Vol 20, No 1 (2018)
- Year: 2018
- Articles: 6
- URL: https://journals.rcsi.science/1994-6309/issue/view/19966
- Description:
Full Issue
TECHNOLOGY
Processing of Antimony-tin Concentrates by Vacuum Distillation
Abstract
Object of research: the paper is devoted to the creation of environmentally friendly, technologically efficient and cost-effective high-performance integrated circuits for the processing of concentrate antimony-tin (CАТ) generated in the control filtering in the chemical and metallurgical shop, with commercial production of single-element products of antimony and tin. To analyze the behavior of multicomponent alloy in the processing, study of values of pressure and temperature, prediction of product composition and degree of separation of the metals during the high temperature sublimation the equilibrium phase diagrams VLE (vapor liquid equilibrium), in particular, the temperature–composition "T–x" are calculated. Objective: to study the influence of temperature and pressure in the system on the completeness of extraction and the degree of separation of antimony and tin from the CАТ. Methods and approaches: in constructing the equilibrium phase diagrams VLE calculation of the activity coefficients of the components of the Sb-Sn alloy was performed using three-dimensional model of molecular interaction volume model (MIVM). Novelty: provide new information on the influence of temperature and vacuum depth on the degree of sublimation and separation of metals from Sb-Sn compositions of different composition. Main results: in the temperature range 823–1073 К the saturated vapor pressure (Pа) Sn (0.00332–81.193).10–6 and Sb (3.954–273.664) are calculated. High values of p*Sb/p*Sn = (118.976–0.337).107 and the separation factor logβSb = 6.262–9.435 assume the theoretical possibility to separate these components by vacuum distillation, while the antimony is concentrated in the composition of the sublimates (βSb > 1), and tin – the distillation residue. The tin content in the gas phase, the mole fraction (m. f.): уSn = (0.002–9498.3).10–4, increases in the temperature interval of 921–1878 K, pressure of 1.33–133 Pа and the amount of metal (m. f.) in the alloy хSn = 0.9–0.9999. According to the values of the MIVM γSb = 0.439–0.992 and γSn = 0.433–0.992 for Sb-Sn alloy composition of 0.1–0.9 in the studied temperature range. Practical relevance: the equilibrium diagrams VLE are used in the preliminary stages of designing optimal technological regimes of industrial installations for vacuum distillation and for a reasonable choice of temperature and pressure of sublimation with the goal of obtaining Sn- and Sb-containing products of a given composition. The concept of CAT refining vacuum distillation is proposed.
Obrabotka Metallov / Metal Working and Material Science. 2018;20(1):6-21
6-21
Empirical Evaluation of Technological Deformations for “Soft” Cutting Modes During Thin-Walled Parts Turning
Abstract
Introduction. The problem of thin-walled parts processing is actual for various areas: aviation and space industries, power machine building and others. The literature review shows that modern methods of thin-walled parts processing suppose applying additional technological equipment that increases product cost. Recently the researchers have suggested a “soft” cutting modes method, which proposes a rational pick of cutting and clamping parameters. The method allows parts processing without additional equipment due to the effective selection of the technological process parameters (feed, rotation frequency, cutting depth) based on deformations numerical modeling. In previous papers, researchers described a computer system which allows a technologist superficially estimate the applicability of the chosen cutting modes and take the suppleness into account. Due to this system, a technologist is able to pick the parameters to minimize deformation of the workpiece before the processing starts. The purpose of the paper is to estimate the efficiently of the developed software. The article considers the case of a hollow cylindrical workpiece clamped by a three-jaw chuck. The methods of investigation: the experiment was carried out on a dedicated facility, constructed on the basis of a lathe. A dial gauge was used to measure deformations in predefined points on the workpiece surface. Results and Discussion. The experimental results are presented as deflection graphs. The graphs show both theoretical and experimental curves for various sections of the workpiece. The behavior and periodicity of the experimental curves fit the theoretical. The conducted experiments show that the developed software system is effective and reliable.
Obrabotka Metallov / Metal Working and Material Science. 2018;20(1):22-32
22-32
EQUIPMENT. INSTRUMENTS
Increase of Efficiency of the Internally Cutting Mill with Composite Cutters when Cutting Trapezoidal Thread with Interrupted Elements
Abstract
Purpose: to increase the efficiency of the internally cutting mill due to the developed method of setting the cutters to the calculated values of the angles of shock-free cutting. This allows expanding the technological capabilities of the fragile cutting tool material when cutting trapezoidal thread with the interrupted elements. An analysis of the stress-related characteristics of cutting tool materials of a group of composites is made. The paper shows that the main reason for the low efficiency of cutting elements of the internally cutting mill is the chipping of its cutting edges when inserting (output) the tool into the workpiece and passing through the interrupted elements of the thread, located on its surface. Methods: experimental studies are carried out on a lathe, with the installation on its support of a special device for threading, equipped with a replaceable internally cutting mill, having a set of thread cutters, the cutting part of which is made of a composite material. The quality of the machined thread surface and the accuracy of the execution are controlled by optical method using standard and special measuring instruments. Results and discussion: the rational values of the geometry of the cutting element and the cutting data of the trapezoidal thread by the internally cutting mill equipped with a set of composite cutting elements tuned for cutting into the workpiece with interrupted elements so that the meeting and thread formation occurred as a region of the front surface of the cutting element as far as possible from the cutting edges are presented. The use of the tuning method, protected by the Russian Federation patent, made it possible to increase the efficiency of the internally cutting mill and to extend the range of application of the composite tool material with interrupted cutting.
Obrabotka Metallov / Metal Working and Material Science. 2018;20(1):33-43
33-43
Features of Machine Cyclogram Optimization with the Account of Interaction of Mechanism Links with Stops
Abstract
Introduction. Cyclogram optimization of a technological machine with the account of interaction of the mechanisms links with stop members is discussed. The analysis of scientific literature indicates that cyclogram optimization for complex machines with the account of elastic-dissipative characteristics of the mechanisms needs additional research. Usually simplified dynamic models, which do not take into account elasticity of driven links are used for cyclogram optimization. The urgency of the study is justified by the fact that the existing dynamic models can not be used to calculate the vibrations excited by impacts of the working bodies on the limit stops, when entering into contact with elastic elements. The goal of the study: to improve the cyclogram synthesis method for a technological machine making it possible to increase its productivity. In this study a cyclogram of a technological machine presented in the form of mathematical models using networks for interaction of mechanisms is investigated. STB shuttleless loom, which is a complex technological machine with many executive mechanisms with interconnected movements, is used as the object of the study. During solution of the optimization problem it is necessary to increase the limiting operation time by decreasing the time for technological operations in mechanism groups. The problem for each group is mathematically formulated as an optimization problem on a network graph. The mechanism of microshuttle lift for the STB loom is used in this study. Method of investigation: cyclogram optimization using dynamic models of mechanisms is used. Results and discussion: dynamic models of mechanisms taking into account the interaction of driven links with limiting stop mechanisms are suggested. Dynamic errors of motion laws for a camshaft mechanism operating at the main shaft rotation rate n = 280…420 min–1 with a stop impact are calculated. The mechanism vibrations at natural frequency after contact with the stop are studied. Limitations of the cyclogram optimization problem with the account of the executive link vibrations and impact interaction with the limiting stop are formulated.
Obrabotka Metallov / Metal Working and Material Science. 2018;20(1):44-54
44-54
MATERIAL SCIENCE
Modeling of the Thermal and Structural States of Hollow Cathode of Vacuum Plasmatron
Abstract
Introduction. Arc plasmatrons are widely used in various fields of science and technology. The resource of continuous work of electrodes determines the efficiency of plasmatron and is one of its most important technological characteristics. A theoretical and experimental study of physical and mechanical processes in cathode material is focused on increasing the duration of its running time and is a relevant objective. The purpose of the work is the creation of physical and mathematical models and numerical study of thermal and recrystallization processes occurring in the hollow cathode of a vacuum plasmatron under the influence of an electric arc. Experimental Technique. To study the temperature field of a cathode under the action of an electric arc, the Fourier differential equation with an internal heat source, Laplace equation for the electric potential, and Ohm's law equation were solved jointly. When the plasmatron is operating, new nuclei are formed and grow in the cathode. Three interrelated phenomena are most important for recrystallization: material heating, new grain nucleation and growth. The distribution of crystalline grain size over the cathode volume was calculated based on the temperature field data and activation model parameters of grain nucleation and growth for tungsten. The proposed mathematical models allow simulating the various modes of hollow cathode operation, evaluating the change in the structure of a material during its heating, and can be used to study and improve the performance characteristics of the hollow cathodes of vacuum plasmatrons. Results and Discussion. The obtained solutions showed that the high heating rates and rapid output to stationary mode characterize the cathode heating. It should be noted there is a sharp change in temperature along the cathode length in the area of the active zone (heating surface). The temperature distribution shows the considerable axial and radial temperature gradients, which can lead to large thermal stresses in the cathode. Calculation showed when the superheating over the temperature of recrystallization starts decreasing, the grain size increases. This is due to the fact that when the superheating grows, the nucleation rate outstrips the rate of grain growth, and the grain size decreases. For the investigated flux density values, the size of the primary recrystallized grain, average along the cathode length, is in the range of 3.7–14 μm. The time required to obtain a single-crystal wall of the hollow cathode due to collective and/or secondary recrystallization is 1–32 hours. As a result, complete recrystallization of the grain in the cross-section of tungsten cathode can occur in one cycle of plasmatron operation. This means that the electrophysical and thermal characteristics of the cathode change significantly during its operation. Also the grain size has a significant effect on the resistance to the destructive effects of thermal stresses.
Obrabotka Metallov / Metal Working and Material Science. 2018;20(1):55-68
55-68
Model of the Formation of the Multilayer Coating Composition During Plasma-assisted Deposition
Abstract
Introduction. A modern technical equipment is working in the conditions of high temperature and stress. The technology development demands to create new material with specific properties. Magnetron and vacuum-arc methods of coatings formation using high-melting-point materials have wide expansion for the improvement of detail performance properties. Mathematical modeling is a good alternative to detailed experimental research, allowing to study individual phenomena at different stages of coating formation and to predict the composition and macroscopic properties of the coating change with varying technological conditions. And this, in turn, allows optimizing the technological process. The purpose of the work: to determine the degree of influence of cross effects, as well as the mutual influence of the transfer processes on the formation of the multilayer coating composition when plasma-assisted deposition to the substrate. Mathematical modeling of the coating growth process taking into account combination of physical and chemical stages is conducted. Methods of research are computational methods. In the paper, coupled model of formation of multilayer coating on the surface of cylindrical detail by plasma-assisted deposition is presented. The model considers such effects, as thermal diffusion, diffusion thermal conductivity, the mass transfer by action of stress gradient and formation of chemical compounds. Results and Discussion. The influence of cross-effects, as well as the mutual influence of the transport processes in the formation of the multilayer coating deposited from the plasma, is theoretically investigated. It is shown that the composition of the plasma affects the evolution of the coating composition. It is determined that taking into account the mass and heat transfer due to the stress gradient has a noticeable effect on the coating composition. It is found that for the selected systems, thermal diffusion and diffusion thermal conductivity affect the distribution of concentrations only at the initial stage of the coating deposition process.
Obrabotka Metallov / Metal Working and Material Science. 2018;20(1):69-79
69-79