Métallurgie
Morphology and Mechanical properties of α-grain boundary in Ti-6Al-4V TIG welds.
In this Work, the effect of the TIG Welding process on the Morphology and mechanical behavior of α grain boundary (α-GB) phase appearing in TA6V welds are investigated. Different morphologies are observed depending on the pulsed frequency parameter, namely, the Zig-Zag morphology, the saw-teeth morphology and the normal continuous layer. The micro-hardness of each morphology has been measured and discussed. Voir les détails
Mots clés : TA6V, TIG Welds, α-Grain Boundary, Microhardness
EFFECT OF MULTI-PASS HOT ROLLING ON RECRYSTALLISATION BEHAVIOUR OF FERRITIC STAINLESS STEEL TYPE 409
The aim of this research is to study the effect of interrupted deformation on the recrystallisation behaviour of ferritic stainless steel type 409. Hot rolling schedules have been performed on an experimental rolling mill using rectangular slabs of this ferritic stainless steel.The research has been carried out using material of ferritic stainless steel type 409, which contains precipitates, initially using experimental rolling of small slabs and quantitative optical metallographic techniques with one pass only. Stainless steel type 409 displays a slower rate of recrystallisation than other ferritic stainless steels and this is attributed to the presence of titanium.The effects of static recovery and full static recrystallisation between two passes on subsequent recrystallisation kinetics have been investigated. In this stainless steel, when recovery occurs between the passes, subsequent recrystallisation is retarded compared with that for a single pass of the combined strain. Increasing the recovery time increases the retardation of recrystallisation even more. Also it has been found that when recrystallisation is complete between the two passes, the rate of subsequent recrystallisation after the second deformation was considerably accelerated. Voir les détails
Mots clés : ferritic stainless steel type 409, precipitates, hot rolling, dynamic recovery, static recovery, static recrystallization.
Study of physico-chemical properties of diatomite Algeria: Application to the thermal insulation of liquid steel bath
The purpose of this paper is to characterize and to evaluate the diatomite powder of Sig region (West Algeria) without fluorine by powder generally used in tundish to thermal insulation of steel bath contain fluorine, that affecting the environment and health of workers. Thermal and physicochemical characterization showed different endothermic and exothermic peaks. The scanning microscopy method was used and a large porosity was observed, which is very beneficial for improving the thermal conductivity of the product. The trial industrial in steelwork with diatomite powder, showed a weak loss temperature of steel (10 °C max), and filled fully function in thermal insulation of the steel bath. Voir les détails
Mots clés : diatomite, fluorine, Tundish, steelwork, thermal insulation, DSC
IMPROVING WEAR PROPERTIES OF HIGH-CHROMIUM CAST IRON BY MANGANESEALLOYING
High-chromium cast irons are widely needed by severalindustrial areas where wear is the dominant environment.They are used in mining, cement- and steel-making plants,and many others. Their microstructure consists of nettedeutectic carbides embedded in an austenitic or martensiticmatrix. The wear behaviour is mainly controlled by thecarbides shape and also matrix type. Several scientificworks try to improve the wear behaviour and to optimizethe life service of this cast iron by using various techniques.In this work, we intend to study the effect of manganesecontent on the microstructure properties and wearbehaviour of a 15 % chromium white cast iron used forball mill production. The present work treats the wearbehaviour, after heat treatment, of a manganese-alloyedhigh-chromium cast iron. A set of specimens were melted inan induction oven by varying the manganese content in therange 0–3 %. Heat-treated samples were analysed byoptical microscopy, MEB (SEM) scanning electronmicroscopy, differential scanning calorimetry, and X-raydiffraction and were wear tested by abrasion and friction.Increasing the manganese addition gave a structural evolutionand a wear resistance improvement. The best wearbehaviour is obtained with samples containing 3 % Mn. Voir les détails
Mots clés : Chromium cast iron, carbide-forming elements, eutectic carbides, secondary precipitation, abrasion, friction
Characterization of diatomitefrom Sig region (West Algeria)for industrial application
Diatomite also known Kieselguhr, is a non-metallic mineral composed of the skeletalremains of microscopic single-celled aquatic algae called diatoms. The purpose of this paper is to testand to evaluate the diatomite of Sig region (West Algeria) to substitute the main mould powder used incontinuous casting of steel for thermal insulation and lubrication.Design/methodology/approach – To assess the behavior of diatomite at different temperatures,a combination of simultaneous scanning calorimetric and thermogravimetric testing was used and toevaluate the structure of diatomite, the scanning microscopy method was applied.Findings – The results showed different endothermic and exothermic peaks, mainly at 84.7°C and783.5°C for endothermic peaks and 894.9°C for exothermic peak. The scanning microscopy methodwas used and a large porosity was observed. The trial industrial in continuous casting of steel showeda weak loss temperature of steel.Originality/value – This product may be used for thermal insulation in continuous casting of steel.Also the characterization showed the hot behavior of this product with the various transformationsand could give the possibility to other use Voir les détails
Mots clés : diatomite, fluorine, lubrication, Mould fluxes, thermal insulation
Evaluation and Chemical Analysis of Particulate Pollution in the Ironworks Site of El-Hadjar
The air that we breathe today is a mixture more or less polluted by location where we are. This mixture of pollutants generating significant and sustainable threats to human health, especially respiratory problems .The environmental concern is becoming increasingly strong, driven in particular by the current debate on sustainable development that is mirrored various international conferences [1] .Also theeffectson a global scale are warming the atmosphere and therefore the Earth, or the destruction of the ozone layer. The air quality management contributes to the mastery of a better knowledge of the pollution generated by the steel industrial activity. This investigation is the first national enterprise approach to the management of environmental problems on an industrial scale, more particularly in the steel sector. Taking into account these principles, it is appropriate to follow the pollution by suspended particles in and around the steel complex of El Hadjar.The objectives of this work are:Knowledge Of highest concentration level of dust inside and outside the workplace. Evaluation Compared to WHO limits values [2] and European Directives [3];[4]. Determination Of heavy metals in dust fallout.For the choice of measurement sites, a clipping entire surface of the steel complex was carried out by a method called mesh. This method we devoted 19 measurement sites. The sampling method used is that of BERGHEROFF. Indicators are the overall amount of dusts deposited chemical analysis elements such as Cr, Cu, Zn, Ni, Pb and Mn [4]. The quantities of dust are analytically weighed and then analyzed atomic absorption analytical chemistrySuspended particles that contaminate the air are the main carriers carry in the wind various polluting compounds (SO2, Cu, Pb, H2SO4, NH3 ...) [3]. At PMA 2, calculations show is discharged 4509 m3 per ton of fumes sinter. The results showed measurement sites S2, S3, S4, S5 and S18 are large emissions dusts. These sites except S18 represent the hot zone of complex. According Opair,the incidence of values of the measured dust on the sites is all above the limit value. For heavy metals in the dusts, there is a high concentration of zinc in all sites. Knowing that is neurotoxic and carcinogenic Pb is present in large quantities with a peak in S3. For S11 and S17 its value is close to the norm. The chromium and nickel both carcinogenic move in the same direction with alarming values. Voir les détails
Mots clés : Air pollution, dust emission, particulate fallout, TPS, method Bergeroff, heavy metals.
Microstructure and residual stresses in Ti-6Al-4V alloy pulsed and unpulsedTIG welds
Increasing the pulse frequency in pulsed Tungsten Inert Gas arc welding refines the prior- grain size in the fusion zoneof Ti-6Al-4V compared to unpulsed arc welding. The microhardness increases in the fusion zones obtained with pulsed welding mode, with respect to this microstructural evolution. The increase of the pulse frequency contributes to the formation of a more important amount of residual phase in the fusion zone which is accompanied by a decrease of microhardness. The tensile residual stress (RS) level in the pulsed process is lower than the one of the unpulsed process. The tensile RS induced by both welding processes in the HAZ are found to decrease when increasing the pulse frequency. In the fusion zone, the transversal RS are of compressive type for both processes whereas the longitudinal ones change from tensile to compressive type when increasing the pulse frequency. Voir les détails
Mots clés : Ti-6Al-4V alloy, welding, pulsed current, microstructure, residual stress.
Study of physico-chemical properties ofdiatomite Algeria: Application to thethermal insulation of liquid steel bath
The purpose of this paper is tocharacterize and to evaluate the diatomitepowder of Sig region (West Algeria) withoutfluorine by powder generally used in tundish tothermal insulation of steel bath contain fluorine,that affecting the environment and health ofworkers. Thermal and physicochemicalcharacterization showed different endothermicand exothermic peaks. The scanning microscopymethod was used and a large porosity wasobserved, which is very beneficial for improvingthe thermal conductivity of the product. The trialindustrial in steelwork with diatomite powder,showed a weak loss temperature of steel (10 °Cmax), and filled fully function in thermalinsulation of the steel bath Voir les détails
Mots clés : diatomite, fluorine, Tundish, steelwork, thermal insulation, DSC
EFFET DE LAMINAGE A CHAUD SURLE COMPORTEMENT DE LARECRYSTALLISATION DE L’ACIERINOXYDABLE FERRITIQUE TYPE 409
The behavior of the static recrystallization of this ferritic stainless steel type 409 which contains precipitateswas examined using hot rolling test of a single pass. Hot rolling tests were carried out at temperature of 870°C from athickness of 15mm to 8,4mm and 4,7mm thickness at a controled strain rate of 3.3s-1. The recrystallized volumeincreases with the increase of the reduction and the holding time after hot rolling. Nucleation of recrystallising grainsappears to be associated with triple points and grain boundaries. This material displays a slower rate of recrystallisationand this is attributed to the presence of titanium Voir les détails
Mots clés : ferritic stainless steel type 409, precipitates, deformation variables, hot rolling, dynamic recovery, static recovery, static recrystallization
Beta to alpha transformation kinetics and microstructure of Ti-6Al-4Valloy during continuous cooling
In the present paper, an approach based on the Kolmogorov-Johnson-Mehl-Avrami (KJMA) model hasbeen developed and applied to study the transformation kinetics of the b phase in Ti-6Al-4V titaniumalloy during cooling. To this purpose, Differential Scanning Calorimetry (DSC) tests have been conductedusing a set of cooling rates ranging from 10 to 50 C/min. This approach allows the kinetics parameters,particularly the activation energy, to be calculated from a single DSC test using a simple linear regression.The microstructural analysis indicates that the microstructure is dominated by the a Widmanstatten €morphology (aW). Microstructural observations along with the calculated values of the Avrami index andof the activation energy suggest that the growth of the aW platelets obeys a mixed mode combining thevanadium diffusion and a displacive mechanism. Voir les détails
Mots clés : Continuous cooling, KJMA model, additivity rule, diffusion, Displacive mechanism