Redneck engineer
Member
Anyone like the 100% co2 over the argon mix? And what pressures do you normally run with either?
Mig gases
- Thread starter Redneck engineer
- Start date
CB
Active member
- Messages
- 30
- Good Post Points
- 51
1. Shielding gas isn't "run" by the weldor at "pressures". Cylinders are filled by pressures. Gas remaining in a cylinder is measured by pressure. But the weldor "runs" the gas by FLOW, not pressure. The flow of shielding gas is expressed as CFH, for cubic feet per hour.
2. The CFH that a weldor might choose depends on the environment being welded in. The surrounding air flow (wind) has a great deal of influence on what a weldor might set the shielding gas to flow at, in order for the weld pool not to become oxidized or porous before it solidifies.
3. Shielding gas is expensive. Argon is more expensive than 100% CO2. Argon blends are more expensive than 100% CO2. Some blended gasses are more expensive than 100% Argon. Certain Tri-Mixes, particularly those containing Helium, often used for welding stainless steel, can be brutally expensive, due to how helium gas is controlled.
4. With the expense of shielding gas, and the constant trouble of potentially running out before the job/project is complete, the most logical practice is to avoid wasting shielding gas, which naturally leads to flowing as little gas as possible to make a sound weld.
5. Indoors, with no drafts, and with small welding puddles squeezed out of low power machines running short arc, 15-25 CFH might be enough, trending toward the higher side of that range with more draft and less experience.
6. Indoors, with the big garage door open, with no wind, and with medium puddles or weaves, 25-35 CFH might be enough.
7. Outdoors, with a big power supply cranked to 30v, with a fat wire or fast wire speed to match, and up to a 3 mile per hour wind, 35-45 CFH might be enough to cover the cone of spray arc and the red lake underneath, trending toward the higher side, the larger the puddle of metal one is carrying, or the stronger the wind.
8. Too much shielding gas can disturb the weld pool from the flow disturbance of the gas shooting out of the cup. So if the wind is strong enough to motivate cranking the flow meter past 50 CFH, then it is time to put the MIG torch down and pick up a stick electrode, or switch to self shielded wire.
9. Backing up to the top where you said "argon mix"... that's more than one type of gas. There is a whole host of argon mixes, and the difference between those mixes makes all the difference in the world, depending on which type of GMAW process is desired (ie, short, globular, spray, pulse). Different argon mixes can influence the energy of the arc and also correlate to the transition current of the wire. If you have a particular argon mix in mind, it is best to identify what blend you are considering, and what process you are planning, when comparing that blend to straight CO2.
10. Generally speaking, the argon level has to be higher than 80-85% in order to achieve true spray transfer, with most procedure guidelines calling for 90-92%, balance CO2. Ever more popular are argon mixes with a little oxygen, such as 98%Ar/2%O, where that little O adds some umph. A hybrid of both of these spray mixes is 90% Ar / 7.5% CO2 / 2.5% O. Then there are a proprietary blends.
11. Some FCAW-G electrodes REQUIRE one type of gas or another, because the decomposition of the gas breaks down into constituent elements that interact with the flux in the FCAW wire, and the chemical reaction is already anticipated and relied upon to influence the properties (strength, hardness, elongation, alloying element retention, etc) of the weld. So it is important to note that the choice of the best shielding gas for the process and electrode being used isn't always a matter of operator preference. It is often a matter of specifications established by the manufacturer of the electrode.
Real Estate answer-It depends. Concur with CB above post. There are lots of variables. For aluminum 100% argon is pretty much the norm. I have never run helium, but understand it is used is some instances. For ferrous metals 75/25 is my preference. Anything over 50% co2 gets a tad messy (like someone tossed some water in the skillet.) As ones skill level increases, the "sound" will help you determine whats happening in the HAZ.
To specifically address your question, ease of joining the work. When out of position (standing on your head) one does not want any distractions and the weld to go smoothly and quickly without any additional crud flying out of work area, and/or into helmet / ear canal. Been there, done that. That alone worth it to me.
TLee
To specifically address your question, ease of joining the work. When out of position (standing on your head) one does not want any distractions and the weld to go smoothly and quickly without any additional crud flying out of work area, and/or into helmet / ear canal. Been there, done that. That alone worth it to me.
TLee
Last edited:
Redneck engineer
Member
WOW! What a post! So much information. Thank you!!! I know much more now.... I didn't realize there were so many combinations.