Microstructure and Magnetic Properties of 6.5 Wt Pct Si Steel Strip Produced by Simulated Strip Casting Process

An improved dip test apparatus was used to simulate the strip casting of 6.5 wt pct Si steel in this study. The results showed that the interfacial heat flux between melt and substrate could reach maximum value of 8.2 MW/m(2), with > 4350 kJ/m(2) heat being removed in the first 1.0 s. The as-cast strip mainly consisted of large columnar grains hundreds of microns in length. The high cooling rate of the as-cast strip suppressed the formation of ordered phases and the precipitation of elements. Only several complex particles of MnS-TiN of a few nanometers were found. After annealing at 1273 K (1000 degrees C) for 30 minutes, a large number of small particles such as TiN precipitated from the ferrite matrix. Within the testing frequency and magnetic field strength, the three strip samples obtained at different conditions showed the lowest iron loss at the frequency of 20 kHz and the magnetic field strength of 0.07 T, which were 22, 18 and 17 W/kg, respectively. The coercive force and iron loss decreased with increasing heat treatment temperature, while the magnetic permeability showed the opposite pattern. The magnetic permeability and iron loss of the silicon steel strip produced by strip casting are comparable to those of the silicon steel products produced by other techniques such as melt spinning and conventional rolling.

Automated summary

An improved dip test apparatus was used to simulate strip casting of 6.5 wt pct Si steel, showing that the high cooling rate resulted in a strip with low iron loss and the magnetic permeability and iron loss varied with increasing heat treatment temperature. The as-cast strip mainly consisted of large columnar grains, with only small particles of MnS-TiN found, and after annealing, a large number of small particles such as TiN precipitated from the ferrite matrix. The magnetic permeability and iron loss of the silicon steel strip produced by strip casting are comparable to those of silicon steel products produced by other techniques.