退火温度对含铜高强无取向硅钢强度和铁损的影响

Effect of annealing temperature on strength and iron loss of Cu-containing high-strength non-oriented silicon steel

新能源汽车驱动电机用硅钢需要具有高强度和低铁损,但两者难以兼得。利用纳米B2富铜析出相与基体错配度低的特性,通过退火工艺调控组织和铜析出相来实现无取向硅钢高强度和低铁损的协同优化,研究了退火温度对含铜无取向硅钢组织、析出相、强度和铁损的影响,制备出了高强度且低铁损的高性能无取向硅钢。结果表明,退火板中有高密度的纳米B2富铜析出相,随着退火温度升高,析出相尺寸先缓慢增大后显著增大,数密度和体积分数先显著减小后缓慢减小;在纳米B2富铜析出相的钉扎作用下,晶粒先显著长大后缓慢长大;纳米B2富铜相的析出强化贡献先减小后增大,细晶强化贡献逐渐减小,在两者的作用下,强度先降低后增加;由于纳米B2富铜析出相与基体错配度低,对铁损恶化作用较小,且晶粒尺寸增大使铁损降低,铁损先显著降低后缓慢增加。在950~1 000℃退火时,纳米B2富铜析出相尺寸和密度合适,可提高屈服强度200 MPa以上,且不会明显恶化铁损,此时能实现无取向硅钢高强度和低铁损的协同优化。

High strength and low iron loss are required for the driving motors of new energy vehicles.However,it is challenging to achieve both.The synergistic optimization of both high strength and low iron loss of non-oriented sili-con steels was realized by adjusting the microstructure and nano-B2Cu-rich precipitates which have a low mismatch with the matrix.The effect of annealing temperature on the microstructure,precipitates,strength,and iron loss of Cu-containing non-oriented silicon steel was studied,and high-performance non-oriented silicon steel with high strength and low iron loss was prepared.The results revealed high-density nano-B2Cu-rich precipitates in the an-nealed sheets.With increased annealing temperature,the size of the precipitates gradually increases at first,fol-lowed by a significant increase,while the number density and volume percent of the precipitates initially decrease significantly and then decrease slowly.Under the pinning action of nano-B2Cu-rich precipitates,the grain grows re-markably first and then slowly.The precipitation strengthening contribution of the nano-B2Cu-rich precipitates de-creases first and then increases,and the grain boundary strengthening contribution is gradually lowered.Under the influence of both,the strength of the silicon steel decreases first and then increases.Due to the low mismatch be-tween the nano-B2Cu-rich precipitate and the matrix,the precipitates do not deteriorate the iron loss of Cu-contai-ning silicon steels,and the increase in grain size reduces the iron loss,which significantly decreases first and then in-creases slowly.When annealed at 950-1000℃,the size and density of the nano-B2Cu-rich precipitate are optimal,which can improve the yield strength by more than 200MPa without deteriorating the iron loss.Therefore,the syn-ergistic optimization of high strength and low iron loss of non-oriented silicon steel can be achieved.