Study On Microstructure And Properties Of Non-oriented Silicon Steel By Strip Casting Process

Based on strip casting process of 0.71%Si + 0.44%A1 no-oriented silicon steel,the microstructure,texture evolution and the magnetic properties effected by initial thickness of the strip,hot rolling process,cold rolling process and the intermediate softening temperature(under semi technological process)was investigated in this work.The main contents and results are as follows:1.The effect of the initial thickness on the evolution of microstructure,texture and magnetic properties during strip casting process were studied.The columnar crystal was significant when the casting strip was thick(2.10mm);the main characteristic was equiaxed crystal when the casting strip was thin(1.35mm).Compared with the final annealed sheet of the thin casting strip,the grain size of the final annealed sheet of thick casting strip was larger and the favorable λ-fiber texture was stronger whether hot rolled or not.Thus the magnetic properties of the finished sheet of thick casting strip were better than the thin casting strip,especially in direct cold rolling process.In addition,both the thick strip and thin strip,with hot rolling process before cold rolling process,can weaken y-fiber texture,strengthen λ-fiber texture,grain coarsening,to improve the magnetic induction B50 and iron loss P15/50.2.The effect of hot rolling temperature(850～1250 ℃)on the evolution of microstructure,texture and magnetic properties during strip casting process were studied.The temperature of hot rolling had great influence on the microstructure evolution and magnetic properties.The excessive high or low temperature of hot rolling damages magnetic properties.Especially for hot rolling temperature of 1150℃,small grains are produced in finished product,in addion,λ-fiber texture weakened,and y-fiber texture enhanced,so the magnetic of finished product is the worst,the magnetic induction B50is 1.778T,iron loss P15/50 is 6.661 w/kg.When the hot rolling temperature is 1050℃,the magnetic property is best and the magnetic induction B50 is 1.796T,iron loss P15/50 is 4.544 W/kg.After hot rolling,the grain size of the finished product could been larged with the increased coiling temperature and further the magnetic properties could be improved.3.The effect of cold rolling reduction(70.2～94.0%)ratio on the evolution of microstructure,texture and magnetic properties were studied.The average grain size of the annealed sheet was gradually decreased from 19.3μm to 11μm with the rolling reduction increased from 70.2%to 91.1%.However,the average grain size increased to 25.8μm instead when the cold rolling reduction increased to 94.0%.The cube texture and the rotation cube texture of the annealed sheet were decreased and the γ-fiber texture was enhanced with the rolling reduction increased from 70.2%to 94.0%.Besides,the magnetic induction index B5o and the iron loss index P10/1000 and P10/400 of the annealed sheet decreased gradually but the P10/1000 decreased more significantly.Compared with the 0.50mm annealed sheet,the P10/1000 of the 0.10mm annealed sheet decreased by 143.8W/kg and the B50 only decreased by 0.063T.This indicated that it is suitable for the production of ultra-thin standard with low iron loss and high magnetic properties based on strip casting.4.The effect of intermediate softening temperature(650～860 ℃)on the evolution of microstructure,texture and magnetic properties under semi-processed during strip casting process were studied.The grain size of the final annealed sheet,first slightlly decreased and then slightly increased when the intermediate softening temperatureincreased from 650℃ to 750℃.However,the grain size of final annealed sheet increased sharply to 118.6μm when the intermediate softening temperature was 860℃.The cube texture was gradually weakened and a-fiber texture was gradually enhanced in the final annealed sheet with the intermediate softening temperature increased from 650 ℃ to 860℃.Thus,the magnetic induction index B50 of the final annealed sheet decreased gradually with the intermediate softening temperature increased and the iron loss index P15/50 increased first and then decreased.When the intermediate softening temperature was 650℃,the magnetic properties of the finished product was best.Compared with the whole process,the B50 decreased slightly by 0.013T,but the P15/50 significantly decreased by 0.657W/kg.This indicated the semi-process was better for the production of low iron loss and high magnetic properties based on strip casting.This work will lay the foundation for comprehensive mastering the evolution of microstructure,texture and process controlling of no-oriented silicon steel produced by strip casting.And also could enrich the theory and connotation of no-oriented silicon steel produced by strip casting.In addition,the results could contribute to provide relevant data for establishing the demonstration production line of strip casting.