A continuous annealing apparatus includes: a pre-treatment device to prepare a strip unwound from a coil; a heating device to heat the strip prepared by the pre-treatment device; a heat holding device to isothermally maintain the strip heated by the heating device; a first cooling device to cool the strip heat-maintained by the heat holding device; an annealing device including a first annealing device for annealing the strip, which, is cooled by the first cooling device, for a first time, and a second annealing device for winding the strip, which is cooled by the first cooling device, into a coil and then unwinding the coil into the strip again after annealing for a second time; a second cooling device to cool the strip annealed by the first annealing device or the second annealing device; and a post-treatment device to wind the strip cooled by the second cooling device into the coil.

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.

Cooling equipment comprising: a plurality of injection units in a continuous annealing furnace including heating zone, soaking zone, and cooling zone through which strip-shaped steel sheet is sequentially fed, the injection units arranged in cooling zone in row along feed direction of steel sheet and injecting, from injection nozzles, cooling gas containing hydrogen, onto steel sheet; and hydrogen concentration adjustment unit adjusts hydrogen concentration of cooling gas such that hydrogen concentration distribution is formed in which, in a space of the cooling zone where plurality of injection units are disposed, hydrogen concentration at upstream region is higher than hydrogen concentration at downstream region; plurality of injection nozzles arranged along feed direction of steel sheet, and each of injection nozzles extending toward steel sheet; and injection nozzles positioned at both sides in array direction inclined to slope toward a center of the array direction on progression toward tips of injection nozzles.

The present invention relates to a high-strength wire rod superior in impact toughness and a manufacturing method therefor and, more particularly, to a high-strength wire rod having superior impact toughness, which can be preferably used as a material for industrial machines or automobiles exposed to various external load environments, and a manufacturing method therefor.

A cooling apparatus includes: a first air nozzle configured to spray air to the metal strip from above; a first water nozzle configured to spray water to the metal strip from above; and a gas discharging part configured to discharge an air around the metal strip upwardly, wherein the first air nozzle, the first water nozzle and the gas discharging part are aligned along a transport direction of the metal strip in the order of the first air nozzle, the first water nozzle and the gas discharging part, wherein the cooling apparatus is adapted to collide the air from the first air nozzle against the metal strip and then the air moves along a surface of the metal strip to a point at which steam is generated by the water from the first water nozzle, and is adapted to discharge the steam using the gas discharging part.

A method for manufacturing a thermally treated steel sheet is described. The method includes: A. a preparation step including: 1) a selection substep, wherein the chemical composition and m.sub.target are compared to a list of predefined products, which microstructure includes predefined phases and predefined proportion of phases, and selecting a product having a microstructure m.sub.standard closest to m.sub.target and a predefined thermal path TP.sub.standard to obtain m.sub.standard, 2) a calculation substep, wherein at least two thermal path TP.sub.x, each TP.sub.x corresponding to a microstructure mx obtained at the end of TP.sub.x, are calculated based on the selected product of step A.1) and TP.sub.standard and the initial microstructure mi of the steel sheet to reach m.sub.target, 3) an selection substep, wherein one thermal path TP.sub.target to reach m.sub.target is selected, TP.sub.target chosen from TP.sub.x and selected such that m.sub.x is the closest to m.sub.target, B. a thermal treatment step, wherein TP.sub.target is performed on the steel sheet.

Systems and methods of quenching a metal substrate include cooling a top surface and a bottom surface of the metal substrate until a strip temperature is cooled to an intermediate temperature. Cooling of the top surface of the metal substrate is discontinued when the strip temperature reaches the intermediate temperature, and cooling of the bottom surface of the metal substrate continues until the metal substrate reaches a target temperature, where the target temperature is less than the intermediate temperature.

A continuous annealer for wire is disclosed, and specifically for annealing and recrystallizing a wire in a continuous process. The continuous annealer for wire comprises: two contact discs for contacting a first wire portion extending therebetween; an annealing zone situated between the two contact discs; and annealing means for annealing the first wire portion in the annealing zone, as a result of which a first partial recrystallisation process in the first wire portion takes place in the annealing zone. A recrystallisation zone is situated downstream of the second contact disc, wherein, downstream of the annealing zone, the first wire portion passes through the recrystallisation zone as the second wire portion, and a second partial recrystallisation process takes place in the second wire portion. The wire has the opportunity to recrystallize further after leaving the annealing zone without further heating. By extending the recrystallisation time, the recrystallisation temperature can be reduced accordingly. As a result, the same degree of recrystallisation can be achieved overall with a significantly lower input of energy than when the wire is cooled immediately after leaving the annealing zone.

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 ?m to 20 ?m 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 ?m 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 method for cooling a steel strip, comprising jetting mist to a steel strip passing through a cooling installation such that an amount of mist jetted to the steel strip is smaller in an edge portion in a width direction of the steel strip than in a center portion, sucking at least part of mist jetted to the steel strip, and cooling the steel strip at a sheet-passing speed such that, during a period between start and end of cooling, a temperature of the steel strip is within a film boiling temperature range and a temperature of the edge portion in the width direction of the steel strip is equal to or higher than a temperature of the center portion in at least a range of or more from the upstream side in the sheet-passing direction of a total cooling length of the cooling installation.