Research on solidification crack on austenitic stainless heat resistance steel with a large amount of Phosphorus

- Development of method to prevent solidification crack in austenitic weld metal with a large amount of Phosphorus -

Abstract

New 18-8 high strength austenitic stainless steel with 0.1%P-0.2%Ti-0.2%Nb for super-heater and re-heater tubes in ultra-super critical power plants has been developed using the precipitation hardening of fine intragranular precipitates such as globular M₂₃C₆ carbides, MC type carbides and needle like FeTiP distributed inside grain. The solidification cracking susceptibility of the new 18-8 heat resistance steel was investigated by varying the Cr_eq/Ni_eq and phosphorus amount. It was clarified that the solidification cracking susceptibility of new 18-8 heat resistance steel decreased by increasing Cr_eq/Ni_eq to increase the amount of δ ferrite crystallization and promote the progress of welding solidification by (Nb,Ti)C crystallization in terms of microsegregation behavior using the numerical model.