In the production process of used HFW tube mills, there are two welding methods: contact welding and induction welding.

1. Contact welding

Contact welding is a kind of copper electrode contacting the two sides of the steel pipe to be welded, and the induced current penetration is good. The two effects of high-frequency current (proximity effect and skin effect) are maximized by the direct contact between the copper electrode and the steel plate. Utilization, so the welding efficiency of contact welding is higher and the power consumption is lower. It is widely used in the production of high-speed and low-precision pipes, and contact welding is generally required when producing extremely thick steel pipes with used HFW tube mills.

Compared with induction welding, contact welding has two disadvantages:

①The copper electrode is in direct contact with the steel plate and wears quickly

② Due to the influence of the flatness of the steel plate surface and the straightness of the edges, the current stability of contact welding is poor, and the internal and external burrs of the weld are relatively high. Contact welding is generally not used when welding high-precision and thin-walled pipes.

2. Induction welding

In induction welding, an induction coil with one or more turns is sheathed outside the welded steel pipe. The effect of multi-turn is better than single-turn, but it is more difficult to manufacture and install multi-turn induction coils. If the distance between the induction coil and the surface of the steel pipe is small, the efficiency is higher, but it is easy to cause discharge between the induction coil and the pipe. Generally, it is advisable to keep the induction coil from the surface of the steel pipe with a gap of 5-8mm. When using induction welding, because the induction coil is not in contact with the steel plate, there is no wear and the induced current is relatively stable, thus ensuring the stability during welding. The welded steel pipe has good surface quality and the weld seam is flat. For high-precision pipes, induction welding is basically used.

Realizing that there are two welding methods in the production process of used HFW tube mills: contact welding and induction welding, as well as their pros and cons. The corresponding welding method should be carried out according to the type of steel pipe actually produced.