Resumen El hierro dúctil (DI) puede modificar sus propiedades con la adición de elementos aleantes y tratamientos térmicos adecuados. En este trabajo se estudiaron los efectos del vanadio y molibdeno en la microestructura y resistencia a la corrosión del DI y el hierro dúctil austemperizado (ADI). La resistencia a la corrosión fue evaluada por la técnica de polarización potencio-dinámica en 0.5 M H2SO4, 0.5 M NaCl y 0.5 M NaOH como electrólito. El ADI aleado con vanadio presenta ausferrita gruesa formada por agujas gruesas de ferrita, mientras que la combinación de vanadio y molibdeno permite obtener una microestructura fina compuesta de ausferrita y agujas delgadas de ferrita; esta microestructura mejora la resistencia a la corrosión en NaCl y NaOH. El DI presenta corrosión debido al par galvánico entre los nódulos de grafito y la ferrita; sin embargo, la presencia de una gran cantidad de carburos incrementa su resistencia a la corrosión en H2SO4.

Abstract Ductile iron (DI) can acquire various properties with the addition of alloying elements and through heat treatment. In this work, the effects of vanadium and molybdenum on the microstructure and corrosion resistance of DI and austempered ductile iron (ADI) were studied. Corrosion resistance was evaluated by potentiodynamic polarization techniques in 0.5 M H2SO4, 0.5 M NaCl, and 05 M NaOH as electrolyte. The ADI alloyed with vanadium presented an upper ausferritic microstructure consisting of broad ferrite needles, while the combination of vanadium and molybdenum allows obtaining a fine microstructure composed of ausferrite and thin needles of ferrite; this microstructure improves the corrosion resistance in NaCI and NaOH. The DI’s showed corrosion due to the galvanic pair between the graphite nodule and the ferrite; however, a high amount of carbide increases the corrosion resistance in H2SO4.

Abstract The motivation of this work is to show that the structural model, which was initially used to estimate the thermodynamic properties of binary silicate systems, can be also used to estimate the viscosity of binary and ternary silicate melts in terms of temperature and composition. The model links the viscosity to the internal structure of melts through the concentration of the oxygen bridges present in the slag. A previously proposed structural thermodynamic model was used to calculate the content of oxygen bridges. The viscosity model requires only three parameters to obtain a good agreement between experimental and calculated data for the SiO2−FeO binary system and for the SiO2−CaO−FeO, SiO2−MgO−FeO and SiO2−MnO−FeO ternary systems. The viscosity of ternary systems was calculated with the model while assuming a linear function of the parameters from binary systems; however, the content of the oxygen bridges was calculated using the thermodynamic model for ternary systems.

Magnesium removal process from molten aluminum using particles of silica sand was studied from a hydrodynamic point of view using computational fluid dynamics (CFD). The gas-liquid flow was modeled by a model of the Euler type for both gas and liquid phase transport. Newton´s law of motion was used to describe the subsurface motion of injected solid particles from the calculated flow field in one-way coupling. The kinetics of the transitory reaction was described by using the model proposed by Ohguchi and Robertson for transitory reactions. The contacting method of reaction for silica particles of 75, 210 and 425 µm was established according to its dynamic interaction with the two phases flow. When the particle size was increased, the residence time increased as well; however, the efficiency for the transitory reaction was decreased. The reaction rate simulation showed a good agreement with experimental results reported in the literature.

A multiphase- hydrodynamic model was solved with the phase field method and the Cahn-Hilliard equation to simulate the behavior of particle injection with nitrogen as conveying gas through a submerged lance into a lead bath in two dimensions. The residence and mixing time were obtained for different operating parameters like gas flow rate, lance depth, and different kettle and lance dimensions. The residence and mixing time decreased when the injection rate and the lance diameter increased. Therefore, the particle will have less opportunity to react with the liquid bath decreasing the refining metal processes efficiency. When the lance height and kettle dimensions were increased, the residence and mixing time also increased. In order to have an efficient disengagement of the particles from the carrier gas within molten lead, the operating parameters must take into account the residence and mixing times. The Cahn-Hilliard equation represents adequately the hydrodynamic behavior in the lance-kettle system studied.

The present study focuses on the effect of various degrees of plastic deformation generated by cold radial forging on the mechanical properties and the fracture morphology of 32 CDV 13 steel. The cold forging percentage was evaluated for 17.45, 33.30, 42.0 and 46.47 %. The microstructural analysis of the steel shows tempered martensite. The tensile strength, yield strength and hardness were found to increase with the increase of cold forging percentage due to the energy stored in the material during cold forging. For higher cold forging percentage, the toughness of the material was decreased according to the reduction of absorbed energy obtained during deformation. Fractography of the Charpy impact specimens shows a surface roughness and dimple pattern for the steel as was acquired and for 17.45 and 33.3 % of cold forging; while for 42 and 46.47 % of cold forging a cleavage fracture pattern was observed.