Argon gas plays an extremely important role in welding, especially in TIG welding (tungsten inert gas shielded welding) and MIG/MAG welding (melting electrode inert/active gas shielded welding).
Its core function can be summarized in three words: ‘protector’.
Below, we will provide a detailed breakdown of the specific functions, principles, and advantages of argon gas.
1、 Core function: Isolate the air and form a protective umbrella
The air contains oxygen, nitrogen, water vapor, etc. Under the high-temperature arc generated by welding (temperatures can reach thousands of degrees Celsius), these gases will undergo violent chemical reactions with the molten metal, leading to welding defects. Specifically:
Oxygen: It can oxidize molten metal, produce oxide inclusions, and burn alloy elements, resulting in brittle weld metal, decreased strength, and reduced toughness.
Nitrogen: It will merge into the molten pool, causing porosity and “nitriding” of the weld metal, resulting in an increase in strength and hardness, but a sharp decrease in plasticity and toughness.
How can argon solve this problem?
Inert: Argon is a “lazy” gas that does not react chemically with other substances and does not dissolve in metals.
Heavier than air: Argon gas has a higher density than air and can be sprayed from the welding gun nozzle to effectively cover the welding area (arc, molten pool, high-temperature weld and tungsten electrode surroundings).
Forming a protective layer: It acts like an invisible “umbrella” or “shield”, completely isolating the molten pool from the surrounding air, thereby preventing the invasion of harmful gases.
2、 The specific role and advantages of argon gas in welding
In addition to its core “protection” function, argon gas also brings a series of key advantages:
Stable arc, easy to initiate arc
Argon gas has a good ionization potential, which means that under the action of an arc, it is easily ionized into ions and electrons, thereby maintaining stable combustion of the arc.
Especially in TIG welding, using pure argon gas is very easy to ignite the arc and maintain its stability, which is crucial for welding quality.
Concentrated arc, energy concentration
In an argon environment, the arc is compressed, and the heat is more concentrated, forming the so-called “beam effect”.
This brings two benefits:
Good melting depth: concentrated heat and strong penetration.
Small heat affected zone: minimal thermal damage to the base metal around the weld seam, reducing deformation of the workpiece.
Improve weld seam formation
The appearance of the weld obtained by using argon gas protection is clean, smooth, and aesthetically pleasing, with clear weld beads and almost no slag.
Suitable for various metals
Argon, due to its excellent inertness, is particularly suitable for welding metals that are chemically active and easily oxidized, such as:
Stainless steel: prevents chromium and other alloying elements from being burned and maintains its corrosion resistance.
Aluminum and aluminum alloys: Aluminum is easily oxidized at high temperatures to form high melting point aluminum oxide films, and argon gas can effectively prevent its oxidation.
Titanium and titanium alloys: Titanium is extremely sensitive to air at high temperatures and must be welded under sufficient protection of argon gas.
Magnesium alloys, copper alloys, high-temperature alloys, etc.
3、 Different application forms of argon gas
Pure argon gas: widely used in TIG welding and MIG welding (welding stainless steel, aluminum, titanium, etc.).
Mixed gas: In order to optimize performance in specific applications, argon gas is often mixed with other gases.
Argon+carbon dioxide: This is the most common mixed gas in carbon steel MAG welding. Adding a small amount of CO2 can increase the penetration depth and improve the wettability of the weld seam, but it may cause a small amount of splashing. The common ratio is 82% Ar/18% CO ₂.
Argon+oxygen: Adding a small amount of oxygen (1-5%) can further stabilize the arc, improve weld formation, and is used for MAG welding of stainless steel.
Argon+helium: Helium can generate higher heat and can be mixed to weld thick aluminum plates or copper, increasing melting depth and speed.
Simply to say, without the protection of argon gas, high-quality, oxidation free modern arc welding (especially TIG and MIG welding) is almost unimaginable. It is a key factor in ensuring excellent mechanical properties and appearance quality of welded joints.