Arc Welding-All We Need To Know

When it was developed, what it consists of, what equipment it requires, and for which applications it is preferable to use this welding method.

Ever since humanity started working with metals, he also began to develop different welding techniques. During the Middle Ages, the traditional welding method consisted of heating the pieces of metal to be joined, making them incandescent until yellow-white heat, then subjecting them to hammering and melting them together. It is evident, however, that this technique, being rudimentary, required a long time and great physical effort on the part of blacksmiths to ensure good results, and the homogeneity of the welding was not guaranteed despite the efforts made.

At the beginning of the twentieth century, it was possible to improve the quality and above all, the homogeneity of the welds, thanks to the introduction of a technique based on the combustion of acetylene and oxygen, and precisely for this defined oxyacetylene. It was only in 1925 that, thanks to the development of high-power electric generators, the resistance welding process, more commonly known as arc welding, was finally developed as it exploits the physical principle of the voltaic arc resulting from the combination of two electrodes.

 

How the arc welding process takes place

In arc welding, therefore, the metal is melted thanks to the high temperature generated by the voltaic arc. This is produced by bringing the pieces to be welded, to which the negative electrode is connected, and the metal rod, which, compared to the clamp of the positive pole, in turn, acts as an electrode.

When the tip of the positive electrode comes into contact with the pieces to be welded, the voltaic arc which merges both the pieces and the electrode, which supplies the welding material.

Immediately after the Second World War, the arc welding process underwent further changes and was refined to produce superior quality welds, with increased strength and homogeneity. This gradually passed first from the bare electrode to the coated one, and then to the submerged arc procedure and the MIG and MAG methods.

The substantial difference between the different methodologies lies in the degree of preservation of the weld pool, which is of the molten metal from the passage of the arc. During electrode welding, the welding bath is exposed both to the waste produced by the process and to the oxygen present in the air, which tends to oxidize the molten metal quickly. With the introduction of the coated electrodes, it was possible to reduce the problem of oxidation, since the coating material, burning, releases a gas that creates an insulating hood between the surface of the welding bath and the surrounding air.

Submerged arc welding and with the coated electrode, therefore, and in this case, the MIG, MAG, and TIG methods produce better quality weldings as regards oxidation resistance. However, they remain subject to the intrusion of the slag, which compromises the structural integrity of the weld, and to other problems due to the lack of experience in handling the clamp with the electrode or the torch with the continuous wire.

 

Arc welding systems

The current required to generate a hot arc to the point of melting the metal is many, which is why this type of welding has been introduced only relatively recently. The first welding machines were very bulky precisely because of the size and weight of the generator, and especially the current transformer. The welding process requires direct current, while the electrical network supplies alternating current.

The old generation welding systems were therefore heavy and bulky due to the transformer needed to supply direct current; thanks to the introduction of inverter technology, however, a new generation of welders with compact dimensions and low weight has appeared, capable of performing MIG, MAG, WIG and TIG arc welding, both electrode and continuous wire.

Consequently, the one based on inverter technology is the best welding machine among all those currently in use, as it allows to weld almost any type of metal alloy, including aluminum, and to make joints of the highest quality as regards sealing. Over time, corrosion resistance, and solidity. It is also compact, relatively light, and easily transportable, all features that have made it very popular with professional welders and hobbyists alike.

 

The various applications and difficulties of the method

Arc welding, therefore, given its peculiar characteristics, is used primarily in the civil industry for the creation of large mechanical machinery or metal structures, in the aerospace industry for the manufacture of rockets and various types of aircraft, in the naval industry and so on.

In the professional field, arc welding is widely used in construction, carpentry, mechanics, and, more generally, in iron working, both in large workshops and specialized laboratories and in the craft and micro-enterprise sector. In the hobby field, on the other hand, arc welders are used by DIY, and DIY enthusiasts, especially by those who love to carry out home maintenance works personally, and by fans of cars and motorcycles.

Although arc welding is also practiced in the hobby field, however, it is still a far more complicated method than oxyacetylene welding and electrode welding. Coated electrode and continuous wire welding, especially those with gas, require an excellent manual and coordination ability, which is why only the most expert can obtain the best results from their welding systems.

This is why less experienced welders and hobby and DIY enthusiasts still prefer arc welders such as the bare electrode one, for example, which is less versatile as regards the different possible welds. Yet, on the other hand, it is far easier to use.

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