| abstract |
An object of the present invention is to perform gas shield welding with an oxygen concentration of 300 ppm or less at or near the welding point in a seal box, thereby reducing penetrator cracks and further suppressing a decrease in fatigue life. A seal box welding apparatus for an ERW steel pipe according to the present invention includes a seal box inlet gas supply pipe (30), a high-frequency heating coil (22), a preheating part gas supply pipe (70) in the seal box (5), It has a first oxygen concentration meter (51), a squeeze roll (23), a welding point gas supply pipe (31), and a gas supply pipe (32) for adjusting the atmosphere of the seal box, and an impeder (8 The inert atmosphere gas supply is controlled such that the oxygen concentration at or near the welding point in the seal box (5) is 300 ppm or less. [Selection] Figure 1 |