| 摘要 |
PURPOSE: A welded steel pipe for a vehicle and a manufacturing method thereof are provided to enhance fatigue resistance by uniformly controlling the hardness of a welded steel pipe based on control of hardness difference between the base and the welded part of the welded steel pipe. CONSTITUTION: A welded steel pipe for a vehicle consists of 0.2-0.5weight% of C, 0.01-0.4weight% of Si, 0.5-1.8weight% of Mn, 0.1-0.5weight% of Cr, 0.01-0.1weight% of Al, 48/14*N(weight%)-0.03weight% of Ti, 0.0005-0.0050weight% of B, below 0.010weight% of N, Fe and other inevitable impurities. The fine structure of the base and the welded part of the welded steel pipe comprises over 80% of martensite by area fraction. The hardness difference between the base and the welded part of the welded steel pipe is below 20 Hv(Vickers hardness). |
