Liquid Oxide Phase Research Articles

The influence of gas atmospheres on the first-stage sintering of high-purity niobium powders

Niobium and tantalum surfaces easily absorb oxygen. With decreasing particle size the content of oxygen increases. The role of this surface oxygen and oxygen in the sintering atmospheres on the first-stage sintering is not well established. Therefore the sintering behavior of high-purity niobium powders was studied by annealing cylindrical powder compacts (particle size 3000 min-1) to temperatures above the melting point of Nb2O5 (Tm = 1495 °C) enhances the neck growth due to the formation of a liquid oxide phase on the surface of the powder particles.

The solubility of the liquid oxysulfide phase in liquid Fe-O-S alloys

The solubility of the liquid oxide phase in liquid Fe-O alloys has been measured for the temperature range of 1378 to 1740 °C. Also the solubility of the liquid oxysulfide phase in liquid Fe-O-S alloys has been determined for the composition range of 0.08 to 0.30 wt pct oxygen and 0 to 0.5 wt pct sulfur. The oxygen content of liquid iron saturated with the liquid oxide phase is log O = −6358/T + 2.76. The standard free energy for the formation of the oxide phase is: xFe(l) + O(pct) = FexO(l); ΔG° = 242.4 − 0.0829T + 166,990/T(kJ). The equation for the standard free energy in the temperature range of 1550 to 1650 °C may be written as: −117.5 + 0.0496T (kJ). The effect of composition on temperature of saturation of liquid Fe-O-S alloys with the oxysulfide phase is:T(K) = −6358/(log pct O − 2.76) - (pct S)x [554 + 135.0(log O − 2.77)]. The relationship applies for the composition range of 0.15 to 0.30 wt pct oxygen and 0.0 to 0.5 wt pct sulfur and temperatures from 1480 to 1680 °C.

Application of phase diagrams to predict phases formed during deoxidation of steel

Phase diagrams for simple ternary systems such as Fe-Al-O, Fe-Si-O and more complex systems Fe-Mn-Al-O, Fe-Mn-Si-O have been used to rationalize some of the observations made during deoxidation. The formation of less stable oxides such as liquid aluminates and spinel is shown to be a consequence of the reaction path followed by the metal-inclusion system. The significance of univariant conditions in which three phases are in equilibrium is brought out. During cooling and solidification inclusions may change from a solid oxide to a liquid oxide phase and vice versa. This causes a change in solidification from eutectic type to a monotectic type. The existence of a saddle point at which either a eutectic or monotectic solidification begins is established and its significance in semi-killed steel is brought out.

Fe-Cr系熔融合金中の酸素の活量および溶解度

The activity of oxygen dissolved in liquid iron-chromium alloy was determined by measuring the equilibrium of the reaction between dissolved oxygen in liquid alloy and H2-H2O gas mixture. The experiments were carried out at 1600°C up to 30% chromium. The effect of chromium on the activity coefficient of oxygen was represented by the following equation: logf_O(%)^Cr = -8.01 ·N_Cr + 5.82 ·N_Cr^1.2, N_Cr < 0.3, 1600°C. In the range 0∼10%Cr, the data were represented approximately by eOCr=−0.047. The gas ratio of H2-H2O mixture in equilibrium with liquid iron-chromium alloy and solid oxide phases was measured at 1600°C up to 20% chromium. Using the data on the equilibrium gas ratio and the activity of oxygen in liquid iron-chromium alloy, the solubility of oxygen was thermodynamically calculated. The results were in good agreement with the work of Chipman(5).

Equilibrium between Titanium in Liquid Iron And Titanium Oxides

The amounts of oxygen in liquid iron-titanium alloys up to 50 pet Ti were measured and the oxide phases in equilibrium with these alloys were determined by using Ti02 crucibles. A minimum of about 0.003 pet O occurs at less than 1 pet Ti. The various liquid and solid oxide phases can be arranged on a ternary isotherm.

The System Iron—Oxygen. II. Equilibrium and Thermodynamics of Liquid Oxide and Other Phases

The System Iron—Oxygen. II. Equilibrium and Thermodynamics of Liquid Oxide and Other Phases