The effect of heat treatments and Si contents on B2 ordering reaction in high-silicon steels

The silicon content was increased up to 6.5% (by weight, unless specified otherwise) to reduce the power loss of the silicon steels. These steels were prepared by the conventional casting method or by spray forming and were investigated with the aid of light optical microscopy (LOM) and transmission electron microscopy (TEM). The difference in the casting method did not result in any difference in suppressing the B2 ordering. The D03 phase was observed only in the as-cast 6.5%Si steel. It was almost impossible to suppress the B2 ordered phase keeping the silicon level as high as 6.5% even after the heat treatment at 1000°C for 24 h or after hot rolling. It was necessary to change the Si level and control the cooling rate to suppress the ordering reaction, especially, in cooling after heat treatment. The silicon level of 5.87% was observed to be a critical value in suppressing the B2 ordering reaction.