The introduction of plasma processing in the industry marked a technological breakthrough and a transition to a qualitatively new level of production. The scope of the beneficial properties of plasma is very extensive. First of all, this is the production of electronics and semiconductor devices. Without plasma chemical etching, modern productive personal computers would hardly have seen light. But that is far from all.
Ion-plasma processing is also used in optics and engineering for polishing products, applying protective coatings, diffusion saturation of the surface of metals and alloys, as well as for welding and cutting of sheet steel. In this paper, the main focus is on plasma welding and cutting technologies.
General Provisions
From school physics lessons, everyone knows that a substance can exist in four states: solid, liquid, gas, and also plasma. Most questions arise when trying to imagine the last state. But in reality, everything is not so complicated. Plasma is also a gas, only its molecules, as they say, are ionized (that is, separated from electrons). This state can be achieved in various ways: as a result of exposure to high temperatures, as well as as a result of electron bombardment of gas atoms in a vacuum.
Such a plasma is called low temperature. Such process physics is used in the implementation of plasma spraying (etching, saturation) in a vacuum. By placing plasma particles in a magnetic field, directional motion can be imparted to them. As practice has shown, such processing is more effective in a number of parameters of classical operations in mechanical engineering technology (saturation in powder media, flame cutting, pouring with a paste based on chromium oxide, and so on).
Types of plasma treatment
Currently, plasma is actively used in almost all sectors of industry and the national economy: medicine, mechanical engineering, instrument making, construction, science and so on.
The pioneer in the application of plasma technology was instrumentation. The industrial application of plasma processing began with the use of the properties of ionized gas for spraying all kinds of materials and applying them to the linings, as well as for etching the channels to obtain microcircuits. Depending on some features of the device of technological installations, plasma-chemical etching, ion-chemical, and also ion-beam are distinguished.
The development of plasma is an incredibly valuable contribution to the development of technology and the improvement, without exaggeration, of the quality of life of all mankind. Over time, the scope of gas ions expanded. And today, plasma processing (in one form or another) is used to create materials with special properties (heat resistance, surface hardness, corrosion resistance and so on), for efficient metal cutting, for welding, for polishing surfaces and eliminating microroughnesses.
This list is not limited to the application of technologies based on the effect of plasma on the treated surface. Currently, plasma spraying tools and methods are being actively developed using various materials and processing modes in order to achieve maximum indicators of mechanical and physical properties.
The essence of plasma welding
In contrast to ion-plasma saturation and sputtering plants, in this case, plasma treatment is carried out using high-temperature plasma. The effectiveness of this method is higher than when using traditional welding methods (flame, electric arc, submerged arc welding and so on). As a working gas mixture, as a rule, ordinary atmospheric air under pressure is used. Thus, this technique is characterized by the absence of costs for consumable gases.
Advantages of Plasma Welding
Compared to traditional types of welding, using a plasma welding machine is safer. The reason is quite clear - the use of atmospheric oxygen under pressure as a working gas. Currently, occupational safety is given very close attention by business owners, managers and supervisory authorities.
Another very important advantage is the high quality of the weld (minimum sagging, lack of fusion and other defects). Although in order to learn how to skillfully use a plasma welding machine, it takes many months of practice. Only in this case, the weld and joints as a whole will meet high standards.
This technology has a number of other advantages. Among them: a high speed of the welding process (productivity increases), low energy consumption (electricity), high accuracy of the connection, the absence of deformation and warping.
Plasma cutting equipment
The process itself is very sensitive to the current sources used. Therefore, it is allowed to use only very high quality and reliable transformers, demonstrating the constancy of the output voltage. Step-down transformers are used that convert high input voltage to low output voltage. The cost of such equipment is several times less than the cost of traditional converters for electric arc welding. In addition, they are more economical.
Plasma cutting equipment is easy to use. Therefore, if you have at least minimal experience and skills, you can do all the welding work yourself.
Plasma welding technology
Depending on the supply voltage, plasma welding is divided into microwelding, medium and high current welding. The process itself is based on the effect of a directed flow of a high-temperature plasma on an electron and on welded surfaces. The electrode is melted, resulting in an integral welding joint.
Plasma cutting
Plasma cutting is a process in which a metal is cut into its constituent parts by a directed flow of high-temperature plasma. This technology provides a perfectly even cut line. After the plasma cutter, there is no need for additional processing of the product circuit (whether it is sheet material or pipe products).
The process can be carried out using either a hand torch or using a plasma cutting machine for cutting sheet steel. Plasma is formed when an electric arc is applied to a working gas stream. As a result of significant local heating, ionization occurs (detachment of negatively charged electrons from positively charged atoms).
Scope of plasma cutting
A jet of high temperature plasma has a very high energy. Its temperature is so high that it literally literally vaporizes many metals and alloys. This technology is mainly used for cutting steel sheets, sheets of aluminum, bronze, brass and even titanium. Moreover, the thickness of the sheet can be very different. This will not affect the quality of the cut line - it will be perfectly smooth and even, without sagging.
However, it should be noted that to obtain a high-quality and even cut when working with thick-walled material, it is necessary to use a plasma cutting machine. The power of a hand torch will not be enough for cutting metal with a thickness of 5 to 30 millimeters.
Gas cutting or plasma?
What kind of metal cutting and cutting do you prefer? Which is better: oxygen-gas cutting or plasma cutting technology? The second option, perhaps, is more universal, since it is suitable for almost any material (even prone to oxidation at elevated temperatures). In addition, plasma cutting is carried out using ordinary atmospheric air, which means that it does not require the purchase of expensive consumables. Yes, and the cut line is perfectly flat and does not require further development. All this in combination significantly reduces the cost of the product and makes the products more competitive.
Plasma Cutting Materials
Keep in mind the fact that the maximum allowable thickness of the metal or alloy being processed depends on the material itself or its grade. Based on many years of production and laboratory research experience, experts make the following recommendations on the thickness of the processed materials: cast iron - not more than nine centimeters, steel (regardless of the chemical composition and the presence of alloying elements) - not more than five centimeters, copper and alloys based on it - no more than eight centimeters, aluminum and its alloys - no more than 12 centimeters.
All listed values are typical for manual processing conditions . An example of such a domestic production unit is the Gorynych plasma apparatus. It is much cheaper than foreign counterparts, while it is not inferior, and perhaps even superior in quality. A wide range of devices of this manufacturer is presented on the market, which are designed to perform various tasks (household welding, cutting and welding of metals of various thicknesses inclusive). Thicker sheets can only be machined on high power machine tools.
Existing Plasma Cutting Methods
All existing methods of plasma cutting can be divided into jet and arc. Moreover, it doesn’t matter at all whether a hand torch or a CNC plasma cutting and cutting machine is used. In the first case, all the necessary conditions for gas ionization are implemented in the torch itself. Such an apparatus can process almost any materials (metals and non-metals). In the second case, the material to be processed must have electrical conductivity (otherwise, an electric arc will not occur and gas ionization will occur).
In addition to differences in the method of plasma formation, plasma processing can also be classified according to the technological features of cutting into simple (without the use of auxiliary substances), treatment with water and processing in a protective gas medium. The last two methods can significantly increase the cutting speed and at the same time not be afraid of metal oxidation.