After the development of inert gas welding and the creation of the TIG torch, the MIG system soon emerged. From 1948 to date, this type of welding has been widely used. Both TIG and MIG are well known and used; However, there are differences between them that distinguish them. MIG welding is a short circuit that, with its own characteristics, will generate a new piece due to the fusion of metals.
MIG or GMAW welding
Referring to it as GMAW welding will probably be understood only by those who know the area very well. In daily use, MIG is the term managed. However, what its initials refer to is an arc welding process with inert gas metal. Metal Inert Gas or Arc Welding Metal Gas refer to a fusion process that is achieved by an electric arc formed by a metal electrode and the part to be welded.
MIG makes use of inert gas as a protection against the effect of oxidation of the atmosphere on the electrode, which in this type of welding is a welding wire. Unlike TIG welding in which the tungsten electrode is not consumable, in MIG the wire is consumed by melting with the part being welded.
The gas used is argon or a mixture of it with CO2. For welding protection, before undertaking the procedure, make sure that the tank has sufficient gas capacity and that everything is in order with its hoses.
The necessary equipment
This is a type of welding that requires certain specific equipment to have optimal results. Let’s start with the guns. These have a system of traction and thrust that, when activated, gives way to gas, current and wire, the latter can be pulled or pushed. There are some guns that bring the reel of wire incorporated allowing welding to meters of the equipment.
A characteristic of the steel wire is its copper cladding. The wire that is usually used is of three types: solid wire for use with protective gas, tubular wire with a core of mineral powders also used with protective gas and the tubular wire without gas with a core of dust that release gas when burning. The use of this last wire is without gas.
The gas tank is commonly full of argon; however, helium or a mixture of them can be used for specific thicknesses. To control the proper flow of gas output, regulators such as the pressure gauge and the flowmeter fulfill the function of indicating the pressure.
In the same way and in relation to the same aspect, hoses for the conduction of gas and water are necessary. The rectifiers and converters are responsible for generating the necessary direct current and a cable with the appropriate caliber and according to the amperage will conduct it .
MIG welding processes
It is a versatile weld that can be applied to aluminium alloys, non-ferrous materials and steel with thin to medium thickness. There are prior and important adjustments to be made before starting the welding procedure itself.
The current intensity influences the heat input, the dimension and depth of weld penetration. The arc voltage controls its profile and the feed speed of the wire controls its intensity. The adjustment and control of these parameters can be done semi-automatically, automatically or robotically.
The robotic process is used at the industrial level where a robot executes the programming. The automatic form occurs when all adjustments are made previously, and the semi-automatic when combining a previous adjustment with the manual drag of the welding gun.
Displacements and characteristic movements
In MIG welding , the ideal position of the gun is horizontal. In this position, it is achieved that the action of the protective gas is optimal and the smooth cords look good. The most common displacement of the gun is from right to left, especially when welding aluminum. This displacement is recommended to achieve better cords in quality and penetration in fine and medium thicknesses.
As for the movements, it is to imagine that pieces are sewn together to join them. The welding can be linear, circular, impulse or pendular . The linear is perfect for use in thin plates for root cords. The circular movement is adequate when the separation between the edges is really large, since a wide cord will prevent penetration.
Pulse welding is done with little material supply when thin cords are needed for small separations between the edges. If the separation to be welded is very, very large, then the recommended movement is the pendulum. In it, quite wide cords are drawn that demand considerable contribution of material.
MIG welding has numerous advantages but also clear limitations . Among its advantages can be mentioned:
- Large cords can be made without interruption or discontinuity. In this way, a good finish is achieved.
- The fact that the reel of wire is in the welder and that it is pushed by rollers allows to avoid waste of time to replace electrodes.
- The efficiency of the electrode is calculated at 98 percent.
- It can be welded in any position without affecting excellent penetration.
- Welding in thin thicknesses is very easy.
- It produces few splashes and a clean welded surface.
As stated earlier, it also has limitations that must be considered before deciding on a MIG welding procedure . Some are:
- The equipment and technique are complex demanding only skilled labor.
- The use of a gas tank makes it less portable.
- The cost of the equipment is much higher.
- Outdoor work is not recommended, since air currents could cause the gas shield to exit the arc.
- For a good effect it cannot be used on rusty surfaces or with any dirty.
Taking all these limitations into account will make the MIG welding procedure successful and safe. It is worth remembering that when contemplating high temperatures and being exposed to ultraviolet rays, the protective equipment for the operator must be head to toe.