No 4 (2017)

Object of research: the paper is devoted to the creation of environmentally friendly, technologically efficient and cost-effective high-performance compatible circuit for the processing of lead-containing industrial products and wastes, in particular, silicate slag (SS), formed during copper electrolytic sludge melting, with commercial production of single products. Vacuum distillation is considered to be the one of the most effective and environmentally friendly methods for the separation and purification, processing and refining of various metals. To analyze the behavior of multicomponent alloy reclamation, pre-selection of temperature and pressure of the system, evaluate the effectiveness of component separation in a vacuum distillation, phase diagrams temperature-composition “ T-x” , pressure-composition “ P-x” is used. It is the purpose of the paper to calculate the equilibrium “gas-liquid” VLE (vapor liquid equilibrium), including the dependence of phase composition on temperature ( T-x ) and pressure ( P-x ) for Sb-Ag alloy with vacuum distillation based on the model MIVM (molecular interaction volume model), as well as determine of thermodynamic parameters of the process. Methods and approaches: calculation of the activity factors of components of Sb-Ag alloy is performed using three-dimensional model of molecular interaction volume model ( MIVM ). Novelty: the calculation of VLE diagrams using the model MIVM . Main results: in the temperature range 823-1073 K, the saturated vapor pressure (Pa) for silver (0.0053…50.544).10-6 and antimony (3.954…273.664) is calculated. High values of the ratio (74.488…0.514) × 107 and the separation factor logβSb = 5,842-12,253 create a theoretical background for the selective separation of these metals by vacuum distillation, when the antimony is enriched in the gas phase (βSb > 1), and silver in liquid. The mole fraction of silver in the gas phase у Ag = (0.00001…1296.8) × 10-8 increases with increasing temperature 823-1073 K and the molar fraction of the metal in the alloy х Ag = 0.1…0.9. Using the MIVM model the activity factors of antimony γSb = 0,060-0,945 and silver γAg = 0,000377-0,974 for Sb-Ag alloy with different composition in the investigated temperature range are calculated. The lever rule (rule lines) can be used for phase diagrams VLE to help predict the quantities of substances, residues and sublimates at a predetermined temperature. For the phase boundary “liquid-gas” Sb-Ag alloy the values of the excess Gibbs energy, enthalpy and entropy are as the follows: = 1.9…6.9 kJ/mol; = 2.03…8.77 kJ/mol; = 0,13…2,55 J/mol. K . Practical relevance: VLE phase diagrams alloys provide the necessary information for the design of technological parameters in industrial production, vacuum metallurgy, as well as for prediction the temperature and pressure of the process when obtaining Ag- and Sb-containing products of a given composition.

Introduction. The advanced steel 10H3G3MFS (C = 0.1, Mn = 2.51, Cr = 2.75, Mo = 0.40, V = 0.12, Si = 1.25), developed for oil-producing engineering, has good workability and strength characteristics, but the level of impact strength after the traditional modes of heat treatment is at a sufficiently low level. The paper is devoted to the investigation the possibility of metastable structural states formation during intercerical quenching of steel 10H3G3MFS for the purpose of increase the level of impact strength without significant loss of strength characteristics. The subjects of study are the steel structure formation processes when heated in an intercerical temperature range (ICTR) with subsequent quenching. The purpose of this work is to study the possibilities of controlling the structure and properties of steel 10H3G3MFS with the use of isothermal austenitization in ICTR to obtain a dispersed structure. Methods. Dilatometric analysis using the Linseis hardening dilatometer R.I.T.A. L78, metallographic analysis using a light inverted microscope OLYMPUS GX 51 and electron microscopy using a transmission electron microscope FEI Tecnai 20 G2 TWIN are being in use. Uniaxial tensile tests are carried out using the universal hydraulic system for static tests INSTRON-SATEC 300 LX and the toughness is determined by pendulum coprometer KM-30, followed by fractographic analysis on a light microscope Olympus SZX-16 and a scanning electron microscope Hitachi S-3400N. Results and Discussion. Based on the results of the study of the process of investigated steel continuous heating, a thermokinetic diagram of the formation of austenite with the designation of the critical points AC1 and AC3 is constructed. It has been established that as the heating rate increases, the critical temperature AC1 decreases and AC3 increases. A study of the isothermal austenitization process showed that 27% of the γ-phase is formed at 710 °C, 59% of the γ-phase is formed at 750 °C, 76% of the γ-phase is formed 800 °C, and during the soaking at 860 °C occurs complete austenitization and 100% of the γ-phase is obtained. It was also found that with an increase in the temperature of isothermal soaking, the proportion of athermic austenite increases, and the isothermal content decreases. An isothermal diagram of austenite formation the initially hardened steel 10H3G3MFS is constructed. The study of steel 10H3G3MFS structure formation process has revealed that during the austenitization process at 715 °С the first stage of austenite formation occurs: austenitic grains form along the boundaries of former austenite grains and martensitic packages. An increase in the austenitization temperature up to 750 °C leads to the development of the second stage of austenitization: austenitic grains form along the martensitic stripe boundary. At a temperature of 800 °C, the second stage is further developed, which, after quenching, leads to the formation of a martensitic framework along the interstitial boundaries of the initial α-phase. These interlayers of the initial α-phase are fragmented by dislocation boundaries and strengthened by a small amount of carbide particles. Thin layers of residual austenite are present in the martensite framework. There are freshly quenched areas of the polyhedral shape that are formed at the grain boundaries of the original austenite or the boundaries of the original packets. The raise of heating temperature to 860 °C causes the end of the α → γ transformation during the soaking process, and after following quenching the structure of packet martensite whith twins is formed. According to the strength and plasticity test, it is established that quenching from 800 °C leads to a slight decrease in the tensile strength brake (by 8%), but the yield strength does not practically decrease. The percent elongation remains at the level of the initially hardened steel, and the percent reduction significantly increases (from 54 to 60%). The KCT toughness level of the steel under study significantly increases up to 0.76 MJ/m2 (by more than 70%). According to the data of fractographic analysis, samples after dynamic tests have viscous fracture mode. The received mode of heat treatment allows to increase the level of toughness of the steel under study without loss in strength of products of any overall dimensions for oil-producing machine building.

Introduction. Welding affect fundamentally on the availability of the constructions operated under the low temperatures due to a decrease in resistance to the nucleation and propagation of cracks in the heat-affected zone and weld metal. Despite the existence of a sufficiently large number of ways to improve the reliability of welded joints, some of them have now completely exhausted its capabilities, while others have not been brought to the stage of wide practical application. Therefore, the development of the necessary special welding technology in low temperature conditions remains an urgent problem. The purpose of the work: to find the ways to improve the reliability of high-duty metal constructions welded at low temperatures. The welded joints of 09G2S steel obtained by welding with direct current and pulsed low-frequency current modulation under conditions of positive (+ 20 °C) and negative (-45 °C) ambient air temperatures are investigated using three new types of welding electrodes. The methods of investigation. Mechanical tests for static tension and impact bending of welded samples, as well as spectral analysis of the chemical composition and metallurgical studies of weld metal are undertaken. Results and Discussion. It is revealed that the metal constructions operational factors depend on the choice of the welding method and welding temperature, as well as the characteristics of the welding material. It is established that to increase the impact strength of samples welded at negative temperatures by the adaptive pulse-arc welding method, an increase in heat input is required, relative to the rat of energy input, realized in the process of welding at positive temperature. The effect of the weld metal structure refinement using adaptive pulse-arc welding with coated electrodes is confirmed, including in conditions of negative ambient air temperature (down to 45 °С below zero). The presented results confirm the prospects of the developed approach aimed at obtaining new classes of materials and products, intended for operation in the conditions of the North and the Arctic.

Purpose: the properties of explosively welded materials to a large extend depend on structure of thin layers which appear near the interface during a high velocity collision of workpieces. The main purpose of this paper was to study formation of materials structure in these layers by simultaneous analysis of numerical simulation results and results of materials characterization. Methods: low carbon steel plates (0.2 wt. %C) were used for explosive welding. The structure of explosively welded material was studied using light microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The numerical simulation was carried out using smooth particle hydrodynamic (SPH) method in Ansys Autodyn software. Results and discussion: the most significant structural changes occur in a thin layer near the interface of explosively welded materials. The main part of the sample is just insignificantly deformed and slightly heated. High strain rate deformation in the vicinity of the interface leads to localization of strain and significant heating of materials. The conditions of the deformation during the welding are close to adiabatic. Due to the high temperature diffusivity and large temperature gradients the subsequent transfer of the heat to slightly heated layers occurs with high rates (104…107 K/s). This leads to formation of metastable structures (in this study, the martensite structures were observed). The structure of the welded plates forms as a result of competition between strain hardening and temperature softening processes. The SPH simulation successfully reproduced wave formation, vortices formation and jetting phenomena. The geometry of the interface predicted by the simulation was in a very good agreement with geometry, observed in metallographic study. The simulation predicts that the strain in a very thin layer near the interface can exceed e = 6.