Metallurgical Transactions B

, Volume 19, Issue 4, pp 643–648 | Cite as

Thermodynamics of Ca-CaF2 and Ca-CaCI2 systems for the dephosphorization of steel

  • N. Masumitsu
  • K. Ito
  • R. J. Fruehan
Physical Chemistry
Received:

Abstract

Calcium is soluble in halide salts which can be used to remove phosphorus from steel as a phosphide ion. The activity and activity coefficient of calcium phosphide, and the equilibrium phosphorus distribution ratio between Ca-CaF2 and Ca-CaCl2 fluxes and pure solid iron were measured as a function of the Ca composition in the flux at 1350 °, 1400 °, and 1450 °. The Ca-Ca halide fluxes were equilibrated with pure solid iron and a Ag-Ca alloy in an iron crucible under an Ar atmosphere. The Ag-Ca alloy was used to maintain a constant chemical potential of calcium. Phosphorus distribution between between these fluxes and solid pure iron increased with increasing calcium activity and decreasing temperature. The activity coefficient of γCa 1.5 P was calculated to be 36.6 at 1350 ° and 11.0 at 1450 ° for a calcium activity of 0.2 (wt pct Ca = 2.5) in the Ca-CaF2; the activity coefficient increases with increasing Ca in the flux. In addition, the activity of Ca in the Ca-Ca halide fluxes was determined. The equilibrium phosphorus distribution ratio between Ca-Ca halide systems and molten chromium steel was calculated as functions of Cr and C contents of the metal and calcium activity in the flux at 1600 °C by using γCa 1.5 P obtained in the present work. This ratio was found to be about 20 for 18 pct Cr stainless steel at 1600 °.

Keywords

Metallurgical Transaction Activity Coefficient Liquid Iron Solid Iron Constant Chemical Potential 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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Copyright information

© The Metallurgical Society and ASM INTERNATIONAL 1988

Authors and Affiliations

  • N. Masumitsu
    • 1
  • K. Ito
    • 2
  • R. J. Fruehan
    • 2
  1. 1.Nippon Steel CorporationJapan
  2. 2.Department of Metallurgical Engineering and Materials ScienceCarnegie Meilen UniversityPittsburgh

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