低压脉冲磁场凝固硅钢的热变形组织和行为

Hot deformation microstructure and behavior of silicon steel solidified under low voltage pulsed magnetic field

为了细化硅钢铸锭组织,提高其加工性能,研究了低压脉冲磁场对硅钢凝固组织的影响规律,并对比了不同凝固组织的热变形行为和组织。研究结果表明,在硅钢的凝固过程中施加脉冲磁场,传统的柱状晶组织转变为等轴晶组织。随着磁场频率的增加,等轴晶比率(等轴晶面积/整体面积)先增加后降低,等轴晶晶粒尺寸先减小后增大。随着励磁电压增加,等轴晶比率增加,等轴晶晶粒尺寸不断增加,获得最佳脉冲磁场工艺参数,磁场频率为5 Hz,励磁电压为200 V。在该脉冲磁场工艺参数下,硅钢凝固组织中的等轴晶尺寸细化至无磁场作用时的1/2,等轴晶比率提高至100%。对无脉冲磁场的柱状晶组织和施加脉冲磁场(磁场频率为5 Hz,励磁电压为200 V)的等轴晶组织,进行了热压缩试验(温度为950℃,应变速率为0.01 s^(-1)和0.1 s^(-1))和热轧试验(初轧温度1100℃)。通过微观组织结果发现,无脉冲磁场作用的柱状晶凝固组织在热压缩过程中发生少量动态再结晶,组织中存在难以消除的变形晶粒,影响后续加工性能。脉冲磁场作用下等轴晶凝固组织在相同热压缩条件下获得细小均匀的再结晶组织,平均晶粒尺寸为670μm。对比热轧板材组织和织构结果,同样发现脉冲磁场作用下的等轴晶凝固组织在热变形过程中更易发生动态再结晶,且轧制织构强度和板材各向异性更弱。

In order to refine the microstructure of silicon steel ingot and improve its processability,the effect of low voltage pulsed magnetic field(LVPMF)on the solidification structure of silicon steel was investigated,and the hot deformation behavior and microstructure of different as-cast microstructures were compared.The fine grains are obtained by employing the low voltage pulsed magnetic field during the solidification of silicon steel.With the increase of frequency of LVPMF,the ratio of equiaxed grains(area of equiaxed grains to whole area)and average grain size of equiaxed grains was increased firstly and then decreased.In addition,the ratio and average grain size of equiaxed grains increased with the voltage of LVPMF.The average size equiaxed grain is refined to half of grains without LVPMF,and the ratio of equiaxed grains increased from 10%to 100%under optimal LVPMF parameter with frequency of 5 Hz and voltage of 200 V.Hot compression experiments(deformation temperature of 950℃,strain rate of 0.01 s^(-1)and 0.1 s^(-1))and hot rolling experiments(blooming temperature 1100℃)were carried out for columnar grains solidified without LVPMF and equiaxed grains solidified with LVPMF(frequency of 5 Hz,voltage of 200 V).A small amount of recrystallization grains occurs and strip-shaped grains are formed in the samples solidified without LVPMF with columnar grains after hot compression.The strip-shaped grains are hard to eliminate and deteriorate processing performance of the alloy.The samples solidified with LVPMF with equiaxed grains can be fully recrystallized after hot compression.Therefore,fine recrystallization grains are acquired with average size of 670μm.By comparing the microstructure and texture of hot-rolled sheets,it is found that the samples with LVPMF with equiaxed grains are more prone to recrystallization during hot rolling,resulting in weaker texture intensity and anisotropy.