Materials Science. Non-Equilibrium Phase Transformations.
Vol. 2 (2016), Issue 2

Table of Contents

  • IMPROVING THE CASTING PROCESS OF PERITECTIC STEEL GRADES

    pg(s) 3-5

    Longitudinal cracking when continuous casting of peritectic steels was studied in this work. Dependency of slab scarfing volume and surface cracking on the steel chemical composition was investigated. The optimum casting speed and taper parameter of the mold were determined based on analytical modeling and statistical analysis of surface cracks observed in industrial billets. It was shown that longitudinal cracks on peritectic slabs could be reduced when the Mn to S ratio was kept above ~150. Such surface defects were decreased to 30-35 % by optimizing the steel composition, melt temperature and casting speed. Also by using an optimum taper of the mold the scarfing volume was reduced to 32-36 %.

  • NUMERICAL STUDY OF HEAT AND MASS TRANSFER AT INOCULATIONS FILING TO THE SLAB CC MOLD

    pg(s) 6-9

    Mathematical and numerical models for calculating heat- and masstransfere of metal bath in the mold of a slab CCM, that equipment the submerged nozzle with inclined discharge openings are developed. The thermal and hydrodynamic regularities of melt’s be-havior, including, in the feed to the mould inoculant in the form of a metal strip with a chemical composition different from the base, with possible oscillation.

  • METALLOGRAPHIC ANALYZE OF PARTS FOR BREAKING SYSTEM MADE OF NODULAR CAST IRON EN-GJS-500-7

    pg(s) 10-12

    In this research work, metallographic investigation of two parts which are implemented to railway wagons breaking system was performed. Both parts are produced from EN-GJS-500-7 nodular iron. One of delivered parts leading nut (part 1) was broken during the exploitation and the second part working nut (part 2) was new. Metallographic investigation based on standard EN 945-1was implemented in order to check the quality of the parts. The reason for breaking of part 1 one was analyzed too. After metallographic preparation, the polished specimens they were analyzed under optical microscope in order to determine form, size, density and distribution of graphite per unite area as first graphite nodules were analyzed after that microstructure of nodular iron. Figures from optical microscope were compared with reference images under the same magnification. After etching the specimens their microstructure was analyzed. It was concluded that quality of the part 2 is much better concerning the requirement of the EN 945 -1 standard.

  • STUDY THE INFLUENCE OF ALLOYING ELEMENTS ON THE STRUCTURE OF IRON-BASED ALLOYS WITH HIGH CONTENT OF CARBON, MANGANESE AND CHROMIUM IN MODES OF HEAT TREATMENT

    pg(s) 13-15

    Demand for alloys with high mechanical performance and optimum qualities in the service conditions require new studies regarding thermal stability, wear resistance and corrosion resistance to them. Of interest are materials in which the deficient and expensive Ni is partially or completely substituted with Mn, such as the alloys of the systems Fe-Cr-Mn-C or Fe-Cr-Mn-Ni. To build an accurate picture of the structural features, properties and their behavior in the operating conditions need to be carried out relevant studies. The objectives of the study are related to clarify the processes of structure formation in heating and cooling of this type of austenitic alloys. Object models are cast with an increased concentration of carbon and constant chromium and manganese in the starting composition, as well as those supplemented with vanadium and nickel.

  • MICROSTRUCTURAL CHARACTERISTICS OF AS CAST Ti-Zr ALLOYS

    pg(s) 16-18

    For many years casting alloys are widely used in dental applications. Among them, titanium and its alloys reveal the best properties for this purpose. However, the casting is difficult but it may be improved by alloying. This research deals with titanium-based alloys with zirconium additions. Investigated alloys were prepared by melting and casting in an electro-arc furnace under argon atmosphere. In order to identify the phases present in alloys, structural analysis was performed by X-ray diffraction method. It was showed two-phases microstructure of alloys. Further, zirconium addition in higher percentage contributes to formation of the beta phase of titanium which possesses more adequate properties then alpha titanium. Microstructural observations by scanning electron microscopy and energy-dispersive spectrometry showed that phases have similar chemical composition. Measured Vickers hardness values were lower than for pure titanium and are acceptable for dental applications.

  • ELECTROCHEMICAL PROPERTIES AND CHARACTERISTICS OF BINARY AND TERNARY ALLOYS OF AL-ZN-MG SYSTEM

    pg(s) 19-21

    Sacrificial materials are widely used to protect metal structures from electrochemical corrosion. As a base of sacrificial alloys are used aluminum, zinc and magnesium. The article presents the main sacrificial, corrosion and casting properties of binary (Al-Zn, Zn-Mg, Mg-Al) and ternary alloys of Al-Zn-Mg system. The results allow reasonably choose alloy compositions with best electrochemical properties with regard to the operation conditions of cast protectors.

  • GENESIS OF ELEMENTS AT PRIMARY ALUMINUM PRODUCTION

    pg(s) 22-24

    The characteristic of the elements present in the primary aluminum at electrolytic method of production is given. Based on elemental analysis of aluminum on regulated and unregulated impurities, with accordance of their initial content and effect on operational characteristics of cast billets, in this paper we describe groups of useful elements, neutral and harmful impurities at production of materials for functional purposes (sacrificial, composite, electrotechnical, etc.).

  • THE TIME FACTOR IN THE SPHEROIDIZING AND GRAPHITIZING MODIFICATION AND CAST

    pg(s) 25-29

    This work was carried out studies on the effect of different ways of modifying the microstructure and mechanical properties of cast ductile irons identical to the final chemical composition. For comparative studies have chosen three ways of modifying the molten iron, characterized the time interval between the introduction of additives into the melt and crystallization of iron – autoclave method, processing method in an open ladle ( "Sandwich process") and a method of in-mold melt processing ("Inmold-process").

    It is found that the process mold inoculation molten iron a more effective compared to other methods studied, by reducing the time interval between entering modifier in liquid iron and the onset of crystallization. This in turn enables the production of castings of several grades of ductile iron in the total process stream without additional alloying and heat treatment.

    Results of research testify in favor of the fluctuation hypothesis about straight line graphitization of cast iron during primary crystallization.

  • EVALUATION OF FATIGUE LIMIT FOR ALUMINIUM ALLOYS BY ULTRASONIC MEASURING

    pg(s) 30-32

    The evaluation of fatigue limit-σ−1 for AlSi7Mg, AlCu6Mn aluminum alloys is frequently encounter in material testing. In this method there is necessity of manufacture of test-tube from tested material or detail and made tension test.. There is destructive method. For many details there is not acceptable. Calculated in the usual ways fatigue limit appear only their statistical averaging between a number of structural factors indicating the influence. In material testing there is interest to non-destructive evaluation of fatigue limit σ−1 for the specimens and details. In this paper is lock at possibility for non-destructive evaluation of fatigue limit σ−1 by means measure velocities of propagation of longitudinal and transversal ultrasonic waves – VL and VT in tested materials and details.