Argon arc welding (TIG welding) is a widely used high-quality welding method, particularly suitable for welding metals such as stainless steel, aluminum, copper, and titanium. The selection of the protective gas is crucial during the argon arc welding process, as it not only affects the shape of the weld and the quality of the welding, but also relates to the welding efficiency and cost control. Therefore, scientifically and reasonably selecting the protective gas is one of the key factors to ensure the success of the welding process.



One, The Role of Shielding Gas in Argon Arc Welding



In argon arc welding, the main function of the shielding gas is to isolate oxygen, nitrogen, and moisture in the air, preventing the oxidation, nitriding, and hydrogen-induced cracking of molten metal. At the same time, the shielding gas also affects the stability of the arc, the fluidity of the molten pool, and the surface shape of the weld.



Two, Common Shielding Gases and Their Characteristics



1. Pure Argon (Ar)



Argon is the most commonly used shielding gas, belonging to inert gases with stable chemical properties, suitable for welding most metal materials, especially stainless steel, aluminum, copper, and titanium. When using pure argon gas for welding, the arc is stable, and the weld shape is beautiful, suitable for applications with high requirements for weld quality.



2. Argon + Helium Mixed Gas (Ar + He)



When welding thick plates or high thermal conductivity materials (such as aluminum and copper), the addition of helium can increase the arc temperature, increase the penetration depth and welding speed. However, mixed gases are more expensive, and helium has a small density, resulting in slightly poorer protection effects, requiring a larger gas flow rate.



3. Argon + Hydrogen Mixed Gas (Ar + H₂)



When welding stainless steel, the addition of a small amount of hydrogen can increase the arc temperature, improve the fluidity of the molten pool and the shape of the weld, and reduce the formation of oxides. However, hydrogen is reducing and is not suitable for welding active metals such as titanium and zirconium to avoid causing hydrogen embrittlement.



4. Argon + Nitrogen or Other Gases



Nitrogen is generally not used alone, but in some special alloy welding, such as nickel-based high-temperature alloys, the addition of an appropriate amount of nitrogen can improve the weld structure. However, nitrogen is highly reactive and should be used with caution.



Three, Criteria for Choosing the Shielding Gas



1. Type of Welded Material

Different materials have different sensitivities to gases, such as pure argon should be used for active metals like aluminum and titanium; stainless steel can consider argon + hydrogen; and copper alloys can consider argon + helium.



2. Welding Quality Requirements

For applications requiring high forming quality and no oxidation, pure argon or appropriate mixed gases should be preferred.



3. Economy and Practicality

Although mixed gases may bring better welding performance, they are more expensive and complex to operate, and should be weighed according to actual production needs.



4. Environmental and Process Conditions

The selection of gas is also affected by factors such as welding position, joint form, and welding current. For example, when welding at high altitudes or outdoors, it may be necessary to consider the density and wind resistance of the gas.



Four, Conclusion



In summary, the selection of shielding gas in argon arc welding should be comprehensively considered from multiple aspects such as the characteristics of the welded material, the requirements of the welding process, and economic factors. Correct gas selection can not only improve the quality of welding but also enhance the efficiency of welding and reduce production costs. Therefore, in practical applications, it is recommended to conduct gas mixing tests according to specific welding tasks, choose the optimal scheme, and achieve the goal of high-quality and efficient welding.