Today it is difficult to imagine heavy industry without the use of welding and cutting metal. At most industrial enterprises engaged in the processing of metal products, a special cutting method is used - plasma.
Plasma cutting is a material processing process in which the plasma jet is the cutting element.
Few people know how to do metal plasma cutting with their own hands and what are the main stages of this process. Most often, the thickness of the processed products is less than 20 cm. It is for cutting metal of such thickness that plasma devices are used.
Characteristics of cutting products using plasma
The scheme of the transformation of gas into a plasma.
Those who use an oxygen cutter to separate the metal know that plasma cutting is very different from this method. Here, instead of cutting gas, a plasma jet is used. As with conventional welding, an electric arc is used for plasma cutting. It ignites directly between the surface of the object and the electrode. The supplied gas then becomes plasma. An interesting fact is that the temperature of the latter can reach several tens of thousands of degrees (from 5 to 30 thousand). At the same time, the jet velocity often reaches 1500 m / s. Plasma cutting of metal is suitable for products up to 20 cm thick. As for the gas supplied to the nozzle, it is of several types: active and inactive.
The first category is oxygen and air mixture, the second is nitrogen, hydrogen, and also some inert gases, for example, argon. The choice of a gas depends on the metal. If it is a black metal, then it is recommended to use active gases. Inactive are more suitable for non-ferrous metals (aluminum, copper) and their alloys. Manual plasma cutting is superficial and separation. The latter is used much more often. You need to know that this method of cutting metal is the most automated. Plasma cutting involves the use of special automatic (programmable) machine tools.Back to table of contents
Positive and negative sides
Plasma cutting parameters.
Plasma cutting has its positive and negative sides. The advantages, firstly, is the possibility of using equipment for cutting any metal. This is achieved due to the increased temperature in the working area. Secondly, an important aspect is the high speed of work. It provides the best productivity. Thirdly, plasma cutting is excellent for cutting products of various geometric shapes. This is not possible with a simple gas method. Fourthly, of great importance is the fact that such cutting of metal is accurate and fast. Here, the probability of obtaining low-quality products is significantly reduced, since the work is automated.
Fifthly, we all know that simple oxygen cutting can be dangerous to people and others. Plasma cutting is the least dangerous. Sixth, such work can be done both outdoors and under water. It is also important that the cost of 1 m of material is much less, because of all this, plasma cutting is increasingly used in large industrial facilities. As for the negative aspects of this process, the equipment is quite expensive, so this technique is rarely used at home.Back to table of contents
Which device to choose
The scheme of assembly and connection of the apparatus for plasma cutting.
Plasma cutting of metal begins with the preparation of equipment. For this you need to choose a quality machine. There are 2 types of equipment: inverter and transformer. Inverters are familiar to many, as with their help welding is carried out. They replaced the transformers. Inverter units have small dimensions, they are compact, aesthetic and consume less energy. When purchasing equipment, you need to pay attention to such characteristics as the duration of work in active mode and power. The disadvantage of this unit is that it is quite sensitive to power surges in the network.
The equipment for cutting by type of transformers is the most reliable and durable. A special feature of transformers is that at high power they can be used for automated cutting. The manual method also applies. If metal cutting is supposed to be carried out in a private workshop or at industrial facilities, then it is more expedient to purchase a transformer-type apparatus. It is also widespread in the manufacture of cars. It must be remembered that any plasma cutting is expensive.
The device will be expensive. An important criterion when choosing equipment is the maximum cutting thickness. For non-ferrous metals (copper) it is always less. If the technical data sheet contains a maximum thickness of 10 mm, then this indicator refers to non-ferrous metals.Back to table of contents
Features of manual arc plasma cutting
The scheme of arc plasma cutting.
For cutting metal products often used manual method. Its peculiarity is that it does not require high qualification to cut the product. Work can be performed by any person, knowing all the main stages of the process. By purchasing a plasma cutter, you can cut not only metal, but also tile, wood and other materials. Plasma cutting by hand begins with the inspection of equipment, nozzles, electrodes. The nozzle and electrodes must be securely fastened. To save materials, it is advisable to ignite the arc as little as possible. In order for the device to start working, it needs to supply compressed air.
For this purpose, you can use cylinders that are filled with air, a compressor, or connect equipment to the central pipeline (if cutting is carried out in an industrial environment). The most reliable devices are equipped with a special regulating device, with which the incoming air is distributed in the device.
The area of optimal modes of air plasma cutting.
The next stage is equipment setup. This requires the correct pick current. It is preferable to start cutting at a high current. At the same time several test cuts are made. Incorrectly selected mode can lead to overheating of the metal and its splashing. At the optimum mode of burning the arc, the cut line should be smooth, and the metal should not be deformed.
If it is necessary to cut the sheet material, the burner nozzle is placed close to the metal surface. To do this, turn on the power button on the device. Soon thereafter, the arc of duty should catch fire, and after it the cutting arc. The arc should be directed at an angle of 90 ° to the metal. The burner moves from top to bottom. If automatic plasma cutting has a high speed, then with the manual method the torch needs to be moved slowly. At the end of the work it is advisable to stop the advancement of the torch briefly to complete the cutting.Back to table of contents
Cutting of various metals
Cutting a metal may have its own characteristics. To date, more often used cutting sheet material. It is usually represented by steel. Often it is necessary to carry out the cutting of aluminum. If the welding of this metal is difficult due to the formation on its surface of a protective film in the form of aluminum oxide, the cutting of aluminum is quite simple. It is important to remember here that it is not necessary to use air and active gases.
Plasma cutting of aluminum is performed using argon or nitrogen.
Argon and nitrogen are chemically less active elements; therefore, in the process of cutting and heating a metal, an oxide film does not form on it. Another common material is steel. In this situation, cutting is carried out without the use of protective gases. Air-arc plasma cutting is great for stainless steel products. This is the most affordable way to cut.Back to table of contents
Plasma jet cutting
The scheme of cutting metal plasma jet.
In contrast to the arc method, when cutting with a plasma jet, the metal does not participate in the formation of an electrical circuit. The arc itself is present, but it is formed directly between the inside of the nozzle and the electrode. Such an electric arc is necessary for plasma to form. This makes it possible to cut materials that do not conduct electrical current. The plasma in this situation is high-speed. Most often, this method is used to separate sheet material. As for the use of electrodes, electrodes based on various tungsten alloys are suitable for plasma cutting.
It must be remembered that for cutting materials using plasma flow, you need to have the necessary tools and materials. They include a cutting machine, a source of electrical current, clothing, shoes, a mask, mittens, a hammer, a chisel, a metal brush. Often, for the implementation of such work apparatus for plasma cutting is done by hand. In power, it can not yield to the factory.Back to table of contents
Observance of precautionary measures
When plasma cutting metal, you must use a protective suit, gloves and shoes.
Plasma cutting is unsafe for humans. When cutting the material on the worker and others may be affected by the following adverse factors:
- heating microclimate;
- ultraviolet radiation;
- exposure to liquid metal;
- increased stress.
The temperature during plasma cutting reaches thousands of degrees. Careless hand cutting can cause severe burns. With an automated process, this risk is reduced. Radiation can cause eye burns, so the employee must use a shield or a protective mask with dark glasses. The shield is less convenient, as it is required to be constantly held in the hand. This limits the amount of movement. To protect the skin from the molten metal used clothing. It includes a protective suit made of flame-resistant material, shoes, mittens.
Safety at the workplace includes equipment inspection for malfunctions. A broken device can not be used. When carrying out cutting, it is not necessary to knock the plasma torch in order to remove the molten splashes, otherwise it may be damaged. Equally important is the test voltage.Back to table of contents
Thus, plasma cutting is very widely used in industry. The plasma cutting machine can be used to separate different materials. In addition, it is suitable for soldering. It can be used for soldering, local annealing, quenching and fire stripping. The metal in this situation is cooled much faster than with simple oxygen cutting.
For the cutting process to be of high quality, you need to purchase a good plasma machine. No need to save money on this. Most cheap devices are disposable, as they quickly become worthless. Welding conditions must be ideal for their normal operation. A very important criterion when choosing a machine is the cutting speed. If you follow all the rules attached, you can even make complex figure cutting.