Mjukglödgning av kullagerstål är en förutsättning för att kunna vidareförädla stålet. Processen är idag väldigt tidskrävande vilket gjort den till en flaskhals i produktionen. Detta examensarbete har gått ut på att titta närmare på en snabbare mjukglödgningscykel, kallad puckelglödgning, som idag används i Hofors och ställa det i förhållande till nuvarande cykel som används i Rullhärdugn 1. Genom labbugnstest, dilatometertester samt en skarp körning har data tagits fram för hårdhet och struktur vilket sedan analyserats och jämförts med motsvarande data från dagens process.   Målet har varit att se om puckelglödgningen är en praktiskt gångbar process och om den uppfyller de krav på struktur och hårdhet som ställs på stålet efter mjukglödgning.   Resultatet har visat på att puckelglödgning ger en godkänd struktur och hårdhet i labbmiljö men att processen i sig ställer höga krav på ugnens kapacitet när det kommer till att använda den i den vanliga produktionen. Resultatet från den skarpa körningen visar att cykeln har svårt att få en likvärdig struktur när större volymer mjukglödgas. Puckelglödgningscykeln som används i Hofors har fördelar jämtemot den cykel som används i Hällefors, men slutsatsen är ändå att en optimering av nuvarande cykel i Hällefors är att föredra framför ett införande av en puckelglödgningscykel. / Soft annealing of ball bearing steels is a prerequisite to be able to further process the steel. The process today is very time-consuming which has made it into a bottleneck. The purpose of this thesis has been to study a faster soft annealing cycle called “hump annealing” which is used in Hofors and compare it to the current cycle used in “Rullhärdugn 1” (Roller hearth furnace 1). Through a test in a lab furnace, dilatometer tests and a live test data has been collected on hardness and structure which then has been analyzed and compared against data from the current day process.   The goal has been to see if hump annealing is a practically feasible process and if it fulfills the requirements in structure and hardness that is demanded of the steel following soft annealing.   The results concluded showed that hump annealing produces an acceptable structure and hardness in lab environment but that the process itself puts high demands on the furnaces capacity when it comes to using it in the regular production. The results from the live test shows that the hump annealing cycle has problems getting an equivalent structure when bigger volumes are soft annealed. The hump annealing cycle do have certain advantages compared to the cycle used in Hällefors but the conclusion is nevertheless that an optimization of the current cycle in Hällefors is preferred to adopting the hump annealing cycle.

Owing to the diverse geological processes of genesis, metals occur in earth’s crust in a variety of minerals that form ore deposits across the globe. These deposits significantly differ in terms of their physical and chemical characteristics, and conditions of hosting. Productivity growth in any given metal industry is therefore governed by not only the advancements in technology, but also this unique variation in its natural input in course of cumulative extraction and depletion. Detailed analysis of the changes in process input intensities and sector productivity corresponding to a representative spectrum of geological transitions in copper ores reveals that the continuous and incremental technological developments had successfully offset the detrimental effects of depletion on sector productivity, often aided by the geological characteristics that changed to the miners’ advantage. However, the transition of ores below a threshold level of purity and then into the next prevalent chemical composition, was found to cause a steep rise in input intensities that would lead to a fall in productivity despite the introduction of a widely acclaimed innovative process of copper extraction. The study shows that the impacts of depletion are neither linear, nor uniform, and not always detrimental to productivity. It shows the usefulness of productivity studies in estimating the impacts depletion that may not proceed in strictly sequential manner in the short and medium term, as well as evaluating the benefits of technological change. Though the study is primarily based on copper industry, the findings hold relevance for other metal industries too.

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In order to clarify the role that water plays in the photocatalytic process, changes in the IR and Raman spectra of P25 TiO₂ thin films were observed upon exposure to liquid water. Further investigation of these spectral changes via dehydration of thin films under nitrogen and oxygen of different humidities led to the observation of spectroscopic features that have been assigned to localised surface phonon modes. When the effect of UV irradiation on these features was investigated, a broad IR absorption due to transitions of electrons in shallow traps was detected under dry nitrogen but not under dry oxygen. Further investigation of the photocatalytic properties of P25 TiO₂ showed a complete removal of a stearic acid film. The final products have been tentatively assigned to a mixture of short chain carbonyl species and adsorbed carbonates as well as carbon dioxide and water. The IR spectrum of the fuel cell membrane material Nafion is complex and literature data varies in some of the assignments. The compound perfluoro(2-ethoxyethane)sulfonic acid was used as a model compound for the Nafion side chain resulting in a clearer assignment of the Nafion IR spectrum. In light of these new assignments changes induced in the region 1100-1300 cm⁻� by variation in humidity and ion exchange have been shown to be mainly the result of changes in the sulfonate asymmetric stretching modes. By flowing a series of solutions containing tetramethylammonium ions and perchlorate ions the surface charge characteristics of a Pt black film were determined in the pH range 2-12. There proved to be a weak positive charge below pH 4 and a weak negative charge above pH 9. Between these points there appeared to be no overall charge on the surface. When perfluoro(2-ethoxyethane)sulfonic acid was adsorbed to a Pt black film changes in its IR spectrum indicated a strong binding via interactions between the sulfonate groups and the Pt surface. The nature of the adsorption of Nafion was less clear cut and, whilst adsorption is strong, it seems possible that hydrophobic interactions between the Nafion backbone and the surface are involved.

Graduation date: 2005

Graduation date: 2004

Graduation date: 2004

This paper documents the investigation into injection molding, or die casting, a bulk metallic glass (BMG). A BMG is an amorphous metal of a thickness greater than 25 ��m, according to leading researchers in the field. This critical thickness differentiates a normal metallic glass from a "bulk" metallic glass. The impetus for studying the ability to process lies in the material properties of the BMG, which has twice the strength of steel and the ability to be formed much like a thermoplastic. An initial discussion of processing options and history precedes a detailed description of the machine concept and design, including the governing parameters placed on the design. An account of methods and materials used has been included, along with problems encountered and resultant remedies. The initial results consist of the verification of the machine concept and the ability to replicate nanometer-sized surface features from a mold. Design issues are addressed and the corresponding revisions described. The final machine revision shows an increase in process repeatability. A presentation of photographs, which show results of forming the BMG against both copper and stainless steel, is offered as a qualitative assessment of the processing capability. A discussion of considerations and paths forward has been included for future research using the machine that was developed, but these processing theories could also be carried over to other experiments. In the end, this study proves the ability to form extremely small surface features in cast BMG parts and makes suggestions on research avenues that may give a better understanding of the variables involved in processing BMG from the molten state. / Graduation date: 2003

By the investigation of the bulk metallic glass-forming liquids that have very low critical cooling rates, the thermodynamics of metallic glasses can be clarified. For studying thermodynamic properties, such as the specific heat capacity, calorimetry (DSC) is utilized and one of the most used instruments is the differential scanning calorimeter. In this study calorimetry was used to investigate the thermodynamics of the Pd������Ni������Cu������P������ alloy. The specific heat capacity of the liquid and crystalline state, enthalpy, entropy, as well as Gibbs free energy difference between the liquid and crystalline state were measured and evaluated in comparison with previous studies of the alloy. The Pd������Ni������Cu������P������ alloy is known as a metallic glass-forming alloy that has high ability for vitrification without crystallization. By observing the onset of heat flux of the exothermic reactions in the DSC, the time-temperature-transformation diagram can be constructed, and the diagram confirms the high ability for the vitrification for the sample. In addition, the effect of fluxing by B���O��� to reduce heterogeneous nucleation is determined by the TTT-diagram. The enthalpy change during the crystallization was directly measured in experiments in which the sample was held isothermally in the DSC. Both enthalpies, calculated from the specific heat capacity measurements and direct measured enthalpy exactly match each other. The very interesting effect in these experiments is an effect of heat treatment in the samples. Two glass transition temperatures can be noticeably recognized by scanning the exothermic event of the sample with the DSC. The material separates into two undercooled liquids. The two phases that are separated during heat treatment can be described by two different fragility parameters. / Graduation date: 2001

This paper summarizes a recently developed continuum theory for the elastic-viscoplastic deformation of amorphous solids such as polymeric and metallic glasses. Introducing an internal-state variable that represents the local free-volume associated with certain metastable states, we are able to capture the highly non-linear stress-strain behavior that precedes the yield-peak and gives rise to post-yield strain-softening. Our theory explicitly accounts for the dependence of the Helmholtz free energy on the plastic deformation in a thermodynamically consistent manner. This dependence leads directly to a backstress in the underlying flow rule, and allows us to model the rapid strain-hardening response after the initial yield-drop in monotonic deformations, as well as the Bauschinger-type reverse-yielding phenomena typically observed in amorphous polymeric solids upon unloading after large plastic deformations. We have implemented a special set of constitutive equations resulting from the general theory in a finite-element computer program. Using this finite-element program, we apply the specialized equations to model the large-deformation response of the amorphous polymeric solid polycarbonate, at ambient temperature and pressure. We show numerical results to some representative problems, and compare them against corresponding results from physical experiments. / Singapore-MIT Alliance (SMA)