Micro-Structure Refinement in Low Carbon High Manganese Steels Through Ti-Deoxidation,Characterization and Effect of Secondary Deoxidation Particle(s)

摘要

This paper investigates the effect of de-oxidation inclusions on micro-structure in low carbon (0.07 mass％),high Mn (0.9 mass％) steel.De-oxidation tests were carried out by adding either aluminum (0.05 mass％) or titanium (0.05,0.03 or 0.015 mass％) to an iron melt in a 400 g-scale vacuum furnace.A Confocal Scanning Laser Microscope (CSLM) was used to evaluate the effect of cooling rate by re-melting and quenching during solidification.Fine secondary de-oxidation particles were obtained in the Ti-killed samples,and the particle density increased with increasing oxygen content,and their size decreased with increasing the cooling rate during solidification.The secondary Ti de-oxidation particles were found to have an effect on microstructure evolution,such as solidifying microstructure,austenite grain growth and austenite decomposition.The de-oxidation particles were examined through FE-TEM and were identified to be TiO,MnTiO3 and Mn2TiO4,in low oxygen ([O]=7ppm) and high oxygen ([O]=56,81ppm) Ti-killed steels respectively.The effect of the particles on ferrite formation was evaluated through thermo-mechanical treatments.TiO was the most effective for promoting ferrite formation through heterogeneous nucleation.The particles contributed to ferrite formation in the following order,TiO＞TiN＞MnS＞MnTiO3＞Ti2O3.