PRODUCTION OF HOT-ROLLED STEEL SHEET FOR WORKING EXCELLENT IN FORMABILITY AND AGING PROPERTY BY USING CONTINUOUS HOT-ROLLING PROCESS

摘要

PROBLEM TO BE SOLVED: To provide a producing method of a hot-rolled steel sheet excellent in the formability and the aging property by using a continuous hot-rolling process which uniformizes the quality of hot-rolled steel sheet over the whole length and prevents the lowering of yield caused by the detective quality at the front end part and improves the cost merit by saving energy in a heating furnace. ;SOLUTION: A steel slab having ≤0.1% carbon content is heated to ≤1150°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°C/s cooling speed for ≥3sac. Thereafter, uncoiling is executed and successively, the front end part of this steel sheet is joined with the rear end part of the steel sheet roughly rolled theretofore and preceding the rolling line, and the hot finish-rolling is continuously executed. After cooling once to ≤300°C at ≥20°C/s cooling speed within 0.5sec after completing the rolling, the temp. of the steel sheet is raised to 350-450°C at ≥20°C/s raising speed and the recoiling is executed.;COPYRIGHT: (C)1998,JPO