• Development of a new technology for carbon steel bars processing

    pg(s) 70-72

    In this paper, bars from carbon steel grade 45 deformed by a new technology are studied. This technology consists in drawing bars from medium carbon steel on a radial-shift rolling mill and subsequent drawing. As a result of deformation, bars with gradient microstructure were obtained. The surface zone of the bar is significantly crushed, the average ferrite size is 0.5 μm. In the neutral zone the deformation is not large enough, so the structure is not so strongly crushed, the ferrite grains are reduced to 2 microns. In the central zone, the microstructure consists of large grains with an average size of 7 μm. The quantitative ratio of large-angle boundaries in the surface zone is much higher than the central zone. To understand the relationship between strength and microstructure, the microhardness of the bar was determined. Thus for three deformation cycles the average value of microhardness in the central zone was 2085 MPa, in the neutral zone – 2505 MPa, and in the surface zone – 2915 MPa. As it can be seen, the hardness decreases as we move away from the surface zone to the central zone, this can be explained in terms of dislocation and boundary hardening.

  • Bead formation during wire and arc additive manufacturing

    pg(s) 66-69

    An experimental study of the formation of beads during the Wire and Arc Additive was carried out. The experiments were carried out in the low energy range of the welding arc. The influence of the wire feeding rate and traverse speed, their ratio and the heat input on the width and height of the resulting layers was monitored. Correlation coefficients were calculated between the linear energy and the ratio of the feed rate to the traverse speed on the one hand and the geometric dimensions of the layers on the other. It is shown that, in the studied range of technological parameters, the heat input is more strongly related to the geometric dimensions than the ratio of the velocities of wire feeding and deposition.

  • Creative wear of C-Cr-Mo-Nb-W-V surface system

    pg(s) 63-65

    The paper presents experimental work focused on the wear resistance of clads made with OPEN ARC technology (MOG) and clads with cycled cladding nozzle. The distribution of carbide phases by electron beam was evaluated. The influence of the tempering temperature of the clads on the hardness of the layers was determined. Tests of the resistance of the clads to abrasive wear were carried out.

  • Defining the positions of clamping elements for the 3-2-1 method in a SolidWorks integrated add-in

    pg(s) 59-62

    This paper presents a methodology and an application presented by the authors in previous publications. The application is integrated into SolidWorks and it’s used to automate the design process of modular fixturing devices. Included in it is a methodology for automated determination of the positions of the clamping elements. Both the application and the methodology are using rule-based logic and mathematical formulas.

  • Improvement of the surface properties of titanium products by reactive electro-spark processing. A short rеview

    pg(s) 53-58

    This work presents a brief overview of the essence, principles and technological features of reactive electrospark processing (RESP), based on a simple, economical and ecological method – electrospark deposition (ESD), which avoids many of the disadvantages inherent in other existing methods. This treatment can optimize the physicochemical properties of the substrate surface and improve the structure, hardness and wear resistance. The application of RESP technology in surface modification of titanium alloys is considered. Research results, including those of the authors of this work, are presented, which demonstrate the possibilities of RESP for reducing
    roughness and surface defects and for the synthesis of new phases and ultrafine structures that are not present in the electrode and substrate. The effect of RESP technology on the wear resistance of titanium and titanium alloys is shown. The main dependences of the quality and properties of the treated surfaces on the process parameters are identified, and ways to form reaction phases, to avoid and remove surface defects and to obtain “in-situ” new intermetallic and wear-resistant compounds are presented. The possibilities and prospects for the use of RESP to improve the surface characteristics and properties of titanium and its alloys are indicated.

  • The creation of stable systems and durable living systems with using of the nanosized particles

    pg(s) 48-52

    In this paper, from the standpoint of a new scientific direction of “chemical mesoscopics”, the features and mechanism of systems stabilization (self-organization) are considered on the example of nanostructures using as additives for the creation of stable systems. The difference between this mechanism and the mechanism of modification by micro-sized modifiers is noted, which consists in the fact that the influence of radiation of negatively charged quants radiated by nanostructures or mesoparticles leads to polarization of the components in the compositions and their self-organization in a certain “stable” order.
    Examples of modification of building cement materials by ultra-small amounts (0.006%) of carbon nanotubes, as well as polymer compositions with the help of metal carbon mesocomposites (a new class of mesoparticles) and experimental evidence of the mechanism of compositions self-organization with using IR spectroscopy, x-ray photoelectron spectroscopy and atomic force microscopy are given.

  • Optimization of the formation of coating layers in mould renovation

    pg(s) 45-47

    Paper presents results of an investigation aimed at determining optimum properties of the additive materials used. Laser welding technology was used for the creation of the clads. Single-layer clads with additive materials Dievar (1.2343), Dratec (1.6356) and UTPA 702 (1.6356) were realized on plates of Dievar material which were heat-treated to a hardness of 45-48 HRc. Their chemical compositions differed in the contents of C, Si, and Mn. The primary objective was to verify the possibilities of innovative use of additive materials based on maraging steels. The quality of the maraging agents was evaluated by stucture and EDX analysis in each selected maraging agent spectra. Due to the influence of the used surfacing technology and parameters, there was only minimal mixing of the surfacing metal with the base material, which is in agreement with the measured HAZ values. Using the energy beam laser welding method, there was no burning of the elements during their transfer to the filler metal, as occurs with arc methods. No oxidation or contamination of the additive metal due to insufficient protection of the cladding site was observed.

  • Cathodic protection for cooling water system

    pg(s) 25-28

    The aim of this research was the installation of a cathodic protection system for the inlet and outlet steel sea water pipeline respectively DN 1800 and DN 1600 mm in Adriatic Sea. It is extremely important to maintain the integrity of metallic structures in contact with aggressive effluents for both economic and environmental reasons. The proper design of cathodic protection system can help maintain this integrity and increase the useful service life of metallic structures. All cathodic protection systems should be installed with the intent of conducting uninterrupted, safe operations. When cathodic protection is applied, it should be operated continuously to maintain polarization for this purpose were calculated the protection current density, coating breakdown, protection current demand, sacrificial material weight, anode contact resistances, anode current outputs and number of anodes to be installed.

  • Cathodic protection for cooling water system

    pg(s) 52-28

    The aim of this research was the installation of a cathodic protection system for the inlet and outlet steel sea water pipeline respectively DN 1800 and DN 1600 mm in Adriatic Sea. It is extremely important to maintain the integrity of metallic structures in contact with aggressive effluents for both economic and environmental reasons. The proper design of cathodic protection system can help maintain this integrity and increase the useful service life of metallic structures. All cathodic protection systems should be installed with the intent of conducting uninterrupted, safe operations. When cathodic protection is applied, it should be operated continuously to maintain polarization for this purpose were calculated the protection current density, coating breakdown, protection current demand, sacrificial material weight, anode contact resistances, anode current outputs and number of anodes to be installed.

  • Technological characteristics of composite mixtures for the preparation of thermal insulation structural elements

    pg(s) 21-24

    The technological characteristics of suspensions used in the development of new thermal insulation composite structural elements based on foam materials and inorganic binders (Portland cement) are investigated. The role of the components of the compositions, the parameters of the technological regime and other factors in ensuring adequate workability of the prepared cementitious solutions is considered. Determination of the necessary technological characteristics of composite mixtures ensures their effective distribution in the formwork moulds when forming the specimens, cost-effective performance at production stage and obtaining products with the planned
    functional properties. The existing opportunities for potential application in modern construction of the developed composite elements are analyzed.

  • Use of gamma irradiation processing for decomposition of aflatoxins in wheat flour

    pg(s) 17-20

    The article presents the effects of different doses of gamma irradiation on the degradation of aflatoxins B1, B2, G1 and G2 in wheat flour. The experiment was conducted after contamination of wheat flour samples with mixture of aflatoxins with concentrations from 3 μg/kg to 12 μg/kg using reference material. Irradiation of flour aliquots with absorbed doses from 5.8 kGy to 27 kGy was carried out in an industrial gamma irradiation facility BULGAMMA. The concentrations of the aflatoxins before and after the radiation processing were measured by HPLC. The results showed that gamma irradiation with 27 kGy caused the highest degree of destruction of aflatoxins B2 (82 %) and G2 (81 %), followed by aflatoxin G1 (65 %) and to the lowest extend of aflatoxin B1 (59 %). Gamma irradiation with the maximum allowable dose for commercial food irradiation of 10 kGy was not sufficient to destroy the studied aflatoxins to the maximum permissible concentrations in wheat flour.

  • Processes for wire and arc additive manufacturing (overview)

    pg(s) 13-16

    Wire and arc additive manufacturing is a rapidly developing technology for the production of metal parts used in various industries such us space, automotive, shipbuilding, etc. Today, it is a potential alternative to traditional manufacturing processes due to its shorter lead time, low material losses and cost-effectiveness. In recent decades, this technology has been used to produce components from various materials. This overview examines the methods of realization, the specifics of the technological process, the process parameters and their influence on the formation of the layers and typical.