Sampling of liquid steel to control the steel making process is very important in the steel industry. However, there are numerous types of disposable samplers and no united standard for sampling. The goal in this study is to investigate the effect of slag protection type and sample geometry on sampling parameters and sample homogeneity. Three sample geometries were selected: i) Björneborg ii) Lollipop with a 6 mm thickness and iii) Lollipop with a 12 mm thickness. These sample geometries have been tested with two types of slag protection: metal-cap-protection and argon-protection. The filling velocity and solidification rate of steel samples have been experimentally measured during plant trials. The sample homogeneity with respect to total oxygen content and inclusion size distribution has been determined in different parts of the samples. The study shows that argon-protected samplers have lower, more even, filling velocities (0.19±0.09 m/s) compared to metal-cap-protected samplers (1.28±2.23 m/s). The solidification rate measurements of the different samplers show that the 6 mm thick Lollipop has the highest solidification rate (99~105 °C/s).  Measurements of total oxygen content in argon-protected samples showed little variation between different zones of the samples. However, metal-cap-protected samples contained much higher total oxygen contents. Light optical microscope studies showed that the increase in total oxygen content was probably caused by entrapment of top slag during sampling. Furthermore, it was found that the contamination of top slag in the metal samples increased with a decreased sample weight. Determination of inclusion size distribution in argon-protected Lollipop samples showed that a larger number of primary inclusions are found in the top part compared to the middle and the bottom part of the samples.

Heavy-metal contamination in soils has become a serious environmental problem. Among all metals, excessive amount of zinc was released to soils over the years. Zinc is not only toxic to human being, but also to plants. High concentration of zinc is extremely phytotoxic. Currently, the most popular method to remediate heavy-metal contaminated soils is stabilization/solidification (S/S) technique as it is cheaper, faster and more effective to remediate heavy metals than other remediation methods. Portland cement is the most-used binder in S/S technique. However, the production of Portland cement has released a significant amount of carbon dioxide, which strongly contributes to global warming. In addition, zinc retards the setting and hydration of Portland cement, which would require more Portland cement to remediate zinc-contaminated sites. Therefore, researchers are looking for new materials to improve the performance of Portland cement in zinc-contaminated soils. In recent years, the application of graphene-based materials in concrete had proved to be effective. Due to relative cost-effectiveness and comparable properties, multi-layer graphene, known as graphene nanoplatelets, may show a promising potential in construction. Moreover, research has reported that graphene nanoplatelets can be exfoliated from graphite and potentially scaled up for full-scale applications. At present, there is no application of graphene nanoplatelets in the S/S of contaminated soils and the roles of graphene nanoplatelets in cement-stabilized zinc-contaminated clay remained unknown. In this research, graphene nanoplatelets were dispersed in solution with a high-shear mixing apparatus. Dispersed graphene nanoplatelets solution was then applied to zinc-contaminated soil along with cement. To evaluate the efficacy of this S/S method, various influencing factors such as mixing sequence, graphene nanoplatelets content, zinc content, cement content, and curing time were studied. An optimum graphene nanoplatelets content was determined through the unconfined compressive strength (UCS) of the stabilized/solidified samples. It was found that at the optimum content, the unconfined compressive strength of cement-stabilized zinc-contaminated clay was improved by 22.3% with the addition of graphene nanoplatelets. Also, graphene nanoplatelets were effective at moderate zinc content and low cement content. Graphene nanoplatelets accelerated cement hydration effectively at early ages. Microstructural analyses indicated that more hydration products were developed in samples with graphene nanoplatelets. At current stage, it is still expensive to apply graphene nanoplatelets in S/S technique; however, it is possible to exfoliate graphite into graphene nanoplatelets in future research. / Graduate / 2022-05-12

<p>Secondary cooling during continuous casting is a delicate process because the cooling rate of water spray directly affects the slab surface and internal quality. Undercooling may lead to slab surface bulging or even breakout, whereas overcooling can cause deformation and crack of slabs due to excessive thermal residual stresses and strains. Any slab which does not meet the required quality will be downgraded or scrapped and remelted. In order to remain competitive and continuously produce high-quality and high-strength steel at the maximum production rate, the secondary cooling process must be carefully designed and controlled. Efficient and uniform heat removal without deforming or crack the slab is a significant challenge during secondary cooling. In the meantime, the on-site thermal measurement techniques are limited due to the harsh environment. In contrast, experimental measurements are only valid for the tested conditions, and the measurement process is not only labor-intensive, but the result might be inapplicable when changes in the process occur. On the other hand, the high-performance computing (HPC)-powered computational fluid dynamics (CFD) approach has become a powerful tool to gain insights into complex fluid flow and heat transfer problems. Yet, few successful numerical models for heat transfer phenomena during secondary cooling have been reported, primarily due to complex phenomena. </p> <p> </p> <p>Therefore, the current study has proposed two three-dimensional continuum numerical models and a three-step coupling procedure for the transport of mass, momentum, and energy during the secondary cooling process. The first numerical model features the simulation of water spray impingement heat and mass transfer on the surface of a moving slab considering atomization, droplet dispersion, droplet-air interaction, droplet-droplet interaction, droplet-wall impingement, the effect of vapor film, and droplet boiling. The model has been validated against five benchmark experiments in terms of droplet size prior to impingement, droplet impingement pressure, and heat transfer coefficient (HTC) on the slab surface. The validated model has been applied to a series of numerical simulations to investigate the effects of spray nozzle type, spray flow rate, standoff distance, spray direction, casting speed, nozzle-to-nozzle distance, row-to-row distance, arrangement of nozzles, roll and roll pitch, spray angle, spray water temperature, slab surface temperature, and spray cooling on the narrow face. Furthermore, the simulation results have been used to generate a mathematically simple HTC correlation, expressed as a function of nine essential operating parameters. A graphic user interface (GUI) has been developed to facilitate the application of correlations. The calculated two-dimensional HTC distribution is stored in the universal comma-separated values (csv) format, and it can be directly applied as a boundary condition to on-site off-line/on-line solidification calculation at steel mills. The proposed numerical model and the generic methodology for HTC correlations should benefit the steel industry by expediting the development process of HTC correlations, achieving real-time dynamic spray cooling control, supporting nozzle selection, troubleshooting malfunctioning nozzles, and can further improve the accuracy of the existing casting control systems.</p> <p> </p> <p>In the second numerical model, the volume-averaged Enthalpy-Porosity method has been extended to include the slurry effect at low solid fractions through a switching function. With the HTC distribution on the slab surface as the thermal boundary condition, the model has been used to investigate the fluid flow, heat transfer, and solidification inside a slab during the secondary cooling process. The model has been validated against the analytical solution for a stationary thin solidifying body and the simulation for a moving thin solidifying body. The effects of secondary dendrite arm spacing, critical solid fraction, crystal constant, switching function constant, cooling rate, rolls, nozzle-to-nozzle distance, and arrangement of nozzles have been evaluated using the validated model. In addition, <a>the solidification model has been coupled with the predictions from the HTC correlations, and the results have demonstrated the availability of the correlations other than on-site continuous casting control. </a>Moreover, the model, along with the three-step coupling procedure, has been applied to simulate the initial solidification process in continuous casting, where a sufficient cooling rate is required to maintain a proper solidification rate. Otherwise, bulging or breakout might occur. The prediction is in good agreement with the measured shell thickness, which was obtained from a breakout incident. With the help of HPC, such comprehensive simulations will continue to serve as a powerful tool for troubleshooting and optimization.</p>

<p>Predmet izučavanja ove disertacije obuhvatio je ispitivanje uticaja starenja stabilizovanog/solidifikovanog&nbsp; (S/S)&nbsp; sedimenta&nbsp; zagađenog te&scaron;kim metalima i arsenom, i efikasnost primenjenih imobilizacionih agenasa (Portland cement, kreč, leteći pepeo, zeolit, montmorilonit i kaolinit) nakon dugogodi&scaron;njeg starenja S/S sme&scaron;a. Shodno tome ispitana je dugoročna stabilnost i postojanost dobijenih S/S sme&scaron;a sa aspekta izluživanja pomenutih metala, promene u minerolo&scaron;kim i strukturnim karakteristikama, kao i uticaj su&scaron;enja i zrenja materijala na pomenute parametre. Istraživanja u disertaciji obuhvatila su dve faze. Prva faza imala je za cilj procenu rizika i&nbsp; početnu karakterizaciju netretiranog sedimenta primenom analize pseudo-ukupnog sadržaja metala kojom je utvrđen sadržaj metala u početnom uzorku sedimenta. Druga faza uključivala je primenu tretmana stabilizacije i solidifikacije na kontaminirani sediment dodavanjem različitih imobilizacionih agenasa. Analize su se vr&scaron;ile nakon 7 i 28 dana od primenjenog S/S tretmana, kao i nakon 7 godina sa ciljem da se utvrdi uticaj vi&scaron;egodi&scaron;njeg starenja i zrenja monolitnih sme&scaron;a na mobilnost metala i strukturne karakteristike sme&scaron;a. U&nbsp; okviru&nbsp; druge faze istraživanja ispitana je toksičnost S/S sme&scaron;a primenom DIN i TCLP testova izluživanja, dok je test toksičnosti primenom bakterija Vibrio Fischeri&nbsp; doprineo u&nbsp; sagledavanju&nbsp; procene rizika S/S sme&scaron;a po organizme. Nakon 28 dana i 7 godina kori&scaron;ćena je sekvencijalna ekstrakcija za&nbsp; određivanje mobilnost i biodostupnost metala u monolitnim matriksima. U cilju&nbsp; utvrđivanja mikrostukturnih karakteristika sedimenta primenjena je rendgenska difrakciona analiza (XRD) za ispitivanje kristalnih struktura&nbsp; S/S sme&scaron;a i detekciju mineralnog sastava. Pomoću elektronskog mikroskopa i energodisperzivnog detektora&nbsp; sa X-zrakom (SEM/EDS) određena je kvalitativna i kvantitativna distribucija metala i&nbsp; drugih elemenata od interesa, dok se za identifikaciju formiranih funkcionalnih grupa u monolitnim sme&scaron;ama primenio spektrometar sa infracrvenom Furijeovom transformacijom (FTIR). Na osnovu dobijenih rezultata zaključeno je da se mobilnost te&scaron;kih metala i arsena značajno smanjila nakon 7 godina za sme&scaron;e tretirane cementom (C5), krečom (L10), letećim pepelom (F30) i kaolinitom&nbsp; (K20), a efekat stabilizacije je pokazan transformacijom metala iz direktne toksične frakcije u&nbsp; stabilnije oblike. Sme&scaron;e C5 i K20 ispoljavaju&nbsp; najmanje toksične efekate od svih sme&scaron;a, jer je procenat inhibicije&nbsp; na&nbsp; bioluminiscentnim&nbsp; bakterijama manji od 13%, dok je u pogledu izdržljivosti monolitna sme&scaron;a C5 pokazala najveću pritisnu čvrstoću od svih sme&scaron;a. Dobijeni podaci su neprocenjivi za dobijanje stvarnog uvida u dugoročnu efikasnost&nbsp; primenjenog&nbsp; tretmana i mogućnost bezbedne upotrebe ili odlaganja dobijenih S/S sme&scaron;a sa aspekta za&scaron;tite životne sredine, kao i ekonomski i ekolo&scaron;ki prihvatljivog upravljanja opasnim otpadom.</p> / <p>The subject of study in this dissertation included to investigate the&nbsp; effect&nbsp; of&nbsp; aging&nbsp; of&nbsp; stabilized/solidified&nbsp; (S/S)&nbsp; sediment&nbsp; contaminated with&nbsp; heavy&nbsp; metals&nbsp; and&nbsp; arsenic,&nbsp; and&nbsp; the&nbsp; efficacy&nbsp; of&nbsp; the&nbsp; applied immobilization&nbsp; agent&nbsp; (Portland&nbsp; cement,&nbsp; lime,&nbsp; fly&nbsp; ash,&nbsp; zeolite, montmorillonite and kaolinite) after long-term aging of S/S mixtures. The<br />long&nbsp; -&nbsp; term stability and stability of the obtained S/S mixtures from the aspect of leaching of the mentioned metals, changes in mineralogical and structural characteristics,&nbsp; as&nbsp; well&nbsp; as&nbsp; the&nbsp; influence&nbsp; of&nbsp; drying&nbsp; and maturation of the material on the mentioned parameters were examined. The&nbsp; research&nbsp; in&nbsp; the&nbsp; dissertation&nbsp; included&nbsp; two&nbsp; phases.&nbsp; The&nbsp; first&nbsp; phase aimed&nbsp; at&nbsp; risk&nbsp; assessment&nbsp; and&nbsp; initial characterization&nbsp; of&nbsp; untreated sediment using pseudo-total metal content analysis which determined the<br />metal content in the initial sediment sample.&nbsp; The second phase involved applying&nbsp; stabilization&nbsp; and&nbsp; solidification&nbsp; treatments&nbsp; to&nbsp; the&nbsp; contaminated sediment&nbsp; by&nbsp; adding&nbsp; various&nbsp; immobilizing&nbsp; agents.&nbsp; The&nbsp; analyzes&nbsp; were performed after 7 and 28&nbsp; days from the applied S/S treatment, as well as after 7 years in order to determine the influence of perennial aging and maturation&nbsp; of&nbsp; monolithic&nbsp; mixtures&nbsp; on&nbsp; metal&nbsp; mobility&nbsp; and&nbsp; structural characteristics&nbsp; of&nbsp; the&nbsp; mixtures.&nbsp; In&nbsp; the&nbsp; second&nbsp; phase&nbsp; of&nbsp; the&nbsp; study,&nbsp; the toxicity&nbsp; of&nbsp; S/S&nbsp; mixtures&nbsp; using&nbsp; DIN&nbsp; and&nbsp; TCLP&nbsp; leaching&nbsp; tests&nbsp; was examined, while&nbsp; the&nbsp; toxicity&nbsp; test&nbsp; using&nbsp; bacteria&nbsp; Vibrio&nbsp; Fischeri contributed&nbsp; to&nbsp; the assessment&nbsp; of&nbsp; the&nbsp; risk&nbsp; of&nbsp; S/S&nbsp; mixtures&nbsp; to&nbsp; organisms. After&nbsp; 28 days&nbsp; and&nbsp; 7 years,&nbsp; sequential extraction was&nbsp; used to&nbsp; determine the mobility and bioavailability of metals in monolithic matrices. In order to&nbsp; determine&nbsp; the&nbsp; microstructural&nbsp; characteristics&nbsp; of&nbsp; the&nbsp; sediment,&nbsp; x-ray diffraction analysis (XRD) was used to examine the crystal structures of&nbsp; S/S mixtures and&nbsp; to detect the mineral composition.&nbsp; The qualitative and quantitative&nbsp; distribution&nbsp; of&nbsp; metals&nbsp; and&nbsp; other&nbsp; elements&nbsp; of&nbsp; interest&nbsp; was determined using an electron microscope and an energy-dispersive X-ray detector&nbsp; (SEM&nbsp; /&nbsp; EDS),&nbsp; while&nbsp; an&nbsp; infrared&nbsp; Fourier&nbsp; transform spectrometer(FTIR) was used to identify the formed functional groups in monolithic mixtures. Based on the obtained results, it was concluded that the mobility of heavy metals and arsenic decreased significantly after 7 years&nbsp; for&nbsp; mixtures&nbsp; treated&nbsp; with&nbsp; cement&nbsp; (C5),&nbsp; lime&nbsp; (L10),&nbsp; fly ash&nbsp; (F30) and&nbsp; kaolinite&nbsp; (K20),&nbsp; and&nbsp; the&nbsp; stabilization&nbsp; effect&nbsp; was&nbsp; shown&nbsp; by transformation&nbsp; of&nbsp; metals&nbsp; from&nbsp; direct&nbsp; toxic&nbsp; fractions&nbsp; into&nbsp; more&nbsp; stable forms. Mixtures&nbsp; C5&nbsp; and&nbsp; K20&nbsp; exhibit&nbsp; the&nbsp; least&nbsp; toxic&nbsp; effects&nbsp; of&nbsp; all mixtures, because the percentage of inhibition on bioluminescent bacteria is less than 13%, while in terms of durability, the monolithic mixture C5 showed&nbsp; the&nbsp; highest&nbsp; compressive&nbsp; strength&nbsp; of&nbsp; all&nbsp; mixtures.&nbsp; The&nbsp; obtained data are invaluable for gaining real insight into the long-term efficiency of the applied treatment and the possibility of safe use&nbsp; or disposal of the obtained&nbsp; S/S&nbsp; mixtures&nbsp; from&nbsp; the&nbsp; aspect&nbsp; of&nbsp; environmental&nbsp; protection,&nbsp; as well&nbsp; as&nbsp; economically&nbsp; and&nbsp; ecologically&nbsp; acceptable&nbsp; hazardous&nbsp; waste management.</p>

No description available.

Analyses of heat and mass transfer between different materials and phases are essential in numerous fundamental scientific problems and practical engineering applications, such as thermal and chemical transport in porous media, design of heat exchangers, dendritic growth during solidification, and thermal/mechanical analysis of additive manufacturing processes. In the numerical simulation, interface treatment can be further divided into sharp interface schemes and diffuse interface schemes according to the morphological features of the interface. This work focuses on the following subjects through computational studies: (1) critical evaluation of the various sharp interface schemes in the literature for conjugate heat and mass transfer modeling with the lattice Boltzmann method (LBM), (2) development of a novel sharp interface scheme in the LBM for conjugate heat and mass transfer between materials/phases with very high transport property ratios, and (3) development of a new diffuse-interface phase-field-lattice Boltzmann method (PFM/LBM) for dendritic growth and solidification modeling. For comparison of the previous sharp interface schemes in the LBM, the numerical accuracy and convergence orders are scrutinized with representative test cases involving both straight and curved geometries. The proposed novel sharp interface scheme in the LBM is validated with both published results in the literature as well as in-house experimental measurements for the effective thermal conductivity (ETC) of porous lattice structures. Furthermore, analytical correlations for the normalized ETC are proposed for various material pairs and over the entire range of porosity based on the detailed LBM simulations. In addition, we provide a modified correlation based on the SS420-air and SS316L-air metal pairs and the high porosity range for specific application. The present PFM/LBM model has several improved features compared to those in the literature and is capable of modeling dendritic growth with fully coupled melt flow and thermosolutal convection-diffusion. The applicability and accuracy of the PFM/LBM model is verified with numerical tests including isothermal, iso-solutal and thermosolutal convection-diffusion problems in both 2D and 3D. Furthermore, the effects of natural convection on the growth of multiple crystals are numerically investigated.

M. Tech. (Department of Metallurgical Engineering, Faculty of Engineering and Technology), Vaal University of Technology. / The production of austenitic stainless-steel pump impellers in foundries present a huge challenge mainly due to its thin-walled blades, pouring temperature, presence of junctions and chemical composition. Two different alloys were used namely nodular cast iron and austenitic stainless-steel. Nodular cast iron was used as a comparison alloy due to its excellent flowability whereas austenitic stainless-steel was chosen due to its attractive corrosion and wear resistant properties. Austenitic stainless-steel alloy showed difficulties during casting because of its chemical composition and freezing range. Thin-walled sections are more susceptible to filling defects like misrun and cold-shut. This results in high scrap rate and high processing costs during high production of thin-walled components. High pouring temperature is considered one of the most effective methods to improve filling ability of thin-walled castings. However, there is a major drawback in using this method owing to the high occurrence of shrinkage defects and hot tearing especially at junctions. 1060 aluminium was used as a benchmark to evaluate the effect of wall thickness on the filling and feeding of thin-walled Al components with complex geometry during sand casting. The aim of this dissertation is therefore to optimize casting process of sand cast austenitic stainless-steel pump impeller. Numerical modelling and additive manufacturing were used to optimize the production of this product. The use of casting simulation software combined with three-dimensional (3D) mould printing technology has enabled optimisation of casting parameters to minimise the occurrence of casting defects. Casting parameters of five test samples of complex geometry and varying thicknesses (1.0 mm;1.5 mm;2 mm;2.5 mm and 3.0 mm) were optimised using MAGMAsoft® at a constant pouring temperature of 700 °C and 1060 Aluminium as an alloy. Simulation and casting results showed that complete filling was only possible at a wall thickness of 3 mm. The simulation results showed that as the wall thickness increased from 1 mm to 3 mm the filling ability increased by 67.5 % whereas experimental casting results showed that filling ability increase by 75 %. The combination of MAGMAsoft® simulation and 3D printed moulds proved to be effective tools in predicting filling and feeding of thin-walled aluminium components during sand casting. MAGMAsoft® casting software was used to simulate metal flow and predict the degree of filling at different pouring temperatures. Test samples were cast using 1060 Aluminium alloy at temperatures of 702 °C, 729 °C, 761 °C, 794 °C, 800 °C and 862 °C. Complete mould filling was predicted at 800 °C using the simulation model and 761°C during actual casting. At temperatures above 761°C tearing at the junction was quite pronounced. An optimal of 761°C pouring temperature was found to be appropriate pouring temperature when casting thin-walled aluminum components using sand casting. MAGMAsoft® casting software proved to be an effective tool in optimizing filling and feeding of thin-walled aluminium components during sand casting. Nodular cast iron pump impeller was optimized at 1500 °C using MAGMAsoft® and 3D mould printing technology. Design variables used were feeder radius (17 mm, 18 mm, 19 mm and 20 mm), feeder height (32 mm, 33 mm, 34 mm, 35 mm) and number of feeders of (3, 4 and 5). Simulation and casting results showed a completely-filled casting. The high fluidity of nodular cast iron promotes mould filling ability and prevent any form of misrun defect. Minimum shrinkage was noted at the junctions and top surface of the casting. A new design was proposed to eliminate shrinkage defects at the junctions of the nodular cast iron pump impeller. The design used a tapered circular runner bar with straight ingates. Optimization of nodular cast iron was now done at 1390 °C with the use of MAGMAsoft® and real casting was done 1385 °C. Simulation and casting were in correlation to each other since both showed completely-filled mould cavity with no misrun, cold-shut and shrinkage porosity defect. Simulation proved to be an effective tool in optimizing filling and solidification of nodular cast iron during sand casting. Austenitic stainless-steel pump impeller was optimized at 1500 °C using MAGMAsoft® and 3D mould printing technology. A high quality mould and core print were printed with the use of Voxeljet VX1000 at a minimum period of time. Design variables used were feeder radius (17 mm, 18 mm, 19 mm and 20 mm), feeder height (32 mm, 33 mm, 34 mm, 35 mm) and number of feeders of (3, 4 and 5). An increase in feeder size and the number of feeders greatly reduced hot spot and porosity of the casting but it also reduced the casting yield. The quality of the casting was found to be inversely proportional to the casting yield. Simulation showed a completely-filled casting with actual casting showing only 50 % filling ability. High viscosity of the molten metal and thin walled blades promote quick solidification which caused misrun defects. A new design was proposed to eliminate misrun defects of the first design. MAGMAsoft® was used to optimize this design at 1550 °C. The design used a tapered circular runner bar with tapered ingates. The actual casting showed improved filling ability from 50 % to 80 % while simulation showed completely-filled mould cavity (100 %). Major factors which contributed to low filling ability of austenitic stainless-steel pump impeller were chemistry, runner system and men. Numerical modelling and additive manufacturing did optimize filling and feeding of sand cast austenitic stainless-steel pump impeller.

This paper presents an investigation on using the variation of ferrostatic pressure exerted by the molten steel in the strand to the support rolls during continuous casting to detect the location of the final solidification. The final solidification point is of high importance for applying soft reduction during continuous casting in order to ensure inner quality and achieve high productivity. The measurement was conducted at one of the casters at SSAB Oxelösund, of which all the support rolls are separately mounted. The project finds that this method shows promising results and can help to narrow down the range of the location due to certain interferences and noises. The ferrostatic pressure decrease during tail-out and the variation of whether a pressure drop exists is the dividing line of full and partial solidification. With the promising results achieved, more effort should be put to further improve the method.

Tensile strength modelling is usually done to predict the mechanical properties of lamellargraphite iron considering microstructural features. This work attempts to create a simplifiedmodel incorporating cooling rate and solidification time without considering themicrostructural features. This model will save time and cost in industry with the presence of acommercially available software such as Magmasoft which simulates solidification time andcooling rate. A plate model was designed for this purpose as the test geometry to createvariation in solidification time and cooling rate. By altering fraction solid, thermalconductivity, specific heat capacity in Magmasoft, a good fit was created between simulatedcooling curve and experimental cooling curves. The experimental UTS data of samples fromthree moulds were investigated and a regression model was created using statistics toolMinitab. The effect of solidification time and alloying on the graphite length Lmax was studiedfor twelve samples from each mould. Quantification of the effect of cooling rate and alloyingon the pearlitic properties of grey iron like matrix microhardness, pearlite inter-lamellarspacing was also investigated in this work.The developed model has sixty three percent correlation and explains UTS well in terms ofsolidification time and cooling rate. Microhardness measurements show that there is an almostlinear relationship between the cooling rate and microhardness of the matrix structure.Microhardness data also provides an overview of the pearlite fineness/interlamellar spacing.Analysis of the outliers showed that the presence of free ferrite on a fully pearlitic structurereduces the UTS significantly. Comparison of the regression model obtained from this workwith previous work showed that, there is a reduction in the predicted strength with this model.The effort to identify the reason for this reduction was not successful and needs furtherinvestigation. Pearlite inter-lamellar spacing measurement was not accurate. The relationshipbetween pearlite interlamellar spacing and matrix microhardness needs to be investigated inthe future using a better technique for pearlite spacing measurement. This will be useful tounderstand the effect of cooling rate on pearlite spacing and consequently on the UTS of greycast iron. / Draghållfasthetsmodellering görs vanligtvis för att förutsäga de mekaniska egenskaperna av lamellärt grafitjärn. Detta arbete har försökt att skapa en förenklad modell som innehåller kylhastighet och stelningstid utan att överväga mikrostrukturella egenskaper. Modellen kommer att spara tid och kostnad i industrin tillsammans med kommersiellt tillgänglig mjukvara som Magmasoft som simulerar stelningstiden och kylningshastighet. En plattformig modell utformades för detta ändamål som testgeometrin för att skapa variation i stelningstid och kylningshastighet. Genom att ändra fraktion fast fas, termisk konduktivitet och specifik värmekapacitet i Magmasoft skapades en bra anpassning mellan simulerade och experimentella kylkurvor. Experimentella draghållfasthetsdata (UTS) för prover från tre gjutningar undersöktes och en regressionsmodell skapades med hjälp av statistikverktyg Minitab. Effekten av stelningstid och legeringshalt på grafitlängden Lmax studerades för tolv prover från varje form. Effekten av kylhastighet och legering på de perlitiska egenskaperna hos grått järn som matrismikrohårdhet och perlitlamellavstånd undersöktes också i detta arbete.  Den utvecklade modellen har sextiotre procent korrelation och förklarar UTS väl med avseende på stelningstid och kylningshastighet. Mikrohårdhetsmätningar visar att det finns ett nästan linjärt förhållande mellan kylhastigheten och mikrohårdheten hos matrisstrukturen. Mikrohårdhetsdata ger också en översikt över perlitens finhet/interlamellära avstånd. Analys av outliers visade att närvaron av fri ferrit på en fullständigt perlitisk struktur minskar UTS betydligt. Jämförelse av regressionsmodellen erhållen från detta arbete med tidigare arbete visade det att det finns en minskning av den förutsagda styrkan med denna modell. Ansträngningen att identifiera orsaken till denna minskning var inte framgångsrik och behöver ytterligare undersökas. Perlit mellan lamellär avståndsmätning var inte korrekt. Förhållandet mellan perlitens interlamellära avstånd och matrismikrohet måste undersökas i framtiden med hjälp av en bättre teknik för perlit-avståndsmätning. Detta kommer att vara användbart att förstå effekten av kylhastighet på perlitavståndet och följaktligen på UTS av grå gjutjärn

Lamellar cast iron is a very important technical alloy and the most used material in the casting production, and especially in the automotive industry which is the major consumer. Beside the many great properties, it is inclined to form casting defects of which some can be prevented, and some may be repaired subsequently. Shrinkage porosity is a randomly returning problem, which is difficult to understand and to avoid. This defect is a volumetric deficiency which appear as cavities inside the casting in connection to the casting surface. Another frequent defect is the metal expansion penetration. This defect is a material surplus squeezed to the casting surface containing sand inclusion from the mold material. Shrinkage porosity is usually mentioned together with metal expansion penetration as the formation mechanism of both defects have common roots. It is also generally agreed, that these type of defects are related to the volumetric changes occurring during solidification. Additionally, the formation of these defects are in connection with the coherency of the primary austenite dendrites. The purpose of this work was to develop knowledge on factors affecting a volume-change related casting defect formation in order to minimize the presence of these defects in engine component production. This was done by extending the existing solidification investigation methods with novel solutions. Introduction of expansion force measurement in the determination of dendrite coherency combined with multi axial volume change measurement refine the interpretation of the solidification. Comparison of registered axial and radial linear deformation in cylindrical samples indicated an anisotropic volume change. Different methods for dendrite coherency determination have been compared. It was shown that the coherency develops over an interval. Dependent on the added inoculant the coherency is reached at different levels of fractions of a solidified primary phase. It is also shown, that inoculation has an effect on the nucleation and growth of the primary phase. Quantitative image analysis has been performed on the primary phase in special designed samples designed to provoke shrinkage porosity and metal expansion penetration. It was found, that the inter-dendritic space varies within a casting. This was explained by the coarsening of the primary dendrites which originates from differences in the local time of solidification. / <p>QC 20131210</p>