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  1. #1
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    Default Examining a fillet bead fracture

    Referring back to the previous thread I have started this new one, so that we can examine what to look for when a fillet weld is fractured. Its a great feedback, as it is immediate .Break the fillet, examine the fillet break, note the defects if any and then work to eliminate them by correct practice and technique.

    First up, let us consider the method of fracture for the fillet bead.
    For most of us not blessed with a hydraulic press, the usual method is application of a large hammer so the the vertical leg of the tee piece "hinges" on the horizontal leg as it is struck. If you are lucky and have a hydraulic press hydrualic muscle replaces our own.

    Safety note! beware that the force used may cause the test piece to slip under the hammer or press ,so a measure of observation and common sense is required. you and you alone are responsible if ithe weld test piece flies and and hits you in the teeth or the ribs OK? A caution here then, to warn that the fillet bead when being hammered or hydraulically pressed, must be uppermost - on top.

    To put this another way, the crack to fracture the bead must start from the back- the un-welded side of the tee piece and work through the weld as the legs of the tee piece are opened. This troops, is why we Tafe people are fond of theory first,so that we can explain to eager new students who want to exit to the workshops and do stuff,do not get injured when doing stuff.

    The question arising then,what do I look for ? First up its an external inspection looking for external faults.

    These are faults /defects that will possibly cause the weld to fail.

    Weld Profile , Bead convexity and concavity,
    Undercut of weld toes
    Craters crater cracking


    There is more but that's a Google job. I wouldn't be a teacher without giving homework ,would I?. Check out MMAW weld defects and I'll answer questions on what you find. We will get to the fracture inspection,but first things first.we need to do an external check before the fillet is broken.

    Grahame

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  3. #2
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    Default

    Oh come on you lazy lot!

    There's two sorts of defects OK!

    External and Internal.

    Before you break the fillet do the external visual inspection.

    For senior eyes a magnifying glass is acceptable.

    You are looking for undercuts along the weld toes where stress cracking from an imposed load can start from. caused by electrode travel speed too fast and/or excess amperage , electrode angle too steep.
    Crater cracks which are the depressions left from breaking an arc at the run end - assemblies all ready under tension can show crater cracks
    Inclusions which are a commonly beginner induced defect - holes in weld filled by weld slag- usually from excess long arc and /or amps set too low for electrode diameter.Some inclusions are gas holes caused fro welding over paint,oil,grease & dirt .usually hydro carbons.

    Cross section profile is important as a big belly in an over filled fillet causes an overoll again its a place where cracks can start under load conditions-not visually attractive.
    An under filled fillet profiles are not desirable as the throat section is to small to to take the load and may crack.
    If I have forgotten something in the range of applicable defects,welders please feel free to chime in with it.
    Newbies are encouraged to ask questions but don't forget theres google.

    If there none of those you can break the fillet as described previously.

    Its over to you then.

    Grahame

  4. #3
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    Default

    I'll have a go later today if I can, but can't understand how you orientate the sample for breaking. If I have the sample fillet up and squash it then the weld will break from the front?
    Can you post a sketch?

    Michael

  5. #4
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    Default

    As the legs are moved by hammer or hydraulic force they tend to fly at the point of fracture. The reason for the set up is to minimize the chance of being struck by the flying lumps of steel
    The axis of the weld is set up north- south to prevent a leg flying back at the operator. The long edges are east west moving to the side/s .

    The fillet bead must be at the top/outside as opposed to the bottom inside as it will not fracture inside.


    See the rough sketch

    Grahame
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  6. #5
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    Default

    Hi Graeme, thanks for starting this thread - I only just saw it. I'm always looking out for ways of improving as I occasionally get those defects you are referring to.

  7. #6
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    Default

    Hi Grahame, I would appreciate some feedback on my welds.
    Like many, I've never had a lesson or even seen a real welder work. I also suffer from the fact that I do no welding for months, then by the end of the project I can do what seem like OK welds, only to forget by the next time.

    The photos are 10mm plate, tig welded at 230 amps, no pedal. I kept away from the corners of the plate because I thought it would make it easier to break. It took some heavy hits with a hammer to break them as it was.

    A lot of faults I can recognise because I read a fair bit on the welding forums. Doesn't make me better though, I know I need more welding practise. As someone else said, after all my reading, I can weld better than most people in my sleep. Its just when i wake up the problems start.

    I've never tried breaking the welds like this though, so I would be interested in what you can tell about the weld from the fracture as I've never read anything on that.

    The weld is pretty rough looking and I can maybe make them look a bit more consistent after a bit of practice, but I have to be honest and say there are a lot of welds like this on my projects.
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  8. #7
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    Quote Originally Posted by sossity View Post
    Hi Grahame, I would appreciate some feedback on my welds.
    Like many, I've never had a lesson or even seen a real welder work. I also suffer from the fact that I do no welding for months, then by the end of the project I can do what seem like OK welds, only to forget by the next time.

    The photos are 10mm plate, tig welded at 230 amps, no pedal. I kept away from the corners of the plate because I thought it would make it easier to break. It took some heavy hits with a hammer to break them as it was.

    A lot of faults I can recognise because I read a fair bit on the welding forums. Doesn't make me better though, I know I need more welding practise. As someone else said, after all my reading, I can weld better than most people in my sleep. Its just when i wake up the problems start.

    I've never tried breaking the welds like this though, so I would be interested in what you can tell about the weld from the fracture as I've never read anything on that.

    The weld is pretty rough looking and I can maybe make them look a bit more consistent after a bit of practice, but I have to be honest and say there are a lot of welds like this on my projects.
    Gday Sossity

    For a self taught tig welder ,those pictured welds are a of a high standard - not perfect like some of the pro;s work but still pretty good.
    I see by your prep in removing the plate scale you already know the problems leaving plate scale causes.
    In pic 1 note that the plate edge still remains. To cure that , I recommend 2 changes .
    One to your prep and one to your technique.

    1. The prep edge on the top plate needs to be sharp and its usually prepped slightly less than 90 degrees say 88 degrees or near. The idea being that instead of the distortion pulling it out of 90 degrees,working with the expected distortion pulls the (finish) angle INTO 90.

    2. The sharp angle presents a face to your arc which should be almost square so that the peno is maximum at this point. The more the drag angle ,the less peno into the face as indicated in the edge break that doesn't come to the edge of the plate..
    If you try that I think that the next break will show a fracture right up to the edged and into the 100mm thickness.

    On the pre break pic your ripple pattern is great. Some are influenced by the American "stack of dimes"fill pattern which I fail to understand.To my way of thinking that particular pattern can induce cracking as there are peaks and hollows and sharp edges in the pattern.

    Other than the suggested changes, work on achieving a parallel and consistent pattern. This is controlled by the timing of the dip into the molten puddle.and the amount of fill in each "dip"

    Another point of interest is noting the grain size of the separate filler metal and the parent metal.The filler metal grains are noticeably finer that the coarse parent metal grains.

    Given that practice is not regular you are going well.

    Cheers
    Grahame

  9. #8
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    Default

    Regarding my comments about taking out the fillet edge in sossity's post.

    For those of you who may be doing fab work that is only lightly loaded ,don't get too worried about this this.
    If your broken test fillet beads are free from inclusions, porosities and other small defects ,don't fret too much about not taking out the edge.
    Remember the application is very different to the norm, as is the process.

    Mind you its great to strive for,but in many cases its just gilding the lily.

    In a lot of cases its all about judgement and application. If its a garden gate some crap welds and it will still hang together.However if its a road going trailer thats often fully loaded and constructed with poor design and technique ,well that,s quite a different matter.

    Some more break photos like sossity has posted will be welcome.There are a bit of a shortage of them to use as examples,available on the net.

    Grahame

  10. #9
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    Default

    Hi Grahame,
    Thanks for the feedback, that's encouraged me to find some time to practise now. I always struggle with time and usually just build whatever it is that needs doing, so this is great

    I've a couple of questions and maybe you could comment on these pictures too. This was my first weld (done before the first set of pictures i posted) but I made a beginner mistake of not doing a dry run, and I got caught out halfway across the weld and couldn't keep the torch position right as I was too stretched. You can see where it all went wrong, that the weld didn't attach to the plate properly at some points and I can even see a bubble in the weld. But the first half was Ok I think, and done on properly squared steel.

    I used the same bit of steel for both runs, and it originally had a sharp edge as you suggest. I just ground the weld off for the second attempt but I guess never made the edges very straight, so I know not to be sloppy now. I had seen the odd edge in the first set of pictures and didn't know what caused that but now you've told me, thanks.

    So these pictures are of the first run I tried. The rhs I thought was going well, but does it look better on penetration at the joint? It seems to have torn unevenly, is that different depths of penetration due to me hesitating? Does it look like I'm not getting good penetration right in the corner of the weld, because it looks where it is torn unevenly, I can see polished steel underneath? Also, on both attempts I actually put a two small tack welds on the backside which I removed with the grinder before breaking the weld. Would I still do the 88 degree trick with tack welds or should I not use them at all? I find the tack weld pulls the steel also, but if you get the pre-angle wrong its much easier to redo, before going for it with the big weld.

    Thanks very much for this, I've never met a real welder I could ask advice from in person.
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  11. #10
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    Sossity,
    pic 1 shows good peno about the three quarter way mark and is about the degree of peno the whole sample should show.The craters need filling at the end of the run and there was one place where the bead was restarted ahaed of the crater. By all means make the arc and then back up into the crater and then begin with fill..With a good practice , someone else will be hard put to see the re start point.
    stated in the code. If distortion is a problem I would use the prep,but otherwise for ordinary work no.Again it is application.

    A job can suffer slight distortion and yet be quite sound.
    The 88 degree thing was something I came up with when the students in cert class looked like failing when the practice pieces were pulling greater than the 5 degrees as set by the code.
    To obtain that consistent peno line, consistent travel speed, consistent angle, consistent arc length etc.is really a must.

    As an aside, for everyday welding though, is Tig really justified in terms of cost, speed and quality required. Perhaps it is all that you have.The DC tig power source will lend itself easily to stick welding if you have the right connections.

    The type of work usually sets the type of welding processes.

    Say you were doing benches, I would just stick weld them. Not even fully welded either.I have a bench that I assembled 23 years ago and it has only 12mm tacks holding the frames together.Its been dragged around and hammered upon bigtime and yet I never had a problem.

    Cheers
    Grahame

  12. #11
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    I suppose it is hard to justify using tig for heavy guage steel, but I haven't used anything but TIG since I got the welder a couple of years ago. I just like using tig.
    Over the summer holiday, I built a decorative gate out of 25 x 12 flat bar. The first sections I welded onto the frame were quite critical for appearance and I find it much easier to set weld angles using tig than MIG. When the mig wire first pokes onto the metal, it always seems to knock it off position. I also wanted the focal point to look perfect and in fact used autogenous welds to give really straight edges. I intended to do the rest of the gate with MIG, but I found by turning up the current and just using the switch, not the pedal, I could go as fast as I could feed the filler in, and decided it wasn't that much slower than the mig anyway. Especially since they were all short welds. Plus more control and I never had to grind any of the welds for appearance. Because I had a load of practise with 12mm thick stuff then, I just used the same settings etc for the test break.

    I tried stick for the first time in 15 years last night. It took me an hour to do 7 weld/break/grind off the weld again , the best of which is shown here. It didn't come easy to me, and in particular, I struggled to get started without getting flux inclusions in the weld right at the start. In the end, I found if I did little circles on the same place when I started, I could start without inclusions. In fact, i can see that is the only place where I got any penetration so maybe that would be a better technique all the way along. The problem i found with starting this way was i got a ton of flux build up round the weld so i couldn't see anything but flux. This was using a 3.2mm rod I got out of supercheapauto a while ago, just to test mma when i got the new welder. I don't know what grade it is or anything, i think it was called satincraft.

    This way of testing your welds is great because its so easy to break rather than cut the weld. I noticed the weld was as hard to break as the tig welds but when it broke it just went, where the tig would need several heavy blows even after the weld started going. I guess its more brittle?

    I suppose was a bit dissapointed after I broke the weld and saw I was getting nowhere near the corner, but now I can see I'm not getting penetration I can try and modify my technique and get the flame into the corner more. I don't know what the two funny marks on the break signify, near the top edge, what do they mean I'm doing wrong?
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  13. #12
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    I'll play too

    20mm and 12mm bar, first test with MIG - UniMIG 165 running 0.8mm wire & CO2 beer gas cranked to the max (14m/min, about 23V).

    Did better than I expected, and the press jack made some "working hard" noises to break it open. I wish I had a pressure gauge on the hydraulics to get some kind of measure of the force involved so I could compare it to stick (which I'll try next).

    MIG1.jpgMIG2.jpgMIG3.jpg

  14. #13
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    Quote Originally Posted by sossity View Post
    I suppose it is hard to justify using tig for heavy guage steel, but I haven't used anything but TIG since I got the welder a couple of years ago. I just like using tig.
    Over the summer holiday, I built a decorative gate out of 25 x 12 flat bar. The first sections I welded onto the frame were quite critical for appearance and I find it much easier to set weld angles using tig than MIG. When the mig wire first pokes onto the metal, it always seems to knock it off position. I also wanted the focal point to look perfect and in fact used autogenous welds to give really straight edges. I intended to do the rest of the gate with MIG, but I found by turning up the current and just using the switch, not the pedal, I could go as fast as I could feed the filler in, and decided it wasn't that much slower than the mig anyway. Especially since they were all short welds. Plus more control and I never had to grind any of the welds for appearance. Because I had a load of practise with 12mm thick stuff then, I just used the same settings etc for the test break.

    I tried stick for the first time in 15 years last night. It took me an hour to do 7 weld/break/grind off the weld again , the best of which is shown here. It didn't come easy This was using a 3.2mm rod I got out of supercheapauto a while ago, just to test mma when i got the new welder. I don't know what grade it is or anything, i think it was called satincraft.

    I guess its more brittle? If you are rapidly quenching the hot weld in water, it maybe a bit hard.

    I don't know what the two funny marks on the break signify, near the top edge, what do they mean I'm doing wrong?
    SHHH!! ,don't tell the others but satincraft are for the beginners.Ok they give an ok shiny finish but are not really tolerant of an arc length just a bit too long.That's where the slag inclusions come from. If you keep the arc short and even boost the amps a bit they work much better for you.

    I can't say for sure what those marks in photos 2 &3 may be ,possibly a spot harder than the surrounding metal.. If your breaks are like the rest of your welds,they are more than adequate for most applications.

  15. #14
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    Quote Originally Posted by RustyArc View Post
    I'll play too

    20mm and 12mm bar, first test with MIG - UniMIG 165 running 0.8mm wire & CO2 beer gas cranked to the max (14m/min, about 23V).

    Did better than I expected, and the press jack made some "working hard" noises to break it open. I wish I had a pressure gauge on the hydraulics to get some kind of measure of the force involved so I could compare it to stick (which I'll try next).

    MIG1.jpgMIG2.jpgMIG3.jpg
    Hi Rusty Arc

    Most of the break looks ok,with the exception of a couple of very short spots on the 20mm edge.Sometimes if you don't get rid of the mill scale, completely the arc doesn't burn in at that spot. Mig and tig and susceptible as unlike stick there's no flux to float any crap out.The job has to be shiny clean wherever the arc will cover.
    See the silicon glass on top of the unbroken bead.Its good to scrub that off too,as I have seen silicon inclusion from where it gets welded over.It comes from the wire alloy and acts as a very light flux.

    Your welds are quite ok too Rusty. The photos are not as good as heaving the piece in your hand to look at,so I hope I don't miss something.

    I was hoping at some stage,for some one to show of those mig passes that show attachment to the vertical and miss the horizontal base plate.They are scarce on the net
    I can't find any.

    Cheers
    Grahame

  16. #15
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    Quote Originally Posted by RustyArc View Post
    I'll play too

    20mm and 12mm bar, first test with MIG - UniMIG 165 running 0.8mm wire & CO2 beer gas cranked to the max (14m/min, about 23V).

    Did better than I expected, and the press jack made some "working hard" noises to break it open. I wish I had a pressure gauge on the hydraulics to get some kind of measure of the force involved so I could compare it to stick (which I'll try next).

    MIG1.jpgMIG2.jpgMIG3.jpg
    Hi RustyArc, Personally I would not be using that size welder on steel that thick, you would be better off with about 250-280A and 0.9-1.2mm wire, if that unit is all you have then bevel the edge and multipass weld it and/or use 4mm MMA. Depending on what you are welding you might get away with it, but not if it was structural standard, even with those amps I mentioned I would still bevel the edge, if it isn't, then why use such thick steel?

    Regards

    Ed.

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