Nitride Capacities of CaO-Al2O3-CaF2 Melts at 1773K.

Abstract

The nitrogen solubility of CaO-Al 2 O 3 -CaF 2 was studied at 1 773 K. It was found that nitride capacity increased with increasing CaO content for a given CaF 2 /Al 2 O 3 ratio, decreased with increasing Al 2 O 3 content for a given CaO/CaF 2 ratio, and increases with increasing CaF 2 content when the CaO/Al 2 O 3 molar ratio was less than about 2, but became unaffected by CaF 2 content when the ratio exceeded about 2. These observations were interpreted that CaO depolymerized the Al 2 O 3 network, allowing for nitrogen to exist as both free and non-bridging nitrides, and that CaF 2 assisted in depolymerization and hence increased nitrogen solubility, provided that there was a sufficient amount of network to be depolymerized. A diagram of iso-nitride capacity was drawn for the CaO-Al 2 O 3 -CaF 2 ternary system at 1 773 K, and the nitride capacity was related to the optical basicity of the melt to obtain the following correlation equation: log C N ϭ7.442LϪ19.05

A study on the mechanism of desulphurisation and dephosphorisation of liquid steel by Na2CO3 flux treatment

“…The presence of various nitrides in the slag (Table 2) indicates that a soda‐rich slag possesses considerable nitride capacity. This is in conformity with the observations of a recent study [5] on the nitride capacity of basic slags.…”

Surface kinetics of nitrogen dissolution and its correlation to the slag structure in the CaO―SiO2, CaO―Al2O3, and CaO―SiO2―Al2O3 slag system

“…A fundamental understanding of the thermodynamics and kinetics of nitrogen dissolution in slags allows the design of optimum slag compositions and process parameters to achieve the required levels of nitrogen in molten steels. While many studies on the thermodynamics of nitrogen dissolution in slags using a gas-slag equilibration technique have been done [1][2][3][4][5][6], there are only a limited number of studies available on the kinetics as far as the authors knowledge. In particular, nitrogen dissolution on the surface of the slag and the effects of additives such as Al 2 O 3 are still unclear.…”

“…Thermodynamic evaluations have shown that nitrogen in molten slag can dissolve as N 3− (free nitride), N 0 (bridged nitride), or N − (non-bridged nitride) and expressed by the following [1][2][3][4][5][6]. Where O 2− is the free oxygen ion, O − is the non-bridged oxygen, and O 0 is the bridged oxygen.…”