Effects of Welding Conditions and Post-Weld Heat Treatment on Precipitation of Widmanstaetten-Austenite of Duplex Stainless Steels

摘要

In the case of welding for duplex stainless steel, the welds change in the morphology and ferrite/austenite phase ratio due to the welding conditions and the alloy composition of the material itself. Especially when using the laser beam welding what has the ultra-high heat input and rapid cooling, the change in the welds is much pronounced. Therefore, in this study, after etching the welds of the samples with 10% KOH solution, we have observed the microstructure changes of three different duplex stainless steels under different welding conditions. The results of the experiment of duplex stainless steels, super duplex, and lean-alloy duplex showed that the structure of the welds was significantly different between the steel grades; it was found that the increase in welding velocity significantly reduced the formation of the austenite phase. To counterbalance the ratio of ferrite/austenite phase by using the laser surface treatment after welding, it has become possible to promote a part of the content of the austenite phase even in the welds. In addition, these results could become a basis and verification for the simulation of the duplex stainless steels' welds microstructure in the future.