Electric arc treatment of parts

Abstract: A part being treated, e.g. cleaned, and one or more electrodes are connected to a power supply and an arc discharge is initiated at a pressure below 10 Pa between the part and the electrode(s) in the mode of a drooping portion of the voltage-ampere characteristic of the arc or using a power supply charging a drooping external volt-ampere characteristic. In one precedure, during arcing, a difference of potentials of electric field approximately equal to zero is created on the treatment zone of the part and/or on the working surface of the electrode(s) and the area of movement of the arc plasma is limited to the said zone and/or the said working surface. In another procedure, a difference of potentials other than zero is created, areas with the highest and/or lowest potential being moved along the treatment zone and/or working surface, and the area of movement of the arc plasma being limited to the treatment zone and/or working surface. In another procedure the region of the arc discharge in the space between the part and the electrode(s) is positively compressed or partly restricted, and the said region and the part are moved relative to each other according to a predetermined program.

Description: The invention relates to the electric arc treatment of parts, and more specifically, it deals with method and apparatuses for electric arc treatement of parts. There is now a problem of high-grade treatment of parts before deposition of coatings. Existing processes for preparation of parts before deposition of coatings basically involved chemical and mechanical treatment which are labour-consuming and low-productive. In addition such methods cause pollution of the environment. Other treatment methods have recently emerged. Known in the art is a method for treating parts (SU-A-322420) wherein a part to be treated is placed between two electrodes in a vacuum chamber, and a glowing discharge is initiated between the electrodes. The product is subjected to ion bombardment in the glowing discharge so that its surface is cleaned and activated. A similar process is disclosed in US-A-4 534 921 for cleaning by ion bombardment in order to remove plastic residue and surface contaminants from parts and polish their surfaces. The process is characterised by uniform cleaning of the part surface, but its productivity is rather inadequate because of a low rate of atomization of materials in the glowing discharge. In addition, this technique is not capable of ensuring removal of fine burs. Known in the art is a method for electric arc cleaning of the surface of metal parts and an apparatus for carrying out this method (SU-A-935141, B 08 B), wherein the surface of a metal part placed into a chamber is acted upon by an arc discharge under a gas pressure of 10² to 10⁴ Pa. The surface being cleaned is exposed to the arc discharge in a pulsed mode, with a pulse rate of 10 to 100 Hz and with an energy of individual pulses of 0.5 to 60 J. The use of a pulsed arc discharge for cleaning allows temperature on the surface of the part being cleaned to be controlled by varying pulse rate and energy of individual pulses so as to intensify the cleaning process. This method of electric arc cleaning cannot bring shout uniform treatment of a part over the entire surface area because of difficulties in controlling position of electrode spots of the pulsed discharge within a predetermined area of the surface. This results in noncleaned portions and nonuniform heating of the part. Sophisticated devices should be used to carry out this method. Known in the art is a method for electric arc treatment, preferably, for cleaning parts, e.g., inner surface of pipes (SU-A-952388, B08B), comprising connecting a part and an electrode to a power supply and initiating an arc discharge between the part being treated and the electrode under a pressure of a medium of 100 to 500 Pa. The electrode is then caused to move with respect to the part so as to move plasma of the arc discharge along the surface of the part being treated which functions as a cathode. This method is carried out by means of an apparatus having an electrode mounted on a holder and connected, by means of a current supply member, to one lead of the power supply having a second lead which is connected to the pipe being treated, an arc excitation system, a mechanism for reciprocating the electrode, and a system for sealing and evacuating the interior space of the pipe being treated. However, with these method and apparatus in use, a medium pressure in the treatment zone should be at least 100 Pa, and the residual gas reacts with the surface of the part being treated heated by the arc discharge. This results in the treated portions of the surface, which are already cleaned, being oxidized. From the physical point of view, mobile electrode spots are not formed under such pressure, and a volumetric discharge develops so that a major part of power released in the discharge is spent for heating of the part and electrode. As a result, only a minor part of power released in the arc is used for producing useful result, i.e., cleaning of the part surface. The formation of a volumetric discharge results in plasma acting upon parts of the apparatus which are in contact with the plasma, in particular, upon the electrode holder and the system for sealing the interior of the pipe so that their service life is shortened. Since density of energy released on the part under such pressure is low, only thin (several µm) oxide films can be removed from the part surface, and thicker (deeper) oxide layers and scale cannot be removed by using this method. For carrying out the prior art method, it is necessary, in any case, to have a sophisticated apparatus having movable electrodes which is not justified in many applications, especially if simple parts of finite dimensions are to be treated. We have discussed disadvantages of known methods and apparatus designed, preferably for electric arc cleaning of parts. Known techniques in such fields of electric arc vacuum treatment as heating, welding, cutting, etc. also have similar disadvantages, and their discussion is not given here. Disclosure of the Invention The invention is based on the problem of providing a method for electric arc treatment of parts in which, owing to the choice of process steps ensuring a predetermined distribution of plasma over the surface of parts, the desired quality of treatment of parts, high productivity, and ecological safety of the process can be achieved. Another problem is to provide an apparatus for carrying out this method and also to provide an optimum construction of components of the apparatus so as to achieve advantages of the invention in the best possible manner. The present invention provides a method for electric arc treatment of a part comprising connecting the part and at least one electrode to a power supply, and initiating an arc discharge between the part and the at least one electrode in a medium below atmospheric pressure, with the formation of plasma moving at least along the cathode, characterised in that: (a) the pressure of the said medium is below 10 Pa; (b) the arc discharge is initiated in the mode of a drooping portion of the volt-ampere characteristic of the arc or/and a power supply with a drooping external volt-ampere characteristic is used; (c1) a difference of potentials of electric field equal to or approximately equal to zero is created at least on the surface to be treated of the part and/or on the working surface of the at least one electrode, or (c2) a difference of potentials of electric field other than zero is created on the surface to be treated of the part or/and on the working surface of the at least one electrode, areas with the highest or/and lowest potential being moved along the said surface to be treated and/or the said working surface, or (c3) the region of the arc discharge in the space between the part and the at least one electrode is positively compressed or partly restricted, the said region and the part being moved relative to each other in accordance with a predetermined program; and (d) the area of movement of plasma of the arc is limited to the surface to be treated of the part and/or the working surface of the at least one electrode. If a medium pressure is below 10 Pa, the electrode spots of the arc, in the first mode of operation (c1) of the method, can spontaneously move over the surface of the part and electrode and, if an arc is initiated in the mode of a drooping portion of the volt-ampere characteristic or, which is the same, if a power supply with a drooping external volt-ampere characteristic is used, mobility of the electrode spots substantially increases as shown by tests. If a difference of potentials of electric field equal, or close to zero is created on the surface of the treatment zone of the part and/or on the working surface of the electrode, the electrode spots of the arc will most likely occur in all areas of respective surfaces. Therefore, if the area of movement of the electrode spots is limited to said surfaces, a sufficiently uniform treatment, in particular, cleaning of parts with the arc can be achieved with minimum erosion of the electrode. It should be noted that, owing to low pressure of a medium, oxidation of the treated surface of the part is eliminated. If a part of finite dimensions is treated, no movement of the part is required during the entire treatment process. In the second mode of operation (c2) of the method, the electrode spots of the arc move to follow up the areas of extremum values of potential so as to ensure treatment of the part in accordance with a preset program. It is preferred that the difference of potentials of electric field be created by supplying electric current to areas of the part or/and electrode remote from the zone of location of the electrode spots of the arc, the areas of the highest or/and lowest potential of electric field being moved by varying position of current supply zones on the part or/and on the electrode This method does not call for additional energy expenditures for moving the electrode spots with respect to a part. In treating elongated parts, e.g., rolled stock, it is preferred that the part be moved with respect to at least one electrode, or/and at least one electrode be moved with respect to the part. This movement allows the whole surface of such parts to be uniformly treated. In the third mode of operation (c3) of the method, the electrode spots of the arc move along the part surface to follow the area of the arc discharge so as to achieve the desired treatment of the part. The electrode spots of the arc are shifted along the part towards the current supply zone but, since their movement is limited, they are concentrated at the boundary of the area to which the arc discharge is limited and, during the relative movement of the part being treated and this area to which the arc discharge is limited, the desired treatment of the desired surface of the part with these spots is achieved. It is preferred that, in the case where there are at least two electrodes, the value of electric current be decreased or electric current be interrupted in accordance with a preset program in the circuit of at least one electrode, the current in the circuit of the other electrode or electrodes remaining unchange or being increased. A change in direction of electric field which will thus occur in the discharge gap is capable of ensuring a respective directional movement of the electrode spots along the part without using movable electrodes so as to ensure treatment of the part in accordance with a preset program. The part being treated may be connected to either negative or positive terminal of the power supply. The former case is most preferable for cleaning, descaling, deburring, and vaporization of the material of a part, and the latter case is most suitable for polishing, heating, welding, and cutting of parts. It is preferred that, during the electric arc cleaning, the value of arc current and treatment time be such that the specific energy consumption be within the range from 0.1 to 0.8 kW-h/m² µm. These conditions can ensure complete removal of scale from the surface being cleaned without an appreciable erosion of the part being treated and with a high enough productivity of the process. The above problem is also solved by the fact that an apparatus for carrying out the method for electric arc treatment of parts, comprising at least one electrode mounted on a holder and connected by means of a current supply member to one lead of a power supply having the other lead connected to a part being treated, and an arc excitation system, according to the invention, is provided with at least one means electrically connected to the power supply for creating, during arcing, a difference of potentials of electric field equal, or close to zero, on the surface of the treatment zone of the part and/or on the working surface of at least one electrode and with a means for limiting movement of plasma of the arc discharge to the treatment zone of the part and/or to the working surface of at least one electrode. The provision of said means for creating a difference of potential of electric field equal, or close to zero and the means for limiting movement of plasma of the arc in the apparatus according to the invention ensures substantially identical probability of occurrence of the electrode spots in all areas of the treatment zone of the part and/or the working surface of the electrode and rules out movement of such spots to other areas of the surface of the part and/or electrode, whereby a sufficiently uniform treatment of the selected zone of the part with the arc is ensured with minimum erosion of the electrode. The means for creating, during arcing, a difference of potentials of electric field equal, or close to zero on at least the working surface of the treatment zone of the part may be in the form of at least two current supply members connected to the part symmetrically with respect to the treatment zone, electrically connected to each other and to one of the leads of the power supply, and a similar means for creating, during arcing, a difference of potentials equal, or close to zero on the working surface of at least one electrode may be in the form of at least two current supply members connected to the electrode symmetrically with respect to the treatment zone of the part or to the working surface of the electrode, electrically connected to each other and connected to the lead of the power supply opposite to that to which current supply members of the part are connected. This construction of the above-mentioned means can be most easily implemented in practice owing to a simple design. If the apparatus has at least two electrodes, it is preferred that they are positioned symmetrically with respect to the treatment zone. This facility prevents asymmetry of erosion of the part being treated. It is preferred that, if the apparatus has at least two electrodes, the electrodes be mounted for movement relative to each other. This facility allows the width of the treatment zone to be controlled. In carrying out the electric arc treatment, preferably, cleaning of parts in the form of bodies of revolution, it is preferred that the electrodes be in the form of coaxially mounted truncated cones having coaxial holes to receive a part being treated therein, their smaller bases facing towards each other, the angle between the generant and height ranging from 35 to 85°. Owing to this construction of the electrodes, products of erosion of the part being cleaned are practically completely removed from the area of the discharge gap, and only a minor fraction of these products will be deposited on the working surface of the electrodes so as to ensure high reliability and prolonged service life of the apparatus. The angle between the generant and height of the cones ranging from 35 to 85° is determined experimentally; with angles smaller than 35° stability of arcing is compromised, and with angles greater than 85°, the major part of erosion products will be deposted on the electrodes so as to result in a rapid failure of the apparatus. The current supply members should be connected to the electrodes at the larger bases of the truncated cones; in addition, the current supply members should be connected to one of the electrodes with an offset towards the other electrode at one-half of the distance between the current supply members. This connection of the current supply members allows a zig-zag movement of the cathode arc spots along the perimeter of the part being treated so as to enhance uniformity of treatment and lower the probability of fusion of the part during its cleaning. In carrying out the electric arc treatment, preferably, of rolled stock, it is preferred that the electrodes be made in the form of at least one pair of mirror-parallel prisms, with an angle between facets facing towards each other ranging from 35 to 85°. Similarly to the above-described embodiment of the electrodes in the form of truncated cones, this construction allows the major fraction of erosion products from the part being cleaned to be removed from the discharge gap area so as to enhance reliability and prolong service life of the apparatus. The range of 35 to 85° for this angle is chosen as described above. In carrying out treatment, preferably cleaning of strip rolled stock, it is preferred that the electrodes in the form of at least one pair of mirror-parallel prisms be mounted with their working surfaces symmetrically with respect to the axis of the rolled stock and in parallel wherewith, and if at least two pairs of electrodes in the form of mirror-parallel prisms are provided, they are preferably positioned along the path of movement of the strip stock. This facility allows a large surface area of the strip stock to be cleaned uniformly thereby enhancing productivity of the process. In certain applications, it is preferred that the electrodes be mounted with respect to each other so that the threatment zone of each of the arc discharges be covered by the treatment zone of at least one other arc discharge. This facility allows a part to be uniformly treated with a plurality of arcs at a time so as to acieve a respective increase in productivity of the process. It should be noted that, in carrying out treatment of strip rolled stock, the apparatus is preferably provided with at least two pairs of identical electrodes mounted on holders, the electrodes being preferably mounted pair-wise symmetrically with respect to a plane drawn at right angles with respect to the direction of movement of the rolled stock substantially through the middle of the treatment zone of the rolled stock. This construction of the apparatus allows cleaning of strip rolled stock to be carried out with any section of the stock at a desired speed owing to the parallel and consecutive coverage of the surface being treated during movement of the rolled stock by arc discharges. It is preferred that the apparatus be provided with additional electrodes mounted symmetrically with respect to the main electrodes on the opposite side of the rolled stock. This facility allows the two-sided treatment of the strip stock to be carried out simultaneously. It is also preferred that, in case the apparatus has at least two electrodes, the apparatus be provided with a switch for switching the current supply members of these electrodes which is capable of ensuring permanent contact of at least one electrode with the power supply. This switch is used for reversing the direction of electric field in the discharge gap without interruption of the arc so as to achieve the directional movement of the electrode spots of the arc along the part without moving the electrodes. The above problem is also solved by the fact that an apparatus for carrying out the method for electric arc treatment of parts, comprising at least one electrode mounted on a holder connected by means of a current supply member to one lead of the power supply having the other lead connected to a part being treated, and an arc excitation system, according to the invention, is provided with at least one means for creating on the surface of the part or/and at least one electrode during arcing, areas with electrical potential which is higher or/and lower than the potential of the rest of the surface and for moving these areas along said surface, said means being connected to the power supply, and with a means for limiting movement of plasma of the arc discharge to the treatment zone of the part and/or the working surface of at least one electrode. The provision of said means for creating, during arcing, areas with a higher or/and lower electrical potential with respect to the potential of the rest of the surface on the surface of the part or/and electrode and for moving these areas along said surface (or surfaces), as well as a means for limiting movement of plasma of the arc in the apparatus according to the invention ensures movement of the extremum potential of the electrode spots of the arc to follow up said areas and eliminates movement of these spots to other areas of the part and/or electrode so as to ensure treatment of a selected zone of the part in accordance with a preset program. It is preferred that the means for creating, during arcing, areas with a higher or/and lower electric potential on the surface of the part and for moving these areas along said surface be in the form of at least two current supply members connected to different portions of the part and a switch of these current supply members which is capable of ensuring permanent contact between the part and the power supply. The means for creating, during arcing, areas with higher or/and lower electrical potential on the surface of the electrode and for moving these areas along said surface may be in the form of at least two current supply members connected to different areas of the electrode, and a switch of these current supply members which is capable of ensuring permanent contact between the electrode and the power supply. This construction of the above-described means is very simple and does not call for additional energy expenditures for movement of the electrode spots. It is preferred that the current supply members be connected to the part or/and electrode symmetrically with respect to the treatment zone of the part or/and working surface of the electrode. If such current supply members are switched at one and the same rate, uniform and directional movement of the arc electrode spots can be achieved along the treatment zone of the part or/and the working surface of the electrode so as to ensure uniform treatment of the part with the arc discharge. It is preferred that the means for limiting movement of plasma of the arc discharge to the treatment zone and/or the working surface of at least one electrode be made in the form of screens insulated from the electric circuit, positioned in a spaced relation to the part and/or electrode, and protecting portions of the part that do not have to be treated and/or non-working surface of the electrode, at least those portions of the screens which are located adjacent to the treatment zone of the part and/or working surface of the electrode being either made of a high-temperature material or positively cooled. This construction of the above-described means is the simplest one and, at the same time, very efficient from the functional point of view so that it is preferred for the practical implementation of this invention. In specific applications of the invention, the form and position of the screens may vary. Thus, in treating parts in the form of bodies of revolution and in case the electrodes are in the form of truncated cones having coaxial holes, the screens are preferably mounted in these holes. In case of the two-sided treatment of strip rolled stock, its is preferred that the screens be positioned between the electrodes located on either side of the strip rolled stock being treated, the screens being installed in the spaces between the electrodes and the surface of the rolled stock being treated. This position of the screens ensures the best performance in such applications. The above problem is also solved by that an apparatus for carrying out the method for electric arc treatment of parts, comprising at least one electrode mounted on a holder, connected by means of a current supply member to one lead of a power supply having its second lead connected by means of at least one other current supply member to a part being treated, and an arc excitation system, according to the invention, is provided with a means for compression or partial restriction of the area of the arc discharge in the space between the part being treated and the electrode and with a mechanism for relative movement of the part and said means for compression or partial restriction of the area of the arc discharge. The provision of said means for compression or partial restriction of the area of the arc discharge in the space between the part being treated and the electrode and the mechanism for relative movement of the part and said means allows the desired treatment of the part to be carried out in accordance with a preset program owing to the movement of the electrode spots along the part to follow up the area of compression or partial restriction of the arc. It is preferred that the means for compression of the area of the arc discharge in the space between the part being treated and the electrode be in the form of a screen positioned between the electrode and the part and having an opening corresponding to the area of the part being treated. This construction of the means is most simple and can be easily implemented. The electrode spots of the arc are thus shifted along the part towards the current supply member and are concentrated adjacent to the boundary of the screen, and, during the relative movement of the part being treated and the screen, these spots carry out the desired treatment of the desired surface of the part. Brief Description of the Drawing The invention will now be described with reference to specific embodiments illustrated in the accompanying drawings, in which: Fig. 1 schematically shows an apparatus illustrating the first embodiment of a method for electric arc treatment of parts according to the invention; Fig. 2 schematically shows an apparatus illustrating an example of the second embodiment of a method for electric arc treatment of parts according to the invention; Fig. 3 shows an apparatus illustrating another example of the second embodiment of a method according to the invention; Fig. 4 is a sectional view taken along line IV-IV in Fig. 3; Fig. 5 schematically shows an apparatus illustrating the third embodiment of a method for electric arc treatment of parts according to the invention; Fig. 6 schematically shows an apparatus illustrating the step of positive movement of electrode spots of the arc along the part by switching the electrodes; Fig. 7 is a sectional view taken along line VII-VII in Fig. 6; Fig. 8 schematically shows an apparatus for electric arc treatment (cleaning) of elongated parts according to the invention; Fig. 9 is a view taken along arrow A in Fig. 8; Fig. 10 is a view taken along arrow B in Fig. 8; Fig. 11 schematically shows an apparatus for electric arc treatment (cleaning) of strip rolled stock according to the invention; Fig.12 illustrated the construction of an electrode unit of the apparatus shown in Fig.11; Fig.13 is a view taken along arrow C in Fig.12; Fig.14 schematically shows an apparatus for electric arc treatment (cleaning) of strip rolled stock according to the invention; Fig.15 illustrated the construction of an electrode unit of the apparatus shown in Fig.14; Fig.16 is a view taken along arrow D of the electrode unit shown in Fig.15. Embodiments of the Invention Let us discuss the gist of various embodiments of a method for electric arc treatment of parts which will be discussed in greater detail in connection with the description of apparatuses for carrying out the method. In its first embodiment, a method for electric arc treatment of parts resides in the fact that a part 1 to be treated (Fig. 1) is placed into a vacuum chamber (not shown in the drawing), and part 1 and at least one electrode 2 surrounding part 1 arc connected to a power supply 3. An arc discharge is excited under a pressure of a medium below 10 Pa between part 1 and electrode 2 in the mode of a drooping portion of the volt-ampere characteristic of the arc or, which is an equivalent, a power supply 3 is used which has a drooping external volt-ampere characteristic. Arc excitation is effected by injecting a small amount of plasma into the interelectrode gap to form a conducting path between part 1 and electrode 2, e.g., by opening up the contact between electrode 2 and an auxiliary firing electrode 4 having its current limited by means of a resistor 5. The arcing mode is set up by controlling discharge current, e.g., by means of a ballast rheostat 6. During arcing, a difference of potential of electric field equal or close to zero is created on the surface of the treatment zone of part 1 and on the working surface of electrode 2. This can be achieved by connecting part 1 to power supply 3 by means of two current supply members 7 and 8 connected to part 1 symmetrically with respect to its treatment zone, electrically connected to each other and to one lead of power supply 3 and by connecting electrode 2 to power supply 3 by means of similar symmetrically connected current supply members 9 and 10. In addition, the area of movement of plasma of the arc is limited to the treated zone of part 1 e.g., by means of screens 11 and 12 and to the working surface of electrode 2, e.g., by means of a screen 13. Electrode, especially cathode spots of the arc at a pressure of a medium below 10 Pa, including the purely vacuum discharge, continually spontaneously move along the surface of part 1 and electrode 2 and, if the arc is excited in the mode of a drooping portion of its volt-ampere characteristic, or if the discharge is supplied by a power supply 3 having a drooping external volt-ampere characteristic, mobility of the spots is substantially enhanced. This phenomenon, which is most frequently undesired in case of a low-pressure arc, is used in the method according to the invention to achieve the useful result - uniform or otherwise programmed treatment of the part surface. In this embodiment of the method, owing to the creation on said surfaces of a difference of potentials of electric field close to zero, a substantially equal probability of the occurrence of the electrode spots of the arc in all areas of the treatment zone of part 1 defined by screens 11 and 12 is ensured. The electrode spots move chaotically along the whole surface of the zone to ensure its uniform treatment. The embodiment of the method is characterized by extreme simplicity of an apparatus for its implementation, and electrode 2 may be in the form of the inner surface of the vacuum chamber. However, in case this embodiment is used, it is necessary to bear in mind that high uniformity of treatment cannot be ensured in all cases and, as a rule, it can be achieved with symmetrical position of parts located adjacent to the treatment zone, the parts being made of nonmagnetic materials. In particular applications of this embodiment of the method, it is necessary either to create a difference of potentials of electric field equal, or close to zero as described above simultaneously on the surface of the treatment zone of part 1 and on the working surface of electrode 2, or, depending on specific application, only on the surface of part 1 or only on the forking surface of electrode 2. If the above-described first embodiment of the method is not capable of ensuring the desired uniformity of treatment for some reason or, if, on the contrary, different portions of the part should be treated in different manners, other embodiments of this method described below can be used. A method for electric arc treatment of parts in the second embodiment differs from that described above in that, during arcing, a difference of potentials of electric field other then zero is created on the surface of a part 14 (Fig. 2), and areas with the highest or lowest potential are directionally moved in accordance with a preset program depending on polarity of the electric arc treatment. It should be noted that the electrode spots of the arc move directionally to follow up these areas of extremum potential along the surface of part 14 so as to ensure treatment of part 14 in accordance with a preset program, and a casing of a vacuum chamber along which the discharge is sufficiently uniformly distributed over the whole inner surface is used as an electrode 15 (cathode). Another application of the second embodiment of the method according to the invention differs from that described above by the fact that, during arcing, a difference of potentials of electric field other than zero is created on the surface of at least one electrode 16 (Figs. 3,4), and areas with the highest or lowest potential depending on polarity of the electric arc treatment are directionally moved in accordance with a preset program. It should be noted that the electrode spots of the arc will directionally move to follow up these areas of extremum potential along the surface of electrode 16 (Figs. 3,4), and the surface of the treatment zone of a part 17, depending on specific application, is either sufficiently uniformly surrounded by a plasma cloud, or the electrode spots of the arc move directionally therealong to follow up the electrode spots moving along electrode 16. A combination of the above-discussed cases of the second embodiment of the method for electric arc treatment is also possible, wherein, during arcing, said areas of extremum potential on the surfaces of both the electrode and part are moved to ensure the positive movement of the electrode spots of the arc on both surfaces. In practice this can be used very rarely since a more complicated apparatus would be required to carry out such method. As mentioned above, it is most preferred that a difference of potentials of electric field be provided by supplying electric current to areas of part 14 (Fig.2) or electrode 16 (Figs.3,4) remote from the zone in which electrode spots of the arc are located, and that movement of the areas of the highest or/and lowest potential of electric field be effected by varying position of current supply zones on part 14 (Fig.2) or electrode 16 (Figs.3,4), e.g., by means of current supply members 18, 19, 20 (Figs.2,3) connected to different portions of part 14 (Fig.2) or electrode 16 (Figs.3,4) and by means of a switch 21 (Figs.2,3) of these current supply members which is capable of ensuring permanent contact between part 14 (Fig.2) or electrode 16 (Figs.3,4) on the one hand and power supply 3 (Figs.2,3,4) on the other. The gist of this step of providing and moving the areas of extremum electric potential ensuring movement of the electrode spots of the arc is in the following. Supplying electric current to areas of part 14 (Fig. 2) or electrode 16 (Figs. 3,4) remote from the zone of location of the electrode spots of the arc causes current to flow through parts 14 (Fig. 2) or electrode 16 (Figs. 3,4) whereby the equilibrium distribution of charges on their surface is brloken, and a tangential component of intensity of electric field emerges. The resulting electric field on the surface of part 14 (Fig. 2) or electrode 16 (Figs. 3,4) as well as magnetic field of the electric current flowing therein act upon the electrode spots of the arc discharge thus causing them to move towards areas of the highest and lowest electric potential depending on polarity of the electric arc treatment. If now, without breaking the electric circuit, the current supply members 18, 19, 20 (Figs. 2,3,4) are switched by switch 21 to change the position of current supply zones on part 14 (Fig. 2) or electrode 16 (Figs. 3,4), areas of extremum potential will move on the surface of the part and electrode, and the electrode spots of the discharge will follow suit. Depending on application, the time during which each of the current supply members 18, 19, 20 is energized may be the same or different so as to treat part 14 (Fig.2) or part 17 (Fig. 4) in accordance with a preset program. Both the above-described embodiments of the method according to the invention may be used for treating elongated parts. For that purpose, part 1 (Fig. 1) or part 17 (Figs. 3,4) should be moved relative to electrode 2 (Fig. 1) or electrode 16 (Figs. 3,4), respectively, or/and electrode 2 (Fig. 1) or electrode 16 (Figs. 3,4) should be moved relative to part 1 (Fig. 1) or part 17 (Fig. 4), respectively, so as to ensure uniform or otherwise movement-programmed electric arc treatment of elongated parts along the whole length thereof. The third embodiment of the method differs from those described above by the fact that an area occupied by arc discharge plasma is positively compressed or partly restricted in the space between the part being treated and at least one electrode, and this area is moved in accordance with a preset program with respect to the part or/and the part is moved with respect to this area of the arc discharge. The positive compression of the area occupied by plasma of the arc discharge in the space between a part 22 being treated (Fig. 5) and an electrode 23 (a so called "discharge column") is preferably carried out by means for compression of this area of the arc discharge in the form of a screen 24 positioned between electrode 23 and part 22 and having an opening 25 corresponding to a treatment zone 26 of part 22, and movement of this area of the arc with respect to part 22 or/and movement of part 22 with respect to this area is carried out by means of a mechanism 27 for their relative movement which in this case is connected to screen 24. This step of the electric arc treatment is based on the fact that when the electrode spots of the arc move beyond the limits of treatment zone 26 of part 22 disposed opposite to opening 25 and corresponding to the shape of opening 25 of screen 24, the length of the discharge column increases to result in its increased resistance and to impair conditions for arcing. The electrode spots will thus either move back to portion 26 or disappear. In the latter case, new electrode spots of the arc are formed in zone 26 through splitting of the available electrode spots. During the relative movement of screen 24 and part 22 by means of mechanism 27, zone 26 disposed opposite to opening 25 moves along part 22. On the other hand, since, for the above-mentioned reasons, the probability that the electrode spots will occur on this portion is much greater, they will move to follow up this portion so as to ensure the electric arc treatment of part 22 in accordance with a program set up by mechanism 27. An example of partial restriction of the area of the arc discharge in the space between the part and electrode is shown in Figs. 3, 4 and 6,7 where such restriction is achieved by means of a screen 28 (Fig. 4) positioned between electrode 16 and part 17 of a screen 28' (Fig. 7) positioned between electrodes 29,30,31 (Figs. 6,7) and part 17 to cover a portion of this part 17 between the treatment zone and a current supply member 32 of the part, the current being supplied to part 17 on the side opposite to the side of arc excitation. The electrode spots of the arc move along paint 17 towards current supply member 32 and concentrate adjacent to the boundary of screen 28, 28', and in case of the relative movement of part 17 and screen 28 with electrode 16 (Fig. 4) or screen 28' (Fig.7) with electrodes 29, 30, 31 (Figs. 6, 7) the necessary treatment of the desired surface of part 17 is achieved by these spots. Another approach to the positive movement of the electrode spots of the arc used in this method resides in the fact that, in case at least two electrodes are used, the value of electric current is lowered, or the electric current is interrupted in accordance with a preset program in the circuit of at least one electrode, the current in the circuit of the electrodes remaining unchanged or being increased. Current can be interrupted in this manner in the circuit of electrodes 29, 30, 31 (Fig.6) by means of a switch 21 of current supply members 33, 34, 35 of these electrodes 29, 30, 31 as described above, and current can be decreased or increased in the circuit of these electrodes 29, 30, 31 in the most simple manner by means of rheostats (not shown in the drawing) connected in series with current supply members 33, 34, 35. With such interruption or variation of current in the circuit of electrodes 29,30,31 the direction of electric field in the discharge gap is reversed so as to cause the directional movement of the electrode spots along part 17 (rotation of such spots along the perimeter of part 17 in a zone adjacent to screen 28' in the example shown in Figs. 6,7). In all the above-described examples of implementation of the method according to the invention, a part being treated can be connected either to negative or to positive terminal of power supply 3, except for examples shown in Figs. 2 and 6,7 in which it is preferred that part 14 (Fig. 2) or part 17 (Figs. 6,7) be connected to the negative terminal of power supply 3. This is due to the fact that with an opposite polarity, erosion of the electrode 15, which functions as the casing of the vacuum chamber (Fig. 2), will take place under the action of the cathode spots, and in the example shown in Figs. 6,7, arc breakage can occur during switching of electrodes 29,30,31, and the probability of such breakage increases with an increase in the switching rate since the cathode spot of the arc may not have time to form on the switched electrodes 29,30,31, and this spot is decisive for discharge to occur. As mentioned above, the negative polarity of the part is preferably used for its cleaning, descaling and deburring and for varporization of the material of the part and the positive polarity is preferably used for heating, welding, cutting, and polishing of parts. The process of electric arc cleaning is based on the fact that the cathode spots of the arc are moved along the surface of the part being treated, the temperature in the area of the spots being as high as 3000 to 5000 °C. The cathode spots move at a speed of 10⁻² to 10² m/s depending on the kind of scale and contamination of the surface of the part, and they remove scale and vaporize it as they move so as to clean the surface. Deburring and removal of minor irregularities from the surface of parts occurs in the same manner. When the electric arc cleaning is carried out as described in any of the above- or below-described examples, it is preferred that the arc current and treatment time during the treatment be maintained at a level at which the specific energy consumption should be within the range from 0.1 to 0.8 kW-h/m²/ µm so as to ensure complete removal of scale from the surface being cleaned without appreciable erosion of the part being treated and with a high enough productivity of the process. Specific embodiments of apparatuses for carrying out the above-described embodiments of the methods will now be described. An apparatus for electric arc treatment, preferably, for cleaning of elongated parts, e.g., bars comprises at least two coaxially mounted and positively cooled electrodes 36 and 37 (Fig. 8) having coaxial holes for receiving part 1 to be treated. Electrodes 36 and 37 are made in the form of truncated cones having their smaller bases facing towards each other, the angle between the generant and height of the cones reanging from 35 to 85°. Screens 38, 39 are positioned between part 1 and electrodes 36 and 37 in holes of electrodes 36, 37, which are made of a high-temperature material and which function as the means for limiting movement of plasma of the arc discharge to the zone of treatment of part 1 and working surfaces of electrodes 36 and 37. The apparatus also comprises a means for creating, during arcing, a difference of potentials of electric field equal or close to zero on the surface of the treatment zone of part 1, which is in the form of two current supply members 7 and 8 connected to part 1 symmetrically with respect to the treatment zone, electrically connected to each other and connected to the negative terminal of power supply 3, and a means for creating a difference of potentials of electric field equal or close to zero on the working surface of electrodes 36, 37 in the form of current supply members 40, 41, 42 (Fig. 9) and 43, 44, 45 (Fig. 10) electrically connected to one another and connected to the positive terminal of power supply 3 (Fig. 8) and to the larger bases of the truncated cones of electrodes 36 and 37 symmetrically with respect to their working surface, the current supply members 40, 41, 42 being connected to electrode 36 with an offset of one-half- the distance between current supply members 43, 44, 45 towards electrode 37 as shown in Figs. 9 and 10. Current supply members 40, 41, 42 also function as holders of electrode 36 and current supply members 43, 44, 45 are used as holders of electrode 37. Electrodes 36, 37 (Fig. 8) are mounted for movement with respect to each other for controlling the width of the treatment zone, and part 1 is capable of reciprocating during the treatment by means of a mechanism 46. At least the portion of part 1 being treated, electrodes 36, 37, firing electrode 4, and screens 38, 39 are mounted inside a vacuum chamber (not shown in the drawing). The apparatus is used for the implementation of the first embodiment of the method according to the invention and functions in the following manner. With a pressure of a medium in the chamber below 10 Pa, an arc discharge is initiated between electrodes 36, 37 (Fig. 8) and part 1 being treated by means of firing electrode 4, the discharge current being adjusted by means of ballast rheostat 6. The cleaning process is based on the fact that the cathode spots of the arc move along the surface being treated of part 1, and temperature at these spots is as high as 3000 to 5000°C. The cathode spots move at a speed of 10⁻² to 10² m/s depending on the kind of scale and contamination of the surface of part 1 and remove scale and vaporize it as they move thus cleaning the surface. Owing to the symmetric supply of current to part 1 and electrodes 36 and 37, even during arcing, a difference of potentials of electric field is maintained on their surface which is close to zero so as to ensure the substantially identical probability of the occurrence of the cathode spots in all areas of the treatment zone of part 1 located between electrodes 36, 37 and defined by screens 38 and 39. The cathode spots move in a random manner over the whole surface of the treatment zone so as to ensure uniform cleaning of part 1 in this zone. For cleaning the whole surface of part 1, it is linearly moved with respect to electrodes 36 and 37 by means of feed mechanism 46. Owing to the conical shape of the working surface of electrodes 36 and 37, products of erosion of part 1 being cleaned are substantially completely removed from the area of the arc gap, and only a minor fraction of these products is deposited on the working surface of electrodes 36, 37 so as to enhance reliability and prolong service life of the apparatus. The value of the angle of inclination of the cone generant ranging from 35 to 85° is chosen by way of experiments bearing in mind the angle of emission of the eroded fraction with the least probability of its deposition on the anodes while retaining high stability of arcing. With the angles between the generant and height of the cone below 35° the arc can break, and with angles in excess of 85°, the major fraction of the eroded scale will be deposited on electrodes 36 and 37 so to result in changes in conditions of arcing. It has been found by way of experiments that connecting current supply members 40, 41, 42 to electrode 36 with an offset at one-half the distance between current supply members 43, 44, 45 towards electrode 37 as shown in Figs. 9, 10 results in a zig-zag movement of the cathode spots of the arc along the perimeter of part 1 so as to enhance uniformity of treatment, lower probability of fusion of the part during its cleaning, and improve quality of cleaning in dealing with parts having a large surface area, in particular, spindles of cotton harvesters. The best cleaning quality is ensured by making choice of the arcing conditions, distance between electrodes 36 and 37, and speed of movement of part 1. Descaling of steel bars of 12 mm diameter and spindles of cotton harvesters in the form of a tube 630 mm long with four rows of teeth on the outer surface was carried out on commercial scale. Good quality of cleaning was achieved with an arc current of 250 A, speed of movement of the part being cleaned of 30 to 50 mm/s, and distance between the electrodes of 30 to 35 mm. An apparatus for electric arc treatment, preferably for cleaning of strip rolled stock is shown in Figs. 11, 12, 13. The apparatus comprises a vacuum chamber 47 (Fig. 11) accommodating in its casing electrodes 48 and firing electrodes 4 and 4'. Electrodes 48 are rigidly mounted on a common holder (not shown in the drawings). The end parts of vacuum chamber 47 incorporate an inlet lock system 49 and an outlet lock system 50. Vacuum chamber 47 is connected, by means of pipelines 51, to a vacuum pump 52 of a vacuum system. Driven pull rollers 53 and 54 are mounted at the inlet and outlet of lock systems 49 and 50, respectively, and are designed for transporting (with tension) strip stock 55 with respect to electrodes 48. The apparatus is also provided with a means for creating, during arcing, a difference of potentials of electric field equal, or close to zero on the surface of the treatment zone of rolled stock 55, which is in the form of current supply members 7' and 8' connected to the rolled stock 55 being treated symmetrically with respect to the treatment zone, electrically connected to each other and connected to the negative terminals of power supplies 3 having their positive terminals connected to electrodes 48. Electrodes 48 are made in the form of at least one pair (four pairs in this embodiment) of mirror-parallel prisms having their facets facing each other which are inclined at an angle of 35 to 85° and which have their working surfaces positioned symmetrically with respect to the axis of strip stock 55 and in parallel with this axis as shown in Fig. 13. If there are two or more pairs of electrodes 48 in the form of mirror-parallel prisms in the apparatus, they are mounted along the path of movement of strip rolled stock 55 (Fig. 12). If its is necessary to carry out the two-sided treatment (cleaning) of rolled stock, the apparatus is provided with auxiliary electrodes 56 (Figs. 11, 12, 13) mounted symmetrically with respect to the main electrodes 48 on the opposite side of rolled stock 55 and connected to power supplies 3 similarly to electrodes 48. Positively cooled screens 57 are designed for limiting movement of plasma of the arc discharge to the treatment zone of rolled stock 55 and to the working surface of electrodes 48 and 56. With the two-sided treatment (cleaning) fof rolled stock, these screens 57 should be preferably placed between electrodes 48 and 56 mounted on the opposite sides of rolled stock 55 (Fig. 13) with a gap to lateral sides of rolled stock 55. It is preferred that screens 57 be secured to the outer facets of electrodes 48 and 56 and insulated therefrom by means of insulating sleeves 58 (Fig. 13). Hoppers 59 having vacuum-tight gates 60 are provided in the bottom part of the casing of vacuum chamber 47. The apparatus functions in the following manner. Strip stock 55 (Fig. 11) is fed by means of pull rollers 53 and 54 to vacuum chamber 47 and is positioned under tension in the space between electrodes 48 and 56. Vacuum pump 52 reduces pressure to a level below 10 Pa in vacuum chamber 47 through pipeline 51. Power supplies 3 are turned on, and an arc discharge is initiated between electrodes 48, 56 and strip stock 55 by means of firing electrodes 4 and 4'. When the discharge is initiated, pull rollers 53 and 54 start transporting strip stock 55 through vacuum chamber 47. As shown by investigations, the exposure to the arc discharge results in a for action of scale being reduced to pure metal, the rest of the scale being vaporized and deposited on the walls of chamber 47. This fraction of the scale is removed by brushes to the bottom of chamber 47, into hoppers 59 having special lock chambers with gates 60, and is transferred outside the chamber without loss of tightness of chamber 47. As regards the released gas, it is removed by continually operating pumps. Therefore, the provision of electrodes 48, 56 in the form of truncated mirror-positioned prisms brings solution simultaneously to two problems: on the one hand it allows eroded fraction to leave the arcing zone unobstructed and do not allow it to be deposited on electrodes 48, 56 (the range of the prism facet inclination angle was discussed above) and, on the other hand, this facility provides uniform electric field adjacent to the cathode surface, i.e., on strip stock 55 being cleaned so as to create conditions for uniform distribution of the cathode spots on this surface to ensure high-quality cleaning of the surface. The number of cathode spots is proportional to the discharge current, but it is not infinite. With a certain current, which can be regarded as critical current, the value of which depends on structural features of the apparatus, material of the rolled stock and pressure of the medium, a change in the arc discharge mode occurs, and the arc discharge changes from the arc with travelling spots to the arc with concentrated spots, strip stock 55 or/and electrodes 48, 56 being fused. This phenomenon limits the maximum width of strip stock 55 which allows a sufficiently uniform distribution of the cathode spots to be achieved. With an increase in the width of rolled stock 55, the arc current should be increased so as to obtain the sufficient number of cathode spots. However, this is only possible within certain limits because of fusion of strip stock 55 or/and electrodes 48,56 with currents in excess of critical current. The arc current cannot be in definitely lowered either in carrying out the treatment of narrow strip stock 55 since the arc will be interrupted. It has been found by way of experiments that the apparatus according to the invention can successfully clean strip stock of 20 to 100mm wide. The above-described apparatus can be used for cleaning strip rolled stock by electric arc discharge in vacuum in dealing with medal strips of ferrous and non-ferrous metals and alloys with high-quality and uniform cleaning of both surfaces of strip stock since power supplies 3 can work independently. Strip stock 55 treated by electric arc discharge in vacuum has good vendible appearance; its corrosion resistance is enhanced and surface area is increased which is especially important for coating deposition. If it is necessary to treat (clean) rolled stock of a width greater than 100 mm, use is made of an apparatus shown in Figs. 14, 15, 16. This apparatus differs from that described above by the fact that electrodes 61 and 62 in the form of mirror-parallel prisms are installed pairwise symmetrically with respect to a plane 63 (Fig. 16) drawn at right angles with respect to the direction of movement of strip stock 64 through the middle of the treatment zone of this rolled stock 64, the adjacent electrodes 61 or 62 (Fig. 15) being mounted with respect to each other for covering the treatment zone of each of the arc discharges by the treatment zone of at least one other discharge, and screens 65 and 66 (Figs. 14, 15, 16) are positioned in spaces between electrodes 61, 62 and the surface being treated of strip stock 64. This construction of the apparatus allows cleaning of strip rolled stock of any section to be carried out at a desired speed owing to the parallel and consecutive coverage of the surface being treated during movement of the rolled stock. Therefore, the methods and apparatuses for electric arc treatment of parts according to the invention ensure the provision of ecologically safe production processes for descaling, cleaning and deburring of parts, for heating, welding and cutting various parts and for any other kinds of electric arc treatment of parts with moving arc in vacuum. It should be noted that movable electrode or external fields are not required for moving the arc, which simplifies the equipment. Parts cleaned with the use of the above-described methods and apparatuses have good vendible appearance; their corrosion resistance is enhanced, and coatings deposited on such parts have improved adhesion. Welding of various parts in vacuum according to the invention allows edges of parts being welded to be preliminary cleaned, and reaction of molten metal with the medium is ruled out so as to enhance quality of welded joint, especially in welding parts of active materials such as titanium and its alloys. The methods and apparatuses according to the invention allow production processes to be carried out both on the Earth and in space and may be used as the basis for the development of promising advanced production equipment for various fields of technology. Industrial Applicability The invention may be used in the mechanical engineering, metallurgy, electrical engineering and electronic technology for cleaning and activation of surfaces before application of coatings, for improvement or tempering of the surface layer, for deburring, welding and cutting of parts, etc.

Claims: A method for electric arc treatment of a part (1; 14; 17; 22) comprising connecting the part and at least one electrode (2; 15; 16; 23; 29-31) to a power supply (3), and initiating an arc discharge between the part and the at least one electrode in a medium below atmospheric pressure, with the formation of plasma moving at least along the cathode, characterised in that: (a) the pressure of the said medium is below 10 Pa; (b) the arc discharge is initiated in the mode of a drooping portion of the volt-ampere characteristic of the arc or/and a power supply (3) with a drooping external volt-ampere characteristic is used; (c1) a difference of potentials of electric field equal to or approximately equal to zero is created at least on the surface to be treated of the part (1) and/or on the working surface of the at least one electrode (2), or (c2) a difference of potentials of electric field other than zero is created on the surface to be treated of the part (14; 17) or/and on the working surface of the at least one electrode (15; 16), areas with the highest or/and lowest potential being moved along the said surface to be treated and/or the said working surface, or (c3) the region of the arc discharge in the space between the part (17; 22) and the at least one electrode (16; 23; 29-31) is positively compressed or partly restricted, the said region and the part being moved relative to each other in accordance with a predetermined program; and (d) the area of movement of plasma of the arc is limited to the surface to be treated of the part and/or the working surface of the at least one electrode. A method according to claim 1, in which, in step (c2), the difference of potentials of electric field is created by supplying electric current to zones of the part (14) or/and electrode (16) remote from the zone of the electrode spots of the arc, and movement of the areas of the highest or/and lowest potential of electric field is effected by varying the position of the current supply zones on the part (14) or/and electrode (16). A method according to claim 1, in which the part is moved with respect to the at least one electrode or/and the at least one electrode is moved with respect to the part. A method according to claim 1, in which at least two electrodes (29, 30, 31) are used, and the value of the electric current is lowered or the electric current is interrupted in the circuit of at least one or some of the electrodes (29, 30, 31) in accordance with a preset program, the electric current in the circuit of the other electrode(s) remaining unchanged or being increased. A method according to claim 1, in which the part (1; 14; 17; 22) being treated is connected to the negative terminal of the power supply (3). Apparatus for carrying out a method for electric arc treatment according to claim 1, comprising at least one electrode (36, 37; 48, 56; 61, 62) mounted on a holder and connected by means of a current supply member (40, 41, 42, 43, 44, 45) to one lead of a power supply (3) having the other lead connected to a part (1, 55, 64) being treated, and an arc excitation system, characterized in that it is provided with at least one means for creating, during arcing, a difference of potentials of electric field equal to or approximately equal to zero at least on the surface of the treatment zone of the part (1; 55; 64) and/or on the working surface of the at least one electrode (36, 37) electrically connected to power supply (3) and with a means for limiting movement of plasma of the arc discharge to the treatment zone of the part (1; 55; 64) and/or to the working surface of the at least one electrode (36, 37; 48, 56; 61, 62). Apparatus according to claim 6, in which the means for creating, during arcing, a difference of potentials equal to or approximately equal to zero at least on the surface of the treated zone of the part (1; 55; 64) comprise at least two current supply members (7,8; 7',8') connected to the part (1;55;64) symmetrically with respect to the treatment zone, electrically connected to each other and to one of the leads of the power supply (3). Apparatus according to claim 6, in which the means for creating, during arcing, a difference of potentials of electric field equal to or approximately equal to zero at least on the working surface of the at least one electrode (36, 37) comprise at least two current supply members (40, 41,42,43,44,45) connected to the at least one electrode (36, 37) symmetrically with respect to the treatment zone of the part (1) or to the working surface of the at least one electrode (36, 37), electrically connected to each other and to the lead of the power supply (3) opposite to that to which are connected current supply members (7, 8) of the part (1). Apparatus according to claim 6, in which at least two electrodes (36, 37) are used, positioned symmetrically with respect to the treatment zone. Apparatus according to claim 6, in which at least two electrodes (36, 37) are used, mounted for movement with respect to each other for controlling the width of the treatment zone. Apparatus according to claim 9 and/or claim 10 in which, for carrying out the electric arc treatment of a part (1) in the form of a body of revolution, the electrodes (36, 37) are in the form of coaxially mounted truncated cones having coaxial holes for receiving the part (1) and having their smaller bases facing towards each other, the angle between the generant and axis of the cones being in the range from 35 to 85°. Apparatus according to claims 8 and 11 in which current supply members (40, 41, 42, 43, 44, 45) are connected to the electrodes (36, 37) at points adjacent to the larger bases of the truncated cones, the current supply members (40, 41, 42) connected to one electrode (36) being offset at one-half the spacing between the current supply members (43, 44, 45) connected to the other electrode (37). Apparatus according to claim 6, in which, for carrying out the electric arc treatment of rolled stock (55; 64), the electrodes (48, 56, 61, 62) are in the form of at least one pair of mirror-parallel prisms with an angle of inclination of their facets facing towards each other ranging from 35 to 85°. Apparatus according to claim 13 in which, for carrying out the treatment of strip stock (55), the electrodes (48) are in the form of at least one pair of mirror-parallel prisms having their working surfaces positioned symmetrically with respect to the axis of the strip stock (55) and in parallel with this axis. Apparatus according to claim 14, in which at least two pairs of electrodes in the form of mirror-parallel prisms (48) are used, positioned along the path of movement of the strip stock (55). Apparatus according to claim 6, in which at least two electrodes (61) are used, positioned with respect to each other in such a manner that the treatment zone of each arc discharge is covered by the treatment zone of at least one other arc discharge. Apparatus according to claims 13 and 16, in which, for carrying out the treatment of strip rolled stock (64), at least two pairs of identical electrodes (61) are mounted on holders, the electrodes being positioned pairwise symmetrically with respect to a plane (63) drawn at right angles with respect to the direction of movement of the rolled stock (64) substantially through the middle of the treatment zone of the rolled stock (64). Apparatus according to any of claims 13 to 17, in which, for carrying out the two-sided treatment of rolled stock (55,64), auxiliary electrodes (56, 62) are positioned symmetrically with respect to main electrodes (48, 61) on the opposite side of the rolled stock (55, 64). Apparatus according to claim 6 or 9, for carrying out the method of claim 4, comprising at least two electrodes (29, 30, 31), with a switch (21) for current supply members (33, 34, 35) for the electrodes (29, 30, 31) which is capable of ensuring permanent contact of at least one electrode (29, 30, 31) with the power supply (3). Apparatus for carrying out a method for electric arc treatment of a part according to claim 1, comprising at least one electrode (15, 16) mounted on a holder and connected by means of a current supply member (18, 19, 20) to one lead of a power supply (3) having a second lead connected to a part (14; 17) being treated, and an arc excitation system, characterized in that it is provided with at least one means for creating, during arcing, areas with higher or/and lower potential of electric field on the surface of the part (14) or/and the at least one electrode (16) with respect to the potential of the rest of the said surface and for moving the said areas along the said surface, the said means being electrically connected to the power supply (3), and with a means for limiting movement of plasma of the arc discharge to the treatment zone of the part (14) and/or to the working surface of the at least one electrode (16). Apparatus according to claim 20, for carrying out the method of claim 2, in which the means for creating, during arcing, areas on the surface of the part with the higher or/and lower potential and for moving the said areas along the said surface comprises at least two current supply members (18, 19, 20) connected to different portions of the part (14) and a switch (21) of the current supply members which is capable of ensuring permanent contact between the part (14) and the power supply (3). Apparatus according to claim 20, for carrying out the method of claim 2, in which the means for creating, during arcing, on the surface of the at least one electrode (16) areas with higher or/and lower potential and for moving these areas along the said surface comprises at least two current supply members (18, 19, 20) connected to different portions of the at least one electrode (16) and a switch (21) of the current supply members which is capable of ensuring permanent contact between the at least one electrode (16) and the power supply (3). Apparatus according to claim 21 and/or 22, in which current supply members (18, 19, 20) are connected to the part (14) and/or the at least one electrode (16) symmetrically with respect to the treatment zone of the part (14) and/or the working surface of the at least one electrode (16). Apparatus according to claim 6 or 20, in which the means for limiting movement of plasma of the arc discharge to the treatment zone of the part (1; 14; 55; 64) and/or to the working surface of the at least one electrode (2; 16; 36, 37; 48, 56; 61, 62) is in the form of a screen or screens (11, 12; 13; 38, 39; 57; 65, 66) mounted in spaced relation to the part (1; 14; 55; 64) and/or the at least one electrode (2; 16; 36, 37; 48, 56; 61, 62), for protecting portions of the part (1; 14; 55; 64) outside the treatment zone and/or the non-working surface of the at least one electrode (2; 16; 36, 37; 48, 56; 61, 62) at least portions of the screen(s) (11, 12; 13; 38, 39; 57; 65, 66) immediately adjacent to the treatment zone of the part (1; 14; 55; 64) and/or to the working surface of the at least one electrode (2; 16; 36, 37; 48, 56; 61, 62) being made of a high-temperature-resistant material or positively cooled. Apparatus according to claim 13 or 14 or 15 and claims 18 and 24, in which, for carrying out two-sided treatment of strip stock (55), screens (57) are positioned between electrodes (48, 56) which are mounted on either side of strip stock (55) being treated. Apparatus according to any claims 15 to 18 and claim 24, in which, for carrying out treatment of strip rolled stock (64), screens (65, 66) are positioned in spaces between electrodes (61, 62) and the surface of strip stock (64) being treated. Apparatus for carrying out the method for electric arc treatment of a part according to claim 1, comprising at least one electrode (16; 23; 29-31) mounted on a holder and connected by means of at least one current supply member (18-20; 33-35) to one lead of a power supply (3) having the other lead connected by means of at least one other current supply member (32) to the part (17; 22) being treated, and an arc excitation system, characterized in that it is provided with a means for compression or partial restriction of the area of the arc discharge in the space between the part (17; 22) and the at least one electrode (16; 23; 29-31) and with a means (27) for relative movement of the part and the said means for compression or partial restriction of the area of the arc discharge. Apparatus according to claim 27, in which the means for compression of the area of the arc discharge in the space between the part (22) being treated and the electrode (23) comprises a screen (24), positioned between the electrode (23) and the part (22), having an opening (25) corresponding to a treatment zone (26) of the part (22).

Inventors: AMINOV EMANUEL ISAKHAROVICH, ARIFOV PULAT UBAEVICH, ARIFOV UBAI, ARUSTAMOV VLADIMIR NIKOLAEVICH, ASTAFIEV ALBERT EVGENIEVICH, BELOBORODOV ALEXEI IVANOVICH, BULAT VLADIMIR EMELYANOVICH, DVORZHAK IVAN FILIPPOVICH, ESTERLIS MOISEI KHAIMOVICH, GERSHOVICH EVGENY USHEROVICH, GRUICH DUSHAN DRAGUTINOVICH, KAZAKOV VALERY NIKOLAEVICH, KHOROSHKHIN JURY VALENTINOVICH, KIRSON PAVEL FELIXOVICH, PLISS GENNADY FILIPPOVICH, SOKOLOV ALEXADER ANATOLIEVICH, TANGRIBERGENOV RUSTAM MADRAIMO, TOKAREV EVGENY NIKOLAEVICH KVA, TSAI JURY MOISEEVICH, AMINOV, EMANUEL ISAKHAROVICH, ARIFOV, PULAT UBAEVICH, ARIFOV, UBAI, ARUSTAMOV, VLADIMIR NIKOLAEVICH, ASTAFIEV, ALBERT EVGENIEVICH, BELOBORODOV, ALEXEI IVANOVICH, BULAT, VLADIMIR EMELYANOVICH, DVORZHAK, IVAN FILIPPOVICH, ESTERLIS, MOISEI KHAIMOVICH, GERSHOVICH, EVGENY USHEROVICH, GRUICH, DUSHAN DRAGUTINOVICH, KAZAKOV, VALERY NIKOLAEVICH, KHOROSHKHIN, JURY VALENTINOVICH, KIRSON, PAVEL FELIXOVICH, PLISS, GENNADY FILIPPOVICH, SOKOLOV, ALEXADER ANATOLIEVICH, TANGRIBERGENOV, RUSTAM MADRAIMOVICH, TOKAREV, EVGENY NIKOLAEVICH, KVARTIRA 49, TSAI, JURY MOISEEVICH
Applicants: INST ELEKTRONIKI IM U A ARIFOV, INSTITUT ELEKTRONIKI IMENI U.A. ARIFOVA AKADEMII NAUK UZBEXKOI SSR
Application year: 1990
Main classification: B08B7
IPC codes: B08B7, H05H1