| 摘要 |
PURPOSE:To permit production of a hot rolled steel sheet having excellent deep drawability with good workability, by subjecting steel added with Ti and Nb at the specific ratios associated to the ratios of C and N to two stages of hot rolling including intermediate cooling under specific conditions then subjecting the steel to a coiling or recrystallization treatment. CONSTITUTION:The steel having the compsn. which consists of <=0.01% C, <=0.005% N, <=0.3% Mn, is added with Ti and Nb so as to satisfy 48X(C/12+N/14)<=Ti<=0.1% in the case of Ti and 93X(C/12+N/14)<=Nb<=0.15% in the case of Nb and consists of the balance Fe and unavoidable impurities is hot rolled. The steel is subjected to 1- plural passes of rolling reduction at >=30% in an Ar3-Ar3+50 deg.C range in the primary rolling and is cooled at >=1 deg.C/sec cooling rate right after the rolling. The steel is in succession hot rolled at >=35% total draft within 0.3sec from the final stage or one stage before the final stage till the final stage at the temp. of >=600 deg.C and the Ar3 or below. The steel is then subjected to the coiling treatment or recrystallization treatment at 600-700 deg.C. The high deep drawability is obtd. if such hot rolled steel sheet is cold rolled and is used.
|
