The conditions for stable formation of vertical slits in the lower part of the sintering bed and their effect on the sintering were investigated. The effect of the slits was evaluated experimentally with a test pot, feeding simulator and commercial plant. The total pressure drop was decreased and the permeability in the bed was improved by the formation of vertical slits. The gas flow rate in the slits was calculated at 1.8 times as large as that of a conventional bed. Moisture condensation, which decreases the void fraction in the sintering bed, is reduced by this increased gas flow rate. To form slits, plates were inserted vertically in the lower part of the raw material on the pallet of sintering machine. The ratio of the height of the plates to the distance between plates should be under 0.5 for stable feeding without stagnation of the raw material.
The surface tension of, and the contact angle formed by, molten iron on three types of commercial zirconia substrates containing 8 mol% Y 2 O 3 , 9 mol% MgO, or 11 mol% CaO were measured over a wide range of oxygen concentration in the molten iron by the sessile drop method. The solidified metal–substrate interface was examined in an SEM equipped with an EPMA. The surface tension of molten iron decreased with increasing oxygen concentration. The contact angle of molten iron increased rapidly with increasing oxygen concentration and reached a local maximum value at an oxgyen concentration of ∼100 ppm, and then decreased with increasing oxygen concentration. At lower oxygen concentration, dissociation of ZrO 2 was observed. For the ZrO 2 –9 mol% MgO substrate, segregation of MgO to the interface was observed. For the ZrO 2 –11 mol% CaO substrate, segregation of CaO and the precipitation of small ZrO 2 particles in the segregation layer of CaO were observed at the interface. Conversely, at higher oxygen concentration, penetration of molten iron into the grain boundaries was observed in all types of zirconia substrates.
The interfacial properties between liquid Fe-O alloy and alumina substrates with different purities, 99.9% and 96%Al2O3, were measured by the sessile drop method. The interfaces of samples after the experiment were examined by SEM and EPMA.It was found that the contact angle increased and the work of adhesion decreased with increasing oxygen concentration in the iron in the range of less than 0.010%. These phenomena were attributed to the dessociation of Al2O3. For 96%Al2O3, the Ca and Mg rich layer was observed at the Fe-Al2O3 interface. Whereas, at higher oxygen concentrations, the contact angle decreased with increasing oxygen concentration. Under these conditions, the formation of the hercynite or the penetration of iron into the grain boundaries of Al2O3 substrates were observed.
The interfacial properties between liquid Fe–O alloy and alumina substrates with different purities, 99.9% and 96% Al2O3, were measured by the sessile drop method. The interfaces of samples were examined by SEM and EPMA after the experiment.It was found that the surface tension decreased with increasing oxygen concentration in the iron for both substrates.The contact angle of 99.9% Al2O3 abruptly increased with increasing oxygen concentration at lower oxygen concentrations. These phenomena were attributed to the dissociation of Al2O3. Moreover, at higher oxygen concentration, the formation of the dense hercynite was observed at the Fe–O/Al2O3 interface, the contact angle slightly decreased with increasing oxygen concentration. For 96% Al2O3, a Ca- or Mg-rich layer was observed at the interface at a lower oxygen concentration, the contact angle abruptly increased with increasing oxygen concentration. Whereas, at higher oxygen concentrations, the contact angle rapidly decreased with increasing oxygen concentration. Under these conditions, the formation of hercynite and the penetration of iron into the grain boundaries of Al2O3 substrates were observed.
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