In some ways, discovering the art of welding is a contradictory experience.
Initially, it seems simple.
After all, most people know that welding is just the act of joining two pieces of metal together, right?
But you begin to read more about the subject and then it appears much more complicated than you first thought.
There are so many types, applications, joints and machines, that the whole project starts to become overwhelming.
And that’s before you actually get down to fixing that car fender (or whatever you want to weld).
This ultimate guide to welding will show you that this process is not as complicated as some videos, books and blogs would lead you to believe.
Once you understand the process, and the different types, it’s actually quite simple.
So, read on and discover everything you need to know about this process called welding.
As I’ve mentioned, the actual concept of welding itself is simple.
Practically, it’s the joining of two (or more) pieces of metal together. In effect, so that they can then act as one piece.
Think of the chassis on your automobile. The frame is constructed from separate horizontal, lateral and diagonal steel tubes and boxes, all of which have been welded together. They do not move or rotate—it is one solid construction.
Usually, welding involves applying heat to the materials to be joined. In doing so, melting occurs, which fuses the two pieces together as the metal cools again. Often, a filler material is added to increase the strength of the bond.
However, just for anyone who is shouting, “that’s not all strictly true!”, there are a couple of exceptions:
Even if you know very little about welding, I am sure you are familiar with the popular image.
You know the one, typically a masked man or woman wielding a white-hot torch with sparks flying through the air.
But this is the face of modern welding; it’s been around for much longer.
Here’s a brief historical overview (don’t be put off, it’s interesting).
Examples still exist today of Bronze Age gold boxes that had been formed through pressure welding.
These old fabrications (1,000 to 500 BCE) are assumed to have been pounded with a hammer to create the bond.
In addition, Herodotus wrote in "The Histories" that Glaucus of Chios single-handedly invented iron welding.
It’s not mentioned what he made, and it’s doubtful he applied for the patent. However, this is probably the earliest written record of welding.
Whether you recall from school texts, or are addicted to Game of Thrones, you will have seen the image of a blacksmith pounding hot metal with a hammer.
The Middle Ages saw the rise of this forge welding. Metals were heated to high temperatures and then bonded together by the blacksmith’s blows.
As most Middle Age history seems to consist of men piercing each other with swords, one must assume that someone skilled in welding had a profitable business.
Humphry Davy discovered the electric arc in 1800, but it was to be over 80 years before the first actual arc welding method was created.
This was developed by Nikolai Benardos and Stanisław Olszewski.
In 1881, they found a way to join metal using carbon electrodes with the arc principle.
The arc method was continually improved and developed up to the beginning of the First World War.
During the war years, demand naturally increased for welded machines and weaponry.
Post-war, this led to the development of automatic welding—a faster and more efficient process.
Further progress included gas tungsten arc welding in 1941, plasma arc welding in 1957 and electrogas welding in 1961.
You don’t have to look far from where you are sitting now, to see the application of welding. It’s everywhere.
Coffee pots, cupboard door handles, stovetops, even curtain rails. Chances are that if it consists of more than one piece of metal, it has been welded. Industry and manufacturing rely on this process.
This is due to the fact that:
Due to these factors, welding is most commonly found in the following industries:
Brazing, soldering and welding all have one thing in common—they are designed to join two or more pieces of metal together. But there are differences.
This method involves the use of a filler metal to create the bond.
Unlike welding, it does not melt the base metals to make a join.
A blazing torch heats up the filler metal around the joint. Through capillary action, this filler flows into all the hard-to-reach areas to create a firm bond.
As the base metals are not required to melt, it’s a practical solution for joining metals with different melting points.
This is a very similar method to brazing, but with one distinct difference—the temperatures involved.
The filler metal in soldering is usually just called “solder” (a tin and lead alloy). Generally speaking, solder melts around 390 degrees Fahrenheit.
Brazing involves temperatures above 800 degrees. Soldering is most often used in electronic bonds, such as circuit boards.
As Seba Smith wrote in The Money Diggers (1840), “There are more ways than one to skin a cat.”
I’m not an expert on felines, so I cannot comment on that statement. However, I can tell you, with some authority, there’s more than one way to weld metal.
Here are the main types:
Sometimes referred to as gas welding, this is one of the oldest methods, being developed back in 1903.
The name simply refers to the flame creation mechanism of this welding process. It’s really simple.
A torch is connected to two different gas tanks—one contains pure oxygen, the other gas fuel. Hence, oxy-fuel.
Most often, this “other” fuel is acetylene, which has given this method its other name—oxy-acetylene welding.
Whatever the fuel used, this is the part which burns and creates the flame.
The 100 percent oxygen raises the temperature of this flame to around 6,332 degrees Fahrenheit.
Hot enough to melt metal into a pool and create a weld.
Despite being very simple, this method has virtually disappeared from industrial use and been replaced with arc welding (all discussed below). That being said, it is sometimes used by hobbyists or small home-based businesses.
Shielded metal arc welding (SMAW) is also known as flux shielded arc welding (FSAW) or manual metal arc welding (MMAW).
However, unless you are at an industry conference, you will not often hear it referred to as such. In general, those “in-the-know” call it stick welding.
Hence, that’s how we will refer to it.
Instead of a welding torch, an electrode is used—which looks like a long stick (hence the name).
This electrode is covered in another material, or “shield”. Imagine getting a pencil and dipping it in paint—the pencil is the electrode, the paint is the shield.
This electrode is consumable. That is, as welding takes place, it becomes shorter and therefore at some point requires replacement.
The electrode is connected to a power supply (AC or DC, it doesn’t matter) which enables the arcing to take place.
The stick touches the metal to be welded, and then withdrawn, which creates the arc. Amperage is usually controlled through a foot pedal.
As the arc is created, three things happen:
The first two steps are creating the actual weld, the third provides a protective layer. As the shield disintegrates, the gases created prevent the weld from being exposed to oxygen. This could otherwise damage or ruin the integrity of the weld.
Furthermore, some of this shield (or flux) forms as slag over the welded joint, again protecting it from oxygen. Once the weld has cooled and hardened, this slag layer can be removed, to expose the weld beneath.
This method is still popular in industry, but due to the time it takes to complete, is being superseded by other processes. It is generally used in the welding of both iron and steel.
Remember how at the beginning of the article I mentioned welding always appears over complicated? Even when it is actually quite simple?
In my opinion, I think that a lot of this is down to the over-explanatory “proper” names of the welding process.
In this case, gas tungsten arc welding (GTAW). All of the welding types have these elongated nomenclatures.
Luckily, my favorite two methods have short names—TIG and MIG. Which is easier to say and more memorable.
MIG is discussed below, but gas tungsten arc welding is also known as TIG (tungsten inert gas welding)—and that’s what I’m going to call it.
The process was perfected in 1941 by Russell Meredith. Although it may at first sound a little technical, in essence it’s quite simple.
In one hand, the welder holds the welding torch, which has a tungsten tip. Unlike stick welding, this tip is not consumable, due to its ability to withstand high temperatures.
This welding torch has two functions:
Once the arc is created, the welder should move the torch in a circular motion making the weld pool. This is where the welder’s other hand comes into play.
Filler metal is added to the weld via means of a rod that is “dipped” into the weld to add to the pool.
This is done in an alternating pattern—weld torch goes in, filler rod comes out and vice versa. With a little practice, this action becomes second nature.
Just one thing to bear in mind. The filler rod should not be withdrawn completely, it needs to remain inside the gas “shield” to prevent its oxidation.
TIG welding and MIG welding (below), in my opinion, are the two most satisfying welding methods—both in enjoyment and final results.
If you want a good example of TIG welding, check out the film “Aliens”—where the characters protect themselves from the Xenomorphs by welding a door shut.
Although, please take more safety precautions than they did (including not going to an alien-infested space colony).
You already know what I am going to say. I’m going to call gas metal arc welding (GMAW) by its other name, MIG welding (metal inert gas).
I have already confessed that TIG and MIG are my favorite methods.
As explained above, I like TIG due to its neatness and the satisfaction of the two-handed technique.
For MIG, my attraction is down to one thing—it is so simple. It is often considered one of the best welding methods for beginners because it is so much easier compared to the other methods.
I have heard some people compare using a MIG welder to using a glue gun. Ok, it’s not exactly that easy, but it’s not far off. That’s what makes MIG welding a perfect choice for beginners.
To be honest, the only complicated aspect of MIG welding is the equipment.
Not that they are difficult to use, but the workings inside are quite complex, which takes the stress off the user.
I always think of it as being similar to my laptop. It can do amazing things, and I find it easy to use. I mean, through some magic I am writing this article to be read around the world. I cannot explain the internal processes—but then I don’t care as long as it fulfills its function.
Luckily though, I do know how a MIG welder works. That’s probably because I am somewhat obsessed with it. It’s addictive. So here’s my brief explanation.
The welding gun is where the “magic” happens. The nozzle on the end of the gun contains a solid electrode wire. When it touches the base metal, an arc is formed.
This electrode is consumable: it forms the filler metal for the weld pool. As the electrode is used up, it is fed continually down the gun nozzle; no other hand is required to feed it.
Furthermore, the shielding gas also comes down the welding gun nozzle, protecting the weld from oxidizing or absorbing water vapor.
All these actions are controlled by a “trigger” on the welding gun itself. There is no need to use three limbs as in TIG welding. You can do it with just one hand. It can also be set to automatic mode.
That being said, I often MIG weld with two hands—I find I achieve better accuracy, have greater control and receive better results.
Although the welding gun does do everything, you still require a machine to provide the current, electrode wire, gas and—naturally—you need safety equipment.
MIG welding is the most common form of industrial welding—suitable for use on most metals. However, as it requires shielding gas, it is not often used outside.
Flux-cored arc welding is, in many ways, a cross between MIG welding and stick welding.
Like MIG, it relies on an electrode that is continuously fed through the nozzle to both create the arc and provide the filler metal.
Like stick welding, the electrode, when burned, creates its own shield gases to protect the weld.
This is opposed to MIG welding, where a separate supply of shielding gas needs to be fed down the nozzle.
This makes flux-cored arc welding highly transportable.
As it is required to do less work, the welding apparatus is generally smaller than for MIG, and no gas bottles are needed.
In certain circumstances, for a “dual-shield” effect, an external gas can be applied to the weld for increased protection.
But in general, this is not the case. If that much protection is required, an alternative welding method might as well be used.
Flux-cored arc welding is not recommended for thin materials, ideally no thinner than 20 gauge (0.0359 inches).
Whereas MIG welding can be used on much slimmer metals. Hence, if dealing with small models or objects, flux-cored is not an ideal method.
No, it’s not time to switch off. Knowing how welding works is not only quite interesting, it will also help you enjoy your welding more and produce better results.
I will take you through a simple step-by-step welding process, and let you into the science behind it.
As we have already seen, there are many different types of welding methods, but all work on very similar principles. For this overview, I will use the Alien-preventing TIG method.
As Tim Curry says in the Rocky Horror Picture Show, you need “...that elusive ingredient, that... spark."
Most modern welding—excluding oxy-fuel—uses a spark, or rather an electrical arc, to generate the heat.
For this, you need a power supply (welding machine) to provide the energy itself. One lead works as a “ground” and is attached to the welding material. The other attaches to the handheld gun.
Electricity always wants to complete a circuit—a little like “Rocket” Rick Mears in the Indy 500. The welding gun has a conductive tip, in the case of TIG, made out of tungsten.
The tungsten is quickly tapped on the base metal and then withdrawn a little. This creates an arc—the electrons in the air are ionized as the electricity fights to complete the circuit.
Arcs create a phenomenal amount of heat and light (hence safety precautions, discussed later, are required). The more current passed from the power supply, the higher the temperature of the arc.
Due to the high temperature of the arc (around 11,000 degrees Fahrenheit), the base metals being joined begin to melt. It is important that the arc is moved in a circular motion to create a weld pool.
As the two (or more pieces) melt, a process known as welding fusion takes place. This enables the two molten pieces, in effect, to become one.
This is why welding is considered the strongest method of connection.
It needs to be observed that the two pieces being joined must have a similar melting point. Otherwise, one will melt much earlier than the other resulting in either a failed or cracked weld.
In TIG welding, the filler is added separately, once “the melt” has started (in MIG, if you recall, it flows down the nozzle).
Theoretically, if the two metals being joined are of identical composition and very close fitting, a filler may not be required.
However, “better safe than sorry” is always a good saying to live by, especially when welding. Using a filler rod will not weaken the join, only strengthen it.
The filler rod in TIG welding is “dipped” into the weld pool, depositing a small amount of metal. This creates a stronger bond and fills any spaces or gaps between the two pieces.
It is important that this rod has a similar composition to the metals being joined—a variety are available to ensure you have the correct material.
As the melt and filler stages are being completed, another important factor is at work.
As the name suggests, this protects the weld itself. But as you cannot use a metal shield (it would end up being attached to your weld), gases are used.
These gases in the case of TIG and MIG are passed onto the weld through the welding gun.
They prevent nitrogen, hydrogen, oxygen and water vapor from contaminating the weld pool.
If these unwanted elements enter, they can lead to holes (weakening the join) and metal “spatter”.
The main quality these gases need is that they are inert. In essence, they do not react with other substances. Most essentially, not highly flammable—otherwise, you personally will join the weld pool.
The most common gases used are helium, argon, and carbon dioxide. Their use depends on cost, preparation and type of the weld. In general:
In addition, the above gases can be combined into different mixes for the ideal weld result.
As you are aware from school, matter exists as solid, liquid or gas.
Actually, just in case any scientists are reading this, that’s not altogether true. There are two further states—plasma and Bose-Einstein condensates (just saves me from having to respond to irate emails at a future date).
In welding, the metal is taken to the liquid stage to enable welding fusion. As it cools, it returns to the solid stage again to form one solid piece.
Some welders cool the weld with water once completed, known as “quenching”. My advice is always, “if you don’t have to, then don’t.”
I understand if time is pressing, and the weld is not “critical” (i.e. if it fails, someone will die), then quenching can be a possibility.
Otherwise, leave it to cool down naturally. Reducing the temperature too quickly can lead to it becoming brittle, due to thermal shock.
The weld will harden after just a few minutes (but don’t touch it with your fingers to check). There is always plenty to do while it’s cooling. Clean up, pack away your equipment or have a coffee.
Doesn’t sound like science, but it is.
Studies have shown that, in some circumstances, beauty can be quantified.
Cleaning the weld improves its appearance and makes both you and others appreciate the time and effort that you have taken.
What’s more, if the area is to be painted, having a clean and smooth base will allow the coating to bond better.
Before I was into welding, I always wondered how ‘fire’ could work underwater to weld metal together. Luckily, I now know. It’s not fire.
There are two types of underwater welding.
This method involves creating a sealed ‘chamber’ around the area to be welded. It is then filled with a gas mixture, relevant for breathing at that depth.
The welder does not, therefore, need to wear diving equipment.
In this scenario, although deep beneath the water, the welder is still operating at around surface pressure (as the chamber is pressurized).
This makes welding at this depth virtually the same procedure as on the surface. The biggest restriction is the lack of room to operate in.
In my opinion, this is a wonder of science. As previously mentioned, there is no “fire” involved. Instead, it is just an electrical arc, as done out of water.
However, there are a couple of significant differences. Firstly, as electricity and water are not the greatest of friends, the electrode required for the arc is waterproof. The most common method used is stick welding, as discussed earlier.
Secondly, something amazing occurs underwater. I know what you are thinking, surely the arc and weld is interfered with by all the surrounding water? Luckily, it’s not. The water creates its own protection.
As the weld is started, carbon dioxide is created as part of the melting process. This builds a bubble around the weld which prevents water from touching the welding area.
Underwater welders are some of the most well-paid in the entirety of the welding industry.
Surprisingly enough, it is not another name for the underwater welding discussed above. It is done on land.
The “submerged” part refers to the actual weld. Prior to commencing work, the area to be welded is covered in a granulated flux—hence it is submerged.
A continuously fed electrode is then pushed into this flux to begin the weld.
As it is covered in the granules (typically silica or lime), the weld is shielded from contaminants.
In addition, it eliminates splatter, sparks and ultraviolet light. Normally, the arc cannot even be seen as it is beneath the blanket of flux.
This type of welding is commonly used in industrial applications. It is most often an automated or semi-automated method, completed by a machine.
There are instances where handheld welding is possible, although it is somewhat rare.
Unsurprisingly, a joint is where two pieces of metal are joined together to form one piece.
I know I keep mentioning it, but welding is simple. So simple, in fact, that there are only five types of joints. That’s it.
This is probably the most common type of welding joint.
It is when two pieces of metal are joined together, side by side. This includes welding together pieces of pipe of the same diameter.
Not only is it common, it is also the easiest of all the joints to do. Making it an ideal starting place for beginners. It’s also known as a square-groove weld—but most people just call it a “butt”.
This joint is used when two pieces of material “overlap” each other.
Think of it like this. Take two square drink coasters and place one on top of the other. Now just push the top coaster about an inch to the right, leaving the other one stationary. Where they meet is the lap joint.
If added strength is required, these two metals can be welded both on the top and on the underside.
A joint like this is often used where the two surfaces have different thicknesses, making a butt joint difficult.
If you’re a healthy type and attend the gym frequently (unlike me,) check out the weight machine frames—they often have lap joints.
Corners of equipment often receive the most “punishment” during their lifetime. It is not unusual, therefore, for these joints to be repaired or replaced frequently.
The joint is made so that the two metals are pushed together to form a right-angle, or L-shape.
When welding, the weld goes on the outside of the joint, not the inside. Typically, this joint is used to create boxes and square frames.
Most often used when one of the metal parts has edges that are flanged. Imagine placing a nickel standing on its edge on a flat piece of steel.
Joints like these often require filler metal to ensure that they remain as strong as possible. This is due to the lack of surface area where the two parts actually meet.
As the name suggests, a joint that, when viewed from the side, looks like a T-shape. For example, take two pieces of identical steel measuring 2 inches high by 1 inch wide.
Lay one piece on a work surface with the 2-inch side flat to it. Take the other piece and lay it on top, with the 1-inch side abutting it.
As we have seen, welding does require the use of other materials, in addition to the welding equipment and metal.
Here are three of the most common types:
These are steel electrode rods surrounded by a flux material.
This electrode works to both create the arc and act as the filler metal.
The flux coating reacts with the heat to provide a gas shield. The covered electrode is used in stick welding.
Used in MIG welding, this wire is small in diameter and is continuously fed down the welding torch.
These are supplied on spools, for home and small business use, or on large drums for industrial work.
As they contain no protective flux, an external supply of shielding gas is required when in use.
Earlier, we discussed submerged arc welding. SAW flux is the granulated material that provides the “blanket” over the weld. Most often, these are supplied in a large sack format.
Different types are available, depending on the heat being used and/or metal to be bonded.
Once you have completed your weld, you inspect it, and yes, the two pieces of metal are definitely joined together. The question is—will it stay that way?
If you have just re-attached an arm to your metal statue of Wolverine, and after a month it drops off, then there’s no issue (well, except to Wolverine).
However, if you’ve replaced a metal ladder rung, and it fails while attaching the Christmas lights to your house, that’s more serious.
Checking the quality of a weld is always something I recommend, even if it is not life threatening.
You want the satisfaction of knowing your handiwork is going to last. Hence a quality check.
Generally speaking, there are three types of quality assurance—visual, non-destructive and, you’ve guessed it, destructive.
Unless you work in the industry, you are unlikely to do any other quality checks apart from visual. However, I have included brief details on the other two. Knowledge is power, right?
Many issues can be spotted simply by inspecting the weld. Or, if someone else has done the weld for you, it’s even more important to examine their work.
Visual checks are the easiest way to check quality, and require no equipment. Here are the things you should be looking out for.
How “clean” is the weld? It should be free from any extraneous materials. Firstly, there should be no slag.
Even if some is generated during welding, it can easily be removed via peeling or a hard brush.
If other elements are obvious (dirt, metal shavings, small animals) it means that the metal was not sufficiently cleaned before welding. A dirty weld is a weak weld.
There should be an even distribution of the welding material in the join with no lumps, bumps or gaps.
If small holes have appeared in the weld, alarm bells should start to ring. This is known as “porosity.”
This will radically reduce the strength of the weld, and should be rejected if you see it. Usually, this is caused by a lack of, or insufficient, shielding gas during the welding process. It means that oxygen and water have been allowed to enter the weld pool.
Where the metals meet, the joint should be tight and without visible gaps. Air spaces create weak spots.
This has usually been caused by poor preparation and failure to secure the metals properly during the welding phase.
If the weld has been done on an item that can (not necessarily by design) hold liquid, test for leaks.
Mix a little soap detergent in water and tip into the welded object. If water or bubbles are seen, you know the weld is insufficient.
These are ways to check the integrity of the weld, which still leaves it usable after use. These methods do involve some specialized equipment.