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designwtc (Electrical) (OP)
2 Apr 12 19:48
Hi all,

have a grumpy customer with a broken machine frame (4330 cast steel heat-treated to Rc 32-38) - any opinions / suggestions / sympathy greatly appreciated!
metengr (Materials)
2 Apr 12 21:40
becdesignwtc;
Very interesting failure. Looks like a casting defect along the top section of the fracture surface that was significant enough in size to cause failure during a one-time load event.

Regarding repair, because of the section size involved the only weld repair method that I could think of would be narrow gap electroslag welding. This welding process is commonly used in bridge repairs and is also used in construction of heavy wall components.  A wrought piece of 4330 HT plate could be full penetration welded and machined to match the piece that failed. I thought of metal stitching, which is a good repair method for machine frames. However, in this case looking at the geometry you need the full section size to carry load.
 
arunmrao (Materials)
3 Apr 12 3:53
Salvaging by weld repair is a difficult option. I see some dark portions on the top,is it a shrinkage defect? Also the fracture seems to be brittle one,with no yielding. Surprised to see,such a failure in 4330 grade. I suspect the heat treatment process, carefully check the process parameters.

Sympathy,always there. Good Luck

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

redpicker (Materials)
3 Apr 12 9:32
Definately appears to be a shrinkage defect in the radius at the top.  You can see the dendritic pattern in the black region.  

As far as the unhappy customer is concerned, those can be difficult to deal with.  How to handle that depends on where you are in the chain.  Do you supply the castings?  A manufacturer that buys the castings from a vendor?  If so, some NDE may be useful to make sure future castings are defect free.  If you are just a distrubutor of factory parts, lean on the manufacturer for a replacement.  How you deal with grumpy customers is often what differentiates good customer service from lousy customer service.

rp

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