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P. Futas

Abstract

The presence of the chunky graphite is unwanted in the cast iron with the spheroidal graphite for this significantly lowers the properties of the ductile iron. This shape of the graphite is formed as the result of the slow cooling rate of the castings with large thermal point and also due to the presence of the elements which suppress the formation of the spheroidal graphite and support formation of the chunky graphite. The spheroidal graphite present in the ductile iron assures the excellent mechanical properties, while the chunky graphite significantly reduces those properties of the ductile iron. Therefore it is of importance to assume conditions under which prevented is the formation of the chunky graphite. The casts were carried out under the conditions of the regular operation of the foundry and tested were various types of modifiers and inoculators and also pre-inoculators containing the elements suppressing the formation of the chunky graphite (Al, Sb a Ba). Applied were also the chromium breaker core to suppress the formation chunky graphite which was present in the structure in the places after the feeders elimination. As whole, executed were eight casts with various types of the modifiers and inoculators.

Open access

A. Pribulová and P. Futáš

Abstract

Foundry dust from blasting and grinding of castings contain a high amount of iron, ergo it is possible its recycling in foundry process. Dust was compacted by briquetting, two kinds of briquettes were prepared (A contained 95% magnetic part of dust from casting blasting +5% bentonite and B contained 95% mixture of dust from casting grinding and magnetic part of dust from casting blasting + 5% bentonite) and used as a part of charge into the electric induction furnace. It was found that addition of briquettes has had an influence of a chemical composition of cast iron above all on content of sulphur, phosphorus and silicon. It was not reflected in decrease in tensile strength and in microstructure. Yield of metal from briquettes was not lower then 70%.

Open access

J. Malik, I. Vasková, D. Fecko and P. Futáš

Homogenity of Die Casting and Returning Material

Homogeneity of die castings is influenced by wide range of technological parameters as piston velocity in filling chamber of die casting machine, filling time of mould cavity, temperature of cast alloy, temperature of the mould, temperature of filling chamber, surface pressure on alloy during mould filling, final pressure and others. Based on stated parameters it is clear, that main parameters of die casting are filling time of die mould cavity and velocity of the melt in the ingates. Filling time must ensure the complete filling of the mould cavity before solidification process can negatively influence it.

Among technological parameters also belong the returning material, which ratio in charge must be constrained according to requirement on final homogeneity of die castings. With the ratio of returning material influenced are the mechanical properties of castings, inner homogeneity and chemical composition.

Open access

A. Kmita, A. Pribulova, M. Holtzer, P. Futas and A. Roczniak

Abstract

Zinc ferrite ZnFe2O4 both in the micro and nano scale is widely used in various fields. The article discusses the structure of this compound and its properties in the nanoscale, which is clearly different from those which the ferrite shows in the microscale. The properties of dust generated electric arc furnace, which can contain up to 40% zinc, substantially in the form of ZnFe2O4 are disscused here. Specific properties (electric, magnetic, thermal) of zinc ferrite nanoparticles determine the very wide possibilities of their use, inter alia as catalysts, absorbents, gas sensors, and a tool to combat cancer.

Open access

A. Pribulová, P. Futáš, A. Kmita, D. Márasová and M. Holtzer

Abstract

The Electro Slag Remelting (ESR) is one of the remelting processes in the field of metal refinery. In this process, the slag plays various roles, such as heat generation, protection of melt, and chemical refining. The main objective of the experiments described in this article was to identify the most appropriate slag composition for the electro slag remelting of the steel in order to achieve the chemical composition compliant with the standard applicable to the given steel, minimum sulphur content, minimum contents of oxide and sulphide inclusions, as well as mechanical properties corresponding to the standard applicable to the steel STN 14 109. Ten electrodes were remelted, whereas the remelting was carried out under 8 slags. The used slags containing 70% of CaF2 and 30% of Al2O3 with different addition of CaO, the slags consisted of the same components as previous slags, whereas the ratio of individual components was 1:1:1, and with SiO2 and MgO and slag without Al2O3. With regard to all the above mentioned facts, the slag types which may be regarded as the most appropriate for the STN 14 109 steel remelting are the basic slags containing 70% of CaF2 - 30% of Al2O3 with added 30 and 45 weight % of CaO.