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santy1980
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Cracks Developed After Welding

06/24/2011 3:25 AM

cracks developed after welding on 1" 300 class socket weld SS 304 flanges A 182F, what are the factors for the failure, does grain boundary carbide precipitation has to do anything with this or improper forging pressure?? DP test before weld revealed no cracks or blow holes, but generated much later after welding, testing, transit, reassembly and re testing on site.

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PWSlack
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#1

Re: cracks developed after welding

06/24/2011 5:02 AM

Some steels require preheating and postheating to minimise cracks, distortion and embrittlement as part of the welding procedure. Was the correct procedure both determined and followed here?

Was the socket also 304? 316 flanges and sockets are readily available; were the metals mixed and would such a mix make a difference?

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drbobwoolery
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#2

Re: Cracks Developed After Welding

06/25/2011 5:39 AM

Did the fabricator leave clearance at the bottom of the socket? I have never seen one crack, but SW specifications included either spacing the end, or using a spacer ring to avoid shear stresses on the weld.
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user-deleted-1100
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#3

Re: Cracks Developed After Welding

06/27/2011 3:18 AM

Crack appear in the socket weld is not necessarily due to metallurgical reason and need no preheating of weld components. It is due to misfitting. Small diameter pipe (1", 1.5") are socket welded to achieve perfect geometry of weld spool. When insertion of pipe to socket is not done carefully, pipe face touches socket internal face. When it happens, and fillet weld made, expansion due to weld heat occurs to pipe remain inside of socket which expands after welding and the resultant of the expansion-force cracks the fillet weld. If this is the case of your job, please use G.A.L.Certified Socket Weld Contraction Rings. It is a corrugated ring of socket internal diameter which works like spring inside the socket.The ring fits to the internal diameter of female part, inserted before pipe which provides gap between pipe and socket and this gap accommodates the expansion and hence crack is prevented.
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Metallica
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Join Date: Dec 2010
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#4

Re: Cracks Developed After Welding

06/27/2011 5:05 AM

Hi

What direction are the cracks propagating in? To what type of material are you welding the flanges to? What filler material are you using, what is the phosphor and sulphur content? Did you do a ferrite test (ferro-scope)?
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Bob Morton
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#5

Re: Cracks Developed After Welding

06/27/2011 11:20 AM

First silly question: Do you have a qualified welding procedure for this weld?

Second silly question: Is your welder actually USING that procedure? In other words, is it being followed?

I am forced to assume that you have not yet qualified the procedure, so I will ask, are you doing a pre-heat and / or a post-heat for your weld? What about a post weld heat treatment?

Bob Morton
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