What special requirements for the selection of the valve stem of the forged stee

Material for manufacturing valve parts shall be selected according to the following factors:
1, working medium pressure, temperature and characteristics.
2, the force of the part and the role of the valve structure.
3, have better technology.
4, in meeting the above conditions, to have a lower cost.
Stem material
Valve stem in the opening and closing process of the open and close, the tension, pressure and torsion force, and with the medium direct contact, while the relative friction between the filler, so the valve stem material must be guaranteed at the specified temperature has sufficient strength and impact toughness, has a certain resistance to corrosion and abrasion resistance, and good technology.
Common stem material has the following.
A, carbon steel
For water, steam medium low and medium temperature does not exceed 300 DEG C, generally used in the A5 plain carbon steel.
For water, steam medium and medium temperature less than 450 DEG C, general selection of 35 carbon steel.
Two, He Jingang
For medium pressure and high pressure, the medium temperature is no more than 450 degrees Celsius water, steam, oil and other media, the general selection of 40Cr (Ge Gang).
For high pressure, medium temperature is not more than 540 degrees Celsius water, steam and other media, can choose 38CrMoALA nitriding steel.
For high pressure steam medium, medium temperature does not exceed 570 DEG C, generally used 25Cr2MoVA chrome molybdenum vanadium steel.
Three, stainless steel
For medium pressure and high pressure, medium temperature is not more than 450 degrees of non corrosive medium and weak corrosive medium, can choose 1Cr13, 3Cr13, 2Cr13 chromium stainless steel.
For corrosive media, Cr17Ni2, 1Cr18Ni9Ti, Cr18Ni12Mo2Ti, Cr18Ni12Mo3Ti and other stainless steel and PH15-7Mo precipitation hardening steels can be used.
Four, heat resistant steel
When the temperature of the medium is not more than 600, the 4Cr10Si2Mo martensitic heat resistant steel and 4Cr14Ni14W2Mo austenitic heat resistant steel can be used.