Electric arc welding is the most common method for inseparable joining of metal parts in various structures, for the restoration of broken or worn parts. Long gone are the days when the pride of the small workshop was the self-made welding transformer, and the retail network did not sell coated welding electrodes at all. And yet, on private construction sites and various workshops outside the state sector, there was massive welding. The supply system had been well worked out for decades and, in general, functioned at the then antediluvian level of technology.

Now on the mass market in our country, not only the most diverse brands and functional characteristics of welding transformers operating with alternating current are sold, but for several years on the stands and in non-specialized stores you can see several models of MIG/MAG welding machines with a body feed device at completely affordable prices for home use. Among the more advanced home craftsmen, the opinion already prevails that whoever has worked with such a device would no longer reach for an ordinary electric generator. In the craft and professional sectors, new welding devices have entered to such an extent that they have completely changed the welding technologies until recently. For example, you will rarely find a workshop using the classic acetylene-oxygen (oxygen) welding, while almost every auto body shop has a body-feeding welding machine. Thanks to new methods and techniques, welding of stainless steel, aluminum and other non-ferrous metals has become a common activity.

As it often happens, this time too, the new technology significantly outstrips the information on its use, and it will be difficult to find a specialist who can advise you in an understandable language, which welding machine is most suitable for your specific applications.

That's why we turned to Mr. Minko Zlatanov, head of the "Welding Technology" department of the company "Kirov" JSC. She is the exclusive representative for Bulgaria of the Austrian company Fronius GmbH - one of the largest manufacturers of welding equipment in the world.

There are several methods of welding metal products:

◊ Manual arc welding with coated electrodes

◊ MIG/MAG (metal inert gas/metal active gas)

◊ TIG (tungsten inert gas)

◊ Electrically resistive

◊ Subflux

◊ Gas flame

◊ Condenser

◊ Plasma

◊ Laser

◊ Electron beam welding


These are just some of the different welding methods. We will consider in more detail only the first three, which are the most widely used, starting with purely domestic applications, passing through auto body shops and auto repair shops, through all kinds of workshops for the manufacture of metal structures and maintenance of agricultural machinery, companies for installing pipelines and pipe installations etc. The main user of welding equipment is, of course, the industry: machine building, shipbuilding, boiler building, construction, oil, gas and water pipelines, the chemical, pharmaceutical, oil, food industry, aircraft building, nuclear energy, etc.

The choice of the most suitable welding method and, accordingly, the technique required for this depends on a number of conditions:

◊ Type, chemical composition and physical-mechanical properties of the metals to be welded

◊ Serialization and production conditions

◊ The requirements for cleanliness and smoothness of the weld

◊ The requirements for automation of the production process

◊ Economic efficiency in terms of cost of consumables, energy and labor costs, etc.

Welding (ROW) with coated electrodes

In mass practice, this is still the most commonly used method for welding steel parts. In it, the welding arc burns between a fusible metal electrode and the welded product. The electrode consists of:

◊ Core – a metal rod with the most commonly used diameters from 2 to 6 mm, and for home applications 2.5 and 3.2 mm.

◊ A coating that is concentrically applied to the metal rod. In principle, the chemical composition of the electrode wire should correspond to the composition of the metal being welded. However, this cannot be followed exactly, as different coatings change the chemical composition of the metal. In addition, the coating is easily moistened by the moisture contained in the air, and moistened electrodes have difficulty igniting the arc and it burns unstable. Therefore, you should always work with completely dry electrodes.

The advantage of this welding method is that it is the easiest to implement in terms of equipment. In the simplest version, only a welding transformer and electrodes are needed, and there is no need to use shielding gases. The most significant disadvantages of welding with electrodes is the very high probability of impurities remaining in the welded part, as well as the impossibility of welding thin products.

It is significantly better welded with direct current, as with rutile electrodes the handle is connected to the negative pole, and when working with basic electrodes - to the positive. Rutile-coated electrodes "ignite" more easily, burn more evenly and produce a smooth and uniform weld. With them, the slag is removed more easily.

Welding with coated electrodes is used in:

◊ Welding at home

◊ Field welding

◊ Connecting pipelines

◊ Construction of metal structures

◊ Repair activities

◊ Welding and welding of hard alloy and wear-resistant parts, etc.

◊ underwater accident.

Welding MIG/MAG

In MIG/MAG welding, the welding arc burns between a fusible metal electrode and the welded product in a protective gas environment: carbon dioxide, argon or a gas mixture. The metal electrode is wound on a roll of wire with a diameter of 0.6 to 3.2 mm. Large diameters, from 1.6 mm upwards, are mainly used for welding worn parts. The wire can have a different chemical composition and is selected according to the parts to be welded. In addition, it can be solid or tube-flux. The wire is pushed out from the wire feeder through a hose with a maximum length of 4.5 m and thus reaches the workpiece to be welded.

Welding with MIG/MAG devices has a number of significant advantages over welding with electrodes and is therefore preferable in many cases, including in the home or craft workshop.It is not by chance that in specialized sources of information, this method is unanimously defined as the most universal and most widespread throughout the world. In the first place, we would put its application in almost all welding conditions. With a MIG/MAG device, for example, vertical and ceiling welds are made much more easily and qualitatively, including by a non-specialist, and in general, welding technology is learned very quickly and easily. Next, we would place the completely clean, impurity-free weld seam, where the slag known from electrode welds is completely absent. In addition to making the seam smooth and even, without cavities or slag residue, MIG/MAG welding is the most productive method of all others. It also lacks the annoying, and often times also causing vision damage due to solid particles falling into the eyes when working without protective transparent glasses hammering of the slag. An irreplaceable advantage of MIG/MAG welding is the possibility of welding, including spot welding, of sheets with a thickness of more than 0.6 mm, as well as of details of miniature dimensions. Anyone familiar with electrode welding would be amazed at how easy it is to weld thin sheet metal and most importantly with minimal burnout. This explains the wide application of MIG/MAG welding in car body repairs. Another very important advantage is the minimal overall heating of the workpiece in and around the weld zone. This means that the otherwise inevitable thermal deformations during MIG/MAG welding are limited to a minimum – another prerequisite for successful sheet metal welding.

In MIG/MAG welding, the electric arc burns between the metal wire and the workpiece in a shielding gas environment of carbon dioxide, argon, or a mixture of gases. The current strength is most often adjusted stepwise with a switch, and the feed rate of bodies is smoothly adjusted depending on the thickness of the welded parts and the strength of the current. In fact, this is the only thing that one needs to learn through practice, and this is where the skill of working with the welding machine mainly lies.

Another major advantage of MIG/MAG welding is the ability to weld a wide range of metals. Carbon dioxide is mainly used for ordinary, low- and high-alloy steels, and argon is used for welding aluminum, copper and its alloys. For these materials, the limit for welding with MIG/MAG devices is that the minimum thickness is 2 mm. For welding thinner products, it is recommended to use devices with pulsed current supply and especially TIG welding devices.

To the advantages of MIG/MAG welding from the point of view of economic expediency outside strictly professional areas of application, we must add their relatively low price, which for lower class devices is no higher than 2-3 times the price of an average good electric

The only disadvantage of this method occurs when welding outdoors, because wind and moisture reduce the protective effect of the gas. Therefore, work must be done on a covenant or indoors.

We do not specifically indicate areas of application, because MIG/MAG welding can be successfully used practically everywhere - from the home workshop and car repair shops to machine building, chemical industry, pipeline construction, etc.

TIG welding

This method now completely falls into the professional sphere of application. In it, the welding arc burns between a non-fusible tungsten electrode and the welded product in a protective inert gas environment (argon or helium). Welding can be done with or without filler material, depending on the configuration of the workpiece to be welded or the technological requirements. The additional material is fed manually or with a special body feeding device with a lower feeding speed, compared to MIG/MAG devices. Here too, the principle that the filler material has the same chemical composition as the welded part applies, but there are exceptions when welding some non-ferrous metals, for example copper to CrNi.

The advantage of this welding method is that it allows the welding of both very thin materials (0.6 mm) and massive parts, for example, the restoration of cracked blocks and heads of car engines. TIG devices can be used to weld ordinary and alloyed steels, aluminum, magnesium alloys, copper and copper alloys, gray cast iron, nickel, titanium, etc.

Dissimilar metals can also be welded to each other using this method. TIG welding is also used in automated and robotic systems.

However, the main applications are the welding of thin and medium-thick workpieces, as well as welding by lamination of the seam on workpieces of great thickness. When welding steel, direct current welding is recommended, with the tungsten electrode connected to the negative, which teaches a deeper burn and melting of the metal. When welding aluminum and aluminum alloys, alternating current is used, which results in an additional effect of self-cleaning of the molten metal under the influence of electric current. The VIG method is used in:

◊ Manufacturing of machines and equipment for the food industry

◊ Construction and repair of CrNi installations in the pharmaceutical and chemical industry

◊ The automotive industry and the auto service business

◊ Aluminum welding

◊ The manufacture of tanks and pressure vessels

◊ Construction of pipelines