Hello everyone, this is my first time posting on this BB, though I have browsed and searched the board many times in search of tech advice.

Today, I was doing a couple practice burns to test out my new mig welder (Miller 251), and out of dumb luck, when I switched from the Aluminum push-pull to the wire over to the standard gun to do a couple practice seams on some 3/16 steel flat stock, I forgot to switch switch out the Argon tank for the mix tank and welded the two pieces using 100 percent argon at 25 CFH. Those beads were gorgeous (for my welding at least)!!! Almost like a TIG bead, no spatter at all, and a perfectly even crown (though the crown was a bit high for my taste, but didnt seem cold). On the other hand I noticed that at the recommened setting for 3/16 steel and 030 wire and 75/25 mix (I don`t recall the exact voltage or wire speed), it only penetrated a little over half way into the material. However I then tried raising the voltage and the wire speed to the respective 1/4 inch steel settings and got perfectly beautiful, full penetration beads across the flat stock.

Ive always heard that pure argon shouldnt be used for welding ferrous metals, but have never gotten any explanation why. Other than a small decrease in penetration per setting, and therefore more power consumption to get the same penetration, are there any other drawbacks to this that I am not considering? I am not a formally trained welder, just a shade tree welder with a decent amount of burn time, a few welding training manuals and an inquisitive mind, so I may very well be failing to consider something that may be obvious.

Frank

welding, using argon on ferrous metals has worked for me for a long time (GTAW) TIG welding steel with strait argon. i have never used strait argon on (GMAW) Mig though, but i have never heard any real reason why it cannot be done.

I think the main reason is mix is cheaper than pure argon

I think the main reason is mix is cheaper than pure argon

I don't think that's the only reason. I asked the guys at my local welding shop and they said not to do it and gave me a reason, but I can't remember what it was now.

I think the main reason is mix is cheaper than pure argon

If you're paying more for pure argon than you are 75/25, you're getting screwed. If anything, the mixed gas should cost a little more, due to the additional labor involved in filling mixed gas cylinders. The reason you don't use pure argon on ferrous metals when mig welding is the Carbon dioxide in the mixed gas is what gives you "penetration". With straight argon, the arc is not as penetrating, thus the high crown on your weld bead. Your deposited wire is all on the surface of the base metal. Your weld will not have any strength. Th added CO2 in your 75/25 mixed gas is what gives you the necessary arc voltage to get good weld penetration, and "wet-out" your weld bead. Use pure argon for TIG, or MIG welding aluminum only.

Thanks everyone! I was getting curious today and I cut some cross sections of the welds to get a closer look at them and, White lightning is right, I thought I was getting penetration, but there is a visible difference from the pieces and the deposited material with a very small part of the cross section where is actually fused together.

Frank

We ran out of C25 late one night at the shop while finish welding some tubework. Unhooked the Ar from the TIG machine and hooked it up to the MIG.

To put it plainly, it didn't work very well...at all.

My last shop I worked at used 98% argon and 2% oxygen mix. This was used for spray transfer welding. It left a pretty nice weld but it was damn near impossible to weld out of position. Sometimes we would get a bad mix ethier to much argon or to much oxygen. You could tell right away.

My last shop I worked at used 98% argon and 2% oxygen mix. This was used for spray transfer welding. It left a pretty nice weld but it was damn near impossible to weld out of position. Sometimes we would get a bad mix ethier to much argon or to much oxygen. You could tell right away.

we use a 92% argon 8%co2 mix at work for spray-arc welding. works rather well, not going to come CLOSE to that penetration with short-arc and 75/25. the inherent downfall of spray-arc (not the choice of gas) is the need to have everything pretty much flat to weld it.

-Scott