Effect of Ce on the Microstructure, High-Temperature Tensile Properties, and Fracture Mode of Strip Casting Non-Oriented 6.5%Si Electrical Steel

Non-oriented 6.5%Si electrical steel exhibits excellent high-frequency magnetic properties, such as low iron loss and near-zero magnetostriction. Moreover, the high Si content causes poor deformability due to the solution strengthening effect of Si and the resulting ordering transformations, delaying the commercial application. Strip casting is a near-net forming technology that directly produces thin strips from the melt and reduces the required rolling deformation for the fabrication of thin sheets. This technology could be a viable option for industrializing the production of non-oriented 6.5%Si electrical steel. Despite this, even in the strip casting process, this brittle material is prone to edge cracks. Thus, improving the intrinsic plasticity of strip casting non-oriented 6.5%Si electrical steel is necessary through chemical modification to eliminate the deforming defects. The effect of Ce on the ordered phase of the solidification microstructure, high-temperature tensile properties, and fracture mode of strip casting non-oriented 6.5%Si electrical steel was investigated in this work. The results showed that the addition of Ce introduced high-melting Ce2O2.5S and Ce4O4S3 during strip casting, which promoted heterogeneous nucleation and refined the solidification microstructure of the as-cast strip. The presence of Ce did not affect the ordering condition of the as-cast strip. In decreasing order, the tensile temperatures corresponding to the ordered degree of the as-cast strip were 650, 400, and 800 degrees C. With the tensile temperature increasing, the yield and tensile strengths of the as-cast strip decreased, whereas the elongation gradually increased. When the tensile temperature exceeded 500 degrees C, the purification and microstructure refining effects of Ce improved grain-boundary cohesion and prevented intergranular cracking. Moreover, the occurrences of dynamic recovery and recrystallization eventually made the as-cast strip doped with Ce fractured by dimples, leading to a considerably enhanced tensile ductility. According to the findings, the rare-earth treatment should be considered as an effective method for increasing the ductility of strip casting non oriented 6.5%Si electrical steel.

Automated summary

This study aims to improve the plasticity of strip casting non-oriented 6.5%Si electrical steel through chemical modification. The results showed that the addition of Ce during strip casting promoted heterogeneous nucleation and refined the solidification microstructure, while not affecting the ordering condition of the as-cast strip. Increasing the tensile temperature improved grain-boundary cohesion and prevented intergranular cracking, eventually enhancing the tensile ductility through dynamic recovery and recrystallization. The rare-earth treatment is considered an effective method for increasing the ductility of strip casting non-oriented 6.5%Si electrical steel.