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Porosity, Why?

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  • Porosity, Why?

    I ran out of gas for my mig so I thought it would be a good time to learn some on tig. The photo shows my problem, porosity. The metal was clean of all mill scale, the cuts were with a band saw and there was no oil on it. I thought maybe I had the flow rate to low on the argon, it was at 20 cfm so I upped it to 30 cfm, no help. The tungeston was 2% thoriated, i made sure not to dip it. I did notice that the tip was yellow after I would weld.

    Any ideas? Thanks, Justin
    Attached Files

  • #2
    First question what size cup?
    2nd, any air circulating around you?

    Comment


    • #3
      Not sure of the cup size, I'd guess about 5/8" or 1/2". There was no air movement at all, it seems that all of them start out fine but about half way through the porosity starts. The welds are in a non critical area, they're ugly know buy I have to learn sometime.

      Thanks, Justin

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      • #4
        I see a black halo around the porosity. Is it possible that your tungsten dabbed (or touched) the weld puddle?

        I also see some mill scale on the parent metal. Try grinding off the mill scale and rust. This can also cause porosity.

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        • #5
          Using a gas lens ?

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          • #6
            In my opinion the most likely culprit would be gas coverage. Outside corner welding like you have there is often the joint that will show up gas coverage problems. The problem lies in that the gas from the torch tends to slide straight past the weld joint as it is the path of least resistance, this can then draw air along with it as in fact you now have a low pressure area.
            The common mistake is to increase gas flow but this simply increases the speed of gas slipping past the weld joint which in turn is an even greater low pressure area drawing in more air.
            Gas lenses slow down the gas flow giving a much more even gas coverage and I love them to bits. If you don't have any gas lenses try decreasing your gas flow out the torch and shorten the amount of tungsten stickout.
            This technique has worked well for me in the past but now I use gas lenses exclusively (except for Magnesium welding ) and the problem doesn't crop up like it used to.
            Regards Andrew from Oz.

            Comment


            • #7
              Only time I had a tig weld look like that is when I grabbed the wrong filler. RG45 instead of 70S6 = not good.

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              • #8
                Originally posted by justinp61 View Post
                The tungeston was 2% thoriated, i made sure not to dip it. I did notice that the tip was yellow after I would weld.

                Any ideas? Thanks, Justin


                Yellow tip males me think you had the tungsten sticking out too far.

                Comment


                • #9
                  The rods are 706s and the torch has a regular cup on it. On the tungeston stick out, it's 3/16" to 1/4". I'll try the lower flow rate and see what happens. I had the same problem with the weld on a 1/2" shaft with a 3/8" thick flat washer welded to it for a slide hammer I'm building. I'm going to figure this thing out if it's the last thing I do, in the mean time, Monday I'll get my mig bottle filled.

                  Thanks Guys, Justin

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                  • #10
                    Use a bigger cup and make sure you keep the cup pointed directly down over the weld with just a slight angle towards the direction of travel.

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                    • #11
                      What size cup would you recommend? I have to go to town Monday to get my bottle filled anyway so i might as well pick one up.


                      Thanks, Justin

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                      • #12
                        I suggest a number 10 with the large gas lens.

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                        • #13
                          Porosity comes from contaminates! Ether the contaminates are getting into the weld from lack of shielding gas or some other contaminate (oil, rust, mill scale, paint, ect). If you rule out the "other contaminates" then it is a lack of or improper shielding gas. And as it has been stated wind could be blowing away your shielding gas.

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                          • #14
                            After you have eliminated all of the root causes mentioned in this post there is still one additional cause of porosity, which is holding too long of an arc. The weld would have porosity that looked the same as porosity caused by improper shielding.

                            Comment


                            • #15
                              Don you may have something. How long should my arc be? I picked some new tungston today but they didn't have a #10 nozzle to replace my #7. Tomorrow I'm going to finish my slide hammer, I'll shorten my arc up some and see if it helps.

                              Thanks, Justin

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