| 摘要 |
The invention relates to a process for making magnetic cores by thermal oxidation of oxidic materials, such as ferrites and perowskites, for making high-frequency circuit components that cannot be obtained by the known processes. According to the invention, the process consists in preparing a homogeneous mixture of metals forming the oxidic compound, in a stoichiometric ratio, where said mixture can be an alloy of two or several metals, a fine alloy powder or a homogeneous mixture of metal powders of a grain size of less than 20 μ , making therefrom a blank having the shape and size required for obtaining the finished piece by lamination, drawing, stamping, cambering or pressing a powder in a mould, the final shape of the blank before the beginning of the heat treatment being obtained with preset dimensions smaller by 5...24% than the final dimension, as the oxidic compound increases the blank volume, in the final stage the blank being heat treated in air, oxygen or other oxidating mixture, at a temperature ranging between 1100...1200°C, where there takes place the oxidation of all component metals, the oxygen diffusing within the entire mass of the blank and oxidizing the component metals by a reaction of the type xA + yB + zC + wO= AO+ BO+ CO, after which there takes place a solid-phase reaction between oxides, by a reaction of the type AO+ BO+ CO= ABCOand the oxidic compound crystals appear and grow and attach to one another, thereby determining a volume increase of the magnetic core and a porosity decrease thereof. |
