High temperature magnetic cores and process for producing the same

摘要

A sheet of ferromagnetic material 30 is coated with glass having a temperature/viscosity characteristic such that at the annealing temperature of the ferromagnetic material the glass coating is sufficiently viscous to bond with a similar coating on an adjacent sheet of material, but will not run off the surface of the sheet. The magnetic sheet is run through a number of tanks (Fig. 1, not shown) in which is carried out successively degreasing, rinsing, pickling, rinsing, electro-plating with a thin coating of nickel, rinsing and neutralizing of any acids picked up by the sheet. It is then run through a coating tank 42 (Fig. 2) containing a suspension of vitreous particles in a vehicle such as amyl acetate or isopropyl alcohol, the coating is dried by infra-red lamps 44 and is fused to form a thin glass layer on the strip in tube furnace 46. The glass coated sheet is made into magnetic cores by winding it or stacking stampings made from it and when the cores are annealed to remove straws the glass coatings bond together or, if the sheet is coated on one side only, bonds with the adjacent uncoated sheet. Ranges of percentages of materials which may be used for making the glass used as the coating material are as follows: SiO2 36.00-54.65, B2O3 5.05-18.00, Al2O3 2.00-7.35, Na2O 3.65-18.00, K2O 7.00-30.45, CaO 0.00-10.00, Ca F2 0.00-5.00, BaO 0.00-20.90, ZnO 0.00-4.05, ZrO2 0.00-1.35, MnO2 0.50-1.00, NiO 0.50-1.00, CoO 0.50-1.50. In these proportions boron oxide can be reduced to 2% or less. Sodium oxide can replace the potassium oxide. Manganese, nickel and cobalt oxides can be left out. Glasses containing up to 15% ZrO2 and 15% TiO2 can also be made.