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Welding various thicknesses

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  • Welding various thicknesses

    Hi there.

    To start I must mention that I am new to welding.

    I have seen several posts asking what thickness of metal a particular machine can do.

    If you prepare the joint properly before welding can't you weld any thickness of steel as long as it is multipass or am I missing something? I am assuming that there will be a limitation when the surrounding metal dissipates the heat quicker than the welder can produce. If you have a puddle forming does that mean that you have the opportunity for a decent weld?

    A previous post indicated that a structural weld could not be done with a particular machine because it did not have enough power. Can't you just do multi-passes and end up with the same strength of weld?

  • #2
    The question of capacity is generally associated with maximum single pass thickness, but you are correct about multipass to some extent also. The trick is if you need to weld 1" plate and you have a 100 amp machine you won't develope enough heat in the base metal for proper fusion. As a rule 1 amp will penetrate only .001 of material so your same 100 amp machine would only penetrate .100" or approx. 3/32"

    I hope this helps,


    • #3
      Thank you for that information.

      I am sure that I will get additional information when I take that course..November.. but until then....

      The penetration concept is a bit blurry with me. What depth of penetration is required in order to acheive a solid weld? You mention that 100A would do about 3/32". Is that enough to achieve acceptable fusion for structural welds?

      This is all theory as I do not intend on making structural welds any time soon but I am interested to know what justifies a good weld.

      I know that if a joint is beveled and then a root pass is placed and subsequent filler passes are made then the weld will be decent in the y direction but there needs to be sufficent fusion in the x direction so that the two plates will be bonded.

      For all of the metal practice welds that I have done I have gotten to the point of being able to put them in a vise and bend them to at least 90 degrees without failure. (Aluminum is a whole other story)

      Just curious. It is good to know what it is that I am attempting to do.

      Thanks for your time.


      • #4
        I have used a 100A machine to repair chassis damage on a pro 4 racecar so in that environment structural work is considerable lighter than say bulldozer structure. As far as penetration your penetration will be basically a circle with the diameter of the amperage used, so if your welding 1" plate is 1/10 of that enough to make it structurally sound, probably not!

        A good weld has many definitions depending on the prupose. A tank must be leak free to be a good weld, whereas a solid weld on say tubing must have complete fusion and smooth, flowing welds.

        I hope this helps,


        • #5
          May be adding more confusion or possible solution, when properly prepared (beveled edges 60 degree included angle) I have welded 1 1/4" plate with 1/8" 7018 at 130 amps (multiple pass, 7 or 8 passes if I remember correctly)that had to pass inspection. I don't know exactly how much penetation I had, but the inspector was a picky one!