All about welding machines. Which welding machine is best for the home

As a result of development and improvement, dozens of different welding methods have appeared. metal products... The differences between each type are determined by such a factor as the need to create permanent joints of materials with a wide variety of properties.

A certain technology, successfully applied to one type of material, turns out to be completely unacceptable to others. The need to choose welding methods and types welding equipment in each case, it is also dictated by the difference in operational requirements for a particular design.

Classification of the types used today welding machines, realizing the whole variety of technological processes, can be built on the basis of several basic properties, which should include:

type of power source for the welding process;
the use of various types of protective media to optimize the formation of the weld joint;
the degree of automation of the welding process.

All this applies to electric welding. And besides it, there is gas welding, laser, diffusion, and many other types. But welding machines powered by action electric current, the most common in small, large-scale production and in everyday life.

Transformers

Transformer devices are at the very origin of welding technology. On their basis, common types of welding machines are built, which to this day are very widely used, both in production and in everyday life.

Structurally, such a device is a conventional step-down transformer with two windings. The primary winding can be rated for 220 volts or 380 volts.

In the first case, the terminals of the transformer are connected to the phase and neutral wires electrical network. Such welding machines are most often found in a compact design, have a relatively low power and are designed to work in a domestic environment.

The terminals of transformers of the second type are connected to two phase wires, are produced in a wider range of capacities and are intended for industrial use.

The voltage of the secondary winding in no-load mode is 40 - 60 volts. The welding current can be controlled in several ways.

The most common method is associated with a smooth change in the size of the air gap in the steel core of the transformer. Regulation is carried out by rotating the handle associated with the lead screw, along which the movable part of the magnetic circuit moves.

Devices with current regulation by switching the taps of the secondary winding are less convenient. The regulation is discrete, possibly in a small range. In addition, when the taps are switched, the open circuit voltage changes, which can hinder the ignition of the arc.

There is a universal method consisting in the use of a ballast resistance included in the welding circuit. The regulator is a conductor made of nichrome or other material with high resistivity.

Rectifiers

This type of apparatus is a rectified current source. DC welding has a more stable arc and a smoother weld bead.

The welding rectifier consists of a transformer and a rectifier itself in the form of powerful diodes assembled in a bridge circuit. A three-phase transformer in such devices is usually used, connected to a 380 volt network.

The secondary rectified voltage of this type of transformer has a low level of ripple, it holds the electric arc well.

Rectifiers continue to hold the lead in the number of devices used in production for manual welding. In large workshops, special highways are usually laid, to which separate welders' workplaces are connected.

The line is powered by a powerful rectifier. The regulation of the welding current in such systems is carried out individually at the posts using ballast resistances.

Generators

Welding machines that independently generate current are designed to work in field conditions in the absence of power supplies. They are units in which a three-phase alternator is combined with an internal combustion drive engine.

The output AC voltage is rectified by a diode bridge. Such generators are equipped with specialized technical assistance vehicles, powerful units are mounted on car trailers.

Modern industry produces units with a capacity of up to 10 kW, the dimensions and weight of which allow them to be transported in the trunk of a car.

Inverters

The appearance of this type of apparatus has opened up a number of new possibilities in the field of welding production. The use of inverter technology made it possible to radically reduce the size and weight, as well as to obtain qualitatively new characteristics of the welding machines.

In an inverter-type apparatus, the mains voltage undergoes a number of transformations. At the first stage, the ripple is rectified and smoothed by a filter capacitor.

The rectified mains voltage is supplied to the inverter, which is the main part of the device. The inverter is built on powerful IGBT transistors, the switching of which creates a voltage at its output with a frequency of several tens of kilohertz.

A high-frequency transformer is installed at the output of the inverter, which lowers the voltage to the level required for welding. The reduced voltage is rectified and applied to the output terminals of the welding machine.

The meaning of the described conversions lies in the fact that a transformer designed for such high frequencies is literally an order of magnitude smaller and lighter than one operating at industrial frequency with the same power.

The same can be said for filter capacitors and chokes. The advent of welding inverters has led to the fact that the machine, which has the size of a small suitcase, easily carried on a shoulder strap, is able to perform the same operations as a rectifier weighing a hundred kilograms.

There are various types of inverters that are powered by single phase or three-phase network... Three-phase devices are focused on industrial applications, single-phase types of the converter are used in household devices.

Types of machines for welding in a protective environment

Airborne gases and vapors of water have a negative effect on the quality of the weld. Therefore, technologies and welding machines are used that create a protective environment in the metal fusion zone.

Inert gas welding

The role of inert gases is played by substances such as argon, helium or their mixture. Inert gases entering the welding zone under pressure displace the air, preventing oxidation and nitriding of the resulting weld. The use of inert gases makes it possible to weld materials that are difficult or impossible to weld in the atmosphere.

Machines that carry out welding in a protective environment differ in the type of electrodes used, which can be melting during welding and infusible.

The technical characteristics of some inverter machines allow for several types of welding processes. For these purposes inverter machines complete with a set of accessories - electrode holders and torches.

Welding with active gases

This type of welding process includes carbon dioxide welding, which is a type of submerged arc welding. The advantage of using carbon dioxide instead of powder flux lies in the good visibility of the ongoing welding process, allowing effective control over it. Typically, the functions of welding in an inert and active environment are combined in one type of inverter machines.

Manual and automated devices

Welding machines can greatly simplify work if equipped with some automatic functions. Depending on the degree of automation, devices are divided into three types.

For manual arc welding

This type of electric welding machines includes the aforementioned transformers and rectifiers, as well as a large segment of inverter converters.

Manual electric welding is characterized by the use of piece replaceable electrodes, usually coated with a special compound. The chemical composition of electrode coatings depends on which materials are welded and what type of current (alternating, direct) the electrode is intended for.

For semi-automatic welding

This is the name of the type of apparatus using a special welding wire wound on a coil as an electrode. Semi-automatic machines are distinguished by the fact that during the welding process the wire is fed automatically, and the welder only has to control the arc and visually monitor the formation of the seam.

Semi-automatic inverters combine the ability to operate in a protective gas environment. The gas is supplied via the same connecting hoses as the welding wire.

It should be noted that some inverter machines are so versatile that they can be used for manual welding, semi-automatic welding in protective environments and welding with a non-fusible electrode in argon.

Full automation

These machines automatically control the welding process. Similar to semiautomatic devices, welding wire and shielding gas supply are used.

The modern designs of such devices are based on inverter technology. The design of the working bodies of automatic welding devices can be different - from a welding head moving along the seam on a trolley to placing it on a manipulator that allows you to weld seams of any configuration from any position.

Fully automated welding is used on large assembly lines.

When choosing welding machines and familiarizing yourself with their characteristics, one has to come across special terms, the meaning of which is desirable to know in order not to make a mistake in the choice. Here is some of them.

AC(English alternating current) - alternating current.
DC(English direct current) - direct current.
MMA(English Manual Metal Arc) - manual arc welding with stick electrodes. We know it under the name RDS.
TIG(English Tungsten Inert Gas) - manual welding with tungsten non-consumable electrodes in a shielding gas (argon).
MIG / MAG(English Metal Inert / Active Gas) - semi-automatic arc welding with a consumable electrode wire in an inert (MIG) or active (MAG) gas environment with automatic feeding wire.
PV(PR, PN, PVR) - ON duration - the time that the device is able to operate at a certain current (the current is indicated together with PV) before automatic shutdown due to overheating. The duty cycle is indicated as a percentage in relation to the standard cycle, taken equal to 10 or 5 minutes. If the duty cycle is 50%, this means that with a cycle of 10 minutes, after 5 minutes of continuous operation, 5 minutes of inactivity is required to cool the machine. This parameter can be equal to 10%, so you need to pay attention to it. The concepts: duration of inclusion (PV), duration of operation (PR), duration of load (PN) have different meanings, but the essence is the same - the continuity of welding.

A welding transformer is a device that converts the alternating voltage of the input network into alternating voltage for electric welding. Its main unit is a power transformer, with the help of which the mains voltage is reduced to an open circuit voltage (secondary voltage), which is usually 50-60V.

An easy-to-understand diagram of a welding transformer is as follows:

A simple diagram of a welding transformer: 1 - transformer; 2 - reactor with variable inductance; 3 - electrode; 4 - part to be welded.

To limit the short-circuit current and stable arc burning, the transformer must have a steeply falling external current-voltage characteristic ( ... To do this, either transformers with increased dissipation are used, as a result of which the short-circuit resistance is several times higher than that of conventional power transformers. Or, in a circuit with a transformer with normal dissipation, a reactive coil with a large inductive resistance is included - a choke (the choke can be included not in the secondary circuit, but in the primary circuit, where there is less current). If the inductance of the inductor can be changed by adjusting it, the shape of the external current-voltage characteristic of the transformer and the arc current I 21 or I 22 corresponding to the arc voltage Uд are changed.

Regulation of welding current... The current strength in welding transformers can be controlled by changing the inductive resistance of the circuit (amplitude control with normal or increased magnetic leakage) or using thyristors (phase control).

In amplitude control transformers, the necessary parameters of the welding current are provided by moving the moving coils, magnetic shunts or using a separate reactive coil as in the figure above. In this case, the sinusoidal form of the alternating current does not change.

Diagram of a welding transformer with movable windings: 1 - primary winding, 2 - secondary, 3 - core magnetic circuit, 4 - screw drive.

Diagram of a welding transformer with a movable magnetic shunt: 1 - primary winding, 2 - secondary, 3 - rod magnetic circuit, 4 - movable magnetic shunt, 5 - screw drive.

It can be simple to switch the number of used turns of the transformer winding, to reduce the no-load voltage and hence the welding current.

Thyristor (phase) control transformers consist of a power transformer and a thyristor phase regulator with two antiparallel thyristors and a control system. The principle of phase control consists in converting a sinusoidal current shape into alternating pulses, the amplitude and duration of which are determined by the angle (phase) of the thyristors switching on.

Diagram of a thyristor-controlled welding transformer. BZ - task block, BFU - phase control block.

The use of a thyristor phase regulator makes it possible to obtain a welding machine whose characteristics compare favorably with those of a transformer with amplitude control. In more complex control circuits than in the figure above, an alternating current is generated rectangular... And in this case, for example, an increased speed of the pulse transition through a zero value is achieved, as a result of which the time of no-current pauses decreases and the stability of the arc burning and the quality of the weld increase. What cannot be said about the oscillogram shown above, there are more currentless gaps on it than for transformers with amplitude control and the quality of welding is worse.

Another advantage of thyristor devices is the simplicity and reliability of the power transformer. The absence of steel shunts, moving parts and associated increased vibrations makes the transformer easy to manufacture and durable in operation.

By the type of supply network, welding transformers are single-phase and three-phase. The latter, as a rule, can be connected to a single-phase network. The figure below shows single-phase and three-phase transformers with magnetic shunt current regulation.

Advantages and disadvantages welding transformers ... The advantages of welding transformers include a relatively high efficiency (70-90%), ease of operation and repair, reliability and low cost.

The list of disadvantages is more extensive. First of all, this is the low stability of the arc burning, due to the properties of the alternating current itself (the presence of currentless pauses when the electric signal crosses zero). For high-quality welding, it is necessary to use special electrodes designed for operation with alternating current. The stability of the arc and fluctuations in the input voltage adversely affect the stability of the arc.

The welding transformer cannot weld stainless steel, which requires direct current, and non-ferrous metals.

If the power of the AC welder is large enough, its weight can be difficult when moving the transformer from place to place.

And yet, an inexpensive, reliable and unpretentious welding transformer is not such a bad choice for the home. Especially if you rarely have to cook, and there is not enough money to buy a more functional model.

Welding rectifiers

Welding rectifiers are devices that convert AC mains voltage into DC voltage for electric welding. There are many schemes for constructing welding rectifiers with various mechanisms for generating the output parameters of current and voltage. Are used different ways regulation of current and formation of external current-voltage characteristics of rectifiers ( read about the current-voltage characteristic at the end of the article): changing the parameters of the transformer itself (moving coils and sectioned windings, magnetic shunts), using a choke, phase control using thyristors and transistors. In the simplest devices, the current is controlled by a transformer, and diodes are used to rectify it. The power section of such devices consists of a transformer, a rectifier unit with uncontrolled valves and a smoothing choke.

Block diagram of the welding rectifier: T - transformer, VD - rectifier unit on uncontrolled valves, L - smoothing choke.

A transformer in such a circuit is used to lower the voltage, form the necessary external characteristics and regulate the mode. More modern and advanced devices include thyristor rectifiers, in which mode control is provided by a thyristor rectifier unit, which carries out phase control of the moment when the thyristors turn on. The formation of the necessary external characteristics is carried out by introducing feedbacks for the welding current and output voltage.

Block diagram of the welding rectifier: T - transformer, VS - thyristor rectifier unit, L - smoothing choke.

Sometimes a thyristor regulator is installed in the primary winding circuit of the transformer, then the rectifier unit can be assembled from uncontrolled valves - diodes.

Block diagram of the welding rectifier: VS - thyristor rectifier unit, T - transformer, VD - rectifier unit on uncontrolled valves, L - smoothing choke.

Semiconductor rectifier elements require forced cooling. For this, radiators are placed on them, blown by a fan.

The figure below shows a diagram of a welding rectifier, in which the change in the resistance of the transformer and the regulation of the current is provided using a magnetic shunt - it is closed or opened using a handle on the front panel of the machine.

Principled electrical circuit welding rectifier with magnetic shunt: A - circuit breaker, T - transformer, Dr - magnetic shunt, L - light-signaling armature, M - electric fan, VD - diode rectifier unit, RS - shunt, PA - ammeter.

Single-phase AC voltage rectification circuits are used in circuits with low power consumption. Compared to single-phase, three-phase circuits provide significantly less rectified voltage ripple. The operation of Larionov's three-phase bridge rectifier circuit using diodes, used in many welding rectifiers, is shown in the figure below.

Advantages and disadvantages of welding rectifiers... The main advantage of rectifiers, in comparison with transformers, is the use in them for direct current welding, which ensures the reliability of ignition and the stability of the welding arc and, as a result, a better seam. It is possible to cook not only carbon and low-alloy steel, but also stainless steel and non-ferrous metals. It is also important that welding with a rectifier gives less spatter. In fact, these advantages are quite enough for an unambiguous answer to the question of which welding machine to choose - a transformer or a rectifier. If, of course, do not take into account the prices.

The disadvantages include relatively heavy weight devices, the loss of a part of the power, a strong "drawdown" of the voltage in the network during welding. The latter also applies to welding transformers.

Welding inverters

The word "inverter" in its original meaning means a device for converting DC to AC. The figure below shows a simplified diagram of an inverter type welding machine.

Block diagram of the welding inverter: 1 - mains rectifier, 2 - mains filter, 3 - frequency converter (inverter), 4 - transformer, 5 - high-frequency rectifier, 6 - control unit.

The work of the welding inverter is as follows. An alternating current with a frequency of 50 Hz is fed to a network rectifier 1. The rectified current is smoothed by filter 2 and converted (inverted) by module 3 into alternating current with a frequency of several tens of kHz. Frequencies of 100 kHz are currently being achieved. It is this stage that is most important in the operation of a welding inverter, which makes it possible to achieve huge advantages over other types of welding machines. Then, with the help of transformer 4, the high-frequency alternating voltage is reduced to no-load values (50-60V), and the currents increase to the values required for welding (100-200A). The high frequency rectifier 5 rectifies the alternating current that makes its useful work in the welding arc. Influencing the parameters of the frequency converter, they regulate the mode and form the external characteristics of the source.

The processes of current transition from one state to another are controlled by the control unit 6. In modern devices, this work is performed by IGBT transistor modules, which are the most expensive elements of a welding inverter.

The feedback control system generates ideal output characteristics for any electric welding method ( read about the current-voltage characteristic at the end of the article)... Due to the high frequency, the weight and dimensions of the transformer are significantly reduced.

In terms of functionality, the following types of inverters are produced:

for manual arc welding (MMA);
for argon-arc welding with a non-consumable electrode (TIG);
for semi-automatic welding in shielded gases (MIG / MAG);
universal devices for working in MMA and TIG modes;
semiautomatic devices for working in MMA and MIG / MAG modes;
devices for air plasma cutting.

As you can see, a significant part of the volume is occupied by radiators of the cooling system.

The advantages of inverters... The advantages of welding inverters are great and numerous. First of all, their low weight (4-10 kg) and small dimensions are impressive, allowing you to easily move the machine from one welding point to another. This advantage is due to the smaller size of the transformer due to the high frequency of the voltage it converts.

The exclusion of the power transformer from the circuit also made it possible to get rid of losses for heating the windings and magnetization reversal of the iron of the core and achieve high efficiency (85-95%) and ideal power factor (0.99). When welding with an electrode with a diameter of 3 mm, the power consumed from the network for an inverter-type welding machine does not exceed 4 kW, and for a welding transformer or rectifier, this figure is 6-7 kW.

The inverter is capable of reproducing almost all types of external volt-ampere characteristics. This means that it can be used to carry out all major types of welding - MMA, TIG, MIG / MAG. The device provides welding of alloyed and stainless steels and non-ferrous metals (in MIG / MAG mode).

The device does not require frequent and long-term cooling during intensive work, as is required by other household types of welding machines. Its PV reaches 80%.

The inverter has a smooth adjustment of welding modes in a wide range of currents and voltages. It has a significantly wider range of adjustment of the welding current than that of conventional machines - from a few amperes to hundreds and even thousands. For domestic use, small currents are especially important, allowing welding with thin (1.6-2 mm) electrodes. Inverters provide high-quality seam formation in any spatial position and minimal spatter during welding.

Microprocessor controlled device provides stable current and voltage feedback. This allows you to provide the most useful and convenient Arc Force, Anti Stick and Hot Start functions. The essence of all of them consists in a qualitatively new control of the welding current, which makes it possible to make welding as comfortable as possible for the welder.

The Hot Start function automatically increases the current at the start of the weld, making it easier to ignite the arc.
The Anti Stick function is a kind of antipode to the Hot Start function. When the electrode comes into contact with the metal and there is a threat of its adhesion, the welding current is automatically reduced to those values that do not cause the electrode to melt and weld to the metal.
The Arc Force function occurs when a large drop of metal separates from the electrode, shortening the arc length and threatening to stick. The automatic increase in the welding current prevents this for a very short time.

These convenient features enable low-skilled welders to successfully weld the most challenging metal structures. For those who have worked with a welding inverter at least once, the question - which welding machine is better - does not exist. After a transformer or rectifier, working with an inverter becomes a pleasure. You no longer need to "hammer" with an electrode in order to ignite an arc that does not want to ignite, or convulsively tear it off if it is tightly welded. You can simply put the electrode on the metal and, tearing it off, calmly ignite the arc - without worrying about the electrode being welded.

Inverter welding machines can be used with large drops in mains voltage. Most of them provide welding in the 160-250V mains voltage range.

Disadvantages of welding inverters... It is difficult to talk about the disadvantages of such a perfect device as a welding inverter and, nevertheless, they are. First of all, it is the relatively high price of the device and the high cost of repairing it. If the IGBT module fails, you will have to pay an amount equal to 1/3 - 1/2 of the cost of a new device.

The inverter makes higher demands, in comparison with other welding machines, to the storage and operation conditions, due to its electronic filling. The device reacts poorly to dust, since it worsens the cooling conditions for transistors, which get very hot during operation. They are cooled using aluminum radiators, the deposition of dust on which impairs heat transfer.

Dislikes electronics and low temperatures. Any minus temperature is undesirable due to the appearance of condensation on the boards, and minus 15 ° C can become critical. Storage and operation of the inverter in unheated garages and workshops in winter time undesirable.

Welding semiautomatic devices

Speaking of welding equipment, one cannot ignore semiautomatic devices - machines for welding in a shielded gas environment with a mechanized welding wire feed.

The semiautomatic welding machine consists of:

current source;
control unit;
a welding wire feed mechanism;
a gun (torch) with a hose-electric wire, through which the supply of shielding gas, wire and an electric signal is carried out;
a gas supply system consisting of a gas cylinder, an electromagnetic gas valve, a gas reducer and a hose.

Welding rectifiers or inverters are used as a power source. The use of the latter improves the quality of welding and increases the amount of materials to be welded.

By design welding semiautomatic devices are double-body and single-body. In the latter, the power source, control unit and wire feeder are housed in one housing. For double-body models, the wire feeder is located in a separate unit. Usually these are professional models that support long-term operation at increased current. Sometimes they are equipped with a water gun cooling system.

Welding with a semiautomatic device in MMA mode is no different from working with a conventional welding machine. When using the MIG / MAG mode, an electric arc burns between the continuously supplied consumable wire and the material. Carbon dioxide (or its mixture with argon), supplied through the gun, protects the welding area from harmful effects oxygen and nitrogen contained in the air. High-alloy and stainless steels, aluminum, copper, brass, titanium are cooked with the use of semiautomatic welding machines.

Semi-automatic welding is one of the most advanced arc welding technologies, ideal not only for production, but also for the home. Semi-automatic machines are widely used in industry and everyday life. There is information that at present in Russia up to 70% of all welding works are carried out by welding semiautomatic devices. This is facilitated by the wide functionality of the equipment, high quality welding and easy operation. The semiautomatic welding machine is very convenient for welding thin metal, in particular, car bodies. Not a single car service enterprise can do without this most convenient equipment.

Choosing a welding machine

The choice of a welding machine should be made according to specific needs. Before heading to the store, you need to know the answers to the following questions.

What kind of metal - by grade and thickness - should you weld?
In what conditions will the work be done?
How much?
What are the requirements for the quality of work and qualifications of the welder?
And finally, how much can be spent on purchasing a welding machine?

Depending on the answers to these questions, the requirements for the purchased equipment should be formed.

If you have to cook not only carbon and low-alloy steel, but also high-alloy and stainless steel, then the choice must be made between a welding rectifier and an inverter. If it is necessary to weld metals that require protection from oxygen or nitrogen in the air, for example, aluminum, then welding in a shielded gas environment will be required, which can be provided by a semiautomatic device with the MIG / MAG mode.

In general, if we talk about the versatility of the equipment, then the best choice, perhaps, there will be a semiautomatic device with MMA and MIG / MAG modes. Its presence will allow you to perform almost any metal welding job that you only have to deal with in everyday life.

If you have to deal with thin (thinner than 1.5 mm) metal, preference should again be given to a semiautomatic device.

Operation in subzero temperatures, especially below 10-15 ° C, is undesirable for inverters. Strong dustiness also has a bad effect on them. The conclusion is as follows. If you have to work with very low temperatures in dusty conditions, there may be no other option but to choose a welding machine without ultra-modern electronics - a welding transformer, a diode rectifier or a semiautomatic device based on the latter.

High requirements for the quality of welding and low qualifications of the welder unambiguously incline to the choice of a welding inverter with its convenience in operation and the functions of Arc Force, Anti Stick, Hot Start.

A large amount of work requires a high duty cycle from the welding machine, otherwise it will take too much time for downtime during its cooling. PV is one of the characteristics that distinguish household welding machines from professional ones. In the latter, it is quite large or even reaches 100%, which means that the device can work without interruption for as long as you like. If we talk about household models, then the PV of inverters is much superior to the PV of welding transformers and rectifiers. It is better to take 30% as the minimum value of duty cycle.

When choosing a welding machine, you also need to think about your neighbors. If you have to cook a lot, and the voltage in the network is low and unstable, you should choose a welding machine for your home, taking into account the power it consumes. The constant blinking of light bulbs, which occurs during the operation of powerful welding transformers and rectifiers, arouses universal hatred of neighboring welders. The inverter with its economical energy consumption and anti-stick function of the electrode will not harm good neighborly relations. When the electrode contacts the metal to be welded, the welding transformer sags the supply network, the inverter simply reduces the welding current (voltage at the terminals), plus the inverter is more efficient at low mains voltage.

Basic requirements for power sources for welding

To meet their intended purpose, power sources must meet certain requirements, the main ones of which are the following:

no-load voltage should provide arc ignition, but not exceed values that are safe for the welder;
power supplies must have devices that regulate the welding current within the required limits;
welding machines must have a given external current-voltage characteristic consistent with the static current-voltage characteristic of the welding arc.

An arc can occur either in the event of a gas (air) breakdown, or as a result of contact of the electrodes with their subsequent withdrawal to a distance of several millimeters. The first method (air breakdown) is possible only at high voltages, for example, at a voltage of 1000V and a gap between the electrodes of 1 mm. This method of striking the arc is usually not used due to the danger of high voltage. When the arc is supplied with a high voltage (more than 3000V) and high frequency (150-250 kHz) current, air breakdown can be obtained with a gap between the electrode and the part up to 10 mm. This method of arc ignition is less dangerous for the welder and is often used.

The second method of arc ignition requires a potential difference between the electrode and the product 40-60V, therefore it is used most often. When the electrode touches the workpiece, a closed welding circuit is created. At the moment when the electrode is removed from the product, the electrons that are on the cathode spot heated from a short circuit break away from the atoms and electrostatically move to the anode, forming an electric arc. The arc quickly stabilizes (within a microsecond). The electrons that leave the cathode spot ionize the gas gap and a current appears in it.

The arc ignition speed depends on the characteristics of the power source, on the current strength at the moment of contact of the electrode with the product, on the time of their contact, on the composition of the gas gap. The arc striking speed is influenced, first of all, by the value of the welding current. The higher the current value (for the same electrode diameter), the larger the cathode spot cross-section becomes and the higher the current will be at the beginning of arc ignition. The large electron current will cause rapid ionization and transition to a stable arc discharge.

With a decrease in the electrode diameter (i.e., with an increase in current density), the transition time to a stable arc discharge is further reduced.

The arc ignition speed is also influenced by the polarity and the type of current. With direct current and reverse polarity (i.e., the plus of the current source is connected to the electrode), the arc striking speed is higher than with alternating current. For alternating current, the ignition voltage must be at least 50-55V, for direct current, at least 30-35V. For transformers that are designed for a welding current of 2000A, the open circuit voltage should not exceed 80V.

Repeated ignition of the welding arc after its extinction due to short circuits by drops of electrode metal will occur spontaneously if the temperature of the end of the electrode is high enough.

The external current-voltage characteristic of the source is the dependence of the voltage at the terminals and the current.

In the diagram, the source has a constant electromotive force (Eu) and an internal resistance (Zi), consisting of active (Ri) and inductive (Xi) components. At the external terminals of the source, we have a voltage (Ui). In the "source-arc" circuit, the welding current (Id) is the same for the arc and the source. The source load is an arc with an active resistance (Rd), the voltage drop across it is Ud = I Rd.

The equation for the voltage at the external terminals of the source is as follows: Ui = Ei - Id Zi.

The source can operate in one of three modes: idle, load, short circuit. At no-load, the arc does not burn, there is no current (Id = 0). In this case, the source voltage, called the open circuit voltage, has a maximum value: Ui = Ei.

With a load along the arc and the source, current (Id) flows, and the voltage (Ui) is lower than during no-load, by the amount of voltage drop inside the source (Id Zi).

With a short circuit, Ud = 0, therefore, the voltage at the source terminals is Ui = 0. Short-circuit current Ik = Ei / Zi.

Experimentally, the external characteristic of the source is taken by measuring the voltage (Ui) and current (Id) with a smooth change in the load resistance (Rd), while the arc is simulated by a linear active resistance - a ballast rheostat.

The graphical representation of the obtained dependence is the external static current-voltage characteristic of the source. As the load resistance decreases, the current increases and the source voltage decreases. Thus, in the general case, the external static characteristic of the source is falling.

There are welding machines with steeply dipping, gently dipping, rigid and even increasing volt-ampere characteristics. There are also universal welding machines, the characteristics of which can be steep and tough.

External volt-ampere characteristics of welding machines: 1 - steeply dipping, 2 - gently dipping, 3 - rigid, 4 - increasing.

For example, a conventional transformer (with normal dissipation) has a stiff characteristic, and the rising characteristic is achieved by feedback, when the electronics increase the source voltage with increasing current.

In manual arc welding, welding machines with a steeply falling characteristic are used.

The welding arc also has a volt-ampere characteristic.

At first, with an increase in current, the voltage drops sharply, since the cross-sectional area of the arc column and its electrical conductivity increase. Then, with an increase in the current, the voltage almost does not change, since the cross-sectional area of the arc column increases in proportion to the current. Then, with an increase in the current, the voltage increases, since the area of the cathode spot does not increase due to the limited cross-section of the electrode.

With increasing arc length, the current-voltage characteristic shifts upward. A change in the diameter of the electrode is reflected in the position of the boundary between the rigid and increasing portions of the characteristic. The larger the diameter, the higher the current, the filling of the end of the electrode with the cathode spot will occur, while the increasing section will shift to the right (shown by the dotted line in the figure below).

Stable arc burning is possible provided the arc voltage is equal to the voltage at the external terminals of the power source. Graphically, this is expressed in the fact that the characteristic of the welding arc intersects with the characteristic of the power source. The figure below shows three characteristics of an arc of different lengths - L 1, L 2, L 3 (L 2> L 1> L 3) and the steep characteristic of the power supply.

The intersection of the current-voltage characteristics of the source and the arc (L 2> L 1> L 3).

Points (A), (B), (C) represent the zones of stable burning of the arc at different lengths. It can be seen that the greater the slope of the source characteristic, the less the change in the welding current will be when the arc length fluctuates. But the length of the arc is maintained manually during the combustion process, therefore it cannot be stable. That is why only with a steeply falling characteristic of the transformer, the oscillations of the tip of the electrode in the hands of the welder will not greatly affect the stability of the arc and the quality of welding.

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There are 50 types of welding. As we write this material, maybe this number is increasing. Embrace complete classification in one article it is difficult and stupid, so let's deal with at least 4 main types of metal welding.

What kind of welding is there? Main types

Manual arc

Gas

Semi-automatic

Welding allows you to connect parts together with a tight or spot seam. The choice of method affects the quality, accuracy of the seam and the cost of work. GOSTs for welding describe the designation of instruments and materials for quality control according to international standards.

Types of welding

View	Principle of operation
Electric (electric arc) submerged arc	The welding arc burns out between the welding material and the electrode wire under a layer of free-flowing fluxes. Due to the heat of the arc, the surfaces to be welded and the wire with flux melt.
Termitnaya	The products are placed in a fire-resistant container, and powder (termite) is poured into the upper groove, where there is a seam. At 2000 °, the metal melts and fills the seam. This seam is then welded.
Ultrasonic	Exposure to vibrations (ultrasonic frequencies) caused by mechanically, for the part to be welded.
Cold	Merging crystals under high pressure.
Electroslag	A welding arc appears under the flux. The flux melts and an electrically conductive slag is formed, which has a high ohmic resistance. Due to the latter, metals are welded. Plus: no need to use heat treatment; savings in flux. Minus: possible deformations.
Contact	Metals heat up, pass through an electric current and deform. Contact welding is used in mechanical engineering for the serial production of parts.
Plasma	Non-standard welding technology. The moving arc heats up, which, due to this unusual property, sharply increases the temperature. Plasma welding is considered to be the most convenient type of welding on aluminum, since with it the temperature is much lower than with gas. This means that it will practically not deform the aluminum part.

All models and types of devices that have received a certificate from NAKS can be used. Below are a few abbreviations.

MP - mechanized consumable electrode welding;
MADP - mechanized argon-arc consumable electrode welding;
ЗН - welding with embedded heaters;
RD - manual arc welding with covered electrodes;
AF - automatic submerged arc welding;
MADPN - mechanized argon-arc consumable electrode surfacing.

Manual arc view

Welding is carried out with stick electrodes, which gradually melt and leave behind a fastening seam. The required distance is made between the surface of the metal and the electrode to melt it.

This is called an arc that maintains a distance of about three millimeters. It decreases over time, so it is difficult for a beginner welder to maintain the same gap.

When welding several objects, they are first point-bonded so that they do not disperse, otherwise the welding will be uneven, and the seam will stretch - on the one side it will be of the specified size, and on the other - wider.

IMPORTANT! Uneven welding can cause metal to burn through.

When welding plates with a thickness of more than two mm to each other, it is imperative to make a small gap between them. Hold the electrode at an angle of 45 °. This will ensure that the welding slag escapes to the outside. The straighter its angle, the more likely it is to burn through the metal.

Before starting welding, the electrode must be brought as close as possible to the place where the seam is applied. If this is not done, you may lose the weld spot when donning the welding helmet.

Fastening the two surfaces, you need to melt the edge of the first and second. Remember that the electrode also melts. We mix the melted edges of the surfaces to be welded and the electrode. To do this, you need to make small movements to the left and right.

If the electrode is led straight, then only one part of the surface will melt, which means the seam will be unreliable.

This method is often used in reinforced concrete structures (reinforcement welding), when installing fences and gates, in various types of pipe welding.

IMPORTANT! If the work is carried out at a height, or if the cable at the holder is just very long, then it will pull, and this can interfere with the imposition correct seam... To do this, hold it in your other hand or hang it on a hook.

Semi-automatic welding

Pros of PS (compared to manual or arc):

versatility - you can cook both structural and stainless steel, as well as other metals (cast iron, aluminum);
ease of learning - you can quickly learn how to work with the type of welding;
can be used for thin metals;
high speed of work;
Convenience - the slag does not interfere with seeing the result of the work: the master sees how the metal melts and can change the settings.

To work with this type of welding, you will need a power source (or the machine itself), special wire and shielding gas.

IMPORTANT! When choosing an electrode wire, you need to make sure that it is close to chemical composition to the welded metal or surpass it in properties in order to obtain a high-quality seam.

We recommend wire for welding ST-3 08G2S steel with a diameter of 0.6 to 1.2 mm.

For working with metal with a thickness of 1 to 4 mm, a wire with a cross section of 0.8 mm is suitable. For large metal thicknesses, choose a wire of 1 or 1.2 mm.

IMPORTANT! Welding without gas is prohibited unless special flux cored wire is used. Then the protective gas is formed during the melting and combustion of the special powder composition.

It is allowed to use both pure CO2 and mixed CO2 + Ar (carbon dioxide and argon) gas. Pure carbon dioxide is the cheapest and most readily available.

Cons: strong metal spatter, not very nice looking seam.

By adjusting the inductance, with such welding, you can change the quality of penetration and the width of the seam. If you reduce it, the arc will be colder. The result of the work is a thin seam and deep penetration. By increasing the inductance, the arc becomes hotter, resulting in a smooth wide bead and shallower penetration.

When welding metal, the torch must be held at 60 ° to the plane of the seam, and the distance from the nozzle to the welding surface is 7-20 mm.

Before starting the welding process, you need to bite off the tip of the wire protruding from the nozzle, because a ball forms on it, which does not conduct current well. When welding surfaces, it is necessary to clean them from paint or rust.

IMPORTANT! If you hear distinct clicks during operation, then the welding machine is set to a high welding voltage or insufficient wire feed speed. At a high feed speed, the wire will not have time to melt.

The application of various seams requires machine adjustments. Welding of thin metals is spot-welding. Do not weld in a continuous seam to avoid warping.

Gas welding

The set of gas welding equipment includes:

oxygen hose of the first category for supplying acetylene under a pressure of 0.63 MPa;
oxygen hose of the third category for oxygen supply under pressure up to 2 MPa;

Before use, you need to clean the metal from rust and paint. The pressure on the acetylene cylinder is set by opening the cylinder screw counterclockwise. The adjusting screw is screwed in clockwise, looking at the pressure gauge.

Its working pressure is 0.2 MPa. To set the pressure on the oxygen cylinder, open the screw counterclockwise. Then screw the adjusting screw clockwise into the gearbox and look at its pressure gauge. The pressure should be 0.5 MPa.

To set a working flame on a gas burner, open the acetylene screw, then ignite the flame. Make sure that the fire does not come off the tip of the gas burner. Then adjust it with the oxygen screw.

The flame should represent the core, recovery zone and torch.

To make a weld pool, you need to position the torch 90 ° to the base metal. The distance between the flame core and the surface must be 1.3 mm.

As in the previous cases, the torch must be moved left and right to melt the edges of the surfaces to be welded.

After the metal has warmed up and the weld pool is ready, place the torch at an angle of 45 ° and feed the filler rod. It can be fed dropwise or so that it is constantly in the weld pool. At the same time, make light movements to the left and right.

Weld requirements

It should be dense, and the scales should be uniform. Width 5-6 mm, height 1-2 mm. After finishing work gas-burner closes: first the acetylene screw, then after blowing out the burner - the oxygen one.

The cylinders are closed alternately. Acetylene first. We close the screw on it, then unscrew the adjusting screw from the gearbox. Oxygen closes in the same way.

After closing the cylinders, it is necessary to release the residual pressure from the hoses. The screws on the burner open: first acetylene, then oxygen. The pressure gauges on both cylinders will show how the pressure drops. After the remaining pressure is released, close it.

Safety precautions when working with gas welding

it is better to choose class 3 hoses. They can withstand pressure up to 40 atmospheres;
on the fittings, fastening should be carried out using clamps, but not wire;
fire-arresting valves are installed on hoses, reducers and burners: they prevent the flame from passing through the hose and entering the cylinder, thereby preventing a gas explosion;
if the burner suddenly begins to melt, you do not need to throw it and run away - near it you need to bend and squeeze the hoses with your hand, and then close the screws on the burner; if not, then on the cylinder.

Argon welding

It is used for joining non-ferrous metals or alloy steel.

Comprises:

a welding machine for operation from alternating or direct current;
argon cylinder;
gas flow meter and regulator;
burner with regulator and air cooling;
inert gas hose;
reducer;
tungsten rods (DC and general purpose).

Before welding, the tungsten rods are sharpened so that the marks are vertical rather than horizontal. Then it is inserted into the burner and closed with a nozzle. For each metal there is a nozzle of the required number.

IMPORTANT! A standard gas cylinder lasts approximately 14 hours at a flow rate of 7 l / min. Before starting welding, the metal surface is cleaned and degreased with acetone or solvent.

To work with different metals, including thickness, different arcs are installed - flat, medium and high-frequency pulse. It makes it possible to work on thin materials, because the arc is interrupted and does not burn through them.

When welding, filler wire is fed. Welding takes place in the same way as the previous ones. By surfacing the edges of the metals being welded and welding the wire into the gap between them.

We must not forget that the electrode in the burner is always energized, therefore it must be handled carefully.

Model	Description
	Designed for arc welding. Small dimensions (56x42 cm) and weight (5.2 kg). Works with electrodes with a diameter of 4 mm.
	Inverter weighing 5.87 kg. Works with electrodes with a diameter of 1.6-5 mm. IGBT technology, which increases the efficiency of the unit.
	Antistick system, which independently reduces the current when the electrode sticks to the metal.
	Designed for surfacing and arc welding. Plus: during welding, the metal is practically not sprayed.
	Electricity consumption is almost 30 percent less compared to analogs.
	Automatic overload protection, neat seam. Efficiency 85%.

Due to its PFC technology, it can operate at a voltage of 100 V, which is very convenient in summer cottages. It copes well with electric arc welding, it is possible to connect to a generator. By reducing the electromagnetic field, electricity consumption is reduced by almost 30%.

It is worth paying attention to the model, which has a “hot start” function (you can plug it in and start working right away) and an anti-stick function for electrodes in the metal. The device can operate at a voltage of 170 V.

Experienced welders, if he needs to choose a welding machine, will rely on his past experience and will focus on the best and most reliable unit. For novice welders who, as a rule, find it difficult to choose a welding machine, this article is intended.

First you need to get acquainted with what types of welding machines are. There are a lot of them, but we will consider the most common ones. The most popular are hand-held welding machines that use electrodes of different diameters. There are also such as:
- machines for mechanical welding, which use a consumable electrode;
- devices that conduct argon-arc welding, that is, with non-consumable electrodes;
- using an automatically consumable electrode in combination with a flux;
- welding transformers;
- welding generators;
- welding inverters;
- devices carrying out contact-spot welding.
Now we will take a closer look at the latter species.

AC welding transformers

The types of welding machines can be described starting with AC welding transformers. They work with melting metal electrodes. This unit is not very expensive and is excellent for overlapping and butt welding of ferrous metals. The design of such a welding machine is quite reliable and it is very easy to operate. The electrodes are rutile or calcium fluoride coated. The operating voltage is 220V, but for different voltages in it, as a rule, there is an adjustment of the current strength, and the choice of its indicator depends on the size of the electrode.

DC welding machines

Such devices are used with consumable electrodes and differ from those described above by more complex design which makes it more expensive. The output current of such a unit is constant and it is obtained due to the use of a diode and thyristor rectifier in the circuit. True, this state of affairs has an impact on the power that is lost. However, the presence of direct current makes it possible to obtain a stable arc. This welding machine allows you to work with both ferrous and non-ferrous metals, you just need to choose the right electrodes. This unit is useful for professional welders, and a simpler welding machine is more suitable for personal home ownership.

Welding machines operating in an active or inert gas environment

If we talk about such a topic as the types of welding machines, then we cannot mention such units. They are needed for semi-automatic welding. These devices are versatile and are used for domestic needs, as well as for auto repair. They are expensive, but they have high performance, are reliable and convenient. It works with gas or without gas and consists of a rectifier, a transformer, a reducer, a wire drive and a hose with a torch. It is possible to install a reel of wire directly on the machine, as for its choice, it depends on what material is used for welding. It should also be borne in mind that for welding different metals, a different gas is required, for example, for iron - carbon dioxide, and for steel - a mixture of argon and carbon dioxide.

Inverter welding machines

At this time, they are very popular and the most modern. They are small in size and light in weight. Among the indisputable advantages: high voltage frequency, autonomy, compactness, high performance. Apparently, that's why it is expensive.

The number of people who prefer to live in a private house or in the country is growing every year. And homeownership requires a lot of work to maintain. Often there is a need for welding. But not every owner has the opportunity to contact a professional welder. Many people prefer to do the welding themselves.

In this article, we will tell you how to choose the right equipment for welding, and which type of welding machine is better.

Welding classification

All welding machines are usually divided into the following types:

Household. Do not allow welding work of a significant duration without interruption. For their use, a 220V network and a current of 200A are sufficient. it the best option for home use. These include, for example, hand-held welding machines.

Professional. They are distinguished by greater versatility and the ability to work not only at a voltage of 220V, but also at 380V. In this case, the current strength can exceed 200A. Another difference is their size. A professional unit is much larger than a household one.

Transformers

This is one of the most simple designs welding equipment. The principle of operation of a transformer-type apparatus is to convert an alternating electric current of a higher voltage into an alternating current of a lower voltage.

Welding is the result of this process. For such a unit, it is preferable to use rutile or calcium fluoride electrodes with a diameter of 1.5-2.5 mm. Transformer advantages:

simple design solution;
reliability;
relatively low cost;
ease of use;
high efficiency.

The disadvantages include:

significant dimensions;
heavy weight;
high energy consumption;
voltage dependence.

Welding rectifiers

Their principle of operation is to convert the voltage (alternating in the network into constant welding). Advantages:

the possibility of welding with cast iron and non-ferrous metals;
constancy and stability of the electric arc;
the ability to work with low-alloy steel and stainless steel.

Inverters

The difference between inverter-type welding machines is a higher frequency. This model was designed for welding under constant voltage conditions, provided by the presence of an electric generator and connecting wires.

high efficiency;
small size;
a light weight;
ease of use;
high level of quality of work;
high stability of the electric arc;
initially flat joint surface;
the ability to work in a significant current range;
overload resistance;
the ability to use for beginners;
versatility with regard to electrodes.

Semiautomatic

The operation of semiautomatic welding machines is carried out on a constant or pulsed current with the use of shielding gases. No electrodes are needed here.

Instead, wire and various types of gas are used, selected depending on the type of metal. Positive sides:

high quality welded seams;
minimal metal spatter;
significant work efficiency;
the ability to weld thin metal sheets.

Welding equipment is quite traumatic. Therefore, it will be useful for every novice welder to familiarize yourself with the following recommendations given by experienced welding professionals:

Welding is permissible only in overalls and in the presence of protective equipment.

During the welding process, the wire must be held in such a way that the direction of the metal spatter is opposite from the welder.

It is necessary to ensure that there is no contact with current-carrying wires. Also, in working order, do not touch the electric holder, work surface and burner.