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1

Negative Shrinkage of Thin-walled Investment Brass Castings

Roy Soumyajit, Pramanick A. K., Datta P. K.

Archives of Foundry Engineering

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2023

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Vol. 23, iss. 1

17--24

EN

Dhokra or Dokra casting is a sophisticated cast metal craft tradition of the Indian subcontinent. It has been practiced by the countryfolk now since the Copper Age. It is a lost wax casting process in the hot clay mold. The technology is such sophisticated that it can produce up to 400 μm thin-walled hollow cast products with complicated and intricate shapes using Brass, Bronze, Copper, and other copper alloys. The investigation was for engraving Brass (2% lead) which is used by Dhokra artisans nowadays. In a field visit during dimensional analysis, one discrepancy was identified. The metal thicknesses of hollow castings are thicker than the thickness of the wax pattern. This cast metal dilation phenomenon is unusual. Shrinkage of metals compared to the pattern dimension is familiar in the casting world. The same abnormalities in the repeated investigation at different sites were observed. All the studies and experiments were organized to explain the reason hidden behind the phenomenon.

2

Physical and Numerical Modeling of Duplex Cast Steel Thin-Walled Castings

Stradomski G., Nadolski M., Zyska A., Kania B., Rydz D.

Archives of Metallurgy and Materials

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2019

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Vol. 64, iss. 4

1449--1456

EN

The paper, which is a summary and supplement of previous works and research, presents the results of numerical and physical modeling of the GX2CrNiMoCuN25-6-3 duplex cast steel thin-walled castings production. To obtain thin-walled castings with wall in the thinnest place even below 1 mm was used the centrifugal casting technology and gravity casting. The analyzed technology (centrifugal casting) enables making elements with high surface quality with reduced consumption of batch materials and, as a result, reducing the costs of making a unitary casting. The idea behind the production of cast steel with the use of centrifugal technology was to find a remedy for the problems associated with unsatisfactory castability of the tested alloy. The technological evaluation of the cast construction was carried out using the Nova Flow & Solid CV 4.3r8 software. Numerical simulations of crystallization and cooling were carried out for a casting without a gating system and sinkhead located in a mold in accordance with the pouring position. It was assumed that the analyzed cast will be made in the sand form with dimensions 250×250×120 mm.

3

Effects of Process Related Variations on Defect Formation in Investment Cast Components

Raza M., Silva P., Irwin M., Fagerström B., Jarfors A. E. W.

Archives of Foundry Engineering

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2018

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Vol. 18, iss. 1

103--108

EN

Castability of thin-walled castings is sensitive to variation in casting parameters. The variation in casting parameters can lead to undesired casting conditions which result in defect formation. Variation in rejection rate due to casting defect from one batch to other is common problem in foundries and the cause of this variation usually remain unknown due to complexity of the process. In this work, variation in casting parameters resulting from human involvement in the process is investigated. Casting practices of different groups of casting operators were evaluated and resulting variations in casting parameters were discussed. The effect of these variations was evaluated by comparing the rejection statistics for each group. In order to minimize process variation, optimized casting practices were implemented by developing specific process instructions for the operators. The significance of variation in casting parameters in terms of their impact on foundry rejections was evaluated by comparing the number of rejected components before and after implementation of optimized casting practices. It was concluded that variation in casting parameters due to variation in casting practices of different groups has significant impact on casting quality. Variation in mould temperature, melt temperature and pouring rate due to variation in handling time and practice resulted in varying quality of component from one batch to other. By implementing the optimized casting instruction, both quality and process reliability were improved significantly.

4

Analysis of temperature distribution in shell mould during thin-wall superalloy casting and its effect on the resultant microstructure

Rakoczy Ł., Cygan R.

Archives of Civil and Mechanical Engineering

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2018

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Vol. 18, no. 4

1441--1450

EN

This work focuses on the influence of temperature distribution in a shell mould during investment casting of thin wall parts on macrostructure, chemical composition of microstructural constituents and γ/γ′ misfit parameter. A reduction of production costs is associated with the optimization of precision casting technology of aircraft engine critical parts, including control of the solidification front in thin-walled castings of nickel superalloys. Appropriate lost-wax casting parameters lead to the creation of coarse grained structure, desired for high-temperature service applications. As a result of non-equilibrium solidification, substantially large chemical inhomogeneities in the dendrite core and interdendritic spaces are formed. Interdendritic spaces are occupied by constituents formed as a consequence of segregation of alloying elements, namely eutectic islands γ/γ′, borides, carbides, and an intermetallic compound of Ni and Zr. Dendrite cores consist of cubic-shaped γ′ precipitates surrounded by Ni-rich γ channels. Low lattice misfit influences cubic morphology of γ′ precipitates, which is favourable for jet engine application because it can guarantee good creep resistance.

5

Development of a technology for the production of ceramic moulds with reduced thermal conductivity to control the solidification of thin-walled castings

Leśniewski W., Wawrylak M., Wieliczko P., Gil A., Małysza M., Szczepaniak-Lalewicz K.

Prace Instytutu Odlewnictwa

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2017

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Vol. 57, no. 4

259--263

EN

During the project a technology of making ceramic moulds using aluminosilicate microspheres was developed. According to the developed technology, ceramic samples were used to determine thermal conductivity in the temperature range of 500°C to 850°C. In this temperature range, thermal conductivity is about 0.5 W/mK. Strength measurements were conducted using a four-point bending technique. The strength of the developed ceramics and typical ceramics made from molochite materials is similar. Computer simulations facilitated the design of experimental moulds. The recording of Al alloy cooling curves in rectangular insulated and non-insulated moulds allowed for comparison of the thermal parameters of both types of moulds (i.e. ceramics). There was also a castability test performed using the moulds with a “grille” model with 1.5 × 1.5 mm channels, which determined the effect of increased material insulation on the number of properly filled mesh of the mould.

6

Development and implementation of the casting technology concerning a new series of types of electric motor housings

Tomczyński Sz.

Hutnik, Wiadomości Hutnicze

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2010

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Vol. 77, nr 5

249-251

EN

The paper presents problems related to the development and the implementation of production technology concerning cast iron housings of CELMA electric motors moulded in furan resin sand in “Terlecki” Foundry at Gruszewnia, Poland. Technological problems encountered in the course of production of large, thin-walled castings of intricate shapes have been presented. There have been discussed the subsequent stages of technological tests which has resulted in developing three various moulding technologies depending on the casting configuration. The proposed technologies have also demanded for implementation of moulding in furan moulding sands.

PL

W artykule omówiono zagadnienia związane z opracowaniem i wdrożeniem w Odlewni Żeliwa „Terlecki” w Gruszewni technologii żeliwnych odlewów korpusów silników elektrycznych CELMA formowanych w samoutwardzalnych furanowych masach formierskich. Przedstawiono problemy technologiczne napotykane przy wytwarzaniu dużych, cienkościennych odlewów o skomplikowanych kształtach. Przedstawiono kolejne etapy prób technologicznych, w wyniku których opracowano 3 różne technologie formowania w zależności od konfiguracji odlewu. Zaproponowane technologie wymagały również opracowania i wdrożenia technologii formowania w furanowych masach formierskich.