The high temperature grades of high temperature valves are divided into five levels, namely, the valve working temperature t>425~550℃ is PI grade, the working temperature t>550~650℃ is PII grade, the working temperature t>650~730℃ is PⅢ grade, the working temperature t>730~816℃ is PⅣ grade, and the working temperature t>816℃ is PV grade. The main materials of PI and PⅡ grade high temperature valves can be selected from stainless heat-resistant steels such as ZG0Cr19Ni11Ti, ZG1Cr18Ni9Ti, 321 and 321H or CF8, 304 and 304H. If the PI grade high temperature valve is used for water and steam, WC6 and WC9 can be selected. If the medium is water, steam and oil, CS (ZG1Cr5Mo) and other Cr-Mo high temperature steels can be selected. CFSM, 316 and 316H stainless heat-resistant steels can be selected for PⅢ and PⅣ grades. PIV grade can also use CK-20, 310 and 310H high chromium nickel stainless heat-resistant steel. PV grade high temperature valves can choose reasonable materials that can meet the use of the valve according to its working medium, working pressure and the special design method adopted. However, the Cr-Mo heat-resistant steel used in high temperature valves should be smelted in an electric arc furnace and a high temperature resistant smelting process should be used.
