| 摘要 |
PURPOSE:To effectively carry out the annealing of a steel sheet in a short time, by using, as a heat-treatment furnace for annealing, a continuous heat-treatment furnace having plural temp. zones at the time of annealing a steel sheet. CONSTITUTION:A steel sheet 1 to be annealed is put into a continuous heat-treatment furnace, where the steel sheet 1 moving on hearth rolls 2 is heated by means of radiant tubes 3 provided to the upper and lower parts in the furnace. The inside of the furnace is partitioned off into plural sections by means of shut-off walls 4, and a shut-off zone [III] is provided between zones [I], [II] so as to shut off the movement of heat flow. That is, for the purpose of subjecting the steel sheet 1 to heating up to the austenitic temp. or above and to holding for the prescribed period so as to carry out perfect austenitizing in the zone [I] and also subjecting the above steel sheet 1, without delay, to pearlite transformation in the zone [II], the heat flow is shut off by means of the shut-off wall 4 or temp. in the zone [III] is set up to a value lower than pearlite transformation temp. by 50 deg.C, so that annealing can be carried out by lowering the temp. in a short time from the austenitic region to the pearlite transformation region.
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