The gasket material should be selected to suit the service environment. The gasket material should be softer than the flanges in which the gasket is installed. The most popular ring joint materials with maximum hardness and identification mark are shown in the table below. For more highly specialized applications, ring joint gaskets can be machined from duplex stainless steels and other exotic materials such as Monel®, Inconel® Incoloy®, and Hastelloy®.
|Material||Maximum Hardness HRB||Mark|
|Carbon and low alloy steel||68||S-4|
|304 stainless steel||83||S304-4|
|316 stainless steel||83||S316-4|
|Nickel alloy UNS N08825||92||825-4|
|Other CRA materials||*A||UNS number-4|