Nombre total de résultats : 200
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Allotropic transformation of cobalt in magnetic induction melted

Abdelhak Fekrache, Mohamed yacine Debili, Halima Boularas, Douniazed Lamrous, Nacira Sassane.  (2014)

In contrast to the abundance of studies in Fe -Al and Fe-Co, those in the Fe-Al-Co ternary system arescarce. Consequently, the phase separation and phase diagram of this system remain still ambiguous. Ternary Fe0.6Al1-x Cox(x values in a molar ratio of 0.05, 0.1, 0.15, and 0.2) have been elaborated by high frequency magnetic induction fusion, in order to study the effect of cobalt ternary addition on the structural behavior such as phase separation, thermal and mechanical properties of Fe-based alloy system, by means of x-ray diffraction, thermal analysis (DSC) and Vickers microhardness. An unexpected allotropic phase transformation from stable HCP to metastable FCC Cobalt has been observed in all alloys. Voir les détails

Mots clés : Fe-Al-Co, phase transformation, phase separation, lattice parameter.

Contribution to characterization of the diatomite forindustrial application

Hazem MERADI, L’hadi ATOUI, Lynda BAHLOUL, kotbia LABIOD, Fadhel Ismail  (2015)

Diatomite also known Kieselguhr, is a non metallic mineral composed of the skeletal remains of microscopic single-celledaquatic algae called diatoms.The aim of this study was to test and to evaluate the diatomite of Sig region (West Algeria)tosubstitute the main mold powder used in continuous casting of steel for thermal insulation and lubrication. Generally, fluorineis added to mould fluxes to improve the viscosity. But this leads to the environmental pollution and the equipment corrosion. Thelaboratory and industrial investigations of diatomite have indicated the good results obtained in continuous casting of steel forthermal insulation and environmental protection against pollution (without fluorine). Also the characterization showed the hotbehavior of this product with the various transformations and could give the possibility to other use. Voir les détails

Mots clés : diatomite, thermal insulation, lubrication, mold fluxes, fluorine

Characterization by thermal analysis of natural kieselguhr and sandfor industrial application

Hazem Meradia, L’hadi ATOUI, Lynda BAHLOUL, Khaled BOUBENDIRA, Abdelhak Bouazdia, Fadhel Ismail  (2015)

Kieselguhr also known diatomite is a silica-based mineral, usually light in color (white if pure). It is very finely porous and verylow in density. It is composed mainly of silica as career sand. The aim of this study was to characterize the kieselguhr and sandfor together use in industry for various applications. Both products come of Sig deposit (West Algeria).The results ofsimultaneous analyses by Thermogravimetric Analysis and Differential Scanning Calorimetry (TGA-DSC) for kieselguhr andsand sample shows almost identical peaks except for the peak which appears at 574° C which corresponds to the transformationof quartz sand that does not appear in the Kieselguhr sample because of its amorphous character and higher exothermic peak at574° C approximately. Voir les détails

Mots clés : Kieselguhr, diatomite, sand, thermal analysis, DSC, TGA

Prediction of Bath Temperature Using Neural Networks

H. MERADI, S. Bouhouche, and M. Lahreche  (2008)

In this work, we consider an application of neuralnetworks in LD converter. Application of this approach assumes areliable prediction of steel temperature and reduces a reblow ratio insteel work.It has been applied a conventional model to charge calculation, theobtained results by this technique are not always good, this is due tothe process complexity. Difficulties are mainly generated by thenoisy measurement and the process non linearities.Artificial Neural Networks (ANNs) have become a powerful toolfor these complex applications. It is used a backpropagationalgorithm to learn the neural nets. (ANNs) is used to predict the steelbath temperature in oxygen converter process for the end condition.This model has 11 inputs process variables and one output.The model was tested in steel work, the obtained results by neuralapproach are better than the conventional model. Voir les détails

Mots clés : LD converter, bath temperature, neural networks

Effect of the austenite hot deformation on the transformation microstructural mechanics parameters of a microalloyed steel

D. BERDJANE, Pr M. L. Fares, G. Goldhahn  (2012)

This study was established to optimize the heat treatments - mechanical and improve the mechanical properties of microalloyed steel with Nb-Ti-V for the production of hot rolled strip. A database of the main parameters of deformation of this steel was developed by dilatometer-plastometer tests. The cooling experiments were used to simulate sequences of the industrial process. The results of these investigations used to analyze the effect of deformation parameters on the evolution of the ferritic structure and mechanical properties of steel. The conditions of rolling deformation bands must be simulated by experimental investigations in order to find a favorable microstructure while choosing the appropriate technological parameters. The microstructural evolution during hot rolling is a dominant factor for achieving the optimal properties. The chemical composition can predict the limits of the desired properties, but these limits depend significantly thermomechanical conditions imposed. A good adaptation of these conditions with the performance of the material allows for a high quality finished product. These investigations will be the basis for determining in advance of the microstructure, mechanical properties for subsequent monitoring of the industrial process. Voir les détails

Mots clés : Microalloyed steel, Austenite, hot deformation, mechanical properties, structure

Effects of Niobium and Molybdenum on Microstructures after Hardeningand Wear Resistance of Austenitic Manganese Steel

ali hadji, BOUHAMLA Khedidja  (2013)

Hadfield steel has been wildly used to manufacture railway crossings because of its excellent workhardening, high strength and toughness properties. The hardness of Hadfield steel is only about 20 HRC whensubjected to water toughening. This low hardness is usually associated with poor wear resistance and severeplastic deformation, as well as abrasion of the working surface of the railway crossing during the initial serviceperiod, which remarkably reduces its service lifetime. In this study we focus on the influence of niobium andmolybdenum on the phenomenon of surface hardening or work hardening and wear resistance. Thetransformation of austenite during operation, thus determines the steel operating lifetime, the rate oftransformation of austenite to martensite can introduce a compromise between ductility and wear resistance ofthe steel to support large efforts without breaking. The objective of this study is to improve the wear resistanceby abrasion and friction after heat treatment of manganese steel alloyed with niobium and molybdenum. Theaddition of niobium and molybdenum promotes secondary hardening and allows slower transformation ofaustenite during the heat treatment. The results showed that the introduction of niobium and molybdenum hasstrongly influenced the character of the structure crystallization before hardening (Part hardened) byprecipitation carbides form and finesse variables is observed in the microstructure before heat treatment andcomplete dissolution is noted after heat treatment, for the hardened part (work hardening) we observed agreater thickness and hardness compared to the base steel and net improvement in wear resistance. Voir les détails

Mots clés : manganese steel, Effects of Niobium and Molybdenum, Hardeningand, Hardeningand Wear Resistance

Monotoring of air quality in an iron foundry(Case of NOx, SO2 , benzene and dust)

M.T. AbedGhars; A. Hadji; S. Bouhouche  (2011)

The requirements as regards ecology are imposed more and more by the legislator. The cast iron foundries,using the cupola furnace like means of fusion and several other materials for the clothes industry of the mouldsand the cores, produce a great quantity of noxious gas and dust. These polluants are discharged into theatmosphere and are very harmful for the human health of the workers and the environment bordering the sitesof production. So, our study relates to the monitoring of polluting gases such as: the so nox and btx ,2continuously during a working station by passive sensors and to measure the dust level reigning in the variousworkshops of the foundry by the method of decantation (method of bergeroff). All these pollutants are knownfor their harmful effect on human health. The strategic aims had by this study is to index the atmosphericemissions, to determine the level of the air pollution generated by the activity of a manufacturing unit ofcastings out of cast iron using like moulding the traditional process, to determine the peaks of concentration ofpolluting gases (so nox and btx), to quantify and analyze pollution by the suspended particles, to work out a2cartography of the air pollution) and to compare the values obtained relating to the current situation withlimiting values who. The results of taken measurements showed a very strong pollution reaching of the values333236.6 µg/m for benzene (c6h6), 508.2 µg/m for the dioxide of sulfur (so ) and 722.4 µg/m for oxides of2nitrogen (nox). The concentrations of dusts are in on this side limiting value of who. Their chemical analysisshowed the presence of much silica and iron. Voir les détails

Mots clés : cast iron foundry, gaseous polluant, atmosphere, dust, values who.

Comportement structural et mécanique de soudures d’acier inoxydable austénitique du type 316l vieillies

Kheira REHOUMA (2013)
Thèse de doctorat

Des tôles d’acier inoxydable austénitique du type 316L d’épaisseur 4 mm ont été soudées à l’arc électrique à l’aide d’un fil nu d’acier inoxydable austénitique du type 308L d’un diamètre de 1.6 mm. Les soudures ont été maintenues à 700 °C pendant 140 h, 500 h et 1000 h. Une phase σ riche en Cr et en Mo a précipité dés les premières heures (140 h) de maintien à 700 °C. Le Mo présent dans la ZF provient des bords de la soudure lors du soudage. Par ailleurs, des profils de dureté Vickers montrent un adoucissement au niveau de la soudure vieillie jusqu’à 1000 heures comparé à la soudure de référence (soudure non vieillie). Lors des essais de traction assistés par la corrélation d’image digitale, la rupture s’est produite dans la zone de liaison pour la soudure de référence. Elle s’est produite au centre de la zone fondue dans la soudure vieillie durant 1000 h à 700 °C. La ferrite présente une fragilisation comparée à l’austénite lors de l’essai de traction pour la soudure de référence (soudure non vieillie).Ceci est confirmé par la littérature. Voir les détails

Mots clés : aciers inoxydables austénitiques, procédé TIG, soudure, traitements de vieillissement, transformation de phase, propriétés mécaniques

Effet des traitements thermomécaniques sur les propriétés mécaniques et électriques du câble électrique (cuivre et aluminium)

Ridha BADI (En préparation)
Thèse de doctorat

Les câbles électriques en cuivre destiné pour le transport de l'énergie électrique nécessitent un compromis de caractéristiques mécaniques – résistivité électrique. Le tréfilage est accompagné par la formation de défauts cristallins, tels que lacunes et dislocations, conduisant à l'élévation de la dureté, donc à l’augmentation de la résistivité, une caractéristique très importante pour la conductibilité et le rendement du câble. L’intérêt particulier de ce travail est de proposer une nouvelle gamme de traitements thermomécaniques appropriés pour l'amélioration des caractéristiques mécaniques et électriques du câble électrique en cuivre. Différentes méthodes expérimentales ont été utilisées à cet égard, à savoir la microscopie optique, la dureté Vickers HV et les essais de corrosion. Voir les détails

Mots clés : recristallisation, grains, textures, déformation, résistivité, température

Apport des champs de déformation a la compréhension des mécanismes d’endommagement des soudures hétérogènes

Khireddine BETTAHAR (En préparation)
Thèse de doctorat

Dans cette thèse nous étudions le comportement structural et mécanique d’un assemblage hétérogène par soudage de deux aciers inoxydables. Les premiers travaux effectués ont consistés en la caractérisation structurale et mécanique des matériaux de base, le métal fondu et les zones affectées thermiquement. Cette première partie nous a révélé les hétérogénéités structurales et les gradients des propriétés mécaniques le long du joint soudé.Des essais de fatigue ont été effectués dans le but d’estimer l’endurance de l’assemblage, il s’est avéré que le métal fondu est le moins résistant. Cette partie sera complétée par des mesures des champs de déformation et une simulation numérique afin de prédire l'évolution du comportement global et local des différentes parties. Voir les détails

Mots clés : aciers inoxydable, duplex, super martensitique, soudage, corrélation d’image, champs de déformation, fatigue