The development of welding can be traced back as far as the Middle ages with the revolutionary progression of blacksmithing. Today welding procedures are completely different from what they were back in those times and we can see that through the huge variety of options available to be utilized. In this article, we are going to cover the basics of the 4 most common types of welding in use today alongside 4 other specialized methods that you may not have heard of.
The four main types of welding are,
- Shielded Metal Arc Welding or Stick Welding
- Oxy-Fuel Welding or Gas Welding
- Gas Tungsten Arc Welding or TIG and,
- Gas Metal Arc Welding or MIG Welding
There are several other unconventional welding methods that we will discuss later in this article.
STICK WELDING
Also known as Shielded Metal Arc Welding (SMAW), stick welding began to be used as a metal joining process back in 1890, where it was first patented by Charles L. Coffin of Detroit. From this moment it has flourished to become one of the most widely employed welding methods today because of its flexibility and uncomplicated operation.
SMAW works through the combination of electrical energy and skill with the purpose of joining various ferrous metals together. The systematics of all welding procedures, including stick welding, behave very much like a circuit.
Shielded Metal Arc Welding Principle
When an AC or DC electrical current is conducted from the stick welding machine into a flux coated electrode, heat is generated. However, this will only happen if an earth clamp – also linked to the welding machine – is attached to the metal to be welded. The electrode is placed near or scratched on the surface of this parent metal and an electrical arc is generated which will range in temperature from 5000 to 8000°C. This extreme heat will allow for the birth of a weld pool (molten metal) and here the electrode is placed thus, creating the weld.
The electrodes of SMAW are always consumable, so when welding commences it is necessary to gently push the electrode into the weld pool to actually create a continuous weld, if not, your arc connection will break, and you will be left with nothing but a spot weld. Refer to the diagram for clear visual reference.
Welding Direction
As you will launch into your weld, the direction in which you move is very important. Stick welding is the only major welding process where you use the “pulling” or “dragging” technique meaning that you will work directly in front of the weld pool, not behind it. A benefit from pulling is that it allows for improved visibility when compared to other welding processes.
When welding has concluded it is noticeable that the weld isn’t very beautiful. Now unless you have made some sort of error, this will be because your weld is coated by the atmosphere protective flux from the electrode also known as slag. SMAW does not use gas to protect its weld pool from contaminants (like other weld processes) but it uses this flux instead. This adds a huge benefit in increasing the weldable locations of the process. This means that stick welding can be used outdoors without the risk of shielding gases blowing away in the wind.
OXY-FUEL WELDING
Straightforward in terms of technology is the Oxy-fuel, Oxy-Acetylene or the Gas Welding process which relies on oxygen and acetylene gas as a consumable fuel source.
How Does Oxy Fuel Welding Work?
A neutral, oxidizing or carburizing flame is produced by the chemical reaction of these two elements which generates heat of up to 3200°C. When the flame is applied over your joint this will create the weld pool when the temperature of the metal reaches 1350°C to 1530°C (for mild steel). Once the weld pool has been created, filler material is added externally beginning the oxy-fuel welding process. You will move in a “pushing” direction whilst adding your filler rod as consistently as possible into the combustion zone of the flame (see diagram). It is possible to use the Oxy-fuel welding process to weld a variety of metals, but usually, it is used on mild steel, copper, and brass works more regularly.
A neutral flame is normally selected for welding as it is equally balanced between oxygen and acetylene. The flame is the most difficult part in the setting up of oxy-fuel welding as it takes experience to identify which adjustments to make to your flame to match your specific metal or joint to be welded. For example, a flame adjusted with a lot of power behind it will simply blow the weld pool away and a flame without power will prove difficult to create the weld pool itself. Experience and practiced flame identification are key to a good weld with Oxy-Fuel welding.
Gas Welding vs Arc Welding
A significant difference between Oxy-fuel and other common welding processes is that the heat source is not electrical but gas-based which also means that electrical earth is not required because of this. This can pose some preventable operational risks such as flashback which is where the gas exiting the mixing chamber (or gas cylinder) backfires from your handpiece, ignites, and can lead to an explosion.
TIG WELDING
Famed for its precision, flexibility and aesthetically pleasing welds is the TIG or Gas Tungsten Arc Welding (GTAW) process. It is selected when these specifications are important with the goal of joining metals precisely, most commonly these are light metals such as stainless steel or aluminum.
How Does TIG Welding Work?
When in action, TIG welding uses an electric arc conducted by an AC or DC current and is channeled through a non-consumable electrode made of tungsten, the parent metal, and an electrical earth attached to the subjected parent metal. The arc is ignited with either scratch start, with the push of a button on the handpiece, or a press on a foot pedal, and this arc will generate a weld pool heat over 3000°C. Filler material is then added to this weld pool in the form of wire, varying thickness and elemental properties are available, and depending on the metal to be welded you will select what works best.
TIG welding utilizes shielding gas which protects the welding pool from atmospheric contamination. The shielding gas is delivered through the gas nozzle tip in which the tungsten electrode is protruding. The type of gas used will also vary depending on the characteristics of the job although pure argon gas is most common.
TIG is a very multi-actional form of welding as it is necessary to all at once:
- Move in the “push” direction steadily while controlling the smaller than standard weld pool.
- Consistently place and withdraw (or dab) the filler wire from the weld pool without allowing it to leave the gas protection zone or enter the weld pool excessively by mistake.
- Keep the gas nozzle close enough to the weld pool to maintain the necessary protection of the weld pool without allowing the tungsten electrode to touch the pool itself.
If any of these steps are mismanaged, the weld is going to look ugly at the least or be defective at worst.
MIG WELDING
The last of the 4 most common types of welding, and arguably most utilized today, is the welding processes known as MIG welding or Gas Metal Arc Welding (GMAW). MIG welding is known for its high levels of productivity.
How MIG Welding Works?
GMAW or MIG (Metal Inert Gas) weld uses a mechanically driven, consumable filler wire electrode that is continuously fed into the weld pool from the welding gun. As the trigger is pulled on the MIG welder handpiece, the wire is released from a spool which is held inside the machine and is fed in a continuous motion along an electrode cable exiting through a copper contact tip. As the filler wire makes physical contact with the earthed metal, an electrical arc ignites producing heat of approximately 3000°C which creates the weld pool.
MIG welding conducts electrical energy through both the electrode, the metal subjected to welding and an earthing clamp attached to this metal. Without this circuit there is no arc ignition. The type of filler wire selected depends upon the material being welded, with solid or cored wires being most commonly selected. Protecting this wire and the weld pool from atmospheric contaminants is gas which is released from the gas nozzle of the MIG handpiece with argon and helium gases being most utilized.
It is possible to weld without a gas bottle with special self-shielding filler wire containing a flux core which when heated, releases the protective gas. This type of wire allows MIG to be used outdoors in windy environments, however, it is not preferred as a welding procedure as it is limited with its uses.
MIG Welding Operation
The operational characteristics of MIG welding require the operator to utilize the “push” movement meaning that the weld pool will always be in front of the user’s hand when welding.
The arc distance is more easily maintained with MIG than with other arc welding methods. Only the gas nozzle distance is necessary to maintain because if this is too far from the weld pool, defects such as porosity will occur.
Unconventional Types of Welding
Welding is such an open topic that it is necessary to cover the basics of some welding procedures which are less common than the above four methods. All, in general, are much more specialized with their purposes, function, and operational procedures.
Resistance Welding
Resistance welding is when metal is joined using a combination of applied pressure and an electric current through an automated system to the metal wanting to be joined. The automation of the machine allows the operator to work accurately as well as quickly and with filler material unnecessary, it makes the process economical and highly suitable for production-based environments.
Spot Welding
Spot-welding is the most widely used form of resistance-welding. It is known for its easy and relatively unskillful operation and efficiency.
Energy-Beam Welding
This welding process fuses the subjective metal through a high-velocity beam of electrons within a machine operating system. When the produced beam makes contact with metal the kinetic energy of the electrons is converted into heat joining the material.
Energy-beam welding was developed relatively recently and is utilized throughout the medical, defense, aerospace, and nuclear industries for its narrow weld bead, precision, and deep penetration. Vacuum seals often house the energy-beam welding system to protect specifically important welds from oxidation which improves weld quality drastically.
Underwater-Welding
Underwater welding is considered one of the most dangerous occupations in the world and is famous for its health risks and skillful operation. It is the only welding process within our uncommon section that requires an operator to physically control the weld.
There are 2 different approaches to underwater-welding:
- working from within a dry-chamber system or
- working within the water itself.
The dry-chamber system houses up to three workers at a time and they are all essentially in a submersible craft which allows them to work on the required job without being in the water. Many dry-chamber systems also allow the worker to exit the craft and physically work out in the open water.
Work in open water can be carried out from depths of 1 meter to upwards of 200 meters, with dry-chamber systems allowing even greater depths. Underwater welding utilizes a specialized form of stick welding, which is fueled by an electrical arc as its energy source.
Robotic-Welding
Robotic-Welding is a highly advanced process that uses automated CNC-controlled robots to create welds. The “robots” are supervised by operators who generally have welding experience and they are the ones responsible for loading CNC programs into the machine which gives the system the information it needs to complete a weld.
The weld produced by robotic welding systems is near perfect, basically without the fault of human errors. Robotic weld is also very fast making the system great for repetitive work or highly important joints. This system is a great alternative to human welders when possible however it is limited with its capabilities meaning a skilled welder will always outmatch the robotic system with versatility.