Effects Of Ti-Mg Complex Inclusion Introduced By Different Methods On Inclusion And Microstructure Of Low Carbon Steel

Oxide metallurgy has provided new idea for the development of steel industry,using its beneficial side while strictly controlling inclusions.Its key is inclusion control,which uses fine inclusions to pin grain boundaries and induce intragranular ferrite formation.This will refine grain,and optimize stell performance.In this thesis,Q235 is used as the raw material.Through external addition of Mg Ti O3(micron),Mg O(nano),and Ti O2(analytical pure),and complex treatment of Mg and Ti alloys,their resulting effects on inclusion and microstructure are discussed.First,thermodynamic calculation is used to analyze the stability of Mg Ti O3 in molten steel and the precipitation type of titanium oxide during solidification.Second,the effects of different addition methods on the inclusion and microstructure are analyzed by SEM-EDS and metallographic microscope.Finally,the possible mechanism of inclusion induced ferrite nucleation is discussed.Based on above studies,the conclusions are shown as follows:(1)The micro Mg Ti O3 particles and micro Ti O2 particles can be effectively added into the molten steel through ball milling pre-dispersion method,and a large number of Ti-bearing inclusions are formed.The nano Mg O particles cannot be effectively added;(2)The external addition of micron Mg Ti O3 particles and analytically pure Ti O2 can refine the inclusion and increase the inclusion density.The Ti-bearing inclusions can induce acicular ferrite nucleation,and Mn-depletion zone may be the possible mechanism for its inclusion induced nucleation.This is similar to the effect of Ti-Mg complex treatment;(3)The Ti and Mg complex treatment can refine the size of inclusions in the steel and increase the density of inclusions.The resulting Ti-Mg complex inclusions can induce acicular ferrite nucleation.