MIG welding makes use of a handheld gun with a gas nozzle that discharges a stream of gas into the weld site and a wire electrode that is supplied from a spool.
By keeping oxygen, nitrogen, and other environmental gases from contacting the weld bead, this gas helps to guarantee reliable, strong results.
Poor-quality welding on your workpiece might result from contamination; thus, selecting the appropriate gas is crucial for optimal performance. Well, in this reading, I’ll be exploring the different types of MIG welding gas and the best type to use for a specific metal.
Let’s begin!
You should learn about Metal Inert Gas (MIG) Welding with this detailed guide!
Different Types of MIG Welding Gas
The four common shielding gases used in MIG welding are argon, helium, carbon dioxide, and oxygen.
Argon
A combination of 75–95 percent Argon and 5–25 percent CO₂ can be the ideal choice for companies that prioritize weld quality, attractiveness, and minimizing post-weld cleaning. Compared to pure CO₂, it will offer a more desired mix of arc stability, puddle control, and less spatter.
Additionally, this combination permits the employment of a spray transfer approach, which can result in welds that are more aesthetically pleasing and productive at greater rates.
Additionally, argon creates a thinner penetration profile, which is advantageous for butt and fillet welds. You must use 100% Argon when welding non-ferrous metals like titanium, magnesium, aluminum, or silver.
Oxygen
Reactive oxygen is also utilized in ratios of nine percent or less to enhance penetration, arc stability, and fluidity of the weld pool in mild carbon, low alloy, and stainless steel.
However, it is not advised to use it with aluminum, magnesium, copper, or other unusual metals, as it oxidizes the weld metal.
Similar to pure argon, helium is usually used with stainless steel and non-ferrous metals. Helium works well with thick materials because it creates a wide, deep penetration profile; it is often employed in a ratio of 25–75 percent Helium to 75–25 percent Argon.
The penetration, bead profile, and travel speed may all be altered by changing these ratios. Higher production rates and quicker travel speeds are made possible by the “hotter” arc that helium produces. But compared to argon, it costs more and needs a greater flow rate.
You must weigh the benefit of the higher output against the rising cost of gas. Helium is usually utilized in a tri-mix mixture with CO2 and Argon while working with stainless steel.
You should also learn about MIG vs Stick Welding with this detailed guide!
CO₂ (Carbon Dioxide)
Compared to inert gases like argon and helium, carbon dioxide is a “semi-inert” gas that is less susceptible to chemical change. It is commonly used in MIG welding, in full (100%) or in minor amounts with argon or helium gas mixtures.
When welding, CO₂ is far less expensive than inert gas and enables the bond to fuse extremely deeply into the metal.
Compared to a noble gas, it has a considerably harsher arc that can be more challenging to control, and because it is semi-inert, there is more weld spattering, which means that more cleanup is required after the weld.
Carbon dioxide is particularly useful when handling ferrous metals like mild steel. Although this is a more “old school” method utilized for specialized wires, 100% CO₂ is occasionally employed for this reason.
A tri-mix of CO₂, argon, and helium, or 72/25 Argon/CO2, is considerably more frequent for conventional MIG welding applications.
Other Gases
Hydrogen functions as a protective gas in high-temperature environments, such as stainless steel. Frequently, it is combined with argon when applied to austenitic stainless steel.
In order to remove contaminants during welding stainless steel tubes, nitrogen is utilized. It can also be used as a shield gas for stainless steel when added in small quantities to argon.
In scrap yards, propane is usually used to cut carbon steel when the quality of the cut is not crucial. Propane is a fairly affordable choice if high-cut quality is not required for your application.
How to Choose the Best MIG Welding Gas
A range of shielding gas options are appropriate for many applications involving MIG welding. To select the best one for your particular application, you must assess both your welding applications and your aims.
As you choose, bear the following in mind: how much gas costs, the qualities of the completed weld, preparation and cleanup after welding, the fundamental component, the method of weld transfer, and your objectives for development.
There are two primary gases used in MIG welding: pure argon and a mixture of argon and carbon dioxide.
The most popular (and advised) Ar/CO₂ mixture is 75/25, meaning that 75% of the mixture is argon and 25% is CO₂. You should utilize an Ar/CO₂ blend when dealing with mild steel or stainless steel. It is best to utilize pure argon when working with aluminum.
An inert gas such as pure argon produces a weld with a broader bead profile but shallower penetration. There is also less splatter as a result. Since CO₂ is less expensive and has a deeper penetration than argon, it can be utilized alone. CO₂ is a semi-inert gas.
But it creates a less steady, harsher arc that makes a lot of splatter.
When you combine the two, you get an excellent arc characteristic and a fully penetrative weld with minimal spatter. Because of this, the ideal gas mixture for mild and stainless steel is 75/25 Ar/CO₂. It is now frequently marketed as “MIG gas” as well.
You should also learn about MIG Welding Wires with this detailed guide!
Mid Welding Shielding Gas For Specific Types of Metals
Below are the best midweld shielding gases for different types of metals:
Gas for Welding Mild Steel
When welding mild steel, a mixture of 75% argon and 25% carbon dioxide—sometimes known as “C25 gas”—is frequently used. It has good arc properties and creates very little spatter.
Additionally, it has an excellent bead profile that makes it easy to wash off at the weld’s toes. There is one disadvantage: this combination costs more than other choices.
One such gas that is utilized for mild steel is C100, or 100% carbon dioxide. Though it can cause a little more splatter and an uneven arc, it’s a decent substitute that costs less than a 75%/25% shielding gas mixture.
Gas for Welding Silicon Bronze
DIY welders are increasingly using silicon bronze filler metal for applications including vehicle repair and sculptural and artistic welding, where it is used to combine different metals or a range of coated materials.
Generally, you should utilize a shielding gas that is 100% argon. When using silicon bronze filler metal, this enables a beautiful short-circuit transfer that aids in the puddle washing away.
Gas for Welding Stainless Steel
There are several gas mixtures that may be used while MIG welding stainless steel. The short-circuit transfer mode of many MIG welding power sources has historically been intended for use with helium trimix shielding gas for stainless steel.
Helium contributes to a pleasing bead profile and excellent bead properties by assisting the puddle in washing away without introducing excessive inductance.
Manufacturers are now designing MIG welding power sources to work with various gas combinations when welding stainless steel, which is a change from previous years.
For stainless, a combination of 98% argon and 2% CO₂ is an excellent choice. Similar to aluminum, too much CO₂ in the mixture while working with stainless steel might result in porosity or other weld defects.
A flexible solution is a blend of CO₂ and argon gas. Spray, short circuit, and pulsed spray transfer modes are among its applications. It is far less expensive than a helium gas combination and still has an excellent bead profile with excellent wetting properties.
You should learn about Tungsten Inert Gas (TIG) Welding with this detailed guide!
Gas for Welding Aluminum
100% argon is the most frequently used gas while MIG welding aluminum. Because of its low ionization value, this gas makes it simple to enter a spray transfer or pulsed spray transfer mode for aluminum.
Utilizing 100% argon gas for TIG welding aluminum has additional advantages. This makes it a useful gas to keep on hand if you MIG weld aluminum and TIG weld as well in your shop, since it covers both methods.
Although there are several helium/argon gas mixes that are effective for welding aluminum, most do-it-yourselfers don’t find these gases to be a viable choice due to the extremely expensive cost of helium.
Furthermore, as aluminum is very susceptible to contamination, stay away from utilizing a gas that contains CO₂, as this might cause carbon to enter the weld.
Conclusion
Choosing the right MIG welding gas is essential for achieving strong welds, minimizing spatter, and improving bead appearance. Common gases like Argon, CO₂, and helium, either pure or in mixtures, are tailored to different materials and welding needs.
For example, 100% CO₂ is economical and offers deep penetration, while Argon-rich mixtures produce smoother, more stable arcs with less spatter. Understanding the properties and effects of each shielding gas helps in selecting the optimal combination for productivity, weld quality, and cost efficiency.
You should also learn about Aluminum Gas Welding with this detailed guide!
Frequently Asked Questions (FAQs)
What are the common types of MIG welding gases?
- 100% CO₂ (Carbon Dioxide)
- 75% Argon / 25% CO₂ (C25)
- 90% Argon / 10% CO₂
- Argon/helium mixtures
- 100% Argon (for non-ferrous metals)
What gas is best for welding mild steel?
C25 (75% Argon / 25% CO₂) is commonly used for clean welds with less spatter on mild steel.
Can I use 100% CO₂ for MIG welding?
Yes, it provides deep penetration and is cost-effective but can result in more spatter and a rougher weld appearance.
What gas should I use for aluminum MIG welding?
100% Argon is typically used for welding aluminum due to its stable arc and clean welds.
What does helium do in a gas mix?
Helium increases heat input, improves penetration, and is useful for thicker materials or faster welding.
Are gas mixtures better than single gases?
Gas mixtures often offer a balance of arc stability, weld quality, and reduced spatter, making them ideal for many applications.
Is it safe to MIG weld without shielding gas?
Only if you’re using flux-cored wire designed for gasless MIG welding. Regular MIG wire needs shielding gas.