METHOD OF DECARBURIZING ANNEALING OF STEEL STRIPS Russian patent published in 2004 - IPC

FIELD: metallurgy; heat treatment of strips in bell-type muffle furnaces; decarburing annealing of cold-rolled for magnetic screens of kinescopes. SUBSTANCE: proposed method includes delivery of nitrogen-hydrogen mixture to under-muffle space, heating strips, forming atmosphere of moistened nitrogen in under-muffle space holding strips at annealing temperature followed by force cooling. Heating is effected temperature of 690-720 C and strips are held at this temperature for 0.8-1.2 h, after which atmosphere of moistened nitrogen is formed in under-muffle space at dew point of 0 to +25 C which is held for 3-4 h; then under-muffle space is filled with hydrogen and strips are held for 2-3 h after which they are subjected to forced cooling. Atmosphere of moistened nitrogen is formed by delivery of water to under-muffle space at flow rate of 0.11- 0.28 l/t.h. Besides that, forced cooling is performed to temperature not higher than 40 C at average rate of 80 to 100 C/h; then, under-muffle space of filled with dehumidified nitrogen 5.5 to 6.5 h after beginning of forced cooling. EFFECT: improved quality of strips due to reduction of content of carbon and enhanced ductility. 4 cl, 2 tbl