METHOD FOR PRODUCING HIGH TENSION STEEL OF 60KGF/MM^2 BY FINING GRADE OF FERRITE

摘要

PURPOSE: A method is provided to produce the high tension steel of more than 60 kgf/mm¬2 of tension intensity by fining ferrite with metamorphic organic deformation in low-carbon steel. CONSTITUTION: A steel slab is composed of 0.05 to 0.20wt% of C, less than 0.5wt% of Si, 0.9 to 20.wt% of Mn, less than 0.3wt% of P, less than 0.02wt% of S, Fe and impurity elements. The steel slab is heated in a temperature range of Ae3 ¯ (Ae3 +50°C) and then is cooled. The steel slab is hot-rolled in a condition to give more than 80% of depression at the temperature of (Ar3 + 25) ¯ (Ar3 - 25) and is cooled up a common temperature at 5 to 30°C/sec. Accordingly, the high tension steel of 60kgf/mm¬2 is produced by fining the grading of ferrite.