Cr对含Nb高强无取向硅钢组织、织构及性能的影响

 高强无取向硅钢主要应用于高速电机,要求其具备高强度和优异磁性能,但目前无取向硅钢的磁性能和强度难以兼顾。因此,设计并制备了添加微量Cr的含Nb高强无取向硅钢,通过光学显微镜、EBSD、万能拉伸试验机、四探针测试仪和磁性能测量仪等研究了Cr对含Nb高强无取向硅钢微观组织、织构、力学性能及磁性能的影响。结果表明,添加质量分数为0.5%的Cr抑制了热轧组织的回复,使常化和退火组织再结晶减弱,常化和退火后有利织构面积分数增加,不利织构面积分数减小。添加质量分数为0.5%的Cr使含Nb无取向硅钢的屈服强度显著增大,磁感略升高,但对铁损几乎没有影响。Cr对屈服强度的影响一方面是由于Cr的固溶强化作用,另一方面Cr促进了Nb的析出而使Nb的析出强化效果增强;而Cr提高含Nb高强无取向硅钢的磁感主要是由于促进有利织构形成的同时抑制了不利织构的形成,使得织构因子增大;添加Cr使无取向硅钢的电阻率增加从而使铁损降低,同时Cr促进了Nb的析出,而这种富Nb析出相不仅抑制晶粒长大且会阻碍磁畴移动而使铁损增高,在两方面因素的综合作用下,添加质量分数为0.5%的Cr对含Nb高强无取向硅钢的铁损几乎没有影响。因此,含Nb高强无取向硅钢中添加微量Cr,会由于Cr的固溶作用以及其促进Nb的析出而提高钢的强度并提高钢的综合磁性能。

Effect of Cr on microstructure,texture and properties of Nb-containing high strength non-oriented silicon steel

High strength non-oriented silicon steel is mainly used in high-speed motors, which requires good mechanical and magnetic properties. However, it is difficult for non-oriented silicon steel to obtain high strength and good magnetic properties at the same time. In this paper, the Cr-microalloyed Nb-containing high strength non-oriented silicon steel was designed and prepared. The effect of Cr on the microstructure, texture, mechanical properties and magnetic properties of Nb-containing high strength non-oriented silicon steel was studied by optical microscopy, EBSD, universal tensile testing machine, four-probe tester and magnetic properties test. The results show that the mass fraction addition of 0.5% Cr impedes the recovery of hot-rolled microstructure, and inhibits the recrystallization of normalized and final annealed microstructure. At the same time, the area fraction of favorable texture increases after normalization and annealing with the mass fraction addition of 0.5% Cr, while the area fraction of unfavorable texture decreases. Moreover, the mass fraction addition of 0.5% Cr increases the yield strength significantly and magnetic induction slightly of Nb-containing non-oriented silicon steel, but almost has no effect on the iron loss of the steel. The increase of yield strength of Nb-containing high strength non-oriented silicon steel after adding Cr is due to the solid solution strengthening effect of Cr, and the promotion of Nb precipitation by adding Cr and hence enhances the precipitation strengthening effect of Nb. The improvement of magnetic induction after adding Cr is owing to the promotion of favorable textures formation and the inhibition of unfavorable texture formation, which increases the texture factor. The resistivity of non-oriented silicon steel is increased after adding Cr, and hence decreases the iron loss. However, on the other hand, the promotion of Nb precipitation after adding Cr will increase iron loss by impeding the growth of crystal grains, and inhibiting the movement of magnetic domain. Thus, the mass fraction addition of 0.5% Cr will almost has no effect on iron loss of Nb-containing high strength non-oriented silicon steel as the co-effect of these two factors. Therefore, adding a small amount of Cr to the Nb-containing high strength non-oriented silicon steel will increase the strength and improve the comprehensive magnetic properties of steel due to the solid solution effect of Cr and its promotion of Nb precipitation.