Austenitic stainless steel can be welded by argon tungsten arc welding (TIG), molten argon arc welding (MIG), plasma argon arc welding (PAW) and submerged arc welding (SAW). Austenitic stainless steel has a low welding current because of its low melting point, low thermal conductivity, and large resistivity. Narrow welds and beads should be used to reduce high temperature residence time, prevent carbide precipitation, reduce weld shrinkage stress, and reduce thermal crack sensitivity. After the welded pipe is formed and welded, the intergranular arrangement of the steel can be restored by heat treatment. Hangao Tech thermal insulation type online bright annealing furnace extends the heating time of the pipe by increasing the thermal insulation section, so that the weld and the base material can be better integrated.
The composition of welding material, especially Cr and Ni alloying elements, is higher than that of base material. Use welding materials containing a small amount (4-12%) of ferrite to ensure good crack resistance (cold cracking, hot cracking, stress corrosion cracking) performance of the weld. When the ferrite phase is not allowed or impossible in the weld, the welding material should be the welding material containing Mo, Mn and other alloy elements.
The C, S, P, Si, and Nb in the welding material should be as low as possible. Nb will cause solidification cracks in the pure austenite weld, but a small amount of ferrite in the weld can be effectively avoided. For welding structures that need to be stabilized or stress-relieved after welding, Nb-containing welding materials are usually used. Submerged arc welding is used to weld the middle plate, and the burning loss of Cr and Ni can be supplemented by the transition of the flux and the alloy elements in the welding wire; due to the large penetration, attention should be paid to prevent the generation of hot cracks in the center of the weld and the corrosion resistance of the heat affected zone Sexual reduction. Attention should be paid to choosing a thinner welding wire and a smaller welding heat input. The welding wire needs to have low Si, S, and P. The ferrite content in the heat-resistant stainless steel weld should not exceed 5%. For austenitic stainless steel with Cr and Ni content greater than 20%, high Mn (6-8%) welding wire should be selected, and alkaline or neutral flux should be used as the flux to prevent the addition of Si to the weld and improve its crack resistance. The special flux for austenitic stainless steel has very little increase of Si, which can transfer alloy to the weld and compensate the burning loss of alloy elements to meet the requirements of weld performance and chemical composition.
