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Investigations Concerning Improvements of the Knock Out Property of Ceramic Moulds Applied in the Investment Casting Technology

Kolczyk-Tylka Joanna, Zych Jerzy

Archives of Foundry Engineering

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2023

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Vol. 23, iss. 4

34--39

EN

In lost wax technology, self-supporting ceramic moulds are made, which must have adequate strength after being filled with liquid metal. The final structural strength is determined by such factors as the thickness of the individual layers applied to the wax model resulting from the viscosity of the liquid mass, the specific strength of the layers formed, and the heat treatment of the moulds. The development of technology and materials is moving in the direction of increasing the specific strength of self-supporting ceramic moulds. The consequence of this is that the final strength of these moulds is too high, making it difficult to knock castings out of the moulds. Removing mould remnants from holes, closed spaces of the casting, corners, sharp edges, variable cross sections and etc. is cumbersome. In order to remove mould remnants from the casting, a method is used to dissolve them in heated solutions of suitable chemical composition and reaction. The paper presents the results of research on a new solution, the essence of which is the production of layers in a ceramic mould, in the middle zone of the mould, characterized by a significantly reduced final strength, achieved after firing. These layers are produced using a different liquid ceramic mass than the base one, based on an organic binder. As a result, thanks to the embedded layer, very good knock-out of castings is achieved and separation of residual ceramic mass. Special layers can be incorporated over the entire surface or only in those places where the bonding of the casting surface and ceramic mass occurs.

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The Influence of Remelting on the Quality of Prosthetic Cobalt Alloys

Nadolski M., Łągiewka M., Konopka Z., Zyska A., Golański G.

Archives of Foundry Engineering

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2015

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Vol. 15, iss. 3 spec.

53--58

EN

A commercial cobalt alloy applied in dental prosthetics was investigated. The scope of the work included the microstructure analysis, performance examination (tensile strength, microhardness, corrosion resistance), and dilatometric examination. The investigated alloy after a single remelting was characterised by higher tensile strength and hardness. There were not found the definite results with regard to the corrosion resistance of the examined materials. No significant change occurred in the coefficient of thermal expansion.

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Examining of slurries and production of moulds by spraying method in lost wax technology

Nadolski M., Konopka Z., Łągiewka M., Zyska A.

Archives of Foundry Engineering

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2008

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Vol. 8, iss. 2

107-110

EN

The work presents the results of investigation centred around the selection of a ceramic slurry composition if ceramic fibre is applied as a component of moulding material used for the lost wax technology. Producing a ceramic material of assumed parameters demands for changing the surface properties of the mineral grains. The critical concentration of solid particles or the gel point depends on the size of mineral particles, their shape and ability to aggregate. This ability has been achieved by modifying their surface properties by adding some polymer and the wetting agent (surfactant), which are adsorbed. Using the fibre material has required developing a method of its applying to the pattern set. The technology of multi-layer spraying has been recognised as the most advantageous one. The performed laboratory experiments have allowed for determining both the material composition and the parameters of its applying, such as air pressure, nozzle diameter, and the spraying distance for gravity pneumatic spraying gun.