What are the special material requirements for cryogenic valves?

Cryogenic valves are used to control cryogenic media (such as liquefied natural gas, liquid oxygen, liquid nitrogen, etc.), and have special performance requirements for materials to ensure safe and reliable operation at extremely low temperatures. The following are the main material requirements for cryogenic valves:

1. Low temperature resistance

Low temperature impact toughness: The material must maintain good impact toughness at low temperatures to prevent brittle fracture. Austenitic stainless steel (such as 304, 316) has a face-centered cubic structure and excellent low temperature toughness, and is a common choice.

Organizational stability: The material should not undergo organizational transformation at low temperatures to avoid performance degradation due to phase change. Austenitic stainless steel and martensitic stainless steel have stable organizations at low temperatures and are suitable for low temperature applications.

2. Compatibility with cryogenic media

Corrosion resistance: The material cannot react chemically with the cryogenic medium to cause corrosion. For example, in oxygen media, antioxidant materials must be selected to avoid combustion and explosion.

Pollution-free: The material must not contaminate the medium, especially in the fields of food and medicine, and non-toxic and odorless materials such as stainless steel and certain polymer materials should be selected.

3. Low thermal conductivity

Reduce cold loss: In order to reduce the evaporation of low-temperature media, materials with lower thermal conductivity should be selected as much as possible. For example, materials with low thermal conductivity are used to manufacture valve bodies and valve covers to reduce cold transfer.

Prevent frost and ice: Low thermal conductivity materials can delay or avoid frost and ice on the valve surface, ensuring normal operation and maintenance of the valve.

4. Good hardness and wear resistance

Prevent damage to the sealing surface: Under low-temperature oil-free lubrication conditions, the material must have sufficient hardness and wear resistance to prevent wear and leakage of the sealing surface. The sealing surface is usually hardened, such as surfacing with hard alloy.

Reduce friction and wear: The materials of moving parts such as valve stems and packings should have good self-lubrication and wear resistance, such as hard chrome plating, nitriding or wear-resistant alloys.

5. Good processing and welding performance

Easy to process and manufacture: The material should have good cutting and forming properties, which is convenient for manufacturing complex valve parts and ensuring dimensional accuracy and surface quality.

Excellent welding performance: For parts that need to be welded, the material should have good weldability, and the welded joints should still maintain sufficient strength and toughness at low temperatures.

6. Other special requirements

Dimensional stability: The material should have good dimensional stability at low temperatures to avoid valve deformation or seal failure due to cold shrinkage.

Anti-fatigue performance: For valves that are frequently operated at low temperatures, the material must have good fatigue resistance to prevent breakage due to cyclic loads.

The material selection of cryogenic valves is crucial, and factors such as low temperature resistance, medium compatibility, thermal conductivity, hardness, wear resistance, and processing and welding performance need to be considered comprehensively. Reasonable material selection and appropriate material processing technology can ensure the safe operation and service life of cryogenic valves under extreme conditions.