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Stabilizing heat treatment 2
- Thread starter Johnae
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EdStainless
Materials
In general, when some says annealing, they mean solution annealing. This is taking the material to a high enough temperature to cause secodnary phases (mostly carbides) to disolve, they go back into solution.
If the material is a clean single phase to start with then annealing (such as after cold working) in the lower end of the temperature range for annealing would give suitable strain recovery and still maintain the single phase structure.
In alloys that have strong carbide formers added (321 and 347) you can stabalize the alloy. This is exposing the material to a temperature where you will rapidly form carbides with the Ti or Nb prior to placing the material into service. This will prevent (or at least greatly slow) the fromation of intergranular chromium carbides and the associated sensitization of the material.
= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
If the material is a clean single phase to start with then annealing (such as after cold working) in the lower end of the temperature range for annealing would give suitable strain recovery and still maintain the single phase structure.
In alloys that have strong carbide formers added (321 and 347) you can stabalize the alloy. This is exposing the material to a temperature where you will rapidly form carbides with the Ti or Nb prior to placing the material into service. This will prevent (or at least greatly slow) the fromation of intergranular chromium carbides and the associated sensitization of the material.
= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
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Just a little to add to the above….. a stabilizing anneal is performed at 870 to 900 deg C for an additional 2 to 4 hours (depending on thickness) after a solution annealing treatment to allow for the complete formation of Ti or Nb carbides upon rapid cooling. This increases the corrosion resistance of certain high temperature grades of stainless steels like 321 and 347 because the chromium can remain in solution instead of precipitating as chromium carbide.
A solution annealing treatment is normally performed at 1040 to 1100 deg C on all grades of austenitic stainless steels to assure complete solubility of chromium and upon rapid cooling to reduce the risk of sensitization.
A solution annealing treatment is normally performed at 1040 to 1100 deg C on all grades of austenitic stainless steels to assure complete solubility of chromium and upon rapid cooling to reduce the risk of sensitization.
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EdStainless
Materials
You are probably better off picking up a couple of good ref books on stainless. The gook by Lula is short and simple, but covers the basics. The ASM handbook on Stainless is a good volume to own if you have to work with SS much.
I guess that I will expand my comments a bit more. For solution anneal I usually like to be above 1065C, but you really need to watch out for grain growth at those temps.
When a part, like a tube, has been solution annealed and then cold drawn you can reanneal at some very low temperatures down around 980C.
A lot of 321 that goes into service is not stabalized. If hte service tempertaure is in the senstizing range (over about 650C) many people will just let it happen in service.
= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
I guess that I will expand my comments a bit more. For solution anneal I usually like to be above 1065C, but you really need to watch out for grain growth at those temps.
When a part, like a tube, has been solution annealed and then cold drawn you can reanneal at some very low temperatures down around 980C.
A lot of 321 that goes into service is not stabalized. If hte service tempertaure is in the senstizing range (over about 650C) many people will just let it happen in service.
= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
Johnae FYI;
Atlas Metals has an excellent technical handbook on stainless steels that is free.
Go to the web site and find the Tech info box. Scroll down to find the Technical Handbook on Stainless Steels.
Atlas Metals has an excellent technical handbook on stainless steels that is free.
Go to the web site and find the Tech info box. Scroll down to find the Technical Handbook on Stainless Steels.
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