The article discusses the research problematics of machines and equipment for casting technologies, with the consideration of the scope of research performed in Poland in the second half of the twentieth century at main domestic university facilities as well as at the Foundry Research Institute in Kraków. General characteristics of the research were performed, with the determination of the effects stimulating the, then, intensive development of the Polish foundry, whose equipment was constituted by domestically produced casting machines and technological apparatus. An analysis was conducted of selected aspects of the condition of the Polish foundry, with the indication of the factors limiting the development and productivity of small and medium casting enterprises, which dominate in the domestic foundry industry. Against the background synthesis of earlier domestic research and the advancement of investigations and technological implementations into the industry in leading Western countries, the need for developing the production of new generation machines and equipment was pointed out, with the purpose to autonomize the domestic enterprises in respect of access to the knowledge aimed at improving efficiency and quality of the casting production. Exemplary investigations were presented, in the scope of a scientific aid in modernizing the foundry machine equipment, conducted at the Faculty of Foundry Engineering of AGH University of Science and Technology in Kraków.
Keywords: casting, machines and technological equipment, research, construction modernization,
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Mariusz Holtzer, Angelika Kmita, Agnieszka Roczniak
The article discusses the thermal processes undergone by the sand mould in contact with the liquid casting alloy. Depending on the character of the atmosphere in the mould, this can be the process of combustion or pyrolysis (when there is no oxygen). These processes, especially when the sand mould contains compounds with carbon, (e.g. sand moulds with resins or bentonite and lustrous carbon formers (LCF)), generating the proper atmosphere inside the mould, have
a significant effect on the presence of such casting defects as: veinings, burn-ons and liquid metal penetration. In order to avoid these defects, a reducing atmosphere should be formed inside the mould cavity. The article provides a comprehensive review of the studies, including the authors’ own works, in the scope of the pyrolysis process taking place in sand moulds with the addition of a carbon-containing substance. Diagrams of the mechanisms of the thermal decomposition of resins and lustrous carbon formers (LCF) given by various authors are presented. The pyrolysis processes generate many hazardous compounds from the group of the so-called Hazardous Air Pollutants (HAPs), including those from the BTEX group (benzene, toluene, ethylbenzene and xylenes) as well as from the PAH group (polycyclic aromatic hydrocarbons), which create risks for the health of the foundry workers.
Keywords: pyrolysis, carbon, graphite, sand moulds, lustrous carbon, GC/MS, FTIR, TG/DTG,
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Tomasz Szymczak, Grzegorz Gumienny, Tadeusz Pacyniak
The article presents the results of studies of hypoeutectic silumin with a molybdenum addition used for pressure casting. The studies included a thermal-derivative analysis of the crystallization process, a metallographic analysis of the microstructure of casts made in a DTA tester and pressure casts, as well as the determination of the basic mechanical properties of the silumin. For the tests, silumin 226 was selected, which is a typical silumin for pressure casting. The AlMo8 master alloy was introduced into the silumin in an amount allowing the Mo concentration in the alloy to be about 0.1; 0.2; 0.3; 0.4 and 0.5%. The examination of the crystallization process showed an analogous course of the DTA curves of the silumin without the Mo addition and the silumins containing about 0.1; 0.2; 0.3 and 0.4% Mo. A change in the crystallization process of the examined silumin was established, caused by an increase of the Mo concentration to 0.5%. This change consisted in the occurrence of an additional thermal effect on the DTA curves, which did not take place in the silumin without the Mo addition or in the silumins with lower Mo concentrations. The microstructure of the silumin cast into the DTA tester with 0.3-0.5% Mo contained phases which were not observed in the alloys without the examined addition or with its lower concentrations. In the pressure casts, these phases were present in all the examined silumins with the Mo addition. The dimensions of these phases increase with the increase of the Mo concentration in the silumin. The performed studies of the basic mechanical properties of the silumins cast under pressure showed that the highest value of tensile strength Rm and unit elongation A were obtained for silumin 226 with the addition of 0.4% Mo. This constitutes an increase of Rm by 7.6% and of A by 13.8% in relative terms with respect to silumin 226 without the Mo addition. The highest values of yield strength Rp0.2 and hardness HB were obtained for silumin 226 without the Mo addition.
Keywords: silumin, molybdenum, microstructure, mechanical properties, pressure casting,
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Marta Homa, Andrzej Gazda, Natalia Sobczak, Katarzyna Pietrzak, Katarzyna Frydman, Danuta Wójcik-Grzybek
Studies of composite materials of the Cu-C type with additives of different forms of carbon (carbon nanopowder, carbon nanotubes and reduced graphene oxide) were performed by the powder metallurgy method. Based on the structural tests conducted by scanning electron microscopy methods and the examinations of the thermophysical properties (differential scanning calorimetry, dilatometry, laser flash analysis), it was stated that the applied procedure of fabricating composite materials ensures a satisfactory distribution of the carbon phase in the metal matrix in the macro- and meso-scale. In the micro-scale, we observe porosity and heterogeneity resulting in a lowered thermal conductivity (TC < 400 W · m-1 · K-1), despite the satisfactory results of the relative dimensional change. Introducing reduced graphene oxide flakes and short carbon nanotubes into the Cu matrix causes dimensional changes in the composites during heating as a result of oxidation/reduction of the Cu matrix, as well as oxidation of the carbon phase by oxygen and emission of gas products of the reaction (CO2, CO, C, H2O and H2 and hydrocarbons). The composite changes its dimensions: it expands, and bulges are observed on its surface.
Keywords: graphene, composites, thermal conductivity, dimensional stability,
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Zofia Kwak, Aldona Garbacz-Klempka, Małgorzata Perek-Nowak
The study was conducted for two selected 7xxx series aluminum alloys according to PN-EN 573-3:2010 - Polish version. The analysis of ingots was carried out on 7003, 7003S and 7010, 7010K alloys with a similar ratio of zirconium content. Symbols S and K are our internal modifications, still compatible with the standard. The ingots were made by semi-continuous casting. Aluminum alloys of this series, with improved properties, are intended for plastic-processing.
The aim of this publication is to show how the microstructure of ingots is being formed during semi-continuous casting. The chemical profiles of ingots were determined using optical emission spectroscopy. Chemical analysis in micro-areas with evaluation by scanning electron microscope SEM with EDS analyzer was performed and the distribution of chemical elements in the microstructures are also presented. An XRD detector was used to show specific phases in the alloys.
The grains are formed in a particular way during crystallization. In the middle of the ingot - further away from the crystallizer - the grains are larger. Semi-continuous casting together with homogenization enables the production of ingots with uniform cross sections as can be seen in the paper.
Keywords: Al-Zn-Mg-Cu alloys, DC casting, quality of ingots, microstructure, micro-structural analysis with scanning electron microscope with included SEM-EDS, phase composition by X-Ray Diffraction (XRD),
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The paper presents research on the possibility of improving the plasticity of near-eutectic AlSi11 alloy by the use of soft annealing treatment. For two assumed input quantities, i.e. temperature and duration of the soaking treatment, based on the trivalent testing plan, have enabled the presentation of changing tensile strength (Rm) and elongation (A5) in function of the soft annealing parameters (temperature in the range from 280°C to 370°C and time from 2 hours to 8 hours).
For average values of assumed range of temperature and time there was an increase in elongation (A5) of about 40% compared to the starting value. The highest increase in elongation (A5) amounted to 96%, compared to the initial alloy, which was obtained in the case of the soaking treatment at temperature 370°C for 8 hours, the tensile strength (Rm) decreased simultaneously within limits of 15%.
Keywords: aluminum alloys, soft annealing, elongation, tensile strength,
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The new technological challenges and the high economical and commercial potential connected with the development of new generation soldering alloys used in the consumer electronics lead-free soldering technology is a subject which is gaining increasing interest both on the side of the electronics industry and the academic community. This study constitutes a review and analysis of the literature in the scope of investigations of new generation advanced lead-free soldering alloys which could potentially replace the currently applied, expensive, lead-free solders based on the Sn-Ag-Cu (SAC) system. On the basis of the literature analysis, the authors determined and characterized the main system groups which are within the focus of interest as new potential replacements for the SAC-type lead-free solders. The study constitutes a compilation of the current knowledge of the broad spectrum of properties of the presently applied lead-free solders of the SAC type as well as their potential replacements from the Sn-Zn and Bi-Sn systems. The work presents a comparative analysis of the effect of selected alloy additions, fluxes and temperatures on the solderability and wettability of soldering alloys in contact with selected types of substrates, as well as change in the microstructure, mechanical properties and reliability of the produced joints. The review is summed up by the description of the perspectives and new trends in the development of new generation lead-free soldering alloys which could be implemented into the consumer electronics lead-free soldering technology as replacements for the currently applied SAC-type solders.
Keywords: lead-free solders, SAC-type solders, Sn-Zn soldering alloy, Bi-Sn soldering alloy, wettability, solderability,
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