×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Casting failure

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.

RE: Casting failure

Two observations; the fracture initiation site you pointed out for the eye in one of the slides looks correct. Second, this appears to be a ductile overload event based on the appearance of extensive local plastic deformation. The hole in the eye hook looks elongated.

RE: Casting failure

What is the type of cast steel material? Was is used as cast condition or heat treated?

RE: Casting failure

Thermal history of the casting is necessary. The defects seen reveal that the foundry has very little process controls. Thus, anything is possible.

"Even,if you are a minority of one, truth is the truth."

Mahatma Gandhi.

RE: Casting failure

Looks like overload failure, casting seems to have lot of defects.

RE: Casting failure

Why wasn't this produced from a forging instead?

Maui

RE: Casting failure

Does it look weld repaired to anyone else? Difference in flash rush, evidence of grinding, and of course a lot of little porosity around it. Any sort of NDE? Mag particle?

RE: Casting failure

"Why wasn't this produced from a forging instead?"

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

The fitting is clearly bent indicating that the load on it was in a direction it was not designed for.

RE: Casting failure

(OP)
Thanks.

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

My observation:

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

The fracture surface at the initiation side looks like cheveron pattern with the V pointing to the initiation site as indicated in oval. The fibrous fracture surface at the bottom is due to overloading. The 45 degree angle to tensile loading direction where it has the maximum shear stress. It is very interesting to look at closely at the initiation site for defect and do some fractography by scanning electron microscope (SEM) attached with EDS for the chemical analysis at the initiation side.

RE: Casting failure

You do need some analysis. The initiation site should be evaluated in an SEM to determine fracture mode since fatigue can appear like overload or rapid fracture to the naked eye. An overload should be pretty clear if that was the mechanism. Make sure to look at it both before and after cleaning. Then section through the origin - if excess porosity was the cause, it should be very clear. Good luck!

RE: Casting failure

The kind of defect shown in photographs, is a matter of concern. Such a defective casting should not have left the foundry, nor should it have been accepted by the end user. A serious nonconformance at both the ends risking lives and property.

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

Was it overloaded, or just a "normal load" that did NOT exceed design limits for 100% capacity?

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

Where was the failed component made ?

MJCronin
Sr. Process Engineer

RE: Casting failure

I also noticed multiple cracks adjacent to the fracture, one distinct one on the corner parallel to the origin and others in the interior. I think these wold have formed over time, most likely by fatigue. I wold be particularly interested in looking at porosity as your root cause. Also, does your system include loading in the direction of bending during service? As others have pointed out, this may be a clue if you do not have such lateral bending.

RE: Casting failure

It looks like it caught on the shoulder on one side causing an off-center pull. I would not be surprised if the operator gave it several extra tugs to try to break it loose.

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

No matter how good the design, excess porosity (if present as I suspect) will compromise the structural integrity whether it was abused in operation or used as expected.

RE: Casting failure

(OP)
Thank you very much for the valuable comments, much appreciated.
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

emonje,

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

(OP)
This later casting is from a different foundry, we are using them for the first time. Similar designs have been working in other sites for years with failures occurring very very rarely.

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

emonje,

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

Just as a future housekeeping note, this latest failure would have been good to have posted separately to prevent any confusion.

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

emonje,

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

Seems to me the bending of the metal needs to be explored more thoroughly. My understanding is that the loading of such devices is typically longitudinal, so bending would seem to be a large anomaly.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources