Oxygen In Iron Research Articles

Thermodynamics of oxygen and nitrogen in liquid iron equilibrated with CaO- SiO2-Al2O3 slags

Nitrogen distribution ratios, LN ( = (mass pct N)/[mass pct N]), between CaO-SiO2-Al2O3 slags and liquid iron were measured at 1823 and 1873 K as a function of Si (or Al) content in metal, using lime and alumina crucibles. Based on these results and the reported values for activities of SiO2 (or Al2O3), nitride capacities, C(N), defined by (mass pct N) · PO2/3/4/PN2/1/2 were evaluated. Activities of SiO2 (or Al2O3) obtained by using the values for LN and C(N) obtained in present and previous gas-slag experiments were compared with previous results.

Determination of Ultra Low Contents of Oxygen in High Purity Iron

Determination of trace oxygen in high purity iron was studied using a LECO TC-436 oxygen/nitrogen determinator. Examined were oxygen blanks due to helium carrier gas, apparatus and graphite crucibles. The blank due to helium carrier gas was reduced and stabilized by using a gas refining system usable for twelve months or more without repack of reagents. The blank in the apparatus was reduced and stabilized by removing the water adsorbed on the wall of a carrier gas tube. The blank in a double graphite crucible was significantly lowered by using an outer crucible deoxidized with silicon at 2373 K and an inner one degassed at 2573 K for 120 s. As a result of these improvements, the blank value for oxygen analysis using the LECO determinator decreased to less than 0.01 mass ppm O

Decarburization Reaction in Ultra-low Carbon Iron Melt under Reduced Pressure.

The kinetics of the decarburization reaction with dissolved oxygen in a liquid iron in the ultraolow carbon concentration range under reduced pressure have been studied, using an induction furnace with a 20 kg melt. The results obtained are as follows:(1) The decarburization reaction proceeds to less than 5 ppm of carbon, and the decarburization rate constant, K, decreases as the carbon content decreases.(2) As the pressure in the chamber decreases, the decarburization rate increases with a carbon content of more than 10 ppm. On the other hand, the dependency of decarburization rate on the pressure in the chamber is small, with less than 10 ppm of carbon.(3) The influence of the sulphur content on the decarburization rate is small with a carbon content of more than 10 ppm. The decarburization rates are not affected by the mass transfer of CO in the gas phase under experimental conditions. Thus, it is concluded that the decarburization rate is controlled by the mass transfer of carbon in liquid iron.(4) The fact that the decarburization rate at a carbon content of more than 10 ppm is affected by the total pressure of the chamber has been explained by the change in interfacial area of the reaction between the gas and liquid phases resulting from CO boiling in the bulk melt.(5) The decrease in the decarburization rate in t he ultra-low carbon concentration range in RH is also caused by the decrease in interfacial area of the reaction between the gas and liquid phases.

The Variation of Hydrogen, Oxygen and Nitrogen Levels in Cast Iron with Varying Blast-air Moisture

The effects of blast moisture on the gas content—hydrogen, oxygen and nitrogen—of molten iron derived from cupola melting have been studied, the dissolved oxygen content being measured by oxygen probes. It has been found that the hydrogen and oxygen contents of molten iron increase with rising levels of air moisture, although the nitrogen content remains almost the same. The rise in oxygen content is mainly the result of an increase in combined oxygen (oxide inclusions), the level of dissolved oxygen remaining almost unchanged.

不活性ガス融解赤外線吸収法による高純度鉄中の極微量酸素定量

不活性ガス融解赤外線吸収法による高純度鉄中の極微量酸素定量

不活性ガス融解法による高純度鉄中の極微量酸素の定量

不活性ガス融解法による高純度鉄中の極微量酸素の定量

極低炭素濃度溶鉄の減圧下における脱炭反応

The kinetics of the decarburization reaction with dissolved oxygen in a liquid iron in the ultraolow carbon concentration range under reduced pressure have been studied, using an induction furnace with a 20 kg melt. The results obtained are as follows:(1) The decarburization reaction proceeds to less than 5 ppm of carbon, and the decarburization rate constant, K, decreases as the carbon content decreases.(2) As the pressure in the chamber decreases, the decarburization rate increases with a carbon content of more than 10 ppm. On the other hand, the dependency of decarburization rate on the pressure in the chamber is small, with less than 10 ppm of carbon.(3) The influence of the sulphur content on the decarburization rate is small with a carbon content of more than 10 ppm. The decarburization rates are not affected by the mass transfer of CO in the gas phase under experimental conditions. Thus, it is concluded that the decarburization rate is controlled by the mass transfer of carbon in liquid iron.(4) The fact that the decarburization rate at a carbon content of more than 10 ppm is affected by the total pressure of the chamber has been explained by the change in interfacial area of the reaction between the gas and liquid phases resulting from CO boiling in the bulk melt.(5) The decrease in the decarburization rate in t he ultra-low carbon concentration range in RH is also caused by the decrease in interfacial area of the reaction between the gas and liquid phases.

Wettability of Al<SUB>2</SUB>O<SUB>3</SUB> Substrate by Liquid Iron <BR>—Effects of Oxygen in Liquid Iron and Purity of Al<SUB>2</SUB>O<SUB>3</SUB> Substrate—

The interfacial properties between liquid Fe-O alloy and alumina substrates with different purities, 99.9% and 96% Al 2 O 3 , were measured by the sessile drop method. The interfaces of samples were examined by SEM and EPMA after the experiment. It was found that the surface tension decreased with increasing oxygen concentration in the iron for both substrates. The contact angle of 99.9% Al 2 O 3 abruptly increased with increasing oxygen concentration at lower oxygen concentrations. These phenomena were attributed to the dissociation of Al 2 O 3

Chemical bonding in the outer core: High‐pressure electronic structures of oxygen and sulfur in metallic iron

From its density the outer core is believed to be an alloy of iron and a light element such as sulfur or oxygen. The nature of the light element in the core is an important constraint for theories of the Earth's formation. In this paper the electronic structures of oxygen and sulfur impurities in metallic iron are investigated to determine if pressure, temperature, and composition‐induced changes in bonding might affect phase equilibria along the Fe‐FeS and Fe‐FeO binaries. The electronic structure of sulfur in metallic iron is consistent with the miscibility between Fe and FeS liquids. Volume compression strengthens the Fe‐S bond, and it is expected that at sufficiently high pressure, sulfur can substitute for Fe and give solid solution behavior between Fe and FeS. In contrast, the electronic structure of oxygen in metallic iron shows that oxygen cannot act as a substitutional impurity (replacing Fe). This explains the observed miscibility gap on the Fe‐FeO binary at 1 atm pressure. Volume compression does not greatly change the electronic structure if oxygen substitutes for iron in bcc and fcc iron. Iron‐oxygen bonding does occur, however, if oxygen occupies interstitial sites. Insofar as the molar volume of FeO incorporated as interstitial oxygen in metallic iron is smaller than that of pure FeO, the incorporation of oxygen into metallic iron may be favored under the pressures of the Earth's core.

Separate Determination of Microamounts of Bulk and Surface Oxygen in Ultra-Pure Iron by a Surface-Area-Variation Method

A microamount of bulk oxygen in ultra-pure iron was determined separately from surface-contaminated oxygen by a surface-area-variation method. In this method, the total oxygen values (μg/g) for specimens with different specific surface areas were determined by means of a vacuum fusion analysis, and were plotted against the specific surface areas (cm2/g); the quantity of oxygen in the bulk (μg/g) was determined from the intercept of the regression line and the oxygen quantity per unit area of surface (μg/cm2) from the slope. A surface treatment method capable of controlling the depth of the surface oxygen layer at an atomic level was developed in order to prevent scattered bulk oxygen values caused by an irregular surface oxygen layer. Specimens were etched in a mixed solution of hydrogen peroxide, hydrofluoric acid and de-ionized water (volume ratio 17:1:2) under an argon atmosphere. A high sensitivity vacuum fusion gas analyzer with a Pirani gauge was used in this experiment. Bulk oxygen over 0.03μg/g in ultra-pure iron could be analyzed independently from the influence of surface oxygen. Bulk oxygen in an electrolytic pure iron sample was determined as 0.08±0.004μg/g with surface oxygen of 0.31±0.001μg/cm2.

溶鉄の表面張力およびアルミナとのぬれ性におよぼす酸素の影響

The surface tension and the contact angle of liquid iron on the alumina substrate were measured at 1823 K over a wide range of oxygen concentration in the iron by the sessile drop method under the condition of oxygen transfer from the gas phase to liquid iron (3.8×10−6 mol/m2s).It was presumed from the considerations of time-dependence of surface tension and the increasing rate of oxygen in liquid iron that the adsorption reaction at the liquid iron surface should be nearly in equilibrium with oxygen in liquid iron under the rate of oxygen transfer in the present study.From the Gibbs adsorption isotherm, the excess quantities for oxygen at the liquid iron surface and the interface between liquid iron and alumina substrate were calculated as 2.1×10−5 mol/m2 and 2.4×10−5 mol/m2, respectively. The excess quantity for oxygen at the liquid iron surface is in good agreement with those obtained by previous investigators under the assumption of adsorption equilibrium of oxygen at the surface.The relation between the surface tension, γlg (N/m), and the oxygen activity in the liquid iron is given by the following equation:(This article is not displayable. Please see full text pdf.) \ oindentThe contact angle of liquid iron on the alumina substrates decreases with increasing oxygen content in the iron. The work of adhesion increases with increasing oxygen content up to 0.03 mass%, while above 0.03 mass%, it increases very gradually with increasing oxygen content. FeO·Al2O3 was detected at the interface for the high oxygen level.

Determination of Oxygen in Iron-Aluminum Alloy by Inert Gas Fusion-Infrared Absorptiometry

The method for the determination of oxygen in iron containing aluminum was studied by use of the inert gas fusion-infrared absorptiometry as a function of flux, temperature and heating pattern. The double graphite crucibles containing Sn in excess of four times as much as the sample weight were first degassed at 3000 K, and the temperature was lowered to 2630-2760 K. Then the sample enclosed by nickel capsule was dropped into the tin bath and fused for 30 s. This analytical procedure made the oxygen determination in an Fe-10∼15 mass% Al alloy possible without observation of «gettering effect» due to aluminum

溶鉄によるアルミナ基板の濡れ性―溶鉄中の酸素および基板の純度の影響

溶鉄によるアルミナ基板の濡れ性―溶鉄中の酸素および基板の純度の影響

High-pressure geochemistry of Cr, V and Mn and implications for the origin of the Moon

CHROMIUM, vanadium and manganese are present in similar abundances in the Earth's mantle and the Moon, and are substantially depleted relative to their Mg-normalized primordial abundances1–6. Experimental studies7,8 of the partitioning of chromium, vanadium and manganese between molten iron and silicates show that these elements are lithophile at the pressures, temperatures and oxygen fugacities prevailing in the Earth's upper mantle and in the Moon. Here, we show that at much higher pressures, corresponding to those in the Earth's lower mantle, the partitioning behaviour of Cr, V and Mn changes owing to increasing solubility of oxygen in molten iron. Cr and V (and perhaps Mn) are preferentially partitioned into molten iron under these conditions. We therefore attribute the depletions of these elements in the Earth's mantle to their siderophile behaviour during formation of the Earth's core, at pressures that were sufficiently high to cause substantial amounts of oxygen to dissolve in molten metallic iron. Similar depletion patterns of Cr, V and Mn in the Earth's mantle and the Moon strongly suggest that a large proportion of the Moon was derived from the Earth's mantle after the Earth's core had segregated.

Recent development of solid ionic sensors to control iron and steel bath composition

A series of attempts were made to measure the activities of other components than oxygen in molten iron and steel using oxygen concentration cells in conjunction with appropriate auxiliary electrode. A survey of such solid state sensors will be provided.

Equilibria between cerium or neodymium and oxygen in molten iron

Autoradiographs show that there is an obvious reaction between Ce and Nd in liquid iron and the MgO/CaO crucible wall. For reaching the Ce-O, Nd-O equilibrium, a long melting period and the addition of rare earth elements (RE’s) in several batches were needed to ensure the full reaction between the RE’s in the melt and crucible wall. The dissolved Ce or Nd content in iron was measured by means of radioactive isotopes141Ce or147Nd and electrolysis in the organic electrolyte. The oxygen activity was measured by solid electrolyte sensors made of ZrO2(MgO) tube. The relationships between the equilibrium constants and the temperatures for reactions Ce2O3 (s) = 2[Ce] + 3[O], CeO2 (s) = [Ce] + 2[O], and Nd2O3 (s) = 2[Nd] + 3[O], as well as the corresponding thermodynamic parameters, have been determined.

The hyperfine field of oxygen in iron

From an on-line nuclear orientation measurement on15O implanted in iron, the hyperfine field of oxygen in iron was deduced as +12.2(16) T. This experiment, together with two measurements on17F, which was implanted in the same foil, also yielded information on the relaxation and implantation behaviour of light impurities when implanted at low dose and at low temperature.

Characterization of alloy-spinel-corundum equilibrium in the system Fe-Ni-Al-O.

The three phase equilibrium between alloy, spinel solid solution and α-alumina in the Fe-Ni-Al-O system has been fully characterized at 1823K as a function of alloy composition using both experimental and computational methods. The oxygen potential was measured using a solid state cell incorporating yttria-doped thoria as the electrolyte and Cr+Cr 2 O 3 as the reference electrode. Oxygen concentration of the alloy was determined by an inert gas fusion technique. The composition of the spinel solid solution, formed at the interface between the alloy and an alumina crucible, was determined by EPMA. The variation of the oxygen concentration and potential and composition of the spinel solid solution with mole fraction of nickel in the alloy have been computed using activities in binary Fe-Ni system, free energies of formation of end member spinels FeO•(1+x)Al 2 O 3 and NiO•(1+x)Al 2 O 3 and free energies of solution of oxygen in liquid iron and nickel, available in the literature. Activities in the spinel solid solution were computed using a cation distribution model. The variation of the activity coefficient of oxygen with alloy composition in Fe-Ni-O system was calculated using both the quasichemical model of Jacob and Alcock and the Wagner's model, with the correlation of Chiang and Chang. The computed results for the oxygen potential and the composition of the spinel solid solution are in good agreement with the measurements. The measured oxygen concentration lies between the values computed using models of Wagner and Jacob and Alcock. The results of the study indicate that the deoxidation hyper-surface in multicomponent systems can be computed with useful accuracy using data for end member systems and thermodynamic models.

Spinel deoxidation equilibria in the Fe—Mn—Al—O system – experiment and computation

The concentration and chemical potential of oxygen in liquid Fe—Mn alloys equilibrated with the spinel solid solution, (Fe, Mn)Al2+2xO4+3x, and α‐Al2O3 have been determined at 1873 K as a function of manganese concentration. The composition of the spinel phase has been determined using electron probe microanalysis. The results are compared with data reported in the literature. The deoxidation equilibrium has been computed using data on free energy of solution of oxygen in liquid iron, free energies of formation of hercynite and galaxite, and interaction parameters reported in the literature. The activity‐composition relationship in spinel solid solution was derived from a cation distribution model. The model is in excellent agreement with the experimental data on oxygen concentration and potential and the composition of the spinel phase.

Influence of Dissolved Oxygen on the Reaction between Molten Iron and Reaction-Bonded Si<sub>3</sub>N<sub>4</sub>

Fundamental investigations of the reaction between Si3N4 and molten iron have shown that Si3N4 material is desirable in steelmaking process. This paper describes the influence of dissolved oxygen in iron on the corrosion of reaction-bonded Si3N4. The results are as follows:Si3N4 specimens dipped into iron containing more-than-300-ppm dissolved oxygen for 30 minutes at 1630°C and rotated at 300rpm were not attacked. However, molten iron of less-than-300-ppm oxygen attacked Si3N4 as oxygen contents decreased. Optical microscope and EPMA observations showed the formation of 50-150-μm thick SiO2 layer on the Si3N4 surface which did not corrode. Otherwise, there was none of the thick layer on specimens dipped in below-300-ppm-oxygen iron. This reaction mechanism was discussed thermodynamically. Iron with a high dissolved oxygen level forms a large amount of SiO2 at the beginning of the reaction, which acts as a protection layer on the Si3N4 surface. On the other hand, a low dissolved oxygen level iron causes the Si of Si3N4 to dissolve into iron without SiO2 formation.