| 摘要 |
PROBLEM TO BE SOLVED: To completely prevent a penetrator crack by carrying out gas shielded welding where an oxygen concentration of a welding point or its periphery in a seal box is 300 ppm or less, and further to suppress degradation of a fatigue life.SOLUTION: Seal box welding equipment of an electric resistance welded tube includes: a seal box entrance gas supply pipe (30), a high-frequency heating coil (22), a preheating part gas supply pipe (70), a first oxygen concentration meter (51), a squeeze roll (23), a welding point gas supply pipe (31), a gas supply pipe (32) for adjusting seal box atmosphere in a seal box (5). An impeder (8) is included in the electric resistance welded tube (6), and inert atmosphere gas supply is controlled so that the oxygen concentration at the welding point or its periphery in the seal box (5) is 300 ppm or less. |
