Stainless steel welded pipe is also called welded stainless steel pipe. Laser cutting pipes to process stainless steel plates or strips is usually rolled into stainless steel pipes through a unit and a die, and then welded into stainless steel pipes. The production process of this product is relatively simple, the production efficiency is also relatively good, and there are many varieties and specifications. Traditionally, its use strength is not as good as seamless steel pipes. However, with the development of technological level and production equipment, the quality of welded pipe welds in laser cutting pipe processing has been continuously improved, and stainless steel seamless pipes have been replaced in many fields, especially in heat exchange equipment, decorative pipes and medium and low pressure fluid pipes.
At present, the main production processes of stainless steel welded pipes mainly include argon arc welding, high frequency welding, combined welding and so on. The advantages and disadvantages of these stainless steel processing techniques are described in detail below.
Stainless steel pipe welding process-argon arc welding
Because stainless steel welded pipes need to be welded through, without oxide inclusions, and the heat-affected zone is as small as possible, the TIG welding process has good adaptability, high welding quality, and good penetration performance. Stainless steel welded pipes of this process are mainly used in chemical, nuclear, food and other industries.
But the disadvantage of argon arc welding is that the welding speed is not high. In order to increase the welding speed, the method of single electrode and single torch was adopted, and the welding method of multiple electrodes and multiple torches was developed. In the 1970s, Germany first used multiple welding torches to arrange in a straight line along the welding seam to form a longer heat flow distribution, which greatly increased the welding speed. Generally, three welding guns are used for argon arc welding. The wall thickness of the welded steel pipe exceeds 2mm, the welding speed is 3-4 times higher than that of single torch welding, and the welding quality is also improved. The combination of argon arc welding and plasma welding can weld steel pipes with larger wall thickness. In addition, 5-10% hydrogen in argon and high-frequency pulse welding power sources can also increase the welding speed. Laser cutting pipe processing multi-torch argon arc welding is suitable for welding austenitic and ferritic stainless steel pipes.
Stainless steel welded pipe technology-high frequency welding
High frequency welding has been used in the production of carbon steel welded pipes for nearly half a century, but it is a relatively new technology for stainless steel welded pipes. Because of its good economic benefits, it is often used in architectural decoration, household appliances, mechanical structures and other fields.
The high frequency welding efficiency is very good, and it has a higher welding speed for stainless steel pipes of different materials, outer diameters and wall thicknesses. The welding speed is more than 10 times that of argon arc welding. Therefore, it is very cost-effective to produce ordinary stainless steel welded pipes.
However, due to the high speed of high-frequency welding, it is difficult to eliminate the internal burrs of the laser cutting pipe. Therefore, high-frequency welded stainless steel pipes cannot be used in industries with high quality requirements such as the chemical and nuclear industries.
In addition, various types of austenitic stainless steel pipes can be welded by high frequency.
Stainless steel welded pipe process-combined welding process
Because various welding methods have advantages and disadvantages, in order to make full use of the advantages and avoid disadvantages, the combination of various welding methods forms a new welding process that can meet the quality and production efficiency of stainless steel welded pipes. This is also the technology of stainless steel welded pipes. The development direction is now and in the future.
Combination welding methods are: argon arc welding and plasma welding, high frequency welding and plasma welding, high frequency preheating and three torch argon arc welding, high frequency preheating and plasma argon arc welding. Combination welding can significantly increase the welding speed. The welding quality of the high-frequency preheating combination welded steel pipe is equivalent to that of conventional argon arc welding and plasma arc welding. The welding operation is simple, and the entire welding system is easy to realize automation. The combination is easy to connect with the existing high-frequency welding equipment, has low investment cost and good returns.
With the continuous growth of stainless steel consumption demand, stainless steel pipes are increasingly used in people’s lives. Even in the traditional application fields of other materials, stainless steel pipes are being replaced, especially industrial stainless steel welded pipes, which have penetrated into various aspects, such as automobiles, shipbuilding, construction, environmental protection, pressure pipes, and mechanical parts.