How To MIG Weld
October 19, 2023Are you considering starting a career in welding, or just want to weld a couple of metal pieces in your garage, but you don't know where to start from? Don't worry - MIG Welding has got you covered. MIG welding, short for Metal Inert Gas welding, is a versatile and widely-used welding process that allows both beginners and experienced welders to join metals with precision and strength.
In this comprehensive guide, we'll dive into the fundamentals of MIG welding, offering detailed instructions and essential tips to ensure your welding projects are a success. From selecting the right equipment and safety precautions to mastering techniques, this article will empower you to harness the power of MIG welding for your DIY or professional endeavors.
What Is MIG (Gas Metal Arc Welding) Welding And How Does It Work?
MIG welding, or Gas Metal Arc Welding, is a semi-automated welding process that uses an electric arc to join metals—an arc forms between continuously fed welding wire and base metal. The heat of an arc melts the electrode and pieces in the joint and fuses them, creating a solid and everlasting bond between them.
The name "Gas" comes from the sole nature of the electrode. Like TIG welding, MIG welding wire is "bare," which means it requires external shielding gas protection. Shielding gas, such as argon, creates a barrier that protects the weld pool from interacting with atmospheric gases, which can cause various defects in the weld.
So, how does the MIG welding work? To start welding, you press the trigger on your MIG torch, and the electricity closes the circuit between your gun, metal surface, and welder, and an arc is formed. Simultaneously, the wire feed mechanism starts feeding the MIG wire at the predetermined wire speed, and shielding gas is supplied through the gun.
The heat of an arc melts the two pieces of metal and welding wire and fuses them. Meanwhile, the shielding gas protects the molten metal from the surrounding and contamination. Once you release the trigger, the electrical circuit is broken, wire feeding and shielding gas distribution stops, and you are not welding anymore. It is as simple as that.
Why Is MIG Welding So Popular?
MIG welding is valued for its ease of use, high welding speed, and versatility. You can use it to weld a wide range of metals, including steel, aluminum, and stainless steel. Additionally, MIG welding is suitable for various applications, from automotive and construction to manufacturing and metal fabrication.
Many beginners prefer the MIG welding arc welding process since it is reasonably straightforward. Unlike stick welding or TIG welding, the skill requirements are minimal. This is a semi-automated process, which means that the machine takes care of amperage, voltage, and wire feed while you, as a welder, pay attention to travel speed, travel angle, and direction of the weld. Due to this approach, you can finish your projects in no time and with little to no trouble.
MIG (Metal Inert Gas) Welding Equipment And Important MIG Welder Parts
Like the process itself, the MIG welding equipment is fairly simple, and once you get to know the role of each piece, you can successfully weld any metal with ease. The most essential parts of MIG welding equipment are:
- Power supply (MIG welder)
- MIG gun
- Wire feeding mechanism
- Welding wire
- Shielding gas
Understanding the importance and role of each of these parts will greatly help you in learning how to MIG weld. That's why we'll first briefly explain them.
MIG Welding Machine (Power Supply)
The welding machine is a central and critical part of each welding system. The MIG welder utilizes power from the electrical grid or generator (input power) to create a welding arc (output power). Output power is generated as current (amperage), which is the heat of the weld, and voltage that controls the arc length. But it is not as simple as that.
The power grid supplies a constant voltage at 110 V (110/115), 208V (200), 230V (220/240), 460V (440-480), or 600 VAC, or volts of Alternating Current, while MIG welders work at DC current. So, the welders transform and generate a high-current electrical arc between the welding wire (electrode) and the workpiece.
Source: https://www.youtube.com/watch?v=i9vIQnFzDoc
Besides transformation, a MIG power supply must provide a stable current and constant voltage. Without constant voltage, the arc length would vary during a single weld. As a result, an arc becomes very short, and the electrode stubs into the plate. Then, as the voltage increased, the arc length would become very long, and the electrode would burn back toward the contact tip.
Photo by kendra_welds22 (TikTok)
MIG Gun
MIG gun is a handheld accessory that allows you to manipulate the welding process, including start, stop, travel angle, speed, and direction of the weld. These ergonomic pieces of equipment are fairly simple. There is a trigger, and once you press it, it enables the welding process, wire feed, and shielding gas supply.
YW-L150-10E European Connector MIG Welding Gun
However, MIG guns can have several consumable pieces , such as contact tips or nozzle, that will affect shielding distribution and process control. Nonetheless, buying and changing them won't require too much effort or money.
YW-100L Series Lincoln Magnum 100L and Tweco Mini/#1 Replaceable MIG Welding Gun Consumables
Wire Feed Mechanism
The wire feed mechanism is located inside the compartment of the MIG welder, and it plays a crucial role in providing smooth and consistent MIG wire feed. This mechanism utilizes an electric motor that communicates with the rest of the welder and wire feed speed settings. The smooth wire feed is crucial for achieving consistent MIG welds, so you should make sure that each part is functioning correctly.
On the mechanism, there are drive rolls that guide the wire into the liner and MIG gun. These drive rolls have grooves that ensure the wire feeds straight without tangling. Tensioner makes sure that the proper tension is applied to the wire to avoid an issue known as birdnesting. The liner guides the welding wire from the wire feeder through the gun cable and up to the contact tip.
Source: https://www.youtube.com/watch?v=twUAa5LWUvk
Welding Wire
In MIG welding, wire is a consumable electrode that comes in various sizes spools. You mount the spool inside the welder, put the wire through the mechanism and into the liner, and it comes out of your MIG gun. The heat of an arc melts the wire inside the welding joint and supplies weld metal that fills the joint.
The composition of MIG wire is similar to base metal, so you can find wires for mild steel, aluminum, or stainless steel . The sizes vary from .023" to 0.045" or higher in industrial applications, but the .030" is a versatile wire diameter for various projects and hobbyists. The spool sizes vary from 2-10 lbs for hobbyists or higher for heavy-duty applications.
Shielding Gas
Shielding gas plays a crucial role in protecting the MIG weld pool from contamination. As the molten metal solidifies, it can pick up the contaminants from the surrounding atmosphere, causing defects such as porosity or cracking. That's why welders utilize either inert gases such as argon gas or semi-inert CO2.
However, since MIG is not a welding method for critical applications, many consider a mixture of CO2 and Argon, or even pure CO2, as the best shielding gas for MIG welding. The best part about them is the lower price and decent results when welding mild steel.
MIG Welding Basics: Learning How to MIG Weld
Now that you are familiar with the essential parts of the MIG welding system and MIG welding basics , it is time for the center part of the article - learning how to MIG weld. Unlike TIG (Tungsten inert gas welding), the entire process, from weld preparation through technique and post-weld cleaning, is not so complicated. Therefore, you won't spend too much time from reading this guide to laying your first bead. So, let’s get started.
Safety First!
Welding is a hazardous profession that includes several risks from burns, radiation, shock, fire, and more, and MIG welding is not an exception. Even though the heat of an arc is not as high as with Stick welding, or there isn't too much spatter like with Flux core wire, you will want to keep yourself protected.
First of all, make sure your skin is well protected, and you can do so by personal protective equipment (PPE). These include a welding helmet, such as YesWelder M800 HP , or at least safety glasses, leather shoes, gloves, and jacket. That way, a welding mask protects your eyes from the IR/UV radiation of an arc, and your skin is protected from burns caused by molten metal.
LYG-M800HP True Color View Auto-Darkening Welding Helmet
Prepare The Metal Surface For Welding
Proper metal preparation is crucial for any welding method, including MIG welding. Unlike Stick welding, MIG is not known for its performance in burning through dirt, rust, paint, or mill scale. Welding through contaminants can compromise the integrity of the weld, cause defects such as porosity or lack of penetration, and also some health risks. Burning paint or zinc coating can release toxic fumes that can cause severe irritations or illnesses, such as metal fume fever.
Therefore, before MIG welding, you should always clean the metal surface. If there are no severe contaminants, you can use an old rag to remove dust or dirt. Otherwise, you will need a wire brush, sanding paper, a grinder, or chemicals to remove rust or paint from your mild or carbon steel. A clean surface means a clean and sound weld.
After cleaning, you will have to align the pieces. You can clamp them to your welding table to make sure the gap is even throughout the entire weld joint. That way, you ensure consistent results and consistent penetration during the whole weld.
Choose The Right MIG Wire
The choice of the proper MIG wire will largely depend on the metal you are about to weld. You want to make sure that the composition of the wire matches the base metal. To make things easy, AWS made a classification for MIG wires, and they are separated into wires for mild steel, aluminum welding, and stainless steel.
If you are MIG welding mild steel, you can choose either ER70S-3 or ER70S-6. These are general-purpose MIG wires suitable for many carbon steel welding applications. However, many welders prefer ER70S-6 since it can withstand the heat of pure CO2 shielding. Performance-wise, these both show excellent results and uniform weld appearance and can work with low levels of mill scale or rust.
ER70S-6/10LB-0.8 .030" 10LB Spool Carbon Steel Solid MIG Welding Wire
If you are about to MIG weld aluminum, you'll need aluminum wires such as ER4043 or ER5356 . These are general-purpose aluminum MIG wires that will cover most of your aluminum applications. For stainless steel MIG welding , you are likely to use ER308/308L , ER309, or ER316 stainless steel MIG wires as a hobbyist or occasional welder.
ER4043/1LB-0.8 1LB Spool .030" Silicon Aluminum MIG Welding Wire
Besides types, you'll have to think about diameters. MIG wires for hobbyists typically come in three different sizes:
- .023-inch, which is suitable for thin materials,
- .030-inch as a decent all-rounder that will cover most of your home projects and repairs
- .035-inch wire for thick metal and higher heat (or even .045-inch if your machine can handle it)
Choose The Proper MIG Welding Shielding Gas
Unlike Flux core welding, which utilizes self-shielded wire, MIG welding will require external shielding. MIG welding shielding gases can be inert, such as argon or helium, semi-inert, such as CO2, or reactive, such as Oxygen or Hydrogen. But which one is the best?
Many welders agree that the best shielding gas for hobbyists and welding enthusiasts that MIG weld steel is actually the mixture of Argon and CO2, also known as the C25 mixture. Mixing 75% of Argon with 25% of carbon dioxide will create a mixture that provides the best of both gases and reduces the drawbacks. You get shielding that provides good weld area coverage, proper shielding, and cleanliness but also good penetration, low spatter, and low costs.
In specific applications, where you need to weld thicker materials fast and with lower costs, you can even use a pure CO2 gas shield. MIG Welding with pure CO2 is often used in industrial applications and home repairs where you need cheap welding gas and don't mind the poor weld appearance and spatter.
Meanwhile, MIG welding aluminum will require argon gas, which is an inert gas, which means it doesn't react with surroundings or metals. Thin aluminum is welded with pure argon (100% Argon), while for thicker pieces, you can add up to 25% helium to increase the heat and penetration. You can MIG weld stainless steel with argon or argon/helium mixtures, but many grades require a specific tri-gas mix of argon, helium, and carbon dioxide.
You will also have to set the gas flow rate on your gas tank. When MIG welding indoors, you can set the flow to 15-20 CFH. This is a recommended flow rate for most medium-scale jobs, but you can also increase it if there is a draft present or you weld outside. However, keep in mind that more is not always better. As you increase the flow, you won't always get better protection. Higher rates can create turbulent forces that suck in the air and contaminants inside the weld.
Setting Up The MIG Welder
Setting up your MIG welder as a beginner might be a difficult task since you'll need to adjust wire feed speed and voltage according to material thickness. Welding current or amperage in MIG welding is represented by wire feed speed, and the higher the setting, the more heat (penetration) you get inside the joint. The voltage affects the arc length, so you don't want it too high to let the wire stub into the workpiece or too low to let the wire fuse into the contact tip.
The issue with MIG welder settings is that each machine responds differently to input settings. That's why many MIG welders for beginners today, including the YesWelder MIG205DS-B , have synergic settings or auto-set features. When turned on, the welder automatically adjusts the WFS and voltage according to material thickness, so you let your welder do all the hard job for you.
YesWelder MIG-205DS-B Multi-Process MIG Aluminum Welder
This is an excellent feature for all beginners, but as a seasoned welder, you will quickly develop your own preferences and controls. Welders who like to fine-tune the machine can manually adjust all the parameters, and here are some recommendations. MIG welding different thickness metal will require some experimentation, and here are some general recommendations.
Also, pay attention to polarity. MIG welding uses DCEP or direct current electrode positive, which means that your MIG gun is connected to a positive side of the welding circuit, while the ground clamp is connected to the negative side of the terminal.
MIG Welding Tips And Techniques
Now that everything is sorted, set, and prepared, it is time to lay your first bead. Instead of working your pieces straight away, use scrap metal that is similar in thickness and run some practice welds. Maintain a stickout of 3/8 inch and listen for a sizzling bacon sound. If the arc sounds irregular, one culprit could be that your stickout is too long, which is a pervasive error.
Travel angle is an angle relative to the gun in a perpendicular position. Normal welding conditions in all positions call for a travel angle of 5 to 15 degrees. Meanwhile, looking at the gun from the end of a seam, the angle of the gun to the work is called the work angle. For a butt joint, 90 degrees is ideal. For a 90-degree fillet weld, you’ll normally hold the gun at 45 degrees, although you may need to modify this for thin metals. The speed you move the gun is very important, too. Going too slow builds up an oversized bead and increases the heat supplied to the joint, and going too quick may result in a lack of penetration.
Photo by @dr.weldz (TikTok)
Push or pull in MIG is an everlasting debate, and the correct choice will depend on specific applications. Pushing the gun away from the weld puddle (Push MIG) will produce lower penetration and a wider, flatter bead, but it allows you to see and better feed wire into the joint. In the backhand technique (also called the pull MIG), the welding gun is pointed back at the weld puddle and pulled away from the deposited metal. Dragging typically produces deeper penetration and a narrower bead with more buildup.
Post Weld Finishing
Even though MIG welding is one of the easiest welding methods, it might take you time until you get everything right. Once you are finished welding, it is time to clean and check it out. Ideally, the weld bead should be slightly crowned, with the toes or edges of the bead flowing nicely into the base metal. You don't have to be an expert to notice holes, spatter, or uneven welds, and these are all signs that you've done something wrong.
Common MIG welding defects include porosity, lack of fusion, burn-through, or excessive spatter. Most of these can be avoided by adequately cleaning metal before welding and getting settings (voltage, wire feed speed, shielding gas flow) and welding technique (work angle, travel angle, travel speed) right. But to get there, you will need some practice.
Practice Makes Things Perfect
This guide is designed to help you get a head start into the world of MIG welding, but practice is the key to becoming a proficient MIG welder. So, start with simple projects and gradually tackle more complex ones as your confidence grows. Always prioritize safety, including proper ventilation, protective gear, and a secure work area.
With your dedication and the knowledge our website provides, MIG welding can open doors to a wide range of welding applications. So don't be bummed out if you fail at first. Like with any profession, practice makes things perfect. Take your time to experiment and get to know your MIG welder, and always look back at what you did wrong and what you can improve.
🧐How To MIG Weld - FAQ
1. What Is MIG Welding?
MIG welding, or Gas Metal Arc Welding, is a semi-automated welding process that uses an electric arc to join metals—an arc forms between continuously fed welding wire and base metal. The heat of an arc melts the electrode and pieces in the joint and fuses them, creating a solid and everlasting bond between them.
2. How does the MIG welding work?
To start welding, you press the trigger on your MIG torch, and the electricity closes the circuit between your gun, metal surface, and welder, and an arc is formed. Simultaneously, the wire feed mechanism starts feeding the MIG wire at the predetermined wire speed, and shielding gas is supplied through the gun.
3. How to choose the proper MIG welding shielding gas?
Many welders agree that the best shielding gas for hobbyists and welding enthusiasts that MIG weld steel is actually the mixture of Argon and CO2, also known as the C25 mixture. Mixing 75% of Argon with 25% of carbon dioxide will create a mixture that provides the best of both gases and reduces the drawbacks. You get shielding that provides good weld area coverage, proper shielding, and cleanliness but also good penetration, low spatter, and low costs.
👏 You may be interested in the following:
- MIG welding wire types
- Best beginner welders reviewed
- How To Setup And Use Your MIG Welder For The First Time