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Get recommended CFH for any process based on cup/nozzle size and wind conditions. Empirical lookup — real shop data, not formulas. Avoid turbulent flow that causes porosity.
Use the lowest effective flow rate that maintains laminar (smooth, layered) coverage. Too high creates turbulence that draws in atmospheric air — same result as too low flow.
Standard indoor still air: 15–25 CFH argon. Start at 20 CFH. Adjust down if you hear turbulence, up if you see discoloration on the bead toes.
Base range 25–30 CFH with C25 mix, add 5 CFH for light draft: 30–35 CFH. Watch for wind-induced porosity at the start of each tack.
Base 20–30 CFH + 10 CFH wind adjustment: 30–40 CFH. Consider a gas lens kit — it produces laminar flow at lower CFH for outdoor work.
Build a code-compliant WPS with gas type, flow rate, and cup size documented — AWS D1.1, ASME IX, or API 1104.
Try WPS Generator free → 14-day free trial · No credit card requiredFor MIG with C25 (75Ar/25CO₂) on steel, start at 20–30 CFH depending on nozzle size. Larger nozzles and drafty shops need higher flow. Pure CO₂ can use slightly less. Adjust up if you see arc instability or bead discoloration.
Wind disrupts the protective gas envelope in TIG, causing oxidation and porosity. In still indoor conditions, 15–25 CFH is sufficient with a #6 cup. For outdoor or drafty environments, increase to 25–40 CFH, or use a gas lens with a larger cup to maintain laminar coverage at lower CFH.
Excessively high flow creates turbulent flow via the Venturi effect, drawing atmospheric air into the shield and causing the same contamination as too-low flow. Start with the minimum effective CFH and increase only until arc stability is achieved — more is not better.