Welding arc is Description and characteristics

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

In order to successfully carry out the welding process, a welding arc is needed. This is an electrical discharge, which is characterized by a very high power and is quite long. It occurs between elements such as electrodes that are in a certain gaseous environment. For an arc to occur, voltage must be applied to the electrodes.

General description of the arc

The main distinguishing properties of the welding arc are a very high temperature, as well as current density. Thanks to these two qualities, in combination, the arc is able to melt metals with a melting point of 3000 degrees Celsius without any problems. We can say that this arc is a conductor, which consists of volatile substances, and the main purpose is the conversion of electrical energy into thermal energy. The electric charge itself is the moment the electric current passes through the gaseous medium.

Discharge varieties

A welding arc is a discharge, and since there are several types of it, there are also several types ofarches:

1. The first variety is called a glow discharge. This appearance only occurs in a low pressure environment, and is only used in things like plasma screens or fluorescent lamps.
2. The second type is the spark discharge. The occurrence of this type occurs at the moment when the pressure is approximately equal to atmospheric. It differs in that it has a rather intermittent shape. A striking example of such a discharge is lightning.
3. The welding arc is an arc discharge. It is this type that is most often used during welding. It occurs in the presence of atmospheric pressure, and its shape is continuous.
4. The last type is called crown. Most often occurs if the electrode surface is rough and uneven.

Nature of the arc

It is worth saying that the electric welding arc is not so complicated as it seems at first glance, it is quite simple to understand its nature. It uses an electric current that flows through an element such as a cathode. After that, it enters the environment with ionized gas. At this moment, a discharge occurs, which is characterized by bright light and very high temperature. In general, a welding arc can have a temperature ranging from 7,000 to 10,000 degrees Celsius. After passing through this stage, the current will pass to the material that is being welded. We can say that the source of the welding arc is an electric current that has undergone changes.

Due to such high temperatures, the arc will emit infraredand ultraviolet rays, which are harmful to human he alth. It is dangerous for human eyes, and can also leave a light burn. For the reasons above, all welders should have good personal protective equipment.

Arc structure

The structure (structure) of the welding arc includes three main components, or sections - the anode and cathode sections, as well as the arc column. It should be noted that during the burning of the welding arc, active spots or areas will form in the areas of the anode and cathode, which are characterized by the maximum temperature value. Through these two areas will pass all the electrical current that the power supply generates. At the same time, the largest voltage drop of the welding arc will also be recorded in these two areas. The arc column is located between these two zones, and such a parameter as voltage drop, in this case, will be minimal.

From the foregoing, we can conclude that, firstly, the power source of the welding arc can produce a fairly high voltage and high current. Secondly, the length of the arc will consist of the totality of those areas that were listed above. Most often, the length of such an arc is several millimeters, provided that the anode and cathode regions are respectively 10-4 and 10-5 cm. The most favorable length is an arc of 4-6 mm. It is with such indicators that it will be possible to achieve stable combustion and high temperatures.

Types of arc

The difference between the welding arc lies in the approach scheme, as well as in the environment in which it can occur. Currently, there are two most common types of arc:

• Arc of direct action. In this case, the welding machine must be parallel to the object to be welded. An electric arc will occur when the angle between the metal workpiece and the electrode is 90 degrees.
• The second main variety is an indirect type of welding arc. It occurs only if two electrodes are used, and they are located at an angle of 40-60 degrees with respect to the surface of the metal part. An arc will form between these two elements and weld the metal together.

Classification

It is worth noting that there is a classification of the arc depending on the atmosphere in which it will occur. To date, three types are known:

• The first type is an open arc. When welding this type, the arc will burn in the open air, and a small gas layer will form around it, which will include vapors of metal, electrodes and their coatings.
• Closed type. The burning of such a welding arc is characterized by the fact that it is carried out under a layer of flux.
• The last variety is the arc with gas supply. In this case, a substance such as helium, argon or carbon dioxide is supplied to it. Some other types of gases can also be used.

The main difference of the last type is thatthe supplied gases will prevent the phenomenon of metal oxidation during welding.

A slight difference is also observed in terms of the duration of such an arc. According to its characteristics, the welding arc can be stationary or pulsed. Stationary is used for continuous welding of metals, that is, it is continuous. Pulse arc type is a single impact on the metal, chiseled touch.

Working elements, that is, electrodes, can be carbon or tungsten. These electrodes are also called non-consumable. Metal elements can also be used, but they will melt in the same way as the workpiece. The most common type of electrode is steel when it comes to melting types. However, the use of non-melting species is becoming more and more popular today.

The moment of arc occurrence

The welding arc occurs at the moment when a fast circuit occurs. This happens when the electrode comes into contact with a metal workpiece. Due to the fact that the temperature is simply huge, the metal begins to melt, and a thin strip of molten metal appears between the electrode and the workpiece. When the electrode and the metal diverge, the latter evaporates almost instantly, since the current density is very high. Next, the gas is ionized, which is why the welding arc appears.

Arc conditions

Under standard conditions, that is, at an average temperature of 25 degrees and a pressure of 1atmosphere, the gas is not able to conduct electricity. The main requirement for the occurrence of an arc is the ionization of the gaseous medium between the electrodes. In other words, the gas must contain some charged particles, electrons or ions.

The second important condition that must be observed is the constant maintenance of the temperature at the cathode. The temperature required will depend on characteristics such as the nature of the cathode and its diameter and size. The ambient temperature will also play an important role. The welding arc must be stable and at the same time have a huge current strength, which will give a high temperature index (7 thousand degrees Celsius or more). If all conditions are met, then any material can be processed with the resulting arc. To ensure the presence of a constant and high temperature, it is necessary that the power supply function as stably as possible. It is for this reason that the power source is the most important part when choosing a welding machine.

Arc Features

There are several things that distinguish the welding arc from other electrical discharges.

The first is the huge current density, which can reach several thousand amperes per square centimeter. This gives a huge temperature during operation. The distribution of the electric field between the electrodes in their space is rather uneven. Near these elements, a strong voltage drop is observed, and towards the center, on the contrary, it greatly decreases. It is impossible not to say about the dependence of temperature on the length of the column. The longer the length, the worse the heating,and vice versa. Using welding arcs, you can get a very different current-voltage characteristic (CVC).

Welding inverter. The arc and its features

It's worth starting right away with the main difference between an inverter power source and a conventional, transformer one. The consumption of electrical energy has been reduced by almost half. The characteristic of the current that occurs when using the inverter allows for faster ignition of the arc, and also ensures stable burning throughout the entire process.

By itself, a welding inverter is a rather complex device that performs operations to change the current to ensure the most stable operation of the arc. For example, the device is connected to the network and receives an alternating current as input, which it is able to convert to direct current. Next, the direct current enters the inverter block, where it is again converted to alternating current, but at a much higher frequency than it was in the network. This current is transferred to the transformer, where its voltage is significantly reduced, which increases its strength. After that, the rectified and tuned alternating current is transferred to the rectifier, where it is converted to direct current and supplied for operation.