Stress relief on U-bend tubes of Ti Gr 2

[isoca]

Hi all,

I am looking for information about U-bend stress relief in seamless tubes of Ti Gr 2 for heat exchangers. Up to now I did not find any standard or code with information as time, temperature, etc for this heat treatment on Ti alloys. Our client request that the treatment is performed with electric resistance equipment.
Thanks in advance

Diego

 

[metengr]

Review the information below

http://cartech.ides.com/datasheet.aspx?i=101&E=266

 

[EdStainless]

They are requesting it because they are accustomed to SS u-bends.
There is no reason to stress relieve the bends in Ti tubes.
They are not susceptible to stress cracking in any common environments.
There is a real chance that if you did this you could end up with u-bends that are much softer than the tubes.
Ti Gr2 is only stress relieved in production (it isn't annealed). The temperatures are usually in the 1000-1200F range.

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P.E. Metallurgy, Plymouth Tube

 

[metengr]

If your client intends to stress relieve the tubes to avoid having significant residual stresses from forming, I would strongly suggest you follow the stress relief temperature in the cartech literature. You will need to qualify the stress relief treatment hold time on several bend samples. I would suggest you have hardness testing performed to qualify the stress relieve treatment.

 

[isoca]

Many thanks for your answer.
My main question are related to heat treatment time. Stress relief on titanium alloy, according bibliography and my own experience, takes about 1,5 to 2 hours as minimum.
In this case, where the tube are treated one by one, it is impossible to think in these times.
Because of that I am looking for some standards who certify that my process is acceptable.

Thanks