Deoxidation of molten titanium by electron-beam remelting technique

The deoxidation of molten titanium was attempted by aluminum suboxide evolution in an electron-beam remelting furnace. Titanium aluminum alloy was deoxidized to about 0.05 to 0.01 wt pct oxygen in a few minutes by adding aluminum to the melt. Aluminum activity in the alloy was estimated by the evaporation rate of aluminum. formerly Graduate Student, Institute of Industrial Science, The University of Tokyo     

Dissolution of solid copper cylinder in molten tin-lead alloys under dynamic conditions

The dissolution of a copper cylinder in molten tin-lead alloys was studied at 673 K under static and dynamic conditions in the peripheral velocity range 1.9 to 75.4 cm per second using an immersion method. The dissolution rate of copper increased with increasing tin concentration and peripheral velocity. The solution rate constant increased with peripheral velocity and with diffusion coefficient of copper in the melt. The constant decreased with kinematic viscosity of the melt and diameter of the specimen. The dissolution of copper in molten tin-lead alloys was mixed control. Flow of the melt under forced convection was turbulent flow with Taylor vortices. Natural convection occurred in dissolution of stationary copper in tin rich alloys due to hydrodynamic instability from density differences in the melt. YOSHIFUSA SHOJI, formerly Graduate Student, Tokai University, Tokyo     

土状石墨用于钢水增碳的研究

采用热重法、XRD检测分析了土状石墨原矿的化学组成,同时研究了在1 600℃下土状石墨原矿及几种企业用增碳剂的增碳效果以及对钢中S、N、O等元素质量分数的影响,并分析讨论了增碳反应动力学.结果表明：土状石墨的固定碳含量为84%~89%,灰分中S、P的质量分数分别为0.02%和0.04%,远低于增碳剂对硫、磷含量的要求;在理论增碳量为0.1%和0.4%时,土状石墨的增碳效果与企业增碳剂相当,对钢中S、N、O基本没有影响;得到了一个动力学模型用以描述增碳剂在钢水中的增碳反应过程.     

Deoxidation equilibria of molten nickel by Mg-Al and Mn-Al

The deoxidation equilibria of aluminum-magnesium and aluminum-manganese in liquid nickel equilibrated with Al₂O₃-saturated MgAl₂O₄ and MnAl₂O₄, respectively, were investigated in the temperature range of 1773 to 1873 K. At 1773 K, the oxygen levels could be reduced to 5.8 to 6.6 ppm with 2.5 to 10 ppm magnesium and 0.05 to 0.9 mass pct aluminum in the Ni-Mg-Al-O system, and to less than 20 ppm with more than 1.5 mass pct manganese and 30 ppm aluminum in the Ni-Mn-Al-O system. With the experimental results mainly obtained in the present work, the interaction parameters, e _Mg ^Al , e _Mn ^Al , e _O ^Mg , e _O ^Mn , and e _O ^Al , and the equilibrium constants, log , log , log K _Mg(Ni), log K _Mn(Ni), and log K _Al(Ni), were estimated using a multiple regression analysis.     

Interaction of copper sulfides with copper oxides in the molten state

Reactions of Cu₂S with Cu₂O, CuS with Cu₂O and CuS with CuO in the molten state were examined in the presence of one atmosphere of argon at 1200°C. A rate law of the form,r _SO2 =kN_SN_O was applicable for each reaction system studied. Comparison of the rate constants for the systems, under conditions of similar initial mole fraction of sulfur to mole fraction of oxygen ratios, showed that Cu₂O was much more reactive than CuO in its reaction with copper sulfides. These results are incorporated in a mechanism in which Cu₂O reacts with the sulfide in the rate determining step. Experiments carried out in the presence of oxygen indicated the importance of a CuO-Cu₂O equilibrium in the overall reaction mechanism.     

Oxidation of molten copper matte

An amount of 80 mg of molten copper matte of a pseudo-ternary Cu₂S-FeS-Fe system contained in a slender alumina sample tube was oxidized at 1503 and 1533 K in a mixed O₂-Ar gas stream and the oxidation path was followed, comparing the overall rate of oxidation with the gaseous diffusion in the sample tube. The following successive reactions were found to be controlled by gas diffusion. Initially, Fe was oxidized to form FeO. After the melt composition reached a pseudo-ternary Cu₂S-FeS-FeO system, FeS was oxidized to form FeO. As the amount of FeO increased, Fe₃O₄ was also formed and subsequently Cu was produced by the oxidation of Cu₂S. In the latter stage, the Cu was oxidized, and the final product under the condition of gas diffusion control was composed of Cu₂O, Fe₃O₄, and CuFeO₂. On the other hand, the rate of formation of Fe₂O₃, CuO, and CuFe₂O₄ was much slower and they were not formed during the oxidation duration where the overall rate of oxidation was controlled by gas diffusion.     

Oxidation kinetics of molten copper sulfide

The oxidation kinetics of molten Cu₂S baths, during top lancing with oxygen/nitrogen (argon) mixtures, have been investigated as a function of oxygen partial pressure (0.2 to 0.78), bath temperature (1200 °C to 1300 °C), gas flow rate (1 to 4 L/min), and bath mixing. Surface-tension-driven flows (the Marangoni effect) were observed both visually and photographically. Thus, the oxidation of molten Cu₂S was found to progress in two distinct stages, the kinetics of which are limited by the mass transfer of oxygen in the gas phase to the melt surface. During the primary stage, the melt is partially desulfurized while oxygen dissolves in the liquid sulfide. Upon saturation of the melt with oxygen, the secondary stage commences in which surface and bath reactions proceed to generate copper and SO₂ electrochemically. A mathematical model of the reaction kinetics has been formulated and tested against the measurements. The results of this study shed light on the process kinetics of the copper blow in a Peirce-Smith converter or Mitsubishi reactor.     

Solidification front shape of the molten metal in a thermally thin cylinder

Reported data are reviewed briefly. When a molten metal is extruded to produce a wire directly from the melt, a capillary stream 0.2–3 mm in diameter is directed into a cooling medium so that external heat exchange ensures faster solidification of the metal as compared to capillary disintegration of the stream into drops. The following two assumptions regarding the shape of the solidification front exist: a planar solidification front normal to the axis and a curved axisymmetric front surface. Both assumptions are considered. The assumption of a curved axisymmetric solidification front surface of the molten metal in a cylinder is shown to be more realistic.     

Arsenic activities in molten copper and copper sulfide melts

In recent years, the concentration of the group Va elements such as arsenic, antimony, and bismuth has been increasing in copper concentrates. The elimination and recovery of these elements during the copper smelting process have presented serious problems. While the distribution of minor elements has been studied extensively, very little knowledge exists on the activities of these minor elements in copper mattes. Consequently, in this study the activities of arsenic were measured to determine activity coefficients of arsenic in the dilute solution region of molten copper, in Cu₂S saturated copper, and in copper mattes equilibrated with copper at 1423 K by a mass spectrometric Knudsen effusion technique. Formerly with the Department of Metallurgy and Materials Science, University of Toronto, Toronto, ON, Canada     

Desulfurization behavior of molten copper alloy by a soda ash

As a basic study on desulfurizing copper alloy scraps in the remelting process, desulfurization experiments were carried out with a molten Cu-8 pct Sn-0.1 pct P by using a Na₂CO₃ flux in a 2-kg high-frequency and a 5000-kg low-frequency melting furnace to investigate the influences of the melting atmosphere, the melting temperature, and the flux composition on the desulfurization behavior of the flux. Desulfurization and dephosphorization began simultaneously. Desulfurization ceased earlier than dephosphorization, and then the reversion of sulfur was found to proceed. Covering the melt with charcoal or a carbon crucible enhanced the desulfurizing ability of Na₂CO₃. The maximum desulfurizing ability was observed at 1473 K. Sulfur distribution between the melt and the flux increased with increasing the basicity of the flux and with decreasing Cu₂O content in the flux. The desulfurization rate was also evaluated based on a two-film model.     

Settling of copper drops in molten slags

The settling of suspended metal and sulfide droplets in liquid metallurgical, slags can be affected by electric fields. The migration of droplets due to electrocapillary motion phenomena may be used to enhance the recovery of suspended matte/metal droplets and thereby to increase the recovery of pay metals. An experimental technique was developed for the purpose of measuring the effect of electric fields on the settling rate of metallic drops in liquid slags. Copper drops suspended in CaO−SiO₂−Al₂O₃−Cu₂O slags were found to migrate toward the cathode. Electric fields can increase the settling rate of 5-mm-diameter copper drops 3 times or decrease the settling until levitation by reversal of the electric field. The enhanced settling due to electric fields decreases with increasing Cu₂O contents in the slag.     

Reduction of iron oxides from liquid slags using a graphite rotating disc

Research work has been carried out on the reduction of FeO from liquid slags of the CaO‐FeO‐SiO₂ ternary system using a graphite rotating disc technique. The investigations were conducted on slags with a basicity of CaO/SiO₂ = 1.27 and FeO contents of 20 and 60%, at temperatures of 1350 and 1420°C. The calculated viscosity range for these slags is within 2.53 – 0.43 dPa·s. It has been found that the factor controlling the reduction process is diffusion of FeO towards the disc surface, both in the case of the reduction from the slag with 20% FeO and in the case of the reduction from the slag with 60% FeO fraction. The diffusion coefficient of FeO at the reduction temperature of 1350°C is of the order of magnitudes of 10^?7 cm²/s, while at 1420°C it reaches the order of 10^?6 cm²/s. The calculated thickness values for the limiting diffusion layers range from 8.54·10^?3 to 0.70·10^?3 cm. It has been found that with increasing reduction rate also Boudouard's reaction starts to be important to the overall reduction rate. The limiting reduction rate at which Boudouard's reaction starts to be important to the entire process is dependent on temperature, being approximately 10.0·10^?6 mol FeO/cm² s at 1350°C, and approximately 15.0·10^?6 mol FeO/cm² s at 1420°C.     

Liquidus temperatures in calcium ferrite slags in equilibrium with molten copper

Experimental laboratory methods have been developed that enable phase-equilibria studies to be carried out on slags in the system Ca-Cu-Fe-O in equilibrium with metallic copper. These techniques involve equilibration at temperature, rapid quenching, and chemical analysis of the phases using electron-probe X-ray microanalysis (EPMA). Equilibration experiments have been carried out in the temperature range of 1150 °C to 1250 °C (1423 to 1523 K) and in the composition range of 4 to 80 wt pct “Cu₂O,” 0 to 25 wt pct CaO, and 20 to 75 wt pct “Fe₂O₃” in equilibrium with metallic copper. Liquidus and solidus data are reported for the primary-phase fields of spinel (magnetite) and dicalcium ferrite. The resulting data have been used to construct liquidus isotherms of the CaO-“Cu₂O”-“Fe₂O₃” system at metallic copper saturation.     

Desulfurization kinetics of molten copper by gas bubbling

Molten copper with 0.74 wt pct sulfur content was desulfurized at 1523 K by bubbling Ar-O₂ gas through a submerged nozzle. The reaction rate was significantly influenced not only by the oxygen partial pressure but also by the gas flow rate. Little evolution of SO₂ gas was observed in the initial 10 seconds of the oxidation; however, this was followed by a period of high evolution rate of SO₂ gas. The partial pressure of SO₂ gas decreased with further progress of the desulfurization. The effect of the immersion depth of the submerged nozzle was negligible. The overall reaction is decomposed to two elementary reactions: the desulfurization and the dissolution rate of oxygen. The assumptions were made that these reactions are at equilibrium and that the reaction rates are controlled by mass transfer rates within and around the gas bubble. The time variations of sulfur and oxygen contents in the melt and the SO₂ partial pressure in the off-gas under various bubbling conditions were well explained by the mathematical model combined with the reported thermodynamic data of these reactions. Based on the present model, it was anticipated that the oxidation rate around a single gas bubble was mainly determined by the rate of gas-phase mass transfer, but all oxygen gas blown into the melt was virtually consumed to the desulfurization and dissolution reactions before it escaped from the melt surface.