When we say “Arc Welding”, the most popular technique that comes to mind immediately is the Stick Welding (Shielded Metal Arc Welding – SMAW or Manual Metal Arc Welding – MMA). This has been the case in the 70s and 80s. But nowadays, MIG or Metal Inert Gas Welding has become quite dominant in small-scale as well as industrial applications. It uses inert gas (Argon or Helium) for shielding instead of flux. Alternatively, the process can also use Carbon Dioxide and hence it is also known as Metal Active Gas (MAG) Welding. To stop the confusing nomenclature, the American Welding Society (AWS) came up with a generic name; Gas Metal Arc Welding or GMAW Welding.
If you’re into the industrial welding domain, you would have heard about the GMAW. It is a popular welding process in industries because of its quick and effective nature If you are new to welding and want to know about GMAW, this guide is just for you. We will discuss the how GMAW works, why is it preferred over other welding techniques, and many more.
What is GMAW?
While TIG (Tungsten Inert Gas) Welding or Gas Tungsten Arc Welding (GTAW) has several advantages, the main limitation is it is not suitable for slightly thicker metals (usually thicker than 1/4″). To solve this problem, they came up with a new technique that uses the similar principle as TIG for shielding i.e., using inert gases instead of flux. This process later became Metal Inert Gas (MIG) Welding.
MIG Welding uses an arc between a consumable electrode and the workpiece. This arc and the molten puddle are shielded from atmospheric contamination by an externally supplied inert gas, such as argon, helium, or an argon-helium mixture. The metallic electrode provides both the arc and the filler metal, eliminating the need for external filler metal.
Initially developed for welding aluminum, MIG welding employs argon shielding. This process is also suitable for deoxidized copper and silicon bronze. However, welding ferritic and austenitic steels requires the addition of 1-2% oxygen to argon for smooth metal transfer. Transitioning to mild steel, the welding process evolved to use 100% carbon dioxide or an argon-CO2 mixture as a shielding gas.
Since these gases are not inert, the process became known as MIG/CO2 or MIG/MAG welding. MAG, meaning Metal Active-Gas, refers to the use of chemically reactive gases like argon-oxygen, carbon dioxide, and argon-CO2 mixtures. These gases, unlike inert gases, react chemically during the welding process.
The American Welding Society designates this process as Gas Metal Arc Welding (GMAW). This term encompasses both inert and active shielding gases, providing a comprehensive description of the welding technique.
Earlier construction and manufacturing industries had to invest a lot in building materials and human labor. The obsolete or traditional methods consumed up to 85% of the total costs. And this is what led to the use of GMAW. This welding process is very effective as it can reduce labor costs by up to 25%. It is the reason why industries are opting for this welding approach.
Principle of Operation of GMAW
The Gas Metal Arc Welding (GMAW) process involves a continuously fed filler wire from a spool, housed either inside the power source or an external wire feeder. This wire is fed through a welding gun and serves two purposes: it acts as a consumable filler material and as an electrode to initiate and maintain the welding arc.
The power source initiates the welding arc, while control systems maintain it during welding. The filler wire, protruding from the welding gun’s nozzle (known as the stick out), also functions as the electrode. This arc melts both the base metal and the filler wire, creating a weld joint. The filler wire used in GMAW is primarily solid, similar to the wire used in the Gas Tungsten Arc Welding (GTAW) process.
Unlike the Shielded Metal Arc Welding (SMAW) process, GMAW does not use flux to protect the weld puddle from atmospheric contamination. Instead, a shielding gas is necessary to protect the weld metal. The choice of shielding gas depends on factors like the material being welded and the required weld quality. These gases range from inert (Argon or Helium) to active (Carbon Dioxide) types, often used in combinations based on specific welding needs.
GMAW shifts several skills from the operator to the machine. The operator sets welding parameters and starts welding, maintaining the wire stick out length for stable arc operations. This reduces the skill level required compared to GTAW and SMAW welding, making GMAW a fast-growing welding process.
In mechanized or automated versions, the machine controls arc length and other parameters, further reducing operator skill requirements. The operator simply holds the gun, squeezes the trigger, and welds. Proper shielding gas use ensures a smooth, stable arc, simplifying the welding process compared to methods requiring precise electrode positioning and manipulation.
How Does GMAW Work?
Gas Metal Arc Welding (GMAW) employs a continuously fed solid wire electrode, which also serves as the filler metal. The weld zone, including the arc, molten pool, and heat-affected area, is shielded by externally supplied gas from a high-pressure cylinder. This shielding gas protects the weld from atmospheric contamination.
The welding wire typically matches the material being welded. For example, carbon and alloy steel wires are electroplated with copper to prevent rusting. The copper coating enhances electrical conductivity, increases contact tip life, and improves arc performance without contaminating the weld.
GMAW is easy to learn, and good technique yields excellent results. Properly executed welds have no slag and minimal spatter. You can use either a push or pull technique. Using a “push” gun angle of about 5 to 15 degrees (or up to 25 degrees) toward the weld direction enhances gas coverage and quality.
For optimal weld quality, ensure the material is free from dirt, rust, or paint. Light grinding is recommended to expose shiny bare metal without reducing material thickness, especially in critical structural areas. GMAW effectively welds low carbon steel, low alloy steel, stainless steel, and aluminum.
The process predominantly uses DC current with the electrode on the positive terminal (DCEP). The weld appearance is excellent, featuring a thin glass-like coating on the bead that is easy to remove.
Electrical parameters like voltage, amperage, travel speed, wire feed rate, and metal transfer method can be tailored.
Is GMAW/MIG Automatic or Manual?
The MIG welding process is semi-automatic. It’s because the power controls arc length and wire feed. But you need to manually control the speed and position.
Why Learn GMAW/MIG Welding?
Learning GMAW or MIG welding offers many advantages. Unlike stick welding (SMAW), GMAW welding uses an automated process that simplifies the welding technique. It employs a continuous feed of wire, which serves as both the filler metal and the electrode. This makes it easier to manage compared to the manual feed process of stick welding, which involves a flux-coated electrode.
The GMAW process activates all components simultaneously once the trigger is pulled. The filler wire is fed through a hose to the gun, and the shielding gas and power supply follow the same path. This automation makes GMAW/MIG welding easier to learn and apply in various situations.
MIG welding is also more user-friendly than TIG welding, which requires significant skill and practice to master. TIG welding offers precise control over the weld but takes longer to produce a weld and is generally more expensive. Conversely, MIG welding provides good control with less training and faster results.
Additionally, GMAW/MIG welding is versatile and widely used in various fields. It is popular in the arts and hobbies world, as well as in professional metalworking. Learning MIG welding allows you to grasp the basic principles and techniques of welding without dealing with the complexities of stick or TIG welding.
Furthermore, MIG welding is well-suited for a range of materials and thicknesses. It works effectively with low carbon steel, low alloy steel, stainless steel, and aluminum. This adaptability makes it an excellent starting point for anyone interested in welding.
How to Ensure Successful GMAW/MIG Welding?
To ensure a successful welding process, welders should learn how to: –
- Optimize the Voltage
- Control the flow rate and wire-feed
- Clean the Gun
Another important thing a welder should know about is the travel speed. After all, it’ll control the shape and quality of the weld.
Equipment
GMAW equipment usually consists of a
- Power supply
- A shielding gas supply system
- Wire Drive system for pulling the wire electrode from the spool
- Source of cool water for cooling the welding gun
When the wire is passed through the gun, it becomes energized on getting in contact by a copper contact tube. It transfers the current from the source of power to the arc. There’s an accurate system of controls which: –
- Initiates and terminates the shielding gas and cooling water
- Operates the welding contractor
- Controls the electrode feed speed according to the requirements
Gas Used for GMAW
GMAW or Gas Metal Arc Welding, as the name says, uses gases for the process. The gases prevent the contaminants from entering the weld pool. Commonly used gases for GMAW are Argon and Helium. Such gases are inert or inactive, which means they won’t react with the workpiece. Alternatively, you can also use Carbon Dioxide (either alone or in combination with Argon).
Power Sources
Most semi-automatic and MIG welding processes require a constant voltage power supply. It’s the power source that delivers constant voltage to the electric arc during the entire procedure. You can also find a self-correcting arc length, which helps in producing better welding conditions.
Tools Used
Common tools used during the GMAW of the MIG welding process are: –
- Pliers
- Welding magnets
- MIG welding machine
- Chop saw
- Angle grinder
- Band saw
- Soapstone
- Chipping hammer
- Clamps
There are several safety equipment like gloves, protective clothing, and auto-darkening helpmeets for added protection.
What is GMAW Used For?
Here are some common applications of GMAW welding: –
- Aerospace
- Automotive maintenance and production
- Manufacturing
- Pipe welding/pipe joints
- Construction
- Custom fabrication
- Shipbuilding
- Underwater welding
- Railroad track repair and construction
It’s the versatile nature of GMAW welding methods that make it a preferred choice for industry workers. You can use it in small repair shops as well as in large industrial settings.
Advantages of GMAW or MIG Welding
Let’s now talk about the advantages of the GMAW welding process:-
- Easy to Master: While the GMAW requires you to be a master of this process, it’s very easy to learn. As it’s a one-hand operation, anyone with basic knowledge can get the job.
- Highly Versatile: Unlike other welding methods, you can use MIG or GMAW welding for numerous alloys and metals. You can also find a good range of filler electrode materials, which further increase the range of welds.
- Easy to Clean: The GMAW welding process involves the use of a shielding gas during the welding process. It protects the arc and minimizes the slag and spatter produced. So, you won’t have to put in much effort in cleaning the job site or the machine.
- Simple Controls: Depending on the machine you buy, you can find numerous settings to tweak the polarity, amperage, and wire speed. So, it offers numerous options to make it easy to use.
- Efficiency: It is one of the benefits that motivate industries to use the GMAW welding method. It’s very easy to clean and offers a one-handed operation, making it easy to control and handle. Its ease of handling helps in completing the jobs more quickly, easily, and effectively.
Disadvantages of GMAW or MIG Welding
GMAW or MIG welding has some good advantages, but it has some disadvantages too. Here are some of them: –
- Not Cost-Effective: The MIG or GMAW welding machine is costly. So, you need to spend good money upfront if you want to use this equipment. On top of it, this machine requires maintenance and regular replacement of parts for better efficiency.
- Limited to Indoor Use: Another downside of MIG welding machines is that they’re not portable. You cannot carry it around. It uses shielding gases that can be blown away by the wind outside. And without stable shielding, you cannot protect the arc, which further affects the process. It’s the reason GMAW is performed only in indoor settings.
- Chances of Burn Through: Burn through is a process that burns the metal if it’s less than the specified width. And this is what happens with MIG welding. All the materials below 0.5mm thickness tend to melt in this process. So, you’ll be limited to the use of a specified set of metals.
- Welding positions are limited: When it comes to welding using the GMAW technique, especially the MIG, the welding positions are limited. It comes with fluidity and high heat input, so you might face difficulty in overhead or vertical welding.
Conclusion
The GMAW welding process is one of the latest and most effective welding processes. It involves the use of shielding gas and a metal arc and offers a strong and permanent bond in the end. However, it’s a process for the experts. So, not anyone can perform it perfectly.
It is most commonly used in industries because of the effectiveness & reduced labor charges. So, if you want to use it, make sure to learn well.
