Abstract: An apparatus for manufacturing a molten zinc coated steel sheet includes a molten zinc coating device, a temper rolling mill, an acid solution contacting device, and a cleaning device connected in tandem, wherein the acid solution contacting device and the cleaning device are separated from each other with a region therebetween and an absolute humidity controller is disposed in the region between the acid solution contacting device and the cleaning device.

Abstract: Cleaning of a hot dip galvanized steel sheet is conducted by bringing a strip-shaped steel sheet which was treated by surface oxidation in advance into contact with a cleaning liquid for 1 second or more, and then bringing the hot dip galvanized steel sheet into contact with pure water, while continuously transferring the hot dip galvanized steel sheet. The method allows efficiently and fully washing off the acidic solution adhered to the surfaces of the hot dip galvanized steel sheet treated by surface oxidation. The invention also provides an apparatus for cleaning the hot dip galvanized steel sheet to carry out the above cleaning method.

Abstract: An apparatus for cleaning a hot dip galvanized steel sheet including: a cleaning liquid spray nozzle which sprays a cleaning liquid to both surfaces of a strip-shaped hot dip galvanized steel sheet which was treated by surface oxidation and which is continuously traveling; and a pure water spray nozzle which sprays pure water to both surfaces of the hot dip galvanized steel sheet a position where the hot dip galvanized steel sheet travels 1 second or more after being sprayed with the cleaning liquid.

Abstract: A method of controlling the concentration of P of cleaning solution waste water starts by providing a waste water buffer tank capable of either sending the waste water to a waste water treatment plant or storing the waste water after the waste water is accepted. The concentration of P in the cleaning solution is set within a target concentration range, and matter to be treated is treated. The concentration of P in the waste water is measured in the waste water buffer tank. When the measured value of the concentration of P is less than a selected upper limit, the waste water is sent from the waste water buffer tank to the waste water treatment plant. When the measured value of the concentration of P is higher than the selected upper limit, sending the waste water to the waste water treatment plant is stopped, and the waste water is stored in the waste water buffer tank. The concentration of P is reduced to a value within the target concentration range, and the matter to be treated is treated.

Abstract: Continuous annealing equipment contains: a heating zone, a soaking zone, and a rapid cooling zone, the rapid cooling zone having gas jet cooling equipment and is provided with at least one pair of seal rolls at each of an inlet and an outlet thereof and bridle roll units each composed of two or more bridle rolls in front of and behind itself; the bridle roll unit behind the rapid cooling zone having two or more heating rolls each having an induction heater thereinside; and the heating roll having a winding angle of 100° or more per heating roll and 380° or more in total of all the heating rolls.

Abstract: An apparatus for manufacturing a molten zinc coated steel sheet includes a molten zinc coating device, a temper rolling mill, an acid solution contacting device, and a cleaning device connected in tandem, wherein the acid solution contacting device and the cleaning device are separated from each other with a region therebetween and an absolute humidity controller is disposed in the region between the acid solution contacting device and the cleaning device.

Abstract: A method of controlling the concentration of P of cleaning solution waste water starts by providing a waste water buffer tank capable of either sending the waste water to a waste water treatment plant or storing the waste water after the waste water is accepted. The concentration of P in the cleaning solution is set within a target concentration range, and matter to be treated is treated. The concentration of P in the waste water is measured in the waste water buffer tank. When the measured value of the concentration of P is less than a selected upper limit, the waste water is sent from the waste water buffer tank to the waste water treatment plant. When the measured value of the concentration of P is higher than the selected upper limit, sending the waste water to the waste water treatment plant is stopped, and the waste water is stored in the waste water buffer tank. The concentration of P is reduced to a value within the target concentration range, and the matter to be treated is treated.

Abstract: Continuous annealing equipment contains: a heating zone, a soaking zone, and a rapid cooling zone, the rapid cooling zone having gas jet cooling equipment and is provided with at least one pair of seal rolls at each of an inlet and an outlet thereof and bridle roll units each composed of two or more bridle rolls in front of and behind itself; the bridle roll unit behind the rapid cooling zone having two or more heating rolls each having an induction heater thereinside; and the heating roll having a winding angle of 100° or more per heating roll and 380° or more in total of all the heating rolls.

Abstract: Cleaning of a hot dip galvanized steel sheet is conducted by bringing a strip-shaped steel sheet which was treated by surface oxidation in advance into contact with a cleaning liquid for 1 second or more, and then bringing the hot dip galvanized steel sheet into contact with pure water, while continuously transferring the hot dip galvanized steel sheet. The method allows efficiently and fully washing off the acidic solution adhered to the surfaces of the hot dip galvanized steel sheet treated by surface oxidation. The invention also provides an apparatus for cleaning the hot dip galvanized steel sheet to carry out the above cleaning method.

Abstract: A roll that can be disposed before and/or after a quenching zone of a continuous annealing furnace is provided. The roll has a predetermined profile satisfying Lc≧0.7×Wmin; R=−0.1×10−3 to +0.2×10−3; and TR≧20, wherein Lc represents the length (mm) of a flat portion in the center of the roll, Wmin represents the minimum width (mm) of a steel strip, R represents the inclination of tapered portions disposed at two sides of the roll, and TR represents the radius of curvature (m) of boundaries between the flat portion and the tapered portions. The roll can be used as a hearth roll and/or a bridle roll disposed at the entry side and/or the exit side of the quenching zone.

Abstract: A molten metal is deposited on the surfaces of a metal strip by continuously dipping the metal strip in a coating bath. The metal strip is lifted at a constant speed while supported with a pair of upper and lower support rolls in the coating bath. The coating weights of the molten metal deposited on the surfaces of the metal strip are adjusted by wiping the molten metal with gases from gas wiping nozzles disposed above the surface of the coating bath.