Effect of cooling rate on the electromagnetic properties of high-carbon ferrochrome powders

The electromagnetic properties of high-carbon ferrochrome powders(HCFCP) obtained at different cooling rates were investigated by means of the vector network method in the frequency range of 1 to 18 GHz. It is found that both the real part and the imaginary part of the relative complex permittivity of HCFCP show an increasing order with a rising in cooling rate at most frequencies,of which prominent peaks occur in the imaginary part of the air-cooled and water-cooled powders on account of polarization relaxation.For comparison,both the relative complex permeability and magnetic loss factor present complex change histories,where the real part of the relative complex permeability decreases as the cooling rate rises,and the imaginary part of the water-cooled powders occupies the dominant except for the frequency range from 3 to 5 GHz. While peaks in the imaginary part of each cooling sample principally result from the effect of nature resonance and magnetic hysteresis respectively corresponding to low frequency and high frequency. The reflection losses of furnace-cooled,air-cooled and water-cooled HCFCP with the values of -2.30,-2.15 and -2.07 d B severally at 2.45 GHz,could meet the need of microwave heating in principle. By overall consideration,the water-cooled powders are determined as the optimal materials for solid-phase decarburization of HCFCP in a microwave field,attributed to a higher dielectric loss factor as well as a higher magnetic loss factor.