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Porosity, Why?

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  • OldSparks
    replied
    justinp61

    Being a newbie, do you know that any stray arc marks are a potential source for porosity. This would include if you happen to scratch start the tungsten into too long an arc, or actually sticking the tungsten to the plate and then breaking away too far, or leaving a stray arc mark after you break off. Slight marks may be harmless but if there is any sign of pitting or a crater, then that area has to be totally ground out. You shouldn't weld over a bad 'pit' and hope to burn it out. Most of the time it will develop into visable porosity and if you do happen to bury it, then you'll never know the quality of your weld. I mention this because there appears to be an example on the extreme left of your picture. The tan smokey residue suggests an excessive long arc has happened and there looks like a crater in the first metal deposit. If there were similar marks further along they could have been your problem. Then again I could be totally off base.
    Attached Files

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  • mooseman63825
    replied
    hmm

    I may have missed it but how thick is the base metal, so far everyone has touched all the other bases, all else fails id say the heck with tiggin it go od school Oxy weld it no need for shielding gas and so much easier to control the heat

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  • justinp61
    replied
    I forget where the post flow is set but yes I'm using it. I have the welder set at 155 amps, after the weld is started I ease up on the pedal and continue. The rods are 3/32 and 3/32 tungston, argon set on 20 cfm with a #7 cup. Like I've said I'm trying to learn this process, but sometime I get frustrated and pick up my mig or switch back to stick. It's most likely a combination of errors on my part, I have a lot to learn.
    Thanks to everyone for the suggestions.

    Justin

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  • man of steel
    replied
    porosity problem

    hi friend ,if youve covered all your other bases, my only other thought is that carbon steel(if thats what your material is) tends to do that when it is overheated,everything else in check(gas coverage etc0 ALSO ARE you keeping the gas post flo going after you stop your arc?

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  • justinp61
    replied
    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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  • Don52
    replied
    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.

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  • Pepe
    replied
    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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  • fabricator
    replied
    I suggest a number 10 with the large gas lens.

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  • justinp61
    replied
    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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  • fabricator
    replied
    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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  • justinp61
    replied
    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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  • FATFAB
    replied
    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.

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  • TS-Off-Road
    replied
    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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  • awill4x4
    replied
    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.

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  • fabricator
    replied
    Using a gas lens ?

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