| 摘要 |
PURPOSE:To prevent generation of surface flaws in spread rolling by drafting a rolled stock up to a part before the dog bone part in the slab rear end area in a 1st pass rolling and drafting a non-drafted area including the dog bone part in the reverse direction in a 2nd pass stage. CONSTITUTION:At the time of spread rolling a slab chamfered in the final stage of forming rolling, first, in a 1st pass stage, the slab 3 is drafted from its top end up to a part before the dog bone part, that is, from A-C by a prescribed light drafting amount to prevent generation of projections to leave the rear end area in the rolling direction as a non-drafted part to prevent generation of projections. Next, the non-drafted part including the rear end and the dog bone part of the slab 3 is drafted in the reverse direction to the rolling direction in a 2nd pass stage. After that time, ordinary spread rolling by plural passes is performed. Hence, generation of surface flaws proper to thick plates is prevented to reduce expenses for reworking, etc.
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