Synopsis : Thermodynamic consideration is an effective procedure for calculation of inclusion composition prediction. In general, Henrian standard state is used, and the activity coefficients of the constituents are represented by Wagner's formalism in thermodynamic calculations. This formalism is commonly used in low alloy steel, and this is not recommended for high alloy steel. High alloy steel is detailed thermodynamically using the Raoultian standard state, and the activity coefficients of the constituents are converted by Miki and Hino's formalism in this study. The equilibrium relation between Al 2 O 3 , MgO, spinel (MgO · Al 2 O 3 ) and dissolved Al, Mg and O in Fe-40mass%Ni-5mass%Cr alloy (Spacer Frame for fluorescent display) were discussed. Plant data of Fe-40mass%Ni-5mass%Cr alloy were compared thermodynamically with the calculated results. It was found that Wagner's formalism can't be useful for inclusion composition prediction of Fe-40mass%Ni-5mass%Cr alloy, Miki and Hino's formalism should be utilized for high alloy steel.
The recycling of valuable resources has currently became a major worldwide subject in the industries from the viewpoint of saving energy and protection of environment. Since the accumulated amount of steel product is reaching almost one billion ton in Japan, it is very important to develop the technology for the removal of tramp-elements such as tin, copper and zinc from steel scrap. In the present work, the rate of tin removal by the evaporation from carbon saturated liquid Fe-Sn-S alloy has been studied at 1,673 K under reduced pressure.Tin evaporates from molten iron and equimolar amount of sulfur is also removed together with tin. The evaporation rate of tin increases with increasing initial sulfur content in the melt. It is confirmed that tin dissolved in liquid iron is removed in the form of SnS under the presence of sulfur in the metal. The rate of tin evaporation becomes faster with reducing the pressure in the reaction chamber. This indicates that the rate is controlled mainly by the mass transfer of SnS in the gas phase.
The new flux of CaO-Al 2 O 3-MgO system was developed for the refining of low impurity and high quality steel from steel scrap or reduced iron by the combination of EAF-LF-RH. The practical tests of 12 heats using 110 ton scale EAF were carried out at 1873K. The chemical composition of final products was [mass ppm S]ϭ40-60, [mass ppm O]ϭ2-5 and [mass ppm N]ϭ50-70 without special troubles like the damage of refractory materials.
Iron nugget making process by rapid heating reduction of powdery iron ore and pulverized coal mixture is regarded as one of the novel ironmaking processes. Iron carburization during smelting reduction is especially important reaction step from the viewpoint of saving energy in this process. If the rate and efficiency of carburization reaction are increased, energy consumption of the process will be reduced to large extent. The purpose of this study is to clarify the carburization degree of iron nugget during smelting reduction of the mixture. The sample was prepared from graphite, electrolytic iron powder and synthetic slag containing iron oxide to simulate iron carburization phenomena during smelting reduction of the mixture in the present work. The sample was quenched immediately after the mixture changed into nugget shape in a rapid heating process. Laser microscope combined with infrared image furnace was used for sample heating and observation of carburization phenomena, and carbon content in the nugget was chemically analyzed after quenching. From above-mentioned investigations, it was revealed that the occurrence of carburization during smelting reduction in the sample mixture is advantageous to obtain higher carbon contain iron nugget.
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