| 摘要 |
PURPOSE:To prevent generation of temper color and to improve surface luster by blowing gaseous mixture for which concentration of hydrogen and dew point are controlled basing on the luster of a steel plate detected at the exit of a furnace against a band steel positioned in specified plate temperature range. CONSTITUTION:The luster of a band steel 20 is estimated by a temper color detector 22 for band steel such as a glossmeter etc. provided at the exit of a bright annealing furnace. At a place where temperature is detected at 650-950 deg.C by a plate temperature measuring device, gaseous mixture of nitrogen and hydrogen for which concentration of hydrogen is controlled to >=55vol% and the dew point is controlled to <=-40 deg.C is blown from a nozzle 26 against the band steel 20. The concentration of hydrogen in the gaseous mixture is adjusted in accordance with the target rank of luster. At the same time, the quantity of AX supplied from an AX gas generator 27 and a valve 28 is adjusted to maintain the furnace pressure at a fixed value. By this way, a product excellent in surface luster can be obtained. |
