DIY DC welding machine: my diagram. DC welding machine - compare with competitors DC welding machine for four stations

Which device should I choose?

What to choose - a rectifier or a transformer?

AC welding machines have the following advantages:

• simple design;
• minimum breakdowns, long working life;
• the ability to regulate the strength of the welding current.

• low efficiency;
• metal spattering during welding;
• large dimensions.

• high quality welds;
• high efficiency;
• the ability to regulate the current strength, protective block;
• welding of any metals, incl. low alloy, etc.

The main characteristic of welding inverters is the current strength; the higher it is, the more productive the device will be. The cost of welding also directly depends on this indicator.

For domestic use, an inverter with parameters up to 160 A, connected to a 220 V power supply network, is sufficient. If there are voltage surges in the power supply network, then it is recommended to purchase a semi-professional device with a current characteristics of 200 A. It is not difficult to measure the current strength of the device. Typically, this indicator of a working inverter corresponds to that declared by the manufacturer, but if there are doubts about the serviceability of the device, then the readings can be measured using a digital millivoltmeter or a pointer microammeter. However, please note that the instrument readings depend on the length of the welding arc, the diameter of the electrode, and the correctness of the measurement.

Also an important indicator is the power of the welding machine. As a rule, it is not indicated in the passport, but knowing the maximum current produced by welding and other parameters, you can calculate the amount of kW consumed.

Inverter BEAM

A welding machine is one of the most popular equipment in the world. Welding work is carried out everywhere and on a very large scale.

Of course, there are many varieties of these devices, differing in operating principles, dimensions, output amperage and other technical characteristics. There is also equipment that operates on alternating and direct current.

The DC welding machine is the most common because... supports 2 operating modes - welding of direct (minus on the electrode, and plus on the part) and reverse (vice versa, plus on the electrode, minus on the part) polarity. Very often it is necessary to change operating modes, because... Some metals adhere well in direct polarity, while others in reverse polarity.

The choice of one or another device is closely related to what goals the welder himself adheres to:

• What metal will be welded (type and thickness);
• What current (its voltage and strength) is present at the work site;
• How long will the welding machine have to work without rest?
• And other situations.

Welding machines used in industry, production, construction, etc. different from those used at home. The main difference between them is power and, accordingly, cost.

Today, so-called inverters - electric arc welding machines - are very successful on the market. They are excellent for carrying out almost any welding work, of any complexity and volume. They are also most often used in everyday life for two simple reasons - they are small in size and low in cost. In addition, inverters are easy to use and easy to repair. And an electronics engineer, even with a basic set of knowledge, is able to create a homemade DC welding machine from numerous circuits available on the network.

Let us consider the above criteria for selecting inverters in more detail.

Some facts about inverters and which one to choose for your home

Let's start with the metal being welded. For example, in production or construction, welding of thick metal parts or metals with a low weldability coefficient (the ability of metals to be welded) is often required. In such situations, you cannot do without a powerful welding machine with an output amperage of about 300-500 A or more. However, metal sheets or parts with a thickness of more than 5 mm are very rarely found in everyday life. And for welding them, an inverter with a current of 160 A is quite suitable.

Svarog 500 at 380V

The voltage that a house, garage, etc. is equipped with is often not enough for the normal functioning of high-power welding machines, because... they require 380V (3 phase). Before purchasing one or another inverter, it is necessary to measure the voltage in the place where welding work will be carried out. It often happens that the owner checks the product before purchasing it in the store to see if it works, and when he arrives home it turns out that it doesn’t work. It's all about the lack of tension. Therefore, you need to buy an inverter with technical characteristics that are suitable for its normal operation at home.

An inverter is most often a DC welding machine, especially if it will be used at home. In order to obtain a constant voltage at the output, special high-voltage converters are used. It is they that get very hot during operation, which requires the use of high-quality cooling. In cheaper models, inverters use metal (aluminum or copper) heat sinks - radiators. More expensive models use air or water cooling, thanks to which the devices are able to operate for a very long time without turning off. However, inverters with radiator cooling of electronic elements are quite suitable for domestic purposes.

Having accurately determined all of the above, you can safely buy this or that inverter model.

stroysvarka.ru

AC/DC Welding Inverter

Numerous low-quality fakes force people to make their own AC and DC welding inverters, which are more reliable and easier to repair. How to make such a unit with your own hands and make it durable and efficient in conditions of unstable voltage in the countryside and in rural areas? We will answer this question in this publication and step by step assemble a reliable and practical welding inverter for connecting different parts. Our task is to ensure small dimensions of the equipment and light weight of the final device for ease of use.

Types of welding machines

To reliably join metals in any construction, welding machines are used, the basis of which is a power transformer, which serves as a voltage and current consumption converter. According to the principle of operation, welding units are divided into the following types:

Until recently, the most popular was the DC welding machine, the main disadvantage of which was its significant weight. At the same time, the simple design of such a product made it possible to make a homemade product at home that is not inferior to industrial designs. In addition to the power transformer, the design includes rectifying diodes and a high-capacity smoothing capacitor, as well as chokes and resistors. Thus, assembling a welding machine with your own hands is not so difficult.

An AC welding machine looks even simpler, which is a power transformer, in the secondary winding of which several terminals with different numbers of turns are made. This is done to adjust the welding current depending on the thickness of the material being joined. Such AC welding machines are easy to manufacture, but have low operating comfort, although the seam is more uniform and durable.

Three-phase units are made of three transformers connected in a star with six diodes connected in a three-phase bridge circuit. This connection allows you to consume a small current and distribute the load evenly across phases.

Next, we will consider welding inverters with high-frequency alternating current, which are distinguished by their low weight and dimensions. The essence of their work is that an alternating mains voltage of 220 volts with a frequency of 50 Hz is rectified and then converted into a high-frequency alternating voltage of 20-50 kHz. This approach allows you to reduce current consumption and reduce the weight of the unit without compromising its technical characteristics.

It is important to remember that homemade DC welding machines are only used with the appropriate electrodes.

Advantages of a homemade inverter

For construction work involving metal structures, it is advisable to have your own welding machine, but its price in retail chains is often too high. You can assemble a homemade welding machine, which will reduce the cost of the final product, but you still cannot do without certain costs. In particular, costs for high-frequency transistors, as well as a thyristor current regulator for the welding machine and rectifier diodes will become necessary.

The inverter has the following advantages:

• light weight, about 10 kg, depending on power;
• efficiency - more than 90%;
• low power consumption;
• wide operating limits of current regulator circuits, which allows you to work using different technologies for welding elements from different metals;
• high voltage stability on the electrode allows you to make an even and high-quality seam;
• you can use different types of electrodes;
• Modern circuits and components make it possible to eliminate sticking of electrodes and provide accelerated ignition of the arc.

Necessary components and tools

We see that an inverter is an indispensable tool in welding work, lightweight and easy to use. In order to ensure its high-quality assembly, you will need, in addition to radio components, the following tools:

• powerful soldering iron with solder and flux;
• a set of screwdrivers and pliers;
• electric drill or screwdriver with a set of drills;
• hacksaw, knife, scissors;
• a suitable sized housing for mounting the inverter.

To understand the essence of the assembly of the device, it is necessary to understand the circuit diagram of the device and the interaction of its components with each other. The welding inverter consists of the following main components:

• mains voltage 220 V, 50 Hz is supplied to the primary low-frequency diode rectifier, after which the DC voltage is filtered by capacitors;
• DC voltage is supplied to the inverter, which produces high-frequency AC voltage at the output;
• Next is a step-down transformer;
• then a secondary high-frequency rectifier;
• direct current goes through the inductor to the electrode;
• the input and output of the high-frequency transformer are connected to a feedback unit, which adjusts the operation of the inverter depending on the parameters of the welding current;
• welding inverter control unit.

Assembly sequence of the welding machine

Assembling an inverter yourself involves using as many ready-made elements as possible, since this unit is quite complex and cannot be done without knowledge of the basics of radio electronics. For final testing and debugging, you will need an oscilloscope and a tester designed for measuring high currents.

You can rewind the transformer yourself, adapting it to your needs, or create a choke. It is possible to place diodes and thyristors on radiators, secure busbars made of aluminum or copper strips, but assembly and debugging of feedback and control units can only be done with the help of a specialist.

When assembling a welding machine, it is very important to follow safety precautions, since electrical equipment is associated with the risk of electric shock.

When carrying out work on the installation of inverter components, it is necessary to comply with a number of requirements, namely:

• the housing for the device must be selected so that all the elements of the inverter are placed in it compactly, but not crowded;
• when winding a transformer, you need to ensure that the winding turns are tightly laid out, reliably insulated and secured;
• power diodes, thyristors and transistors are securely mounted on radiators using heat-conducting paste;
• it is best to use copper wires and busbars, since their conductive properties are higher than those of aluminum;
• the quality of all components should be treated very carefully, because the durability of the device depends on them;
• ensure uninterrupted operation of the cooling system using powerful fans, and drill holes in the case for air circulation;
• Carefully solder all electrical connections.

Final debugging of the welding inverter should be carried out under the supervision of a specialist.

Results

When assembling a welding inverter with your own hands, you will provide yourself with an indispensable and convenient device for welding metals, and in addition, you will be able to save a lot. It is important to take a responsible approach to the selection of parts and electronic components, and if necessary, seek help from professionals. During final debugging, their help and equipment will ensure flawless and long-term operation of the inverter.

Sergey Odintsov

electrod.biz

We assemble a DC welding machine with our own hands

• What is electric welding
• The simplest welding machine: instructions
• Let's make a DC welding machine with our own hands
• Precautions when working with welding electrical equipment

Any tool store can currently offer a fairly large assortment of various welding machines in various price categories. The majority of welding units, up to 70%, are occupied by welding inverters, and the rest of the “welders” are transformer-type devices. Not all people can purchase an industrial product for electric welding work, and some people want to make a welding machine with their own hands.

A home welding machine will not be able to perform complex tasks, but for small jobs the power will be sufficient.

Connecting metal products to each other by heating the metal with an electric arc and then fusing it into a permanent seam is called electric welding. The main equipment in such a welding process is a welding machine, and the main tool for joining metal things is an electrode. The welding unit serves as a source of alternating or direct current, which, through an electrode, ignites an arc that melts the metal. The quality of the welded joint when welding with direct currents is much higher than the same joint made by alternating currents. The experience of an electric welder should not be discounted, although welding inverters that are popular today allow high-quality welding of metals almost the first time. That is why, for most of the various welding jobs, welding machines are used that use direct current in their work.

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Diagram of a homemade DC welding machine.

For small home welding jobs, you can assemble a homemade compact device with low power. This is, of course, not an inverter, but a necessary thing. When solving the problem of creating a welding “assistant”, you can use various design features.

The simplest welding device is a welding transformer with two windings: mains and working. The network voltage is calculated for the mains voltage, usually 220-240 volts, and the working one is calculated for a reduced voltage from 70 to 45 volts, and the change in current usually occurs by changing the number of turns of the working winding and its taps. Old asynchronous motors or industrial step-down three-phase transformers such as TOZ, etc. can be used as iron for transformers.

The primary winding must be designed for a 25-amp current, the secondary or working winding must be designed for 160 A. This is reflected in the cross-section of the wires used. For a rough estimate of the current load per 1 sq. mm we allow 10 A, for aluminum - 4 A. We determine the cross-sectional area of ​​the transformer iron window in sq. cm, then we find the number of turns of the windings, if the required number for one volt is determined as 48, divided by the cross-sectional area of ​​the transformer iron window. Calculating the device is half the battle; the main thing is to assemble it.

The product created according to calculations is the simplest alternating current welding device; the design of the device depends on the materials used.

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In order for alternating current welding machines to turn into direct current “welders,” it is necessary to limit the rate of change of current with a choke and rectify the alternating current with diodes or a rectifier bridge.

The device of a homemade semi-automatic welding machine.

The diodes must correspond to an output current of 200 A and have sufficiently good cooling so that the first welding does not damage them. This fully applies to the throttle. The use of these devices in conjunction with an alternating current welding unit turns it into a direct current apparatus. Welding with DC electrodes becomes possible, and the range of welded metals expands. Stainless steel and cast iron become available for welding. A welding machine can weld like an inverter, although the welder requires quite a lot of experience.

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Welding is a rather dangerous and traumatic activity, and electric welding adds to it the possibility of electric shock to the welder. The most important thing that an electric welder must clearly understand is that electric current is invisible and dangerous to life, but all equipment must be reliably grounded, and this grounding must be strong and visible. This simplest commandment saved many who kept it. The presence of dangerous voltage for humans on ungrounded equipment will lead to electrical injury, while the same damage on a grounded unit will simply be turned off by a circuit breaker.

Another danger to humans is the ultraviolet spectrum of the electric arc, which affects the organs of vision (quickly) and the skin, causing burns. Therefore, the presence of protective special welding clothing and a mask for the welder is mandatory. Protect those around you from the welding arc, as they may get eye burns when looking at it.

Compliance with the stated rules will make welding work safe.

moyakovka.ru

Welding equipment: how is direct current useful?

Once upon a time, welding transformers were popular; they remained in the memory of experienced welders due to the instability of welding current, operating parameters, significant weight and dimensions. The popularity of the equipment at that time was explained by the lack of alternative options. A DC welding machine is a modern, cost-effective assistant when it comes to welding, surfacing metals using direct current or a stick electrode. Popular models of the equipment in question deserve the attention of potential consumers and ordinary interested people.

Popular models

The choice of a suitable welding device that satisfies all professional or domestic needs is directly related to high-quality preliminary information to the potential buyer. First of all, you should know about the most common models of welding equipment. Below are the best selling welding power sources.

Common models:

• BRIMA ARC-200A;
• DECA DECASTAR 135E No Gas/Mig Mag;
• Awelco Mikrotig 200R;
• ORION 160;
• ERGUS E161 CDI;
• Awelco Tornado 250;
• Elektrosila TDM-160;
• KAISER NBC-200;
• KENDE MS-160L;
• TELWIN FORTE 165 ACX;
• FORTE MIG-195 and others.

In order for the choice to be accurate and definite, you will need a researcher of the most popular options for welding equipment, descriptions, technical characteristics, welding current parameters, advantages, features and benefits. Below are the sources of welding current and descriptions of them with accompanying characteristics.

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BRIMA ARC-200A: description and characteristics

The ARC-200A equipment is an excellent choice for a person who wants to get all the delights of direct current when joining metals. For a person who has made a choice in favor of the DC machine in question, all sorts of advantages of the modern welding process become possible. The device of this model is designed for joining and surfacing metals using direct current. They work using a coated piece electrode

Compactness, energy saving, the possibility of mating steels in domestic and industrial conditions, simple ignition of an electric arc, useful functionality - all these modern and high-tech welding advantages are ready to be offered by the equipment in question. The device is equipped with automatic protection against current and voltage overloads. Due to its compactness and low weight, the device can be used in confined spaces, when welding work on hard-to-reach metal structures is required.

Specifications:

• Welding current strength (nom.) – 200A;
• Welding current limits – 20-200A;
• Duration of switching on (DS) – 40%;
• Power consumption – 7 kW;
• Power supply parameters (type/voltage/frequency) – alternating, 220V, 50 Hz;
• Weight – 8 kilograms.

Industrial-style welding transformers are critical equipment. Of course, the characteristics, parameters and set of functions are somewhat different than in the case of household appliances, since industrial needs

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KAISER NBC-250: description and characteristics

Welding transformers, which provide the opportunity to take advantage of the delights of direct current, are useful assistants in everyday life, on a construction site, in the manufacturing sector, agriculture, etc. Thanks to the stability of the electric arc and the effect of direct current, the inverter in question helps to carry out high-quality, reliable, accurate and along with this, durable seams and connections.

KAISER NBC-250 is a portable type of equipment. Its purpose is welding under direct current conditions, and the work can be done with rutile, cast iron electrodes in the MMA mode. Electrode diameter limits can vary from 1.6 to 5 millimeters. The device in question is an inverter with a single-phase connection.

The device has thermal protection that blocks the possibility of overheating. The body of the device, as well as all its components, are made of high-quality materials, in accordance with European Union standards (welding inverter transformers of this series are manufactured in China, but despite this, the quality requirements are somewhat different). This model has INVERTER technology, which controls current parameters, thereby ensuring stability of the arc, which, in turn, improves the quality of the connecting process.

A standard set of functions, including anti-sticking of the electrode and hot start, help minimize the likelihood of the electrode sticking to the working surface of the metal being welded, as well as simplify the start of the work process. The forced cooling system prevents the inverter from overheating, which some welding transformers do not have. Simplicity of operation, compactness and lightness make the device even more attractive for workers operating equipment in various conditions and spatial positions.

Specifications:

• Supply voltage – 220V;
• Network frequency - 50 Hz;
• Weight – 6.6 kilograms;
• Current control limits – 20-250A;
• Electrode diameters – 1.6-5.0 millimeters;
• Type of cooling – forced;
• PV – 40%;
• Protection class - IP 21.

There are special industrial welding transformers, as already mentioned, that operate using direct current. Their characteristics are somewhat different, since the industry needs to process metals of large thickness.

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Deca MMA Mastro 50 EVO: description and characteristics

Deca MMA Mastro 50 EVO is an inverter-type device designed for the production of joints and seams using electric arc and argon arc welding. The inverter allows you to use arc stability and other advantageous parameters obtained through direct current. It is possible to work with positive as well as negative cathodes. It is worth noting that it is possible to perform connecting work in an argon-arc environment using a tungsten electrode.

The equipment has reduced dimensions and low weight, and all this became possible thanks to inverter technology. A set of inverter functions, including hot start, simplify ignition of the electric arc and stabilize its combustion. It is possible to connect copper, steel, nickel, as well as stainless steel, etc. We are ready to offer the owner of the equipment anti-stick electrode and easy arc ignition with functionality that is not available in outdated welding transformers. The diffusion of the cathode material with the metal of the workpiece being connected is increased in the device.

Modern transformers allow the use of inverter technologies, which improve productivity, control arc characteristics, and much more. This makes it possible to improve the quality of the seam and connection. The internal components of the welding device in question comply with European quality standards, since all the manufacturer’s welding transformers are manufactured in Italy.

Specifications:

• Country of origin: Italy;
• Input mains voltage – 230V;
• Power consumption – 5.7 kW;
• Fuse – 25A;
• Open circuit voltage – 80V;
• Adjustable current limits – 30-180A;
• The diameters of the electrodes used are 1.6-5.0 millimeters;
• Equipment class – household;
• Weight – 6.8 kilograms.

It is not advisable to dispute the advantages of direct current in combination with modern inverter technologies, because they are obvious and understandable. The main thing that is needed to clearly understand and identify quality equipment is knowledge regarding the characteristics of advantages and disadvantages and much more. etc.

Using alternating current, it is only possible to weld ordinary low-carbon steel (except for welding with an oscillator). In practice, there are many cases of welding parts made of cast iron, medium and high carbon steel, non-ferrous metals, and alloy steel. A constant current is required here. The fact is that electrodes for the above metals burn steadily mainly at direct current. In addition, the use of an arc of direct or reverse polarity provides additional technological advantages.

Professional welding of pressure vessels is also performed using direct current.

Diagram of a homemade DC welding machine

Transformer Tr 1 is a regular welding transformer, without any modifications. It is better if it has a rigid characteristic, that is, the secondary winding is wound on top of the primary. Diodes D 1 – D 4 – any, designed for a current of at least 100 A.

Diode radiators are selected in such an area that the heating of the diodes during operation does not exceed 100°C. A fan can be used for additional cooling.

Capacitor C1 is a composite of oxide capacitors with a total capacity of at least 40,000 μF. Capacitors can be used of any brand with a capacity of 100 μF each, including them in parallel. The operating voltage is at least 100 V. If such capacitors overheat during operation, then their operating voltage should be at least 150 V. It is possible to use capacitors of other ratings.

If you plan to work only at high currents, then you don’t need to install capacitors at all. Choke Dr 1 is the usual secondary winding of a welding transformer. It is desirable that the core be made of rectangular plates. No bias current flows through it. If a toroidal core is used, then it is necessary to cut through the magnetic gap in it with a hacksaw.

Resistor R 1 is a wire resistor. You can use steel wire with a diameter of 6 - 8 mm and a length of several meters. The length depends on the secondary voltage of your transformer and the current you want to draw. The longer the wire, the less current. For convenience, it is better to wind it in the form of a spiral.

The resulting welding rectifier allows for straight and reverse polarity welding.

Welding with straight polarity - “minus” is applied to the electrode, “plus” is applied to the product.

Reverse polarity welding - “plus” is applied to the electrode, “minus” is applied to the product (shown in Fig. 4. 1.).

If the transformer Tr 1 has its own current regulation, then it is best to set the maximum current on it, and extinguish the excess current with resistance R 1.

Welding cast iron

The practice of private welders has developed two reliable and effective methods of welding cast iron.

The first is used for welding products of a simple configuration, where cast iron can “stretch” after the cooling seam. It should be borne in mind that cast iron is a completely non-ductile metal, and each cooling seam causes transverse shrinkage of approximately 1 mm.

In this way, you can weld a fallen-off eye of a frame, a cast-iron body that has burst in half, and so on.

Before welding, the crack is cut using a V-shaped groove over the entire thickness of the metal.

You can weld the groove with any electrode, although the best results are obtained by welding with a UONI brand electrode (with any numbers) using direct current of reverse polarity.

Overlays should be welded in all possible places. The more there are, the stronger the welded joint. The linings should be welded along the current force.

Welded structures with overlays are often stronger than the original cast iron.

The second method is designed for products with complex configurations: cylinder blocks, crankcases, and so on. Most often it is used to eliminate leaks of various liquids.

Before welding, the crack is cleaned of dirt, oil, and rust.

For welding, a copper electrode of the Komsomolets brand with a diameter of 3–4 mm is used. Constant current of reverse polarity.

Before welding, the crack or patch is placed on spot tacks.

Welding is carried out with short, scattered seams. The first seam is made anywhere. Its length is no more than 3 cm.

Immediately after welding the seam, it is intensively hammered.

The cooling seam decreases in size, and forging, on the contrary, expands it. Forging takes about half a minute.

Then wait until the metal cools completely. Cooling is controlled by hand. If touching the seam does not cause pain, weld a second short seam of the same length.

The second and all subsequent seams are welded as far as possible from the previous ones. After welding each short seam there is forging and cooling.

The last to be welded are the closing sections between the short seams. The result is a continuous seam.

Determination of steel grade by spark

In repair practice, there are quite a lot of cases of welding steels of unknown chemical composition. Without determining the composition of such steels, their high-quality welding is impossible.

There is a method for determining the carbon content in steel with an accuracy of ±0.05%. It is based on the contact of the metal being tested with a rotating emery wheel. By the shape of the sparks formed, one can judge both the percentage of carbon and the presence of alloying impurities.

The carbon in the separated metal particles burns, forming star-shaped flares. The asterisks characterize the carbon content of the steel being tested. The higher the carbon content in it, the more intensely the carbon particles burn and the greater the number of stars (Fig. 4. 7.).

It is advisable to carry out such a test on a carborundum wheel with a grain size of 35 - 46. The rotation speed is 25 - 30 m/sec. The room must be darkened.

1 – the spark looks like a light, long, straight line with two thickenings at the end, of which the first is light and the second is dark red. The entire beam of sparks is light and has an oblong shape;

2 – new light sparks begin to separate from the first thickening. The beam of sparks becomes shorter and wider than the previous one, but also light.

3 – the beam of sparks is shorter and wider. A whole sheaf of light yellow sparks is separated from the first thickening;

4 – at the ends of the sparks separating from the first thickening, brilliant white stars are observed;

5 – long sparks of a reddish color with characteristic separating stars are formed;

6 – long intermittent (dotted) spark of dark red color with a light thickening at the end;

7 – double intermittent (dotted) spark with light thickenings at the ends, thick and long - red, thin and short - dark red;

8 - the spark is the same as in point No. 7, with the only difference being that the sparks have a gap.

Training in the spark test method should begin with samples of well-known steel grades.

When using this method, it should be taken into account that hardened steel produces a shorter spark beam than unhardened steel.

The spark test must be taken at a depth of 1 - 2 mm from the surface, since there may be a decarbonized layer on the surface of the metal.

When non-ferrous metals and their alloys, in which there is no carbon, come into contact with the emery wheel, no sparks are produced.

Welding medium and high carbon steel

Medium-carbon steels are welded with electrodes with a low carbon content. The penetration depth should be small, so direct current of direct polarity is used. The current value is selected to be reduced.

All these measures reduce the carbon content in the weld metal and prevent the occurrence of cracks.

For welding, electrodes UONI-13/45 or UONI-13/55 are used.

Some products must be heated to a temperature of 250 - 300°C before welding. Full heating of the product is best; if this is not possible, then use local heating with a gas burner or cutter. Heating to a higher temperature is unacceptable, as it causes cracks to appear due to an increase in the penetration depth of the base metal and the resulting increase in carbon content in the weld metal.

After welding, the product is wrapped in thermal insulating material and allowed to cool slowly.

If necessary, heat treatment is carried out after welding: the product is heated to a dark cherry color and slow cooling is provided.

High carbon steel is the most difficult to weld. Welded structures are not made from it, but welding is used in repair production. For welding such steel, it is best to use the same methods as previously described for welding cast iron.

Welding manganese steel

Manganese steel is used for parts with high wear resistance: dredge buckets, excavator bucket teeth, railway crosses, rock crusher journals, tractor tracks, and so on.

Electrodes TsL-2 or UONI-13nzh are used for welding.

The welding current is selected at the rate of 30 - 35A per 1 mm of electrode diameter.

Welding produces a large amount of gases. To facilitate their exit from the molten metal, surfacing should be carried out in wide beads and short sections, otherwise the weld will be porous.

Immediately after welding, forging is required.

To increase the hardness, strength, toughness and wear resistance of the surfacing, it is necessary to quench it with cold water after applying each bead, while it is still heated to red heat.

Welding Chromium Steel

Chromium steels are used as stainless and acid-resistant steels for the manufacture of equipment for the oil refining industry.

Welding of chromium steels must be performed with preheating to a temperature of 200 - 400°C.

When welding, a reduced current is used at the rate of 25 - 30 A per 1 mm of electrode diameter.

Electrodes TsL-17-63, SL-16, UONI-13/85 are used on direct current of reverse polarity.

After welding, the product is cooled in air to a temperature of 150 - 200°C, and then tempered.

Tempering is carried out by heating the product to a temperature of 720 - 750°C, holding it at this temperature for at least an hour and then slowly cooling it in air.

Welding tungsten and chrome tungsten steel

This steel is used to make cutting tools.

Using welding, a cutting tool can be made in two ways:

1) by welding finished high-speed steel plates onto a low-carbon steel holder;

2) surfacing high-speed steel onto low-carbon steel.

The finished plates are welded in the following ways:

1) using resistance welding;

2) using argon welding with a non-consumable electrode;

3) using gas soldering with high-temperature solder;

4) DC consumable electrode.

For surfacing, you can use waste high-speed steel: broken drills, cutters, countersinks, reamers, etc.

These wastes can be welded using gas or argon welding, as well as by making electrodes for electric arc welding.

After surfacing, the tool is annealed, mechanically processed, and then subjected to triple hardening and tempering.

Welding high alloy stainless steel

Stainless steel has found quite wide application in everyday life: various containers, heat exchangers, and water heaters are made from it. Used in private baths as heat-resistant.

You can distinguish such steel from ordinary steel by three characteristic features:

1) “stainless steel” has a light steel color;

2) when a permanent magnet is applied, it is not attracted, although there are exceptions;

3) when processed on an emery wheel, it produces few sparks (or none at all).

Stainless steel has an increased linear expansion coefficient and a reduced thermal conductivity coefficient.

The increased coefficient of linear expansion causes large deformations of the welded joint, up to the appearance of cracks. It is advisable to heat some welded stainless steel structures to a temperature of 100 - 300°C before welding.

Low thermal conductivity causes heat concentration and can lead to metal burning. Compared to welding conventional steel of the same thickness, when welding stainless steel, the current is reduced by 10 - 20%.

For welding, direct current of reverse polarity is used.

Electrodes of the OZL-8, OZL-14, ZIO-3, TsL-11, TsT-15-1 brands are used.

One of the main conditions when welding is maintaining a short arc, this provides better protection of the molten metal from oxygen and nitrogen in the air.

The corrosion resistance of seams increases with accelerated cooling. Therefore, immediately after welding, the seams are watered. Watering is permissible only for steel that does not crack after welding.

Welding of aluminum and its alloys

Welding with coated electrodes is used for aluminum and alloys with a thickness of more than 4 mm.

For welding technical aluminum, electrodes of the OZA-1 brand are used.

OZA-2 electrodes are used to weld casting defects.

Recently, OZA brand electrodes have been replaced by more advanced OZANA brand electrodes.

The coating of electrodes for aluminum welding strongly absorbs moisture. When storing such electrodes without moisture protection, the coating can literally drain from the rod. Therefore, such electrodes are stored in a plastic case with moisture absorption means. Before welding, they are additionally dried at a temperature of 70 – 100°C.

Before welding, aluminum parts are degreased with acetone and cleaned to a shine with a wire brush.

Welding is carried out using direct current of reverse polarity.

Welding current 25 - 32 A per 1 mm diameter of the electrode rod.

Before welding, the part is heated to a temperature of 250 - 400°C.

Welding must be performed continuously with one electrode, since the slag film on the part and the end of the electrode prevents the arc from re-igniting.

If possible, pads are placed on the back side of the seam (see gas welding of aluminum).

Electric arc welding produces seams of average quality.

Welding of copper and its alloys

Pure copper lends itself well to welding, and it is recommended to weld it in two ways. The welding method depends on the thickness of the part.

When the thickness of the product is no more than 3 mm, it is best to use carbon electrode welding. Welding is performed with direct current of direct polarity with an arc length of 35 - 40 mm.

Electrical wire can be used as a filler material. Don't forget to remove the insulation before welding.

To improve the quality of the seam, a flux consisting of 95% calcined borax and 5% metal powdered magnesium is applied to the edges being welded and to the filler wire. You can use borax alone, but the results will be worse. If high quality welds are not required, flux is not used.

Safety precautions for electric arc welding

Electric arc welding has several factors harmful to the health of the welder: electric voltage, electric arc radiation, gases, sparks and metal splashes, thermal heating, drafts.

The maximum permissible no-load voltage of a welding transformer is considered to be 80 V, and of a welding rectifier 100 V. In dry weather conditions, such voltage is practically not felt, but in humid conditions, a rather noticeable tingling of the hand begins. The same thing can be observed when the welder is on the metal part being welded, and even more so inside it.

When welding in wet weather, as well as standing on metal, regardless of the weather, you must use rubber gloves, a rubber mat, and rubber galoshes. Gloves, mats and galoshes should be made of dielectric rubber, that is, the kind that electricians use. Rubber products sold for household use are not electrically insulating.

To protect the welder from accidental breakdown of the transformer, protective grounding is used. The grounding device is described in Chapter 1.

To reduce the likelihood of electric shock, it is best to use transformers with low open circuit voltage.

Protection against arc radiation is a welder's suit, a mask with a set of glasses, and gloves. Always fasten the top collar of your suit, otherwise you will end up with a permanent “tie.”

The ultraviolet radiation of the arc is reliably attenuated by an air column of 10 m, so do not allow anyone closer than 10 m to the welding site (especially children!).

The coating of the electrodes contains gas-forming substances, so the coated electrodes smoke heavily. The only way to protect against smoke is forced ventilation. The design of such ventilation is described in Chapter 1.

Another unfavorable factor in a welder’s work is associated with ventilation – drafts. The welder's load during work is most often static, that is, the welder works almost motionless. In this case, the body does not self-heat, which can lead to hypothermia.

As the experience of many welders shows, no amount of hardening against drafts helps. More reliable protection is warm clothing, especially around the waist (the welder works bent over).

Warm clothing can also have a negative effect. When switching to dynamic load, the welder begins to sweat; sweat, together with a draft, causes a guaranteed cold.

The best option to avoid colds is to install a supply fan heater. It should heat the supply air to above-zero temperatures even in severe frost. If you prefer not to work in such frosts, then the fan power of 3 kW is sufficient.

Metal splashes are considered a rather unpleasant phenomenon. When they get on a suit or shoes, they cause smoldering of protective clothing or a fire if there are flammable substances nearby. Buy leather protective clothing and tarpaulin boots - and you will sufficiently protect your body.

When welding at high currents and arc cutting metal, the electrode holder, welding wires and welding helmet may overheat. Therefore, do not touch the metal parts of the mask with your face, and put a heat-insulating sleeve on the handle of the holder. Check all wire connections regularly as they may cause a fire.

The above rules apply to other types of electric welding: argon, semi-automatic, contact.

Welding is a simple and reliable way to connect permanent metal. Welding work is carried out using special equipment, ranging from microelectronics to heavy construction.

Today, welding is carried out using direct and alternating voltage. In AC welding installations, the main element is a transformer of any structure. And in welding devices with constant flow energy they use power rectifier blocks. Correctly selected electric welding electrodes are the key to quality work.

What is alternating current in welding

Alternating voltage gets its name because the flow of electrons continuously changes the direction of its movement. During a welding process using alternating current, the arc continuously "jumping". This happens due to regular deviation from the axis of the welding arc. Of course, this affects the quality of the resulting seam. As a result, the scar is wide, and metal droplets form at the junction. If the arc goes out, the ignition can be restarted by increasing the voltage.

With all this, equipment for alternating electric welding has its advantages:

1. Simple design.
2. Great working resource.
3. The strength of the welding current can be adjusted.

Transformers continue to enjoy their popularity.

DC Welding

Welding machines permanently support 2 operating modes - the process of connecting with direct and reverse polarity. When using such installations, it is necessary to regularly monitor their operating mode, since some metals are seized in direct polarity, while others are seized in reverse polarity.

Most widely used straight polarity. The welded crater is deep and narrow. The heat supply decreases, the passage speed increases. It is used for cutting metal, has a stable arc, resulting in a high-quality connection. Used when working with steel, thickness from 4 mm. Most materials are welded using straight polarity.

Reverse polarity is used to join thin metals of medium thickness. The electric welding seam is not deep, but wide enough. With this polarity, you cannot use electrodes that are sensitive to overheating.

The main advantages of constant voltage welding are:

1. No splashes of molten metal.
2. Electric arc stability.

Differences between DC and AC electrodes

Electrodes conditionally do not differ. But constant power flow is not suitable for AC connection. Electric welding materials that are designed for alternating periods are also successfully used for electric welding using direct electricity. Experts call the resulting electrodes universal.

Universal electrodes are characterized by:

• A good and stable arc that even re-ignites easily.
• Volumetric production of work.
• High profitability.
• Low degree of splashing.
• Good separation of impurities.
• The ability to safely weld contaminated, oxidized, rusty and wet materials.
• The simplest requirements for the device and the employee.

A feature of universal electric welding electrodes is the ability to make a connection of metal products, even if there is large distance between metal parts. They are excellent for electric welding short seams and spot tack welding.

Comparing welding with direct and alternating voltage, devices with a constant flow of energy have more advantages. Welding materials are saved, since spattering is minimal. The constant is simple and easy to use and is used for thin-walled products. Exposure to weather conditions does not affect arc stability, ensuring high performance. All areas of the structure are boiled, as a result the specialist receives a high-quality and neat scar.

The variable device provides good connection quality, simplicity and convenience of the welding process. Equipment that operates on this type of voltage is much cheaper.

The main difference between alternating and direct electricity is that the electrode is supplied with current or alternating frequency during operation. 50 Hz or constant. The design of a constant flow welding machine has rectifiers in the form of diodes, which rectify the electricity at the output and create a constant-sign pulsating value. Modern semiconductor rectifiers guarantee high performance and high efficiency. Consequently, better welding will be achieved using a constant flow. As practice has shown, alternating electrodes are a thing of the past.

Welding current is the most important parameter on which a quality connection depends. The diameter of the electrode must be selected taking into account the thickness of the metal. And based on its diameter, electricity is set. This information can be found on the packaging. There are no exact and specific voltage settings - each master is guided by his own feelings and sets the desired voltage parameter.

Special stores have a very wide selection of electrodes for arc welding. When purchasing, pay attention to the quality of the product and the presence of a license.

There are many types of welding machines, among which the most famous are the following: mechanical welding devices using consumable electrodes; equipment for argon-arc welding with non-consumable electrodes; for welding using flux with automatically consumable electrodes. In addition, there are generators for welding, transformers, inverters and devices for resistance spot welding. There are specific electrodes for working with each type of metal.

In terms of its design, a device for working with direct current is much more complex than an alternating current unit, since a rectifier with a diode or thyristor bridge is installed in it to obtain a constant voltage at the output. However, the output power of the welding machine is significantly less than that consumed due to its drop on the rectifier itself.

In other words, its efficiency is low, and this is a serious drawback from the point of view of energy savings. However, thanks to the stable arc and the ability to work with various metals, it could be classified as professional equipment.

AC welding machine - what is its feature?

Much cheaper than the previous model AC welding machine, also working with consumable electrodes. It is excellent for working with ferrous metals, allowing them to be overlapped and butt welded.

If this welding machine is used, 220 volts is the operating voltage, but at no load it may vary depending on the electrodes used, which can be either calcium fluoride or rutile coated. The device is very easy to use and provides for smooth adjustment of the current strength, which depends on the electrode selected for operation.

This transformer welding machine can be successfully used both at home and in factories. Electric welding machines are designed to operate from a 220 or 380 volt network and are accordingly called single- or three-phase. Depending on this, the connection diagram of the welding wires changes.

A single-phase welding machine is connected by connecting one welding wire to the “phase”, another to the “neutral” connector and a third to the “zero” ground. Otherwise, a three-phase welding machine is connected. The two ends of the welding cable are connected to any two “phases”, and the third - to the protective “zero”.

It should be noted that if a 380-volt welding machine is used, then it is considered more powerful than one connected to a 220-volt network, but this is not the only way to increase productivity.

Inverters - increasing the power of the welding machine

Until now, we have considered welding machines that use a conventional power transformer as an input voltage converter. This is what determines the solid dimensions and heavy weight of this type of equipment. However, it is reliable and inexpensive.

But there are other types of devices in which so-called inverters– semiconductor amplifiers. Small dimensions and weight have made them perhaps the most popular type of welding units.

With an efficiency level reaching 85%, the device works with different metals, guaranteeing high speed, quality and accuracy of welding. Inverter devices have different powers and can be connected to networks of both 220 and 380 volts.