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ELECTRIC furnaces, ARC furnaces, DIRECT-fired heaters, ELECTRIC arc, and FURNACES

This work has aimed at evaluating the deoxidation characteristics for Si-Mn in Electric Arc Furnace (EAF) melt shops. A statistical methodology led to the identification of the key EAF tapping process parameters that affect Si and O evolution during secondary refining. A first order kinetic equation estimated the deoxidation constants at the beginning of the ladle furnace process. The experimental values were5,3·10-3 s-1 and 3,6·10-3 s-1 As expected, these values are higher than that estimated for the reduction of the total oxygen content based on the gas injection agitation energy, which was 1,67·10-3 s-1, confirming the importance of the agitation caused by tapping. A model that couples slag and metal composition evolution in special from tapping to arrival at the ladle furnace (LF) was developed. The model confirmed the presence of undissolved slag solid fraction on arrival at the LF and made reasonable prediction for the liquid phase composition. The potential, limitations and applicability of each model are discussed, aiming at defining the next steps for a complete model for ferro-alloys additions to Si-Mn steels. [ABSTRACT FROM AUTHOR]

TECHNICAL literature, MICROALLOYING, STEEL, AUSTENITE, MARTENSITE, and DUAL-phase steel

In this work, martensitic kinetic models, available in the technical literature, were studied aiming to model and to predict the austenite to martensite transformation for the USISAR 80T steel, which is a structural, microalloyed, with high hardenability and considered a great weldable steel. Dilatometrictests were performed with a heating rate of 3°C/s until 920°C, with a soaking time of 180 seconds and cooling rates of 25°C/s, 50°C/s, 75°C/s and 100°C/s. One of the studied models showed good agreement with the experimental data for all the employed cooling rates, and it was possible to determinetransformation characteristic constants and suggest a previsibility model for the USISAR 80T steel. [ABSTRACT FROM AUTHOR]

CRYSTALLIZATION, METAL refining, SILICON, HYDROCHLORIC acid, LEACHING, and SOLUBILIZATION

This study aims to evaluate the process of acid leaching, in HCl, for purification of silicon metal, obtained by magnesiothermic reduction of silica and promote greater removal of impurities. The reaction product formed is a powder which is physically and/or chemically bound, with approximately 75% of MgO and approximately 25% of silicon metal, among other elements. Acid leaching is an technique used in the solubilization of oxides by an acid solvent. The silicon metal with purities up to 94% can be obtained in one step. Thus, it has been tested the effect of the following concentration of hydrochloric acid HCl (1, 2, and 3 M), temperature (50, 65, and 80° C) and time (60, 90 and 120 min). The leaching kinetics was studied under non-isothermal condition. After the treatments, it was shown that concentration is the main effect of leaching. In some analyses, it was possible to convert up to 76%, i.e., 99.66% of MgO has been extracted. [ABSTRACT FROM AUTHOR]

At high levels the element phosphorus demand dephosphorization operations in steel manufacturing steps resulting in high costs. Thus, it has been proposed the development of techniques for removing phosphorus contained in the iron ore before use in the steelmaking process. In this paper, it is proposed the evaluation of the kinetics mechanism of phosphorus removal by acid leaching technique before and after the pre heating and cooling of iron ore using microwave energy. Based on experimental results the mechanisms and reaction rates were discussed. It was shown that for larger particles (about 2.380 mm), the diffusional control mechanism is predominant for both processing conditions of microwave heating pretreatment and without pretreatment, indicating that the granulometric distributions is the main factor controlling the leaching kinetics. [ABSTRACT FROM AUTHOR]

MICROALLOYING, SLABS, HEATING of metals, HEAT resistant steel, and OSCILLATIONS

This work describes a mathematical model for the calculation of the solution kinetics of microalloying elements during steel slab reheating previous to hot rolling. That model shows that, under the industrial practical conditions of slab reheating, eutectoid precipitates with size greater than 250 nm are not completely dissolved, decreasing the free Nb content in austenite. It is also verified that the solution efficiency varies according to small oscillations in chemical composition of the microalloyed steels, a situation that is particularly important in the so called "skid marks" (colder regions) in the reheated slabs. [ABSTRACT FROM AUTHOR]

METAL crystal growth, METALLURGICAL research, VOLUMETRIC analysis, HEAT treatment of metals, and KINETIC theory of matter

During abnormal grain growth, in contrast with the normal grain growth, only few large grains dominate the grain growth process. The present study deals with the evolution of the abnormal grains in an AI-I mass% Mn alloy. Volumetric fraction of the abnormal grains as a function of the heat treatment time is showed. The experimental data are compared with equations of JMAK type. The results suggest that the beginning of the abnormal grain growth occurs in the interface between the abnormal grains and the small grains of the matrix. [ABSTRACT FROM AUTHOR]