The general low-temperature valve means below -29 ℃ ~ -196 ℃ range, -196 ℃ ~ -269 ℃ for the ultra-low temperature range. Petrochemical companies require less than -20 ℃ even at low temperatures. General carbon steel, low alloy steel, ferritic steel, a sharp decline in toughness at low temperatures, increased brittleness. This phenomenon is called the cold brittle phenomenon of the material. In order to ensure the performance of the material, it not only requires the material to have sufficient strength, toughness and processability at normal temperature, but also requires the material to resist the embrittlement at low temperature. In addition, the material shrinks at low temperatures, with various parts shrinkage rates, which is why some seals leak. Therefore, to study the various parts of the material, structure, to prevent the formation of gaps at low temperatures. During the period from the 1970s to the 1980s before the introduction of equipment into our country, the material for making cryogenic control valves was also copper alloy and austenitic stainless steel. At that time, there was no steel standard for cryogenic valves. In 1976, the valve industry for the first time held a cryogenic valve exchange to understand the 300,000 t / a, 115,000 t / a ethylene project cryogenic valve requirements, materials and so on. National "Seventh Five-Year" major equipment research project, listed on the low-temperature valve. Until 1994, formulated the mechanical industry standard JB / T7248-1994 "valve low temperature steel casting technical conditions." In 1995 developed a JB / T \ 7749-1995 "cryogenic valve technical conditions." The company has also been exploring the technological innovation of cryogenic valves, has been gradually introduced in recent years: cryogenic valve, low temperature valve, cryogenic valve and some meet the requirements of the cryogenic valve, the majority of users have won praise, the company in the service users After the launch of various low-temperature valves, to return the majority of users love.