Abstract: Part of an atmosphere gas in a heating zone and/or a soaking zone is sucked out and is cooled through a high-temperature gas passage of a heat exchanger by heat exchange with a gas in a low-temperature gas passage, then cooled through a gas cooler, then dehumidified to a dew point of ?45° C. or less in a dryer, then heated through the low-temperature gas passage of the heat exchanger by heat exchange with a gas in the high-temperature gas passage, and returned to the heating zone and/or the soaking zone. Part of gas flowing from the dryer toward the low-temperature gas passage of the heat exchanger is returned to a cooling zone. These can achieve a low dew point of ?45° C. or less with high energy efficiency.

Abstract: An annealing and manufacturing method of hot-dip galvanized steel strips includes suppression of oxide formation of elements in the steel strips. An annealing furnace includes a heating zone, a soaking zone, and a cooling zone in which a portion of gas is introduced to decrease the gas dew point. A gas suction rate Qo1 in a portion of the cooling zone, a gas suction rate Qo2 in an upper portion and a gas feed rate Qi2 in a lower portion of the soaking zone, a gas feed rate Qi1 in a connection part between the soaking and cooling zones, an atmosphere gas supply rate Qf1 into the cooling zone and its subsequent zone, an atmosphere gas supply rate Qf2 into the soaking zone, an internal volume Vs of the soaking zone, and an average furnace temperature Ts of the soaking zone satisfy relationships including 0.3×Qf1<Qo1.

Abstract: Part of an ambient gas in a heating zone and/or a soaking zone is sucked out and is cooled through a high-temperature gas passage of a heat exchanger by heat exchange with a gas in a low-temperature gas passage, further cooled by mixing with part of an ambient gas in a cooling zone, further cooled through a gas cooler, dehumidified to a dew point of ?45° C. or less in a dryer, heated through the low-temperature gas passage of the heat exchanger by heat exchange with a gas in the high-temperature gas passage, and returned to the heating zone and/or the soaking zone.

Abstract: Part of an atmosphere gas in a heating zone and/or a soaking zone is sucked out and is cooled through a high-temperature gas passage of a heat exchanger by heat exchange with a gas in a low-temperature gas passage, then cooled through a gas cooler, then dehumidified to a dew point of ?45° C. or less in a dryer, then heated through the low-temperature gas passage of the heat exchanger by heat exchange with a gas in the high-temperature gas passage, and returned to the heating zone and/or the soaking zone. Part of gas flowing from the dryer toward the low-temperature gas passage of the heat exchanger is returned to a cooling zone. These can achieve a low dew point of ?45° C. or less with high energy efficiency.

Abstract: An annealing and manufacturing method of hot-dip galvanized steel strips includes suppression of oxide formation of elements in the steel strips. An annealing furnace includes a heating zone, a soaking zone, and a cooling zone in which a portion of gas is introduced to decrease the gas dew point. A gas suction rate Qo1 in a portion of the cooling zone, a gas suction rate Qo2 in an upper portion and a gas feed rate Qi2 in a lower portion of the soaking zone, a gas feed rate Qi1 in a connection part between the soaking and cooling zones, an atmosphere gas supply rate Qf1 into the cooling zone and its subsequent zone, an atmosphere gas supply rate Qf2 into the soaking zone, an internal volume Vs of the soaking zone, and an average furnace temperature Ts of the soaking zone satisfy relationships including 0.3×Qf1<Qo1.

Abstract: A flaw detecting method and apparatus for continuously testing a strip that is continuously carried through a liquid includes features for reducing air bubble generation in a liquid. The apparatus includes a liquid, carrying rolls for passage of the strip through the liquid, and ultrasonic testing probes arranged in the liquid for testing the strip. A carrying roll in contact with the liquid is fully immersed. Air bubble generation is inhibited to improve the testing reliability by at least one of (a) shielding the liquid dropping from the portion of the strip leaving the liquid, (b) reducing the dropping force of the liquid onto the liquid surface by inclining the strip, (c) installing the fully immersed carrying roll at a depth of at least 5 mm in the liquid, and (d) using a carrying speed of less than about 200 m/min. Upon manufacturing steel strips, testing is carried out in the stage of hot-rolled steel sheet, or, preferably, in pickling equipment.