High frequency welded spiral finned tube is a welding method that has gradually developed and matured based on a highly efficient material-saving welding method that used to connect pipes and profiles. As the high-frequency welded finned tube has a larger heat transfer area, higher heat transfer efficiency and smaller pressure drop, thus the comprehensive heat transfer performance is significantly better than the ordinary heat transfer tube and nailhead tube of the same specification and material in the gas furnace and oil-gas mixture heating furnace.

Because of this, different heat exchange equipment with high-frequency welded finned tubes as core components are being used more and more widely in electric power, fertilizer, chemical and oil refinery installations. With the continuous improvement of finned tube production technology and production equipment technology, more and more types of finned tubes are produced. In the production process, the corresponding inspection and testing is carried out for various types of finned tubes.

The finned tube is wound on the outer circle of the seamless steel tube according to a certain pitch (the steel strip is perpendicular to the surface of the outer circle of the steel tube), and the high frequency current is used as the welding heat source, using the skin effect and the electrothermal effect of the high frequency current to locally heat the contact surface of the steel tube and the steel strip and the area to be welded, so that the contact surface reaches a plastic weldable state.

At the same time, a certain force should be exerted on the outside of the fins of the high-frequency welded finned tube, so that the metal oxide, local melting matter and excess plastic metal at the contact will be squeezed out, so that the solid inter-atomic bond between the steel pipe and the fin material will be achieved, thus realizing the plastic welding of the contact surface. In high-frequency welding of finned tubes, the depth of current penetration and the area of influence are small due to the highly concentrated electrothermal effect of the high-frequency current during the welding process.

In addition, in the process of high-frequency finned tube welding, high-frequency welding is carried out at a faster speed, and the heating process is short, the molten volume of the base material is small, and the molten metal is basically all discharged, the heat-affected zone is quite narrow, and the main reliance on the characteristics of atomic force bonding, so the adverse effects on the base material due to the material is relatively small.