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Evaluation of Collapsibility of Selected Core Systems

Obzina Tomas, Merta V., Rygel J., Lichý P., Drobíková K.

Archives of Foundry Engineering

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2022

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Vol. 22, iss. 1

48--52

EN

There are mainly two different ways of producing sand cores in the industry. The most used is the shooting moulding process. A mixture of sand and binder is injected by compressed air into a cavity (core), where it is then thermally or chemically cured. Another relatively new method of manufacturing cores is the use of 3D printing. The principle is based on the method of local curing of the sand bed. The ability to destroy sand cores after casting can be evaluated by means of tests that are carried out directly on the test core. In most cases, the core is thermally degraded and the mechanical properties before and after thermal exposure are measured. Another possible way to determine the collapsibility of core mixtures can be performed on test castings, where a specific casting is designed for different binder systems. The residual strength is measured by subsequent shake-out or knock-out tests. In this paper, attention will be paid to the collapsibility of core mixtures in aluminium castings.

2

Design of Proven Technology of Metal Foam and Porous Metal Casting Production

Radkovský F., Merta V., Obzina T.

Archives of Foundry Engineering

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2021

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Vol. 21, iss. 1

125--131

EN

The article describes the design of a proven technology for the production of metal foam and porous metal by the foundry. Porous metal formed by infiltrating liquid metal into a mould cavity appears to be the fastest and most economical method. However, even here we cannot do without the right production parameters. Based on the research, the production process was optimised and subsequently a functional sample of metal foam with an irregular internal structure - a filter - was produced. The copper alloy filter was cast into a gypsum mould using an evaporable model. Furthermore, a functional sample of porous metal with a regular internal structure was produced - a heat exchanger. The aluminium alloy heat exchanger was cast into a green sand mould using preforms. Also, a porous metal casting with a regular internal structure was formed for use as an element in deformation zones. This aluminium alloy casting was made by the Lost Foam method. The aim is therefore to ensure the production of healthy castings, which would find use in the field of filtration of liquid metal or flue gases, in vehicles in the field of shock energy absorption and also in energy as a heat exchanger.

3

Influence of Silica Sand on Surface Casting Quality

Beňo J., Adamusová K., Merta V., Bajer T.

Archives of Foundry Engineering

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2019

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iss. 2

5--8

EN

The current casting production of castings brings increased demands for surface and internal quality of the castings. Important factors, that influence the quality of casted components, are the materials used for the manufacture of moulds and cores. For the preparation and production of moulds and cores, in order to achieve a low level of casting defects, then it used a high quality input materials, including various types of sands, modified binders, additives, etc. However, even the most expensive raw materials are not a guarantee to achieve the quality of production. It is always necessary to choose the appropriate combination of input material together with an appropriate proposal for the way of the production, the metallurgical treatment of cast alloy, etc. The aim of this paper is to establish the basic principles for the selection of the base core mixtures components – sands to eliminate defects from the tension, specifically veining. Various silica sand, which are commonly used in foundries of Middle Europe region, were selected and tested.

4

Optimizing of Metal Foam Design for the Use as a Heat Exchanger

Radkovský F., Gebauer M., Merta V.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 4

1875--1881

EN

The work deals with possibilities of using this specific material. It is focused on cast metal foams with a regular arrangement of internal cells and it refers to already used casting technologies – the production of metal foams with the aid of sand cores. Metal foams are used in many industries, such as: automotive, aerospace, construction, power engineering. They have unique propertiesand due to lower weight with sufficient strength and greater contact surface can be used, for example, for the conduction of heat. This article deals with the use of the metal foam as a heat exchanger. The efficiency of the heat exchanger depends on its shape and size and therefore the study is focused first on the optimization of the shape before the proper manufacture.