| 摘要 |
PURPOSE:To save descaling step of hot rolled steel hoops by the cold rolling the hot rolled steel hoop in succession then annealing the same in an annealing furnace of reducing gas atmosphere. CONSTITUTION:The steel hoop produced through hot rolling is cold rolled without removing the sale of its surfaces. At this time, cracks are produced in the scale of the steel hoop surfaces by making draft more than 40%, due to which the scale peels and its pickup reduces down to more than 1/5. This cold rolled steel hoop is annealed in an open coil annealing furnace and continuous annealing furnace. The atmosphere in the annealing furnace is the mixed reducing atmosphere of nitrogen-hydrogen of more than 4% of a hydrogen density and the annealing is accomplished for more than 30 secodns at the annealing temperature above 500 deg.C. Since the oxide film slightly remained on the steel hoop surface is reduced, the need for facilities and treatment costs for descaling after hot rolling as with conventional processes may be eliminated. |
