So, how strong are welds?

Discussion in 'Tools and Fabrication' started by e9999, Apr 12, 2009.

  1. e9999

    e9999 You want to do what...? Moderator

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    I'm going to ask the question that's impossible to answer... but you guys are smart:

    We have already talked about checking welds but I'm wondering about the big picture. Trying to assess risks statistically, if you will.


    I hear it routinely said that a good weld is as strong or stronger than the surrounding metal.

    OK. I can buy that.



    But, what about the other welds? Consider the typical scenario of a home fabber who has little experience in welding. Maybe a dozen hours with a flux core, say. Let us say he can do welds that look sorta OK. Not pretty smooth, but not random floating blobs and holes either.

    What would be your assessment in big broad impossible overgeneralization terms?:

    a) welds are likely to be completely unreliable and should not be used at all in real life until he has xx hours practice.
    b) welds are probably reasonably strong and should be OK for non-critical situations (say mounting brackets for accessories, maybe bumpers etc) only.
    c) welds are likely close to as strong as the rest of the metal and one should not hesitate to use them for serious stuff (steering, suspension, winch plates, recovery points, etc).


    I'm thinking -well, OK, really hoping- b).

    What say ya?
  2. fj40charles

    fj40charles GOLD Star

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    I would not even choose option b since you have not spent enough time welding. With training and practice you'll be able to see what you're doing. I would not try to build bumper with a little 110v welder.

    Spend the money and get a decent 230v mig welder, research or take a class, and lots of practice.

    I cannot over emphasize the need for a decent 230v welder. Stay away from chinese made junk.
  3. Weedhopper

    Weedhopper

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  4. e9999

    e9999 You want to do what...? Moderator

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    OK, but I'm not talking about the welding machine, I'm talking about the person's experience.

    IOW, assuming good equipment, yes, the average guy can go out there and turn out reasonable welds with FCAW or MIG -that will hold up OK- after a dozen hours or so. Or No, the average guy needs 100 hrs before he should even think about building anything that would go on the truck or in the garage. Sounds like Charles leans towards the latter.

    In a sense it's a question about how forgiving the nature of the process and the equipment are.
  5. fj40charles

    fj40charles GOLD Star

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    I'm not saying the average guy needs 100 hours of training. The average guy could have 100 bad hours of training and still produce crappy welds. 10 hours of actual welding time is alot of welding. You just need to have someone teach you the proper technique for welding using the proper sized welding machine.

    Also realize that a 110v welder is not suitable for building bumpers. I would limit a 110v welder for up to 1/8" thick metal. Get a decent 230v welder if you want something that is capable of producing high quality welds on metal thicker than 1/8" thick. High quality welder will be more forgiving when it comes to arc stability/quality since it will be able to produce a constant voltage even though the wire stickout will vary. Also, it will have the proper level of inductance to produce nice wet out of the bead.

    Highly unlikely you will produce high quality welds using cheap chinese or undersized welders.
  6. sixty

    sixty

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    Any one who wants to do more than welding on lawn furniture, needs to do alot of reading on welding and have a good knowledge of structural design. Then practice your welding and do some cuts thru your welds to ensure proper penetration and fusion occurs. For some they can pick up a mig gun and make sound welds after 10 minuites of good instruction, and others may still not get it after 100 hours.

    Most welding filler is rated at 70ksi while mild steel is 60ksi, so a proper weld should be 16% stronger than the base metal as long as the root of the weld is atleast as thick as basemetal. Good weldng is only the first half of the equation, the sound welds need to be supported by a sound, engineered design.

    That being said, overkill and redundancy can be your friend! If your not sure about your welding and design, its probably best left to the professionals
  7. -Spike-

    -Spike-

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    If you're not confident, don't do it.

    Try proving yourself. Weld some 1/8" scrap together with butt welds. Use long enough stock that you can bend the material to try to break the weld. Grind the welds down so they are no thicker than the material. Only you or a professional in person can evaluate your welding prowess.

    -Spike
  8. e9999

    e9999 You want to do what...? Moderator

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    thanks, but this is not about me. This came up in a conversation when somebody was talking about getting started.

    I'm asking in general to get a rough idea.

    As in "The average guy can do OK welds with FCAW or MIG that will hold up after something like "

    - 10 hours of actual welding
    - 25
    - 50
    - ?

    What would be your best guess?

    I know this surely varies a lot but one can still come up with an average figure, I'm sure.

    Allright, I'll guess 25 hrs then... A few days should be OK I would think. So there... :)
  9. Joe_E

    Joe_E

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    Here's a little scenario about weld strenghths, saw this on the job.
    When welders show up to work on pipelines, talking the real pipelines like 36 or 48", they have to take a test by the pipeline owner.
    They need to take a piece of pipe, make a bunch of torch cuts, make bevels and such then weld the pieces together. Let's say for instance .750 wall.
    They then cut out a piece that composes both welded together parts and put it in a hydraulic machine that pulls from both ends.
    The 3/4" steel will rip apart but the welded area will be fine.
    Just like something you would see on tv for reals.:hillbilly:
  10. D'Animal

    D'Animal Rescuer of Beagle and Landcruisers Moderator

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    FC Fabrication builds my Cages and Shock hoops, etc. Anything Structural or Safety related, I pay a pro to do it.

    I make gas can holders and tire swing outs, etc.
  11. BDSeff1fitty

    BDSeff1fitty 1975 FJ40

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    my friend is a welder for RTI. he welds pipeline for them he said. he had to do the 6g test to get hired. he is gonna be welding my cage for me when i get around to it and offered to re-do some of my mounts also, just need to find time that hes free. hes 19 and been working as a welder for 3 years just started full time after graduation. its ridiculous the money he is bringing in. pisses me off lol.

    i have tried a little bit of everything and if i was to do it again i would never touch an arc welder again. mig wasn't terrible, i kinda got decent, but one weld would be good and one would be bad mainly because some pipe i was welding was thicker than other and i had no clue at the time how to adjust the welder, tig well didn't turn out so well but it was fun to try and eventually i hope to try again to get better. i think 25 hours sounds like a good number, maybe not even, but it depends on the person and how quick they pick up something. if the average joe just goes home with no instruction its going to take him much longer than someone who is being taught by a welder.

  12. D'Animal

    D'Animal Rescuer of Beagle and Landcruisers Moderator

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    LOL!

    So you are saying you could walk into a welding/fabricating shop and work 2 12 hours days melting metal and walk out and be a welder?

    LOL!

    You are funny!

    I know guys who spend a year or so as an apprentice or welders assistant.

    A smart person told me the following;

    Just because you own welder doesn't mean you are a welder.
  13. BDSeff1fitty

    BDSeff1fitty 1975 FJ40

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    me? hell no. i am pissed how much money he makes, but the hours he works sucks! he was 5pm-5am 5 days a week minimum, sometimes 7 days a week. he went a month with not one day off. now he works 3pm-2am and next month goes back to 5am-(1:30-3:00pm). i didn't think my post made is sound like that thats not what i intended it to do. i was saying 25 hours i think you could get decent enough to do basic work on your rig w/out screwing it up if you had a welder teach you the skills . i will never be confident enough to weld a cage, i need to know 100% the person that welded the cage knew what they were doing so i dont die

    my friend is good at what he does, but i could never do it.
  14. D'Animal

    D'Animal Rescuer of Beagle and Landcruisers Moderator

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    Not you. E9999 said he thinks it takes 25 hours to learn to weld.

  15. e9999

    e9999 You want to do what...? Moderator

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    obviously, there is a big difference between being a professional welder and doing some welds that will hold on a tire swingout, esthetics be damned. I'm talking about the latter.

    In my own trials, I've been able to do reasonable welds on thicker stuff after only a few hours (like 8 or 10), and that I'm pretty sure would hold fine. I did do some tests where I banged on them hard and they held strong. Unfortunately, sometime I get nice ones, sometime they are terrible. The biggest problem seems to be to be able -or not- to adjust the power and wire speed and hand speed to the situation at hand. That I am not able to do reliably yet.

    That said, I'm pretty sure that if I had to weld some specific pieces of metal (not too thin cuz I suck at those) of given thickness and shape, and I had some similar spare pieces to practice with, and 3 or 4 hours to fiddle with the settings, well, I think I'd be able to get decent welds for that particular situation at the end of that practice period. Unfortunately, I'd have to do that all over again for a different thickness etc... I do have about a dozen hours of practice so far.
    Last edited: Apr 13, 2009
  16. MaddBaggins

    MaddBaggins Remember the KnightRider!

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    I picked up MIG after about 20 minutes of weld time. I have no doubt my welds are structuraly sound.

    Of course I learned to weld on Oxy/Acetylene then brazing, then arc. SO, I already knew HOW to weld and MIG is easy compared to Oxy/Acetylene.
  17. justweldit

    justweldit

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    i welded the cage on my cruiser, got in a roll over at 55 !! it spun sideways so fast it high sided and landed on the cage!!! not a single weld broken . BTW dont recomend this test procedure:hillbilly:
  18. Pin_Head

    Pin_Head

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    Take a welding class. They will teach you not only proper technique, but proper joint design and how to test welds. You don't just bang on them. You cut a "coupon" strip out of the weldment and bend it back 180 degrees. If it doesn't crack or tear when you bend it, it passes.
  19. if you are starting to weld....as in less than say 800-1000 hours behind your welding mask/in the shop as a welder-cutting, welding ect...go with option A. if you have spent more that that, go with B. if you do it for a living...go with C. i went to school for welding and had to do welds as pin head describes with stick (all positions), solid wire and 2 flux cored wires (all pos except for overhead) do it with backing and then try open roots...when it bends without any cracks then think about doing a cage (make at least 2 cupons, grind metal flat and test both root and face of weld)...

    strength can also depend on electrode or rod selection...7018 rods and S-6 wire both have tensile strength of 70,000 psi...however 6010 or 6011 rods as well as T-11 flux cored wire dig deeper and have better penitration, if i was really worried about something i would run my root with 6010, hot pass with 6010 and then fill with 7018 as needed, i prefer stick welding for anything like that because i have more control and a better feeling as to how the weld is going.

    hth
  20. Dieseler

    Dieseler SILVER Star

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    If its structual ie:frame,roll cage,or supension related leave it up to professional welders ,most backyard welders rate a A-B but would never achieve C without 100s of hours of all welding applications and proper training and schooling.

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