Improvement of transverse microstructure uniformity of high grade non-oriented silicon steel in hot rolling
In response to the problem of severe edge cracks in cold rolled strip caused by uneven transverse structure of high grade non-oriented silicon steel in hot rolling,the recrystallization degree was analyzed by thermal simulation testing machine at differ-ent temperatures and reduction rates.The results showed that the roughing rolling temperature dropped from 1 100 ℃ to 1 000 ℃,and the critical pressure rate of complete recrystallization increased from 30％to more than 40％.According to the re-sults of thermal simulation,the hot rolling process was optimized by changing the roughing pass combination to 1+3,putting the edge heater setting 50 ℃ before finishing rolling,controlling the finishing rolling temperature according to the target upper limit of 865 ℃+20 ℃,and adopting post-cooling for laminar cooling.The transverse temperature difference,uniformity of mi-crostructure and mechanical properties and dislocation of hot rolled strip before and after process optimization were analyzed by using the test results of thermal imager,metallographic microscope,tensile testing machine and transmission electron micro-scope.The results show that by increasing the rolling temperature,increasing the pass reduction rate,increasing the rolling speed and temperature compensation on the edge,the dislocation on the edge of the rolled piece quickly accumulated in large quantity at the grain boundary,and the dislocation density in some positions in the grain began to decrease,reaching a critical state and dynamic recrystallization occurred,which improved the transverse microstructure and property uniformity of the hot rolled strip.The correction rate of cold rolled products is reduced from about 25％to 5％.
high grade non-oriented siliconedge crackingtransverse microstructureuniformityrecrystallizationprocess opti-mizationcorrection rate
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