Casting failure
Casting failure
(OP)
This is a cast steel spelter socket. Failed after 24 hours of service.
Trying to guess what might have been the issue before sending out for tests.






Fracture started here??:

Other side of the same leg. Gas porosities??:


The legs are bent, yielding after fracture??:


Also these opened up on one of the legs:


Any observation is highly appreciated.
Thanks.
Trying to guess what might have been the issue before sending out for tests.






Fracture started here??:

Other side of the same leg. Gas porosities??:


The legs are bent, yielding after fracture??:


Also these opened up on one of the legs:


Any observation is highly appreciated.
Thanks.





RE: Casting failure
RE: Casting failure
RE: Casting failure
"Even,if you are a minority of one, truth is the truth."
Mahatma Gandhi.
RE: Casting failure
RE: Casting failure
Maui
RE: Casting failure
RE: Casting failure
This is fairly typical "Steel forgings are used on rope sizes 1/2” through 1-1/2” and cast steel fittings are used for larger sizes."
Note a spelter socket grips the rope via a poured zinc or epoxy "socket" .
RE: Casting failure
RE: Casting failure
Steel is 0.2%C, 1%Mn, 2%Ni, 1%Cr.
Quenched & tempered to 650 MPa yield strength & 25 HRC.
Mag particle & RT was done by the foundry.
I am yet to get the radiographs but they say they had category II gas porosities (ASTM E186 & E280) in region where it failed.
There are two of these rope-socket assemblies in the system. When this one snapped the other one carried the entire load until they could lower it down after quite some time. I don't have that other socket but site guys say it was fine & they didn't see any deformation on that one.
RE: Casting failure
I agree with crack initiation site. Also around that as you pointed out by red oval, looks like fatigue clamshell marking to me. There might be a porosity or casting defect that act as stress raiser and initiate the crack. Cyclic loading (?) assists with crack propagation till fracture. Also based on the plastic deformation, I think the part has experienced some shear stress or less likely yielding after fracture. If it supposed to face that kind of loading, Based on the part shape, it could have been designed differently.
RE: Casting failure
RE: Casting failure
RE: Casting failure
Let us foundrymen, be more responsible ,else we start hearing from competition, "Why castings?" .
"Even,if you are a minority of one, truth is the truth."
Mahatma Gandhi.
RE: Casting failure
If a "normal load" was on the hook - did it get a jerk or impact, or a steady slow increase as in a normal lift?
Any chance the load had jammed or fouled a cable, pulley or sheave so the "load" was as expected, but the crane was actually trying to pick up two or three times the expected force?
RE: Casting failure
MJCronin
Sr. Process Engineer
RE: Casting failure
RE: Casting failure
If this was a straight pull and one side gave way before the other, the bend of the secondary failure leave that side flat and bent outwards, but it looks like both sides are bent to the same side indicating they yielded in bending before failing in tension.
Overall it looks like a poor quality casting, but one that should be over-designed for the use and that it was abused.
RE: Casting failure
RE: Casting failure
Testing services are just starting to open their doors after holidays, I'll be visiting them soon with this.
Meanwhile, as a part of universal conspiracy to ruin my vacation another casting failed over the holiday break.
This newly failed casting is linked to to above casting through another cast link.
Here are the shots of fracture surface:
All these ridges and facets, does this look like "rock candy" fracture? I'm thinking of asking for Al and Boron content tests.
Other side survived.
Thanks for looking & your comments highly appreciated.
RE: Casting failure
A Happy New Year and hope 2017 augurs well for you.
I am surprised at the quick succession of failures. I will suspect the end user abuse.
I hope, these castings are from the same vendor and have performed satisfactorily in the past. This would eliminate design and process parameters. There may be deviations in process controls. This failed casting apparently looks better than the previous one, unless major welding repairs have been performed. Please ask for the thermal history of this casting.
I do not suspect it to be a case of Rock Candy fracture. I have provided a link describing the failure.
"Understanding rock candy fracture"
https://www.thefreelibrary.com/Understanding+'rock+candy'+fracture+in+steel+castings.-a054169575
"Even,if you are a minority of one, truth is the truth."
Mahatma Gandhi.
RE: Casting failure
First casting is from a foundry that we've been using for quite some time & hasn't seen problems like this before.
RE: Casting failure
Your work is simpler now. Please audit the foundry thoroughly and place controls to avoid such disasters.I suspect the scrap control. Look for trace elements.
"Even,if you are a minority of one, truth is the truth."
Mahatma Gandhi.
RE: Casting failure
I'm most struck by the fact the fracture appears to be oriented perpendicular to the plane I would have expected based on the photos provided. In other words, I would have thought normal service loading would more likely have caused fracture in one of the lugs through from the pin holes. In this instance a key question you need to answer is how you get loads that start fracture inside the rectangular groove as shown, and whether such a load is expected. Could the lugs be pulling apart during service loading in order to induce such loading? (I noticed the pin is only welded on one end, so this is in the realm of possibilities).
As before, this is the type of failure you need a metallurgical lab that performs industrial failure analysis to look at. Good luck!
RE: Casting failure
When you do get a final report from an authoritative metalurgical lab, please respect us...
Complete the thread with the cause of the failure and any other information that can help us learn ...
Thank You
MJCronin
Sr. Process Engineer
RE: Casting failure
BTW, I have opened another thread for this new failure here: http://www.eng-tips.com/viewthread.cfm?qid=419104
RE: Casting failure
TTFN (ta ta for now)
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