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Thread: Stresses in GTAW

  1. #1
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    Stresses in GTAW

    Hey all,

    I was just cleaning up some bits for next weld and noticed these ďlinesĒ on the back side of the weld. Iím guessing they are stresses created by the weld?

    3mm mild steel plate and bracket. Fillet weld both sides. ~135 amps
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  2. #2
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    Re: Stresses in GTAW

    Quote Originally Posted by husq2100 View Post
    Iím guessing they are stresses created by the weld?
    I've never seen that before, but it sure looks like it, doesn't it?

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    Re: Stresses in GTAW

    I often get involved in adding brackets on material hopper, and tanks. The tanks are usually between 14ga, and 18ga stainless steel, but some carbon, and the brackets between 14ga., and 3/32". Most times I will get instructions/marked up drawing from an engineer with fillet size, location, and length of welds. Brackets that are used for shakers/vibrators are almost never fully welded (can't remember ever getting one, but I'm sure there are exceptions, consult your engineer, your mileage may vary.) . They usually specify not to weld ends , and corners. I guess this is part of the reason, although I've done similar welds, I've never noticed ripples in the steel like that . Is the Plate flat , or did it warp ? Can you feel the ripples, or is it an optical illusion( it looks worse than it appears) ? Oh, BTW nice welding.


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    Re: Stresses in GTAW

    Quote Originally Posted by albrightree View Post
    I often get involved in adding brackets on material hopper, and tanks. The tanks are usually between 14ga, and 18ga stainless steel, but some carbon, and the brackets between 14ga., and 3/32". Most times I will get instructions/marked up drawing from an engineer with fillet size, location, and length of welds. Brackets that are used for shakers/vibrators are almost never fully welded (can't remember ever getting one, but I'm sure there are exceptions, consult your engineer, your mileage may vary.) . They usually specify not to weld ends , and corners. I guess this is part of the reason, although I've done similar welds, I've never noticed ripples in the steel like that . Is the Plate flat , or did it warp ? Can you feel the ripples, or is it an optical illusion( it looks worse than it appears) ? Oh, BTW nice welding.


    Cheers
    That's really interesting stuff. So if you were adding something like a piece of 2 x 6 " channel they might specify a 4" bead on both sides of the long end and 1" beads on both sides of the short ends, skipping all four corners and both ends, or something along those lines? I can see how corners and ends could easily be stress risers....but never thought of it that way.
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    Re: Stresses in GTAW

    Quote Originally Posted by albrightree View Post
    I often get involved in adding brackets on material hopper, and tanks. The tanks are usually between 14ga, and 18ga stainless steel, but some carbon, and the brackets between 14ga., and 3/32". Most times I will get instructions/marked up drawing from an engineer with fillet size, location, and length of welds. Brackets that are used for shakers/vibrators are almost never fully welded (can't remember ever getting one, but I'm sure there are exceptions, consult your engineer, your mileage may vary.) . They usually specify not to weld ends , and corners. I guess this is part of the reason, although I've done similar welds, I've never noticed ripples in the steel like that . Is the Plate flat , or did it warp ? Can you feel the ripples, or is it an optical illusion( it looks worse than it appears) ? Oh, BTW nice welding.


    Cheers
    On shakers that are often added on to existing hoppers they generally send a mounting plan. Typically they will spec out the size and weight of the C channel with a weld scheme. It's also important to radius the ends of the flanges where they make contact with the bin or hopper. Even with all that it's usually not an issue if they will crack but when they will crack.

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    Re: Stresses in GTAW

    This is typically for dump truck application, notice the safety chain. : http://www.vibco.com/docs/quick-ref-...nce-manual.pdf https://www.weldingweb.com/images/smilies/eek.gif



    This is for stationary equipment. : http://www.vibco.com/docs/quick-ref-...nce-manual.pdf
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  9. #7
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    Re: Stresses in GTAW

    Looks like some serious vibration going on.
    It seemed like a good idea at the time!

  10. #8
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    Re: Stresses in GTAW

    Not sure what caused the cracking in your piece, but depending on materials and design, many fabrications require a post weld heat treatment:
    https://www.metalworkmasters.com/pro...eat-treatment/

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    Re: Stresses in GTAW

    Quote Originally Posted by albrightree View Post
    ..... Is the Plate flat , or did it warp ? Can you feel the ripples, or is it an optical illusion( it looks worse than it appears) ? Oh, BTW nice welding.


    Cheers

    I had the plate bolted and tacked to another 3/16 plate the same size to help reduce weld distortion. It still warped but was easily brought fairly flat again. I doubt any weld like that on a flat plate isnt going to suffer some distortion. You can definitely feel the two main weld lines and slightly feel some of the "stress swirls" (just)

    Its one side of a transmission mount and cross member, I cut the brackets off a factory mount. The factory mount is GMAW of course. Ill take a look when im back at it to see where they did and did not weld. Thankfully the bushes are rubber and very compliant.

  12. #10
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    Re: Stresses in GTAW

    Here are some more pictures

    This is the other side mounting plate and itís bracket. Same material, thicknesses and settings. Not near the number or definition of ďswirlsĒ, but still a few....

    Sorry about rotation, this website does that and Iím not sure how to correct it.
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    Re: Stresses in GTAW

    Some of the 100x50x3 RHS cross member ďtubeĒ (4x2x1/8) and the folded 3mm plate I laminated it with for impact resistance. Some very faint lines radiating outward around the cutouts.
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    Re: Stresses in GTAW

    The welds before I sprayed them with lanotec (penetrant /corrosion inhibitor). It helps save prep for next stage as surface rust starts within hours and is visible next day.
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    Re: Stresses in GTAW

    Quote Originally Posted by albrightree View Post
    ....Brackets that are used for shakers/vibrators are almost never fully welded (can't remember ever getting one, but I'm sure there are exceptions, consult your engineer, your mileage may vary.) . They usually specify not to weld ends , and corners. I guess this is part of the reason......


    Cheers
    Got a look at the factory crossmember and mounts. The side mount in my first pics is fully GMAW one side, no stops or short of ends.

    The other mount is GMAW both sides where it can be except where it meets the RHS, then only one side.

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    Re: Stresses in GTAW

    Is there some type of coating on the steel? It would be interesting to know how deep the cracks go. If parts are too restrained (held in place to try and control distortion) could do the opposite and create stress in the welds, especially if higher heat/amps are used.

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    Re: Stresses in GTAW

    I will have to say I have never seen that before. Do you have MTRs on the material?
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    Re: Stresses in GTAW

    Good morning,

    After reading the thread several times, it’s not clear if there are physical cracks or just indications of cracks from the backside. The thing that jumps to mind are brittle coating materials for stress analysis.

    Long shot here: has the oxide layer formed an equivalent brittle coating material during the weld and once cooled, cracked accordingly?

    If this was a brittle coating test, the crack lines would make perfect sense from the point of thermal stresses. That is, they would be perpendicular to the tensile stress.

    Short note on brittle coating.

    https://www.oreilly.com/library/view...apter010.xhtml

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    Re: Stresses in GTAW

    Yes I have seen this,, I Googled it, 91% of the time, it is due to applying filler metal left handed,, because of the swirl direction of the gas coming out of the torch.

    Also, people gotta learn that left handed adjustable wrenches can only be used in Australia,, THAT is why we do not have them in the tool room,,,













  20. #18
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    Re: Stresses in GTAW

    What about metric crescent wrenches?

  21. #19
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    Re: Stresses in GTAW

    Quote Originally Posted by Welder Dave View Post
    Is there some type of coating on the steel? It would be interesting to know how deep the cracks go. If parts are too restrained (held in place to try and control distortion) could do the opposite and create stress in the welds, especially if higher heat/amps are used.
    Not that Iím aware. Itís just plain old hot rolled mild steel plate. The brackets are off a mass produced Land Rover crossmember and would only be the equivalent. All my steel I acid dip in a bucket, good rinse clean with fresh water, dry and sand with a orbital sander. All sides/edges are done ( so it canít suck the mill scale in from the back)

    I did one of those 4 part dye penetration tests and nothing showed up.

    I wonder if this ( the smaller or lesser version) is more common and people just arenít cleaning up post weld like that and or noticing it???
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    Re: Stresses in GTAW

    Quote Originally Posted by shovelon View Post
    I will have to say I have never seen that before. Do you have MTRs on the material?
    It’s just hot rolled mild steel plate and I’m pretty sure the brackets are not anything special, ie the same.

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