Size distribution of multi-phase deoxidation particles for heterogeneous crystallization of TiN and solidification structure in ti-added ferritic stainless steel

Single (Ti and Mg) and multiple (Ti/M: M=Mg, Ca, Zr or Ce and Ti/M/M': Ti/Mg/Al, Al/Mg/Ti, Al/Ti/Ca, Ti/ Al(Ca)/Ca(Al), Ti/Mg(Ca)/Ca(Mg), Ti/Zr/Ca(Mg) or Ti/Ce/(Ca) deoxidations were carried out at 1 600°C to study the effect of TiN crystallization on the solidification structure in an Fe-17.5(11)%Cr-0.25%Mn-0.20%Si-0.2 to 0.3%Ti-0.01%C alloy containing 0.0030 to 0.04 ppm N on a mass percent basis. Planar size distributions of TiN, TiN+oxide and oxide particles above 1.5 μ m in size and spatial size distributions of particles with different compositions greater than 0.1 μ m in size were measured and the characteristics of these size distributions have been discussed. The crystallization and precipitation of TiN and TiN on oxide particles were studied as functions of particle number, [Ti]·[N] solubility product and composition of the deoxidation particles. It was found that the solidification structure was not influenced by the number of TiN and TiN+oxide particles of size greater than 1.5 μ m, but by the deoxidation method. A very fine structure was observed in Ti/Mg, Ti/Mg/Al and Ti/Mg(Ca)/Mg(Ca) deoxidations and a fine structure was observed in Ti(Al)/Al(Ti)/Ca deoxidation using a MgO crucible both with and without the presence of CaO-MgO-Al₂O₃ slag.