I noticed yesterday that my gas flow rate is about 15 CFHR. I thought I remembered reading that 10 CFHR is usually enough. Am I wasting gas? I'm using a 75%/25% Argon/CO2 mix and welding mild steel. There is little/no wind.
How much you'll need (I can't begin to think in CFHR) is going to depend on a lot of things: you might try starting at a rate that produces nice welds then cutting it till the weld suffers and splitting the difference.
Hmmm... 10 liters/minute = 0.353146 CF/minute X 60 minutes/hour = 21.19 CFHR, so Steve is right on the money... So my flow is actually a little low, rather than high. Could low flow increase the brown powder around my welds, as seen below?
The brown powder is rust and oxidizers. CO2 adds heat by burning the surface of the weld pool (CO2 breaks down to O2). Some of it vaporizes. That exits the gas shielding, it cools and oxidizes.
Adding more gas lets it get cooler before getting exposed to air. Lower levels of CO2 will also decrease the amount of brown deposits. Torch angle and gun/work distance also effect the amount of dust.
Whan I used 100% argon, there was no deposits at all. Then again the welds looked like caterpillars .