Evolution Behavior Of IAF Induced Inclusions During Thermal Cycling

The key of oxide metallurgy technology is how to obtain effective inclusions in steel which are large in quantity,small in size,suitable in composition,dispersed and can be used as heteronucleation core to induce the formation of intracrystalline acicular ferrite.It is important to control the formation of such inclusions in steel.The results show that the deoxidation order of alloy elements in steel is Mg>Al>Ti>Si>Mn at 1873K,The equilibrium relation of alloy composite deoxidation and the precipitation behavior of Mn S and Ti N in steel were obtained.,the compound deoxidization equilibrium relationship between the elements in molten steel and the precipitation behavior of Mn S and Ti N were obtained.The inclusions are mainly composed of Mg O·Al₂O₃,2Mg O·Ti O₂,Mg O,Ti N and Mn S.After magnesium treatment of ship plate steel,the inclusions in Central Plain steel are denatured,and a large number of small size and dispersed inclusions containing magnesium are introduced,typical Ti,Nb composite particles and Ti N composite particles were formed,and their stability was weaker than that of the second phase particles.The optimum temperature for inducing IAF was 1100℃and 1200℃,respectively,The specimens were analyzed in situ by a high temperature confocal microscope.It was found that when the cooling rate was 5℃/s,the induced effect and fining degree of IAF were the best.The composition of inclusions is mainly composed of Mg-Al-Ti-O composite inclusions surrounded by Mn S and Ti N particles.The nucleation mechanism of IAF induced by inclusions in magnesium-treated sheet steel can be explained from the viewpoint of solute element change mechanism.The formation mechanism of inclusions and precipitates in steel was analyzed from the point of view of mismatch mechanism.It can be concluded that inclusion-induced IAF nucleation is a complex process,which is accomplished by a variety of mechanisms.Figure 45;Table 15;Reference 79...