| 摘要 |
A fabrication method of welded steel pipe using dual-phase stainless steel, comprises the steps of preparing a hot-rolled dualphase stainless steel plate containing 0.03 wt.% or less C, 1 wt.% or less Si, 0.8 to 2.0 wt.% Mn, 0.03 wt.% or less P, 0.01 wt.% or less S, 20 to 30 wt.% Cr, 2.5 to 4 wt.% Mo, 4 to 7 wt.% Ni, 0.08 to 0.2 wt.% N and the balance essentially Fe. Forming said hot-rolled steel plate continuously into an open pipe using multistage forming rolls. Welding both edges of the open pipe facing each other while upsetting by laser radiated heat. Grinding the portion that increased in plate thickness on the welded part. Applying solid solution treatment to the welded part at a temperature range of from 950 to 1100 .degree.C for 30 to 300 sec of holding time. The invention also provides a method in which welded part by a laser beam and applying the aforedescribed solid solution treatment to the welded part. |
