| 摘要 |
PURPOSE:To shorten the time required for slow cooling and enhance the activity rate of a slow cooling furnace by estimating the slow cooling time on he basis of the concentration of hydrogen in the bloom or billet before slow cooling and the change of furnace temperature with time, when slowly cooling the bloom or billet. CONSTITUTION:The initial hydrogen concentration of the bloom or billet, that is, the amount of hydrogen in the steel before slow cooling, is determined by analysis when the steel is molten. Then, the bloom or billet is placed in the slow cooling furnace and the furnace temperature is measured with the progress of time so as to estimate a curve of furnace temperature against time. On the other hand, in order to estimate the concentration of hydrogen in the steel, the diffusion coefficient of hydrogen in the steel is obtained on the assumption that the temperature of the bloom or billet is equal to the furnace temperature, and the amount of residual hydrogen at a given time is obtained by using the initial hydrogen concentration which is measured in advance. Based on the value thus obtained and a reference value of residual hydrogen concentration which is predetermined for each material, the slow cooling time for the bloom or billet is estimated and the latter is taken out from the furnace in accordance with the estimated time. |
