What is arc welding? Arc Welding is the most common type of welding in the world. With a diverse range of substyles, it can help welders accomplish nearly any welding task.
Arc welders use an electric current that bonds with the metal, creating an intense heat (over 6,000 degrees Fahrenheit) which breaks the metals down. Once the metal has been broken down to its molten state, it can be joined with another piece of metal. After the molten metal cools, the two pieces are permanently bonded, resulting in a finished product.
So what is arc welding’s primary purpose, and when is it best used? There are many unique types of welding that involve an electric arc, and each has a specific purpose. In this article, we’ll discuss everything you need to know about the different styles, and help you determine which makes the most sense considering project costs, scope, and your personal expertise.
Before we dive into the question, “what is arc welding?”, and breakdown the pros and cons of the different types, let’s run through some of the terms and phrases you’ll see throughout this article.
The electrode is a metal substance at the end of the welding rod. When arc welding, a power source is hooked up to the rod, and the electrode is responsible for conducting the current through the rod and to the metal being welded, thus creating the arc used to weld.
Parent metal simply refers to the metal that’s being welded. Because there’s other metal that’s used in the arc welding process, it’s important to be clear when it’s the parent (also referred to as base) metal being referred to.
Filler metal is the metal used to strengthen the bond. While the heat from the arc is generally enough to create the initial bond between the parent metals, the filler metal is necessary to strengthen and reinforce that bond.
During the weld, the point of contact between the arc and the parent metal will be dangerously hot. This creates a molten pool of gooey liquid metal, which is referred to as the weld pool.
The weld pool requires a lot of additional protection throughout the welding process because it’s where all potential integrity failures and material corruption will take place.
There are multiple types of bonds that can be established between pieces of metal in the welding process. These bonds describe the relationship between the parent metal and the filler metal.
- Homogenous: Filler and base material are the same
- Heterogenous: Filler and base material are different
- Autonomous: No filler material is needed
Recognizing the difference between these bond types and understanding the relationship between parent and filler metals will be helpful in determining your approach to arc welding.
The Role of Electrodes in Arc Welding
The best place to start when deciding which type of weld will work best for a particular project is to determine whether the electrode method should be consumable or non-consumable.
Electrodes are the catalyst for every arc weld. Positioned at the end of the metal rod that the welder holds, they conduct the direct current from the power source to the parent metal, forming the arc.
Think of it like a phone call. The electrode is on one end of the line, the parent material is on the other, and the arc connects them.
Common types of metal used are steel, tungsten, and magnesium, depending on the type of weld. Steel has a lower melting point, which means that it will actually burn away with the metal during the welding process, while tungsten and magnesium will stay intact the entire time.
Both of these methods have purpose, and choosing these two welding procedures between these two consumable or non-consumable electrodes typically depends on the project and the welder.
Consumable Electrode Method
The consumable electrode method uses an electrode with a lower burning point, so the electrode gradually burns away over the course of the weld. The excess material is actually repurposed as filler material to help strengthen the metallurgical bond between the metals being welded.
Because the electrodes are constantly burning away, they need to be replaced over the course of the weld. While periodic replacement will be needed, the frequency will depend on the electrode size and filler deposition rate.
Consumable Electrode methods are generally friendlier to beginners for a few reasons.
Firstly, most don’t require the use of a protective shielding gas to protect the weld pool. Shielding gas is typically used to ensure that the bond is resistant to chemical forces that can weaken it, such as oxygen.
However, the rods used in consumable methods are generally coated with a consumable flux coating, which is a layer of chemicals that offer the same protections as a shielding gas.
Because this coating burns off with the electrode, it will offer an inherent protection to the bond. This means you aren’t having to simultaneously apply shielding gas to the weld pool – instead, the flux coating protects it for you!
The second reason consumable electrodes methods are more beginner-friendly is that they don’t require the welder to have experience applying an outside filler metal to the bond.
The application of outside metals can be a tricky process, and needs to be done expertly, or else the integrity of the entire weld could be in danger. Because the filler materials burn off from the electrode directly into the base material, this isn’t a concern in consumable methods.
Common types of arc welding under the consumable electrode umbrella are:
- Metal Inert Gas Welding
- Shielded Metal Arc Welding
- Gas Metal Arc Welding
- Flux Cored Arc Welding
- Electro Slag Welding
Non-Consumable Electrode Method
On the flip side, it’s sometimes necessary to use an electrode with a higher burn point. These electrodes won’t melt during the process, and therefore won’t be used as the filler metal. This can be a plus, as it allows the welder more variety in the type of filler material used.
Non-consumable methods are generally prefered in projects that require an homogenous bond. Since the filler material needs to match the original metal, the non-consumable method works best because it doesn’t require that the electrode and welded metal match. Instead, the welder can just use an outside source of filler metal during the weld to ensure homogeneity.
Even with a heterogenous bond — in which the filler is different from the welded metal — a non-consumable method can offer some advantages.
For instance, just because the two metals are different, doesn’t mean that the metal being used in the electrode is the same that should be used as the filler. With the non-consumable method, a welder can choose any type of filler metal they want, granting them greater flexibility with the bond type.
In the autonomous method, which requires a high skill level and isn’t always achievable, a non-consumable method is required. This is because, in the consumable method, it’s impossible to keep the electrode from melting away into a filler metal.
While the non-consumable electrode methods require more experience and technical skill, it also offers more flexibility and has more expansive industry applications.
Common types of arc welding under the non-consumable electrode method umbrella are:
- Gas Tungsten Arc Welding
- Carbon Arc Welding
- Tungsten Inert Gas Welding
- Plasma Welding
Subtypes of Arc Welding
Looking to just fuse a couple pieces of iron together? How about aluminum? Or are you looking to pull off a skilled weld, with an emphasis on precision?
No matter the specifics of the projects, there’s an arc welding process for the job. However, not every style will work with every weld. Below, we overview some of the most popular approaches, and help you answer these two questions:
- “What style of weld will work best for me?”
- “What is arc welding and its role in my project?”
Shielded Metal Arc Welding
Shielded Metal Arc Welding is one of the most popular styles of welding in the world, due to its ease of accessibility. It’s equipment and process are fairly simple, which makes it a great entry point for anyone who’s new to the craft, or that doesn’t have the resources for expensive equipment.
It’s a consumable electrode method, which means that it’s flux shielded. So there’s no need to apply an outside filler metal.
The shielded metal style has been around for over 200 years, and has become many welders’ favored method for welding iron and steels. It’s main function in commercial welding is in the maintenance and repair industries.
If you’re a beginner, it’s crucial that this style of welling is performed at a flat angle. While more complicated projects might require that the parent metals are angled up or down, this dramatically increases the level of skill involved in the process.
One of the biggest drawbacks to this method is excessive weld spatter. Weld spatter doesn’t necessarily harm the integrity of the structure, but it’s not pretty to look at. If the finished project is going to be something visible, it will oftentimes take a lengthy post-weld scrape down to clear off excess debris.
It’s important to note that in both this style and flux cored arc welding (which we’ll cover next), you can’t weld with non-ferrous (meaning non-iron) metals such as aluminum.
If you’re a beginner looking to keep your costs low, and planning on working with primarily steel or iron, shielded metal arc welding is for you.
Flux Cored Arc Welding
Flux Cored Arc Welding (FCAW) is a relatively new style, originating in the 1950s as an alternative to the shielded metal style.
FCAW is very similar to shielded arc welding. Both are consumable electrode methods and fairly accessible to beginners. It’s also most effective with steels.
Its primary difference hinges on the type of electrode it uses. While a shielded metal arc employs solid electrodes composed entirely of metal, the fluxed core uses only the hollowed out shell electrode, filled with flux and other protective substances.
Some of the advantages of this style include less pre-cleaning of the materials, as well as less weld splatter. If the look of the finished product is important, and you’re unfamiliar with how to properly scrape down the work afterwards, the slightly more laborious process of flux cored arc welding might best suit your needs.
Gas Metal Arc Welding
Gas Metal Arc Welding (GMAW) is a style with a few key differences from the other consumable methods we’ve covered so far.
- Uses a continuously-fed wire instead of an electrode
- Requires the use of a shielding gas
The use of the wire instead of the electrode simplifies the process, making GMAW one of the easiest styles to learn. In fact, most equipment allows for this portion to be automated, so the welder can focus on some of the more important aspects of the weld, such as voltage and flow rate.
As long as the welder can successfully manage those two things, and make precise cuts, a gas metal arc weld is almost certain to be a success.
The use of the shielding gas makes GMAW a perfect fit for some projects, while making it nearly impossible for others.
If you need to weld non-ferrous metals, such as aluminum, GMAW is the preferred style of professional welders. Aluminum is difficult to weld because it’s encased by a substance called aluminum oxide.
Aluminum oxide is essentially a protective layer that’s difficult to cut through, making it almost impossible to reach the metal itself. The burning point for the aluminum oxide is almost 3x higher than it is for the base metal. So, the heat required to burn through the outer layer will scorch the metal underneath, ruining the weld.
Certain gases used during the GMAW process, such as helium, allow the welder deep penetration, which breaks down this protective layer. So if you’re looking to work with non-ferrous metals such as aluminum, a gas metal arc weld is likely your best bet.
The main drawback to the GMAW process is that it can only be done indoors. This is because even a small amount of wind will interfere with the use of the shielding gas, which can render the weld both dangerous and ineffective.
So if you don’t have access to an indoor workspace, or you’re attempting a repair in which the object can’t be moved from it’s outdoor location, then gas metal arc welding simply won’t work.
The final drawback to this approach is its price. The cost of equipment is high, and repairs can be costly. If budget is a big concern for your welding project, this is something to keep in mind.
Gas Tungsten Arc Welding
Gas Tungsten Arc Welding (GTAW) is a non-consumable method, meaning that the electrode doesn’t burn into filler material during the weld. Instead, a single non-consumable tungsten electrode, which has a very high burning point, is used throughout the duration of the weld.
GTAW requires a high level of skill. However, it also grants the arc welder an extremely high level of precision, not attainable with other styles. This makes GTAW a popular style for working with stainless steel and other fine metals (aluminum, magnesium, and copper). It’s most commonly used when exactitude is the paramount focus of the project, such as on a bicycle.
Because the electrode is non-consumable, the welder must manually apply filler metal. This allows more control over where and how the filler metal is used, but forces the welder to use only a single hand to operate the weld.
Gas tungsten arc welding only makes sense for welders who already have some experience, or who are willing to invest a lot of time into the craft to perfect the style. Despite the effort required, the high quality welds it produces are worth it for many welders.
Safety For Welders
One of the main factors stopping everyday people from learning about welding is it’s reputation as a dangerous job. This reputation isn’t without reason; the act of fusing metal together requires a very high powered heat source. With high temps, flying sparks, and sometimes the simultaneous execution of operating tasks, arc welding accidents can be common and severe.
The good news is, almost all arc welding accidents are preventable with the right equipment and with a thorough and careful understanding of correct safety procedures.
Let’s take a look at some of the most important safety tips for welders.
Fire Hazards are the most common type of welding accident. Due to the high temperatures involved, anything remotely flammable is liable to light fire and burn.
The best way to circumvent this issue is by wearing the correct type of clothing. It might be tempting for some welders to not change out of their street clothes before welding, especially if the project seems small, short, or routine.
However, accidents tend to strike when we don’t plan for them. Wearing leather gloves and flame repellent jackets are effective ways to ensure that nothing on you will catch ablaze.
Protecting your eyes is important whenever you’re working with tools. However, welding poses perhaps the greatest ocular threat of any type of project. Not only are welders liable to have stray materials fly into their eyes at any time, but they also have to deal with damage coming from the intense light from the weld.
This light has been known to be so intense that it causes damage to the retina of the eyes for those who stare at it unfiltered for too long.
There are two main precautions that can be taken to make your welding space a safe place for eyes:
- Light-adjusting goggles for the welder and anyone else in the room
- Curtains outlining the room to protect those who look at the workspace from the outside
There are many high quality brands of goggles that are designed specifically for welders to use, which will shield their eyes from light damage and debris.
Inhalation of Toxic Fumes
When an individual is working with burning metal, they need to be conscious of the toxins in the air. Over time, these toxins can poison your body and damage your lungs. If too many of these toxins are breathed in at once, it can lead to asphyxiation and death.
There are a few important ways that welders can work with lung safety in mind. First, they must recognize the danger present in some commonly used degreasing solvents. Hydrogen chloride and phosgene are two toxic chemicals that are released when these solvents are exposed to the ultraviolet light produced from welding.
The Canadian Center for Occupational Health and Safety recommends not using chlorinated hydrocarbon degreasers. If you’re using this type, they suggest making sure that the surface is not still wet with the material when the welder begins.
Degreaser fumes aren’t the only dangers present when welding. Many dangerous metals (such as chromium, nickel, and manganese) are present in the fumes that come from burning steel.
To avoid breathing in these chemicals in dangerous amounts, welders need to have a workstation that’s properly ventilated. This doesn’t mean just opening a door and getting some “fresh air”. This means having a high quality exhaust ventilation system that captures and expels these gases from the workspace.
Choosing the Method Right For You
While there are an abundance of arc welding sub-types, finding which method works best on your project is essential. To best determine your approach, take some time to clarify your needs and match it with the style that best meets them.
Whether you’re a beginner looking to work outdoors with simple metals, or an expert with an indoor workspace welding soft metals, there’s an approach that will work for you. We hope we answered the question, “what is arc welding?”, and provided you with helpful information!