| 摘要 |
PURPOSE:To control the surface temp. of cooling rolls as desired and to prevent the defective shape of a steel strip in the stage of cooling the steel strip in a continuous annealing furnace, by using a refrigerant having a high b.p. while controlling the same at a required temp. CONSTITUTION:Plural cooling rolls 10 are provided in a cooling zone 3 in a continuous annealing furnace consisting of a heating zone 1, a holding zone 2 and a cooling zone 3 and an overaging zone 4, and a cooling medium harring a high b.p. (e.g.; polyvinyl pyrrolidone) is kept heated and circulated in said rolls. In the figure, 11 is pump for circulation, 12 a heating chamber for the cooling medium, 13 a heater and 14 a pipe for cooling. The cooling medium is maintained at a prescribed temp. by means of the heater 13 and the pipe 14 and is circulated in the rolls 10 by means of the pump 11 to maintain the surface of the rolls at the prescribed temp. More particularly, the surface of the rolls 10 can be maintained at a high temp. of >=100 deg.C which is not possible with water in the prior part; therefore, the steel strip is precooled at a cooling rate as high as 20- 150 deg.C/sec without using gas jet zones. The surface temp. of the rolls is controlled preferably at about 300-500 deg.C in the case of precooling the steel strip. |
