Influence of flame straightening on the properties of welded joints made of X2CrNi22-2 duplex steel

The study investigates the optimal conditions associated with flame straightening of welded joints in duplex steel grade X2CrNi22-2. The research aimed to assess the influence of heat, applied during flame straightening of welded structures in X2CrNi22-2 grade steel, on the properties of the welded joints. Based on the macroscopic, microscopic, and strength tests conducted on welding joints in X2CrNiN22-2-grade duplex steel that have been subjected to flame straightening, it was ascertained that post-welding flame straightening of this grade of steel, at a treatment temperature of 730°C, should not take place for >1 min. The temperature of 730°C has been chosen as a reference because of the assumption that the welded joints are heated to the temperature of 700–730°C during straightening with an acetylene-oxygen flame. The paper scrutinizes the questions of (i) what changes occur in the welded joints as a result of flame straightening carried out in this temperature range and (ii) what impact those changes have on the joint strength. The results of our study indicate that the duration of post-welding flame straightening of X2CrNiN22-2-grade duplex steel, at a treatment temperature of 730°C, should not exceed 1 min.