PURPOSE: To manufacture a high strength cold rolled steel sheet having superior press formability by successively subjecting a steel sheet contg. specified amts. of C, Si, Mn and Al and obtd. by finish hot rolling at a specified temp. to cold rolling at a specified draft, heating to a specified temp. and cooling at stepwise varied cooling rates.
CONSTITUTION: A steel contg., by weight, 0.12W0.40% C, 0.50W2.00% Si, 0.20W2.50% Mn and 0.005W0.10% sol. Al is hot rolled at 700W850°C finishing temp., cold rolled and heat-treated to regulate the ratio of pearlite : retained austenite to (1.5W2.5):1. The resulting steel sheet is pickled and cold rolled at 35W65% draft. This cold rolled steel sheet is heated to 730W900°C, cooled to 600W700°C at 1W10°C/sec cooling rate, further cooled to 200W400°C at 20W200°C/sec cooling rate, held for 2W50sec, further held at 350W450°C for 15secW10min and then cooled to ≤150°C within 30sec. A high strength cold rolled steel sheet having superior press formability can be manufactured.
KATO HIROSHI
MATSUMURA OSAMU
SAKUMA KOJI
| JPS61217529A | 1986-09-27 | |||
| JPS62139821A | 1987-06-23 |