| Author |
Message |
John Biundo (Jbiundo) (64.175.36.124)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 20, 2002 - 4:57 pm: | |
I'm trying to weld mild steel to stainless steel with my MIG welder. My practice welds aren't very good. They don't look good (they appear porous), and I'm not satisfied with the penetration - especially on the mild steel.
I've double-checked that I'm using the right wire (309 stainless) and gas, and have experimented with several different voltages and wire speeds, without much luck.
I can run a pretty decent bead using a regular mild steel setup, so I think my technique is adequate.
Here's my question: when I try welding mild and stainless using flux core wire, the welds look pretty decent, I get decent penetration, and they test out pretty strong. All in all, the results *seem* alot better. Aside from the obvious drawback that the weld itself is not rust-proof when I use the flux-core wire, is it OK to weld mild steel and stainless with the flux-core (or, alternatively, the normal mild-steel gas welding) technique?
Thanks for any advice!
John |
Dwight (67.213.8.242)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 21, 2002 - 12:47 am: | |
I find it does a better job if I move backwards with the gas set up, moving forward I find you loose the gas seal too fast....Just my opinion??? |
Gary Stadler (Boogiethecat) (68.7.217.217)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 21, 2002 - 1:52 am: | |
If nothing else, stainless needs to have a gas blanket over it until it's cool, or it will oxidize and look horrible. It needs to be covered in gas much longer than mild steel. You'd also do a lot better if you can afford pure argon as the gas... co2 won't work well at all, and a mixture is better but never as good as pure argon. Most of the successful welds I've done with these two metals were done with Tig, but if you can get enough gas covering things, Mig oughta work ok. I have a "master-welder" at my shop and i'll ask him more Monday if need be
Cheers
Gary |
John Biundo (Jbiundo) (64.175.36.124)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 22, 2002 - 1:44 am: | |
Thanks for the great suggestions guys. I plan to give them a try tomorrow.
Gary - if you don't mind asking your master-welder friend, here's my biggest question. If, after tweaking and playing around with all the variables, my best welds appear to be (visually, and through testing them by trying to break butt welds in a vice) using the self-shielded mild steel wire, will this produce a relatively strong weld? I know the weld itself won't be rust-proof, but that's OK since the other materials are mild steel anyway, and I'll put a decent primer on the whole thing. Other than that disadvantage, are there any other technical problems (related to the strength of the weld) if I use the mild steel wire?
Thanks,
John |
Gary Stadler (Boogiethecat) (68.7.217.217)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 22, 2002 - 8:12 pm: | |
Ok, I got the scoop from the master... the following is as close to a quote as I could get:
When welding steel, it doesn't matter if it's stainless or mild, it's still steel. The only difference of course is the alloy. When you weld SS together with mild, the weld puddle is a mixture of both. This is where the fun comes in. The mild steel will "rob" the stainless of it's "nobler" alloy components while it's molten, so what you want to do if you want a weld that won't rust is to use a welding filler that's more "noble" than the stainless you're using, so when the mild steel "robs" the filler, it ends up being almost "normal" SS in alloy. The 309 wire you got is almost the right stuff.... he says use 309CB (CB= Colombium) -the deal is that during cooling, the colombium pulls the carbon out of the solution before the carbon can steal the chromium in the SS alloy. Without doing that, the weld would rust.
Other than that, he said that I was right, the reason you are experiencing better welds with the flux core is that the gas you were using was probably not pure argon, which is a must. Mixtures with CO2 in them will ruin it... the CO2 disassociates into carbon monoxide and a free oxygen when welding SS and messes it all up. Another thing is that with TIG welders on stainless, the gas supply is left on for a few seconds after the arc is stopped, so that the cooling SS still has protection. MIG welders don't usually do that, so you might want to see if you can defeat your gas solenoid and leave the gas on all the time when you're welding SS, or maybe make a little "blow hose" that you can aim argon onto the cooling metal to keep it protected from air until it's no longer red...
In any case, the strength of the weld is not much different if you use SS or mild filler, as long as the weld looks nice.
Hope that helps!!!
Cheers
Gary |
John Biundo (Jbiundo) (64.175.36.124)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 22, 2002 - 11:11 pm: | |
Thanks Gary. It's great to get an explanation like this. I've learned so much by trying to tackle these kinds of issues, and I owe alot of it to the people willing to put the time in to help out.
I also heard back from Lincoln Electric today, and the combination of your info, what they told me, and what I heard from a few other bus nuts leads me to the decision to use the mild steel flux core wire. I think my problems are gas related -- either leaks, wrong gas (I have argon/C02/helium mix), wrong pressure, or something.
I'm given to understand that a mild steel weld will be sufficiently strong, though obviously subject to corrosion. I'm willing to deal with that by painting the joints, and I'm very confident that I can get a good weld this way. Some further experimentation today produced more good welds using this combination ("good" measured by appearance and by trying to break the test welds -- the SS always broke before the actual weld).
Thanks again!
John |
Larry Baird (Airhog) (159.115.147.139)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, April 23, 2002 - 7:00 pm: | |
Twenty years of welding says, use the tri-mix gas. |
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