What are the production characteristics of stainless steel welded pipes?

Stainless steel welded pipes with a pipe diameter less than φ219mm use continuous roll forming, which is basically the same as high-frequency straight seam welded pipes. For pipes with a diameter greater than φ219mm, pressure forming or spiral welding is used. Capillary tubes whose diameter is less than φ4.76mm are made by post-weld drawing method.
The main welding processes include high frequency welding, tungsten electrode inert gas shielded welding, laser welding and electron beam welding. High-frequency welding cannot ensure the welding quality of the weld, but the welding speed is relatively high and is suitable for the production of ordinary structural and decorative stainless steel welded pipes.
Most stainless steel welded pipes are welded using argon arc welding or a combination of argon arc welding and plasma welding. Decorative stainless steel welded pipes require grinding and polishing of the pipe surface. Stainless steel welded pipes used in chemical machinery and boiler heat exchangers require the welding spurs on the inner wall of the pipe to be smoothed. The weld structure must be solid solution treated and equipped with a weld quality monitoring and non-destructive testing system.
The production process flow of argon arc welded stainless steel pipes is coil slitting, strip steel, uncoiling, leveling, cutting butt welding, looper, forming, argon arc welding, external welding spur removal, cooling, sizing, Eddy current flaw detection, followed by saw cutting.
The stainless steel welded pipes after cutting are divided into three situations according to the use of the stainless steel welded pipes. One is the welded pipes that do not need to be heat treated and drawn, which have been straightened, flattened, hydraulically pressed, inspected, packaged and stored; the second is those that require heat treatment. The welded pipe undergoes degreasing, bright heat treatment, straightening, ultrasonic flaw detection, flat head, hydraulic pressure, inspection, packaging and final storage; thirdly, the welded pipe to be drawn undergoes degreasing, forging, annealing, straightening, pickling, lubrication, Drawing, cutting, degreasing, bright annealing, finishing, inspection, packaging and final storage.
At present, a new welding process technology has emerged for stainless steel welded pipes, that is, multi-torch welding using multiple electrodes, or a combination of argon arc welding and plasma welding. Multi-torch welding is suitable for welded pipes with a wall thickness greater than 2mm. Its welding speed is 3-4 times faster than single-torch welding, and the quality of the pipe after welding is also optimized. In addition, adding 5%-10% hydrogen to argon and then using a high-frequency pulse welding power source can effectively increase the welding speed; to ensure the welding quality, an automatic tracking device for the welding seam by the welding torch and an automatic arc voltage control system are used. Computer controlled welding process etc.
The main method to remove internal welding spurs is the inner wall gas support technology. The inner wall is filled with a certain pressure of inert gas to support the molten droplets to ensure that they do not sag so that no welding spurs are generated; the second is the inner wall hammering technology, which is used for low-diameter welding. For pipes with a diameter of φ30mm; the latter is inner wall rolling technology, which is suitable for welded pipes with a diameter greater than φ50mm; decorative pipes must be equipped with high-efficiency grinding and polishing equipment to increase the surface finish of the stainless steel welded pipes.