Electrochemical deoxidation of titanium

Removal of oxygen in titanium using an electrochemical technique was examined at temperatures around 1223 K with the purpose of obtaining nearly oxygen-free titanium. Titanium and carbon electrodes, immersed in molten CaCl₂, served as cathode and anode, respectively, with an external DC source. CaCl₂ was employed to produce the deoxidant calcium and to facilitate the reaction by decreasing the activity of the by-product CaO. By applying about 3 V between the electrodes, the calcium potential in CaCl₂ was increased at the titanium cathode surface and titanium samples of the cathode could be deoxidized by the electrolytically produced deoxidant calcium or by calcium of high activity in the CaCl₂ flux. Resulting O²⁻ species, mainly present as the deoxidation product CaO in the flux, reacted at the carbon anode to form CO (or CO₂) gas which was removed from the system. Titanium wires containing 1400 mass ppm oxygen were deoxidized to less than 100 mass ppm, whereas the carbon concentration increased by about 50 mass ppm. In some cases, the oxygen concentration in titanium samples was lowered to a level less than 10 mass ppm that could be determined by conventional inert gas fusion analysis. The behavior of contaminants, such as carbon and nitrogen, is also discussed.     

Thermodynamics of calcium and oxygen in molten titanium and titanium-aluminum alloy

The deoxidation equilibrium of molten titanium and titanium-aluminum alloys saturated with solid CaO has been measured in the temperature range from 1823 to 2023 K. The equilibrium constant of reaction CaO (s)=Ca (mass pct in Ti,Ti-Al)+O (mass pct in Ti,Ti-Al) and the interaction parameter between calcium and oxygen were determined for Ti, TiAl, and TiAl₃. The standard Gibbs energy of reaction for TiAl was obtained as follows: $$\Delta G^\circ = 279,000 - 103TJ/mol$$ The possibilities for the deoxidation of titanium and titanium-aluminum alloys by using calcium-based fluxes are discussed.     

Calciothermic reduction of titanium oxide in molten CaCl<Subscript>2</Subscript>

Titanium oxides were reduced to metallic titanium using the liquid calcium floating on the molten CaCl₂. A part of Ca dissolved into CaCl₂ and reacted with TiO₂ settled below CaCl₂. The by-product CaO also dissolved by about 20 mol pct into CaCl₂, which was effective in reducing the oxygen concentration in the obtained Ti particles. The compositional region in the Ca-CaCl₂-CaO system was examined for the less oxygen contamination in Ti and the better handling in leaching. A large amount of the residual calcium oxidized the titanium powder in leaching. The metallic Ti powder less than 1000 mass ppm oxygen could be obtained only for 3.6 ks using 5 to 7 mol pct Ca-CaCl₂ at 1173 K. The powder was slightly sintered like sponge, and contained approximately 1500 ppm Ca. The anatase phae, the intermediate product in the refining process of TiO₂, could be also supplied as raw material as well as rutile.     

Calciothermic reduction of titanium oxide and <Emphasis Type="Italic">in-situ</Emphasis> electrolysis in molten CaCl<Subscript>2</Subscript>

A concept for calciothermic direct reduction of titanium dioxide in molten CaCl₂ is proposed and experimentally tested. This production process consists of a single cell, where both the thermochemical reaction of the calciothermic reduction and the electrochemical reaction for recovery of the reducing agent, Ca, coexist in the same molten CaCl₂ bath. A few molar percentages of Ca dissolve in the melt, which gives the media a strong reducing power. Using a carbon anode and a Ti basket-type cathode in which anatase-type TiO₂ powder was filled, a metallic titanium sponge containing 2000 ppm oxygen was produced after 10.8 ks at 1173 K in the CaCl₂ bath. The optimum concentration of CaO in the molten CaCl₂ was 0.5 to 1 mol pct, to shorten the operating time and to achieve a lower oxygen content in Ti.     

Kinetics of deoxidation of liquid copper by graphite particles during submerged injection

Liquid copper can be deoxidized by submerged injection of inert gas in the presence of graphite particles. This paper describes the results of experiments in which approximately 20 kg copper melts were deoxidized by injection of N₂, CO₂, and air in the presence of low sulfur graphite particles. The apparent kinetics of the deoxidation process are first order with respect to the concentration of dissolved oxygen, and the concentration of oxygen in the melt could be reduced to less than 10 ppm by weight after less than 30 minutes of injection. The kinetics are consistent with mixed rate control with both mass transfer and chemical reaction rate affecting the rate of deoxidation. In these experiments, the rate of deoxidation under a graphite covering was slower when particles were injected with the gas stream than when gas was injected alone, although this result may have been influenced by the small size of the melt. Y. W. Chang, formerly Graduate Student with the Department of Civil Engineering, Mechanics, and Metallurgy, University of Illinois at Chicago This paper is based on a presentation made in the T.B. King Memorial Symposium on “Physical Chemistry in Metals Processing” presented at the Annual Meeting of The Metallurgical Society, Denver, CO, February, 1987, under the auspices of the Physical Chemistry Committee and the PTD/ISS.     

铝镁合金脱氧热力学分析与实验研究

通过对铝脱氧存在诸多问题的进一步认识，在钢液精炼温度范围内，通过热力学方法分析了镁的溶解度、蒸汽压和镁的脱氧反应，并分析了AIMg合金脱氧后夹杂物的生成区域。在感应炉上采用MgO质坩锅对低碳钢进行了镁合金脱氧剂脱氧行为的研究。实验中主要选取AIMg合金脱氧与Al脱氧进行对比，考察了脱氧后钢水的T[O]、[S]以及夹杂物的变化情况。实验中MMgl^＃最低达到33．77ppm，脱硫效果明显；铝镁合金脱氧后夹杂物的粒径不同程度减少。     

Thermodynamic Analysis of Deoxidation of Titanium Through the Formation of Rare-Earth Oxyfluorides

In this work, the possibility of the direct removal of oxygen species from metallic Ti through the formation of rare-earth oxyfluorides has been investigated from a thermodynamic viewpoint. The deoxidation limit of β-Ti using rare-earth metals (M: Y, La, Ce, and Nd) as deoxidants was evaluated. It was found that Ti metal with an oxygen concentration of 200 mass ppm or less could be theoretically obtained under the M/MOF/MF₃ equilibrium at 1300 K (1027 °C), which suggested a possibility of reducing the oxygen content in Ti below 500 mass ppm utilizing a fluoride-based molten salt. Furthermore, a new deoxidation process, in which oxygen was removed in the form of MOF compounds using Mg deoxidant, was discussed as well. The obtained results revealed that the oxygen content in β-Ti could be theoretically reduced to a level below 1000 mass ppm using a MF₃-containing molten salt equilibrated with Mg. Rare-earth metals and their alloys are usually produced by the electrolysis in a fluoride-based molten salt; hence, the modern industrial electrolysis techniques can be potentially utilized for deoxidizing Ti scrap.     

Microwave Absorption Characteristics of Conventionally Heated Nonstoichiometric Ferrous Oxide

The temperature dependence of the microwave absorption of conventionally heated nonstoichiometric ferrous oxide (Fe_0.925O) was characterized via the cavity perturbation technique between 294 K and 1373 K (21 °C and 1100 °C). The complex relative permittivity and permeability of the heated Fe_0.925O sample slightly change with temperature from 294 K to 473 K (21 °C to 200 °C). The dramatic variations of permittivity and permeability of the sample from 473 K to 823 K (200 °C to 550 °C) are partially attributed to the formation of magnetite (Fe₃O₄) and metal iron (Fe) from the thermal decomposition of Fe_0.925O, as confirmed by the high-temperature X-ray diffraction (HT-XRD). At higher temperatures up to 1373 K (1100 °C), it is found that Fe_0.925O regenerates and remains as a stable phase with high permittivity. Since the permittivity dominates the microwave absorption of Fe_0.925O above 823 K (550 °C), resulting in shallow microwave penetration depth (~0.11 and ~0.015 m at 915 and 2450 MHz, respectively), the regenerated nonstoichiometric ferrous oxide exhibits useful microwave absorption capability in the temperature range of 823 K to1373 K (550 °C to 1100 °C).     

Electrochemical Measurements of Oxygen Potentials in the Slag System CaO‐P2O5‐SiO2‐FexO

The liquidus compositions of the four‐phase assemblages in the quaternary system of CaO‐P₂O₅‐SiO₂‐Fe_xO were determined at 1473 and 1573 K by employing electron probe microanalysis. Measurements were also made on the Fe_xO activities at temperatures between 1373K and 1699K by employing an electrochemical technique involving stabilized zirconia electrolyte.     

冷轧薄板钙镁铝尖晶石类夹杂物成因分析

摘要：针对超低碳铝脱氧镇静钢在冷轧冲压过程中出现开裂情况进行了电镜和能谱成分分析,确定了主要夹杂物含有Al2O3、CaO及MgO,为钙镁铝尖晶石类夹杂物。研究了该问题炉次的钢包顶渣组分、中间包覆盖剂及涂层侵蚀情况,讨论了夹杂物的来源。结果显示,Al2O3为脱氧产物及二次氧化的产物;CaO的来源为渣中较高活度的CaO与钢水中酸溶铝Als反应导致Ca元素进入钢水,进而与钢水中的O生成CaO。MgO主要为中间包覆盖剂氧化镁及涂层融蚀的氧化镁进入中间包渣系,与钢水中的Als反应导致Mg元素进入钢水,再与钢水中的O生成MgO。     

Analysis of formation mechanism about Ca-Mg-Al spinel type inclusions in cold thin rolling sheet

The cracking of ultra low carbon Al deoxidized killed steel during cold rolling and stamping was analyzed by SEM and EDS. It was determined that the main inclusions consisted of Al2O3, CaO and MgO, which are Ca-Mg-Al spinel inclusions. The composition of the ladle top slag and corrosion of the tundish covering agent and coating were investigated, and the source of inclusions was discussed. It was found that Al2O3 is the product of deoxidation and secondary oxidation. The source of CaO is the reaction between CaO of higher activity in slag with acid soluble aluminum Als in molten steel, which leads to the entry of element Ca into molten steel and the formation of CaO with oxygen in molten steel. The reaction of MgO, which comes from MgO in tundish covering slag and MgO corroded from tundish coating, with Als in molten steel leads to element Mg entering molten steel, and then MgO is formed with oxygen in molten steel.     

Phase Equilibria Studies of the Cu-Fe-O-Si System in Equilibrium with Air and with Metallic Copper

Phase equilibria of the Cu-Fe-O-Si system have been investigated in equilibrium: (1) with air atmosphere at temperatures between 1373?K and 1673?K (1100?°C and 1400?°C) and (2) with metallic copper at temperatures between 1373?K and 1573?K (1100?°C and 1300?°C). High-temperature equilibration/quenching/electron-probe X-ray microanalysis (EPMA) techniques have been used to accurately determine the compositions of the phases in equilibrium in the system. The new experimental results are presented in the form of ??Cu₂O??-??Fe₂O₃??-SiO₂ ternary sections. The relationships between the activity of CuO_0.5(l) and the composition of slag in equilibrium with metallic copper are discussed. The phase equilibria information of the Cu-Fe-O-Si system is of practical importance for industrial copper production processes and for the improvement of the existing thermodynamic database of copper-containing slag systems.     

Analysis of various versions of the deoxidation of rail steel at OAO NTMK

The deoxidation of steel melted using various types of deoxidizers during out-of-furnace treatment is studied. The total oxygen and nitrogen content and the oxygen contents in the main types of oxide nonmetallic inclusions are determined by fractional gas analysis of steel samples taken from heats performed by various schedules. The main types of nonmetallic inclusions and their size distributions are found with qualitative and quantitative metallography. The oxygen content in the rail steel is minimal (5 ppm) when calcium carbide CaC₂ is introduced into the metal in tapping of a converter. When the metal is deoxidized using a steel wire filled with calcium or a steel wire filled with silicocalcium, the oxygen content in rail steel is ≈8 and ≈11 ppm, respectively. A comparison of various processes of rail steel deoxidation under the OAO NTMK conditions shows that the limitation of the aluminum content (no more than 30 ppm) or the use of a wire with a calcium or calcium carbide filler is more effective than the use of a wire filled with silicocalcium.     

Desulfurization and deoxidation of Cu-S-O alloy in induction melting and solidification under argon and their rates of elimination in vacuum induction melting

Solid Cu-S-O alloy (about 150 g) containing 0.05 pct S and 0.04 pct O (by weight) was heated to 1473 or 1573 K under argon at 6.5 to 101 kPa. Desulfurization of 64 to 80 pct and deoxidation of 75 to 82 pct were observed. The extent did not depend on argon pressure, and this desulfurization and deoxidation probably occurred during melting. In the course of solidification and remelting of molten Cu-S-O alloys containing sulfur and oxygen at approximately the same concentration,i.e., 0.027 pct S and 0.026 pct O, and 0.0456 pct S and 0.0416 pct O under argon at 1.33 to 102 kPa, the percentage of sulfur removed was 49 to 75, the percentage of oxygen removed was 63 to 81, and the extent did not depend on argon pressure. The alloys containing more oxygen than sulfur before cooling,i.e., 0.0216 pct S and 0.081 pct O and 0.0185 pct S and 0.15 pct O, 73 to 90 pct of the sulfur was eliminated. Most desulfurization and deoxidation probably occurred in the course of solidification, because vigorous boiling was observed at this stage. The rates of removal of oxygen and sulfur from molten Cu-S-O alloys maintained at 1373, 1473, and 1573 K under vacuum were expressed by a first-order rate equation, and the dependence of their rate constants on the reciprocal of temperature was determined. In alloys in which pct S ≃pct O before evacuation and pct S ranges from 0.0202 to 0.042 and pct O ranges from 0.023 to 0.048, 79 to 96 pct desulfurization and 66 to 87 pct deoxidation were observed. For the alloys with pct O > pct S initially,i.e., 0.081 pct O and 0.0216 pct S, and 0.15 pct O and 0.0176 pct S, 85 to 94 pct desulfurization was observed and was close to the observed levels of desulfurization in solidification and remelting of the alloys with pct O > pct S under argon.     

Deoxidatlon rate of copper droplet levitated in Ar-H2 gas stream

Levitated copper droplets, 5 mm in diameter with initial oxygen contents of 0.036 to 1.9 wt pct, were deoxidized at about 1970 K in an Ar-H₂ gas stream. The Ar-H₂ gas mixture having hydrogen partial pressure less than 4 kPa was introduced into a silica reaction tube of 11-mm ID at gas flow rates up to 2 x 10^-4 Nm³s^-1. The effects of initial oxygen content of the droplets, hydrogen partial pressure, and gas flow rate on the deoxidation process were examined. A mixed control model for the deoxidation rate involving both gas and liquid film mass-transfer resistances was combined with a thermodynamic relationship for the dissolved species in molten copper. The value of 2 × 10^-4 m 73x00D7; s^-1 was assigned to the liquid film mass-transfer coefficient of dissolved oxygen throughout all experimental conditions. Under the experimental conditions of low initial oxygen content and high hydrogen partial pressure, the liquid film mass-transfer resistance was significant. When a droplet of high initial oxygen content was deoxidized, transition phenomena from gas to liquid film mass-transfer control were noticed in the later stage of reaction. It was deduced from the present model that the accumulation of dissolved hydrogen was indispensable to these phenomena. Formerly Student     

钛稳定超纯铁素体不锈钢硅铝复合脱氧的试验研究

 为改进超纯铁素体不锈钢的脱氧工艺,提高夹杂物控制水平,在硅钼高温电阻炉内对钛稳定超纯铁素体不锈钢的精炼过程进行了试验研究。结合热力学计算,研究了不同Si、Al含量(质量分数,下同)比值的硅铝合金的脱氧效果,以及脱氧、钛合金化和钙处理后钢中典型夹杂物的组成和形貌及粒度分布。结果表明：钢中初始氧含量相近的条件下,硅铝合金复合脱氧的钢中酸溶铝、全氧量与纯铝脱氧结果相近。硅铝复合脱氧后钢中夹杂物主要为(MgO-)Al2O3-SiO2复合脱氧产物。钛合金化后夹杂物的类型主要为Al2O3-MgO-(SiO2)-TiOx复合夹杂物和TiN。钙处理后的夹杂物主要为球形的MgO-Al2O3-CaO-SiO2-TiOx类复合氧化物。采用硅铝合金复合脱氧比纯铝脱氧钢的夹杂物的总数量、总面积和平均粒径均要小。     

碳化硅的冶金性能及其在钢铁工业中的应用

在分析SiC的脱氧性质、溶解特性等冶金性能的基础上,结合部分钢铁企业应用SiC脱氧剂的实例,分析了SiC脱氧剂在钢铁冶炼过程中脱氧合金化、精炼脱氧及钢水提温的冶金性能及机理。SiC在脱氧合金化过程中,脱氧反应迅速,能使钢液增Si、增C,净化钢液,提高钢水流动性,并且能提高合金收得率,降低炼钢成本。     

Deoxidation of molten copper with a rotating graphite cylinder

The kinetics of deoxidation of molten copper by the “vacuum-suction degassing” (VSD) method is investigated. The molten copper is deoxidized by a rotating porous graphite tube immersed in the copper bath. The inside space of the porous graphite tube is evacuated so that the CO gas formed at the graphite-metal interface is removed through the tube wall. The experimental results suggest that the mass transfer of oxygen in the metal phase controls the reaction rate. The kinetic data are arranged with a first-order rate equation. At (ppm O)≥10, the rate constant increases by decreasing the porosity of the graphite and increasing the thickness of the tube wall. This result suggests that the suction of CO gas weakens CO bubble stirring and, thereby, the mass transfer at the tube-melt interface. However, when the rate of CO suction becomes comparable to or larger than the CO gas evolution rate, the effect of CO stirring becomes negligible. This situation appears under the conditions of high porosity and large wall thickness at (ppm O) ≥ 10. At the low oxygen concentration range of (ppm O) ≤ 4, the effect of CO stirring becomes negligible, regardless of the CO suction condition, because of the considerably low CO formation rate. The achievement of deoxidation by the VSD method is evaluated in connection with the final oxygen concentration.     

含钙钡合金脱氧和非金属夹杂物控制技术研究

采用MoSi2电阻炉在1〖KG-*9〗873 K下开展了含钙钡合金脱氧和非金属夹杂物控制技术研究。结果表明，各组实验终点钢中夹杂物平均长度均小于8 μm，并都有纯三氧化二铝夹杂物存在。采用含钙钡合金的复合脱氧工艺，终点钢中未发现含钡夹杂物，有较多以CaO Al2O3为主要成分的复合夹杂物，w（T.O）＞50×10-6。用AlMnCa脱氧，终点钢样w（T.O）＝37×10-6，含氧化钙夹杂物较少，大于20 μm的夹杂物数量占总夹杂物数量的1.2%。