THE EFFECT OF VOLATILE MATTER OF NON-COKING COAL ON THE REDUCTION OF IRON OXIDE AT NON-ISOTHERMAL CONDITION

The volatile matter of non-coking coal was used for the reduction of hematite in argon atmosphere at nonisothermal condition. A thermal gravimeter furnace enable to use an 80 mm-height crucible was designed for the experiments to measure the weight changes of about 10 grams samples. A two-layered array of coal and alumina and four-layered array of iron oxide, alumina, coal and alumina was used for the devolatilization and reduction experiments, respectively. The net effect of volatile reduction of Fe 2O3was determined and it was observe that 45% reduction has been achieved. Three distinct regions were recognized on the reduction curve. The reduction of hematite to magnetite could be completely distinguished from the two other regions on the reduction curve. At 600-950°C, the reduction was accelerated. 63% of volatile matter resulted in 25% of total reduction before 600°C while the remaining volatile matter contributed to 75% of the total reduction. From the reduction rate diagram, the stepwise reduction of the iron oxides could be concluded. The partial overlap of the reduction steps were identified through the XRD studies. The starting temperature of magnetite and wüstite reduction were determined at about 585°C and at 810°C, respectively

Simulation of induction tempering process of carbon steel using finite element method

A numerical model was developed to simulate an induction tempering process, solving an electromagnetic-thermal coupled problem. The temperature distribution inside an alloy steel work-piece was computed and the final hardness was predicted using Jaffe and Gordon relation. The experiments were undertaken with different induction process settings at some industrial conditions. The effects of induction parameters i.e. input AC current density, coil velocity and coil stay time were investigated by employing the proposed model and the results were compared to the experimental data. The computed results are in a good agreement with the experimental data. As an example, the model predicted the final hardness at three given points 47, 45 and 37 HRC. For this tempering condition the experimental results were 51, 45 and 36 HRC, respectively. © 2011

Investigation on decomposition behavior of austenite under continuous cooling in vanadium microalloyed steel (30MSV6)

In the present study, investigations are focused on microstructural evolution and the resulting hardness during continuous cooling transformation (CCT) in a commercial vanadium microalloyed steel (30MSV6). Furthermore, the effects of cooling rate and austenite grain size (AGS) on CCT behavior of the steel have been studied by employing high-resolution dilatometry. Quantitative metallography accompanied with scanning electron microscopy (SEM) has efficiently confirmed the dilatometric measurements of transformation kinetics and austenite decomposition products. A semi-empirical model has been proposed for prediction of microstructural development during austenite decomposition of the steel and the resultant hardness. The model consists of 8 sub-models including ferrite transformation start temperature, ferrite growth, pearlite start temperature, pearlite growth, bainite start temperature, bainite growth, martensite start temperature and hardness. The transformed fractions of ferrite, pearlite and bainite have been described using semi-empirical Johnson-Mehl-Avrami-Kolmogorov (JMAK) approach in combination with Scheil\u27s equation of additivity. The JMAK rate parameter for bainite has been formulated using a diffusion-controlled model. Predictions of the proposed model were found to be in close agreement with the experimental measurements