Welding technologies

 

Welding technologies

Content:

• Thermal connection of parts
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• The main types of welding
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• Arc welding
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• Gas welding
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• Semi-automatic welding
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• Automatic welding
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• TIG welding
• Electroslag welding
• Electron beam welding
• Diffusion welding
• Contact welding
• Welding technical process

Novice craftsmen often ask the question - what is best welding? The answer will be unexpected - welding is the art of creating a strong and reliable connection of metal products. The word " art " is not accidental here. Welding also has a definition in scientific language - the formation of a seam at the inter atomic level with strong heating of the connected parts.

The theory of welding is very extensive and includes, among other things, various welding technologies. Only professionals with many years of experience know everything about welding, but even beginners in this business need to know at least the basics of welding work.

Thermal connection of parts

You can learn everything about metal welding at special courses for welders. However, novice craftsmen should first determine the very concept of welding, the theory and the main thing about it. To start studying these basics, it is necessary to understand, first of all, what is called welding and how welding occurs.

Metal parts can be connected to each other mechanically without using their heating. In contrast to the mechanical connection, with the thermal method, the parts are heated to their melting point. Therefore, the definition of "what is welding" implies exactly this method of forming joints that differ in strength and reliability. Welding is the process of obtaining an integral connection of elements by means of their strong heating.

There are many different types of welding, the equipment used in this process, the technologies and control methods used. Welding theory says that welding refers to high-temperature processes. This is ensured by the formation of a welded arc, which contributes to the melting of the metal elements being connected.

The main types of welding

There are various welding methods available. Welding methods and types of welded joints need to be known in order to choose the right equipment, consumables and set the necessary modes. Types of welding and their brief description should be the knowledge that will allow you to get a high-quality, beautiful and durable seam as a result. Each method has its own nuances, advantages and disadvantages.

In welding, heating or pressure can be used, as well as a combination of them. In accordance with this, the types of welding and their characteristics are divided into two large groups - melting and pressure.

The welding technology consists in the formation of an interatomic bond between metal products and the resulting strong permanent connection. The first stage of the process consists in the closest approximation of the welded elements to each other.

However, at this stage, sufficient mutual penetration of atoms is impossible. This is due to the fact that even significant efforts will not help at normal temperatures. This will be prevented by the hardness of the material, as well as the fact that even with the best processing, contact between the parts will not occur over the entire surface, but only at several points. In addition, the remnants of dirt, oxides, and fat films on the surfaces will prevent a strong connection.

A strong physical contact will be possible only as a result of the application of strong pressure or by melting the edges of the metal parts being connected. At the same time, the gap between the connected parts disappears, and they begin to represent a single whole.

Types of classification of welding methods involve melting welding without pressure, thermomechanical welding using thermal energy and pressure, and pressure welding. A common method is the melting of the connected elements.

• Methods of welding metals:
• Manual electric arc.
• Gas.
• Semi-automatic.
• Automatic.
• TIG welding.
• Electron-beam.
• Electroslag.
• Plasma.
• Diffusive.
• Contact electrical.
• Butt contact.
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• Suture contact.
• Point contact.
• Point condensate.

The electrodes used in this case are melting and non-melting. A brief description of the main types of welding will help you choose the most suitable method for a particular process. All types of welding work involve the use of suitable equipment for them.

Welding of different metals also has its own features. For example, the difficulty in welding carbon steels is to harden the area near the seam, and the formation of numerous cracks. Therefore, when welding products made of such materials, it is recommended to preheat the parts to a temperature of 100-300 degrees, apply a multilayer seam, use coated electrodes, after the end of the process, the resulting product is released to a temperature of 300 degrees.

The difficulty in welding ferrite steels with a high chromium content is that during cooling there is a danger of precipitation of chromium carbide grains, which reduces the resistance to corrosion. To prevent this phenomenon, a current of a small value should be set so that a more significant cooling rate can be provided. Also, to equalize the amount of chromium in the grains and at the boundaries, annealing can be carried out after the end of welding.

Welding of cast-iron products is carried out with cast-iron electrodes with preheating of the parts. The diameter of cast-iron electrodes is selected in the range of 8-25 millimeters.

The weldability of copper is reduced by impurities of oxygen, hydrogen and lead. The use of gas welding is effective. If arc welding is used, then the electrodes are chosen carbon or metal. The presence of oxides prevents the welding of aluminum parts. The use of fluxes helps to dissolve them.

Arc welding

Types of fusion welding can be started with MMA, as manual arc welding is called. It can deservedly be attributed to the leader of popular popularity. Such a metal welding process can be carried out using an inverter or transformer. In both cases, the use of electrodes is necessary. This method is simple and inexpensive.

The source of heat is an electric arc formed between the electrodes, one of which is a consumable material, and the other is the elements being welded. Such an arc is a powerful discharge in a gas environment.

The coating of the electrode can be compared to a "frozen" gas cloud. At the beginning of the metal melting, the electrode coating also begins to melt. The released gas cloud provides protection against the penetration of oxygen into the place of formation of the weld, and provides a conductive ionized medium for the arc. This phenomenon significantly reduces the risk of porosity formation.

Advantages of MMA:

Versatility. With the help of this technology, it is possible to weld products made of almost all types of metal.

It is possible to weld parts in this way at any spatial position of the product. This includes limited spaces, which is not possible for other methods.

The technology of metal welding by the MMA method allows this to be carried out under various adverse environmental conditions.

The ease of use and inexpensive cost make it possible to use this method not only in industrial, but also at home.

The disadvantages include low productivity, the presence of at least a little experience, a rather complex process of igniting the arc with the risk of sticking the electrode, causing harm to health when the coating of some types of electrodes evaporates.

The use of modern equipment that has functions against the appearance of such an effect will help to avoid sticking of the electrode. The equipment for arc welding is divided into transformers and inverters, which have undeniable advantages and greatly facilitate the process of electric welding.

Transformers, which have held the championship for a long time, are now considered outdated equipment, heavy and having large dimensions. It is possible to weld metal parts with their help only on alternating current.

The way out of this situation is the use of welding rectifiers. Their function is to convert alternating current to direct current. This gives a significant advantage, since when using direct current, the seams are of higher quality, smooth, strong and neat. However, rectifiers also have a large mass and large dimensions, besides, professional skills are necessary when using them.

Inverters, which are modern equipment, are the most optimal choice for the implementation of the process. This can be recommended even for beginners, since it is not difficult to understand the principles of working with them. The rectifier is built into the inverter device, so no additional equipment is required. The available functions will help to avoid sticking of the electrodes and help to quickly ignite the arc. Inverters are so light in weight and small in size that they can easily be carried in your hands.

The electrodes should be selected according to such parameters as their diameter and the composition of the metal inside. The choice of the type of metal is important, because during the welding process, it melts, and it flows drop by drop into the total mass and is fused with it. The uniformity of the metals of the parts and the electrode serves as a guarantee of a strong connection and obtaining a uniform seam.

It is not difficult to make the right choice when buying electrodes, since the packaging usually indicates for which types of metals these consumables are suitable. When buying, it is also necessary to determine the thickness of these consumables. This directly depends on the thickness of the products being welded.

It is important to acquire skills when lighting an arc. You can choose to use the touch or swipe methods. When touching, the electrode comes into rapid contact with the surface of the product and then it is withdrawn for a short distance. Continue to do such tapping with the electrode on the surface until an arc appears. Striking an electrode on the surface according to the type of match ignition is more preferable, but it is inconvenient in hard-to-reach places. The skills of fast arc ignition come with experience.

After the arc is ignited, it is important to maintain the stability of its gorenje. To do this, the electrode must be kept at a constant distance from the surface, equal to approximately two millimeters. As the electrode burns, do not forget to lower it. If you hold the electrode too close to the surface of the product, it can stick to it, and if it is far away, there is a danger that the lit arc will go out.

The basics of welding with an electrode say that it is better to warm up the metal with circular movements so that the so-called welding bath has time to form. To make the seam smooth, after heating the electrode should not be carried out too slowly, but also not particularly fast, in order to avoid the appearance of defects.

Gas welding

Welding methods include such a common method of joining products as gas-melting. The essence of gas welding is that the edges of the parts at their junctions are heated to the desired temperature using a burner included in the equipment used.

Knowledge of all about welding involves the study of this time-tested method of joining metals. Gas welding is not difficult to perform, the equipment for it is not particularly expensive, electric energy is consumed a little, which is an undeniable advantage.

A relative disadvantage is the low heating rate of the metal, which is further reduced if thick parts have to be welded. Therefore, it is recommended to use it when welding metal sheets with a thickness of no more than six millimeters. There may also be such an unpleasant drawback as warping. Almost all types of metals can be welded using the gas method.

Unlike arc welding, electrodes are not used here. In their role, the filler wire acts, and the burner serves as a heating source. Passing into a liquid state, the metal forms a welding bath, which in the future will be protected by a gas environment that displaces air. The molten metal cools slowly and hardens.

A high-temperature flame is formed when a mixture of acetylene and oxygen is burned. Such a mixture performs the functions of an oxidizer. Instead of acetylene, you can use its substitutes, for example, methane or propane-butane, but it should be borne in mind that this will lower the combustion temperature, so such a replacement is mainly carried out when cutting metals or when welding metals with a low melting point, such as copper, brass, bronze. Gorenje The highest gorenje temperature is provided by acetylene.