A stainless steel pipe with a diameter of less than 219mm is used in continuous roll forming, which is basically similar to that of a high frequency welded pipe. When the diameter of the tube is greater than 219mm, the pressure forming or spiral welding is used. The tube diameter is less than 4.76mm, and the tube is drawn by drawing after welding.
The welding technology mainly includes high frequency welding, tungsten electrode inert gas protection welding, laser welding and electron beam welding. High frequency welding can not ensure the welding quality of the weld, but the welding speed is relatively large, it is suitable for the production of ordinary structure and decoration of stainless steel welded pipe.
Most of the stainless steel welded pipes are combined with argon arc or argon arc welding and plasma welding. The stainless steel welded pipe for decoration requires grinding and polishing on the surface of the tube. The stainless steel welded pipe used in chemical machinery and boiler heat exchanger requires the welding of the inner wall of the pipe to be leveled. The weld structure is disposed by solid solution and must be equipped with the weld quality monitoring and nondestructive testing system.
Argon arc welding stainless steel welded pipe production process sequence is plate coil longitudinal shear, strip steel, uncoiling, leveling, cutting head and tail butt welding, looper, forming, argon arc welding, welding, puncture, cooling, sizing, eddy current inspection, and finally sawing.
But after cutting stainless steel pipe, stainless steel pipe according to use also divided into three kinds, one is without heat treatment and cold drawing pipe by straightening, flat, pressure, inspection, packing and storage; secondly to heat treatment of welded pipe after degreasing, bright heat treatment, straightening, ultrasonic inspection, flat, water pressure, inspection, packing and final storage; the third is to drawing pipe after degreasing, swaging, annealing, straightening, pickling, lubrication, drawing, cutting head, degreasing, bright annealing, finishing, inspection, packing and storage of the final.
At present, a new welding technology has appeared in stainless steel welded pipe, that is, multi torch welding with multiple electrodes, or combination of argon arc welding and plasma welding. Multi torch welding is suitable for welded pipe with wall thickness greater than 2mm, its welding speed is 3-4 times faster than single torch welding, and the quality of pipe after welding is also optimized. Besides, adding hydrogen to 5%-10% and adding high frequency pulse welding power in argon can effectively enhance the welding speed. In order to ensure the quality of welding, the automatic tracking device for welding seam, arc voltage automatic control system and computer controlled welding process are used.
Remove the thorn inside welding methods are the inner gas holder, droplet wall filled with inert gas to hold the melt pressure, to ensure that no sagging, so as not to generate welding spines; followed by wall hammer technology for diameter less than 30mm diameter pipe; the last is the inner wall of rolling technology for diameter larger than the diameter of 50mm welded pipe; decorative tube to polishing equipment with high efficiency, to increase the degree of surface finish of stainless steel welded pipe.
Source: China Stainless Steel Welded Pipes Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)