Métallurgie

Nombre total de résultats : 204
Pertinence Titre A-Z Plus récents Plus anciens
10 25 50
Année de publication
et

Heat transfer in the mold of continuous casting

K. Hamlaoui, H. Bendjama, H.TAYOUB, KH.SLIMANI, S.AOUABDI (2019)
Article de conférence

Continuous slab casting is a process of solidification of the molten metal. It consists in filling liquid metal in the mold. During solidification, the molten steel in contact with the mold creates a first phase of steel called solid skin. A lubricant powder is deposited on the surface of the steel in the upper part of the mold. This lubricant, in contact with the liquid steel infiltrated between the mold and the solid skin creates liquid slag film. The thickness of the slag, which infiltrates between the steel and the mold, plays the role of a thermal resistance.This thickness increases with the value of the viscosity at 1500 ° C of the slag and with a speed of extraction. When the starting crystallization temperature is high (> 1100 ° C), thickening of the slag film can occur at the bottom of the mold.As long as a liquid slag film is present in contact with the steel, the hydrodynamic friction forces remain quite low. Problems can arise when this liquid film is no longer present: a solid-solid friction can then occur. The lubricant used in the mold can have a significant influence on thermal extraction. When using powders, it may happen that the optimal lubrication conditions (melting temperature and powder viscosity) do not coincide with the highest thermal extraction rates. The heat balances in the mold show that the nature of the lubricant plays an important role in the heat transfer between the solid steel skin and the mold.Voir les détails

Mots clés : continuous casting, steel, mold, lubricant, heat transfer.

Effets des éléments (vanadium et niobium) sur la structure et le comportement à la corrosion de l’acier inoxydable austénitique de type AISI309

Gharbi amel (2019)
Thèse de doctorat

Les aciers inoxydables austénitiques sont utilisés dans des environnements agressifs couvrant de larges domaines tels que le secteur alimentaire, chimique et nucléaire. Par ailleurs, ils doivent présenter des propriétés d’emploi adéquates et une durée de vie optimale. Ainsi, plusieurs méthodes sont employées afin d’améliorer ces propriétés à savoir l’addition des éléments chimiques, le traitement thermique et le traitement de surface. Cette étude porte sur l'influence de l'addition du vanadium et du niobium sur la variation de la microstructure, l’évolution des propriétés mécaniques et le comportement électrochimique d’un acier inoxydable austénitique de type AISI309.  Un traitement de mise en solution a été appliqué sur l’acier inoxydable de base et l’acier inoxydable allié au vanadium et au niobium à une température de 1100°C pendant trois heures suivi d’un refroidissement rapide à l’eau. Ce traitement a été suivi d’un revenu à différentes températures suivi d'un refroidissement à l’air. La caractérisation microstructurale a été effectuée par microscopie optique, MEB, EDS, DRX, DSC. Afin, d’évaluer la résistance à l’usure des matériaux étudiés, une caractérisation mécanique des échantillons étudiés a été réalisée au moyen des mesures de dureté et des essais d’usure par frottement. De plus, pour examiner le comportement à la corrosion, des tests potentiodynamiques et des mesures d’impédances électrochimiques (EIS) ont été réalisés dans deux milieux HCl et H2SO4.  L'inhibition à la corrosion de l'acier inoxydable austénitique de type AISI309 avec et sans ajout de vanadium et de niobium par 2,2’-Bipyridyl dans H2SO4 a été étudiée en utilisant la polarisation potentiodynamique (Tafel), la polarisation linéaire (LRP) et la spectroscopie d'impédance électrochimique (SIE). D’après les résultats expérimentaux il a été constaté la présence d’une précipitation des carbures de niobium et de vanadium de type MC (VC, NbC) au détriment d’une précipitation intergranulaire de carbures riches en chrome, ainsi qu’une amélioration des propriétés mécaniques tels que la résistance à l’usure et la dureté suite à l’ajout des éléments d’alliage (vanadium et du niobium) avec et sans traitements thermiques. Par conséquent, l’addition du vanadium et du niobium a contribué à l’amélioration du comportement à la corrosion dans les milieux envisagés ainsi que l’efficacité inhibitrice de l’acier étudié en présence d’inhibiteur (2,2’-Bipyridyl). Voir les détails

Mots clés : AISI309, Cr23C6, Vanadium, niobium, 2, 2'-bipyridyle, corrosion, microstructure, propriétés mécaniques, comportement électrochimique, dureté, usure par frottement

Contribution à la diminution des criques de rives qui apparaissent dans les bramesd’acier en coulée continue.

HAMLAOUI Katib (2016)
Mémoire de magister

En coulée continue, la qualité des produits et la productivité de l'installation sontfortement dépendantes du réglage du refroidissement secondaire adopté.Le problème de recherche concerne l’ACO1 (aciérie à oxygène numéro1) localiséeà Arcelor-Mittal/Annaba. Il concerne les brames présentant des défauts de criques derives.La rupture à chaud, ou crique à chaud est un défaut majeur en solidification, quiconduit au rebut de nombreuses pièces dans différents procédés industriels tels que lasolidification en lingotière, la coulée continue de brames.Les défauts les plus répandus au niveau de la coulée continue (Arcelor-Mittal -Annaba) sont les criques de rives : Elles sont petites et fines, sur les coins, longueurenviron 50 mm, profondeur 1 à 2 mm. Elles sont à cheval sur la face et sur la rive.L’élaboration d’un modèle thermomécanique permettant de prédire les profils detempérature sur les différentes faces de la brame en fonction de son passage d’unezone de refroidissement à une autre de la machine de coulée continue et notammentsur les bords.Cette étude confirme la nécessité de considérer les défauts de criques de rives vis-àvisde leur présence au niveau des brames lesquelles sont laminées à chaud ; leproduit final étant une bobine qui doit être saine. Voir les détails

Mots clés : coulée continue, acier, brames, criques de rives

Effect of deformation on dry sliding wear behavior of 13Cr5Ni2Mo supermartensitic stainless steel

Samira. Tlili, Chems Eddine RAMOUL, Soumaya MEDDAH, Amel OULABASS (2019)
Article de conférence

During drilling, the tubings are subjected to tensile, compressive and torsional stresses. In this present work, the effect of deformation on wear of 13Cr5Ni2Mo SMSS in dry conditions is investigated using the tensile test. All samples were taken for the calibrated area of the 2%, 10% and 15% deformed specimens. The tribological tests were carried out at room temperature under a 6N against an alumina ball. The results showed that the deformed samples have the highest wear rate. Maximum wear rate was obtained for 2% deformed samples. This state can therefore affect the reliability of the material. The wear mechanisms involved were observed by scanning electron microscopy.Voir les détails

Mots clés : SMSS, mechanical properties, deformation, wear, friction

Thermal Treatment Effect on Tribological and Corrosion Performances of 13Cr5Ni2Mo Super- Martensitic Stainless Steel

S. TLILI, N.E. BELIARDOUH, C.E. RAMOUL, O . I . A bdullah, H . K aleli, M . A . S amad (2018)
Article de journal

Wear behavior of 13Cr5Ni2Mo supermartensitic stainless steel (SMSS) were investigated in air and in argillaceous paste at room temperature. Prior to wear testing, the samples were subjected to two treatments, namely; quenching followed by double tempering. A pin-on- disc test rig was used to conduct the wear test with a tribo-pair consisting of supermartensitic stainless steel sliding against itself. It was observed that the microstructure of the thermally treated samples mainly consisted of tempered martensite and carbides. Wear results showed that oxidative and abrasive wear dominated the wear process of the treated samples in both dry conditions and in argillaceous paste. Additionally corrosion tests were performed in 5.0% NaCl solution via potentiodynamic polarization tests. It was found that the passive film formation provides a good corrosion resistance to the samples.Voir les détails

Mots clés : Martensitic Stainless Steel, Thermal Treatments, wear, corrosion

Frittage et nitruration liquide des comprimés de l’alliage Fe-Ni-Mo-Al-Ti

MEDDAH Soumaya (2008)
Mémoire de magister

One of the disadvantages of sintered materials obtained by solid phase sintering is the open residual porosity which limits the application of certain treatments such as thermochemical treatments in a liquid medium. Therefore, nitriding is not recommended for sintered materials because of risks of infiltration of the saturating liquid medium in the open porosity generating in the long term internal corrosion of the structure.Our study presents the results of the nitriding of sintered Fe-20% Ni-1% Mo-X% Al-Y% Ti alloy tablets (where X and Y vary from 1 to 6 and 1 to 4 respectively). . During sintering, these compositions cause the formation of an aluminum-based liquid phase which favors the partial elimination of the open porosity. Our interest was in the first place, in the study of the influence of aluminum additions on the character of diffusion, as well as on the evolution of porosity and on the formation of the structure of the sinter, and second, on the repercussions of nitriding on this new structure.The results of the micrographic analysis revealed a clear evolution of the character of the porosity, with a tendency to the elimination of open pores. Structurally, sintering has resulted in an array of intermetallics as a result of the interaction of liquid aluminum with other solid particles. The microhardness profiles showed that despite the selective nature of the diffusion of nitrogen and carbon during cyanidation, the saturation was at heart, with the formation of islands of AlN, TiC (C, N) . As for the properties, the appearance of Fe-Al, Ni-Al and Ti-Al intermetallics during sintering gave the material good resistance to hot oxidation. Cyanidation modifies the oxidation behavior of the material and significantly improves its hardness. Voir les détails

Mots clés : composite, Sintering, Porosity, liquid nitriding, Oxidation

Tribological behaviour of a continuous hot dip galvanized steel

A.Taleb, M. Labaiz, A. Iost, A. Montagne, A. Ourdjini, A. Grairia, S. Meddah (2018)
Article de journal

The aim of this work is to investigate the tribological behaviour of a continuous hot dip galvanizedsteel. This paper presents a fundamental study of the characteristics of zinc coating in terms ofmorphology, surface roughness and tribological behavior according to process parameters typical ofindustrial processes continuous galvanization. The morphology of the zinc coating was observed byscanning electron microscope (SEM), optical microscopy, and the mechanical properties of thecoating layers were determined by nanoindentation. The tribological tests were carried out on arotating ball-disk tribometer under loads of 1, 2, 3Nwith a sliding distance of 15, 30 and 50 m. Theresults showed a marked increase of the coefficient of friction with increasing applied load. Under thesame conditions, wear slightly increased due to the hardness of intermetallic phases. The resultspresented show that heating promotes the diffusion of iron in the zinc coating giving shape to a binaryalloy Fe–Zn whose characteristics depend on the parameters; moreover, it is proved that thetribological characteristics of the surface of the metal blank in terms of coefficient of friction dependon the temperature of the contact pressure.Voir les détails

Mots clés : galvanized steel, wear, roughness, Nanoindentation, intermetallic phases

Prediction of the Friction Coefficient of 13Cr5Ni2Mo Steel Using Experiments Plans-Study of Wear Behavior

S. Meddah, M. BOUREBIA, A. Oulabbas, C. E. RAMOUL, S. TLILI, A. Taleb, S. Achouri (2019)
Article de conférence

Metal materials used in industrial applications deteriorate under the effect mechanical and chemical phenomena occurring under operating conditions, such as pipes carrying gas or fluid that are subject to internal wall wear. From where an experimental study was conducted through friction tests on supermartensitic stainless steel Cr13Ni5Mo2, in order to estimate the effect of test parameters on friction coefficient and wear behavior of this steel by adopting the factorial plans 2<sup>2</sup> methodology at two factors (Load "P" and linear sliding "V"), each at two levels (-1, +1). The results have been demonstrated using a mathematical model predicting the coefficient of friction "f" in every point of the study field. The factorial plans make it possible to establish a modeling of the studied phenomenon with a maximum of efficiency and a minimum of experiences. The experimental results showed that the friction coefficient "f" reaches a max value for an applied load P=10N combined with a linear speed V=5cm/s. In addition, the wear morphology of surfaces after the friction test indicates that for 2N and at all speeds, friction is dominated by an abrasive wear mechanism. However, for 10N, it is observed the predominance of adhesive wear with a higher wear rate.Voir les détails

Mots clés : friction, factorial design, Mathematical model, wear mechanism

Tribological and Eelectrochemical Characterization of a Titanium Alloy in a Physiological Solution.

S. Meddah, H. Chadli, S. TLILI, C. Ramoul, S. Challi, F. Sehab, A. Oulabbas (2017)
Article de conférence

Titanium alloys are used primarily for biomedical and / or dental applications. They are characterized by a better mechanical compatibility with the tissues and a good biocompatibility in the body fluids. The alloy TA6V4 used in orthodontics is subject to degradation by wear and corrosion. In this context, we are primarily interested in the study of the dry friction wear of the TA6V4 / Al2O3 torque by means of a rotating Ball / Disc tribometer. In order to evaluate the biocompatibility of this alloy, an electrochemical study in a physiological solution was carried out using conventional electrochemical measurement methods (time-dependent monitoring of the corrosion potential, potentiodynamic curve) as well as Electrochemical impedance spectroscopy. The results of tribology, the friction of the torque TA6V4 / Al2O3 against each other, revealed a friction coefficient of 0.2 and a wear volume of the order of 22.579.10-12 mm3/N.mm. The wear mechanism studied by scanning electron microscopy revealed abrasive and adhesive degradation. From the electrochemical point of view, the TA6V4 alloy in Hank's solution exhibited good corrosion resistance with a polarization resistance of 44 540 Ω. Analysis by electrochemical impedance spectroscopy indicated that this alloy is passive in nature, following the formation of a surface-stable two-phase oxide layer composed of an internal compact layer which has good corrosion resistance And an external porous layer which is favorable to osteointegration.Voir les détails

Mots clés : Alloy TA6V4, Corrosion behavior, friction

ETUDE DES PROPRIETES MECANIQUES DES VERRESOXYGENES ET OXYHALOGENES

BACHIRI Abdalkader (2012)
Mémoire de magister

The rapid development of photonics technology requires increasingly efficient materials,suitable for photonic devices such as amplifiers and materials for high power lasers. Theoptical amplification based on the principle of the laser effect can be obtained in crystalline orglassy matrix through radiative emission of rare earth ions.The glasses are among the interesting matrices for transparency in a wide optical region andtheir ability to receive large amounts of rare earth ions. For this purpose, a new family ofglasses stable oxide and halide in the ternary systems Sb2O3-PbCl2-As2O3 and Sb2O3-PbCl2-AgCl has been developed. Several characterizations were made on two ternary systems. Allproperties changes almost linearly with the variation of the composition. The results obtainedare similar to those of other work. It appears that the structure of these glasses is more openwhere the low values of mechanical properties. Because of these glasses good candidates innonlinear optics. Differential scanning calorimetry has shown that certain compositions do notexhibit crystallization peaks where their high thermal stability.In this work, we also find the study of the devitrification of glasses in the ternary systemoxyhalogenated Sb2O3-PbCl2-AgCl has been studied by differential scanning calorimetry.A single exothermic peak of recrystallization is observed beyond the glass transitiontemperature, which allows the application of relations Mehl-Avrami-Kolmogorov-Johnson.The use of non-isothermal procedures for determining the values of the Avrami exponent nand activation energy E.The mechanism of crystal decay is discussed in relation to the observations in scanningelectron microscopy Voir les détails

Mots clés : transparency, ternary systems, glasses, Differential scanning calorimetry, Thermal stability