Metal cutting with gas and oxygen
Required equipment
In order to use a gas cutter, you need to have at least one propane and oxygen cylinder, hoses designed for high pressure, a cutter. Each cylinder comes complete with a reducer, with which you can adjust the gas flow. The propane tank is reverse-threaded, so it is not possible to use another reducer on it.
There is not much difference between different metal cutters. All have 3 gates:
- one for propane supply;
- the second is for regulating oxygen;
- third. cutting oxygen.
All oxygen valves are blue and for propane they are red. The metal is cut with a jet of flame.
The gas cutter can cut metal with a thickness of up to 300 mm. The device is very easy to repair, since many parts of the device are replaceable.
Types of gas cutting of metal
The technologies of the modern world have made great strides forward. Now anyone can cope with the gas cutting procedure, because it is much easier than gas welding, so almost no skills are required for admission. The main thing to understand is gas cutting technology. and more propane torches are used and require a combination of propane and oxygen to work with them. Such a mixture provides the required temperature, due to which, gas cutting of metal is carried out.
Cutting process
Before starting cutting, you need to remove rust from the metal.
When cutting, the workpiece must be positioned so that the outgoing jet can easily pass through it.
At the very beginning of the procedure, the surface of the material is heated to the temperature of the metal burning. Oxygen and combustible gas are used. After reaching the desired temperature, oxygen is supplied, which will ignite, due to contact with a hot surface, and it is he who will cut.
At this point, it is important to achieve the continuity of the oxygen supply, otherwise, the flame will go out and the surface will quickly cool down, and then it will have to be reheated.
There is a clear correlation in the cutting procedure. the purer the oxygen used, the better the cut quality. And also sometimes a situation arises in which the oxygen jet abruptly cuts into the metal and the cutting power drops, and the curvature of the flow begins. In order to avoid such a situation, you need to slightly tilt the jet.
It is important to understand that the jet has a conical shape and expands closer to the bottom. Because of this, the width of cut increases as the end of the cut is approached and dross forms.
You can correct the situation by increasing the power of the cutter, but do not get carried away too much, if you overdo it, then dross will appear on the upper part of the metal.
The quality of the cut is strongly influenced by the oxygen pressure. High pressure inevitably leads to a bad cut, and the oxygen consumption becomes enormous. Low pressure will not allow cutting through the metal and it will be difficult to remove oxidation. Therefore, it is necessary to observe the average indicators, which are individual for each metal, and regulate the oxygen supply from the oxygen cylinder.
Pros and cons of flame cutting
This cutting method has many advantages:
- Flame cutting allows you to cut thick material. And also with the help of it, you can make a neat cut along the stencil. It is simply impossible to achieve the accuracy of the work when using an angle grinder, and if it becomes necessary to cut a hole to a certain depth, then only gas cutting will cope with this.
- Flame cutting requires a torch that is light and lightweight. This allows you to achieve comfort during work, and if you compare the cutter with gasoline counterparts, the difference is enormous. Gasoline cutters make a lot of noise, they are difficult to make accurate cuts due to their heavy weight, and strong vibrations force the operator to apply force when cutting. Oxygen pressure saves energy.
- Gas cutting allows you to speed up the cutting process by almost 2 times when comparing the results shown by gasoline counterparts.
- The cut accuracy is worse than that of an acetylene cutter, but much better than that of a gasoline and angle grinder.
- Propane is a very cheap gas. Its use is beneficial in cases where a large amount of work is required.
Alas, there are also disadvantages, however, there are much fewer of them, or to be more precise, one is a limited range of metals that can be cut.
For example, flame cutting of metal with propane and oxygen cannot cut steel with high carbon content. Therefore, the use of this type of cutting is justified only for low and medium carbon steel.
This limitation arises due to the fact that the melting point of high-carbon steels is equal to the burning temperature of the torch, therefore, when cutting, the material melts and does not allow oxygen to get inside.
Hence the rule: for successful cutting, the burning temperature of the cut metal must be less than its melting temperature.
Special moments in cutting
Metal cutting technology says that there is no need to rush to open the valve of the propane cutter, because in this case, you expose yourself to the danger that can arise from the interaction of oxygen with a heated metal. To exclude a back blow of the flame, it is required to remove the oxygen stream, strictly following the angle of inclination of the burner.
At first, it is equal to 90 degrees, after which a small deviation is made, by about 6 degrees, in the opposite direction to the movement. If you are cutting thick metal, then the deviation can increase up to 70 degrees.
It is important to remember that the cutting process for metal must occur at the same speed, which is selected by the visual method, for example, you can estimate the speed of spark spread.
At optimum speed, sparks are emitted at a 90 degree angle. If the sparks are flying in a direction other than the direction of travel of the torch, the cutting speed is very slow. Informs about high speed if the angle of emission of sparks is less than 80 degrees.
The thickness of the metal plays an important role, because if the thickness of the metal is quite large, then it is impossible to monotonously move the cutter until the moment when the sheet is cut across the entire thickness. Towards the end of the cut, an increase in the angle of inclination by about 15 degrees is required.
During the procedure, there should be no prolonged pauses. If the work was still stopped at some point, then the cutting should be started from the very beginning and a new starting point should be chosen.
The end of the cut must be followed by the following actions, in this order:
- stopping the supply of cutting oxygen;
- stopping the supply of regulating oxygen;
- propane shutdown.
How is cutting done?
Cutting is performed with simultaneous heating. For this very purpose, the torch tip has 3 nozzles. The lateral ones are used to supply the heating mixture, and the thinnest nozzle is located in the center, through which oxygen is supplied under very high pressure.
If we talk about pressure, then it can reach 12 atmospheres, this power is enough for a person who puts his hand under the stream of air to damage his skin. When this jet is ignited, metal structures are cut.
With this cutting method, a flux is formed, which is scattered by the flame to the sides, and if through cutting is performed, then it is burned through the entire thickness of the material. This makes cutting metal much better than electric cutting. After all, the resulting seam is very neat.
If we go back to metals, the melting point of which is below 600 degrees Celsius, then cutting them will not work due to the removal of the upper layer of metal, which will be repeated until the very end of cutting. In order to still carry out cutting, it is required to use mobile heaters. These are small canisters of compressed gas with a nozzle.
Safety engineering
You need to understand that cutting metal with gas is a process that even a beginner can master, but this process does not become less dangerous. Therefore, training can only be carried out under the supervision of an experienced specialist.
To carry out work on cutting metal, you should adhere to the following safety precautions:
- Good ventilation must be provided in the work area.
- Remove all hot substances within 5 meters of the cutting site.
- Work can only be carried out in special clothing: protective mask, fireproof clothing.
- Do not direct the flame towards the gas source. Its direction should be diametrically opposite.
- During the operation of the cutter, it is forbidden to step on the hoses, wiggle them, physically influence them in every possible way.
- During a break, you need to extinguish the flame at the torch, tighten the valves on the gas cylinders.
Effective and safe cutting can only be achieved by following all these rules, which are difficult only at first glance.
Advantages and disadvantages of oxy-fuel cutting
Oxy-fuel cutting of metal has the following advantages: the ability to cut thick sheets and products; the possibility of surface treatment of the material; speed of work.
The disadvantages of this method include:
- the inability to use metals that melt at temperatures below 600 degrees Celsius;
- not the safety of the method, since an explosion of the gas-air mixture is possible;
- not always good cut quality;
- impossibility of cutting along curved contours of a small radius;
- high thermal effect on metal.
Gas consumption when cutting metal
Gas consumption to cutting volumes depends primarily on the selected method of carrying out the operation. For example, air arc efficient metal cutting involves more gas use than oxygen flux metal cutting. Also, the consumption depends on the following parameters:
- the experience of the welder, the beginner will spend more volume per meter than the master;
- integrity and technological parameters of the equipment used;
- the grade of the metal with which to work, and its thickness;
- width and depth of the cut.
Below is a table if propane is used for cutting metal:
How to prepare the surface before cutting
Before cutting metal with oxygen, it is necessary to clean the surface from corrosion, dirt, oil stains and scales. If you are cutting by hand, you just need to clean the cutting area with a plasma cutter. If the process is mechanized, then the sheets are straightened on rolling machines, and cleaned using chemical or shot blasting.
Oxy-fuel cutting of metal. technology, types, conditions, process
The essence of the process lies in the combustion of metal in a jet of chemically pure oxygen, followed by the removal of oxidation products from the cutting zone by this jet (by blowing out).
Features of oxygen pipe cutting
The manual method of oxygen cutting is used to process the ends of the pipeline before welding, to remove defects. The operation can be performed in any spatial position. For its implementation, plug-in and universal cutters are used. Mode setting depends on the thickness of the workpiece.
Before igniting the cutter
Make sure the hardware is working properly and check:
a) tightness of connection of hoses, all detachable and soldered joints;
Preparation for cutting metal
All metal supplied for hand cutting must be thoroughly cleaned of scale, rust, paint, oils, grease and other contaminants that can lead to a decrease in cutting speed and deterioration in the quality of edge processing.
Under the influence of the flame, some contaminants burn out, forming gaseous products that are sucked into the cutting zone, mix with oxygen and worsen the conditions for metal combustion. Contamination on the lower edge of the cut is heated to high temperatures and contributes to the adhesion of slag.
Oxygen cutting of medium thick steel
Installations for automatic welding of longitudinal seams of shells. in stock! High performance, convenience, ease of use and reliability in operation.
Welding screens and protective shutters. in stock! Protection against radiation during welding and cutting. Big choice. Delivery all over Russia!
In oxygen separation cutting of steel, in accordance with the technological features, the cutting of metal of small thicknesses (up to 5 mm), medium thicknesses (5-300 mm) and large thicknesses (over 300 mm) is distinguished. This division is rather arbitrary, however, for each range of cut thicknesses, there are general patterns.
The most important technological parameters of oxygen cutting are cutting oxygen consumption, heating flame power, cutting speed.
Metal cutting with an oxygen lance.
For calculating the consumption of cutting oxygen, the following formula can be recommended, obtained on the basis of the results of processing data from VNIIavtogenmash and foreign firms,
where Vcr. consumption of “cutting” oxygen, m 3 / s; k2 is a coefficient that takes into account the state of the metal before cutting (k2 = 0.3. for rolled products; k2 = 0.6. for casting and forgings with a thickness of 0.3 to 0.6 m), kp, kp, km. see table 26.1.
The heating flame heats the surface layers of the metal to the ignition temperature at the beginning of cutting, and in the process of cutting. the front surface of the metal. The power of the heating flame will increase with an increase in the thickness of the cut metal, the distance between the end of the torch and the metal. When cutting contaminated metal, the flame power must be increased. The power of the flame is determined by the consumption of combustible gas, its type and the ratio of the consumption of combustible gas and heating oxygen. Oxy-fuel cutting uses gaseous and liquid hydrocarbons as fuel. When these fuels are burned in a mixture with oxygen, a high-temperature flame is formed.
Table 26.2 provides information on the basic properties of combustible gases.
The consumption of combustible gas and heating oxygen during cutting can be determined from the following dependencies:
where VR.r is the consumption of combustible gas, m 3 / s; Vc.p. heating oxygen consumption, m 3 / s; δ is the thickness of the metal being cut, m. The values of the coefficients included in the above equations for different cutting conditions are given in table. 26.1 and 26.2. The consumption of iron powder (qf, kg / s) when cutting high-alloy steels is determined by the formula:
At a given gas flow rate, the cutting speed decreases exponentially with an increase in the thickness of the cut metal, since the dynamic effect of the jet on the melt sharply decreases with distance from the nozzle exit. The cutting speed increases with an increase in the heating temperature of the metal due to an increase in the thickness of the liquid layer of the metal in the section, oxygen purity and oxygen pressure in front of the nozzle. An increase in the pressure of the “cutting” oxygen in front of the nozzle promotes an increase in its flow rate and its dynamic effect on the oxidized metal. The largest increase in the oxygen flow rate (up to 90%) is observed in the pressure range at the nozzle inlet from 98 to 2940 kPa, a further increase in the oxygen pressure in front of the nozzle from 2940 to 9800 kPa makes it possible to increase the oxygen flow rate by only 8%.
Based on the generalization of the experimental data, the following dependence was obtained to determine the cutting speed:
where v is the cutting speed, m / s; δ. thickness of the cut metal, m; kд. coefficient of cutting speed, depending on the pressure of the “cutting” oxygen,
where рk. pressure of “cutting” oxygen, kPa; kch. coefficient of cutting speed, depending on the purity of oxygen,
where ε. oxygen purity,%; kt, km, kp are selected in accordance with table 26.1.
Lower cutting speeds are selected for precise cutting of shaped parts, the highest for rectilinear separation oxygen cutting of metal into scrap (table, 26.3).
Volchenko V.N. “Welding and materials to be welded”.
Necessary equipment
The very first cutter was the P1-01 device, it was designed back in the USSR, then more modernized models appeared. P2 and P3. The devices differ in the size of the nozzles and the power of the reducer. modern manual settings:
They differ in a set of additional functions and performance.
Quicky-E can carry out shaped cutting according to the given drawings, the speed of work reaches 1000 mm per minute, the maximum allowable metal thickness is up to 100 mm. The device has a set of removable nozzles for processing metal sheets or pipes of various thicknesses.
This apparatus can operate using various types of combustible gas, in contrast to the prototype P1-01, which only runs on acetylene.
Secator handheld cutter has improved performance compared to peers.
With its help, you can process metal up to 300 mm thick, this is provided by additional nozzles included in the kit, they are removable and can be purchased additionally, as they wear out. Secator can do the following types of cutting:
The speed can be adjusted from 100 to 1200 mm per minute, and the built-in freewheel ensures smooth movement of the machine on the sheet of metal. Air-cooled gearbox for cleaner operation and reduced fuel consumption.
The above models are manual, that is, they are compact, controlled by the hands of a master. But for large volumes of processed metal, work with such
installations are inconvenient and ineffective. For industrial production, stationary cutting units are used. this is, in fact, the same technology.
They represent a machine with a table top in which the cutting mechanism is built. It is powered by an electric
a compressor that requires a mains supply with at least 380 V and three-phase sockets. The technology of operation of models of stationary cutting units is nothing, but different from manual ones. The only difference is in performance, maximum heating temperature, and the ability to process metal with a thickness of more than 300 mm.
Cutting process
With the correct choice of the speed of movement of the torch, a stream of sparks and slag flies out of the cut straight down, while the edges are clean, there are no smudges and fusion.
If in the process of performing work your oxygen hose breaks, do not panic. Close the propane supply and then both cylinders. The flame that has disappeared during the adjustment process must be re-ignited, having previously closed the cutter valves.
How to properly use an oxygen acetylene torch for cutting
To work, you must have
All parts of the gas equipment are standard and can be replaced in the event of a breakdown.
Oxygen and propane consumption when cutting metal
When it becomes necessary to work with thick metal, a gas cutter is used. It cuts the sheet metal using a hot flame jet. It is formed due to the mixing of two gases. propane and oxygen.
It is impossible to cut high-carbon metals, copper and its alloys, aluminum with an oxygen-propane cutter. The range of influencing materials is limited to low-carbon steels of grade 08 to 20G in accordance with GOST (1050-60) and medium-carbon steels. from 30 to 50G2 (GOST 1050-60).
Propane cutter cuts metal no more than 300 mm thick.
Metal cutting technologies
Today, the industry uses three typical technologies for thermal separation of metal blanks:
- Oxygen cutting.
- Plasma cutting.
- Laser cutting.
The first technology, oxyfuel cutting, is used to separate carbon and low alloy steel workpieces. In addition, the oxygen cutter can trim the edges of already cut workpieces, prepare the seam zone before welding and “clean up” the surface of the cast part. The flow rate of working gases, in this case, is determined by the consumption of both fuel (combustible gas) and oxidizer (oxygen).
The second technology. plasma cutting. is used for the separation of all types of steels (from structural to high-alloyed), non-ferrous metals and their alloys. There are no unavailable materials for a plasma cutter. it cuts even the most refractory metals.
The third technology. laser cutting. is used to separate thin-sheet workpieces. Accordingly, the volumes of consumed gases, in this case, will be significantly less than that of oxygen and plasma cutting, which are designed to work with large, thick-walled workpieces.
Safety engineering
It is better to entrust the implementation of metal cutting using a gas installation to an experienced specialist, since if carelessly handled, the consequences can be quite sad.
Safety precautions assume the following conditions are met:
Observance of these simple conditions will ensure safe and efficient work on metal cutting with a gas installation.
Oxygen and propane consumption for metal cutting
Therefore, we will begin our article with a description of the cutting methods.
Gas consumption when cutting metal
Gas consumption to cutting volumes depends primarily on the selected method of carrying out the operation. For example, air arc efficient metal cutting involves more gas use than oxygen flux metal cutting. Also, the consumption depends on the following parameters:
- the experience of the welder, the beginner will spend more volume per meter than the master;
- integrity and technological parameters of the equipment used;
- the grade of the metal with which to work, and its thickness;
- width and depth of the cut.
Below is a table if propane is used for cutting metal:
Types of metal cutting with gas
For example, if it is possible to connect to the network, then oxygen-electric arc cutting can be used, or when working with low-carbon steels, it is better to use an air-gas mixture with propane. The following methods are most in demand in practice:
- Propane cutting. Cutting metal with propane and oxygen is one of the most popular ways to work, but it has some limitations. The operation is feasible for titanium alloys, low carbon and low alloy steels. If the carbon or alloying component in the material exceeds 1%, it is necessary to look for other methods of oxygen efficient metal cutting. This method involves the use of other gases: methane, acetylene, propane and some others.
- Air arc cutting. Oxygen arc cutting is a very effective method. The metal is melted with an electric arc, and the air jet removes the residues. Oxygen-electric arc cutting involves the flow of gas directly along the electrode. The disadvantage of this method is shallow cuts. But their width when performing work with oxygen-electric arc welding can be any.
Oxygen-flux cutting. A feature of oxygen-flux metal cutting is the supply of an additional component to the working area. It is a flux in powder form. This component makes the material more pliable during oxy-flux metal cutting. The method is used to cut materials that form carbide oxides. Using the method of oxygen-flux metal cutting allows you to create an additional thermal effect.
In this way, the cutting jet performs the operation efficiently. Oxygen flux metal cutting is applicable for cast iron, alloy steel, aluminum, copper and copper alloys, slagged metals and reinforced concrete.
Gas cutting technology
In this article you will learn about the features of gas cutting of metal, the advantages and disadvantages of this method, the principle of operation of the equipment and its types.
Today, flame cutting is the most popular method due to the absence of strict requirements for the place of work and the ease of performing operations. In this article, you will learn about the features of the technology, the advantages and disadvantages of this method, the principle of operation of the equipment and its types.
how to cut with a torch. oxygen acetylene welding cutting torch
Gas cutting of metal is a technology that is widely used today, since it involves simplicity of performing the operation, does not require additional energy sources and sophisticated equipment.
This method is used by specialists in repair, construction and agricultural work. Almost all devices designed for cutting metal with gas are mobile, easy to transport and use elsewhere.
Gas cutting technology
The essence of the oxygen cutting process is as follows. The heater heats up the metal to an average temperature of 1100 degrees C. Then a stream of oxygen is supplied to the working area. The stream, in contact with a heated metal, ignites.
The burning jet easily cuts the metal sheet, provided there is a constant and stable gas supply.
For metal, the combustion temperature should be lower than the melting temperature. Otherwise, melted but not burnt masses are difficult to remove from the working area.
Thus, the cutting operation is performed by burning the material in the gas jet. The main module of the flame cutting tool is the torch. It provides accurate dosage of mixing gases or vapors of liquid fuel with oxygen masses into the gas-air mixture.
Also, the cutter provides ignition of the resulting mixture, and a separate supply of oxygen to the workplace.
Gas cutting refers to the thermal methods of metal processing. Its advantages are that you can work with material of any thickness, and with high productivity. The daily output of a welder can be measured in tons.
Experts note the advantages of this technology in that gas-plasma cutting is completely autonomous and does not depend on the presence / absence of power sources. Since the welder often has to work in the field or does not have the ability to connect to a power source at a specific object.
Oxy-fuel hand cutting is available for a wide range of materials, excluding brass, stainless steel, copper and aluminum.
Advantages and disadvantages of technology
- the ability to cut sheets and products of considerable thickness;
- the cut can be performed of any degree of complexity;
- the possibility of surface treatment of the material;
- the optimal ratio of the cost of work and its quality;
- fast enough way and versatile.
if a specialist has little work experience, he should not undertake precise operations, since skills and knowledge are needed to complete;
- the method is not safe, since an explosion of the gas-air mixture is possible;
- a significant area is exposed to thermal effects;
- low cutting accuracy.
Deformation of the material when cutting with gas
Since cutting metal with gas involves thermal action on the material, deformation is a natural consequence of the operation. Uneven heating and cooling can measure the shape of the workpiece. But there are several ways to eliminate this defect:
- use of tempering or roasting;
- straightening of sheet steel on rollers, after which the material becomes more stable;
- to avoid warping, you can fix the product before the operation;
- perform the operation at the maximum permissible speed and others.
Throttle kickback
There are also risks of significant damage to the health of the welder and other people in the vicinity. An effective solution to these dangers would be to install a valve.
You can look at some more features of cutting metal with gas at
If you have information on this topic, interesting facts or tips for using this technology, we invite you to share them in the Комментарии и мнения владельцев block.