Bright annealing of steel strip coils - by adjusting inert gas flow rate to correspond to emulsion evaporation

摘要

The carbon pick-up during the bright annealing of solid coils rolled steel strip in top hat furnaces under a protective gas atmosphere is minimised by varying, during the heating of the coldest spot to the final temperature, the admission of the inert gas as a function of the released amount of evaporated emulsion which had been applied during the rolling operation. The gas is admitted, e.g. by one sharp increase and is followed by a decrease. The inert gas flow is kept to a low level until the temperature has reached the point where the emulsion evaporates. When this occurs, the flow rate is increased in one or two steps to raise the flushing rate. When the evaporation ends, the flow rate can again be reduced. ADVANTAGE - This can reduce the carbon pick-up to one tenth. It also reduces the specific inert gas consumption and the specific heating gas consumption.