Definition principle and characteristics of high frequency welding

High frequency welding was invented in the early 1950s and has been rapidly applied in industrial production. It uses 10 ~ 500KHz At present, high frequency welding is mainly used in pipe and profile production lines with high degree of mechanization or automation. Weldments can be made of steel or non-ferrous metals, with pipe diameter ranging from 6 to 1420 mm and wall thickness of 0 In recent years, as one of the connection methods, high frequency welding technology has attracted people's attention and become a new research hotspot in the field of connection.

Definition of high frequency welding

High frequency welding uses solid resistance heat as energy. In the welding process, the resistance heat generated by high-frequency current of workpiece heats the surface layer of welding area of workpiece to molten or nearly plastic state, and then applies (or does not apply) forging force to realize metal combination. Therefore, it is a solid phase resistance welding method. High frequency welding can be divided into contact high-frequency welding according to the way of heat generated by high-frequency current in workpiece High frequency welding and induction high-frequency welding. In contact high-frequency welding, the high-frequency current is transmitted to the workpiece through mechanical contact with the workpiece. In induction high-frequency welding, the high-frequency current is generated in the workpiece through the coupling effect of the external induction coil of the workpiece. High frequency welding is a highly specialized welding method, which should be equipped with special equipment according to the product, with high productivity and welding speed of 30 m / min, It is mainly used for welding longitudinal seam or spiral seam in pipe manufacturing.

Principle of high frequency welding

High frequency welding principle: high frequency electric energy is concentrated on the surface of the weldment through the skin effect of high frequency current, and the position and range of high frequency current flow path are controlled through proximity effect. When high frequency current is required to be concentrated on a certain part of the weldment, as long as the conductor and the weldment form a current loop and make the conductor close to this part of the weldment, so that they form proximity to each other According to the specific form and requirements of the weldment structure, high frequency welding mainly uses skin effect and proximity effect to make the surface metal of the weldment heated rapidly and realize welding.

The two main effects of high-frequency current in high-frequency welding are skin effect: when the conductor is supplied with AC current, the current distribution on the conductor section is uneven, the current density gradually increases from the center of the conductor to the surface, and most of the current only flows along the surface of the conductor. The lower the resistivity is, the higher the permeability is, and the higher the current frequency is, the more significant the skin effect is Effect is a physical phenomenon. When high frequency current flows in opposite directions in two conductors or reciprocating conductors, the current will concentrate on the adjacent side of the conductor. The frequency range of high frequency welding current is 300 ~ 450 kHz, sometimes as low as 10 kHz.

Characteristics of high frequency welding:

Because the current is highly concentrated in the welding area, the heating speed is very fast, and the welding speed can reach 150~ 200m / min. due to the fast welding speed, strong self cooling effect of weldment, small heat affected zone and less oxidation, the weld has good microstructure and performance. The surface of weldment can not be cleaned before welding, so the efficiency is increased. There are many kinds of metals that can be welded, and there are many shapes and specifications of products.