| 摘要 |
PURPOSE:To inexpensively manufacture a high tensile steel with superior homogeneity by coiling at a low temp. by forming a billet from a steel contg. specified percentages of C, Mn, Si and Al and subjecting the billet to reheating, rollling and water cooling under specified conditions. CONSTITUTION:A steel consisting of 0.03-0.15% C, 0.1-2.0 Mn and the balance Fe with inevitable impurities or further contg. <=2.0% Si and/or <=0.10% Al is formed into a billet by continuous casting or blooming. The billet is directly reheated or cooled once and reheated, and it is rolled at a temp. above the Ar3 point with a hot strip mill. The rolled steel is water-cooled with a run-out table while controlling the total density of flows of water along the upper and under surfaces to 200-2,000l/m<2>.min and cooling parameter P decided by the equation to 3.5-5.0sec/mm.. The S content of the steel is restricted to <= about 0.015%, and to the steel may be added Ca, REM and Zr in about 0.5<=Ca/S<= about 1.5, about 1.3<=REM/S<=5 and about 2<=Zr/S<= about 10. |
