Research and Development of a New Austenitic Heat-Resisting Steel SP2215 for 600-620°C USC Boiler Superheater/Reheater Application

Abstract For raising thermal efficiency and decreasing CO2 emission, China had constructed the first 600°C ultra-supercritical(USC) fossil power plant in 2006. Now more than a hundred 600°C, 1000MW USC electric power units have been put in service. Recently, China has also developed 620°C USC power units and some of them have been put in service already. Meanwhile, more than fifty 620°C USC boilers will be produced by various China boiler companies. The austenitic steels TP347H, Super304H and HR3C are routinely used for 600°C USC boilers. Among these steels, a big amount of Super304H has been used for boiler superheater/reheater components application. However, Super304H is characterized by good stress-rupture strength but poor corrosion/oxidation resistance. On the other side, HR3C is characterized by very good corrosion/oxidation resistance but lower stress-rupture strength than Super304H. Now, the China 620°C USC project needs a new austenitic heat resisting steel with high stress-rupture strength and good corrosion/oxidation resistance to fulfill the superheater/reheater tube components application requirement. A new austenitic heat resisting steel SP2215 is based on 22Cr-15Ni with certain amount of Cu and also Nb and N for multiphase precipitation (MX, Cu-rich phase, NbCrN) strengthening in Fe-Cr-Ni austenitic matrix and M23C6 carbide precipitation at grain boundaries. This SP2215 new austenitic steel is characterized by high stress-rupture strength (650°C, 105h>130MPa) and good corrosion/oxidation resistance. SP2215 austenitic steel has been commercially produced in tube product form. This SP2215 new austenitic heat-resisting steel is recommended to be used as superheater/reheater components for 620°C USC boiler application.