| 摘要 |
PURPOSE:To surely prevent front end tear by forming a projection having the section smaller than a rolling finish size to the central part at the front end face of a stock and subjecting the stock to hot rolling. CONSTITUTION:The projection having the section smaller than the rolling size is formed to the central part at the front end of the stock at the time of rolling the stock such as a sulfur free-cutting steel or alloy tool steel having the tendency to easily cause the front end tear and having poor hot workability, and then the hot rolling is carried out, cast ingot of a cold working tool steel SKD-11 is pressed and forged to 350mm square and the riser part thereof is scored to 150mm square smaller than the rolling size and is forged and elongated by using chisels 3 simultaneously; finally, the projection having 100mm length is formed and the ingot is hot rolled. The front end part is then not rolled down even if the temp. drop at said part is earlier. The front end tear is thus surely prevented even with the steel, etc. having the tendency to easily cause the front end tear. |
