Decarburising high carbon contg. magnetic conductor sheet - by heating, recrystallisation and oxidn. cooling in protective gas atmos. having controlled moisture content

摘要

Magnetic conductor sheets having a high C content are heated >750 degrees C in a protective gas atmos., long enough to remove C excess and form the desired ferrite grain size, and then cooled to complete recrystallisation. Cooling is continued to form an oxide layer on magnetic conductor sheet surface. Novelty consists in using a protective gas atmos. contg. 2% CO, 1.5-4% H2, balance, to 100% N2. Moisture content in protective gas atmos. corresponds to dew point 7-10 degrees C during heating, 30-40 degrees C while holding >750 degrees C and during re-crystallisation cooling and 70-80 degrees C during oxidn. cooling. The sheets are used in electrical machinery and instruments. Treatment can be carried out economically in a simple continuous heating furnace. Explosion hazards are excluded.