Im learning about MIG on my own, currently I'm on gas mixtures pros n cons. I do not understand why oxygen is used in MIG. I was taught in school that in TIG welding: oxygen, nitrogen, hydrogen contaminate the tungsten and the weld, making it porous and brittle. I do understand that TIG and MIG are two different processes, but the job of both processes is to achieve a sound weld, free of contamination (within tolerances). I've read that in MIG, adding 1-5% oxygen or 3-25% co2 can make the arc more stable (reducing undercut) on ferrous alloys vs just using 100% Argon. A stable arc and less undercut are desirable traits but I can't understand contamination from oxygen being good. Can someone explain this to me please.
Thanks
I've never heard of this before, but here's a link to help explain it.
http://www.bernardwelds.com/mig-welding ... XQOAqJg_I8
http://www.bernardwelds.com/mig-welding ... XQOAqJg_I8
Desmo.
The link WerkSpace cited seemed helpful.
In a general quality sense, something else to consider is that each finished weld needs to achieve the minimal agreed upon (buyer/fabricator) acceptance criteria. The concept of 'perfect welds' is alien to welding. Instead we refer to acceptable welds as welds conforming to some acceptance criteria. Weld flaws, weld indications, weld discontinuities ... may not necessarily be weld unacceptable weld defects.
In an attempt to understand a weld, we try to understand the history of that weld. Including the past (history) of the base metals that will be welded. The past of those filler metals (electrodes, etc.). The way it was welded (the welding procedure, with its various variables ... gas protection being one of them). Then we must consider if the welder stuck with the procedure or strayed. At the end of the day ... we have a weld with its own history, at times, a complicated history.
Hope I did not bore you.
Alexa
The link WerkSpace cited seemed helpful.
In a general quality sense, something else to consider is that each finished weld needs to achieve the minimal agreed upon (buyer/fabricator) acceptance criteria. The concept of 'perfect welds' is alien to welding. Instead we refer to acceptable welds as welds conforming to some acceptance criteria. Weld flaws, weld indications, weld discontinuities ... may not necessarily be weld unacceptable weld defects.
In an attempt to understand a weld, we try to understand the history of that weld. Including the past (history) of the base metals that will be welded. The past of those filler metals (electrodes, etc.). The way it was welded (the welding procedure, with its various variables ... gas protection being one of them). Then we must consider if the welder stuck with the procedure or strayed. At the end of the day ... we have a weld with its own history, at times, a complicated history.
Hope I did not bore you.
Alexa
- Otto Nobedder
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Weldmonger
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Joined:Thu Jan 06, 2011 11:40 pm
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What we call MIG welding usually isn't. Only if the gas is pure argon, argon/helium, or more rarely, neon, xenon (exponentially more expensive gasses) is it truly MIG. What we ususally do is MAG welding, short for Metal/Active Gas.
Each component of the gas mixture serves a purpose for the desired end result. As Alexa said, there is no "perfect" weld, only "acceptible" vs. "unacceptible".
Oxygen, in controlled amounts in the mix, will increase heat in the weld zone by combining both with the base metal and the silicon in the wire (E70-S6 as the example). The O2 is low enough for the silicon to compensate for the oxides formed, but the extra heat allows for a deeper penetrating weld than straight 75/25. The ionization properties of the gass allow for different processes, as well. Spray-arc requires a different gas mix from short-circuit, for example.
One of the members here (RedIron881) does stainless steel vacuum welds similar to mine, but on much heavier sections, so he TIGs with an ar/he/O2 mix.
Steve S
Each component of the gas mixture serves a purpose for the desired end result. As Alexa said, there is no "perfect" weld, only "acceptible" vs. "unacceptible".
Oxygen, in controlled amounts in the mix, will increase heat in the weld zone by combining both with the base metal and the silicon in the wire (E70-S6 as the example). The O2 is low enough for the silicon to compensate for the oxides formed, but the extra heat allows for a deeper penetrating weld than straight 75/25. The ionization properties of the gass allow for different processes, as well. Spray-arc requires a different gas mix from short-circuit, for example.
One of the members here (RedIron881) does stainless steel vacuum welds similar to mine, but on much heavier sections, so he TIGs with an ar/he/O2 mix.
Steve S