Métallurgie

Nombre total de résultats : 204
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Contribution à la modélisation du processus de refroidissement secondaire d’acier coulée en continue

H. Tayoub, H. Bendjama, K. Hamlaoui, K.Slimani, S. AOUABDI (2019)
Article de conférence

Dans l’industrie sidérurgique, la coulée continue est le procédé qui se situe entre l’élaboration d’acier et le laminage. Ce procédé a pris, depuis 30 ans, une place de plus en plus importante dans la filière de production en raison des avantages par rapport à la technique traditionnelle de coulée en lingots ; économie d’énergie et de main d’œuvre, meilleur rendement et amélioration de la qualité du produit, ainsi l’amélioration du rendement métallique de la coulée et la possibilité de couler des produits de plus faible section, directement adaptés aux laminoirs finisseurs. La coulée continue permet de transformer le métal liquide en métal solide en des formes simples, et de façon continue. Un des soucis majeurs dans l’industrie de l’acier est l’amélioration de la qualité finale du produit. Certes, le produit final présente parfois des défauts, qui sont difficiles à détecter pendant la fabrication ; la plupart du temps, ils ne sont détectés que dans les phases finales de fabrication. L’objectif de ce travail consiste à fournir un modèle numérique du refroidissement secondaire permettant de prédire l’évolution du débit de refroidissement secondaire en fonction de la vitesse de coulée dans chaque zone des nuances de l’acier.Voir les détails

Mots clés : Modélisation thermomécanique, coulée continue, refroidissement secondaire, acier, Défaut.

ETUDE ÉLECTROCHIMIQUE COMPARATIVE D’UN ALLIAGE (TiNi) ÉLABORÉ, AVEC UN IMPLANT DENTAIRE EN MILIEU SIMULÉ

Soumaya MEDDAH (2018)
Thèse de doctorat

Good mechanical compatibility with cellular tissue and corrosion resistance, as well as excellent biocompatibility in body fluids, are required for titanium-based alloys to be materials of choice for biomedical applications such as orthopedic implants and dental. The present thesis aims to obtain TiNi binary alloys developed by vacuum induction, as a possible alternative for dental applications. The TiNi alloys developed as part of this thesis work contain Ni contents ranging from 40 to 60%. The choice of this composition was made, first to check the influence of the Ni content on the formation of the structure and the morphology of the phases and secondly the repercussions of this structure on the final properties of the alloy to know; the mechanical properties, tribological and electrochemical and bioactivity. TA6V4 alloy is used for comparison.For this purpose, the chemical composition of the TiNi alloys and the microstructural evolution was determined by scanning electron microscopy (SEM) coupled to the EDS. The formation and growth of the phases was followed by X-ray diffraction. Instrumented hardness measurements were made to assess the hardness and Young's modulus of the alloys. The coefficient of friction of the TiNi alloys and the wear rate were determined by dry sliding at different loads. The electrochemical characterization in Hank's solution and artificial saliva has been studied by stationary techniques and by EIS at different immersion times. The tribocorrosion behavior was performed in artificial saliva to understand the tribocorrosion mechanisms of TiNi and TA6V4 alloys. The bioactivity tests were performed in the SBF solution after 21 days of immersion. The SEM / EDS and RX results show that the two alloys Ti50Ni50 and Ti40Ni60 have a TiNi type matrix (NiTi), and Ti2Ni and Ni2Ti type precipitated phases. The revealed microstructure for the Ti60Ni40 alloy is a Ti2Ni-based matrix comprising the NiTi intermetallic. This same alloy had the lowest Young's modulus, while the Ti40Ni60 alloy had superior superelasticity, than the other titanium alloys (Ti50Ni50, Ti60Ni40 and TA6V4).All TiNi alloys exhibit better tribological behavior compared to the TA6V4 alloy which results in high wear resistance and low wear. Abrasive and adhesive wear mechanisms have been identified as degradation mechanisms for TiNi and TA6V4 alloys, with the predominant adhesive mechanism for TiNi alloys. The Nyquist and Bode impedance diagrams for all TiNi and TA6V4 alloys show capacitive loops with two time constants, indicating that the passive film is formed of two layers namely, a compact passive internal barrier layer and a porous outer layer. The electrochemical study revealed that all alloys have a passive character. The corrosion resistance of the TA6V4 alloy is greater than that exhibited by the various TiNi alloys. TiNi alloys showed hydroxyapatite formation under in vitro bioactivity conditions of SBF. Voir les détails

Mots clés : Titanium alloys, Young module, superelasticity, wear behavior, corrosion resistance, impedance, bioactivity.

Simulation and Modeling of Uncertainties in the Calibration of a Fluorescence Chemical Spectrometer (FRX)

S. Djemili, A. HAMOUDA, D. BERDJANE, B. Maalem (2018)
Article de conférence

Sensitivity analysis and uncertainty estimation are of major importance for the declaration of conformity of finished products. Models must be sought to analyze the test data. The main objective of this work is to establish reliable models to analyze our experimental data and validate them. So we have studied and used the Monte Carlo and Bootstrap simulation methods, we have been able to realize programs that calculate the uncertainty according to the ISO 8466 standard on X-ray fluorescence spectrometer samples from the URASM CRTI chemical analysis laboratory. Programs and interfaces are made with Matlab (GUI).Voir les détails

Mots clés : Simulation; uncertainties; Monte carlo; Bootstrap; calibration

Qualitative and Quantitative Assessment of γ and δ Phases in Duplex Stainless Steel Weldments by the X-Ray Diffraction Technique

A. Kellai, S. Dehimi, M.F. Benlamnouar, S. Kahla, S. Ouallam, Z. Boutaghou (2018)
Article de conférence

This paper is focused on the quantitative and qualitative characterization of austenitic-ferritic stainless steel welds by the X-ray diffraction technique. The first weldment realized by gas tungsten arc welding process GTAW with ER2209 electrode, the second weldment by shielded metal arc welding process SMAW with E2209-15 electrode. The results show that the presence of two phases, austenite γ and ferrite δ without any precipitation of secondary phases either in the base metal BM or in the two welded zones. Moreover, there is an increase in the ferrite content and the existence of non-uniform compressive stress in the GTAW weld zone.Voir les détails

Mots clés : welding, X-ray diffraction technique, duplex stainless steel, ferrite and austenite

MODELING AND SIMULATION OF THE COLD ROLLING PROCESS

K.Slimani, H.Bendjama, H.Katib, H.TAYOUB, S.AOUABDI (2018)
Article de conférence

The prediction of the power and torque, the stresses and the speeds is essential to drive in an optimal way an industrial operation like that of rolling. The prior knowledge of its mechanical quantities allows the good development of a rolling program. We present in this work a mathematical model of sheet rolling in the elastoplastic frame. This model is based on the slices method, the latter method is conventionally used in the rigid plastic frame independent speeds. We started by developing a model based on the slices method under MATLAB environment. In the second step, we introduced in this model the elasticity of the cylinders and the comparison of the results with another developed model based on the finite element method.Voir les détails

Mots clés : modeling, simulation, rolling, Slice method.

Microstructural Analysis of the deformed 316Ti and 904L StainlessSteel

L. Rabahi, N. KHERROUBA, I. Hadji, B. Mehdi, R. Badji (2018)
Article de conférence

ch are used in the petroleum industry. The two steels have been cold rolled with two widthreductions of 50 and 95%. Results of the microhardness measurements performed on the twosteels indicated that the 316L stainless steel is harder than the 904L stainless steel. In addition,the higher the deformation amount the higher the microhardness values for the two steels. X-raydiffraction analysis based on the Rietveld refinement method has been conducted and revealed adecrease of the size of the coherent domain of diffraction as a function of the deformation. Thisdecrease is accompanied by an increase of the dislocation density. A correlation withmicrohardness and a comparative discussion between the two steels is presented in this sudy.Voir les détails

Mots clés : Cold rolling, 316Ti, 904L, Micro-hardness, Dislocation density.

Contribution to the improvement of the quality of continuous casting steels at Sider El-Hadjar-Annaba

K.HAMLAOUI, H.Bendjama, H.TAYOUB, KH.SLIMANI (2018)
Article de conférence

Continuous casting is the process between steel making and rolling. It consists of turning liquid steel into slabs, blooms, or billets. The molten steel comes into contact with the mold, it will solidify and the first phases of the steel will form. This study confirms the need to check the steel quality and the continuous casting parameters such as; casting speed, extraction rate, oscillation of the mold and lubrication during primary cooling. The main objective is to build a thermal model that is an important task for predicting temperature profiles on different sides and edges of the product, in order to optimize the crust of steel.Voir les détails

Mots clés : continuous casting - steel - mold - primary cooling – slab.

Contribution to the improvement of the quality of continuous casting steel at Sider El-Hadjar-Annaba

HAMLAOUI Katib, BENDJAMA Hocine, TAYOUB Hadjira, SLIMANI Khair-Eddine (2018)
Article de conférence

Continuous casting is the process between steel making and rolling. It consists of turning liquid steel into slabs, blooms, or billets. The molten steel comes into contact with the mold, it will solidify and the first phases of the steel will form. This study confirms the need to check the steel quality and the continuous casting parameters such as; casting speed, extraction rate, oscillation of the mold and lubrication during primary cooling. The main objective is to build a thermal model that is an important task for predicting temperature profiles on different sides and edges of the product, in order to optimize the crust of steel.Voir les détails

Mots clés : continuous casting - steel - mold - primary cooling – slab

Effect of root pass filler metal on microstructure and mechanicalproperties in the multi-pass welding of duplex stainless steels

Ahmed KELLAI, Azzedine Lounis, Sami KAHLA, Brahim IDIR (2018)
Article de journal

This paper is focused on the estimation of the effect of root pass chemical composition, in multi-pass GTA Weldments, onmicrostructure and mechanical properties of duplex stainless steel welds.We used two different fillermetals, the super duplex ER2594 and duplex ER 2209. Microstructures of different passes of welded joints are investigated using optical microscope andscanning electron microscope. The relationship between mechanical properties, corrosion resistance, and microstructure ofwelded joints is evaluated. It is found that the tensile and toughness properties of the first weldment, employing the combinationof ER 2594 in the root pass and ER 2209 in the remaining, are better than that of the second weldment employing ER 2209 allpasses, due to the root pass grains refinement and its alloy elements content as chromium Cr and nitrogen N. The microstructureindicates the presence of austenite in different forms on the weld zone of ER 2209, same in the case of ER 2594, but with highercontent and finer grains size, in particularWidmanstätten austeniteWA. Potentiodynamic polarization tests of the first weld metalevaluated in 3.5% NaCl solution at room temperature have been demonstrated a corrosion resistance higher than that of thesecond weld metal. This work addressed the improvement of the corrosion resistance using appropriate filler metal withoutgetting any structural heterogeneity and detrimental changes in the mechanical properties.Voir les détails

Mots clés : Gas tungsten arc welding (GTAW), duplex stainless steel, Root pass, Filler metal, Microstructure and mechanical properties

BEHAVIOURS OF DEFORMATION AND RECRYSTALLIZATION OF 3% SILICON STEEL USING WEDGE-SHAPE SPECIMEN

R. Benchouieb, S. Achouri, W. Ghelloudj, S. TLILI (2018)
Article de conférence

Hot deformation and static recrystallization behaviours of a low carbon 3% Silicon steel, which is ferritic structure at high temperatures, has been investigated using wedge-shape specimen with a single-pass hot rolling experiments. The hot-rolling tests were carried out at temperature of 900?C to 9mm thickness followed by holding at the same temperature (900oC). The volume fraction recrystallized increased with the increase in rolling reduction and holding time after rolling, although a plateau was observed in the relationship between the volume fraction recrystallized and the effective strain. The preferential area for the recrystallization was the previous grain boundaries, particularly triple points of boundaries where the strain was concentrated. An inhomogeneity of recrystallization in the transverse sections through the thickness of the deformed wedges was observed. It was concluded that in this fine grain size material of 3% Silicon steel, the knowledge of deformation and recrystallization behaviors needs better control of strain and temperature under wedge-shape material.Voir les détails

Mots clés : 3% Silicon steel, wedge-shape specimen, hot rolling, deformation variables, dynamic recovery, static recovery, static recrystallization.