A thermodynamic study on the Ti-bearing inclusions in the 17Cr stainless steel

In order to utilize the advantage of oxides in stainless steel, the formation of titanium nitride (TiN) and oxide (Ti sub( x)O sub( y)) in the 17Cr steel was investigated by the calculation of the free energy of reaction and thermodynamic calculation with Thermo-calc software. The result indicates that the competitive reaction between the dissolved (O) and the dissolved (N) with the dissolved (Ti) in molten steel results in different precipitation sequences of TiN and Ti sub( x)O sub( y). The increase of (Ti) causes a higher precipitation temperature of TiN and Ti sub( x)O sub( y) in both Ti-N and Ti-O alloy systems. Equilibrium relations of (Ti) vs (N) and (Ti) vs (O) show that the solubility products fall with the decrease of the temperature, and then the precipitation of the inclusions becomes easier. In the Ti-O alloy system, a high (O) and a low (Ti) are favorable to the precipitation of Ti sub( 3)O sub(5), and a high (Ti) content and a low (O) favorable to the Ti sub( 2)O sub( 3) precipitation.