Vertical continuous annealing furnace and its operating method

A vertical continuous annealing furnace has two furnace covers vertically spaced away from each other. Each furnace cover is laterally slidable with respect to the furnace proper and has two long narrow openings through which strip is passed. There is a relatively small pre-chamber between the first furnace cover above and the second furnace cover below. The space below the second furnace cover constitutes a heating chamber. A partition extends from the undersurface of the second furnace cover to near the bottom of the furnace, dividing the heating chamber into a heating zone and a soaking zone. In charging and discharging the strip, the two furnace covers are alternately opened and closed, thereby keeping the heating chamber out of exposure to the outside air.