General requirements for common materials for GB valves

1) The material of the valve body, valve cover and flange should be selected according to the use conditions and manufacturing requirements, and should comply with the provisions of GB 12228, GB 12229, GB 12230 and GB 3077.
2) Bolt and stud materials can be used A5, 25, 35, 30CrMoA and 40MnVB, etc., should be selected according to the use pressure and temperature, and should meet the requirements of GB 700, GB 699 and GB 3077.
3) Nut material can be used A3, 20, 30, 35, 45, 3030CrMoA and 40MnVB, etc., should be selected according to the use pressure and temperature, and should meet the requirements of GB 700, GB 699 and GB 3077.
4) Precision castings shall not be used for valves with a nominal pressure PN > 10.0 MPa.
5) Attention should be paid to the possible graphitization of materials in the following cases:
a. When the carbon steel is higher than 425 ° C;
b. carbon molybdenum steel is higher than 470 ° C;
c. Chromium-molybdenum steel (containing less than 0.6% chromium) is higher than 525 °C.
6) In the following various situations, attention should be paid to the possible peroxygen reaction (epiding):
a. 1Cr-0.5Mo steel, 1.25Cr-0.5Mo steel, 2Cr-1Mo steel and 3Cr-1Mo steel above 565 °C;
b. 5Cr-0.5Mo steel above about 595 °C.