HIGH STRENGTH STEEL TUBE EXCELLENT IN FORMABILITY AND ITS PRODUCTION METHOD

摘要

PROBLEM TO BE SOLVED: To provide a high strength steel tube having excellent formability suitable for hydroforming and to provide its production method. SOLUTION: This high strength steel tube excellent in formability has a composite structure consisting of ferrite of >=50% by volume fractional ratio and a second phase containing residual austenite of >=3% by volume fractional ratio, in which the average of the X-ray intensity ratios in the orientation groups of 110}<110> to 332}<110> in the sheet face at a sheet thickness of 1/2 in the steel sheet is >=2.0 and/or the X-ray random intensity ratio in 110}<110> in the sheet face at a sheet thickness of 1/2 in the steel sheet is >=3.0, and its production method.