Metallurgical and Materials Transactions B

The clogging behavior of a submerged entry nozzle for the casting of sulfur-containing Ca-treated Al-killed Ti-bearing steel was ex situ investigated. The surface of clogging consisted of CaO-TiOx phase, Al2O3-MgO phase, and Al2O3-CaO-SiO2 phase. The TiOx in the clogging was originated from the adhesion of inclusions in molten steel. The silicate inclusions were formed by the reaction between low-melting-point impurities in the nozzle base material, which can alleviate the nozzle clogging.

All the iron oxides (FeO, Fe3O4, Fe2O3, and FeAl2O4) dissolve in cryolite-alumina melts to give solutions containing both Fe(II) and Fe(III). The factor controlling the Fe(II)/Fe(III) ratio is the oxygen pressure, and experimental results are interpreted on that basis. Predictions are made of the variation of solubility with oxygen pressure, and the standard potential of the Fe2+/Fe3+ redox couple is calculated. The anode and anode gas of an industrial Hall-Heroult cell appear to be insufficiently oxidizing to cause significant conversion of Fe(II) to Fe(III). An anomaly in the liquidus diagrams for FeF2 – Na3AlF6 and FeO – Na3AlF6 is accounted for in terms of solid solution of FeF2 in cryolite.

The viscosities and free-running temperatures of slag in a La2O3-SiO2-Al2O3 slag system were measured using an internal rotating cylinder method. For different La2O3 mass contents (45, 50, and 55 pct) in the La2O3-SiO2-Al2O3 ternary slag, the slag viscosity and free-running temperature decreased with a decrease in SiO2 content and an increase in Al2O3 content, and decreased with an increase in La2O3 content. Minor components B2O3, FeO, and MnO could decrease the viscosity and free-running temperature of La2O3-SiO2-Al2O3 ternary slag, especially FeO, and a small amount of FeO and B2O3 had an additive effect on slag viscosity and free-running temperature reduction.

Our proposed method, i.e., a controlled molten oxidation process under 1 vol pct oxygen, leads to selective precipitation of magnetite in a copper smelter slag for downstream iron separation. In the present study, the preroasted magnetite precipitated copper slag was treated via magnetite liberation, which was realized by using high-voltage electrical pulses. The mineral distribution was determined by using a laser microscope and its image analysis; and it revealed that the 100-µm under-sieve product contains approximately 70 pct of liberated mineral particles. The study affirms the positive outcome of using this new technology for comminution to obtain micrometer-scale particles that yield monominerals via selective liberation. Using magnetic separation, iron was capable of finally separating into high- and low-iron-bearing concentrate and tailing that can be used in specific applications.

Measurements of liquid permeability in the mushy zones of Al-15.42 pct Cu and Al-8.68 pct Cu alloy samples were performed isothermally just above the eutectic temperature, using eutectic liquid as the fluid. A modified method was developed to determine the specific permeability as a function of time (K s) during the test from the data collected on these alloys. Factors affecting permeability measurements are discussed. The permeabilities are observed to vary throughout the experiment. This is attributed to microstructural coarsening and channeling that occur in the sample during the experiment. Coarsening rates are determined for the isothermal coarsening tests without fluid flow, and the results are observed to be less than the rates indicated from permeability tests where fluid flow is present. Careful measurement of the volume fraction of liquid (g L) shows that g L decreases during the test. The permeability is then related to the microstructure of the sample using the Kozeny-Carman equation. The correlation between the measured K S, g L, and specific solid surface area (S V) improves markedly when compared to previous studies, when microstructural parameters at the initial stage of the test are used.

Return fines of sinter were used to prepare cold-bonded briquette (CBB) with different briquetting pressure and properties, and reduction behavior and reduction kinetics of CBB were investigated in the current study. Increasing the briquetting pressure leads to the increase of the CBB’s compressive strength. The changing tendency of the CBB’s compressive strength after reduction disintegration index (RDI) experiment is similar with the CBB. With the increase of briquetting pressure, the particle size distribution of raw materials changes greatly, and the proportion of < 0.5 and 0.5–2 mm increased significantly. The porosity and reducibility index (RI) of the CBB decrease with the increase of briquetting pressure. The compressive strength of the CBB after the RI experiment and the reduction time both increase as the briquetting pressure is increased. After RI experiment, the main phases of 0 MPa CBB (briquetting pressure absent) are wüstite, metallic iron, calcium ferrite, and silicate, the main phases of periphery part of 20 to 240 MPa CBBs are wüstite, metallic iron, and silicate, and the main phases of core part of 20 to 240 MPa CBBs are wüstite, calcium ferrite, and silicate. Increasing the briquetting pressure from 0 to 240 MPa causes the reduction rate decrease. The effective diffusion coefficient of CO decreases when increasing the briquetting pressure.

The experimental study of the phase equilibria between calcium ferrite slag, metallic copper, spinel and/or dicalcium ferrite in the Cu₂O-FeO _x -CaO system has been carried out. Effects of temperature, oxygen partial pressure and Fe/CaO ratio on phase assemblages and compositions have been estimated. The advanced experimental technique including high-temperature equilibration on primary phase substrates, rapid quenching of the samples and quantitative measurements of equilibrated phase compositions using electron probe X-ray microanalysis has been applied. Spinel and dicalcium ferrite substrates have been specially designed to study phase equilibria at certain primary phase fields. Obtained experimental results have been compared with thermodynamic assessment of the Cu₂O-FeO _x -CaO system and available literature data.