The Principle of High Frequency Welding of Erw Tube Mill

High frequency welding originated in the 1950s as a novel welding process that utilizes the skin effect and proximity effect generated by high frequency current to join steel plates and other metal materials. The emergence and maturation of high frequency welding technology directly drove significant advancements in the longitudinal welded pipe industry, serving as a key process in ERW (Electric Resistance Welding) pipe production. The quality of high frequency welding directly impacts the overall strength, quality grade, and production speed of welded pipe products.

Basic Principles of High Frequency Welding:

High frequency refers to frequencies between 50 kHz and 400 kHz, contrasting with the 50 Hz frequency of alternating current. When high frequency current passes through a metal conductor, two peculiar effects occur: the skin effect and the proximity effect, forming the foundation of high frequency welding. The skin effect causes the current to concentrate mainly on the surface of the conductor, while the proximity effect directs the current to flow along the edges of adjacent conductors. These effects enable the rapid heating, melting, and joining of adjacent steel plate edges through high frequency welding.

Structure and Operating Principles of High Frequency Welding Equipment:

High frequency welding equipment comprises electrical-mechanical systems, typically consisting of a high frequency welding machine and a pipe forming unit. The welding machine typically comprises a high frequency generator and a feed device, responsible for generating and controlling high frequency current, while the forming unit consists of squeeze roller frames to melt and fuse the portions subjected to high frequency current, ensuring complete fusion of the steel plates.

High Frequency Generator: In the past, high frequency generators in welding units were three-circuit systems, including high frequency power generator, solid-state frequency converter, and electronic high frequency oscillator. Later, these were generally improved to single-circuit systems.

Feed Device: This component is used to transmit high frequency current to the pipes and includes electrode contacts, induction coils, and impedance devices.

These two effects, along with advancements in equipment structures, serve as the foundation of metal high frequency welding, enabling precise control of the flow path and range of high frequency current during welding operations. The rapid heating and melting of adjacent steel plate edges, followed by compression, enable seamless joining.

Understanding the principles of high frequency welding is essential for implementing this advanced welding technique effectively. High frequency welding equipment, comprising electrical-mechanical systems, plays a crucial role in ensuring the success and quality of high frequency welding operations.