Three Welding Technologies for Stainless Steel Welded Pipes

Currently, the welding methods of stainless steel welded pipes used in the industry mainly include argon arc welding, high-frequency welding, plasma welding, and laser welding. Several welding methods have their characteristics. At present, the most commonly used ones are argon arc welding and high-frequency welding.

Stainless steel welded pipe technology - Argon arc welding.
Stainless steel welded pipes require deep penetration, no oxide inclusions, and a heat-affected zone as small as possible. Tungsten arc welding with tungsten inert gas protection has good adaptability, high welding quality, and good penetration performance. Its products are widely used in the chemical industry. It is widely used in industries such as the nuclear industry and food. The low welding speed is a shortcoming of argon arc welding. To increase the welding speed, argon arc welding with a three-electrode welding torch is generally used. The wall thickness of the welded steel pipe is S≥2mm. The welding speed is 3-4 times higher than that of a single welding torch. Quality has also improved. The combination of argon arc welding and plasma welding can weld steel pipes with larger wall thickness. In addition, using 5-10% hydrogen in argon gas and using a high-frequency pulse welding power source can also increase the welding speed.

Stainless steel welded pipe technology - High-frequency welding.
Frequency welding has a higher power supply and can achieve higher welding speeds for steel pipes of different materials, outer diameters, and wall thicknesses. Compared with argon arc welding, its welding speed is more than 10 times. Therefore, the production of general-purpose stainless steel pipes has higher productivity. Because of the high speed of high-frequency welding, it makes it difficult to remove burrs in welded pipes. At present, the chemical and nuclear industries do not accept high-frequency welded stainless steel pipes, and this is also the reason. From the perspective of welding materials, high-frequency welding can weld various types of austenitic stainless steel pipes. At the same time, the development of new steel types and the advancement of form welding methods have also successfully welded ferritic stainless steel AISI409 and other steel types.

Stainless steel welded pipe technology - Combined welding technology.
The combined welding methods include argon arc welding plus plasma welding, high-frequency welding plus plasma welding, high-frequency preheating plus three-torch argon arc welding, and high-frequency preheating plus plasma plus argon arc welding. Combination welding can significantly increase the welding speed. For combined welding steel pipes using high-frequency preheating, the weld quality is equivalent to conventional argon arc welding and plasma welding. The welding operation is simple and the entire welding system is easy to automate. This combination is easy to connect with existing high-frequency welding equipment and requires investment: low cost and good benefits.

Various welding methods of stainless steel welded pipes have their advantages and disadvantages. How to maximize strengths and avoid weaknesses and combine several welding methods to form a new welding process to meet people's requirements for stainless steel welded pipe quality and production efficiency is a new trend in the current development of stainless steel welded pipe technology.