Method of producing a high tensile steel sheet having excellent stretch flanging formability

摘要

A high tensile steel sheet excelling in workability and stretch flanging formability, which is of a composite texture composed of a ferrite phase and a 2nd phase selected from the group consisting of martensite, bainite, pearlite, retained austenite and cold-transformed ferrite, wherein the volume fraction of the 2nd phase is hoe less than about 1.3 times higher at an outer region of the steel sheet than the volume fraction of the 2nd phase in a central region of the sheet thickness.