Rapid cooling section of a continuous metal strip treatment line, where the strip is cooled with a spray of liquid or a mixture of gas and liquid using nozzles located on each side of the strip. Along the direction of movement of the strip, it includes at least one row of flat spray nozzles across the strip followed by at least one row of cone spray nozzles across the strip.

A gas blower device for blowing gas onto a surface of a traveling strip includes a plenum in the form of a hollow box for containing gas and comprising two side surfaces, a back surface and a front surface opposite to the back surface. The front surface having a profile of convex type symmetry with respect to a mid-plane perpendicular to the plane of the strip, so that a middle ridge of the front surface is located at the smallest distance from the plane of the strip. The front surface further presenting multiple tubular nozzles protruding at the front surface and having a gas outlet orifice facing in use the traveling strip. All the outlet orifices are essentially in a plane parallel to the strip plane. The gas blower device further includes a gas intake tube for feeding the plenum with gas.

The invention relates to a method for removing residues present on a metal strip at the outlet of a cooling stage of a continuous line, the residues being formed during a cooling of said metal strip by a non-oxidizing liquid solution for the metal strip and a stripping liquid solution for the oxides present on the surface of the strip, or by a mixture of this liquid solution and a gas. The method according to the invention is characterized in that it comprises a step of reducing the residues by hydrogen.

Provided is a cooling device, where a hot-finish-rolling mill includes a plurality of nozzles which spray cooling water toward one of or both of upper and lower surfaces of a hot-rolled steel sheet just after rolled by rolling stands, the nozzles are provided on the inside of the upper and lower guides or adjoining to the guides on a downstream side, and a nozzle spray distance changes depending on a position of the nozzle in a rolling direction, wherein a spray angle of the nozzle at a position whose nozzle spray distance is the largest is smaller than a spray angle of the nozzle at a position whose nozzle spray distance is the smallest, and the spray angle of the nozzle becomes the same or smaller as the nozzle spray distance becomes large.

A gas blower device for blowing gas onto a surface of a traveling strip includes a plenum in the form of a hollow box for containing gas and comprising two side surfaces, a back surface and a front surface opposite to the back surface. The front surface having a profile of convex type symmetry with respect to a mid-plane perpendicular to the plane of the strip, so that a middle ridge of the front surface is located at the smallest distance from the plane of the strip. The front surface further presenting multiple tubular nozzles protruding at the front surface and having a gas outlet orifice facing in use the traveling strip. All the outlet orifices are essentially in a plane parallel to the strip plane. The gas blower device further includes a gas intake tube for feeding the plenum with gas.

A continuous induction heat treating apparatus is provided including a conveyor path defining an axis for a workpiece to be conveyed through the apparatus. The apparatus includes an induction heating station positioned along the conveyor path and operable to induce heating in the workpiece as the workpiece is conveyed through the induction heating station. A quenching station is positioned in a downstream direction from the induction heating station. The quenching station is coupled to a water supply and includes a plurality of sprayers in fluid communication with the water supply and operable to spray water toward the axis for quenching the workpiece as the workpiece is conveyed through the quenching station. The apparatus further includes a quench adjustment mechanism including an actuator coupled to at least a first one of the plurality of sprayers for re-positioning a point of intersection defined between the first sprayer and the axis.

A high-strength galvanized steel sheet includes a steel sheet having a steel composition having a specific component composition, a steel structure containing martensite and bainite at more than or equal to 70% (including 100%), ferrite at less than 20% (including 0%), and retained austenite at less than 5% (including 0%) in terms of area ratio, the amount of diffusible hydrogen in steel being less than or equal to 0.20 mass ppm; and a galvanizing layer provided on a surface of the steel sheet, having a content amount of Fe of 8 to 15% in mass %, and having an coating weight per one surface of 20 to 120 g/m.sup.2, wherein the amount of Mn oxides contained in the galvanizing layer is less than or equal to 0.050 g/m.sup.2, and a tensile strength is more than or equal to 1100 MPa and a yield ratio is more than or equal to 0.85.

A cooling device for a metal plate includes a plurality of first nozzles and a plurality of second nozzles disposed on both sides of the metal plate, respectively, in a thickness direction of the metal plate across a pass line of the metal plate. The plurality of first nozzles form a staggered array in which a pitch in a width direction of the metal plate is Xn, a pitch in a longitudinal direction of the metal plate is Yn, and an offset amount in the width direction of a pair of first nozzles disposed adjacent to each other in the longitudinal direction is ΔXn. The plurality of second nozzles form a staggered array in which a pitch in the width direction is Xn, a pitch in the longitudinal direction is Yn, and an offset amount in the width direction of a pair of second nozzles disposed adjacent to each other in the longitudinal direction is ΔXn. The staggered array of the first nozzles and the staggered array of the second nozzles are disposed offset from each other such that, a center of the second nozzle is at a position offset by a shift amount S from a center of the first nozzle in the width direction, and the center of the second nozzle is positioned in a region defined by an oval having a semi-axis of ΔXn/4 in the width direction and a semi-axis of Yn/3 in the longitudinal direction. The shift amount S is expressed by S=m×ΔXn/2, where m is an odd number such that S is closest to Xn/2.

A thin steel sheet has a steel structure which has a ferrite area fraction of 30% or less, a bainite area fraction of 5% or less, a martensite and tempered martensite area fraction of 70% or more, and a retained austenite area fraction of 2.0% or less and in which the ratio of the dislocation density in the range of 0 μm to 20 μm from a surface of the steel sheet to the dislocation density of a through-thickness central portion of the steel sheet is 90% to 110% and the average of the top 10% of the sizes of cementite grains located in a depth of up to 100 μm from a surface of the steel sheet is 300 nm or less. The maximum camber of the steel sheet sheared to a length of 1 m in a longitudinal direction of the steel sheet is 15 mm or less.

A cooling apparatus according to an embodiment of the present invention may comprise: a chamber member to which a cooling fluid is supplied from the outside; a discharge member, provided in the chamber member, for discharging the cooling fluid inside the chamber unit; and a resistance member, provided in an inlet portion of the chamber member, for inhibiting an initial flow of the cooling fluid supplied into the chamber member.