Reversed Polarity Current Research Articles

Адаптация системы ЧПУ станка к условиям комбинированной обработки

Introduction. Increasing the efficiency of processing technologies for products made from modern high-strength, difficult-to-process materials with increased physical, mechanical and operational properties consists not only in improving the technology itself, the tools for its implementation, but also in modernizing technological equipment taking into account new achievements in the field of mechanical engineering. Modern computer numerical control (CNC) equipment is now quite advanced in terms of controlling basic cutting movements. Adaptive monitoring and control systems, as a rule, additionally installed on processing equipment, make it possible to further improve the quality of processing parameters. With the development of new hybrid and combined technologies that combine several types of influence on the product being processed, the issue of synchronizing the automatic control of the movements of parts of technological equipment with the control and management of accompanying processes of combined technologies has become acute. One example of such technologies is electrochemical diamond grinding with periodic dressing of the working surface of a diamond wheel using reverse polarity current. The polarity of the current and the duration of its pulses are controlled by special programmable devices. Current switching units are connected to it. It serves to supply alternating currents of direct and reverse polarity to the electrical circuit and is made on the basis of key elements. Installing such programmable devices on CNC machines leads to its’ equipping with an additional autonomous automatic control system. At the same time, it is difficult to coordinate the operation of the machine’s CNC system, which controls the movements of its working parts, and the programmable device used to control the polarity and duration of current pulses during combined processing. The purpose of the work is to synchronize the CNC system of the machine with the control system for the process of periodically changing the polarity of the current. The study was carried out on an experimental stand. Methods. The research methodology involved conducting an experiment consisting of synchronizing the operation of the machine’s CNC system with the operation of the control system for the process of periodically changing the polarity of the current. To evaluate the results, the time of movement of the diamond wheel as a result of the working stroke was compared with the duration of current pulses of different polarities specified in the control program of the developed software. Results and discussions. As a result of the research, it is established that the developed software and hardware complex makes it possible to synchronize in the CNC system of the machine tool the control of the movements of the working parts with automatic control of the periodic change of current polarity during electrochemical diamond grinding, which can significantly expand the technical capabilities of CNC machines.

Formation of 04Cr18Ni9 steel structure and properties during additive manufacturing of blanks

This work presents results of studying specifics of structure and properties of 04Cr18Ni9 steel formation in additive processes, namely, in СМТ (Сold Меtal Тransfer) additive manufacturing and plasma additive manufacturing at reverse polarity current and consumable electrode plasma additive manufacturing (Plasma MIG). The main problem that arises when additive technologies are applied is to ensure that properties of laminates are no lower than those produced using traditional methods. Typical defects of laminates produced by additive manufacturing are increased porosity, nonmetallic inclusions, reduced plasticity, and for high-alloy steels, loss of special properties. The work includes a comparison in structure and mechanical characteristics of materials obtained by CMT additive manufacturing, plasma additive manufacturing at reverse polarity current, and consumable electrode plasma additive manufacturing. It is established that mechanical characteristics of samples made of 04Cr18Ni9 steel obtained by additive manufacturing are no lower than those of steel of similar composition in the deformed state.

The Comparison Research of Plasma Surface Hardening of 34CrNiMo6 Steel Produced on Direct and Reversed Polarity Current

Many product parameters are basically determined by the state of the surface layer of the material from which it is produced. Increasing the hardness of the surface layer with unique core characteristics will significantly improve the performance characteristics of products and expand field of application of 34CrNiMo6 steel. The paper presents the results of a study of the surface plasma hardening of 34CrNiMo6 steel on direct and reversed polarity current. Studies of four possible variants of plasma surface quenching, including processing with scanning and processing in closed arc mode were carried out. The results of measuring geometric characteristics and hardness of the produced hardened layers are given. The possibility of producing hardened layers with a hardness up to 52 HRC is shown. The macro-and microstructure of the produced hardened layers using light microscopy was studied. The features of structure formation in layers hardened in different variants are analyzed. It is shown that it is possible to produce hardened layers with a depth of 1.7 mm and a width of up to 24 mm in the finishing plasma treatment without significant changes in the surface roughness.

Formation of the Properties of the Working Surfaces of Important Parts by Plasma Surfacing and Surface Heat Treatment by a Reversed-Polarity Current

The properties of surface layers can be formed by changing their structure using heat treatment and their composition and structure via the supply of an additional material to a treatment zone. The structural and phase transformations in the near-surface layer are determined by the thermal cycle in a treatment zone. To control the heating spot area at a uniform energy distribution and a high energy concentration is a challenging problem for surface heat treatment and deposition (surfacing). The results of studying plasma surface heat treatment and surfacing with a reversed-polarity current are presented. The contribution of the heat transfer from nonstationary cathode spots to an article during plasma surface treatment using a reversed-polarity current is separated. The advantages of surface heat treatment of medium- and high-alloy steels and the deposition of similar and dissimilar alloys using a reversed-polarity current constricted direct arc are presented.

Control of Surface Layer Structure with Copper Plasma Surfacing on Steel

Results are given for a study of plasma surfacing of copper on steel in a reverse polarity current. Surfacing layer microstructure is studied. It is shown that the plasma surfacing with reverse polarity current makes it possible to prepare a surfacing layer of almost pure copper without mixing with the base material. Under certain conditions during surfacing with pure copper, it is possible to create a composite surface layer consisting of highly alloyed bronze and a uniform distribution of second materials particles within it.

Plasma Welding of Aluminum Alloys with the Use of Two Direct ARCS on Reverse-Polarity Current

The use of plasma-based technologies elevates productivity and product quality in the fabrication of welded structures made of aluminum and its alloys. High-power heat sources must be used to achieve high levels of productivity in the welding of aluminum structures. Also, the presence of an oxide fi lm that impedes the formation of the weld dictates the use of reverse-polarity current in the arc welding of such structures. The use of combination heat sources can resolve the problem of improving quality and productivity in the welding of aluminum alloys. This article presents results from a study of the plasma welding of aluminum alloys with the use of a dual-arc plasmotron that provides for the combustion of two direct arcs on reversepolarity current. It is shown that the plasmotron can operate stably under these conditions. Use of the given technology reduces the thermal load on the plasmotron, enhances its ability to melt through the alloys, improves cathodic cleaning of the metal’s surface in the region of the weld, and ensures the formation of welds that are free of defects.

Obtaining Hardened Layers of Heat-Resistant Steels by Plasma-Welding Deposition of Congeneric Materials

The paper presents the research results on plasma-hardening of heat-resistant steel layers by plasma-welding deposition of congeneric materials under straight and reverse polarity current. The dependence of the deposited layer quality on the current polarity has been determined. A metallographic examination and measurement of micro-hardness of the deposited layer have been conducted. The dependence of the deposited layer characteristics on the welding parameters has been determined. The obtained results allow the use of plasma-welding deposition to obtain layers with the required strength characteristics using the material, congeneric to the parent material.

Calculation of the heating rate of a preheated electrode in CO2 welding

The empirical equation describing the dependence of the melting rate (feed rate) of a welding wire on current, preheat temperature, and the diameter and extension of the electrode in CO2 welding with reversed polarity current is derived. The dependence of the empirical coefficients of the equation on the process parameters is determined and the physical content of the parameters explained.

Effect of activating composite electrode coatings on the properties of the arc in CO2 welding

The results of investigations of the technological and physical properties of the arc in MAG CO2 welding with reversed polarity current using electrode wires with activating microcomposite coatings based on a copper matrix and halide-containing salts of alkali and alkali-earth metals are presented.

Experimental Analysis on the Variable Polarity Plasma Arc Pressure

Arc pressure is one of the key factors for variable polarity plasma arc(VPPA) and welding pool formation. In this paper, VPPA pressure is measured by pressure transducer and U-tube barometer methods, and advantages and disadvantages of the two methods are compared. The effects of welding parameters, including with straight polarity(SP) current, reverse polarity(RP) current, time ratio of SP to RP, plasma gas flow rate, on VPPA pressure are investigated by using an orthogonal design. The experimental results indicate that the influencing degree of the welding parameters are in the order of plasma gas flow rate, SP current, time ratio of SP to RP, RP current. These results are important to researches of VPPA welding process and its mechanism. The physics behavior of VPPA is taken into account when the above influence mechanisms are analyzed. Firstly, according to the mechanism of the cooling compression to the arc, the compression to VPPA is enhanced with the increase of plasma gas flow, so the VPPA pressure would increase obviously. Secondly, although the temperature of VPPA is as a function of the welding current, the radius of VPPA is also enhanced. So the effects of SP current on VPPA pressure are inferior to the effects of plasma gas flow. Thirdly, VPPA pressure increases as a function of time ratio of SP to RP because the frequency of welding current influences the arc pressure to the some degree; Finally, the RP intervals are farther less than the SP intervals, so the influence to the pressure is minimal.

Effect of easily ionised substances on jet transfer in welding with straight and reversed polarity current

Effect of easily ionised substances on jet transfer in welding with straight and reversed polarity current

Effect of the surface tension forces on spray transfer of metal in welding with reversed polarity current

Effect of the surface tension forces on spray transfer of metal in welding with reversed polarity current

Development of a tungsten cathode for microplasma welding of components with reversed polarity current

Development of a tungsten cathode for microplasma welding of components with reversed polarity current