Two Ways of High-frequency Welding

Steel pipe has a variety of production processes. High-frequency welding technology is one of them, it usually used by pipe manufacturers to produce ERW steel pipe. Actually, high-frequency welding can be divided into two ways, resistance welding and IWinduction welding.

What is resistance welding?

The resistance welding is carried out by using a pair of copper electrodes to contact on both sides of the welded steel pipe, induction current penetration is good, the two effects of high frequency current are maximized using since the copper electrode directly contact with the steel plate. The welding efficiency of the resistance welding is high and the power consumption is low, so it is widely used in the production of high speed and low precision pipe. And in the production of special thick steel pipe, it is also necessary to use resistance welding.

But there are two shortcomings in resistance welding: first, copper electrode is in touch with steel plate, so it will wear quickly; second, due to the influence of the flatness of the surface of the steel plate and the straightness of the edge, the current stability of resistance welding is poor, the burr inside and outside the weld is higher. So pipe manufacturers generally do not used this way when welding high-precision and thin-walled tube.

What is IWinduction welding?

IWinduction welding is way that using a turn or more turns of the induction coil harness the outside of welded steel pipe. The effect of multi-turn is better than that of single turn, but the fabrication and installation of multi-turn induction coil is more difficult. When the spacing between induction coil and the steel pipe surface is small, the efficiency is higher, but it is easy to cause electro-discharge between the induction coil and the pipe. Generally, it is appropriate that keep the induction coil from the surface of the steel pipe having 5 ~ 8 mm gap. When using IWinduction welding, as the induction ring is not in contact with the steel plate, there is no wear, which ensures the stability of the welding. The quality of welding steel pipe surface is good, and the weld is flat, so in the production of high-precision pipe,such as API and others, it basically uses the form of induction welding.