| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a steel sheet for a rotor core by which, when used as a rotor core of an IPM motor, strength can be increased without reducing a reluctance torque of the IPM motor. <P>SOLUTION: A hot rolled steel sheet, which has a component composition containing, by mass, 0.06 to 0.90% C, 0.05 to 3.0% Si, 0.2 to 2.5% Mn, ≤0.05% P, ≤0.02% S and 0.005 to 4.95% acid-soluble Al under the condition satisfying Si+Al=5.0% and having the balance Fe with inevitable impurities, is cold rolled. The resulting cold rolled steel sheet is subjected, in a continuous annealing line or a continuous hardening line, to heating to ≥750°C, cooling to ≤450°C at ≥10°C/s cooling rate and holding in a range of 200 to 500°C for ≥120 sec to obtain a steel sheet showing ≥780 N/mm<SP>2</SP>yield strength at a tensile test and ≥1.2 T magnetic flux density B<SB>4000</SB>at 4000 A/m. <P>COPYRIGHT: (C)2009,JPO&INPIT |
