| 摘要 |
PURPOSE:To obtain an electric welded steel pipe whose weld zone has high toughness, by electrically welding a steel pipe, and immediately after that, exectuting fixed form working, and subsequently, executing a heat treatment to the weld. CONSTITUTION:In a manufacturing line of an electric welded steel pipe, immediately after electric welding, fixed form working is executed. After that, a heat treatment of a heating temperature of about 900-1,000 deg.C exceeding an A3 transformation point of steel is executed to a weld. As a result, quench-hardened structure after high frequency welding is improved, also working hardness caused by the fixed form working is annihilated,and toughness of the weld is elevated. Also, since the heat treatment is executed only once, an energy saving effect is obtained. |
