High yield rate production manner null of continual annealing cold rolling steel sheet or hot rolling original plate for continual melting galvanize cold rolling steel sheet

摘要

PURPOSE: To offer a manufacturing method of a hot rolled original sheet for a continuously annealed cold rolled steel sheet or a continuously galvanized cold rolled steel sheet used for automobile parts or the like at a high yield. ;CONSTITUTION: At the time of subjecting a steel contg. 0.01 to 0.025% C, 0.05 to 0.2% Mn, ≤0.015% P, 0.004 to 0.015% S, 0.05 to 0.15% Al and ≤0.0025% N to hot rolling and coiling it at 640 to 700°C, the coiling temp. in the part with each ≥3% length of both edge parts of the coil is regulated to 680 to 850°C to prevent loosening, and the cooling rate at the edge parts is regulated to ≤3°C/min from the temp. of ≥550°C. Furthermore, immediately after the start of the coiling, it is possible to expand a mandrel and to seam the inner circumferential part tight.;COPYRIGHT: (C)1993,JPO&Japio