2017 Volume 57 Issue 10 Pages 1883-1886
A method was developed for the measurement of BH curves for steels from room temperature to the Curie point (Tc). A closed magnetic circuit measurement was applied to obtain accurate temperature-dependent magnetic characteristics. BH curves were successfully measured at temperatures over 473 K (200°C), which was not possible before the development of this method.
In addition, at room temperature BH curves measured by the proposed method and a conventional method correspond well, which indicates the validity of the proposed method.
In the measurement for a medium-carbon steel and a electromagnetic soft iron, the difference in the magnetic flux density at 8000 A·m−1 (B8k) came from the low saturation magnetic flux density of cementite in the medium-carbon steel. B8k for the medium-carbon steel clearly decreased as the temperature increased from room temperature to 473 K (200°C), which corresponds to Tc for cementite.
In addition, B8k for the electromagnetic soft iron decreased almost linearly from 973 K (700°C) to 1048 K (775°C), whereas B8k for the medium-carbon steel decreased significantly from 998 K (725°C) to 1023 K (750°C). This difference indicates that magnetic transformation occurs only in the electromagnetic soft iron at around Tc, while magnetic and phase transformations, from ferrite to austenite, occur simultaneously in the medium-carbon steel. The differences in the temperature-dependent coercive force for electromagnetic soft iron, and for the low and medium-carbon steels were observed in detail.
The proposed method provided exact BH curves at high temperature, which were reflected by the complex and detailed magnetic behavior.