| 摘要 |
PROBLEM TO BE SOLVED: To provide a heat treatment method capable of keeping a prescribed heat treatment temp. even at the time of changing the size (thickness, width) of a metallic strip and heat treatment speed and dealing with either of acceleration or deceleration particularly in the case of quickly changing the heat treatment speed. SOLUTION: In this heat treatment method an auxiliary heating zone 21 high in the responsiveness of an induction heating or an electric heating system and fast in heating rate is disposed at the inlet side of a heating zone 11 of a radiant tube heating system. At the time of normal operation, the operation is performed so that the output of the auxiliary heating zone is regulated to almost half to the max. output or increased/decreased in the proportion with the ratio of the present heat treatment quantity to the max. heat treatment capacity in the heating zone and/or the ratio of the present speed to the max. speed of the heat treatment apparatus. At the time of changing the metallic strip size, heat treatment speed or heat treatment temp., the output of the auxiliary heating zone is instantially increased/decreased so as to keep or change the prescribed heat treatment temp. of the metallic strip, and then the output of the auxiliary heating zone is gradually returned to the output at the time of normal operating by adjusting the heating capacity of the heating zone.
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