| 摘要 |
PURPOSE:To improve the workability in high-nitrogen cold-rolled steel-plate production by a method wherein a low-carbon rimmed steel plate finished to a specified thickness is subjected to recrystallization annealing and then is nitrized at a specified temperature. CONSTITUTION:A slab is subjected to normal hot and cold rolling processes to form into a low-carbon rimmed steel plate in 0.5-2.3mm. thickness. In a loose coil condition, the steel plate undergoes recrystallization annealing in an atmospheric gas of hydrogen and nitrogen. A preferably composition of the atmospheric gas is of about 2-20% of hydrogen and about 80-98% nitrogen. Then, at steel temperature exceeding 500 deg.C, a small amount of ammonia gas (less than about 1%) is added to and mixed into the atmospheric gas, the temperature is maintained at a specified period, and then steel plate is gradually cooled. The process improves the workability in casting operation and the surface properties of slab. |
