Liste des documents
Characterization and Microstructural of Hot Rolling Mill Scale
In the IMETAL-El Hadjar complex, during the steel manufacturing process, a significant amount of scale is produced onthe surface of slabs and billets of hot-rolled steel. In the various rolling mills, the quantity of scale produced is estimated to be about0.1% of the annual production of the steel complex. The quality of the thin steel sheet during the rolling process is affected by thebehavior of the iron oxide layers formed on their surfaces (scale).This amount of scale which is a fatal by-product of the forging and rolling processes can be reused in certain areas and applied byappropriate recycling techniques such as agglomeration of iron ores in the blast furnace as a raw material. This aspect of recycling istaken into consideration.The objective of this study is to identify the microstructural properties of the scale, using different analytical methods such as X-raydiffraction and scanning microscopy.Several samples were used for characterization of the locally produced scale.The analyzes of the results given by SEM showed that hematite and magnetite, the main phases present in the scale, are stacked inthin layers of a magnitude of the order of a micron meter. These phases of iron oxides are confirmed by the analysis of the spectragiven by the X-ray diffractometer.The presence of silicon in the scale is due to the covering powder used on the wall layers of the ladles. Voir les détails
Mots clés : mill scale, Oxidation, hot rolling, Microstructural properties, SEM, X-ray.
Characterization and Microstructural of HotRolling Mill Scale
In the IMETAL-El Hadjar complex, during the steel manufacturing process, a significant amount of scale is produced on the surface of slabs and billets of hot-rolled steel. In the various rolling mills, the quantity of scale produced is estimated to be about 0.1% of the annual production of the steel complex. The quality of the thin steel sheet during the rolling process is affected by the behavior of the iron oxide layers formed on their surfaces (scale).This amount of scale which is a fatal by-product of the forging and rolling processes can be reused in certain areas and applied by appropriate recycling techniques such as agglomeration of iron ores in the blast furnace as a raw material. This aspect of recycling is taken into consideration.The objective of this study is to identify the microstructural properties of the scale, using different analytical methods such as X-ray diffraction and scanning microscopy.Several samples were used for characterization of the locally produced scale.The analyzes of the results given by SEM showed that hematite and magnetite, the main phases present in the scale, are stacked in thin layers of a magnitude of the order of a micron meter. These phases of iron oxides are confirmed by the analysis of the spectra given by the X-ray diffractometer.The presence of silicon in the scale is due to the covering powder used on the wall layers of the ladles. Voir les détails
Mots clés : mill scale, Oxidation, hot rolling, Microstructural properties, SEM, X-ray
Dephosphorization of Western Algerian Oolitic iron ore
A Combination of roasting and acid leaching processes was tested for the dephosphorisation of Gara Djebilet oolitic iron ore (Algerian Western Sahara) that contains a high phosphorus content of 0.91% which exceed-acceptable limits. A laboratory scale, this process involving a chemical attack after roasting of the raw sample of iron ore that mixed with alkaline additives (CaCl 2 or NaCl) followed by an acid leaching using nitric acid, perchloric acid, hydrochloric acid and sulfuric acid. 89% of phosphorus is removed by the addition of the salt (NaCl) then attacked by nitric acid. The laboratory tests carried out for a dephosphorisation show that the combination of roasting with alkaline additives, followed by an acid leaching makes it possible to obtain high quality iron concentrate. Despite the phosphorus content decreases from 0.91 to 0.1%. Voir les détails
Mots clés : Oolitic iron ore, acid leaching, dephosphorisation, alkaline additive.
Exploitation des sous-produits sidérurgiques du complexe Elhadjar -Annaba-.
Le présent travail de recherche se base sur l'exploitation du sous-produit sidérurgique (calamine) et sa transformation en produit utilisable dans le domaine des peintures anticorrosion. Ces oxydes de fer ont été examinés comme pigment et inhibiteur de corrosion dans deux types de peintures à concentrations différentes (1%, 3%, 7%, 15%) pour déterminer la meilleure formulation. Le meilleur temps de broyage de calamine est 2 minutes avec une distribution volumique D(0,9) des particules à une taille inférieure de 32 micromètre et une surface spécifique égale à 1.6 m2/g. L’analyse chimique montre une teneur en fer total moyenne de 72 % et des faibles teneurs en des oxydes de manganèse et de silice. L’analyse électrochimique a prouvé que les propriétés anticorrosives ou plutôt le rendement d’inhibition augmentent avec l’augmentation de concentration de la calamine dans les peintures testées (15% pour Glylac et 7% pour Glycar). Voir les détails
Mots clés : calamine, agent anticorrosif, analyse granulométrique, analyse électrochimique.
Acoustic emission source localization in plate-likestructure
This article proposes a geometric approach foracoustic emission source (AE) localization in plate-like structure.In order to determine the arrival time of the acoustic emissionwaves for each sensor with more precision, we have used twotechniques, the first one is based on thresholding and the secondis based on the continuous wavelet transform. Experimental testhave been carried out on steel plate shown that the continuouswavelet transform allows to be improve the accuracy of theacoustic emission source localization. Voir les détails
Mots clés : acoustic emission signal, acoustic emission source location, arrival time, threshold, continuous wavelet transform
Complexity Reduction of UltrasoundSub-Ultra-Harmonic Modeling by an Input Modified Volterra Approach
Contrast of echographic images has been highly improved by the injection of microbubbles, due to their nonlinearbehavior. However, this contrast enhancement is limited by the nonlinear acoustic propagation in tissue. To overcome this drawback,sub and ultra-harmonic contrast imaging can be used, since only microbubbles can generate these components. Nonlinear modeling is aprimordial step in the analysis of microbubble signals for sub and ultra-harmonic imaging. Nonlinear models like Volterra model hasbeen applied in harmonic imaging to model harmonics optimally. However, it can model harmonics only. For sub and ultra-harmonicmodeling, a multiple input single output (MISO) Volterra has been proposed. The aim of this study is to propose a simpler alternativefor the modeling of sub and ultra-harmonics. We propose a modified single input single output (SMISO) Volterra model based on inputdemodulation. The model is tested using simulated and experimental signals. Results showed that sub and ultra-harmonics aremodeled. The number of kernels is reduced to its half using SMISO model compared to MISO model. The relative mean square errorbetween the simulated signal and the modeled signal with SMISO Volterra model is −15.8 dB and it is −60.7 dB for experimentalsignals. The computational time is reduced by a factor of 4 and 5 in simulated and experimental cases respectively. SMISO model canmake easier the sub and ultra-harmonics modeling. Voir les détails
Mots clés : modeling, sub-ultra-harmonics, SMISO Volterra, demodulation, microbubble.
Modeling of Electromagnetic Behavior of CompositeThin Layers using Genetic Algorithm
In this paper, we present a new model using the highfrequency electromagnetic simulator for several binary mixtureswhere the load is in the lossless thin film form with a permittivityof (? = 100, 200, 300, and 400) and for various thickness values ina range of 10 µm to 250 µm with respect to the host matrix. Themodel operates in a variety of frequencies from 8.2 GHz to 12.4GHz. The effective permittivity of composites is evaluated usingNicholson Ross Weir (NRW) algorithm in a rectangularwaveguide. The implementation of NRW algorithm is conductedon various samples simulated by HFSS, in order to estimate thedielectric composite behavior. Furthermore, we employ a geneticalgorithm methodology (GA) for the filling factor optimization ofthe proposed model by Mosallaei. The obtained results show agood agreement with the theoretical models, which ensure thevalidity of our proposed model for characterizing theelectromagnetic behaviour of dielectric thin films. Voir les détails
Mots clés : Thin films, electromagnetic behaviour, dielectric mixtures, Genetic optimization, mico wave.
Etude de l’effet des conditions de polarisation sur le mode de relaxation principale (α) du PLA par la technique des courants thermostimulés (CTS)
Dans ce travail nous nous sommes intéressé à l’étude de l’influence des conditions de polarisation (champ et température), sur le mode de relaxation principal(α) du polylactic acide (PLA) par la technique des courants thermo-stimulés (CTS). L’influence du champ électrique se traduit parune augmentation linéaire de l’intensité du thermocourant relatif au mode α ainsi que celle de la polarisation totale de ce pic, affirmant ainsi le caractère dipolaire de la relaxation. L’élévation de la température de polarisation conduit à une augmentation progressive de l’intensité et de la polarisation jusqu’à saturation au voisinage de la transition vitreuse. Les énergies d’activations évaluées par la méthode des demi-hauteurs, augmentent pour des températures de polarisation inférieures à 70°C, puis rejoignes un palier de saturation. Un tel résultat est dû à un processus thermiquement activé et à une distribution du temps de relaxation. La température de transition vitreuse Tgaugmente avec la vitesse de chauffage. Ce résultat confirme la nature cinétique de la transition vitreuse. Voir les détails
Mots clés : Transition vitreuse, relaxation, PLA, CTS.
NDT Characterization of FeCu Nanostructured
The mechanical alloying process has been used to synthesis Fe-Cu nanostructured powder in a high energy planetary ball-mill PM400. Structural and magnetic, properties of the powders milled were investigated by scanning X-ray diffraction and vibrating sample magnetometer, respectively, the elemental micrometer-sized Cu and Fe powders were first mixed in Fe70Cu30 compositions, the added of Cu in Fe formed the solid solutions of Cu in Fe and Fe in Cu, a solid solution face-centred cubic and solid solution body-centred cubic nanograined composite has been formedKeywords: Mechanical alloying, Fe–Cu alloy, Structural and magnetic. Voir les détails
Mots clés : Mechanical Alloying, Fe–Cu alloy, Structural and magnetic
Eddy current characterization and Magnetic properties of iron alumina nanostructured alloy
The mechanical alloying technique has been used to synthesis iron alumina nanostructred powder in a high energy planetary ball-mill PM400. Electromagnetic and magnetic characterizations of the powders was investigated by eddy current and vibrating sample magnetometer, the impedance, the coercivity and saturation magnetization of the iron alumina mixtures changes in function of x% (wt). Voir les détails
Mots clés : iron alumina, electromagnetic and magnetic properties, Eddy Current, VSM.