Abstract: A top hat furnace especially adapted for annealing steel sheet metal using a protective gas includes a protective top surrounding the batches of sheet steel metal. A cooling top is arranged above the protective top forming an intermediate space. The cooling top has a cover and a lid. The cover of the cooling top has a plurality of air nozzles so that cooling air impacts the protective top in the form of jets. At least one fan produces a flow of cooling air in the intermediate space. The distance between the air nozzles increases from the bottom of the cover towards it upper end. The distance between the nozzles is from four to twelve times greater than is the diameter of each nozzle. The cooling lid is also provided with a plurality of air nozzles. The distance between the nozzles in the cooling lid is from four to seven times greater than is the diameter of each of these nozzles.

Abstract: Fresh gas is blown into the ring-shaped space between the annealing charge and the hood as an upwardly directed high-speed jet (9) at a velocity of approximately 80 m/s. The gas mixture which forms is evacuated through a gas outlet (10) arranged in the pedestal and diametrically opposite to the gas inlet. At a volume flow rate of about 130 m.sup.3 /s, rinsing takes about 6 minutes.