E. Dudrová, M. Kabátová, Ľ. Parilák, E. Košč - Microstructure and Properties of Fe-3Mn-Cx Sintered Steels

    The influence of processing conditions (the influence of starting characteristics of powders, i. e. characteristics of iron powder as dominant and C and Mn as minor components, and processing conditions, such as pressing and sintering parameters) on mechanical properties and microstructure of Fe-3Mn-(0.26 - 0.9) %C are analyzed in the paper. At suitable processing conditions the tensile strength higher than 650 MPa, hardness higher than 200 HV 30, impact energy up to 17 J cm^-2, and 3-point bend strength higher than 1000 MPa were achieved. From the viewpoint of iron powder and Mn-alloying component used, the sponge iron NC 100.24 and electrolytical manganese seem to be advantageous when compared with iron powders SC 100.26 and ASC 100.29 and ferromanganese powders. The highest strength properties correspond to carbon content of 0.6 %. In sintering processes, the cooling rate of 40 °C/min is more advantageous than 10 °C/min.

L. Vehovar, A. Vehovar, M. Tandler - The Corrosion Resistance of Austenitic Stainless Steel, Alloyed with Nitrogen

     The results of corrosion investigations have shown that, even in a very aggressive medium, the austenitic nitrogen-enriched stainless steel NTR50, which was solution heat treated at 1150 °C/ quenched - i.e. steel with interstitially dissolved nitrogen in the austenitic base, passivizes directly at a low anodic current density. This is the not case for the comparative AISI 316L stainless steel, although the pitting potentials of both materials are similar. However, significant differences exist between the repassivation capability of nitrogen-enriched steel and that of the comparative AISI 316L steel, which can be attributed to the important role of the nitrogen. Investigations of the passive film confirmed that nitrogen, in the form of N^3- and NH₄⁺ ions, acts as an inhibitor of the corrosion process. This means that the time for the initiation of corrosion pits, which are usually the source of stress corrosion cracking, is extended. Due to rapid changes in the character of the electrolyte in the corrosion crack and the repulsing action of the N^3- ions towards the aggressive chloride ions, the growth of the crack is either prevented or greatly retarded.

L. Fröhlich, V. Mikloš - Leaching of As, Sb and Hg from Tetrahedrite Concentrate in the Na₂S Medium at Increased Temperatures

    The present article contains knowledge about an alternative method of hydrometallurgical processing of the Slovak tetrahedrite concentrate from the area of Rudňany. The stated concentrate is characterized by its high content of Hg, order of units of mass %. It also contains other dominant accompanying elements - As and Sb. Our experimental study monitored the efficiency of leaching the stated accompanying elements into solutions with various concentrations of Na₂S, without and with the addition of 30 g/l NaOH, at increased temperatures. A rotary autoclave without the possibility of intensive mixing was used, which had an impact on the results obtained, mainly in the area of kinetic study. Leaching within a temperature range between 120 °C and 220 °C under various conditions was performed, in a six series of experiments. The results obtained show the suitability of using the autoclave process for the extraction of As, Sb and Hg from the tetrahedrite concentrate into a basic solution of Na₂S.

E. Stroffek, I. Lesso - Acoustic Method for Measurement of Young’s Modulus of Steel Wire Ropes

     The classical methods for estimation of Young’s modulus of steel wire ropes are time consuming. One of the additional disadvantages of these methods is that they could not be applied in situ but only in laboratories. We have designed a new acoustical method and as the results show it seems to be promising and usable in plant. In this contribution we compare the results of Young’s modulus measurement with the new method for different wire and charge conditions.

V. Vítek - Study of Flow Pattern Solution Possibilities in the Furnace Zonal Models

    The present paper deals with the conditions estimation for the flow pattern solution possibilities inside the furnace as dependant on the inner space division in the volume zones. Provided solutions with the application of the free and finite turbulent stream model show that in principle it is possible to solve rather complex problems for the need of the zone models without the necessity to solve the sets of the partial differential equations for the case of the viscous flowing media. The methodology of the solution process and the results are presented for the flow pattern estimation in the chamber furnace equipped with two burners and for the flow patter inside the tunnel kiln out of the burners zone.

J. Kizek, Z. Zsigraiová - Combustion of Gaseous Fuels with high Content of Inert

    In the paper authors deal with experimental investigation of an inert gas influence on combustion parameters of gaseous fuels such as flame stability and outlet velocity. The aim is to supplement knowledge of combustion process of gaseous fuel with high content of inert compounds.

J. Kijac, M. Pivovarči - Contribution to the Casting Powders Assimilation Power Study

    T he main characteristics of the casting powders for the continuous casting - their chemical composition, melting temperature, dynamic viscosity and specific consumption. Decisive factors of casting powders effect CC course. Effect of the casting powders properties on the cast products surface quality. Same field experiment results obtained with variety of casting powders application based on the domestic production (MOLDCAST). Evaluation of assimilation ability. Change of chemical composition of the CC casting powder in course of the casting. Ability of casting powders to absorb the alumina inclusions. Change of the physical and chemical parameters of the formed slag in course of casting. Analysis of the obtained information.