Browsing by Author "Repiakh, Serhii I."
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Item Kinetics of Quartz Sand and Its Mixtures Drying by Microwave Radiation(Dnipro University of Technology, 2021) Solonenko, L. I.; Repiakh, Serhii I.; Uzlov, Kostiantyn; Mamuzich, I.; Kimstach, Tetiana; Bilyi, OleksandrENG: Purpose. Kinetics research and description of drying by microwave radiation mechanism development of quartz sand and its mixes with sodium silicate in limited quantity of water steam medium. Methodology. Distilled water, sodium silicate solute and quartz sand have been used in this research. Study has been performed on sand samples weighing 200 g. Mixtures drying and structuring have been performed by microwave radiation with power of 700W with frequency of 2.45 GHz in air and in saturated water weighing 1 g steam medium. Accuracy of temperature measurement is 1, mass is 0.02 g. Realized in this investigation drying kinetics has been specified as specimen weight change dependence and moisture evaporation from this mixture rate vs. drying duration. Dependencies have been built on the results of video recording and corresponding chrono-gravimetric measurements data digitalization. Mixtures during heating by microwave radiation temperature changes registration has been performed with an interval of 1560 s. Samples average heating rate has been estimated by calculation based on results in their temperature change determination during first 2 minutes of heating with microwave radiation. Findings. For the first time, microwave drying kinetics of quartz sand and its mixtures with sodium silicate in limited water medium (structured by SMS-process) has been studied. For the first time, based on SMS-process material balance, analytical dependence has been developed. This dependence application allows sand-sodium-silicate mixture structured by SMS-process maximum mass to calculate when using sodium silicate solute (silicate module 2.83.0) for quartz sand cladding and 1 g of saturated water steam for mixture structuring. It has been established that when mixtures structuring according to SMS-process water extraction from them takes place in three stages at ~100, 100108 and at 125138. Maximum appropriate heating temperature of sand-sodium-silicate mixture during structuring by SMS-process has been recommended as ~125. Exceeding of specified temperature leads to hydrated water from mixture releasing in steam form and its condensation on colder working surface of model-rod rigging. Resulting condensate leads to mixture restructuring in contact with equipment places and, accordingly, sharp quality deterioration in prepared molds and rods. For manufactured molds and rods quality stabilization, it has been recommended to pre-dry the quartz sand cladded with sodium silicate solute in microwave field for at least 3 minutes before structuring according to SMS-process. Originality. For the first time, data on drying kinetics has been obtained and quartz sand and its mixtures with sodium silicate in limited water steam medium microwave drying mechanism description has been developed. Influence of number of SMS-process basic parameters on structured quartz sand weight regularities has been established. Practical value. Research results will be useful in terms of ideas expanding about the processes that accompany granular materials drying, as well as in technologies and equipment for drying and structuring fine-grained dielectric materials and their mixtures development, creating new capillary-porous media, etc. under microwave radiation influence.Item Sand-Sodium-Silicate Mixtures Structured in Steam-Microwave Environment Effective Values of Thermo-Physical Properties(Dnipro University of Technology, Ukraine, 2021) Solonenko, L. I.; Repiakh, Serhii I.; Uzlov, Kostiantyn I.; Dziubina, A. V.; Abramov, Serhii O.ENG: Purpose. Sand-sodium-silicate mixtures, structured by steam-microwave solidification, thermo-physical properties integral-effective values during Al-Mg alloy and graphite cast iron pouring determination. Sand-sodium-silicate mixture apparent density changing according to quartz sand, cladded with sodium silicate solute, fractional composition and its influence on BrA9Zh3L bronze microstructure establishment. Methodology. Quartz sand with 0.23 mm average particle size, sodium silicate solute, aluminum alloy with 8.5 % Mg, flake graphite cast iron SCh200 (DSTU 8833:2019), bronze BrA9Zh3L (GOST 493-79) were used. Mixtures structuring was carried out in 700 W magnetron power microwave furnace. Sand-sodium-silicate mixture thermo-physical properties integral-effective values were calculated by G. A. Anisovich method, using castings results and molds thermography. Structured mixtures apparent density was determined on samples 50x120 mm dimension. Metallographic studies were realized using Neophot-21 optical microscope. Findings. It was found that with sodium silicate solute, used for sand cladding, amount increasing from 0.5 to 3 % mold material apparent density decreases and thermal activity lowers. This leads to castings grains size increasing. Mixture sodium silicate solute content was recommended limiting 1.5 % for fine-grained microstructure castings obtaining and cladded sand using, which particles pass through mesh side less 0.315 mm sieve. Sands with sodium silicate solute content more than 1.5 %, which don’t pass through sieve 0.4 mm mesh side, were recommended as casting molds heat-insulating material using. Originality. For the first time, when aluminum-magnesium alloy and graphite cast iron pouring, quartz sand cladded with sodium silicate solute in amount from 0.5 to 3.0 % (weight, over 100 % quartz sand), steam-microwave radiation structured, thermo-physical properties integral-effective values were determined. Practical value. Data obtained using will improve castings solidification time and rate analytical calculations accuracy, forecast level and residual stresses sign in them, shrinkage defects locations. This will reduce casting technology developing time and costs and castings manufacturability.Item Water Resistance of Structured Sand-Sodium-Silicate Mixtures(Dnipro University of Technology, 2021) Solonenko, L. I.; Repiakh, Serhii I.; Uzlov, Kostiantyn I.; Mamuzich, I.; Bilyi, Oleksandr P.; Kimstach, Tetiana V.ENG: Purpose. To establish regularities of changes in sand-sodium-silicate mixtures (SSSM) relative water resistance, structured by steam-microwave solidification method (SMS), on their structuring parameters and sodium silicate solute (SSS) dissolution conditions. Methodology. Technical purity water, SSS with 2.8–3.0 silicate modulus, quartz sand with 0.23 mm average particle size were used in this work. Studies were carried out on quartz sand samples, which were preliminarily cladded with 0.5–2.5 % (by weight) SSS and structured by SMS method. The fracture time of structured mixtures was evaluated on cubic specimens with 20 mm rib length, which were immersed in water at different temperatures. Findings. Changes in SSSM water resistance in water regularities depending on their manufacturing, use and storage conditions were established. Recommendations for SSSM rods removal from castings in water were developed. Originality. For the first time, it has been established that relative water resistance of the SSSM structured by SMS method decreases along with increase in water temperature in which it is destroyed. Depending on SSS mass used for quartz sand cladding in range 0.5–2.5 %, water resistance dependence on treatment in steam-microwave environment with 2–7 minutes’ running time acquires an inversion character with inversion point ∼3.1 minutes into the processing. For the first time, it has been discovered that in boiling water the relative water resistance of SSSM, structured by SMS-process and having preheating, monotonically increases with preheating temperature rising from 100 to 600 °С, sharply increases when heated to 600–700 °С and practically becomes absolute after preliminarily preheating to higher temperatures. Practical value. Research results will be useful in concepts of processes accompanying destruction of structured sands with water-soluble binders expanding, as well as in technologies and equipment development designed for SSS rods and mold rests removing from castings.