Stainless steel fasteners
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For connection using rings (RJ), with a pressure of 26 MPa and a temperature of 485°C, what are the requirements for using fully threaded studs made of 0Cr18Ni9?
Using 0Cr18Ni9 studs, what size is the flange? Will the calculation show it’s feasible?
1. The most important thing is to ensure that the calculations are successful, that the requirements regarding flange pre-tensioning and operating forces are met, and that a certain margin is left compared to the actual required forces; it’s best to use Lansys or SW6 for these analyses. 2. Thread processing requirements are needed during manufacturing. 3. Check if there are any requirements regarding the supply of materials.
It is not recommended to use stainless steel at high temperatures; 35CrMoA is suggested instead
Why are stainless steel used for fasteners as well?
Stainless steel threads tend to seize, so they are not recommended. It is possible to check the allowable temperature for 35CrMoA as well as the allowable stress at 485 degrees, in order to determine whether the strength requirements are met.
If studs made of 35CrMoA material are used, it is best to coat them with cadmium for corrosion protection.
Under normal circumstances, the use of stainless steel fasteners is not recommended for the following reasons: 1. The strength of stainless steel is relatively low compared to that of Cr-Mo fasteners； 2. Stainless steel has too good ductility, and during pressure testing, it is more prone to stress relaxation than Cr-Mo steels ； 3. It is difficult to ensure a consistent hardness difference among stainless steel fasteners, which makes them prone to seizing during installation and use ； If factors such as corrosion resistance are not a concern, 35CrMoA or 25Cr2MoVA are generally used. If the temperature exceeds 550 degrees, ASME B16 materials can be considered; if relaxation is a concern, disc springs can be added. The above represents only my personal understanding; please feel free to point out any errors