冷却速率对高碳铬铁粉电磁性能的影响

采用矢量网络参数法在1~18 GНz频段内分别对电阻炉、空气和水浴中冷却的高碳铬铁粉的电磁性能进行研究.随着冷却速率的提高，高碳铬铁粉的相对复介电常数实部和虚部在大多数频率下均增大.空冷和水冷粉料的相对复介电常数虚部在12~18 GНz频率范围内因极化弛豫而产生较大的峰值.同一频率下相对复磁导率实部随冷却速率变化的趋势与相对复介电常数相反.水冷粉料的相对复磁导率虚部在3~5GНz以外的频段内均大于另两组冷却粉料，且三组粉料的虚部在低频及高频条件下均具有峰值.在2.45 GНz的微波加热频率下，炉冷、空冷及水冷粉料的反射损耗分别为-2.30、-2.15和-2.07 dB.水冷粉料的介电损耗因子及磁损耗因子最大，微波场下具有最佳的升温速率与反应效果.

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

The electromagnetic properties of high-carbon ferrochrome powders (НCFCP) obtained at different cooling rates were investigated by means of the vector network method in the frequency range of 1 to 18 GНz. It is found that both the real part and the imaginary part of the relative complex permittivity ofНCFCP 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 GНz. 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 reflec-tion losses of furnace-cooled, air-cooled and water-cooledНCFCP with the values of -2. 30, -2. 15 and -2. 07 dB severally at 2. 45 GНz, 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 ofНCFCP in a microwave field, attributed to a higher dielectric loss factor as well as a higher magnetic loss factor.