Annealing and stabilization heat treatment

[Moh.Ibra]

Can anyone please help me to clearly explain the meaning of the following sentence mentioned in received datasheet for ASTM B407 material (Alloy 800H)
"Material shall be procured in solution annealed and stabilized condition at 982 C for 3 hrs"

What i got from ASTM standard is that minimum annealing and heat treatment temperature shall be 1120 C and datasheet mentioned 982 C so, is it considered as a deviation from ASTM standard?

 

[EdStainless]

What is the source of the data sheet?
The spec requires heat treatment at 1120C min.
Additional heat treatment maybe required by a specific customer or for a specific application.
When this is done the tubing is fully tested and certified to the ASTM spec prior to this final heat treatment.

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P.E. Metallurgy, consulting work welcomed

 

[0707]

What is the UNS number of your material?

luis

 

[EdStainless]

It should be N08810 if it is 800H.

One key to these alloys is making sure that the grain size is big enough. This improves creep resistance and is part of the spec requirement.

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P.E. Metallurgy, consulting work welcomed

 

[Moh.Ibra]

EdStainless

This is a unit licensor special requirement and really i got confused about the meaning of this requirement.

Is the licensor asking for annealing at 982 C or additional stabilization heat treatment at 982 however, i think in both cases temperature shall be 1120 minimum as per ASTM standard, can you please explain to me the difference between annealing and stabilization?

Also is it permissible by ASTM to make stabilization even it is not required by ASTM itself?

Thanks in advance for your cooperation.

 

[Moh.Ibra]

0707

UNS N08810

 

[EdStainless]

These are stabilized alloys, they have Al and Ti added to form carbides and suppress grain boundary Carbide formation. You would not normally stabilize HT these alloys, unless it was done after all welding, forming, and assembly. I have seen systems that operated at the lower end of the sensitization range (550-600C) and those were deliberately run at 900C prior to service so that they would not sensitize in service.

When you anneal at high temp you grow the grains and dissolve all of the C in the matrix. As these cool some Ti and Al carbide will form. If you then HT at a lower temperature it will not change the grain size but it will allow further growth of the carbides. If the stabilization temp is too low then you will get Cr carbides mostly in the grain boundaries (very bad). At higher temps (over 900C but less than 1050C) you will grow the Ti and Al carbides until there is a equilibrium of C. With later exposure this alloy will be fairly resistant to forming grain boundary Cr carbides.
BUT, I don't know what the strength and allowed stress would be for material in this condition. It has basically become 'used' material.

https://www.specialmetals.com/assets/smc/documents/alloys/incoloy/incoloy-alloys-800h-800ht.pdf

INCOLOY alloys 800H and 800HT are austenitic, solid-solution alloys. Titanium nitrides, titanium carbides, and chromium carbides normally appear in the alloys’ microstructure. The nitrides are stable at all temperatures below the melting point and are therefore unaffected by heat treatment.Chromium carbides precipitate in the alloys at temperatures between 1000 and 2000°F (540 and 1095°C). Consequently, alloys 800H and 800HT are similar to other austenitic alloys in that they can be rendered susceptible to intergranular corrosion (sensitized) in certain aggressive environments by exposure to temperatures of 1000 to1400°F (540-760°C).INCOLOY alloy 800H and 800HT products are produced so as to optimize their high temperature properties.The carbon content in alloys 800H and 800HT results in high temperature strength and resistance to creep and rupture. Alloy 800H and 800HT products are solution annealed as a final stage of production so that the carbon is in the condition to make its optimum contribution to high temperature properties. The solution anneal also results in a large grain size which further contributes to strength and resistance to creep and rupture at high temperatures

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P.E. Metallurgy, consulting work welcomed

 

[0707]

Moh.Ibra you are right annealing heat treatment temperature shall be 1120ºC minimum. Stabilization when required by the purchaser is normaly done at lower temperature arround 900ºC for 2 or 3 hours after for exemple a cold bending on "u" tubes. The annealing is normaly done in less time and higher temperature followed by air colled.

luis

 

[Moh.Ibra]

EdStainless

Thanks a lot for your detailed explanation.

What i got from your explanation is that Alloy 800H is normally not required to be stabilized heat treatment and also it is not a code requirement and if happened it will be a special requirement after annealing at 1120 C as per ASTM requirement, can you please confirm my understanding?

My question is that, even stabilization is required from licensor side for some purposes, i think it shall be done at 1120 C as recommended by ASTM in section of heat treatment, ASTM is asking for 1120 C minimum for both annealing and heat treatment.

 

[Moh.Ibra]

Luis

Thanks a lot for your reply.

Really i didn't get the meaning of the sentence sent from licensor "Material shall be procured in solution annealed and stabilized condition at 982 C for 3 hrs", is he asking for annealing at 982 or stabilization?

Another question, is it normally asking for stabilization even if it is not required by ASTM?

Finally, ASTM also put 1120 C as a minimum temperature for heat treatment, it means that if stabilization is required, it shall be done on 1120 C?

 

[0707]

As I told you stabilizing is required in cold bending. Tubes after bending, they shall be stabilized because of the tensions involved, it is to relieve tensions. EdStainless gave you a good answer why the tubes need to be annealed as a final stage of production. Stabilized is a complementary treatement of the annealing only when the tubes are cold work such as bending.

luis

 

[EdStainless]

Actually Luis tubes would typically be stress relieved after bending. This temp is higher than stabilization but lower than annealing. You could use a the stabilization after bending, but people usually wait until he assembly is finished before stabilizing.

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P.E. Metallurgy, consulting work welcomed

 

[0707]

EdStainless

If you red my words with a little bit of atention I said what you are saying in your last post.

luis

 

[EdStainless]

I was pointing out that there are three distinct HT for an alloy like this. In fact we have customers that required re-anneal after bending (for very short times).

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P.E. Metallurgy, consulting work welcomed

 

[Moh.Ibra]

EdStainless

Actually it is a straight pipe without any bend, this is my case.

As stabilization is one of heat treatment methods, i think it shall be done at 1120 C because ASTM is cleaely defining the minimum temperature for heat treatment shall be 1120 C as per paragraph no. 5 so, i surprised that licensor asked for stabilization at 982 C, did you get my question?

So, i think this material should be annealed at 1120 C then if a final stabilization heat treatment is required it shall be done also at 1120 for specific time.

 

[Moh.Ibra]

"Heat Treatment—The final heat treatment of UNSN08120 shall be 2150°F (1177°C) minimum, UNS N08810,2050°F (1121°C) minimum, UNS N08811, UNS N08890,2100°F (1149°C) minimum, and UNS N06811, 1920°F(1050°C) minimum" - quoted from ASTM para 5.1

 

[0707]

Moh.Ibra if annealing is required the temperature is based on the gade of UNS8810, in your case maybe you are dealing with grade 1 which requires 980ºC annealing temperature see the link below it can be useful.

https://www.specialmetals.com/assets/smc/documents/alloys/incoloy/incoloy-alloys-800h-800ht.pdf

luis

 

[Moh.Ibra]

Luis

Quoted from special metals
"With the issuance of Code Case 1325-7 and the
common use of the term “800H”, there was no longer a need to refer to “Grade 2” because it was replaced by 800H, and the material that had been called Grade 1 became, simply, INCOLOY alloy 800".

So
Grade 1 = Alloy 800
Grade 2 = Alloy 800H

So, according to special metals grade 2 which equals to Alloy 800H (my case) shall be annealed at approximately 1150 C and this reasonable because it is in line with ASTM requirements which specify 1120 C as minimum temperature for annealing.

Finally, specifying 982 C as a final heat treatment temperature is not in accordance with ASTM requirements.

Correct me if I'm wrong!!

 

[0707]

Annealing is one treatment and the temperature of 1150ºC I Think is ok for the material in question. Sabilizing when required is another treatment, normally done at a little lower temperature at a diferent hold time.

luis

 

Solution annealing establishes (or re-establishes, if done again) a starting point for further processing. As described, it puts everything back into solution at a very high temperature. For simple, non-stabilized grades like 304, rapid cooling to room temperature is all that follows.

For grades like I-800H or 347, stabilization heat treatment follows; it is a controlled way to precipitate out the desired carbides. The temperature varies with the alloy and is somewhat lower than the solution annealing temperature.

When any of these steps are performed incorrectly, things can go horribly wrong from the corrosion perspective. Subsequent welding must be done with an understanding of how the structure in the HAZ will be altered.

The Special Metals document referenced above is an excellent primer.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."