temperature fluctuation can be suppressed at the part of innermost layer 1. Consequently, damage on the innermost layer 1 and the heat insulating material 4 can be reduced. Furthermore, damage of the heat insulating material 4 due to convection of gas can be eliminated because the heat insulating material is shielded from the space for placing an article to be heated by means of the graphite plate.
FUKAGAWA TOSHIHIRO
YOSHITANI AKIHIKO
TAKADA MASAYUKI
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