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1
Goode, B. J. "The use of ultrasound to enhance the pickling of hot rolled low carbon steel strip." Thesis, Swansea University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637075.
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This study examines four aspects of the use of ultrasonics in steel strip pickling: the cavitation process, the kinetics of scale removal, the relative significance of variables in ultrasonic pickling and the application of ultrasound in a pilot-scale operation. To ensure optimum location of transducers in relation to their cavitational effects, studies were carried out in water tanks using two techniques to map cavitational activity: resistance thermometry and quantified mechanical damage to coupons of lead or aluminium. Both techniques gave similar results. Thermometric mapping had the advantage of speed but the use of a panel of lead coupons provided more tangible evidence of the mechanical influence of ultrasound in water. A cylindrical bar transducer was the most effective of those tested and could readily be adapted for use in wide strip pickling. The kinetics of pickling were analysed using a Johnson-Mehl type equation. Time exponents 'n' were in the range 2.03 - 2.56 with activation energies in the range 42.18 - 50.54 kJ/mol. The process both in normal and ultrasonic pickling was envisaged to occur by progressive undercutting and fracture of the scale. The application of ultrasonics reduced completion times considerably. To explore the individual and linked influences of variables on the pickling process, and the effect of applying ultrasonics, a statistical factorial analysis was carried out. Acid temperature was found to be the most important single variable while the most significant interaction was that between acid temperature and acid concentration. An equation has been derived reflecting the influence of all the pickling variables and their interactions. Finally, to assess better the applicability of ultrasonics to full-scale commercial operations, tests were carried out on a large pilot plant funded as part of a European Coal and Steel Community project between British Steel plc and Hoogovens Staal. The results of the smaller tests were confirmed and, furthermore, the influence of ultrasound on inhibitor efficiency was found to be insignificant.
2
Kim, Kisoo. "Effects of rolling conditions on microstructure and mechanical properties of ultra low carbon steel strip." Thesis, University of Sheffield, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369851.
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Xu, Wanqiang Materials Science & Engineering Faculty of Science UNSW. "Effect of initial microstructure on the deformation and annealing behaviour of low carbon steel." Awarded by:University of New South Wales. School of Materials Science and Engineering, 2006. http://handle.unsw.edu.au/1959.4/26801.
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The effect of initial microstructures of an 0.05 wt.% C low carbon steel, acicular ferrite (AF), Bainite (B), polygonal ferrite (PF), fine polygonal ferrite (FPF), and a microstructure produced by direct strip casting (DSC) (termed SC), on the deformation and recrystallization behaviour of cold rolled low carbon (LC) steel, was investigated. The initially prepared samples with the initial microstructures were cold rolled to 50, 70 and 90% reductions, then annealed isothermally in the temperature range 580 ??? 680 oC. The microstructures and textures produced by deformation and annealing were studied by optical microscopy, XRD, TEM, SEM and EBSD. The initial microstructures were characterized mainly by optical microscopy and EBSD. Using EBSD, the ferrite grain size of the AF, B and SC samples was considerably larger than that found by optical microscopy with a large fraction of low angle grain boundaries (LAGBs) observed within prior austenite grains. All samples exhibited a very weak texture close to random. After cold rolling, the microstructures of AF and SC contained shear bands with PF and FPF generating deformation bands. For AF and SC, the pearlite phase was more extensively elongated in rolling direction compared with PF and FPF. After 90% cold rolling reduction, PF, FPF and SC consist mainly of the texture component and AF and B . It was found that FPF recrystallized most rapidly followed by B, PF and AF with SC recrystallizing orders of magnitude more slowly due to the solution drag caused by its uniformly distributed higher Mn content. Very strong (???-fibre) texture was generated in cold rolled PF followed by FPF, with AF, SC and B generating very weak textures. The texture evolution during annealing 90% reduction PF was examined in further detail. The behaviour of nucleation and grain growth provides strong evidence of orientated nucleation as the dominant factor for CRA texture development in this material.
4
Bérard, Jean-Yves Adrien. "Low cycle fatigue behavior of a low carbon steel." Thesis, Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/20130.
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McCallum, Roger David Ian. "The drawability of low carbon steel wire /." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56905.
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Four low carbon steels were drawn from rod to wire on a commercial multi-die wire drawing machine. Samples were obtained from between dies. Internal damage, as a function of cold work, was determined using precision density measurements. Nitrogen was observed to have the greatest effect on the ductility of low carbon steel. Interstitial nitrogen causes internal damage, which results in wire breaks. The mobility of nitrogen increases with temperature, which could account for the increased probability of wire breaks at high drawing speeds.
6
Kim, Bae-Kyun. "High temperature oxidation of low carbon steel." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19519.
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The quality of steel may be seriously affected by the surface defects that appear on slab surfaces after hot rolling. These defects are related to iron oxidation and, in order to reduce the occurrence of these defects, it is necessary to better understand the formation of iron oxides during high temperature oxidation and the oxide descaling mechanisms. However, systematic research tools and experimental strategies for addressing these issues have not yet been developed. In addition, the mechanisms of oxide cracking and failure have not been understood. In this thesis, research tools and strategies are proposed for studying the high temperature oxidation of low carbon steels. These tools allow the presentation of new data on the phase composition of iron oxides at elevated temperature, characteristics of iron oxide formation, oxide microstructure and texture, oxide defects, and stress distributions in different oxide layers, as well as residual stresses. The microscopic model that was proposed for description of oxide failure allows better understanding of the mechanism for surface defect formation during hot rolling. To describe the dynamics of phase composition changes in textured oxides at elevated temperature, a new phase analysis method is proposed. This x-ray diffraction phase analysis is based on the Rietveld and Dickson's methods, and is used for investigating the effect of alloying elements on the oxidation process. This method was also adopted to track in-situ phase composition changes during high temperature oxidation of commercial low carbon steels. The structure of oxides on low carbon steels, pure iron, and Si-steels was systematically examined by orientation imaging microscopy (OIM). It is demonstrated that OIM can be an invaluable tool for visualizing the oxide microstructure texture and studies of oxide defects. In order to simulate industrial hot rolling of oxidized steel sheet, high temperature oxidations tests were made in the tube furnace up to 950°C, in air. The oxidation process and microstructure development were described using OIM maps including image quality (IQ) and inverse pole figure (IPF) maps. The three different iron oxides phases could be distinguished and the characteristics of oxides with different oxidation histories were compared. Iron oxides developed during high temperature oxidation consisted of wustite (FeO), magnetite (Fe304), and hematite (Fe20s) structures with varying texture, grain shape and size. In order to understand the mechanical properties of iron oxides, residual stresses in the three iron oxides phases were assessed using a specially designed x-ray stress measurement system. The stress distributions in the oxide layers were also simulated using finite element simulation of the hot rolling process.
7
Chatterjee, Amit. "Hydrogen degradation of plain carbon and low alloy steels /." The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487264603219536.
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8
Akhtar, Mst Alpona. "Hydrophobicity of Magnetite Coating on Low Carbon Steel." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1248389/.
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Superhydrophobic coatings (SHC) with excellent self-cleaning and corrosion resistance property is developed on magnetite coated AISI SAE 1020 steel by using a simple immersion method. Roughness measurement, scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), contact angle measurement (CAM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), potentiodynamic polarization test, electrochemical impedance spectroscopy (EIS), and qualitative characterization of self-cleaning behavior, antifouling property and durability of the coatings are assessed. A water contact angle as high as 152o on the coated surface with excellent self-cleaning and resistivity to corrosion and good longevity in atmospheric air is obtained. Self-cleaning test results prove that these surfaces can find applications in large scale production of engineering materials. Potentiodynamic polarization tests and EIS tests confirm that the superhydrophobic low carbon steel surfaces have better resistance to corrosion compared to bare steel and magnetite coated steel in 3.5% NaCl solution. But the longevity of the coated steel surfaces in 3.5% salt solution is limited, which is revealed by the immersion durability test. However, hydrophobic coatings (HC) have better stability in normal tap water, and it can stay unharmed up to 15 days. Finally, hydrophobic coatings on low carbon steel surface retains hydrophobic in open atmosphere for more than two months. Results of this investigation show surface roughness is a critical factor in manufacturing hydrophobic steel surfaces. Higher contact angles are obtained for rougher and more uniform surfaces. A linear mathematical relationship (y =6x+104; R2 = 0.93) is obtained between contact angle (y) and surface roughness (x).
9
Liu, Jin. "Decarburization of ultra-low carbon steel by vacuum levitation." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61306.
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Vacuum levitation experiments have been conducted to study the decarburization kinetics of levitated steel droplets in order to determine the factors and relationships which control the rate of decarburization especially at C levels below 30 ppm. It was found from the experiments that (1) vacuum chamber pressure had a significant effect on the rate of decarburization when the carbon content was below 35 ppm; (2) sulfur did not show any significant effect on the rate of decarburization due to the strong stirring inside the droplet caused by magnetic levitation field; (3) the rate of decarburization of levitated droplets was 3 ppm/sec at (C) = 30 ppm which was 40 times higher than the overall rate of decarburization in the RH process at (C) 30 ppm; (4) high initial oxygen contents improved the rate of decarburization at high carbon contents.The following suggestions are made: (1) increase the amount of liquid steel droplets without increasing the size of the droplets; (2) increase the fraction of the amount of decarburization reaction inside the molten steel by gas and powder injection; (3) further reduce the partial pressure of CO and CO$ sb2$ gas in the gas phase. (Abstract shortened by UMI.)
10
Åkefeldt, Jon. "Optimization of laser welding process : Hermetical weld between a medium carbon steel and a low carbon steel shim." Thesis, Karlstads universitet, Avdelningen för maskin- och materialteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-62619.
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11
Victor, Ngea Njoume. "Characterising the structural integrity of mechanical formed low carbon steel." Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1012089.
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The contribution of the clamping force in the technique used in this study to stretch-bend low carbon steel samples was investigated to support the subsequent changes in the microstructure and properties of the formed material with regard to parent material. Although plastic deformation by cold working is known to induce texture or preferred orientation to the grains of a formed material while decreasing its ductility and increasing the strength, as well as inducing residual stress, it is not known how the different directions (rolling, transverse and oblique/45°) of the sheet steel will respond to this stretch bending technique. The first part of the research work involved a thorough literature review on sheet metal forming processes and their effect on the formed material with interest on the above mentioned directions of the sheet. It became clear from the literature overview that cold working of a material will induce strain-hardening which varies with the magnitude of cold work, resulting in changes in the strength and ductility of the material. Besides, when plastic deformation is not uniform (e.g., tensile and compressive) throughout the entire cross section of the formed part, residual stresses remain in the material with the grains been elongated along the direction of the maximum strain. The main parameters that were considered and controlled in this study are as follows: strain experienced / stress induced into the form sample, the sample direction, the stroke length and the clamping torque, the generated radius of curvature. The chapters that follow the literature review, deal with the set-up of the different equipment used in this study, the specimen preparation as well as the recording, the calculation and interpretation of the results. It was found that the stress magnitude that generated the different radii of curvature (120 mm, 150 mm and 185 mm) was between 1 percent & 13 percent higher than the parent material’s yield strength with the lower stress been associated to the smaller radius of curvature and the higher stress to the higher radius. The stress induced into the sample during forming was not only proportional to the stroke length but also to the distance between the punch’s tip and the sample and the sample to the die’s nadir. The clamping torque adopted was restricted to the manual capacity of the operator who used a preset torque wrench to fasten the plate sample into the jig. Plate samples of low carbon steel were cut to angles of 0°, 45°, and 90° to the rolling direction of the sheet material and stretch-bent on a single-action mechanical press to 120 mm, 150 mm, and 185 mm radii of curvature. The preliminary results indicate that stretch-bent samples had increased hardness to the parent plate, in particular below the surface layers up to around 1.1 mm depth. Since there is a well established relationship between hardness, yield and tensile strengths for steel, the yield and tensile strengths of the formed material were estimated using the Nobre et al [34] incremental relation, which relates the linearity between relative increments of hardness and yield strength. Changes were not noticeable at the microstructural level of the formed samples. Meanwhile, samples from which higher plastic deformation stress values were calculated were not those absorbing higher impact energy when Charpy specimen cut from plate and stretch-bent samples were tested. The maximum relieved residual stress in the parent material was predominantly compressive and represents in magnitude approximately 12 percent (average for the three directions) of its original yield strength. In the stretch-bent samples, the relieved residual stress was compressive in the outer curved section with a magnitude about 50 percent of the parent material yield strength and tensile in the inner curved section with a magnitude approximately 25 percent of the parent material yield strength.
12
Pandi, Rassoul. "Dynamic transformation of austenite to ferrite in low carbon steel." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=26064.
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The design of thermomechanical processing schedules to control microstructures requires the knowledge of the austenite-to-ferrite transformation start temperature (Ar$ sb3$). Further, in curved mold continuous casting, transverse cracking occurs during the unbending procedure to straighten the solidified curved strand, and this can also strongly depend on the austenite-to-ferrite transformation. In both of these industrial processes, during deformation, the temperature usually decreases continuously. Thus, two new methods to determine the Ar$ sb3$, based on continuous cooling compression (CCC) and continuous cooling torsion (CCT), have been developed. While the latter is applicable for low and high strains, the former can be only used for low strains.The aim of this investigation was to determine the effect of deformation in the single phase austenite and two phase austenite plus ferrite region on the transformation and dynamic transformation behaviour of austenite-to-ferrite. CCC tests were carried out on a low carbon steel and the influence of strain, strain rate, cooling rate and austenite grain size, was examined.
During the application of strain, the generated dislocations cause an increase in stored strain energy. This energy adds to the driving force for austenite-to-ferrite transformation, increasing the kinetics of this transformation, raising the Ar$ sb3$ in this way. The faster kinetics leads to a finer polygonal ferrite grain size after transformation. In contrast to the effect of increasing strain, accelerated cooling rates decrease the transformation start temperature, but can still lead to grain refinement via high nucleation rates. By increasing the cooling rate, fine acicular ferrite with a high aspect ratio could be obtained. Since, the ferrite grain size is directly related to austenite grain size, by varying austenite grain size, a wide range of ferrite grain sizes could be obtained. Finally, deforming close to the Ar$ sb3$ maximizes the strain effect on dynamically transformed ferrite.
13
O'Neill, Daniel Scott Materials Science & Engineering Faculty of Science UNSW. "An investigation of surface hot shortness in low carbon steel." Awarded by:University of New South Wales. Materials Science and Engineering, 2002. http://handle.unsw.edu.au/1959.4/18274.
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A series of model steels containing copper levels up to 0.48wt%, nickel up to 0.22wt% and silicon levels of 0.52wt% were oxidised in air at 1050 and 1150??C, and in a CO2-N2 mixture at 1250??C for times of up to 3 hours. The scaling kinetics were measured and the behaviour of copper-rich phase formation at the scale/metal interface was investigated. When oxidised at 1050/1150??C, significant quantities of copper-rich phase were observed for most model steels. The relatively high oxidation rate under these conditions led to the rapid development of a copper-rich layer with little copper diffusing into the metal. However, when oxidised at 1250??C, the copper-rich phase did not form for a significant amount of time; and for some model steels, not at all. This was attributed to the considerably lower oxidation rate and the fact that more copper was found to have diffused into the metal. Alloying additions of nickel and silicon were found to be beneficial in reducing the amount of copper-rich phase measured at the scale/metal interface under the conditions investigated at 1150??C and 1250??C. This occurred because nickel and silicon addition promoted the occlusion of copper-rich phase into the scale. Copper enrichment during oxidation was modelled using a numerical description of the diffusion processes involved. Predictions of the time for commencement of copper-rich phase formation at 1250??C were in close agreement with observation. Agreement between predicted and observed copper-rich layer thickness was less successful under conditions where occlusion was significant, and the measured thickness varied non-uniformly with time. The cracking susceptibility of the model steels was examined using a hot compression test. Oxidation was performed in air at 1050, 1150 and 1250??C and most specimens were compressed at 1050??C. The amount of cracking was found to increase with the amount of copper-rich phase precipitated at the scale/metal interface during oxidation. In general, nickel addition reduced the amount of cracking at all temperatures; and under some conditions prevented cracking altogether. Silicon reduced or completely suppressed cracking when the subscale formed was liquid. The beneficial effects of nickel and silicon addition were attributed to their effect of promoting copper occlusion.
14
Kendall, J. M. "Aspects of fatigue crack growth in a low carbon steel." Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383813.
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Phadnis, Ameya. "Corrosion Protection of Low Carbon Steel By Cation Substituted Magnetite." Thesis, University of North Texas, 2013. https://digital.library.unt.edu/ark:/67531/metadc271878/.
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Surfaces of low carbon steel sheet were modified by exposure to highly caustic aqueous solutions containing either chromium or aluminum cations. Corrosion resistances of such surfaces were compared with that of steel surfaces exposed to plain caustic aqueous solution. In all cases a highly uniform, black coating having a spinel structure similar to magnetite (Fe3O4) was obtained. The coated steel surfaces were characterized using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Fourier transform infrared spectrophotometry (FTIR). Polarization resistances (Rp) of modified steel surfaces were measured and compared with that of bare steel surfaces. Results indicate that chromium (Fe2+ Fe3+x Cr3+1-x) or aluminum (Fe2+ Fe3+x Al3+1-x) substituted spinel phases formed on steel surfaces showed higher Rp values compared to only magnetite (Fe2+ 2Fe3+O4) phase formed in the absence of either chromium or aluminum cations. Average Rp values for steel surfaces with chromium containing spinel phase were much higher (21.8 k?) as compared to 1.7 k? for bare steel surfaces. Steel surfaces with aluminum containing spinel phase and steels with plain magnetite coated samples showed average Rp values of 3.3 k? and 2.5 k? respectively. XPS and EDS analysis confirmed presence of cations of chromium and aluminum in Fe3O4 in cation substituted samples. FTIR results showed all coating phases were of spinel form with major absorption bands centered at either 570 cm-1 or 600 cm-1 assigned to Fe3O4 and ?-Fe2O3 respectively.
16
Joenoes, Ahmad T. "Quantitative analysis of fatigue behavior, fatigue damage and fatigue fracture surfaces of low carbon bainitic steel (SAE 15B13)." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/19671.
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17
Lu, Yu 1977. "Effect of boron on microstructure and mechanical properties of low carbon microalloyed steels." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=112575.
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Low carbon bainitic steels microalloyed with Nb, Ti and V are widely used for the pipeline, construction and automobile industries because of their excellent combination of strength, toughness and weldability. Boron as another major alloying element has been also frequently used in this type of steels since the 1970s. The purpose of adding boron is to improve the hardenability of the steel by promoting bainite formation.It has been realized that Boron can only be effective as a strengthening element when it is prevented from forming BN and/or Fe23(C, B) 6 precipitates. Therefore, Boron is always added together with other alloying elements which are stronger Nitride or Carbide formers, such as Ti and Nb. However, the formation of complex bainitic structures and the interaction with precipitates at industrial coiling temperature are not adequately understood.
In this study, the effect of boron on the microstructure and mechanical properties of a low carbon Nb-B steel was studied by a hot compression test (50% reduction at 850°C) followed by quenching samples into a salt bath. The microstructures of the tested samples were examined through optical microscopy and SEM; and the mechanical properties of these samples were investigated by micro-hardness and shear punch tests.
The results indicate that during thermo-mechanical controlled rolling (TCR), the final properties of the products not only depend on the applied deformation but also depend on the coiling temperature where phase transformation takes place. According to the investigation, two strengthening mechanisms are responsible for the strength of the steel at the coiling temperature: phase transformation and precipitation. Under optical microscopy, the microstructures of all specimens appear to be bainite in a temperature range from 350°C to 600°C without distinct differences. However, the SEM micrographs revealed that the microstructures at 550°C are very different from the microstructures transformed at the other holding temperatures.
Two strength peaks were observed at 350°C and 550°C in the temperature range studied. It is believed that the NbC precipitates are the main contributor to the peak strength observed at 550°C because the kinetics of NbC is quite rapid at this temperature. The strength peak at 350°C is mainly due to the harder bainitic phase, which formed at relatively lower temperature.
18
Abuluwefa, Husein. "Characterization of oxides (scale) growth of low carbon steel during reheating." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40307.
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This study involved characterizing the oxidation behaviour of low carbon steel in various gas mixtures of O$ rm sb2, CO sb2, H sb2O$ and N$ sb2,$ at different oxidation temperatures. Rate measurements for the oxidation of the low carbon steel during reheating in a walking-beam steel reheat furnace were also carried out. Scaling rates during reheating were predicted from oxidation rates obtained in the laboratory.In-situ characterization of the phase compositions of the iron oxides, "scale", that form on low carbon steels during their oxidation at elevated temperatures was carried out using a neutron diffraction technique. Growths in the intensities of the diffraction peaks associated with characteristic crystal planes of the various oxides (Fe$ rm sb{x}$O, Fe$ rm sb3O sb4$ and Fe$ rm sb2O sb3)$ were monitored on-line. The volume fractions of the oxides in the developing scale were calculated on the basis of ideal structure factors and measured relative intensities of diffraction peaks.
Oxidation in binary gas mixtures of oxygen and nitrogen in the temperature range from 1000 to 1250$ sp circ$C was carried out. Sample weight gain versus time data were analyzed, along with measurements and calculations of sample heating rates due to exothermic reactions at the sample surface. It was found that initial rates of oxidation depended on oxygen content in the gas mixture and that these rates were linear up to oxide thicknesses between 0.4 and 0.5 mm. The linear rates of oxidation were found to be controlled by the mass transport of oxygen from the gas phase, to the reaction surface, through a gas boundary layer. Subsequent oxidation rates followed a parabolic oxidation mechanism.
Oxidation experiments were also carried out in binary, ternary and quaternary gas mixtures of O$ rm sb2, CO sb2, H sb2O$ and N$ sb2$ at various temperatures. Reaction rates during oxidation in binary gas mixtures of CO$ sb2$-N$ sb2$ and H$ sb2$O-N$ sb2$ followed a linear rate law and were found to be proportional to the partial pressures of CO$ sb2$ and H$ sb2$O in the gas mixtures. The oxidation rates showed a strong dependency on temperature. Oxidation in oxygen containing atmospheres showed that the main oxidizing agent was free O$ sb2.$ Additions of CO$ sb2$ and H$ sb2$O had little effect on the magnitude of oxidation rates. Oxidation in these atmospheres exhibited an initial linear rate law which gradually transformed to a parabolic rate law.
During reheating in a walking-beam steel reheat furnace, it was observed that scaling rates can be reduced by lowering input air/fuel ratios to the furnace, which resulted in lowering concentrations of free oxygen in the combustion products from about 3% to about 1.5%. The predicted scaling rates during reheating using isothermal oxidation rate constants suggested that rates of oxidation during reheating in the industrial reheat furnace followed a combination of linear and parabolic rate laws, with the components of the linear oxidation rates being predominant. The observed reduction in scaling rates was a result of the decrease in the free oxygen within the furnace atmosphere.
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Basabe, Mancheno Vladimir Vinicio 1968. "Scale formation and descaling in hot rolling of low carbon steel." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=115671.
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In this research, the effects of gas composition, elapsed time of reaction and temperature on scale formation and descaling of low carbon steel were investigated and results were discussed from the viewpoint of the phase composition of the scales, oxidation rates, oxidation mechanisms, adhesion, fracture mechanics, porosity and residual scale.The phase composition and morphology of scales grown under conditions similar to those of reheating furnaces were analyzed. Low carbon steel was oxidized over the temperature range 1000-1250°C in gas mixtures of O 2-CO2-H2O-N2, O2-H 2O-N2 and O2-CO2-N2. The mole fraction of each phase, wustite (FeO), magnetite (Fe3O 4) and hematite (Fe2O3) was determined by the direct comparison method Two types of scales were observed. The first type was a crystalline scale with an irregular outer surface composed mostly of wustite, and a negligible amount of magnetite. The second type was the classical three-layer scale composed of wustite, magnetite and hematite. In general, the experiments showed that the furnace atmosphere, oxidation time and temperature influence the phase composition of the scales.
Low carbon steel was oxidized in air over the temperature range 600-1200°C for 120 s to approximate the formation of secondary and tertiary scale in hot rolling. The mole fraction of wustite, magnetite and hematite was determined by the direct comparison method The phase composition of the scales changed with temperature and time. During the initial 30 s of oxidation, wustite was the predominant phase in the temperature range 800-1200°C, and as oxidation proceeded, the percentages of magnetite and hematite increased. In addition, the texture of the scales was investigated by orientation imaging microscopy (OIM); it was found that temperature influences the texture of the scales. The experiments indicated that 850°C is the ideal temperature for the finishing mill in order to reduce surface defects and work roll wear.
The adhesion of scales formed in air on low carbon steel in continuous heating and isothermal conditions was investigated with a four-point bending test. The separation (crack) always occurred inside the scale indicating that the strength of the scale is lower than the strength of the scale/steel interface. It was found that scale adhesion is related to scale porosity, blister formation and stresses acting in the scale. A spallation process was observed when cooling from 800°C to room temperature. The microscopic observations revealed that spallation followed route 1 "strong interface and weak oxide."
Low carbon steel was oxidized over the temperature range 1050-1250°C in O2-CO2H2O-N2 gas mixtures in order to study the hydraulic descaling process. The oxidation times were 15-120 min. and the scales were 130-2000 mum thick. The experimental parameters were chosen to approximate scale formation under conditions similar to those of reheating furnaces. In the hydraulic descaling tests, two modes of scale removal were observed. In the first mode, observed in classical three-layer scales that developed an inner porous layer with low or medium porosity, the horizontal undercutting occurred at the boundary of the inner porous layer and dense scale. The second mode was observed in classical three-layer scales that developed an inner porous layer with high porosity and in crystalline scales. In the second mode, the horizontal undercutting occurred at the first plane of large pores relative to the scale/steel interface. In general, the experiments showed that scale morphology controlled the removability of scale.
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Mazinani, Mohammad. "Deformation and fracture behaviour of a low-carbon dual-phase steel." Thesis, University of British Columbia, 2006. http://hdl.handle.net/2429/30951.
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The primary goal of this study was to evaluate the effect of martensite plasticity on the
deformation and fracture behaviour of an intercritically annealed commercial low carbon (0.06
wt.%) dual phase steel. The volume fraction and the morphology (banded and almost equiaxed)
of the martensite phase were systematically varied by control of the intercritical annealing
temperature and the heating rate to this temperature. It was observed that the yield and tensile
strengths were dependent on the martensite content but not on the martensite morphology. On
the other hand, the true uniform strain, fracture strain and fracture stress were found to have a
significant dependence on martensite morphology.
An Eshelby based model, which allowed for the calculation of the stress in the martensite
islands, was employed in order to rationalize the tensile properties of the dual-phase steel
samples with different martensite contents and morphologies. In addition, by comparing the
calculated stress in the martensite with an estimate of yield stress, it was possible to examine
the conditions under which martensite plasticity occurs. The work hardening behaviour and the
fracture properties of the steel samples were rationalized by the implications of martensite
plasticity. For the cases where martensite showed significant plasticity (or co-deformed with
the ferrite matrix), the void nucleation rate during post-necking deformation decreased
considerably and hence, the final fracture properties were dramatically improved.
The deformation of martensite in different dual-phase steel samples was examined both
qualitatively (using optical micrographs of the undeformed and deformed sections of fractured tensile samples) and quantitatively (through image analysis of the microstructures before and
after tensile deformation). The tensile stress-strain responses of different dual-phase steel
samples were modeled using the modified Eshelby method. This approach was found
appropriate for modelling the stress-strain behaviour of the steels with equiaxed morphology
and martensite contents below approximately 30%. In the case of banded morphology, the
stress-strain behaviour of the steel sample with 17% martensite was successfully predicted by
the model. However, the model overestimated the flow stress of the steel with 30% martensite.
For the martensite contents greater than 30%, the overestimation of the flow stress of the steel
samples with banded morphology was greater than that for the equiaxed samples.
Finally, the void formation process during tensile deformation was examined quantitatively
through image analysis of the fracture surface of the steels. The experimental results showed
very little void growth during ductile fracture of the steel samples with 17% and 41%
martensite. Modelling the void formation process in these steels assuming no void growth stage
resulted in the same observation. This confirmed the quantitative observation that void
nucleation is the dominant effect during ductile fracture of these steels.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
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Kay, Helen. "Deoxidation mechanisms in liquid steel." Thesis, Sheffield Hallam University, 1996. http://shura.shu.ac.uk/19899/.
Full textAbstract:
Quantitative chemical and scanning electron microscopical techniques have been employed to investigate the deoxidation kinetics and changes in oxidation product morphology in low carbon steel melts. The techniques have been used to study the deoxidation processes associated with aluminium, titanium, silicon, zirconium and a calcium-aluminium alloy. After the addition of the deoxidant, the total oxygen concentrations of all melts rapidly decreased corresponding with a decrease in the size and number of inclusions observed. This continued to a plateau level of total oxygen concentration and mean inclusion diameter. Samples removed from the melts prior to deoxidation were found to contain globular MnO-FeO inclusions. It was discovered that the morphological sequence for single element deoxidants involved a progressive evolution from liquid globular to solid spherical inclusions followed by polyhedral, dendritic and coralline morphologies. Finally, sintered agglomerates were formed when inclusion clusters collapsed. The extent to which the oxidation products went down the sequence depended on: the dissolution characteristics of the deoxidant; the thermodynamic affinity of the deoxidant for oxygen in the melt; the inclusion/melt interfacial energy characteristics; the refractoriness of the oxidation products and intermediate compounds; and the degree of turbulence experienced by the melt. Explanations have been postulated which elucidate the behaviour of the different deoxidants, as not all displayed the whole morphological sequence. Silicon deoxidation produced spherical silicates, whereas the zirconia inclusions were either spherical or dendritic and the titanium oxidation products had spherical or polyhedral morphologies. Aluminium exhibited all morphologies in the sequence. Deoxidation with the calcium-aluminium alloy was found to have preceded by a two stage process. The initial stage was dominated by the formation of aluminium rich solid oxides followed by the progressive reduction by calcium, resulting in an adhesive liquid calcium-aluminate surface coating. The role of refractory crucible as a collecting surface for the capture and removal of deoxidation products from the melt was investigated, which confirmed that the inclusions were generally incorporated into the low melting point matrix phases. Turbulence also increased the probability that emergence would take place at these capture sites.
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Reck, Victor. "Mechanical and microstructural properties of ultra-low carbon bainitic steel weld metal." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA302955.
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Gwin, Mary Elizabeth. "Factors affecting the impact toughness of ultra low carbon steel weld metal." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1996. http://handle.dtic.mil/100.2/ADA320665.
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Gillström, Peter. "Alternatives to pickling; preparation of carbon and low alloyed steel wire rod /." Örebro : Örebro universitetsbibliotek, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-376.
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Fang, Haitao. "Low Temperature and High Salt Concentration Effects on General CO2 Corrosion for Carbon Steel." Ohio : Ohio University, 2006. http://www.ohiolink.edu/etd/view.cgi?ohiou1163794555.
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Damri, Daniel. "Transient fatigue crack growth in a structural steel." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386012.
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Su, Xiaoyan. "Surface initiated rolling/sliding contact fatigue in pearlitic and low/medium carbon bainitic steels /." Full text open access at:, 1996. http://content.ohsu.edu/u?/etd,253.
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Liu, Jikai. "Influence of metallurgical phase transformation on crack propagation of 15-5PH stainless steel and 16MND5 low carbon steel." Phd thesis, INSA de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-00833206.
Full textAbstract:
Ou study focuses on the effects of phase transformations on crack propagation. We want to understand the changes of fracture toughness during welding. In this work, fracture toughness is expressed by J-integral. There are many experimental methods to obtain the critical toughness JIC but they are impractical for our investigation during phase transformation. That is the reason why we have proposed a method coupling mechanical tests, digital image correlation and finite element simulation. The fracture tests are implemented on pre-cracked single edge notched plate sample which is easy for machining and heat conduct during phase transformation. The tests are conducted at different temperatures until rupture. Digital image correlation gives us the displacement information on every sample. Each test is then simulated by finite element where the fracture toughness is evaluated by the method G-Theta at the crack propagation starting moment found by potential drop method and digital image correlation technical. Two materials have been studied, 15Cr-5Ni martensitic precipitation hardening stainless steel and 16MND5 ferritic low carbon steel. For these two materials, different test temperatures were chosen before, during and after phase transformation for testing and failure characterization of the mechanical behavior. Investigation result shows that metallurgical phase transformation has an influence on fracture toughness and further crack propagation. For 15-5PH, the result of J1C shows that the as received 15-5PH has higher fracture toughness than the one at 200°C. The toughness is also higher than the original material after one cycle heat treatment probably due to some residual austenite. Meanwhile, pure austenite 15-5PH at 200°C has higher fracture toughness than pure martensitic 15-5PH at 200°C. For 16MND5, the result also proves that the phase transformation affects fracture toughness. The as received material has bigger J1C than the situation where it was heated to 600°C. On the other hand, the material at 600°C just before isothermal bainite transformation after the austenitization during cooling process also has higher fracture toughness than the one at 600°C before austenitization. These two conclusions are consistent well with the result of 15-5PH. But the final situation of 16MND5 after one cycle heat treatment has a slightly smaller J1C than the receiving situation. It means that one cycle heat treatment hasn't an significant influence on 16MND5fracture toughness. Conclusions show that one should pay attention to the heating period before austenitization of the substrate material when people do the welding as the higher temperature will bring the lower fracture toughness during this process. While during cooling period, the fracture toughness doesn't change a lot during, before or after the cooling induced phase transformation. Even for 15-5PH, it has a better fracture toughness after the martensite transformation than before.
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Van, Slyke Jonathon J. "Factors affecting the strength and toughness of ultra-low carbon steel weld metal." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1999. http://handle.dtic.mil/100.2/ADA374133.
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Thesis (Degree of Mechanical Engineer) Naval Postgraduate School, December 1999."December 1999". Thesis advisor(S): A.G. Fox. Includes bibliographical references (p. 63-64). Also available online.
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Johns, Eyioma Izuwah. "Influence of weldiing modes to strength and residual of low carbon steel joints." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2014. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2014~D_20140617_122036-53782.
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In this study, microstructural, micro hardness evaluation and residual stress distribution, of low carbon steel after single pass gas metal arc welding technique (GMAW) were investigated. The goal of this investigation were to reveal the microstructures, micro hardness, residual stress distribution and tensile strength of welded joints by using welding current as varying parameter. In order to realize this objective, welded plate of low carbon steel with thickness of 2.5mm and 250mm long by 200mm wide were welded together with different welding current of 70A, 100A through MIG process. Four different parts of samples were tried. The first part of samples was annealed in a furnace to a temperature of 750 and allowed to cool in air before welding. While the second was not heated, third and fourth trials were heated to a temperature of 200˚C and 580˚C respectively after the welding and allowed cooling in air. Nikon optic microscope and CSM micro hardness testing instrument were used to determine the microstructure of the weld bead and HAZ of the samples, and hardness tests were carried out at different zones of welded joint.
Micro hardness behavior was observed by using CSM instrument using 20N load for indentation, which reveals the correlation between hardness, elasticity and plasticity on the heat affected zone (HAZ) and weld bead of the welded plates. The samples were subjected to tensile strength and the distribution of residual stress of the weld. Tensile strength test... [to full text]Šiame darbe aprašomi mikrostruktūros, mikrokietumo nustatymo bei liekamųjų įtempimų pasiskirstymo tyrimai mažo anglingumo plienuose po lankinio suvirinimo. Tyrimo tiksla - nustatyti suvirintos jungties mikrostuktūros ir mikrokietųmo priklausomybę nuo suvirinimo srovės, kaip kintamo dydžio. Remiantis užduotimi buvo suvirintos 2.5 mm storio, 250 mm ilgio ir 200 mm pločio mažaanglio plieno plokštės, naudojant skirting dydžio (70A ir 100A) suvirininant apsauginių dujų aplinkoje (MIG) srovę. Buvo paruoštos keturios partijos bandinių. Pirmoji partija, proies suvirinant, buvo atkaitinta 750°C temperatųroje, ir ataušintas ore. Tuo tarpu antroji partija nebuvo apdorojama, o trečioji ir ketvirtoji atleista 200 C° ir 580°C temperatūroje ir atvėsinta ore. Suvirinimo vonelės ir erminio poveikio zonos mikrostruktūrai tirti bei mikrokietumui nustatyti buvo naudotas Nicon optinis mikroskopas bei CSM mikrokietumo bandymų įrenginys. Matuojant CSM įrenginiu, 20N įspaudimo apkrova, buvo pastebėtas įdomus kietuvo būvis, kuris atskleidė ryšį tarp kietumo, elastingumo ir plastiškumo esantį suvirintų plokštelių terminio poveikio zonoje bei suvirinimo vonelėje. Buvo matuojamas suvirintų bandinių stiprumas tempiant ir liekamųjų įtempimų pasiskirstymas. Tempimo stiprumo bandymų duomenys parodė ducharakteringus suirimo atvejus – plastiio-elastinio bei trapaus tipo. Liekamųjų įtempimų bandymų rezultati neparodė rėikšmingos liekamųjų įtempimų įtakos pasirinktomis sąlygomis suvirintuose bandiniuose.
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Gubner, Rolf Juergen. "Biofilms and accelerated low-water corrosion of carbon steel piling in tidal waters." Thesis, University of Portsmouth, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244479.
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SOUZA, CLARISSA FERREIRA MARTINS DE. "NUMERICAL AND EXPERIMENTAL ANALYSIS OF RESIDUAL STRESSES IN LOW CARBON STEEL WELDED JOINTS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2016. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=29707@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
A soldagem é um processo de união de materiais que possui grande aplicação em diversos setores da indústria, como automotiva, óleo e gás, nuclear, naval, dentre outros. Dentre os fatores responsáveis pelo comprometimento da vida útil pós-soldagem de componentes mecânicos e estruturais se destacam as tensões residuais, cuja análise qualitativa e quantitativa é de extrema importância no projeto, na garantia da qualidade e prevenção de falhas de estruturas soldadas. No presente trabalho aplicou-se uma metodologia composta por análise numérica e experimental, que se complementaram. Chapas do aço AISI 1020 foram soldadas pelo processo Metal Active Gas (MAG), em um único passe. Os experimentos foram conduzidos com duas velocidades, visando avaliar a influência deste parâmetro sobre o nível das tensões residuais geradas. Na sequência, as tensões residuais foram analisadas por difração de raios-X. Simultaneamente, procedeu-se a análise numérica das tensões residuais, com o emprego do código comercial de elementos finitos ANSYS, através de um modelo sólido 3D, em análise não linear termo-elastoplástica, utilizando-se a técnica Birth and Death, ativando e desativando os elementos, à medida que o cordão de solda foi depositado. Parâmetros experimentais da soldagem, geometria das amostras, coeficiente de transmissão de calor, propriedades térmicas e mecânicas do material, que variam com a temperatura, foram utilizados como dados de entrada no modelo numérico. Por fim, realizou-se a comparação entre as tensões residuais determinadas experimentalmente por difração de raios-X e as calculadas numericamente pelo método de elementos finitos, observando-se uma boa concordância entre os resultados obtidos pelas duas metodologias.
Welding is a process of joining materials that have wide application in various industry sectors such as automotive, oil and gas, nuclear, naval, among others. Residual Stresses is often a cause of premature failure of critical components. The qualitative and quantitative analysis of residual stresses is extremely important in the design, on quality assurance and prevention of weldment failures. The objective of this study was developing a methodology that includes numerical and experimental analyses that are complementary. AISI 1020 steel samples were butt welded by GMAW process with weld metal in a single pass. Experiments were conducted at different heat source speeds in order to evaluate the influence of this parameter on the level of residual stresses generated. Subsequently, the samples were subjected to measurement of residual stress by diffraction X-ray method. Simultaneously, a numerical analysis of the residual stresses was performed with a commercial finite element software called ANSYS (17.0), and a 3D solid model for a nonlinear thermo-elastic-plastic analysis using the Birth and Death technique, where the elements are enabled and disabled along weld metal deposition. Experimental welding parameters such as geometry of the samples, heat transfer coefficients, thermal and mechanical properties which vary with temperature were used as input data in the numerical model. Finally, there was a comparison between the residual stresses determined experimentally by diffraction of X-rays and computed data by finite element method. A good agreement was observed between the two methods.
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Mojtaba, Mansouri Arani. "Static strain aging in low carbon ferrite-pearlite steel : forward and reverse loading." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/55894.
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The combination of static strain aging and plastic strain reversal is important to understand for both the forming of components and also analysis of in service performance, for example, in the case of fabrication of pipeline, motor shafts or structural components in buildings and ships.
Static strain aging phenomenon has been experimentally studied for the cases of forward and reverse re-straining after aging on a low carbon steel (0.16 wt% C) with a ferrite-pearlite microstructure. Torsion tests on hollow tubular samples were used for the mechanical tests. The shear strain on the surface of the sample was measured with the digital image correlation. The influence of the amount of pre-strain, aging time and temperature, and the strain path reversals on the stress-strain response after aging has been measured experimentally. A maximum increase of 46 MPa was obtained in the yield stress of the samples re-strained after full aging in the same direction as the initial straining. This maximum increase in yield stress as well as the rate of increment in yield strength during aging was almost independent of the amount of pre-strain and the increase in the flow stress occurred without a significant variation in the work hardening behavior. Further, it was shown that a yield point phenomenon was absent if the direction of re-straining after aging was reversed and the increase in the flow stress level after aging was proportional to the amount of pre-strain and increased with extended aging time. In this case, the absence of a sharp yield point after prolonged aging time led to the speculation that the activation of dislocations sources, rather than unpinning of locked dislocations in re-straining after aging was the controlling mechanisms although proof of this requires further investigation.
Although it is difficult to unambiguously identify all of the underlying physical mechanisms, nevertheless, a comprehensive set of experimental results has been measured which can be used by the design engineer when considering cases where static strain ageing and strain path reversals are relevant for a ferrite-pearlite steel with 0.16 wt% carbon.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
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LI, Jr-Hung. "INFRARED BRAZING OF LOW CARBON SPEED WITH COPPER FILLER." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin990736063.
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Sheng, Yongwei Will 1967. "Ultrafine ferrite production in low carbon steel by means of dynamic strain-induced transformation." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=79260.
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Ferrite grain refinement is one of the best methods to improve the mechanical properties of low carbon steels.The present work is a continuation of this past research and was conducted using a torsion machine. The aim was to improve the understanding of the strain levels and deformation temperatures required for UFF formation, as well as the influence of silicon addition. Two steels were studied: a low silicon (LSi) steel containing 0.09% C-0.02%Si-1.3%Mn-0.07%Al-0.036%Nb and a high silicon (HSi) steel containing 0.09%C-0.48%Si-1.2%Mn-0.02%Al-0.038%Nb. In the hot torsion tests, both steels were deformed to 5 true strain levels: 2, 2.5, 3.2, 3.5 and 4 at a strain rate of 3/s. The Ar3 temperatures for the two steels were measured as 758°C for LSi and 776°C for HSi. It was found that at a strain level of 4 or above, UFF was formed. The optimum deformation temperature was just above the Ar3 and the higher the strain, the finer the ferrite grain size achieved. The results indicated that silicon addition impedes ferrite grain size refinement.
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Díaz, Jorge G. "Effect of Amines as Corrosion Inhibitors for a Low Carbon Steel in Power Industry." Thesis, University of North Texas, 2004. https://digital.library.unt.edu/ark:/67531/metadc4666/.
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Commonly used amines in power industry, including morpholine, DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), and DMA (dimethylallylamine) were evaluated for their effect on AISI 1018 steel at 250oF. Samples were exposed to an autoclave containing amine added aqueous solution at pH of 9.5 for 1, 2, 4, 6, 8, and 12 hours. Morphology studies were carried using scanning electron microscope (SEM), phase analysis was done utilizing Fourier transform infrared spectroscopy (FTIR), and weight loss was performed to assess kinetics of oxidation. Control samples showed the highest metal dissolution rate. DBU showed the best performance in metal protection and SEM indicated the presence of a free-crack layer formed by fine particles in that set. FTIR showed that DBU apparently favored the formation of magnetite. It is believed that fine particles impede intrusion of aggressive ions into the metal surface by forming a barrier layer. FTIR demonstrated that DMA formed more oxyhydroxides, whereas morpholine presented magnetite to hematite transformation as early as 2 hours. SEM revealed that control and DMA produced acicular particles characteristic of oxyhydroxides while morpholine and DBU presented more equiaxed particles.
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Akhlaghi-Esfahani, Siamak. "Effect of a thermomechanical history on the hot ductility of a Nb-Ti microalloyed steel and a low carbon steel." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=36866.
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The susceptibility of steels to transverse cracking during continuous casting depends, in part, on the hot ductility of the steel. In the past, hot ductility has been measured in the laboratory by tensile testing specimens reheated to a high temperature (preferably melted), and then cooled down to the desired test temperature before isothermally testing to fracture. More recently, isothermal tensile testing has been performed after imposing different thermal histories prior to reaching the test temperature. The most relevant thermal history is that of the solidifying strand surface. Such thermal histories have been found to be quite complex, and invariably involve rapid cooling and heating cycles. This will therefore lead to high thermal gradients, which, in turn, can generate strains in the surface of the solidifying strand. Thus, the purpose of this thesis was to consider the effect of the thermomechanical history on the hot ductility of steel.A Nb-Ti microalloyed steel was chosen to be studied, since microalloying often increases susceptibility to transverse cracking. After in-situ melting and solidification, tensile test specimens were subjected to the thermal history typical of a continuously cast billet. Different amounts of prior deformations in various schedules were imposed on the specimens at selected stages during the thermal history, before tensile testing to fracture at the time and temperature corresponding to the unbending stage of the billet casting. It was found that the hot ductility varied from 1% to 98%, depending on the stage in the thermal history at which prior deformation was executed. Microstructural studies showed remarkable changes in the precipitation pattern occurred due to the employed prior deformation. Similar hot ductility measurements executed on a low carbon steel, that was free from microalloy elements, exhibited an effect of prior hot deformation which was quite different to the Nb-Ti microalloyed steel. In particular, the effect on the hot ductility was not as dramatic. The effects were also postulated to be due to precipitation.
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Chou, Kuo-chin. "Hydrogen diffusion, trapping and crack growth in two low carbon steels with different contents of sulfur /." The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu148758461216328.
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Lundberg, Axel. "Temperature profiles and hardness estimation of laser welded heat affected zone in low carbon steel." Thesis, Malmö högskola, Fakulteten för teknik och samhälle (TS), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-20830.
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Termisk modellring av hårdhet genom beräkning och simulering av den värmepåverkade zonen i en lasersvetsad stålplatta är en omfattande process. Dock är analysen viktig då mikrostrukturella fastransformationer förorsakade av svetsningen kan ge oönskade hårdhetsnivåer av den värmepåverkade zonen jämfört med hårdeheten i basmaterialet. I denna avhandling har analytiska ekvationer implementerats och testats för validitet mot simuleringar gjorda av andra författare och mot experimentella värden.Eftersom termisk modellering av svetsar är ett omfattande område var avhandlingen tvungen att smalnas av för att göra analysen mer fokuserad. Begränsningar gjordes för den matematiska modelleringen genom att endast titta på två-dimensionellt värmeflöde i svetsade plattor där endast den analytiska lösningen är av intresse. Arbetet har också inriktats mot stål då detta material är vida använt över hela världen. Då lasersvetsning är en snabb och kostnadseffektiv process så är hårdhetsanalysen av största vikt. Avhandlingen är uppdelad i tre övergripande delar; den första är att ta fram och förstå arbetet som gjorts inom termisk modellering av svetsar, alltså förstå matematiken bakom problemet. Modelleringen är till för att producera diagram parametrar från en termisk cykel, för att kunna fortgå med korrekt hårdhets analys. För det andra så sätts den matematiska modelleringen på prov i ett antal situationer som var och en simulerar olika förutsättningar. Detta gjordes i ett grafiskt användargränssnitt av ren bekvämlighet. Detta gör att ingenjörer lätt kan implementera olika egenskaper för materialet och få fram diagram och kurvor.Sist, ett liknande grafisk användargränssnitt för att simulera hårdheten i valfri punkt i den värmepåverkade zonen programmerades och därigenom implementerades ekvationerna som denna avhandling handlar om i grund och botten. En teoretisk bakgrund till fasomvandlingen är också inkluderad som förklaring till grundproblemet med oönskad hårdhet i den värmepåverkade zonen i lasersvetsat stål.Huvudslutsatser i avhandlingen:•Matematisk modellering av värmeöverföring i svetsar genomförd av Rosenthal är fortfarande applicerbar på modern lasersvetsningsapparatur. •Den empiriska modellen från Ion et al. (1984) är ej applicerbar med godkänt resultat för hårdhetsuppskattning.•Ekvationerna från Ion (2005) är statistiskt godkända för att simulera hårdhet.•Den analytiska lösningen är överlägsen den numeriska när det gäller snabb och enkel implementering för att simulera termiska cykler och hårdhet, medan den numeriska lösningen kan ta i beaktning mera avancerade egenskaper.•Förvärming av stålet innan svetsning kan vara mycket fördelaktigt för hårdheten i den värme-påverkade zonen, speciellt vid högre kolekvivalent.Thermal modelling of hardness in the heat-affected zone (HAZ) in a laser welded steel plate is a cumbersome process both in calculation and simulation. The analysis is however important as the microstructural phase transformations induced by welding may cause unwanted hardness levels in the HAZ compared with that of the parent material. In this thesis analytical equations have been implemented and checked for validity against simulations made by other authors and against experimental values.With such a large field as thermal modelling, the thesis had to be narrowed down to make the analysis more subject focused. Limitations made were for mathematical modelling only looking at a two-dimensional heat flow in welded plates; in this thesis only the analytical solution to the heat flow is considered. The work was also directed towards steel; such a material as used largely all over the globe. As laser welding is a fast and cost-effective process, an analysis of hardness is of great importance. Work was divided into three overlapping parts; the first was to derive and understand the work done in the field of thermal modelling of welds, thus understanding the mathematics behind the basic problem. This modelling provides a number of curves and parameters from a thermal cycle, thus enabling one to do the hardness analysis correctly. Secondly, this mathematical modelling was applied to a number of cases, simulating different circumstances. This was done using self-programmed Graphical User Interfaces (GUI) for convenience. This enables engineers to easily plug in the materials and processing properties and thus simulate the required parameters and curves for further analysis.Lastly, a GUI for simulating the hardness of any point in the HAZ was programmed and used, thus implementing and validating the equations. A theoretical introduction of the phases induced in the HAZ is also included, in order of understanding the problems of unwanted hardness in the HAZ of laser-welded steel.Main conclusions of this thesis:•Mathematical modelling of heat transfer in welds by Rosenthal (1946) is still applicable for modern laser welding apparatus.•The empirical model presented by Ion et al. (1984) is not applicable with experimental results of hardness in the HAZ of the steels investigated here.•Equations by Ion (2005) are accurate for simulating the hardness.•The analytical solutions investigated are superior to numerical solutions with regard to quick, simple simulations of thermal cycles and hardness. Numerical solutions allows for more advanced modelling, which can be lengthy.•Preheating the steel prior to welding is favourable in reducing hardness levels, especially with steel of higher carbon equivalent.
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Chinthala, Sai Prasanna Prasanna. "Study of Corrosion Inhibitors for Reinforcement Corrosion of Low Carbon Steel in Simulated Pore Solution." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1555601685519345.
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Tang, Zhenghua. "Optimising the transformation and yield to ultimate strength ration of Nb-Ti micro-alloyed low carbon line pipe steels through alloy and microstructural control." Pretoria : [s.n.], 2006. http://upetd.up.ac.za/thesis/available/etd-07212007-110711.
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Wu, Hou-Chen. "A study of the susceptibility to stress corrosion cracking of AISI 1018 carbon steel under low NO 2-air aqueous environment." Ohio : Ohio University, 1992. http://www.ohiolink.edu/etd/view.cgi?ohiou1173277576.
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Hutchings, C. L. "Weld nugget growth when resistance spot welding two and three thickness uncoated low carbon steel sheets." Thesis, Swansea University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637360.
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The majority of spot welds in a wide range of sheet metal products e.g. automotive body in white structures and general engineering applications involve the joining of two or more dissimilar sheet thickness. Research to date has concentrated on the welding of two similar thicknesses. Work was therefore carried out to determine the differences in the heat patterns developed in two and three thickness welding and the effect on initial melting and weld nugget growth. Metallographic examination of partially completed welds, temperature profiles determined using thermal imaging techniques and measurement of the dynamic resistance at the electrode-sheet and sheet-sheet interfaces were used for this purpose. In addition, an FE model of the process has been developed to study the effect of contact characteristics and temperature dependent material properties on weld formation. The heat produced from the electrode-sheet and sheet-sheet interfaces as a result of current flow is conducted into the bulk of the material being welded leading to the thermal runaway cycle of increasing temperature/resistivity which aids the development of a weld nugget. This effect is considered essential to the process. Whilst the above accounts for heat generation, the end result in terms of weld nugget geometry can be markedly influenced by the extent of heat abstraction through the water-cooled electrodes and along the sheet thickness. The cooling effect can be the determining factor whether a weld nugget is formed. The results presented in this thesis indicate that cooling effects need to be given greater emphasis when developing a model to account for all the various factors of weld growth than has been given in the past.
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Amey, Stephen Leonard. "The determination/control of hydrogen behavior in low carbon steel as a function of surface treatment." Case Western Reserve University School of Graduate Studies / OhioLINK, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=case1060195239.
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Sanchez, Camacho Lizeth J. ""Effect of AC interference on the corrosion cracking susceptibility of low carbon steel under cathodic protection."." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1531157966071788.
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Siyasiya, Charles W. "Effect of sulphur content on the recrystallisation behaviour of cold worked low carbon aluminium-killed strip steels." 2007. http://upetd.up.ac.za/thesis/available/etd-04302008-160842.
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Siyasiya, Charles Witness. "Effect of sulphur content on the recrystallisation behaviour of cold worked low carbon aluminium-killed strip steels." Thesis, 2007. http://hdl.handle.net/2263/24240.
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Huang, Bo-Ming, and 黃柏銘. "Effect of Mo addition on the development of microstructure in Nb Containing Low Carbon Bainitic Hot Rolled Steel Strips." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/34194340895258958554.
Full textAbstract:
博士國立臺灣大學
材料科學與工程學研究所
102
In related research, Mo element was shown to effectively enhance precipitation strengthening via nanometer-sized carbides and retard the recovery of dislocations in Nb-containing low-carbon bainitic fire-resistant steel. It is of some interest to apply the concept to another steel product, hot-rolled strips. In addition, the present study investigated the effects of adding Mo on interphase precipitation in ferritic hot-rolled strips to promote precipitation strengthening. After the comparison of the effects of Mo on the two types of hot-rolled strips, it was possible to determine whether the addition of Mo is beneficial to bainitic hot-rolled strips. The composition was primarily designed to be 0.05C-1.7Mn-0.08Nb (wt% based composition) with 0 and 0.1 wt% Mo, separately labeled Nb and Nb-Mo strips. In the practical hot-rolling process, the residual strain in prior austenite grains inevitably promotes greater transformation of ferrite, so in the present study, it was necessary to reduce the coiling temperature and accelerate the cooling rate so as to prevent the formation of a fully ferrite structure in present study. The coiling temperatures (C.T.) in the hot rolling process in this study were 450oC and 550oC. Observations of the microstructure revealed that C.T. 450oC and Mo both efficiently suppressed the ferrite transformation and promoted the granular bainite structure in bainitic hot-rolled strips. Then during the simulated coiling procedure, tempering treatment at 600oC, the strips with granular bainite demonstrated a significant secondary hardening effect. Elevating the coiling temperature to 650oC produced a fully ferrite structure with interphase precipitation in the hot-rolled strips. The strips achieved the same strength as the strips with the secondary hardening effect. However, the addition of 0.1 wt% Mo did not improve the precipitation strengthening by interphase precipitation and induced more unstable second phases in the coiling procedure in Nb-Mo strips with C.T. 650o C. From the above, it is concluded that Mo alloy has a positive effect on Nb-containing low-carbon bainitic strips. In order to increase the volume fraction of bainite and enhance the secondary hardening effect, the concentration of Mo in Nb-Mo strip with C.T. 450oC was increased to 0.3wt%, labeled the Nb-3Mo strip. In the microstructure, the morphology of bainite was the same as that of granular bainite, and the amount seems to increase with the greater addition of Mo. In further analysis to quantitate granular bainite, the electron backscattering diffraction technique was used to feature the unique misorientation gradient in granular bainite because scanning electron microscopy was unable to distinguish ferrite from granular bainite due to their similar morphologies. In the phase qualification of three hot-rolled strips with C.T. 450oC, it was surprising to find that only the high addition of Mo, 0.3wt%, effectively increased the volume fraction of granular bainite. Further dilatometry experiments led to the conclusion that the formation of ferrite must have been prohibited, allowing more prior austenite regions and the grain boundaries in the promotion of granular bainite. During tempering treatment, the high addition of Mo rarely promoted the secondary hardening effect of tempered granular bainite in Nb-3Mo strip. To determine the reason, Electron Energy Loss Spectroscopy (EELS), high resolution TEM (HR TEM), Energy dispersive X-ray spectroscopy (EDX), and atom probe tomography (APT) were used to investigate the effect of Mo solute on nanometer carbides and the dislocation structures in tempered bainite. Measurements of dislocation density revealed that no obvious recovery occurred in the three strips. It is probable that, unlike in the high temperature tensile test, the slipping of dislocation lines was slight in the current tempering treatment lacking external stress. Thus, the Mo solute could not retard the movement of static dislocation lines in granular bainite during tempering. In the evolution of nanometer carbides in tempered bainite with increasing Mo, Mo solute was homogeneously dissolved in (Nb,Mo) carbides in tempered bainite. Furthermore, the Mo solute became a significant carbide-forming element, and the carbides were slightly coarsened by absorption of excess Mo solute. In the reports on fire-resistant steel, the carbon replica method allowed confusion of the nanometer carbides in tempered bainite with strain-induced Nb carbides in prior austenite. This confusion is likely to have caused misunderstanding of the refinement of nanometer carbides by the addition of Mo in tempered bainite . In the present study, HR TEM images were used to focus on the nanometer carbides and statistically analyze their sizes during tempering because the featured Baker-Nutting orientation relationship between carbides and matrix could be recognized accurately with the technique. In addition, the signal of Mo occurred in strain-induced Nb carbides after tempering. It was concluded that Nb and Mo solute segregated toward the strain-induced Nb carbides and then formed a layer of carbides on the surface. It is likely that in previous research, segregation of Mo solute was believed to occur in the nanometer carbides in tempered bainite because the two types of carbides could not be resolved. Therefore, in the present study, it was necessary to dispel the fallacy that the addition of Mo can promote precipitation strengthening via nanometer carbides in tempered bainite in steels. Mo alloy strengthens the Nb-containing low-carbon bainitic hot-rolled strips by increasing the hardenability, rather than by a synergistic effect of Nb and Mo.
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Chao, Tien-Ming, and 趙天明. "Heat Treatment of Electroless Nickel Plated Low Carbon Steel." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/gb267a.
Full textAbstract:
碩士逢甲大學
材料與製造工程所
91
Low carbon steel was plated with Ni-P alloy by using the solution containing sodium hypophosphite as reducing agent. The amount of phosphorous in deposit was varied with pH values of plating solution. Different time and temperature of heat treatment (650, 700, 750℃ / 2 hr,800℃ / 1, 2, 3, 4 hr) under the argon atmosphere were performed. The phase transformation, surface morphology, and the elemental distribution were investigated by XRD, SEM, and EPMA. The behavior of diffusion mechanism between low carbon steel matrix and coating layer was examined in this study. In addition, electrochemical analysis and salt spray testing were used to study the variation of anti-corrosion properties of the as-plated and heat-treated deposits. The as-plated deposit by acid bath was amorphous, where as crystalline structure with Ni (111) was obtained by alkaline bath. A diffusion layer about 3.5 ~ 8.4μm was formed at the interface between coating layer and substrate during heat treatment. A transition from grain-boundary diffusion to volume diffusion was found with in the temperature range between 740 ℃and 755℃. According to results of linear polarization analysis, corrosion resistance of heat-treated sample under argon or atmosphere was studied. It shows that heat treatment at 700℃/ 2 hr is the optimal condition for plated sample with the best corrosion polarization . A diffusion layer can separate pitting in salt spray 600hr.
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Bau-MingSu and 蘇保鳴. "Modeling Phase Transformation in Hot Rolled Low Carbon Steel." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/88203810772786159899.
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