Study On The External Addition Method And Induced Nucleation Characteristics Of Ti-bearing Inclusion

Oxide metallurgy is the method,which utilizes the non-metallic inclusions in steel to pin the austenite grain boundaries and induce intragranular ferrite(IGF)nucleation.This technology can improve the strength and toughness of steel,and has practical application potential.Titanium oxide,as one of the most effective oxides for inducing IGF nucleation,is still a research hotspot in terms of its formation method and induced nucleation characteristics.Therefore,this thesis focuses on the application of titanium oxide in oxide metallurgy,from the external addition method to the induced nucleation characteristics.On the one hand,nano-Ti O₂ particles were effectively introduced into the molten steel by external addition method.Through agglomeration and reaction,micron-sized Ti-containing oxides were formed and uniformly distributed in the steel.This led to the morphology improvement,size reduction and density increament.Moreover,the corresponding Ti-containing oxides can effectively induced IGF nucleation.Based on the theoretical discussion and contrast test,high energy,wettability and reactivity are attributed as the main factors for the effectiveness of external addition method.Among them,reactivity may be the key factor.Furthermore,alloy treatment was performed after the externally adding of nano-Ti O₂ particles.It was found that the resulting titanium-containing composite oxides can also effectively induce IGF nucleation.On the other hand,the number of IGFs induced by inclusions is used as a scale to measure its ability to induce nucleation.The correlation between the characteristics of Ti-containing oxides(size,Ti content and Al content at the edge of inclusions)and their ability to induce nucleation was explored.Statistical analysis shows that the ability of inclusions to induce nucleation is related to the size of the inclusions,but not directly related to the content of Ti₂O₃ in the inclusions.The former can be explained by the classic heterogeneous nucleation theory,and the latter may be related to the amount of Mn adsorption and its solubility in Ti₂O₃.