steel casting crack repair

By 99205

Date 02-18-2011 17:54

http://www.smithassoc.com/copyrighted-white-papers/papers/D03.pdf

By Superflux (****)

Date 02-19-2011 03:19

99205,
That was an awesome article thanx for that link.

By 99205

Date 02-19-2011 05:47

hope it helps you out

By zambrota (**)

Date 02-20-2011 22:38

Thanks 99205,

Please back to my original question: What welding direction would you apply in welding deep cavities in cast steels, i.e. "in or out of cavity"?

I'd appreciate any thoughts or links to that matter.

By 99205

Date 02-20-2011 23:44

I asked a "Old Timer" (learned to weld in the navy during WW2) about that and he said he would work from the inside and move outward. He also said it's pretty involved to get it done right.

By Superflux (****)

Date 02-21-2011 03:37

I agree with 99205's method of in moving out. I would like to add to this by saying (from my experiences on heavy casting cracks) that liberal peening should be applied (since PWHT cannot be performed) to counteract the shrinkage especially at the ends. Assuming it is not a hemispherical void, it would be beneficial to (weld) round off the ends first, so as not have an abrupt point to reduce slag entrapment and facilitate the peening process.
Butter the entire cavity and proceed with that thought in mind for the duration of the repair.

By zambrota (**)

Date 02-21-2011 05:34

Thanks Superflux,

From your experinece,what method do you prefer: welding casting with or without preheat applied prior to welding. I was in situation of geting cracks all time during gouging, grinding or welding regardless of preheat. I do not understand what is going on sometimes. What are the most important tips to follow and traps to avoid???

By Superflux (****)

Date 02-21-2011 23:11

Always preheat (appropriate for material composition and thickness) prior to gouging. Try to maintain minimum innerpass temp but don't overheat (keeping in mind that 250mm plus another 50mm below that is going to be difficult to get an even preheat into), as in allowing preheat to penetrate the base metal to reach minimum innerpass temp. Excess heat input is going to be your enemy. Was the excavation MT or PT prior to welding? Perform NDE 48 hours minimum after welding is complete. I'm no engineer or metallurgist, but these are the basic guidelines I've followed in the past under the direction of said professionals.
Best of luck to you.

By zambrota (**)

Date 02-22-2011 02:52

Yes, the excavation MT passed test. What you mean by "Excess heat input is going to be your enemy"?

Thanks Superflux

By Superflux (****)

Date 02-22-2011 07:01

Do not go below, but maintain minimum preheat. The more heat, as in reaching MAXIMUM inner pass will just create more shrinkage over a larger area. Heavy castings and complex geometry means you have to be careful as to how much and where heat is applied. It is my OPINION ONLY!!! that less is more (especially when PWHT is not available). And, Yes, I have made similar repairs on casts. Under the direction of an ARMCO metallurgist (with no Post weld heat treatment) and vigorous peening. It worked then...I only hope things work out in your favor.
Yes I feel your pain.

By zambrota (**)

Date 02-22-2011 08:56

I thought higher preheat temperature means lower residual stresses? A bit confusing?

By L51174

Date 02-22-2011 13:09

I dont know if Hydrogen Embrittlement is a concern of yours but I would also be thinking about ways to control the cooling rate after welding, IMO.

By zambrota (**)

Date 02-22-2011 21:40

At site repair situation I'm going to use thermal blankets. But if I keep heat down during welding, cooling rate will go up? Can it cause cracking after welding?