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Investigation on the effect of electrode tip on formation of metal droplets and temperature profile in a vibrating electrode electroslag remelting process
No full textAbstract In the present work, a transient full-coupled modelling approach has been put forward to study the effect of electrode tip on formation of metal droplets and temperature profile in the electromagnetically-controlled electroslag-remelting furnace with vibrating electrode. The electromagnetic field, momentum and energy conservation equations are solved simultaneously based on the finite volume method. The interface of slag and metal is traced using the volume of fluid approach. The results show that in the case of cone tip electrode the average dimension of metal droplets is smaller compared to the flat tip electrode. In addition, the bigger and stretched metal droplets are not observed with the cone tip electrode. The temperature fields with the cone tip electrode are distributed in a prominent periodic pattern compared to the case with flat tip electrode. The maximum temperature zone with the cone tip electrode is located along the z axial in the upper part of slag, not in the lower part. When the frequency changes from 0.17 Hz to 1 Hz, the maximum temperature reduces from 2050 K to 1985 K and the peak value of velocity decreases from 0.20 m/s to 0.125 m/s. When the vibration amplitude varies from 3mm to 6mm, the maximum temperature in the slag cover drops by 3.9% and the peak value of velocity rises by 16.7%
"Proceedings Book of 18th International Foundrymen Conference: Coexistence of Material Science and Sustainable Technology in Economic Growth"
No full textFoundry industry as a base branch represents an important factor contributing to the economic potential of each country. Current market development as well as technical and economic objective, the production of high-quality, low-cost and environmentally friendly casting, requires application of recent and advanced materials, as well as production technologies, followed and supported by understanding of production process.
Production imperative is pointed into the recent technologies and improved materials for everyday usage in our homes, workplaces, as well as materials with special requirements for specific applications such as those for the automotive or space industry. Industrial activities, which are defined as strategic activities in the Republic of Croatia are Metal Casting and Production of Final Metal Products, recognized as "economic growth drivers" because they are expected to realize higher rates of growth and employment.
The importance of "Coexistence of material science and sustainable technology in economic growth" reveals in collaboration between small and medium enterprises’ (SMEs´), industry and higher education institutions (HEI). International Foundrymen Conference organized by University of Zagreb Faculty of Metallurgy, Sisak, Croatia in cooperation with University of Ljubljana Faculty of Natural Sciences and Engineering, Ljubljana, Slovenia, University North, Koprivnica, Croatia, Technical University of Košice Faculty of Materials, Metallurgy and Recycling, Košice, Slovakia, and ELKEM ASA, Norway found its significant position due to aforementioned reasons.
Coexistence of material science and sustainable technology in economic growth comprehends to recent technology and educated and skilled engineers. The Conference topics were designed as presentations of the current "state of the art" research in collaboration with industry, and production innovation with the aim to improve the competitiveness.The scope of 18th International Foundrymen Conference (IFC) covers scientific, technological and practical aspects concerning research, development and application of casting technology with the common perspective – increase of competitiveness. Special attention will be focused towards the competitiveness ability of foundries, improvement of materials features and casting technologies, environmental protection as well as subjects connected to the application of castings
Modeling of stress distribution on the basis of the measured values of strain and temperature changes
No full textThis paper proposes a new mathematical model for calculation of stresses on the basis of
experimentally measured values of strains and temperature changes for niobium microalloyed steel.
Construction of model was done using a multiple regression analysis of the measured values of
temperature change, deformation and stresses at four different stretching rates. All investigations
were conducted on samples from the niobium microalloyed steel, using thermography and digital
image correlation during static tensile testing. Constructed model was tested and validated on the
experimentally obtained results. Model showed a good agreement of calculated stress values with
experimentally obtained ones
Investigation of iron containing intermetallics in AlSi12 alloy with w (Mn/Fe) = 0.99
Get PDFThe precipitation of iron-rich intermetallic phases in AlSi12 alloy with manganese/iron weight ratio w (Mn/Fe) = 0.99 was investigated. Calculation of solidification sequence under equilibrium conditions, obtained using Computer Aided Thermodynamic Diagram Calculation, comprehended precipitation of α-Al15(FeMn)3Si2 and β-Al5FeSi. However, the microstructural investigations performed using light and electron microscopy indicated the lack of β- Al5FeSi in needle-like morphology. The intermetallic phases in Chinese script, transitional and polyhedral morphology were found, respectively. The results of Energy Dispersive Spectroscopy showed the minimum difference in the chemical composition between the intermetallic phases in Chinese script and polyhedral morphology due to high w (Mn/Fe) weight ratio
The effect of sodium and strontium on modification of eutectic silicon
Get PDFModification of eutectic (αAl+βSi) is usually performed during treatment of Al-Si based alloys in order to obtain higher mechanical properties. Chemical modification is usually performed using modifying elements such as Na and Sr. The research was performed in order to estimate the efficiency of Na and Sr additions in eutectic AlSi12 alloy using chemical analysis, simple thermal analysis (STA) and metallographic analysis. The metallographic analysis revealed fully modified (αAl+βSi) eutectic microstructure in alloy treated with Na. The Sr additions widened solidification interval and, lowered the eutectic area temperatures as indicated by STA
Change of microstructure of Nb microalloyed steel at start of the plastic flow during the cold deformation
No full textMicrostructure has significant impact on the properties and behavior of materials, so it is a subject of intensive investigation nowdays. In this paper, special attention is paid to study on the beginning of the plastic material flow in Nb microalloyed steel during the cold deformation. Specific behavior of this steel can present a significant problem during the metalworking in terms of inhomogeneous deformations appearance. Due to many available methods now it is possible to observe what is happening during the deformation of certain material. Hence, investigation of material flow and stress distribution in deformation zone is growing up today. Therefore, the aim of this work was to establish the change of microstructure of low carbon steel microalloyed with niobium at start of the plastic flow during the cold deformation. For that purpose Nb microalloyed steel was hot rolled into strip and then static tensile test was carried out. Thermography method was used to study the changes of temperature during the deformation. Microstructure before and after deformation was observed by scanning electron microscope. These investigations showed the fine grained ferrite -pearlitic microstructure and its significant changes at start of the plastic flow during the cold deformatio
Effects of bismuth on the matrix structure of ductile iron castings
No full textThis paper deals with the effects of the addition of 0.00031, 0.00064, 0.001 and 0.0042 wt.% Bi on the matrix structure of ductile iron castings consisting of 7 sections of different thicknesses (3, 12, 25, 38, 50, 75 and 100 mm) and contain low content of Si (2.11 wt.%) and pearlite promoting element (0.018 wt.% Cu, 0.0055 wt.% Sn, 0.00041 wt.% Sb, 0.098 wt.% Mn). The Bi contents of 0.00031, 0.00064 and 0.001 wt.% were not significantly affected the share of ferrite and pearlite in the section thicknesses of 12, 25, 38, 50, 75 and 100 mm compared to the casting which does not contain Bi. In all these sections the share of pearlite was increased and the share of ferrite was decreased by the addition of 0.0042 wt.% Bi. All of the above-mentioned Bi contents were resulted in the formation of iron carbides in the section thickness of 3 mm. The share of carbides increases with increasing Bi content
Effect of the steel's heating time in furnace regarding thickness of the oxide layer
Get PDFU prvom dijelu rada dan je teorijski pregled o konstrukcijskim čelicima s naglaskom na čelike za poboljšavanje. Opisana je njihova podjela i primjena. U teorijski dio rada uključene su i teorijske osnove o koroziji, a detaljnije je opisana kemijska korozija i korozija uzrokovana visokotemperaturnim zagrijavanjem. U eksperimentalnom dijelu rada korišteni su uzorci čelika za poboljšavanje HRN Č.4732, koji su u različitoj duljini trajanja bili podvrgnuti visokotemperaturnom zagrijavanju. Eksperiment je osmišljen u svrhu praćenja stvaranja oksida u ovisnosti o vremenu zagrijavanja. Uzorcima čelika izmjeren je prirast mase i debljina oksidnog sloja nakon zagrijavanja, pri čemu je ustanovljeno da se prirast mase povećava s vremenom zagrijavanja u peći. Napravljena je i analiza mikrostrukture čelika u nagriženom stanju, gdje se uočila pojava razugljičavanja po rubovima uzoraka.First part consists of theoretical overview of structural steels with an emphasis on quenching and tempering steels with description of their use and classification. Followed by theoretical basis about corrosion with detailed description of chemical corrosion and corrosion caused by high temperature heating.
In the experimental part of the thesis the samples of quenching and tempering steels HRN Č.4732 were used, which were subjected to high temperature heating. The experiment was design to monitor the formation of oxides in relation to the heating time. After the heating, the weight gain and the thickness of the oxide layer were measured. It was found out that the weight gain increases with the heating time in the furnace. The analysis of the microstructure of steel in etched condition was performed, where the appearance of the decarburization on the edges of the sample was observed
Materials characterization and biodegradation by composting
Get PDFU ovom radu pripremljene su binarne i ternarne mješavine na bazi biorazgradivih polimera polikaprolaktona (PCL), polilaktida (PLA) te termoplastičnog škroba (TPS). Istražena je morfološka struktura pomoću pretražne elektronske mikroskopije (SEM). Toplinska svojstva istražena su diferencijalnom pretražnom kalorimetrijom (DSC), a toplinska stabilnost određena je termogravimetrijskom analizom (TGA). Mehanička svojstva mješavina ispitana su rasteznim ispitivanjem provedenim na mehaničkoj kidalici. Biorazgradivost mješavina provedena je procesom kompostiranja na laboratorijskoj razini. SEM analizom utvrđena je bolja mješljivost binarne PLA/TPS mješavine nego PCL/TPS mješavine, dok je kod PCL/PLA mješavina naglašena dvofazna morfološka struktura koja za posljedicu ima loša mehanička svojstva. Dodatkom TPS-a u binarne PCL/PLA mješavine nije postignuta bolja mješljivost niti je primijećeno kompatibilizirajuće djelovanje TPS –a. DSC analizom utvrđeno je da dodataka TPS-a doprinosi povećava stupanj kristalnosti PLA, a ograničava pokretljivost PCL lanaca što rezultira nižim stupnjem kristalnosti PCL-a u ternarnim PCL/PLA/TPS mješavinama. TGA analiza pokazala je sniženje temperature razgradnje binarnih mješavina dodatkom TPS-a. Umješavanjem TPS-a u PCL/PLA mješavine narušavaju se mehanička svojstva. Potpuna biorazgradnja procesom kompostiranja dobivena je kod uzoraka s većim udjelom PLA. Dodatak TPS-a u binarnih i ternarnim mješavinama pogoduje biorazgradnji, jer naglašena amorfna struktura kao i hidrofilni karakter TPS-a pogoduje mikroorganizmima.In this paper, binary and ternary blends were prepared based on biodegradable polymers polycaprolactone (PCL), polylactide (PLA) and thermoplastic starch (TPS). The morphological structure was investigated using scanning electron microscopy (SEM). Thermal properties were investigated by differential scanning calorimetry (DSC) and thermal stability was determined by thermogravimetric analysis (TGA). The mechanical properties of the blends were tested by tensile testing performed on a mechanical machine. The biodegradability of the blends was carried out at the laboratory level composting process. The SEM analysis revealed a better miscibility with the binary PLA/TPS blend than with the PCL/TPS blend, while the PCL/PLA blend emphasized a two-phase morphological structure resulting in poor mechanical properties. By adding TPS to binary PCL/PLA blends, no better miscibility or compatibility was observed. DSC analysis found that the addition of TPS contributes to the increase in crystallinity of PLA, and limits the mobility of PCL chains resulting in a lower degree of crystallinity of PCL in ternary PCL/PLA/TPS blends. TGA analysis showed a decrease in the decomposition temperature of binary blends by the addition of TPS. By mixing TPS in PCL/PLA blends, the mechanical properties are impaired. Complete biodegradation was obtained for samples with a higher content of PLA. The addition of TPS in binary and ternary blends favours biodegradation, since the amorphous structure as well as the hydrophilic character of TPS favours microorganisms
Effect of cooling rate and silicon content on graphite morphology and austenite transformation in solid solution strengthened ferritic ductile cast irons
No full textEffect of the cooling rate (section thickness) on the graphite morphology and austenite transformation in solid solution strengthened ferritic ductile cast irons was analysed in this paper. Three melts with the following silicon contents were made: 3.11, 3.8 and 4.22 wt.%. The analysis was carried out on test castings containing seven different section thicknesses: 3, 12, 25, 38, 50, 75, and 100 mm. Obtained results show that the nodule count and nodularity decrease with increasing section thickness (i.e. with a decrease in the cooling rate). The increase in silicon content from 3.11 to 4.22 wt.% resulted in an increase in nodule count and nodularity in section thicknesses of 3, 12, 25 and 38 mm. However, in thick sections, i.e. in section thicknesses of 50, 75 and 100 mm, the increase in silicon content resulted in a decrease in nodule count and nodularity. In these sections, the number of very small irregular graphite particles and clusters of graphite particles that look like chunky graphite increased with the increase in silicon content. In test castings containing 3.8 and 4.22 wt.% Si the amount of ferrite in the metal matrix increases with increasing section thickness. Fully ferritic metal matrix is obtained in section thicknesses of 25, 38, 50, 75 and 100 mm. All sections of the test casting containing 3.11 wt.% Si have a certain proportion of pearlite