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How do you select a shielding gas?
There are a variety of gas blends that can be chosen for MIG, TIG, or Flux Cored Welding applications.
To make a well-informed selection, a number of approaches can be used, but all are based on a basic understanding of the requirements for the finished weldment.
Shielding gas questions that need to be answered first may include:
- How important is weld appearance?
- Is spatter near the weld area a concern?
- Is deep penetration required or should penetration be limited to minimize burn- through of the joint?
- Is there a concern about the amount of welding fume generated and should it be reduced?
Depending on the requirements for the finished weld, a number of other questions might be asked as well.
To select a gas blend, the following four-step process can be followed:
- Consider the material type – carbon steel, stainless steel, aluminum, nickel alloys, copper alloys or other non-ferrous materials
- Know the base material thickness and understand its condition – clean, oily, scaled, etc.
- Determine the welding position as this will impact the type of process/metal transfer you plan to utilize. Process selection may be further impacted by the availability of equipment, operator skills and desired productivity.
- Review the requirements of the job. Consult the selection chart to determine the gas blend that provides the best performance for the application at hand.
Simple, isn’t it? This selection process should help you make a good first attempt at matching the best shielding gas to your application. Refinement may be needed depending on the specific equipment and skills available. Other needs may have to be identified as work progresses. For further information on Linde’s Star™ family of shielding gases, please consult your local Linde representative.
Gas Metal Arc Welding (GMAW or MIG)
| Material Type | Thickness | Condition | Transfer Mode | Shielding Gas Recommended | Travel Speed | Weld Appearance | Penetration | Spatter Reduction | Fume Reduction |
|---|---|---|---|---|---|---|---|---|---|
| Mild Steel | 22 to 10 ga (0.9-2.5mm) | clean | short-circuit | StarGold C-25 | G | E | E | E | G |
| Mild Steel | 22 to 10 ga (0.9-2.5mm) | minor scale/oil | short-circuit | StarGold C-25, Stargon | G | E | E | G | G |
| Mild Steel | 22 to 10 ga (0.9-2.5mm) | clean | pulsed | MIG Mix Gold, StarGold C-25 | E | E | G | E | E |
| Mild Steel | 1/8" - 1/2" (3.2-12.7mm) | clean | short & spray | Stargon, MIG Mix Gold, StarGold C-10 to C-15 | E | E | G | G | E |
| Mild Steel | 1/8" - 1/2" (3.2-12.7mm) | minor scale/oil | spray | StarGold C-10 to C-15, HeliStar CS | G | G | G | E | G |
| Mild Steel | 1/8" - 1/2" (3.2-12.7mm) | clean | pulsed | StarGold C-5, MIG Mix Gold | E | E | G | E | E |
| Mild Steel | 1/8" - 1/2" (3.2-12.7mm) | clean | spray & pulsed | StarGold O-5 | E | G | F | E | E |
| Mild Steel | Over 1/2" (12.7mm) | clean | spray & pulsed | StarGold C-10* to C-15 | E | G | G | E | E |
| Mild Steel | Over 1/2" (12.7mm) | light scale/oil | spray & pulsed | HeliStar CS* | E | E | E | G | G |
| Mild Steel (coated) | 22-16 ga (0.9-1.6mm) | galvanized | short arc | StarGold C-25** | G | G | G | F | P |
| Mild Steel (coated) | 22-16 ga (0.9-1.6mm) | galvanized | spray* Si-bronze only | Argon | E | E | F | E | F |
| Stainless Steel | 16-10 ga (1.6-2.5mm) | clean | short-circuit | HeliStar A-1025, HeliStar SS | G | G | E | G | F |
| Stainless Steel | 11 ga - 1/2" (2.3-12.7mm) | clean | spray | HeliStar SS, StarGold C-2 to C-5 | E | E | G | G | G |
| Stainless Steel | 11 ga - 1/2" (2.3-12.7mm) | clean | spray & pulsed | StarGold O-2 | E | F | F | G | G |
| Stainless Steel | 16 ga - 1/2" (1.6-12.7mm) | clean | pulsed | HeliStar SS | G | E | G | E | G |
| Low Alloy Steel | 16 ga - 1/2" (1.6-12.7mm) | clean | short-circuit | Stargon, MIG Mix Gold | G | G | G | G | G |
| Low Alloy Steel | 16 ga - 1/2" (1.6-12.7mm) | clean | spray & pulsed | Stargon, MIG Mix Gold, StarGold C-5 to C-10 | E | E | E | E | G |
| Low Alloy Steel | 16 ga - 1/2" (1.6-12.7mm) | clean | pulsed | StarGold O-5 | G | G | F | E | E |
| Aluminum Alloys | All Thicknesses | clean | pulsed | Argon | G | G | F | E | G |
| Aluminum Alloys | All Thicknesses | clean | spray | Argon, HeliStar A-25, A-50, A-75 | E | E | E | G | F |
| Copper Alloys | All Thicknesses | clean | pulsed & spray | Argon | G | F | F | G | E |
| Copper Alloys | All Thicknesses | clean | pulsed & spray | HeliStar A-25, A-50 | E | G | G | G | G |
| Nickel Alloys | All Thicknesses | clean | pulsed, spray mechanized | HeliStar A-25, A-50, SS | E | E | G | G | G |
Performance Measures: E=Excellent, F=Fair, G=Good, P=Poor
* 0.045 to 0.063 wire diameter recommended
** ER70S3 wire recommended
Flux-Cored & Metal-Cored Arc Welding
| Material Type | Thickness | Condition | Transfer Mode | Shielding Gas Recommended | Travel Speed | Deposition Efficiency | Weld Appearance | Penetration | Spatter Reduction | Fume Reduction* |
|---|---|---|---|---|---|---|---|---|---|---|
| Mild Steel | 14 - 10 ga (1.8-2.5mm) | clean | globular | StarGold C-25, C-40, C-50 | E | G | E | G | G | G |
| Mild Steel | 14 - 10 ga (1.8-2.5mm) | some oxide | globular | StarGold C-25, C-40, C-50 | G | G | G | G | G | F |
| Mild Steel | 1/4" - 1/2" (6.4-12.7mm) | clean | globular | StarGold C-25, C-40, C-50 | E | G | E | G | G | G |
| Mild Steel | 1/4" - 1/2" (6.4-12.7mm) | clean | globular | CO2 | G | G | G | E | F | P |
| Mild Steel | 1/4" - 1/2" (6.4-12.7mm) | clean | spray** | StarGold C-10 to C-15, MIG Mix Gold | E | E | E | F | E | E |
| Mild Steel | 1/4" - 1/2" (6.4-12.7mm) | some oxide | globular | StarGold C-25, C-50 | E | G | G | G | G | G |
| Mild Steel | 1/4" - 1/2" (6.4-12.7mm) | some oxide | globular | CO2 | G | F | G | E | F | P |
| Mild Steel | 1/4" - 1/2" (6.4-12.7mm) | some oxide | spray** | StarGold C-10 to C-15, MIG Mix Gold | E | E | G | F | E | E |
| Mild Steel | over 1/2" (12.7mm) | clean | globular | StarGold C-25, C-50 | G | G | E | G | G | G |
| Mild Steel | over 1/2" (12.7mm) | clean | globular | CO2 | G | F | G | E | F | P |
| Mild Steel | over 1/2" (12.7mm) | clean | spray** | StarGold C-10 to C-15, MIG Mix Gold | G | E | E | F | E | E |
| Mild Steel | over 1/2" (12.7mm) | some oxide | globular | StarGold C-25, C-50 | F | F | G | G | F | F |
| Mild Steel | over 1/2" (12.7mm) | some oxide | globular | CO2 | F | F | F | E | F | P |
| Mild Steel | over 1/2" (12.7mm) | some oxide | spray** | StarGold C-10 to C-15, MIG Mix Gold | F | E | G | F | E | G |
Performance Measures: E=Excellent, F=Fair, G=Good, P=Poor
* Welding fume varies with wire chemistry selected.
** Metal-cored wire recommended.
Gas Tungsten Arc Welding (GTAW or TIG)
| Material Type | Condition | Transfer Mode | Shielding Gas Recommended | Travel Speed | Penetration | Color Match | Fume Reduction | Arc Stability |
|---|---|---|---|---|---|---|---|---|
| Mild Steel | clean | manual | Argon | F | G | G | E | E |
| Stainless Steel | clean | manual | Argon | P | G | F | E | E |
| Stainless Steel | clean | mechanized | HeliStar A-25 | F | G | G | E | G |
| Austentic SS (300 Series) | slight oxide | manual | HydroStar H-2, H-5 | F | G | E | E | G |
| Austentic SS (300 Series) | slight oxide | mechanized | HydroStar H-5, H-10 | G | G | E | E | G |
| Aluminum Alloys | clean | manual | Argon, HeliStar A-75 | F | E | E | E | G |
| Aluminum Alloys | clean | mechanized | HeliStar A-25, A-50 | G | E | E | E | F |
| Copper Alloys | clean | manual | Argon | F | F | G | E | E |
| Copper Alloys | clean | mechanized | HeliStar A-25, A-50 | G | G | G | E | G |
| Nickel | clean | manual | Argon | P | G | F | E | E |
Performance Measures: E=Excellent, F=Fair, G=Good, P=Poor
Note: Thickness foil to 1/8". Base metal thickness greater than 1/8" can be more effectively joined with MIG.