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1.
《钢铁冶炼》2013,40(1):32-36
AbstractA theoretical concept is presented on the slag–oxygen sensors for in situ measurements of the FeO, SiO2 , and CaO contents of steelmaking slags in the furnace and in the ladle. The purpose of this disclosure is to stimulate R & D interest in academia and technical institutes to further the development of new measuring devices applicable in steelmaking operations. The slag–oxygen sensor conceived* consists of two dissimilar electrodes such that when immersed in molten slag there will be a difference in oxygen potentials at the slag/ electrode interface between the two electrodes, registering an open circuit cell emf. Examples are given of different types of electrodes for different oxides in the slag; also, equations are derived for the theoretical relation between the oxide activity and sensor emf reading. 相似文献
2.
Accurate and instantaneous analysis of dissolved nonmetallic or metallic species in molten metals at elevated temperatures
using an online electrochemical sensor is important for continuous process control during metal refining and alloying operations
in metallurgical industries. In this article, the application of long-life, solid-state electrochemical sensors for oxygen
has been demonstrated to measure the oxygen potential as a function of the lead concentration in a molten Ag-Pb system at
1323 K. Yttria-stabilized zirconia (YSZ) in the form of one end-closed tube 20 mm long, 3 mm inner diameter, and 1 mm wall
thickness has been used as a solid electrolyte in the oxygen sensor. Electromotive force (EMF) of the solid-state electrochemical
cell (−)Pt, Ni-NiO//YSZ//O
Ag-Pb, Mo(+) has been measured at 1323 K. The reference electrode consisted of Ni + NiO biphasic mixture; the working electrode
was composed of a molten Ag-Pb alloy of varying concentrations of lead. The concentrations of lead in silver ranged from 0.02
to 10.20 wt pct. Samples of the molten alloy were drawn after each addition of Pb to Ag and analyzed by induction coupled
plasma (ICP). 相似文献
3.
Alberto Vzquez Monroy Antonio Romero Serrano Jorge Araujo Osorio Federico Chvez Alcal Elia Palacios Beas Simn Lpez Ramírez 《国际钢铁研究》2006,77(2):97-102
A solid electrolyte oxygen sensing cell employing yttria‐stabilized zirconia (YSZ) was used to determine the oxygen content and activity in molten copper on a laboratory scale at temperatures between 1200 and 1400 °C. The effects of temperature and time of treatment were investigated on the deoxidizing process with Cu3P. The amount of Cu3P added ranged from 1 to 3% of the mass of molten copper. At 1200 and 1300°C, fair agreement was obtained between the oxygen contents calculated from the measured probe EMF and those obtained by chemical analysis. It was found that the oxygen is more efficiently removed at lower temperatures. A metallographic analysis of rapidly cooled samples showed that oxygen and phosphorus are present in the copper mainly as oxide dendrites. 相似文献
4.
H. Hoshino T. Shimada M. Yamamoto M. Iwase 《Metallurgical and Materials Transactions B》1992,23(2):169-173
In order to obtain the activities of titanium in molten copper at dilute concentrations,i.e., between 5 x 10-6 and 3.4 x 10-3 titanium mole fractions, liquid copper was brought into equilibrium with molten {CaCl2 + Ti2O3} slag saturated with Ti2O3 (s) at 1373 K and the equilibrium oxygen partial pressures were measured by means of a solid-oxide galvanic cell of the type
Mo/Mo + MoO2/ZrO2(MgO)/(Cu + Ti)alloy + Ti2O3 + CaCl2 + Ti2O3
slag/Mo The free energy change for the dissolution of solid titanium in molten copper at infinite dilution referred to 1 wt pet
was determined as Ti (s) = Ti(1 wt pet in Cu) ΔG°/J = -86,100 ± 8900 at 1373 K 相似文献
5.
In the frame of the continuous efforts to thein situ monitoring of the chemical composition of melts in steelmaking, the solid-state electrochemical probe (−)Pt/Nb-NbO/Caβ″-alumina-CaS/S,
Fe (1)/C/Pt (+) was developed and tested to measure the sulfur content in carbon-saturated iron. The solid electrolyte used
is calcium β″-Alumina, which behaves as a good ionic conductor by calcium vacancies at steelmaking temperatures. The calcium
chemical-potential gradient is fixed at the electrolyte interfaces, on the left side, by keeping constant the oxygen chemical
potential through the Nb-NbO coexistence mixture and, on the right side, by the activity of dissolved sulfurvia the solubility equilibrium of CaS. A theoretical equation of the probe electromotive force (emf), as a function of the dissolved
concentration of sulfur in the bath, was derived. From this equation, which agrees well with the experimental results, it
is clearly shown that the emf of the probe can be approximately linear against log ([S]/pct) in small intervals of sulfur
concentration. The experimental emf s were taken up in the sulfur concentration range from 13 to 140 ppm. In this interval,
the average slope of emfvs log ([S]/pct) curve is about −50 mV/decade. The effect of dissolved oxygen is discussed because it generates a mixed potential
related to the CaS instability. The lower sulfur concentration limit, that can be detected, depends on the concentration of
the oxygen dissolved in the melt because CaS tends to react with it. Some characteristic quantities of the theoretical equation
were chosen as fitting parameters to fit the equation itself through the experimental emfvs log ([S]/pct) data. By this procedure, it was also found that the CO supersaturation in the bath was 10.2 bar. 相似文献
6.
Ethem Tugrul Turkdogan 《国际钢铁研究》1991,62(9):379-382
The solubility products of CaO and MgO in liquid iron, measured using the emf oxygen sensor, are several orders of magnitude greater than those calculated from the thermochemical data. This would imply that the values of Δ and Δ derived from the solubility products are, by a large amount, less negative than those given in the compiled thermochemical tables. As is shown in this paper, the values of Δ derived indirectly from numerous experimental data on various gas-solid (-liquid) reactions involving pure CaO, are in general accord with the compiled thermochemical data. It is surmised from these observations that the oxygen activities in liquid iron saturated with CaO or MgO, measured by the emf cell, giving high solubility products of CaO and MgO, may be attributed to the failure of the emf oxygen sensor in liquid iron containing dissolved calcium or magnesium. Two reaction mechanisms are discussed in the paper to account for the malfunction of the oxygen sensor under highly reducing conditions, which will prevail in liquid iron containing even a small amount of dissolved calcium or magnesium. These two mechanisms are (i) redox reaction at the (Y2O3)ThO2 electrolyte/melt interface and (ii) oxygen flux through the electrolyte from the reference electrode Cr–Cr2O3 to the melt/electrolyte interface. Suggestions are made for some experimental work to confirm or refute the argument presented in this communication. 相似文献
7.
An electrochemical deoxidation using a ZrO2 based solid electrolyte was investigated to control the interfacial oxygen concentration between the molten steel and ZrO2. The electrochemical deoxidation cell consisted of an MgO stabilized ZrO2 and an external power supply. In a previous study with constant external DC voltage, the oxygen concentration at the interface between the solid electrolyte and the molten steel was decreased to 2.2 ppm, which was the limit caused by the cathodic over‐potential when a constant external DC voltage was applied. In the present study, a novel process of using a periodic or cyclic voltage for the electrochemical deoxidation cell was developed, to surpass this limitation caused by the over‐optential of the electrochemical cell and thus decreasing the oxygen concentration to sub‐ppm levels at the interface between the molten Fe and the solid electrolyte. 相似文献
8.
J. L. Speelman W. F. Caley K. G. Leewis 《Metallurgical and Materials Transactions B》1989,20(1):31-37
The transfer of oxygen in molten ionic slags is believed to be limited by the conduction of electrons in the slag. As a result,
oxygen transfer might be enhanced by improving the electronic conduction capability of a predominantly ionic conducting slag.
In order to examine this possibility, a series of experiments was undertaken whereby the oxygen transport across a CaO-SiO2-Al2O2 slag was al-tered, both by placing an electronic conductor through the slag, and by adding water vapor to the atmosphere.
The results indicate that oxygen transport across the slag was improved in both cases. In the presence of an electronic conductor,
the rate controlling step was determined to be the discharge of electrons at the perimeter of the conductor; increasing this
perimeter caused an increase in the oxygen transfer rate which was directly proportional to the conductor perimeter. With
the addition of water vapor at a dew point of 273 K, this rate essentially doubled.
Formerly Associate Professor, Technical University of Nova Scotia, Halifax, NS 相似文献
9.
Masanori Iwase Hiroshi Akizuki Hiroyasu Fujiwara Eiji Ichise Noriaki Yamada 《国际钢铁研究》1987,58(5):215-219
An electrochemical method was tested in order to find a suitable experimental technique for the determinations of the activities of P2O5 in molten fluxes used for external dephosphorization of hot metal. This technique consists of equilibrating phosphorus-containing copper with molten slag and measuring the equilibrium oxygen partial pressure by means of solid state galvanic cells. The activities of P2O5 in MgO—P2O5 were determined with this technique. 相似文献
10.
Activities of chromium in molten copper at dilute concentrations by solid-state electrochemical cell
In order to obtain the activities of chromium in molten copper at dilute concentrations (<0.008 chromium mole fractions),
liquid copper was brought to equilibrium with molten CaCl2 + Cr2O3 slag saturated with Cr2O3 (s), at temperatures between 1423 and 1573 K, and the equilibrium oxygen partial pressures were measured by means of solid-oxide
galvanic cells of the type Mo/Mo + MoO2/ZrO2(MgO)/(Cu + Cr))alloy + Cr2O3 + (CaCl2 + Cr2O3)slag/Mo. The free energy changes for the dissolution of solid chromium in molten copper at infinite dilution referred to 1 wt
pct were determined as Cr (s) = Cr(1 wt pct, in Cu) and ΔG° = + 97,000 + 73.3(T/K) ± 2,000 J mol−1. 相似文献
11.
Xue-Min Yang Cheng-Bin Shi Meng Zhang Guo-Ming Chai Fei Wang 《Metallurgical and Materials Transactions B》2011,42(6):1150-1180
A thermodynamic model for calculating the sulfur distribution ratio between ladle furnace (LF) refining slags and molten steel
has been developed by coupling with a developed thermodynamic model for calculating the mass action concentrations of structural
units in LF refining slags, i.e., CaO–SiO2–MgO–FeO–MnO–Al2O3 hexabasic slags, based on the ion and molecule coexistence theory (IMCT). The calculated mass action concentrations of structural
units in CaO–SiO2–MgO–FeO–Al2O3–MnO slags equilibrated or reacted with molten steel show that the calculated equilibrium mole numbers or mass action concentrations
of structural units or ion couples, rather than mass percentage of components, in the slags can represent their reaction abilities.
The calculated total sulfur distribution ratio shows a reliable agreement with the measured or the calculated sulfur distribution
ratio between the slags and molten steel by other models under the condition of choosing oxygen activity based on (FeO)–[O]
equilibrium. Meanwhile, the developed thermodynamic model for calculating sulfur distribution ratio can quantitatively determine
the respective contribution of free CaO, MgO, FeO, and MnO in the LF refining slags. A significant difference of desulfurization
ability among free component as CaO, MgO, FeO, and MnO has been found with approximately 87–93 pct, 11.43–5.85 pct, 0.81–0.60 pct
and 0.30–0.27 pct at both middle and final stages during LF refining process, respectively. A large difference of oxygen activity
is found in molten steel at the slag–metal interface and in bulk molten steel. The oxygen activity in molten steel at the
slag–metal interface is controlled by (FeO)–[O] equilibrium, whereas the oxygen activity in bulk molten steel is controlled
by [Al]–[O] equilibrium. Decreasing the high-oxygen-activity boundary layer beneath the slag–metal interface can promote the
desulfurization reaction rate effectively or shorten the refining period during the LF refining process. 相似文献
12.
Seung-Am Cho Roberto Camisotti Mariano H. Vélez 《Metallurgical and Materials Transactions B》1990,21(1):87-96
All the partial thermodynamic quantities, including the activity and activity coefficient of tin,a
Sn
and γSn, in the liquid Bi-Sn alloys between 300 °C and 500 °C are assessed in detail from electromotive force (emf) data. The emf
values were obtained from a modified molten salt electrolyte concentration cell that had extraordinary stability within +0.005
mV. The composition dependence of γSn did not follow Darken’s quadratic formalism, nor did the alloy behave as a regular solution. The excess partial quantities,
ΔˉH
Sn
,ΔˉS
Sn
xs
, and ΔˉG
Sn
xs
, are oscillating across the composition, and the activity curve exhibits double, positive and negative, deviations from Raoult’s
law. The aSn, γSn, and ΔˉG
Sn
xs
change from positive to negative departure from ideality in the tin-rich region beyond about xSn = 0.82. All those partial quantities and γ
Sn
o
, including the β° (the α function of tin) at infinite dilution, are determined accurately by means of Chiotti’s method.
ROBERTO CAMISOTTI, formerly Undergraduate Student, Central University of Venezuela.
Formerly Assistant Professor, Central University of Venezuela. 相似文献
13.
Tri-phasic zirconia electrolyte, which consists of cubic ZrO2–MgO solid solution, monoclinic ZrO2 and 2MgO · SiO2, was applied to solid state electrochemical sensor for rapid determinations of silicon activities in hot metal. The performance of the cell: Mo + MoO2 / tri-phasic zirconia electrolyte / Fe + Si + C was tested with molten iron at 1723 K. The cell potentials showed good sensitivity to the variation of silicon content in the melt. 相似文献
14.
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
15.
The distribution of lead and of nickel between molten copper and a ternary cuprous oxide-metal oxide-silica saturated slag
was measured at 1498 K. The results are correlated using ion fractions, calculated either according to Temkin’s method, or
as electrically equivalent ion fractions. The simpler method suggested by Temkin correlates slightly better than the other
giving the following relations between the ionic concentration quotients and impurity concentration in the metal: logN
Pb
++/N
2
Cu
+ = logX
Pb + 2.40 ± 0.05, valid up toX
Pb = 0.003 logN
Ni
++/N
2
Cu
+ = 0.44 logX
Pb + 0.15 ± 0.07, valid up toX
Ni = 0.004. In the nickel systems, an Ni rich phase, identified as NiO, separates from the metal at XNi = 0.04 (0.4 wt pct). A tentative phase diagram of the Cu2O-NiO-SiO2 system at 1498 K is presented. The data found in this investigation explain why the impurities Pb or Ni cannot be practically
reduced to low levels by oxidation. This results from the large amounts of copper that are oxidized in going to low impurity
levels. Use of a two-slag refining process is shown to cut slag losses of copper to less than half those encountered with
a single slag operation. 相似文献
16.
Mitsuru Tanahashi Kunihiko Takeda Zhijian Su Hong Yong Sohn Chikabumi Yamauchi 《Metallurgical and Materials Transactions B》2003,34(6):869-879
The rate of Sb elimination from molten copper by the use of Na2CO3 slag was measured at 1523 K. The results obtained under the present experimental conditions show that Sb in molten copper
is eliminated in a tri-valent or a penta-valent form, depending on the oxygen concentration at the slag-metal interface, and
its elimination rate increases with increasing initial oxygen concentration in molten copper. The overall elimination rate
of Sb is affected by the stirring condition of the molten copper, which indicates a rate control by mass transfer in that
phase. The mass-transfer coefficients of Sb and oxygen in molten copper at 1523 K without external stirring were determined,
respectively, to be
based on the mass balances of Sb and oxygen in the molten copper and slag phases and the equilibrium relation of the Sb elimination
reaction at the slag-metal interface. 相似文献
17.
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
18.
The protonic transference number of SrCe0.95Yb0.05O3-α (SCYB) ceramic pellets was determined to be above 0.9 in the temperature range of 873 to 1073 K using a hydrogen concentration
cell. The density of the ceramic disk and tube is above 96 pct of the theoretical. Highly dense SCYB tube and glass seal improved
the reliability and life of an electrochemical hydrogen probe. When the probe was immersed in molten aluminum, a hydrogen
concentration cell was established as Mo, Ca/CaH2|SrCe0.95Yb0.05O3-α|[H]in molten Al, Mo The probe under different conditions generated stable electromotive force within 5 minutes after immersion and responded
rapidly to the change in the atmosphere. The thermodynamic stability of the solid electrolyte under the testing conditions
is also discussed. 相似文献
19.
WANG Maoyuan 《中国稀土学报(英文版)》2009,27(5):819-824
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20.
Previous studies by Oberg, Friedman, Boorstein and Rapp on the electrochemical deoxidation of induction-stirred copper melts
have been extended by the measurement and interpretation of the pumping current and the emf of an auxiliary galvanic cell
to monitor oxygen contents at the pumping surface. Imperfect seals in the high-temperature apparatus allowed the pickup of
gaseous oxygen by the melt to counteract partly the electrochemical deoxidation of the melt. The observed pumping current
was divided into fractions accounting for this oxygen pickup as well as the oxygen removed from the bulk of the melt. Consistent
with the deoxidation mechanism of Oberg,et al, the deoxidation rate is limited by ionic conduction in the zirconia electrolyte crucible at high oxygen contents, and by
the mass transport of oxygen in the induction-stirred melt at low oxygen contents. A mass transport coefficient for oxygen
was calculated by several methods. 相似文献