Metallurgical characteristics of refining slag used for high manganese steel

High manganese steel has excellent mechanical properties, which has garnered much attention. Whereas the research on the refining slag used for high Mn steel is very limited. In this study, the metallurgical characteristics of refining slag for high Mn steel were investigated based on thermodynamic calculation with FactSage 6.3 and slag-metal equilibrium reaction in MgO crucible. The calculated liquid zones of T ≤ 1873 K of CaO-SiO2-Al2O3-8%MgO-5%MnO system are located in the middle region of pseudo-ternary CaO-SiO2-Al2O3. For CaO-SiO2-Al2O3-8%MgO-MnO system, the apparent liquid zone at 1873 K enlarges with MnO content in slag increasing, and moves toward the direction of SiO2 and Al2O3 content increasing. For CaO-SiO2-Al2O3-MgO-MnO system, the liquidus zone shrinks with the basicity increasing, and moves toward the direction of Al2O3 content increasing. The measured MnO content in top slag reacted with high Mn steel was much higher than that reacted with conventional steels. In present experiments, the MnO content was around 5% when CaO-SiO2-Al2O3-MgO slag with basicity of 4 was in equilibrium with high Mn steel (Mn = 10, 20%) at 1873 K. The inclusions in master high Mn steel were mainly MnO type. After reaction with top slag, most inclusions transformed to MnO-SiO2 system and MnO-Al2O3-MgO system, in which the MnO content still shared the majority. Thermodynamic calculations show that SiO2 in top slag can be reduced by [Mn] in steel to supply [Si] under present experimental condition, which subsequently reacts with [O] in steel bath to form SiO2.

The Rate of Boron Removal from Molten Silicon by CaO-SiO2 Slag and Cl2 Treatment

In order to optimize a boron removal process by slag refining to obtain solar grade silicon, the rate of boron removal from molten silicon using CaO-SiO2 slag was investigated at 1823 K in an Ar atmosphere. The rate of boron removal was found to be controlled by mass transfer in molten slags, and the mass-transfer coefficient of boron in molten slag in the present experimental condition was evaluated. Some experiments on chlorination of boron in silicon and that of borate in slag using Cl2 gas were also carried out. Experimental results showed that the slag refining process with chlorination was proposed as a promising method for the boron removal from molten silicon.

Mechanism of decrease in plasma renin activity during volume expansion

The importance of filtered load of sodium and extracellular volume expansion (ECVE( per se on plasma renin activity (PRA) was studied in two groups of hydropenic dogs. Group I protocol consisted of bilateral ureteral obstruction (UO) followed by isotonic ECVE and finally UO release. During UO, PRA rose significantly above control (15.4 leads to 41.7 ng/ml per h). Superimposition of ECVE did not significantly alter PRA, but UO release returned PRA toward control (24.8 ng/ml per h). Fractional sodium excretion (FE(Na)) after UO release was higher than control (0.6 leads to 12.6%). In group II, ECVE preceded UO and caused a fall in PRA below control (16.8 leads to 4.8 ng/ml per h). FE(Na) was significantly increased over control (0.3 leads to 14.7%). Superimposition of UO reversed the fall in PRA to a value not significantly different from control. On release of UO PRA fell, but not significantly, whereas FE(Na) fell to 12.6%, a value not different from that during ECVE alone. The results indicate that filtration is required for ECVE to elicit a fall in PRA, under the present experimental condition.