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Key points of welding process for duplex steel and stainless steel pipe

Jan 19,2022

Dual-phase stainless steel pipe is restricted by its own metallurgical characteristics, which limits the choice of welding methods. Too high welding line energy and too low welding line energy are not ideal. When the energy of the welding line is too high, the cooling speed of the welded joint is reduced, which is conducive to the transition of ferrite to austenite in the heat affected zone and the weld metal to obtain a sufficient amount of austenite, but it is easy to lead to the growth of ferrite grains, produce harmful intermetallic phases and reduce toughness. Then, let's learn what are the main points of the welding process of dual-phase stainless steel pipes!

Therefore, in addition to the use of electroslag welding, the use of submerged arc welding and molten arc welding is also limited. If the energy of the welding line is too low, the heat affected zone and the austenite precipitation of the weld metal will be reduced, and a single ferrite structure will be produced, which will greatly reduce the performance. Therefore, electron beam welding and plasma arc welding should not be used. At present, the commonly used welding methods of duplex stainless steel are manual arc welding and tungsten argon arc welding.

Manual arc welding of duplex stainless steel pipes is the most commonly used welding method for duplex stainless steel. It is flexible and convenient for all-position welding. Duplex stainless steel is mostly ultra-low carbon, so the coating of the electrode is mostly acidic, and the process performance of the electrode is generally good. Tungsten arc welding is usually used for weld welding at the root of the joint, as well as the welding of pipes, and is also often used for sheet welding. Tungsten arc welding guarantees excellent mechanical properties, especially low temperature toughness.

In recent years, submerged arc welding is also used when welding dual-phase steel and stainless steel pipes, but the energy and interlayer temperature must be controlled, and the appropriate groove form must be selected at the same time. In order to obtain the best performance results, the welding line energy and interlayer temperature need to be optimally selected, and the austenite content of the welding metal is usually controlled within the range of 60% ~ 70%.

When welding duplex steel and stainless steel pipes, multiple welding should be considered as far as possible. Because the back-end welding has a heat treatment effect on the front-end welding, the ferrite in the welding metal is further changed into Auschus, Auschus becomes the dominant two-phase tissue, the number of Auschus in the heat-affected zone adjacent to the welding is also increased, and the overall tissue and performance of the welded joint are improved. On the final welding surface, another process welding is welded. In this way, the so-called heat treatment can be performed on the surface welding and the adjacent welding heat affected zone, which contributes to the improvement of the structure and the improvement of the performance. This process weld can finally be removed by machining. After welding, it is easy to embrittlement without heat treatment (including stress relief treatment and solution treatment). In addition, since care is taken to control the interlayer temperature and line energy, sensitization problems generally do not arise.

The above introduction is the main points of the welding process of duplex steel stainless steel pipe. If you need to know more about stainless steel seamless pipe, stainless steel square rectangular pipe and stainless steel sanitary pipe, please feel free to contact us!