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

N. Masumitsu, Kimihisa Ito, R. J. Fruehan

Research output: Contribution to journalArticle

22 Citations (Scopus)

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 γCa1.5P 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 γCa1.5P obtained in the present work. This ratio was found to be about 20 for 18 pct Cr stainless steel at 1600 °.

Original languageEnglish
Pages (from-to)643-648
Number of pages6
JournalMetallurgical Transactions B
Volume19
Issue number4
DOIs
Publication statusPublished - 1988 Aug
Externally publishedYes

Fingerprint

Steel
Calcium
steels
Thermodynamics
Fluxes
calcium
thermodynamics
Phosphorus
Activity coefficients
halides
Iron
phosphorus
iron
phosphides
coefficients
chromium steels
Chemical potential
Stainless Steel
Crucibles
Chromium

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Metals and Alloys
  • Materials Chemistry
  • Mechanics of Materials

Cite this

Thermodynamics of Ca-CaF2 and Ca-CaCI2 systems for the dephosphorization of steel. / Masumitsu, N.; Ito, Kimihisa; Fruehan, R. J.

In: Metallurgical Transactions B, Vol. 19, No. 4, 08.1988, p. 643-648.

Research output: Contribution to journalArticle

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