The speed of the welded steel pipe unit is limited by the high-frequency welding speed. Generally speaking, the unit speed can be opened at a speed of 100 m/s, and the speed of the unit in the world is even 400 m/s Welding, especially in the induction welding can only be 60 meters/second or less, more than 10mm of steel plate molding, the domestic unit production molding speed can only reach 8 to 12 m/s. The welding speed affects the welding quality of welded steel pipe. When the welding speed is high, it will help to shorten the heat affected zone and facilitate the extrusion of the oxide layer from the molten groove. On the other hand, when the welding speed is very low, the heat affected zone becomes wider, resulting in a larger welding burr, , Weld quality deteriorated. Of course, the welding speed of welded steel pipe unit by the output power limit, it is impossible to mention very high. Domestic unit operating experience shows that 2 ~ 3 mm steel pipe welding speed can reach 40 m/s, 4 ~ 6mm steel pipe welding speed can reach 25 m/s, 6 ~ 8 mm welded steel pipe welding speed can reach 12 m/10 ~ 16 mm welded steel pipe welding speed of 12 m/s or less. Contact welding speed can be higher, induction welding will be lower.