Abstract
Obtaining castings of given quality is the main task of foundry production. One of the stages of casting technology is solidification of melt in the mold. When studying the process of castings solidification, it is necessary to fully take into account all the features of heat transfer between casting and mold. Influence of various thermophysical parameters of alloy and mold material on casting formation is considered. In the analysis, original mathematical models were used to calculate the coefficient and time of complete solidification of castings in sand-clay and metal forms. These models take into account geometric parameters of casting, main thermophysical parameters of casting metal and mold material, heat transfer conditions at crystallization front, on casting-mold boundary and on the mold surface. Analysis of dependence of time and rate of castings solidification on thermophysical parameters (heat capacity, density, heat conductivity of casting material and mold, specific heat of metal crystallization) was carried out. Storage capacity and process of heat storage are quite fully characterized by the value of heat storage coefficient. This coefficient practically determines the rate of heat loss by the casting which plays a decisive role in its properties forming. Therefore, this parameter is selected for a comprehensive analysis of thermal processes occurring in casting and mold. The influence of thickness and thermal conductivity of chill paint layer on solidification of castings in metal molds is considered. The basic calculation formulas and initial data are presented. Calculations were carried out for castings of the following types: endless plate, endless cylinder, ball. The results of simulation of solidification process parameters are presented in graphic form. Using various alloys as an example, it has been shown by calculation that when changing composition and properties of mold material, it is possible to change time and speed of alloys solidification in a wide range. In this case, processes of forming the structure and properties of castings are controlled.
Highlights
Obtaining castings of given quality is the main task of foundry production
Original mathematical models were used to calculate the coefficient and time of complete solidification of castings in sand-clay and metal forms. These models take into account geometric parameters of casting, main thermophysical parameters of casting metal and mold material, heat transfer conditions at crystallization front, on casting-mold boundary and on the mold surface
Storage capacity and process of heat storage are quite fully characterized by the value of heat storage coefficient
Summary
(119049, Россия, Москва, Ленинский пр-т, 4) 3 Владимирский государственный университет имени Александра Григорьевича и. При анализе использованы оригинальные математические модели для расчета коэффициента и времени полного затвердевания отливок в песчано-глинистой и металлической формах, которые учитывает геометрические параметры отливки, основные теплофизические параметры металла отливки и материала формы, условия теплообмена на фронте кристаллизации, на границе отливка – форма и на поверхности формы. Проведен анализ зависимости времени и скорости затвердевания отливок от теплофизических параметров: теплоемкости, плотности, теплопроводности материала отливки и формы, удельной теплоты кристаллизации металла. На примере различных сплавов расчетным путем показано, что при изменении состава и свойств материала формы можно изменять время и скорость затвердевания сплавов в широком диапазоне. Подобный подход позволяет с достаточной точностью прогнозировать усадочные процессы, в том числе формирование различных литейных дефектов, а также особенности макро- и микроструктуры получаемых отливок и, как следствие, уровень их механических свойств [16]. В результате полученные решения, несмотря на их несомненную теоретическую значимость, зачастую не представляют существенной практической ценности
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