热处理工艺对0.25%Si含铌无取向硅钢显微组织和铁损的影响

Effects of heat treatment process on microstructure and iron loss of 0.25% Si non-oriented silicon steel sheets containing niobium

向无取向硅钢中添加适量的铌元素,可以有效改善成品钢的显微组织和机械性能,但会对电磁性能产生不利影响。截至目前,尚不清楚铌元素在无取向硅钢中的存在形式、作用机理,以及在不同热处理工艺条件下对电磁性能的影响效果。研究结合0.25%Si含铌无取向硅钢生产实际,探讨了铌元素在钢中的存在形式、作用机理和影响效果,并借助热处理工艺优化以减轻铌元素对钢电磁性能的影响。结果表明,铌元素在钢中会形成百纳米级、数量众多的有害夹杂物,钉扎晶界和降低晶界扩散率,并推迟钢的再结晶开始温度和结束温度,因而,导致晶粒细化和铁损升高。随着钢中铌含量增加,钢的涡流损耗基本相当,但磁滞损耗不断增加。合理的热处理工艺,可以促进消除应力退火之后的晶粒尺寸长大,并在一定程度上减少磁滞损耗之间的差异。

The microstructure and mechanical properties can be greatly improved by adding proper niobium concentration in liquid steel, but the magnetic properties will sharply decrease as the increase of niobium concentration in non-oriented silicon steel sheets. So far, the formation state and effect mechanism of niobium element as well as its influence on the change of magnetic properties under different hot treatment technology are yet to clarify. In present work, the formation type of the Nb-containing inclusion and its negative effect was discussed based on 0.25% Si non-oriented silicon steel sheets containing niobium. It is expected that the proper heat treatment techniques can be used to decrease the harmful effect of the magnetic properties by niobium element. The results showed that, there is multiple harmful inclusions with hundreds of nanoscale in size, that can pin grain boundary and decrease grain boundary diffusion rate, and retard the started temperature and the finished temperature of recrystallization of the cold rolled steel sheets. Thus, the grain size will be refined and the iron loss will be poor. As the increase of niobium concentration, the eddy loss will be stable and the hysteresis loss will be increase, respectively. The suitable heat treatment techniques can improve the grain size after stress release annealing, and decrease the deviation of hysteresis loss for the different niobium concentrations as possible.