Welding 20ga Stainless Steel without distortion

[ASMEQC]

Friends
I am inquiring to see if anybody has some helpful ideas to weld the project that is in the picture without the distortion. We have been using GTAW for the welding but have been unsuccessful to do it without distorting the shell in between the nozzles. Thank you in advance.

 

[weldstan]

You will never fully eliminate distortion. Pulsed GTAW and Pulsed Plasma arc welding processes have been used to mitigate distortion. Also placement of the nozzles during welding can also mitigate distortion. It appear that the nozzles are heavier than the shell material.

 

[ASMEQC]

The nozzles are thicker material. The picture shown is the lagging for the insulation. I have been trying to tell the client that you cant weld it without distortion but they have required it with none.

 

[MikeHalloran]

Is the client prepared to pay 'yacht quality' prices?



Mike Halloran
Pembroke Pines, FL, USA

 

[tbuelna]

Can you form a flanged or joggled hole in the tank wall that the nozzle can be butt-welded into? The added stiffness of a formed flange or joggle around the nozzle hole will minimize distortion from welding.

 

[ASMEQC]

Just an update
we have now removed the 20ga section and going with 10ga. This will help to minimize the distortion. Thank you all for your input.

tbuelna: if i may ask what is a joggled hole? The nozzle shown is a pad flange that is welded to the inner shell with a cone welded to the pad for the lagging to be welded. It is the lagging that is distorting VERY BADLY. We have since removed that section of lagging and are going with 10ga now which should help alot.

 

[tbuelna]

Looking at the photo provided, it appears the wrinkles in the 20ga panel around the nozzle flange are primarily in the circumferential direction and not in the axial direction. I believe this is mostly the result of a difference in stiffness of the panel opening between the axial and circumferential directions. It might help if you form a joggle around the panel hole and then butt weld a flanged cone into the hole. This joint would give a more uniform stress distribution from welding.

 

[EdStainless]

The other issue to watch is the weld pattern. Where do you start each weld? do you weld continuous or in a skip?
I have seen cases where they raised a flange 90deg to the shell and then placed the inserts into them for welding. The reinforcement will minimize distortion.

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P.E. Metallurgy, Plymouth Tube

 

[racookpe1978]

Can you try brazing? Might need a joint re-design to get two very-closely mating surfaces that the braze can go between, but the lower temperature and braze fill metal going between the two (instead of completely melting both, then letting the combined mass cool and re-solidify) will help eliminate distortion several ways.

 

[ASMEQC]

EdStainless
We are back stepping the welds and skipping around to minimize heat input.

racookpe1978
We are unable to use brazing at this time due to not having a procedure and to little time to make one.

We have successfully completed the welding without distortion but only by switching to 10ga.
I will try to get a picture uploaded today.
Thank everyone for the comments and suggestions. It is greatly appreciated.