The effects of the difference of the heat flux between the wide face and narrow face of the mould, the mould taper, casting speed and cooling rate on unevenness of hypo-peritectic steel at the off-corner in the mould, which leads to longitudinal cracking, bleeding and breakout during continuous casting, were evaluated by a finite element model (FEM) simulation and a plant test with a commercial continuous caster. The simulation results show that an increase in the difference in the heat flux between the wide and narrow face increases the off-corner unevenness of solidification because the solidified shell on the low heat flux side is pulled toward the high heat flux side. The analysis results were in good agreement with the plant test results. These results revealed the importance of optimizing the heat flux ratio between the wide face and narrow face mould even under a high casting speed condition.

Flux leakage in the rotor core bridges is a problem specific to interior permanent magnet motors and has been unsolved till date. It is widely known that if the bridges are partially non-magnetically improved with low magnetic polarization, the leakage flux will be smaller, and the rotor will have a higher magnetic flux. We proposed that the portion of the silicon steel sheets that becomes the bridge after pressing can be nonmagnetized and laminated to fabricate the rotor core. Partially non-magnetic material with a polarization of almost zero was obtained by melting and mixing NiCr alloy powder with the silicon steel sheets. This non-magnetic improvement treatment was applied to the bridge in the rotor core sheet, in which the non-magnetic area width was 1.45 mm, and the prototype rotor core was fabricated by laminating 60 rotor core sheets. Upon measurement, the rotor core showed approximately 35% higher magnetic flux than a conventional one, with the actual value nearly identical to that obtained from the magnetic field analysis.

The influence of mould level instability during continuous casting on the unevenness of the initial solidified shell in hypo-peritectic steels has been investigated. Water model experiments and inplant casting experiments revealed that mould level instability, which increases with increasing casting speed, is related to longitudinal cracking resulting from the unevenness of the solidification shell. A numerical model which considers the effect of mould level instability was developed and used to simulate the formation of the unevenness of the solidification shell and solidified shell deflections. The calculation results show that an increase in the non-uniform infiltration of mould flux increases the unevenness of the solidified shell. On the other hand, the unevenness of the solidified shell decreases due to mild cooling. Overall, the results of the plant tests and calculations show that non-uniform infiltration of mould flux dramatically affects air gap formation and the unevenness of the solidified shell.