Learn how to select the right shielding gas for different materials and processes. Discover gas mixtures, flow rates, and their effects on weld quality.
Introduction
Shielding gas protects the weld pool from atmospheric contamination and affects weld quality, penetration, and appearance. At Fulei Metal, we select appropriate gases for each material and process.
Functions of Shielding Gas
Protects molten weld pool from oxygen and nitrogen. Prevents porosity and oxidation. Stabilizes the arc. Affects weld penetration and bead shape. Influences weld appearance and cleaning.
Gas Types
Argon
Inert gas. Suitable for all materials. Standard for TIG welding. Good arc stability. Good cleaning action in AC TIG (aluminum). Limited penetration for MIG on steel.
Helium
Inert gas. Hotter arc than argon. Deeper penetration. Faster travel speed. More expensive. Used in mixtures for thick materials.
CO2
Active gas. Used for MIG on carbon steel. Deep penetration. Low cost. Produces more spatter. Not suitable for stainless or aluminum.
Oxygen
Active gas. Small amounts (2-5%) added to argon. Improves arc stability. Better wetting. Used for MIG on stainless and some steel.
Hydrogen
Reactive gas. Small amounts (1-5%) added to argon. Reduces oxide. Increases heat. Used for TIG on stainless. Never use on carbon steel (cracking risk).
Gas Mixtures by Material
Carbon Steel MIG
100% CO2: deep penetration, more spatter, lowest cost. 75% Ar / 25% CO2 (C25): best all-around, smooth arc, less spatter. 85% Ar / 15% CO2: good for spray transfer. 90% Ar / 10% CO2: for pulsed spray.
Carbon Steel TIG
100% Argon: standard for all TIG on steel.
Stainless Steel MIG
98% Ar / 2% O2: good wetting, stable arc. Tri-mix (90% He / 7.5% Ar / 2.5% CO2): excellent for short-circuit. Never use standard CO2 mixtures.
Stainless Steel TIG
100% Argon: standard. Argon + 2-5% H2: for faster travel and better oxide reduction. Never use hydrogen on carbon steel.
Aluminum MIG
100% Argon: standard for thin materials. 75% Ar / 25% He: for thicker sections, hotter arc. 50% Ar / 50% He: for very thick aluminum.
Aluminum TIG
100% Argon: standard AC TIG. 50% Ar / 50% He: for thick aluminum, more heat.
Flow Rates
TIG
8-15 liters per minute. Too low: porosity, contamination. Too high: turbulence, waste. Larger cups need more flow.
MIG
10-15 liters per minute for indoor work. 15-20 for outdoor or drafty areas. Too low: porosity. Too high: turbulence draws in air.
Gas Quality
Use welding-grade gas (99.996% purity minimum for argon). Moisture causes porosity. Impurities affect weld quality. Verify gas certificates. Use proper regulators.
Back Purging
For full-penetration stainless welds: purge the back side with argon. Prevents oxidation (sugar). Flow rate: 5-10 lpm. Use soluble purge plugs or dams. Critical for food, medical, and corrosive applications.
Conclusion
Selecting the right shielding gas is essential for weld quality. At Fulei Metal, we use appropriate gases and mixtures for each material and process, ensuring optimal weld quality.