When the tube is mainly used for manufacture

 Therefore, it is a solid-phase resistance welding method. High-frequency welding parts according to high-frequency current generated in the heat of welding can be divided into contact with high frequency and high frequency induction welding. Exposure to high-frequency welding, high frequency current through mechanical contact with the workpiece incoming workpiece. High frequency induction welding, high frequency induction loop current through the workpiece external coupling and induced current in the workpiece. Strong high-frequency welding is specialized welding method, according to the product is equipped with special equipment. Production rate, welding speed up to 30m/min. When the tube is mainly used for manufacture of longitudinal seam or spiral seam welding.
The absorption rate of the laser material and the material is proportional to the square root of the DC resistivity, and the laser wavelength is inversely proportional to the square root relationship. Angle of incidence greater the absorption rate is smaller. When the laser light perpendicular to the metal surface, the metal absorption maximum of the laser. But usually to protect the laser exit lens, the need to maintain a certain angle of incidence. For low reflectivity can be coated with a thin metal surface layer of metal powder, but both must be able to form alloys. Such as copper, gold, silver can cover the sharp thin layer, then the same penetration in the case of welding the energy required is about the original copper, gold, silver and required a quarter. Quality of the YAG laser welding device, the focus of the (spot size) is the optical path through the device itself precision coaxial output fiber and outgoing head of the imaging ratio to be guaranteed. Laser emitted when the focus falls just above the location of the work is zero. Defocus amount is zero distance from the focus away from this amount. Focus position than the position is called a negative zero defocus (focus down to internal parts), the distance is negative defocus amount. Instead, the focus distance value is less than zero is the amount of defocus. To obtain a larger penetration depth, focus position can be selected within a certain location on the workpiece, that is, using the negative defocus amount of welding. Submerged arc welding can be used to a larger current. Compared with manual arc welding, its biggest advantage is that the weld quality, high welding speed.