Effect of sulfur content on inclusion characteristics and magnetic properties of non-oriented silicon steel
The magnetic properties of non-oriented silicon steel are greatly affected by micrometer and nano-sized sulfide.The effect mechanism of deep desulfurization of liquid steel on the inclusion characteristics and magnetic properties of the finished non-oriented silicon steels was investigated.The composition,number,and size of inclusions and precipitates in the finished non-oriented silicon steels with different sulfur contents were studied using SEM/TEM-EDS and image analysis software,and the magnetic properties of the finished steel were measured.The statistical results indicated that the main inclusions in the experimental steels are AlN,(Al,Si)xNy,MnS,and AlN/(Al,Si)xNy-MnS composite inclusions.There are small amounts of composite oxides containing MgO·Al2O3 or oxides-MnS composite inclusions.The precipitates are mainly composed of CuxS and MnS+CuxS composite precipitates.The segregation of[S]at the solidification front decreases with the decrease in sulfur content,resulting in a decrease in the number of nitrogen sulfides in the steel.The research results indicate that the lower the sulfur content is in the steel,the higher the residual nitrogen content is in the steel,and the number density of nitrides increases.The change of sulfur content has little effect on the number of oxides,sulfides,and oxysulphides in the fully deoxygenated steels.During the solidification process of the molten steel,the precipitation amount of MnS decreases in sequence with the decrease of sulfur content,so the precipitation amounts and size of inclusions containing MnS are changed,resulting in a decrease in the total amount of inclusions and an inhomogeneous distribution of inclusion size.The difference of MnS-bearing inclusions precipitating mainly originates from the segregation difference of[S]until the solidification ratio of the liquid steel is higher than 0.7,and when the content of sulfur in the steel decreases to 15 × 10-4％or less,the segregation difference of[S]at the solidification front is very small.When sulfur content is 10 × 10-4％,the number density of the inclusions and precipitates in the experimental steels is less than those in the other samples.The average size of the inclusions is about 2.0 μm and the average size of the fine precipitates is 52 nm.The excellent number and size control effect of inclusions and precipitates are in return with the best magnetic properties of the 10 × 10-4％S-bearing samples,and the iron loss P1.5/50 is 4.16 W/kg and the magnetic induction B50 is 1.751 T.The iron loss Pi.5/50 increases by 0.27W/kg and the magnetic induction B50 decreases by 0.040T after sulfur content in the steel decreased to 5 × 10-4％,which is related to the increase of aluminum and nitrogen contents and inclusions above 3 μm caused by deep desulfurization of liquid steel.Excessive reduction of sulfur content of the non-oriented silicon steels in smelting process deteriorates the magnetic properties of the steels.
万方数据
维普
