Small guide for operators and enthusiasts on the different working methods of modern welding systems made with IGBT inverter technology.
Welding technology has made steady progress over the years, and especially during the period of the Second World War when the American military industry was looking for a method that would allow the construction of aircraft with a lighter and more resistant cell.
The new welding methods could not always be applied, however, and before reaching the current point it was necessary to wait for other branches of technological development to reach an adequate level to allow their application; as in the case of Inverter technology, introduced only from the 80s.
The inverter models
The inverter is nothing more than an electronic input and output device, capable of converting the current from alternating to direct and vice versa, depending on the type of device on which it is mounted, all thanks to a special insulated gate bipolar transistor, known by the acronym IGBT, which allows to switch high voltages and high currents.
Since the welds require direct current, but that the power supply networks only supply alternating current, the first welding systems had to necessarily integrate a current transformer into their structure.
The old welders, therefore, were much bulkier and heavier, and posed a serious problem especially when they had to be transported. The new inverters, on the other hand, instead of the transformer use the electronic device of the same name, which is far smaller and lighter.
Consequently, the inverter welder offers the advantage of being more compact and lighter than the traditional one, and it is much more manageable to use, practical and also easy to transport; moreover, apart from the improved structural features, this type of welding machine also has the advantage of having a high versatility of use, as it is capable of performing any type of arc welding, from traditional electrode to wire welding continuous with or without gas and with or without filler material.
The electrode method is one of the most used, as it is particularly suitable for welding thicknesses of a few millimeters. The electrode welding must be done by connecting the cable with the earth clamp to a part of the piece to be welded and, subsequently, placing the electrode close to close the circuit and trigger the arc. This method is used for the production of wrought iron products, bodywork for electrical appliances or other devices, construction of mechanical parts, and so on, as well as for maintenance, repair, or renovation, which is why it is very widespread both in the professional and hobby level.
By varying the type of electrodes it is possible to weld different types of metal alloys, from copper to aluminum, steels, and cast iron; the limitation, however, is always given by the maximum thickness of the pieces to be welded, which is limited to a few millimeters. The positive side, however, lies in the ease of execution; in fact, electrode welding does not require particular skills and therefore can also be performed by non-professional operators.
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The discourse changes considerably when it comes to the continuous wire welding method also known as TIG, to differentiate it from the MIG and MAG welds which, although based on the same principle, can also be made by the electrode. The acronym TIG stands for Tungsten Inert Gas, and precisely indicates a type of welding with tungsten-coated wire and protection gas supply.
This method requires higher temperatures and therefore is able to weld pieces of metal with a higher thickness, wire welding is also more robust than electrode welding, but it is much more complex and difficult to perform. The welding bath, in fact, must be protected by a gas jacket, in order to prevent oxygen and any slag from coming into contact with it and contaminating the molten metal; the solidity and integrity of the weld, in fact, depend on the absolute lack of intrusions or oxidations inside or on the surface of the bead.
In place of the electrode, then, a wire is used that can be coated or not with different materials, depending on the alloys to be welded; the wire is extruded continuously through the torch, and the movements with the other hand must be coordinated quickly and quickly, which must bring the pipes or the inert gas emitter to be poured onto the welding bath.
Even the gasless welds are completely similar to those with gas, only that they are defined in this way because the latter, instead of being made from the outside, is produced directly by the arc at the exact moment when it goes to burn the electrode coating; the gas released from combustion then saturates the area of the weld pool, protecting it from slag and oxides.
For example, MIG, MAG, and WIG welds exploit this principle in that they use electrodes coated with tungsten or wolfram, instead of those with basic or rutile coating used in the traditional electrode welds.
Continuous wire inverter welders, of course, are more expensive than electrode ones, require greater dexterity, skill, and experience to ensure the best performance, and also greater installation power since wire welding requires a higher amperage. compared to electrode welds.
For these reasons, continuous wire welders, even though they are also produced for the hobby user sector, are still not very widespread in this specific market segment.
The inverter welding machines currently on the market, however, differ not only in the price and the intended use but also in the types of welding they can perform; the basic models only allow manual MMA electrode welding, then there are some models capable of welding both with traditional basic and rutile MMA electrodes and with tungsten and wolfram electrodes for MIG-MAG-WIG electrode welding.
The best inverter welder, on the other hand, remains the professional one because it is able to cover the entire range of possible arc welding methods, both electrode and continuous wire ones and relative variants; this type of welding machine, however, is characterized by a fairly high price and is intended exclusively for professional welders.