Damascus barrels and magnafluxing question

Posted by: kray

Damascus barrels and magnafluxing question - 10/28/06 11:33 AM

What is magnafluxing? Is magnafluxing nessessary to confirm the condition of damascus barrels (1890s Greener with nitro proof marks not marked in tons) and if so, where can you send a gun to have damascus barrels magnafluxed?
Posted by: HIGH$TRAP

Re: Damascus barrels and magnafluxing question - 10/28/06 12:05 PM

http://www.domson.ca/Technical_Articles/FAQ_MPI.htm
HTH :>) Bob.
Posted by: gil russell

Re: Damascus barrels and magnafluxing question - 10/28/06 12:54 PM

In reality, is it necessary to go beyond a close examination of a set of Damascus barrels for pits and wall thickness? I would think that if those two aspects were in order that the high-tech approach (I don't even know what it is) would be superfluous. Just MHO.
Posted by: Paul Harm

Re: Damascus barrels and magnafluxing question - 10/28/06 03:33 PM

IMHO . as Gil said - if it looks good , shoot it - paul
Posted by: 2-piper

Re: Damascus barrels and magnafluxing question - 10/28/06 05:40 PM

I have a twist bbl which I "Know" has about a ΒΌ" long crack following the twist. Knowing where it is I can only find it with the aid of a magnifing glass. Anyone who didn't know it was there would never find it from a visual inspection. I have no idea if magna-flux would work on it or not. I would presume if properly set up by a knowledable operator it would. Possibly dye penertrant & a black light would also find it.
Posted by: Dick_dup1

Re: Damascus barrels and magnafluxing question - 10/28/06 05:58 PM

Magnifluxing (MT) and dye penetrant testing (PT) are surface examinations versas radiography (RT) and Ultrasonic Testing (UT) which are volumetric tests. Surface exminations look for pits and cracks. MT has some slight subsurface capabilties. Because a Damascus barrel is pattern wleded and one can readily see the welds, both MT and PT would be useless for surface examination. Becuase the welds extend throughout the material, volumetric testing will also not work. This is precisely the problem with Damascus barrels. One cannot determine by any method if a pit or crack exists. -Dick
Posted by: 2-piper

Re: Damascus barrels and magnafluxing question - 10/28/06 06:24 PM

Dick; The magna-fluxing I am familar with worked by applying a magnetic field to opposite ends of the part. A crack causes opposite poles to form at the crack & the dye (magnetic) to concentrate there. This would of course not work on an internal flaw, which I assume is what you were referring to. The one I referred to in my bbl goes completely through the wall. It seems to me this is the type of flaw magna-flux detects.
Posted by: Jim Legg

Re: Damascus barrels and magnafluxing question - 10/28/06 06:36 PM

I'd think that magnafluxing would show a perfect Damascus barrel to be FULL of flaws that are not really there. JL
Posted by: Dick_dup1

Re: Damascus barrels and magnafluxing question - 10/28/06 07:50 PM

The problem is that MT or PT would not only find your flaw but would find the surface welds of a Damascus barrel. MT uses a ferrous powder and then it is wiped off. The powder stays in the crack and is visable upon magnetization. PT uses a red dye that seaks cracks. The red die is then removed from the surface but stays in the crack. A white developer is then sprayed onto the surface and the red in the crack shows. Radiography (RT) might show the crack if is was much larger than the welds in the barrel but with a defect that big, you would not need any form of NDE to find it. -Dick
Posted by: 2-piper

Re: Damascus barrels and magnafluxing question - 10/28/06 09:44 PM

Dick; I worked as a machinist for 35 yrs & have been around both processes, but never saw a damascus or twist bbl checked. I know where this crack is, but it is not open & definately not evident. I doubt many could find it even if told it was there. My thinking was that even if the MT process picks up on the welds, this spot would stand out much more prominent, but I could be wrong. Not trying to be argumental, incidently, but to discuss what will & will not work.
Posted by: tanky

Re: Damascus barrels and magnafluxing question - 10/28/06 10:18 PM

I can assure you that if a mag particle test or a dye penetrant test were performed on a damascus barrel that it will not show the welds between the ribbons unless they were not fused. It will only show where a flaw is such as a crack or lack of fusion between the welds. These two tests can be used on a damascus barrel but can only tell you if flaws exist where the barrel is visible. You cannot check between the ribs. One way to check the barrels with the dye penetrant method is to dye the inside of the barrels, let the dye penetrate,clean off the dye and then spray the developer on the outside of the barrels. If you get some red indications on the developer it means that you have a porous spot in your barrel. This may be a crack,lack of fusion, or a small hole. There is a test method called an eddy current that can be used to test tubing but it's probably used by seamless tubing manufacturers in the quality control process. You should be able to look in your phone book and look for a testing company in your area. The more industry you have around you the more you will find. If you live way out in farm country they may be a bit scarce. I'd bet that there are some really suitable test methods available in this computer age that I am not aware of that could be used to get a really good test on some old damascus barrels. Xray has sum limitations and probably would only have limited use in this application.
Posted by: smlekid

Re: Damascus barrels and magnafluxing question - 10/29/06 06:42 AM

the amount of times I have Magnafluxed things that have been welded you always see the edge of the weld regardless of the qaulity of work I will have to take my H Grade Lefever barrels to work and try it and see what it looks like I would imagine a series of radial marks following the twist I will have to try it this week and report back
dont forget with a crack test you have to apply the charge across the crack it will show up on a parrell charge but it works much better across it at least in my field of work (engine reconditioning)
Posted by: Marc Stokeld

Re: Damascus barrels and magnafluxing question - 10/29/06 07:31 AM

I am not an NDE technicain, but at one time did have a low-level certification in NDE/NDT. I have taken courses on it and managed NDE folks in several countries, so I have seen a lot of it "up close and personal."

one little pet peave-people involved in NDE/NDT (non-destructive evaluation/non-destructive testing) never use the term "magnaflux." At least I have never met one who did. Instead they refer to "mag-particle testing," usually just called "mag particle" or they say they will "mag" a part. It is kinda like calling a Parker a Fox. Minor pet peave.

What NDE shows you is an "indication," not a crack. A good magparticle technician can examine a set of barrels and find abnormal indications, usually indicationd a "crack," "slag inclusion," and whatnot. They can also give you a qualified opnion on how likely the indication is to cause problems later on. They can find these inside the wall of the tubes, not just on the surface. If it were me and I wanted some testing to give me a warm and fuzzy about my tubes, I would "wet mag" the barrels and be happy with that. In this case, you acutally use a liquid that holds suspended paricles. I would also use the liquid requireing a black light to see the florescent indications. I think this would give the best of finding menaingful indications in the tubes for the least cash outlay. Most "bang for oyur buck," if you will.

If all you are worried about is surface indications, then a good visual inspection or PT (dye-penetrant testing, or "dye checking") will reveal indications quite nicely, quickly, and cheaply. Without going into detail, there are several different ways to MT and PT.

Also, a good technician can find an amazing amount of indications from a straight visual inspection. They do it every week of the year and can find things I sure can't always see, and I consider myself to be above average at finding indications.

One thing I have not seen here is UT, or "ultrasonic testing. And no, we are not checking to see if your damascus tubes are knocked up!!! A good UT technican can tell you loads of information about the indications. UT, especialy "shear wave," makes my brain hurt and eyes cross. you need a very experienced technician to perform this test. But a good one can tell you a lot about your tubes and any indications they may have. The hard part here is finding a technician with a lot of UT experience who you trust. A relatively small number of them in the NDE world.

And there is nothing wrong with good ole' RT, or x-ray. Yes, there will be tons of lines on the film due to all of the welds, but again, a good technician can find indications there.

If you are really worried about the integriy of your tubes and will spend some cash to be warm and fuzzy, RT them and UT them if RT shows an indication that worries you.

Of course, the easiet way to check the tubes is to have the gun proof tested in good proof house. Remember, a pressure test ALWAYS supercedes any NDE/NET findings. Basically, the "proof is in the pudding," or in this case "the pudding is in the proffing!"
Posted by: Lowell Glenthorne

Re: Damascus barrels and magnafluxing question - 10/29/06 08:26 AM

Stop the hocus-pocus, with today's health care costs - send the gun to be re-proofed.
Posted by: Chuck H

Re: Damascus barrels and magnafluxing question - 10/29/06 08:39 AM

There have been some interesting posts on this. Seems like lots of opinions on whether or not Mag Particle inspection would be of any value for inspection of damascus. Marc has some good input based on real experience. Good stuff.

I'm not a NDT tech but have been around it all my 30 yrs in aerospace. My take on Mag Particle inspection is that Fluorescent Mag Particle should be used for this application since is has the capability to resolve small flaws much more readily. This method has the superfine magnetic reactive dust suspended in an oil solution. The oil solution is flushed over the part and then the part is energized and a black light is used to reveal the accumulation of the particles where they collect.

I haven't done this on a damascus barrel but the late Dr Oscar Gaddy related to me that he did indeed use Fluorescent Mag Particle on a set and said the damascus pattern is a very dim background in the visual inspection and that a crack did indeed reveal itself. So, I have only one actual example of someone having done an crack inspection with FMP. But, it was a trusted source.
Posted by: Dick_dup1

Re: Damascus barrels and magnafluxing question - 10/29/06 09:42 AM

I have set up, staffed and managed Quality Control and NDE Departments in the Nuclear Industry. I assure you that i am familiar with just about any NDE procedure including UT. The one thing that has not been metioned in this discussion is the requirements for 'Passing' an NDE exmaination. These requirements are rigerous and refer to porosity size, number of indications, linear defects among others. A 'Tech' does not give you an opinion, he is not qualified to make a determination of what is safe and what is not safe but tells you what is there and then the code tells you what is acceptable. Interpretations are done by qualifed Welding and NDE inspectors to written criteria.
In all the conjecture I have read, there is no rigerous standard for what is safe and what is not in testing a damascus barrel with NDE. Coupled with the manufacturing methods and materials of the day, there is no way to determine if what you find or don't find is safe. If you think that you can make that determination for yourself simply purchase the NDE materials and do the testing. Dye Penetrant (PT) is very simple, spray on the penetrant, wait, wipe it off and then spray on the developer and look for red indications. As I said in another post, it will be a 'crap shoot'.
I understand the romance with wanting to safely shoot these old shotguns. One of my first doubles was an Ithaca 'Long Range' Double manufactured by Western Arms. I shot a few doves with that gun but research showed the reciever to not tensile steel but a cast type of steel. This type can be subject to brittle fracture. I sold the gun to my dealer. I can not predict the future.
Perhaps it my mathematical and physical science traning but I examin what I am doing and make a determination of what is safe. As the Quality Assurance and Nuclear Safety Manager, that is what I am trained to do i.e make safety decisions which adhere to Code, State and Federal Law and if there are no standards, make them in a controlled and rigerous manner. So I have no problem in making the determination, that you will not obtain any data that will allow you to make any objective determination about your barrel or barrels. -Dick
Posted by: Chuck H

Re: Damascus barrels and magnafluxing question - 10/29/06 01:27 PM

Dick,
While I did work in the QA biz for many years, I've been in the engineering side for the last 10 yrs where our guys set the criteria for inspections or more often I'm involved in evaluating what happened on failed parts and what to do about preventing failures thru inspections.

The studies I've seen suggest that probabilities of detection (POD) at 95% is about a .050" crack/flaw for FMP on most stuff. On most parts we don't allow for any detectable cracks/flaws. That says the minimum detectable crack size is acceptable for strength up to at least twice that size. But, we allow for 2 opportunities to detect. Establishing the inspection interval is at least as important as the type of inspection. The repeated stresses need to be assessed along with the strength of the part in order to intelligently establish intervals. As a NDI pro you're undoubtedly familiar with all of this, I just wanted the crowd here to understand that there's more to it than just inspecting a barrel with a NDI method and declaring it crack free. It ain't necessarily so. It may have a crack below the detectable threshold or may develop a crack right after being inspected. That's why critical components on commercial airplanes get regularly scheduled inspections for cracks.
Posted by: Dick_dup1

Re: Damascus barrels and magnafluxing question - 10/31/06 05:28 AM

Chuck, you are indeed correct.
What we are responding to is the desire of individuals with Damascus barreled shotguns to assure them selves of the barrels integrity and the ability to function in the future without a catastrophic failure. What I pointed out is that the inspection of a Damascus barrel with MT will not yield any objective evidence and that NDE relies on objective evidence and established criteria to make a determination of safety.
You correctly pointed out that any detection method may not find all indications, the theory then being that the flaw is below a size where it will not grow to a size that will cause catastrophic failure before the next detection interval. In another post I talked about the ability of a homogeneous material to sustain an umilited number of cycles if the stress was below the yeild strenght. This ability is predicated on a homogeneous material i.e. without any defects. In an aircarft the material used is not homogeneous, there are various rivits(holes) and welds that expereince stress cycles every flight. These fastening are sources of cracks because they act as stress risers and any undetected crack/flaw may grow to where if large enough will cause a failure.
Unfortuneatly what we cannot provide is assurance that MT provides a method to assure Damascus barrels are safe to shot. -Dick
Posted by: Chuck H

Re: Damascus barrels and magnafluxing question - 10/31/06 09:07 AM

Dick,
I agree with most of what you're saying. A few things you mentioned, I think need a clarification.

I do indeed believe that a good Fluorescent Mag Particle Inspection of a set of damascus barrels (or homog steel) will provide objective evidence. I think what you're saying is; there are no standards to tell either the inspector or the evaluator what is detectable (coupons with engineered flaws) or what to do about indications of various sizes. While this significantly puts the inspection in question as to what it can detect in the barrels, it still has a fairly high level of detectability based on it's history of generic parts. What to do about indications is another matter.

Your understanding of a homogenous material's ability to sustain unlimited cycles if the stress is below the yield strength and no flaws exist is pretty close. But to clarify, this applies to steels (not aluminums) only and my understanding is that the material is said to be able to sustain unlimited stress cycles if stress typically is in the area of 1/2 the ultimate strength and assumes a pre-existing flaw just at or below detectable size (.050" typically). At least this is my passing understanding with my failing memory.

I agree whole heartedly with you that any NDI method will not guarantee any barrel is safe to shoot. It may, however, help a prudent, intellegent person, in adding another piece of information about a set of barrels in his assessment of them along with more conventional methods of inspection such as wall thickness and surface condition.
Posted by: Zircon

Re: Damascus barrels and magnafluxing question - 11/05/06 12:22 PM

Dick, in addition to standard codes (how large of an indication is rejectable), there is the issue of standards to set up the inspection process - especially with UT. The instrumentation needs to be calibrated with a standard that has similar metallurgical characteristics to the barrel being tested. For all practical purposes this means the standard needs to be a damascus, twist, or what have you barrel, equivalent in metallurgical condition (chemistry, thermomechanical processing, and final heat treatment) to the barrel being tested. The standard has reference notches, flat bottomed holes or what have you that the instrumentation must "see" and detect at a specified level. Then, and only then, is the test valid. I believe there are way too many variables to conduct NDE and then make a conclusion as to the safety of any given set of barrels.

As far as proofing goes, it's been around a long while, but it isn't the be-all, end-all either. There are some barrels in the "barrel study" that show definite signs of fatigue failure - something that no single overpressure shooting event will be able to detect.
Posted by: HomelessjOe

Re: Damascus barrels and magnafluxing question - 11/05/06 03:24 PM

Interesting post. I guess shooting damascus barreled guns is as close as I'll ever get to sky diving or bungee jumping.
L.F.
Posted by: Dick_dup1

Re: Damascus barrels and magnafluxing question - 11/05/06 03:25 PM

Originally Posted By: Zircon
Dick, in addition to standard codes (how large of an indication is rejectable), there is the issue of standards to set up the inspection process - especially with UT. The instrumentation needs to be calibrated with a standard that has similar metallurgical characteristics to the barrel being tested. For all practical purposes this means the standard needs to be a damascus, twist, or what have you barrel, equivalent in metallurgical condition (chemistry, thermomechanical processing, and final heat treatment) to the barrel being tested. The standard has reference notches, flat bottomed holes or what have you that the instrumentation must "see" and detect at a specified level. Then, and only then, is the test valid. I believe there are way too many variables to conduct NDE and then make a conclusion as to the safety of any given set of barrels.

As far as proofing goes, it's been around a long while, but it isn't the be-all, end-all either. There are some barrels in the "barrel study" that show definite signs of fatigue failure - something that no single overpressure shooting event will be able to detect.



You are indeed correct.
As I said, I set up, staffed and managed an NDE Department as part of a Quality Control Department. I had Level I, II and III Inspectors for every NDE discipline working for me. I have participated in the NDE of everything from welds on 35" SS piping, Inservice Inspections by underwater UT, radiography and eddy current testing of Steam Generator tubing. I have not listed all the standards because I wanted to keep things simple.-Dick
Posted by: Zircon

Re: Damascus barrels and magnafluxing question - 11/05/06 07:13 PM

I'm in a similar circumstance, Dick. Have a QA and Inspection group that includes Level II inspectors and Level III examiners for UT, PT, RT, and ET. Not questioning your veracity, just wanting to add some commentary so that those outside the profession understand some of the limitations.
Posted by: Jim Haynes

Re: Damascus barrels and magnafluxing question - 11/06/06 03:34 PM

A very interesting series of posts. As an ASNT certified Level II inspector in Mag Particle Testing (MT) among others, I agree with everything Dick_dup1 stated. Someone suggested a wet flourescent test, but I can ascertain that would be a near impossibility to come to any conclusions. I asked my Level III what procedure would he write and what code would he use to perform such test on damascus barrels. He came back with the answer that first he would have to find from a customer or appropriate source what would be the acceptable and reject criteria. This is because a damascus barrel by nature of construction will display continuous bands of discontinuities. He knew of no source of reject criteria for relevant indications. In fact, it would be very difficult to determine between relevant and non-relevant indications, depending upon the type/quality of damascus or twist construction.

For fun, I took the damascus barrels of one of my wall hangar guild guns (a JABC) and did a head shot followed by a coil shot. Under the black light I had a beautiful yellow/green graphic of the welds. A discontinuity that was relevant would have been very hard to find, much less interpret.

As an afterword, cleaning the barrels after the test required intensive work. Nonetheless, I found lines of rust beginning where the microfine particles had imbedded themselves. I would not want to put damascus barrels from a high quality gun in such a test. Jim Haynes
Posted by: I. Flues

Re: Damascus barrels and magnafluxing question - 11/06/06 10:34 PM

Awwww....come on guys! Jist get those Damascus barrels Magnaported and be done with it!


Sorry, I couldn't resist.....;-)

Mike Doerner
Posted by: Dave Weber

Re: Damascus barrels and magnafluxing question - 11/11/06 01:55 PM

http://www.domson.ca/Technical_Articles/FAQ_MPI.htm

What is Magnetic Particle Inspection?
Magnetic Particle Inspection or MPI is a nondestructive testing (NDT) method that is used to detect surface or near to surface discontinuities (such as cracks) in iron or steel. This NDT method is also often referred to as "Magnafluxing."

How does it work?
As its name implies, Magnetic Particle Inspection works using magnetism. Thus it will only work on a ferromagnetic material such as iron or steel.
The part or surface to be tested is placed in a magnetic field. The field is made up of flux lines that by nature move from the north pole of a magnet to the south pole. For this to happen the flux lines can either move through the air, or they can move through the metal. It is "easier" for the flux lines to move through the metal. Thus, most of them do just that; they travel in a path that is parallel to the surface being tested.
If, there were a crack in the test surface, the path of the flux lines through the metal would be interrupted. The flux lines, in order to cross this "ditch" would be forced to "jump over" it by temporarily leaving the metal, and travel through the air, before returning to the metal. This causes what is called a flux leakage at the crack. The flux leakage causes the crack to become a mini magnet. At this point, if one were to sprinkle some iron filings over the area with the crack, the filings would immediately be attracted to the crack. They would form up along it in such a way that the filings would form the complete outline of the crack. This would be easily visible to the naked eye, especially if the iron filings were themselves red in color, and the test surface were painted white.

What are some of the advantages and disadvantages of MPI?
MPI has the following advantages:
1) It's considered to be the best method for the detection of fine, shallow surface cracks in iron and steel. Thus, it's ideally suited to look for fatigue cracks, heat cracks, and other discontinuities, in weldments, on shafts, etc.
2) It will work through thin coatings of paint. This is not true for some of the other NDT methods. Thus new paint jobs on equipment need not be marred for this method to work.
3) It is highly portable. This method can be used anywhere, such as out in the field on construction sites, and even under water.
4) It's not limited by the size and shape of the specimen being tested. Small tanks to large cranes can be inspected using this method.
5) Inexpensive. The powders and liquids used for this test method are readily available.

MPI has the following disadvantages:
1) It will only work on ferromagnetic materials such as iron or steel. For other materials such as aluminum or plastic, alternative methods such as liquid penetrant would have to be used.
2) Although it can detect problems that are close to the surface of the material, ones that are very deep in the material will not be found when using this method.

How does Domson make use of MPI?
Of all the various NDT methods, Magnetic particle inspection is the method that Domson employs the most. It is always used extensively throughout our equipment certification programmes.
MPI is used on all the critical welds on lift equipment, and other structural members. It is also used on the main bodies/sections of lifting equipment and structural steel. Examples of this include the saddle areas of lifting hooks, and the high stress corner areas of structural steels.

MPI is best suited for finding surface cracks. Why would you use it on structural steel; wouldn't you miss the internal cracks?
Lift equipment and structural steels can be subjected to continuous and/or dynamic loads (i.e. shock loads). These can cause fatigue cracks to form in the cross sections of the steel. However, whether the steel is subjected to bending or shear, or shear due to angular twisting, or any combinations of these, it is the surface of the part that is typically subjected to the highest stresses. This means that if a fatigue crack were to form on the cross section of a part, it will always form on the outer surface of the part, rather than starting somewhere in the middle or interior of the cross section. Therefore, MPI is ideally suited for finding fatigue cracks.