The Study on Welding HAZ Microstructure of SAF 2507 Duplex Stainless Steel by Simulation Tests

Thermal simulation by GLEEBLE3800 is adopted to obtain the simulated welding HAZ microstructures in SAF 2507 duplex stainless steel with the GLEEBLE3800 thermal simulation machine. The simulation peak temperatures are 800oC, 900oC, 950oC, 1000oC, 1050oC and 1100oC, The cooling velocities are t12/8=3.6s, 7s, 20s and 40s (t12/8 is cooling time of 1200oC to 800oC which is used to describe the cooling rate). The results indicate that the peak temperatures have significant influence on the microstructures of austenite and ferrite. At 900oC, the content of σ phase precipitation reaches the maximum, which is distributed mainly in α or at α/γ junction. When the temperature is set above 1050oC, the σ phase disappears. A faster cooling rate passing through 800~1050oC is required to avoid brittle σ phase precipitation.