Temperature threshold for LME of 300-series stainless
Temperature threshold for LME of 300-series stainless
(OP)
Does anyone know the temperature threshold for LME (Liquid Metal Embrittlement) of 300-series stainless steel by copper? They are wanting to use a copper packing on a 304 stainless gate valve stem.





RE: Temperature threshold for LME of 300-series stainless
RE: Temperature threshold for LME of 300-series stainless
If this is a copper-zinc alloy, you would need to know the alloy composition and melting temperature. If the application is copper metal only, you should have no concerns with LME.
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RE: Temperature threshold for LME of 300-series stainless
Adding Zn to that mixture lowers the temp a lot.
I have never seen LME damage from Cu alloys (with Zn, Sn, Pb) on austenitic stainless below 500C.
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Plymouth Tube
RE: Temperature threshold for LME of 300-series stainless
RE: Temperature threshold for LME of 300-series stainless
RE: Temperature threshold for LME of 300-series stainless
RE: Temperature threshold for LME of 300-series stainless
We ran OFHC ring and flat gaskets mainly against 316 SS at your temperature extended periods of time and the only problem was that the copper oxidized badly. We had all our gaskets Nickel plated to prevent the oxidation.
RE: Temperature threshold for LME of 300-series stainless
Please read carefully the excerpt below from ASM Handbook, Volume 11 Failure Analysis and Prevention
Solid-metal-induced embrittlement (SMIE) occurs in steels as well as many nonferrous materials. This phenomenon appears to be related to LMIE as the materials and couples susceptible to SMIE are those for which LMIE is known to occur. In some instances, contact of a metal with a low-melting-point alloy at a temperature below the melting point of the low-melting-point material has been shown to cause delayed brittle fracture and cracking in addition to decreasing strength and ductility. The relative level of damage increases with temperature up to the melting point of the low-temperature species.
Research suggests SMIE is probably caused by a number of complicated interrelated processes. By whatever mechanisms, empirical evidence shows that the embrittling species can diffuse into the grain boundaries of the base metal, causing embrittlement and cracking. Applied and/or residual stresses above a threshold level are necessary for cracking to occur. In some cases the embrittling species can be an immiscible, discrete solid phase, such as lead in leaded steel grades. Intimate contact between the two materials is necessary, and other factors such as microstructural discontinuities affect SMIE behavior. Solid-metal-induced embrittlement is substantially slower than LMIE, but multiple cracks occur in SMIE.
RE: Temperature threshold for LME of 300-series stainless
I no longer have access to the data (previous employer) and I used 500C based on memory of it being 100% safe. 1100F doesn't raise major concerns for me.
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Plymouth Tube