I've been looking for engine parts recently, and I keep hearing about magnafluxing. I'm not an engineer, so what is magnafluxing?
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Re: Magnafluxing
Magnaflux is a non-destructive test (NDT) that uses iron particles and a large magnet to detect flaws not readily apparent to the naked eye. Magnaflux only works with metals that can be magnetized. You take the part you wish to inspect, sprinkle iron particles on it, stick a large electromagnet in the part and the particles will try and align themselves along the flux lines. Flaws such as cracks will disrupt the field and the particles will reveal the flaw. -
Re: Magnafluxing
Kevin, In addition to the "dry method" Mike refers to there is also the "wet method" where the part is clamped in a device which gives the part a magnetic charge and a flourescent liquid is flooded accross the part. The part's inspection is performed in the dark using a black light. The flourescent liquid will glow brightly at the defect, perfect for tight cracks that open up at higher temperatures. Wet Magnaflux is much more sensitive than the dry method and will show smaller defects. Magnaflux will even show locations of defects below the parts surface where other tests like Liquid Penetrant NDT will only show defects open to the parts surface. Unfortunately neither Magnaflux nor Liguid Penetrant will show defect depth, but Ultrasonic testing will. Ultrasonic NDT introduces sound waves into the part which are reflected off the defect and back to the Ultrasonic unit's transducer head. The Ultrasonic unit is calibrated to the material being tested using a piece of material of known thickness and very accurately measures the time it takes for the sound waves to be sent out and return then calculates the defects depth. I'd suggest taking any parts that are mission critical such as connecting rods, cranks or engine blocks to a qualified NDT service for testing. The operators are highly trained to pick up defects.Comment
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Re: Magnafluxing
eugene: just when i thought i knew all there was to know of magnafluxing, along comes your post. thanks much for enlightening me and i'm sure others. mikeComment
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Isn't....
the term 'Magnaflux' a registered trademark of a particular company with the generic term being 'magnetic inspection' for the process? If so, do all the variations mentioned in various threads address the specific form of magnetic inspection referenced (Magnaflux) or are they more properly associated with other forms of the inspection process?Comment
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Re: Isn't....
In the "old days", the "wet" method was commonly referred to as "Zyglo" inspection.Comment
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Re: Magnafluxing
Is the Ultrasonic NDT used only when defects are found with other methods, or can the Ultrasonic test be used alone? In my uninformed opinion, it seems the Ultrasonic test is so sensitive, it may be extremely tedious and inefficient to do an entire block.
And thanks to all for the great info.Comment
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Re: Magnafluxing
The correct name is Magnetic Particle Inspection. Saying the trade name Maganflux is kind of like saying you made a xerox of a document in place of saying, made a copy.
Ultrasonic Testing is very labor intensive and performing that type of NDT on an entire engine block would be cost prohibitive. When I was first starting out in the foundry industry I used Ultrasonics for two distint purposes. First was for determining if subsurface defects existed in critical zones such as cylinder walls and on cylinder head firefaces. This operation was not performed on a production basis, only on Samples and on castings to be used for special applications like race engines. The second use of Ultrasonics was as a thickness gage. I'd draw quadrants onto a block casting's bores then using a curved transducer search for the highest and lowest readings. Engine blocks and cylinder heads in the old days were created by using sand cores that were stacked together in a sand mold. The sand cores would stand the heat of the molten metal but would have a tendancy to become slightly plastic and could warp during the melt solidification process. We'd use Ultrasonic thickness testing to determine how much the lower water jacket core of a cylinder head warped by reading the fireface thickness. The cylinder heads would be color coded and machined in different batches so the fireface would always be with-in low and high thickness tolerance. On engine blocks we would measure the cylinder bore wall thickness then cut the machining target points accordingly. The walls had to meet a plus and minus specification which also took into account clean-up in the cam bore.
Back when Ralph Nader was all over Pontiac because they ran out of replacement cylinder heads for the SD455 engine before warrenties had expired we tried running GM supplied tooling at our foundry. By using Ultrasonics we determined that we were never able to produce a head without a warped lower water jacket which caused our castings to be unusable. I guess by our trying GM was able to get Ralph Nader off their backs.Comment
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Re: Magnafluxing
Eugene,
What you write is really interesting. Can you be persuaded to write an article on Megatic Particle Inspection such as what you posted for "The Restorer"? Regards,Comment
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Re: Magnafluxing
Hello Jim,
If there is a interest an article on NDT could be written. I left the sand cast iron foundry in 1990 for a position at a steel foundry that uses sand cast and Investemnt (lost wax) process. We produce castings for use in Nuclear and Naval applications and have a NDT Laboratory Service facility onsite. I'm not in Quality Management any longer, moved on to Sales, but I'm pretty certain the current Quality Director can be talked into helping writ an article.
As a new member of NCRS I'm not sure if anyone has written an article on the casting process in general. It might be of greater benefit if the readers would get a flavor of how castings are produced before jumping into the NDT topic.
EugeneComment
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Re: Magnafluxing *TL*
Eugene,
We have had only a few articles that touch on the casting process, and none that explain it in detail. There have been none on NDT. Any submissions you care to make would be welcome.
TerryComment
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Re: Magnafluxing
Hello Terry,
It would be an honor and a pleasure to submit an article starting with the casting process and moving to NDT.
When I get back home after the Chevrolet Corvette Celebration in Nashville event next week I'll e-mail you for article submission information such as article length limits and preferred digital photograph formats.
This is our first long roadtrip in a C2. In my wife's opinion it's seriously lacking in storage space compared to the Tahoe so the laptop must stay at home.
EugeneComment
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