I feel like I've read about reasons for using flux with gas before, but I can't remember why or what blend of gas.
Are they any advantages?
I'm not trying to be cheap or anything, wire isn't very expensive, but I've got 2 good rolls of flux core left and finally got a gas tank, and not sure how separate I should keep them or if it would make a difference.
In reply to RevRico :
I was just thinking about this today. I remember someone within the last year or so saying it gave the cleanest welds. Hope for more information also.
That's what I do with flux core. "Double Shielded."
Disagree. Gas OR flux, not both.
Gas shields from the outside. That means you get nothing but heat and molten metal. Flux shields from the inside out. The flux burns and bubbles out of the puddle to shield the arc, meaning that your welds are inherently porous.
It might look lovely, but the bottom line is that you're purposely putting inclusions of foreign junk in the weld with flux. Strength trumps appearance.
I suppose if you're just looking for pretty and intentionally not as strong, combine them, but flux core by its nature can't really be as strong as shield gas with no flux.
IMO, people who "double shield" are thinking that more is better when it isn't. If you want more shielding, turn up the regulator on the tank or use a better shield gas. There is more than enough shielding from the gas. No need to add more, especially when it comes by boiling out of the puddle.
No affiliation just tons of good tech.
Again, I am not affiliated.
In industrial welding, you often use dual shield. You need the right machine, wire, gas, etc. It produces an exceptionally strong , smooth weld. (edit, looks like 75% 25% argon/CO2)
This sort of thing is not really applicable to a 115 Hobart.
Double shield is used on thick steel in manufacturing to get a proper weld with one pass and at increased speeds. It helps.
I used to help a friend build shrimp boat stabilizers. We were welding 1" plate masts to 3/4" plate wings with one pass at 300 amps. The welds came out perfect every time. Double shield cut the weld time per piece in half compared to gas alone.
Interesting discussion...
The bulk of my MIG welding is on car body panels. We all know that the best welds are when the metal is perfectly clean of oxides and organic matter. Cleaning the front of the weldment is easy enough. What is often not easy is to clean the backside of the weld to the same degree. If your penetration is correct, your weld puddle is going to go to the backside of the seam, absorb the impurities and contaminate the weld pool. Craters and blow-outs tend to be the result.
For the most part this is something we all learn to weld around: much like welding gaps and filling blow-outs. But I wonder? Would a double shield help with this?
Pete
tester said:No affiliation just tons of good tech.
Again, I am not affiliated.
From the first link...
There are two types of flux-cored wires — gas-shielded and self-shielded. Gas-shielded flux-cored wires require external shielding gas, and the slag is easy to remove. Consider using gas-shielded flux-cored wires when welding on thicker metals or in out-of-position applications. Gas-shielded flux-cored wires have a flux coating that solidifies more quickly than the molten weld material. As a result, it creates a shelf to hold the molten pool when welding overhead or vertically up. Self-shielding flux-cored wire does not require external shielding gas because the weld pool is protected by gas generated when flux from the wire is burned. As a result, self-shielding flux-cored wire is more portable because it does not require an external gas tank.
so there is a specific flux-jacketed wire designed for use with shield gas? Is that what I'm seeing? Am I learning?
In reply to Curtis :
Yes. There are flux core wires specifically for for gas shielding.
There are even applications for purging while "stick" welding, typically on pipe.
In reply to NOHOME :
I don't do body work, but if I were working on a frame rail or sheet metal box then I would definitely consider a back purge in that application. We back purge pipe welds all the time. It is standard practice to clear contaminants and protect the weld. It needs to be low volume and low pressure or it may blow out the weld.
Obviously, flux isn't the right choice for thin sheet metal so you would need to have your valves set up to run the MIG gun and a separate feed for the back purge. It may be too much trouble for most situations.
By the way, I love the thread on the MGs. Cutting the side off a car and putting new metal back on so it is "right" when you are done is impressive.
I usually always have gas when welding or working in the shop, and while it makes it hard to keep good helpers around I don't find it really effects my welding other than when in really confined spaces.
In reply to tester :
Good to hear that someone is entertained by my Brit car antics. I spent another 3 hours in the shop today cursing at the fact that the owner brough me non factory panels to splice in to the car.
Back on topic back purging is not so much the solution to what you have to deal with when doing rustorations. Back purging is done to avoid creating an oxide layer on the back of the weldment. In the case of say a quarter panel that has been on there for 50 years, you already have a layer of oxide and organics on the inside of the panels that are going to be impossible to completely remove. Flux tends to float these contaminants to the surface of the weld so I was o wondering if the use of gas AND flux would be a good thing?
Lincoln makes, or used to make a MIG wire that was kinda like a normal wire but the insid was like a granular matrix of I dont know what. It was touted as specifically for sheet metal welding. The word "flux core" was used, but it needed to be used with shielding gas. I bought a roll ( like $80) and did a bunch of welding with it, but ultimately never found it to be any better than normal MIG wire.
Pete
In my shop all we use is flux core with gas. These are heavy weldaments welded with .045" or 1/16" wire. The wire is made for use with gas, and the type of gas required depends on the type of wire. Most of our welding is on mild steel with straight CO2. We do some specialty stuff that requires an Argon/CO2 mix. The welds have much less spatter than using a hardwire with gas.
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