Thermophysical Property Measurements on Mold Materials: Thermal Expansion and Density

Diószegi

International Journal of Cast Metals Research

2020

In this study, thermophysical properties of a commonly used silica sand were investigated and their relation to its granulometric and chemical composition was studied. Thermal expansion and differential scanning calorimetry tests were performed on individual fractions of the silica sand together with X-ray fluorescence measurements to determine their constituents. It was found that the various size fractions of silica sand exhibit different levels of thermal expansion based on the differences in SiO 2 content. The expansion behaviour of two additional silica samples and a recycled olivine sand was also investigated in relation to its grain size to justify the findings.

Section: Introductionmentioning

confidence: 99%

The origin of thermal expansion differences in various size fractions of silica sand

Diószegi

International Journal of Cast Metals Research

2020

Archives of Metallurgy and Materials

“…The heating rate was set to 10°C/min, the maximum temperature was 1100°C. In order obtain additional information compared to the literature [2,[6][7][8], the volume change was registered not only during heating up, but also during cooling down in the function of temperature. The measurements were first performed by Al 2 O 3 standard with the same layout to obtain a correction file containing the expansion of the system and the sample holder.…”

Section: Experimental Methodsmentioning

confidence: 99%

The Influence of Thermal Expansion of Unbonded Foundry Sands on the Deformation of Resin Bonded Cores

Svidró¹,

Diószegi²,

Tóth³

et al. 2017

Depending on the preparation and the applied materials, moulds and cores can be of high rigidity or can be flexible. Although, chemically bonded moulding materials have relatively good flexibility, their high temperature behaviour determines the dimensional accuracy, the stresses in the castings and can induce several casting defects, such as rattail, veining, etc. The phenomenon is based on two major effects: the thermal expansion of the unbonded foundry sands and the deformation of the sand mixtures. The main objective of the present work was to study the relationship between these two effects, and to improve the knowledge related to the thermo-mechanical interactions between the casting and the mould. Dilatometric analysis of unbonded sand samples were performed and compared to the results of hot distortion tests of moulding mixture specimens. The results showed, that the thermal expansion of foundry sand largely influences the hot distortion behaviour, but depending on the type of binder used.

“…The relationship between grain size distribution and thermal properties such as thermal expansion is commonly studied in foundry research on unbonded and bonded sand samples [ 9 , 10 , 11 , 12 , 13 ]. From the mould/metal interface, the mould layers heat up to a certain temperature range due to the relatively low thermal conductivity of the porous mould.…”

Section: Introductionmentioning

confidence: 99%

Effect of the Composition of Hybrid Sands on the Change in Thermal Expansion

et al. 2022

In the foundry industry, silica sands are the most commonly used type of sands for the production of sand foundry moulds using various types of binders. Their greatest disadvantage is their significant volume changes at elevated temperatures, which are associated with the formation of many foundry defects from stress, such as veining, and thus have a direct influence on the final quality of the casting. In the case of non-silica sands and synthetic sands, the volume stability is more pronounced, but this is accompanied by a higher purchase price. Therefore, a combination of silica sand and synthetic sand CERABEADS is considered in order to influence and reduce the thermal expansion. The hybrid mixtures of sands, and their most suitable ratios, were evaluated in detail using sieve analysis, log W and cumulative curve of granularity. It was found that the addition of 50% CERABEADS achieves a 32.2% reduction in dilatation but may increase the risk of higher stresses. The measurements showed a significant effect of the granulometric composition of the sand on the resulting thermal expansion, where the choice of grain size and sorting can achieve a significant reduction in dilatation with a small addition of CERABEADS.