| 摘要 |
PURPOSE:To improve surface characteristics of steel sheet to be treated, by controlling air ratio so that H2 gas may be present always in the furnace atmosphere of a direct heating type nonoxidation heating furnace. CONSTITUTION:The furnace atmosphere gas of a direct heating type nonoxidation heating furnace, especially a nonoxidation furnace for use in continuous annealing of cold rolled steel sheet, is detected and is controlled so as to contain always at least 0.1% hydrogen. Pref. air ratio is controlled so that the atmosphere gas contains hydrogen gas ranging from 0.5 to 2%. Hereby the heat treated steel is excellent in surface characteristics. |
