problem mig welding

i am using a lincoln 175 mig welder. my problem is that when i am trying to weld something thicker, say upwards of 1/4 inch, i put the
welder hot and try to stich weld and my welds end up hollow. on the outside it looks like any amature welders job, then when i dress them, i find that the bulges of weld are hollow. or i will get bulges that look like little tubes.
what am i doing wrong?
thanks willie
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By "hollow", do you mean there are bubbles? As in too little or too much gas? It may be an issue of being too far away with the nozzle as opposed to the the CFM.
On Thu, 25 Sep 2003 17:56:02 GMT, Steel City Phantom

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Sounds like you have no shield gas...Or not near enough...
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On Thu, 25 Sep 2003 17:56:02 GMT, Steel City Phantom
......and in reply I say!:
Is this a butt weld, or a fillet? You could be getting problems with a fillet weld, because of technique, in that you are maybe weaving too much, and not really filling the root of the fillet. MIG _should_ be really good at this, with the fine wire and hot, small work zone.
Often this is a sign of gassing in the weld. This can be caused by: * lack of gas         - try more gas             - you may have regulator problems, that are masked at lower flows/currents         - work closer to the work to avoid losing the shield             - this may also allow/require lower welding currents         - make _sure_ you have no breeze blowing across the job. This will destroy the shield very badly.
* dirty/rusty/painty workpiece.
* water in the join     - I would look a these last two if the job is really a hollow, and is not bubbling obviously as you weld.             - Lack of gas usually causes bubbles that show straight away.
I am not sure what happens if you try to run a MIG with the current set too high for the wire _thickness_,         - except that you can get burnback (which would not cause your problem AFAIK).         - you can start to "spray" weld , rather than transfer weld. I have done this and not had the problems you are talking of.

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like the others said, not enough sheild gas. is the tip clean? welding dirty/oily steel usually = lots of spatter. clean out the tip to get the gas going.
-tony
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wrote something ......and in reply I say!:
forgot that one....thanks
Be nice to hear back from the Phantom about how they went....

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Less than an inch. Practice, practice, practice...
my 2 cents
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Another problem I have seen before and took us awhile to discover it was a pinhole in the gas line from the valve to the gun. A spark must have went through the ventalation louvers and burned the vinyl line. This looked just like as someone had mentioned the breeze problem. I think what was happening was since this is a no pressure line(downstream of valve) that it was drawing air in and contaminating the weld. Check out your orings where the gun plugs into the machine and make sure that the gun is plugged in well, I know this machine and it is possible for the gun to leak at the gun to machine interface.
wrote something

i
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