THERMODYNAMIC INVESTIGATION OF NONMETALLIC INCLUSIONS IN STEEL (I)

Behaviour of Aluminum-, Silicon- and Iron-nitrides and Their Effect on Austenitic Grain Size of Steel-Part 1.

Abstract

When aluminum, silicon and nitrogen are contained in steel, nitrides of these elements are formed according to the degree of stability, of these nitrides. The free energy equations of the formation of nitrides in steel are derived from the data already reported and by a rough calculating method of using equilibrium diagrams. The equilibrium relations of the forma- tion of aluminum-, silicon- and iron-nitrides are calculated by these equations ranging from the state of solid at room temperature to that of liquid, by assumption that the content of these elements is as follows:
According to the results of calculation, both aluminum- and silicon-nitrides are estimated to be effective as grain-growth inhibitors, although the latter may be less effective than the former. Some considerations are made about nonmetallic inclusions which act as grain-growth inhibitors.