| 摘要 |
PURPOSE:To perform subzero treatment efficiently in less liquid nitrogen original units, at the time of subjecting a steel material such as rolling roll to subzero treatment, by separating cooling liquid nitrogen to liquid and gas by a vapor-liquid separator, directly cooling the steel material by the liquid nitrogen and cooling the treating vessel by the low temperature nitrogen gas. CONSTITUTION:A steel material 2 such as rolling roll is placed in a cooling vessel 1. The cooling vessel 1 is constituted by side walls 3A, bottom wall 3B and cover body 4 made of heat-insulating materials, and a gas flow space 7 made of steel plate is formed in its inside. Liquid nitrogen is supplied to a vapor-liquid separator 12 from a liquefied gas supply source 9 such as of liquid nitrogen. In the separator 12, it is separated to liquid nitrogen and vaporized low-temperature nitrogen gas. The liquid nitrogen is supplied to nozzles 10A, 10B, 10C, from which it is sprayed onto the roll material 2, whereby subzero treatment is accomplished. The gaseous nitrogen of a low temperature flows in the gas flow space 7 so that the wasteful use of the liquid nitrogen by the heat insulating material is prevented and the cooling effect of the roll material 2 is improved. |
