No abstract

Mechanical stirring is widely used for hot metal desulfurization in Japan. In this process, solid lime is added as flux and emulsified into molten iron using a vortex formed by the stirrer. However, in addition to the added solid lime, the liquid top slag on the ladle is emulsified and forms granules. To clarify the roles of the solid lime and liquid slag in hot metal desulfurization, the reaction rates of slag, solid lime, and slag with solid lime are determined and the interfacial layers are observed.The results are summarized as follows:(1) The desulfurization rate is very slow when a solid lime rod is immersed into hot metal without slag. The reason for the slow desulfurization is the formation of an interfacial layer, which inhibits the mass transfer of sulfur.(2) Because sulfur is not detected inside the solid CaO, the mass transfer of sulfur from the liquid slag to the solid CaO does not occur. Therefore, it is believed that solid CaO does not play a direct role in the desulfurization reaction, and thus, the reaction is solely due to the liquid slag. A good relationship between the desulfurization rates and the sulfide capacity of the liquid slag is found.(3) When tricalcium aluminate forms at the interface, the desulfurization rate is increased by the immersion of a CaO rod. This is due to the supply of CaO to the slag because this interfacial layer does not inhibit the mass transfer.

The activity coefficient of strontium in a copper melt has been investigated by a chemical equilibrium technique in the temperature range from 1473 to 1773 K. A graphite crucible was used to control the oxygen partial pursuer in CO gas. The activity coefficient was derived from the standard free energy of formation of SrO, the oxygen partial pressure, and the concentration of strontium in copper.The standard free energies of formation for SrOÁ6Al 2 O 3 and SrOÁ2Al 2 O 3 at 1723 K are also derived by equilibrating Al 2 O 3 , SrOÁ6Al 2 O 3 , and SrOÁ2Al 2 O 3 with Cu.