Method for manufacturing high strength sheet steel with tensile strength of 45kg/mm2 grade having excellent fatigue property and brittle failure resistant property

摘要

The present invention relates to a method for producing a high strength steel sheet used in automobile, electrical appliances, building materials and so on for will ; in the manufacturing method of a high strength steel sheet are in weight percent, C:. 0.02 ~ 0.12%, Si: 0.02% or less (excluding 0), Mn: 0.1 ~ 0.6%, P: 0.03% or less (excluding 0), S: 0.020% or less (excluding 0), Al: 0.01 ~ 0.20%, N: 0.005 ~ 0.015%, and the composition balance of Fe and other unavoidable impurities, wherein C, Mn, P and N The content of the following relationship, ; 29.1 + 90C (%) + 4.8Mn (%) + 85P (%) + 510N (%) 45 ; satisfies a and the Al and the amount of N, the following relation, ; 1.5 Al / N 5.0 ; Reheat the river to meet the and austenite finish hot rolling temperature range from single station and then wound and then, 65 ~ 70%, and cold rolling at a reduction ratio of the range, and comprises the continuous annealing at 750 ~ 785 range. ; This method of manufacturing a high strength steel sheet has a high strength steel sheet manufactured is in the addition to the strength P, Mn, by increasing the content of N in place of reducing the content of Si, fatigue property and surface quality due to my have the effect of improving the brittle fracture characteristics as well as reduction in the Si content There is also improved, and the secondary effect of reducing manufacturing costs by reducing the Mn content.