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Arc Welding: The 5 Welding Processes You Need to Know

Basic Arc Welding Circuit Diagram

Arc welding is the process of melting two metals together. It uses electricity to create intense heat which melts the two metals together in a molten pool, effectively making them one material. This is called welding fusion and is the reason welded structures are so strong.

How does arc welding work?

Arc welding uses electricity to create a circuit between two metals: the base metal and the electrode, which is attached to the welding gun. When the circuit is broken by removing the electrode from the base metal, it creates an arc of electricity which is extremely hot – temperatures of 11,000 Fahrenheit can be achieved!

This molten pool of metal is what creates the weld – but it can be affected by gases and other contaminants in the air. A Welding Shield of inert gas is used to protect the weld while it’s in progress. Depending on the type of arc welding process you’re using, this gas will either be supplied externally (via the welding machine) or through an electrode (via a flux coating).

There are a few ways arc welding can be achieved, and the most common processes are:

  • Metal inert gas welding (MIG)
  • Tungsten inert gas welding (TIG)
  • Flux-cored arc welding (FCAW)
  • Welding Shield metal arc welding (SMAW)
  • Plasma arc welding

The Basics of Arc Welding

There are a few things in arc welding that don’t change, regardless of the process you’re using:

  • The materials being welded need to have a similar melting point, otherwise one will melt before the other, resulting in a failed weld.
  • Power can usually be supplied via alternating (AC) or direct (DC) currents. The type of power supply can affect the settings for the weld so always check before you start.
  • The more power, the higher the temperature of the arc. Manufacturers usually provide the standard settings for the equipment, but voltages should be changed to suit the job at hand.
  • The choice of electrode can massively affect the outcome of the weld.
  • Always clean the base metal with a metal brush or grinder before you start, even if you’re using a welding process that is compatible with contaminated base metals.
  • Safety is essential! You’re dealing with seriously powerful electricity and extremely high temperatures. Protect yourself. Wear safety gear and keep a suitable fire extinguisher nearby.

Below is a basic diagram of how arc welding works.

Basic Arc Welding Circuit Diagram

Basic Arc Welding Circuit Diagram

Basic Arc Welding Circuit Diagram

Arc Welding Terminology

If you’re new to welding, there are a few technical terms you need to know.

Electrode – the material that transfers the arc to the base metal, and controls the weld

Arc – the arc of electricity between the base metal and electrode, which creates the heat required to weld

Gas shield – the shield of inert gas surrounding the weld, usually carbon dioxide, argon, helium or a combination of the three

Weld pool – the pool of molten metal that is formed from the base metal and electrode, and filler material if it is being used

Base metal – the metal that is being worked on

MIG welding

  • Highly versatile
  • Easy to learn
  • Semi-automatic process
  • Not suitable for outdoors
  • Can be used on metals of various thicknesses

MIG welding is arguably the most common type of welding, and the easiest type to learn. MIG stands for metal inert gas, though it is sometimes referred to as gas metal arc welding (GMAW). MIG welding is a semi-automatic process that is best suited to indoor applications where there is shelter from the wind.

The MIG welding process

A MIG welding gun uses a continuously fed solid wire electrode to create the arc of electricity to meld two metals together. An electric current is fed to the electrode which, in MIG welding, also acts as the filler material to improve the weld. The electrode controls the arc, which produces the heat to melt the electrode, filler and base metal. Shielding gas is supplied externally via the welding machine to protect the process.

MIG welding is suitable for a range of metals of varying thicknesses including steel, aluminium, nickel and various alloys. The shielding gas can also be changed, depending on the metals being used. Generally, MIG shielding gas is a concoction of CO2, oxygen and carbon. The voltage can also be preset via the MIG welding machine to suit the application.

What is MIG welding used for?

MIG welding is a highly versatile process that can be used for a variety of applications. It is most commonly used projects such as automotive repairs, structural steelwork and the manufacture of various objects such as furniture, computer components and machinery for agriculture or mining.

TIG welding

  • Uses a pointed electrode for precision
  • Produces high quality, attractive welds
  • Slow process
  • Minimal cleanup required
  • Filler material optional
  • Best performed indoors
  • More difficult to learn
  • Good for welding round things

TIG welding, also known as tungsten gas arc welding (GTAW). It uses a non-consumable, pointed tungsten electrode, which allows for superior precision. TIG welding produces high-quality welds when it’s done properly – but it is quite difficult to master the skill. TIG welding isn’t the easiest to learn but the results are worth it!

The TIG welding process

A TIG welding gun features a pointed tungsten electrode, a connector and a shielding gas. An arc is created when the electrode is applied to the base metal and then removed. It is a small, intense arc, which makes it ideal for high quality, precision welding.

TIG welding is one of the few processes that does not require a filler metal, but you can use one if needed. The absence of filler makes TIG welding clean, with little to no cleanup required upon completion of the weld. If you do use a filler, you’ll need to feed it manually by hand.

Various tungsten electrodes are available to suit different types of welds. Pure tungsten electrodes are the most common and are applicable for metals such as aluminium. The shielding gas should also be changed depending on the metals being used – argon is the most common. As with MIG welding, the external gas supply of TIG welding means it’s best performed indoors away from wind and draughts.

Where is TIG welding used?

With high precision and minimal mess, TIG welding is ideal for thin sheet metals and projects that will be on show. It is commonly used in metal art sculptures.

Stick welding

  • Fixed length electrode
  • Can be used on dirty, painted and rusty surfaces
  • Difficult to master
  • Some cleanup required

Stick welding is the most widely used form of arc welding. It is also known as shield metal arc welding (SMAW) and is suitable for both indoor and outdoor environments. Stick welding can be used on most common metals and alloys including steel, aluminium and iron. It can also be used on dirty and rusted surfaces, which makes it incredibly popular in the repair and maintenance industries.

Stick welding isn’t easy to learn though. It’s a highly skilled process – the ability to strike an arc can be difficult and the learning process is usually long, but well worth it!

The stick welding process

The ‘stick’ of stick welding is a fixed-length electrode, which is coated in a flux of powdered metals. When heated with electricity, the flux creates the shielding gas, while the melting electrode produces the filler material to create the weld with the base metal. As such, there’s no need for an external gas supply, which is why stick welding is usually the process of choice for remote and difficult environments.

Stick welding can be a bit messy and produce spatter, so there’s usually some cleaning up to do afterwards. The end result varies on the skill of the welder, but it must be said that stick welding doesn’t usually produce the most attractive of welds.

The characteristics of the weld can be changed by choosing a different flux coating and altering the angle of the weld.

Where is stick welding used?

Stick welding equipment is easily transportable, so it can be carried out almost anywhere. As there is no need for an external gas supply, stick welding is ideally suited to outdoor and hard to reach places. You can even stick weld in the wind and rain.

Flux Cored Arc Welding (FCAW)

  • High productivity
  • No external gas supply required
  • Easy to transport
  • Not recommended for thin metals
  • Can be used on dirty base metals
  • Some cleanup required

The flux-cored welding process is like a combination of MIG and stick welding. It’s fast like MIG and does not require a shielding gas, like stick welding.

The flux-cored arc welding process

As the name says, with FCAW the electrode has a flux core consisting of various compounds and powdered metals. The electricity is transferred through the electrode to the base metal, forming the arc. When heated with the arc, the flux produces the gas shield around the molten electrode, filler metal and base metal in the weld pool. The weld will be covered with residual slag which also provides protection, and it can be easily removed when needed.

Flux-cored welding is usually performed with a drag technique, where the weld gun is pointing back into the weld pool and being pulled away from the completed weld.

Where is flux-cored welding used?

Flux core arc welding is commonly used for heavy-duty industrial fabrication and manufacturing processes. It’s generally not recommended for beginners and those with little experience as the technique can be difficult to master.

As there’s no need for a shield gas, flux-cored arc welding can be used outdoors.

Plasma arc welding

  • Can be used on incredibly thin and thick base metals
  • Uses a non-consumable pointed tungsten electrode
  • High productivity
  • Precise and accurate
  • Produces high quality, attractive welds
  • Difficult to master

Plasma arc welding (PAW) is similar to TIG welding in that it uses a pointed tungsten electrode, and requires no filler material. Unlike with TIG welding, the electrode is positioned inside the torch. This allows the plasma to be kept separate from the shield gas, which envelops the arc and weld.

A plasma arc is incredibly powerful, bursting from the electrode at almost the speed of sound! Plasma welding arcs can reach temperatures over 55,000 Fahrenheit – over 5 times the heat of a typical welding arc!

A PAW welding torch uses pressurised gas to create plasma, which creates incredibly precise and strong welds that look great too. Plasma arc welding also offers a high productivity rate.

The Plasma arc welding process

Inside a PAW nozzle, gas is pressurized to create plasma. This plasma is then ionized so it can then conduct electricity, which produces the arc from the non-consumable tungsten electrode, which is pointed to increase precision. The arc that is produced is small and incredibly powerful. The power of the arc can be adjusted by changing the voltage on the machine. The shielding gas – usually argon or hydrogen – surrounds the weld.

Where is Plasma arc welding used?

Plasma arc welding can be used in a range of applications, though it is most commonly used for electronic applications. The aerospace, marine and healthcare industries also use PAW for its high precision.

Getting Started Welding

Just getting started with welding? Perfect Power Welder has you covered. Check out our guide to getting started with welding, which covers the welding process in more detail and the equipment you’ll need for a successful and safe weld. You can also learn more about the career opportunities that welding offers – you can work anywhere from under the sea to the International Space Station.

If it’s the equipment you’re after, we offer a fantastic range of welding machines at entry-level prices, so if you fancy trying your hand at welding it won’t cost you a fortune. You can also stock up on welding equipment like guns, torches, helmets and accessories.

Getting Started with Welding: A Welding Guide for Beginners
How To Optimize MIG Welding Shielding Gas Pressure

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