Main indicators of oxygen cutting mode. Basic information about oxyfuel cutting technology

Technological processes of metal processing by removing chips are carried out with cutting tools in order to give parts specified shapes, sizes and quality of surface layers.

To obtain a surface of a given shape, workpieces and tools are fixed on metalworking machines, the working parts of which communicate to them the movements of the desired trajectory with a set speed and force.

Determination of rational metal cutting mode

Any type of processing such as metal cutting is characterized by a metal cutting mode, which is a combination of the following basic elements: cutting speed, depth of cut and feed.

The cutting mode assigned for processing a workpiece determines the main technological time for its processing and, accordingly, labor productivity. The cutting work turns into heat. 80% of the heat or more is lost with the chips, the rest is distributed between the cutter, the workpiece and the environment. Under the influence of heat, the structure and hardness of the surface layers of the cutter and its cutting ability change, and the properties of the surface layer of the workpiece also change.

Cutting conditions for each case can be calculated using empirical formulas, taking into account the properties of the material being processed, the established standards for the durability of the cutter, its geometry and the applied cooling, as well as taking into account the accuracy parameters of the processed workpiece, the features of the machine equipment and tooling. The assignment of cutting modes begins with determining the maximum permissible cutting depths, then determine valid serve And cutting speed.

Depth of cut - the thickness of the metal layer removed in one pass (the distance between the machined and machined surfaces, measured along the normal).

Cutting speed- the speed of the tool or workpiece in the direction of the main movement, as a result of which the chips are separated from the workpiece, feed - the speed in the direction of the feed movement. In other words, this is the path traveled per minute by a point lying on the machined surface relative to the cutting edge of the cutter. For example, when turning, the cutting speed is the speed of movement of the workpiece relative to the cutting edge of the cutter (peripheral speed).

Once the cutting speed is determined, it is possible to determine rotation speed spindle (rpm).

Based on the calculated cutting force and cutting speed, the power required for cutting is determined.

Depending on the cutting conditions, the chips removed by the cutting tool during the cutting process of the material can be elemental, chipping, draining and fracture.

The nature of chip formation and metal deformation is usually considered for specific cases, depending on the cutting conditions; on the chemical composition and physical and mechanical properties of the metal being processed, the cutting mode, the geometry of the cutting part of the tool, the orientation of its cutting edges relative to the cutting speed vector, the cutting fluid, etc. The deformation of the metal in different chip formation zones is different, and it also covers the surface layer processed part, as a result of which it becomes hardened and internal (residual) stresses arise, which affects the quality of the parts as a whole.

As a result of the transformation of mechanical energy consumed during metal cutting into heat, heat sources arise (in the deformation zones of the cut layer, as well as in the friction zones of tool-chip and tool-workpiece contacts), affecting cutting tool life(working time between regrinds to the established dullness criterion) and the quality of the surface layer of the machined part. Thermal phenomena cause a change in the structure and physical and mechanical properties of both the cut metal layer and the surface layer of the part, as well as the structure and hardness of the surface layers of the cutting tool.

The heat generation process also depends on the cutting conditions. The cutting speed and the machinability of metals by cutting significantly affect the cutting temperature in the contact zone of the chips with the front surface of the cutter. The friction of chips and the workpiece on the surface of the cutting tool, thermal and electrical phenomena during metal cutting cause its wear. The following types of wear are distinguished: adhesive, abrasive-mechanical, abrasive-chemical, diffusion, electrodiffusion. The wear pattern of a metal-cutting tool is one of the main factors that determines the choice of the optimal geometry of its cutting part. When choosing a tool, depending on the material of its cutting part and other cutting conditions, they are guided by one or another wear criterion.

Metal cutting has a significant influence on active cutting fluids, with the correct selection, as well as with the optimal feeding method, the durability of the cutting tool increases, the permissible cutting speed increases, the quality of the surface layer improves and the roughness of machined surfaces decreases, especially parts made of tough, heat-resistant and refractory hard-to-cut steels and alloys.

The efficiency of metal cutting is determined by the establishment of rational cutting conditions that take into account all influencing factors. Increasing labor productivity and reducing metal (chips) losses during metal cutting is associated with the expansion of the use of methods for producing workpieces, the shape and dimensions of which are as close as possible to the finished parts. This ensures a sharp reduction (or complete elimination) of stripping (roughing) operations and leads to a predominance of the share of finishing and finishing operations in the total volume of metal cutting.

Further directions for the development of metal cutting

Further directions for the development of metal cutting include:

• intensification of cutting processes,
• mastering the processing of new materials,
• increasing the accuracy and quality of processing,
• application of hardening processes.

Laser metalworking is a technology in which the material is heated in the processing zone, followed by destruction by a beam stream. This process is used in mass production, as well as in private workshops. The use of laser cutting has made it possible to modernize the production of many parts. It is used for processing almost all types of metal products and can be ordinary, artistic and figured. This diversity makes it possible to make objects of very unusual shapes. For different metal products, appropriate equipment is used, taking into account the characteristics of the material. Thanks to this, products of the required configuration are produced, and defects are eliminated.

Despite the fact that the technology is an expensive process, it is in great demand due to its capabilities. High cutting quality and speed of the procedure are carried out with virtually no waste generation. The metal edges are almost perfectly smooth and do not require additional mechanical processing. This allows us to obtain a finished product that is completely suitable for further use for its intended purpose. The photos below show laser cutting of various metals.

Technology

In special devices for cutting metals with a laser, the main organ is the beam unit. The metal area is destroyed under the influence of high energy flux density. The technology of laser cutting of metal is to use the properties of this beam. It has constant wavelengths as well as frequencies (monochromatic), which ensures its stability. In addition, a small beam can be easily concentrated into a small area.

This is the basis for a metal laser cutting system, the principle of which is to expose the material to a bunch of energy. At the same time, the flow power increases tens of times due to special types of vibrations that cause resonance. The treated area is heated to the melting temperature of the metal product. Over a short period of time, the melting process increases and passes to the main thickness of the object. If the temperature increases significantly, the material may begin to evaporate.

The technology for cutting metal in production is performed using two methods: melting and evaporation. Moreover, the second method is accompanied by increased energy costs, which is not always justified. As the thickness of the material increases, the quality of the cut surface deteriorates. Melting is most widely used when working with metal products.

Cutting equipment

Installations that actively use laser cutting of metal contain several basic elements:

• energy source;
• block of special mirrors (optical cavity);
• working body that creates the radial flow.

The installations themselves are divided according to the power of the working body:

• up to 6 kW – solid-state lasers for metal cutting;
• over 6 and up to 20 kW - gas operating devices;
• from 20 to 100 kW – gas-dynamic type devices.

Solid-state installations use ruby ​​or specially processed glass containing calcium fluorite as an additional component. A powerful impulse of energy is created in a fraction of a second, and the work is carried out both in continuous cutting mode and in intermittent mode.

Gas-fueled metal laser cutting equipment uses an electric current to heat the gas. The composition includes nitrogen, as well as carbon dioxide and helium.

Gas-dynamic devices use carbon dioxide as a base. It heats up and, passing through a narrow nozzle, expands and immediately cools. In this case, a huge amount of thermal energy is released, capable of cutting off metal products of large thickness. High power ensures the highest cutting accuracy with minimal radiation energy consumption.

Devices that perform laser cutting of steel, as well as other metal materials, are among the most advanced and high-tech equipment. Using special machines, high-quality and very accurate cuts are obtained that absolutely do not require additional mechanical processing. These machines have a very high cost and are used in reputable enterprises that perform precision processing of a variety of metal products. Equipment using laser cutting is not intended for use in small private workshops, or for household work.

At the same time, it can be pointed out that this technique is occasionally used to perform engraving and other work that requires minimal error; the accuracy of laser cutting of metal is at the highest level. These machines provide the ability to perform cuts according to pre-specified parameters. After preliminary setup by the operator, the further process switches to automatic mode.

Installations for cutting products of any configuration are capable of cutting out depressions, as well as milling according to specified values. In addition, these universal devices are capable of performing artistic engraving on a wide variety of surfaces. Their cost directly depends on indicators such as functionality, laser power for cutting metal, as well as the manufacturer’s brand.

Machines of this type are equipped with special software that requires prior operator training. Having mastered the course of working on this technique, managing the process itself will not be difficult at all. Installations of this type are sold in specialized stores that work with complex equipment.

Cutting modes

Laser processing of metal products is carried out using special equipment operating in one of three modes:

• evaporation;
• melting;
• combustion.

Evaporation

Laser cutting of metal by evaporation requires high beam intensity. This is necessary to minimize heat loss from conduction. For this purpose, special solid-state installations are used that use a pulsating mode for operation. With this method, the material in the treated area is completely melted, after which it is removed using a special process gas (argon, nitrogen or others). This metalworking mode is used very rarely.

Melting

With this method, the material does not burn out, and the melt is carried away from the processing area by a gas jet. This method is used to work with aluminum and its alloys, as well as copper. This is achieved by creating refractory type alloys with active interaction with oxygen. These metals can only be cut by high power beam flow.

Combustion

This mode uses intense oxidation, which absorbs laser radiation and increases the locality of the treated area. With this method, waste is removed evenly. The combustion mode is divided into controlled and autogenous, in which combustion of the metal surface occurs throughout the entire area of ​​oxygen exposure. This mode does not allow you to get an even cut and people try to avoid it.

These modes of laser cutting of metals are selected according to the parameters of the material and the required processing accuracy. It should be remembered that the quality of the process directly depends on the thickness of the product and the speed of metal processing.

Processed materials

Laser metal processing is used to process aluminum, as well as its numerous alloys, bronze, titanium, stainless steel, copper and other materials. At the same time, aluminum products, titanium, and stainless steel have good reflectivity, which negatively affects the speed of their processing. It is better to treat sheet parts up to 6 mm with a nitrogen unit.

For metal alloys, the cutting quality directly depends on their thickness. Items made of black steel have a maximum processing thickness of 20 mm, stainless steel – 15 mm, copper – 5 mm, and aluminum – 10 mm.

Brass processing is carried out both automatically and manually. There are no special features or difficulties. The machine is self-programming very quickly and allows you to obtain parts of the required configuration.

Advantages of laser cutting

Devices that use special laser cutting of metal make it possible to process objects of almost any thickness. These machines work with both simple metal parts and stainless steel, as well as a variety of aluminum alloys. The absence of direct mechanical contact maintains the shape of the product and does not cause damage or surface deformation. The automated system operates through control programs that provide the ability to perform cutting with the highest precision.

The installations operate not only in automatic mode, but also in manual mode, in which the laser cutting process is performed by the operator himself at high speed. These machines have high functionality and versatility. There is no need for them to use a variety of molds and molds, which significantly reduces costs. High operating speed significantly increases the productivity of the process, in which consumables are used with minimal waste.

The oxygen cutting process is based on the property of metal combustion in a stream of oxygen and the removal of the resulting oxides by this stream.

Before starting this process, you should familiarize yourself with the technique of oxygen cutting.

The cutting process begins with heating the metal to the ignition temperature, the heat of the metal combustion reaction that develops in this case contributes to the further heating of neighboring particles to the ignition temperature, due to which the cutting stream of oxygen continuously penetrates to the entire depth and cuts through it, while part of the metal along the cutting plane turns into metal oxides and blown out with a stream of oxygen.

For a stable cutting process, the following conditions must be met:

1.The combustion temperature of the metal must be lower than the melting temperature of the metal; otherwise, the metal will melt and drain before it has time to burn.

2. The slag formed during cutting, consisting mainly of metal oxides, must be fusible and fluid, and drain under the influence of a stream of cutting oxygen.

3. The heat released by the combustion reaction of the metal must be sufficient to ensure the continuous continuation of the cutting process that has begun.

4. The thermal conductivity of the metal must be low enough to prevent large heat losses from the cutting site for useless heating of the entire mass of metal.

5. The melting point of the metal must be higher than the melting point of the oxides; otherwise, the oxides formed during the cutting process will not be able to separate from the base metal and will not be continuous. These conditions are met by iron (steel), titanium (and its alloys), and manganese.

Cutability of steel and the influence of carbon and alloying elements on oxygen cutting of steels

The ability of metals to undergo oxyfuel cutting depends on how fully the above conditions are satisfied.

Effect of carbon on cutability

Metal	Cutability characteristics
Low carbon steel	Cutability is good at carbon contents up to 0.3%
Medium carbon steel	As the carbon content increases from 0.3% to 0.7%, cutting becomes more difficult
High carbon steel	When the carbon content is above 0.7% to 1%, cutting is difficult and preheating of the steel to a temperature of 300-700°C is required. If the carbon content is more than 1-1.2%, cutting is impossible (without using flux)

Manganese (Mn)- makes cutting easier. Impairs cutting when the content is more than 4%.

Silicon (Si)- steels with a carbon content of up to 0.2% and Si up to 4% are cut well.

Chromium (Cr)- steels with a Cr content of up to 1.5% are cut well, with an increase in the content, cutting becomes difficult, and with a content above 8-10% - oxygen cutting is impossible (oxygen-flux or air-plasma cutting is used here).

Nickel (Ni)- steels with a Ni content of up to 0.7% cut well; if the carbon content in the steel is no more than 0.5%, then it cuts well with a Ni content of up to 4-7%; with a content of more than 34%, cutting deteriorates.

Copper (Cu)- steels with a Cu content of up to 0.7% are cut well.

Molybdenum (Mo)- ordinary molybdenum steels are cut satisfactorily at a content of up to 0.25-0.3%, cutting is not difficult, but the cutting edge is hardened.

Tungsten (W)- steels with a W content of up to 10% are cut well and satisfactorily; with a content of more than 10%, cutting is very difficult.

Sulfur and Phosphorus (S and P)- when these elements are contained within the limits specified by the standards, they do not affect cutting.

Main indicators of oxygen cutting mode:

• flame power
• cutting oxygen pressure
• cutting speed

The power of the flame depends on the metal being cut, the composition and condition of the steel (rolled, forged, casting). When cutting manually, due to the uneven movement of the cutter, the flame power is usually increased by 1.5-2 times compared to machine cutting. When cutting castings, because The surface of the casting is usually covered with molding earth and burnt marks, the flame power increases by 3-4 times.

For cutting steels up to 300 mm thick, a normal flame is used, and for metal thicknesses over 400 mm, it is advisable to use a preheating flame with excess acetylene (carburizing) to increase the length of the torch (in addition to using a higher oxygen pressure) and warming up the lower part of the cut.

The choice of cutting oxygen pressure depends primarily on the thickness of the metal being cut and the purity of the oxygen. At higher pressures, mouthpieces with a larger diameter cutting oxygen channel are used. For each mouthpiece (external and internal) there is an optimal pressure value, when changing in one direction or another, the quality of the cut deteriorates and the cutting speed changes. Accordingly, oxygen consumption may increase by 1 linear. m. For these reasons, you should strictly follow the operating documentation for hand and machine cutters.

The cutting speed must correspond to the rate of oxidation (burning) of the metal across the thickness of the sheet being cut.

At a slower speed, the upper edges of the cut sheet melt and molten oxides (slag, flash) fly out of the cut in the form of a beam of sparks in the direction of the cut.

If the speed is too high, the emission of sparks from the cut is weak and directed in the opposite direction of the cutter's movement. The cut mark on a vertical surface lags significantly behind the vertical. Possible failure to cut through metal.

At optimal cutting speed, the flow of sparks from the back side of the sheet being cut is relatively calm and directed almost parallel to the oxygen stream. The cut mark is only slightly behind the vertical, the roughness of the cut is insignificant and the burr is easily separated from the lower edge of the cut. The cut is smooth.

The article was developed with the support of the site www.pgn.su. This is the official website of NPP PromGrafit, which offers modern sealing materials and thermal insulation of its own domestic production.

When performing separation oxygen cutting, it is necessary to take into account the requirements for cutting accuracy and quality of the cut surface. The preparation of the metal for cutting has a great influence on the quality of the cut and cutting performance. Before cutting begins, the sheets are brought to the workplace and placed on pads so as to ensure unhindered removal of slag from the cutting area. There should be at least 100-150 mm between the floor and the bottom sheet. The metal surface must be cleaned before cutting. In practice, scale, rust, paint and other contaminants are removed from the metal surface by heating the cutting zone with a gas flame, followed by cleaning with a steel brush. The cut parts are marked with a metal ruler, scriber and chalk. Often the sheet to be cut is delivered to the cutter’s workplace already marked.

Before starting oxygen cutting, the gas cutter must set the required gas pressure on the acetylene and oxygen reducers, select the required numbers of the outer and inner nozzles, depending on the type and thickness of the metal being cut.

The process of oxygen cutting begins with heating the metal at the beginning of the cut to the ignition temperature of the metal in oxygen. Then the cutting one is started (continuous oxidation of the metal occurs throughout the entire thickness) and the cutter is moved along the cutting line.

The main parameters of the oxygen cutting mode are: the power of the preheating flame, the pressure of the cutting oxygen and the cutting speed.

Preheating flame power characterized by the consumption of flammable gas per unit time and depends on the thickness of the metal being cut. It should ensure rapid heating of the metal at the beginning of cutting to the ignition temperature and the necessary heating during the cutting process. For cutting metal up to 300 mm thick, a normal flame is used. When cutting thick metal, the best results are obtained when using a flame with an excess of fuel (carburizing flame). In this case, the length of the visible flame (with the oxygen valve closed) must be greater than the thickness of the metal being cut.

Selecting cutting oxygen pressure depends on the thickness of the metal being cut, the size of the cutting nozzle, etc. purity of oxygen. As oxygen pressure increases, its consumption increases.

The purer the oxygen, the lower its consumption per 1 linear. m cut. The absolute value of oxygen pressure depends on the design of the cutter and mouthpieces, the resistance values ​​in the oxygen supply fittings and communications.

Torch speed must correspond to the burning rate of the metal. The stability of the process and the parts being cut depends on the cutting speed. Low speed leads to melting of the cut parts, and high speed leads to the appearance of cut sections that are not completely cut through. The cutting speed depends on the thickness and properties of the cut areas. The cutting speed depends on the thickness and properties of the metal being cut. When cutting thin steels (up to 20 mm), the cutting speed depends on the power of the heating flame. For example, when cutting 5 mm thick steel, about 35% of the heat comes from the preheating flame.

a - cutting speed is low, b - optimal speed, c - speed is high

Figure 1 - Nature of slag release

The speed of oxygen cutting is also influenced by the cutting method (manual or machine), the shape of the cut line (straight or figured) and the type of cutting (blank or finishing). Therefore, permissible cutting speeds are determined experimentally depending on the thickness of the metal, type and cutting method. With the correct cutting speed, the cut line lag should not exceed 10-15% of the thickness of the metal being cut.

Figure 1 schematically shows the nature of slag release from the open pit. If the oxygen cutting speed is low, then a deflection of the spark beam in the cutting direction is observed (Fig. 1, a). When the cutting speed is too high, the spark beam is deflected in the direction opposite to the cutting direction (Fig. 1, c). The speed of movement of the cutter is considered normal if the beam of sparks comes out almost parallel to the oxygen stream (Fig. 1, b).

The width and cleanliness of the cut depend on the cutting method. Machine cutting produces cleaner and smaller cuts than hand cutting. The greater the thickness of the metal being cut, the greater the roughness of the edges and the width of the cut. Depending on the thickness of the metal, the approximate cutting width is:

Oxygen cutting based on the combustion of metal in a stream of technically pure oxygen. When cutting, the metal is heated by a flame that is formed by the combustion of any flammable gas in oxygen. Oxygen that burns heated metal is called cutting oxygen. During the cutting process, a stream of cutting oxygen is supplied to the cutting site separately from the oxygen used to form a combustible mixture to heat the metal. The combustion process of the metal being cut spreads over the entire thickness, the resulting oxides are blown out of the cut site by a stream of cutting oxygen.

The metal to be cut with oxygen must meet the following requirements: the ignition temperature of the metal in oxygen must be lower than its melting point; metal oxides must have a melting point lower than the melting point of the metal itself and have good fluidity; the metal should not have high thermal conductivity. Low carbon steels are easy to cut.

For oxy-fuel cutting, flammable gases and vapors of flammable liquids are suitable, giving a flame temperature during combustion in a mixture with oxygen of at least 1800 degrees. Celsius. The purity of oxygen plays a particularly important role in cutting. For cutting, it is necessary to use oxygen with a purity of 98.5-99.5%. As oxygen purity decreases, cutting performance decreases greatly and oxygen consumption increases. So, when purity decreases from 99.5 to 97.5% (i.e. by 2%), productivity decreases by 31%, and oxygen consumption increases by 68.1%.

Oxygen cutting technology. When separating cutting, the surface of the metal being cut must be cleaned of rust, scale, oil and other contaminants. Separating cutting usually starts from the edge of the sheet. First, the metal is heated with a heating flame, and then a cutting stream of oxygen is released and the cutter is evenly moved along the cut contour. The cutter should be located at such a distance from the metal surface that the metal is heated by the reduction zone of the flame, which is 1.5-2 mm from the core, i.e. the highest temperature point of the preheating flame. For cutting thin sheets (no more than 8-10 mm thick), batch cutting is used. In this case, the sheets are tightly stacked one on top of the other and compressed with clamps; however, significant air gaps between the sheets in the package impair cutting.

On MTP "Crystal" machines, the "Effect-M" cutter is used. A special feature of the cutter is the presence of a fitting for compressed air, which, having passed through the internal cavity of the casing, flows through the annular gap above the mouthpiece and creates a bell-shaped curtain, which localizes the spread of combustion products and protects the structural elements of the machine from overheating.

The parameters of cutting modes for low-carbon steel are shown below in Table 1:

Thickness Nozzle Sleeve Camera Pressure Speed Consumption Consumption2 Width Distance mm mPa mm/min m.cub./hour m.cub./hour 1 2 3 4 5 6 7 8 9 10 5 01 3P 1PB 0,3 650 2,5 0,5 3 4 10 2 0,4 550 3,75 0,52 3,3 5 20 0,45 475 5,25 0,55 3,5 30 3 0,5 380 7 0,58 4 6 40 0,55 340 8 0,6 5 50 0,6 320 9 0,65 60 5P 0,65 300 10 0,7 80 4 0,7 275 12 0,75 100 0,75 225 14 0,85 5,5 8 160 5 0,8 170 18 0,95 6 10 200 6 0,85 150 22 1,1 7,5 12 300 6P 0,9 90 25 1,2 9

1. Thickness of the metal being cut
5. Oxygen pressure
6. Cutting speed
7. Oxygen consumption
8. Propane consumption
9. Cutting width
10. Distance to sheet

Air plasma cutting

The plasma cutting process is based on the use of a direct current direct current air-plasma arc (electrode-cathode, metal being cut - anode). The essence of the process is the local melting and blowing of molten metal to form a cutting cavity when the plasma cutter moves relative to the metal being cut.

To excite the working arc (electrode is the metal being cut), an auxiliary arc between the electrode and the nozzle is ignited using an oscillator - the so-called pilot arc, which is blown out of the nozzle by starting air in the form of a torch 20-40 mm long. The pilot arc current is 25 or 40-60 A, depending on the source of the plasma arc. When the pilot arc torch touches the metal, a cutting arc appears - a working one, and increased air flow is switched on; The pilot arc is automatically switched off.

The use of air plasma cutting, in which compressed air is used as a plasma-forming gas, opens up wide possibilities for cutting low-carbon and alloy steels, as well as non-ferrous metals and their alloys

Advantages of air plasma cutting compared to mechanized oxygen and plasma cutting in inert gases are as follows: simplicity of the cutting process; the use of inexpensive plasma-forming gas - air; high cut cleanliness (when processing carbon and low-alloy steels); reduced degree of deformation; more stable process than cutting in hydrogen-containing mixtures.

Rice. 1 Scheme of connecting the plasma torch to the device.

Rice. 2 Phases of formation of the working arc
a - origin of the pilot arc; b - blowing a pilot arc from the nozzle until it touches the surface of the sheet being cut;
c - the appearance of a working (cutting) arc and penetration of metal through the cut.

Air plasma cutting technology. To ensure a normal process, a rational choice of mode parameters is necessary. The mode parameters are: nozzle diameter, current strength, arc voltage, cutting speed, distance between the nozzle end and the product and air flow. The shape and dimensions of the nozzle channel determine the properties and parameters of the arc. With a decrease in diameter and an increase in channel length, the plasma flow speed, energy concentration in the arc, its voltage and cutting ability increase. The service life of the nozzle and cathode depends on the intensity of their cooling (with water or air), rational energy and technological parameters and the amount of air flow.

When air plasma cutting of steels, the range of cut thicknesses can be divided into two - up to 50 mm and above. In the first range, when process reliability is required at low cutting speeds, the recommended current is 200-250 A. Increasing the current to 300 A and higher leads to an increase in cutting speed by 1.5-2 times. Increasing the current to 400 A does not provide a significant increase in cutting speeds for metal up to 50 mm thick. When cutting metal more than 50 mm thick, a current of 400 A or higher should be used. As the thickness of the metal being cut increases, the cutting speed quickly decreases. Maximum cutting speeds and amperages for various materials and thicknesses performed on a 400 amp installation are shown in the table below.

Air plasma cutting speed depending on metal thickness: table 2

Material to be cut Current strength A Maximum cutting speed (m/mm) of metal depending on its thickness, mm 10 20 30 40 50 60 80 Steel 200 3,6 1,6 1 0,5 0,4 0,2 0,1 300 6 3 1,8 0,9 0,6 0,4 0,2 400 7 3,2 2,1 1,2 0,8 0,7 0,4 Copper 200 1,2 0,5 0,3 0,1 300 3 1,5 0,7 0,5 0,3 400 4,6 2 1 0,7 0,4 0,2 Aluminum 200 4,5 2 1,2 0,8 0,5 300 7,5 3,8 2,6 1,8 1,2 0,8 0,4 400 10,5 5 3,2 2 1,4 1 0,6

Modes. table 3

Material to be cut Thickness, mm Nozzle diameter, mm Current strength, A Air consumption, l/min Voltage, V Cutting speed, m/min Cutting width (average), mm Low carbon steel 1 - 3 0,8 30 10 130 3 - 5 1 - 1,5 3 - 5 1 50 12 110 2 - 3 1,6 - 1,8 5 - 7 1,4 75 - 100 15 1,5 - 2 1,8 - 2 7 - 10 10 120 1 - 1,5 2 - 2,5 6 - 15 3 300 40 - 60 160 - 180 5 - 2,5 3 - 3,5 15 - 25 2,5 - 1,5 3,5 - 4 25 - 40 1,5 - 0,8 4 - 4,5 40 - 60 0,8 - 0,3 4,5 - 5,5 Steel 12Х18Н10Т 5 - 15 250 - 300 140 - 160 5,5 - 2,6 3 10 - 30 160 - 180 2,2 - 1 4 31 - 50 170 - 190 1 - 0,3 5 Copper 10 300 160 - 180 3 20 1,5 3,5 30 0,7 4 40 0,5 4,5 50 0,3 5,5 60 3,5 400 0,4 6,5 Aluminum 5 - 15 2 120 - 200 70 170 - 180 2 - 1 3 30 - 50 3 280 - 300 40 - 50 170 - 190 1,2 - 0,6 7

Modes of air plasma cutting of metals. table 4

Material to be cut Thickness, mm Nozzle diameter, mm Current strength, A Cutting speed, m/min Cutting width (average), mm Steel 1 - 5 1,1 25 - 40 1,5 - 4 1,5 - 2,5 3 - 10 1,3 50 - 60 1,5 - 3 1,8 - 3 7 - 12 1,6 70 - 80 1,5 - 2 1,8 - 2 8 - 25 1,8 85 - 100 1 - 1,5 2 - 2,5 12 - 40 2 110 - 125 5 - 2,5 3 - 3,5 Aluminum 5 - 15 1,3 60 2 -1 3 30 - 50 1,8 100 1,2 - 0,6 7

Rice. 3 Areas of optimal metal cutting conditions for an air-cooled plasma torch (current 40A and 60A)

Rice. 4 Areas of optimal modes for an air-cooled plasma torch (current 90A).

Rice. 5 Dependence of the choice of nozzle diameter on the plasma current.

Rice. 6 Recommended currents for punching holes.

The speed of air plasma cutting, compared to oxygen gas cutting, increases 2-3 times (see Fig. 7).

Rice. 7 Cutting speed of carbon steel depending on metal thickness and arc power.
The flat bottom line is oxy-fuel cutting.

Good cut quality when cutting aluminum using air as a plasma-forming gas can be achieved only for small thicknesses (up to 30 mm) at currents of 200 A. Removing burrs from sheets of large thickness is difficult. Air plasma cutting of aluminum can only be recommended as a separation method when preparing parts that require subsequent mechanical processing. Allowance for processing is allowed at least 3 mm.