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.
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 2.83.0 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 0.52.5% (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 0.52.5%, water resistance dependence on treatment in steam-microwave environment with 27 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 , sharply increases when heated to 600700 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.
Purpose.Influence of preheating temperature and sodium silicate solute content in sand-sodium-silicate mixtures structured by SMS-process on their destruction work under knock loading action has been established. Methodology. Quartz sand brand 1K2O202, water, sodium silicate solute with specific gravity of 1.42…1.44 g/cm3 and silicate modulus of 2.8… 3.0 have been used in this work. Mixtures structuring has been realized in microwave furnace with frequency of 2.45 GHz and magnetron power of 0.9 kW. Samples heat treatment has been performed in laboratory resistance furnace in temperature range from 100 to 1100С with sample isothermal tempering at fixed temperature for 45...50 minutes. Samples knockout work has been calculated according to CNIITMASH method. Samples of structured by SMS-process mixtures destruction has been performed on laboratory impact machine brand 5033A. Samples structure has been examined on optical microscope at 100-times magnification. Results. With preheating temperature increasing sand-sodium-silicate mixtures structured in steam-microwave environment by SMS-method, containing from 0.5 to 2.5% sodium silicate solute with modulus of 2.8 ... 3.0, knockout work decreases exponentially. At preheating temperature from 800 to 1100°C it becomes practically zero. Mixtures, preheated to 600°C, knockout work does not exceed 20J. It follows that such rods or their individual parts can be removed from castings by shock-vibration method, even from copper and aluminum based alloys. Knockout the rods or their parts, in which after contact with poured into mold melt temperature did not exceed 600°C, has been recommended to carry out by castings immersing in water. Scientific originality. Mold and core mixtures structuring in steam-microwave environment solves the problem of sandsodium-silicate mixtures, containing sodium silicate solute up to 2.5%, knockout from castings for most foundry alloys used in industry. Practicalvalue. Investigation results will be useful for removal of sand-sodium-silicate rods and molds, structured by the SMS-process, technologies and equipment development.
Properties and structures of Sodium silicatesand mixtures componentsСтаттю присвячено питанням виявлення закономірностей структурування піщано-рідкоскляних сумішей, вивченню можливості прогнозування і зміни їх властивостей. Дослідження виконані з використанням кварцового піску та рідкого скла, а також кварцового піску, плакованого рідким склом. Встановлено, що сипкість піску не залежить від розмірів його частинок і найбільшу величину набуває при вмісті вільної води (вологи) менше 0,2% за масою, уявна щільність чистого і плакованого піску, ущільненого вібрацією, адитивна пайовому масовому вмісту в ньому нормованих фракцій піщинок і зростає від 1100 до 1900 кг/м 3 зі зменшенням середнього розміру його зерен від 0,81 до 0,16 мм і зі збільшенням модуля їх дрібноти від 20 до 60. За експериментальними даними розроблено аналітичну залежність між вмістом в рідкому склі силікату натрію і питомою щільністю рідкого скла, проведена оцінка впливу способу сушіння рідкого скла на залишковий вміст в ньому води. Показано, що в залежності від кількості рідкого скла в суміші, його фізичного стану до моменту початку структурування суміші і способу його затвердіння структура затверділого рідкого скла в структурованій піщано-рідкоскляній суміші може змінюватися від щільно-орієнтованої до пінно-дезорієнтованої, містити і не містити залишкову воду. Використання і облік отриманих даних дозволить не тільки скоротити витрати на розробку нових піщано-рідкоскляних сумішей, підвищити точність прогнозування їх властивостей, але і відкриває новий напрям в способах виготовлення з них ливарних форм і стрижнів.Ключові слова: рідке скло, пісок, вода, сушка, випаровування, випромінювання, пара Article is devoted to the questions of structuring regularities detection in sodium silicatesand mixtures and possibility of forecasting and changing their properties determination. Studies have been performed using quartz sand and sodium silicate solute, and also quartz sand placket with sodium silicate solute. It has been discovered that sand flow ability does not depend on the size of its particles, and the largest value acquires with the content of free water (moisture) less than 0.2% by weight. It has been established that apparent density of rare and placket sand, compacted by vibration, is additive to fractional mass content in it of particles normalized fractions and increases from 1100 to 1900 kg/m 3 with average size of its grains decreasing from 0.82 to 0.16 mm and with their fineness modulus increasing from 20 to 60. According to experimental data, analytical relationship between content of sodium silicate in sodium silicate solute and specific density of sodium silicate solute has been elaborated. Estimation of sodium silicate solute drying method influence on residual water content in it has been realized. It has been shown that depending on sodium silicate solute amount in mixture, its physical state up to the time of mixture structuring beginning and method of solidification, the structure of solidified sodium silicate solute in structured s...
Influence of sand-sodium-silicate mixtures structured by steam-microwave solidification method on small castings qualityThe purpose of the research is to evaluate the influence of the method of making molds from sand-sodium-silicate mixtures, structured by steam-microwave solidification method on the surface quality and cast products size accuracy and to establish the steam-microwave solidification method suitability for the production of small castings for general engineering purposes. Cast surface accuracy degree according to DSTU 8981:2020 and its roughness parameters have been investigated on Ø30×150 mm castings of steels 40Cr24Ni18Si2L and 30L, flake graphite iron FGI20, bronzes BrSn5Si5Zn5 and BrAl9Fe3L. Castings have been prepared in foundry forms manufactured of structured quartz sand cladded with silicon silicate solute in steam-microwave medium. Roughness parameters determination has been carried out by profilometry device equipped with information and computing complex of model 170622. Influence of molding mixture structuring method determination on casting dimensions accuracy has been carried out on "Grating plate" casting from steel 40Cr24Ni18Si2L. Investigation has been realized by comparing of "Grating plate" overall dimensions and their nominal value variables deviations, as well as comparison of defective castings number, which have been manufactured in forms that were structured by CO 2 process and by the method of steam-microwave solidification. Castings sizes have been measured by caliper with measurement error value up to 0.01 mm. Surface quality of castings from surface defects presence point of view has been evaluated visually. As per research results it has been found that in accordance with DSTU 8981:2020 degree of castings cast surfaces in the range 100 to 250 mm accuracy corresponds to 7-10 classes, which is at the level of accuracy degree of bronze shell forms molding from thermosetting mixtures. Steel and cast-iron castings are at the level of low pressure casting in chill mold without sand rods and higher than in castings produced in sandy-clay, vacuum-film forms and forms of sodium-silicate-solute selfhardened mixtures. Accuracy of castings dimensions made in forms by steam-microwave solidification method is slightly higher than castings made in forms of CO 2 process. In this case, in castings obtained in forms by steam-microwave solidification process, there are no gas cavities and cold laps, and the final lack of sizes mismatches and castings surface defects correctional lack, respectively in 3.7 and 13.5 times lower than in castings that have been made in forms of CO 2 process. The first examination and in accordance with DSTU 8981:2020 established the level of accuracy of the cast surface and parameters of its roughness for castings of size 100-250 mm of steels 40Cr24Ni18Si2L and 30L, flake graphite iron FGI20, bronzes BrSn5Si5Zn5 and BrAl9Fe3L, which were poured in foundry molds, the mixture of which was structured by steammicrowave solidification method. Obtained data will be ...
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