Sigma Phase Formation of Type 310 Stainless Steel in a Lime Kiln Burner Nozzle

摘要

Sigma phase formation in type 310 SS between 1,500 and l,800 deg F, after a year of service, substantially reduces ductility and impact energy when compared to the unexposed condition. The remaining ductility is enough to allow partial nozzle replacement of wrought material by welding without annealing, however. Welding of type 310 SS can be performed using the matching filler metal and maintaining preheat and interpass temperatures approx 300 deg F to prevent fissuring of the fully austenitic weld. Annealing to redis-solve sigma phase in the microstructure and improve impact energy should be considered if the nozzle could be subject to impact conditions in operation.