The effect of vacuum conditioning heat treatment temperature (800

825

850

875

900 ) on the primary recrystallization microstructure

secondary recrystallization structure and magnetic properties of 0.3 mm cold-rolled sheel of grain-oriented silicon steel 30Q140 (/% ：0.035C

3.25Si

0.08Mn

0.010P

0. 025S

0.023Al

0. 0065N) is studied. The results show that the partial decarburization of grain-oriented silicon steel can be achieved by using the decomposition water of Mg(OH)

2

in MgO coating on the steel sheet surface in rapid healing in vacuum conditioning heat treatment. With increasing vacuum conditioning heat treatment temperature

the average grain diameter of vacuum conditioning heat treatment temperature + 1200 ℃ high-temperature annealing steel 30Q140 first increases and then decreases

and the magnetic properties first become better and then worse. The vacuum conditioning heat treatment temperature of the most perfect secondary recrystallization structure and the best magnetic property of steel is 850 °C.