You’ve seen the movie “Love Actually,” right? And, since the film was made in 2003 and spoilers don’t exist at this point, you know that its whole premise is based on the declaration: “love actually is all around.” Well, substitute “love” with “welding,” and you’ve arrived at one of the world’s fundamental elements of architecture, construction, transportation, and the very backbone of IKEA: welding actually is all around.
Truly. It’s everywhere. When metal is joined to metal, welding is the cause. When metal breaks away from metal, welding is the solution. Thanks to Stephen Christena’s new book, Learn to Weld: Beginning MIG Welding and Metal Fabrication Basics, the art and science of welding is available to all readers, whether you’re a novice with the MIG welder, or you’ve been joining metal for ages.
Today, we get to the heart of things by taking a look at what welding is and how it works.
How Welding Works
There are several different methods of welding. Today, the most common welding process is electrode arc welding. There are three types, or systems, of arc welding in this family: stick, MIG, and TIG. All three types of arc welding use the same three components.
The first and most obvious is electricity, which creates the arc. Each type also uses a filler material, and the third component is flux. The differences between stick, MIG, and TIG arise in how the three of these elements are used to create a bead (a bead being the weld that is created); each type of welding has a different method of execution.
Before we talk about the differences in welders and the methods of execution, we should go over how arc welding works in general. The best way to explain this process is to clearly define the elements of welding and what they do.
The Arc
Static shock, lighting, and spark plugs firing in a vehicle’s engine are all examples of an electric arc. Not many people are aware of this, but an electric arc is actually a state of matter called plasma, which is similar to gas. The arc is created by an electrical current moving through the work piece from the welding machine’s ground clamp to the electrode. The electrode is an electrical conductor used to complete the circuit, which allows the welding machine to create an arc. The arc is created by a breakdown of a gas that discharges plasma. Certain gases such as argon, carbon dioxide, and helium have a higher conductivity and ionization that assists in creating and maintaining the arc, making them candidates for a shielding gas.
In the stick and MIG welding processes, the electrode is also the filler metal. When the filler material comes into contact with the grounded piece of base metal, it completes a circuit that creates the electric arc. The arc forms at the very end of the filler material, which melts into the weld zone, creating the joint.
In the TIG welding processes, the electrode is a rod of tungsten. The arc temperature can range, depending on the welding process used and the setting of the machine or power supply, from around 5,000°F to around 18,000°F (2,760°C to 9982°C). Carbon steel, or mild steel, the most common form of steel you will be using, liquefies around 2,600°F (1,427°C). The arc’s high temperature heats the base metal to the point at which it becomes liquid. This is known as the “puddle” or “pool”.
The Filler Metal
Appropriately named, the “filler,” or “filet,” metal is just that. It is a rod or wire of metal that is fed into the puddle that forms at the point where the arc makes contact with the base metal. It adds more material to fill the weld zone, feeding the puddle and creating the bead. The filler metal is usually the same type of metal as the type being welded, but in certain cases, it can be other metals. In the stick and MIG welding processes, it also acts as the electrode. Stick and TIG welding require the operator to manually feed the filler metal into the weld zone.
Flux and Shielding Gas
The word flux comes from the Latin word fluxus, meaning to flow. That is exactly what flux does in welding. It helps stabilize the arc and keeps contaminants or oxides out of the weld zone. In stick welding, flux is a chemical coating over the filler rod that burns off, producing a shielding gas that prevents oxidation of the base and filler materials. Flux can be made from a wide variation of compounds depending on the application and material to be welded.
Flux is a component of welding with many jobs to do. The number one job of the flux is to protect the base and filler materials from oxygen and other ambient gases. It creates a barrier called the shielding gas, protecting the arc and metal from outside ambient gases that cause oxidation. It creates a purified environment for the arc to exist in. The flux keeps the liquid metal clean from impurities, also called inclusions, which would otherwise contaminate the metal. And last but not least, it controls the arc, helping the arc come up to a higher temperature to create the puddle of liquid metal.
Flux is most commonly used in stick welding, where it coats the filler metal. When the filler metal arcs to the base material, the flux is engaged. As it burns, it creates a carbon dioxide semi-inert gaseous shield that protects the arc. Once the weld is laid, the bead is covered in a byproduct of the flux called “slag.” Agents that come from oxides in the molten metal are absorbed and removed by the flux, creating slag. This hard shell is usually removed afterwards with a chipping hammer and a wire brush.
Flux is also used in autofeed machines, similar to MIG welders, which take a spool called “flux core” wire. This wire has the same properties and behavior as a flux-covered stick welder electrode. These machines are not considered MIG welders because they do not have the hookup for a shielding gas. Most MIG welders can use flux core wire, but their polarity needs to be switched over from DC+ to DC–. Some flux core processes can use a shielding gas in tandem with the wire.
Shielding gas is an inert gas that takes the place of a chemical flux. It does all the same duties as the flux. The first advantage of shield gas welding is that it has much better control over the arc. Just like blowing on the embers of a fire, the air pressure not only fuels the embers with gases, but also concentrates the direction of flow. Second, there is no slag byproduct. The shield gas process is cleaner. Third and most important, using a shielding gas makes it much easier to see the entire weld zone while welding. One drawback is that using shield gas outdoors has a tendency to not work very well. The pressure of the gas coming out of the nozzle can be easily blown away by the wind. Flux core and stick welding are the best options for outdoor welding.
The most commonly used shield gases are argon and a mixture of argon and carbon dioxide. Pure argon has great conductivity and heat transfer properties that will assist in creating a cleaner environment for the arc. And argon’s ionization properties allow the arc to start and be maintained more effectively and efficiently.
Pure argon is used in the MIG and TIG processes when welding on stainless steel and nonferrous metals (metals that do not contain iron) such as aluminum, titanium, or zinc. Hobbyist and beginning welders should focus on an argon/CO2 gas mixture (75 percent argon, 25 percent CO2). This mixture is ideal for carbon steel and will be the focus of this book.
The Ground
The ground is a crucial part of the power supply. All electric arc welders use one. In essence, you are creating a circuit, and without the ground, the circuit cannot be created. The ground clamp has to be clamped to the work piece or a conductive metal table that the work piece rests on or comes into contact with. The electrical current feeds though the ground and through the work piece, finding the shortest distance to the electrode as possible. The contact point between the ground and the machine’s electrode is where the arc forms. If there is no ground, there is no arc.
Spatter
MIG and stick welding, as well as welding with flux core, create “spatter,” small molten balls of metal that are ejected from the weld zone at the arc point. These small molten balls can fuse themselves to the work piece and to the gun’s tip and nozzle. Using nozzle spatter protection will help the tip and nozzle last longer and prevent double arcing.
There is a variety of spray spatter protection that can be sprayed onto the work piece. These products help to protect the work piece from needing to have dozens of little metal balls ground off of the surface. They’re especially ideal for projects with moving parts or precision work; you don’t want these little balls of metal inside a crank case or gear housing.
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Master MIG welding and the metal fabrication techniques you need to repair, create, and duplicate projects in your home welding studio. Learn to Weld starts with the basics: setting up your studio, the right safety gear and safety procedures, and the equipment and materials you will need to begin with welding. With the help of step-by-step metalworking photos and tutorials, you will learn detailed techniques for cutting and grinding, and for joinery using a MIG welder. Practice the techniques and projects, and you’ll soon be able to repair, create, and duplicate metal fabrication projects in your own welding studio. Best of all, you will have both the fundamental skills and the confidence you need to create whatever is in your imagination. With Learn to Weld you’ll be equipped to conquer a world of welding projects.
Stephen Blake Christena is the owner of Midwest Metal Works in Chicago, IL. MW2 offers custom fabrication services and a learning center for hobbyists interested in MIG welding. Christena teaches small-size courses designed to cover the basics and explore students’ projects and interests. He is also a spokesman for Miller welding equipment. Originally from Flint, Michigan, Christena moved to Chicago in 1998 after graduating from Western Michigan University with a degree in art. During his time at WMU, his primary focus was directed toward metal sculpture, photography, and painting. He opened his first custom metal sculpture studio in August of 1998. www.midwestmetalworks.org
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