PURPOSE: To execute bright annealing with excellent surface brightness under safe workability by adjusting the leak rate of the in-furnace atmosphere gases from the sealing parts at the steel strip inlet and outlet of a bright annealing furnace for stainless steel strips to prevent the infiltration of the air from the inlet sealing part into the furnace.
CONSTITUTION: The stainless steel strip 1 is admitted from the inlet sealing part 3 into the bright annealing furnace 2 of a vertical type and gaseous Ar consisting of 75% H 2 and 25% N 2 is supplied from a feed port 19 into the furnace. This steel strip is subjected to bright annealing by heating in the reducing atmosphere of a heating zone 5 and is continuously taken out of the outlet sealing part 7. Revolving rolls 11 coated with elastic bodies 11a, such as silicone rubber, are mounted to the inlet 3 and outlet 7 of the stainless steel strip 1 and are revolved in follow up to the passage of the steel strip 1 while the front and rear surfaces of the steel strip 1 are lightly pressed by heat applying means. The gaseous Ax is injected little by little from the feed port 19 into the furnace at all times to maintain the in-furnace pressure higher than the outdoor air pressure to prevent the infiltration of the outdoor air together with the steel sheet from the inlet sealing part 3 into the furnace. The bright annealed stainless steel sheet having the excellent surface brightness is thus produced without generating an explosion by mixing with the gaseous Ax.