As a student of welding, it’s important that you understand the “why” behind your job and not just the how. While in your career, you will often be doing the actual physical tasks of welding, and you will need to troubleshoot, design, and solve problems for your customers, which will entail creating metal pieces to their specifications and needs. For that, you need an understanding of the best metals to use when, how they mix properly, and the best join designs.

Missouri Welding Institute offers the best welding program in the country. Our mission is to prepare you for a welding career, either at a company or on your own. With our welding certifications, you will be prepared for a career in all industries, from oil and gas to manufacturing. We aim to give you a solid understanding of basic welding principles, as well as a ton of hands-on experience. When you graduate from Missouri Welding Institute, you will be on your way to success. Below, we’ll explain some of the content of our welding theory course. Contact us today for your free information packet!

Welding Theory At Missouri Welding Institute


As you can probably guess, metallurgy is the science of the physical and chemical components of metal, their elements, their compounds, and their basic structure. When you study metallurgy, you are studying what exactly is metal. Metallurgy dives deep into the study of alloys as well, which are different types of metals that are mixed together. This is huge when it comes to welding because for the most part, the strongest metals are alloys of some sort.

Metallurgy, at its most basic, is the extraction of metals from their ores, refining them, and preparing them for end use, be it in welding or some other use. While welders are more concerned about the practical application side of metallurgy, Missouri Welding Institute will spend time diving into the microstructure of particular metals, its structural features, its elasticity, and its other properties.

Metallurgy has a long and varied history since humans have been interested in metals for tools, building, and weaponry for millenia. The first metals were those that could be easily extracted by simply applying heat, which is a process called smelting that is still practiced today. Tin, lead, and copper are examples of metals that can be separated by heat. There is evidence that this process has been known since at least 6,000 BC.

Bronze is an alloy made up of copper and tin and was first combined somewhere around 3,500 BC. It is a vastly superior metal, and this discovery could be considered one of the greatest of all time for humans.

The extraction of iron from its ore around 1,200 BC (a much more difficult practice than the extraction of copper or tin) again changed the course of human history.

Without these discoveries and huge leap forwards in technology, there would have been no blast furnace, cast iron, happers, bellows, engines, trains, cars, and most other modern convenience made out of alloys. Even the aluminum can you are drinking soda of right now would have been impossible without these innovations in metallurgy.

Identification of Metals and Electrodes

In our welding theory course, Missouri Welding Institute will go over how to identify metals, as well as cover electrodes. Electrodes are central to welding. In fact, a welder needs an electrode in order to generate an electrical current for arc welding, the most common type of welding. As this electrical current flows through the electrode, the metals are then joined. There are two main types of welding electrodes:

  1. Consumable Electrodes
  2. Non-Consumable Electrodes

Consumable electrodes are distinguishable by the fact that they have a low melting point, and are thus preferred in some welding applications, such as Metal Inert Gas (MIG) welding. Consumable electrodes are further classified as bare electrodes and coated electrodes.

Non-consumable electrodes, or refractory electrodes, are not consumed during the welding process, which means they do not melt during welding. These welding electrodes have high melting points and are popular in Tungsten Inert Gas (TIG) welding.

Missouri Welding Institute will go into the nitty-gritty of the classification of welding electrodes in this course.

Types of Welding Processes

As a welding student, it’s important to know the tools of the trade. There are many types of welding processes, some more used than others, that you will need to know in order to choose which one will work better for your particular welding project at hand. We cover most welding processes here at Missouri Welding Institute, including:

  • Shielded Metal Arc Welding (SMAW / MMA)
  • Gas Metal Arc Welding (GMAW/MIG / MAG)
  • Flux Cored Arc Welding (FCAW)
  • Gas Tungsten Arc Gas Welding (GTAW/TIG)

Testing Methods in Welding

Welding is no doubt a skill — one that takes precision, practice, discipline, and expertise to perfect. Since welding is such an integral part of the construction and fabrication processes of many industries, it’s imperative that welding is done right. After all, when you think of such things as bridges and walkways, a weld needs to hold or people may be harmed.

Missouri Welding Institute trains our students how to test their welds to ensure strength, durability, and longevity. There are two broad types of testing welds:

  1. Non-destructive weld testing
  2. Destructive weld testing

Non-destructive weld testing ensures the structural soundness of components without causing damage. Some of the methods used in non-destructive weld testing include:

  • Ultrasonic inspections
  • Radiographic inspections
  • Visual inspections
  • Magnetic permeability
  • Positive material identification (PMI)

Destructive weld testing is designed to test the physical properties of the materials you are making products from, more so than the finished product itself. Some of the methods used in destructive weld testing include:

  • Tensile testing
  • Compression testing
  • Fatigue testing
  • Pressure testing
  • Impact testing
  • Shear testing

Welding Gases

Welding makes use of various gases in order to make metals weld together easier. Some are pure gases, while others are a mixture of gases. Known as shielding gases in welding, the purpose of these gases to to keep oxygen and water vapor at bay. Oxygen promotes oxidation, which weakens the weld bond — something you definitely don’t want as a welder.

Some of the most common gases used in welding include argon, hydrogen,nitrogen, and mixed gas combinations, such as argon and carbon dioxide and argon and helium. These gases help to break down oxides and help stabilize the arc when welding. They can also create a better surface as well.

Missouri Welding Institute notes that over the years, the exact combination of welding gases have been developed that yields the perfect weld. There are many reasons for determining these, which this course will investigate. Suffice it to say for now that welding gases makes your life as a welder much easier.

Joint Design & Configuration

A welding joint is like a joint in your body — a place where two or more pieces of metal come together. There are five types of joints commonly seen in welding, which include the butt, corner, edge, lap, and tee. It’s important to know these different types of joints and when to use which for your particular application. Missouri Welding Institute will spend quite a lot of time not only discussing joint configurations, but also practicing them in our shops.

As a welder, you will be called on to design many parts, joints, and mechanisms for customers. Having a good grasp of joint design will be vital for your welding success. In joint design, you’ll have to consider size, type of weld, the edge, the thickness of the metal you are working with, and distortion. Another consideration when designing parts or machines for customers to account for is the skill of the welder. Missouri Welding Institute notes that a new welder will probably do best with a less technical joint and design, and a skilled welder can add in the aesthetics as well as functionality to the design.


If you think polarity has to do with polar opposites, you’d be correct. Electrical current in a welder has a negative and a positive pole, which are known as polarities. The polarity can greatly affect the strength and quality of the weld, so it’s important that you have an understanding of it.

Polarity in welding is often classified as straight or reverse polarity, or electrode-negative or electrode-positive. Reverse polarity results in a deeper penetration weld, while a straight polarity has a faster melt-off and deposition rate. Using shielding gases as well as your knowledge of polarity can greatly affect the quality of your weld as well.

As if that weren’t enough, AC and DC current will affect your weld as well. Alternating current (AC) alternates the direction it is flowing; direct current (DC) flows in one direction, which creates smoother and more stable arcs. However, using AC current has its place, as it is cheaper and runs on machines that are easier to use.


Missouri Welding Institute notes that there is much more to welding than meets the eye. Our welding theory course is designed to lay a solid foundation to build upon throughout your tenure here and throughout your welding career. While there is much to learn, we are confident you will succeed. Also included in our welding course is the basic welding procedures, welding positions, and welding currents. Qualifications to be a welder will also be covered.

Missouri Welding Institute aims to give all of our welding students the knowledge they need to be successful no matter which industry they choose. Our 18-week welding program will give you everything you need to become proficient in welding. This welding program prepares a graduate for journeyman level positions as a pipe welder, a pipe fitter, manufacturing and shop positions, field construction jobs, power plants, and so much more. Most of our courses consist of one hour of lecture followed by seven hours of hands-on experience in our welding shops.

Missouri Welding Institute concentrates on developing your inner craftsman through giving you the tools you’ll need to tackle any project you are given, anywhere, and anytime. Welding theory is the foundation of all of our welding courses. Contact us today for enrollment information!