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How to choose the shielding gas in welding？
Shielding gases are primarily categorized into inert gases (Ar, He), active gases (CO₂, O₂, N₂, H₂), and their mixtures.
Mixtures are most commonly used in welding, as they combine the advantages of different gases to optimize welding performance.
For Carbon & Low-Alloy Steels (GMAW):
Ar + CO₂ (C-Mixes):
C25 (75% Ar + 25% CO₂): The gold standard. Offers more stable arc, significantly less spatter, and better bead appearance than pure CO₂, while maintaining good penetration. Suitable for short-circuit and spray transfer.
C10/C15 (90/85% Ar + 10/15% CO₂): Even less spatter, used for applications with extreme spatter control requirements (e.g., robotic welding).
Ar + O₂: e.g., 98%Ar + 2%O₂. Used for spray transfer on carbon steel, providing excellent bead appearance.
For Stainless Steel (GMAW/GTAW):
Ternary Mixtures (Ar + He + CO₂): e.g., 90%He + 7.5%Ar + 2.5%CO₂. The top choice, combining He's heat, Ar's stability, and a small amount of CO₂ for arc improvement and wetting.
Ar + H₂: As mentioned, used in GTAW to achieve very clean welds.
For Aluminum & Alloys (GMAW/GTAW):
Pure Argon (100% Ar): Suitable for most applications, especially thin plate.
Ar + He: Common ratios are Ar/He 50/50 or 70/30. Increasing He content raises heat input, used for thick aluminum plate to improve speed, penetration, and reduce porosity.
For Nickel Alloys, Copper Alloys, Titanium Alloys:
Typically use pure argon or argon-helium mixtures. For titanium & its alloys, high-purity argon (99.999%) is mandatory, with adequate backside and trailing shield protection.
Three-Step Quick Selection Method
Step 1: Identify Base Material
Al, Mg, Ti, Cu → Choose Inert Gases (Pure Ar or Ar/He mix).
Carbon Steel → Prefer Mixtures (e.g., C25). Pure CO₂ for low-cost scenarios.
Stainless Steel → Choose Ternary Mixtures or special mixes.
Step 2: Identify Welding Process
GTAW (TIG) → Almost exclusively pure inert gases (Ar/He).
GMAW (MIG/MAG) → Select gas based on Step 1.
FCAW → Follow filler wire manufacturer's recommendation (often C25 or pure CO₂).
Step 3: Fine-tune Based on Requirements
For better appearance & less spatter → Increase Argon proportion.
For deeper penetration & thicker plate → Increase Helium (for non-ferrous) or CO₂ (for steel) proportion.
To control costs → Choose gases with higher CO₂ proportion, provided quality requirements are met.
Reminder:Before proceeding with critical welding operations, it is essential to consult the technical data sheets provided by the filler metal (Welding wire, Welding electrode) manufacturer.
Three-Step Quick Selection Method 
