The device of welding inverters and their technical characteristics. What are the types and types of welding machines

The welding machine is an electrical device with which welding is carried out, namely the most reliable and durable method of fastening metal parts that has been in existence for over a century.

This electrical equipment performs the joining or cutting of parts made of metals and their various compounds with minimized costs. Let us consider in more detail the types of such devices and their main functions.

Welding power sources

These types welding machines needed to convert voltage to current. Depending on the circuit at the output, we obtain an electric arc having a constant or variable potential. By type, the following devices are distinguished:

transformer;
rectifier;
inverter.

The transformer source is the easiest to use, it works at the expense of a transformer, which reduces the mains voltage to the welding one and has an alternating current at the output. The current strength is regulated by changing the distance between the windings.

To improve arc burning, the transformer welding machine is understaffed additional elements, which increases its weight by several. The most critical work is carried out through the use of alternating current electrodes.

In the modern model of the transformer apparatus, powerful fans, because most of its energy comes from heating. This machine for welding has an efficiency of about 90%.

Advantages:

acceptable cost;
reliability;
durability is a quality that allows you to use various AC welding machines for many years.

Disadvantages:

has a fairly large weight;
rarely used, despite all its advantages.

Rectifier source - equipment used for welding after converting AC to DC. It consists of the following components:

current-reducing transformer;
diode;
adjustment and protection sensor.

This welding machine provides, in comparison with the transformer machine, the highest quality seams during welding. The rectifier has the greatest stability in the part welding current and electric arc.

Advantages:

low cost;
reliability.

Disadvantages:

big weight;
difficulty in work, because during the cooking process there is a strong overvoltage of the network.

The inverter source is currently the most popular type of welding machine. Consider its differences from transformer and rectifier welding machines:

Operates at a frequency current of several tens of kilohertz (usually up to 50 Hz).
Requires a small transformer.
Better quality seams.
The inverter transformer weighs several hundred grams at a current of 160A, the rest - 18 kg.
The total weight of the entire inverter is not more than 7 kg.

The inverter consists of electrical energy converters, a surge protector, and a transformer. Additionally, sensors for cooling, fuses, surge arresters are used to protect inverters.

There is a drawback: it is not advisable to work in dusty rooms, in the rain.

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Main characteristics of the welding machine

Let us consider in more detail each of their characteristics according to the catalog of models:

On duration.

Depending on the manufacturer of the welding machine, the ON time is measured differently. For example, the European standard EN 60974-1 takes into account the duration of welding only at a temperature of 40º C before the initial stop from overheating.

The Italian company Telwin in the calculations applies a temperature of no more than 20º C when working intermittently and takes into account the number of electrodes used during this period. In the calculations of this company, the PV turns out to be slightly overestimated, so the choice of welding machine is very important in terms of the methodology for calculating the PV.

From the foregoing, we can conclude that the apparatus of a European company with a duty cycle of 10-20% will have the same duration of operation as an Italian one (60-80% duty cycle).

Idle current.

Its limits are 60-85V. The higher the voltage, the easier it is to strike the arc.

There are models of devices for welding with inert gas or wire. In everyday life, they are used very rarely, since their main drawback is their high cost (compared to other models).

But if you do hard work on professional level, then the application of these models will be very relevant.

Welding current measurement range.

Partially shows the power of the device. The higher the power, the more likely it is to install larger electrodes. The PV also increases when working with small electrodes with a uniform distribution of current strength.

In everyday life, for all types of transformers, a 3 mm electrode is used with a permissible maximum power at 150A, and for inverter devices- 4 mm with a lower power rating.

When choosing electrodes, you need to pay attention to the recommended currents when working with welding machines.

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Varieties of welding

The method of manual arc welding is currently the most relevant type of welding with grease wire. When melting the wire, the metal is securely fastened, and the lubricant that coats the wire protects the seams from exposure to air, thereby improving the quality of the seams.

This method is used when welding ferrous and some non-ferrous metals (alloys). When welding only non-ferrous metals, instantaneous melting occurs with the release of steam, which leads to a poor-quality seam.

Method of manual welding with shielding gases

A frequently used mixture is an inert gas (argon) with the addition of oxygen. This is necessary to clean the welded metal from impurities and dirt. When welding, electrodes made of allotropic carbon (graphite) or refractory material (tungsten) are used.

Advantages:

high quality seam;
complete protection of the weld pool from air ingress;
no slag formation.

Disadvantages:

low speed of work;
expensive materials.

Despite its shortcomings, this method of manual welding is very popular today.

Welding method in semi-automatic mode

When welding, welding wire or non-metallic welding electrodes(see any catalog) in rare cases. Semi-automatic welding does not provide for automated movement. Welding is carried out using direct or pulsed current. The types of welding are as follows:

With inert gas (MIG).
With carbon dioxide or oxygen (MAG).
With the help of tubular wire (cored).

The semi-automatic welding method is used when joining thin metal, non-ferrous alloys and metals, and is widely used in industry.

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Additional Welding Methods

Today (mainly in industrial production) the following metal welding methods are used.

Plasma welding method

This industrial method has the following welding methods:

heat is released due to the plasma jet, which is obtained as a result of air ionization between the electrodes;
two electrodes are placed in the plasma torch.

The above methods are used for cutting metals rather than for welding.

Contact welding method

When using this welding method, the connected parts of the metal are in contact with each other, heated to deformation, and then compressed back. Contact welding has the following varieties:

spot welding technology;
butt welding technology;
relief welding technology;
seam welding technology.

Let's consider each of them in more detail.

Spot Welding Technology

This type of work is performed using a capacitor welding machine by laying workpieces on top of each other and clamping between two electrodes, while applying a small current and a significant voltage.

Thus, a weld point is obtained between the workpieces. When contact welding, you need to prepare the surface well for work. Welding is carried out in manual and automated modes and is suitable for all types of metal.

Embossed Welding Technology

This is a welding process that connects workpieces simultaneously at several points. This technology is similar to spot welding. They differ in that relief welding depends on the shape of the surface to be welded, and spot welding depends on the working area of the electrode.

Advantages:

parts are connected at several points at the same time;
a reliable weld is obtained.

The relief welding machine is used for fastening individual parts in cars, for connecting hardware. This method is used in radio electronics to connect small circuits.

Socket welding machines

Scope - welding of plastic pipes and galvanized products with a diameter of at least 16 mm and not more than 125 mm. There are the following types of these devices:

Devices for manual work with pipes of mini-sizes and diameters (coupling welding method).
Automated devices for working with tubes of large diameters.

Magnetically conductive welding machine from an electric motor - homemade apparatus used in the last century. For its manufacture, first you need a scheme, according to which all the parts will be connected to each other. You also need to choose suitable materials in normal condition. The main components for assembling this welding machine are:

case of asynchronous electric motor of small power;
magnetic circuit;
keeper tape;
electric cardboard circles;
enamel wire with a cross section of 7.5 mm 2;
the bus is rectangular with a section of 25 mm 2.

A magnetic circuit is placed in the motor housing, closed on both sides with circles of electric cardboard and wrapped with keeper tape. Then the primary (enamel wire) and secondary (copper rectangular bus) windings are performed.

The maximum current output in the primary winding is 25A, and in the secondary - 200A. When welding for 30 minutes, the AC welding machine heats up to a maximum of 70º C. The main disadvantage is that a lot of power is consumed when welding.

A welding machine is an electrical device with which welding is performed. It is this process that provides durable and reliable fastening of metal parts. With the help of welding, a huge number of works are carried out in various fields, ranging from microelectronics to the creation of multi-ton structures. Among the main advantages of electric welding stands out a reliable and fast connection of materials with minimal cost. If necessary, using this device, you can even cut metal. In recent decades, they have been manufactured using electronic components. Due to this, their weight and dimensions have been significantly reduced, which made it possible to expand their application.

Species and types

Welding equipment is characterized by a wide variety, which is due to the constant development of welding production, the creation of new techniques and methods of welding. Based on the design features, including the principle of operation of the devices, the following types can be distinguished:

Welding rectifier. It is equipped with a block of semiconductor diodes, as a result of which the current changes from alternating to direct. The main advantages are minimal spattering, welding of high-quality seams. It is used for welding ferrous and non-ferrous metal, cast iron, aluminum, steel.

welding transformer. Works with alternating current. There are several types - with increased and standard magnetic scattering. The welding process, due to the heavy weight with it, is a rather laborious work.

Semi-automatic welding. It is applied to welding works in the gas sphere.

Welding inverter. These are light and compact units.

Welder.

Apparatus for argon arc welding.

Base metal fusion welding equipment can perform the following operations:

Fusion welding.
Arc welding and surfacing.
Gas welding.
Electroslag welding and surfacing.
Electron beam welding.
Welding and cutting.
Special types of welding.

According to the degree of mechanization, welding machines can be:

Manual.
Semi-automatic.
Automatic.

The following classification of welding machines sounds like this:

household. They are distinguished by low productivity, they are not adapted for long-term work. However, their scope is very wide, such units are used for welding arches, boilers, pipes, and so on;
Professional. They are distinguished by heavy weight and dimensions, they work from a network of 220 or 380 watts. Most of these models are equipped with special wheels to facilitate movement. They are used in many areas of construction, workshops, gas pipeline installations, factories and the like.

Device

The device of each inverter model may have a number of features, but most technical nodes are repeated. The technique board mainly includes the following items:

Each welding machine is a kind of energy converter. The unit receives electric current from the network, after which it reduces its voltage, increases the current strength to the required value. In this case, a change in the frequency of the current occurs, or a direct current is formed from an alternating current. The only exceptions are devices where the electric arc is formed from the energy of generators with an internal combustion engine or batteries.

The welding semiautomatic device has the following device:

Cylinder with gas (argon or carbon dioxide).
Gas supply hose.
Wire cassettes.
Wire feeder.
Wire feed pipeline.
Source of power.
Gas-burner.
Gas equipment.
Control block.
Control circuit wire.

Welding machine. Operating principle

Consider a welding inverter. The whole essence of inverter technology lies in the rectification of the alternating current of the network into a direct welding current with an intermediate frequency change.

The rectifier is a conventional diode bridge. This unit receives alternating current, which has an industrial frequency of 50 Hz.
The filter is made of a capacitor and a choke. The rectified current is sent to the filter where it is smoothed out. As a result, a direct current appears, the inverter converts it into an alternating current, having a frequency of 20-50 kHz. At the moment, there are technologies with the help of which a current with a frequency of 100 kHz is obtained.
The power transformer provides a reduction in high-frequency alternating voltage to 25-40V. In addition, this element increases the current value to the required current for welding. By converting high-frequency currents, the welding current reaches the required strength. Thanks to the multi-stage current conversion, it is possible to use a small transformer. So, to obtain a current of 160 A in the welding unit, it is required to put a copper transformer weighing 18 kg. It is enough to put a transformer weighing 0.25 kg in the inverter.
The high-frequency rectifier provides equalization of the alternating current. Then it is sent to a high-frequency filter, which allows you to get a constant welding current.

These energy conversion processes are controlled by a microprocessor control unit. This part of the welding machine is the most expensive element. inverter welding devices Today they are produced using two different semiconductor technologies:

MOSFET.
IGBT.

Their main difference lies in the transistors, which differ in switching current. MOSFET transistors, when compared to IGBTs, are distinguished by large dimensions and weight, but their cost is lower. At the same time, they will need an order of magnitude more to ensure the same performance.

With the semi-automatic method, the welding machine works as follows:

The shielding gas is directed to the zone of the electric arc, which allows protecting the metal from exposure to air from oxidation and nitriding. The protective gas in this case can be active in the form of carbon dioxide or inert in the form of helium and argon. Working with metal in an inert gas environment is called MIG. Working with metal in an active gas medium is called MAG.
The welding wire is fed into the welding zone by means of an electric motor, a gearbox, as well as feed rollers.
A permanent connection is obtained in a gaseous environment under the action of an electric arc due to the melting of the electrode wire, which enters the burner. The required surfaces are glued together using molten metal created by thermal energy. The result is a strong, durable seam.

The semi-automatic welding method is called so due to the fact that the wire is fed automatically, while the feed control, as well as the welding process, is performed by the welder manually. The tip acts as a welding contact, it is powered by the main unit. The current strength is selected according to the characteristics of the material being processed. The feed rate is set using a gear or gearbox.

Application. Advantages and disadvantages of welding machines

The welding apparatus finds wide application. It is often used in everyday life, as well as in professional activity. Such a device is indispensable in many areas of production, industries and specialized workshops, for example, for car repair. These machines are used for reliable welding metal frames and other critical structures in construction. Without the use of professional welding equipment, it is also impossible to install oil pipelines and gas pipes.

transformers are very heavy and bulky devices. They possess hypersensitivity to voltage fluctuations and consume a lot of electrical energy. This is not an inexpensive device. You can cook them both butt and overlap. An experienced welder is able to weld even a critical seam well using a transformer. By means of alternating current, only certain grades of cast iron and steel of "running" grades are usually welded.
semi-automatic welding is ideal for both home and production. In our country, about 70% of all welding work is carried out by semi-automatic welding. This is due to ease of operation, high quality welding, wide functionality of the equipment. The semi-automatic welding machine is convenient for welding thin metal, especially car bodies. Semiautomatic devices are almost always found at car service enterprises.
Rectifiers have a high stability of the electric arc, which makes it possible to weld high-quality and tight seams of uniform depth. This significantly reduces spatter. The connection due to the security of the arc is quite strong and uniform. There is no need for additional cleaning of products from drops of "splashing" melt. In this case it is possible to work with all types of electrodes.

The scope of rectifiers is an order of magnitude wider: non-ferrous metals (nickel, titanium, copper, their alloys), any steel (including high-alloyed) and cast iron.

inverters. They have been very popular lately. They stand out for their functionality, power, compactness and low weight. This welding machine is optimal for beginners. Professionals can use them to increase their productivity. They are used everywhere, because they allow you to weld even thin-walled metal. Inverters can cook non-ferrous and ferrous metals of any thickness in various positions in space. All kinds of electrodes are used.

How to choose a welding machine

The welding machine can be three-phase or single-phase. For domestic use you need a device for 220 V. You can also choose a universal unit "220/380".
Open circuit voltage. Determines the ability of the apparatus to initially and re-ignite the electric arc, including maintaining its combustion. It is believed that the higher the open circuit voltage, the better.
Power. You should choose devices with at least a small margin of power, about 30%.
Protection class. The welding machine must be standardized and have a two-digit IP code, eg IP23. Two - objects with a thickness of more than 12 mm will not get inside the case. The second number is moisture protection. The number 3 means that water, even at an angle of 60 degrees, cannot enter the unit body.
Many modern devices are equipped with additional options: "Anti-stick on shutdown", "Arc forcing" or "Hot start". They will help with welding, especially for a beginner.

Non-standard application

The welding machine can be used as a charger car battery. However, it must be borne in mind that such a device must have an adjustment for lowering amperes and volts. If you have such a device, you need to switch it to the mode of the launcher-charger. You should set 12 volts at the output, and set the amperes to 1 to 20 battery power (if the power is 60A, we charge 3A).

The battery should be charged for about 40-60 minutes. This is enough to start the engine. For thorough charging, you will need to reduce the current by half and increase the time by 3 times.

Welding as a type of connection metal elements, became widespread a little over a century ago. However, today it is used in many areas of activity, from the production of electronics to the construction of giant structures. Since the composition of the metals used in this process is very diverse, many types of equipment have been invented and implemented to obtain reliable welding seams. The most popular among them are welding machines. Consider what are the welding machines, types, pros and cons of each.

transformers

The transformer is the most traditional kind of electric welding machine. At the same time, it is one of the simplest in design. The main structural element of this type of welder is a step-down transformer that converts the mains voltage to the value required for welding. In this case, the current strength changes using different methods, the most famous is the displacement of one winding relative to the second. As the gap between the windings changes, the current changes.

A feature is the alternating current at the output, which leads to a noticeable spatter of the metal and a deterioration in the quality of the seams. To carry out welding of non-ferrous metals, to improve the quality of arc burning, rather massive and bulky components must be added to the structure of the apparatus. The main element - the transformer - also does not differ in compactness and low weight. When using the machine to produce serious work specific (for alternating current) electrodes and considerable experience of the welder are required.

The efficiency of the device is quite high, reaches 90%, but part of the energy is spent on heating. Cooling is done by fans different power, since it is required to cool the unit weighing several tens, and sometimes hundreds of kilograms. The use of this type of welding machine is declining today, but they are still in demand due to low cost, reliability and durability. Transformers are used for welding low alloy types of steel.

Rectifiers

Welding rectifiers can be considered an improvement in transformer devices. In welding seams obtained with the help of rectifiers, those flaws that are caused by the use of alternating current are practically excluded. The devices, in addition to the step-down transformer, have a diode block (rectifier), control, start-up and protection elements in their design. Alternating current not only changes voltage, but is also converted to direct current. This makes it possible to obtain a smooth, stable arc. Accordingly, spattering of the metal is reduced, the seam is of better quality. You can work with any electrodes.

The scope of use of a welder is also expanding - it is possible to connect not only low-alloy "black" steels, but also non-ferrous metals, stainless steel, cast iron (using appropriate electrodes). Since the direct current has a polarity, we should not forget about it - this parameter should be taken into account when connecting the electrodes. Some welding work is deliberately carried out with reversed polarity (aluminum welding).

Many manufacturers today reduce the production of this type of household appliances. If we talk about professional use, they are still used quite widely . The disadvantages can be considered a lot of weight, the need for a qualified welder, a serious “drawdown” of voltage in the mains during the welding process. Advantages - low price, reliability and good quality of the seam.

semi-automatic

Semi-automatic welding machines in an inert or active gas environment, or simply semi-automatic devices, are more complex devices than transformers or rectifiers. However, they are more convenient to use. Often used for body repair cars are widely used in everyday life, private households.

The design consists of the following components:

transformer;
rectifier;
wire feed drive;
gas cylinder;
burner sleeves.

Welding of parts is carried out by a wire melting in an electric arc, which in the process is located in a shielding gas environment. The current is most often adjusted in steps, and the wire feed speed is also subject to change. The ratio of these parameters sets the required mode of operation.

Various models of semi-automatic machines work:

only with gas;
with gas or without gas (switchable);
only without gas.

If the work is done without gas, a special wire (flux) is used. Flux wire differs from ordinary flux wire in that its composition, in addition to metal, includes flux. When the components of the flux are burned, a shielding gas cloud is formed, which prevents the air from oxidizing the weld pool. In addition, the active elements of the flux composition give the metal the necessary parameters, the arc becomes more stable. In this case, a gas cylinder is not needed, which is convenient, but the wire itself is much more expensive.

When working with different metals, different gases are used - carbon dioxide when welding iron, a mixture of argon and carbon dioxide when working with steel, when welding aluminum - argon. Gas cylinders should be used industrial or branded.

Semi-automatic machines are characterized by high productivity, give an excellent quality seam on various metals. The disadvantages include spattering of metal and a high consumption of materials for waste.

inverters

Devices of this type are also called pulsed. Today, welding inverters are considered one of the most common devices due to their low weight and general availability. And if even 10 years ago inverters were expensive and not very reliable, now these shortcomings have been eliminated. The use of the inverter technique today gives a reduction in the size of the transformer, an increase quality properties arc, optimization of efficiency, reduction of metal spatter during welding.

The welding inverter consists of power transformer, the purpose of which is to reduce the mains voltage to the desired value, a block of electrical circuits and a stabilizer choke, necessary to minimize current ripples.

The mains voltage is supplied in the inverter to the rectifier, at the output of which the block circuit transforms direct current into alternating current, which has a high frequency. This, obtained at the output of the power unit, alternating current is supplied to welding transformer high frequency, more compact and lighter than a conventional mains converter. The voltage at the output of the welding transformer is rectified again and fed to the arc.

Argon arc welding machine

This type of welding equipment uses special non-consumable tungsten electrodes, helium or argon serves as protection gas.

The argon arc apparatus using a tungsten electrode contains the following components:

a source that provides direct or alternating welding current;
regulation device for working with current;
set of burners for use with different voltages;
a control circuit that provides coordination of the welding cycle and protection;
stabilizing device for excitation as well as alignment of the arc.

Units of this type are used if there is a need for high-quality welding of non-ferrous metals.

Spot welding machine

Spot welding is one of the types of resistance welding of the thermomechanical class. The process itself consists of several steps. To begin with, the parts, folded in the necessary way, are placed between the electrodes and compressed with each other, after which they are heated until plasticity is reached and deformed together. Welding speed in factory conditions - up to 10 points per second.

The parts are heated with an instantaneous (0.01–0.1 sec.) welding current pulse. This fast pulse makes it possible to achieve heating of the metal to melting, which leads to the formation of a liquid zone combined for both parts. After the current stops, the parts are still aligned, pressed against each other until the temperature drops and the molten point solidifies. Compression of parts is stopped with a time delay to create conditions for better crystallization of the metal.

The advantages of spot welding include cost-effectiveness, reliability and strength of the seam, and the ease of achieving automation. Unfortunately, this type of welding seam does not have tightness, which limits its scope.

Apparatus for gas cutting and welding

Gas welding involves heating the part to a melt with a high-temperature flame. In this case, combustible gases are used - hydrogen, natural gas, acetylene. The characteristic property of these gases is good burning on air. Most often, gas welding machines use acetylene, which is easily obtained using calcium carbide and water. The combustion temperature of this gas is 3200–3400 °C.

Advantages of gas welding and metal cutting:

Uncomplicated technology.
Access to the electrical network is not required, there is no need to use electric current.
The equipment on the basis of which welding is performed is quite simple.

However, it should be noted that gas welding will not provide high speed work and productivity, because it is done only manually.

Serious attention in gas welding is paid to the preparation of parts, regulating the power of the burner, and setting it to the desired position.

Plasma welding

Plasma welding (cutting) of metals is an operation during which the metal is melted by a plasma stream. Plasma is a gas containing charged particles that conduct electricity. The gas is ionized by heating with an arc coming out of the plasma torch. The higher the temperature of the gas, the higher the ionization. The temperature of the arc in plasma welding machines reaches tens of thousands of degrees.

The technology is as follows: gas and electric current are supplied to the burner at a fast pace to form an arc. Cutting occurs not only due to the melting of the metal, but also due to the fact that the high-speed ionized flow washes the metal out of the plasma area.

In addition to knowing what welding machines are, the user's needs should be taken into account when choosing. And if a professional device may be needed in a car repair shop or in production, then an inexpensive device is enough for domestic needs.

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

AC(English alternating current) - alternating current.
DC(English direct current) - direct current.
MMA(Eng. Manual Metal Arc) - manual arc welding with stick electrodes. We know it under the name RDS.
TIG(Eng. Tungsten Inert Gas) - manual welding tungsten non-consumable electrodes in a protective gas environment (argon).
MIG/MAG(Eng. Metal Inert / Active Gas) - semi-automatic arc welding with a consumable electrode wire in an inert (MIG) or active (MAG) gas 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) up to automatic shutdown due to overheating. The PV value is indicated as a percentage relative to the standard cycle, which is 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 for the machine to cool down. This parameter can be equal to 10%, so you need to pay attention to it. In the concepts: on-duration (PV), duration of work (PR), load duration (PN) are invested different meaning, 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 node is a power transformer, with the help of which the mains voltage is reduced to no-load 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 - welded part.

To limit the short-circuit current and stable arcing, the transformer must have a steeply falling external current-voltage characteristic ( . To do this, either transformers with increased scattering are used, as a result of which the short-circuit resistance is several times greater than that of conventional power transformers. Or, a reactive coil with a large inductive resistance is included in the circuit with a transformer with normal scattering - a choke (the choke can be included not in the secondary winding circuit, but in the primary circuit, where the current is less). If the choke can change the inductance by adjusting it, they change 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 Ud.

Welding current control. The current strength in welding transformers can be regulated by changing the inductive resistance of the circuit (amplitude regulation with normal or increased magnetic scattering) or by means of thyristors (phase regulation).

In amplitude control transformers, the required welding current parameters are provided by moving 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.

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

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

There may be a simple change in the number of turns used in the transformer winding, to reduce the open-circuit voltage and hence the welding current.

Transformers with thyristor (phase) regulation consist of a power transformer and a thyristor phase regulator with two anti-parallel thyristors and a control system. The principle of phase regulation consists in converting a sinusoidal current form into sign-alternating pulses, the amplitude and duration of which are determined by the angle (phase) of thyristor activation.

Scheme of a welding transformer with thyristor control. BZ - task block, BFU - phase control block.

The use of a thyristor phase regulator makes it possible to obtain a welding machine, the characteristics of which compare favorably with the characteristics of a transformer with amplitude regulation. In more complex control circuits than in the figure above, a square-wave alternating current is generated. And in this case, for example, an increased rate of transition of the pulse through the zero value is achieved, as a result of which the time of current-free pauses is reduced and the stability of the arc burning and the quality of the weld are increased. What can not be said about the oscillogram shown above, on it the current-free gaps are larger than those of transformers with amplitude regulation 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.

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

Advantages and disadvantages of 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 longer. First of all, this is the low stability of the arc, due to the properties of the alternating current itself (the presence of current-free pauses when the electric signal passes through zero). For high-quality welding, it is necessary to use special electrodes designed to work with alternating current. Negatively affect the stability of the arc and fluctuations in the input voltage.

Welding transformer cannot be welded stainless steel, which requires direct current, and non-ferrous metals.

If the power of the AC welding machine is large enough, its weight may cause certain difficulties when moving the transformer from place to place.

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

Welding rectifiers

Welding rectifiers are devices that convert the alternating mains voltage into a direct welding voltage. There are many schemes for constructing welding rectifiers with various mechanisms for generating the output parameters of current and voltage. Various methods of current regulation and formation of the external current-voltage characteristic of rectifiers are used ( 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 regulation using thyristors and transistors. In the simplest devices, the current is regulated by a transformer, and diodes are used to rectify it. The power part of such devices consists of a transformer, a rectifier unit on uncontrolled valves and a smoothing choke.

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

The transformer in such a circuit is used to lower the voltage, form the necessary external characteristic and control the mode. More modern and advanced devices include thyristor rectifiers, in which mode control is provided by a thyristor rectifier unit, which performs phase control of the thyristor turn-on moment. The formation of the necessary external characteristics is carried out by introducing feedback on 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 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 elements of rectifiers need forced cooling. To do this, they put radiators blown by a fan.

The figure below shows a diagram of a welding rectifier in which a change in the resistance of the transformer and current regulation is provided using a magnetic shunt - by closing or opening it using the knob on the front panel of the device.

Schematic diagram of a welding rectifier with a magnetic shunt: A - circuit breaker, T - transformer, Dr - magnetic shunt, L - light-signal fittings, M - electric fan, VD - diode rectifier unit, RS - shunt, PA - ammeter.

Single-phase AC rectification circuits are used in circuits with low power consumption. Compared to single phase three-phase circuits provide significantly less ripple of the rectified voltage. The operation of a three-phase Larionov bridge rectification 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, compared with transformers, is the use of direct current for welding, which ensures ignition reliability and stability of the welding arc and, as a result, a better weld. It is possible to cook not only carbon and low-alloy, but also stainless steel and non-ferrous metals. It is also important that welding with a rectifier produces less spatter. In essence, 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 prices.

The disadvantages include the relatively large weight of the devices, the loss of 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 direct current into alternating current. 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 operation of the welding inverter is as follows. Alternating current with a frequency of 50 Hz is supplied to the mains 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 the most important in the operation of the welding inverter, which allows to achieve huge advantages over other types of welding machines. Further, with the help of transformer 4, the high-frequency alternating voltage is reduced to idle values (50-60V), and the currents are increased to the values necessary for welding (100-200A). The high-frequency rectifier 5 rectifies the alternating current, which does 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 done by IGBT transistor modules, which are the most expensive elements welding inverter.

The feedback control system generates ideal output characteristics for any method of electric welding ( 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 reduced significantly.

According to their functionality, inverters of the following types are produced:

for manual arc welding (MMA);
for argon-arc welding with non-consumable electrode (TIG);
for semi-automatic welding in shielding gases (MIG/MAG);
universal devices for operation in MMA and TIG modes;
semiautomatic devices for work 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.

Advantages of inverters. The advantages of welding inverters are great and numerous. First of all, their low weight (4-10 kg) and small size, allowing you to easily move the machine from one welding site 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 remagnetization of the iron core and achieve high efficiency (85-95%) and an 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 kinds of external current-voltage characteristics. This means that it can be used to perform all major types of welding - MMA, TIG, MIG/MAG. The device provides welding of the alloyed and stainless steels and non-ferrous metals (in the MIG/MAG mode).

The device does not require frequent and prolonged cooling during intensive work, as 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 much wider range of welding current adjustment than conventional devices - from several amperes to hundreds and even thousands. For domestic use, low currents are especially important, which allow welding with thin (1.6-2 mm) electrodes. Inverters provide high-quality formation of the seam in any spatial position and minimal spatter during welding.

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

The Hot Start function provides an automatic increase in current at the start of welding, making it easier to strike the arc.
The Anti Stick function (anti-sticking) is a kind of antipode of the Hot Start function. When the electrode comes into contact with the metal and there is a threat of its sticking, 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 (arc forcing) is realized when a large drop of metal separates from the electrode, reducing the length of the arc and threatening to stick. Automatic increase in welding current by very a short time prevents this.

These convenient features allow low-skilled welders to successfully cope with the welding of the most complex metal structures. For those who have ever worked with a welding inverter, the question - which welding machine is better - does not exist. After a transformer or rectifier, working with an inverter turns into a pleasure. It is no longer necessary to "hollow" the electrode in order to ignite an arc that does not want to ignite, or frantically 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 that the electrode can be welded.

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

Disadvantages of welding inverters. It is difficult to talk about the shortcomings of such a perfect device as a welding inverter, and, nevertheless, they exist. First of all, this is the relatively high price of the device and the high cost of its repair. 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 imposes increased requirements, in comparison with other welding machines, to the conditions of storage and operation, due to its electronic filling. The device does not respond well to dust, since it worsens the cooling conditions for transistors, which get very hot during operation. They are cooled with 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 condensate 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 semi-automatic

Speaking of welding equipment, you can not ignore semi-automatic devices - devices for welding in a shielding gas environment with a mechanized feed of the welding wire.

Welding semiautomatic device consists of:

current source;
control unit;
welding wire feed mechanism;
a gun (torch) with a sleeve-electric wire, through which the supply of protective gas, wire and electric signal is carried out;
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 current source. The use of the latter improves the quality of welding and increases the amount of welded materials.

According to the design, semi-automatic welding machines are double-case and single-case. In the latter, the power source, control unit and wire feeder are housed in one housing. For double-case models, the wire feed mechanism is placed in a separate unit. Usually this professional models, supporting long-term operation at high current. Sometimes they are equipped with a pistol water cooling system.

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

Semi-automatic welding is one of the most modern arc welding technologies, ideal not only for production, but also for the home. Semiautomatic devices are widely used in industry and everyday life. There is information that at present in Russia up to 70% of all welding work is carried out by semi-automatic welding. This is facilitated by the wide functionality of the equipment, high quality welding and ease of operation. The semi-automatic 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 welding machine should be made according to specific needs. Before you go to the store, you need to know the answers to the following questions.

What metal - by brand and thickness - is to be welded?
Under what conditions will the work be carried out?
To what extent?
What are the requirements for the quality of work and qualifications of the welder?
And, finally, how much can be spent on the purchase of a welding machine?

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

If you have to weld 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 you have to weld metals that require protection from oxygen or nitrogen in the air, such as aluminum, then you will need welding in a shielding gas environment, which can be provided by a semiautomatic device with MIG / MAG mode.

In general, if we talk about the versatility of equipment, then the best choice, perhaps, would be a semi-automatic device with MMA and MIG / MAG modes. Its presence will allow you to perform almost any work on welding metals, which 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 at sub-zero temperatures, especially at values below 10-15 °C, is undesirable for inverters. Strong dustiness also affects them badly. The conclusion is this. If you have to work at very low temperatures in conditions of high dust content, there may be no other option but to choose a welding machine without state-of-the-art electronics - a welding transformer, a diode rectifier or a semi-automatic device based on the latter.

High requirements for the quality of welding and low qualification of the welder definitely incline to the choice of a welding inverter with its ease of use and Arc Force, Anti Stick, Hot Start functions.

A large amount of work requires a high duty cycle (duty cycle) from the welding machine, otherwise too much time will be spent on downtime during its cooling. PV is one of the characteristics that distinguish household welding machines from professional ones. For 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 significantly superior to the PV of welding transformers and rectifiers. It is better to take 30% as the minimum value of PV.

When choosing a welding machine, you need to think about the neighbors. If you have to cook a lot, and the mains voltage is low and unstable, you should choose a welding machine for your home, taking into account the power it consumes. The constant flashing of light bulbs, which occurs during the operation of powerful welding transformers and rectifiers, excites universal hatred for welder neighbors. The inverter with its energy saving and anti-stick function will not harm good neighborly relations. When the electrode comes into contact with the metal to be welded, the welding transformer drains the mains, while the inverter simply reduces the welding current (terminal voltage), plus the inverter is more efficient at low mains voltage.

Basic requirements for power sources for welding

To meet their intended purpose, current sources must meet certain requirements, the main of which include the following:

the open circuit voltage must ensure the ignition of the arc, but not be higher than values that are safe for the welder;
power sources must have devices that regulate the welding current within the required limits;
welding machines must have a specified 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 the 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 1000 V and a gap between the electrodes of 1 mm. This method of starting an arc is usually not used due to the danger of high voltage. When the arc is powered by high voltage current (more than 3000V) and high frequency (150-250 kHz), air breakdown can be obtained with a gap between the electrode and the workpiece up to 10 mm. This method of ignition of the arc is less dangerous for the welder and is often used.

The second method of ignition of the arc requires a potential difference between the electrode and the product of 40-60V, therefore it is used most often. When the electrode comes into contact with 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 move towards the anode by electrostatic attraction, forming an electric arc. The arc quickly stabilizes (within a microsecond). The electrons that come out of 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 the electrode contacts the workpiece, on the time of their contact, and on the composition of the gas gap. The arc excitation speed is affected, first of all, by the magnitude of the welding current. The greater the current value (with the same electrode diameter), the greater the cross section of the cathode spot becomes and the greater the current will be at the beginning of the arc ignition. A large electron current will cause rapid ionization and transition to a stable arc discharge.

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

The arc ignition speed is also affected by the polarity and type of current. With direct current and reverse polarity (i.e., the plus of the current source is connected to the electrode), the arc excitation 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.

Re-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 electrode end 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 (Ei) and internal resistance (Zi), consisting of active (Ri) and inductive (Xi) components. At the external terminals of the source we have voltage (Ui). In the "source-arc" circuit, there is a welding current (Id), which is the same for the arc and the source. The source load is an arc with 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 the following: Ui = Ei - Id Zi.

The source can operate in one of three modes: idle, load, short circuit. When idling, 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, a current (Id) flows through the arc and the source, and the voltage (Ui) is lower than at idle by the amount of voltage drop inside the source (Id Zi).

In case of a short circuit, Ud=0, therefore, the voltage at the source terminals 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. When 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 falling, gently dipping, rigid and even increasing current-voltage characteristics. There are also universal welding machines, the characteristics of which can be steeply falling and hard.

External current-voltage characteristics of welding machines: 1 - steeply falling, 2 - gently falling, 3 - rigid, 4 - increasing.

For example, a conventional (normally dissipated) transformer has a rigid characteristic, and a rising characteristic is achieved by feedback, when the electronics increase the source voltage as the current increases.

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

The welding arc also has a current-voltage characteristic.

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

As the arc length increases, the volt-ampere characteristic shifts upward. A change in the electrode diameter is reflected in the position of the boundary between the rigid and increasing sections of the characteristic. The larger the diameter, the higher the current will fill the end of the electrode with a cathode spot, while the growing area will shift to the right (shown in the figure below by a dotted line).

Stable arcing is possible provided that 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 the arc various lengths- L 1 , L 2 , L 3 (L 2 >L 1 >L 3) and the steeply falling 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) express the zones of stable burning of the arc at different arc lengths. It can be seen that the greater the slope of the source characteristic, the smaller the change in the welding current with fluctuations in the arc length. But the length of the arc is maintained during the combustion process manually, therefore it cannot be stable. That is why only with a steeply falling characteristic of the transformer, fluctuations in 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. While we are writing this material, maybe this number is increasing. Reach complete classification in one article it is difficult and stupid, so let's deal with at least 4 main types of metal welding.

What is welding like? Main types

Manual arc

Gas

semi-automatic

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

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 loose fluxes. Due to the heat of the arc, the surfaces to be welded and the wire with flux melt.
Thermite	Products are placed in a fire-resistant container, and powder (termite) is poured into the upper strobe, where there is a seam. At 2000° the metal melts and fills the seam. This seam is then welded.
Ultrasonic	The effect of mechanically induced vibrations (ultrasonic frequencies) on the part to be welded.
Cold	Fusion of crystals under high pressure.
Electroslag	A welding arc appears under the flux. The flux melts and an electrically conductive slag appears, which has a high ohmic resistance. Due to the latter, metals are welded. Pros: no need to use heat treatment; flux savings. Minus: possible deformations.
Contact	Metals are heated, passed through an electric current and deformed. Contact welding is used in mechanical engineering in the mass production of parts.
Plasma	Non-standard welding technology. The moving arc is heated, which due to this unusual property the temperature rises sharply. by the most comfortable view welding on aluminum is considered plasma, 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 welding with a consumable electrode;
ЗН - welding with embedded heaters;
RD - manual arc welding with coated electrodes;
AF - automatic submerged arc welding;
MADPN - mechanized argon-arc surfacing with a consumable electrode.

Manual arc view

Welding is carried out with stick electrodes, which gradually melt and leave behind a bonding seam. The required distance is made between the metal surface and the electrode for its melting.

This is called the arc, which 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 spot-fastened so that they do not move apart, otherwise the welding will be uneven, and the seam will stretch - on the one hand it will fixed 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 between 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 comes out. 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. Failure to do so may result in the welding site being lost when putting on the welding helmet.

When fastening two surfaces, it is necessary 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 takes place at a height or just the cable at the holder is very long, then it will pull, and this may interfere with the correct seam. To do this, hold it in your other hand or hang it on a hook.

Semi-automatic welding

PS advantages (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 - 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), a special wire and shielding gas.

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

We recommend a 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 thicknesses metal should 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 a special powder composition.

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

Cons: strong spattering of the metal, not a very beautiful appearance of the seam.

By adjusting the inductance, with such welding, it is possible to change the quality of penetration and the width of the seam. If it is reduced, the arc will be colder. The result of the work is a thin seam and deep penetration. By increasing the inductance, the arc gets hotter, resulting in a smooth, wide bead and less deep 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 sticking out of the nozzle, because a ball is formed on it, which does not conduct current well. When welding surfaces, they must be cleaned of paint or rust.

IMPORTANT! If distinct clicks are heard during operation, it means that the welding machine is set to a high value of the welding voltage or insufficient wire feed speed. At a high feed rate, the wire will not have time to melt.

Application various seams requires device settings. Welding of thin metals occurs spot. Do not weld with 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 pressure of 0.63 MPa;
oxygen hose of the third category for supplying oxygen under pressure up to 2 MPa;

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

Its working pressure is 0.2 MPa. To set the pressure on the oxygen cylinder, turn 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 the working flame on a gas burner, open the acetylene screw, then light the flame. Make sure that the flame does not break away from the tip of the gas burner. After that, adjust it with a screw with oxygen.

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

To make a weld pool, you need to position the torch at 90 ° to the base metal. The distance between the core of the flame and the surface should 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, we position 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 slight 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 the end of work, the gas burner closes: first, the acetylene propeller, then, after the burner is purged, the oxygen one.

The balloons are closed one by one. Acetylene first. We close the screw on it, then unscrew the adjusting screw from the gearbox. Oxygen closes similarly.

After closing the cylinders, it is necessary to release the residual pressure from the sleeves. The screws on the burner open: first acetylene, then oxygen. On the pressure gauges of both cylinders, you will see how the pressure drops. After the release of the remaining pressure, close.

Safety precautions when working with gas welding

it is better to choose hoses of class 3. They withstand pressure up to 40 atmospheres;
fastening on fittings should be carried out using clamps, but not wire;
fire safety valves are installed on hoses, reducers and burners: they prevent the flame from passing inside the hose and getting into the cylinder, thereby preventing a gas explosion;
if the burner suddenly starts to melt, you don’t need to throw it and run away - near it you need to bend and pinch the hoses with your hand, and then close the screws on the burner; if not in time, then on the balloon.

Argon welding

It is applied to connection of non-ferrous metals or the alloyed steel.

Consists of:

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

Before welding, tungsten rods are sharpened so that the risks are located vertically, and not horizontally. Then it is inserted into the burner and closed with a nozzle. Under each metal there is a nozzle of the required number.

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

To work with different metals, including the thickness, different arcs are installed - even, 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.

During welding, a filler wire is fed. Welding occurs in the same way as the previous ones. By surfacing the edges of the metals to be welded and welding the wire into the gap between them.

We must not forget that the electrode in the burner is always energized, so you need to handle it 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 practically does not splatter.
	Electricity consumption is almost 30 percent less compared to analogues.
	Automatic overload protection, neat seam. Efficiency 85%.

Due to its PFC technologies, it can operate at a voltage of 100 V, which is very convenient in country conditions. It copes well with arc welding, it is possible to connect to a generator. By reducing 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 into the network and start working immediately) and an anti-sticking function for electrodes in metal. The device can operate at a voltage of 170 V.

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