The widespread use of stainless steel expansion bellows is owing to the excellent compensation capacity and reliability, and reliability is assured by multiple factors as design, material selection and manufacturing level, false on any procedure will lower the reliability of ss expansion bellows.
It is strict to select material for ss expansion bellows, because material selection is related to many crucial parameter performance. Comprehensive consideration is necessary, including working temperature, working medium, external environment, stress corrosion, also take material welding forming and cost performance into account.
ss expansion bellows
The material selection of ss expansion bellows should meet following requirements:
1.Cyclic stress must be taken into account. It’s necessary to choose high yield strength and long fatigue life material for the stainless steel expansion bellows.
2.Another factor can’t be ignored is working temperature. The normal working temperature of ss expansion bellows is form -196℃ to 750℃. Under high temperature, most material will drop value on elasticity and fatigue life.
3.Plasticity should be excellent enough to convenient for process and forming. Also to pass the treatment process of cold hardening and heat treatment to obtain sufficient hardness and strength.
4.Since thin-wall stainless steel expansion bellows is really sensitive to stress corrosion, so the bellows material must be corrosion resistant to working environment.
5.Ensure a high elastic limit, tensile strength and fatigue strength to ensure normal operation of ss expansion bellows.
6.Welding property should be satisfied to meet the requirements of welding process.
Austenitic stainless steel is the most commonly applied material for ss expansion bellows, familiar seen material types includes SS304, SS304L, SS316, SS316L. For some special application such as heat supply pipe network laying in trench, when bellows is installed in lower terrain, bellows dipped in rain water or sewage water, it is suggest to choose iron-nickel alloy or high-nickel alloy which owns higher corrosion resisting performance. But consider of high cost, we can only add one layer of corrosion resistant alloy on the touch surface of bellows to save cost.
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