Surface and interfacial phenomena of liquid iron alloys

Surface tension of a liquid steel and interfacial tension between a liquid steel and a liquid slag play an important role in iron and steelmaking processes as they are key parameters in the understanding of inclusion removal and slag emulsification. The ultimate goal of this work is to better understand the interfacial energies and phenomena that occur during actual steel processing.; The effect of sulfur on the surface tension of Fe-30%Cr alloys was determined by a sessile drop technique at 1550°C. Sulfur was found to be strongly surface active in liquid Fe-30%Cr alloy and the variation of surface tension of the alloy with sulfur activity is expressed as: g=1592-178ln1+145 asa s>21ppm The contact angles between liquid Fe-30%Cr-S alloys and alumina decreased significantly with increasing sulfur activity. The surface tension of Fe-Cr alloys decreased slightly with increasing Cr content. The contact angle of Fe-13% Cr on alumina increased by 6° and remained unchanged in the range between 13% and 30% Cr. The interfacial tensions of Fe-Cr alloys were determined with three different slags by a sessile drop technique combined with X-ray radiography. Silica and iron oxide additions to the CaO-Al 2O3 slag lead to a significant decrease in the interfacial tension. Chromium addition did not affect interacting force at the interface, which indicates that the interfacial structure between Fe-Cr alloy and the slag is identical to the one between Fe and the slag.; Dynamic interfacial tension phenomena between Fe-Al and Fe-Ti alloys in contact with CaO-SiO2-Al2O3 (2:2:1 by weight) slag have been studied by X-ray radiography and by scanning electron microscopy. For Fe-Al alloys, dynamic interfacial tension phenomena were noticed at aluminum content as low as 0.25%. Significant spreading of the alloy interfacial turbulence and spontaneous emulsification were observed in experiments with a Fe-3.28% Al alloy. Generation of Marangoni flow is suggested at the steel-slag interface during reaction as the driving force for instability of interface. For Fe-Ti alloys, dynamic interfacial tension phenomena were observed over 5.8% Ti. Significant spreading of the alloy was observed by X-ray photography at Fe-11% Ti alloy. A less perturbed interface and a film-type of metal emulsification were observed in the quenched sample during reaction.; The effect of CaF2, Al2O3 and Na 2O additions to CaO-SiO2 slag on the interfacial tension was determined at 1550°C. CaF2 led to a significant decrease in the interfacial tension while the Na2O and Al2O 3 additions led to an increase in the interfacial tension. Carbon addition to mold slag that was in contact with 321 stainless steel led to a decrease in the interfacial tension.; A correlation model was developed to predict the equilibrium interfacial tension between Fe-O alloys and an oxide slag. The formation energy difference of the slag was found to be a good linear relationship with the interaction coefficient from the Girifalco-Good's equation: F=0.89-0.0015•DGDi The model calculations of interaction coefficient ( F ) and interfacial tension ( g ms) were validated with experimental data. (Abstract shortened by UMI.)...