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1.
Martin E. Valdez Pello Uranga Katsuhiro Fuchigami H. Shibata Alan W. Cramb 《Metallurgical and Materials Transactions B》2006,37(5):811-821
The objective of this study was to determine the conditions under which alumina can act as a heterogeneous nucleant to initiate
the solidification of undercooled liquid iron. The undercooling of a pure iron sessile droplet in contact with Al2O3 substrates was measured under controlled oxygen partial pressures by observing droplet recalescence. The experimental results
indicated that the undercooling of liquid iron, in contact with an Al2O3 substrate, did not have a unique value, varied from 0 °C to 290 °C, and was significantly affected by the oxygen content
of the gas phase and the degree of interaction between the oxide and the metal. Deep undercoolings are possible at low oxygen
potentials, provided the oxygen potential is such that substantial substrate decomposition does not occur. The measured undercooling
was a strong function of gas phase oxygen content and a maximum in undercooling of 290 °C was measured at PO2=10−19 atm. The variation in undercooling was related to the wetting of the substrate by the liquid metal, where the deepest undercoolings
occurred when the highest contact angle between the substrate and the liquid droplet was achieved. 相似文献
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Carbon and oxygen activities have been established in molten iron using CO-CO2 mixtures in the temperature range 1550 to 1750°C. Pressures of up to 70 atm were used to establish the required carbon activities
up to carbon saturation at 1550°C in gas mixtures with CO2 contents between 0.76 and 8.21 pct. The levitation technique was used to avoid any possible contamination and the effect
of thermal diffusion in the gas mixture was measured and corrected for. The data obtained on carbon activities fall between
those of previous workers at low carbon but measurements have been extended to the much higher carbon concentrations which
had not been investigated previously. By using the same CO-CO2 mixture and varying the total pressure it was possible to measure the effect of carbon on oxygen concentration at fixed oxygen
activity and it was found that carbonincreases the activity coefficient of oxygen. 相似文献
5.
Carbon and oxygen activities have been established in molten iron using CO-CO2 mixtures in the temperature range 1550 to 1750°C. Pressures of up to 70 atm were used to establish the required carbon activities
up to carbon saturation at 1550°C in gas mixtures with CO2 contents between 0.76 and 8.21 pct. The lévitation technique was used to avoid any possible contamination and the effect
of thermal diffusion in the gas mixture was measured and corrected for. The data obtained on carbon activities fall between
those of previous workers at low carbon but measurements have been extended to the much higher carbon concentrations which
had not been investigated previously. By using the same CO-CO2 mixture and varying the total pressure it was possible to measure the effect of carbon on oxygen concentration at fixed oxygen
activity and it was found that carbonincreases the activity coefficient of oxygen. 相似文献
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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.
FUMIHIKO TAMURA formerly Graduate Student with the Department of Metallurgical Engineering, Tohoku University. 相似文献
8.
Francisco J. Tavera William G. Davenport 《Metallurgical and Materials Transactions B》1979,10(2):237-241
Equilibrium distributions of Cu, S and O between silica saturated fayalite slags and copper mattes (25 to 79 pct Cu) have
been examined experimentally under controlled partial pressures of SO2. The temperature range of the experiments was 1423 to 1573 K and pSO2 was varied between 0.1 and 1 atm. Concentrations of copper in the experimental slags were found to be low (<1 pct Cu) under
these conditions, as long as the grade of the coexistent matte was below 60 pct copper. Copper in slag concentration rose
dramatically, however, when matte grade was increased above this level. The work also showed that whereas FeS has a high solubility
for oxygen and is itself soluble in slag under oxidizing conditions, Cu2S and slag are almost completely immiscible. Cu-Fe-S mattes behave in an intermediate manner.
Formerly graduate student with the Department of Mining and Metallurgical Engineering, McGill University. 相似文献
9.
为阐述烧结过程熔融机制和成矿机制,明确MgO、Al2O3质量分数对烧结液相生成和矿物组成的影响是至关重要的。利用Factsage软件计算Fe2O3 SiO2 CaO Al2O3 MgO体系的液相生成,计算氧分压在500Pa时,不同温度,不同MgO、Al2O3质量分数下体系液相生成和液相区分布的影响。通过烧结试验,分析烧结矿的矿相和矿物成分,结合软件计算得出烧结矿中MgO质量分数为2.0%、Al2O3质量分数为3.0%时其液相量、矿相、矿物成分达到最优适合烧结冶炼的标准。 相似文献
10.
Equilibria between CaO-TiOx or CaO-Al2O3-TiOx melts and liquid iron with respect to O, N and S were studied at 1873 K as a function of Ti (or Al) content in metal, using a CaO or an Al2O3 crucible. The Al-O and Ti-O relations in liquid iron were studied, and nitride and sulfide capacities defined by and , respectively, were obtained from nitrogen and sulfur distribution ratios, coupled with the analyzed oxygen content in liquid iron or the PO2 determined by Ti/TiO2 equilibrium. Based on these results, activities of Al2O3 and activity coefficients of TiO2 and TiO1.5 were evaluated. 相似文献
11.
为了研究MgO对烧结过程中CaO Fe2O3系初期液相生成的影响及作用机理,通过DSC研究了不同MgO含量试样在升温过程中液相生成的变化,并通过XRD确定液相生成前MgO对矿物组成的影响。结果表明,试样中MgO含量的增加使得升温过程中初期液相生成量减少,但是初期液相的生成温度没有明显变化。MgO对初期液相的抑制分为两种方式,一种为MgO与Fe2O3反应生成含镁磁铁矿,另一种为MgO添加导致CaFe2O4分解。这两种方式都使CaO含量升高,促进了高熔点矿物Ca2Fe2O5和含镁磁铁矿的生成,导致液相量降低。通过研究MgO对初期液相生成的影响,为烧结矿中合理添加含镁熔剂提供理论基础。 相似文献
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Y. Li R. J. Fruehan J. A. Lucas G. R. Belton 《Metallurgical and Materials Transactions B》2000,31(5):1059-1068
Measurements have been made of the chemical diffusion coefficient of oxygen in liquid iron oxide at temperatures from 1673
to 1888 K and in a calcium ferrite (Fe/Ca = 2.57) at temperatures from 1573 to 1873 K. A gravimetric method was used to measure
the oxygen uptake during the oxidation of the melts by oxygen or CO2-CO mixtures. The rate was shown to be controlled by mass transfer in the liquid melt. The chemical diffusivity of oxygen
in liquid iron oxide at oxygen potential between air and oxygen was found to be 4.2±0.3 × 10−3 cm2/s at 1888 K. That in iron oxide at oxidation state close to iron saturation was established to be given by the empirical
expression log D=−6220/T + 1.12 for temperatures between 1673 and 1773 K. For the calcium ferrite (Fe/Ca=2.57) at oxygen potential between air and
oxygen, the diffusivity of oxygen was found to be given by log D=−1760/T−1.31 for temperatures between 1673 and 1873 K.
This article is based on a presentation made in the “Geoffrey Belton Memorial Symposium,” held in January 2000, in Sydney,
Australia, under the joint sponsorship of ISS and TMS. 相似文献
14.
BACKGROUND: Although plastic arterial sampling syringes are now commonly used, the effects of sample storage time and temperature on blood gas tensions are poorly described for samples with a high oxygen partial pressure (PaO2) taken with these high density polypropylene syringes. METHODS: Two ml samples of tonometered whole blood (PaO2 86.7 kPa, PaCO2 4.27 kPa) were placed in glass syringes and in three brands of plastic blood gas syringes. The syringes were placed either at room temperature or in iced water and blood gas analysis was performed at baseline and after 5, 10, 20, 40, 60, 90, and 120 minutes. RESULTS: In the first 10 minutes measured PaO2 in plastic syringes at room temperature fell by an average of 1.21 kPa/min; placing the sample on ice reduced the rate of PaO2 decline to 0.19 kPa/min. The rate of fall of PaO2 in glass at room temperature was 0.49 kPa/min. The changes in PaCO2 were less dramatic and at room temperature averaged increases of 0.47 kPa for plastic syringes and 0.71 kPa for glass syringes over the entire two hour period. These changes in gas tension for plastic syringes would lead to an overestimation of pulmonary shunt measured by the 100% oxygen technique of 0.6% for each minute left at room temperature before analysis. CONCLUSIONS: Glass syringes are superior to plastic syringes in preserving samples with a high PaO2, and prompt and adequate cooling of such samples is essential for accurate blood gas analysis. 相似文献
15.
S. Ueda A. W. Cramb H. Shi X. Jiang H. Shibata 《Metallurgical and Materials Transactions B》2003,34(5):503-508
The contact angle for iron on a single-crystal alumina substrate varied from 40 to 120 deg by changing the gas atmosphere
and droplet size. At constant droplet size, the contact angle was a strong function of the partial pressure of oxygen and
increased as oxygen partial pressure decreased. However, at oxygen partial pressures less than 10−18 atm, the contact angle markedly decreased as a zone of reactive wetting was reached due to interaction between alumina and
the droplet. The effect of droplet size on the contact angle between liquid iron and a single-crystal alumina substrate was
measured at constant oxygen activity and temperature. In an argon-hydrogen atmosphere where oxygen activity was constant,
the contact angle increased with increasing droplet size and varied from 40 to 80 deg as the droplet radius increased from
1.5 to 4 mm. A similar though smaller effect was measured in CO atmospheres that were in equilibrium with carbon. In this
case, the contact angle ranged from 105 to 118 deg as droplet size increased. Experiments in CO/CO2 atmospheres showed little effect of droplet size at oxygen partial pressures less than 5×10−12 atm, but indicated a significant effect at oxygen partial pressures greater than 10−11 atm.
This article is based on a presentation given in the Mills Symposium entitled “Metals, Slags, Glasses: High Temperature Properties
& Phenomena,” which took place at The Institute of Materials in London, England, on August 22–23, 2002. 相似文献
16.
The relationship between slag composition and oxygen partial pressure of dilute FexO‐CaO‐Al2O3 slag in equilibrium with iron the activity of which is below 1 was extrapolated to give the oxygen partial pressure of a slag equilibrated with iron of the activity 1. In the process of extrapolation, the oxygen partial pressure and the activity of iron were unified to give a single thermodynamic quantity which is defined as: , where K(x) is the equilibrium constant for the formation reaction of FexO and is considered to be a function of x. The dependence of on the slag composition was obtained experimentally. On the other hand, it was found that the plot of against log aFe has the slope ?1 as expected from the theoretical consideration. The relation has been employed to estimate the composition of slag in equilibrium with liquid iron. Thus, the obtained composition is used to calculate the values of and of the slag in equilibrium with liquid iron. 相似文献
17.
Grain-growth inhibition in an Fe-10 mass pct Ni alloy, which was continuously cooled from a melt, was studied at 1673 K in
the presence of primary deoxidation products of ZrO2 or MgO particles. The mean grain size and grain-size distribution in a cross section were measured as a function of holding
time for up to 240 minutes. The grain growth was strongly inhibited by the inclusion particles and was influenced by the dissolved
Zr. In the Zr deoxidation, the number of particles per unit area (N
A) ranged from 80 to 650 mm−2, the ZrO2 particle size (
) varied from 1.1 to 1.6 μm, and the dissolved Zr level was below 1800 mass ppm. In the Mg deoxidation, the particle-number density was 90 to 270 mm−2, the MgO particle size was 1.1 to 1.7 μm, and the dissolved Mg level was below 20 mass ppm. In a logarithmic plot of the ratio of limiting mean grain diameter (
) to the mean particle diameter (
) against the volume fraction of particles (f
V), both the
value for a given f
V value, which ranged from 0.014 to 0.074 pct, and the slope were significantly lower than that predicted from the two-dimensional
relation
=(4/π) · f
V
/−1
, i.e., Zener’s limit. This discrepancy is discussed in light of the fraction of particles at the grain boundaries measured experimentally.
Normal grain growth was confirmed from the grain-size distribution observed as a function of holding time, which was best
described by the log-normal distribution. 相似文献
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The rate of nitrogen absorption into and desorption from liquid iron containing sulfur and/or oxygen was measured by employing
a constant-volume technique with a highly sensitive pressure transducer. Critical evaluation of the results demonstrated conclusively
that the chemical rate at high oxygen or sulfur contents is second order with respect to nitrogen content in the metal and
probably controlled by the dissociation of the nitrogen molecule on the surface. The effect of sulfur on the rate is complex
because of the influence of 1) liquid-phase mass transfer at low sulfur contents, 2) the chemical rate on vacant iron sites
at intermediate sulfur contents, and 3) the rate on the adsorbed sulfur layer or the limiting rate at high sulfur contents.
However, at intermediate concentrations the limiting case for the adsorption isotherm for sulfur is adhered to and the rate
is inversely proportional to the sulfur concentration. For Fe-O melts the rate is inversely proportional to the oxygen content
except at low oxygen levels where mass transfer affects the rate. The rate for Fe-S-O melts can be calculated reasonably well
from the results for the Fe-S and Fe-0 alloys, assuming that oxygen does not effect the adsorption of sulfur andvice versa and that there is nearly complete coverage of the surface with oxygen and sulfur atoms. 相似文献
20.
Calcium ferrite slag has been successfully used in the copper smelting process, but no attempt has been made to use it in
the nickel smelting process. The phase equilibrium and the distribution of minor elements between the Ni3S2-FeS matte and the CaO-FeOx-based slag (containing about 2 wt pct MgO) in a magnesia crucible were investigated at 1523 K under controlled partial pressures
of S2, O2, and SO2 of 10.1, 50.7, and 101.3 kPa, respectively. The results were compared with those for the iron-silicate-based slag, and the
following conclusions were obtained: (1) there is no significant difference in the solubility of nickel between both slags
in the high-matte-grade range, (2) the dissolution of cobalt in the calcium ferrite slag is clearly smaller than that in the
iron silicate slag, (3) detrimental arsenic, antimony, and bismuth are preferentially collected and fixed in the calcium ferrite
slag rather than in the iron silicate slag, and (4) it is considered, with regard to technical feasibility, that the use of
the calcium ferrite slag in a converting process of the Bessemer matte will have a prominent future for the nickel converting
stage. 相似文献