What is direct plasma welding

Plasma welding - technology, equipment, principle of operation

With the increasing accuracy of parts manufactured in industry and private enterprises, there is a need for new technologies for welding and cutting metals. One such innovation is plasma welding. Despite the fact that the method appeared relatively recently, it has already managed to gain and occupy its niche in industry and in the hands of individuals. Let's look at what plasma arc welding technology is?

Working principle of plasma welding

In many ways, plasma welding machines resemble the operating principle of argon-arc welding machines and have a similar torch design, which in our case is called a plasma torch. The process of plasma formation occurs precisely in the burner (more on this later).

Plasma is one of the states of gas that is formed when it is passed through an arc. At this moment, complex chemical and physical processes occur, and the gas acquires special properties. In this case, we are interested in the fact that the temperature of the plasma escaping from the nozzle can reach up to 30 thousand degrees, and this is 6 times more than the hottest arc.

Thus, the essence of plasma welding is the ionization of gas passing under pressure.

Under such conditions, metal is cut, which melts instantly, and part of it simply evaporates. For welding, more gentle modes are used, as well as arc control technology. Plasma cutters are considered one of the most accurate and efficient methods for cutting various metals.

Scheme of plasma welding with an open and closed plasma jet

To understand the principle of operation of plasma welding, you need to go directly to the device. Plasma welding itself is a small installation, weighing 5–9 kg, inside which there is a step-down transformer, a rectifier and a set of control circuits.

An air compressor is connected to it (if compressed air is supplied to the nozzle) or special cylinders with plasma-forming gas and inert gas. Nitrogen, oxygen, argon, and air are used as gas to create plasma. At the output of the device we have a torch with a set of gases (for welding) or one type of gas for cutting, as well as a positive terminal (for direct welding).

Since the operating temperature of this component is very high, there is liquid cooling inside the torch.

Note! Not only the quality of the weld, but also the durability of the electrode and other components will depend on the cooling efficiency of the torch. The welder must carefully monitor not only the progress of welding, but also the flow of water.

Further description of the technology leads us to its two varieties:

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Direct plasma welding

The first and most common plasma welding method involves direct action of the arc on the part. Welding occurs with a direct arc formed between the part and the electrode, but the plasma ignition process itself has a two-stage scheme.

Direct plasma welding

In the first stage, the inner rod of the plasma torch (image below) has a negative polarity, while the near wall of the nozzle receives a positive charge due to the closed switch (0). Arcs (marked in red) are formed inside the nozzle, which ionize the passing gas (2) and turn it into plasma.

The next stage is welding itself; for this, a positive terminal is attached to the part and a working plasma torch is brought in.

At this moment, the product has better conductivity, so the arcs are concentrated at the end of the tungsten electrode, the switch opens the internal circuit of the plasmatron and under the influence of pressure, as well as the natural expansion of the gas when converted into plasma, a directed burst of energy occurs.

At the same time, the plasma arc has high stability, and minimal spatter and insulation of the welded area is ensured by the inert gas passing through channel (1). The gas not only protects the plasma arc, but also insulates the weld pool.

Indirect plasma welding

The mechanism of plasma formation in this case is similar to the previous method. The main difference is that the direction of the plasma flow is controlled not by the direction of the electrical flow, but by the gas pressure created by the system and the internal pressure of the nozzle. What helps here is the fact that when it transitions to the plasma state, the gas begins to increase in volume up to 50 times, so with increased pressure it naturally tends to escape from the nozzle.

Indirect plasma

Both described methods take place in the modern world, but the direct method has more advantages. This way, it guarantees more stable operation at low currents, allows less consumption of expensive gas and has a noticeably lower degree of spattering. Metal cutting occurs in a similar way, only without the use of inert gas (1).

We recommend! Welding of reinforcement joints using the bath method

Plasma welding equipment

Modern plasma welding machines are compact devices comparable in size to argon-arc, inverter or transformer machines. The simplest models have a compact size and a minimum of settings for ease of use. With their help you can weld and cut metal.

Equipment assembly diagram for manual plasma cutting

As the price increases, the functionality of the devices increases, so on sale you can find equipment with a soldering function. Professional-level devices allow for bluing, thermal oxidation, powder coating and hardening operations.

Equipment pricing policy can be divided into several categories. Starter devices include devices with a capacity of 8 - 12 A. Their cost is in the range of 25 - 40 thousand rubles, these are the cheapest devices that can be purchased and they are already several times more expensive than inverters and semi-automatic devices. Some devices support the function of microplasma cutting, in other words, operation at low currents from 0.1A.

In the middle price category there are welding machines with a power of 25 - 150A. They have advanced settings, allow you to connect several types of gases and often have advanced functionality. The cost of such devices is from 40 to 150 thousand rubles.

The most expensive of the non-automated ones are welding with a power above 150 A. Their design includes almost all the possible functionality of plasma technology, but all work is performed by a welder. The price starts at 100 thousand and can exceed 1 million rubles.

Application area

Thanks to working at temperatures reaching up to 30,000 degrees, the technology allows you to work with many types of metals: stainless steel, carbon steel, cast iron, copper, brass, bronze, titanium, aluminum and others. Together with the high precision of work, this leads to the following areas of use of the technology:

1. food industry;
2. energy sector;
3. chemical production;
4. jewelry making;
5. mechanical engineering;
6. instrument making;
7. medical equipment;
8. production of high precision parts.

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Advantages and disadvantages of the method

As you can see, the use of plasma has its advantages, but it is not without its disadvantages. Below, we have highlighted the main positive and negative aspects.

pros

1. High quality and speed of work.
2. Control of penetration depth.
3. Availability of technology to individuals.
4. Work safety.
5. There is no waste left during the work process.
6. High cutting accuracy allows no additional processing of edges.

The main positive aspect of technology is its irreplaceability. Most of the work can be done by other methods, but when it comes to the best speed, quality and convenience of welding, we inevitably come to the plasma method.

Flaws

1. Expensive devices and high cost of work.
2. High requirements for welder qualifications.
3. The need for high-quality cooling due to high temperature losses.

The main disadvantage of the technology is its complexity. It takes time and money to train a good specialist, otherwise the method will not bring the desired results. This is due to the fact that during the work it is important not only to control the welding process, but also to closely monitor cooling, gas flow and many other parameters.

Conclusion

Now you know how plasma welding works. If the cost of the equipment does not scare you, then the technology can be quite successfully used to perform high-precision work at home or in a small enterprise.

For creating hermetic seams and making high-precision joints, such devices will be indispensable, especially if we are talking about an industrial scale.

This is where automated plasma complexes come into play, minimizing the human factor and operational errors.

Source: https://svarkagid.ru/tehnologii/plazmennaya-pryamogo-i-kosvennogo-dejstviya.html

Plasma jet welding

One of the relatively new types of connections of metals and alloys is plasma welding. This type, similar to the version of argon arc welding with a non-consumable electrode, allows you to obtain a better result much faster. Plasma welding technology involves the use of an electric arc burning in a fully or partially ionized gas environment. The gas is called plasma-forming.

Features and characteristics of the process

The main feature of the plasma method is the very high temperature in the welding zone due to a forced reduction in the cross-sectional dimensions of the arc and an increase in its power.

As a result, welding occurs with a so-called plasma jet, the temperature of which can reach up to 30,000 °C, in contrast to 5000-7000 °C with conventional argon arc welding.

In addition, the arc takes on a cylindrical shape, in contrast to the usual conical one, which allows it to maintain the same power along its entire length. In practice, this is successfully used for deeper and more precise heating of the metal.

The arc pressure on the surface of the parts being welded during plasma welding is very high, which makes it possible to act on almost any metals and alloys.

The technological process of plasma welding allows it to be used at low currents of only 0.2 - 30.0 A.

All these features make plasma welding almost universal. It can be successfully used in hard-to-reach places, when connecting thin aluminum sheet blanks without fear of burning them.

A slight change in the distance between the electrode and the workpiece does not have a strong effect on heating, and therefore on the quality of the seam, as with other types of welding.

The large depth of heating of parts makes it possible to do without preliminary preparation of their edges. Welding of metals with non-metals is allowed.

As a result, work productivity increases, the thermal deformation of the seam decreases, that is, the part does not “lead.” Using plasma welding technology, a plasma jet can quickly and efficiently cut metals and non-metals in almost any position.

How it works

To implement the idea of ​​plasma welding, the design of the torch uses a device (torch) called a plasma torch. It is a conical nozzle containing coolant inside.

The electric arc in plasma welding is excited using a welding machine with a built-in oscillator. It burns inside the plasma torch, and during combustion a plasma-forming gas is supplied to it.

As a rule, this is argon with small admixtures of hydrogen or helium. The gas is supplied under low pressure, but inside the burner it heats up and, increasing in volume up to 30 times, creates a powerful jet at the exit of the nozzle.

The design of the nozzle itself endows the gas with high kinetic energy, which is realized into a powerful flow that has a high temperature. This is plasma.

Since it is difficult to initiate an arc between the electrode and the part being welded, the design of the torch provides for the constant maintenance of a “pilot” arc between the electrode and the nozzle. It is converted into a working one when the torch touches the connected products.

The shielding gas, and this, as a rule, is also argon, is supplied to the welding zone through a separate channel and, as it were, envelops the jet and the area of ​​​​the metal heated by it. In this case, the shielding gas, displacing air from the future seam, prevents oxidation of the material of the parts being joined and the filler material until a strong, uniform seam is formed.

Connection methods

Depending on the design of the torch and the connection diagram to the current source, there are two methods of plasma welding:

• direct action arc;
• arc of indirect action.

The first connection method is to supply current from a power source to a tungsten electrode and the part being welded.

In this case, the arc burns stably between the electrode and the metal, and its characteristics are enhanced and brought to the required values ​​by a jet of plasma-forming gas inside the nozzle, which is electrically neutral relative to the entire system. The direct action method is used for metal cutting, surfacing and direct welding. It is often used in everyday life.

In the second method, current is supplied to the electrode and nozzle. In this case, an arc is formed between the electrode and the nozzle body, and the plasma-forming gas blows it out, turning it into a powerful plasma jet.

The arc temperature in the indirect welding method is lower than in the direct welding method. The indirect method is used for metal spraying and heating of parts. It can be used to weld and cut materials that do not conduct electricity.

When plasma welding and cutting, it is necessary to take into account the correct choice of mode. The modes must take into account the correct current supply, the types of materials being welded, their thickness, and the diameter of the plasma torch nozzle. Different gases are used when cutting different materials. .

Requirements for compliance with technology

Despite the apparent simplicity of the plasma welding process, it is very demanding in terms of precise adherence to technology and equipment. The main mistakes are:

• belated replacement of replaceable plasma torch elements;
• use of low-quality or defective parts;
• use of incorrect modes that shorten the service life of elements;
• lack of control over the parameters of the plasma-forming material;
• high or low cutting speed compared to the specified mode;

To successfully carry out work using plasma welding, you need a welding machine that provides the necessary characteristics of the welding current.

You will also need a special burner with a non-consumable electrode, a set of hoses for supplying or circulating coolant, argon cylinders and a set of gas hoses.

How to make a plasmatron with your own hands

A hand-held plasma welding machine can be made from a conventional inverter-type welding machine. The main task is to manufacture the plasma torch itself, since otherwise the whole process is similar to conventional argon arc welding.

Anode and nozzle

For the plasma torch you will need a bronze blank, which will have to be processed on a lathe. From this blank it is necessary to turn two parts of a near-cylindrical shape, which, having inserted one into the other, must be soldered together so that a cavity is formed inside according to the principle of a thermos.

This cavity will be used to pump coolant. This will be the anode of the burner. It can also be a nozzle in plasma welding. The nozzle diameter should be 1.8-2.0 millimeters. You can make a nozzle from a more refractory material and screw it into the anode, having previously provided threads on both parts.

Cooling

Coolant circulation can be achieved by connecting a conventional car windshield washer system through a hose system. That is, not the washer itself, but only the reservoir with the transfer pump. The pump is powered with 12 V DC voltage from a battery or through a suitable power supply.

Cathode

For the cathode, you can use a rod made of a tungsten electrode, sharpened to a cone. The diameter of the rod should be 4.0 millimeters. On the back side of the rod it is necessary to provide a threaded device that allows for controlled insertion of the rod into the plasma torch body.

Frame

The body itself can be made of a non-metallic solid refractory material. Inside, it is necessary to provide the possibility of supplying plasma-forming and protective gas, for which it is necessary to solder pipes of suitable sizes.

Arc initiation

A positive charge is supplied from the main power source, which can now be called a plasma inverter. A minimum current value of 5-7 A will have to support the pilot arc.

If the device has a built-in oscillator, then igniting the arc should not cause problems. If there is no oscillator, you will have to complicate the design of the plasma torch by spring-loading the cathode in such a way that you can briefly touch the anode.

It is at the moment of contact that the pilot arc will light up. The spring must be sufficiently rigid so that the contact time is as short as possible, otherwise the cathode may burn to the anode.

Gas injection

When working, it is necessary to take into account a significant drawback - in a homemade device for plasma welding, the argon consumption will be unreasonably high. Therefore, when cutting metals or other materials, it is advisable to use compressed air or water vapor. But they can only be used for cutting, since both air and steam are not chemically neutral to the metal and can cause oxidation of the seam.

Compressors are used to pump compressed air. It is better to connect the compressor to the plasma torch not directly, but through a receiver - a cylinder in which air is accumulated under some pressure.

If the receiver is not used, the air supply will be uneven and the quality of the plasma arc will be poor. Various steam generators are used to supply water steam.

Microplasma devices

Very often, home craftsmen make devices for plasma cutting and soldering, in which the plasma temperature does not exceed only 8000-9000 °C. A distinctive feature of such a microplasma device is that it uses alcohol-water liquid to form plasma, which evaporates directly in the plasma torch.

For this purpose, the design provides a special tank. Such devices are very convenient for small jobs due to their mobility, because there is no need to transport bulky gas cylinders or gas generators.

With proper operation of welding equipment and adherence to welding modes, using high-quality consumables, plasma welding is the most effective way of cutting or joining materials.

Currently, only laser welding is more technologically advanced, but its cost and equipment requirements are an order of magnitude higher than plasma welding.

Source: https://svaring.com/welding/vidy/plazmennaja-svarka

Types and features of plasma welding

Plasma welding is a fairly new method of joining parts. Despite the fact that it appeared relatively recently, it has already gained great popularity due to its advantages and capabilities. Let's take a closer look at what plasma welding is, what it is, and how it differs from other types of welding.

The essence of plasma welding

Plasma is the state of gas into which it transforms under the influence of an electric arc. It is formed in a special tip called a plasmatron (it’s like a torch in gas welding). Plasma melting is a technique that uses a torch containing a tungsten electrode, plasma nozzles, and gas supply and water cooling pipes to produce plasma.

This type is indispensable for processing metal products of high strength and thickness (up to 9 mm). It is slightly similar to the arc welding technique, but unlike the electrode, which provides heating up to 5-7 thousand degrees, it affects the product with ultra-high temperatures - up to 30 thousand degrees. This is why this method is often called “plasma arc welding”.

You can perform work with such a device in any spatial position of the product.

Plasma welding of metal, due to the high temperature of the impact on the product, allows you to process a wide range of metals - bronze, titanium, stainless steel, carbon steel, brass, cast iron, aluminum.

This method is used in various industries - instrument making, mechanical engineering, food industry, medical equipment manufacturing, jewelry, chemical production and many others.

Plasma welding and cutting of metals is necessary and indispensable in almost every production.

Plasma welding and cutting of metals comes in two types:

1. Melting of metal by an arc that occurs between the product and a non-consumable electrode
2. Welding with a plasma jet, which is formed due to the arc burning between the tip of the plasma torch and the non-consumable electrode.

The most commonly used materials for plasma formation are air, oxygen, argon and nitrogen. The magnitude of the current in the plasma can be different, and there are three subtypes:

1. Microplasma welding, which is implemented at low current up to 25 A
2. Operation at medium currents – up to 150A
3. At high currents, over 150A.

In simple terms, the essence of this method is the ionization of the working gas, which under pressure turns into a plasma state and provides a high temperature used to melt metals for cutting or joining.

Plasma welding technology is divided into two types:

• direct plasma welding;
• indirect plasma welding.

Apparatus for work

An air plasma welding machine is a small technical equipment weighing no more than 9-10 kilograms. Its operating principle is as follows: inside there are control circuits, a current rectifier and a transformer. To operate, a unit with working gases in cylinders is connected to it - for the formation of plasma and an inert gas necessary to protect the welding seam from oxidation.

At the outlet, a burner with gases is connected separately for cutting. Due to the fact that this method creates too high a temperature regime, the burner has a special compartment for coolant. This device is similar in appearance to an inverter. There are many models on sale with different functions.

If we talk about the simplest, it is the most compact (about 5 kg) with a minimum number of settings, which not only a beginner, but even a child can understand.

Models that are more expensive have additional settings and functions that, in addition to cutting and welding, can perform soldering, bluing, oxidation and hardening of metal. The simplest products are considered to have a minimum power of up to 12A. Their cost ranges from 30 thousand Russian rubles.

Equipment a class higher and more powerful, up to 150A, costs from 40 to 150 thousand, depending on the manufacturer and additional functions. The most expensive models have a power of 150A, and their cost can even exceed a million rubles. For professionals who constantly engage in fusion, it is recommended to purchase high-quality and expensive equipment.

By paying once you can get a multifunctional device with which you can perform all kinds of metalworking procedures.

Advantages and disadvantages

Direct and indirect plasma welding has its advantages and disadvantages, like other types of welding. The main advantages that make this method indispensable for use in many industrial sectors are the following:

• high efficiency and high speed of work;
• high-quality metal cutting leaves smooth edges and does not require additional processing;
• the ability to cook and cut products almost a centimeter thick;
• there is no slag or waste during operation;
• control of the depth of metal penetration, which avoids leaks and deformation;
• ease of use of the device.

In addition to the positive aspects, several disadvantages can be noted:

• high cost of equipment and high cost of work;
• in the field of professional use there are high requirements for the master;
• the need for constant monitoring of cooling due to the high operating temperature.

In principle, all these disadvantages can be turned into advantages if you look at it from the other side. A professional craftsman with high-quality equipment can work in any field and still earn good money.

Tips from the professionals

• before starting to connect the parts, prepare a workplace and a form for the master;
• check the serviceability of the device and the pressure in the cylinders;
• plasma welding of aluminum should be carried out at low current;
• The plasma torch for welding must be cleaned (blown) before starting the process;
• microplasma welding is an ideal option for beginners to master this technique;
• Plasma welding technology is chosen by the master himself, since both methods have their advantages.

Source: https://svarkaed.ru/svarka/vidy-i-sposoby-svarki/plazmennay-svarka.html

Plasma welding: the principle of operation of the installation and what is the essence of the operation of a plasma torch

page » Plasma welding » The operating principle of plasma welding

Plasma welding is a high-tech method of metal processing. Without unnecessary exaggeration, it can be called the best among existing welding methods.

Features of plasma welding

The heat-generating parameters of plasma are much higher than those of other welding methods. To control the heating mode, you need a cooling circuit - the water circulating through it removes excess heat, which results in large energy losses.

The main consumables are a nozzle (the burner fails when overheated), refractory tungsten electrodes.

The production of plasma equipment requires fire-resistant materials, so the cost of welding machines is several times higher than for electric arc or argon welding.

Technological difficulties are not scary; plasma welding is often used in industry, especially if high-quality connections are needed. Smooth seams do not need to be sanded. The method is applicable to aluminum and other complex alloys.

Design and principle of operation

The fundamental difference between the plasma method is the high temperature of the plasma (up to 8000°C) supplied to the working area. The melt bath is protected by an argon atmosphere, and the cooling system stabilizes the constant temperature. Without it, the plasma torch will melt, the plasma heats up to 30 thousand degrees.

In essence, plasma welding is the ability of argon to transform into plasma under the action of an arc. The current acts as a plasma generator and penetrates electrically conductive argon.

Plasma formation under the influence of direct or alternating current occurs in a plasma torch. This is a cone open on both sides, tapering towards the bottom, in which a refractory electrode is located in the center (for this, tungsten electrodes with additives of lanthanum, thorium, zirconium, yttrium are used), and at the bottom there is a nozzle. Plasma bursts out of it under high pressure.

Argon with the addition of hydrogen is used as a plasma-forming gas. It is forced into the cone from above. The field is created by applying current to two poles: the electrode and the outer part of the burner. When ionized and heated, the gas instantly expands; it is displaced due to internal forces by a powerful jet. The plasma supply regulator is the nozzle.

The thickness of the plasma flow depends on its diameter. The size of the plasma torch depends on the operating mode. The higher the currents, the larger the upper and outlet diameters. Simultaneously with the plasma jet, argon is continuously supplied to the working area to create a protective cloud that protects the melt from contact with oxygen contained in the air.

Thanks to argon, the seams are clean, without scale inclusions.

Plasma welding is the ability of argon to transform into plasma under the action of an arc

By current strength

Plasma welding comes in three types, depending on the current strength:

• microplasma;
• on average current;
• at high current.

Each method is effective in its area of ​​use. This once again emphasizes the progressiveness and popularity of the plasma welding method.

Microplasma welding

Plasma and microplasma welding is a method of joining (as well as cutting) parts using ionized gas with a temperature of 5,000 to 30,000 C, called plasma.

What it is

How can you distinguish plasma welding from microplasma welding? If the current used in welding is up to 25 A, the welding is called microplasma welding; if the current is higher, we are talking about plasma welding. Unlike the plasma process, microplasma welding occurs under the influence of microcurrents, which makes it possible to connect parts of small thickness from 0.025 to 0.8 mm.

Microplasma welding has the following differences:

• occurs at a current strength of 0.1 to 25 A;
• a tungsten electrode is used;
• the size of the plasma torch is smaller (a micro plasma torch is used).

Most often, microplasma welding is used to join thin-walled parts of devices, to join difficult-to-weld metals, for example, aluminum, plastics, even fabrics.

To perform the welding process, a plasma-forming gas is needed, this is usually argon, and a shielding gas. Most often it is also argon or helium, carbon dioxide, or a mixture of argon with helium, hydrogen.

To produce plasma, a device called a plasmatron is used. When the power source is turned on, a pilot electric arc passes from the tungsten electrode to the nozzle.

As the torch approaches the parts being welded, when 1-1.5 mm remains between them, an arc is formed between the electrode and the workpiece, at this moment the plasma-forming and shielding gases are mixed. In a very small nozzle, the arc is tightly enveloped in protective gas and forms a narrow plasma jet in the form of an “awwl”.

With this form, welds of small thickness are obtained. In this case, deformation of parts is rare, since the heating area is insignificant. Welding can be carried out using direct current or pulsed mode.

Advantages of the microplasma method:

• Possibility of connecting parts of small thickness.
• The stable combustion of the plasma allows even inexperienced welders to produce high-quality welds.
• Possibility of welding parts made of plastics and textiles.
• Possibility to mechanize the process.

The disadvantages of this method include the low durability of plasma torches. The durability of burners is increased by introducing water or natural air cooling.

The process can be performed using manual or automatic equipment.

Devices for microplasma cutting

In all devices for microplasma welding there are two main components that determine the possibilities of connections.

First node: power supply , inverter. They also contain a device for igniting an electric arc and automation. Differ by:

• load duration , %;
• current strength ( nominal and adjustable), A;
• open circuit voltage
• consumed electrical power , kVA.

To connect black, refractory parts, MPU-4, N-146 is used. The UMPS-0301, I-167 installations are considered more modern and convenient; they weld almost all metals, including aluminum.

The second component is the plasmatron . They differ from each other in design characteristics, such as:

• The greatest thickness of steel that can be welded in 1 pass.
• Current strength (direct arc and standby), A.
• Electrode size, mm.
• Size of nozzles (plasma-forming and for protective gases), mm.

Plasmatrons of the USDS.R-45 and T-169 types can weld steel up to 2.5 mm thick; they are equipped with MPU-4 and N-136 installations. Plasmatrons OB-2592 and OB-2628 were developed later, are more convenient, have a better, more economical design, and are ergonomic. They supplemented the new power sources UMPS-0301, I-167, N-155.

There are also ready-made installations, immediately equipped with all the necessary components. These include Microplasma 20,50,150 devices, which differ from each other in installation power, as well as Multiplaz 3500, 4000, 7500, which have the ability to weld with a water-alcohol mixture.

Types of plasma welding

Two methods of connecting current are used: part-electrode; electrode-burner body. A conditional division is carried out into types based on generator power and equipment operating parameters:

• microplasma is carried out at low currents, the welding is shallow, the metal is not damaged (a separate section is devoted to it);
• welding at medium currents, up to 25A, connecting parts from 3 mm and above;
• work with high amperage, up to 150 A, the method is suitable for welding thick-walled parts or piercing welding of metal.

Advantages and disadvantages of plasma welding

So what is plasma welding? This is the process of local melting of a metal product by a plasma flow. It is formed by a high-speed arc at a temperature of 5000-30000°C.

The gas stream passing through the arc is heated and ionized, due to which it turns into a plasma stream and is blown out by the plasmatron nozzle for welding. This is the essence of her work.

In order for this device to function, only electricity and a flow of compressed gas are needed. If a compressor is used, then only electricity is sufficient.

To operate, you only need to change the plasma torch and electrodes. This is where the maintenance of this type of equipment ends. While other types of welds require more maintenance work. In addition, they are more explosive.

Features of plasma welding.

The main advantages of these devices include:

• high speed cutting of metals;
• the ability to use the device with almost all metals and alloys;
• high precision and quality of seam;
• lower cost of work compared to other methods;
• no metal deformation during plasma treatment;
• high level of work safety.

Varieties

Plasma welding is divided into several types, depending on the current strength:

• microplasma;
• at medium currents;
• at high currents.

The first type is most often used. The fact is that the arc can burn at fairly low currents if tungsten electrodes with a diameter of up to two millimeters are used. This is possible due to the high degree of electric arc ionization of the gas.

The microplasma welding diagram is presented below.

Plasma welding drawing.

This technology option is most effective for connecting thin parts up to one and a half millimeters thick. In this case, the diameter of the arc does not exceed 2 mm. This allows you to focus the heat in a fairly small area and not heat neighboring areas.

The main gas in this method is argon. However, depending on the type of product, various impurities may be added to it, which help to increase the efficiency of the process.

Microplasma welding devices allow you to operate in several modes:

• continuous;
• pulse;
• continuous reverse polarity.

Medium current plasma welding is in many ways similar to argon arc welding. However, the first one has higher temperatures, while at the same time the heating area is significantly smaller. This determines its high productivity.

Plasma welding allows the material to be melted more deeply, while the width of the seam is smaller than in argon arc welding.

Plasma welding at high currents has a strong force effect on the material. It completely melts the metal. As a result, a hole is formed in the bath, that is, the parts are first cut, as it were, and then fused again.

Characteristics

The operating principle of plasma welding makes it clear that it is best used for thin materials, stainless steel, non-ferrous metals and alloys based on them. It is worth immediately noting that in many cases the use of other technologies, argon arc welding, is not possible.

At the same time, in metallurgy and other areas of industry it is necessary to carry out work with precisely such products.

Scheme of plasma welding technology.

The main characteristics of the microplasma welding arc include:

• cylindrical shape;
• concentration of energy in a small area;
• small flow divergence angle;
• immunity to changes in the distance between the plasma torch and the product;
• high ignition safety.

All of the above characteristics are also advantages of the method. For example, the cylindrical shape and the possibility of increasing the length allow welding work even in the most inaccessible places.

Also, the features of the technology simplify welding in the presence of vibrations of products, due to insensitivity to changes in distance.

Welding technology

The specificity of the plasma-arc welding technology method is that plasma is supplied to the joint area from a special torch - a plasma torch. In some cases, if necessary, argon or helium can be used to create an inert environment in the area where the parts meet.

Drawing of a welding machine.

All energy is concentrated in the plasma jet. Due to this, the heating does not spread over the entire area of ​​the product, but is focused only near the connection. In this case, the temperature in such an area can be 10000-15000°C. However, due to the rapid removal of heat by the metal, it is reduced to the melting temperature in the joint area.

If the joint is protected with an inert gas during this procedure, a high-quality seam can be obtained that does not require additional manual processing.

The burner body is made of steel, the anode is made of copper. The latter is cooled with water. The arc is powered by gas supplied under high pressure into the cavity between the anode and cathode.

At the same time, it is important to keep in mind that argon does not ionize. It quickly evaporates, mixing with air. In order for it to reliably perform its protective functions, it is necessary to maintain a certain distance between the burner and the part.

Since the method provides high heating only in the joint area, this can lead to undesirable consequences. Sometimes it is necessary to preheat the product or use several burners to avoid a sharp temperature difference across the surface of the material.

When using microplasma welding, it is possible to obtain high-quality seams on thin materials. The implementation of this technology is possible even without the use of filler wire.

Equipment used

Plasma welding installations are widely used not only in large-scale production, but also in domestic conditions. It is worth noting that the demand for this equipment is constantly growing, which once again confirms its relevance.

Installation of equipment for welding.

All equipment designed to perform this work can be divided into the following features:

• type of impact;
• arc stabilization method;
• current strength.

It is worth noting that we should not forget about other technologies. Thus, argon arc welding is widely used for welding parts in serious industries, for example, in aircraft manufacturing and aerospace.

Plasma, in turn, is most often used for cutting metals, since it allows this process to be carried out at high speed.

It becomes especially indispensable when processing alloys with minimal subsequent warping and the development of stresses, as well as deformations.

Bottom line

Plasma welding technology is the only possible and affordable method for processing some metals and alloys. This especially applies to stainless steels, copper, brass, etc. This method allows you to obtain high-quality, reliable and thin seams, as well as cut with high efficiency.

It has found particular application in joining thin sheet metal without the use of filler wire. In addition, this type of welding provides local heating only in the joint area, which can be very convenient when solving many problems.

Source: https://tutsvarka.ru/vidy/plazmennaya

What is direct plasma welding - Metalworker's Guide

Plasma welding is a fairly new method of joining parts. Despite the fact that it appeared relatively recently, it has already gained great popularity due to its advantages and capabilities. Let's take a closer look at what plasma welding is, what it is, and how it differs from other types of welding.

Plasma welding machine: what it is, how it works and where it is used, pros and cons

Plasma was first used for welding in the mid-twentieth century, with the creation of an industrial-type plasma generator - a plasmatron.

In the beginning, plasma welding was used only in narrow areas, in astronautics, for example. However, over time it has become common in other areas of production as well.

Technological progress developed, and private specialists began to use plasma welding. And now plasma welding devices are even more accessible and anyone can buy them.

This article contains basic information about what a plasma cutting machine is, how it works and its varieties.

General information

Plasma consists of ionized gas, and, at the same time, is one of the four physical states of matter. Current plasma welding devices can produce temperatures between 5,000 and 10,000 °C.

Such devices are also called plasmatrons. These plasma cutting and welding devices can form three types of arcs: direct, indirect, and combined.

The arc is prone to decay, so before starting work it is “twisted” in a special way. After this procedure, a thin, stable arc is created, since the gas is almost instantly ionized.

As a result, a high power arc is formed, which can create energy at a certain point. The melting of the base metal is carried out precisely at this point.

Regardless of the composition and density of the metal, a plasma arc can heat almost anyone. It is capable of heating even to the melting or boiling point. To do this, you just need to create an arc of sufficient power.

The additional welding zone is protected by inert gas. Organic acetone vapor, argon or nitrogen are suitable for this. The design of the plasma torch is such that it is capable of simultaneously supplying both plasma and shielding gas.

Thus, the weld pool is protected during the work process. The seams are of good quality, and the metal does not corrode.

What does it consist of?

Source: https://prosvarku.info/apparaty/plazmennyj-svarochnyj-apparat

The operating principle of plasma welding, available methods

The development of modern industry is inextricably linked with the emergence of new methods of processing and joining various materials. Welding in these cases is one of the most reliable. Welding technology is also developing and improving. One of the young and promising areas is plasma welding. This method greatly simplifies and facilitates the work, which deserves more detailed consideration.

Process Features

This method of joining parts is reminiscent of argon arc welding due to working with inert gases. However, there are still differences. For example, welding work is carried out with a special apparatus - a plasma torch.

Plasma is the state into which a gas transforms when exposed to an electric arc. All this happens at temperatures of many thousands, so the main feature of plasma welding is the high operating temperature - from 5 to 30 thousand degrees. This allows you to work with elements of any composition and size.

Another feature of plasma technology is the high pressure at the joint. This occurs due to the cylindrical shape of the welding arc, which ensures heating and equal distribution of power over the entire surface of the working jet. In conventional welding, this is more difficult to do, since the arc is conical and it is very difficult to evenly distribute the pressure force and heating.

And the third important feature of working with plasma is working at low currents. Yes, it is plasma technology that allows welding of both thin sheets of material and in hard-to-reach places.

These features make the plasma welding method almost universal. Over time, types and varieties have appeared, since in addition to welding work using plasma, it is easy to cut metals.

Kinds

Plasma welding differs in the type of processing, current value and connection method.

Welding is classified according to the type of processing:

1. An arc formed between the surfaces to be joined and an infusible electrode.
2. A jet formed between a non-consumable electrode and the tip of a plasma torch.

Since plasma operation is possible at various current values, the following are distinguished:

• microplasma treatment - carried out at voltages up to 25 amperes;
• work with medium currents - performed at currents up to 150 A;
• interaction with currents over 150 amperes.

The plasma torch and the torch circuit determine the type of connection to the current source:

• direct action;
• indirect action.

Each method is unique and in demand in a specific area. Let's look at the popular ones.

Microplasma method

Connecting parts using microplasma technology is one of the most popular methods. Microplasma welding allows you to fasten thin-walled parts and pipes, metal sheets up to 1.5 mm thick, and is even used in the production of jewelry.

When this method is used, the diameter of the working plasma jet usually does not exceed 2 millimeters. The arc is powerful with high thermal radiation. The gas used during operation is usually argon, less often argon with an admixture of helium.

Direct connection

In addition to fine work using microplasma, the connection diagram to the current source is no less important.

This method is considered the main one in welding work. It is carried out using plasma formed between the electrode and the workpiece. The arc is excited gradually; first, a pilot jet is formed at a low current, which, after contact with the working surface, turns into a direct arc. Work can take place with both alternating and direct current.

This method is effective for cutting metals and non-metals, welding and surfacing. In everyday life, direct action is also in demand.

Due to the fact that during direct exposure the temperature of the working jet is very high, control of the heating of the plasmatron nozzle is a prerequisite. If it overheats (which is almost impossible), it is advisable to stop working for a while. Subsequently, it is worth checking the serviceability of the equipment, and, if necessary, eliminating the malfunction or purchasing a new device.

Indirect welding

In this case, an arc is formed between the tip of the plasma torch and the electrode, the gas squeezes it out of the nozzle, resulting in a powerful plasma jet at the output.

The temperature of the jet in this case is much lower than with direct exposure. For this reason, indirect impact is often used for joining and cutting parts made of materials with low electrical conductivity.

Gas pressure controls the force of the plasma jet. Due to this, the indirect impact method is used for metal spraying and heating of workpieces.

The quality of the connection depends on the choice of operating mode. When selecting a mode, it is necessary to take into account the type of current supply, what material is to be welded, and most importantly, the diameter of the working jet.

Advantages and disadvantages

Like any technology, plasma welding has positive and negative sides.

The advantages can be identified:

• high melting speed of workpieces;
• precise and high-quality seams;
• no slag;
• smooth edges of parts when cutting;
• environmental friendliness;
• safety;
• ease of use;
• penetration depth control.

The negative points include:

• high cost of equipment;
• plasma torch cooling control.

Although there are disadvantages to plasma technology, they are minor. And the cost of the equipment pays off quite quickly, especially by a qualified craftsman.

About equipment

Working with plasma is impossible without the appropriate equipment. A welding machine for plasma welding is quite compact, usually its weight does not exceed 10 kilograms (the most compact one is about 5 kg). To form plasma, you need to connect a gas installation to the device for operation. An inert gas, also connected to the device, will help protect the welded joint from oxides. And of course the burner, it is connected at the output of the device.

Let us remember that plasma welding is performed at very high temperatures, and this requires cooling of the plasma torch nozzle. Any plasma welding machine has a compartment with coolant.

Equipment for plasma welding is really expensive - a low-power machine with a minimal set of functions costs about 30 thousand rubles. Accordingly, the more settings (soldering, hardening), the more expensive the unit.

Recommendations

It is not always a professional who works with a welding machine; it is often self-taught. For this category of people, qualified specialists give several recommendations:

• before work, check the serviceability of the equipment and the gas pressure in the installation;
• clean the plasma torch before starting welding;
• prepare and clear the work area of ​​foreign objects;
• weld (or cut) aluminum parts at low currents.

Plasma welding is a modern technology for joining and cutting not only metals, but also other materials. Plasma welding is in demand among both professionals and amateurs - it is easy to work with and brings good income regardless of the season. Despite the high cost, the equipment necessary for work is in demand, because by spending money once, you can become the owner of a wonderful unit with many additional functions.

Source: https://svarkoy.ru/teoriya/plazmennaya-svarka.html

What is plasma welding and what equipment is used

The scope of plasma welding is wide. This equipment is used to cook foil and thick metal. Equipment for industrial and domestic use appears on the shelves. Sometimes plasma welding is confused with argon welding. The devices are externally similar. The methods have much in common, but there are fundamental differences. We will talk about them.