IMPACT OF CHANGES IN THE TERMS OF STRAIN FOR HOT ROLLED ON THE STRUCTURE OF LOW CARBON WIRE RODS

Wires of SAE 1008 steel, processed in the coil-forming head at two different temperatures to optimize the scale, were studied. It is relevant determine the impact of the changes of hot rolling process conditions in order to predict the mechanical properties of the final product. The structural characteristics of the steel wire and the scale layers generated during the processing conditions are evaluated. The structural study was carried out by light microscopy and scanning electron microscopy (SEM). Grain size and the phases percentage in the steel are determined. In addition, the phases present and layer thicknesses in the scale, are determined. Microhardness profiles on the product structure allows evaluating the effect of process conditions on the product. 8% variation in the coil forming temperature not produce structural changes or behavior in the steel product. It has generated a crust consisting mainly of wustite, suitable for chemical descaling

Efectos de las variaciones en las condiciones de deformación por laminado en caliente sobre la estructura de alambrones de bajo carbono.

Se estudian alambrones de bajo carbono SAE 1008 laminados y procesados en el cabezal formador de espiras a dos temperaturas diferentes, para optimizar la cascarilla. Es fundamental, conocer el impacto de las variaciones de las condiciones durante el conformado para predecir las propiedades del producto final. Se evalúa la estructura del alambrón y de la cascarilla generada. En el estudio estructural se aplica microscopía óptica y electrónica de barrido (SEM), se determina el tamaño de grano y los porcentajes de fases presentes. Se identifican las fases y se miden los espesores de las capas de la cascarilla. Mediante perfiles de microdureza se establece el efecto de las condiciones de procesamiento sobre el producto. La variación de 8% en la temperatura de formación de espiras no produjo cambios estructurales ni de comportamiento en el producto de acero. Se ha generado una cascarilla constituida principalmente por wüstita, apta para decapado químico.Wires of SAE 1008 steel, processed in the coil-forming head at two different temperatures to optimize the scale, were studied. It is relevant determine the impact of the changes of hot rolling process conditions in order to predict the mechanical properties of the final product. The structural characteristics of the steel wire and the scale layers generated during the processing conditions are evaluated. The structural study was carried out by light microscopy and scanning electron microscopy (SEM). Grain size and the phases percentage in the steel are determined. In addition, the phases present and layer thicknesses in the scale, are determined. Microhardness profiles on the product structure allows evaluating the effect of process conditions on the product. 8% variation in the coil forming temperature not produce structural changes or behavior in the steel product. It has generated a crust consisting mainly of wustite, suitable for chemical descaling

Master decomposition curve of carbonaceous materials used in casting powders

Casting powders are used in the continuous casting process of steels. These powders contain several oxides, fluoride compounds and carbonaceous materials. The decomposition kinetics of these carbonaceous materials regulates the melting rate of casting powders. In a previous work, a decomposition kinetics of two carbonaceous materials (coke and graphite) added to a casting powder was studied. Based on those data, in the present work, master decomposition curves (MDC) of these powders were constructed. For this, the values of both the activation energy (E) and the degree of decomposition (α), obtained in the thermogravimetric tests, were used for each heating rate (β). Then, the work of decomposition (θD) was calculated and the MDC was obtained. From the MDC, it was possible to predict the time (t) needed to produce a given degree of decomposition (α) at different temperatures (T). Taking this into account, it was possible to validate the master decomposition curves through different thermal treatments, where the degree of decomposition was calculated by interpolating the MDCs. These values were compared with those determined experimentally by measuring the mass loss in each heat treatment. In all cases, the results showed a good correlation between the predicted and measured values. It is concluded that the use of the MDC represents a useful tool to evaluate and compare the behavior of carbonaceous materials added to casting powder.Fil: Benavidez, E.. Universidad Tecnológica Nacional. Facultad Regional San Nicolás. Centro para el Desarrollo Tecnológico de Materiales; ArgentinaFil: Santini, Leandro Matias. Universidad Tecnológica Nacional. Facultad Regional San Nicolás. Centro para el Desarrollo Tecnológico de Materiales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Martín, A.. Universidad Tecnológica Nacional. Facultad Regional San Nicolás. Centro para el Desarrollo Tecnológico de Materiales; ArgentinaFil: Brandaleze, Elena. Universidad Tecnológica Nacional. Facultad Regional San Nicolás. Centro para el Desarrollo Tecnológico de Materiales; Argentin

Characterisation of inclusions in resulphurised microalloyed steel

Resulphurised steels, due to their good mechanical properties and machinability, are employed inthe manufacture parts of trucks and high strength components. The microstructure control ofthese steels can improve their toughness without losing strength. In this sense, the chemicalcomposition, morphology and distribution of MnS achieved with different thermomechanical processes affect the mechanical properties of the steel. In this work, the morphology and distribution of MnS inclusions in resulphurised steel 15V45 were analysed. Samples of the steel in its as cast condition and after hot rolling were examined using light and scanning electron (SEM)microscopies. Microhardness measurements and chemical composition of different MnS types were carried out to evaluate the plastic behaviour of each inclusion. The SEM images have provided information about the nucleation sites and size of the inclusions. Applying a Fe-Mn-S diagram under different thermomechanical conditions, this study could predict ductility problems and crack generation during hot rolling processes.Fil: Brandaleze, E.. Universidad Tecnologica Nacional. Facultad Regional San Nicolas; ArgentinaFil: Hereñu, Silvina Andrea Noemi. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); ArgentinaFil: Tormo, J.. Universidad Tecnologica Nacional. Facultad Regional San Nicolas; ArgentinaFil: Alvarez, Iris. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); Argentin