The working principle of high-frequency welding:
High frequency welding is a new welding process that uses skin effect and proximity effect generated by high frequency current to connect steel plates and other metal materials. The emergence and maturity of high-frequency welding technology is the key link in steel pipe production. The quality of high frequency welding directly affects the overall strength and quality level of welded pipe products.
The so-called high frequency, generally refers to 50KHz ~ 400KHz high frequency current. When a high frequency current passes through a metal conductor, two special effects occur: the skin effect and the proximity effect. High-frequency welding is the use of these two effects to weld steel pipes.
“Skin effect” means that when alternating current of a certain frequency passes through the same conductor, the current density is not evenly distributed in all parts of the conductor. It will be mainly concentrated on the conductor surface, that is, the conductor surface has a high current density. The density inside the conductor is very small, so we figuratively call it the "skin effect." The skin effect is usually measured by the penetration depth of the current.
“Proximity effect” refers to the fact that when a high frequency current flows in the opposite direction between two adjacent conductors, the current will concentrate on the edge of the two conductors. Even if the other side of these two conductors is shorter, the current will not follow. The shorter route flow, we call this effect: "proximity effect".
Proximity effect is essentially due to induced reactance, which plays a dominant role in high frequency currents. The proximity effect increases as the frequency increases and the distance between adjacent conductors gets closer. If a magnetic core is added around an adjacent conductor, the high-frequency current will be more concentrated on the surface of the work-piece.
These two effects are the basis of high frequency metal welding. High-frequency welding uses skin effect to concentrate the energy of high-frequency current on the workpiece surface; The proximity effect is used to control the position and range of the high frequency current flow path. The speed of electricity is very fast. It can heat and melt the edge of the adjacent steel plate in a short time, and realize the butt connection by extrusion, thus completing the welding of the steel pipe.
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