home Business blogs Modern welding machines - review. Cast iron welding technology

Modern welding machines - review. Cast iron welding technology

And the history of the permanent connection of metals by heating them and dynamically influencing each other begins with the Bronze Age. We now call this process welding, which began to acquire modern features at the end of the 18th century thanks to the Italian A. Volta, who first received a voltaic column. Subsequently, it was improved by the Russian physicist V.V. Petrov into an electric arc. But only 80 years later N.N. Benardos managed to translate their achievements into carbon arc welding. From this moment on, an unbroken series of inventions of new methods begins.

Nowadays, welding is classified into categories: thermal (welding arc, electric arc, gas flame, electroslag, plasma, electron beam, laser), thermomechanical (spot, butt, relief, diffusion, forge, high-frequency current, friction welding) and mechanical (welding explosion and ultrasound).

Seam quality hybrid laser welding structural steel volumetric honeycomb panels in CO2 with the parallel use of a melting electrode is disproportionately higher than in traditional technologies; The welding speed is also significant - 40...450 m/h with controlled laser radiation from 1.5 to 4.0 kW. An absolute advantage this method can be considered a high-speed welding mode for thin steel sheets, which represents interest for the automotive industry.

D For high-performance welding of large-sized structures made of thick sheet (d> 30mm) hardening steel 30KhGSA was developed twin arc welding method, which is based on the combined use of two high-alloy welding wires of different compositions with a diameter of 5 mm. Welding is performed using ANK-51A ceramic flux. Test results have shown that this method dramatically improves quality welded joint.

Another incentive for the development and implementation of new welding methods is welding joint of composite materials, the basis of which is a metal matrix with fibrous or dispersion strengthening. But the particular difficulty is the welding connection of the latter with steel or titanium. In this regard it is interesting welding-soldering method, in which an intermediate alloy is applied to the surface of the parts, and welding is performed by compression under tension on spot, relief or capacitor machines. For welding thin-sheet composites on an aluminum base with fiber reinforcement or dispersion-strengthened particles of SiC, Al2O3 and C, use argon arc welding with intermediate inserts.

The strength of lap welds is 70% of the strength of the composite, but given the high strength of the composite itself (up to 1500 MPa) in comparison with high-strength aluminum alloys (>700 MPa), it should be noted that the welding-brazing method allows you to create reliable and, importantly, lightweight designs. This makes it indispensable in the aviation and aerospace industries.

Structural cast iron is a fairly difficult material for high-quality and hermetic welding. Modern technologies its welding is based on the use of special thin wire brand PAHCh-11 made of nickel-based alloy, the main achievement of which is low heat generation. This is especially true for thin-walled parts, given the fragility of cast iron as a material. Since the weld seam obtained using this technology is a highly plastic iron-nickel alloy, the destruction of the structure, as a rule, occurs along the cast iron, and not along the seam, which is typical for traditional arc welding. This method makes it possible to produce cast iron structures for critical purposes.

Another metal that is difficult to weld is, of course, titanium, its alpha and alpha+beta alloys. An obvious breakthrough in this area was the development method of magnetically controlled electroslag welding(MES), which makes it possible to connect large-sized parts in the manufacture of aircraft center sections, wing carriages, landing gear traverses, frames and power bulkheads sea vessels. This welding is carried out in slag and metal baths with a current of up to 12000A and a voltage at the electrodes of up to 36 V and ensures high quality welds with a thickness of welded edges of 30-600 mm, thanks to the cleaning of the weld metal from impurities and gas pores. This allows the use of equipment manufactured using the MES method under conditions of enormous dynamic and static loads.

Engineers promise a great future welding programming and, above all, heat input. This method is based on the electron beam principle, successfully used for joining high-strength aluminum alloys. Programming of heat input is carried out in the beam scan circuit, which allows you to control and control penetration, shape, and eliminate the formation of cracks and pores in the weld metal. Obvious advantage is a guaranteed seam when connecting aluminum alloys in critical, highly loaded machines and assemblies, which is especially important in aircraft construction.

The new technologies that are the subject of this review site include innovative orbital argon arc welding method tungsten electrode (OASVE) for complex parts, for example, fixed joints of pipes with a diameter of 20 to 1440 mm. Activating flux is applied to 1 g/m of the weld, which helps solve a number of important technological problems: firstly, welding is carried out with a reduced current, which allows reducing the volume and weight of the weld pool; secondly, a high-quality seam in any spatial position is ensured by regulating the arc pressure on the liquid metal; thirdly, welding can be automated without cutting edges. This method (OASVE) is effective for pipe joints with a thickness of up to 6 mm, above - it is used in combination with other methods and only for forming a root weld.

seem interesting gentle welding technologies in mixtures of protective gases Ar+CO2 and Ar+O2+CO2. The seam is of higher quality compared to welding in CO2, wire consumption is 20% more economical than standard schemes, the transition to the parts being welded becomes smooth, and the spattering of electrode metal is sharply reduced.

Among the new methods that have become widely used in practice is two-component welding method for seamless railway track, based on the cast welding method, which allows solving rather contradictory problems, i.e. ensure the specified ductility of the weld metal with the required wear resistance.

This technology is complex because it requires the use of molten steel, which is poured into the gap of the rail joint. To ensure high viscosity, a low-alloy melt is used, but to impart the required wear resistance, special ceramic linings are used to separate alloying additives from the base metal. After filling the joint with molten steel, the ceramic linings are destroyed and the alloying additives melt at the top of the joint, giving the weld head increased wear resistance.

The idea of harnessing a “short circuit” and harnessing it for welding is not new, but only specialists from Lincoln Electric managed to put it into practice. This root welding method called “Surface Tension Transfer” (STT) and is based on high-speed inverter current sources and microprocessors. During the welding process, both current and voltage are variable but controllable, which significantly expands the capabilities of this method.

Modern science is multifaceted, allows you to use the advantages of nanotechnology, so the future of welding is seen in the improvement of computer control schemes and the introduction of new welding materials.

Thanks to welding machines, welders have made their work much easier, this is mainly due to modern inverters. Such a modern device has made a big leap in working with electric welding of metals.

Of all the power tools, the most popular and frequently used is welding machine. The inverter today works in many industries, it is applicable both for welding window grilles, constructing barbecues, and repairing water pipes, installing a fence in the country and others. With such a welding machine you can not only join metal, but also quickly cut it; it is in demand where an angle grinder is not suitable for cutting. A modern inverter is important for dismantling foundations and old buildings, as well as removing iron and heating threaded connections.

Advantages:

The design is lightweight;
More convenient than other models;
Small sizes;
It is easier to learn how to operate than with other devices;
Meets Europe's EN 61000-3-12 standards, which is important for welding;
You can safely work from a standard outlet, and the wiring in the house will definitely not burn out;
The welding will be beautiful.

Inverters are slightly more expensive than conventional welding machines, however, they have become the most popular in the world and are suitable for various jobs. Such a device operates at high frequencies and has complex electronic filling, thanks to which welding is better controlled. It can work with metals of very different thicknesses, since it has current regulation, the arc will burn more stable than other types of welding, and the amplitude of the pulses will be regular.

How to choose an inverter

It is better to buy modern inverters only ours or European ones, since most of Chinese products of poor quality. It is necessary to take into account the country of the manufacturer, since there will be breakdowns, and there are currently no spare parts for Asian equipment or they are difficult to obtain. Also, be sure to know what to pay attention to, the main thing is the temperature indicator during operation, which should be indicated in the characteristics of the inverter. It is better not to use the device in places where there is a lot of dust; dust easily enters the product through the fan for cooling.

The most important characteristics when choosing a device

1. Total operating time at max. current, this is the ability to work as long as possible at maximum operating values;

The no-load operating voltage, the higher it is, the faster the welding arc is formed, usually it is 40-80 V;
Arc forcing, this function will automatically regulate currents, increasing them when required;
Anti-stick, serves to recognize the moment the working electrode sticks to the metal;
Hot start, this function is required when working with electrodes of terrible workmanship and welding rusty metal;
More great importance has a price indicator, product dimensions;
Before purchasing, find out reviews online, check the quality of workmanship and when the inverter fails.

Before purchasing a welding inverter, you should clarify whether it is required for a home or for construction and major works. Find out right away which model will be the best so that the unit functions as long as possible and does not cost much. Modern welding machines can be clearly divided into three groups; they can be household, special or industrial; each group has its own characteristics. The inverter is the most fashionable welding machine today, although its price is not so low. To buy best models Consider which company has a better quality product, and not just its cost.

Welding inverters, 2019 rating

Best Most Affordable Inverters

Interskol ISA-160/7.1

Interskol ISA-160/7.1 is one of the available welding inverters, ideal for welding. The product has such an important advantage as working with rapidly changing current; even with large network drawdowns of up to 150 V, the arc is retained in the electrode. It works great, it is mobile and convenient, and the kit includes a special strap, so you can easily carry the product on yourself. Even if the air temperature is high, this device will not heat up too much, so it can work for a long time without interruption, which is often required. To work, you may need to purchase special cable mounts and a wire for the inverter.

Characteristics:

Type: manual arc welding MMA;
Operating current: 20-160 A;
Operating output voltage 170-242 V;
Power phase: one;
Output currents: constant for operation;
Power 8.2 kVA;
Duration at max. currents 100%;
Electrode with a diameter of 1.60-4 mm;
Class F insulation;
Anti-stick;
Hot start.

Video review of characteristics:

Advantages:

Flaws:

The button for operating the device is located inconveniently;
Anti-stack is terrible;
The anti-stick of the electrode is weak;
Terminals;
The design is small, although this is not a minus;
No serious disadvantages were noticed on the network.

Result: The inverter device is used to operate in MMA mode with DC current when using standard piece electrodes. The average price for the Internet is from 5223 rubles, although in city stores the cost reaches up to 7000; Interskol products will be the most inexpensive high-quality models.

Resanta SAI-220

Resanta SAI-220 is equipment of a Latvian company, assembled in China. Welding inverter has a duration indicator of 70%, that is, it works up to 7 minutes, when the loads are maximum. This is an excellent performance indicator, as other products can work up to 6 minutes. The weight of this device is only 5 kg, which is less than other designs, it is easy to operate, there are no problems with purchasing spare parts when the product breaks down. This inverter is the best in terms of quality and price, today Resanta has become fashionable in the CIS countries, the product can be easily purchased at a low price, this popular model is one of the best.

Characteristics:

Product type: welding inverter;
Manual arc welding MMA;
Welding current: 10-220 A;
Single phase;
Idling 80 V;
Operating time with max. electric shock;
Electrode diameter up to 5 mm;
Hot start;
Protection degree IP21;
The package includes two cables.

How to use the device - in the video:

Advantages:

Light weight;
Dimensions are minimal;
The seam is high quality;
The arc is caught immediately;
The product works without interruption for a long time;
The electrode ignites perfectly;
The price is reasonable;
Works with 1-5 mm electrodes;
Smooth seams;
Housing protection class IP21.

Flaws:

Power and amperage are overestimated;
The power cable is weak;
The strap fastening is terrible;
Regulator knob;
There is no work case;
The current adjustment is too easy to get confused.

Bottom line: The inverter has all the required functions, the weight is small and there will be no problems with the operation of the device, the price is reasonable, and the quality is excellent. The cost of this popular model is 5,600 rubles, while in a city store the price is up to 6,500 rubles.

The FUBAG IR 200 inverter provides welding with an output voltage of 150 V, which is a remarkable advantage. This quality is required for working in difficult conditions, where there are difficulties with electricity and there is no current stability. This device uses a standard electrode with a diameter of 1-5 mm. Ignition is excellent; a light touch of the weld to the metal is enough to work, and the arc is smooth and stable. The product is compact and light in weight, the only downside is the short cable included in the package; in addition, the fan installed here is too noisy. It is necessary to regularly clean the device from dust, and it is better to do this consistently and often.

Characteristics:

Work at rated welding current;
Welding current 5-200 A;
Operating output voltage 150-240 V;
Operating time at max. current 40% or more;
There are all additional functions;
Fast and furious and anti-stick;
Network 220 V;
Operating current 5-200 A;
MMA current at duty cycle 74 A;
Weight 4.68 kg.

Video review of the welding machine:

Advantages:

Efficiency - 85%;
Combustion is stable;
Welding voltage does not jump;
Electronic drift of metal fine droplets;
The suture is fine-scaled and precise;
Cooling system;
The indicators are conveniently located;
Weight is small;
The cost is reasonable.

Flaws:

The operating duty cycle is small and reaches 40% at maximum current;
The operating current quickly decreases when there is a drop in the network;
The ground cable is too short;
Few cons were found online.

Result: The inverter has all the required functions, provides excellent welding, and you can safely work with the product even with little experience. The average price is 12,000 rubles, the quality of the device is ideal, therefore it is among the inexpensive and best.

The best expensive models

EWM PICO 162 is an expensive welding inverter, the operating currents are low, and wires of 30 m or more will not cause difficulties in work. If other models stop welding on their own due to a voltage drop, this machine welds even in this case with a very high quality of seams.

The device works perfectly, this device is a single-phase professional, it is accessible for use even by those who do not know about MMA and TIG. The inverter is used for welding using a stable current and has adjustable operation, is portable and can be carried on the shoulder with a belt. Manual welding is carried out using special rod electrodes, and is also carried out by TIG Liftarc; there is protection here, so accidental changes in current strength will not lead to difficulties.

Characteristics:

Advantages:

Welding type: MMA and TIG;
Welding currents 10-160 A;
The duration at maximum currents is 35%;
Welding maximum 100 A;
Operating input current 138-265 V;
One phase power supply from the network;
Maintainability.

Flaws:

The price is high;
If the product breaks down, you will have to wait a long time for spare parts;
The terminals here are rather weak;
Few cons were noticed.

Result: An ideal inverter, the arc is smooth and the current is clear, the welding seams will be smooth and of high quality, there are practically no disadvantages other than the price. The cost of an average product is from 39,000 rubles.

Fubag INMIG 200 PLUS

Fubag INMIG 200 PLUS is a universal welding product that implements the capabilities of manual arc, argon and semi-automatic welding. The device operates even at different current values, max. the current is 200 A, and the minimum threshold depends on the type of welding. There are many technical trivialities, as well as a number of additional features that differ in quality.

The inverter is manufactured by a German company and embodies world achievements, taking into account the difficulties in this area. The operating current ranges here are large: 86-256 V, the model is easy to use and has ideal characteristics. The main advantages are the unique workmanship and safety; working with the inverter will be pleasant and comfortable.

Characteristics:

Product type: inverter;
Minimum sizes;
Weight 6.4 kg;
High class insulation;
The level of protection is high;
There is a hot start, arc forced and anti-stick;
Welding current 5-200 A;
Input currents 150-240 V;
The temperature range is large.

Learn more about the device in the video:

Advantages:

Versatility;
Many functions;
Minimum sizes;
Protection;
Large range of welding currents;
Single phase power supply for operation;
The product is excellent;
Welding proceeds without difficulty;
Can cook easily.

Flaws:

The product does not remember the employee’s settings;
Difficulties with wire feeding in idle mode;
The price is not small;
Indication;
The model is one of the best, so there were definitely few cons on the Internet.

Bottom line: Fubag inmig 200 works perfectly, and the build quality is excellent, traditional for Germany, and is the embodiment of the achievements of this century. The average price of an inverter today is 33,000 rubles on the Internet.

AuroraPRO SPEEDWAY 175

SPEEDWAY 175 is the flagship among the line of best semi-automatic inverters from the AuroraPRO company, this is a universal product for welding in a MIG-MAG gas environment with special wire, used for manual and argon arc welding. This modern special semi-automatic machine has synergetic control; operating parameters can be easily adjusted with one handle.

The factory control of the device is adjusted manually; the product will be indispensable in the work of professionals when it is necessary to perform specific complex tasks. The product is used both in everyday life and in production, indispensable for car service. Gives excellent results when welding metals; in semi-automatic mode it masters workpieces with a thickness of 8-10 mm or more.

Characteristics:

Advantages:

Synergetic management;
Manual correction;
High-quality unique metal welding;
Easy polarity change for operation;
Power block based on IGBT;
Diagnostics is easy and simple, works using LEDs;
Automatic protection;
Rich equipment;
Ergonomic beautiful design;
Many new additional features.

Learn more about the advantages of the device in the video:

Flaws:

Argon arc welding is difficult to master;
Price;
There are few cons on the network, there are only good reviews.

Bottom line: The Aurora product is one of the best modern inverters, it has a number of welding methods, the ergonomics of the design are excellent, and the workmanship is ideal. The average price is 34,000 rubles.

Svarog PRO ARC 160 (Z211S)

The modern product Svarog PRO ARC 160 Z211S is the latest product where used high tech, developed back in 2014. The company that created Svarog is famous in the country; their equipment has become very fashionable today. This design has many advantages, such as ease of current adjustment, and thanks to the range it is already possible to work with electrodes up to 3 mm for welding metal 5 mm thick. The design is ergonomic, the model is lightweight and has a digital display, and there is a plastic handle for delivering the product. The Svarog design is practical to use, has extensive functional capabilities, the product is reliable and designed for a wide range, there are many additional functions.

Characteristics:

MMA and TIG welding;
Welding current 10-160 A;
Total input current 187-253 V;
Single phase;
Idling 63 V;
Power 7.20 kVA;
Electrode with a diameter of 1.50-3.20 mm;
Ignition of the arc through touch;
Hot start;
Fast and Furious;
Efficiency 85%.

Review of PRO series inverters:

Advantages:

Flaws:

There is a guarantee here, but its conditions are too special;
Case missing;
No delivery belt;
An extension cord is often required;
The model is one of the best, so there are few cons on the Internet.

Result: The device cooks perfectly, the seam is smooth, and the work proceeds without splashing, the inverter is quite light and compact, the assembly is perfect. The average price is 11,170 rubles.

Inverter manual arc welding

The welding inverter has a maximum operating current of 200 A, which makes it possible to weld and cut metal with all electrodes up to 5 mm exactly. The product has a large range of operation, and its effect is maintained even if the current drops to 150 V, which is important in welding. There is such an important working function as anti-sticking, as well as afterburner and hot start; a welder can work with this design even with little experience.

The only negative is welding at maximum current, when 6 minutes are required every 4 minutes. for cooling. The inverter is ideal for both professional work and home welding. This series has unique transistors, and the module is suitable for complex welding.

Characteristics:

Advantages:

Equipment;
Easy;
Famous brand;
There are all the required functions;
Works without difficulties;
There is protection against dust and condensation;
Works great even with low current;
Even an inexperienced welder can work with this device;
Welds with old UONI electrodes;
Anti-stick.

Flaws:

There is a belt installed, not a handle, although it is also convenient;
Requires regular cleaning.

Bottom line: Welding inverter is of ideal quality, everything is there to improve work modern features, such as anti-stick and others. The average price is 5130 rubles.

Resanta SAI-220A

Inverters with the Resanta brand have become relevant today, as this product is distinguished by quality and price. This model is one of the best and has a high max. current 220 A. Thanks to its unique characteristics, it can weld with electrodes up to 5 mm, welds massive structures, and cuts easily. Such a unit provides high currents and operates for a long time, since the duty cycle coefficient is 70%, which is important for operation. This design had all the special functions, that is, anti-stick, afterburner, hot start.

There is one drawback here - it will be difficult for a welder with little experience to work, unlike other welding structures. The product has a range of operating currents up to 260 V, the inverter requires careful storage, technical General characteristics perfect here. The company is one of the best modern manufacturers in the world, whose equipment is relatively cheap.

Characteristics:

Welding inverter;
Manual arc welding;
Current 10-220 A;
Single phase;
Idling;
Operating time at max. currents 70% exactly;
Electrodes up to 5 mm;
Start hot and anti-stick;
The equipment is excellent;
Minimum size.

Advantages:

Can be used at high welding currents;
Performance will be excellent even with strong and frequent current drops;
The price is affordable;
Power is great;
Lightweight model;
Decent welding;
Value for money;
The body is not made of plastic, so it lasts a very long time;
Entry machine;
Special working cables.

Flaws:

The current regulator has a weak knob;
Case missing;
The scale on the current adjustment knob is terrible;
The material used to make the welding fan is weak;
The ground wire design is poor here;
There are some downsides, although the product is excellent for this price.

Bottom line: The workmanship is excellent and the price is affordable, it can easily weld large structures, and cuts metal perfectly. The average price is 5,759 rubles, the quality of work of this inverter is excellent, there are few comments.

Inverters, their advantages and disadvantages

The welding inverter is a convenient and compact special tool for welding metals. Modern equipment can be used by both qualified specialists with extensive and limited experience. Professionals will say that the best unit is the one that operates with direct current, works with electrodes different types and where there are the required functions, such as hot start, anti-sticking. In addition, the device has the following important element, as greater stability when the current drops. If an employee is interested in the issue of quality, as well as how much the model costs, then it is better for him to take into account the rating of this article.

Main characteristics:

Power. This characteristic is indicated in the document for the design, this is the welding current at which the inverter operates without interruption and overheating. When you buy structures for welding, make a reserve of currents of exactly 50%.
Duration of working general loads. It is a characteristic of product operation in rotary short-term mode.
Current range for power supply. If welding takes place outside the city, then the mains current may have strong deviations from the required value; it is better to use the unit taking into account a jump of 10-20% on average.
Additional qualities. For convenience, ARC FORCE, HOT START and ANTI STICK are required.

Today, inverters have taken the best leadership position among welding equipment, which is due to their advantages: the products are convenient to transport and efficient in operation. Among the main technical advantages, such characteristics as light weight of the equipment and economical indicators of electricity used, which are better than those of transformer conventional welding, are important.

One of the most important crafts for humans. With the help of welding technologies, we manage to create truly amazing things: from the simplest household appliances to space rockets. In this article we will tell you how welding occurs, what types of welding exist and their brief characteristics.

What is welding? What are the basics of welding? Many beginning craftsmen ask these questions. At its core, welding is the process of joining different metals. The compound (also called) is formed at the interatomic level using heat or mechanical deformation.

The theory of metal welding is very extensive and it is impossible to describe all the nuances within one article. Just as it is impossible to describe all methods of welding metals, since this moment about a hundred ways. But we will try to briefly classify welding methods so that beginners do not get confused.

So, at the moment, thermal, thermomechanical and completely mechanical welding of parts made of metal or other materials (for example, glass) is possible. When choosing a welding method, every nuance is taken into account: the thickness of the parts, their composition, working conditions, etc. The metal welding technology depends on this.

Thermal welding is the process of joining parts using only high temperatures. The metal melts and a reliable product is formed. Thermal methods include, for example, and (we'll talk about them later).

Thermo-mechanical welding is the process of joining parts using high temperatures and mechanical influence, such as pressure. Belongs to this type. The part does not heat up as much as in the case of conventional thermal welding, and mechanical load is used to form the seam, rather than melting the metal itself.

Mechanical welding is the process of joining parts without the use of high temperatures and generally thermal energy. The key element here is mechanical action. This type includes ultrasonic welding or friction joining of parts.

There is also a classification of welding methods according to technical characteristics. Using this classification, we can quite briefly describe all available types of welding. They are divided into:

Welding in a protective environment (for protection, inert gas, active gas, vacuum can be used, protection can be combined and consist of several materials at once).
Intermittent and continuous welding.
Welding: manual, mechanized, semi-automatic, automatic, robotic.

If you have never encountered welding before and everything listed above seems confusing and incomprehensible, then don’t worry. Next, we will tell you what the most popular welding methods are used in home and industrial settings.

You will be given a description of the main types of welding and some features that need to be taken into account. By the way, we have devoted separate articles to many types of welding, which you can read by opening the “” section on our website.

Manual arc welding using non-consumable electrodes

The method of different metals using non-consumable electrodes is one of the most popular methods both among home craftsmen and among professionals in their field. Manual arc welding is generally one of the oldest welding methods. Thanks to the large capacity of arc welding, this method has become available to a wide range of welders.

An electrode is a rod that acts as a current conductor. It can be made of various materials and have a special coating.

Arc welding technology is extremely simple: the parts are adjusted to each other, then the electrode is tapped or struck on the surface of the metal, igniting the welding machine. Welding inverters are used as the main equipment.

For welding with an inverter, choose non-consumable electrodes made from, tungsten or. During welding, the electrode heats up to high temperature, melting the metal and forming a weld pool in which the seam is formed. This method is used for welding non-ferrous metals.

Manual arc welding using consumable electrodes

Types of metal fusion welding do not end with the use of non-consumable rods. You can also use consumable electrodes for work. The technology for welding metal using consumable rods is the same as when working with non-consumable materials.

The only difference is in the composition of the electrode itself: melting rods are usually made of low-melting metals. These rods are also suitable for welding at home. Here the seam is formed not only by the molten metal of the part, but also by the molten electrode.

Arc welding using shielding gas

The method of arc welding of different metals using shielding gas is performed using consumable and non-consumable electrodes. The welding technology is the same as with classic manual arc welding. But here, for additional protection of the weld pool, a special shielding gas supplied in cylinders is supplied to the welding zone.

The fact is that the weld pool is easily susceptible to the negative influence of oxygen and under its influence the seam can oxidize and turn out to be of poor quality. Gas helps to avoid these problems. When it is supplied to the welding zone, a dense gas cloud is formed, which prevents oxygen from penetrating into the weld pool.

Automatic and semi-automatic welding using flux or gas

Automatic and using flux or - this is a more advanced method of joining metals. Here, some of the work is mechanized, for example, feeding the electrode into the welding zone. This means that the welder feeds the rod not with his hands, but with the help of a special mechanism.

Automatic welding involves mechanized feeding and further movement of the electrode, while semi-automatic welding implies only mechanized feeding. The welder carries out further movement of the electrode manually.

Here, protecting the weld pool from oxygen is simply mandatory, so gas is used (similar to arc welding using gases) or special. Flux can be liquid, paste or crystalline. Using flux, you can significantly improve the quality of the seam.

Other methods of joining metals

In addition to traditional welding methods, modern industry uses methods that allow joining unique metals. Often such metals have pronounced chemical or refractory properties, which is why conventional welding methods are not suitable for joining them. Of course, such metals are not used in home welding, but they are widely used to create critical parts in large-scale production.

We will talk about the types of fusion welding, when the essence of welding is to supply a large amount of heat to a small welding area. These methods include laser welding and plasma welding.

metal processing is performed using automatic and semi-automatic equipment. This welding process can be completely robotic and does not require human presence. Here the part heats up and then melts under the influence of heat emanating from a laser beam and directed to a specific point.

The heat is concentrated strictly at one point, allowing you to weld very small parts less than one millimeter in size. Also, using a prism, the laser can be split and directed in different directions to weld several parts at once.

Metal cutting is performed using an ionized gas called plasma. The gas is jetted into the welding zone, forming plasma. It works in conjunction with a tungsten electrode and the gas is heated by an electric arc.

The ionized gas itself has the property of a current conductor, therefore in the case of plasma welding it is the plasma that is key element in the work process. Plasma also actively protects the weld pool from the negative effects of oxygen. This welding method is used when working with metals up to 9 millimeters thick.

Welding process

It is not enough to know welding methods; you also need to understand what documents are required for welding and what stages the welding process consists of. Of course, this is only true for professional welders performing work in a workshop or production environment. You don’t need this if you are going to weld a fence at your dacha, but additional knowledge won’t hurt either.

So here's ours short description welding process:

Drawing development
Drawing up a technological map
Preparation of the welder's workplace and metal preparation
Direct welding
Metal cleaning
Quality control

The technical process itself is a complete description of the welding stages. The technical process is developed after the drawings of the future metal structure are ready. The drawing is made based on (GOST, for example), while the quality of the future design and reasonable savings are put at the forefront.

The technological process of welding is drawn up on forms specially designed for this purpose. The standard form for describing a technical process is called a “technological map”. IN technological map and describes all stages of production. If the production is serial or large-scale, then the presentation can be quite detailed, with a description of every nuance.

The flow chart includes the type of metal from which the parts are made, the metal welding methods used to connect these parts, the welding or other equipment used for these purposes, the types of filler materials, electrodes, gases or fluxes used in the work. The sequence of formation of seams, their sizes and other characteristics are also indicated.

Also in the technological map they indicate their diameter, their feed speed, welding speed, the number of layers at the seam, the recommended ones (polarity parameter and welding current value), and indicate the brand of flux. Before welding, the parts are carefully prepared, cleaning them from corrosion, dirt and oil. The metal surface is degreased using a solvent. If a part has significant visible defects (for example, cracks), then it is not allowed for welding.

After welding, the weld seams will be inspected. We have devoted this topic, but here we will briefly talk about the main control methods. First of all, visual inspection is used, when the welder himself can determine the presence of defects in the welding joint. Carried out by specialists additional control using special devices (this can be magnetic control, radiation or ultrasonic).

Of course, not all defects are considered bad. For each welding job, a list is compiled with defects that are acceptable and will not greatly affect the quality finished product. The controller can be a welder or a separate specialist. His name must be indicated in documents; he is responsible person at the control stage.

Instead of a conclusion

In this article we covered the most basic things. Of course, we will not be able to list and describe all types of welding work in this one article, but on our website you can find materials where we tell everything about welding and explain the basics of welding various metals.

Chapter 1
A little history
1.1. Invention of electric welding
1.2. Development of electric welding in the 20th century

Chapter 2
Arc Welding Basics
2.1. Electric arc
Physical entity
Volt-ampere characteristics
Manual welding on DC
Semi-automatic DC welding
AC Welding
2.2. Welding process
Non-consumable electrode welding
Consumable electrode welding
Metal transfer
2.3. Main characteristics of welding arc power sources

Chapter 3
Simulator LTspice IV
3.1. Simulation of power supply operation
Simulation capabilities
Electronic circuit simulation programs
Features of the LTspice IV program
3.2. How LTspice IV works
Starting the program
Drawing a circuit of a simple multivibrator on a PC
Defining numerical parameters and types of circuit components
Simulation of multivibrator operation
3.3. Simulation of a simple power supply
Low Voltage DC Power Supply
Test node

Chapter 4
AC Welding Power Sources
4.1. Features of terminology
4.2. Basic requirements for a welding source
4.3. AC Electric Arc Model
4.4. Welding source with ballast rheostat (active resistance)
4.5. Welding source with linear choke (inductive reactance)
4.6. Welding transformer
4.7. How to calculate leakage inductance?
Leakage inductance of a transformer with cylindrical windings
Leakage inductance of a transformer with windings spaced apart
Leakage inductance of a transformer with disc windings
4.8. Requirements for a welding transformer
4.9. Classic AC power source
Calculation of a welding transformer with developed magnetic leakage

Design of AC Welding Power Source
4.10. Budyonny welding source
Ways to reduce the amount of current consumed
Structural electrical diagram of Budyonny's welding source
General principles for designing a welding source
Budyonny welding source model
Overcoming the design limitations of the Budenny welding source
Determining the overall power of a transformer
Core selection
Winding calculation
Magnetic shunt calculation
Leakage inductance calculation
Simulation of calculation results
Welding source design with alternative transformer design
4.11. Welding source with resonant capacitor
Calculation of a welding source with a resonant capacitor
Calculation of a welding transformer
Checking the placement of windings in the welding transformer window
Leakage inductance calculation
Welding source simulation
4.12. AC Arc Stabilizers
Features of AC welding arc
Operating principle of the arc stabilizer
First version of arc stabilizer
Details
Second version of the arc stabilizer
Details

Chapter 5
Welding source for semi-automatic welding
5.1. Basics of semi-automatic welding
5.2. Calculations of circuit elements
Determination of parameters and calculation of the source power transformer
Model setup procedure
Calculation of ohmic resistance of windings
Calculation of inductance and resistance of transformer windings
Calculation of overall dimensions of the transformer
Completing the transformer calculation
Calculation of the feed current source choke
5.3. Description of the design of a simple source for semi-automatic welding
Diagram of a simple source for semi-automatic welding
Parts for semi-automatic welding machine
Design and manufacture of welding transformer
Throttle design
Source connection

Chapter 6
Welding source for semi-automatic welding with thyristor regulator
6.1. Adjusting the welding current
6.2. Ensuring continuity of welding current
6.3. Calculation of a welding transformer
6.4. Control block
6.5. Description of the design of a welding source with a thyristor regulator
Electrical circuit diagram
Details
Welding transformer design
Throttle design
Source connection

Chapter 7
Electronic welding current regulator
7.1. Multi-station welding
Multi-station welding with connection
through an individual ballast rheostat
Electronic analogue of the ballast rheostat ERST
7.2. Calculation of the main components of ERST
7.3. Description of ERST
Basic protection options
Purpose of the main components of ERST
Operating principle
Operating principle and configuration of block A1
Details
Operating principle and configuration of block A2
The principle of operation of the stabilizer
Details
Settings
Formation external characteristics ERST
Operating principle of the ERST control unit
Operating principle of the key transistor driver unit
Final setup of ERST

Chapter 8
Inverter welding source
8.1. A little history
8.2. General description of the source
8.3. Recommendations for self-made ISI
8.4. Calculation of a forward converter transformer
8.5. Transformer manufacturing
8.6. Calculation of power losses on converter transistors
8.7. Calculation of the welding current filter choke
8.8. Simulation of converter operation
8.9. Current transformer calculation
8.10. Calculation of galvanic isolation transformer
8.11. PWM controller TDA4718A
8.12. Schematic diagram control unit for inverter welding source “RytmArc”
8.13. Formation of the load characteristic of the source
8.14. Methodology for setting up the control unit
8.15. Remote control panel (modulator)
8.16. Using an alternative PWM controller
8.17. Transformer driver
8.18. Damping chain that does not dissipate energy

Chapter 9
Inverter welding source COLT-1300
9.1. general description
What is this chapter about?
Purpose
Main characteristics
9.2. Power part
Winding unit data
9.3. Control block
Functional diagram
Operating principle
Schematic diagram
Implementation of the Anty-Stick function
Implementation of the Arc Force function
9.4. Settings

Chapter 10
Helpful information
10.1. How to test unknown hardware?
10.2. How to calculate a transformer?
10.3. How to calculate a choke with a core?
Calculation features
Example of calculation of throttle No. 1
Example of calculation of throttle No. 2
Example of calculation of throttle No. 3
10.4. Calculation of chokes with powder core
Advantages of Powder Cores
Inductor Design Software address and installation
Automatic calculation functions of Inductor Design Software
Additional Features of Inductor Design Software
Inductor Design Software menu bar
Example of choke calculation in Inductor Design Software
Magnetics Inductor Design Using Powder Cores
Example of inductor calculation in Magnetics Inductor Design Using Powder Cores
10.5. How to calculate a radiator?
10.6. Hysteresis model of nonlinear inductance of the LTspice simulator
Brief description of the hysteresis model of nonlinear inductance
Selection of parameters of the hysteresis model of nonlinear inductance
10.7. Modeling complex electromagnetic components using LTspice
Modeling problem
The principle of similarity of electric and magnetic circuits
Duality of physical circuits
Model of an unbranched magnetic circuit
Simulation of a branched magnetic circuit
Simulation of a complex magnetic circuit
Adaptation of the model for magnetic circuits operating with partial or full magnetization
Creating an Integrated Magnetic Component Model
10.8. How to make welding electrodes?

1. Physical Basics welding

Welding is technological process obtaining a permanent connection of materials due to the formation of atomic bonds. The process of creating a welded joint occurs in two stages.

At the first stage, it is necessary to bring the surfaces of the materials being welded closer to the distance of action of interatomic interaction forces (about 3 A). Ordinary metals at room temperature do not bond when compressed even with significant forces. The joining of materials is hampered by their hardness; when they come together, actual contact occurs only at a few points, no matter how carefully they are processed. The joining process is strongly influenced by surface contamination - oxides, fatty films, etc., as well as layers of absorbed impurity atoms. Due to these reasons, it is impossible to fulfill the condition of good contact under normal conditions. Therefore, the formation of physical contact between the joined edges over the entire surface is achieved either due to the melting of the material or as a result of plastic deformations resulting from the applied pressure. At the second stage it is carried out electronic interaction between the atoms of the connected surfaces. As a result, the interface between the parts disappears and either atomic metal bonds are formed (metals are welded) or covalent or ionic bonds are formed (when welding dielectrics or semiconductors). Based on the physical essence of the process of formation of a welded joint, three classes of welding are distinguished: fusion welding, pressure welding and thermomechanical welding (Fig. 1.25).

Rice. 1.25.

For fusion welding These are types of welding carried out by fusion without applied pressure. The main sources of heat in fusion welding are the welding arc, gas flame, beam energy sources and “Joule heat”. In this case, the melts of the metals being joined are combined into a common weld pool, and upon cooling, the melt crystallizes into a cast weld.

For thermomechanical welding used thermal energy and pressure. The joining of the connected parts into a monolithic whole is carried out through the application of mechanical loads, and heating of the workpieces ensures the required plasticity of the material.

For pressure welding refers to operations carried out with the application of mechanical energy in the form of pressure. As a result, the metal becomes deformed and begins to flow like a liquid. The metal moves along the interface, taking the contaminated layer with it. Thus, fresh layers of material come into direct contact, which enter into chemical interaction.

2. Main types of welding

Manual electric arc welding. Electric arc welding is currently the most important type of metal welding. The heat source in this case is an electric arc between two electrodes, one of which is the workpiece being welded. An electric arc is a powerful discharge in a gaseous environment.

The arc ignition process consists of three stages: short circuit of the electrode to the workpiece, withdrawal of the electrode by 3-5 mm and the occurrence of a stable arc discharge. A short circuit is performed in order to heat the electrode (cathode) to the temperature of intense exo-emission of electrons.

At the second stage, electrons emitted by the electrode are accelerated in the electric field and cause ionization of the cathode-anode gas gap, which leads to the occurrence of a stable arc discharge. An electric arc is a concentrated source of heat with temperatures up to 6000 °C. Welding currents reach 2-3 kA at arc voltage (10-50) V. Covered electrode arc welding is most often used. This is manual arc welding with an electrode coated with an appropriate composition that has the following purpose:

1. Gas and slag protection of the melt from the surrounding atmosphere.

2. Alloying the weld material with the necessary elements.

The composition of the coatings includes substances: slag-forming substances - to protect the melt with a shell (oxides, feldspars, marble, chalk); forming gases CO2, CH4, CCl4; alloying - to improve the properties of the weld (ferrovanadium, ferrochrome, ferrotitanium, aluminum, etc.); deoxidizers - to eliminate iron oxides (Ti, Mn, Al, Si, etc.) Example of a deoxidation reaction: Fe2O3+Al = Al2O3+Fe.

Rice. 1.26. : 1 - parts to be welded, 2 - weld seam, 3 - flux crust, 4 - gas protection, 5 - electrode, 6 - electrode coating, 7 - weld pool

Rice. Figure 1.26 illustrates coated electrode welding. According to the above diagram, a welding arc is ignited between the parts (1) and the electrode (6). When melted, the coating (5) protects the weld from oxidation and improves its properties by alloying. Under the influence of the arc temperature, the electrode and the workpiece material melt, forming a weld pool (7), which subsequently crystallizes into a weld seam (2), on top of which the latter is covered with a flux crust (3), designed to protect the seam. To obtain a high-quality seam, the welder places the electrode at an angle of (15-20)0 and moves it downward as it melts to maintain a constant arc length (3-5) mm and along the axis of the seam to fill the seam groove with metal. In this case, the end of the electrode usually makes transverse oscillatory movements to obtain rollers of the required width.

Automatic submerged arc welding.

Automatic welding with a consumable electrode under a layer of flux is widely used. The flux is poured onto the product in a layer (50-60) mm thick, as a result of which the arc burns not in the air, but in a gas bubble located under the flux melted during welding and isolated from direct contact with air. This is enough to eliminate splashing of liquid metal and disruption of the shape of the seam, even at high currents. When welding under a layer of flux, a current of up to (1000-1200) A is usually used, which is impossible with an open arc. Thus, in submerged arc welding, the welding current can be increased by 4-8 times compared to open arc welding, while maintaining good quality welding at high performance. In submerged arc welding, the weld metal is formed by melting the base metal (about 2/3) and only about 1/3 by the electrode metal. The arc under a layer of flux is more stable than with an open arc. Welding under a layer of flux is carried out with bare electrode wire, which is fed from a reel into the arc burning zone by the welding head of an automatic machine, which is moved along the seam. Ahead of the head, granular flux enters the weld through the pipe, which, melting during the welding process, evenly covers the seam, forming a hard slag crust.

Thus, automatic welding under a layer of flux differs from manual welding in the following indicators: stable quality of the seam, productivity is (4-8) times higher than with manual welding, the thickness of the flux layer is (50-60) mm, the current strength is (1000-1200) A, the optimal arc length is maintained automatically, the weld consists of 2/3 of the base metal and 1/3 of the arc burns in a gas bubble, which ensures excellent welding quality.

Electroslag welding.

Electroslag welding is a fundamentally new type of metal joining process, invented and developed at the Electric Welding Institute named after. Paton. The parts to be welded are covered with slag, heated to a temperature exceeding the melting point of the base metal and electrode wire.

At the first stage, the process proceeds in the same way as with submerged arc welding. After the formation of a bath of liquid slag, the burning of the arc stops and the melting of the edges of the product occurs due to the heat released when current passes through the melt. Electroslag welding allows you to weld large thicknesses of metal in one pass, provides greater productivity, and high quality welds.

Rice. 1.27. :

1 - parts to be welded, 2 - weld seam, 3 - molten slag, 4 - sliders, 5 - electrode

The electroslag welding diagram is shown in Fig. 1.27. Welding is carried out with a vertical arrangement of parts (1), the edges of which are also vertical or have an inclination of no more than 30 o to the vertical. A small gap is installed between the parts to be welded, into which slag powder is poured. At the initial moment, an arc is ignited between the electrode (5) and the metal strip installed below. The arc melts the flux, which fills the space between the edges of the parts being welded and the water-cooled copper forming slides (4). Thus, a slag bath (3) appears from the molten flux, after which the arc is shunted by the molten slag and goes out. At this point, electric arc melting turns into an electroslag process. When current passes through molten slag, Joule heat is released. The slag bath is heated to temperatures (1600-1700) 0C, exceeding the melting point of the base and electrode metals. The slag melts the edges of the parts being welded and the electrode immersed in the slag bath. The molten metal flows to the bottom of the slag pool, where it forms a weld pool. The slag pool reliably protects the weld pool from the surrounding atmosphere. After removing the heat source, the metal of the weld pool crystallizes. The formed seam is covered with a slag crust, the thickness of which reaches 2 mm.

A number of processes contribute to improving the quality of the weld in electroslag welding. In conclusion, we note the main advantages of electroslag welding.

Gas bubbles, slag and light impurities are removed from the welding zone due to the vertical position of the welding device.

High weld density.

The weld seam is less susceptible to cracking.

The productivity of electroslag welding for large material thicknesses is almost 20 times higher than that of automatic submerged arc welding.

It is possible to obtain seams of complex configuration.

This type of welding is most effective when connecting large parts such as ship hulls, bridges, rolling mills etc.

Electron beam welding.

The heat source is a powerful beam of electrons with an energy of tens of kiloelectronvolts. Fast electrons, penetrating into the workpiece, transfer their energy to the electrons and atoms of the substance, causing intense heating of the welded material to the melting point. The welding process is carried out in a vacuum, which ensures high quality seams. Due to the fact that the electron beam can be focused to very small sizes (less than a micron in diameter), this technology is exclusive to welding micro parts.

Plasma welding.

In plasma welding, the source of energy for heating the material is plasma - ionized gas. The presence of electrically charged particles makes plasma sensitive to the effects of electric fields. In an electric field, electrons and ions are accelerated, that is, they increase their energy, and this is equivalent to heating the plasma up to 20-30 thousand degrees. Arc and high-frequency plasma torches are used for welding (see Fig. 1.17 - 1.19). For welding metals, as a rule, direct plasma torches are used, and for welding dielectrics and semiconductors, indirect plasma torches are used. High-frequency plasma torches (Fig. 1.19) are also used for welding. In the plasmatron chamber, the gas is heated by eddy currents created by high-frequency currents of the inductor. There are no electrodes, so the plasma is highly pure. A torch of such plasma can be effectively used in welding production.

Diffusion welding.

The method is based on the mutual diffusion of atoms in the surface layers of contacting materials under high vacuum. The high diffusivity of atoms is ensured by heating the material to a temperature close to the melting point. The absence of air in the chamber prevents the formation of an oxide film that could impede diffusion. Reliable contact between the welded surfaces is ensured machining to a high level of cleanliness. The compressive force required to increase the actual contact area is (10-20) MPa.

The diffusion welding technology is as follows. The workpieces to be welded are placed in a vacuum chamber and compressed with slight force. Then the workpieces are heated with current and kept for some time at a given temperature. Diffusion welding is used to join poorly compatible materials: steel with cast iron, titanium, tungsten, ceramics, etc.

Contact electric welding.

In electric resistance welding, or resistance welding, heating is achieved by passing an electric current from a sufficient needle through the weld site. Parts heated by electric current to a melting or plastic state are mechanically compressed or upset, which ensures the chemical interaction of metal atoms. Thus, resistance welding belongs to the group of pressure welding. Resistance welding is one of the high-performance welding methods; it can easily be automated and mechanized, as a result of which it is widely used in mechanical engineering and construction. Based on the shape of the connections being made, there are three types of resistance welding: butt, roller (suture) and spot welding.

Butt contact welding.

This is a type of contact welding in which the parts to be welded are connected along the surface of the butt ends. The parts are clamped in sponge electrodes, then pressed against each other by the surfaces to be joined and the welding current is passed through. Butt welding is used to connect wire, rods, pipes, strips, rails, chains and other parts over the entire area of their ends. There are two methods of butt welding:

Resistance: plastic deformation occurs at the joint and the joint is formed without melting the metal (the temperature of the joints is 0.8-0.9 from the melting temperature).

By melting: the parts come into contact at the beginning at separate small contact points through which a high-density current passes, causing the parts to melt. As a result of melting, a layer of liquid metal is formed at the end, which, during sedimentation, along with contaminants and oxide films, is squeezed out of the joint.

Table 1.4

Parameters of Butt Welding Machines

Machine type	W,(kVA)	U slave,(B)	Welding per hour.	F,(kN)

Column designations: W - machine power, Uwork - operating voltage, productivity, F - compression force of welded parts, S - area of the welded surface.

Heating temperature and compressive pressure during butt welding are interrelated. As follows from Fig. 1.28, the force F decreases significantly with increasing heating temperature of the workpieces during welding.

Seam contact welding.

A type of resistance welding in which the elements are overlapped with rotating disk electrodes in the form of a continuous or intermittent seam. In seam welding, the formation of a continuous joint (seam) occurs by sequentially overlapping points one after another; to obtain a hermetic seam, the points overlap each other by at least half their diameter. In practice, seam welding is used:

Continuous;

Intermittent with continuous rotation rollers;

Intermittent with periodic rotation.

Rice. 1.28.

Seam welding is used in mass production in the manufacture of various vessels. It is carried out using alternating current with a force of (2000-5000) A. The diameter of the rollers is (40-350) mm, the compression force of the welded parts reaches 0.6 tons, the welding speed is (0.53.5) m/min.

Spot resistance welding.

In spot welding, the parts to be joined are usually placed between two electrodes. Under the action of a pressure mechanism, the electrodes tightly compress the parts to be welded, after which the current is turned on. Due to the passage of current, the parts being welded quickly heat up to the welding temperature. The diameter of the molten core determines the diameter of the weld spot, usually equal to the diameter contact surface electrode.

Depending on the location of the electrodes in relation to the parts being welded, spot welding can be double-sided or single-sided.

When spot welding parts of different thicknesses, the resulting asymmetrical core is shifted towards the thicker part and, if there is a large difference in thickness, does not capture the thin part. Therefore, various technological methods are used to ensure the displacement of the core to the mating surfaces, increase the heating of a thin sheet due to overlays, create a relief on a thin sheet, use more massive electrodes on the side of a thick part, etc.

A type of spot welding is relief welding, when the initial contact of parts occurs along previously prepared protrusions (reliefs). The current, passing through the place where all the reliefs touch the lower part, heats them and partially melts them. Under pressure, the reliefs are deformed, and the upper part becomes flat. This method is used for welding small parts. In table 1.5 shows the characteristics of machines for spot welding.

Table 1.5

Characteristics of Spot Welding Machines

Machine type	W,(kVA)	U slave,(B)	D,(mm)	F,(kN)	Welding per hour

Column designations: W - machine power, irab - operating voltage, D - electrode diameter, F - compression force of welded parts, welds per hour - productivity.

Spot capacitor welding.

One of the common types of resistance welding is capacitor welding or welding with stored energy stored in electric capacitors. Energy in capacitors is accumulated when they are charged from a constant voltage source (generator or rectifier), and then, during the discharge process, is converted into heat used for welding. The energy stored in capacitors can be regulated by changing the capacitance of the capacitor (C) and the charging voltage (U).

There are two types of capacitor welding:

Transformerless (capacitors are discharged directly onto the parts being welded);

Transformer (the capacitor is discharged onto the primary winding of the welding transformer, in the secondary circuit of which there are pre-compressed parts to be welded).

The schematic diagram of capacitor welding is shown in Fig. 1.29.

Rice. 1.29. : Tr - step-up transformer, B - rectifier, C - capacitor with a capacity of 500 μF, Rk - resistance of the parts being welded, K - key switch

In switch position 1, the capacitor is charged to voltage U0. When the switch is moved to position. 2, the capacitor is discharged through the contact resistance of the parts being welded. This creates a powerful current pulse.

The voltage from the capacitor is supplied to the workpiece through point contacts with an area of ~ 2 mm. The resulting current pulse, in accordance with the Joule-Lenz law, heats the contact area to operating temperature welding To ensure reliable pressing of the surfaces being welded, a mechanical stress about 100 MPa.

The main application of capacitor welding is to join metals and alloys of small thicknesses. The advantage of capacitor welding is its low power consumption.

To determine the efficiency of welding, we estimate the maximum temperature in the area of contact of the parts being welded (Tmax).

Due to the fact that the duration of the discharge current pulse does not exceed 10 -6 s, the calculation was carried out in the adiabatic approximation, that is, neglecting heat removal from the region of current flow.

The principle of contact heating of parts is shown in Fig. 1.30.

Rice. 1.30.: 1 - parts to be welded with thickness d = 5*10 -2 cm, 2 - electrodes with area S = 3*10 -2 cm, C - capacitor with a capacity of 500 μF, Rk - contact resistance

The advantage of capacitor welding is its low power consumption, which is (0.1-0.2) kVA. The duration of the welding current pulse is thousandths of a second. The range of welded metal thicknesses is from 0.005 mm to 1 mm. Capacitor welding allows you to successfully join metals of small thicknesses, small parts and micro parts that are poorly visible to the naked eye and require application during assembly. optical instruments. This progressive welding method has found application in the production of electrical measuring instruments and aircraft instruments, watch mechanisms, cameras, etc.

Cold welding.

The connection of workpieces during cold welding is carried out by plastic deformation at room and even at negative temperatures. The formation of a permanent connection occurs as a result of the emergence of a metallic bond when the contacting surfaces approach each other to a distance at which the action of interatomic forces is possible, and as a result of a large compression force, the oxide film breaks and clean metal surfaces are formed.

The surfaces to be welded must be thoroughly cleaned of adsorbed impurities and fatty films. Cold welding can be used to make spot, seam and butt joints.

In Fig. Figure 1.31 shows the cold spot welding process. Sheets of metal (1) with a thoroughly cleaned surface at the welding site are placed between punches (2) having projections (3). The punch is compressed with some force P, the projections (3) are pressed into the metal to their entire height until the supporting surfaces (4) of the punches rest against the outer surface of the workpieces being welded.

Rice. 1.31.

Cold welding is used to make overlapped and butt joints of wires, busbars, and pipes. The pressure is selected depending on the composition and thickness of the material being welded; on average it is (1-3) GPa.

Induction welding.

Using this method, longitudinal seams of pipes are mainly welded during their manufacture on continuous mills and welded hard alloys on steel bases in the manufacture of cutters, drill bits and other tools.

With this method, the metal is heated by passing high-frequency currents through it and is compressed. Induction welding is convenient because it is non-contact; high-frequency currents are localized near the surface of the heated workpiece. Such installations work as follows. The high-frequency generator current is supplied to the inductor, which induces eddy currents in the workpiece, and the pipe heats up. Mills of this type are successfully used for the production of pipes with a diameter of (12-60) mm at speeds of up to 50 m/min. The current is supplied from tube generators with a power of up to 260 kW at a frequency of 440 kHz and 880 kHz. Pipes of large diameters (325 mm and 426 mm) with a wall thickness of (7-8) mm, with a welding speed of up to (30-40) m/min are also manufactured.

Features of welding various metals and alloys

Weldability is understood as the ability of metals and alloys to form a compound with the same properties as the metals being welded, and not to have defects in the form of cracks, pores, cavities and non-metallic inclusions.

When welding, residual welding stresses almost always occur (usually tensile stresses in the weld and compressive stresses in the base metal). To stabilize the properties of the connection, it is necessary to reduce these voltages.

Welding carbon steels.

Electric arc welding of carbon and alloy steels is carried out with electrode materials that provide the necessary mechanical properties. The main difficulty in this case lies in the hardening of the heat-affected zone and the formation of cracks. To prevent the formation of cracks, it is recommended:

1) heat products to temperatures (100-300) 0C;

2) replace single-layer welding with multi-layer welding;

3) use coated electrodes (welding is carried out using direct current of reverse polarity);

4) temper the product after welding to a temperature of 300 0C.

Welding of high chromium steels.

High-chromium steels containing (12-28)% Cr have stainless and heat-resistant properties. Depending on the content of chromium and carbon, high-chromium steels are divided according to their structure into ferritic, ferritic-martensitic and martensitic.

Difficulties in welding ferritic steels are associated with the fact that during the cooling process in the region of 1000 0C, chromium carbide may precipitate at the grain boundaries. This reduces the corrosion resistance of steel. To prevent these phenomena it is necessary:

1) use reduced current values in order to ensure high cooling rates during welding;

2) introduce strong carbide formers (Ti, Cr, Zr, V) into the steel;

3) anneal after welding at 900 0C to level the chromium content in the grains and at the boundaries.

Ferrite-martensitic and martensitic steels are recommended to be welded with heating to (200-300) 0C.

Welding cast iron.

Welding of cast iron is carried out with heating to (400-600) 0C. Welding is carried out with cast iron electrodes with a diameter of (8-25) mm. Good results are obtained by diffusion welding of cast iron to cast iron and cast iron to steel.

Welding of copper and its alloys.

The weldability of copper is negatively affected by impurities of oxygen, hydrogen, and lead. Most common gas welding. Arc welding with carbon and metal electrodes is promising.

Aluminum welding.

Prevents welding oxide film Al2O3. Only the use of fluxes (NaCl, RCl, LiF) makes it possible to dissolve aluminum oxide and ensure normal formation of the weld. Aluminum is welded well by diffusion welding.