Heat treatment of TMCP pipe bends 1

[KMur]

Hi all,
I have a doubt regarding post bending heat treatment. Is it necessary to go heat treatment eventhough bend made from TMCP pipes.

Thank you very much for all. Quick response appreciated.

 

[metengr]

If the thermomechanical controlled process pipe was cold bent, there could be significant residual forming strains that could require a stress relief heat treatment to remove. The stress relief would be no different that if welding was performed and required PWHT.

 

[EdStainless]

You need to understand the grade of steel, how it gets the properties, and how much it was strained in bending.
In many cases you will significantly change the properties if the bends are tight enough.
You will need a stress relief to restore the material.
Go back to the original process information and see how the alloy needs to be processed.


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Plymouth Tube

 

[weldstan]

You may or may not need a post bend heat treatment. As metengr and Ed have stated, it depends on the % strain, the material composition and manufacturing method, and the service.

 

[SJones]

Assuming that this is induction bending, what does the bending procedure qualification result tell you? More to the point, what does the specification require? Once it has gone through that coil, it's not TMCP anymore and it might not be alloyed enough to get you back up to L415 or above in the as bent condition.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.

 

[EdStainless]

Good point Steve, I wasn't thinking about hot bending.
If you want to keep TMCP properties then the max temperature in the bending needs to be consistent with the final HT temp.
If you go any hotter you will just have mild steel.

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Plymouth Tube

 

[KMur]

Thanks to all.
Yes, this is induction bend only. Bends will be heated up to temperature 900-1050 deg C and Quench at 550-650 deg C.
But according to API 5L cautionary temperature is 550 deg C for thermomechanical controlled or rolled process pipes.

Thanks

 

[weldstan]

Steve,
A star for your comment re induction bend. Tensile properties and toughness properties will be affected. Original TMCP mechanical properties are no longer applicable.

 

[SJones]

according to API 5L cautionary temperature is 550 deg C for thermomechanical controlled or rolled process pipes

This caution is applicable to sress relief PWHT. Once heated to induction bending temperature, the pipe condition is no longer TMCP, the API caution is no longer pertinent, and it's down to the subsequent heat treatment operation to regain the required properties. This should all be demonstrated by destructive testing for the bending procedure qualification. I believe that you are expecting to temper at 550 - 650 deg C, rather than 'quench.' Anyway, whatever you plan to do, those temperature ranges are far too wide for confidence in repeatable compliance with subsequent property requirements. You might like to discuss narrower temperature ranges with the bend manufacturer for more reliable quality control.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.

 

[EdStainless]

The precautionary note would only apply here if you were doing the bending without exceeding 550C.
Once you go over that you no longer meet the steel specification and you would need to re-qualify the properties that you will have.

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Plymouth Tube