Kinetics of reduction of iron oxides by H2: Part I: Low temperature reduction of hematite

Penetration and dissolution mechanisms are reviewed for predominantly single phase oxide, two phase oxide, and oxide–carbon composite refractories by liquid silicates. Theoretical models of these processes, as well as static (sessile drop, dipping, and crucible) and dynamic (rotating finger and rotary slag) experimental tests, along with their practical limitations are considered. Direct (congruent or homogeneous) attack involves dissolution of a solid into a liquid with no intermediate solid phase leading to active corrosion. Indirect (incongruent or heterogeneous) attack leads to formation of one or more new solid phases at the original solid/liquid interface. This may lead to passive corrosion. Examples of direct and indirect attack in a range of refractory–liquid systems are described highlighting the critical influence of the composition and hence viscosity of the local liquid adjacent to the solid. Penetration and corrosion can be controlled either through the local liquid composition via th...

Melt corrosion of oxide and oxide–carbon refractories

The extant data for the physical properties of BOS slags and for slag systems relevant to BOS have been collated and evaluated. Data for the following physical properties have been reviewed: phase equilibria, viscosities, densities, electrical conductivities, thermal conductivities, and the surface and interfacial tension between the metal and slag. In addition, various mathematical models have been developed for the estimation of the liquidus temperature, density, viscosity, surface tension, heat capacity, and enthalpy of slags. The efficacies of these different models have been evaluated and their reliability in predicting physical property for molten BOS slags has been assessed.

Physical properties of bos slags

A review has been conducted of the literature data pertaining to the surface tensions of pure iron and iron binary alloys. Approximate values for the respective surface activities of the alloying elements have been deduced. Of particular note are the high surface activities exhibited by Group VI elements in iron, together with the positive temperature coefficients of surface tension found with these alloys. Literature data for the suggested surface structures of the melts, based upon adsorption measurements, are included in this review.

Review of data for the surface tension of iron and its binary alloys

In order to understand the effect of slag composition on foaming in iron and steelmaking processes, slag foaming was quantitatively studied for CaO-SiO2-FeO slags in the temperature range of 1250 °C to 1400 °C. It was found that slag foaming could be characterized by a foaming index (Σ), which is equal to the retention or traveling time of the gas in the slag, and the average foam life ( τ). The effects of P2O5, S, MgO, and CaF2 on foaming were studied. As expected, slag foaming increased with increasing viscosity and decreasing surface tension. It was found that suspended second-phase solid particles such as CaO, 2CaO SiO2, and MgO stabilized the foam and had a larger effect on foaming than changes in viscosity and surface tension for the slags studied.

Study on the foaming of CaO-SiO 2 -FeO slags: Part I. Foaming parameters and experimental results

The rate of dissolu tion of solid lime in to liquid slag was determinedfrom the decrease of diameter of the lime cylillder rotated ill CaOSiO.-AI ,0 3 or FcOCa OSi02 slag. T he j)enetration of the slag to the solid phase and the distribution of componellts in liquid slag alijacent into the solidliquid inter.face were examined by the E. P.M.A. technique. The rate of dissolution increased with temperatllre and with rotating s/)eed of Ihe ~ylinder, sllptJorling the assumption that the diffilsioll of calcizlln through a slag phase boulldary layer would be the rate-determining step . The dissolution rate into the slag containing FeO was several times greater than thai into slag without FeO , because q{ the differences ill /)hysi cal /)roperties of slag and ill the morphology of 2CaO · Si02 formation . S lag componellts jJellelrated into solid lime Wire maillly AI, O , and FeO, alld the SiO, content was very little . This can be inter/lTeled by the formation of AI , O \" or FeO rich slag layer betweell solid lime alld 2CaO· SiO ,jilm.

A Fundamental Study on the Dissolution Rate of Solid Lime into Liquid Slag

Cylinders of burnt dolomite with the apparent porosities of 20 to 35% were immersed into molten FetO-CaO-SiO2 slags at temperatures of 1350 to 1425°C and rotated at 100 to 400rpm. The dissolution rates were determined by measuring the decrease in radius of cylinder.The dissolution rate increased with increases in temperature and revolutional speed of cylinder, but was not affected by the difference in apparent porosity of burnt dolomite. From the analysis of experimental results, it was concluded that the dissolution rate was controlled by the mass transport of CaO in burnt dolomite for low FetO slag (slag A) and that of MgO for other slags in the boundary layer of molten slag. Mass transport coefficients calculated were in the range of 4.7×10-4 to 1.7×10-3cm/s at 1400°C.It was found that the burnt dolomite after the experiment was widely covered with (Fe, Mg) O solid solution in the case of high FetO slag.

https://www.jstage.jst.go.jp/article/isijinternational1966/24/7/24_7_532/_pdf

Dissolution rate of burnt dolomite in molten FetO-CaO-SiO2 slags.

perature and the carbon content, and the temperature coefficient decreased with increase of carbon content. The surface tension and the density of iron-silicon alloys decreased with increase of silicon content , but abnormal phenomena were found at 50 at % Si, that is, the temperature coefficients of surface tension and density were positive. The surface tension of iron containing carbon reached a maximum value when some amounts of silicon was added, although individual addition of carbon or silicon decreased the surface tansion of iron.

Surface Tension of Liquid Fe-C-Si Alloys

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Surface Tension and Density of Liquid Cu-Sn Alloys

Synopsis: The surface tension and density of FeO-CaO, FeO-SiO2, and FeO-CaO-SiO2 melts, CaO content up to 40 mol% and SiO2 up to 50 mol%, in contact with solid iron, have been measured at temperatures from melting points to 1430•Ž by the maximum bubble pressure method. Surface tension values of these melts are in the range from 350 to 530 dyn/cm. Surface tension and density of liquid iron oxides show an abnormal behavior, that is, a positive dependence on temperature. The addition of CaO or SiO2 to iron oxide lead to monotonous decreases of surface tension and density of melts, but the maximum of surface tension is observed in the iso-thermal curve of surface tension of FeO-CaO-SiO2 ternary melts of constant CaO content at 1400•Ž. It is found that surface tension values of melts calculated from the equation containing terms of surface tension coefficients and the effect of ferric oxide agree well with the experimental results in the composition range of this experiment. Molar volumes of FeO-CaO and FeO-30CaO-Si02 melts show negative deviations from ideal mixture of components.

Yasuji Kawai

Papers

A Fundamental Study on the Dissolution Rate of Solid Lime into Liquid Slag

Dissolution rate of burnt dolomite in molten FetO-CaO-SiO2 slags.

Surface Tension of Liquid Fe-C-Si Alloys

Surface Tension and Density of Liquid Cu-Sn Alloys

Surface Tension and Density of FeO-CaO-SiO2 Melts