Duplex stainless steel welding characteristics

After the normal solid solution treatment (1020℃ ~ 1100℃ heating and water cooling), the steel contains about 50% ~ 60% austenite and 50% ~ 40% ferrite structure. With the increase of heating temperature, the ratio of two phases does not change significantly.
Duplex stainless steel has good low temperature impact toughness, such as 20mm thick plate transverse sample at -80℃ impact absorption work can reach more than 100J. In most media, its uniform corrosion resistance and point corrosion resistance are good, but it should be noted that this kind of steel in the heat treatment below 950℃, due to the precipitation of σ phase, its stress corrosion resistance will be significantly worse. Due to the appropriate ratio of Cr equivalent to Ni equivalent of the steel, there is still a large number of primary austenite structure after high temperature heating, and secondary austenite can be generated in the cooling process, and the total amount of austenite phase in the steel is not less than 30% to 40%, so that the steel has good intergranular corrosion resistance.
In addition, as mentioned earlier, the tendency to crack is very low when welding this steel, and preheating and post-welding heat treatment are not required. Due to the high N content in the base material, the welding near the seam zone will not form a single phase ferrite zone, and the austenite content is generally not less than 30%. Applicable welding methods include argon tungsten arc welding and electrode arc welding, generally in order to prevent grain coarsening in the near seam area, low line energy welding should be used as far as possible when welding.