Best Gas for MIG Welding Mild Steel

MIG welding is an excellent way of working with Mild steel. Here, the electrode is fed through the welding gun that makes a weld pool on the welded metal’s surface for connecting two base metals.

To protect the weld from the contamination of the atmospheric gases, shielding gas or gases is also passed through the same welding gun.

Now, the best gas for MIG welding mild steel is Carbon dioxide if you only care about the weld’s durability. However, to achieve robustness and smoothness in your weld at an affordable price, you should get a mix of 75-25 C02-Argon combinations.

I have prepared a comprehensive guideline to let you know more about MIG welding gas. So, keep reading…

Best Gas for MIG Welding Mild Steel

What is the best gas for MIG welding mild steel?

MIG Welding is also Called GMAW or Gas Metal Arc Welding. This welding machine is preferred over other welding machines to deal with mild steel, and gas plays a vital role in ensuring a perfect weld. Gas around us like Oxygen, Nitrogen, and Hydrogen hamper MIG welding’s sturdiness by causing porosity. So, the shielding gas stops these unwanted substances from having free access while making the weld.

There are different types of gases that could be used to serve this purpose. Let’s have a look.

Inert gases for MIG welding

You may have read about this class of gas in your school’s chemistry book. Yes, it is the same gas that doesn’t show any chemical reaction.  These gases are also called Noble gas. Can you remember?

Don’t worry; you don’t need to study your high-school books again. There’s no need for you to grind your theoretical knowledge as you will use this gas up close and personal with your welding machine.

Now, for MIG welding, you need to get Argon and Helium as inert gas for good reasons. These gases are top picks of professionals and they are also available abundantly.

Between these two gases, Argon is more used; however, it is not cheap, and that is why people mix other gases with it to reduce the welding cost. But as soon as you add any other gas, the final weld’s smoothness will be lost.

The more you add other gases, the more you have to consider the weld’s delicacy. There will be more spatter around the weld.

While contaminated Argon has an unpleasant appearance, it won’t make the weld vulnerable. If you are welding something that needs to be visually attractive, you shouldn’t mix inert and semi-inert gases too much.

On the other hand, if the final weld stays underneath any other object in a way that it remains hidden, you are allowed to use less inert gas.

In addition to that, Inert gases are less reactive than non-inert gases. So, you will get an uncontaminated arc plus pure melt of electrode wire into the mild steels.

To achieve a more effective weld rate and visually appealing appearance, Inert gases are given priority over others. Also, it ensures a super stable arc. But you will rarely find someone using 100% Argon as MIG welding gas.

Non-Inert and semi-inert gases for MIG welding

On the scale of efficient shielding, semi or non-inert gas can’t beat the resistance offered by the inert gas. They show moderate shielding nature so you will find some chemicals and less protection of the arc and final weld.

But this gas won’t empty your wallet as you can get them at a much lesser price than Argon or Helium. And, you can mix these semi and non-inert gases with inert gas at a different ratio to get your desired shielding while welding mild steel.

You will see the abundance of these gases in projects where solid welding is required, but nobody cares about the final weld’s smooth finished look. The main semi-inert gas that is widely used for MIG welding is Carbon dioxide.

Besides, this gas shows good shielding performance, which is why it is considered a counterpart of Argon or Helium in many projects. You can also use 100% Carbon dioxide to get the most economical MIG welding, and it will provide deep penetration on the mild steel surface too.

Nonetheless, you will be bothered by lots of spatter. So, if you want to weld the underside of any car or inner part of any mild steel-made object, then it is totally okay to use 100% CO2. Otherwise, you should apply a high ratio of Inert with semi-inert gas to get a stunning and shining weld.

Apart from the semi-inert gas Carbon Dioxide, you can also utilize Oxygen as a non-inert shielding gas for MIG welding. Oxygen is mainly used to penetrate thick steel. However, applying an excessive amount of Oxygen will cause more oxidization of the metal, which is not a good sign.

Purpose and mixing ratio of Inert and non-inert gas

Some kinds of welding need less inert gas, while others require more. According to your workpiece’s state and conditions, you need to vary the proportion of these gases. Sometimes you have to mix them, keeping the outcome in mind. There are three different gas combinations that are very popular among professional welders.

Very high argon mixture

This mixture is rarely seen in DIYers or normal welding projects as it consists of 90% Argon and 10% Carbon Dioxide blend. Therefore, you need to spend more money on this kind of welding gas mixture. In return, it will make a clean weld having very little spatter. Also, you can achieve fast weld.

In addition to that, this mixture allows your MIG welder to attain spray transfer mode where metal is sprayed into the weld pool. But, your MIG welding machine needs high voltage to accomplish this. This High Argon mixed welding gas can deal up to 15mm mild steel.

Regarding the high inert gas ratio, smart welders also go for a 80:15 ratio of Argon and carbon dioxide. However, keep in mind, this ratio may not turn on the spray transfer mode, and you should weld around 10mm mild steel with this ratio.

C25 mixture

This is the most popular mixture where you will add 25% Carbon dioxide with 75% inert gas. It will reduce the cost of the weld significantly compared to very high Argon mixture gas.

However, it is not the cheapest option, but it will allow you to have a seamless welding finish at a much lower price. In other words, this blend will make a noteworthy balance between cost and attractiveness.

Moreover, this mixture is readily accessible in the online marketplace and local hardware or welder supply shop in different sizes of the gas cylinder.

The mixture strongly tackles the porosity, so you won’t be bothered by spattering after the weld.  So, you can apply this setting to weld a nice motorcycle or car’s outer surface that you want to show somewhere.

Only Carbon dioxide

Here is the most economic shielding gas option, which contains no inert gas. That means it has 100% carbon dioxide. Even though it creates a pretty weld, the cuts aren’t clean. Therefore, you will find lots of spatter around the finished weld.

However, this gas is widely used by DIYers worldwide because of its cost-efficiency and shielding ability. This gas also lasts longer compared to other options because it remains in a cool and liquefied state inside the gas cylinder.

This weld is mostly picked in situations where you want to weld the inner part of any metal object.  Though it doesn’t make a super stable arc, it ensures that you get a deep penetration while joining mild steel.

So, you need to be careful during the thinner metal welding process, as higher penetration may damage the workpiece.  However, the low cost of gas will minimize the overall welding cost of a professional welder.

Choosing the best gas for MIG welding mild steel

Now you know the gases and gas mixtures that are applied for MIG welding mild steel. You have also got enough info regarding their usability, performance, and quality. Now, you should make a decision about which one to pick. Allow me to help you by breaking the matter further so that you don’t make any wrong turn.

So, consider the following aspects, and you will never regret it.

  1. Welding cost

You should learn to keep the welding cost under control. It’s a crucial thing, and it’s the key to becoming a professional welder who makes a handsome amount of profit at the end of the year. Therefore, you must keep an eye on the gas’s cost. So, 100% Co2 would be the best option in terms of cost-efficiency.

However, a 25-75 Argon and Carbon dioxide blend is also affordable and popularly adopted while dealing with mild steel.

  1. Finished look

In the welding aesthetic parameter, the pocket-friendly 100% Carbon Dioxide won’t do well as a shielding gas. As you know, carbon dioxide causes excessive spatters, which will hamper the metal workpiece’s beauty. So, a high Argon- Carbon dioxide combo such as 10% CO2 with 90% Argon will be ideal.

But, it will increase the welding cost significantly.

  1. Depth of the workpiece

As Inert gases like Helium and Argon generate tremendous heat with less penetration, they might not work well with thicker mild steel. On the flip side of the coin, as CO2 creates a remarkable amount of penetration; 100% Carbon dioxide is not recommended as a shielding gas for thin metal.

Last words

After reading about various MIG welding shielding gases, it would be easier for you to get the best gas for MIG welding mild steel according to your budget and requirements.

Please contact us through the comment section if you have queries about anything related to this topic. And, don’t forget to wear your protection gears while welding.  Best of luck.

Last Updated on March 24, 2021 by Gary Hargrave