| 摘要 |
PROBLEM TO BE SOLVED: To uniformize the quality of a hot-rolled steel sheet over the whole length, to avoid the defective quality at the front end part, to improve the cost merit by saving energy in a heating furnace and to produce the hot-rolled steel sheet for working excellent in the ductility, deep drawability and aging property. SOLUTION: A steel slab having <=0.1% carbon content is heated to <=1150 deg.C extraction temp. in the heating furnace, and the roughly rolled steel sheet is coiled at >=0.5% bending strain and >=0.05s<-1> bending strain speed and held at <=1 deg.C/s cooling speed for >=3sec. Thereafter, this steel sheet is uncoiled and successively, the front end part of it is joined with the rear end part of a steel sheet which is roughly rolled and is running in the preceding rolling line, and is subjected continuously to hot finish-rolling in the temp. range ofαzone at >=50% draft. After cooling once to <=300 deg.C at >=20 deg.C/s cooling speed within 0.5sec after completing the rolling, the temp. of the steel sheet is raised to 350-450 deg.C at >=20 deg.C/s raising speed and recoiled.
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