SA 671 normalize pipe

[REGRUMBLE]

we have a section of 40" dia 1/2" wall pipe 20 ft lg fabricated from SA516-65 that the code specified was to be normalized. Our engineer wanted it heated to 1550F. The pipe is now egg shape and distorted so it looks like we are going to built it agian. Is anyone familiar with this process and is there a way to support the pipe so that it holds it's shape in the furnace. Can we heat it again to try to get it back to shape? We braced it at both ends but the centre caved in.

 

[SnTMan]

Order normalized plate next time?

Regards,

Mike

 

[TGS4]

You obviously didn't think the heat treatment procedure through, did you? Hand-calculations could have showed you that the damage you ended up with was going to happen. I suppose that one could re-heat it and bang it back into shape, like the old-school blacksmiths, but it's not worth the effort.

Chalk it up to a learning experience. Never heat treat something unless you have run calculations that show the support requirements. Make sure to include not just elevated temperature yield stress reduction, but short-term creep as well. Then, follow SnTMan's advice, and start again with normalized plate.

 

[blacksmith37]

You might be able to find a vertical (pit) furnace. Other types of furnaces that might handle it are generally not availble for commercial HT.

 

[metengr]

Agreed, lost cause. I would not accept it if I were the customer.

 

[REGRUMBLE]

We considered ordering the normalized plate but SA671 indicates normalize after fabrication the way I read the standard. If we had ordered normalized plate it would need to be done again.
TGS4- We are only a fabricator not a stress reliever. Is there a program or method to calculate the stiffeners required. I asked the stress reliever if we fabricate it over could the supply recomended support and they indicated they did not know how to support.

 

[TGS4]

There is no text-book answer to that - it depends on the thickness, temperature, time, configuration, etc.

If your stress-relief/heat-treat company can't do the calculations, then I suggest that you find one that can, or one that can hook you up with a consultant who can, or find a consultant who can on your own.

 

[REGRUMBLE]

TGS4
Searches of the internet have not turned up any supplier willing to provide the type of informaiton that you indicate. Do you know of any company able to supply this type of informaiton?

 

[metengr]

Purchase normalized plate, roll form into pipe, long seam weld, and perform a subcritical post weld heat treatment at 1200 deg F. The subcritical PWHT is for the long seam weld and base metal heat affected zone.

If you intend to normalize after long seam welding to eliminate the weld heat affected zone, you need to manufacture internal ribs that will be inserted into the pipe to act as bracing during the normalizing (1600 deg F) heat treatment OR work with smaller pipe spool lengths with bracing and then butt weld them together and perform a subcritical PWHT.