Métallurgie
CONTRIBUTION TO CHARACTERIZATION OF NATURAL DIATOMITE
With the complex examination of raw material from a Sig deposit in Algeria in the region of Mascara area, physical, chemical and mineralogical properties of diatomite have been defined. It has been found that it is a dominantly amorphous material, sedimentary rock of the type silica-diatomite. The raw material consists of approximately 60% SiO2. Of the physical properties, more significant is porosity, which is higher than 60%. The raw material has a wide spectrum of possibilities for practical application: intensive absorbent for several types of liquids and chemical properties of the soil, natural insecticide, and filter water etc. For determination of the chemical contents, properties and origin of the raw material the following methods have been used, such as, chemical analysis, XRD analysis, optical microscopy and thermal analysis. Voir les détails
Mots clés : diatomite, X-ray, XRD, Sig.
BEHAVIOURS OF DEFORMATION AND RECRYSTALLIZATION OF 3% SILICON STEEL USING WEDGE-SHAPE SPECIMEN
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.
Contribution to the improvement of the quality of continuous casting steels at Sider El-Hadjar-Annaba
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.
Qualitative and Quantitative Assessment of γ and δ Phases in Duplex Stainless Steel Weldments by the X-Ray Diffraction Technique
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
Simulation and Modeling of Uncertainties in the Calibration of a Fluorescence Chemical Spectrometer (FRX)
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
Effect of root pass filler metal on microstructure and mechanicalproperties in the multi-pass welding of duplex stainless steels
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
Tribological behaviour of a continuous hot dip galvanized steel
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
Thermal Treatment Effect on Tribological and Corrosion Performances of 13Cr5Ni2Mo Super- Martensitic Stainless Steel
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
Correlation Between the Pitting Potential Evolution and σσ Phase Precipitation Kinetics in the 2205 Duplex Stainless Steel
The aim of this work is to correlate the pitting potential (Epit) evolution with the kinetics ofrphaseprecipitation in the 2205 duplex stainless steel aged at 850°C after solution treatment at 1150°C. Thepotentiodynamic polarization curves indicate a reduction of the pitting corrosion resistance with the agingtime, which is revealed by a decrease in theEpitvalues from 0.65 to 0.40 VSCE. Thus,Epitvalues are used todetermine the kinetics parameters of therphase precipitation. The experimental transformed fractionagrees well with the one calculated by using the modified Kolmogorov–Johnson–Mehl–Avrami equationwith an impingement parameterc= 0.6. Voir les détails
Mots clés : kinetic, KJMA, Pitting corrosion, otentiodynamic polarization, r phase precipitation
Approche analytique du comportement viscoplastique et microstructural d'un acier microallié au Nb-Ti-V lors des essais de simulation à chaud
L'objectif de cette thèse est de fournir des données sur les propriétés mécaniques d’aciers microalliés Nb-Ti-V (HLE) à bas carbone destinés à la fabrication de tubes pour le transport de gaz et de pétrole, obtenus dans le processus industriel et de développer par la même une compréhension globale sur l’évolution microstructurale en termes de paramètres de déformation. Plus précisément, l'objectif principal est de développer un matériau avec un meilleur équilibre des propriétés à partir d’acier microallié existant X60 afin élargir la production vers des grades supérieurs type X80 et cela à partir de la même composition chimique. A cet effet, des essais expérimentaux incluant la dilatométrie, un laminoir pilote et la torsion à chaud (selon une gamme de vitesses de déformation) ont été réalisés pour simuler les séquences de laminage du procédé industriel. Les résultats de ces protocoles expérimentaux ont permis de mettre en évidence l'effet significatif de paramètres de déformation sur l'évolution de la microstructure finale, donc sur les propriétés mécaniques de l'acier étudié, et de faire des propositions technologiques pour obtenir des grades élevés pour ce type d'acier laminé. Un modèle de prédiction de l'évolution de la microstructure de l'austénite lors de la déformation à chaud qui est une étape clé dans la modélisation des transformations de phase a été également développé pour prévenir plus précisément la taille des grains, les fractions recristallisées ainsi que les déformations et les contraintes critiques qui leur sont associées. Ces différentes approches de prédiction des propriétés d’écoulement basées sur les aspects analytiques et sur les observations microstructurales ont permis de déterminer des relations quantitatives des lois de comportement macroscopique tout en décrivant les phénomènes physiques qui sous-tendent les comportements rhéologiques.NB : Ce travail académique, entrant dans le cadre de projet de recherche interne URASM CSC ANNABA (dont Mr Berdjane était chef d’équipe) et une partie de thèse de doctorat, été consacré à l’étude du comportement viscoplastique des aciers HLE. Mr Berdjane a été mandaté officiellement en tant que chef d’équipe laminage par la Direction DRA CERSIM SIDER et l’URASM CRTI Annaba de valoriser une partie technique du projet de recherche de coopération DRA/SIDER-Freiberg Allemagne par un aboutissement à une thèse de doctorat. Voir les détails
Mots clés : Traitements thermomécaniques, aciers HLE, Laminage à chaud, torsion à chaud, comportement viscoplastique, modèle microstructural