Experimental procedures have been developed to measure heat losses and temperature in a laboratory scale, high temperature furnace under different conditions and thereby, to estimate various thermal properties of steelrefractory system such as emissivity, thermal conductivity and thermal contact resistance between refractory and steel plates etc. To these ends, a large number of experiments were carried out in an in-house designed resistance furnace with the help of pyrometers, contact thermocouples and heat flux transducer etc. Prior to detailed experimental work, calibrations of different measuring devices viz. thermocouple, pyrometer, heat flux transducers was carried out and measurements evaluated against available data bases, well established theoretical frameworks as well as against a computational procedure developed in-house. It is shown that while thermo-physical properties tend to depend on specific composition of material chosen, present estimates are not largely different from values reported for similar material in the literature. Thermal properties of the materials and contact resistances thus determined were finally embodied in a mathematical model, to calculate (i) transient thermal profile in a steel ladle lining during pre-heating operation and (ii) in situ wear (or thinning) of refractory lining in an industrial scale steelmaking furnace.
To understand and predict the microstructure evolution in various grades of steel, a heat transfer coupled with phase transformation model has been formulated with an enhanced stelmor cooling module. This module is capable of handling both blower assisted high cooling and retarded cooling using hoods. The stelmor module incorporates the change in ring spacing of the wire loops on the stelmor due to a change in mill speed and conveyor speed of the wire rod mill. A geometrical approach to convective and radiative losses taking into account the void fraction and shape factor of wire loop is reported. This makes the model robust by strengthening the heat transfer formulation. This paper deals with the correlation of wire rod mill process parameters on the cooling curve of wire rods. The cooling of wire rods is dependent on the stelmor operating parameters. Commercial high carbon grades require high capacity blowers for efficient cooling to refine the pearlite microstructure and impart greater strength. Welding grade wire rods (low carbon grades) on the other hand require retarded cooling to increase the ferrite grain size and decrease the ultimate tensile strength.
The strength in a high carbon wire is attributed to the pearlitic microstructure, which is required for ease of wire drawing. During cold drawing of high carbon steel wires, residual stress develops which has to be relieved in order to obtain the desired mechanical properties. To achieve this, the wire is passed through a closed loop online an induction furnace at a particular speed in order to heat it to a uniform temperature range. This research work presents the electromagnetic‐thermal modeling of the induction heating of a moving wire based on the finite element method using the software package, COMSOL MultiphysicsTM. The furnace had a complicated geometry for the coils and this is, perhaps, for the first time an exhaustive study which is being reported. A unique grid generation technique was developed considering the skin effect. This work is aimed at enabling modeling of the process and will in turn be useful when defining individual parameters affecting the temperature distribution in a component, subjected to induction heating. The temperature distribution in the work piece depends primarily on parameters like coil position, line speed, frequency of the current, thermal and magnetic properties of the work piece, and so on. The impact of power supply frequency and line speed were studied during the heating of the moving wire (workpiece). An in‐situ customized furnace of lower capacity was developed to carry out the validation experiments. The present modeling results are validated with online plant trial data and found to be in good agreement. Finally, the desired mechanical property achieved during trials was confirmed through tensile testing.
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