Modern types of metal welding: their features and advantages

Physics, chemistry, a little poetry

Welding is the process of permanently joining different structures by heating, deformation, or both.

In short, from a physics point of view, welding uses either heat or pressure, or heat and pressure together. In short, from a chemical point of view, welding uses a huge number of different types of flux-cored tapes, fluxes, electrodes, gases and other components. It depends on the materials and conditions. Thanks to chemistry, we have a huge number of technical options.

Important! We will not burden you with complete lists of welding types or all the classifications that exist. We don't have enough paper to write, you don't have the patience to read. Understand the logic of grouping welding methods so that you can easily find information on each specific type. There are many sites on the Internet dedicated to welding: you can find everything you need.

How to cook properly

To understand how to cook properly, a small amount of theory should be supplemented with a large amount of practice. It’s best to start learning by welding scraps of corners, fittings, and metal plates. Only after you “feel the seam” with your own hands can you begin to connect more or less important structures.

Arc Welding Process

There are several types of devices; in order to learn how to cook correctly, it is best to start with an inverter. It allows you to smoothly regulate and maintain a stable operating current, is slightly independent of the level and stability of the voltage in the supply network, and does not create voltage surges in this network.

Principles of classifications, overview

Classification of arc welding methods.
The classification of welding types is carried out according to a variety of criteria; they neatly fit into a semantic framework. What criteria are the most important? Let's go through some of them; first, it's better to see the big picture.

How many types of welding exist today? You can say the number 150 with the word “about”. Maybe 250. But we don’t recommend naming numbers. While you are reading this article, the number of species may change - technology does not stand still. But what kind of welding there is according to materials, physical processes, popularity, control methods - we need to talk, these are precisely the very principles of classification that we need to understand.

An example of a simple, understandable classification by energy source in welding:

• electricity;
• electric arc;
• friction;
• gas flame;
• laser radiation;
• electron beam;
• ultrasound.

Another example of a list by type of weld. There are many of them, whole bunches of different types:

• butt, corner welds - along the connection of the edges;
• by shape, length - horizontal, vertical, circular, straight, intermittent, continuous, long, short, medium seams;
• by type of material used - seams for steel, non-ferrous metals, bimetals, polyethylene, etc.;
• by volume of deposited metal - reinforced, weakened, normal welds;
• in shape - longitudinal, transverse seams;
• by the number of layers – continuous, intermittent, tack, multi-layer.

The “sewing” list can be continued, but it is important for us to understand the general principles, so let’s finish with the lyrics and move on to the main methods.

Features of gas welding

At the end of the 19th century, a technology for fusing metal elements using gas was developed. This method of metal processing was one of the first to appear.

Improved arc and resistance electric welding could not supplant the use of the gas method. Gas welding is ideal for welding high-strength steels and is used for joining elements made of cast iron, bronze, and brass.

When performing this type of metal welding, the high-temperature flame of the welding gas heats and melts the edges of the parts being welded and the electrode part of the filler material. The molten liquid metal forms a weld pool - an area protected by a flame and a gaseous environment that displaces air. The weld seam is formed during the process of cooling and hardening of the metal.

To carry out the welding process, a mixture of oxygen and combustible gas, which is an oxidizing agent, is used. The highest temperature (+3200...+3400 °C) is provided by acetylene, obtained during the fusion process from the chemical reaction of calcium carbide with ordinary water. Propane is also well suited for gas welding; its combustion temperature reaches +2800 °C.

Less commonly used gases:

• methane;
• hydrogen;
• kerosene vapor;
• bluegas.

The above substances are used less frequently, since their flame temperature is much lower than that of acetylene. They are only suitable for processing non-ferrous metals with a low melting point, such as copper, bronze, brass.

Gas welding has its own characteristics, advantages and some disadvantages.

The main feature of gas welding is the wider boundaries of the melting zone and its low heating rate. Under certain conditions this can be a plus.

For example, if it is necessary to connect elements or process parts made of tool steel, cast iron, non-ferrous metals, special-purpose steels, which require smooth heating and slow cooling.

Other advantages of gas welding:

• simplicity of the technological process;
• low cost of equipment;
• availability of gas mixture or calcium carbide;
• no need for a powerful energy source;
• the ability to control the power and type of flame;
• performing mode control.

The main disadvantages of gas welding:

• Relatively low efficiency due to low heating rate and significant heat dissipation. This does not allow fastening metal sheets with a thickness of 5 mm or more.
• Wide heating zone (thermal influence).
• Higher cost. Using acetylene is more expensive than energy costs when performing electric welding.
• Low level of mechanization. Gas technology allows for only manual metal welding.

There is no possibility of using a semi-automatic method, and automatic gas welding can only be done using a multi-flame torch and only when welding metals of small thickness. Gas technology refers to complex and unprofitable methods of creating permanent connections, but is quite in demand when processing non-ferrous alloys, cast iron, and aluminum.

Basic concept of the welding process

Welding is a technological process of creating reliable connections by heating or plastic deformation with the establishment of interatomic bonds subsequently. The structure of the products is continuous. Energy is supplied to the electrode and welding material through an inverter. First, the metal of the electrode melts, this creates a weld pool, in this pool the electrode is mixed with the base material, and the slag that floats to the surface serves as a protective film. The welding process is nothing more than the hardening of the metal after all of the above influences. Electrodes come in several types - consumable (the electrode rod melts) and non-consumable (with a non-consumable electrode, filler wire is used, which melts separately in the bath).

Precautions before welding with electrodes

Cooking correctly means cooking safely. Precautionary measures when welding with electrodes will help maintain the health and performance of the welder:

• Before starting work, it is necessary to inspect the device, holder and cables for mechanical damage and insulation damage.
• Work should be carried out at positive temperatures and humidity up to 80%;
• The use of personal protective equipment is mandatory.
• Fire-resistant protective clothing should be used.
• Near the workplace you should have a fire extinguisher suitable for extinguishing live electrical installations.

Careful and strict adherence to the rules for welding metal with an electrode will not require much time and will help preserve material values ​​and people’s health.

Technological properties of welding works

There are many technological varieties of types of welding work depending on the material and equipment, the most common of them are: arc, electroslag, gas, light, plasma and electron beam.

Types of welding by type of mechanization and uninterrupted technological properties: air, vacuum, foam, flux and submerged types.

Based on the degree of metal melting, welding is divided into atmospheric and jet welding. Jet welding is characterized by molten material at the weld.

Electron beam welding

Metal welding techniques include rapidly evolving technologies. These include electron beam welding. Its essence lies in the fact that the heating of products and their further melting occurs under the influence of a flow of high-speed electrons that move in a vacuum under the influence of an electric field.

Under the influence of a focused flow of electrons, the edges of the parts melt and join together. The range of its capabilities is very extensive - refractory and chemically active metals, durable alloys.

The features of this type of welding include the fact that since welding occurs in a vacuum, the surfaces of the parts remain clean, and also the fact that the seam is produced quickly and has minimal thickness. It maintains increased quality even if parts of different thicknesses, having different compositions and melting temperatures are welded. The welding equipment is easy to operate and does not require extensive training.

Welding process

Regardless of the number of types of welding, there are 3 main stages of the welding process, inherent in all technological varieties, these are:

1. Formation of contact;
2. Education Communications;
3. Creating a seam.

Forming a contact

The formation of contact occurs as a result of bringing the metal to the melting or boiling point; the main thing is not to confuse the weld pool with the melting of iron.

Formation of chemical and metallic bonds

The second, most important step is the formation of a weld pool; it always looks the same, regardless of the type of welding. The bath appears as a result of the fusion of metal and auxiliary material, for example an electrode, under the influence of temperature, and appears as a white spot. The quality of the seam depends on the width and length of this spot.

Creation and types of strong connection

The main qualitative characteristics of seams are their width and height.

By type of connection there are (the most common):

• butt – parts in one plane (pipes, sheets, etc. are welded).
• overlapped - the parts are arranged in parallel, only one overlaps the other (sheets are welded, the thickness of which is no more than 12 mm).
• end - weld 2 ends of the elements.
• angular - elements are located at an angle to each other.

TIG welding

It is one of the modern methods of welding various products. The essence of this method is the combustion of an electric arc in argon, a gas that has a number of remarkable qualities. Since it is heavier than air, after penetrating the weld pool, argon begins to protect it from other gases living in the atmosphere. The result is a seam without an oxide film.

This method uses a tungsten electrode, which makes it possible to weld various types of steel. It requires constant care, which includes regular sharpening of its tip. For ignition, an oscillator is required that generates a high-frequency current, which is connected to the inverter.

The operating principle of automatic argon arc welding is similar to the manual version, with the difference that control occurs automatically according to the program set by the operator. This type of welding uses an inverter. When welding with an inverter, the theory of the process is that such a device allows you to convert direct current into alternating current. The inverter can then change the frequency of the resulting alternating current.

We will weld tightly, inexpensively, call

Tacking structures before welding.
Basic welding methods are a common but incorrect classification in this context. “The most popular” would be more correct.

Here are three well-deserved winners:

1. Manual arc - gold.
2. Gas - silver.
3. Semi-automatic - bronze.

Each winner belongs to a different welding family; in theory, it is better to describe them in their rightful places together with their close “relatives.” But we will do the wrong thing - we will introduce welding champions at the beginning of the review.

Manual arc welding RD

People's favorite No. 1, the most common type in everyday life and in industry. The three main words in RD are simplicity, cheapness, and transportability. The physics of the process consists of melting a special coated electrode, which leaves behind a mark in the form of a weld seam. Different electrodes are used, depending on the metal. The arc is the distance between the electrode and the surface of the metal, which plays the role of a second electrode.

Essentially, an arc is a powerful discharge in a gas space (air). During RD, three objects melt: the edges of the two surfaces connected to the electrode. The better the triple melting products are mixed (to do this, the electrode is moved left and right), the better the quality of the seam.

RD welding has serious advantages over other types:

• the RD method is easy to learn;
• you can cook in any position in space;
• You can cook a wide variety of metals; there are electrodes for sale for every taste;
• accessible transportable equipment

Gas welding

People's champion No. 2, well-deserved silver medal.
This is when welders carry gas cylinders with them: they need a mixture of oxygen with some flammable gas - acetylene, propane or butane. The physics of the process is also melting, but the heat is supplied not by an electrode, but by a gas burner. The metal surfaces are melted by the torch, the process occurs smoothly and rather slowly. The thicker the metal layer, the slower it melts. Why gas welding is better than other methods:

• Non-ferrous metals are excellently welded;
• the equipment is simpler than electrical methods;
• the ability to control the mixture and flame;
• no powerful energy source is needed, the method is autonomous.

You can’t do without disadvantages, the “gas” disadvantages are as follows:

• very slow heating of surfaces;
• low heat concentration due to dissipation;
• high cost of electricity.

In terms of the cost of electricity, arc methods can compete with gas methods: with RD, electricity is also wasted mercilessly. But in the end, the gas method, due to its “low speed,” is much more expensive.

Important! Where there is a pair of words “flammable gas”, there is always a second pair “safety precautions”. Safety rules are well regulated, but compliance with the requirements requires additional costs of money and time. By the way, gas welding is more than 100 years old - here it is, a stainless classic, applause.

Semi-automatic welding

Classification of the welding arc.
Bronze champion, closes the popular top three, but in terms of his prospects he will easily surpass the first prize-winners. In fact, this is a type of arc type familiar to us, a progressive evolution of the RD. It features a large number of technological nuances, options, and instructions. It is enough for us to know that the “automatic part” of the method is the feeding of the welding wire.

The manual part is the welding process itself with wire feed control. You can cook with gas (carbon dioxide for beginners, argon for professionals), or without gas, with direct current. The option without gas is popular in garages and summer cottages; in this case, a special flux-cored or flux-cored wire is needed. When it burns, a gas with vapor is formed that protects the combustion area.

Semi-automatic is the only method at a service station: body work is carried out only with its help. The semi-automatic machine uses gas and a special wire instead of the usual electrode. Gas from the torch with wire is supplied to the welding sleeve. As a result, the process is protected from environmental influences. The process modes are determined by the welder depending on the thickness of the metal.

The semi-automatic method has serious advantages over other types:

• excellent seam quality;
• high speed;
• ease of use;
• welded as non-ferrous and ferrous metals;
• You can cook rusted or galvanized metals;
• wide selection of materials, modest financial costs.

Semi-automatic welding

All types of welding work include another popular type - welding using a semi-automatic machine. Semi-automatic welding can be called a type of arc welding. The difference lies in the fact that at the same time, wire is supplied to the welding zone and gas is exposed, which protects all materials from the negative effects of ambient air, which can slow down the process or even stop it completely.

When semi-automatic welding occurs in carbon dioxide, this type is called MAG, and if in inert, then MIG. Semi-automatic welding machines are a simple type of equipment. Its main parts consist of a direct current source that supplies voltage, and a special mechanism for feeding wire into the welding zone, which acts as an electrode. The wire is wound on a special bobbin. Its feed speed is adjustable.

The advantages of this method include the ability to work in hard-to-reach places, a small amount of waste, obtaining a thin and durable seam, and the speed of the process. Semiautomatic machines use aluminum or steel wires. Protection of the resulting seam is possible in the following ways: flux; protective gases; using flux cored wire. Shielding gases are most often used. There are stationary devices and household ones, more convenient for home use.

The semi-automatic body contains a control unit and a power source. Using cables, the device is connected to a wire feeding mechanism wound on a reel and a welding torch.

Wire feeding is carried out in one of three ways:

1. Pulling. The drive is located on the burner handle. The wire is pulled out from the bobbin on which it is wound.
2. Pushing. The drive pushes the wire towards the torch.
3. The push-pull feed is a hybrid of the two previous methods.

Using a welding sleeve, gas, wire and, in some models, cooling liquid are supplied to the work site. The length of the hose determines the ability to work in hard-to-reach places. A unified connector is used to connect the welding hose.

In the center there is a large fitting through which the welding wire exits. At the top there are two contacts for switching modes. Wires are connected to the connector to supply current. A burner is also connected to the hose. The contact tip is a replaceable part. It is selected depending on the diameters of the wire used. In turn, the size of the nozzle depends on the diameter of the tip.

The wire is wound onto spools. They have different sizes depending on the diameter of the wire. The wire feeder has a roller mechanism. The feeder rotates using an electric motor. The wire tension is adjusted manually by the operator. The welding wire enters the welding zone continuously. The arc occurs between the wire and the parts to be welded. The nozzle serves to form a gas cloud.

Semi-automatic welding without the use of gas is possible. In this case, it is necessary to use a special type of wire containing flux inside. This type of wire is called flux-cored wire. When the wire burns, the freed flux creates a protective environment. If you have to weld critical structures, you should choose gas welding, which is more reliable. A competent choice of welding wire is necessary.

The main criterion is the correspondence of the wire composition to the material of the products being welded. Marking the wires will help with this. The choice of wire diameter depends on the thickness of the products. The theory of metal welding assumes that the set welding current depends on the thickness of the materials and the selected diameter of the electrodes.

It is necessary to establish the speed at which the wire will be fed, as well as the gas flow, set using a valve on the gearbox. The main feature of using a semi-automatic machine is that initially the wire is fed towards the welding site mechanically, but then it is moved manually.

We cook metals

We’ve sorted out the people’s favorites, let’s move on to the “correct” classifications.

Let's start with the real heavyweights - types of metal welding, which are divided into three groups according to:

1. Physical signs.
2. Technical characteristics (mechanization, process continuity, metal protection).
3. Technological characteristics (separate classifications for each method - for example, types of electrodes).

According to physical characteristics, we have three main classes for all types of metal welding:

Thermal class - the welding process involves melting with thermal energy:

• gas;
• arc;
• laser;
• radiation, thermite, etc.

Important! The main types of fusion welding are the most common in everyday life and in industry. This is the most populous class; the vast majority of welding methods belong to it.

Mechanical class using mechanical energy:

• ultrasonic;
• cold;
• friction;
• explosion, etc.

Metal welding table.
Thermo-mechanical class, methods of combined action of thermal energy and pressure:

• blacksmiths;
• diffusion;
• contact, etc.

As an example of metal welding, we present MAWP - mechanized argon arc welding with a consumable electrode. A true hybrid for electro-gas joining of metals. Without it, welding of non-ferrous metals or complex alloys is impossible.

Advantages of MADP:

• connection of any alloys;
• stability of the product’s shape due to low heating;
• electrodes need to be changed rarely;
• widest scope of use;

Flaws:

• difficult for beginners;
• low execution speed.

Let's take a closer look at the main parameters

Welding current selection

The parameter depends on the diameter of the electrode, its coating, and the spatial position of the seam. The depth of penetration and welding performance depend on the current value. If the current strength is insufficient, then the amount of heat entering the bath will be small, resulting in lack of penetration, which worsens the quality of the connection of parts.

Electric arc welding with too high a current can also lead to lack of penetration, since the quickly melting electrode can fall on the unmelted base metal. The recommended current is indicated on the electrode packages. In addition, the following should be considered:

• when using reverse polarity current, the penetration depth is almost 50% greater than when using direct polarity. Therefore, when welding thin-sheet and alloy materials, reverse polarity current should be used to avoid burnouts and overheating;
• when welding with alternating current, the penetration depth will be 15-20% less than when welding with direct current of reverse polarity.

Selecting welding current and electrode diameter

Selecting the electrode diameter

The diameter of the electrode depends on the thickness of the edges of the material being welded and the cutting of the edges. If the edges are not cut, then the diameter of the electrode is selected depending on the thickness of the metal being welded. So, for example, with a metal thickness of 20 mm, electrodes with a diameter of 12 mm are used.

If the edge is cut, then, regardless of the grade of metal, the root seam is made with a 2-3 mm electrode. Subsequent layers are applied with a diameter of 4 mm. True, if the thickness of the base metal exceeds 12 mm, subsequent layers can be made with a five-millimeter electrode.

The choice of root electrode depends on the type of connection. But the main principle of choice is that the more critical the seam, the smaller the diameter of the electrode used.

3.Welding speed must be optimal

The higher the speed, the narrower the seam. But if the speed is too high, there may be a lack of fusion between the base metal and the weld metal.

We cook polyethylene

Applications of plastic welding.
What can you cook besides metals? Ceramics. Glass. But in second place of honor are plastics or polymers, primarily polyethylene pipes. You can work with polyethylene using thermistor, electrofusion methods, or electrical resistance: these terms are listed in the technical literature. Don’t be alarmed, all options can be called briefly – NC welding. NZ – embedded heaters.

The essence of the process is the melting of polyethylene at the joints using metal spirals of an electric heater, which is embedded in the part. The method is extremely popular, it has great prospects in industry: it is used in various pipelines, replacing old metal pipes with new polyethylene ones, installation and repair, and the development of new polymer technologies.

When working with plastics, another method is used: welding or welding with a heated tool. The simplest option for supplying heat to heat polymer surfaces. There are many options for welding tools for working with NI - from a simple electric soldering iron for small parts to special welding machines of various sizes. Self-respecting plumbers keep this kind of equipment in their work suitcases without fail.

By the way, welding methods NZ and NI are included in the list of mandatory methods of a professional welder with confirmed qualifications, for example, certification from NAKS - the National Agency for Welding Control.

Now classification by type of process mechanization:

1. Automatic
2. Automated
3. Mechanized
4. Manual, let's start with it.

Types of metal protection during welding

Hot metal spatter is a major problem in any welding job. This happens not only with the manual electric arc method, but also with the semi-automatic method, even in a protective gas environment. The splashes harden and form carbon deposits and other defects on the surface of the structure, thereby reducing the quality of the finished metal structures.

In some cases, for example, due to the location of the seam in a hard-to-reach place, it is not possible to remove metal splashes mechanically: by cutting down or grinding. Therefore, it is recommended to pre-treat the seam area on the surfaces of the elements being welded with special means for protection - paste or liquid from the adhesion of metal splashes.

Today, many protective compounds are produced for various types of metal welding:

• liquid products, packaged in canisters and bottles, are applied to metal surfaces with a brush or sprayed through a spray bottle;
• aerosols produced in special bottles;
• pastes packaged in metal or plastic jars with a wide neck.

It is recommended to apply all protective agents in strict accordance with the manufacturer's instructions supplied.

Welders with extensive experience sometimes use their own recipes for protective compounds. For example, chalk, dissolved in water to the consistency of a paste, protects surfaces well from the adhesion of metal splashes. This homemade paste is applied to the area around the future seam, leaving the edges clean.

Upon completion of welding work, it is necessary to thoroughly clean the surfaces of the seam and the area around it from the protective coating. Many products for protecting metal surfaces from splashes contain oil and fat-containing components that significantly reduce adhesion. Therefore, before applying a protective layer, it is necessary to thoroughly degrease the area of ​​the metal surface being treated.

The inventors of welding technologies have made a great contribution to the development of scientific and technological progress. Along with the already known methods of creating an inextricable connection, new types of metal welding have appeared. CMT technology (Cold Metal Transfer), based on cold metal transfer, allows you to perform many types of welding work with high quality.

New methods of fusing metal surfaces are being successfully introduced into all areas of industry, mechanical engineering and construction. It was thanks to welding that humanity received large ships, airplanes, modern cars and bridges capable of withstanding multi-ton loads.

Manual welding

Examples of welded joints.
Despite the rapid growth of new automated methods, manual methods are indispensable in many cases, this type of welding has long occupied a legitimately important place in modern technology.

Advantages of manual methods:

• can be cooked in hard-to-reach places;
• in different positions in space;
• you can quickly move from one material that we melt to another;
• selection of electrodes for every taste for all types of steel;
• The equipment is easy to transport and easy to maintain.

In addition to the familiar electric arc method, this group includes a manual version of argon arc welding with the same operating principles as the mechanized version described above.

Manual types include do-it-yourself spot welding, a contact method that is possible at home, unlike other contact methods used only in industry.

Classic gas welding also refers to manual methods.

Arc welding

Types of fusion welding can start with MMA, as manual arc welding is called. She can deservedly be considered a leader of popular popularity. This metal welding process can be carried out using an inverter or transformer. In both cases, the use of electrodes is necessary. This method is simple and inexpensive.

The source of heat is an electric arc formed between the electrodes, one of which is a consumable material, and the other is the elements being welded. Such an arc is a powerful discharge in a gaseous environment.

The electrode coating can be compared to a “frozen” gas cloud. When the metal begins to melt, the electrode coating also begins to melt. The released cloud of gas provides protection against the penetration of oxygen into the weld formation site, and provides a conductive ionized environment for the arc. This phenomenon significantly reduces the risk of porosity formation.

Advantages of MMA:

1. Versatility. Using this technology, you can weld products made from almost all types of metal.
2. Parts can be welded using this method in any spatial position of the product. This includes confined spaces that may not be possible with other methods.
3. The technology of metal welding using the MMA method allows this to be done under various unfavorable environmental conditions.
4. Ease of use and low cost make it possible to use this method not only in industrial settings, but also at home.

The disadvantages include low productivity, the presence of at least a little experience, a rather complex process of igniting the arc with the risk of electrode sticking, and harm to health when the coating of some types of electrodes evaporates.

The use of modern equipment that has functions against the occurrence of such an effect will help to avoid electrode sticking. Equipment for arc welding is divided into transformers and inverters, which have undeniable advantages and greatly facilitate the process of electric welding.

Transformers, which have held the lead for a long time, are now considered obsolete equipment, heavy and large in size. They can only be used to weld metal parts using alternating current.

The way out is to use welding rectifiers. Their function is to convert alternating current into direct current. This provides a significant advantage, since when using direct current, the seams are of higher quality, smoother, stronger and neater. However, rectifiers are also heavy and large in size, and their use requires professional skills.

Inverters, which are modern equipment, are the best choice for implementing the process. This can be recommended even for beginners, since it is not difficult to understand the principles of working with them. The current rectifier is built into the inverter device, so no additional equipment is required. The available functions will help avoid sticking of the electrodes and help quickly ignite the arc. Inverters are so light in weight and small in size that they can be easily carried in your hands.

Electrodes should be selected according to parameters such as their diameter and the composition of the metal inside. The choice of the type of metal is important, since during the welding process it melts, and it flows drop by drop into the total mass and fuses with it. The homogeneity of the metals of the parts and the electrode guarantees a strong connection and a uniform seam.

It is not difficult to make the right choice when purchasing electrodes, since the packaging usually indicates what types of metals these consumables are suitable for. When purchasing, you also need to decide on the thickness of these consumables. This directly depends on the thickness of the products being welded.

It is important to acquire skills when igniting an arc. You can choose to use touch or swipe methods. When touched, the electrode quickly comes into contact with the surface of the product and then moves away a short distance. You should continue tapping the electrode on the surface until an arc appears. Striking the electrode over the surface like lighting a match is more preferable, but is inconvenient in hard-to-reach places. The skills to quickly ignite an arc come with experience.

After ignition of the arc, it is important to maintain its combustion stability. To do this, the electrode must be kept from the surface at a constant distance of approximately two millimeters. As the electrode burns, do not forget to lower it. If you hold the electrode too close to the surface of the product, it may stick to it, and if it is too far away, there is a danger that the ignited arc will go out.

The basics of electrode welding suggest that it is better to heat the metal in a circular motion so that the so-called weld pool has time to form. To ensure an even seam, after heating, the electrode should not be moved too slowly, but not particularly quickly, in order to avoid the appearance of defects.

Automatic methods

Classification of welding methods using automation:

1. Electric arc technology.
2. A gas-electric arc is protected by gas, most often an inert gas such as argon or helium.
3. Electroslag technology.

Tungsten welding - application diagrams.
Electric arc method: A close relative of the manual arc method, automatic submerged arc welding or AF is a type of arc method with excellent performance indicators. Here, too, a consumable electrode is used; all work is carried out under a special protective layer of flux. In the manual arc method, there is a serious risk of the arc itself burning in the air, so the strength of the supplied current is limited.

With AF, the arc is protected by a layer of flux, there is no risk of burning. The strength of the welding current is not limited in any way. This makes it possible to penetrate the metal deeply, resulting in a seam of excellent quality. The flux layer prevents metal splashing and loss during the process. Complete mechanization of the method allows less qualified welders to be admitted to AF. As a result, the productivity of the AF method is 5 to 10 times higher than that of manual arc AF. Let's be honest and present the shortcomings of AF, there are few of them:

• fluxes are not cheap;
• there is a harmful effect on the operator;
• You can only work in a limited space.

Electroslag technology, “heavy artillery” on the modern industrial front. This is a fundamentally new arcless method of melting. The source of thermal energy is not an arc, but an alternating current that passes through the molten slag. The metal surfaces are covered with slag, which is heated. This way you can weld metals of almost any thickness.

Advantages of arcless technology:

• high-quality tight seams;
• seams of complex shape;
• absence of deformations, especially angular ones;
• no need to process edges;
• ease of implementation
• labor automation, minimal human participation

The method is used mainly for large-sized structures.

What defects are worth knowing about in order to make the correct welding seam?

Knowledge about welding defects is very important so that you recognize them in time and do not start operating a welded structure with an unreliable connection.

If the seam is welded correctly, it looks uniform and neat, with equal thickness and height along the entire length.

The following main defects are distinguished:

• Lack of penetration. Insufficient filling with suture material, and its strength is reduced. The reason is insufficient voltage in the circuit or excessive speed of electrode guidance.
• Undercut Longitudinal groove. Occurs due to excessive arc length. To eliminate the defect, you should choose the correct current strength and increase it slightly.
• Burns. Formation of through holes in the material. It is caused by exceeding the current required for a given material thickness, as well as by moving the electrode too slowly. It is also necessary to check whether the gap between the edges of the workpieces is not exceeded.
• Porosity. Occurs due to a draft in the work area, blowing away the cloud of protective gases.

Lack of penetration

Undercut

There are also other welding defects, such as longitudinal and transverse cracks

Arc methods

Above we dealt with the basic concepts and physics of the arc (the famous RDS - manual arc, the absolute champion in popularity).

But the classification of welding methods is a strict matter, so we present the types of arc welding as a separate family:

Structure and properties of the electric arc.

Manual arc:

• RAD – manual argon-arc non-consumable electrode;
• RADN – manual argon arc surfacing.

Automatic arc methods:

• AAD, AADN, ALSN, APPGN, etc. - an extensive family of methods using either electrodes (consumable and non-consumable), or wires, or flux-cored wires. You can cook with or without gas.

Submerged arc:

• the familiar AF, automatic submerged arc;
• various weldings, surfacing with strip or wire electrodes;
• mechanized arc.

Arc with coated electrodes:

• this is where the right place is for the people's champion of the RDS;
• manual arc surfacing;

Mechanized arc:

• MADP, MPGN, MSOD, etc. – a large “mechanical” family.

Characteristics of argon welding

Sometimes it becomes necessary to fuse metal elements that cannot be joined by conventional types of welding, for example, parts made of aluminum, titanium, and copper. To make the structure durable and reliable, argon technology is used.

This type of welding combines the properties of the electric arc and gas methods - it is necessary to use an electric arc, use gas and some technological methods for forming a seam.

When argon arc welding of metals, the inert gas argon is used. It covers the area where the seam is formed and provides reliable protection against the oxidation process that can occur from the contact of metal surfaces with oxygen contained in the air. Argon does not allow oxygen to penetrate into the area of ​​mating surfaces.

Welding operations can be carried out in manual, semi-automatic or automatic mode. Depending on the mode, two types of electrodes are used: consumable and non-consumable. The latter uses tungsten wire, which ensures the strength of the connection even between dissimilar metals.

Advantages of argon arc welding technology:

• The low heating temperature allows you to maintain the size and shape of the elements being welded.
• The inert gas argon is heavier and denser than air, it provides reliable protection of the weld formation zone from the penetration of oxygen.
• High arc heating power allows you to perform welding work in a short period of time.
• The simplicity and accessibility of welding technology allows you to quickly master skills.

Disadvantages of argon arc welding technology:

• Argon evaporates in strong winds and drafts. This leads to reduced protection and deterioration in seam quality. There is a need to carry out argon welding work in well-ventilated areas.
• The complexity of the equipment makes it difficult to configure modes.
• When using a high-ampere arc, additional cooling of the metals being connected is necessary.

The main advantage of argon-arc technology is the ability to permanently join metal elements even in cases where the use of other types of fusion does not produce results.

Mechanical class

All types mentioned above belong to the first thermal class. The main character in it is thermal energy with melting. The next class is mechanical. The main “mechanical” words in this context are pressure and plastic deformation.

It also has a neat classification of welding:

1. Cold welding (forging)
2. Friction welding
3. Ultrasonic
4. Explosion

Sometimes mechanical methods are combined under the name “pressure welding”; there is logic here, but we are talking about the same thing.

One of the promising mechanical technologies is friction welding. Heat is also present in it, but it is formed from the force of friction. The surfaces to be welded rotate and are compressed with force. Friction welding technology is especially effective when working with round parts - drills, cutters, reamers.

Table of welding types.

Types of friction welding:

1. Friction stir welding.
2. Radial friction welding.
3. Friction pin welding.
4. Linear.
5. Inertial.

Let's take a closer look at these types of welding:

1. Friction stir welding is a fairly new method, it requires special equipment for friction welding - a rotating tool with two elements - a base (shoulder) and a tip (pin). The seam is formed by two processes of extrusion and mixing.
2. Radial friction welding is used in pipe work: it rotates a ring between the joints, which creates friction.
3. Friction pin welding: a hole is drilled and a pin made of the same metal as the parts is inserted. The pin rotates, generates heat, and forms a connection in the form of metal threads. Excellent friction welding technology when “you need to fill a hole.”
4. Linear method. There is no rotation here. The parts simply rub against each other until heat is released, plasticity increases, then the pressure is increased until an irreversible connection is achieved. With this method, an ideal, flat surface is formed; no other methods have this.
5. Inertia welding. The movement of the surfaces occurs due to a massive rotating flywheel, which is accelerated by a special engine.

The mechanical class involves the use of pressure and mechanical action, energy.

Friction welding (friction)

This method differs from the others - the basis of its method is to obtain elevated temperatures by friction of metal workpieces. One of the parts rotates, then the workpieces are pressed against each other with a gradual increase in pressure.

Friction welding

Cold welding

Cold welding is performed using plastic deformation, which destroys the oxide film on surfaces and brings metal elements together until a bond is formed between them without the use of elevated temperatures. This method is applicable to those metals that have good plastic properties: aluminum, silver, idle, zinc, nickel, etc.

Explosion welding

This method is not very common due to the lack of accuracy of the technological process. The moving part is positioned at an angle to the main part, parallel, and with the help of a controlled part the parts are connected by joint plastic deformation.

Ultrasonic welding

The connection and fastening of parts occurs due to their squeezing together and the influence of ultrasonic vibrations. This method is applicable for spot and contour welding. Ultrasound heats the products and activates diffusion, then molecular bonds are formed and at the end the seam crystallizes, thus creating a strong connection.

Special types of welding

Special types of welding.

Welding

- the process of obtaining a permanent connection by establishing interatomic bonds between the parts being welded during their local or general heating, or plastic deformation, or the combined action of both. Typically used for joining metals, their alloys or thermoplastics, as well as in medicine.

Various energy sources are used for welding: electric arc, gas flame, laser radiation, electron beam, friction, ultrasound. The development of technology now makes it possible to carry out welding not only in industrial enterprises, but also in the open air, under water and even in space. Welding carries the risk of fire, electric shock, poisoning by harmful gases, exposure to ultraviolet rays, and eye damage.

. General information Modern technology is characterized by the increasingly widespread use of new structural materials with special properties: high heat resistance, heat resistance, corrosion resistance, radiation resistance, etc. For these purposes, refractory metals Ti, Zr, Nb, Mo, W and alloys based on them are used, multilayer (composite) materials, as well as non-metallic materials based on ceramics and polymers. Welding of these materials with high quality welded joints can, in principle, be carried out under the following conditions: short heating of the metal to high temperatures, ideal protection of the metal from the air atmosphere, and the use in some cases of high speeds of the welding process. Most of these metals are distinguished by very high chemical activity not only in the molten state, but also in the solid state, and at temperatures above 200-300 ° C they react intensively with all known fluxes used for conventional structural materials. Therefore, such types of welding as manual arc with a consumable electrode, submerged arc welding, gas welding, and welding in inert gases are of limited applicability for these materials. The disadvantages of these types of welding are the relatively low concentration of energy in the heat source and insufficient protection of the metal from the action of oxygen and nitrogen in the air. Prolonged exposure to high temperatures on the metal of a welded joint with insufficient protection leads to loss of ductility, anti-corrosion and other properties, high energy consumption, significant residual deformations, saturation of the weld metal with gases, etc. These disadvantages can be eliminated by using special types of fusion welding and pressure welding in a solid state. As special types of welding, fusion and in welding technology, radial heat sources are used, the energy concentration in which is 100-1000 times higher than that of traditional sources. Beam energy sources are used in electron beam welding, laser and light welding. In electron beam welding, the energy carrier is electrons; in laser and light welding, it is photons. High energy density in the heating spot is achieved by concentrating the energy flow using focusing devices. The heating area by an electron beam can be 1000 times smaller compared to a gas flame and arc (see Table 1) with an energy density 1000 times greater. When using a photon beam, this difference is even greater. The high energy density in a small heating spot determines the main advantages when welding with an electron beam and laser - an advantageous form of penetration (knife, dagger) and the possibility of obtaining precision joints. At the same time, when welding with a deeply embedded beam, additional difficulties arise: a greater danger of pores and hot cracks, fluctuations in the depth of penetration and undercuts, high requirements for the quality of assembly and preparation of metal for welding. Special types of fusion welding also include plasma and microplasma welding. Special types of pressure welding (cold, ultrasonic, friction, explosion, diffusion), unlike resistance electric welding, are carried out, as a rule, without melting the contact surfaces. The formation of metallic bonds between the joined surfaces during these types of welding occurs in the solid state of the metal as a result of joint plastic deformation. Types of solid state welding differ in the methods by which plastic deformation is carried out, the amount of plastic deformation and the temperature regime. These types of welding are divided according to the degree of heating - with and without heating, the degree of force - with low-intensity and high-intensity force. Heated pressure welding is usually performed with low-intensity force. These include: diffusion and thermocompression welding. Pressure welding without heating is usually performed with high-intensity force. These types include explosion welding, cold welding, magnetic pulse welding, etc. Ultrasonic welding refers to welding without heating under low-intensity external force. The parameters of these types of welding (pressure, heating temperature, heating time, specific pressure, intensity of application of pressure and temperature) depend on the properties of the materials being joined, the state of their surfaces, design features, etc. Solid state welding significantly expands the scope of welding, allowing connect together not only homogeneous, but also dissimilar metals, the fusion welding of which would be impossible, connect non-metallic materials with metals, etc. The use of vacuum as protection in a number of special types of welding (electron beam, diffusion, etc.) gives the ability to protect the materials being welded and obtain high quality welded joints. Special types of welding make it possible to carry out so-called precision welding, i.e., obtain structures with specified design dimensions, and automate welding production using advanced welding equipment with program control.

1. Plasma welding - fusion welding, in which heating is produced by a compressed arc. A compressed arc is an arc whose column is compressed using a plasma torch nozzle or a gas flow (argon, nitrogen, etc.). Plasma is a gas consisting of positively and negatively charged particles, the total charge of which is zero.

Plasma is generated in the nozzle channel, compressed and stabilized by its water-cooled walls and cold plasma-forming gas. Compression and cooling of the outer surface of the arc column causes its concentration, which leads to a sharp increase in the number of collisions between plasma particles, an increase in the degree of ionization and a sharp increase in the temperature of the arc column (up to 10,000–20,000 K) and the kinetic energy of the plasma, which is used for welding and cutting A device for creating a directed plasma flow moving at high speed and having a large supply of energy is called a plasma torch or plasma torch. There are several schemes of devices for producing plasma arcs and jets: to produce a plasma arc, when the nozzle and channel are combined, the plasma jet coincides with the arc column, one of the electrodes is the material being processed (Fig. 76, a); to obtain a plasma jet separated from the arc column with a separate nozzle and channel (Fig. 76, b); the same, but with a combined nozzle and channel. The plasma jet is created by an arc discharge 4, excited between electrode 1 and a second electrode, which can be product 7, a separate nozzle 5, or the walls of channel 2. The effective efficiency of plasma-arc heating is lower than the efficiency of . arc, which is explained by the large heat transfer to the walls of the nozzle and the surrounding space, and amounts to m] = 0, 3 - 0.8. Plasma arc welding is carried out with alternating or direct current of straight polarity. The arc is excited using an oscillator. To facilitate the initiation of a direct arc, a pilot arc is used, burning between the torch nozzle and the electrode. To power the plasma arc, welding current power supplies G with an operating voltage of up to 120 V, and in some cases higher, are required. A plasma (compressed) arc can be used to weld almost all metals in various spatial positions. Argon and helium are used as plasma-forming gases, which can also be protective. The advantages of plasma welding include high productivity, low sensitivity to fluctuations in arc length, and elimination of tungsten inclusions in the weld metal. Without bevelling the edges, it is possible to weld metal up to 15 mm thick with the formation of weld penetration of a specific mushroom-shaped shape, which is explained by the formation of a through hole in the base metal through which the plasma jet exits to the back side of the product. Essentially, the process is cutting through the product with welding of the cutting area. Butt and fillet welds are welded using a plasma jet. Butt joints on metal up to 2 mm thick can be welded with flanged edges; for thicknesses over 10 mm, it is recommended to bevel the edges. If necessary, additional metal is used. When welding sheets up to 25 mm thick, a V- or U-shaped groove of the edges is required, and the depth and angle of the groove are much smaller than for argon arc welding. When plasma-arc welding, the amount of filler metal is reduced by about 3 times. The filler metal is introduced into the plasma jet at the end of the weld pool. Plasma arc welding provides the greatest advantages when joining sheets without cutting edges and without filler metal. Multi-pass plasma-arc welding of thick sheets should not be accompanied by through penetration, therefore, when laying subsequent layers, the force action of the plasma jet is controlled by changing the flow rate of the plasma-forming gas so that the molten metal is not displaced from the weld pool. Approximate modes of plasma arc welding of some metals with through penetration are given in table. 17 (welding of aluminum was carried out with reverse polarity, welding of other metals with direct polarity). A significant amount of welding work consists of welding metals and alloys of small thicknesses (0.05-1.5 mm). Among the known methods of joining thin metals, gas welding, soldering and arc welding with a non-consumable electrode in continuous and pulsed modes have become widespread. However, the low heating rate, large heat-affected zone in gas welding, and in arc welding - low stability of the arc at low currents and the strong dependence of the weld parameters on the arc length make the welding process difficult, and in some cases make it impossible. The use of other welding methods (resistance, electron beam, laser, diffusion) is not always possible due to a number of design, technological and operational factors.

Work on plasma welding at high currents has shown that a compressed arc formed by a plasma torch channel has significantly greater spatial stability than a freely burning arc, and the separate supply of plasma-forming and shielding gases makes it possible to use various mixtures of gases during welding. The indicated advantages of a compressed arc are also suitable for welding metals of small thickness (<1 mm), which led to the emergence of essentially a new welding method - microplasma, i.e. welding with a compressed low-ampere arc of thin and especially thin materials. The compressed arc used in this method as a concentrated heat source is called microplasma. Microplasma is formed by special burners - plasma torches, the circuit diagram of which corresponds to Fig. 76. The use of a pilot arc ensures the stability of the process even at very low currents, down to / d ^0.1 A, which makes it possible to weld metal of such small thicknesses (~0.01 mm) that are inaccessible to argon arc welding. The vast majority of metals are welded in continuous or pulsed modes with an arc of direct polarity, burning between the tungsten electrode of the plasma torch and the product in a stream of plasma-forming inert gas (usually argon). To prevent interaction of the molten pool of liquid metal and the heat-affected zone with the atmosphere, shielding gas is supplied along the periphery of the arc: Ar, He, N2, CO2, mixtures of Ar with H2, Ar with He, Ar with N2 and others, depending on the properties of the metal being welded. The separate supply of plasma-forming and protective gases determines the distinctive feature of microplasma: its near-cathode region (on the electrode) exists in the plasma-forming gas environment, and the column and near-anode region (on the product) exist primarily in the environment of the protective gas. This circumstance allows you to flexibly control the shape of the arc and its technological capabilities. In table 18 shows the optimal modes of mechanized microplasma welding of low-carbon steel 08kp with a thickness of 0.5 mm. When welding chemically active and refractory metals (Ti, Zr, Nb, Ta, Mo, W), it is necessary to use more effective means of protection with a minimum gas content. For welding such metals, a method of plasma welding in a vacuum of 133•(10~1-5-10"4) Pa has been developed, which ensures good quality of metal joints with a thickness of more than 1 mm. This is achieved due to the contraction (compression) of the low-pressure arc, observed at currents above 80 A. Powering the arc with pulses allows you to reduce the average welding current while maintaining a high density during the pulse. By choosing the parameters of the pulse mode (current amplitude, pulse duration, pulse repetition frequency), the average current (2.5–50 A) and power (0.1–2.5 kW) of the low-pressure plasma arc can be adjusted over a wide range. In this case, it is possible to weld metal of very small thickness (0.1–0.2 mm). Direct microplasma is widely used for welding and cutting thin metals: carbon and stainless steels, non-ferrous metals and their alloys, chemically active metals. Indirect microplasma is used for soldering, welding foil and thin mesh, and for processing thin non-metallic materials. § 38. Beam types of welding Electronic welding - fusion welding, in which the metal is heated by an electron beam. An electron beam is a stream of electrons emitted by one source and moving along close trajectories in a certain direction. The essence of the electron beam welding process in a vacuum is the use of the kinetic energy of electrons. When electrons bombard a metal surface, the vast majority of their kinetic energy is converted into heat, which is used to melt the metal.

The electron beam is created in a special device - an electron gun (Fig. 77), with the help of which narrow electron beams with a high energy density are obtained. The gun has a cathode /, which can heat up to high temperatures. The cathode is located inside the near-cathode electrode 2. At some distance from the cathode there is an accelerating electrode (anode) 3 with a hole. Electrons leaving the cathode are focused using an electric field between the near-cathode and accelerating electrodes into a beam with a diameter equal to the diameter of the hole in the anode 3. The positive potential of the accelerating electrode can reach several tens of thousands of volts, so the electrons emitted by the cathode acquire significant speed and energy. The gun is powered by electrical energy from a high-voltage DC source 7. To increase the energy density in the beam, after the electrons leave the first anode, the electrons are focused by a magnetic field in a special magnetic lens 4. The flying electrons, focused into a dense beam, strike at high speed a small, sharply limited area (heating spot) on product b, while the kinetic energy Due to braking, electrons are converted into heat, heating the metal to very high temperatures. To move the beam along the workpiece being welded, a magnetic deflection system 5 is placed in the path of the electrons, allowing the beam to be positioned exactly along the joint line. To ensure the free movement of electrons from the cathode to the anode and further to the product, for thermal and chemical insulation of the cathode, as well as to prevent the occurrence of an arc discharge between the electrodes, a deep vacuum of about 133 Pa is created in the welding installation, provided by the vacuum pump system of the installation. The power of the electron beam can reach very high values, which makes it promising for welding large thicknesses (200-500 mm). The possibility of high energy concentration while using low power makes it possible to weld microelectronic products with an electron beam. The main parameters of the electron beam welding mode are current strength, electron beam voltage, and welding speed. The accelerating voltage and beam current determine the power of the energy source. For example, the recommended modes for electron beam welding of titanium alloys with a thickness of 8-15 mm in the lower position on the remaining technological lining: U = 30 kV; /sv=110-180 mA; condition = 25h-35 m/h. In the pulsed mode of electron beam welding, the heat release is additionally regulated by the frequency and duration of the welding pulses. The effective efficiency of electron beam heating varies within the range of 0.7-0.9. Laser welding is fusion welding in which the energy of a light beam received from an optical quantum generator is used to locally melt the parts being joined. The essence of obtaining a laser beam is as follows. Due to the pumping of external energy (electrical, light, thermal, chemical), the atoms of the active substance of the emitter pass into an excited state. After a certain period of time, the excited atom can emit the resulting energy in the form of a photon and return to its original state. A photon is an elementary particle, a portion of light, having zero rest mass and moving at a speed equal to the speed of light in a vacuum. Photons arise (emit) in the processes of transition of atoms, molecules, ions and atomic nuclei from excited states to more stable states with lower energy. At a certain degree of excitation, an avalanche-like transition of the excited atoms of the active substance-emitter to a more stable state occurs. This creates coherent, i.e. associated with excitation, monochromatic light radiation, which is amplified in the emitter by multiple reflection from its walls and released in the form of a narrow directed beam. Monochromatic radiation is electromagnetic radiation of one specific frequency. Thus, a laser beam is created - a monochromatic directed stream of photons. Based on the type of active substance-emitter, lasers are divided into solid, gas, liquid and semiconductor; based on the principle of laser beam generation - pulsed and continuous. Currently, solid-state and gas lasers are used for welding. Modern solid-state lasers use optical glass mixed with neodymium and other rare earth elements as an active element. This allows you to increase the output radiation power. Solid-state lasers operate in pulsed mode. A diagram of the general layout of a solid-state laser welding installation is shown in Fig. 78. The installation consists of a working fluid Y, a pump lamp 2, which provides light energy to excite the atoms of the active substance-emitter. The resulting radiation is focused and directed using an optical system 3 onto the product being welded 4. The power of solid-state lasers is low - 0.015 - 2 kW. Gas lasers have a higher output power, operate in continuous and pulsed modes and, in their technological capabilities, become competitive with electron beam welding. The advantages of a laser beam are: the ability to transfer energy over long distances in a non-contact manner; welding through transparent shells, since transparent media do not serve as barriers for light rays; obtaining high-quality compounds on metals that are especially sensitive to prolonged exposure to heat; welding in air, in a protective atmosphere, vacuum. An important area of ​​application of laser welding is welding in microelectronics, radio electronics and electronic engineering of micro-joints both from homogeneous metals and from various compositions (gold - germanium, gold - silicon, nickel - tantalum, copper - aluminum, etc.).

The use of continuous-wave carbon dioxide lasers makes it possible to obtain welded joints with a thickness of up to 15 mm and higher. In the future, it is possible to increase the thickness of the welded products and use a laser for heat treatment and cutting of metal. The main disadvantages of a laser energy source are low efficiency values. installations, high cost of equipment, insufficient capacity of serial equipment. In installations for welding incandescent lamps. For technological purposes, the most promising and convenient emitters are ultra-high pressure xecon arc lamps. A xenon arc lamp is a spherical cylinder made of optically transparent quartz with two tungsten electrodes placed in it. The xenon pressure in the lamp when not in use reaches 1 MPa. In systems used for welding with a light beam, the energy concentration in the heating spot reaches 103 W/cm2 and can be increased by using special lenses and reflectors. A schematic diagram of optical systems for welding and soldering is shown in Fig. 79. The area of ​​rational application of the process is instrument making.

Special types of pressure welding Cold welding - pressure welding with significant plastic deformation without external heating of the surfaces being joined. The physical essence of the process is to bring together the surfaces being welded due to plastic deformation until metallic bonds are formed between them and thus obtain a strong welded joint. A distinctive feature of cold welding is the need for significant volumetric plastic deformation and a small degree of its localization in the contact zone of the materials being joined. This is due to the need to destroy and remove oxide films from the contact zone mechanically, i.e., due to intense joint deformation. A large compression force ensures the rupture of oxide films, their crushing and the formation of clean surfaces capable of setting. The weldability of metals during cold welding depends on their ductility and the quality of surface preparation. The more ductile the metals, the smoother and cleaner their surfaces, the better the quality of their welding. Plastic alloys of aluminum, copper, nickel, silver, gold and similar metals and alloys in homogeneous and dissimilar combinations are well welded. In metals that are not sufficiently ductile, cracks may form under large deformations. High-strength metals and alloys are not cold welded. Cold welding is most widely used in the production of household products made of aluminum and its alloys, in the electrical industry and transport for connecting copper and aluminum wires. Cold welding is used to make spot, seam, and butt joints. Before welding, the surfaces to be welded are cleaned of contamination by degreasing, treating with a rotating wire brush, and scraping. When butt welding, only the ends of the wires are cut off. For cold welding, standard pressing and rolling equipment is used, which is equipped with special tools in accordance with the parts being welded, and specialized machines are also used. Cold welding is used to connect metals and alloys with a thickness of 0.2–15 mm. The main characteristics of the process are pressure and the magnitude of deformations. Depending on the composition and thickness of the metal being welded, the pressure is 150–1000 MPa, the degree of relative deformation is 50–90%, which has the following values ​​for various metals, %: Au – 35–40, Al – 55–60, Ti – 70 - 75, Pb and Ag - 80-85, Sn, Ni, Cu - 85--90, aluminum alloys - 75-80. Sheets with a thickness of 0.2-15 mm are overlap welded by pressing punches into the thickness of the metal on one or both sides. Connections are made in the form of individual points or a continuous seam. The width or diameter of the punch d^ is chosen depending on the thickness S of the material being welded, dn=(l-3)S. A geometric seam joint can be obtained by pressing a punch along the entire length of the seam or by rolling a roller. Rods, strips, profiles and wires are joined end-to-end by squeezing the welded elements. The pressure during cold butt welding is 700–800 MPa for A1, 2000–2500 MPa for Cu, 1500–2000 MPa for Cu with A1. The amount of plastic deformation depends on the length of the ends of the welded rods released from the clamps, which are then completely squeezed out of the joint zone during the welding process. To ensure the strength of the connection, which depends on the amount of plastic deformation, the extension length of the rod is for A1 (1-H.2)d, for Cu - (I.25-~l.5)d, where d is the diameter of the rod. When welding A1 with C, the protrusion of the copper rod should be 30-40% greater than that of the aluminum one. The degree of required deformation when welding dissimilar metals is determined by the properties of the metal being welded for which less deformation is required. This is used when welding low-plasticity metals, using spacers made of ductile metals or layers applied electrolytically. A type of pressure welding, similar in physical essence to cold welding, is thermocompression welding, which differs from cold welding in that the joint is heated to temperatures below the temperatures of formation of liquid phases, and then compressed. The main parameters of the process are compression force, heating temperature and holding time. Ultrasonic welding is pressure welding carried out under the influence of ultrasonic vibrations. With this type of welding, a permanent joint is formed under the combined influence of mechanical vibrations of high (ultrasonic) frequency and relatively small compressive forces on the parts being welded. Welding is carried out as a result of mutual friction of the welded surfaces, heat and pressure. Friction forces arise when workpieces, compressed by axial force, are exposed to mechanical vibrations of ultrasonic frequency (20-30 kHz). To obtain this frequency, the magnetostrictive effect is used, which consists in changing the dimensions of certain metals, alloys and ceramic materials under the influence of an alternating magnetic field. Ultrasonic welding machines consist of a power source, control equipment, mechanical oscillating system and pressure drive. In Fig. Figure 80 shows the simplest ultrasonic welding scheme. The workpieces 5 to be welded are placed on the support 6. The tip 3 is connected to the magnetostrictive transducer 1 through an elastic vibration transformer 2f representing, together with the working tool 4, a waveguide (the figure shows how the amplitude of vibrations changes along the length of the waveguide). Ultrasound is emitted continuously during the welding process. An element of the oscillatory system that excites elastic vibrations is an electromechanical transducer that uses the magnetostrictive effect. The alternating voltage creates a magnetizing current in the converter winding, which excites an alternating magnetic field in the converter material. When the magnetic field strength changes in the material, a periodic change in size occurs, and the frequency of elastic vibrations is equal to double the frequency of the current. The oscillation amplitude at the end of the waveguide is ~20–40 μm at idle. Welding occurs under the influence of friction caused by the microscopic back-and-forth movement of particles on rubbing surfaces. Thus, as a result of ultrasonic vibrations, shear deformations are created in thin layers of contacting surfaces, destroying surface films. As the films are destroyed, setting nodes are formed, the near-surface layers of the metal heat up, soften slightly and, under the influence of compressive force, are plastically deformed, the welded surfaces come closer to the distance of action of interatomic forces, and a strong welded joint occurs. The relatively small thermal effect on the metals being welded ensures minimal changes in their structure and properties. For example, for Cu the temperature in the contact zone does not exceed 600°C, for welding A1 - 200-300°C. The parameters of ultrasonic welding are the power of the vibration generator, vibration amplitude, pressure and welding time. Ultrasonic welding is used to produce spot and seam joints of metals and alloys of small thickness (usually less than 1 mm) and for welding plastics. Advantages of ultrasonic welding: welding in the solid state without significant heating of the parts being welded, which makes it possible to weld chemically active materials and alloys that form brittle joints; possibility of welding and welding of thin and ultra-thin parts; . the use of small compressive forces (0.1-2.5 kN), as a result of which the deformation at the joint is insignificant (dents 5-10%); low power of welding equipment and simplicity of its design. The disadvantages of ultrasonic welding are the limited thickness of the welded parts (less than 1 mm), the high cost of high-frequency generators, and the effect of high frequencies on the human body. In the USSR, ultrasonic machines for welding various elements of microcircuits, equipped with automatic devices (automatic feeding of conductors, welding, cutting conductors, etc.), as well as installations for welding polymer materials, have been developed and produced in series, allowing to significantly increase productivity. Diffusion welding is pressure welding, carried out due to the mutual diffusion of atoms of the contacting parts under relatively long-term exposure to elevated temperature and slight plastic deformation. The main parameters of diffusion welding are heating temperature, pressure, heating time, and the environment in which welding is carried out. The temperature for homogeneous metals, as a rule, should be 0.5-0.8 of the melting temperature of the metal or alloy, and when welding dissimilar metals - 0.5-0.7 of the temperature of the lower-melting metal. This temperature accelerates the mutual diffusion of atoms of materials through the joint surface and facilitates the removal of surface irregularities and plastic deformation of the metal. Heating is carried out primarily by induction currents; other heating sources can also be used: ordinary resistances, electric current passed through the parts themselves, an electron beam, etc.

Thermomechanical class

Third class from the point of view of physics: both types of influence on the surface are used here: heat and pressure. We present the types and methods of thermomechanical welding:

• Diffusion. The surfaces are compressed, then heated in a high vacuum, achieving mutual diffusion of atoms. It is effective when the metals to be welded do not fit well with each other or the materials are different in nature, for example, metal and ceramics. The method is not cheap, it is used mainly in the aerospace sector and other high-tech industries.

Types of pressure welding.
All the following points are types of resistance welding

• Contact electric. Everything is simple here: before pressing, you need to warm it up thoroughly. The surfaces are heated with current at the joints, then compressed or upset. An excellent, high-performance method that lends itself well to automation. Widely used in construction and mechanical engineering.
• Seam contact welding is a type of resistance welding: the seam is formed by overlapping electrodes.
• Point contact. Surfaces are placed between the two electrodes. The current is turned on after tight compression, resulting in a weld spot with a diameter equal to the diameter of the electrode surface. An extremely interesting variety is relief welding. The contact of the electrodes is carried out along protrusions determined in advance - reliefs, which are eventually deformed, the surface is leveled.
• Spot capacitor welding - “welding with stored energy in capacitors.” It features low power consumption and is used when working with small parts and when using optical instruments - watch mechanisms, aircraft instruments, etc.

The thermomechanical class is characterized by a combination of the use of elevated temperatures and mechanical products.

Forge welding

Forging welding and hand forging are some of the oldest welding methods. The metal is heated to the required temperature and its further connection occurs under the action of a forging hammer or a hydraulic press.

contact welding

Resistance welding uses electric current to join metals. This method involves the formation of an electric arc that melts the metal. Adjusting the current power allows you to process thicker metals.

Spot welding

The most common type is resistance spot welding, since this method can also be used at home. The parts are clamped in electrodes or special pliers, then a current is passed between the electrodes, the metal heats up, the electrodes are compressed more strongly and “forging” occurs, the metal crystallizes under pressure.

Relief welding

Metal workpieces have specially prepared convexities - reliefs, and the welding surfaces contact only in the zones of these reliefs, plastic deformation of these same reliefs occurs; in all other respects, the principle of the method is the same - current is passed through the parts under the compression force of the metals.

Diffusion welding

The basis of the method is the physical process of diffusion. As is known, metals pressed tightly against each other can merge at the molecular level.

Welding occurs in a protective environment - vacuum or special protective gases. The parts are treated to remove roughness, washed with acetone to degrease, then the metals are heated and compressed.

Welding with high frequency currents

When heated by high-frequency currents, the metal is placed in a magnetic field, during this process an electromotive force is induced in the metal, which causes a current in it, a surface effect (the current is distributed unevenly, it is greater at the surface, due to this the metal heats up faster) and the proximity effect (energy is more intensely concentrated near the surface due to the spread of the influence of its own alternating magnetic field and the field of other sources).

Types of Welding Machines

There are a large number of models of welding machines of different types on the market.

Of all their diversity:

• transformers;
• rectifiers;
• inverters;
• semi-automatic;
• machine guns;
• plasma;

In a home workshop, transformers are most often used because of their low cost, and inverters because of their simplicity and ease of use. The rest require either special working conditions, achievable only in production, or special training and long-term acquisition of skills.

Transformer

The design of such devices is extremely simple - it is a powerful step-down transformer, in the secondary winding of which a working electrical circuit is connected.

Transformer welding machine

Transformer advantages:

• unpretentiousness;
• survivability;
• simplicity;
• cheapness.

Flaws

• very large weight and dimensions;
• low arc stability;
• AC operation;
• causes voltage surges in the supply network.

Such a device requires skill and extensive experience from the welder. It is not suitable for teaching a novice welder how to weld correctly.

Inverters

The inverter device has a much more complex design. The inverter unit repeatedly converts the input mains voltage, bringing its parameters to the required ones. Due to the transformation of high frequency current, the dimensions and weight of the transformer are many times smaller.

Inverter

Inverter advantages:

• low weight and dimensions;
• stabilized voltage and current in the circuit;
• additional anti-stick and hot start functions;
• possibility of precise adjustment of current and arc parameters;
• does not cause voltage surges in the supply network.

The inverter also has disadvantages:

• high price;
• low frost resistance.

It’s best to start learning how to cook properly with an inverter. The stability of the arc parameters and additional functions that make starting easier and preventing “sticking” will allow the beginner to concentrate on the seam and quickly master the technology.

Thermal class of welding

Using thermal energy, the surfaces of workpieces and parts are melted locally. Heat is obtained using various methods; they are discussed in detail below.

Arc welding

This type is the most popular. The welding arc uses direct, alternating or pulsating current. The arc is produced by a powerful discharge. The electrode comes into contact with the metal, a short circuit is produced, and the tool is withdrawn no more than 5 mm, due to this continuous action the metal is heated. The stability of the arc charge occurs due to the acceleration of the electrodes in the electromagnetic field, then ionization of the gas connection between the anode and the cathode occurs.

Gas welding

Gas welding is a type of fusion welding with the additional use of gases - oxygen, acetylene. The heat generated during the combustion of gases melts the surfaces along with the filler material, thereby forming a weld pool. The gas supply is regulated using a reducer on the cylinder.

Arc welding

The operating principle of electric arc welding is based on the melting of metals under the influence of an electric arc. An electric arc is formed by increasing the voltage between two electrodes, resulting in an electrical breakdown. The basis of the technological method of electric arc welding is a short circuit, or, more precisely, the saturation of the interatomic space with electrically charged particles. At the moment of contact between the electrode and the product, a current flows, the resulting electric arc, the temperature of which reaches 7000 ° C, melts the metal and forms a weld pool.

Manual arc welding

Devices for manual arc welding are widely used in everyday life due to the relative inexpensiveness of the devices. Also, this method does not require gas or flux, since their functions are performed by the electrode. The principle of arc welding is preserved: melting of surfaces occurs due to the contact of the electrode with the metal product, which forms a short circuit and the arc is ignited.

Non-consumable electrode welding (TIG)

This is a gas welding technology, its essence is as follows: an electric arc is ignited in an inert gas atmosphere between the electrode and the material, thus melting the metal and filler material. The electrode is made of refractory metals - tungsten, zirconium, hafnium. This technology requires highly qualified specialists.

Gas shielded welding

This type of welding can be performed with either a consumable electrode or a non-consumable one. For non-consumable electrodes, an additive is needed, and the consumable electrode itself participates in the process of creating a seam. Inert gases are used to ensure stable arc operation. The choice of gas determines the composition of the product being welded. Gas is supplied either centrally or from the side at higher capacities.

Submerged arc welding

The use of flux is necessary to maintain even burning of the arc and, when forming a weld, affects its chemical composition. Different flux compositions have different stabilizing properties. By varying the content of carbon, sulfur, manganese and others, strength and resistance to cold can be adjusted.

Hyperbaric welding

Hyperbaric welding is welding under conditions of high pressure, for example, in water or a specially created dry environment. Underwater welding uses a waterproof electrode that melts and hits the metal with a gas bubble. Underwater welding is one of the most difficult types of work, which, among other things, has an increased risk of electric shock.

Electric arc welding

This is the most common implementation option. Heating of the metal is carried out through the interaction of the anode and cathode, releasing high-power energy. Melting of the workpiece in such a situation results in the formation of a weld pool. Crystallization of the alloy also occurs during the cooling process. The strength of the resulting joint is similar to that of the metals being welded. In this embodiment, the classification of various types of welding includes the following types.

Manual Arc MMA

When carrying out, piece electrodes are used, which are a metal rod coated with coating. Performed under constant influence of alternating or direct current. The advantage is the formation during melting of consumables of a cloud consisting of a mixture of gases (mostly CO2), which forms protection against oxidation of the metal being welded.

When coating, a variety of chemical compounds are used. In the weld pool, they contribute to the formation of additional protection for the weld seam and support stable combustion of the electric arc. The devices are able to work in any position, including in hard-to-reach places, welding any metals. The technology is equally accessible to beginners and professionals. Areas of use: creation of metal structures, in private enterprise, at vehicle service stations.

TIG (argon welding)

Tungsten, graphite, non-consumable, carbon electrodes are used. Nitrogen, argon, helium or a mixture of them are used as inert gas. The weld includes only the workpiece metal and additives. An additive, which is a metal strip or rod, identical in composition to the metals being welded. The use of inert gases is required for protection from atmospheric air. This ensures stable combustion of the electric arc and eliminates metal oxidation.

Semi-automatic MAG (MIG)

Wire is used as a filler material and enters the working area through the torch. In parallel, active or inert gas is supplied, the composition of which is determined depending on the selected work material. Execution is possible only with continuous contact with electric current, which produces a lot of splashes. Due to this, the seam loses accuracy, which is compensated by high productivity. Consumables are supplied automatically. Welding of a wide range of materials from manganese or cast iron to copper and aluminum. Different types of materials are combined.

What is submerged arc welding?

It is carried out using special flux powders, which provide the working area with protective gas released during the melting process. The flux maintains the melting arc and provides protection for the melt. The process is fully automated from flux supply to movement along the joint. Among the areas of use are the creation of:

• satellite modules;
• tower cranes;
• hulls of sea vessels;
• other equipment where long seams and seams of large thickness are used.

A high-strength seam is formed, which is necessary to create equipment that can withstand difficult operating conditions. Such as enormous pressure and extreme temperatures.

Gas plasma

Today, types of welding and, of course, their brief descriptions include this increasingly less used option. It consists of the formation of new pools along the welding seam under the influence of the torch. Its combustion is maintained by supplying one or more combustible gases mixed with oxygen. The technology is more complex than arc technology. It is most often used by experienced specialists due to its versatility and mobility.

Welding is ensured by the high temperature of an open flame, formed by the combustion of oxygen with flammable gases such as acetylene, hydrogen, butane, propane and others. The most effective is the use of methyl acetylene fraction. Depending on the type of flammable gas, the temperature is:

• 2927 with oxygen;
• 4500 when combining oxygen and MAF;
• acetylenedinitrile 5000.

An open flame is used, independent of the power supply. Due to this, it is widely used in “field” conditions. Cooling occurs gradually, which is convenient when working with sheet materials.

The use of the method is unsuitable in industrial conditions due to the lack of automation and low level of productivity. High complexity of the work requires the invitation of a professional. When considering what types of welding there are and what level of qualification, this is considered one of the most difficult.

Electroslag type

The edges of the parts are connected when heated under the influence of electric flux. It is pre-filled between the elements to be connected. Additionally, molten rod or wire is used. Recommended for joining parts made of cast iron or, less commonly, non-ferrous metals. Used to connect large parts in industry. Effective on all types of metals.

Termite

The name comes from the use of thermite when heating metal. Required in “field” conditions, in the absence of a constant source of electricity and gas cylinders. It is an easy activity option to perform. Most often used for surfacing structures, as well as joining brittle and cast iron alloys in accordance with the requirements of GOST R 57181-2016. When connecting, powder mixtures are used, during the combustion of which a large amount of energy is generated under the influence of which the metals pass into a semi-liquid state.

Foundry method

Another type of work that is used less and less these days. It consists of filling a previously prepared work site with liquid superheated metal. Heating can be carried out, for example, in a crucible. The process is similar to making castings. The welding site must be molded, dried and calcined. When the product is heated, superheated molten metal is poured into the molded joint.

In modern production, the technique is most applicable when working with precious noble materials. We work with bronze products, dishes, and jewelry. This is exactly how lead pipes were made in ancient times.

Using a laser

One of the modern types of technology. The laser becomes the energy source, providing special strength to the finished products. Recommended when working with structures of complex configuration. When joining, a smooth and aesthetically pleasing even seam is created, devoid of the slightest curvature. Used to connect elements made of aluminum, silver, stainless steel. Melting and heating uses a laser beam with a monochrome stream of laser-generated light. Flow control is ensured by focusing the lenses and deflecting the prisms. When working, automatic, semi-automatic and robotic devices are used. Melting occurs smoothly and accurately. There is no need to use a vacuum.

Electron beam (EB)

One of the newest and most modern methods of joining refractory materials. The method was developed in the middle of the twentieth century. Convenient for the purpose of reliable connection of thick-walled and thin-walled products, eliminating or minimizing the possibility of deformation when heated. Can also be used when processing ceramics.

The main method of use is the readiness of electrons to transfer energy. Streams of infected particles are formed under vacuum conditions.

Glow discharge

Glow discharge welding is carried out by diffusion interaction through the use of induction heating. Due to this, the connection occurs at the atomic level.

Light

A powerful light beam is used to make the connection. The source of its supply is a carbon arc and gas-charging arc lamps. The most promising today are considered to be arc xeon lamps, the cylinders of which are filled with xeon under a pressure of 4-10 atm (0.4-1 MN/m2). The pressure during lamp operation further increases to 10-30 at (1-3 MN/m2). In this case, the arc discharge is strongly compressed and forms a highly concentrated source of radiant energy, reaching a discharge temperature of 12,000 °C. An increase in the radiant flux density is formed through the use of combined polyellipsoidal systems. Xeon arc lamps provide focusing of the flow.

Induction

Welding provides heating under the influence of induction current generated in the welding machine under the influence of induction current. Such innovative types are characterized by increased accuracy. The induction coil is excited by using high frequency current.

And for dessert

Special types of welding are a vague concept, given the huge number of technical options, groups, types, subtypes. Everyone sees this list differently.

In our list, the classification of welding is determined by manufacturability. These are unique methods that rightfully belong to aerobatics technologies.

Electron beam and plasma welding:

• Electron beam welding. Here an electron gun and a beam of accelerated electrons from this gun are used. The work is carried out in large vacuum chambers. The energy concentration and heat output are fantastic. The seams are narrow and deep. It is used for the production of high-precision parts from special alloys - not a cheap pleasure.
• Plasma welding. One of the most high-tech types - the name speaks for itself. Plasma is a stream of ionized gas (argon, helium, hydrogen) of the highest temperature. This jet cooks everything - from the most refractory metals to non-metallic surfaces. Outstanding performance with fantastic seam and surface quality.

Choosing a machine for household welding

There are many types of welding today. But most of them are intended for special work or are designed for industrial scale. For domestic needs, it is unlikely that you will need to master a laser machine or an electron beam gun. And gas welding for beginners is not the best option.

The easiest way to melt metal to connect parts is to pointly influence it with the high temperature of an electric arc that occurs between elements with different charges.

Electric arc

It is this process that is provided by electric arc welding machines operating on direct or alternating current:

• The welding transformer welds with alternating current. For a beginner, such a device is unlikely to be suitable, since it is more difficult to work with due to the “jumping” arc, which requires considerable experience to control. Other disadvantages of transformers include a negative impact on the network (causes voltage surges that can lead to breakdown of household appliances), loud noise during operation, impressive dimensions of the device and heavy weight.

Welding transformer

• An inverter has many advantages over a transformer. It generates an electric arc with direct current, it does not “jump”, so the welding process is more calm and controlled for the welder and without consequences for home appliances. In addition, inverters are compact, lightweight and virtually silent.

Therefore, if you are faced with the task of learning how to cook with electric welding, then it is best to purchase an inverter machine.

Welding inverter

Let's generalize and loop

Welding is the process of forming inseparable joints between surfaces of different structures.

First, all types and methods of welding are divided into three powerful classes from the point of view of physics:

• Thermal (heat and melt)
• Mechanical (three, push, push, etc.)
• Thermomechanical (heat and press at the same time)

Tig welding of aluminum.
Within these classes, methods can be grouped as desired:

• with or without arc;
• with or without gas, possible with arc and gas together;
• manual or automatic. Or semi-automatic;
• what types of welding electrodes do you use;
• all types of resistance welding;
• types of welding of metal or, conversely, polymers;
• and so on, the list of options is long.

The main thing is to find out, try, learn and move forward to professional heights. Don't forget to read the reviews, you need to stay informed. We cannot stand still. We wish you pure metal, good orders and a working mood.

https://www.youtube.com/watch?v=ocJFw1HwOpw

Nuances for beginners in welding

There are several nuances that can be useful to anyone who wants to learn how to cook correctly:

• Do not forget about grounding and the importance of regularly checking the quality of contact between the clamp and the workpiece.
• Check the cable insulation regularly.
• The current strength is selected immediately after connecting the ground.
• Before igniting the arc, the electrode should be installed at an angle of approximately 60 degrees to the plane of the part, and the distance between its end and the part should be about 0.5 cm.

  Electrode positions when welding

By mastering increasingly complex types of seams and joint configurations, the home craftsman will be able to learn how to weld correctly and will provide his household with all the necessary welded structures.

Requirements for welding seams

The requirements that may be placed on welding seams largely depend on the final purpose of the finished structure. Nevertheless, several general requirements can be identified that connections of this type must satisfy. The hardness and tensile strength of the welded joint must have the same indicators (or similar) as those of the base metal. Tests are carried out on special equipment with a sample of the finished product.

Visually check the quality of the seam as follows. After completing the welding work, the seams are cleaned of slag and oxides, and all auxiliary devices are also removed. The seam should be uniform, fine-scaled and have a uniform width. There should be no sagging, burns, narrowing or breaks. The metal that is deposited must be homogeneous and not have pores or surface cracks.

Electric welding technology

It is better to learn how to properly weld parts using electric welding under the guidance of experienced welders. If for some reason this does not work out, you can try it yourself. First you need to properly organize your workplace. This is very important, since welding is a high-temperature and therefore fire-hazardous process.

To work, you need to choose a workbench or any other base made of non-combustible material. Wooden tables and similar products are strictly prohibited. It is advisable that there are no flammable objects near the place where welding will be carried out.

Be sure to place a bucket of water near you to eliminate possible fires. In addition, you need to determine a safe place where the remains of used electrodes will be stored. Even the smallest of them can cause a fire.

You can find welding electrodes of different diameters on sale. The required rod size is selected based on the thickness of the metal being welded

For the first independent seams, you need to prepare an unnecessary piece of metal and select electrodes for it. Experts recommend using 3 mm rods in such cases. The smaller diameter is used for welding thin sheets, which are inconvenient to learn from. Larger diameter electrodes require high power equipment.

We start by stripping the area of ​​metal where the seam will be located. There should be no rust or any contamination.

After the part is prepared, take the electrode and insert it into the clamp of the welding machine. Then we take the “grounding” clamp and firmly attach it to the part. Let's check the cable again. It should be tucked into the holder and well insulated.

Now you need to select the operating current power for the welding machine. It is selected according to the diameter of the electrode. We set the selected power on the panel of the welding equipment.

The next step is igniting the arc. To do this, you need to bring the electrode to the part at an angle of about 60° and very slowly move it along the base. Sparks should appear. As soon as this happens, lightly touch the part with the electrode and immediately raise it to a height of no more than 5 mm.

The welding inverter is ready for use. Two cables are connected to it: one with a clamp for the electrode, the second with a grounding clamp

At this moment, an arc flashes, which must be maintained throughout the entire operation. Its length should be 3-5 mm. This is the distance between the end of the electrode and the workpiece.

When maintaining the arc in working condition, you need to remember that during operation the electrode burns out and becomes shorter. If the electrode gets too close to the workpiece, sticking may occur. In this case, you need to slightly swing it to the side. The arc may not ignite the first time. Perhaps there is not enough current, then it needs to be increased.

After the novice welder has learned to ignite the arc and keep it in working condition, you can begin to weld the bead. This is the simplest of all operations. We light the arc and begin to very smoothly and carefully move the electrode along the future seam.

At the same time, we perform oscillatory movements resembling a crescent with a small amplitude. We seem to be “raking” the molten metal towards the center of the arc. This way you should get an even seam that looks like a roller. There will be small wave-like metal sagging on it. After the seam has cooled, you need to knock the scale into it.