PROCESS EXTRACTION BY PLASMA OF JUNCTION IN OBTAINED PIECES BY MOLDING POWDERS BY INJECTION

Abstract: Process extraction by plasma of junction in obtained pieces for molding of powders for injection is a thermalchemical process accomplished in a plasma reactor, that it uses the electric discharge in gaseous environment of low pressure, which contains hydrogen or other atomic or molecular gas capable to produce reactivates species, which increase significantly the kinetics of removal of the junction of injected pieces. In the case of use a mixture containing hydrogen as main gas, the reactivate species are constituted by atomic hydrogen and by hydrogen molecule in high potential energy state, besides the molecular ion of hydrogen. The pieces (1) to be processed are placed in the support (2) inside the oven (3), where the group is involved by the plasma (6). The gaseous mixture is admitted through (4), being the residues removed through the vacuum bomb (5). In the plasma (6) the reactivate species are formed as described above, which are responsible for the reduction of the necessary time to extract the junction, which is of the order of 10 times less than the necessary time in the main processes today existent. Besides the reduction of the energy consumption and of the present process to be practically non pollute, there are an accentuated increase of the productivity and consequent reduction of the costs of the produced pieces through the technology of powders injection.

Description: PROCESS EXTRACTION BY PLASMA OF JUNCTION IN OBTAINED PIECES BY MOLDING POWDERS BY INJECTION It is a thermochemichal process for junction removal of injected pieces by powder metallic and/or ceramic, which uses electric discharge in an environment containing hydrogen or other atomic or molecular gas at low pressure to produce reactive species and for the heating of the pieces, causing the junction removal contained inside the pieces in much smaller times than the conventional processes. The techniques of powder metallurgy come highlighting itself as very efficient under the technological and economically competitive point of view in the production in series of pieces of complex geometry in iron and steel and other metallic leagues. Within these techniques, the injection of metallic and/or ceramic powders with organic junction mixture, in molds, is one of the most promising. Even so, the retreat of these organic junction after the injection, before processing the definitive sintering, is still a limiting factor, because the existent extraction process demand an excessively long processing time, coming close to dozens of hours, reducing the productivity, this way, raising the products price obtained by the technology of molding powders by injection. The processes of junction extraction used today, besides demanding an excessively long time, they are plenty of pollutes, because they liberate short chains hydrocarbons or they involve its burns, producing residues as, for example, the carbon monoxide. The most commonly used junction are mixtures of waxes and other polymeric, as, for example, the polyethylene, the polypropylene and the polyacetate. In the process of junction extraction by plasma, object of this patent request, there is an elimination much less of gases, which they are formed essentially by long chains hydrocarbons gases, predominantly methane, without any oxygen burns, avoiding liberation of carbon monoxide Processes where the plasma technology is used now include nitrating, carbonitratring, sementation, oxidation, sintering, among others The piece heating happens by the ions bombing on the cathode The cathode acts as the piece support, the piece is bombarded together with the cathode and consequently it becomes warm The pieces heating happens because the electric discharge of the cathode is tied up the negative voltage of the source of high tension, the ions are strongly accelerated in the electric field cathode sheath in direction to the cathode, if they collide with the cathode, they heat up it The sintering process by plasma described in to PI 9603488-2 it is an example The process of junction extraction by plasma described in this report consists of using the plasma technology to produce, besides the heating of the pieces, reactivate species These species reactivate are fundamental for the kinetics increase of the process of junction extraction, doing that the extraction happens in order of 10 times less than in the traditional processes The reactivate species are obtained by the electrons collisions of high kinetic discharge, presents in the electric discharge, with molecules of hydrogen The presence of these reactivates species is constituted in a fundamental difference between the process object of the patent request and the other processes of junction extraction The process of junction extraction by plasma uses electric discharge in environment of low pressure, plasma reactor, which contains a gaseous mixture contending H as main gas The process is described in the illustration 1 The illustration 1 exhibits the simplified outline of the plasma reactor environment, used for the junction extraction, with the pieces (1) to be processed, the support (2) of the pieces (1), the body of the oven (3), the entrance (4) of the gaseous mixture, the vacuum system (5) and the plasma (6) The pieces ( 1) to be processed are placed in the support (2) The group, support (2) and pieces (1), is involved by the plasma (6), and the group is heated up by the bombing of the ions and atoms or fast molecules or even by heat radiation starting from the cathode of the electric discharge circuit In the electric discharge, besides the ions and atoms or molecules with high kinetic energy, that are used for the components heating, there are also electrons that are much lighter than the ions and have much highest speeds With that, happen three important reactions to the process of retreat of organic junction in injected pieces e + H 2 ■ » e + 2H means, a high-speed electron collides with a H 2 molecule, producing the molecule dissociation, with kinetic energy loss of the electron The other verified reaction e + H 2 -» e + H 2 * means, a high-speed electron collides with a H molecule, producing the excitement of this molecule, with kinetic energy loss of the electron Another observed reaction is e + H 2 -»2e + H 2 " means, a high-speed electron collides with a H 2 molecule, producing a molecular ion of hydrogen, with kinetic energy loss of the electron As a result of those reactions, the gaseous environment of the oven (3) contains particles as atomic hydrogen or hydrogen molecule, in a high potential energy level, and contains, still, the molecular ion of hydrogen The first two reactions presented above constitute the chemical part of the thermalchemical process of removal of the junction, while the third reaction is responsible for the thermal part of the process, once it is responsible for the pieces heating All those are high chemical reactivity particles Thus, once in contact with the junction of the injected piece (1), they produce an activated chemical reaction, breaking the carbonic chain of the organic material in a much smaller time than the conventional processes, being obtained as result carbon and volatile hydrogen that are retired of the reactor environment (3) by the vacuum bomb (5) It is important to point out that other atomic or molecular gases, like the oxygen, can also be used to obtain reactivate species Besides the smallest time for extraction of the junction, of the smallest energy consumption, and of the smallest pollution levels of the process here described, other characteristic is that the same plasma oven used for extraction of the junction may also be used for the pieces sintering injected by plasma This way, after the retreat of the junction by plasma finalization, it is enough to adjust the oven to accomplish the plasma sintering, what consists on changing the gases and the temperature conditions and internal oven pressure As consequence, are obtained the extraction of the junction and the sintering in the same equipment and in a same thermal cycle, with economy of energy, with smaller investment, and in much less time The process here described, compared to the existent processes, extracts the junction in times up to 10 times less Besides, it is a process much less pollute, because the residues are gaseous components of small carbonic chains and hydrogen The process can be monitored and automated, since the retreat of the junction can be controlled by mass spectrometry or optic spectrometry, defining the final point of the process accurately It is possible to execute the retreat of the junction and the plasma sintering in the same reactor (3), allowing the process to take place in a same thermal cycle

Claims: CLAIMING 1 - PROCESS EXTRACTION BY PLASMA OF JUNCTION IN OBTAINED PIECES BY POWDERS MOLDING BY INJECTION, characterized by being a thermalchemical process accomplished in a plasma reactor that uses a gaseous mixture contends hydrogen at low pressure, in which electric discharges, acting on the hydrogen, promote the plasma formation (6) contends reactivate species, these constituted by atomic hydrogen and by the hydrogen molecule in high potential energy state, besides the molecular ion of hydrogen, which serve for, besides heating up the pieces (1) placed in the support (2) inside the oven (3), to provoke the chemical decomposition and removal of the existent junction in the pieces interior (1), to increase the kinetics of extraction of the junction and to significantly reduce the necessary time to make the referred extraction 2 - PROCESS EXTRACTION BY PLASM OF JUNCTION IN OBTAINED PIECES FOR MOLDING OF POWDERS FOR INJECTION, in agreement with the claiming 1, characterized by the fact of another atomic or molecular gases, as the argon, the oxygen, or the nitrogen in variable proportions, also can be used to obtain reactivate species for junction extraction by plasma 3 - PROCESS EXTRACTION BY PLASM OF JUNCTION IN OBTAINED PIECES FOR MOLDING OF POWDERS FOR INJECTION, in agreement with the claiming 1, characterized by the junction to be extracted to be anyone of the junctions used in the production technology of powders metallic and/or ceramic injected pieces, including mixtures of waxes and other polymeric ones as the polyethylene, the polypropylene, the polyacetate and other organic junction

Inventors: FREDEL MARCIO CELSO, KLEIN ALOISIO NELMO, MUZART JOEL LOUIZ R, RUBENS MARIBONDO DO NASCIMENTO, SOUZA ANTONIO ROGERIO, WENDHAUSEN PAULO ANTONIO PEREI, FREDEL, MARCIO, CELSO, KLEIN, ALOISIO, NELMO, MUZART, JOEL, LOUIZ, R., RUBENS, MARIBONDO DO NASCIMENTO, SOUZA, ANTONIO, ROGERIO, WENDHAUSEN, PAULO, ANTONIO, PEREIRA
Applicants: FREDEL MARCIO CELSO, KLEIN ALOISIO NELMO, LUPATECH S A, MUZART JOEL LOUIZ R, RUBENS MARIBONDO DO NASCIMENTO, SOUZA ANTONIO ROGERIO, WENDHAUSEN PAULO ANTONIO PEREI, FREDEL, MARCIO, CELSO, KLEIN, ALOISIO, NELMO, LUPATECH S.A., MUZART, JOEL, LOUIZ, R., RUBENS, MARIBONDO DO NASCIMENTO, SOUZA, ANTONIO, ROGERIO, WENDHAUSEN, PAULO, ANTONIO, PEREIRA
Application year: 2000
Main classification: B22F9
IPC codes: B22F3, B29C59, C23C8