MIG Welding

Ignoramus21227 · 2008-10-17T12:38:03+00:00

The welding class is now in full swing, with plenty of time to weld. Of all the welding processed that we tried, we are now on GMAW. I hadfull two hours to practice. The welding machine was a digital LincolnMIG welder the size of a Millermatic 250. I was pleasantly surprised how it lets me make nice looking welds(relatively speaking) without too much practice. I set the machine in full accordance with the diagram.Then I tried making a inside corner weld, which looked fairly decent,using 1/4" plates and (IIRC) 320 IPM of 0.035 at 19v.Then, recalling Gunner's infamous tire holder incident, I took it to aanvil and pounded on this weldment, trying to flatten it.To my disappointment, this solid looking weld failed in severalplaces, obviously revealing no fusion at all in those places. Theassembly held because in other places, the weld did not fail,but itwas not what I would call an encouraging experience. I am not complaining, as such, the instructor told me that I shouldhave chosen different settings, etc and I am sure that he isright. But, I think, given my low skill etc, I would not trust MIGwith anything critical.

Oct 17, 2008 41 Replies

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Don Foreman 17 years ago

I have certainly done this but I don't do it much anymore unless it's easy. I might section one (cut with bandsaw) to inspect it. I kinda know what fused metal looks like by now.

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matthew maguire 17 years ago

Hey Iggy,

I checked the chart on the PM300, non synergic GMAW for 1/4" settings are

375IPM @ 19.4V C25, 22V Co2. With .045 it says 220IPM @ 20V C25 and 200 @ 21V Co2.

There would be a fair difference in the amperages and current density from .035 to .045 settings so I would assume slight weaving with the .035 to get the correct bead size.

Matt

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