SU860357A1 - Plasma generator - Google Patents

Description

(54) PLASMOTUN

one

The invention relates to mechanical engineering, more specifically to devices generating plasma for heating and surface treatment of various products, for the treatment of non-conductive materials, and may find application in mechanical engineering for quenching, annealing, surface treatment and hardening of metal. products, as well as in metallurgy for plasma remelting of metals.

Known electric arc plasma torches are designed to treat metal surfaces with a plasma jet. They contain a cooled cathode assembly, a housing, which is at the same time an insulator and a nozzle assembly with a replaceable insert, in which the plasma jet 1 is formed.

The disadvantage of such plasmatrons is the obtaining of a plasma jet of small geometrical dimensions, which does not allow to treat large surfaces and to obtain high performance when processing extended metallic and nonmetallic surfaces. KpOFvie addition, expire the plasma jet at high speed, which together with

 the spot appearing on the product causes the destruction of the surface, a cutting effect occurs, which requires special measures to reduce the rate of outflow of the stream of yush, and this reduces the thermal efficiency of the plasma torch. Non-metal products such plasma torches can not handle.

A plasma torch is known, which consists of two annular electrodes arranged parallel to each other, a DC solenoid encompassing both electrodes, and a housing. Nlama-forming gas is fed into the gap between the electrodes and heated by a rotating arc. The arc rotates under the influence of electrodynamic forces resulting from the interaction of the arc current and the magnetic field created by the solenoid. Due to the above arc, a large surface 2j is covered.

The disadvantage of such a plasma torch is the difficulty of processing flat and profiled extended surfaces due to the bulkiness of its design, which reduces productivity. In addition, the arc in the plasma torch is located at a considerable distance from the surface to be treated and, as a consequence, the tag efficiency of such a plasma torch is low. Also known is a plasma torch containing an electrode made in the form of a helix with current-carrying end and pitch, measuring 1) Dims according to the law ykx D, where y is the step of the open helix, k is the coefficient of proportionality, X is the distance from the current-carrying end along the helix electrode 3. The disadvantage of this plasmatron is the impossibility of treating it with nonconductive materials. The purpose of the invention is to increase labor productivity in the processing of non-conducting materials. This circuit is achieved by the fact that a plasma torch containing an electrode made in the form of a spiral with a current lead. by the end and the root, varying according to the law, where y is the step of an unclosed spiral, k is the coefficient of proportionality, x is the distance from the current of the feed end along the spiral, an additional electrode is inserted, installed inside the main one and made in the form of an open torus the end, and the non-feed ends of the main and auxiliary electrodes are located at a distance greater than the current lead. The construction of electrodes according to the proposed design allows the fullest use of the ponderomotive forces that act on the arc. the density of forces is equal to, where j is the current density; B - magnetic field intensity. The force F is directed perpendicularly to the current density and magnetic field strength vector. The arc tends to occupy such a position that the value inductance is maximum, for this purpose a cut is made in the electrode as a torus.1 A preliminary calculation of the magnetic field strength showed that if the distance between the electrodes changes according to the law y-x, then the ponderomotive the force acting on the arc from its own magnetic field will be maximum. The arc under the action of this force moves with a maximum speed from the current lead along the electrodes. Experimental verification confirmed the above specified law. The rapid movement of the arc between the electrodes allows one to heat the extended surfaces of the products at high speed without destroying their surface. This arc is equivalent to a distributed heat source. FIG. 1 shows a plasma torch, a common vi cut; in fig. 2 - the same, bottom view. The plasma torch consists of a spiral electrode 1, which is cooled, an electrode 2 7-4 made in the form of an open torus with a break in the place of the current lead, cooled by water. Moreover, the distance between the electrodes varies, since one of the electrodes is molar with a step varying according to the law ai l yk X. Electrodes 1 and 2 are fixed in a housing 3 made of heat-resistant material using fittings 4 and 5. Channels 6 serve to supply plasma-forming gas through fitting 7. Water is supplied to cool the electrodes through fittings 8 and 9. They are also a current lead the ends of the electrodes (the drawing conventionally shows the supply and output of cooling water to the electrodes and the supply of plasma-forming gas). The plasma torch works as follows. Cooling water is supplied to electrodes I and 2, plasma-forming gas (nitrogen, carbon dioxide, etc.) flows through nozzle 7 through channels 6. Electrodes 1 and 2 are connected to the power source through unions 8 and 9, and an oscillator is also connected to the same poles. The gap between the electrodes 1 and 2 is broken, as a result of which an electrical arc arises, which, by the action of ponderomotive forces, moves between the electrodes 1 and 2, starting from the point of the current supply. Thus, in order to maximize the inductance of the circuit, the change in the distance between the electrodes must comply with the law yk, which allows the most complete use of the ponderomotive forces. The resulting electric arc, moving between electrodes 1 and 2, heats the plasma-forming gas, which heats the product. . The arc travels to the end of the helix electrode 1, where it is extinguished with the flow of the plasma clot into the smallest gap between the electrodes 1 and 2 to facilitate re-ignition of the shower. The speed of the arc movement with an alternating current of 200-600 A reaches 100-600 m / s (determined with the help of high-speed filming). Since the oscillator is permanently connected between the electrodes 1 and 2, after the extinction at the end of the electrode 1, the arc reappears at the point of shortest distance between the electrodes and the cycle repeats. Since the length of the electrode is quite long, the arc passes through a relatively large area and heats a significant amount of gas, which heats the surface to be treated in a relatively short time. This allows heating of large, flat surfaces, which increases labor productivity, leads to more uniform heating, which improves the quality of heat treatment.

The plasma torch of the proposed design makes it possible to increase labor productivity in plasma heat treatment of extended non-conductive surfaces by 5–8 times. In addition, the design of the plasmatron is simplified, its dimensions are reduced, uniform heating of the surface to be treated is achieved, and the thermal efficiency is increased. The economic effect from the introduction of this plasma torch will be 35. thousand pyi6. in year.

Claims (3)

1. The UK patent N 1268843, cl. H 05 H 4/10, 1970. 2. Zhukov MF, etc. Electric arc gas heaters. M., Science, 1973, p. 25 3. USSR author's certificate on application no. 2581266 / 25-27, 20.02.78. water fig.Ch Type A QJuz. 2