| 摘要 |
PROBLEM TO BE SOLVED: To provide a heat treatment apparatus which can realize an environment being clean and having higher temperature, and a filter used therefor. SOLUTION: A clean oven has an opening frame 2 forming an opening 1, a filter 3 of which the filter part 31 is surrounded by a filter frame 32 constituted of ferrite-series special heat-resisting steel having a composition enhancing heat resistance, a packing 4, short tightening shafts 5 between P1-P2, nuts 5a, retainer plate 19, etc. According to this constitution, the filter frame is kept from rust, although it is constituted of the ferrite-series material. Since the filter frame 32 is constituted of the same ferrite-series material as that of an inner tank 6, a thermal expansion difference between the filter frame 32 and the opening frame 2 on the opposite sides of the packing 4 is eliminated and the sealing properties of this part are made excellent. Since the tightening shafts 5 are short, a change in the amount of compression of the packing is small and deterioration of the sealing properties can be prevented.
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