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1.
Reduction of surface defects by optimization of casting speed using genetic programming : an industrial case study
Miha Kovačič, Uroš Župerl, Leo Gusel, Miran Brezočnik, 2023, izvirni znanstveni članek

Opis: Štore Steel Ltd. produces more than 200 different types of steel with a continuous caster installed in 2016. Several defects, mostly related to thermomechanical behaviour in the mould, originate from the continuous casting process. The same casting speed of 1.6 m/min was used for all steel grades. In May 2023, a project was launched to adjust the casting speed according to the casting temperature. This adjustment included the steel grades with the highest number of surface defects and different carbon content: 16MnCrS5, C22, 30MnVS5, and 46MnVS5. For every 10 °C deviation from the prescribed casting temperature, the speed was changed by 0.02 m/min. During the 2-month period, the ratio of rolled bars with detected surface defects (inspected by an automatic control line) decreased for the mentioned steel grades. The decreases were from 11.27 % to 7.93 %, from 12.73 % to 4.11 %, from 16.28 % to 13.40 %, and from 25.52 % to 16.99 % for 16MnCrS5, C22, 30MnVS5, and 46MnVS5, respectively. Based on the collected chemical composition and casting parameters from these two months, models were obtained using linear regression and genetic programming. These models predict the ratio of rolled bars with detected surface defects and the length of detected surface defects. According to the modelling results, the ratio of rolled bars with detected surface defects and the length of detected surface defects could be minimally reduced by 14 % and 189 %, respectively, using casting speed adjustments. A similar result was achieved from July to November 2023 by adjusting the casting speed for the other 27 types of steel. The same was predicted with the already obtained models. Genetic programming outperformed linear regression.
Ključne besede: continuous casting of steel, surface defects, automatic control, machine learning, modelling, optimisation, prediction, linear regression, genetic programming
Objavljeno v DKUM: 25.03.2024; Ogledov: 80; Prenosov: 5
.pdf Celotno besedilo (1,19 MB)
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2.
Comparative study of the microstructure and properties of cast-fabricated and 3D-printed laser-sintered Co–Cr alloys for removable partial denture frameworks
Dejan Stamenković, Miljana Popović, Rebeka Rudolf, Milorad Zrilić, Karlo Raić, Kosovka Obradović-Đuričić, Dragoslav Stamenković, 2023, izvirni znanstveni članek

Opis: Since additive technologies in dentistry are gradually replacing metal casting technology, it is necessary to evaluate new dental constructions intended for the development of removable partial denture frameworks. The aim of this research was to evaluate the microstructure and mechanical properties of 3D-printed, laser-melted and -sintered Co–Cr alloys, and perform a comparative study with Co–Cr castings for the same dental purposes. The experiments were divided into two groups. The first group consisted of samples produced by conventional casting of the Co–Cr alloy. The second group consisted of 3D-printed, laser-melted and -sintered specimens produced from a Co–Cr alloy powder divided into three subgroups, depending on the technological parameters chosen for manufacturing (angle, location and heat treatment). Examination of the microstructure was carried out by classical metallographic sample preparation, using optical microscopy and scanning electron microscopy with energy dispersive X-ray spectroscopy (EDX) analysis. A structural phase analysis was also performed by XRD. The mechanical properties were determined using a standard tensile test. The microstructure observation showed a dendritic character in the case of castings, while in the case of 3D-printed, laser-melted and -sintered Co–Cr alloys, the microstructure was typical for additive technologies. The XRD phase analysis confirmed the presence of Co–Cr phases (ε and γ). The results of the tensile test showed remarkably higher yield and tensile strength values and slightly lower elongation of the 3D-printed, laser-melted and -sintered samples than those produced by conventional casting.
Ključne besede: Co–Cr dental alloys, 3D printing, laser melting and sintering, casting, microstructure, mechanical properties, characterization
Objavljeno v DKUM: 21.04.2023; Ogledov: 340; Prenosov: 30
.pdf Celotno besedilo (16,55 MB)
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3.
Casting process optimization by the regression analysis applied on the wear resistant parts molding
Radomir Slavković, Slavko Arsovski, Aleksandar Veg, Zvonimir Jugović, Aleksandar Jovićić, Nedeljko Dučić, 2012, izvirni znanstveni članek

Opis: Conducting a comprehensive research of the casting process of wear resistant parts (white hard casting), a significant correlation is established between the technological parameters (temperature, aging time in the mold and coolant flow) and the final product hardness. The fundamental theory of Box-Wilson's gradient method marked the baseline for the foreseen researches. The method defines the coherence of the process parameters, since their dispersion in the examined process is relatively small. Main target of the experiment was a definition of the optimal casting conditions. Therefore the different technological routes are identified and the casting process is modified until the best outcome is achieved. Target function was initially in a hypothesized form, while later on evolved into a consistent form due to the application of experiment-statistics, process optimization and process management based on empirical feedback.
Ključne besede: casting, mathematical model, quality management, wear resistance
Objavljeno v DKUM: 11.07.2017; Ogledov: 1125; Prenosov: 115
.pdf Celotno besedilo (595,79 KB)
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4.
Simulation of the casting process - a powerfull tool for enchanced design of the cutting teeth in surface mining
Radomir Slavković, Zvonimir Jugović, Dražan Kozak, Aleksandar Veg, Radomir Radiša, Snežana Dragićević, Marko Popović, 2013, izvirni znanstveni članek

Opis: Recent development in the computer simulation technology caused a tremendous influence on a rapid prototyping in casting process. These computational tools facilitate engineering work and urge moulding verification in foundries. Among dedicated software packages the MAGMASoft is selected for availability reasons. Its effectiveness is proved with the simulation of moulding process of the cutting teeth for a bucket wheel excavator Use of MAGMASoft enables a shortcut to a forceful and durable product, without internal cavities and micro-porosity. Such advancement of the moulding process is described in this paper.
Ključne besede: casting, porosity, wear, simulation, MAGMASoft
Objavljeno v DKUM: 03.07.2017; Ogledov: 2242; Prenosov: 138
.pdf Celotno besedilo (1,03 MB)
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5.
Advanced procedure for fabrication of substructure in dentistry
Ivan Matin, Miodrag Hadžistević, Đorđe Vukelič, Branka Trifković, Mihal Potran, Tomaž Brajlih, Igor Drstvenšek, 2016, izvirni znanstveni članek

Opis: The paper presents some aspects of the novel integrated system, procedure for fabrication of metal substructure of metal-ceramic crowns. The results been shown that the CAD/CAE/RP technology integration presented in this paper can be fully applied to casting metal substructures. The substructure fabricated in this way, confirm the reduction of the total manufacturing time, with an increase in the percentage of high quality castings that use integrated system.
Ključne besede: casting, metal, ceramic, dental, fabrication
Objavljeno v DKUM: 03.07.2017; Ogledov: 1001; Prenosov: 124
.pdf Celotno besedilo (219,11 KB)
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6.
Microstructural and phase analysis of CuAlNi shape-memory alloy after continuous casting
Mirko Gojić, Stjepan Kožuh, Ivan Anžel, Gorazd Lojen, Ivana Ivanić, Borut Kosec, 2013, izvirni znanstveni članek

Opis: The results of the characterization of a CuAlNi shape-memory alloy after continuous casting technology are shown. Using this procedure a bar with a diameter of 8 mm was manufactured. After solidification of the alloy the microstructure characterization was carried out using optic microscopy (OM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) methods. Our results showed that the as-cast alloy consisted of the parent β1 and β1’ martensite phases. The martensite phase primary as the needle-like inside grains was observed. Martensite laths have different orientations inside particular grains. It was found that the average grains size is 98.78 µm. The grain diameter near to the external surface is higher than in the center. The average hardness of the alloy was 275 HV1.
Ključne besede: shape memory alloys, martensite, continuous casting, grain size
Objavljeno v DKUM: 16.03.2017; Ogledov: 1101; Prenosov: 117
.pdf Celotno besedilo (1,28 MB)
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7.
Influence of the working technology on the development of alloys H13-w(Cu) 87.5 %
Uroš Artiček, Marko Bojinović, Mihael Brunčko, Ivan Anžel, 2014, izvirni znanstveni članek

Opis: Most dies in the casting industry for injection moulding are machined from the premium-grade H13 tool steel. They provide excellent performance in terms of mechanical properties and service life; however, these dies are characterised by a relatively low thermal conductivity. The tool-and-die industry is interested in depositing a material of a high thermal conductivity onto steel in order to improve the thermal management and productivity. We have explored the possibility of using copper with a new technology. In this study, the microstructure evolution and mechanical properties are discussed using the Laser Engineered Net ShapingTM (LENSTM) technology. For a better understanding of the solidification, the microstructure of a LENS sample was compared with the microstructure of a reference alloy produced with the ingot-casting technology having the same chemical composition of H13-w(Cu) 87.5 %. We carried out light microscopy, scanning electron microscopy, an EDS microchemical analysis, the tensile test and microhardness testing. The results show a successful fabrication of LENS samples; their microstructure is more homogeneous compared to the castings; they show better mechanical properties and represent a good potential for further development and use.
Ključne besede: casting, laser engineered net shaping technology, microstructure, mechanical properties
Objavljeno v DKUM: 16.03.2017; Ogledov: 1757; Prenosov: 123
.pdf Celotno besedilo (3,28 MB)
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8.
Continuous vertical casting of a NiTi alloy
Aleš Stambolić, Ivan Anžel, Gorazd Lojen, Aleksandra Kocijan, Monika Jenko, Rebeka Rudolf, 2016, izvirni znanstveni članek

Opis: In this paper we present research that is connected to the performance of a series of experiments combined with the vacuum-induction melting and continuous vertical casting of a NiTi alloy in order to produce the strand. The theoretical chosen parameters made it possible to obtain a continuously cast strand with a diameter of 11 mm. The strand microstructures were investigated with a light and scanning electron microscope, while the chemical composition of the single phase was identified with the semi-quantitative micro-analysis energy-dispersive X-ray spectroscopy and inductively coupled plasma – optical emission spectrometry. The research showed that the microstructure is dendritic, where in the inter-dendritic region the eutectic is composed of a dark NiTi phase and a bright TiNi3–x phase. In some areas we found Ti carbides and phases rich in Fe. The micro-chemical analysis of the NiTi strand showed that the composition changed over the cross and longitudinal sections, which is proof that the as-cast alloys are inhomogeneous. In the final part, the electrochemical behaviours of NiTi strand samples were compared to a commercially available NiTi cast alloy with the same composition.
Ključne besede: NiTi alloy, continuous vertical casting, microstructure, potentiodynamic and impedance test
Objavljeno v DKUM: 14.03.2017; Ogledov: 1314; Prenosov: 373
.pdf Celotno besedilo (586,88 KB)
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9.
Structure of the continuously cast Ni-based superalloy GMR 235
Franc Zupanič, Tonica Bončina, Gorazd Lojen, Boštjan Markoli, Savo Spaić, 2007, izvirni znanstveni članek

Opis: In this work we characterized the structure of continuously cast small cross-section rods (O10 mm) of the Ni-based superalloy GMR 235. In the microstructure prevailed dendritic columnar ?-grains with ?'-precipitates. In the interdendritic regions MC-carbide and M3B2-boride were identified. The inverse macrosegregation was very faint, except at the secondary witness marks and natural corrugations. It was found that the alternating drawing mode had much greater influence on microstructure than other casting parameters. Special attention was given to explanation of processes leading to formation of surface marks (primary and secondary witness marks and natural corrugations). Formation of hot tears and appearance of inverse segregation is also discussed.
Ključne besede: Ni-based superalloy, solidification, microstructure, continuous casting, surface marks
Objavljeno v DKUM: 01.06.2012; Ogledov: 1632; Prenosov: 101
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10.
Additive fabrication in metallurgy - case study of grey cast iron valve production
Bogdan Valentan, Igor Drstvenšek, Tomaž Brajlih, Peter Sever, Simon Brezovnik, Jože Balič, 2010, strokovni članek

Opis: Additive Fabrication technologies are well known from the last two decades. In that time Additive Fabrication technologies have evolved from strictly prototype part production into an option that can also be used to produce end-user parts. With development of Additive Fabrication machines capable of producing metal parts, a complete substitution of conventional metal casting technologies is possible. However, direct Additive Fabrication of metal parts is still not time/cost effective when producing large volume parts, and nowadays there is still lack of materials that can be used on those machines. This paper presents a method how a conventional sand casting process can be assisted by Additive Fabrication technologies. A sand mould pattern is produced by Selective Laser Sintering. Additive Fabrication is also used in direct manufacturing of cores.
Ključne besede: gray cast iron, layered technologies, rapid prototyping, rapid manufacturing, sand casting
Objavljeno v DKUM: 31.05.2012; Ogledov: 2152; Prenosov: 22
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