| 摘要 |
PURPOSE:To prevent the generation of irreglarity in mechanical properties of a steel plate, in subjecting a thin and long steel plate to direct hardening after hot rolling, by a method wherein the steel plate after hot rolling is once wound up and, thereafter, subjected to direct hardening while being unwound. CONSTITUTION:A thin and long steel plate 4 rolled by a hot rolling machine 1 is wound up by a wind-up apparatus 5 in a coil form and held once by wrapper rolls 8. This wound-up steel plate is sent to a hardening apparatus 3 by guide rollers 9 to be subjected to direct hardening. Because the steel plate 4 is once wound up, a time exposed to the atmosphere is short and, therefore, the lowering in a temp. is small while the coil comes to a uniform temp. as a whole by heat recovery effect when the steel plate is wound up in a coil form and a hardening temp. becomes constant. As the result, a steel plate free from irregularity in mechanical properties due to hardening and having excellent quality is obtained. |
