METHOD FOR PRODUCING HIGH-CARBON COLD-ROLLED STEEL SHEET EXCELLENT IN PUNCHING-WORKABILITY AND HIGH-CARBON COLD-ROLLED STEEL SHEET

摘要

PROBLEM TO BE SOLVED: To provide a method for producing a high-carbon cold-rolled steel sheet and the same product with which this producing process can be simplified without deteriorating a punching-workability.;SOLUTION: The high-carbon cold-rolled steel sheet in this invention is produced as the followings, that is; the steel composed by mass% of 0.2-0.7% C, 0.10-0.35% Si, 0.1-0.9% Mn, ≤0.03% P, ≤0.035% S, ≤0.08% Al, ≤0.01% N, 0.05-0.30% Cr and the balance Fe with inevitable impurities, is hot-rolled at ≥(Ar3 transformation temperature minus 20°C) finish temperature and cooled to 400-550°C cooling-stop temperature at 120°C/s cooling rate, and after raising the temperature to a winding temperature range of 600°C to Ac1 transportation temperature, this hot-rolled steel plate is wound as a coil-state in the above temperature range and cooled to 400°C steel plate temperature at ≤20°C/hr average cooling rate to make the hot-rolled steel plate, and after picking, a cold-rolling having ≥30% rolling ratio is performed and an annealing is performed at 600°C to Ac1 transformation temperature.;COPYRIGHT: (C)2007,JPO&INPIT