What are the requirements of national standard valves are commonly used materials

Valve body, valve cover, flange material, should be selected according to conditions of use and manufacturing requirements, and shall comply with GB, 12229 GB, 12228 GB and 12230 GB 3077. Nut, bolt, stud material available A5, 25, 35, 30 crmoa and 40 MNVB, etc. , should be selected according to working pressure and temperature, and shall comply with the provisions of GB 700, GB and 699 GB 3077. Shall not be used for precision casting nominal pressure PN > 10. 0 mpa. The graphite materials should be paid attention to the following situations might occur: carbon steel is higher than 425 ℃; When carbon molybdenum steel is higher than 470 ℃; Chrome molybdenum steel ( Chromium 0. Less than 6%) Higher than 525 ℃. The following situations should be paid attention to the possibility of peroxide reaction ( Scale) : 1 cr - higher than 565 ℃ or more 0. 5 mo steel, 1. 25 cr - 0. 5 mo steel, 2 cr - 1 and 3 cr - mo steel 1 mo steel is higher than 595 ℃ or more cr - 5 0. 5 mo steel.