How To Set Up A MIG Welder for Mild Steel? With Tips & Tricks

Whether you are a beginner or have been practicing welding for a while, MIG welding mild steel can feel like a tricky thing to get into. But, believe me, it is actually not. In this article, I will demystify the entire topic and give you a thorough guide on how to set up a MIG welder for mild steel.

MIG welding mild steel is a fairly simple process if you take into account the different settings. The voltage, amperage, and wire-speed to thickness ratio for MIG welding mild steel are a bit different from other metals. You should also use CO2 or a CO2 and Argon mix as the shielding gas.

That is just the tip of the iceberg. There’s quite a bit to unpack here. But, fear not, I will explain every step of the process in the easiest way possible here. Hopefully, by the end of this article, you will be absolutely confident while MIG welding mild steel. So, let’s not beat around the bush anymore and get right to it.

Getting Started with MIG Welding Mild Steel

MIG or Metal Inert Gas welding is a relatively easy method of welding. In this process, a metal wire is fed through a tube with electricity running through it. That wire both heats the metal parts you want to join together and acts as a filler. The wire melts and fills up the gap to create a clean and simple weld (source).

Mild steel is a kind of steel that has a low amount of carbon mixed in it. Mild steel, for that reason, is also known as low-carbon steel. Mild steel is much more malleable and ductile. They are also cheaper than other kinds of steel.

Mild steel is easier to handle and weld. These qualities make mild steel a top choice in a large list of use cases. From construction to making machine parts, decoration, and even furniture, mild steel has a ton of uses.

MIG welding is relatively easier than other forms of welding, and as mild steel also is easier to handle; you have a lot less to worry about. Some people even compare MIG welding to using a hot glue gun! While it might not be that easy, it is indeed quite easy to handle if you are just a little bit careful about the settings and preparations.

Now that I have made you familiar with both MIG welding and mild steel we can go on to discuss the more specific steps of the processes.

Preparing Mild Steel for Welding

Preparations for MIG welding mild steel are fairly simple. There isn’t any kind of a complicated situation you would need to figure out, just some general precautions. First of all, make sure your equipment is all okay. You do not want any kind of faults or quirks in your welder, wire, or gas cylinder.

Then you need to make sure that you have enough shielding gas and wire. You do not want to be welding without shielding gas, it just won’t work. Make sure that the surface you are going to weld on is clean and free of all kinds of dust and grease. These things can interact with the welding and mess up the texture.

You want a nice, clean, and straight surface to work on. Do not start working on a rough workbench. It is a good idea to have metal plating over your workbench while welding.

You also want the metal parts you are working with to be nice and clean too. They cannot have any kind of dirt, grease, or rust on them. You need to first remove the rust; you can do so by using some kind of DIY or market-bought solution. There are quite a few good ones such as Evapo-rust or WD40.

You can also scrape off some rust if it is low in amount, make sure you don’t damage the plate you are going to weld. After all of it is nice and clean, you can begin to worry about the other parts of this welding process.

What Settings Should You Use to MIG Weld Mild Steel?

In MIG welding, there’s a sweet spot of settings for every kind of welding scenario. With enough experience, you will be able to figure it out on your own. But, before that, you will need some guidelines.

There are four different things you need to worry about in the settings. The amperage, the voltage, the wire feed speed, and wire thickness. These four settings are dependent on each other, there is also the thickness of the metal. To find the sweet spot you need to find the right balance within these things.

Thickness And Amperage

There is a good rule of thumb for MIG welding mild steel. For every 0.001 inches of thickness, you should crank up the amperage of your welder by 1 amp. The amperage controls the heat distribution. The thicker the material the more heat is needed.

You want to heat the metal properly so you need to crank up the amperage properly. But, if you crank it up too high then the metal might start deforming. You do not want that. While there may be other settings that work better in certain scenarios, for most cases you should go with the calculations mentioned above.

Amperage And Wire Thickness

Every thickness of wires has a specific ampere range where it works best. Too thick for the amperage and it won’t meld properly, too thin and it will burn out. There are specifics based on wire type here too but there are some standard ampere ranges for the most common types of mild steel welding.

The ranges for different wire thicknesses are;

  • 30-130 amps: .023 inches
  • 40-145 amps: .030 inches
  • 50-180 amps: .035 inches
  • 75-250 amps: .045 inches

While you may find that you can get better results with different settings in some specific scenarios, this should be good enough for almost any situation. And if nothing else it is a good starting point.

Voltage Settings

This is a welder-specific one. While there isn’t an overall system here, this should be easy to figure out. Your welder should come with voltage settings instructions already. It is either on a chart attached to your welder or included in the user manual.

You should check the user manual for the best voltage settings for each situation. But, on the off chance, you can’t find the instructions or the manual, no need to fret. There actually is a way to figure out the voltage sweet spot without direct instructions.

You should take a bit of scrap metal of the same material you want to weld and test on it. Voltage basically dictates the size of the metal droplets. So, if you see the welding pattern is smooth you can be sure that the voltage is correct.

Start welding the two scrap pieces together. If you see it crackling too much then you need to crank the voltage down. And if the pattern is too faint you need to increase the voltage. Somewhere in the middle is the sweet spot.

Wire Feed Speed

The speed at which the wire comes out of your MIG gun is very important. You need to set the correct speed at all times. Too fast and it will burn through the weld. Too slow and your weld will be choppy and uneven, the fusion won’t happen properly.

The wire feed speed depends on both the thickness of the wire and the amperage. For a 0.023-inch-thick wire, you should multiply it 3.5 inches per amp. Likewise, 0.030-inch-thick wire, 2 inches per amp; 0.035-inch-thick wire, 1.6 inches per amp; and 0.045-inch-thick wire should be 1 inch per amp.

This is a general rule of thumb which you should follow for optimal results. Be very careful while experimenting with wire feed speeds as any missteps might compromise the welding and structural integrity of whatever it is you are building.

What Is the Best Shielding Gas to MIG Weld Mild Steel?

As the name suggests the gasses you are supposed to use here are inert, or noble gasses. The most commonly used inert gas is Argon. Either 100% Argon or a mix of Argon and 2 or 3 other gasses is what is mostly used for mild steel welding.

A very common mix is 75% Argon with 25% CO2. While CO2 is not inert, it does prevent chemical interactions and offers enough protection so that it can be used as an efficient shielding gas.

The problem with Argon gas, more specifically 100% Argon shielding mix, is that it is too costly. For the average welder, using 100% Argon can be unaffordable sometimes. Argon also decreases penetration so it can sometimes be very slow to complete the weld.

The Argon and CO2 mix is a good solution for this. 100% CO2 is another good option, it is incredibly cheap. But, the problem with CO2 is that it reacts with the heated part of the metal and increases heat and penetration. CO2 causes it to crackle a lot more and there is a lot more penetration.

Using a CO2-only gas mix can speed up your welding process with an increased penetration rate. But it can also feel a bit unstable as the heat increases a lot and it crackles a lot more.

If you are a beginner in welding and want to use a slower and easy-to-handle process you should go for the 100% Argon mix. If you are an expert who is confident that they would be able to handle the extra heat and penetration then you could go with the 100% CO2 mix.

For most cases, however, the Argon and CO2 combined mixture provides a healthy balance. It is neither too costly nor too cheap. It makes the weld both easy to penetrate and easy to control. The 75% Argon and 25% CO2 mix is overall the best gas to use for MIG welding mild steel.

In Metal Inert Gas welding, the shielding gas is the most vital part of the entire process. The metal you are melting and using as filler is protected by the shielding gas. If the melting metal is not shielded then it will react with the environment and ruin the weld.

What Wires Should You Use to MIG Weld Mild Steel?

Hardwire or solid wires are what most people use for MIG welding mild steel. These are specially chosen for a smooth and easy weld.

We have already discussed the different wire thicknesses, what remains is the material type. You can check the packages of different wires to see if they are meant to be used on mild steel or not.

The kind of wires you can use to MIG weld mild steel needs to have 70,000 PSI tensile strength. On the standardized system, the kinds of wires suitable for mild steel are ER70S-3 and ER70S-6. The “70” in the code represents the tensile strength.

There are of course other kinds of wires too that can be used for mild steel, you will need to check the instructions to see if they are suitable or not. If there are no instructions then going with either the ER70S-3 or the ER70S-6 would give you optimal results.

ER70S-3 is the one you should choose if you are working on clean and smooth surfaces. This type of wire is not meant to handle any sort of contaminants. On a clean surface, this gives an even weld and can prevent any glassy feel on the finish, known as “silicon islands”. This makes paint stay a lot better on the surface.

On the other hand, ER70S-6 can handle rough, textured, and even dirty surfaces filled with contaminants. While it does not create the smoothest finish, it does make a very even weld. It is also great for creating a smooth transition between the base metal and the weld.

ER70S-6 has the proper deoxidizer incorporated with it so it can combat any kind of contaminants and create a smooth and consistent weld on any kind of surface.

You must pick the right kind of wire. For general purposes try to determine what kind of surface you will be working with and then choose accordingly. And if you want to experiment with some more unorthodox choices, you should do so after gaining some amount of expertise in this area.

Proper MIG Welding Process for Mild Steel

Okay, now let’s take a look at the process that goes behind MIG welding mild steel.

Before Welding

Mild steel is a lot more malleable than other kinds of steel so you have to be very careful with it. If you are not careful you could risk deforming the metal part you are working with.

So, first, you need to check that everything is in place and working properly. Make sure that you have enough wire and shielding gas. After that use the settings required for your specific process according to the instructions, I have mentioned before.

You can both use automatic or manual mode to feed the wire through while welding. For a beginner and more simple processes, you can go with automatic mode as it makes it all very streamlined.

You should use manual mode for welds where there are more complex joints and curves. Manual mode gives you a lot more control over your weld and it becomes a lot easier to maneuver through tight curves and corners.

Make Sure the Welding Pattern Is Consistent

When you start welding, make sure the voltage is correct before pointing the MIG gun at your final project. You do not want it to crackle too much, nor do you want the sound to be too faint. It should be somewhere in the middle and consistent. When you are satisfied with the sound, you can move on to forming the beads.

When you MIG weld, the molten filler metal forms beads that join the two metal parts together. You do not want the beads to clump together at spots, it should be even throughout.

To make the pattern even you can use a few different methods. There’s the push and pull method, where you push and pull the MIG gun forward and backward a bit at a time until you are satisfied with the density.

There are also the cursive v and the cursive e method. You move the MIG gun in those shapes respectively. The zigzag and the spiraling pattern create a smooth and consistent welding finish.

Check The Transition

You can have an amazing finish and yet a very bad weld if the weld does not fuse the base metals together that well. You need a smooth transition between the base metal and the molten filler metal.

The arc in a MIG welding process does not only melt the filler metal but also heats up the base metal enough so that it can fuse with the weld properly. If you don’t have smooth transitions then it could mean that you did not put enough heat on the base metal.

The base metal will not fuse properly without enough heat. If you have enough heat then the fusion will be smooth and seamless. A good fusion is key to having better structural integrity.

Tips and Tricks to Remember While MIG Welding Mild Steel

Now that you have all the basics of MIG welding mild steel figured out I will give you some tips and tricks to make your welding process much easier. So, let us take a look at these hacks.

  • Use Scrap Metal

Don’t throw away scrap metal pieces, they can help you a lot. When starting a new project, you should always test out the weld on pieces of scrap metal of similar material first. This gives you a chance to experiment without ruining your final project.

You can try different voltage settings, different wires, different patterns on scrap pieces without worrying at all. And when you are happy with how the finishing turns out to be you can move on to working on your actual process.

While this might seem like an extra bit of work, this can save you a ton of hassle down the line. Working with mild steel can be tricky, and you can end up ruining a huge project with just one mistake. Testing methods on scrap metal make sure you don’t mess up.

  • Keep Your Inventory Stocked

This one will be a bit handier to the people working on several projects. While this might sound obvious, a lot of people do forget about it. It is always helpful to have more than one option for both wires and shielding gas in your inventory.

Mild steel has a lot of uses. And you can MIG weld mild steel and make a ton of stuff. While all of them are made from the same metal, they can require multiple different methods.

So, it can be immensely helpful for you to keep options. You might need more penetration for one project and more control on the other, having multiple gasses will help you with that. Similarly, different wires help you achieve different finishes

  • Be Careful with Angles

Angular joints can be tricky. You need to prop up your MIG gun at different angles to compensate. While you can just go however you feel is convenient, a general rule of thumb is to keep an equal amount of angular distance between the two base metals.

Even while joining two flat parts, you should have a 90-degree angle so there is equal distance. Keeping equal distance can be hard if there are parts that need to be propped up while welding.

You should try to clamp the base part with your workbench so it doesn’t move around. You should also tack on the part that needs to be propped up on a few spots beforehand. Just put a bit of welding on 3 or 4 spots before to keep it in place and then weld the whole joint properly.

Some General Safety Measures

If you have been welding for any amount of time you should be familiar with the safety precautions necessary for MIG welding. Nonetheless, I will go over them once so you can make sure that you are perfectly prepared.

Your welding area should be well ventilated. You do not want to weld in a confined space with all the fumes created by welding. MIG welding uses a shielding gas which is usually a mix of Argon and CO2, you do not want to be in an enclosed space filled with those glasses, it could lead to suffocation.

Your welding space needs to have good ventilation for fire safety purposes too. You need to practice proper fire safety protocols while welding. MIG welding uses heat and electricity so there is always a fire risk involved.

Your floors and walls need to be protected with flameproof welding blankets. These blankets will make sure that nothing catches on fire through a spark or something. You also need to keep fire extinguishers nearby and check periodically that they work properly.

Personal safety gears are another must-have thing in your welding workshop. Things like flameproof jackets, protective pants, and leather boots that you can tuck your protective pants in are essential. You’ll also need good welding gloves that go beyond your wrists.

You need to protect your eyes too; the high heat and dense light can cause damage to your eyesight when welding. A pair of protective glasses and a welding helmet should do the trick. While some dim the lights automatically, some require you to turn it on manually, so make sure the helmet dims the harsh light beforehand.

Finally, keep all of your equipment and materials in check. Make sure all the power and gas lines are connected properly and have no leaks. Any kind of kinks in the system could lead to an unwanted accident.

Make sure that all of your equipment works properly before working. And make sure that nothing is turned on and stay for at least 30 minutes after your work is done to make sure nothing has caught on fire.

And last but not least, do not have any metal parts or scraps lying around as they can create problems. Keep these few things in check and you should be just fine while MIG welding mild steel.


MIG welding mild steel is a relatively simple process to set up if you keep a few things in check. The proper wire, the proper amp and voltage, and a good shielding as, that is all you need to worry about. Use carefully with a bit of technique and you should be all good to go.

Thanks a lot for reading till the end. Hopefully, I was able to answer all your questions related to how to set up a MIG welder for mild steel and you are now confident about practicing the process on your own. Until next time, stay safe, and happy welding!

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