Method and apparatus for batch coil annealing metal strip

A batch coil annealing process for annealing cold rolled strip comprising the steps of:

• a) vertically stacking coils of rolled strip onto a base and covering said coils with an inner cover sealed to said base;
• b) heating said cover to, in turn, heat said coils to a preheat temperature of at least about 500.degree. F.;
• c) drawing a vacuum within said cover while said coils are being heated to vaporize oils and other hydrocarbon deposits within said cover and exhaust same from said cover;
• d) condensing said vaporized hydrocarbons into liquid outside said cover for collecting and removing same;
• and thereafter;
• e) backfilling said cover with a treatment gas composed substantially of hydrogen while said coils are heated to their annealing process transformation temperature, said vacuum within said cover decreasing to as little as standard atmosphere pressure or above when backfilled with said treatment gas;
• and
• f) periodically increasing the vacuum within said cover followed by periodic introduction of said treatment gas into said cover whereby the cycle time of said annealing process is reduced.