Posted by Valerie on October 06, 1997 at 18:23:29:

In Reply to: Mig weld bubbles posted by Chris Ray on October 03, 1997 at 10:16:41:

At the Artisan's Journal, there is a good reply from Chris on this question. Main topics were checking the shield gas flow and excessive air motion that may blow the shield gas away.

Roger also had a question about posting a long post here. Seems a portion of his post did not show. Make sure to click at bottom where it says submit post and then it will let you check over and change post. Then you need to click at bottom of the post again.

: The original post from Rodger Edberg is:

: >I am trying to diagnose the problem behind bubbles in some of my MIG welds.

Bubbles in the weld indicate that the shielding gas is probably not doing its job. This could be due to too low shielding gas flow. As Chris indicated, 15-30 cfh (cubic feet per hour) is typical. It relates to the size of your nozzle. If the flow of shielding gas is too high, it can also cause this porosity because of the turbulence of the air. The shield gas actually gets blown away.

There could be a hole in the shielding gas line. Check that sparks have not melted a hole through. Also check for loose connections through the whole system.

If you have a water cooled torch, there is the possibility of moisture getting into the gas line or into the weld area.

The porosity can also be caused by the metal that you are welding on. If it is greasy, you may be having a problem with the gases escaping from the molten pool.

I sincerely doubt that this is the problem, but if there is moisture in the gas cylinder, it can cause porosity. This is rare because the suppliers are careful not to ruin their product and reputation by not keeping close tabs on this.

So to solve the problem, I would check over the hoses, regulator, flow meter and torch connections first. It is usually the simple things first.

Post again if this doesn't solve it!

Follow Ups:

I am trying to diagnose the problem behind bubbles in some of my MIG welds. : Bubbles in the weld indicate that the shielding gas is probably not doing its job. This could be due to too low shielding gas flow. As Chris indicated, 15-30 cfh (cubic feet per hour) is typical. It relates to the size of your nozzle. If the flow of shielding gas is too high, it can also cause this porosity because of the turbulence of the air. The shield gas actually gets blown away. : There could be a hole in the shielding gas line. Check that sparks have not melted a hole through. Also check for loose connections through the whole system. : If you have a water cooled torch, there is the possibility of moisture getting into the gas line or into the weld area. : The porosity can also be caused by the metal that you are welding on. If it is greasy, you may be having a problem with the gases escaping from the molten pool. : I sincerely doubt that this is the problem, but if there is moisture in the gas cylinder, it can cause porosity. This is rare because the suppliers are careful not to ruin their product and reputation by not keeping close tabs on this. : So to solve the problem, I would check over the hoses, regulator, flow meter and torch connections first. It is usually the simple things first. : Post again if this doesn't solve it! " />

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