Di bawah rendah suhu syarat, the tensile kekuatan dan kekerasan daripada bahan peningkatan, keplastikan dan keliatan berkurangan, and exhibit varying degrees of low-temperature brittleness, seriously affecting the normal operation of the valve. Therefore, in the selection of materials for low-temperature valve components, the following points must be noted:
(1) The minimum operating temperature of the valve;
(2) The mechanical properties necessary to ensure that the parts do not lose their working ability at low temperatures, especially low-temperature impact toughness, relative elongation, and organizational stability;
(3) Pastikan itu the parts meet the compatibility conditions for low-temperature medium explosion-proof performance,
(4) Pastikan the necessary thermal physical properties of the parts, including thermal conductivity, cold shrinkage performance, etc;
(5) Pastikan itu bahagian mempunyai perlu haus rintangan bawah rendah suhu dan bebas minyak pelinciran syarat;
(6) Ensure that the parts have the necessary corrosion resistance;
(7) Bila menggunakan kimpalan, the welding performance of the material should also be considered.
1. Material pemilihan for low-temperature valve body, valve cover, valve seat, opening and closing parts, etc
Ferritic stainless steel can be used when the temperature is above -100 degree , austenitic stainless steel can be used when the temperature is below -100 degree , and copper alloy or aluminium alloy can be used for low pressure and small diameter valves.
2. Pemilihan daripada Rendah Suhu Injap Stem Bahan
Made of austenitic stainless and acid resistant steel, appropriate heat treatment is required to improve tensile strength, and hard chromium plating (coating ketebalan 0.04-0.06mm) or nitriding treatment must be carried out to improve surface hardness.
3. Pemilihan daripada Pengikat Bahan untuk Rendah Suhu Injap
Bila the temperature is higher than -100 degree , the bolt material is made of alloy steel such as Ni and Cr Mo, which needs to undergo appropriate heat treatment to prevent thread bite; When the temperature is low {{}} degree , austenitic stainless steel can be used as the bolt material. The nut material is generally Mo steel or Ni steel, and the thread surface is bersalut with disulfide key.
4. Pemilihan daripada gasket bahan untuk suhu rendah injap
Bila the operating temperature is above -196 degree and the maximum operating pressure at low temperatures is 3MPa, asbestos rubber sheets made of long fiber self asbestos can be used; When the operating temperature is above -196 degree and the maximum operating pressure at low temperatures is 5MPa, stainless steel asbestos wound gaskets, stainless steel PTFE wound gaskets, or stainless steel expanded graphite luka gaskets can be used.
It should be emphasized that all low-temperature material components must undergo cryogenic treatment before precision machining to reduce the shrinkage deformation of low-temperature valves under low-temperature conditions.
