What is welding arc voltage - Metals and their processing

Welding arc: everything you wanted to know

For more than half a century, welding has been one of the most important crafts for humans. Thanks to the welding machine, spaceships are built, factories operate, and for many craftsmen, welding has turned into a hobby. But even the most technologically advanced welding machine will not bring the desired result without a stable welding electric arc and its quality characteristics.

The electric welding arc allows you to reliably weld even the most complex metal structures. To obtain high-quality welds, you need to take into account all its characteristics, know the features and structure of the arc. Additionally, it is important to consider the temperature and arc voltage when manual arc welding. From this article you will learn what a welding arc is and the essence of the processes occurring in it, and learn to apply the acquired knowledge in practice.

Welding arc: definition

So, what is a welding arc and what are its characteristics? Electrodes energized in a mixture of gases and vapors form a powerful discharge. What is an electrical discharge? A discharge is the result of an electric current passing through a gas. Well, the result of the whole process is generally called a welding arc.

The welding arc and its properties are characterized by high temperature and current density, so the arc is capable of melting almost any metal. In simpler terms, the welding arc is an excellent conductor that converts the received electrical energy into thermal energy. Due to this thermal energy, the metal melts.

The essence and structure of the arc

The essence of the welding arc is extremely simple. Let's divide the process into several points:

First, an electric current passes through the cathode and anode region and penetrates into the gaseous environment. An electrical discharge with a strong glow is formed.
An arc is formed. The temperature of the welding arc can reach up to 10 thousand degrees Celsius, and this is enough to melt almost any material.
Then the current from the arc passes to the metal being welded. That's all its characteristics.

The glow and temperature of the discharge are so strong that they can cause burns and deprive the welder of his vision. Therefore, craftsmen use welding masks, protective gloves and a suit. Never weld without proper protection.

The structure of the welding arc is shown in the picture below.

During arc burning, spots are formed in the area of the cathode and anode where the temperature reaches its limit. It is through the anode and cathode areas that electric current passes, and in these areas the voltage drops significantly, but on the column the voltage of the welding arc is maintained, since the column is located between the anode and the cathode.

Many beginners ask how to measure arc length. Just look at the cathode and anode areas, as well as the welding column. Their combination is called a long welding arc. The average length is 5 millimeters. In this case, the temperature of the resulting thermal energy is optimal and allows most welding work to be performed.

Now that we have learned what a welding arc is, let's turn to the varieties.

Types of welding arc

The welding arc and its characteristics may differ in the direct and indirect action of the welding current, as well as in the atmosphere in which they are formed.

Let's look at this topic in more detail. The direct action of the welding arc is characterized by a special direction of the current.

The electrode is positioned almost parallel to the surface to be welded and the arc is formed at an angle of 90 degrees. The electric welding arc and its characteristics can also be of indirect action. It can only be formed using two electrodes located at an angle above the surface of the part being welded. Here a welding arc also occurs and the metal melts.

As we wrote above, welding arcs are also divided according to the atmosphere in which they are formed. Here is their brief classification:

Open environment. In an open environment (atmosphere), an arc is formed by oxygen from the air. A gas is formed around it, containing vapors of the metal being welded, the selected electrode and its coating. This is the most common medium used in arc welding.
Closed environment. In a closed environment, the arc burns under a thick layer of protective flux and a gas is also formed, but containing not only metal and electrode vapors, but also flux vapors.
Gas environment. The arc is ignited and one of the types of compressed gas is supplied (it can be helium or hydrogen). An additional supply of compressed gas also protects the parts being welded from oxidation; the gases form a neutral environment. Here, as in other cases, a gas is formed, which contains vapors of the metal, electrode and compressed gas, which the welder additionally supplies during the burning of the arc.

Welding arcs can also be stationary or pulsed. Stationary ones are used for long, painstaking work without the need to frequently move the arc. And pulse is used for fast one-time work.

Also, the welding arc and its characteristics can be indirectly classified according to the type of electrode used in the work (for example, carbon or tungsten, consumable and non-consumable). Experienced welders most often use a non-consumable electrode to better control the quality of the resulting welded joint. As you can see, the welding process with a simple welding arc can have many features, and they need to be taken into account in your work.

Under what conditions does an arc burn?

In an ordinary workshop or in your garage, the average temperature is 20 degrees Celsius, and the pressure does not exceed one atmosphere. Under such conditions, the gas is practically unable to conduct electric current and thereby form an arc. To solve this problem, you need to add ions to the resulting gases. This is what professional craftsmen call ionization.

Also in the cathode region it is necessary to constantly maintain a constant temperature. This is necessary for the arc to occur and maintain combustion. But since it is in the area of the cathode and anode that the temperature can drop faster, many beginners have a lot of problems.

In addition, the temperature of the cathode region can vary greatly depending on the temperature in the room where the welding process takes place. Problems can be avoided if you monitor the health of the power source and the stability of the electricity supply (a particularly important point for home welders with unstable voltage in the household electrical network).

All this has a great influence on the properties of the welding arc and the essence of the processes occurring in it.

Arc Features

The welding arc and its characteristics have a number of features that need to be taken into account in your work:

As we have said many times, the arc has a very high temperature. It is achieved due to the high density of electric current (density can reach thousands of amperes per square centimeter). For this reason, it is important to set up the machine correctly and be careful when welding thin metals.
The electric field is unevenly distributed between the electrodes if two of them are used. At the same time, the voltage in the welding column practically does not change, but in the cathode region this voltage decreases noticeably, which can lead to deterioration in the quality of the weld.
In the welding column, in turn, the highest temperature is observed, which cannot be said about other parts of the arc. Keep in mind that if you need to increase the arc length, you will likely lose some of that temperature. This indicator is especially important when welding metals with a high melting point.

You can also adjust the voltage drop of the welding arc by selecting the current density. The higher the current density, the more likely it is that the welding arc voltage will drop. But there are cases when the voltage of the welding arc increases due to increasing current. To control this process you will need some experience. Don't be afraid to experiment if your job allows you. These were the main properties of the welding arc that you should pay attention to.

Instead of a conclusion

Now you know everything about the welding arc and its properties, and you also know its characteristics. Experienced welders can share in the comments their understanding of what a welding arc is and the essence of the processes occurring in it. This will be especially useful for beginner welders.

Briefly summarized, a welding arc consists of a welding column, anode and cathode regions. It is in these areas that the current passes. As a result, an electrical discharge is formed.

An arc is formed and converts the resulting current into heat, the temperature can reach 10 thousand degrees Celsius!
The arc itself can be ignited using two methods: striking and tapping.

Beginners prefer the tapping method, but we recommend mastering the scratching method as it will improve your proficiency and prevent electrodes from sticking. Good luck!

Source: https://svarkaed.ru/svarka/poleznaya-informatsiya/svarochnaya-duga-vse-chto-vy-hoteli-znat.html

What is the most correct definition of a welding arc?

· 09.09.2019

Does arc voltage depend on welding current? — Metals, equipment, instructions

The conditions for ignition and burning of the arc depend on the type of current, polarity, chemical composition of the electrodes, gas gap and its length.

Ignition and burning of the arc proceed better with direct current.

The no-load voltage supplied to the electrodes, taking into account labor safety during welding, does not exceed 80 V on alternating current and 90 V on direct current. Typically, the arc ignition voltage is 1.2-2.5 times greater than the arc voltage on alternating current, and 1.2-1.4 times greater on direct current.

To ignite an arc, a higher voltage is required than for burning an arc.

First condition

The arc is ignited by heating the end of the electrode (cathode).

When the electrode comes into contact with the workpiece, a closed welding circuit is created, the end of the cathode electrode heats up due to the release of heat when current passes through a contact that has high electrical resistance, and when the electrode is separated from the workpiece at a distance of 1 mm (or slightly more), the arc is ignited.

At the moment the electrode is separated from the product, thermionic emission begins from the cathode heated by the short circuit. The electron current ionizes the gases and metal vapors located in the interelectrode gap, and from this moment electron and ion currents appear in the arc.

Maintaining continuous arc burning will be carried out if the energy influx into the arc exceeds losses in it due to radiation, convection, dissociation, electromagnetic losses, etc.

In the event of short circuits by drops of electrode material formed at the end of the melting electrode and transferred to the workpiece, re-ignition of the arc occurs spontaneously if the cathode temperature remains high enough. This temperature depends on the composition of the cathode material, the current density in it, etc.

Thus, the first condition for ignition and burning of the arc is the presence of a special electrical power source for the arc, which allows the cathode to be quickly heated to the required temperature.

Second condition

The second condition for the ignition and burning of an arc is the presence of ionization in the arc column. A consumable arc is essentially an arc in metal vapor rather than gas. This occurs because the ionization potential of metal vapors is significantly lower than that of gases; for example, the ionization potentials of the gases He, F, Ar, H2, N2, CO2, O2 are respectively 24.5 - 12.5, and for the metals Fe, Al, Na, K - 7.83-4.32 eV.

The burning arc can be stretched to a certain length, after which it goes out. The higher the degree of ionization, the longer the arc will be.

The length of the arc burning without breaking characterizes the stability of the arc.

Arc stability

The stability of the arc depends on a number of its characteristics, for example, on the temperature of the cathode, its thermionic ability, the degree of ionization of the atmosphere, etc.

The stability of the arc increases with the increase in its atmosphere of elements with low ionization potential, such as potassium, sodium, etc.

Stable arcs are installed in gases with relatively low thermal conductivity (argon, krypton), and in gases with relatively high thermal conductivity (helium, hydrogen, nitrogen), increased arc voltage is required for stable combustion. In the latter case, welding is performed with a shorter arc using a non-consumable electrode.

Third condition

The third condition for welding with alternating current is the presence of reactance (increased inductance) in the welding circuit, which increases the stability of the arc. In an AC welding circuit that has only ohmic resistance, breaks occur when the arc burns (100 breaks per second at an alternating current frequency of 50 Hz).

When the reactance is included in the AC welding circuit, there are no breaks in the arc.

Electrical inductance is included not only in the AC welding circuit, but even in the DC circuit. Currently, some welding rectifiers are manufactured with an inductance included in the welding circuit in order to improve arc stability and welding quality. This is especially necessary if semi-automatic hose welding is carried out in CO; The larger the diameter of the welding wire and the current, the greater the inductance value should be in the welding circuit.

Fourth condition

The fourth condition for ignition and burning of an arc at any type of current depends on the characteristics of the arc power source: the power source must support the arc in the presence of disturbances in the form of changes in the voltage in the network, the surface topography of the product being welded, the feed speed of the welding wire, etc.

Source: https://spb-metalloobrabotka.com/zavisit-li-napryazhenie-dugi-ot-svarochnogo-toka/

Arc voltage during welding - what are the features? Welding arc. Characteristics of the welding arc

The process of arc formation during welding proceeds as follows: when the end of the electrode touches the metal being welded, a short circuit occurs in the welding circuit. Passing through individual protrusions, the current, which has a very high density at the points of contact of the electrode with the metal, instantly melts them, as a result of which a thin layer of liquid metal is formed between the electrode and the metal.

At the next moment, the welder withdraws the electrode slightly, causing a neck to form in the liquid metal, where the current density and temperature of the metal increase. Then, due to the evaporation of the molten metal, the neck ruptures and in the ionized space

The arc voltage, i.e. the voltage between the electrode and the metal being welded, depends mainly on its length.

The shorter the arc, the lower the voltage, although the current in the arc may remain unchanged. This is due to the fact that with a long arc the resistance of the gas gap will be greater. As is known from electrical engineering, the higher the resistance, the higher the voltage must be in order to ensure the passage of the same current in the circuit.

The total voltage drop in the arc (Ua) is the sum of the voltage drop in the cathode zone (ξ/k), in the arc column (UCT) and in the anode zone (t/a), i.e.

The absolute value of the arc voltage can also be influenced by the composition of the electrode and the metal being welded, the composition and pressure of the gas environment surrounding the arc (air, argon, helium, carbon dioxide) and other factors.

When welding with a metal electrode, the arc burns steadily at a voltage of 18-28 V, and when welding with carbon or graphite, at a voltage of 30-35 V.

To initiate an arc, a higher voltage is required than that required to maintain its normal combustion.

This is explained by the fact that at the initial moment the air gap is not yet sufficiently heated and it is necessary to give electrons a higher speed to ionize the atoms of the gas gap, which can only be achieved at a higher voltage at the moment of arc ignition.

In Fig. Figure 22 shows graphs of changes in voltage and current in the arc during its ignition and stable combustion.

The curve showing the relationship between voltage and current in the arc is called the static (or current-voltage) characteristic of the arc and corresponds to a steady (stationary) arc. Point A marks the moment of arc ignition.

Then the arc voltage quickly drops to a normal value, corresponding to a stable arc. A further increase in current increases the heating of the electrode and the rate of its melting, but does not affect the stability of the arc.

An arc has a falling static characteristic at a relatively low current density, used in manual arc welding or in automatic submerged arc welding at medium modes. At higher current densities (submerged arc welding at high current, welding with small diameter wire in a shielding gas environment), the static characteristic of the arc will increase, as is conventionally shown in Fig. 22 dotted lines 3 and 4.

A stable arc is one that burns evenly, without arbitrary breaks requiring re-ignition. If the arc burns unevenly, often breaks and goes out, then such an arc is called unstable. The stability of the arc depends on many reasons, the main ones being the type of current, the composition of the electrode coating, the polarity and length of the arc.

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The arc length is equal to the distance between the end of the electrode and the surface of the molten metal of the work being welded. Typically, the normal arc length should not exceed 3-4 mm for the remaining electrode. Such an arc is called short. A short arc burns steadily and ensures the normal flow of the welding process. For electrodes with a diameter of 4-5 mm coated with OMM-5, the normal arc length is 5-6 mm. An arc whose length is more than 6 mm is called long.

The process of melting the electrode metal in such an arc proceeds unevenly. In this case, the drops of metal flowing from the end of the electrode can be oxidized to a greater extent by oxygen and enriched with air nitrogen. The deposited metal turns out to be porous, the seam has an uneven surface, and the arc burns unsteadily.

With a long arc, productivity decreases, metal spatter increases, and places with lack of penetration and insufficient fusion of the deposited metal with the base metal are more often formed.

The arc can be powered from a direct or alternating current source. The arc can be powered by direct current of direct and “reverse” polarity. “With direct polarity, the minus of the current source is connected to the electrode, and with reverse polarity - to the workpiece being welded.

When welding with a carbon electrode, the arc is more easily excited and burns more steadily if the current has straight polarity. Reverse polarity current is used in cases where it is necessary to reduce the heat generation on the product being welded: when welding thin or low-melting metal, alloy, stainless and high-carbon steels that are sensitive to overheating, etc.

etc., as well as when using certain types of electrodes (for example, with UONI-13 coating).

To determine the polarity of a DC circuit, dissolve half a teaspoon of table salt in a glass of water, dip both wires of the circuit into the solution and turn on the welding current. The wire near which intense release of gas (hydrogen) bubbles occurs will be negative, and the second will be positive. The ends of the wires at a length of 1-2 cm must be cleared of insulation. To determine the polarity of the current, special pole indicators are also used.

In Fig. Figure 23 shows the curves of changes in voltage and current in an AC arc for one period. Since in each half-cycle the current (1d) and arc voltage ({/j change from zero to maximum values, then during the same period of time the temperature of the arc column and the degree of ionization of the arc gap decreases. As a result, to excite the arc after the current passes through the zero value an increased voltage is required, equal to U3ax, which is greater than the normal arc voltage UR.

To increase the stability of the AC arc, elements with a low ionization potential are introduced into the electrode coatings and welding fluxes: potassium, sodium and calcium, which facilitate the initiation of the arc after the current decreases to zero, and at the same time changes its direction to the opposite.

Magnetic fields arise around the arc and in the metal being welded. If these fields are located asymmetrically relative to the arc axis, then they can deflect the arc, which is a flexible current conductor, which makes welding difficult. The deflecting effect of magnetic fields on the welding arc is called magnetic blast.

The strength of the magnetic field is proportional to the square of the current, so magnetic blast is especially noticeable when welding with direct current of significant magnitude (over 300-400 A). When welding with alternating current with thickly coated electrodes and submerged arc welding, the effect of magnetic blast is much weaker than with direct current and when using bare or thinly coated electrodes.

The magnitude of the magnetic blast is also influenced by the location of iron (ferromagnetic) masses near the welding site, the location of the current supply to the product, the shape of the product, the type of welded joint, the presence of gaps and other reasons.

To reduce the deflecting effect of magnetic fields on the arc, welding should be carried out with the shortest arc possible, the welding current should be supplied to the workpiece at a point located as close as possible to the arc, and also the angle of inclination of the electrode should be changed so that the lower ring of the electrode faces away action of magnetic blast.

In Fig. Figure 24 shows how the influence of the location of the current supply to the product affects the deflection of the arc.

To reduce the influence of large ferromagnetic masses on the product being welded, a massive steel plate is laid on the side opposite to the direction of arc deflection. One wire from the source is connected to a steel plate, which is laid at a distance of 200-250 mm from the welding site, gradually moving it along the seam as it moves arcs.

What is the working principle of arc welding? From the welding transformer, electric current is supplied to the electrode and the work being welded, which creates and maintains an electric arc.

The electric arc heats up to 7000 degrees, due to which the electrode and the edges of the welded products melt and form a so-called weld pool. The weld pool remains in a molten state for a short time.

At this time, the molten metal of the electrode is mixed with the molten metal of the product, and a protective film is formed. After the weld pool solidifies, a welded joint is formed.

The electrical energy that is needed to create and maintain an electric arc is generated in alternating or direct current sources.

Current-voltage characteristics of the arc

Volt-ampere (static) characteristic of the arc - the dependence of the arc voltage on the external network current.

The arc voltage during welding directly depends on the magnitude of the welding current and the length of the arc itself. In manual arc welding, the lower the current voltage, the lower the arc voltage. In an automatic welding process, the arc voltage depends only on the length of the arc itself: the longer the electric arc, the higher its voltage, resulting in an increase in the amount of heat used to melt the metal and flux.

The arc voltage increases to a maximum value, after which it remains unchanged until the electric arc goes out.

The arc voltage affects the final result of welding - the quality of the seam and the thickness of the penetration. The higher the voltage, the wider the seam and the shallower the penetration depth of the product. A change in arc voltage can lead to the appearance of so-called pores and drops of molten metal.

The arc voltage during manual welding fluctuates within a small range - 15-30 Volts, however, when the electrode is replaced, the voltage can increase to 70 Volts.

Dependence of arc voltage on current voltage in automatic welding

When the current voltage increases to 80 V, the arc voltage during welding decreases sharply (region I, Fig. 2). At low arc power, as the current increases, the cross-sectional area and ability of the arc column to conduct electricity expands. This static characteristic of the arc is called incident ; the falling arc has low stability.

When the current voltage increases from 80 to 800 V (region II, Fig. 2), the arc voltage is almost constant. This is primarily due to the fact that the cross section of the arc column and the active spot increases. This increase occurs in proportion to the change in the value of the welding current, which is why the current density, and therefore the arc voltage, does not change.

This static characteristic of the arc is called rigid. A rigid arc is most often used in welding technology. When the current voltage increases above 800 V, the voltage of the arc itself increases again (region III, Fig. 2). The growth of the cathode spot does not increase with increasing current voltage, due to which the current density increases, and with it the arc voltage.

This arc, called increasing , is actively used in submerged arc welding and in shielding gases and gas mixtures.

The arc voltage depends on either the current voltage or the length of the arc, depending on the type of welding work - automatic or manual. Regarding manual welding, I would like to note that when replacing the electrode, the arc voltage rises to 70 V, so the welder must be extremely careful. In the automatic welding process, the likelihood of receiving an electric shock is much lower.

Source: https://ogonbar.ru/voltage-on-the-arc-during-welding-what-are-the-features-welding-arc.html

Does arc voltage depend on welding current - Machine tools, welding, metalworking

A welding arc is an electric arc discharge in an ionized mixture of gases, metal vapors and components that make up electrode coatings, fluxes and other means.

Physical and electrical properties of the welding arc

For an electrical discharge to occur, the gas gap between the electrodes must be ionized. The ionization process proceeds in the following order. When the end of the electrode and the workpiece come into contact, the protrusions of the rough surfaces are instantly heated by current to the melting and evaporation temperature due to the high ohmic resistance of the contact.

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After the electrode is separated from the product, the heated end of the electrode (negative pole) begins to emit electrons, rushing to the anode under the influence of the potential difference between the electrodes. When colliding with electrode metal particles, which are present in the form of vapors in the interelectrode gap, electrons ionize them. Ionization instantly covers the entire interelectrode gap, and it becomes electrically conductive.

During the arcing process, ionization is maintained due to high temperature.

The arc voltage is equal to the sum of the voltage drops in its three main (Fig. 1) areas:

Uд=Uк+ Uc+ Ua =f(Iд),

where Ud is the arc voltage, V; UK is the voltage drop at the cathode, V; Uc is the voltage drop in the arc column, V; Ua is the voltage drop across the anode, V; Id is the current strength in the arc.

Fig.1. Arc voltage drop distribution

The dependence of the arc voltage on the strength of the welding current is called the static (volt-ampere) characteristic of the arc.

In general, the static characteristics of the arc are shown in Fig. 2. At low current values in the electrode (region 1), the static characteristic of the arc decreases. At average current values (for manual and automatic submerged arc welding), the arc voltage does not depend on the current strength (region 2, hard characteristic). In this case, with sufficient accuracy, the static characteristic can be expressed by the equation

Ud= a+ bld,

where ld is the length of the arc, mm; a, b are constant coefficients depending on the material of the electrodes, pressure and properties of the gaseous medium.

Fig.2. General view of the static characteristics of the arc

From this equation it follows that the voltage on the arc, all other things being equal, will depend on the length of the arc column.

An increasing static characteristic of the arc (region 3, see Fig. 2) is obtained at high current strength (with automatic submerged arc welding or when welding in a shielding gas environment).

AC welding arc

Due to the fact that the instantaneous values of the alternating current pass through zero 100 times per second, and the cathode spot, which is the source of electron emission, also changes its location, the ionization of the arc gap turns out to be less stable and the welding arc is less stable, other things being equal, compared to the arc direct current.

If the arc is connected to an alternating current circuit in series with an active resistance, then the instantaneous values of the source voltage and welding current are in phase. During each half-cycle, the arc dies out and is re-ignited (restored) after a certain period of time until the voltage of the current source rises to a certain value, called the re-ignition voltage.

Ignition of the arc is characterized by the beginning of the passage of current in the welding circuit. In each half-cycle there is a break in the passage of current when the arc fades. These breaks are called arc extinction times.

The moment of extinction occurs at a slightly lower instantaneous value of the source voltage than at the moment of ignition, for which higher values are required to obtain ionization of the cooled gap.

The arc extinction time depends on the maximum arc ignition voltage and the frequency of the alternating current.

The arc recovery time decreases with increasing open circuit voltage and when using higher frequencies. This time also decreases when the ignition voltage is reduced. Of these measures to increase the stability of the arc, the most common is to reduce the ignition voltage, which is achieved by using electrodes with ionizing coatings.

The magnitude of the ignition voltage depends on a number of factors, primarily on the magnitude of the arc current. As the welding current increases, the arc ignition voltage decreases.

For open arc welding, the ignition voltage Uz and arc voltage Ud have the following relationship:

Uз = (1.3 – 2.5) Uд

When welding at high currents under submerged arc, the ignition voltage is almost equal to the arc voltage.

Increasing the open circuit voltage of the power supply is limited by safety regulations, and the use of high frequencies requires the use of special equipment.

A generally accepted measure to increase the stability of an alternating current welding arc is to include coils with a steel core (chokes) in the welding circuit, which allow welding to be carried out with metal electrodes at a welding transformer voltage of the order of 60 - 65V and a standard frequency. In this case, the coating of the electrodes must contain a sufficient amount of ionizing components.

Source: https://stanki-info.com/zavisit-li-napryazhenie-dugi-ot-svarochnogo-toka/

What is the current-voltage characteristic of an arc

In modern production, great importance is attached to such a high-tech process as welding. The nature of welding directly depends on the welding arc used. A welding arc is the result of an electrical discharge between a live electrode and the base metal. This arc is characterized by high temperature and high current density.

Different welding methods have different characteristics of the welding arc.

Static current-voltage characteristic

The static current-voltage characteristic is the dependence of the arc voltage on the supplied welding current at a constant arc length. This characteristic directly depends on the power source. There are three types of static characteristics:

Welding performed under normal conditions or using argon is characterized by the first type of current-voltage characteristic. In this case, the welding current used has low current values (up to 80 Amperes), allowing for small-sized welds.

With an increase in the current used during welding under normal conditions, the ionization process is activated and at the same time the area of the resulting arc cross-section increases, which greatly facilitates the welding process. During a welding arc in an argon environment, intense ionization of the gas environment itself occurs with a significant increase in the temperature of the shielding gas.

The welding arc, which occurs at a current strength of 80 to 300 Amperes, is characterized by the second type, which is characterized by the addition of low voltage values. In this case, the resulting cross-sectional area will be proportional to the current used during welding, which makes it possible to obtain seams of the required size and connect various structures made of various materials. The conductivity of the welding arc remains constant.

When welding with a current exceeding 300 Amperes, they speak of an increasing current-voltage characteristic. In this case, the resulting voltage increases as a result of the accumulation of a large number of charged particles on the electrode, automatically causing a voltage drop at the cathode.

Thus, we can say that a falling static current-voltage characteristic is characterized by an increase in current strength with a decrease in voltage. Rigid type is characterized by independence of voltage from current. For increasing - the voltage increases with increasing welding electric current.

In the process of manual welding with an electrode with an alloy coating, the characteristic will decrease; as the current increases, it will become hard. When welding using flux or in a carbon dioxide environment, a rigid static characteristic will turn into an increasing one. With a constant current, the voltage can only change depending on the length of the arc.

Elasticity of the welding arc

When welding, it is necessary to take into account the length of the arc used in welding, since such an important characteristic as elasticity directly depends on it.

To obtain a high-quality weld, uninterrupted combustion of the welding arc is necessary, which is characterized by the elasticity of the welding arc. An arc is said to be sufficiently elastic if the welding process remains stable as the length of the welded arc increases.

The resulting elasticity is directly proportional to the current value. With high changing parameters of the power source, the transition period is shortened during various changes in the electrical system, which allows you to obtain a high-quality connection in a short period of time.

Efficiency

Welding is always accompanied by the release of a large amount of heat, which is used to melt the parts being welded. Almost all consumed electrical energy is transformed into thermal energy, with the help of which the metal melts and the surrounding air is heated.

The efficiency in any welding operation has different values and largely depends on the brand of electrodes, the chemical composition of the flux, the type of welded joint and the speed of welding.

To obtain high-quality welds, when organizing the welding process, it is imperative to take into account all the characteristics of the welding arc and control them during operation.

This will optimize the entire process and minimize side energy costs. Compliance with all parameters of the welding arc for the selected type of welding is a necessary condition for ensuring high quality work.

In addition, this will ensure a long service life of the connected structures.

The most important characteristic of the arc is the dependence of the voltage on it on the current value. This characteristic is called current-voltage. There is a static current-voltage characteristic and a dynamic current-voltage characteristic.

With increasing current i , the arc temperature increases, thermal ionization increases, the number of ionized particles in the discharge increases, and the electrical resistance of the arc decreases . The arc voltage is equal to .

Source: https://MyTooling.ru/instrumenty/chto-takoe-volt-ampernaja-harakteristika-dugi