Determination of Heat Accumulation Coefficient for Selected Moulding Materials
Thermophysical properties of moulding materials affect very significantly the structure and properties of castings.From these properties depends from the rate of heat transfer through the form.To date, there is no calculation methods of molding properties, can result both from their complex structure and the complexity of the mechanism of heat transfer across a sand mould, involving heat conduction through a single grain, contact heat transfer between adjoining grains, as well as radiation and convection heat exchange between grains.The possibility of controlling the solidification and cooling time of castings creates prospects of improving their structure and by the same their properties The presented work illustrates the method of determining some basic thermal coefficients of moulding material,i.e.the coefficient of temperature equalisation a2, known also as the temperature diffusivity, and the heat accumulation coefficient b2, which characterises the ability of moulding material to draw away the heat from a casting.The method consists in experimental determining the temperature field within the mould during the processes of pouring,solidification and cooling of the casting.The performed measurements allow for convenient and exact calculations of the sought-after coefficients.Examinations were performed by using two types of moulding sand: for the oil bonded moulding sand of trade name OBB SAND E and either bentonite moulding sand.The performed experiments allow to determining the basic thermophysical properties of the oil-bonded moulding sand, i.e.the coefficient of temperature equalisation a2 and the heat accumulation coefficient b2 in the selected points within the mould.The applied methods allows for convenient and sufficiently precise calculation of their values.The experiment showed that the obtained value of b2 coefficient differs from the value calculated on the basis of theoretical considerations available in publications.Therefore it can be stated that theoretical calculations of the heat accumulation coefficient are thus far not sufficient and not quite reliable, so that these calculations should be verified experimentally.The a2 and b2 coefficients are decisive for the heat transfer from the casting to the mould.Since their values can be affected by the appropriate selection of moulding material composition and the way in which the mould is prepared for pouring, one can control to a certain degree the rate of heat transfer from a casting to the mould.This is equivalent with the possibility of influencing the solidification rate and solidification time, what can in turn affect the structure and properties of the final casting.
chemically bonded sand permeability test thermal distortion test loss on ignition
Malgorzata Lagiewka
Foundry Department, the Faculty of Production Engineering and Materials Technology, Czestochowa University of Technology, ul.Dabrowskiego 69, 42-201 Czestochowa, Poland
国际会议
长沙
英文
169-173
2015-10-25（万方平台首次上网日期，不代表论文的发表时间）