| 摘要 |
PURPOSE:To produce the titled cold rolled steel sheet by devising the heating pattern of a steel slab so as to accelerate the sepn. and solutionizing of the carbide and nitride of Nb and Ti into austenite and devising the water cooling region of a strip after finish rolling so as to allow the adequate precipitation of the C and N solutionized during heating. CONSTITUTION:The steel slab is composed, by weight %, of <0.005 C, <1 Si, <1 Mn, <0.15 P, <0.015 S, 0.01-0.1 Al and <0.005 N, 1 or >=2 kinds of 0.01-0.05 Ti and 0.004-0.03 Nb and the balance Fe. Such steel slab is so heated that the rate of heating attains >=1.5 deg.C/sec only in the temp. region of 1,100-1,200 deg.C. The steel strip is thereafter subjected to a hot rolling stage in which both edges of the strip are passed in the masked state from the end of the hot finishing until coiling. The strip is then subjected to continuous annealing after the cold rolling conforming to the conventional practice.
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