Partitioning of Calcium Between Liquid Silver and Liquid Iron
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of the common methods for performing thermodynamic studies on metallurgical systems is to equilibrate a suitable reference system, for which the thermodynamic properties are well known, with the system of interest. Due to the very low solubility of calcium in liquid iron,[1–4] iron-calcium alloys are not suitable as reference system for thermodynamic measurements on calcium containing phases at steelmaking temperatures. An alternative is the silver-calcium system. This, however, requires good knowledge of the thermodynamic properties of the silver-calcium system at the temperature of interest. Experimental measurements on the silver-calcium system over the whole composition range have been made at 1073 K to 1273 K (800 °C to 1000 °C), by Delcet and Egan[5] and Fischbach[6] using EMF technique and Knudsen effusion technique, respectively. Wakasugi and Sano[7] as well as Tago et al.[8] measured the activity coefficient of calcium in liquid silver at low calcium contents in the temperature range 1570 K to 1831 K (1297 °C to 1558 °C) using CaC2- and CaO-saturated slags in equilibrium with liquid silver. Fujiwara et al.[9] studied the partitioning of calcium between liquid silver and liquid iron at 1823 K (1550 °C). The aim of the present work is to provide additional experimental measurements on the
MARTIN BERG and DU SICHEN are with the Department of Materials Science and Engineering, Royal Institute of Technology, Brinellva¨gen 23, 100 44 Stockholm, Sweden. Contact e-mail: [email protected] JAEWOO LEE is with Hyundai Steel, 1480 Bukbusaneop-ro, Songak-Eup, Dangjin-Si, Chungnam, 31719, Korea. Manuscript submitted August 2, 2017. METALLURGICAL AND MATERIALS TRANSACTIONS B
silver-calcium system at steelmaking temperatures and discuss the applicability of the existing experimental data and models. Experimental measurements were made in order to study the partitioning of calcium between liquid silver and liquid iron at 1823 K and 1873 K (1550 °C and 1600 °C). A detailed description of the furnace setup can be found in a previously published work[1] and only a brief description is given here. A vertical resistance furnace with Kanthal Super heating elements and an alumina reaction tube was used. To enable fast cooling of the samples after equilibration without withdrawing them from the furnace, the upper part of the reaction tube was interconnected to a water cooled aluminum chamber. By suspending the samples from a steel rod connected to a computer-controlled lifting system, they could be moved quickly from the hot zone of the furnace into the cooling chamber. The furnace was sealed using O-rings and radial seals. Two separate gas inlets, one at the bottom of the furnace and one in the upper aluminum chamber, allowed for both keeping a constant gas flow during the experiments as well as injecting a higher flow of gas directly at the sample during cooling. The furnace temperature was controlled by a type B thermocouple (70 pct Pt/30 pct Rh to 94 pct Pt/6 pct Rh). A second type B thermocouple, placed with its tip just below the sam
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