Austenitic stainless steel valves uses in ultra-low temperature

Austenitic stainless steel is in the austenite under the conditions of use or to the austenite-based stainless steel. Austenitic stainless steel with a variety of superior performance because it contains ferritic, ferritic stainless steel carbon seamless steel pipe is formed containing austenitic weakened elements such as high chromium content ferritic become the dominant phase composition can be used for a variety of different fields, especially excellent low temperature toughness to make it as a structural material has been widely used in cryogenic engineering. Currently, most utilize ultra-low temperature austenitic stainless steel valves. Cryogenics, cryogenic valves are indispensable fluid control device pipeline. Cryogenic valves function consistent with the ordinary valve is utilized to turn on or off line media, adjust the media pressure and flow. Nowadays, cryogenic valves have valve, globe valves, check valves, ball valves, butterfly valves and throttle valves and other types, mainly for the liquefied gas, separation, transport and storage equipment. Temperature up to -270 or less. Cryogenic valves are valves in the low temperature range cryogenic work. Delimitation of its operating temperature, there is not any uniform requirement. Such as Russia (former Soviet Union) the valve of -272 ~ -153 temperature range is called ultra-low temperature valves. Japanese liquefied petroleum gas management rules work less than -150 valve called ultra-low temperature valves. China has already provided ultra-low temperature limit valve. In the valve industry, tend to -100 working temperature limit as cryogenic valves, which is the temperature below -100 valve set at ultra-low temperature valve. This is a material employed to press the valve boundaries approach. That is when the working temperature <100, the main material of the valve selection austenitic stainless steel. Ultra-low temperature working fluid valve not only soothing temperature, and most or toxic, or flammable, and permeability, and therefore determines the valve timber many special requirements. (A) superior low temperature resistance cryogenic valve requires not only can work at the set temperature, but also to ensure performance at normal temperature. Therefore, the selected material is necessary in order to meet the mechanical properties at room temperature, but also subject to the use of temperature on the mechanical performance requirements. In particular, the requirement that materials at extremely low temperatures should have sufficient toughness to prevent brittle fracture under minimal stress. Organizational stability also requires the material to assure that the phase change will not cause dimensional changes during use, resulting in valve seal failure. Compatibility with media cryogenic valve timber should be compatible with the work of the media, that the media has sufficient chemical resistance, ensure that the valve within a period of use, the medium in contact with the chemical and physical properties of the material does not significantly change . Meanwhile, valve timber shall comply with the explosion of media compatibility cryogenic conditions. Low thermal conductivity due to the cryogenic operating temperature of the valve is very low, in order to reduce heat transfer, heat leak control valve in addition to the use of a special structure (heat insulating means), but also selection of a relatively low thermal conductivity material, to reduce heat loss. Valve body material. Good body materials or butt welding performance forge welding structure connected, you should consider welding properties of materials and the use of temperature weld reliability. Deposited required special alloys (such as Co-Cr-W alloy) of the sealing surface should be considered surfacing (spray) the feasibility of the material itself. After analysis, with a face-centered cubic lattice of copper, aluminum alloy and austenitic stainless steel and other materials, because there is no low-temperature brittleness phenomenon, it can be utilized as cryogenic valves timber. Although copper, aluminum has certain advantages, but low-intensity, generally used only for low pressure and small diameter valves. And although 9% nickel steel can be used to -196 conditions, but since complex process, it seldom chooses. Only austenitic stainless steel is suitable as a variety of different pressure levels of ultra-low temperature valve timber.