General requirements for common materials of GB valves shared by JIS Marine valve Supplier.
1) the materials of valve body, bonnet and flange shall be selected according to the service conditions and manufacturing requirements, and shall comply with the provisions of GB 12228, GB 12229, GB 12230 and GB 3077.
2) the bolt and stud materials can be A5, 25, 35, 30CrMoA and 40MnVB, etc., which should be selected according to the use pressure and temperature, and should meet the provisions of GB 700, GB 699 and GB 3077.
3) nut materials available A3, 20, 30, 35, 45, 3030CrMoA and 40MnVB, should be selected according to the use of pressure and temperature, and should be in accordance with the provisions of GB 700, GB 699 and GB 3077.
4) precision casting parts shall not be used for valves with nominal pressure PN>10.0MPa.
5) attention should be paid to the possibility of graphitization of materials in the following situations:
A. carbon steel is higher than 425 ℃;
B. carbon molybdenum steel is higher than 470 ℃;
C. chrome molybdenum steel (including chromium below 0.6%) is higher than 525 ℃.
6) attention should be paid to possible peroxide reactions (peeling) in the following situations:
A. higher than 565 ℃ or more Cr 1-0.5, 1.25 Cr – 0.5 Mo Mo steel steel, 2 Cr Mo – 1 and 3 Cr Mo steel – 1 steel;
B. about higher than 595 ℃ above 5 cr – 0.5 Mo steel.