Temperature of plasma cutting of metal. Plasma cutting - the principle of operation of the plasma torch

Plasma cutting is very often used in industries such as shipbuilding, mechanical engineering, as well as in the manufacture of metal structures, utilities, etc. In addition, a plasma cutter is quite often used in a private workshop. With its help, any material that conducts current, and some non-conductive materials - wood, stone and plastic, are quickly and efficiently cut.

Plasma cutting technology allows you to cut sheet metal and pipes, make curved cuts or make parts. The work is carried out using high temperature plasma arc. To create it, you only need a power source, air and a cutter. In order for the work to be done quite easily, and the cut to be smooth and beautiful, you should find out how the principle of plasma cutting works.

How does a plasma cutter work?

This apparatus consists of the following elements:

• source of power;
• air compressor;
• plasma cutter or plasma torch;
• cable-hose package.

The power source for the plasma cutting machine supplies a certain current to the plasma torch. It is an inverter or transformer.

Inverters are quite light, economical in terms of energy consumption, inexpensive, however, they are able to cut workpieces of small thickness. Because of this, they are only used in private workshops and small industries. Inverter plasma cutters have 30% more efficiency than transformer ones and their arc burns better. They are often used for work in hard-to-reach places.

Transformers are much heavier, they spend a lot of energy, but at the same time they have less sensitivity to voltage drops, and with their help they cut thick workpieces.

The plasma cutter is considered the main element of the plasma cutter. Its main elements are:

• nozzle;
• cooler/insulator;
• channel required for supplying compressed air;

A compressor is required to supply air. The principle of operation of plasma cutting involves the use of protective and plasma gases. For devices that rated for current up to 200 A, applies only compressed air for both cooling and plasma generation. They are able to cut workpieces with a thickness of 50 mm.

The cable-hose package is used to connect the compressor, power source and plasma torch. By electrical cable a current begins to flow from the inverter or transformer to excite an electric arc, and compressed air is supplied through the hose, which is required for the occurrence of plasma inside the plasma torch.

Principle of operation

When the ignition button is pressed, the high frequency current is supplied from the power source (inverter or transformer). As a result, a standby electric arc is formed inside the plasma torch, the temperature of which reaches 8 thousand degrees. The column of this arc begins to fill the entire channel.

After the pilot arc has arisen, compressed air begins to flow into the chamber. Breaking out of the pipe, he passes through an electric arc, heats up, while increasing in volume by 50 or 100 times. In addition, the air begins to ionize and ceases to be a dielectric, acquiring the properties of conducting current.

The plasma torch nozzle, narrowed down, compresses the air, creating a flow from it, which begins to escape from there at a speed of 2–3 m/s. At this moment, the air temperature often reaches 30 thousand degrees. It is this hot ionized air that is plasma.

At the time when the plasma begins to escape from the nozzle, it comes into contact with the surface of the metal being processed, the pilot arc goes out at this moment, and the cutting one lights up. She starts heat the workpiece at the cutting point. As a result, the metal melts and a cut appears. On the surface of the metal being cut, small particles of molten metal are formed, which are blown away from it by a stream of air. Thus, the operation of the plasma torch is carried out.

Benefits of Plasma Cutting

Metal cutting work is often carried out on a construction site, in a workshop or workshop. You can use an autogen for this, but not everyone is happy with it. If the amount of work associated with metal cutting is too large, and the requirements for cut quality are very high, then you should consider using a plasma cutter that has the following advantages:

Disadvantages of Plasma Cutting

There are also disadvantages in the operation of plasma cutting. The first of them - the maximum allowable cut thickness is quite small, and for the most powerful units it rarely exceeds 80 - 100 mm.

The next disadvantage is the rather stringent requirements for the deviation from the perpendicularity of the cut. Deflection angle should not be more than 10 - 50 degrees and it depends on the thickness of the part. If it happens to go beyond these limits, then a rather significant expansion of the cut occurs, which results in rapid wear. Supplies.

Besides, working equipment quite complex, which makes it completely impossible to use two cutters at the same time, which are connected to one machine.

Conclusion

The principle of plasma cutting is quite simple. In addition, the apparatus used for this has a large number of advantages that are several times greater than the existing disadvantages. If you use it correctly, you can save a lot of time and get a quality result.

Plasma cutting is a great new technology that allows you to cut metals of solid thickness and any nature, even the most capricious. It is not a knife that acts as a cutting object, but a dense plasma jet, which allows you to form an ideally accurate cut pattern per unit of a given time.

This method of working with metal has many advantages, which we will discuss below. And now let's start with physics - you need to understand the essence of the process.

Plasma metal cutting technology gives the female lead to our beloved electric arc. It is formed between the electrode and the nozzle. Sometimes, instead of an electrode, there is metal that needs to be cut. Let's understand what plasma cutting is.

Starting the process - turning on the source electrical supply and supplying high frequency current to the plasma torch. The power source turns on automatically after pressing the ignition switch in the device.

First, the so-called intermediate arc is formed - it is temporary and connects the electrode to the tip of the torch nozzle. This pilot arc is heated to a temperature level of about 8000°C.

it important point overall process plasma cutting - you need to remember that the real arc between the electrode and the metal is not formed immediately, but through its intermediate version.

The next stage of the process is the intake of air from the compressor, which is usually attached to the metal cutting machine. The compressor delivers compressed air. This air enters the plasma torch chamber, in which a temporary electric arc is already heated.

The arc heats the compressed air, the volume of which increases many times over when heated. In addition to heating and increasing the volume, the air begins to ionize and transform into a real conductor of electric current. It turns into the same plasma

The small diameter of the nozzle makes it possible to accelerate the flow of this incandescent plasma to enormous speeds, with which the jet flies out of the apparatus. The flow rate can reach three meters per second.

Scheme of plasma cutting.

The air temperature is prohibitive, up to 30,000 ° С. Under these conditions, the electrical conductivity of the air-plasma is practically equal to the conductivity of the metal being cut.

A true end arc appears instantly as soon as the plasma flow reaches and touches the metal surface. The temporary arc, in turn, is automatically turned off. The metal begins to melt exactly at the cut point.

Liquid metal droplets are immediately blown away by compressed air. This is the principle of plasma cutting. As you can see, everything is simple, logical and understandable.

Classification of types of plasma cutting

The types of plasma cutting will depend on the environment in which metal work is carried out:

Simple

The main difference of the method is the limited electric arc. Used for cutting electricity and air. Sometimes gas in the form of nitrogen is used instead of air. If the metal sheet is thin - just a few millimeters, the process can be compared to laser cutting.

With this method, the thickness of the metals should not exceed 10 mm. The method works well for low alloy steels and other soft metals. The cutting element is oxygen, from which a compressed jet is formed, which eventually turns into a plasma.

In cuts, very smooth edges are obtained that do not require further refinement.

With shielding gas

In this method, protective gases are used instead of air, which turn into a plasma stream after conversion in a plasma torch. The quality of cuts in this case significantly increased due to the excellent protection of the process from environmental influences.

Plasma cutting gas is nothing unusual: it can be hydrogen or argon - "gas classics".

With water instead of air

An excellent method with many advantages, one of which is the absence of the need for an expensive and bulky cooling system.

There are other criteria for classifying plasma cutting. For example, types of cutting are separating and surface. The first one is used more often.

Another parameter is the cutting method. One type is arc cutting, in which the metal being cut acts as an element electrical circuit. Another type is jet cutting, when an electric arc connects the electrodes, and not the metal workpiece.

Plasma cutters are available on the market in a wide variety of options, so that they can be classified by brands, manufacturers and many other technical and commercial parameters.

There is, for example, manual plasma cutting - the most affordable way both in terms of price and ease of execution. There are machine automatic technologies, devices for which are much more expensive and more complicated.

Benefits of Plasma Cutting

Working principle of plasma cutting.

The closest technology is laser cutting of metals, so it would be logical to list the advantages in comparison with the "neighbor":

• Plasma cutting on the shoulder of metals of any nature, including non-ferrous, refractory and others that are difficult to process.
• The speed of the process is much higher than cutting with a gas torch.
• One of the significant features is the ability to produce cuts of any shape, including both geometric patterns and curly cutting the highest difficulty. In other words, plasma cutting is the realization of the most daring creative ideas for metal and other difficult materials.
• Plasma cutter can handle any metal thickness: speed and quality are not lost in any way.
• This method lends itself not only to metals, but also to other materials: it is quite universal.
• Plasma cutting is both faster and more efficient in edge quality than any other mechanical cutting method.
• In this method, it is possible to work not only perpendicular to the metal surface, but at an angle, which helps to master wide sheets of metal.
• From an environmental point of view, this is a completely safe type of metal work with minimal emissions. harmful substances or air pollution.
• An excellent time saver due to the absence of the need to preheat the metal.
• Since the method does not use explosive gas cylinders, it is much safer than other methods.

Disadvantages of a plasma cutter

No metal processing method is without drawbacks, and plasma cutting is no exception.

The disadvantages of plasma cutting are as follows:

• The high cost of everything model range plasma cutting machines, including even the simplest manual options.
• Limits of metal thickness for plasma cutting: the maximum thickness is only 100 millimeters.
• This is a noisy way of working because the compressed air or gas is delivered at a tremendous speed.
• The equipment is not simple, expensive and requires competent and constant maintenance.

Another distinctive positive characteristic of the method is that only a small local area is heated during the process. Yes, and this area cools down much faster than with laser or mechanical cutting.

Cooling is necessary only for two components - the cathode and the nozzle, as the most loaded. This is done without problems with the help of a working fluid.

Plasma arc and jet.

The arc begins to work stably as a result of the working ratio of the cathode and nozzle with steam from compressed hot air. A negative charge is localized at the cathode, and a positive charge is localized at the nozzle tip. As a result, an intermediate arc is formed.

Excess moisture is absorbed by a special material, which is located in the tank of the plasma torch chamber.

The safety rules for this method are of the strictest nature, because all plasma cutting machines can be very traumatic for the master. This is especially true for models with manual control.

Everything will be all right if you follow the recommendations for protective ammunition of the master: a shield, tinted glasses, safety boots etc. In this case, you can protect yourself from the main risk factors of this method - drops of molten metal, high voltage and hot air.

Another safety tip is to never hit the metal with a cutter to remove metal splashes, as some craftsmen do. You run the risk of damaging the apparatus, but the main thing is to catch pieces of molten metal, for example, on the face or other unprotected part of the body. Better save yourself.

Saving consumables is not the last place in efficient cutting. To do this, we ignite the electric arc not too often, but precisely and on time, so as not to break it unnecessarily.

The resource saving also extends to the strength and power of the current. If you calculate it correctly, you will get not only savings, but also an excellent cut without burrs, scale and metal deformation.

To do this, you need to work on following scheme: first apply a high power current, make a couple of cuts with it. If the current strength and power are too high, scale will immediately form on the metal due to significant overheating.

After examining the sections, it will be clear whether to leave the current at this level or change it. In other words, we work experimentally - in small samples.

How to work with a plasma cutter?

Electrical circuit of the plasma generator.

Cutting metals with a plasma stream is too serious a business to do without prior study and thorough preparation. This will help you cut more efficiently from all points of view, and, most importantly, minimize the risks associated with occupational hazards.

First of all, you need to know the principle of plasma cutting - see the picture physical phenomena entirely.

The plasma torch should be held very close to the surface and edge of the metal, unlike laser cutting. When the “start” toggle switch is turned on, the temporary electric arc will light up first, and only then the real one, which will be the main cutting element. The cutting arc torch must be driven smoothly and slowly over the material.

Cutting speed should be strictly controlled. This can be done by observing the sparks from the back of the sheet of metal being cut. If these sparks are not present, then this means that the cutting of the metal was incomplete.

This can happen for several reasons: due to too high speed of the burner or the passage of the apparatus, or too insufficient power of the supplied current, or non-compliance right angle 90° between torch and metal surface.

The fact is that complete melting of the metal occurs only when the plasma cutter is tilted to the metal surface at a right angle and not a degree more or less.

After the work is completed, the cutter must be tilted. Air will come out even after the device is turned off - for a short time.

Before work, it is not harmful to study the diagram of your apparatus: it is in it that you can read the most reliable information on the permissible thickness of the metal, which can be cut or made a hole in it. The device of a plasma cutter may vary, it all depends on the functions of its purpose.

Choosing a Plasma Cutting Machine

Buying any technical equipment- a business for which you do not need to spare time and effort: the risk of an unsuccessful decision and loss of money is too high. And the money here is a lot, you will not find a plasma cutter cheaper than 500 USD in principle.

First, we deal with the parameters and technical characteristics of the device.

Two large groups plasma cutters are inverter and transformer. The names speak for themselves.

Open and closed plasma jet.

If you're looking for a compact torch for cutting thin metals, you can opt for an inverter type torch. They take a little energy, light and with small dimensions.

However, they work intermittently and easily fail when the mains voltage drops. The price of such devices is quite moderate, of all plasma cutters, these are the most inexpensive.

Another thing is transformer cutters. Here, both with dimensions and with weight, “everything is in order”: serious devices in all respects.

They consume a lot of energy, but they can work almost without interruption for a whole day. And the thickness of the metal can be larger than when cutting with an inverter model. The cost of such devices is high - from 3000 to 20000 USD.

Choosing a plasma cutter by power

We start the discussion with the properties and technical characteristics of the parts that you plan to process and cut. It is precisely this that calculates the power of the cutting device, because it will differ in both the nozzle in its diameter and the type of gas used.

The application of plasma cutting is an extremely wide area, so you need to talk only about your specific needs.

For example, if the thickness of metal blanks is about 30 mm, a cutter with a power of 90A will be enough for you. He can easily handle your material.

But if your metal is thicker, look for a suitable model in the power range from 90 to 170A.

Torch selection by time and material cutting speed

The speed of plasma cutting of metal is measured in centimeters per minute. This speed is also different for different devices and depends on their total power and the nature of the metal being cut.

For example, all other things being equal, steel is cut the slowest, and copper and its alloys are slightly faster. And even faster - aluminum with its aluminum alloys.

Plasma cutting device.

If speed is important to you, do not forget about such an indicator as the duration of work without overheating, that is, without a break. If the technical specification for the device says that the duration of the work is 70%, this means that after seven minutes of cutting, the device must be turned off for three minutes to cool down.

Among the transformer cutters, there are champions with a run time of 100%. In other words, they can work all day long without shutting down. They cost a lot, of course. But if you have long cuts ahead of you, consider buying "champion" transformer plasma cutters.

A few words about the burner

Again, we evaluate the nature of the metal or other material that we plan to cut. The power of the plasma cutter burner will depend on this. It should be sufficient for a quality cut.

When calculating, you need to take into account the fact that you can meet with difficult working conditions, which, unfortunately, must be carried out in the most short time, that is, cutting should be pronounced intense.

We do not lose the burner handle from the zone of attention, this is an important part for comfortable, which means quality work. Can be attached to the handle additional elements, which will help keep the nozzle at the same distance from the metal surface. This advice only applies to manual models devices.

If you are going to cut thin metal, choose a model with a torch that is designed for air intake.

If your plans are connected with massive thick workpieces, buy a cutter with a torch to receive a protective gas - nitrogen, for example.

Metal cutting - technological process dividing a monolithic part into separate parts. Operation in progress mechanically(cutting, sawing), hydroabrasive (suspension of water and abrasive material) or thermal (heating).

The last type is oxy-fuel, laser and plasma cutting of metal.

What is plasma cutting? This is processing metal products, where the plasma jet serves as a cutter.

Plasma is a stream of ionized gas heated to several thousand degrees. Contains particles with a positive and negative charge. It has quasi-neutral properties. That is, in an infinitely small volume, the total charge is balanced and equal to zero.

However, the presence of free radicals means that the plasma is a conductor of electricity. The combination of high temperature, electrical conductivity and high flow velocity (greater than the speed of sound) made it possible in the last century to develop and create plasma equipment for metal cutting.

Operating principle

How plasma works - there are two methods of processing metal parts:

• direct action cut, or plasma-arc cutting of metals;
• cut by indirect influence.

Direct cutter

An electric arc is ignited between the cutter (cathode assembly) and the workpiece (anode). The cathode (electrode) is placed inside a housing with a nozzle. The gas, under pressure, passing by the electrode, is heated to high temperatures and ionized. A high flow velocity is created as the nozzle passes. The electric arc melts the metal. Hot gas provides an exit from a zone of heating.

Indirect cutter

This method allows you to process common metals, but, and with low electrical conductivity, and dielectrics. Unlike the previous scheme, the electric spark source is placed in the cutter. Therefore, only the plasma flow affects the workpieces. Such equipment costs much more than direct-acting models.

Both types of cutters have a common scientific and technical name - a plasma torch (literally, a plasma generator).

Benefits of Plasma Processing

Compared with other types of metal processing, this method has a number of consumer properties:

• the possibility of processing workpieces from various metals, as well as non-metallic products;
• the processing speed of small thicknesses (up to 50 mm) is 25 times higher than with;
• local heating of the part occurs only at the point of impact, which contributes to the absence of thermal stresses and deformation of the product;
• high-quality and clean cutting of metal, - low surface roughness in the place of processing;
• absence of explosive substances and objects, - combustible gases, pressure cylinders, etc.;
• the method allows to produce complex geometric cuts.

What equipment is used

For cutting metal with plasma, units for industrial and domestic purposes are produced. The first ones are a complex multifunctional complex with an automated process (CNC machines). The second ones are small devices operating from a 220V or 380 V network.

The source of plasma cutting in household appliances is an inverter (welding generator) or a transformer. The first type is smaller in size, easier to handle. The second is highly reliable long term operation. The working fluid is prepared atmospheric air.

The power of the manual unit is enough to cut metal up to 15–20 mm thick. Some models are equipped with a non-contact arc ignition function. The package includes a plasma torch and an air preparation device.

Used in home workshops professional production and construction:

• sheet metal plasma river;
• processing of cylindrical products, including steel pipes;
• tenderloin complex geometric shapes, including holes;
• processing of ceramic and stone products and other types of craft.

This type of equipment is significantly superior in its functionality and ease of use to conventional oxy-fuel cutting. Not only in terms of dimensions, but also in terms of safety.

A model of a household plasma torch is shown in the photo.

Technology Properties

Industrial and Appliances unite general principles Plasma cutting jobs:

• creating an electric arc;
• the formation of ionized gas;
• creation of a high-speed plasma flow;
• the impact of this active medium on the material being processed.

Plasma-arc cutting is characterized by:

• flow temperature. The values ​​are in the range of 5000–30000°C. It is determined by the type of material being processed: the lower values ​​​​are used for non-ferrous metals, the upper ones - for refractory steels.
• Flow rate. Values ​​in the range of 500–1500 m/s. Customized for a specific type of processing:
  • workpiece thickness;
  • type of material;
  • type of cut (straight or curved);
  • the duration of the plasmatron.
• The gas used for plasma cutting. When processing ferrous metals (steels), an active group is used - oxygen (O2) and air. For non-ferrous metals and alloys - inactive: nitrogen (N2), argon (Ar), hydrogen (H2), steam. It is explained by the fact that non-ferrous metals are oxidized by oxygen (begin to burn), therefore, a protective gas environment is used. In addition, by combining the composition of the gas mixture, it is possible to improve the quality of processing.
• The width of the cut. There is a direct sequence here: with an increase in indicators, the width of the cut increases. Its value is affected by:
  • the thickness of the metal and its type;
  • nozzle diameter;
  • current strength;
  • gas consumption;
  • cutting speed.
• Performance. Determined by processing speed. For example, for household units and according to GOST, the value does not exceed 6.5–7 m / min (~ 0.11 m / s). Depends on the thickness, type of metal, speed of the gas jet. Naturally, with an increase in size, the processing speed decreases.

Processing quality

The quality of the cut is an important factor in metal processing, especially if it is plasma cutting of pipes. It is determined by the mode of operation, the skill of the performer. Plasma-arc cutting is regulated by GOST 14792-80. international standard quality - ISO 9013-2002.

The documents define the main criteria:

1. Tolerance for perpendicularity or angularity. Shows deviations from the perpendicular and plane of the cut to the surface of the workpiece.
2. Melting of the top edge. Cracks at processing points are not allowed. The upper edge can be sharp, fused, fused-overhanging.
3. Roughness. According to GOST, it is divided into three classes, 1, 2 and 3.

Types of plasma cutting

Plasma metal cutting technology is a set of several methods. Plasma-arc cutting is divided into:

1. air-plasma method of metal cutting;
2. gas-plasma;
3. laser-plasma cutting method.

The first two types are similar in principle of operation - an electric arc plus an ionized stream of hot gas. The difference is in the working body. In the first case - air, in the second - any gas or water vapor.

According to the method of processing workpieces up to 200 mm thick, combined equipment is used. A modern industrial installation combines heat treatment with a gas jet or the use of a plasma torch. The cutting machines are equipped with a CNC (Computer Numerical Control) module. Carry out cutting of sheet metal along a straight or curved path.

Manual plasma cutting is a classic plasma arc cutting. Portable units (household level) cut ferrous metal using an ionized air jet. Expansion of the range of gases entails a significant complication of equipment and an increase in its cost.

Laser-plasma

It is a combination on one machine. laser cutting used for work with thicknesses up to 6 mm. Larger sheets are processed using plasma arc cutting.

Laser and flame cutting combined on the same CNC machine increases productivity. Allow to form various lines cutting, including cutting holes.

Laser or plasma cutting, combined on one device, significantly saves production space. Plasma-arc cutting is used on dimensional workpieces. Laser - during processing small parts with increased requirements for cutting accuracy.

The fundamental difference between the laser method and the plasma method is the heating source. In a laser, this is a focused light beam. The contact zone is extremely small, so it is possible to obtain a local effect on the part. Due to this, the cutting width is small, the cutting quality is higher than with a plasma torch.

Because of this, plasma cutting of pipes is gradually losing ground where it is required. high accuracy cutting and increased quality is presented to the edge of the product.

Titanium processing

In the space, aviation, medical and other industries, titanium and its alloys are gaining great popularity. The combination of strength, low density - main advantages this substance. But, this metal is chemically active and refractory.

Due to such characteristics, it is difficult to subject it to mechanical and heat treatment. Cutting can not be used - the metal will burn. Hence, the cutting of titanium is well mastered on a plasma torch and by a laser method.

In addition to the usual direct cutting, the plasma-laser method allows you to perform spatial processing of complex geometric shapes, for example, pairing several holes.

An example of plasma cutting of metal using a plasma torch can be seen in the video.

Plasma cutting- a type of plasma processing of materials, in which, as cutting tool instead of a cutter, a plasma jet is used.

(Wikipedia)

Plasma cutting is considered one of the most effective ways rectilinear and figured cutting of metal. Allows you to cut all types of steels, aluminum, copper, cast iron, titanium, sheet and profile rolled products, to carry out the beveling of edges at a certain angle.

Characteristic advantages of the process

Plasma cutting of metal is characterized by the following features:

1. High performance. The cutting speed is 5-10 times higher compared to the gas-oxygen method. It is second only to laser cutting in this parameter.
2. Versatility. It is possible to cut almost any material, it is enough to install optimal parameters process - power and gas pressure.
3. The quality of preparation doesn't really matter - paintwork, dirt or rust on the metal for plasma cutting is not terrible.
4. Improved quality and accuracy. Modern units provide a minimum width of cut, relatively clean without excessive dross on the edges - in most cases they do not need additional machining and even cleaning.
5. A small heat-affected zone helps to minimize the deformation of cut-out blanks as a result of exposure to elevated temperatures.
6. Possibility of curly cutting of complex geometric shapes.
7. Process safety in contrast to oxy-fuel cutting, where cylinders with compressed oxygen and combustible gas are present.
8. Units for plasma cutting of metal are easy to maintain and operate.

What is the process of plasma cutting of metal?

Plasma is a conductive ionized gas of high temperature. A jet is formed in a special device - a plasma torch. It consists of the following main elements:

1. Electrode (cathode) - equipped with an insert made of a material with high thermionic emission (hafnium, zirconium), which burns out during operation and requires replacement when worn out more than 2 mm.
2. Gas flow swirling mechanism.
3. Nozzle - as a rule, isolated from the cathode by a special sleeve.
4. Shroud - Protects internal components from splashes of molten metal and metal dust.

It has 2 wires - an anode (with a positive charge) and a cathode (with a negative charge). The "positive" wire is connected to the rolled metal being cut, the "negative" wire is connected to the electrode.

At the beginning of the process of plasma cutting of metal, a duty arc is ignited between the cathode and the tip, which is blown out of the nozzle, and when it touches the workpiece, it forms a cutting arc.

When the forming channel in the plasma torch is filled with an arc column, plasma-forming gas begins to be supplied to the arc chamber under a pressure of several atmospheres, which is subjected to heating and ionization, which contributes to its increase in volume. This leads to its outflow from the nozzle with high speed(up to 3 km/s), and the temperature of the arc at this moment can reach from 5000 to 30000 °C.

A small hole in the nozzle narrows the arc, which contributes to its directed action at a certain point on the metal, which almost instantly heats up to the melting temperature and is blown out of the cut zone.

After the passage of the plasma torch along a given contour, a workpiece is obtained required sizes and shapes with smooth edges and a minimum amount of scale on them.

Plasma gases for cutting various metals

Both active and inactive gases can be used for plasma cutting of metals. Their choice is made depending on the type of metal and its thickness:

• Nitrogen mixture is intended for copper, aluminum and alloys based on them. The maximum possible thickness is 100 mm. Not applicable for titanium and all steel grades.
• Nitrogen with argon is mainly used for plasma cutting of high-alloy steel grades, the thickness of which does not exceed 50 mm, but the mixture is not recommended for ferrous metals, titanium, copper and aluminum.
• Nitrogen. With its help, cutting of steels with a low carbon content and alloying elements up to 30 mm thick, high-alloyed - up to 75 mm, copper and aluminum - up to 20 mm, brass - up to 90 mm, titanium of unlimited thickness.
• Compressed air. Ideal for air plasma cutting of ferrous metals and copper up to 60 mm thick, as well as aluminum up to 70 mm thick. Not intended for titanium.
• A mixture of argon and hydrogen - cutting alloys based on aluminum and copper, steels with a high content of alloying elements with a thickness of over 100 mm. Not recommended for low carbon, carbon, low alloy steels and titanium.

But it is not enough just to connect a cylinder with the necessary plasma gas, since many specifications equipment:

• power and external (statistical and dynamic) characteristics of the power supply;
• apparatus cyclogram;
• method of mounting the cathode in the plasma torch, as well as the material from which it is made;
• type of design of the cooling mechanism for the plasma torch nozzle.

Plasma cutting tips for non-ferrous and alloy metals:

• When manually cutting high-alloy steel grades, it is recommended to use nitrogen as a plasma gas.
• To ensure stable arc burning during manual cutting of aluminum with an argon-hydrogen mixture, it should contain no more than 20% hydrogen.
• Brass is best cut with nitrogen and nitric mixture, and is also characterized by a higher cutting speed.
• Copper after parting cut in without fail is subjected to cleaning along the cut plane to a depth of 1-1.5 mm. This requirement does not apply to brass.

Plasma cutting applications

Due to its high productivity, versatility and affordable cost, plasma cutting of metals is in great demand in many industries:

• metalworking enterprises and companies;
• aviation, shipbuilding and automotive industry;
• construction industry;
• heavy engineering enterprises;
• metallurgical plants;
• manufacturing of metal structures.

It is simply impossible to list all areas of use - manual devices and automatic machines for plasma cutting of metals can be found almost everywhere. They are used both by large factories for the manufacture of metal structures, and by small firms specializing in artistic forging and processing of parts.

A special place among this equipment is occupied by machines for plasma cutting of metals with CNC - they minimize the human factor, significantly increase productivity. But their main advantage is the reduction in the consumption of rolled metal due to the possibility of creating special programs. Highly qualified technologists develop cutting charts, which are a virtual sheet of metal of certain dimensions, on which they stack workpieces as tightly as possible, taking into account the width of the cut and many other process parameters in order to more rational use rolled metal products.

Subtleties of the metal cutting process

To obtain a high-quality workpiece in the plasma cutting process, it is necessary to maintain a constant distance between the nozzle and the metal being cut - as a rule, within 3-15 mm. Otherwise, it is possible to increase the width of the cut, the heat-affected zone, the mismatch of the workpiece with the specified dimensions.

The current during operation should be minimal for a certain material and thickness. Its overestimated values ​​and, accordingly, the increased consumption of the plasma-forming gas are the cause of accelerated wear of the cathode and the plasma torch nozzle.

The most difficult operation in the process of plasma cutting of metal is punching holes. This is caused by a high probability of double arc formation and breakdown of the plasma torch. Punching is carried out at an increased distance between the cathode and the anode - between the nozzle and the surface of the material should be 20-25 mm. After through punching, the plasma torch is lowered into the working position.

One of the popular types of metal processing is its cutting. There are many ways to get the desired shape from a solid sheet, but in this material we will consider the principle of plasma cutting.

Plasma cutting. In fact - golden mean. The advantages of cutting metal with plasma combine all of the above technologies. The main advantage is that there are no restrictions on the type of material being processed. Except for the thickness.

• aluminum alloys 120 mm
• copper alloys 80 mm
• steel 50 mm
• cast iron 90 mm

The equipment is different - from industrial to household, so that the technology is available to everyone. Let's consider it in more detail.

Plasma cutting of metal - the principle of operation

A two-component medium acts as a cutter:

• An electric arc operating according to the classical scheme is a discharge between the cathode and the anode. Moreover, the material itself can act as an anode if it is a conductor.
• Gas arc. Heating up under the influence of an electric arc (the temperature reaches 25,000º C), the gas is ionized and turns into an electric current conductor.

How plasma cutting works is shown in detail in this video.

As a result, plasma is formed, which is fed under high pressure into the cut zone. This hot gas jet literally evaporates the metal, and only in working area. Despite the fact that the temperature of plasma cutting is measured in tens of thousands of degrees, there is practically no impact on the border zone.

Important! Properly selected speed allows you to get a very narrow cut without damaging the edge of the material.

The source of plasma cutting is a plasma torch.


His task is to ignite the arc, to support operating temperature, and blow out the molten metal from the cut zone. Since plasma cutters are designed to process any hard materials, including dielectrics - the formation of an electric arc is carried out in two ways:


Figure a) shows a direct cutter. Cathode assembly (8) along with fixed cathode (6) are one of the electrodes. The second electrode (anode) is workpiece (4)- a metal with good electrical conductivity.

The power cable of the plasma torch is connected to it. Plasma cutting tip (5) in this scheme, it plays the role of a body. From separated from the cathode insulator (7). The gas is supplied in fitting (1) and forms a plasma jet consisting of electric (2) and gas (3) arc.