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Main material of low temperature valve

(1) Factors to be considered in the selection of main material

From the metallographic perspective, in addition to austenitic steel, copper and aluminum with face-centered cubic lattice in metal materials, the general steel will appear low-temperature brittleness at low temperature, thus reducing the strength and service life of the valve. When selecting the main material, the material suitable for working at low temperature should be selected first. Aluminum will not appear low temperature brittleness at low temperature, but because the hardness of aluminum and aluminum alloy is not high, the wear resistance and abrasion resistance of aluminum sealing surface is poor, so the use of low temperature valve has certain restrictions, only in low pressure and small diameter valve selection.

The material working at low temperature should ensure its low temperature performance, mainly to ensure its cold impact strength. The inner parts of the valve must have sufficient cold impact strength through correct material selection

Degree, in order to prevent breakage. C and Cr alloy steels quickly lose impact strength below -20 ° C, so service temperatures are limited to -30 ° C and -50 ° C, respectively. Nickel steel containing 3.5% Ni can be used up to -100℃, and nickel steel containing 9% Ni can be used up to -192℃. Austenitic stainless steel, nickel, Monel, Hastelloy, titanium, aluminum alloy and bronze can be used at lower temperatures (-273 ° C). In addition, the selection of low temperature valve materials should also consider the following factors: 1) the minimum service temperature of the valve;

(2) mechanical properties of metal materials required to maintain working conditions at low temperatures, especially impact toughness, relative elongation and tissue stability;

(3) under the condition of low temperature and no oil lubrication, it has good friction resistance;

(4) It has good corrosion resistance;

(5) The welding performance of the material should also be considered when welding connection is adopted.