Vol 22, No 3 (2020)
- Year: 2020
- Articles: 9
- URL: https://journal-vniispk.ru/1994-6309/issue/view/19958
- Description:
Full Issue
TECHNOLOGY
Ensuring the Accuracy of Wire-cutting EDM processing of Products made of Hard-to-Handle Materials
Abstract
Introduction. In order to improve operational properties of the manufactured product range in engineering, materials, which have enhanced physical and mechanical properties, are used. The application of such materials makes it possible to manufacture the items of small dimensions, but with high functionality. When processing such materials, significant wear of the cutting tool occurs, and when processing items of complex profile, it is necessary to use additional equipment. These factors increase the cost of manufacturing suitable products. For the processing of such products, it is advisable to use electrophysical processing methods, one of which is the technology of wire-cutting electrodischarge maching (EDM). The paper is devoted to theoretical and regression modeling of the width of the cut during EDM difficult to process materials. Subjects of research are: the magnitude of the interelectrode gap, the accuracy of EDM hard-to-handle materials. The aim of the work is to increase the accuracy of the process of EDM complex products, made of hard-to-handle materials. Methods. Experimental studies are carried out according to the method of the classical experiment. For the experiments, an Electronica EcoCut wire-cutting EDM machine is used. The experiments are carried out in the middle processing mode: pulse turn-on time Ton = 10 μs, pulse fill factor Tau = 30 %, average voltage U = 75 V. The electrode tool is a brass wire having a diameter of 0.25 mm. The working fluid is distilled water. Results and Discussion. Theoretical and regression models are obtained for calculating the cutting width during EDM products made of hard-to-handle materials. The dependence of the parameter on the processing conditions and the physicomechanical properties of the material is shown. It is found that with varying fill factor Tau, the response function changes according to the quadratic dependence. The maximum value of the cutting width B = 350 μm is achieved at Tau = 40 %, Ton = 15 μs. A work program is written, which gives opportunity to calculate the value of the cut width, as well as the amount of correction introduced into the work program to complete a suitable size. The accuracy of manufacturing the “stator margin plate” part is ensured. This technology is introduced in the production of oil-producing equipment.
Obrabotka Metallov / Metal Working and Material Science. 2020;22(3):6-17
6-17
Mechanical and Tribological Properties of a Metal Wall Grown by an Electric Arc Method in an Atmosphere of Shielding Gas
Abstract
Introduction. At present, additive manufacturing is one of the most promising methods to optimize the production processes of complex metal products. It is based on the layer-by-layer metal deposition in accordance with a three-dimensional model created using computer aided design software. Various metal powders and wires are applied as a feedstock, and a laser or electron beam, as well as an arc can be employed as a heat source. Despite the existing rather large number of developed methods for the complex metal product additive manufacturing, some of them are very expensive that results in a high production cost. Due to this fact, developing equipment and procedures for the layer-by-layer gas metal arc deposition using carbon dioxide as a shielding gas is an urgent task. The aim of the paper is to investigate the mechanical and tribological properties of carbon steel samples built by the layer-by-layer gas metal arc deposition according to the developed procedure. The carbon steel samples, built by layer-by-layer gas metal arc deposition using carbon dioxide as a shielding gas, are studied. The research methods are mechanical tests of tensile strength, yield strength and elongation of grown samples, as well as tribological properties (wear surface area, friction coefficient and amplitude of vibrational accelerations). Results and Discussion. It is found that the samples built by the developed additive manufacturing procedure possessed the mechanical properties commensurate with hot-rolled steel. It is established that there is a decrease in linear energy when growing a metal wall according to the developed technology due to preheating of the electrode wire to 400...600 ° C by installing an additional current supply located at a distance of 250…400 mm from the end of the wire to pass the heating current. As a result, the tribological properties of the grown samples are increased and its wear became more uniform.
Obrabotka Metallov / Metal Working and Material Science. 2020;22(3):18-32
18-32
Investigation of the Possibility of Finishing Laser processing of Aluminum Alloy D16 Workpieces
Abstract
Introduction: One of the most important tasks in the production of metal parts is to ensure the necessary quality of the processed surface. There are many ways to achieve the required quality, but one of the least studied is laser micro-processing. The purpose of the work is to experimentally determine the possibility of reducing the roughness of the workpiece surface using laser processing. Methods: Laser treatment in these studies is performed using a laser marking system (LMS) “Turbomaster-B20”. The idea of the research is that using laser processing with rational modes it is possible to reduce the roughness of the workpiece surface by removing the vertices of micro-irregularities. The density of lines (r, lines/mm), described by the laser during processing, and the laser power (N, %) are selected as the laser processing modes. Results and Discussion: As a result of the experiments and calculations, the response surface is constructed and the formula for the dependence of Raav=f(r; N) is established. Evaluation of the established dependence showed that the reduction of roughness can be achieved by the following this modes: r = 120 lines/mm; N = 1...5 %. Then, laser processing of pre-milled and grounded workpieces with the obtained modes is performed. Based on the results of experimental studies presented in this paper, the following conclusions can be made: 1) laser processing can be applied for the purpose of final (finishing) processing, because it reduces the surface roughness of the milled billet made of D16 alloy by 23.8 %, and the ground one – by 6.6 %; 2) despite the fact that the decrease in roughness after processing the grounded workpiece is insignificant, it is possible that the applied modes were not optimal for these conditions. Therefore, further research should be directed to the definition of such modes, as well as to the establishment of physical processes in the processing zone and its impact on the workpiece.
Obrabotka Metallov / Metal Working and Material Science. 2020;22(3):33-43
33-43
EQUIPMENT. INSTRUMENTS
Relationship of Temperature and Cutting Force with Tool Wear and Vibration in Metal Turning
Abstract
Introduction. The processes that occur in the machine when cutting metals are interconnected with each other. In the process of cutting, the complex dynamics of processing includes both rapidly changing factors and factors that are more evolutionary (slow) in nature. By such factors the following is meant: changes in stationary components of cutting forces, temperature in the processing zone and tool wear. There is no single and consistent mathematical model describing this connectivity today. Therefore, the paper proposes an approach based on the processing of experimental data obtained in a series of experiments, which allows to identify the structure of feedbacks formed during cutting and linking subsystems that describe the force, heat and vibration responses from the cutting process to the shaping movements of the tool. Purpose of work: Due to the formation of a consistent model of communication between subsystems that describe the force, heat and vibration responses from the cutting process to the shaping movements of the tool, to obtain a description of the mechanism of self-organization of the cutting process in the process of evolutionary changes of the tool. The resulting mechanism is needed to find a certain mode of operation of the cutting system, in which further wear of the wedge, cutting force, temperature in the cutting zone and tool vibration can be stabilized. The paper examines: the process of metal processing by cutting on a lathe for the case of longitudinal turning of the product. Research methods: the Research consists of a series of field experiments on real equipment using a modern measuring stand STD.201-1, which allows simultaneously measuring the force, temperature and vibration components of the reaction from the cutting process to the shaping movements of the tool. For processing and analysis of the experimental data obtained, a package of mathematical programs Matlab is used, in which a subroutine is developed that allows spectral analysis of vibration signals, as well as graphical interpretation of the measured values. Results and discussion. The results of processing experimental data, in particular, the spectra of vibration signals, obtained the dependence of forces and temperature on tool wear, and also revealed the effect of wear on the vibration dynamics of the cutting process. The influence of vibration energy of the tool on the temperature field in the cutting zone is estimated. The main conclusion of the work is the position put forward by us about the self-organization of the cutting system, through the process of tool evolution, which is expressed in the wear of the wedge, the purpose of which is the formation of a certain quasi-stationary cutting mode.
Obrabotka Metallov / Metal Working and Material Science. 2020;22(3):44-58
44-58
MATERIAL SCIENCE
Mineral Ceramic Composite Material: Synthesis and Friction Behavior
Abstract
Introduction. The composition and structure of mineral ceramic composite materials affect its physicomechanical and tribotechnical properties. Despite its wide variety, some part does not have high tribotechnical characteristics. Therefore, the development of a technology for producing new mineral ceramic composite material is a relevant objective. The paper proposes to develop the fundamentals of the technology for producing a new mineral ceramic material by microarc oxidation of sintered diamond-aluminum blank. The material consists of an aluminum oxide matrix and dispersed inclusions of copper metallized diamond. The technological characteristics of its production and tribotechnical characteristics are still understudied. Work objective: to work through the stages of synthesis of a new mineral ceramic composite material, to study its frictional properties and to determine the application area. The paper studies the modes of blank pressing, sintering and further microplasma synthesis of mineral ceramic material with different relative density of samples, diamond concentration and dispersion, its degree of copper metallization. Tribotechnical properties of the obtained materials are also investigated. The research methods are compression tests, material surface studies, and comparative friction tests. Results and discussion. It is revealed that the main factors that determine the product performance are: the relative density of samples, the degree of copper metallization of diamonds and alkali concentration in an electrolyte. The grain size of diamonds determines tribotechnical characteristics and the practical application of cermet. Materials with diamond grain size more than 28/20 showed high cutting characteristics and good diamond holding ability. The volumetric cutting ability is higher than traditional counterparts have, and it does not decrease over time. Tribotechnical tests of ceramic materials with diamond grain size less than 20/14 showed that it has good antifriction properties even without lubricating media. The wear rate of antifriction cermet is comparable to D16 oxidized alloy; its friction coefficient is significantly lower. The authors propose a criterion called a critical nominal pressure that determines the transition from a predominantly elastic contact to brittle fracture of a mineral ceramic material. The created mineral ceramic materials with high diamond grain size are promising as instrumental materials for precision abrasive microprocessing of hard materials. Ceramic materials with a small grain size of diamonds are good for producing parts of friction units operating under lubricant shortage.
Obrabotka Metallov / Metal Working and Material Science. 2020;22(3):59-68
59-68
The Phase Composition of the Nickel-based Inconel 718 Alloy obtained by Additive Technology
Abstract
Introduction. Over the past decade, additive manufacturing (AM) aimed to get the object by 3D model through layer-by-layer manner in a single pass has been actively applied in manufacturing of complex-shaped parts. However, standards for AM materials have not yet been developed. Engineers and researchers are trying to achieve the mechanical properties of AM materials as those formed by standard technologies. Precipitation hardened Ni-based alloys are desirable materials for aircraft engines parts. Usually the complex geometry of such metal parts is formed by a combination of several standard technologies with complex heat treatment. Changing this labor-intensive process to AM is a promising industry direction. Phase transition occurring during layer-by-layer production with a complex thermal effect is one of the main tasks for researches. Focus of this work is made in the study of phase composition and mechanical properties of Ni-based alloy fabricated by high-speed direct laser deposition in different layer areas. Materials and methods. Microstructure of the as-deposited sample is performed using optical microscopy and SEM. Phase composition is analyzed using XRD and TEM. Mechanical properties are evaluated with microhardness and tensile tests at room temperature. Results and Discussion. The as-deposited structure is columnar; grains growing epitaxially along the deposition direction with the presence of transition areas. Laves phase, MC and M23C6 carbides appear as discrete particles and change morphology in different layer areas. The main γ′/γ″ phases are not detected. The initial formations of δ-phase are identified. The microhardness test has the standard level value. With the high value of elongation, the yield strength and tensile strength of the as-deposited sample are lower than those of standard.
Obrabotka Metallov / Metal Working and Material Science. 2020;22(3):69-81
69-81
The Structure, Phase Composition and Micromechanical Properties of Briquetted Aluminum
Abstract
Introduction. The technology of roll briquetting is successfully used for the disposal of waste aluminum alloys for the purpose of subsequent use in metallurgical production during deoxidation and alloying of steels, in aluminothermy, for the production of non-ferrous alloys, as well as in the manufacture of welding electrodes. The received blanks are required to maintain its integrity during loading and unloading and transportation. This is ensured by the selection of effective pressing modes that ensure the minimum porosity. In addition, it is practically interesting to develop a technology for additional processing of briquettes by pressure and cutting, for example, for the formation of welding electrodes. The purpose of the work is to study the chemical and phase compositions of briquetted aluminum, to determine the nature of the distribution of microhardness and micromechanical properties over the briquette cross section. Research methods: measurement of microhardness and porosity, scanning electron microscopy and micro-X-ray spectral analysis, instrumental microindentation. Results and Discussion. It is found that briquetted aluminum is a composite material with an aluminum matrix, the filler is particles of oxides Al2O3, MgO, SiO2 and graphite, which got into the material from the lubricant used when rolling the briquette in roller presses. Dispersed particles of intermetallic compounds Al8FeMg4Si6 and Al15(Fe,Mn)3Si, which are hardening phases, are unevenly distributed in the aluminum matrix. The average density of the composite is 2160 kg / m3, the total porosity is no more than 20%. The central part of the briquetted cell with a hardness of 65 HV 0.1 is dense and does not contain pores. The pores are presented near the surface and have dimensions of 0.1-0.3 mm, which reduces the hardness to 30 HV 0.1. Some areas of the composite are distinguished by higher values of microhardness (up to 140 НV 0.1) and normal modulus of elasticity, as compared to the base material, and a decrease in plasticity and creep indicators. Uneven distribution of micromechanical properties should be taken into account both when developing briquetting technology and additional pressure treatment, as well as when choosing a cutting method.
Obrabotka Metallov / Metal Working and Material Science. 2020;22(3):82-94
82-94
The Influence of Salt fog Exposure on Corrosion Resistance of Detonation Coatings Fe66Cr10Nb5B19
Abstract
Introduction. Nowadays, the development of alloys with a high glass-forming ability and the study of its physical and mechanical properties are among the most important directions in materials science. Iron-based multi-component alloys with high glass-forming ability have high corrosion resistance, wear resistance and relatively low cost, which makes it promising for application on the working surfaces of parts that work under conditions of abrasive wear and aggressive environment. Methods of thermal spraying (plasma spraying, detonation spraying, high-velocity oxy-fuel spraying, etc.) allow producing coatings with amorphous structure from iron-based alloys. Due to the process features, detonation spraying allows to obtain high quality coatings with the structure of metal glass in comparison with other methods of thermal spraying. The purpose of the work is to study the influence of phase composition of detonation coatings from a multi-component iron-based alloy on the resistance to atmospheric corrosion in conditions of neutral salt spray. Detonation coatings from amorphous alloy Fe66Cr10Nb5B19 obtained at different charges of explosive mixture are investigated. The methods of investigation: testing of detonation coatings under simulated conditions of atmospheric corrosion in salt spray chamber according to ASTM B117 in an atmosphere of a spray 5% sodium chloride solution in water for 600 hours at room temperature, as well as conducting X-ray phase and metallographic studies of coatings before and after tests. Results and Discussion. The results of investigation the phase composition and morphology of the coatings after the tests showed its high corrosion resistance in a neutral salt fog containing a large amount of chlorine anions. On the cross sections of those coatings no traces of corrosion penetration were found, which confirms the effectiveness of detonation coatings with the structure of metal glass from the alloy Fe66Cr10Nb5B19 for protection of parts that work under conditions of high atmospheric humidity, without sealing the surface.
Obrabotka Metallov / Metal Working and Material Science. 2020;22(3):95-105
95-105
Determination of the Relationship between the Factor of Grain Size Factor and the Corrosion Rate of Structural Steel
Abstract
Introduction: Equipment using at hazardous production facilities is in most cases made of the structural steels, which are subject to severe corrosion damage in contact with aggressive environments. In aggressive environments, the process of corrosion destruction of the material has a multi-component nature. The multicomponent nature of corrosion processes still leaves the question as to what factors have a greater effect on the process of corrosion. In the literature, the size of the grain structure is indicated as the main corrosion-determining factor. However, in addition to the sizes of the grain, corrosion is also affected by the corresponding factor of grain size variation, characterizing the dispersion of the system as a whole. Therefore, differentiation of factors affecting the course of corrosion processes remains an urgent problem. Purpose: To analyze the possibility of using the grain size variation factor as a diagnostic parameter for determining the rate of the corrosive destruction of structural steel. In article were studied a heat-treated steel samples 15HSND, 09G2S and St3 made from rolled steel. Methods of research: For the study of steels 15KHSND, St3 and 09G2S was applied in the work: scanning electron and optical microscopes-to study the grain structure and intergranular boundaries; SIAMS 700 software package-to find the boundaries and average statistical data on the grain structure; a portable x-ray fluorescence chemical analyzer-to determine the chemical composition of the samples under study; laboratory balance with a measurement error of 0.001 g – to measure the mass of the samples. Results and Discussion: It is established that for the rate of corrosion of structural steels and the factor of heterogeneity, a single satisfactory linear correlation is observed, which can be used to predict the corrosion-hazardous States of structures. It is noted that the loss of some values from the General regression curve can be associated with the processes of reducing distortions in the crystal lattices of steel during a certain heat treatment. The severity of these processes for the considered steels may be different due to the presence of different amounts of alloying elements in their composition.
Obrabotka Metallov / Metal Working and Material Science. 2020;22(3):106-125
106-125