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The Influence of Silica Sand Granulometry and Sorting Level on Thermal Expansion

M. Bašistová P. Lichý
Archives of Foundry Engineering | 2023 | vol. 23 | No 3 | 12-15 | DOI: 10.24425/afe.2023.144309
Keywords Foundry sand Dilatometry Sand grains distribution Sieve analysis Moulding mixtures
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Abstract

The quality of the castings depends, among other influences, on the quality of the moulding mixture used. The silica sands used are characterized by high thermal expansion compared to other sands. The tendency to dilatation of the moulding mixture can be influenced by the choice of the granulometric composition of the basic sand and the grain size. The aim of this work is to present the influence of grain distribution of foundry silica sand BG 21 from Biala Góra (Poland) and the degree of sorting (unsorted, monofraction, polyfraction) on the degree of thermal dilatation of the sand and thus on the resulting quality of the casting and susceptibility to foundry defects. For the purpose of measuring thermal dilatation, clay wash analysis was performed, sieve analysis of the sand was carried out, and individual sand fractions were carefully sorted. The measurements confirmed a higher thermal expansion in the case of monofractional sand grading, up to 51.8 %. Therefore, a higher risk of foundry stress-strain defects, such as veining, can be assumed.
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Bibliography

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[2] Brůna, M. & Galčík, M. (2021). Casting quality improvement by gating system optimization. Archives of Foundry Engineering. 21(1), 132-136. https://doi.org/10.24425/afe.2021.136089.
[3] Monroe, R. (2005). Porosity in castings. AFS Transactions. 113, 519-546.
[4] Kowalski, J.S. (2010). Thermal aspects of temperature transformation in silica sand. Archives of Foundry Engineering. 10(3), 111-114. ISSN (1897-3310).
[5] Jelínek, P. (2004). Binder systems of foundry moulding mixtures – chemistry of foundry binders. (1st ed.). Ostrava. ISBN: 80-239-2188-6. (in Czech).
[6] Svidró, J., Svidró J. T., & Diószegi, A. (2020). The role of purity level in foundry silica sand on its thermal properties. Journal of Physics: Conference Series. 1527(1), 012039, 1-8. DOI 10.1088/1742-6596/1527/1/012039.
[7] Chao, Ch. & Lu, H. (2002). Stress-induced β→ α-cristobalite phase transformation in (Na2O+Al2O3)-codoped silica. Materials Science and Engineering: A. 328(1-2), 267-276. DOI: 10.1016/S0921-5093(01)01703-8.
[8] Hrubovčáková, M., Vasková, I., Benková, M. & Conev, M. (2016). Opening material as the possibility of elimination veining in foundries. Archives of Foundry Engineering. 16(3), 157-161. DOI: 10.1515/afe-2016-0070.
[9] Beňo, J., Adamusová, K., Merta, V., Bajer, T. (2019). Influence of silica sand on surface casting quality. Archives of Foundry Engineering. 19(2), 5-8. DOI: 10.24425/afe.2019.127107.
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Authors and Affiliations

M. Bašistová
1
ORCID: ORCID
P. Lichý
1
ORCID: ORCID
  1. VSB-Technical University of Ostrava, Faculty of Materials Science and Technology, Department of Metallurgical Technologies, Czech Republic

Granulation of Cu-Al-Fe-Ni Bronze

B.P. Pisarek
Archives of Foundry Engineering | 2014 | No 3 | DOI: 10.2478/afe-2014-0063
Keywords Innovative foundry technologies and materials Complex aluminium bronze Granulation Sieve analysis Microstructure Microhardness
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Abstract

With the increase in wall thickness of the casting of iron-nickel-aluminium-bronze, by the reduction of the cooling rate the size of κII phase

precipitates increases. This process, in the case of complex aluminium bronzes with additions of Cr, Mo and W is increased. Crystallization

of big κII phase, during slow cooling of the casting, reduces the concentration of additives introduced to the bronze matrix and hardness.

Undertaken research to develop technology of thick-walled products (g> 6 mm) of complex aluminium bronzes. Particular attention

was paid to the metallurgy of granules. As a result, a large cooling speed of the alloy, and also high-speed solidification casting a light

weight of the granules allows: to avoid micro-and macrosegregation, decreasing the particle size, increase the dispersion of phases in

multiphase alloys. Depending on the size granules as possible is to provide finished products with a wall thickness greater than 6 mm by

infiltration of liquid alloy of granules (composites). Preliminary studies was conducted using drip method granulate of CuAl10Fe5Ni5

bronze melted in a INDUTHERM-VC 500 D Vacuum Pressure Casting Machine. This bronze is a starting alloy for the preparation of the

complex aluminium bronzes with additions of Cr, Mo, W and C or Si. Optimizations of granulation process was carried out. As the process

control parameters taken a casting temperature t (°C) and the path h (mm) of free-fall of the metal droplets in the surrounding atmosphere

before it is intensively cooled in a container of water. The granulate was subjected to a sieve analysis. For the objective function was

assume maximize of the product of Um*n, the percentage weight "Um" and the quantity of granules 'n' in the mesh fraction. The maximum

value of the ratio obtained for mesh fraction a sieve with a mesh aperture of 6.3 mm. In the intensively cooled granule of bronze was

identified microstructure composed of phases: β and fine bainite (α+β'+β'1) and a small quantity of small precipitates κII phase. Get high

microhardness bronze at the level of 323±27,9 HV0,1.

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Authors and Affiliations

B.P. Pisarek

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