With the Single Hot Thermocouple Technique (SHTT) the solidification behaviour of metallurgical slags has been studied using the apparatus of the Freiberg University of Mining and Technology, Germany, in cooperation with the Federal... more
With the Single Hot Thermocouple Technique (SHTT) the solidification behaviour of metallurgical slags has been studied using the apparatus of the Freiberg University of Mining and Technology, Germany, in cooperation with the Federal University of Rio Grande do Sul, Brazil. With this technique, which is suitable to build TTT or CCT diagrams, the sample is put on a thermocouple tip and can be heated or cooled at very high rates (> 3000 °C/min) due to the low mass of the system. One advantage is to allow in situ observation of melting and solidification under various thermal conditions. The motivation for this work is to provide basic information related to crystallisation control, for the development of fluorine-free mould slags for continuous casting of steel. Slags in the systems CaO-Al2O3, CaO-SiO2, CaO-SiO2-TiO2, and CaO-SiO2-TiO2-Na2O were studied, analysing the kinetics of crystals growth and crystals morphology. Following findings are reported: (i) for the slag CS (%CaO/%SiO...
During continuous casting the liquid slag infiltrates into the gap between the solidified strand and the mould generating a thin slag film. Due to the high temperature gradient the slag solidifies partially and remains partially liquid on... more
During continuous casting the liquid slag infiltrates into the gap between the solidified strand and the mould generating a thin slag film. Due to the high temperature gradient the slag solidifies partially and remains partially liquid on the hot side. In the solid films taken in the tail-out phase at the end of the cast the cuspidine as the crystalline phase in the most part of the square section was detected. The crystalline phase in the slag film is formed partially during the solidification and partially via the devitrification process from solid phase and undergo changes with time. It is known that the solid film adhere at the mould wall with residence times of up to several hours. The crystallization of the solid layer affects the heat flux from the liquid steel into the mould cooling water and it affects the rate and uniformity of the steel shell solidification. The understanding and the control of the crystallization phenomena in the solid layer is important to be able to ob...
Nowadays, there are increasing demands for developing mould fluxes without fluoride due to environmental concerns. Slag bearing titanium oxide and/or boron oxide proved to be promising substitute for traditional mould fluxes with... more
Nowadays, there are increasing demands for developing mould fluxes without fluoride due to environmental concerns. Slag bearing titanium oxide and/or boron oxide proved to be promising substitute for traditional mould fluxes with fluoride. In the present work, Crystallization behaviors of some slags in Al2O3–CaO–MgO–Na2O–SiO2–B2O3–TiO2 system were investigated using single hot thermocouple technique (SHTT), differential thermal analysis (DTA), and X‐ray diffraction (XRD) technique. It was found that liquidus temperature of slag decreases with increases of B2O3 content. The XRD analysis on the crystallized samples shows that crystallization products are perovskite, gehlenite, and wollastonite. Time–temperature–transformation diagrams (TTT) for various slags have been constructed using SHTT technique. It was found that B2O3 can significantly increase the incubation time for crystallization of slags. Incubation time for crystallization of slags at nose temperature decreases with increa...
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The majority of hazardous solid waste generated in “Rio Grande do Sul” State, Brazil, is produced from footwear leather industry. Thermal treatment leather waste is considered as a good alternative to deal with this problem, by generating... more
The majority of hazardous solid waste generated in “Rio Grande do Sul” State, Brazil, is produced from footwear leather industry. Thermal treatment leather waste is considered as a good alternative to deal with this problem, by generating energy. It is also possible to recover chromium from the ash generated during incineration. The aim of this work is to evaluate high carbon ferrochromium alloy production from leather waste ash, through computational and laboratory analysis. Computational thermodynamics was used to simulate ash Cr2O3 carbothermic reduction and to determine composition of the laboratory alloys. Several runs were done using a laboratory furnace at 1600oC to get ferrochromium alloys from the ashes. Different kinds of analyses were done to determine alloys and slags compositions. It was demonstrated that it is possible to use the chromium from leather waste ash for a production of high carbon ferrochromium alloy through carbothermic reduction at 1600oC. The results obt...