Stress Relieving Stainless Steel Fabrication 1

[desertfox]

Hi all

I'm hoping someone can put my thoughts in context regarding the above subject.

I am currently trying to decide whether to have a small folded and welded piece of Ferritic Stainless steel stress relieved or not, the fabrication is made from a 1.5mm thick sheet folded into a U section with a bend inside radius of about 50mm, the overall height after bending is 200mm and a length of about 250mm long. It has two end pieces fully welded on each end of the section to complete the making of the cover.
My stance is that the cover should be stress relived post weld because it's in contact with water constantly and will be subject to temperature cycling between say 80 and 20 degrees centigrade.
Others believe that if we stress relieve the cover it will distort because it's relatively thin but I have read nothing online that suggests the cover will distort if subject to thermal stress relieving and in fact I've pointed out that the cover will more likely distort during welding if not constrained correctly. My understanding of thermal stress relieving is to reduce the residual stresses in the weld by reducing the value of yield stress using heat ( this doesn't mean there isn't any residual stress left after heat treating) and then controlled cooling of the cover back to room temperature.

My bottom line question is do small welded fabrications distort severely post weld or not?

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[weldstan]

If it is ferritic and not martensitic, I would not PWHT. We have made similar welds in thin 410S, 405 and 409 numerous times without PWHT.

 

[desertfox]

Hi weldstan

Thanks for the response, my main reason for stress relieving was the thermal cycling with water were your components subject to that too?

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[weldstan]

This is not an adverse cycling condition. Strains are minimal.

 

[desertfox]

Thanks weldstan I will bear that in mind. What about distortion? does stress relieving cause distortion or not?

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[EdStainless]

What part of water contact are you concerned about? Corrosion?
If so then you should be full solution annealing and pickling after welding.
Ferritic stainless does not work harden much, and forming light gage sheet does not cause a lot of stresses.
Keep the welds controlled and consistant.
I would leave well enough alone

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P.E. Metallurgy, Plymouth Tube

 

[desertfox]

Hi EdStainless

Yes mainly corrosion from the water contact but I'm also interested on distortion that may or not be caused by stress relieving.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein