Double-sided argon arc welding process in the stainless steel tank welding application

I. Process Summary

Stainless steel storage tanks, as atmospheric pressure vessels, have large volume, thin design wall plate and other characteristics. The traditional manual electrode welding process in the welding process spatter, welding stress, and one-sided welding easily lead to deformation, welding quality is difficult to ensure. In contrast, the argon arc welding process has the advantages of no spatter and no slag, which is more suitable for welding stainless steel tanks. However, single-sided TIG welding exists ‘slag weld’, chromium depletion, not welded through, the root is not fused and other defects, and the welding internal stress is easy to cause deformation. Therefore, in order to improve the welding quality and non-destructive testing qualification rate, it is recommended to use double-sided weld at the same time for welding double-sided TIG welding process.

Second, application considerations

Weld bevel processing and assembly: strictly control the processing quality of weld bevel and assembly size, including clearance, wrong edge amount, etc., to ensure the smooth progress of the welding process and welding quality stability.

Bevel and heat-affected zone cleaning: the bevel and heat-affected zone must be cleaned and kept dry to prevent impurities and defects in the welding process.

Welding speed and wire feeding speed: the main welding side of the welding process is the same as single-sided argon arc welding, but the auxiliary side of the welder needs to work closely with the main welding side of the welder to maintain the same welding speed. Wire feeding speed needs to be adjusted according to the shape of the molten pool and the experience of the welder to ensure that the inner wall weld is shaped beautifully.

Argon flow and nozzle selection: according to the thickness of the base material and the size of the weld bevel reasonable selection of argon arc welding gun nozzle specifications, and control the argon flow, to ensure that the weld pool and heat-affected zone is fully protected.

Arc quenching and protection: two welders need to arc quenching at the same time, and in the welding arc quenching continued to pass into the argon gas 1 ~ 2 minutes to protect the arc pit from oxidation.

Positioning weld cleaning: wall plate positioning weld must be mechanically cleaned before formal welding to ensure welding quality.

Third, the advantages of the process

Welding quality is high: double-sided TIG welding process can significantly improve the welding quality, high pass rate of radiography, the weld in the wall of the tank is shaped beautifully.

Small deformation: due to the double-sided simultaneous welding, welding stress distribution uniformity, reducing the welding deformation, the tank wall weld forming good.

High working efficiency: the same working surface increases the labour force, which makes the working efficiency increase significantly.

Reduce costs: no need to weld the back of the argon protection and the reverse side of the clear root grinding, saving the argon gas and labour costs.

Fourth, the disadvantages of the process

Difficulty of welding: require each group of welders to cooperate with each other to maintain the same welding speed, increasing the difficulty of welding.

High grouping requirements: strict control of the weld grouping gap, the weld grouping accuracy requirements are high.

In summary, double-sided TIG welding process in stainless steel tank welding has significant advantages, but there are also certain challenges. In practical application, comprehensive consideration needs to be made according to the specific situation to ensure welding quality and safety.