Equilibrium of calcium vapor with liquid iron and the interaction of third elements
- PDF / 210,243 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 65 Downloads / 185 Views
The relation between dissolved calcium in liquid iron and calcium vapor can be expressed as [pct Ca] 5 0.0235 PCa/(1 2 0.305 PCa) The interaction parameters of third elements on calcium determined at 1873 K are as follows: Cr eNi Ca 5 20.097 5 0.007, eCa 5 20.18 5 0.02,
Ti eCa 5 20.13 5 0.009
eSiCa 5 20.11 5 0.005, eVCa 5 20.15 5 0.015, eMn Ca 5 20.10 5 0.013 Sn eCu Ca 5 20.023 5 0.003, eCa 5 20.026 5 0.003 Bi eSb Ca 5 20.043 5 0.005, eCa 5 20.15 5 0.035
I.
INTRODUCTION
CALCIUM and its compounds have been used successfully in steelmaking processes to refine liquid steel. Because of the low boiling point and high chemical activity of calcium, the thermodynamic data for calcium in iron at steelmaking temperatures are very scarce. The dissolution of calcium in molten iron under different calcium vapor pressures and the effects of the third elements by equilibrating liquid iron with a known calcium vapor pressure have been studied in this article. The equilibrium constant and the Gibbs energy of solution of calcium in liquid iron as well as the interaction coefficients of the third elements on calcium have been evaluated. II.
EXPERIMENT
Pure iron was melted and deoxidized by metallic barium (99.9 pct purity). The composition of the iron charge before deoxidation was (wt pct) 0.003C, ,0.005Si, 0.0009Mn, 0.005P, 0.005S, 0.005Al, 0.0005Bi, 0.0005As, 0.0005Sn, and 0.08O. After deoxidation, the contents of oxygen, sulfur, and barium were 10, 15, and 4 to 6 ppm, respectively. The purity of Ca used was greater than 99.9 wt pct. The CaO crucible was fabricated by isostatic pressing and then fired at 1700 7C. Experiments were carried out in a two-temperature zone
BO SONG, Associate Professor, and QIYONG HAN, Professor, are with the Department of Physical Chemistry of Metallurgy, University of Science and Technology Beijing, Beijing 100083, China. Manuscript submitted December 12, 1996.
METALLURGICAL AND MATERIALS TRANSACTIONS B
furnace, which was heated by two groups of Mo wires controlled by two individual temperature controllers and thermocouples. The higher temperature zone was kept at 1873 K, while the lower one was varied between 1440 and 1650 K in order to change vapor pressure of Ca in the sealed Mo reaction chamber. The scheme of the experimental apparatus and the experimental details are shown elsewhere.[1,2] Four or five CaO crucibles containing the iron charge were located in the higher temperature zone of the furnace, a Mo crucible containing calcium was suspended in the lower temperature zone. The CaO crucibles and Mo crucible were sealed in a Mo reaction chamber with a Mo cover tightly sealed by means of a soft graphite ring. The temperature of the lower temperature zone was measured by a Pt-PtRh10 thermocouple fitted inside the wall of the Mo cover; the temperature of the high-temperature zone was measured by a PtRh6-PtRh30 thermocouple inserted at the bottom of the Mo reaction chamber. To conduct the experiments on the effects of the third elements on the dissolved amount of calcium in liquid iron, iro
Data Loading...
