| 摘要 |
PURPOSE: Provided are welded steel pipe which has excellent hydroforming properties, and its production method, producing the welded steel pipe having a tensile strength of 590 MPa or more, nx r of 0.22 or more and excellent hydroforming properties. CONSTITUTION: A welded steel pipe comprises, by mass, 0.03 to 0.2% of C, 2.0% or less of Si, 1.0 to 1.5% of Mn, 0.01% or less of S, 0.1% or less of Ti, 0.1% of less of Nb and 1.0% or less of Cr, 0.1% or less of Al, 0.1% or less of V, 0.01% or less of N, and the balance of Fe and impurities. |
