Bellows material selection is the emphasis in manufacturing process, most performance of steel bellows expansion joint is decided by bellows material. Improper bellows material selection may cause unbalance welding, irregular corrugation, surface injury, etc..
The bellows material selection of steel bellows expansion joint should take flowing medium and working temperature into account, besides, stress corrosion, water treatment agent and pipe cleaning agent affect, welding, material cost performance also should be considered.
So what conditions that the steel bellows material should satisfy? Firstly, good corrosion resistance property. The bellows material of steel bellows expansion joint should meet the working requirements in different environment. Secondly, high elastic limit, high fatigue strength and high strength of extension. Thirdly, good plasticity to convenient for the processing of steel bellows expansion joint, also to afford later cold hardening and heat treatment. Last, good welding performance.
As we known, most steel bellows expansion joint manufacture use stainless steel material as the bellows material. But actually there are so many type of stainless steel such as 304, 304L, 310S, 316, 316L, 321 and so on, each material has unique temperature and corrosion resistance property. If the flowing medium is non-corrosive medium like water, oil or gas, and temperature between 100 to 200 degree Celsius, SS304 is a good choice; and if the flowing medium is seawater or acid-base oil or gas, SS316 or SS316L is a preferential choice.
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