| Oxide inclusions not only affect the smelting of non-oriented electrical steel,but also have harmful influence on magnetic properties and surface quality.The research on the control of oxide inclusions in electrical steel will help to improve the cleanliness of steel and the magnetic properties of final products.In this paper,the industrial production of 50W800 non-oriented electrical steel by BOF-RH-CSP process was studied.By means of theory analysis in combination with industry experimentation,studies on the rational control of oxygen content in molten steel during the smelting process,the evolution rule of oxide and the evolution mechanism of oxide inclusion in electrical steel were systematically studied,with the aim to provide theoretical basis for the control of oxide inclusion in the industrial production of electrical steel.The results are as follows:?1?Control of oxygen content in molten steel in smelting process,with the decrease of end-point carbon content,end-point oxygen content increased and the stability was poor.In order to ensure rational oxygen content in molten steel and T.Fe?24%in slag,the final carbon content of converter is controlled from 0.03%to0.05%.Argon blowing at the bottom of the ladle could effectively decrease the excess oxygen in molten steel and carbon and oxygen equilibruim dropped to 0.00150.0017.In order to reach end-point oxygen content of RH end-point decarbonization at150300ppm,carbon content of BOF was controlled at 0.030.04%,respectively before RH refining the carbon and oxygen content were 0.0250.035%and500650×10-6.?2?Test results of oxide inclusions in steels of various processes show that there were irregular Al2O3 inclusions in each procedure.Among them,after RH deoxidization and alloying,the inclusions in steel were mainly Al2O3 and MgO·Al2O3.There were angular MgO·Al2O3 inclusions of RH outgoing station and tundish.As smelting progresses,the proportion of MgO in inclusion increased.There were spherical CaO·MgO·Al2O3 and CaO·Al2O3 low melting point inclusions in tundish and slab samples.After deoxidation alloying,the size of inclusions less than 3?m in molten steel accounted for 80%.The area fraction of inclusions in steel decreased from 90100/mm2 after deoxidization alloying to 7580/mm2 in slab,and the average size of inclusions increased gradually.The number of inclusions with size less than3?m decreased greatly,while the number of inclusions with size greater than 5?m increased continuously..?3?Thermodynamic calculation of generation and transformation of oxide inclusions in the smelting process shows that as the Als content was 0.20.4%in electrical steel,deoxidation product was Al2O3.Within the range of 0.00008-0.005%Mg content,there was generation of stabilized MgO·Al2O3 inclusion in the steel.When Ca content was 0.001%,the ideal transformation of Al2O3 inclusion to12CaO·7Al2O3 with low melting point could be achieved.Ca was converted into CaO·MgO·Al2O3 by replacing Mg element in MgO·Al2O3. |
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