-For devices operating at 110 degrees, since a stainless steel casing is used, does the issue of carburization also need to be considered?
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In general, stainless steel equipment should be kept away from carbon steel to prevent decarburization. For equipment for which corrosion protection is not a concern and that operates at temperatures as low as -110 degrees Celsius, if the casing is made of stainless steel, it is necessary to consider whether carbon penetration may occur in the internal components as well. And why choose stainless steel?
If it is only -110 degrees and there are no corrosion requirements, it is best to use nickel-grade steel, such as 5Ni steel; **standards already exist for this.
It’s best to use stainless steel for built-in components, as it is convenient for procurement and manufacturing
For corrosive media, if the internal components are made of carbon steel, corrosion occurs particularly rapidly under stress.
Reply to 2# dqgousw: It’s not allowed. Carburization takes into account not only resistance to chemical corrosion; in an atmospheric environment, stainless steel contaminated by carbon steel will also rust rapidly. Therefore, direct contact should never occur, unless stainless steel gaskets are used. Furthermore, ignoring economic factors, 304 is definitely a better low-temperature steel than 5Ni in terms of toughness, weldability, and corrosion resistance. It’s just that the tensile strength and yield strength are lower; therefore, unless it’s a large storage tank, 304 is recommended
5Ni and 9Ni steels are currently difficult to obtain, as the domestic manufacturing processes are not very advanced, especially in terms of welding. Stainless steel does not have this kind of drawback, but it has certain limitations; for example, its strength is relatively low. When constructing large-scale shells, a much greater thickness is required, which is not cost-effective. Thick stainless steel is also more difficult to obtain. In such cases, 5Ni and 9Ni steels are better choices. The common grades of 5Ni steel in China are A645; for 9Ni steel, they are A353/A553 and 06Ni9DR. Our company sells these low-temperature nickel steels, with no minimum order quantity required. Wugang Panglong
304 is the best choice; our cryogenic liquid storage tanks are also made of 304