What is the exact material of the octagonal gasket labeled as \"soft iron\"?
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What is the exact material of the octagonal gasket labeled as \"soft iron\"? Can it be used in an environment with hydrogen, hydrogen sulfide, and ammonia, at a pressure of 13.63 MPa and temperatures ranging from 366 to 260 Rankine? The flange is made of 16MnR-HIC. Thank you!! This post was last edited by HeartOfTheOcean on 2009-3-27 at 22:25
Soft iron generally refers to steel grades 08 or 10; the material of the gasket should be the same as that of the flange, although its hardness should be lower than that of the flange in order to ensure a good sealing effect. You only mentioned the pressure of the medium – temperature also needs to be taken into account. It’s not possible to determine everything solely based on the medium and pressure, but it is basically not suitable.
Soft iron should be a pure iron gasket; octagonal gaskets are available in various materials such as soft iron, grade 10 steel, 304, 316, 304L, 316L, and Cr-Mo alloy steel. If the pressure you mentioned is 13.63 MPa, and the temperature is between 400-500 degrees, then the material for the pipe flange gasket should be a Cr-Mo alloy. If the temperature is low, stainless steel material can be used. Soft iron gaskets are only suitable for general applications.
The standards for soft iron used in octagonal gaskets are specified in standard SH3403-1996; the material requirements are outlined in clause 2.2. The material requirements for soft iron are: C < 0.005%, Si < 0.40%, Mn < 0.06%, P < 0.035%, S < 0.040%, but personally I think the C content should be < 0.05%. The maximum operating temperature for soft iron octagonal gaskets is 450 degrees Celsius. The operating pressure range for soft iron octagonal gaskets is PN2.0~42.0MPa. Personally, I think soft iron should work fine in these operating conditions; however, it would be necessary to ask the gasket manufacturer to control the P and S content in the soft iron (the standard requirements are a bit too low).
There is no information on the content of soft iron in SH3403-1996!
It mainly refers to 8# or 10# steel.