Dissertations / Theses on the topic 'Tréfilage'
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Lamontagne, Aude. "Etude des mécanismes physiques responsables des évolutions microstructurales des aciers perlitiques au cours du tréfilage et du vieillissement post-tréfilage." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0109/document.
Full textSteelcords are produced by assembling cold-drawn pearlitic steel wires with a composition close to the eutectoid one. The cold-drawing step has two goals: it provides the final shape of the wire and its very high mechanical resistance (about 3500 MPa for wires with a diameter of 200 µm). Nowadays, the industrial target aims at achieving a mechanical resistance of about 5000 MPa in order to lower the quantity of steelcord introduced into tires so decreasing their weight and their cost. However, there are two major obstacles to obtaining these ultra-high strength wires. Indeed, the steel reinforcement during cold-drawing induces significant microstructural and mechanical evolutions, which embrittle the wires. This phenomenon is considered as the limit of drawability beyond which wires cannot be plastically deformed anymore. In addition to that, post-drawing ageing can also induce a microstructural evolution and a loss of ductility due to storage at room temperature or during heat treatments at low temperatures (< 200°C). This instability of the wires microstructure can be very damaging for the assembly step leading to wire breakage. The aim of this work was to contribute to the assessment of the microstructural evolution responsible for the variations of mechanical properties that appear during drawing and post-drawing ageing. To achieve this goal, an original experimental approach combining global and indirect characterization techniques (thermoelectric power, electrical resistivity, mechanical spectroscopy, calorimetry…) with Atom Probe Tomography analyses has been set up in order to provide a range of evidences that converge towards a unique scenario to interpret the different microstructural evolution. It was thus shown that cold-drawing leads to cementite dissolution inducing over saturation of ferrite in carbon atoms. This non-equilibrium microstructure tends to return to a more stable state during post-drawing ageing through three different ageing mechanisms: the segregation of carbon atoms on microstructural defects, the precipitation of secondary carbides and their transformation in cementite
Morisot, Pierre. "Elaboration et étude de l'usure de filières en métal dur WC-Co : application au tréfilage." Dijon, 2009. http://www.theses.fr/2009DIJOS036.
Full textChevalier, Luc. "Etude des caractéristiques des matériaux tréfiles après l'opération de tréfilage." Paris 6, 1988. http://www.theses.fr/1988PA066145.
Full textBouré, Philippe. "Lubrification et usure du contact fil/outil en tréfilage humide." Ecully, Ecole centrale de Lyon, 1999. http://www.theses.fr/1999ECDL0047.
Full textFor the past ten years, the use of high tensile steel and the productivity requirements have les respectively to an increase in pressure and speeds in the drawing process of steelcord. The control of both lubrication and wear of the wire/die contact is a key point for the process optimisation. This study deals with built-up of the interfacial lubricating film in this high pressure contact lubricated with an emulsion. The rheological behaviour and the wetting properties of the lubricant in the inlet zone of the wire/die contact are important parameters. The inlet zone, where the lubrication regime is elastohydrodynamic, governs the formation of the lubricating film and the lubricant supply of the contact. The knowledge of the lubricant behaviour in this inlet zone is crucial to understand the lubrication in the drawing process of steelcord. This has been experimentally investigated with an EHL tribometer and chemical analyses of the lubricant film. It has been shown that a change in the physical structure of the lubricant due to ageing is a necessary condition to build-up a lubricant film. A model based on the analysis of the starvation process has been developed to evaluate the rheaological properties of the lubricant film formed on the contacting bodies. The adherence and slippage at the wall of the lubricating film is explained by electrical interactions between the metallic surfaces and lubricant particles. Both formation and breakage of the lubricating film are connected with the industrial process. The wear of the drawing die is studied in details with an instrumented drawing machine especially developed for this purpose. This study demonstrates that the interactions between the transfert layers observed on the surface of the drawing dies and the lubrication process. In the first step of the process, the lubrication regime appears to be essentially plastohydrodynamic. As the running conditions become more and more severe in the last steps of the process, a boundary regime is reached. Finally, hypothesis based on the different observations pointed out in this study are proposed to explain the wear mechanisms
Morgado, Norbert. "Tréfilage à chaud de l'aluminium 6060 : nouvelle méthodologie d'identification du comportement tribologique." Valenciennes, 2003. http://ged.univ-valenciennes.fr/nuxeo/site/esupversions/38039928-2561-413f-987a-d3f0fe90893f.
Full textThe proposed study is based on the specific hot wire drawing process of aluminium. This process is thermomechanically analysed in order to point out the importance of interface parameters in the process control. The main parameters are the friction coefficient and the heat transfer coefficient. A new test device is developed to evaluate them. This test is made of a heating induction system and a servo-hydraulic system. It allows to reproduce accurately the thermomechanical contact conditions observed in hot metal forming. A multi level methodology, using exploitation of test device results, is presented. It allows to optimize the process, to identify friction conditions, to analyse surface damages (sticking) or to estimate tribological laws
Krummeich, Raphaëlle. "Contribution micromécanique au comportement multi-échelles d'un matériau composite élastoplastique lamellaire : Application à l'étude des effets du recyclage sur la tréfilabilité d'un acier perlitique industriel." Metz, 2001. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/2001/Krummeich.Raphaelle.SMZ0140.pdf.
Full textPearlitic steel cords may reach a tensile strength up to 4 GPa and still exhibit some ductility. This unusual property (close to wiskers strength) is related to the process of cold drawing which reduces the size λ [lambda] of the lamellar substructure, in proportion to the wire diameter (Embury's similitude principle) and induces the formation of crystalline and morphological textures : the single crystal lamellae behave elastoplastically. Usually, the draw hardening is theoretically explained in terms of the combination of a macroscopic Hall-Petch law in λ [exposant] -½ , with the similitude principle applied to wire drawing. In the case studied, the initial size of the substructure (some 10 nm) does not allow a dislocation's pile-up mechanism. However, the experimental draw hardening exhhibit a slope (In(Rm) = k ∈drawing) with k=1/4, which is consitent with a macroscopic Hall-Petch law of type kH. P. λ -½. Using a scale transition method based on a non pile-up model for dislocations, the theory proposed here aimed to model the draw hardening of lamellar pearlitic steel. The reduction of the dislocation's mean free path in proportion to the lamellar spacing λ is the main factor studied here, taking no account of the cristalline textures developped during wire drawing. This simple method for calculating the draw hardening curve results in a slope of value ¼ , which is the experimental one's. Thus, a draw hardening slope of 1/4 does not mean a dislocation's pile-up mechanism at the microscale. In other words, the averaging process used to relate the macroscopic strength to the size and the history evolution of the microstructure needs refinements as proposed in this model
Schuman, Christophe. "Etude de l'évolution de la texture cristallographique d'acier extra-doux au cours du tréfilage et d'une opération particulière de laminage : détermination des contraintes internes." Metz, 1994. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/1994/Schuman.Christophe.SMZ941.pdf.
Full textThe aim of yhis work is to determine the influence which the texture of the material in the case of the IFS and Al-killed steels may have on the drawability limit according to different drawing and metallurgical conditions. A study of the texture during a specific cold rolled process has also been carried out to compare the obtained textures with two different deformation processes. Since any plastic deformation introduces residual stresses in the material, it was necessary to quantify them in order to predict the in-use behaviour of the material. These residual stresses by means of X-ray diffraction have been determined by taking the crystallographic texture into account
Massé, Thomas. "Study and optimization of a high carbon steel flat wires." Paris, ENMP, 2010. http://www.theses.fr/2010ENMP1672.
Full textThis thesis deals with the numerical simulation of cold forming processes, i. E. Wire drawing and rolling. First, high carbon steel mechanical behaviour was measured from experiments throughout this range of steel forming and a progressive mechanical anisotropy has been observed during drawing. Secondly, numerical simulations, with FORGE2005®, have been run to simulate the material behaviour during wire drawing and rolling. The main results show that the widening prediction, with an isotropic behaviour law, is not accurate with an underestimation of 10% on the total width. This underestimation is only 5% when an anisotropic behaviour is used. Then, a microstructural study coupled with an analysis of damage mechanisms was done on high carbon pearlitic steels during wire drawing and rolling. The mechanical anisotropy comes from the orientation of the pearlitic colonies in the drawing, and by the emergence of a preferential crystallographic texture. Three damage mechanisms have been identified during drawing. During rolling, damage expansion kinetics are changed because of heterogeneous strain. Simulation enabled to bring further information and to validate previous experimental observations. Finally, drawing optimization calculations have been performed and enabled to study the sensitivity of the cost functions (damage and drawing force) to optimization parameters (drawing die geometry). Moreover this study highlighted that optimal solution depends on the choice of the cost function and identified an opportunity to reduce damage by reducing the die angle without increasing the axial stresses and the fracture risk
Montesin, Tony. "Influence des conditions de tréfilage sur la texture cristallographique et sur les propriétés mécaniques des fils fins : application au steelcord." Metz, 1991. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/1991/Montesin.Tony.SMZ9122.pdf.
Full textThe steelcord is a steel wire drawn until 0,2 mm which is used in the tire manufacturing. In this study the cristallographic texture evolution is determined across the wire diameter by X ray diffraction. This determination needs intensity corrections due to X ray absorption and irradiated volume variations occuring during the movement of the sample. Thr corrections are computed for a set of adjoining wires and are usable for any sample having this geometry. The texture determination of steelcord with the use of these corrections show two kinds of fiber texture in the wire : one is "classical", the other is "circular" or "cyclic". A texture index Ti is defined to describe the texture evolution across the diameter. This index gives the texture sharpness of the wire with respect to an isotropic one. The study of the texture index evolution according to the drawing process conditions is done. This can had to undertake new improvements of the process and to envisage the possibility of an increasing of the wire drawability
Farget, Claude. "Etude et réalisation d'un banc pré-industriel de fabrication de coupleurs à fibres par fusion-étirage." Saint-Etienne, 1997. http://www.theses.fr/1997STET4014.
Full textGenin, Christelle. "Optimisation de systèmes colloïdaux en phase aqueuse pour la lubrification en conditions extrêmes : application au tréfilage." Ecully, Ecole centrale de Lyon, 2007. http://bibli.ec-lyon.fr/exl-doc/cgenin.pdf.
Full textWater based lubricants are widely used in metal forming process, particularly during drawing process because they combine good cooling and lubrication capabilities. Wet drawing is a key step in steelcord manufacturing. Lubrication must ensure good mechanical properties of the steelcord, brass coated steel wires composing the casing of radial tires. The will to improve the productivity of the metal working hardest materials leads to increase loads and drawing speed. So, the development of a new range of lubricant is necessary. This study focuses on the behaviour of aqueous wax dispersions under extreme conditions. The efficiency of fluids, containing only wax particles dispersed in water by a surfactant has been proved and was confirmed in industrial conditions. The experimental simulation of wire drawing process on an EHD tribometer, completed with surfaces analyses, shows that particles adhere to surfaces and ensures film formation only by simple adsorption without any tribochemical reactions. Thanks to all this observations, a lubrication mechanism has been established : A monolayer of surfactant appears quasi instantaneously and is progressively replaced by particles which enter in the contact. A lubricating film was gradually created by particles that are crushed under pressure contact. Particles nature seems to determine the capacities of wax dispersion to form a shear resistant film. EGDS wax particles are more efficient than EBS wax particles, may be because interactions generated by EGDS particles are stronger. This work constitutes a first step in the development of a new range of water based lubricant containing EGDS wax particles
Vega, Guillaume. "Optimisation de la mise en forme par tréfilage : approche expérimentale, modélisation et simulation numérique." Thesis, Lille 1, 2009. http://www.theses.fr/2009LIL10173/document.
Full textThe aim of this thesis work is to optimize the process of forming by wiredrawing, using an experimental approach, an analytical modeling and a numerical simulation by finite elements. This study is to analyze the mechanisms of deformation and damage, being involved in this process, which is a multi complex physical problem. This complexity is reflected by the influence of many intrinsic and extrinsic parameters on the properties of materials drawability. A parametric analysis of the drawing process has shown that different parameters and their mutual interactions have significant effects on the drawing stress during the plastic deformation process, taking into account the tool geometry and the hardening of the drawn material. The effects of temperature in the die and the strain rate on the coefficient of friction at the interface wire-die have been taken into account in the analytical formulations. The numerical simulation of a copper wiredrawing was done based on modeling using a behavior law for material taking account the hardening and the strain rate dependence, and validated by experimental results. Contact problems, the thermo mechanical effects were taken into account in these calculations. A coupled damage model based on an energy criterion is used to predict the location and the shape of defects in a wire deformed by critical conditions of drawing. The results have validated using experimental data and microscopie observations of damage in the central part of the wire and the die wear
Abdellaoui, Abdellatif. "Etude de la texture cristallographique de fils d'acier perlitiques en fonction des conditions de tréfilage : influence sur les propriétés mécaniques." Metz, 1995. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/1995/Abdellaoui.Abdellatif.SMZ9543.pdf.
Full textThe crystallographic texture of the wires evolves during the process as the strength of the wire ; this paraameter allows us to know the local deformation in the wire and helps us in the knowledge of the drawing. Texture experiments and mechanical tests on wire picked up at different steps of the industrial drawing process show that there is an heterogeneity of the deformation during the drawing ; this heterogeneity is studied during the deformation of the wire and a limit of drawability can be proposed from the texture indexes of the wire. Laboratory and industrial experiments on the friction between the wire and the dies show the importance of the lubrication on the homogeneity of the deformation. Patenting conditions are studied to improve the drawability. During the drawing, two kinds of texture are observed : a fiber texture <110> and a circular texture <110> (110). Experiments according to the dies angles show their influence on the circular texture and on the torsional behaviour of the wires. Some simulations of the texture evolution are made with the use of the Taylor model
Levrau, Carole. "Compréhension et modélisation des mécanismes de lubrification lors du tréfilage des aciers inoxydables avec des savons secs." Phd thesis, École Nationale Supérieure des Mines de Paris, 2006. http://pastel.archives-ouvertes.fr/pastel-00002049.
Full textHollinger, Sébastien. "Comportement d'un lubrifiant aqueux dans un contact à très hautes pressions : application au tréfilage de fils d'acier laitonnés." Ecully, Ecole centrale de Lyon, 1999. http://www.theses.fr/1999ECDL0054.
Full textThis work presents an analysis of the lubrication mechanisms of a tungsten carbide/brass sliding contact, lubricated by a water-based emulsion, under very high pressure conditions. An original mechanism of materials autoadaptation associated with the formation of a protective film bearing the shear stress was put forward. This protective layer, called servocite, is composed of an anchoring layer, formed on the brass surface, and of an organic film supporting the shear stress. The friction of brass leads to a preferential extraction of zinc and to a copper enrichment of the surface, easily recognisable. This electrochemical effect, coupled with tribochemical reaction is responsible for the formation of a protective zinc phosphate layer on the extreme surface. This extreme pressure film acts as an anchoring layer for the organic film. The charecteristics of this organic film are highly dependent upon the nature of the lubricant. Two types of water-based emulsions (>95%) co,posed of surfactant aggregates are studied. Vesicular aggregates emulsions can form protective films resistant to high pressures up to 1GPa. The generation of divalent metallic ions, due to brass electrochemical erosion, induces a transformation, called ageing, of vesicles into crystallites characterised by a lamellar structure. Lamellar crystallites solutions form lubricating films that can bear contact pressures up to 1. 5GPa and maintain a low friction coefficient value. These properties are due to the lamellar structure which is more compact and has a favourable low friction plane. Moreover, because of their planar shape and hogh elasticity, the crystallites bring an additional bearing and thus create thicker films compared to vesicles. Friction experiments were performed on a Falex tribometer at variable pressures, up to brass hardness, and using a constant sliding speed. The industrial subject of this work is the understanding of the lubrication mechanisms encountered in the multipass drawing process of brass coated steel wires, composing the metallic casing of the radial ply tires. In this situation, the interface considered is made of the wire and the tungsten carbide conical die. The phenomenon observed on the Falex machine can be transposed to the lubrification of the first drawing dies. On the other hand, the friction in the last dies can not be fully explained due to the choice of a constant experimental sliding speed. In the last passes the thermal effects can not be neglected any futher because of high sliding speeds. A shift of the shear plane from the organic film to the brass layer is assumed for this case. This work resulted in the development of a new lubricant reducing die wear
Denker, Ulrike. "Influence du type de recuit industriel sur la recristallisation de fils en acier extra-doux tréfilé à froid." Metz, 1995. http://www.theses.fr/1995METZ042S.
Full textTow low carbon steels (<0,03% c) for thin wire drawing have been studied during the intermediate process of industrial heat treatment with a view to replacing the long heat carried out in a bell jar furnace by the short continuous on-line heat treatment. The short heat treatment process (under industrial test conditions) was found to produce wires with high yield strength and elastic limits as well as a very low elongation before necking which is considered as being a disadvantage in thin wire drawing. Some short heat treatment cycles simulated in the research laboratory showed the local formation of an austenite in the grain boundaries (high carbon content). When quenching, the partial austenite precipitation may lead to the formation of martensite. The influence of ageing on the mechanical characteristics (Rm, Ag) needs also to be mentioned. When studying microstructure of longitudindale sections in the hard drawn state, two types of grains could be seen : "light" grains and "dark" grains (this had already been observed in the sheets). The surface of the "light" grains is smooth whereas that of the dark grains is rough. The microhardness of the "dark" grains is higher and their reformation is faster than that of the "light" grains. EBSP measurements carried out on a wire, which has been bored in its centre before being "unrolled" (orthorhombic symmetry) have evidenced that both types of grains have different orientations. The "dark" grains have the (111) <110>, (112) <110> et (123)<110> main orientations, whereas the "light" grains have the (001)<110> orientations. Moreover, by calculating the Schmid ratio for the main gliding systems of bcc materials, when the <111>, <112>, <123> ou <001> directions are parallel to the normal direction that is to say, parallel to the maximum stress applied, the following indications could be observed : the orientation factors for the "light" grains are all high, those of the "dark" grains are numerous but have weaker values
Languillaume, Jacques. "Microstructure d'un acier perlitique fortement déformé par tréfilage : évolution avec les traitements thermiques et influence sur la résistance mécanique." Grenoble INPG, 1995. http://www.theses.fr/1995INPG0155.
Full textPhelippeau, Antoine. "Etude expérimentale du rôle de la microstructure et du vieillissement sur les propriétés mécaniques des aciers perlitiques fortement tréfilés." Châtenay-Malabry, Ecole centrale de Paris, 2003. http://www.theses.fr/2003ECAP0928.
Full textThe aim of this study was to contribute to the understanding of both the plasticity mechanisms and the post-drawing ageing phenomenon of heavily drawn pearlitic steel wires which tensile strength is commonly higher than 3000 MPa. The first part, dedicated to a multi-scale experimental study of the mechanical properties of heavily drawn wires ( =3. 5), shows that more than half of the tensile strain hardening is due to kinematic hardening. The latter is would be related to the internal stresses caused by the plastic strain heterogeneities between ex-pearlitic colonies, according to observations at micro- and nanometric scales. Some results lead to the hypothesis of a "pseudo-martensitic" lattice formation due to the combined effect of the deformation and cementite dissolution in the die. Well-known mechanisms involved during martensite tempering have been considered but no evidence of such mechanisms is observed
Massé, Thomas. "Etude et optimisation d'une gamme de mise en forme à froid en acier haut carbone." Phd thesis, École Nationale Supérieure des Mines de Paris, 2010. http://tel.archives-ouvertes.fr/tel-00457046.
Full textSauvage, Xavier. "Transformations de phases induites par déformation plastique intense. Cas des aciers perlitiques tréfilés et des nanocomposites filamentaires Cu/Nb." Rouen, 2001. http://www.theses.fr/2001ROUES032.
Full textBelhadj, Ahmed. "Procédés de fabrication, microstructure et propriétés supraconductrices des alliages Nb-Ti." Lille 1, 1999. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/1999/50376-1999-265.pdf.
Full textTardieu, Simon. "Fils conducteurs composites (microfils d'argent - cuivre) pour application en champs magnétiques intenses." Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30186.
Full textLNCMI-Toulouse produces some of the most intense non-destructive pulsed magnetic fields in the world (98.8 T). The wires used in coils which generate these magnetic fields require high ultimate tensile strength (UTS) in order to resist the Lorentz forces. Moreover, to obtain the longest possible pulse duration, these wires must have an electrical resistivity closest to that of pure Cu. LNCMI and CIRIMAT explore the design and preparation of Cu-based nanocomposite wires obtained by a combination of powder metallurgy, Spark Plasma Sintering (SPS) and wire-drawing. Composite powders with low Ag contents (< 10 % vol. Ag) are prepared by dispersing Ag microwires (diameter 200 nm, length 30 µm) synthesized at CIRIMAT in a commercial spherical Cu powder (diameter 0.5-1 µm). The so-obtained composite powders are consolidated by SPS in the form of cylinders. These cylinders are drawn, without breaking, in the form of fine wires (1 - 0.2 mm). The microstructure of the wires is made up of Cu ultrafine grains (200 - 400 nm) elongated over several micrometers in the drawing direction. Ag microwires are dispersed along the grain boundaries of Cu. The measurement of the electrical resistivity and the UTS of the wires (at 293 K and 77 K) shows that the wires containing only 1 vol. % Ag present the best compromise between high UTS and low electrical resistivity (1100 MPa / 0.49 µÔmega.cm at 77 K). The formation of Cu/Ag alloys during the SPS cycle significantly increases the resistivity of the wires and thus must be avoided. A Cu matrix with a bimodal grain size distribution makes it possible to reduce the electrical resistivity of the wires while keeping high UTS (1080 MPa / 0.45 µÔmega.cm at 77 K). Ag-Cu nanocomposite wires present high UTS, equivalent to that of Cu/Ag alloy wires containing about 20 times more Ag produced by melting and solidification, but their electrical resistivity is about 1.5 times lower
Yama, Nzoma Evarice. "Elaboration par Déformation Plastique Intense et Caractérisatioin de Composites Multifilamentaires nanostructurés Cuivre-Carbone." Rouen, 2009. http://www.theses.fr/2009ROUES052.
Full textThe nanostructuring by severe plastic deformation has a clear interest in the development of nanomaterials. Our work contributes to the development of bimetallic multifilamentary materials, where structural dimensions are of the order of the micron or nanometer. The production process based on the so-called "Levi process" developed in the sixties, consists in a serie of steps that include a cold drawing, bundling of drawn materials, then re-stacking of these elements, followed by another cold drawing. Two materials : Cu-CGr and Cu-C60, were developed. The result is a material with a multifilamentary and multiscale microstructure with properties that combine a high yield stress, good electrical conductivity and low thermal expansion coefficient. In, this system, the properties of composites do not follow the "linear law of mixtures" due to the microstructure of the composites
El, Maana Sana. "Elaboration des composites Cuivre-Nanotubes de carbone (Cu-CNT) par métallurgie liquide pour des applications électriques." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMR145.
Full textCopper (Cu) is the most widely used metal in wire conductors, as its electrical conductivity exceeds that of other metals except silver. Interestingly, carbon nanotubes (CNT) show higher electrical conductivity than metals. Thus, a composite based on these two materials appears to be a good candidate for the manufacture of wire conductors with very good electrical conductivity and high ampacity. In order to optimize the final electrical and mechanical properties of such a composite, several criteria must be considered. Some of these criteria are related to the quality and purity of nanotubes and the matrix. Others depend on the composite processing, influencing the dispersion of CNTs in the matrix, the interface Cu/CNT quality, and nanotubes orientation in the wire. In this work, we adopt several strategies to produce Cu-CNT composites by liquid metallurgy satisfying, at best, those criteria. In order to improve the dispersion of CNTs in the matrix, in addition to the optimization of the elaboration process (liquid metallurgy), we test different techniques to introduce CNTs during composites manufacturing. We also add elements such as chromium and tin to improve the quality of the Cu/CNT interface. Thus, three types of composites (Cu-CNT, Cu-Cr-CNT, Cu-Sn-CNT) are produced by liquid metallurgy and subsequently drawn. A study of the dispersion of CNTs in the composites at different scales is carried out using Optical Microscopy (OM), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM) techniques. The results reveal micrometric clusters of nanotubes in both raw cast and drawn states. TEM observations carried out on Cu-Cr-CNT composites allow the identification of the isolated CNTs in the matrix, whereas chromium carbides were not observed. For the Cu-Sn-CNT composite, in addition to clusters, TEM observations also reveal individual CNTs at fine scales. Importantly, the previously deposited tin on CNTs is totally diffused in the matrix during the composite manufacturing. Moreover, Raman investigations carried out on Cu-CNT and Cu-Sn-CNT composites, allow the identification of CNTs and don't reveals any degradation of CNTs by the manufacturing process. Electrical conductivity and mechanical properties are evaluated for all composites. There is no significant degradation of electrical conductivity by the addition of CNTs in copper. Thus, Cu-Cr-CNT and Cu-Sn-CNT composites have lower electrical conductivities. It is also important to mention that composites (Cu-CNT) also have higher thermal stability comparing to pure copper. Finally, tensile tests reveal that carbon nanotubes reduce the ductility of the composites but allow a slight increase in their yield strength
Godon, Julie. "Influence of steel cleanliness on the wire drawing of hypereutectoid steel fine filaments." Thesis, Lille 1, 2020. http://www.theses.fr/2020LIL1R005.
Full textThe production of very fine filaments (60 µm in diameter) of high carbon and high strength steels remains atechnological challenge. Indeed, during the drawing of these filaments, fractures have been observed limiting theobtaining of coils of great length. This study, in collaboration with company BEKAERT NV, is to understand therole of the microstructure of steel, and more specifically the steel cleanliness on the occurrence of fracture duringwet drawing.Methodologies for inclusion identification and for inclusion count were developed. 90 % of the fractured filamentswere associated with an inclusion which was SiO2, or SiO2-CaO or SiO2-MgO. The fracture of the wires resultedfrom debonding of the inclusion from the matrix. Inclusions exhibited a wide range of sizes but mostly around6µm. The inclusion density did not appear as the only parameter that affects the fracture occurrence. An importanteffect of size and of chemical composition inclusion of the inclusions was found. A critical size of inclusions forfracture was observed but it depends on the chemical composition of inclusions. The drawing parameters also playan important role in the fracture occurrence. The wire mechanical properties and the die angle appears to beimportant parameters in view to reduce the fracture ratio.A deeper analysis of the microstructural changes around the inclusion by EBSD and modelling underlines a realimpact of the inclusion on the local deformation around the inclusion. The local analysis (TEM and ACOM -Automated Crystal Orientation Mapping) of inclusion/matrix interface shows a difference of microstructure at theinclusion edge along the drawing axis and a higher local deformation. The study of these different parametersmakes possible to propose a fracture mechanism that takes into account the part of the material subjected to shearand the one subjected to tensile stress
Godon, Julie. "Influence of steel cleanliness on the wire drawing of hypereutectoid steel fine filaments." Electronic Thesis or Diss., Université de Lille (2018-2021), 2020. http://www.theses.fr/2020LILUR005.
Full textThe production of very fine filaments (60 µm in diameter) of high carbon and high strength steels remains atechnological challenge. Indeed, during the drawing of these filaments, fractures have been observed limiting theobtaining of coils of great length. This study, in collaboration with company BEKAERT NV, is to understand therole of the microstructure of steel, and more specifically the steel cleanliness on the occurrence of fracture duringwet drawing.Methodologies for inclusion identification and for inclusion count were developed. 90 % of the fractured filamentswere associated with an inclusion which was SiO2, or SiO2-CaO or SiO2-MgO. The fracture of the wires resultedfrom debonding of the inclusion from the matrix. Inclusions exhibited a wide range of sizes but mostly around6µm. The inclusion density did not appear as the only parameter that affects the fracture occurrence. An importanteffect of size and of chemical composition inclusion of the inclusions was found. A critical size of inclusions forfracture was observed but it depends on the chemical composition of inclusions. The drawing parameters also playan important role in the fracture occurrence. The wire mechanical properties and the die angle appears to beimportant parameters in view to reduce the fracture ratio.A deeper analysis of the microstructural changes around the inclusion by EBSD and modelling underlines a realimpact of the inclusion on the local deformation around the inclusion. The local analysis (TEM and ACOM -Automated Crystal Orientation Mapping) of inclusion/matrix interface shows a difference of microstructure at theinclusion edge along the drawing axis and a higher local deformation. The study of these different parametersmakes possible to propose a fracture mechanism that takes into account the part of the material subjected to shearand the one subjected to tensile stress
Jamoneau, Aurélie. "Etude du comportement et de la rupture de fil d’acier perlitique haute résistance lors de l’assemblage." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLC018.
Full textDrawn pearlitic steel wires have a remarkable tensile strength, which can reach 4000 MPa. After drawing, however, wires have to pass through the cabling step where they undergo traction – torsion – bending solicitations. Under such loading conditions the wires that are the most effective in tension tend to lack ductility.First, torsion was identified as the most critical solicitation, and delamination as the associated rupture mode. Then, the formation of delamination cracks in torsion was examined, as well as the impact of some drawing parameters on properties influencing the formation of cracks, such as residual stresses, defects and cracks on the wire surface, microstructure type and textures. Conclusions were drawn on the existence of a critical defect size and residual stress level for the propagation of a delamination crack transverse to the wire section. A study at the microscopic scale showed three successive steps to be needed for a delamination crack to propagate: shear localization accompanied with longitudinal cracking, unsteady crack propagation across the wire’s cross-section and longitudinal crack propagation. A curled microstructure, also named “Van Gogh skies”, in addition to structural anisotropy make shear deformation in the wire section difficult, and thus favor localization. The stability of the crack across the section is most influenced by macroscopic mechanical parameters such as stress level in localization’s zones and size of propagated cracks. The last longitudinal propagation step is more related to the torsional shear stress and to the microstructural anisotropy.In conclusion, a phenomenology for delamination of high strength pearlitic steel wires was outlined. It allows one to demonstrate the impact of the residual stress field and of the crack size in addition to identifying the influence of the microstructure. An interesting future perspective of this study could be the investigation of microstructures less sensitive to shear localization and to crack propagation
Oliveira, Anicio Costa Isadora Maria. "Relations entre la microstructure, les propriétés mécaniques et électromagnétiques de fils d'acier au carbone traités thermomécaniquement." Thesis, Lille 1, 2020. http://www.theses.fr/2020LIL1R047.
Full textPearlite is a common constituent of a large variety of high strength steel grades typically used in many structural engineering applications, which demand a good combination of high strength and ductility. With the increasing requirements for product quality and in-service reliability, the non-destructive inspection of materials enables the evaluation of their properties including electromagnetic methods, such as eddy current testing (ECT). However, the influence of microstructural parameters on the physical properties indirectly measured by an electromagnetic sensor has not yet been completely elucidated. The objective of the present work is thereby to understand the relations between microstructure, mechanical properties, and electromagnetic behavior of carbon steel wires submitted to different thermomechanical treatments. It aims also at improving the knowledge of the physical and mechanical metallurgy of these steels. The effect of microstructure and plastic deformation on the electromagnetic responses of different steels with various tensile strengths was investigated through resistivity down to 2 K and magnetic measurements, as well as by ECT. In addition, magnetic domains could be imaged by magnetic force microscopy despite the complex microstructures. The electromagnetic responses changed according to the electrical conductivity and magnetic permeability variations of each material, which were mainly related to changes in the volume fraction, distribution, and morphology of the cementite phase within the α-ferrite matrix. The increase of carbon concentration enhances the localization of electrons at the atomic sites, assisting the covalent character of interatomic bonds and thereby reducing the conductivity of steels. Besides, the α-Fe3C interfaces that act as a physical barrier for dislocation slip in ferrite, affecting as well the main free-path for conductive electrons and magnetic domain walls displacements within the material. Conductivity and permeability increased in the order of martensite, sorbite, pearlite, proeutectoid ferrite-pearlite, spheroidite, and ferrite microstructures. Also, the electrical and magnetic behavior of fully pearlitic steels was observed to depend on the deformation resulted from the cold-drawing and in-service application where fatigue may occur. Low-cycle fatigue experiments have pointed out that the resistance can be managed by relevant thermo-mechanical treatments. The potentiality of ECT was highlighted as a characterization tool of the microstructural state and mechanical properties of steel wires during manufacturing processes or in-service environment. Finally, this technique has been shown to be useful for monitoring cyclic elastic deformation and plastic accommodation of pearlitic steels responding to fatigue-loading conditions
Avila, de oliveira silva Lais. "Investigation de l’effet du gradient microstructural généré pendant le patentage sur les propriétés mécaniques finales des fils d’acier perlitiques." Electronic Thesis or Diss., Centrale Lille Institut, 2022. http://www.theses.fr/2022CLIL0007.
Full text: Pearlitic steels could appear to be a simple and classic microstructure, with a rather simple eutectoid composition containing twophases (cementite and ferrite) in a lamellar distribution. However, they feature a hierarchical microstructure, which is composed of nodulesthat present the same crystallography and are grain-equivalent, then the nodules comprise the colonies that contain the parallel ferrite andcementite lamellas at a nanometric scale. As a result, pearlitic steels offer high strength and ductility at a reasonable cost, which fits verywell for various structural and reinforcement applications, e.g., steel core, bridge cables, wire ropes, springs…Although pearlitic steels areknown and vastly studied for over 150 years, it could appear outrageous to still propose manners of improving their mechanical properties.However, some options have not yet been considered such as the microstructural gradient or the control of the pearlite morphologies. Themicrostructural gradient concept has been widely explored in simple microstructure in steels, such as ferrite or austenite, but it is morecomplicated to export it in the pearlitic steel. The present Ph.D. aims to investigate the feasibility of producing a microstructural gradient infully pearlitic steels and of controlling the pearlite morphology. It is sought the understanding of the involved metallurgical mechanisms andthe impact on the mechanical properties, especially fatigue, considering the final application of this material. The control of themicrostructure and the gradient is based on the transformation of austenite into pearlite and, therefore, all the parameters that couldinfluence this transformation must be studied. It includes heat treatment parameters (heating rates, cooling rates, cooling modes,temperature of transformation…) and materials ones (initial interlamellar spacing, deformation state of pearlite…). The spacing between theferrite and cementite lamella, known to govern the mechanical properties of pearlitic steels, varies with the transformation temperature,which results in coarse and fine pearlite when transformed at high or low temperatures, respectively. It is found that a microstructuralgradient of interlamellar spacing is possible to be formed but is limited by the rod diameter. Using the dilatometer, it was successfullyprocessed in a 6 and 12 mm diameter rod. The gradient-containing wires were then drawn and the mechanical properties before and afterdrawing are compared to assure that the gradients formed during the heat treatment of the 6 mm diameter wires are still present on the2.25 mm final diameter wires. The morphology of pearlite has also been modified by control of heat treatments using continuous andisotherm cooling. Divorced, connected and well-aligned perfect pearlites with the same interlamellar distance have been processed. It turnsout that the morphology of the monolithic pearlite specimen has a higher impact on cyclic plasticity than the presence of a gradient. Theresults obtained in this Ph.D. gave rise to discussions on the pearlitic transformation under continuous and isotherm cooling, on themechanisms controlling the morphology of pearlite (mostly divorced or lamellar), on the phenomena happening during heating,(recrystallization, recovery, and spheroidization), and also on the mechanisms of plasticity of pearlite. Finally, the feasibility of the productionof the gradients by real cooling technologies is assessed by transforming the wires in a pilot line. It is of most interest that the gradients areproduced by alternative cooling technologies since the lead patenting technique is not the most environmentally friendly, although the mostwidely used
Oliveira, Anicio Costa Isadora Maria. "Relations entre la microstructure, les propriétés mécaniques et électromagnétiques de fils d'acier au carbone traités thermomécaniquement." Electronic Thesis or Diss., Université de Lille (2018-2021), 2020. http://www.theses.fr/2020LILUR047.
Full textPearlite is a common constituent of a large variety of high strength steel grades typically used in many structural engineering applications, which demand a good combination of high strength and ductility. With the increasing requirements for product quality and in-service reliability, the non-destructive inspection of materials enables the evaluation of their properties including electromagnetic methods, such as eddy current testing (ECT). However, the influence of microstructural parameters on the physical properties indirectly measured by an electromagnetic sensor has not yet been completely elucidated. The objective of the present work is thereby to understand the relations between microstructure, mechanical properties, and electromagnetic behavior of carbon steel wires submitted to different thermomechanical treatments. It aims also at improving the knowledge of the physical and mechanical metallurgy of these steels. The effect of microstructure and plastic deformation on the electromagnetic responses of different steels with various tensile strengths was investigated through resistivity down to 2 K and magnetic measurements, as well as by ECT. In addition, magnetic domains could be imaged by magnetic force microscopy despite the complex microstructures. The electromagnetic responses changed according to the electrical conductivity and magnetic permeability variations of each material, which were mainly related to changes in the volume fraction, distribution, and morphology of the cementite phase within the α-ferrite matrix. The increase of carbon concentration enhances the localization of electrons at the atomic sites, assisting the covalent character of interatomic bonds and thereby reducing the conductivity of steels. Besides, the α-Fe3C interfaces that act as a physical barrier for dislocation slip in ferrite, affecting as well the main free-path for conductive electrons and magnetic domain walls displacements within the material. Conductivity and permeability increased in the order of martensite, sorbite, pearlite, proeutectoid ferrite-pearlite, spheroidite, and ferrite microstructures. Also, the electrical and magnetic behavior of fully pearlitic steels was observed to depend on the deformation resulted from the cold-drawing and in-service application where fatigue may occur. Low-cycle fatigue experiments have pointed out that the resistance can be managed by relevant thermo-mechanical treatments. The potentiality of ECT was highlighted as a characterization tool of the microstructural state and mechanical properties of steel wires during manufacturing processes or in-service environment. Finally, this technique has been shown to be useful for monitoring cyclic elastic deformation and plastic accommodation of pearlitic steels responding to fatigue-loading conditions
Ripert, Ugo. "Méthode itérative de recherche de l'état stationnaire des procédés de mise en forme : application au laminage." Phd thesis, Ecole Nationale Supérieure des Mines de Paris, 2014. http://pastel.archives-ouvertes.fr/pastel-01018391.
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