Dissertations / Theses on the topic 'Metallurgy'

The crust of a neutron star plays an important role in the emission observed from it. The thermal emission generated in the core of the neutron star passes through the crust, thus it is important to know what is in the crust in order to understand how the emission is shaped and altered. The crust itself may be responsible for the observations of glitches from neutron stars and also as a source of gravitational waves. This thesis is two-fold. The first goal is to calculate the composition of the neutron star crust of a non-accreting neutron star. The second is to use the calculated crustal compositions in molecular dynamics simulations in order to determine the shear modulus and breaking strain of the crustal material. The composition of the crust is found to be dependent on how the neutron star cooled. Nuclear reactions within the crust are quenched as the star cools. The composition of the crust, envelope, and atmosphere are calculated after the nuclear reactions are quenched. With the settling timescales of the various isotopes in the crust, some of these isotopes are able to float up to the neutron star surface and form the atmosphere. Three different cooling methods were used in these calculations – modified Urca cooling, a thick crust and a thin crust – each produces different atmospheric and crustal compositions. The calculated crustal abundances are then used as initial conditions in molecular dynamics simulations. A shear force is introduced by deforming the simulation box. The shear modulus and breaking strain are calculated for the three different crustal compositions as well as for perfect pure face-centered cubic (FCC) and body-centered cubic (BCC) systems. The upper limit, from the perfect crystal lattice structure, on the breaking strain is found to ~0.11 − 0.12 and the shear modulus is found to be 6.5 × 10³º dyne/cm². These properties predict glitch amplitudes of ∆Ω/Ω∼10⁻³. The gravitational wave strain amplitudes for PSR J2124- 3358 are also predicted to be greater than the observed upper limits. This indicates that the neutron star crust is not a perfect BCC lattice which deformed to 10% of the maximum.

The consumption of coal and coke in the blast furnace is met on the one hand by the market or on the other hand by the own production. It depends on the conditions of the market and the availability of production facilities. World-wide the production of hot metal and crude steel via the blast furnace/converter route is regarded as the dominant process line also in future. Consequently, after their successes in the past, the ironmaking and steelmaking industry have joined their efforts with the cokemaking industry to exploit still more development potentials for hot metal production. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/12836

According to the report of international analytical organization World Steel Association (WSA), Ukraine took the 10th place in the world’s steel production in 2012. Traditional steel smelting technology such as usage of Marten’s furnaces with natural gas as fuel causes 3 million tons of waste products a year per one furnace. Pollutants include NOx, CO, SOx and heavy metals dust. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/31624

Interactions in culture, science, and technology in early Islamic North Africa are studied through an examination of Maghribi metallurgy. My dissertation, based on the Social/Cultural Construction of Technology (SCOT) model (Bijker 1997), explores the impact of the Islamic religion and culture on scientific and technological change in the spheres of gold and silver minting, copper working, and iron smelting towards reconstructing the role and impact of metals in Islamic society. The purpose of my reconstruction is to define and contextualize early Islamic Maghribi metallurgy for a region and time period poorly defined in the history of metallurgical technology. The development of this history of technology involves the investigation of technical design within a religious framework, presenting explanations for the motivations of the use of certain metals from both their intrinsic and instrumental properties. This specialized history is important in that it provides information of significance on the larger scope of the history of technology and science and on the structure of Islamic society. This study uses multiple lines of evidence, including historical documents, numismatic evidence, and archaeological data in an effort to situate the role of early Islamic Maghribi metallurgy into the framework of the history of African metallurgy. The religious and cultural meanings of metals are outlined through the compilation of their mention in the qur’ān, the Hadīth, and the chronicles of travelers. Coinage survey positions the political and economic role of the Islamic state, and addresses the stability of western-periphery polities within the state and the concerns of a dogmatically motivated bimetal system. The site of al-Basra, Morocco, a state mint under the Idrisid rule (A.D. 788-959), is the source for the excavated metal materials; the metal artifacts, unprocessed minerals, slag, non-metal tools associated with the metal production, and metallurgical facilities are described in their historical context. This dissertation presents, for the first time ever, an English translation of al-dawHa al-mushtabika fī DawābiT dār al-sika (The Intricate Tree in the Realm of the House of Minting). This fourteenth century Arabic text details the meaning, production, and uses of metals in medieval Islamic society, and serves as a unit of study within Maghribi metallurgical technology. An ethnographic study of the metal artisans of Fes, Morocco provides a modern-day reflection to this reconstruction. This study supports the SCOT methodology by identifying the relationships between scientific and technological practices and systems of belief. The Islamic culture and its practices -- which were part codified religion, part belief system -- were subject to change based on the contextual situations of the society. This study demonstrates that the society’s metallurgical practices were subject to the same conditions. The metallurgical know-how within Islamic Maghribi society was, and is, a direct reflection of the unifying themes embedded in the culture.

The thesis presents a study of early metal production, exchange and use in the Gulf region. The focus is exclusively on the use of copper and its alloys, from the Bronze Age to the late pre-Islamic period. Issues addressed include technological aspects of early alloy production, the trade in metallic resources in the Gulf region, and the socioeconomic importance of the early use of tin and tin-bronze in early Western Asia.

Powder metallurgy is a growing field with much potential. The core purpose and problem in this work is attempting to describe and understand what and how metal powder properties impact powder flowability. Several powder flow experiments have been performed on eight different metal powders with varying size and of material types to examine correlations and seeing what parameters are important for a well flowing metal powder. Experiments performed consists of hall flow, tap density, angle of repose and a more complex Rheometer analysis. The results found display plenty correlations between different experiments with some deviations as expected due to the nature of occurring errors. The results are all displayed in tables comparing the different metal powders for all experiments. The powder with the best flowability (highly free flowing) scored best across all experiments and tests indicating all tests as significant. A well and free flowing powder is characterized by low values in cohesion, angle of repose, specific energy, etc.
Pulvermetallurgi är en växande industri med stor potential. Syftet samt problemet med detta arbete är att försöka beskriva och förstå vilka pulveregenskaper som är betydande för flödet och hur dessa egenskaper påverkar hur pulvret flödar. Flera olika experiment har utförts på åtta olika metallpulver, av varierande sorter material och pulverstorlek, har utförts för att undersöka samband och se vilka pulveregenskaper som är viktiga för ett metallpulver ska ha eftertraktade flödesegenskaper. Utförda experiment består av Hall flöde, tappdensitet, rasvinkel (angle of repose) samt en mer komplex Rheometer analys. Resultaten visar många samband mellan olika experiment och metallpulver med en del avvikelser som väntat på grund av flertalet felkällor. Resultaten för alla pulver och experiment uppvisas i stapelgrafer för enkel överblick och jämförelse. Metallpulvret som påvisade bäst flödesegenskaper (fritt flödande pulver) rankades som bästa pulver i varje experiment vilket indikerar att alla experiment är relevanta. Ett väl flödande metallpulver indikeras av låga värden på kohesion, rasvinkel, specifik energi osv.

In the present study
the effects of the powder metallurgical parameters such as the mixing method, compaction pressure, initial tungsten (W) particle size, composition, sintering temperature and sintering time on the sintering behavior of selected high density W-Ni-Cu alloys were investigated. The alloys were produced through conventional powder metallurgy route of mixing, cold compaction and sintering. The total solute (Ni-Cu) content in the produced alloys was kept constant at 10 wt%, while the copper concentration of the solutes was varied from 2.5 wt% to 10 wt%. Mainly liquid phase sintering method was applied in the production of the alloys. The results of the study were based on the density measurements, microstructural characterizations including optical and scanning electron microscopy and mechanical characterizations including hardness measurements. The results showed that the nature of the mixing method applied in the preparation of the powder mixtures has a considerable effect on the final sintered state of W-Ni-Cu alloys. Within the experimental limits of the study, the compaction v pressure and initial W particle size did not seem to affect the densification behavior. It was found that the sintering behavior of W-Ni-Cu alloys investigated in this study was essentially dominated by the Ni content in the alloy and the sintering temperature. A high degree of densification was observed in these alloys with an increase in the Ni content and sintering temperature which was suggested to be due to an increase in the solubility and diffusivity of W in the binder matrix phase with an increase in these parameters, leading to an increase in the overall sintering kinetics. Based on the results obtained in the present study, a model explaining the kinetics of the diffusional processes governing the densification and coarsening behavior of W-Ni-Cu alloys was proposed.

The Anglo Research Nickel (ArNi) process is a novel extractive metallurgical process that arose out of the need to develop a processing route for the recovery of nickel from lateritic ore deposits that is both economical and environmentally acceptable.

In this work, the metal and slag phase mixing in three steps of a ladle refining operation of steel melts and for an oxygen balance during cooling of cast iron melts have been studied at two Swedish steel plants and at two Swedish cast iron foundries, respectively. In order to predict the oxygen activity in the steel bulk in equilibrium with the top slag as well as in metal droplets in the top slag in equilibrium with the top slag, three slag models were used. In addition, the assumptions of a sulphur-oxygen equilibrium between steel and slag and the dilute solution model for the liquid steel phase were utilized in the calculations. Measured oxygen activities in steel bulk, which varied between 3.5-6 ppm, were compared to predicted oxygen activities. The differences between the predicted and measured oxygen activities were found to be significant (0-500%) and the reasons for the differences are discussed in the thesis. Slag samples have been evaluated to determine the distribution of the metal droplets. The results show that the relatively largest numbers of metal droplets are present in the slag samples taken before vacuum degassing. Also, the projected interfacial area between steel bulk and top slag has been compared to the interfacial area between the metal droplets and slag. The results show that the droplet-slag interfacial area is 3 to 14 times larger than the flat projected interfacial area between the steel and top slag. Furthermore, the effect of the reactions between top slag and steel and the slag viscosity on the metal droplet formation is discussed. The results show significant differences between the steel bulk and steel droplet compositions and the reasons for the differences are discussed in the thesis. The oxygen activity in different cast irons was studied. Plant trials were performed at three occasions for lamellar, compacted and nodular iron melts. The results show that at temperatures close to the liquidus temperature the oxygen activities were 0.03-0.1 ppm for LGI, around 0.02 ppm for CGI, and 0.001ppm for SGI. In addition, it was found that as the oxygen activities increased with time after an Mg treatment, the ability to form a compact graphite or a nodular graphite in Mg-treated iron melts was decreased. Also, extrapolated oxygen activity differences up to 0.07 ppm were found for different hypoeutectic iron compositions for lamellar graphite iron at the liquidus temperature. Overall, the observed differences in the dissolved oxygen levels were believed to influence how graphite particles are incorporated into the austenite matrix and how the graphite morphology will be in the cast product.

QC 20160518

This thesis presents the results of an investigation into the effect of surface metallurgy on the rolling contact fatigue behaviour of rail. The investigation has used laboratory based rolling/sliding twin disc testing of samples with a surface metallurgical feature simulated on them. The samples used in laboratory testing have been compared with samples of rail removed from track. Two surface metallurgical features have been investigated: decarburisation and white etching layer. Decarburisation is the loss of carbon from the surface of the rail due to oxidation at high temperatures, resulting in a softer layer at the surface (180HV compared to 250HV bulk). The decarburised layer has been simulated in this research by heat treating discs in a laboratory furnace with an air atmosphere. The results show that by increasing the depth of decarburisation the growth rate of cracks within the sample, along with the wear rate, increases. At the maximum depth of decarburisation allowed on rail by the standard (O.5mm) there was little difference in the wear or rolling contact fatigue behaviour with or without decarburisation. White etching layer (WEL) forms on the surface of rail due to the action of the wheels and is a very hard layer (>850HV) up to 250mm deep. White etching layer has been simulated in two ways: spot welding and gross sliding of the discs. The results have shown that cracks initiate preferentially at weak spots at the surface, such as the interface between the WEL and pearlite or along proeutectoid ferrite boundaries. It has been found that the growth of cracks below the surface depends on the strain history of the subsurface pearlite. The results indicate that white etching layer is detrimental to rail life through either the promotion of rolling contact fatigue and/or wear.

Vývoj nových materiálů pro součásti v moderních technologiích vystavené extrémním podmínkám má v současné době rostoucí význam. Děje se tak v důsledku neustále se zvyšujících požadavků průmyslových odvětví na lepší konstrukční vlastnosti nosných materiálů. Ve světle těchto faktů si tato studie klade za cíl posoudit nové složení slitin s vysokou entropií, které se vyznačují vysokým aplikačním potenciálem pro kritické aplikace. Slitiny jsou připravovány práškovou metalurgií, t.j. kombinací mechanického legování a slinování v pevné fázi. Pro účely srovnávaní vlastností jsou vybrané kompozice vyrobeny také tradičními metalurgickými metodami v roztaveném stavu, jako je vakuové indukční tavení a následné lití nebo vakuové obloukové tavení. Prášková metalurgie umožňuje postupný vývoj kompozitů s kovovou matricí (MMC) prostřednictvím přípravy oxidicky zpevněných HEA slitin. To je možné díky inherentním in-situ reakcím během procesu výroby. Když se naopak zvolí výrobní postup z taveniny, připravený kovový materiál vykazuje velké rozdíly v mikrostrukturách a souvisejících vlastnostech, v porovnání se stejným materiálem vyrobeným práškovou cestou (PM). Vyrobené práškové a tavené materiály jsou detailně charakterizovány s ohledem na komplexní vyhodnocení vlivu různých metod zpracování. Práce se zejména orientuje na mikrostrukturní charakteristiky materiálů a jejich mechanické vlastnosti, včetně vlivu tepelného zpracování na fázové transformaci a mikrostrukturní stabilitu připravených materiálů.

Ve všeobecnosti, poznatky o design slitin, jejich výrobě a výběru legujúcich prvků sú omezené na slitiny s jedním základním prvkem. Tento fakt ale výrazně limituje možnosti a volnost výběru prvků pro dosáhnuti speciálních vlastností a mikrostruktur. V poslední dekádě se ukázalo, že materiálová věda a inženýrství nejsou ještě zdaleka prozkoumané v důsledku objevu nové třídy materiálů nazvané vysoko entropické slitiny (HEA high entropy alloys). Jejich objev upoutal pozornost vědecké komunity. Základní koncept pro jejich design je, že namísto jednoho, nebo dvou základních prvků obsahují minimálně 5 prvků v podobných atomových koncentracích. V posledních letech se objevila skupina materiálů odvozená od HEA, nazvaná slitiny so střednou entropii (MEA medium entropy alloys). Na rozdíl od HEA ale obsahují 3, nebo 4 prvky. Táto práce je věnovaná studiu přípravy a charakterizaci HEA, MEA a jejich kompozitů s pomocí metod práškové metalurgie. V této práci byli dohromady zkoumány tři kompozice: AlCoCrFeNiTi0.5, Co1.5Ni1.5CrFeTi0.5 a CoCrNi, kompozity s kovovou matricí (MMC metal matrix composites) vyztužené částicemi B4C s CoCrNi jako matricí. Hloubková mikrostrukturní a mechanická analýza těchto materiálů byla provedena pomoví metod rastrovací a transmisní elektronové mikroskopie spojené s tahovými a ohybovými zkouškami. V průběhu celé studie se objevovaly problémy s kontaminací kyslíkem, co se projevilo vznikem značného množství oxidů v připravených materiálech. U Slitiny AlCoCrFeNiTi0.5 byla naměřena tvrdost přesahující 800 HV. Její houževnatost ale byla velice omezena. V její mikrostruktuře byly identifikovány částice in-situ TiC v důsledku přítomnosti organického, anti-aglomeračního činidla (metanolu) v mlecí misce. Tato reakce může být použita v budoucnu k přípravě MMC se záměrnou disperzí TiC. Na druhé straně, slitina CoCrNi ukázala vysoké hodnoty tažnosti (26%) a meze pevnosti přes 1000 MPa. Mikrostruktura obsahovala majoritní FCC fázi s BCC precipitáty. Tahle slitina byla z důvodu vysoké tažnosti zvolena pro přípravu kompozitu s výztuží B4C. V průběhu slinování ale došlo k reakci mezi přítomným Cr a B4C, které výsledkem byl Cr5B3 borid. Tento kompozit mel pevnost v tahu 1400 MP a extrémne jemnozrnnou strukturu. Celková tažnost ale klesla na 1.9 %. Slitina AlCoCrFeNiTi0.5, která mela strukturu složenou jen z FCC tuhého roztoku dosáhla nejlepší kombinaci mechanických vlastností s pevností přesahující 1300 MPa a dostatečnou tažností 4%. Prášková metalurgie se ukázala jako vhodná metoda pro přípravu HEA a MEA slitin a jejich kompozitů, s dobrou kombinací pevnosti a tažnosti. Tato metoda dovoluje měnit mikrostrukturní parametry připravených materiálů jednoduchou úpravou parametrů procesu.

La ricerca verte sulla metallurgia dell’Età del Bronzo nello Xinjiang (ca.2000-1000 a.C.). L’obiettivo è triplice: 1) indagare l’occupazione della regione da parte delle prime comunità dell’Età del Bronzo, in termini spazio-temporali, e delineare il contesto economico-culturale in cui la metallurgia si è sviluppata; 2) individuare i contributi apportati da influenze esterne riconoscendo, ove possibile, interazioni culturali tra le comunità dello Xinjiang e delle regioni circostanti (specialmente Asia Centrale, Siberia sud-occidentale e Cina); 3) fare luce sul ruolo dello Xinjiang nel sistema di scambi culturali in Eurasia durante l’Età del Bronzo. La ricerca è basata sull’analisi di quattro aree principali: gli Altai, le oasi di Hami e Turfan (chiamate “regione orientale”), la regione occidentale (che include le aree di Ili-Tacheng e Pamir) e il margine meridionale del bacino del Tarim. A ognuna di esse è dedicato un capitolo comprendente cinque sezioni: introduzione, assetto geografico (che include lo studio del paleoambiente e del paleoclima), contesto archeologico, metallurgia e riepilogo finale. Il capitolo conclusivo offre una mappatura e una descrizione delle comunità dell’Età del Bronzo nelle aree esaminate nonché una panoramica dettagliata dello sviluppo della metallurgia, dagli esordi alla fine dell’Età del Bronzo, in cui sono messi in luce contributi esterni ed evoluzioni locali. Infine, in base ai risultati dell’analisi, la ricerca si prefigge di delineare possibili meccanismi d’interazione tra le comunità dell’Età del Bronzo e le regioni circostanti, e altresì di proporre una reinterpretazione del ruolo dello Xinjiang nel sistema di scambi economico-culturali durante il secondo millennio a.C. in Eurasia. The research focuses on Bronze Age metallurgy in the present-day Xinjiang Province (about 2000-1000 BC). The goal is threefold: 1) to investigate the occupation of Xinjiang by the early Bronze Age communities in terms of space and time, and to delineate the regional economic-cultural context, in which bronze metallurgy developed; 2) to identify contributions from external influences and to recognise, when possible, cultural interactions between the communities of Xinjiang and the surrounding regions (especially Central Asia, South-Western Siberia and China); 3) to shed light on the role of Xinjiang in the system of cultural exchanges in Eurasia during the Bronze Age. In order to reach these goals, four main areas have been analysed: the Altay, the Hami and Turfan oases (called “the eastern region”), the western region (which includes the areas of Ili-Tacheng and Pamir) and the southern rim of the Tarim Basin. To each of these regions is devoted a chapter, consisting of five sections: introduction, geographical setting (including the paleo-environment and the paleo-climate), archaeological context, metallurgy and summary. The conclusive chapter provides a map and description of the Bronze Age communities in the examined areas, as well as a detailed overview of the development of metallurgy, from the beginnings to the end of the Bronze Age, in which external contributions and internal evolutions have been highlighted. Finally, in light of the results of this study, this research aims to trace possible mechanisms of interaction between the Bronze Age communities and the surrounding regions, proposing a reinterpretation of the role of Xinjiang in the system of economic-cultural exchanges during the second millennium BC in Eurasia.

The relationship between alloy composition, microstructure, mechanical and thermal processing and mechanical properties (strength and toughness) in 2xxx (Al-Cu-Mg) and 7xxx (Al-Mg-ZnCu) series aluminium alloys has been investigated for use in the production of high-strength lightweight components.

Homogenization of alloying elements is desired during sintering of powder metallurgy components. The redistribution processes such as penetration of liquid phase into the interparticle/grain boundaries of solid particles and subsequent solid-state  diffusion of alloy element(s) in the base powder, are important for the effective homogenization of alloy element(s) during liquid phase sintering of the mixed powders. The aim of this study is to increase the understanding of alloy element redistribution processes and their effect on the dimensional properties of the compact by means of numerical and experimental techniques. The phase field model coupled with Navier-Stokes equations is used for the simulations of dynamic wetting of millimeter- and micrometer-sized metal drops and liquid phase penetration into interparticle boundaries. The simulations of solid particle rearrangement under the action of capillary forces exerted by the liquid phase are carried out by using the equilibrium equation for a linear elastic material. Thermodynamic and kinetic calculations are performed to predict the phase diagram and the diffusion distances respectively. The test materials used for the experimental studies are three different powder mixes; Fe-2%Cu, Fe-2%Cu-0.5%C, and Fe-2%(Cu-2%Ni-1.5%Si)-0.5%C. Light optical microscopy, energy dispersive X-ray spectroscopy and dilatometry are used to study the microstructure, kinetics of the liquid phase penetration, solid-state diffusion of the Cu, and the dimensional changes during sintering. The wetting simulations are verified by matching the spreading experiments of millimeter-sized metal drops and it is observed that wetting kinetics is much faster for a micrometer-sized drop compared to the millimeter-sized drop. The simulations predicted the liquid phase penetration kinetics and the motion of solid particles during the primary rearrangement stage of liquid phase sintering in agreement with the analytical model. Microscopy revealed that the C addition delayed the penetration of the Cu rich liquid phase into interparticle/grain boundaries of Fe particles, especially into the grain boundaries of large Fe particles, and consequently the Cu diffusion in Fe is also delayed. We propose that the relatively lower magnitude of the sudden volumetric expansion in the master alloy system could be due to the continuous melting of liquid forming master alloy particles.

QC 20140515

Particulate reinforced Al alloy composites (AlMCs) are recognized as important structural materials due to their lightweight, high modulus and strength and high wear resistance. In order to understand the effect of matrix, reinforcement and secondary processing techniques on the microstructure development and mechanical properties of AlMCs produced by powder metallurgy routes, Al alloy composites reinforced with three types of reinforcements by different secondary processing techniques have been produced and examined. Fabrication of Al or 6061Al alloy based composites reinforced with nano-sized SiC particles (~500nm), micro-sized (<25µm) quasicrystalline alloy particles (hereinafter referred to as “NQX”) and micro-sized Nb particles (~130µm) has been carried out by powder metallurgy routes followed by extrusion or cold rolling. After extrusion, a homogeneous distribution of secondary particles has been obtained with rare interfacial reaction products. The 6061Al/SiC composites exhibit superior mechanical properties than either monolithic alloys or composites reinforced with micro-sized particles with retained ductility while the 6061Al/NQX and 6061Al/Nb composites show limited improvement in tensile strength mainly due to their reinforcement size and poor interfacial bonding. After cold rolling, the evolution in microstructure, texture and strength has been analysed. A typical near β fibre texture with highest intensities near Copper and Brass orientations has been developed for 6061Al/NQX and 6061Al/Nb composites. For 6061Al/SiC composites, a randomized texture with very small grains has achieved due to the presence of the non-deformable SiC particles. Mechanical property tests including microhardness, three-point bending tests and tensile tests have been carried out on cold rolled samples and the results exhibit some level of improvement when compared with as-extruded samples due to work hardening. Finally, the work moves on to the general discussion based on the previous result chapters. The microstructural development related to reinforcement, matrix and interfacial areas during extrusion and cold rolling has been summarised and the correlation between microstructure and mechanical properties has been discussed. The thesis provides a thorough understanding of AlMCs produced by powder metallurgy routes in terms of matrix, reinforcement and processing techniques. It can provide reference to the future development of AlMCs for high strength applications.

Iron- and steel production is a material- and energy intensive industrial activity. The production of one tonne of steel commonly results in some 400 kilograms of residual materials such as metallurgical slags, dusts, sludge and scales generated in the processes. Much work is continuously devoted to finding possible ways of using residual materials and minimising landfilled volumes. As these materials often contain considerable amounts of valuable elements such as iron, coal, manganese and calcium, it may be profitable to use them to replace virgin raw materials or to sell them as products that may be useful in other industries and/or processes.    The thesis is based on case studies that exemplify how the use of process integration, through system analysis, can assist in assessing effects and opportunities for different concepts for increased material efficiency in Nordic ore-based steelmaking systems. The process integration approach taken for this research work was the simulation of a specific iron- and steel production system and the use of an optimisation tool for the evaluation of an extended system including the symbiosis between four steel plants.   Three different cases were studied including: system effects of increased magnesium oxide content in the lime raw material, investigation of the prospects for vanadium enrichment and slag reduction concept and a study of the logistics perspective for a joint residual material upgrading and recycling venture between four steel plants. The analysed cases present possibilities to improve the material efficiency by: •      Enhanced recovery of residual materials; •      Upgrading of residual materials to products; •      Specific elements recovery; •      Decreased use of virgin raw material; •      Improved quality of residual materials; •      Decreased amounts of materials placed in long-term storage or landfills.   From the results of the cases studied, the best scenarios and potential gains by enhanced material efficiency is presented. In the case of system effects of increased magnesium oxide content in the lime raw material, the issue was mainly to obtain maximum usage of metallurgical slags without compromising the quality of the main product. The calculated possibility of increased slag recirculation enabled further a decreased consumption of iron ore pellet and limestone. Regarding the investigation of the vanadium enrichment and slag reduction concept, the best scenario markedly increased the internal slag recirculation in order to enrich the vanadium content in the slag for ferrovanadium production. By the vanadium enrichment and recovery concept, considerable amounts of vanadium would be made useful instead of ending up in long-term storage. The study of a shared Nordic concept for residual materials upgrading and use demonstrated the potential for upgrading the materials to a direct reduced iron product for recovery in blast furnace. The concept showed high potential for significantly reducing the amount of material being long-term stored or deposited to landfill and thus a potential step towards achieving the zero-waste philosophy target.   None of the concepts for enhanced material efficiency studied in this thesis work has been implemented; however, they are still of relevance for the Nordic steel industry.

Extensive computer predictions have been carried out by the author to study flow, addition dispersion and particle motion during central gas injection into cylindrical vessels. In conjunction with numerical computations, experiments were conducted in a 0.30 scale water model of a 150 ton steel processing ladle, using a Froude number scaling criterion. Two typical gas injection configurations (i.e., conventional central injection and C.A.S. alloy addition procedure) were investigated.
Flow visualization studies were carried out using a suspended network of silken threads, mean velocity vectors and overall flow patterns were determined by video recording techniques, while mean velocity vectors and associated turbulence level were also measured with laser doppler velocimetry. These measurements show very reasonable agreement with equivalent numerical predictions.
To simulate the subsurface motion of additions, spherical wooden balls of various densities were dropped from typical heights, and their subsurface trajectories, immersion times, etc., recorded by means of a video recorder. Frame by frame analysis of the video tapes showed trends which are in good accord with computed trajectories.
Mixing times of simulated molten additions were measured by the conductivity measurement technique. These were compared with prediction from an equivalent tracer dispersion model and excellent agreement achieved.
For industrial application, flow, particle motion, and mixing times in a 150 ton steel processing ladle have been predicted and their technological significance discussed.

Titanium and its alloys have been widely used in oral implantology due to their mechanical properties, corrosion resistance and biocompatibility. However, under in vivo conditions the implants are subjected to the tribocorrosion phenomenon, which consists in the degradation mechanisms due to the combined effect of wear and corrosion. This process contributes to limiting the life span of the implant and may generate clinical problems in patients as metallic ions are released. Another cause of dental implant failure may be the loosening of the implant as metal does not promote osseointegration. The powder-metallurgy process is a promising alternative to the traditional casting fabrication process of titanium alloys for bone implants design, as the porous structure would allow the bone to grow into the pores. This would result in a better fixation of the metal implant without the need of sandblasting /acid etching the surface. The present Doctoral thesis aims at describing the corrosion and tribocorrosion behavior of titanium alloys and their degradation mechanisms when processed by powder metallurgy, as a possible alternative to standard casting for dental implant application. For this, model Ti6Al4V titanium alloy and possible substitute Ti6Al7Nb alloy, where Vanadium has been replaced by Niobium in order to avoid cytotoxicity of the resulting biomaterial, have been studied. Electrochemical and tribo-electrochemical characterization of the biomaterials have been carried out under different physico-chemical conditions with biological relevance (in artificial saliva (AS) with different fluoride content, pH and oxidising conditions) which noticeably influences the degradation mechanisms of the studied materials. A new tribocorrosion technique that allows measuring the galvanic potential and current between the wear track (anode) and the passive material (cathode) through Zero-Resistance Ammetry (ZRA) has been also used to elucidate tribocorrosion mechanisms of the model Ti6Al4V cast alloy in AS. The ZRA technique for tribocorrosion allowed predicting the real depassivated area and therefore, the deviation of the wear mechanisms from Archard wear law at Open Circuit Potential (OCP). All alloys show passivity in artificial saliva although active dissolution occurs in presence of high fluoride concentration (1000 ppm) and acidic conditions, pH 3. The degradation mechanism of sintered alloys is mainly governed by the mechanical wear in AS and only determined by the active dissolution when fluorides are added to acidified artificial saliva (pH 3). Wear was found to be governed by the prevailing oxidizing condition (simulated by changes in the electrode potential). Ti6Al4V alloy processed by powder metallurgy showed a similar tribocorrosion resistance when compared to commercially available cast alloy suggesting that powder metallurgy is a promising fabrication process for implant applications. The influence of the alloying elements, Al and Nb, on the corrosion and tribocorrosion behavior of different titanium alloys, Ti6Al7Nb, Ti7Nb and Ti6Al has been studied and in all cases, the corrosion resistance is improved when compared to pure titanium. Wear damage was found to be critically affected by the ductility of the material, thus by the alloying element. Ti6Al7Nb showed a better corrosion resistance and similar tribocorrosion behaviour when compared to Ti6Al4V. The results of this thesis have shown that Ti6Al7Nb obtained by Powder metallurgy is a promising biomedical alloy for oral implants. Wear damage of sintered Ti alloys depends on the electrochemical potential and their tribocorrosion behaviour is critically affected by a high content of fluoride found in common daily dental health care products.
El titanio y sus aleaciones han sido utilizados en implantología oral debido a sus propiedades mecánicas, resistencia a la corrosión y biocompatibilidad. Sin embargo, bajo condiciones in vivo los implantes están sometidos al fenómeno de tribocorrosión, que consiste en mecanismos de degradación debido al efecto combinado de desgaste y corrosión. Este proceso disminuye la vida útil del implante y genera problemas clínicos a medida que se liberan iones metálicos. La pérdida de fijación del implante es otra causa de fracaso del implante, por falta de osteointegración. El proceso de pulvimetalurgia es una alternativa prometedora al proceso tradicional de fabricación (colada, forja) de aleaciones de titanio para el diseño de implantes óseos, ya que la estructura porosa permitiría que el hueso crezca dentro de los poros, dando lugar a una mejor fijación del implante. La presente tesis doctoral pretende describir el comportamiento frente a la corrosión y tribocorrosión de las aleaciones de titanio y sus mecanismos de degradación cuando se procesan mediante pulvimetalurgia, como una posible alternativa a la colada estándar para la aplicación de implantes dentales. Se ha estudiado el modelo de aleación de titanio Ti6Al4V y posible sustitución por la aleación Ti6Al7Nb, donde el Vanadio ha sido sustituido por Niobio para evitar la citotoxicidad del biomaterial. La caracterización electroquímica y tribo-electroquímica de los biomateriales se ha llevado a cabo en diferentes condiciones físico-químicas con relevancia biológica (en saliva artificial (AS) con fluoruro, pH y condiciones oxidantes) que influye notablemente en los mecanismos de degradación de los materiales estudiados. También se ha utilizado una nueva técnica de tribocorrosión que permite medir el potencial galvánico y la corriente entre la pista de desgaste (ánodo) y el material pasivo (cátodo) a través de la ametría de resistencia cero (Zero-Resistence Ammetry, ZRA) para elucidar los mecanismos de tribocorrosión de la aleación de forja Ti6Al4V en AS. La técnica ZRA para tribocorrosión permitió predecir el área real despasivada y, por tanto, la desviación de los mecanismos de desgaste de la ley de desgaste de Archard en OCP. Las aleaciones muestran pasividad en AS, aunque la disolución activa se produce en presencia de alta concentración de fluoruro (1000 ppm) y condiciones ácidas, pH 3. El mecanismo de degradación de las aleaciones sinterizadas se rige principalmente por el desgaste mecánico en AS y sólo determinado por la disolución activa cuando se añaden fluoruros a la saliva artificial acidificada (pH3). Se encontró que el desgaste se rige por la condición oxidante predominante (simulada por cambios en el potencial de electrodo). La aleación Ti6Al4V procesada por pulvimetalurgia mostró una resistencia similar a la tribocorrosión cuando se comparó con la aleación forjada comercial disponible, lo que sugiere que la pulimetalurgia es un prometedor proceso de fabricación para aplicaciones de implantes. Se ha estudiado la influencia de los elementos aleantes Al y Nb sobre el comportamiento de corrosión y tribocorrosión de diferentes aleaciones de titanio Ti6Al7Nb, Ti7Nb y Ti6Al y en todos los casos la resistencia a la corrosión se mejora en comparación con el titanio puro. El daño de desgaste está afectado críticamente por la ductilidad del material, por lo tanto, por el elemento de aleación. La aleación Ti6Al7Nb mostró una mejor resistencia a la corrosión y un comportamiento similar de tribocorrosión en comparación con la aleación Ti6Al4V. Los resultados de esta tesis han demostrado que el Ti6Al7Nb obtenido por pulvimetalurgia es una prometedora aleación biomédica para implantes orales. El deterioro del desgaste de las aleaciones de Ti sinterizadas depende del potencial electroquímico y su comportamiento a tribocorrosión se ve afectado de manera crítica por un alto contenido de ion flúor
El titani i els seus aliatges s'han utilitzat en l'implantologia oral degut a les seves propietats mecàniques, resistència a la corrosió i biocompatibilitat. No obstant això, en condicions in vivo els implants són sotmesos al fenomen de tribocorrosió, que consisteix en els mecanismes de degradació causats per l'efecte combinat de desgast i corrosió. Aquest procés contribueix a limitar la vida útil de l'implant i pot generar problemes clínics com l'alliberament d'ions metàl¿lics. Una altra causa de fracàs de l'implant dental pot ser la pèrdua de fixació de l'implant, ja que el metall no promou l'osteointegració. El procés de pulvimetal¿lúrgia és una alternativa prometedora al procés tradicional de fabricació (colada i forja) d'aliatges de titani per al disseny d'implants ossis, ja que l'estructura porosa permetria que l'os creixca dins dels porus. Això donaria lloc a una millor fixació de l'implant metàl¿lic. La present tesi doctoral pretén descriure el comportament enfront de la corrosió i tribocorrosió dels aliatges de titani i els seus mecanismes de degradació quan es processen mitjançant pulverimetal¿lúrgia, com una possible alternativa a la fabricació estàndard per forja per a l'aplicació d'implants dentals. Per a això, s'ha estudiat el model d'aliatge de titani Ti6Al4V i possible substitució per l'aliatge Ti6Al7Nb, on el vanadi ha estat substituït per niobi per evitar la citotoxicitat del biomaterial resultant. La caracterització electroquímica i tribo-electroquímica dels biomaterials s'ha dut a terme en diferents condicions fisicoquímiques amb rellevància biològica (en saliva artificial (AS) amb fluorur, pH i condicions oxidants) que influix notablement en els mecanismes de degradació dels materials estudiats. També s'ha utilitzat una nova tècnica de tribocorrosió que permet mesurar el potencial galvànic i el corrent entre la pista de desgast (ànode) i el material passiu (càtode) a través de la ametria de resistència zero (Zero-Resistence Ammetry, ZRA) per elucidar els mecanismes de tribocorrosió de l'aliatge de forja Ti6Al4V en AS. La tècnica ZRA per tribocorrosió va permetre predir l'àrea real despassivada i, per tant, la desviació dels mecanismes de desgast de la llei de desgast de Archard en OCP. Tots els aliatges mostren passivitat en la saliva artificial, tot i que la dissolució activa es produix en presència d'alta concentració de fluorur (1000 ppm) i condicions àcides, pH 3. El mecanisme de degradació dels aliatges sinteritzats es regix principalment pel desgast mecànic en AS i només determinat per la dissolució activa quan s'afegixen fluorurs a la saliva artificial acidificada (pH 3). Es va trobar que el desgast es regix per la condició oxidant predominant (simulada per canvis en el potencial d'elèctrode). L'aliatge Ti6Al4V processada per pulverimetal¿lúrgia va mostrar una resistència similar a la tribocorrosió quan es va comparar amb l'aliatge forjada comercial disponible, el que suggerix que la pulverimetal¿lúrgia és un prometedor procés de fabricació per a aplicacions d'implants. S'ha estudiat la influència dels elements d'aliatge Al i Nb sobre el comportament de corrosió i tribocorrosió de diferents aliatges de titani Ti6Al7Nb, Ti7Nb i Ti6Al i en tots els casos la resistència a la corrosió es millora en comparació amb el titani pur. Es va trobar que el dany de desgast està afectat críticament per la ductilitat del material, per tant, per l'element d'aliatge. L'aliatge Ti6Al7Nb va mostrar una millor resistència a la corrosió i un comportament similar de tribocorrosió en comparació amb l'aliatge Ti6Al4V. Els resultats d'aquesta tesi han demostrat que el Ti6Al7Nb obtingut per pulverimetal¿lúrgia és un prometedor aliatge biomèdic per a implants orals. El deteriorament del desgast dels aliatges de Ti sinteritzats depèn del potencial electroquímic i el seu comportament a tribocorrosió es veu afectat de manera crí
Licausi, M. (2017). Analysis of tribocorrosion behavior of biomedical powder metallurgy titanium alloys [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/90448
TESIS

Developing the third generation of Calphad databases with more physical basis valid within a wider temperature range is the aim of the present work. Atomistic scale (ab-initio) methods, particularly techniques based on DFT theory, are used for modelling dierent phenomena, so as to gauge the capacity for use in Calphad modelling. Several systems are investigated in this work for studying dierent phenomena, such as magnetism and vibration of atoms. In the case of pure elements (unaries), thermodynamic properties of Mn, Al and C are optimized in the whole temperature range by the help of new models. In addition, DFT results and specic characteristics of these elements are also used to develop models for describing magnetic properties and atomic vibrations. With regards to coupling between DFT and Calphad, the EMTO technique is used for determining the magnetic ground state of the metastable hcp phase in Fe and Mn, and the TU-TILD technique is used for modelling solid phases above the melting point. TU-TILD is also used for calculating thermodynamic properties of bcc Mn at nite temperatures. The same phenomena are investigated in higher-order systems, i.e. the binaries Fe-Mn and Mn-C. Thermodynamic properties and phase diagrams of these systems are assessed against experimental data. Moreover, the revised magnetic model is used for modelling magnetic properties in these systems. It is shown through this investigation that although the DFT methods are powerful tools for model development and for resolving discrepancies between dierent experimental datasets, they should not be overly-trusted. Caution must be taken when using DFT results, since the approximations and assumptions for computational implementations may cause some errors in the results. Moreover, implementing them into Calphad software as a connected methodology is not currently accessible due to the computational limitations. It is concluded that coupling between the DFT and Calphad approaches can currently be achieved by using DFT results as an input in Calphad modelling. This will help to improve them until they can be integrated into the Calphad approach by the progress of computational possibilities. One of the advantages of developing the third generation Calphad databases is the possibility of using the 0 K DFT results in Calphad modelling, since the new databases are valid down to 0 K. This has not been possible in the past, and such potential opens a new door to bring more physics into the Calphad approach.

QC 20171006

In the present study, magnetite pellets with the additives olivine, calcite and quartzite were isothermally reduced in a tubular furnace to study the interaction between iron oxides and the additives. Exaggerated amounts of additives were used in order to enable analyses of phases that do not otherwise occur in sufficient amounts for X-ray diffraction and EDS-analyses. The reduction was set to yield either magnetite or wüstite in the temperature range 500-1300ºC. For olivine, reduction tests were also performed to allow metallization in the range 1000-1300ºC. The mineralogical phases which had formed were studied after oxidation as well as after reduction. The results showed that it was possible to identify, by X-ray diffraction, the main phases formed by the additives in all samples, after oxidation as well as reduction.In the olivine sample, the forsteritic olivine particles react partly during the oxidation pre-treatment to form magnesioferrite and vitreous silica along the particle corona. This breakdown of the olivine particles during oxidation liberates magnesium from the particles, which do not react until temperatures of above 1150°C in reducing atmosphere. When the hematite in the sample is reduced, and when temperature is high enough to allow solid-state diffusion at ~800ºC, the magnesium of the magnesioferrite redistributes so that the magnesium concentration approaches the same level throughout the structure. For magnetite, this does not occur below 800°C. At 1000°C, this magnesium reacts further with the silica in the glassy slag phase, which crystallizes into fayalitic olivine. At this temperature the magnesium diffuses over distances more than 600µm from the olivine particles. From this point the binding media to resist the swelling tensions in the pellet is mainly solid fayalite. The metallization front concentrates the MgO in the remaining wustite which can lead to MgO levels of up to 10% locally. The melting point of the fayalite is raised from 1145ºC to a melting range of 1238-1264ºC due to the MgO-increase, as estimated based on the phase diagram tuned to the pellets tested. Much of the olivine which remained unaltered in the oxidation process will be encapsulated by iron before the magnesium begin to dissolve in reducing conditions, and therefore play no role in the reduction before final melting of the particles occur.The quartzite particles are not affected by the oxidation pre-treatment. The binding strength of quartzite pellets therefore comes from the sintering of quartzite particles to neighboring hematite as well as the glassy slag resulting from the acid gangue and the bentonite. Substantial reaction of the quartzite particles during reduction did not occur before 1000ºC even though the process has occurred to a very low extent already at 900ºC. Also the glassy slag crystallizes into fayalite in the presence of quartzite. From this point fayalite represents the binding media in the pellet. Pure fayalite melts already at 1177ºC and can at this temperature dissolve up to 76wt% FeO. This leads to early softening, which is one of the main concerns for the softening/melting properties of the pellet. In the pellets with calcite, CaO reacts with Fe2O3 during induration to form a low-melting calcium ferrite slag in the pellet that melts to react with silica in the pellets. If more calcium is added than what is required to react with the silica, calciumferrites becomes part of the binding mass together with the dicalciumsilicate. The calciumferrites forming in pellets with larger additions of calcite are weak to resist the tensions arising due to the low-temperature reduction of hematite and are associated with low temperature disintegration. As the reduction proceeds to wustite, the calcium from the ferrite dissolves in the wustite so that porous calciumwustite forms. The dicalciumsilicate remain stable during the entire reduction until reaction and melting of the phase begin at 1283ºC.
Godkänd; 2013; 20130411 (parsem); Tillkännagivande disputation 2013-05-20 Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Pär Semberg Ämne: Processmetallurgi/Process Metallurgy Avhandling: Interactions Between Iron Oxides and the Additives Olivine, Quartzite and Calcite in Magnetite Pellets Opponent: Professor Abdel-Hady Abdel-Hady El-Geassy, CMRDI, Cairo, Egypt Ordförande: Professor Bo Björkman, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Tid: Måndag den 10 juni 2013, kl 10.00 Plats: F531, Luleå tekniska universitet

Coal is the single largest fossil fuel used world-wide and accounts for more than 60% of the total commercial energy consumed. Between 60 to 80% of this coal is used for electric power generation and most of which through a system of pulverised coal combustion. Major portion of the coal used for such power generation is not clean enough to maintain environmental standards. This problem is attributed to high sulphur content in coal used in most of the western countries or ash as is the case in countries like India. In India at present nearly 200 million tonnes per year of coal is used for power generation and the average ash in coals used is invariably above 40%. A substantial portion of ash is liberated as it enters the boiler from the mill. It is crucial to reduce the amount of ash going from the mill to the boilers not only to improve the performance of power generation and increase the life of the boilers but also became mandatory due to environmental regulations. Thus the main objective of the work is to develop a dry tribo-electrostatic process for the separation of ash forming inorganic matter from coal material with a thorough understanding of the response and behaviour of coal and non-coal matters to contact electrification and in electric field. This work is financially supported by the Department for Research Cooperation of the Swedish International Development Cooperation Agency (SIDA). The literature on dry coal preparation processes has been reviewed and the advantages of triboelectric process compared to other processes have been highlighted and further research needs to make it a viable industrial technology are outlined. Three Indian coal samples from three different major coal fields, i.e., Ramagundam, Ib-valley and Talcher, have been collected and characterised for macerals and mineral composition by microscopic and XRD analyses. The beneficiation potential at different size fractions of the coal samples is judged by the washability studies. The charge polarity and magnitude of pure quartz, kaolinite, illite and carbon after contact electrification with different tribo-charging media have been measured by Faraday cup method using Keithley electrometer. The predicted work functions of the tribo charging material and mineral phases agree closely with the reported values. The electron accepting and donating (acid-base) property of mineral phases determined by Krüss Tensiometer through polar and non-polar liquid contact angles on solids also corroborated the acquired charge polarity in contact electrification with copper, aluminium and brass materials underlying their work functions. This methodology is being applied for the choice of organic acidic/basic solvents treatment of coal material to enlarge the difference in work functions between the tribo-charger and mineral phases, and to achieve greater separation efficiency of inorganic matter from coal. The coal samples have been tested for the separation between coal and non-coal matters in a laboratory in-house built tribo electric separator and the influence of equipment and process variables have been evaluated. The results showed that the ash content was reduced from 45% to about 18%, and a clean coal product as judged by the washability studies can be obtained.
Godkänd; 2006; 20070110 (haneit)

Slag is a vital part of metal production since it removes impurities from the metal. As slag is continuously produced, the options are either to dispose slag in landfill or acknowledge slag as a product. Slag can be used in many different applications, ranging from fertilizer to construction material; in some cases, the properties of slag make it a superior alternative to virgin stone materials. The properties and thereby the field of application is determined by the mineralogical composition of the slag. Slag is considered an environmentally friendly material as long as the leaching of certain elements stay below specified thresholds, for leaching of chromium the limit is at 0.5 mg/kg for slag to be considered inert material. The most common leaching approach is to compare leaching analyses from slag samples to deduce which elements and/or phases contribute or prevent leaching of specific elements. With this method each slag need to be investigated separately and the result may only apply for that specific slag type. In this thesis the approach is different: individual minerals are synthesized and dissolved separately at various pH to accurately assess their dissolution capabilities. By studying the dissolution of individual minerals the leaching of any type of slag with known mineralogical composition can be anticipated. Slag leaching can then be tailored, for example, chromium leaching can be eliminated if all chromium containing phases are removed or not capable of dissolving. In this thesis the dissolution of akermanite, β- and γ-dicalciumsilicate, merwinte, monticellite, pseudowollastonite and magnesiowüstite with varying FeO/MgO ratios are studied. Leaching tests of magnesiowüstite with 4 wt% Cr2O3 were also included. The dissolution of each mineral is calculated by the acid addition required to maintain a constant pH with 50 mg of mineral in 100 ml water. As expected, the dissolution decreases as pH increases, with exception of the dicalcium silicates which dissolved completely at pH 4 to 10. The dissolution of the minerals is largely connected to the elemental composition. In the silica based minerals a high Ca ratio promotes dissolution while a high Si ratio impedes the dissolution rate. Both dissolution and chromium leaching of magnesiowüstite depends on the FeO content, with increasing FeO content the dissolution and leaching decreases, magnesiowüstite with at least 60 wt% FeO does not dissolve at pH 10. None of the magnesiowüstite compositions were close to the chromium leaching limit of inert material, 0.5 mg/kg, as the highest leaching sample, with 52 wt% FeO, leached 0.069 mg/kg.

The first objective of the thesis was to reveal the characteristic magnetic behaviour of natural weakly magnetic minerals (such as hematite and chromite), and the size limits of the particles recoverable by the existing modem high intensity and high gradient magnetic separators. The second objective was to enhance the particle aggregation andlor the magnetic response for wet magnetic concentration of the ultrafines which escaped from the separators. It was observed that weakly magnetic natural minerals (hematite and chromite) exhibited variations in the magnetic behaviour with respect to magnetizing field, temperature and even particle size, It was indicated that high gradient magnetic separation with industrial matrices was efficient for weakly magnetic minerals as small as 10 um, but below this size, poor separation efficiency was obtained. In this thesis, modifications to the existing magnetic technology or alternative methods were investigated for the efficient recovery of particles below 10 gm. The technology or methods included "carrier" or "piggy-back" method, aggregation with magnetic bonding (with permanent or fieldinduced magnetic moment), and hydrophobic magnetite seeding. The thesis discusses the theoretical aspects of the problem and the experimental work. It was clearly demonstrated that wet magnetic concentration was more efficient for the ultrafine fractions whereas other methods could be used to increase the effective particle size dimensions andlor the magnetic susceptibilities.
Godkänd; 1993; 20070426 (ysko)

Recycling of flotation effluents through the ore processing plant is one of the ways of reducing both plant-operating costs and industrial impact onto the local ecosystem. Such waters named acid mine drainage (AMD), if discharged from sulphide flotation are gypsum (CaSO4.H2O) saturated and have a high salinity (on the order of 1000 ppm). As minor species, they commonly contain reduced sulphur compounds (RSC) (sulfoxyanions with sulphur in the oxidation state below (VI) such as SO32-, S2O32-, S2O52-, and S4O62-), cations of ferrous and non-ferrous metals, frothing molecules, residual chemical reagents and products of their degradation. Tailing ponds also host communities of chemolithotrophic and heterotrophic microorganisms which play an important role in dictating their aqueous and solid phase chemical speciation. Consequently, the key step towards developing scientific approaches of recycling of the tailing waters is elucidation of how, in what extent, and why the tailing water components, taken singly or jointly influence flotation of sulphides. In this work, the influence of main process water components of calcium and sulphate on chalcopyrite, galena, sphalerite and pyrite flotation has been investigated through Hallimond flotation, zeta-potential and diffuse reflectance FTIR spectroscopy measurements using pure mineral samples as well as bench scale flotation tests using complex sulphide ore. The significance of process water species in flotation has been assessed using deionised water, process water and simulated water containing calcium and sulphate ions in experiments. In addition, the effect of temperature in bench scale flotation tests has also been examined. Hallimond flotation indicated depression of chalcopyrite, galena and sphalerite and activation of pyrite in the presence of calcium and sulphate ions with potassium amyl xanthate as collector. Calcium ions have significant influence on zeta-potential characteristics and xanthate adsorption behaviour of chalcopyrite, galena, sphalerite and pyrite compared to sulphate ions. FTIR studies revealed the presence of surface oxidised sulfoxy species and surface iron and calcium carbonates on chalcopyrite in the presence of process water and water containing calcium ions, surface oxidised sulfoxy and carbonate species on galena in the presence of deionised water, process water and water containing calcium and sulphate ions, hydrated surface oxidised species and surface iron and calcium carbonates on pyrite in the presence of process water and water containing calcium ions all at pH 10.5 in which the surface species influenced xanthate adsorption. The presence of surface oxidised sulfoxy and carbonate species on sphalerite were also revealed at pH 11.5 in the presence of deionised water, process water and water containing calcium and sulphate ions in which surface species does not influence xanthate adsorption. Bench scale flotation using two different complex sulphide ores showed that chalcopyrite recovery is better in process water than tap water and general depression of chalcopyrite at temperatures lower than 22oC in either tap water or process water, activation of chalcopyrite at all temperatures in process water and depression of chalcopyrite when tap water containing calcium and sulphate ions was used at 22oC. It also showed that galena recovery is better in tap water than process water and depression of galena at temperatures lower than 22oC in either tap water or process water. It also showed that sphalerite recovery is better in process water than in tap water better recovery of sphalerite at temperatures lower than 22oC in either tap water or process water.
Godkänd; 2010; 20101114 (fatiku); LICENTIATSEMINARIUM Ämnesområde: Mineralteknik/Mineral Processing Examinator: Professor Kota Hanumantha Rao, Luleå tekniska universitet Diskutant: PhD Jaakko Leppinen, Outotec, Non-Ferrous Solutions, Espoo, Finland Tid: Fredag den 10 december 2010 kl 10.00 Plats: F531 Bergrum, Luleå tekniska universitet

The Swedish steelmaking industry produces large amounts of by-products. In 2006, the total amount of slag produced reached approximately 1 375 000 metric tons, of which 30% was deposited. Due to its strength, durability and chemistry, steel slag is of interest in the field of construction due to it's similarities with ordinary ballast stone. However, some steel slags face an array of quality concerns that might hinder their use. These concerns generally involve the following physical and chemical properties: Volume expansion, Disintegration, Leaching of metals By controlling and modifying process parameters during slag handling in liquid state, the physical properties of steel slags can be adequately modified to obtain a high-quality product for external application. The present work was undertaken as a research project within the Minerals and Metals Recycling Research Centre, MiMeR. The major objectives of this work have been to investigate how different cooling methods and cooling rates influence the properties of slag products. Four types of steel slags, Ladle slag, BOF (Basic Oxygen Furnace) slag and two different EAF (Electric Arc Furnace) slags, were characterized and modified by semi-rapid cooling in crucibles and rapid cooling by water granulation. Experiments were conducted in laboratory scale using an induction furnace. Analysis techniques used in this investigation include: thermodynamic calculations using FactSageTM, X-ray diffraction analyses (XRD), scanning electron microscope (SEM) and a standard leaching test (prEN 12457-2/3). The experimental results show that disintegrating ladle slag is volume stabilized by water granulation resulting in a product consisting of 98% glass. However EAF slag 1, EAF slag 2 and the BOF slag formed only 17%, 1% and 1% glass, respectively. The leaching tests showed that water granulation did not prevent leaching of minor elements from the modified slags. The solubility of chromium, molybdenum and vanadium varied in the different modifications, probably due to their presence in different minerals. Variations in crystal size as well as phase composition and distribution were observed in the different materials as a result of different cooling methods. The magnesium content of the wustite-type solid solution (Fe,Mg,Mn)O in BOF slag increased when rapid cooling was used. The reactivity factor, á, was calculated for the BOF and EAF slag 1. A majority of the elements of interests in the slags became more reactive when cooled rapidly. The reactivity for silica in BOF and EAF slag 1 was increased by ~4700% and ~1200%, respectively, and for chromium by ~5300% and ~1500%.
Godkänd; 2007; 20071121 (ysko)

Copper was one of the first metals ever extracted and used by mankind. It is used for its unique properties, like corrosion resistance, good workability, high thermal conductivity and attractive appearance. New mines are opened to maintain a supply of primary feedstock to copper smelters. These new deposits are in many instances found to have a more complex mineralogy with several minor elements. Besides treating primary material, copper smelters also show an increasing interest in treating secondary material, such as copper containing scrap from waste electric and electronic equipment, which also have a complex composition.Waste electric and electronic equipment are first disassembled and upgraded by mechanical processing, generating a product stream called e-scrap, that can be added directly to the smelting processes as cold material or melted in a separate furnace producing a metallic alloy (referred to as black copper) and a slag phase. The black copper can be refined in different ways, whereof one is by using it as a secondary feed material for input to Peirce-Smith converters. Consequently the load of minor elements to the converter can be expected to increase with an increased treatment of e-scrap.This increased complexity of the raw material can potentially lead to smelter plants having to deal with a feedstock containing several minor elements such as; antimony, bismuth, arsenic, gold, silver, etc. in levels that can influence the ability to, in a cost effective way, maintain the final grade of the copper cathode. Process simulations can be an important tool for understanding the impact of process parameters on the product quality and for the purpose of process optimisation. In the present work a dynamic, non-equilibrium model based on thermodynamics over the Peirce-Smith converter has been developed. The non-equilibrium conditions have been simulated by introducing individual but linked segments. The purpose of using segments was to consider different reaction zones which yield different conditions within the converter. The model was validated using plant data and showed good agreement for the major elements. The agreement between plant and calculated data for Pb, and Zn was not as good and more work is required regarding this aspect. The model was used to investigate the influence on the distribution of Bi and Sb during addition of black copper with or without slag. When black copper is added to a blow, the removal of Bi and Sb becomes lower compared to a blow without addition of black copper. Similar result is obtained during addition of black copper with slag. To maintain a total removal of Bi and Sb in similar levels as a blow without black copper, the black copper should be added as early as possible during the converting operation.

Godkänd; 2013; 20131008 (lenann); Tillkännagivande licentiatseminarium 2013-11-06 Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Andreas Lennartsson Ämne: Processmetallurgi/Process Metallurgy Uppsats: Development of a Process Model for a Peirce-Smith Converter Examinator: Bitr professor Caisa Samuelsson, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Diskutant: Dr Universitetslärare Eetu-Pekka Heikkinen, Department of Process and Environmental Engineering, University of Oulu, Finland Tid: Måndag den 9 december 2013 kl 13.00 Plats: F341, Luleå tekniska universitet

Chromium is an important alloying element for stainless steels and other Cr-bearing steels. During the steelmaking process chromium is added to the steels mainly in the form of ferrochrome, which is largely produced by the energy-intensive smelting reduction process of chromite ore in the submerged arc furnace. To reduce the overall energy consumption during the ferrochrome production process and the chromium alloying process, direct chromiumalloying by chromite ore has been proposed. The application of this process will integrate the processes for ferrochrome production and chromium alloying, and thus has the potential to cut the production costs of the Cr-bearing steels by avoiding, or at least partially avoiding, the usage of ferrochrome. Further, this new alloying process has the capacity to improve therecovery of chromium from chromite ore. This thesis presents fundamental studies on the carbothermic reduction of synthetic iron chromite (FeCr2O4) and chromite ore, which aim at designing a direct alloying precursor to be applied in the industrial process. Thermogravimetric Analysis (TGA) experiments have been carried out to investigate the carbothermic reduction processes of FeCr2O4 in the absence/presence of metallic iron, and of chromite ore in the absence/presence of mill scale. In the case of using the mixture ‘FeCr2O4 +iron powder + graphite’, it is found that the presence of metallic iron enhances the reduction of FeCr2O4, and this enhancing effect increases with increasing iron addition. The enhancing effect of iron addition on the reduction of FeCr2O4 is due to the fact that the reduction of component Cr2O3 in FeCr2O4 is enhanced, and this effect is attributed to the presence of solidiron which can decrease the activity of chromium by having chromium in situ dissolved in the iron. In the case of using the mixture ‘chromite ore + petcoke’, it is found that the reduction of iron ions in the chromite ore starts before that of chromium ions in the ore and the reduction of iron ions and chromium ions in the ore overlaps to some degree. (Cr,Fe)7C3 is found to bethe intermediate phase during the reduction and a chromium gradient is found in the spinel phase of the fractional reduced sample at 1673 K. A four-stage reduction process is proposed: one stage involving the reduction of iron ions in the chromite ore and three stages involving the reduction of chromium ions in the ore. The activity aspects of component FeCr2O4 and component MgCr2O4 in the chromite ore have been considered. The difficulty in the reductionof the chromite ore is attributed to the fact that, as the reduction proceeds, the activity of component MgCr2O4 in the fractional reduced ore will decrease to a very low level, which makes the further reduction very difficult. In the case of using the mixture ‘chromite ore + mill scale + petcoke’, it is found that mill scale is reduced to iron before 1573 K. The asreduced iron is disseminated around chromite ore particles and, at the same time, some carbonis dissolved in the iron via diffusion. Reduction of chromite ore is enhanced with the addition of mill scale at temperatures higher than 1623 K, and the enhancing effect increases with increasing mill scale addition. The enhancing effect, in this case, is attributed to the presence of molten Fe-Cr-C phase in the vicinity of chromite ore, which can decrease the activity of chromium by having chromium in situ dissolved into the melt. Induction furnace experiments have been carried out to investigate the effectiveness of some different alloying mixtures. The experimental results have confirmed the necessity ofadjusting the composition of the slag to ensure high chromium yield in the final product and the experimental results show that, by using iron scrap, chromium yield can reach 90%. The present findings have led to the proposal of using ‘chromite ore + mill scale + petcoke’ as alloying precursor for direct chromium alloying. The effectiveness of this alloying precursor needs to be further explored by induction furnace experiments, followed by full scale Electric Arc Furnace experiments.

Godkänd; 2014; 20141027 (andbra); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Xianfeng Hu Ämne: Processmetallurgi /Process Metallurgy Uppsats: Fundamental Studies on Direct Chromium Alloying by Chromite Ore with Designed Alloying Precursor Examinator: Professor Bo Björkman Institutionen för samhällsbyggnad och naturresurser Avdelning Mineralteknik och metallurgi Luleå tekniska universitet Diskutant: Professor Timo Fabritsius University of Oulu Finland Tid: Fredag den 15 december 2014 kl 10.00 Plats: E246, Luleå tekniska universitet

Comminution test methods used within mineral processing have mainly been developed for selecting the most appropriate comminution technology for a given ore, designing a grinding circuit as well as sizing the equipment needed. Existing test methods usually require comparatively large sample amounts and are time-consuming to conduct. This makes comprehensive testing of ore comminution behavior – as required in the geometallurgical context – quite expensive. Currently the main interest in the conduct of comminution test lies in the determination of particle size reduction and related energy consumption by grindability test methods, which provide the necessary information about mill throughput. In this procedure mineral liberation is regarded as a fixed parameter due to missing this information in ore characterization as well as a lack of suitable comminution models. However, ignoring the connection between particle size and mineral liberation prevents the scheduling and controlling of the production process from being optimal.For these reasons new comminution tests need to be developed or alternatively the existing test methods need to be suited to geometallurgical testing where the aim is to map the variation of processing properties of an entire ore body. The objective of this research work is on the one hand to develop small-scale comminution test methods that allow linking comminution behavior and liberation characteristics to mineralogical parameters, and on the other hand establish a modeling framework including mineral liberation information.Within the first stage of the study the comminution of drill cores from Malmberget’s magnetite ore, classified by modal mineralogy and texture information, have been investigated. It was found that there is a direct correlation between the mechanical strength of the rock, as received from unconfined compressive or point load tests, and the crusher reduction ratio as a measure for crushability. However, a negative correlation was found between crushability and grindability for the same samples. The grindability showed inverse correlation with both magnetite grade and the magnetite’s mineral grain size. The preliminary conclusion is that modal mineralogy and micro-texture (grain size) can be used to quantitatively describe the ore comminution behavior although the applied fracture mechanism of the mill cannot be excluded.With crushed ore samples from Malmberget also grindability tests and mineral liberation analyses were conducted using laboratory tumbling mills of different size. Starting from the dimensions of the Bond ball mill a modified test method was developed where small size samples of approximately 220 g were pre-crushed and ground in a down-scaled one-stage grindability test. Down-scaling was done by keeping similar impact effects between the mills. Mill speed and grinding time were used for adjusting the number of fracture events in order to receive similar particle size distributions and specific grinding energy when decreasing mill size by the factor 1.63. A detailed description of the novel geometallurgical comminution test (GCT) is given.With respect to ore crushability and autogenous and semiautogenous grinding (AG/SAG) also drop weight tests were conducted. For a more accurate and precise measurement of the energy transferred to the sample a novel instrumented drop weight was used. Initial tests with fractions of drill cores and pre-crushed ore particles showed that the simple energy calculation based on potential energy needs to be corrected. For the future work these tests will be extended to other ore types in order to investigate the effects of mineralogy and to include mineral liberation in comminution models suitable for geometallurgy.

Godkänd; 2014; 20140402 (abdmwa); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Abdul Mwanga Ämne: Mineralteknik/Mineral Processing Uppsats: Test Methods for Characterising Ore Comminution Behavior in Geometallurgy Examinator: Professor Jan Rosenkranz, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Diskutant: Professor Hakan Benzer, Hacettepe University, Department of Mining Engineering Beytepe, Ankara, Turkey Tid: Torsdag den 12 juni 2014 kl 10.00 Plats: F531, Luleå tekniska universitet