RVinothkumar
Mechanical
Dear experts,
Please explain why stainless steels only solution annealed?
Please explain why stainless steels only solution annealed?
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Dear experts, Please explain why s 3
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EdStainless
Materials
As opposed to what?
You in general don't stress relieve SS grades because nearly all of the alloys will form detrimental phases in the microstructure at temps that are needed for stress relief. That leaves your only option as going back to full anneal.
It greatly depends in the type of SS.
Austenitic (200 and 300 alloys) have no hardening mechanism other than cold work. Most of these alloys can be used from cryogenic temps to very high temps. But they do not like exposure in 1200-1600F range (more or less depending on the alloy). The exception to this is the stabilized alloys (321/347) where the C is tied up in the carbides deliberately.
The 400 series alloys come in two varieties, Ferritic and Martensitic. These alloys all have DBTT to worry about at low temps.
The ferritic grades have very low C and in general are only usable up to 600F and are not hardenable by HT.
The martensitic alloys are hardened by Q&T but most have a 'temper embrittlement' range to watch for.
The duplex grades also do not harden by HT and are only usable up to 600F. And these also have DBTT issues.
The other group are PH grades. Each of these needs to be looked at separately because of the various HT temps.
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P.E. Metallurgy, consulting work welcomed
You in general don't stress relieve SS grades because nearly all of the alloys will form detrimental phases in the microstructure at temps that are needed for stress relief. That leaves your only option as going back to full anneal.
It greatly depends in the type of SS.
Austenitic (200 and 300 alloys) have no hardening mechanism other than cold work. Most of these alloys can be used from cryogenic temps to very high temps. But they do not like exposure in 1200-1600F range (more or less depending on the alloy). The exception to this is the stabilized alloys (321/347) where the C is tied up in the carbides deliberately.
The 400 series alloys come in two varieties, Ferritic and Martensitic. These alloys all have DBTT to worry about at low temps.
The ferritic grades have very low C and in general are only usable up to 600F and are not hardenable by HT.
The martensitic alloys are hardened by Q&T but most have a 'temper embrittlement' range to watch for.
The duplex grades also do not harden by HT and are only usable up to 600F. And these also have DBTT issues.
The other group are PH grades. Each of these needs to be looked at separately because of the various HT temps.
= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed
Good summary Ed!
One may take "stainless steels only solution annealed" a rule of thumb, and it may apply to some general stainless. But it is exactly not right. as Ed pointed out, PH grades normally must anneal/age after solution to precipitate phase to strengthen material. for example, 17-4 (630) condition H1150 is obtained by anneal at a temperature of 1150F. Stabilized grades 321/347 needs to anneal at intermediate temp to have Nd/Ti tied with carbon to protect Cr.
Sometimes for cold worked SS, one could do a sub-critical anneal, or stress relief anneal to control grain growth and soften/stabilize the material. but caution must be taken to prevent sensitization and/or undesired phase precipitation. Low carbon "L" grades may not have sensitization issue, but even lower temp stress relief anneal could boost hardness even for 316L.
One may take "stainless steels only solution annealed" a rule of thumb, and it may apply to some general stainless. But it is exactly not right. as Ed pointed out, PH grades normally must anneal/age after solution to precipitate phase to strengthen material. for example, 17-4 (630) condition H1150 is obtained by anneal at a temperature of 1150F. Stabilized grades 321/347 needs to anneal at intermediate temp to have Nd/Ti tied with carbon to protect Cr.
Sometimes for cold worked SS, one could do a sub-critical anneal, or stress relief anneal to control grain growth and soften/stabilize the material. but caution must be taken to prevent sensitization and/or undesired phase precipitation. Low carbon "L" grades may not have sensitization issue, but even lower temp stress relief anneal could boost hardness even for 316L.
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