| 摘要 |
PURPOSE:To enhance the safety and to facilitate the maintenance and control of equipment by mixing an inert gas such as nitrogen as a base with a reduced amount of hydrogen and using the gaseous mixture in place of a modified gas having high reducing power. CONSTITUTION:Gaseous nitrogen 1 and gaseous hydrogen 2 each having a low dew point are fed to a mixer 5 and mixed after the ratio is regulated through flowmeters 4, and the dew point of the gaseous mixture is regulated to <=0 deg.C by bubbling in a hot water tank 6. The gaseous mixture 13 is introduced into a furnace by 10-100l/kg electrical steel sheets in the furnace so that <=50ppm oxygen and <=1,000ppm hydrogen remain in the furnace and the electrical steel sheets are heated to 730-800 deg.C to carry out strain relief annealing in a piled state. |
