How A Mig Welder Works

mig welder

MIG welding is a semi-automatic welding process. To do MIG welding, you need a MIG welding machine, earth cables, a MIG torch (water or air cooled), a regulator and consumables (coil of MIG wire) without forgetting the Personal Protective Equipment ( PPE) to weld while protecting you as much as you work.

How does the MIG welding process work?
The MIG welding consists of an electric arc established between an electrode and the base metal. The electrode (roll of wire) in this case is fed continuously. The formation of the electric arc welding, however, requires a totally shielded atmosphere from the oxygen we breathe.

At this moment the protective gas comes into action. It is responsible for isolating the environment to be welded, injecting gas and producing a protective curtain during the activity. Its adjustment must be done in advance through the welding torch nozzle.

It is noteworthy that although the MIG MAG welding process can not receive the influence of air. It is not recommended to work outdoors because of wind currents. In this way, the chosen location must have sufficient ventilation to eliminate the welding fumes / vapors produced.

welding wire

Mig Welding Shielding Gases

The function of protective gas in welding
Gas plays an essential role in the MIG welding process. It will prevent the liquid metal from the melt pool and the molten drops from being contaminated by atmospheric air. This protection can be done in three ways: by inert gas, active gas or the mixture of both. The choice needs to take into account the base material and the wire that will be used.

A good tip for choosing the perfect gas for the job that will be developed is to answer five questions:

1. What kind of materials should be joined?
2. How important is the appearance of the weld?
3. What is the acceptable level of splash?
4. High penetration is required, or should it be minimal to decrease drilling or burn-through at the joint?
5. Is it necessary to reduce the fumes generated?

shielding mig gases

The composition of the shielding gas

Having made the decision on which gas to work will be developed, then you need to know a little more about them. In the case of aluminum, the indication argon, as we have already said. For carbon steels and low alloys and stainless steels, the compositional options are as follows:

Carbon steel or low alloy
• Argon + CO² (5-15%) + O² (2-6%)
• Argon + CO² (25-50%)
• Argon + CO² (15-20%)
• Argon + CO² (4-8%)
Stainless steel
• Argon + CO² (10-30%) + O² (1-2%)
• Argon + O² (1-2%)
• Argon + CO² (2-4%)
• Argon + H² (1-7%)

How does the electric arc work?

 The electric arc concentrates heat at high intensity. Both at the tip of the MIG wire and at the base metal. This causes a metal transfer that causes the wire to melt toward the base metal. This transfer occurs basically in three ways:

The most recommended form for the MIG process.


Allows for high deposition rates. Its limitation lies in the fact that it can not be used in positions other than flat and horizontal because of the difficulty of controlling the melting pool. Also it should not be the option in the case of thin plates, because it needs high current. It is indicated to use pulsed current as a sort of “variation” of the transfer by spray that is more uniform and stable. In addition to opening the possibility of employment in positions other than flat.


It occurs when the transfer is by drops which, in this case, have a larger diameter than the electrode used. The diameter of the droplets decreases as welding current increases. It can cause splashes, which are avoided by keeping the bow as short as possible, to the point that it appears that the tip of the bow is dipped in the melting puddle.

Short circuit

Usually used in welding processes that are made in positions other than flat or when it comes to thin plates or root of greater aperture. When the drop of molten metal and the base metal come in contact, the current increases in intensity enough to heat the electrode and then allow the metal transfer. Soon after, this cycle restarts.

Automatic and semi-automatic processes in MIG / MAG welding

Automatic and semi-automatic processes in MIG / MAG welding
In the work with MIG / MAG welding, the professional can choose between two processes: semiautomatic and automatic. In the case of the semiautomatic, the torch inclination, the speed of advance and the oscillating movements that are necessary for the execution of the service are under control of the welder.

The main advantage in this case is that the professional can, if necessary, correct any deviations and adjust imperfections of the weld bead during the process.

In the case of the automatic process, an automated device assists in the operation. Thus, the feed rate, torch tilt and oscillating movements are pre-defined. If you choose this method, you need to be aware that there will be no possibility of correction during the service.

MIG / MAG welding is used as the basis for automated industrial production lines around the world.

No Mig Welding Experience

If you still do not have experience in the MIG / MAG welding process, you may encounter some initial difficulty, especially to find the correct metal distance and speed of movement. As for distance, if you get too close and touch the plate being welded, it will overheat.

What can influence MIG / MAG welding?

What can influence MIG / MAG welding?
• Protective gas
It directly influences the weld. For welding carbon steel, for example, it is possible to choose whether to use the air + CO² mixture or pure CO² only. But if the option is for pure CO² the consequence will be the greater generation of splashes during the process, as well as a greater penetration.

Current intensity

 Current Intensity                                                                      The greater the welding voltage, the thickness of the plate and the gauge of the wire, the greater the current or the amperage. It is worth mentioning that in the MIG / MAG welding the current is variable – the welding machines must provide constant voltage.
• Electric Arc Voltage:
The welding voltage of the arc must be proportional to the thickness of the plate and the gauge of the wire. The thicker the material to be welded and the wire to be used, the greater the need for heat and therefore the welding voltage for the electric arc.

Wire Diameter

• Wire diameter
The welding speed is determined by the wire gauge. As an example, we can imagine a 3/16 “plate that can be welded either by a 0.8 millimeter wire or by a 1.0 millimeter wire. If the option is the thinnest, the welding speed and wire speed must necessarily be higher.
• Chemical composition of wire
The wire will be specific to the base metal that will be welded. The options, in this case, are for aluminum, stainless steel or carbon steel.

roll of mig wire

Extension wire or stick out

•Extension wire or stick out
The distance between the tip of the contact tip and the melt pool is called a stick out. As a precaution, the contact tip should be kept out of the nozzle. This would force an excessive stick out, which creates instability in the process. This is because excess heat causes the wire to lose its ability to remain linear to the original position.

What do I need to Start MIG / MAG welding ?

What do I need to  start MIG / MAG welding ?

To start MIG / MAG welding  you need a basic set of equipment and it consists of:
1. Basic Mig Welding machine
2. Wire Feeder
3. MIG torch
4. Protective gas (inert or active)
5. Gas regulator

The Gas Regulator,

On the gas regulator, it’s worth explaining how it works. They are two manometers. The one on the right of the one looking at the equipment marks the cylinder’s internal pressure. So it is possible to calculate how much gas has already been used and, of course, how much it has still stored.

The left gauge is the cylinder gas outlet flow marker, the so-called “working pressure”. There is also a safety valve that breaks if the cylinder pressure exceeds 220 kgf / cm². Automatically the excess pressure is released, thus avoiding an accident like the explosion of the compartment.

Duty Cycle

Duty Cycle: 
As we said above, the productive capacity of the MIG / MAG weld suffers direct influence of the working cycle of the machines. In some cases, it is limited to 10%, that is, every ten minutes the equipment can operate for only one minute and needs to be in rest mode by the other nine.

But that is not a rule. You can opt for a modern machine and advanced technology, capable of increasing this duty cycle to an impressive 60%. This means being able to work uninterruptedly for six minutes and to restart the process after a four-minute pause.

Also it is worth as tip  to pay attention to the amperage of the equipment. Not always the most potent theoretically is also the most efficient. This 60% duty cycle, for example, was obtained by a 200A machine and is equivalent to another 250A machine, which is more expensive. That is, it is possible to do the same service by spending less.

Disadvantages of MIG / MAG welding?

What are the disadvantages of MIG / MAG welding?
As we have seen, the advantages of the MIG welding process are many, and they make the work more practical, fast and with good quality.

Setting up  Mig welder
It may be a little more complex, especially if compared to a stick welding using a coated electrode. Especially for the need to regulate the voltage, wire speed and gas pressure. In this case, the solution is to bet on technology. Already it is possible to opt for a machine with digital display that allows the precise regulation to execute each of the services. And, believe me, this is a big advantage.

 Welding Environment
It must be done in a closed place, since any wind currents in external places will hinder the protection of the puddle obtained with the gas curtain.

 Weld Quality
The chances of porosity or imperfections in the weld bead are relatively greater. The experience of the professional counts a lot to soften this aspect.

It is more complex than other equipment, such as welding inverters, for example. This type of equipment has been gaining ground in the market for its characteristic high-tech and private and be portable (easy to carry and store) and operate both indoors and in external interventions in high places or without the availability of a source of conventional energy.

The cost of acquiring the set (machine + torch + gas cylinder) is higher than that of  stick welding machines  or  TIG welding.

Multiprocessing Equipment

Multiprocessing equipment is solution available in the market
When we analyze the process of MIG / MAG welding, we are inevitably led to compare it with methods that use coated electrodes or even with TIG welding.

It is worth remembering, however, that the market already offers equipment capable of welding MIG / MAG, MMA (with coated electrode) and TIG in the same machine. This means optimizing space and the possibility of working with multiple forms of process without the need to purchase multiple machines.

Because it is a multiprocessing machine capable of meeting the welder’s varied demands, this type of equipment is ideal for modern locksmiths because it has state-of-the-art technology and provides a final service of proven quality.

Performance / Optimization

Performance, optimization and use of material
After analyzing the MIG / MAG process, we can conclude that the process has become increasingly widespread in industries due to the high deposition rates, the ease of training of the welder, the versatility of welding positions, and especially , due to the lower operating cost compared to the available alternatives. 

• High yield.
• Few interruptions in the process.
• Deposition rate higher than the process with coated electrodes.
• Optimization of the workforce.
• Full utilization of the wire.
• Weld in all positions
• Welds in various thicknesses.
• Allows automation.

Mig Welding torch and accessories

1. Welding torch and accessories
The welding torch has two specific functions. The first one is to guide the wire and the shielding gas to the area that will be welded. The second is to conduct the welding energy to the wire. They may be suitable for heavy duty work, with high currents, or for light services, which use low currents and can be made out of position. They can also be dried – in this case cooled by the gas protection itself – or cooled to water, straight or curved.

It has a copper contact tip that conducts the weld energy and the wire to the part, a nozzle, which directs the gas to the welded area and a conduit that carries the wire to the torch and the contact tip .

2. Feed motor 
The wire feeder combines the functions of wire feed motor and welding process control. It is he who pulls the wire from the spool and feeds the bow. It also supports the determined speed of the wire.

3. Power supply
The MIG / MAG welding process usually runs with reverse polarity (DC +), ie the part is the negative pole and the electrode or wire is the positive pole.

What you can weld

What you can weld and what you need to use
The MIG / MAG process, as we have said, is suitable for three types of materials: aluminum, carbon steel and stainless steel. And you need to follow different guidelines depending on which material to choose to work with.

The required power of your MIG / MAG welding machine is directly related to the thickness of the plate you intend to weld. 110 volt machines will usually be able to work with plates up to 3 millimeters. For thicker materials, the correct thing is to choose a 220 volt equipment, which can usually weld plates up to 6 millimeters.

As for amperage, a modern and advanced 200 A technology is capable of performing the same work as a 250 A and will cost less. Consider this suggestion. The shielding gas needs to be argon and the electrodes specific for aluminum.

Use wide nozzles – aluminum when heated expands more than steel and you will need to compensate for this expansion – use rollers that do not scrape material so as not to damage it and nonmetallic aligners to reduce friction.

Carbon steel
For welding steel, carbon dioxide (CO²) is an economical choice as a shielding gas and ensures greater penetration of the weld. The drawback is that this type of gas is very hot for thin metal sheets. In these cases, it is better to mix argon (75%) and CO² (25%) when the thickness is thin.

Welding Thin Materials

For welding thin materials, to close large openings and welds out of position, it is recommended to use short-circuit transfer. In thicker plates, aerosol transfer is indicated.
Both the “pulling” and the “pushing” welding technique can be used by the professional. “Pushing” tends to be the choice of many because it allows for better visibility of the weld joint and at the same time provides a smoother puddle.

Stainless steel
In the case of stainless steels, use the short-circuit transfer in the same recommendations made for carbon steel. The designation of protective gas is He (90%) + Ar (7.5%) and O² (2.5%) for welding with corrosion resistance, arc stability and good penetration of the solder both for mono- pass as to multi-pass. If you are working with mono-pass welds and do not require corrosion resistance, you can choose to mix Ar + CO² (25%).

For materials with a larger thickness, the aerosol transfer is the most appropriate considering the flat position for single pass and multipass. The Ar + O² (1%) blend ensures a good-looking weld bead. If necessary, you can increase the percentage of Chromium Oxide to 2%, but this may interfere with the appearance of the cord.

Normally, the welding technique chosen for the material is “pushing”, because with it a weld bead can be deposited as flatter.

Regardless of the material you intend to work with, remember that it is essential to use appropriate personal protective equipment (PPE) for welding work.

Now that you know more about MIG / MAG welding, are you ready to make your choice? And you already working with the process, share your experiences with us.