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Number of results: 8
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Abstract

The paper presents the properties of plastics under the trade names of PMMA and Midas, and of Formowax, Romocast 305 and Romocast 930 casting waxes. Their effect on the quality of foundry patterns used in the manufacture of ceramic moulds for precision casting is also discussed. From the selected materials for foundry patterns, samples were made for testing using the following methods: (i) 3D printing in the case of plastics, and (ii) conventional method based on tooling in the form of metal moulds (dies) in the case of casting waxes.

The most important physico-mechanical properties of materials for foundry patterns were determined, i.e. linear shrinkage, softening temperature, relative elongation and coefficient of thermal linear expansion. Bending tests were carried out on samples of patterns printed and made in metal moulds, including determination of the surface roughness of patterns.

After the process of melting out patterns from the cavities of ceramic moulds in an autoclave, the degree of their melting out was visually assessed (i.e. the residues from pattern removal were evaluated). The ash content after burning out of foundry patterns was also determined. The conducted tests allowed comparing the important parameters of materials used for foundry patterns and assessing the suitability of selected plastics as a material for foundry patterns used in the manufacture of high-quality precision castings.

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Authors and Affiliations

A. Dydak
M. Książek
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Abstract

Submitted work deals with the analysis of reoxidation processes for aluminium alloys. Due to the aluminium high affinity to the oxygen, the oxidation and consequently reoxidation will occur. Paper focuses on the gating system design in order to suppress and minimize reoxidation processes. Design of the gating system is considered as one of the most important aspect, which can reduce the presence of reoxidation products - bifilms. The main reason for the reoxidation occurrence is turbulence during filling of the mold. By correctly designing the individual parts of gating system, it is possible to minimize turbulence and to ensure a smooth process of the mold filling. The aim of the work is an innovative approach in the construction of gating system by using unconventional elements, such as a naturally pressurized system or vortex elements. The aim is also to clarify the phenomenon during the gating system filling by visualization with the aid of ProCAST numerical simulation software. ProCAST can calculate different indicators which allow to better quantify the filling pattern.

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Authors and Affiliations

A. Remišová
M. Brůna
ORCID: ORCID
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Abstract

The influence of the cooling rate on the extent of precipitation hardening of cast aluminum alloy (ADC12) was investigated experimentally. This study explored the cooling rate of the solidification of Cu in the α-Al phase to improve the mechanical properties of ADC12 after an aging process (Cu based precipitation hardening). The solid solution of Cu occurred in the α-Al phases during the casting process at cooling rates exceeding 0.03 °C/s. This process was replaced with a solid solution process of T6 treatments. The extent of the solid solution varied depending on the cooling rate; with a higher cooling rate, a more extensive solid solution was formed. For the cast ADC12 alloy made at a high cooling rate, high precipitation hardening occurred after low-temperature heating (at 175 °C for 20 h), which improved the mechanical properties of the cast Al alloys. However, the low-temperature heating at the higher temperature for a longer time decreased the hardness due to over aging. Keywords: Aluminum alloy, Casting, Precipitation, Solid solution, Aging, Solidification rate
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Bibliography

[1] Sepehrband, P., Mahmudi, R. & Khomamizadeh, F. (2005). Effect of Zr addition on the aging behavior of A319 aluminum cast alloy. Scripta Materialia. 52(4), 253-257.
[2] Rana, G., Zhoua, J.E. & Wang, Q.G. (2008). Precipitates and tensile fracture mechanism in a sand cast A356 aluminum alloy. Journal of Materials Processing Technology. 207(1-3), 46-52.
[3] Tian, L., Guo, Y., Li, J., Xia, F., Liang, M. & Bai, Y. (2018). Effects of solidification cooling rate on the microstructure and mechanical properties of a Cast Al-Si-Cu-Mg-Ni piston alloy. Materials. 11(7), 1230.
[4] Choi, S.W., Kima, Y.M., Leea, K.M., Cho, H.S., Hong, S.K., Kim, Y.C., Kang, C.S. & Kumai, S. (2014). The effects of cooling rate and heat treatment on mechanical and thermal characteristics of Al–Si–Cu–Mg foundry alloys. Journal of Alloys and Compounds. 617, 654-659.
[5] Dobrzański, L.A., Maniara, R., Sokołowski, J. & Kasprzak, W. (2007). Effect of cooling rate on the solidification behavior of AC AlSi7Cu2 alloy. Journal of Materials Processing Technology. 191(1-3), 317-320.
[6] Shabel, B.S., Granger, D.A., Trucker, W.G. (1992). Friction and wear of aluminum-silicon alloys. In P.J. Blau (Eds.), ASM Handbook: Friction, Lubrication, and Wear Technology (pp. 785-794), ASM International.
[7] Son, S.K., Takeda, M., Mitome, M., Bando, Y. & Endo,T. (2005). Precipitation behavior of an Al–Cu alloy during isothermal aging at low temperatures. Materials Letters. 59(6), 629-632.
[8] Wen-jun, T., Lin, Q. & Pi-xiang, Q. (2007). Study on heat treatment blister of squeeze casting parts. China Foundry. 4(2), 108-111.
[9] Okayasu, M., Sahara, N. & Mayama, K. (2021). Effect of microstructural characteristics on mechanical properties of cast Al–Si–Cu alloy controlled by Na. Materials Science and Engineering. A (in press).
[10] Hamasaki, M. & Miyahara, H. (2013). Solidification microstructure and critical conditions of shrinkage porosity generation in die casting process of JIS-ADC12 (A383) alloy. Materials Transactions. 54(7), 1131-1139.
[11] Kamio, A. (1996). Refinement of solidification structure in aluminum alloys. Japan Foundry Engineering Society. 68, 1075-1083.
[12] Okayasu, M. & Go, S. (2015). Precise analysis of effects of aging on mechanical properties of cast ADC12 aluminum alloy. Materials Science and Engineering. A 638, 208-218.
[13] David, S.A. & Vitek, J.M. (1989). Correlation between solidification parameters and weld microstructures. International Materials Reviews. 34(1), 213-245.

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Authors and Affiliations

M. Okayasu
1
N. Sahara
1
M. Touda
2

  1. Graduate School of Natural Science and Technology, Okayama University3-1-1 Tsushimanaka, Kita-ku, Okayama city, Okayama, 700-8530, Japan
  2. Kyowa Casting Co., Ltd.5418-3 Nishi Ebara-cho, Ibara city, Okayama, 715-0006, Japan
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Abstract

An incarcerated epigastric hernia (localized in linea alba) is a very rare observation. Here, we present a case of a 66-year-old white male who was admitted to the emergency department due to vomiting and epigastric pain. On physical examination, the only observed abnormality was a painless soft epigastric tumor located in the upper midline, measuring about 12 cm in diameter. The patient claimed that he had the tumor for more than 30 years and it never changed in diameter nor caused him any discomfort. A lipoma was initially suspected. However, an ultrasound of the abdomen revealed an incarcerated stomach, trapped due to the defect in the epigastric abdominal wall. The patient was sent for surgery and the presence of an incarcerated epigastric hernia of the linea alba, which contained the anterior wall of the stomach was confirmed. The presented case confirms that the use of ultrasonography may be an effective method to recognize unusual types of hernias, and that ultrasonography should be routinely used in emergency departments.

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Authors and Affiliations

Andrzej Gryglewski
Krystyna Wantuch
Sabina Wojciak
Zbigniew Opach
Piotr Richter
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Abstract

Cladocera are a group of water animals, which are strongly dependent on environmental conditions. The ratio of planktonie to littoral Cladocera species is a widely used tool in palaeohydrological reconstruction of lakes' water level changes. Interpretation of this ratio is still unclear and requires further evidence. The simplest indicator of water level, which can be used in tracing lake-peat bog transitions, is the presence or absence of Cladocera and the character of its disappearance. In general, two models of Cladocera decline are observed. The first model is characterized by a very abrupt disappearance of all species, whereas the second one. with an intermediate stage, is characterized by domination of specific species. These two models are related to different types of terminal history of the water body. Even after a total disappearance of water in the peat bogs, there were episodes of some pioneer cladoceran species presence, correlated with periods of humid climate.
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Authors and Affiliations

Krystyna Szeroczyńska
Michał Gąsiorowski
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Abstract

In this paper we studied the intensification of the water clarification process on contact clarifiers with quartz sand fil-tering bed, which was modified with a solution of aluminum sulphate coagulant. The modification of the quartz sand filter-ing bed was carried out by applying to the surface of grains of quartz sand solution of coagulant aluminum sulphate with different doses. Investigation of the electrokinetic potential of the filtering material (quartz sand) was carried out by the percolation potential method.

The influence of electrical properties (size and sign of the charge) of the filtering bed itself and suspended solids in the water on the filtration process was studied. The filter material – quartz sand used in contact clarifiers has a negative electric charge. When the electric charge of the particles decreases, that is, as the ζ-potential decreases, the repulsive forces de-crease and it the adhesion of particles becomes possible. This is the process of coagulation of the colloid. The forces of mu-tual gravity between the colloidal particles begin to predominate over the electric repulsive forces at the ζ-potential of thesystem less than 0.03 V.

Modification of quarts filtering bed with a solution of coagulant aluminum sulphate recommended for the purification of surface water allows: to intensify the process of water clarification, to reduce the consumption of reagents by 25–30%, with the obtaining purified water of the required quality, to reduce the production areas necessary for reagent management of treatment facilities, and to reduce the cost of water treatment by 20–25%.

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Authors and Affiliations

Stanislav S. Dushkin
Serhii Martynov
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Abstract

A significant development of the foundry industry contributes to the creation of high reliability and operational strength castings so that they meet specific standards in accordance with customers’ needs. This technology, however, is inseparably connected with casting defects in finished products. Cast products are subject to various defects which are considered acceptable or not, which is conditioned by the alloy chemical composition and strength characteristics, that is, generally – qualities to be agreed between the foundry and the customer. It is the latter that led the authors to research on designing a tool enabling the most reliable possible assessment of the emerging casting defects, which after proper consultations can be repaired and the casting – sold. The paper presents an original tool named the Open Atlas of Defects (OAD), developed for the last few years to support the evaluation of cast iron defects using Non-Destructive Testing (NDT) casting defects analysis tools (DCC card – Demerit Control Chart, Pareto-Lorenz analysis and ABC analysis). The OAD tool structure was presented as an integral part of the original system module for acquisition and data mining (A&DM) in conjunction with the possibilities of using selected tools for defect analysis support on the example of cast iron casting.

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Authors and Affiliations

R. Sika
M. Rogalewicz
A. Kroma
Z. Ignaszak

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