Production facility and production process for hot dip galvannealed steel plate

A production facility of hot dip galvannealed steel plate dipping steel plate in a plating bath, then alloying it, said production facility of hot dip galvannealed steel plate comprising:

• a rapid heating furnace set above a plating bath tank, and
• a soaking/cooling furnace set above said rapid heating furnace and being comprised of a soaking region and a cooling region,
• said soaking/cooling furnace comprising a pair of hot-air heat sources at the entry side of the soaking/cooling furnace, pairs of exhaust devices and pairs of spray nozzles for spraying cooling gas,
• said pair of hot-air heat sources, said pairs of exhaust devices and said pairs of spray nozzles being provided along a vertical or line direction arranged facing two surfaces of the steel plate as it is running,
• wherein said pairs of exhaust devices and said pairs of spray nozzles are alternately arranged at predetermined intervals along the line direction through said soaking/cooling furnace, and said pair of hot-air heat sources, said pairs of exhaust devices and said pairs of spray nozzles are configured to be independently controlled in operation for each facing pair,
• said pairs of exhaust devices can be individually opened or closed to switch between an exhaust state and a closed state,
• a ratio of lengths of the two regions in the furnace being freely settable,
• a layout of said soaking region and cooling region being freely settable, and
• having an air curtain in said soaking/cooling furnace wherein said spray nozzles are configured with ejection ports able to rotate about an axis parallel to a width direction of the steel plate and said spray nozzles at the boundary of said soaking region and said cooling region can spray cooling gas vertical to the steel plate and form a barrier to the flow of gas.