What Is Welding? Definition and Processes – In-depth Guide


Welding is the intricate art of joining metals together. It plays a vital role in the infrastructure of nearly every single construction project on the globe. No wonder it’s a big deal!

Mastering welding isn’t the most straightforward task on earth. Yet, it’s doable. You might be surprised to know that there’s an increasing demand for welders now more than ever. So, here’s another feasible career than you can pursue!

The thing is that welding entails tons of details. Various welding techniques, different equipment, and dealing with safety hazards. How do welders do all that?

That’s what we’ll be talking about in this in-depth guide on welding’s definition and processes.

What Is Welding?

What is welding? In the simplest terms, welding is the act of joining two metal pieces together. Using high heat levels and introducing other metals or gases, the metallic structures of the two parts combine to become one.

In this way, it’s different from brazing and soldering.

I have recently written an article in which I describe what Soldering is in more detail, read this article here

On the other hand, soldering requires heating the metal instead of melting it. At the same time, brazing works by melting the two base metals and flowing another filler metal right into the joint.

What Is Welding? >> Check out the video below:

Welding Types – A World of Techniques

Now Let’s move to the main welding types and take a look at their techniques, differences, variations, and applications.

First, let’s start off with the most primitive type of welding; it developed of our ancestors trying to use fire to melt metal pieces together thousands of years ago.

Back to the Basics – Gas Welding (Oxy-Acetylene)

Better known as Oxy-Acetylene Welding, this technique is probably the oldest and simplest welding technique out there. Despite being surpassed by TIG welding -which we’ll be getting into in a minute- it’s still in the game because of its wide scope of applications.

The basic principle of gas welding is that you heat the two ends of the materials you want to join until they melt and fuse.


By utilizing two cylinders of gas mixed at the welding torch chamber, one of them is the fuel, which is commonly acetylene or sometimes propane. The other is oxygen.

The two combined produce a flame as hot as 5800°F. This can literally melt off any material you want to weld; cast iron, steel, aluminum, or copper.

Related reading: Different Types of Gas Welding Flames and Their Applications

Once the material starts to melt, a weld pool will be formed, on which the welder dips the filler rod concisely. The process can be carried out without filler material, as well.


  • Can weld ferrous and non-ferrous materials together
  • Easy to master
  • Low cost
  • Portable equipment
  • Provides the welder superior control over temperature
  • No electricity is required
  • It can be used to cut some metals


  • Relatively slow
  • Inefficient when it comes to thick metals
  • Welding finish isn’t neat
  • Not suitable for reactive elements

Applications of Oxy-Acetylene Welding

  • Mostly used for repair works
  • Welding chassis and automotive’ frames
  • Fabricating thin sheet metals

So, how many types of welding are there?

Well, this is a hard question in and of itself. References disagree on this. Practically speaking, there are about 60 different types of welding. However, the most famous and commonly used are just 4.

1.   Arc Welding – Stick Welding

Stick welding is probably what you picture when you think of a welder. It’s the old fashioned way to do it.

In stick welding, also known as Shielded Metal Arc Welding (SMAW), the welder is a stinger with an electrode (stick) attached to it.

The stinger runs an electric current through the electrode, forming a short circuit with the workpiece. The material and size of the electrode are what determine the required voltage.

Welders love stick welding because of how versatile and portable it is. You probably can use it to weld anything anywhere with pretty satisfying results. However, it requires a high skill level.

I recently wrote an article about Stick welding (Stick Welding: Ultimate SMAW Guide You´ll Ever Need), have a look at it.


  • Inexpensive equipment
  • Convenient for narrow areas
  • Doesn’t require a shielding gas
  • Works well with thin metals like aluminum


  • Manual method
  • Time-consuming
  • Demands a high skill level


  • Construction
  • Shipbuilding
  • Automotive industry

2.   TIG – Gas Metal Arc Welding 

TIG welding is the common industry name for (GMAW) Gas Metal Arc Welding, in which the weld is formed as a product of an arc between a metal electrode -usually tungsten- and the base metal.

The technique was first developed in the aircraft industry around the 1930s with the purpose of welding magnesium in mind.

In TIG welding, the welder uses a non-consumable tungsten electrode to melt your workpiece. Plus, an inert gas -probably argon- to protect your weld pool from airborne contaminants.

With his other hand, he hand-feeds the filler material rod to the weld pool.

TIG welding gives the welder superior control over the heat, where he can control it through a foot pedal. This means that TIG requires a higher level of skill than other techniques.

Related reading: What Is TIG Welding Used For? Why Choose TIG Welding?

Here’s the deal, though. For its perfect results and versatile applications, TIG welding is tough to master.

That’s why beginners often opt for MIG welding instead. It produces acceptable results in a shorter time and using an easier technique.


  • Versatile and can be used to weld multiple materials
  • Produces a clean welding bead for when appearance matters
  • Minimal spark and spatter
  • No flux or slag
  • It can be performed in all positions; vertical, horizontal, and overhead
  • Works well on thin metal sheets


  • Not the easiest technique to master
  • Relatively high cost
  • Low speed
  • Time-consuming


  • Most commonly used in airplanes
  • Wagons and bike frames
  • Lawnmowers and fences
  • Heavily used in auto body repair shops
  • Artworks and sculptures due to its high precision

3.   MIG – Gas Metal Arc Welding

Welding beginners love MIG, and they have every right to do so!

MIG welding is also known as Gas Metal Arc Welding. It’s fast, efficient, and learning it is no rocket science. That’s why it’s usually used in high production welding operations in factories.

Its basic principle is pretty similar to TIG. That is forming an electric circuit between the base materials and a welding wire, where they form a weld pool in which they merge in and solidify later.

Related reading: How To Properly Set Your MIG Welding Polarity Settings?

The only difference here is that instead of using a non-consumable tungsten electrode and another filler material electrode, the gun has one consumable metal electrode that does both heats and fills the weld pool.

As the welding electrode is consumed, the welder feeds the gun with a new one. All of that is shielded by the gas diffused by the welding gun to protect the whole thing from contamination.

Related reading: Can You MIG Weld Mild Steel with Pure or 100% Argon? (Straight Argon)

One of the limitations of using MIG welding is that it requires an external shielding gas most of the time, which makes it impractical for outdoor use. It won’t perform well when faced with wind, or even a strong breeze.


  • Fast working action
  • Easy to learn
  • Creates continuous welds
  • Low cost
  • Ideal for thin metals


  • Complex equipment
  • Requires a shielding gas
  • Leaves dusty deposits


  • Manufacturing pipelines
  • Home improvement sector
  • Automotive industry
  • Producing steel structures

4.   Flux Core Welding – FCAW

Flux Core welding isn’t that different from MIG welding. It relies on an electrode tube that’s continuously fed into the welder, at the core of the tube, there’s a flux agent. Hence, the name.

The flux melts, forming a liquid slag that does the welding itself. It produces a shielding gas as well to keep contaminants at bay.

Related reading: What Purpose Does Flux Serve In Welding Aluminum?

Flux core welding is usually used in machine welding. It works well with most metal types, cast iron, stainless steel, and carbon steel. It’s not convenient for non-ferrous metal alloys like aluminum, though.


  • Suitable for outdoor work
  • Portable
  • Produces high-quality welds
  • High deposition rate


  • Generates a lot of smoke and slag
  • Produces more spatter than most welding types
  • Flux wires are relatively expensive


  • Shipbuilding
  • Surfacing
  • Mechanical industries

Welding Joints – How Do Metals Connect?

Depending on the geometry and position of the base metal pieces, a welding joint is formed. Each type of joint is welded differently.

Let’s first distinguish two types of welding; a butt weld and fillet weld. A welder can perform these two types in different joints.

I have recently written an article in which I describe welding joints in more detail, read this article here (5 Types of Welding Joints and Their Use – Complete Guide)

A butt weld is the most common welding type, where the two metals are in one plane, lying against each other end to end. Hence, the name.

There might be a slight angle between them sometimes, but usually, they’re in straight alignment.

If the two base metals are perpendicular to each other (at a 90-degree angle), then you’ll need to “fill” in-between them, forming a 45-degree angle between them. This is called a fillet weld.

There are five types of welding joints. We’ll explore them below.

Tee Joint

As the name suggests, a Tee joint resembles the shape of the letter T. One metal piece lies flat, while the other is welded on top of it from its side or end. Usually, the weld is applied on both sides of that metal piece to ensure stability.

The challenging part of Tee Joints is that the welded surface area is minimal, so it gets tricky to make sure that the welding is tight and the upper metal piece is placed at a right angle.

Square Joint

A square joint -also known as Corner Joint- is a typical joint to perform a fillet weld on. It takes the shape of the letter L, with one base metal piece lying on the floor, and the other on top of its left or right end at 90 degrees facing upwards.

Corner joints are one of the most common welds in the industry with a ton of applications. Think of how all boxes and frames need a corner joint.

The plates here can be of different lengths, widths, and thicknesses. Most of the time, a square joint has a fillet weld on one side and a butt weld on the other side.

This affects its strength due to the difference in thickness and strength between the two. It’s one of the reasons why a Tee joint is considered to be a better option.

Butt Joint

You guessed that right. A butt joint is similar to a butt weld that the two plates lie flat against each other.

The tricky part is that the welder wants to achieve a surface that’s as straight and flat as possible, which isn’t an easy task, given the invisible guiding lines.

Butt joints are commonly used in welding pipes, valves, and fittings. It’s not recommended to use butt joints in places that are subject to heavy loads.

Lap Joint

A lap joint is what you get when you put the metal plates on top of each other, then slide one of them to overlap the other—making space for two fillet welds, one on top and another at the bottom.

You can weld either on one side or both sides. Lap joints are usually the go-to solution for metals of varying thickness. Practically, they’re easy to master, so many welding rookies love to start with learning them.

Edge Joint

Edge joints are when two adjacent parallel pieces need to be welded together. It’s usually applied to parts with flanging edges. The welder sets the pieces side by side and welds them together.

As you might imagine, this is not the strongest welding joint out there, so it’s used for low stress and low-pressure applications.

What Gases Are Used in Welding?

When the air gets into the arc or the weld pool while the welder is working, it can lead to the formation of gas bubbles that might ruin the weld.

Related: What Gases Do MIG Welders Use? >> Welding Shielding Gas | Complete Guide

Besides, anything like air or debris might contaminant the weld pool. That’s why welders require a shielding gas to protect the weld from atmospheric air to prevent porosity and excessive spatter.

Here are the most commonly used gases in welding.


Argon is commonly used as a shielding gas in welding since it’s an inert gas that doesn’t react with other substances.

However, they recently discovered that it changes form at very high temperatures, which limited its uses. Yet, it’s still the most commonly used shielding gas to keep contaminants away from the weld pool.


Carbon dioxide is extracted from nature and pressured into cylinders to be used as a shielding gas too. It’s an alternative to argon. It’s a cheaper alternative and one of less quality as well.

Due to its less than perfect performance and the spatter it produces, it’s mostly used in mixtures, along with other gases. Flux core welding and plasma cutting require using CO2 in its pure form, though.


Helium is used as a shielding gas, as well. It provides deeper penetration, but it doesn’t excel when it comes to arc consistency. When it comes to TIG welding, the perfect shielding gas is a mix of helium and argon.


Oxygen is added in small amounts to shielding gases to introduce some fluidity to the mix. The goal is to add fluidity to the weld pool to speed up the welding process.

Known for its combustion properties, oxygen is used to amplify heat for gas welding.

Related reading: Is Welding Oxygen The Same as Medical Oxygen?

Testing in Welding – How Do They Ensure Quality?

Being a highly specialized discipline, the welding process doesn’t stop at producing the final product.

It goes further to test the fabricated weld under conditions that are similar to -sometimes harder- than those at the welded piece site to ensure satisfactory performance of the welded structure.

I have recently written an article in which I describe weld Testing in more detail, read this article here (Physical Weld Testing: Destructive and Non-Destructive)

Here’s a glimpse of the most common welding tests. Some of them require destroying the piece to inspect it, while others are non-destructive.

Nick Break Test

This is probably the most known type of welding tests. In the nick break test, the welding joint is intentionally broken to examine the fractured pieces closely.

Examining these pieces will detect defects like porosity, slag inclusions, and gas pockets.

The pressure is applied to the piece and then with a strong press or a hammer blow, it’s broken into pieces, and the inspection starts.

Bend Test

A bend test is one of the most straightforward welding tests. Plus, it’s easy to perform. It relies on the premise that each metal piece that’s welded at the top should withstand a certain amount of bending before it breaks.

It’s often used in quality control of butt joints because it’s inexpensive. There are various ways to perform this test, through jigs, a wrap-around guided bend test, or a side bend test.

Acid Etch Test

This is the cleanest and most clever test of them. You cut a cross-section of the weld and immerse it in an etching solution like nitric acid.

This way, the acid will react with the welded material and show the boundary between the metal surface and the weld, revealing the imperfect of the welds.

Visual Inspection

The friendliest non-destructive test is a visual inspection. In this test, a qualified, trained observer watches over the welder while he’s working. He inspects everything!

Typically, he’s looking for inclusions, gas pockets, or undercutting. He spots these mistakes.

When the welding process is over, the detected piece is terminated, and the welder is required to remake the weld.

Ultrasonic Inspection

This method uses an ultrasonic wave probe to go into the metal. The results are displayed on a monitor screen, and when the waves encounter a discontinuity, they bounce back to the probe, indicating a flaw.

Moreover, ultrasonic inspection enables us to know the exact size of the defect from the wavelength of the detected wave. The rule is that the defect is half the size of the wavelength.

Welding Safety – Is It That Dangerous?

It’s crystal clear that welding isn’t the safest job out there. A big part of being a professional welder is knowing all the possible safety hazards and working your way to avoid them.

Welding Safety Hazards

Here, we’ll take a look at the four common welding hazards and their safety precautions.

Physical Hazards

Physical Hazards are the ones that might cause burns, eye injury, cuts, or even crushed fingers. To protect yourself from these, you need to wear complete personal protective equipment from head to toe.

Fumes & Gas Exposure

Frequent exposure to fumes and gas makes welders prone to plenty of diseases like respiratory illness and impaired speech.

Fire & Explosions

The number one cause of fires and explosions in welding work sites are flammable material lying around the workplace unattended. That’s why keeping a clean, well-organized area is a must.

Labeling materials clearly is also essential, in addition to marking emergency exits and having fire extinguishers.

Electric Shock

What makes electrocution probably the worst hazard is that it’s immediate. Once the electric discharge reaches the human body, it’ll suffer from injury or death. That’s why inspecting welding equipment and electrodes shall be taken seriously.

Personal Protection Equipment – PPE

Here’s how welders protect their bodies while they’re at the worksite.

Eyes & Face

You need something to protect your eyes and face against spatter, hot slag, and debris, as these can lead to serious burns. On top of that, you need protection against radiation and intense light.

For these reasons, you undoubtedly need a face shield, preferably with eye protection. Eye goggles are a must in most welding types. Hand shields come in handy, as well.

Head & Ears

A welding cap is a necessity when you’re working. People with long hair must tie it up and tuck it inside the cap. This is essential for protection against flying spatter.

It depends on your shield, if it doesn’t cover your head and ears, then you need a helmet. There is some head covering that welders wear under their helmets that’s fire-resistant, this definitely helps with the protection.

Add to these ear muffs or plugs, especially when you’re working in an odd position, like overhead welding. They’ll be an asset if you’re in a loud workplace too.


The fumes and gases produced from welding are greater than the normal lungs’ capacity. That’s why it’s vital to wear a filer mask with a respirator, especially for those who work for long hours.

Hands & Feet

You need something to protect your hands and feet against the heat. The goal is to provide protection against burns, fires, and electric shocks.

For this purpose, welders wear dry insulated gloves. Ideally, they should be flame resistant to get the job done. Mostly, they’ll be made of thick leather, especially when it comes to SMAW and FCAW.

As for boots, welders need to make sure that their boots comply with ASTM F2412 and ASTM F2413 requirements. Leather boots with metal toes are the best for welders. Flame resistant boots are definitely a plus.

One well-known tip is not to tuck your pants into your welder’s boots so as not to catch a spark if any.


Any part of exposed skin other than your hands and head needs to be covered. These body parts are still prone to burns, excessive heat, and fire.

You need to wear overall protective gear that’s made of heavy material. The heavier the material, the better.

Long shirts are favored over short sleeves. Long pants with no cuffs are preferable too. The clothes should be clean, dry, and oil-free. Also, try to cover any pockets or cuffs as they might catch fire.

Depending on the welding technique you use, it’ll always be better to wear a leather apron for an extra layer of protection. Well, regular clothes do not offer protection anyhow. You can add leather sleeves or leggings if you want.

Finally, never wear synthetic material in there, they catch fire easily.

Is Welding a Good Career?

In short, yes. Welding is a good career with good pay, and welders are in demand nowadays. According to the American Welding Society, the average age of a welder is 55 years. This number is among a rough estimate of 450,000 welders in the U.S.

Two takeaways here, there are not enough welders to cover demand, and you can pursue welding at any age!

Welding will be in demand as long as there’s metal in industry, which doesn’t seem to be ending soon. Skillful welders are an integral part of several industries, construction, aerospace, automobiles, maintenance, etc.

Even Hollywood knows how integral welders are to every industry!

Welding in Popular Culture >> Check out the video below:

Average Salary of a Welder

The average salary of a welder is around $40,000 – $45,000 annually. Other highly skilled welders might take off to take welding jobs in the military or underwater welding, where they can earn as much as $150,000 per year.

The skill level is the main determinant of the salary here, so there are always opportunities to climb up this career ladder.

Related reading: Do Welders Make Good Money? Highest Paying Welding Jobs


There you have it, an in-depth guide into welding.

We tried to make the article as inclusive as we can, to give you a deeper understanding of the welding skill, its details, how to learn it, and how to turn it into a prospering career.

After all, we have to salute welders. They put themselves through a lot and only gain small appreciation. All hail to welders!

Recommended Reading

David Harper

David is the Co-Founder and Senior Editor at weldingtroop.com. David's an experienced fitter and tuner/welder who's passionate about helping others develop in life through new skills and opportunities.

Recent Posts

error: Content is protected !!