Method for coating magnetic powder core with sodium silicate

A method for coating a magnetic powder core with sodium silicate, comprising:

• step 1, pretreatment of sodium silicate:
• mixing sodium silicate and deionized water in a mass ratio of 1:
• (1-5), adding polyoxyethylene lauryl ether phosphate thereto, and mixing uniformly to obtain a sodium silicate solution, wherein the polyoxyethylene lauryl ether phosphate serves to uniformly disperse the sodium silicate in an aqueous solution, and results in antirust that prevents the metal magnetic powder from rusting;
• step 2, pretreatment of a metal magnetic powder:
• adding the metal magnetic powder to a coating furnace, setting the coating furnace at a temperature of 60-80° C., adding lignosulfonate to the coating furnace after reaching the set temperature, and stirring for 10-30 minutes, wherein the lignosulfonate serves to uniformly disperse the metal magnetic powder;
• step 3, coating:
• adding the sodium silicate solution obtained in step 1 to the metal magnetic powder obtained in step 2, and stirring for 10-30 minutes, wherein the sodium silicate solution is added in an amount of 1-10 wt % of the metal magnetic powder;
• step 4, baking:
• baking the powder obtained in step 3 at a temperature of 120-150° C. for 60-120 minutes to obtain a coated powder;
• step 5, adding an insulating adhesive and a lubricant:
• adding an inorganic insulating adhesive in an amount of 0.1%-1% by weight of the coated powder and a stearate as a lubricant in an amount of 0.1%-1% by weight of the coated powder to the coated powder obtained in step 4, and mixing uniformly;
• step 6, compression molding:
• subjecting the magnetic powder mixed uniformly in step 5 to a compression molding at a molding pressure of 1500-2300 MPa;
• and
• step 7, heat treatment:
• keeping the magnetic powder core molded in step 6 under the protection of a N2 or H2 atmosphere at a temperature of 600-800° C. for 30-90 minutes to obtain a sodium silicate-coated magnetic powder core.