Disclosed is a continuous thermal treatment line for a steel strip. The strip passes through consecutive thermal treatment chambers, is quickly cooled in at least one of the chambers by spraying liquid onto the strip, or by spraying a fluid made up of gas and liquid or spraying a combination of gas and liquid forming a mist. After quick cooling, a protective metal layer is deposited on the strip by dip coating. The cooling fluid strips iron oxides or other alloy elements contained in the steel to be treated, minimizing oxidation and reducing the oxides on the strip. Spray pressure and distance are chosen to facilitate the stripping property and the mechanical action of the sprayed fluid, reducing the layer of oxides on the strip. The temperature of the strip at the end of the cooling step is the temperature necessary for carrying out the desired treatment cycle.

Energy-efficient production of a ferritic hot-rolled strip (6) in an integrated casting-rolling plant (1), which modifies the known processes for producing a ferritic hot-rolled strip (6) in an integrated casting-rolling plant (1) so that the ferritic hot-rolled strip (6) can be produced significantly more energy-efficiently but nevertheless has good metallurgical properties and a good surface quality.

A plant for cleaning rolled metal strips provided with a superficial layer of oxide, the plant comprising unwinding means for unwinding at least one coil of rolled strip and pickling means for pickling said rolled strip; wherein there are provided measuring means for measuring the thickness of the superficial layer of oxide, arranged between said unwinding means and said pickling means. A relating cleaning method is also claimed.

An acid solution preparation device is an acid solution preparation device for preparing an acid solution used for pickling of a steel plate, the device including a sealed tank for storing the acid solution, a gas supply part for supplying an oxygen-containing gas from outside of the sealed tank to the sealed tank, and a purge part for discharging a gas in the sealed tank to the outside.

A continuous cleaning installation 1 of a passing strip S includes a tank 2, an aqueous solution 3 inside the tank 2. It also includes at least a roller 4 immerged in the aqueous solution 3, at least an ultrasound emitter-5, a feed for feeding 6 an aqueous solution and emptying 7 the tank. Moreover, it also includes an aqueous solution level estimator for estimating 8 the aqueous solution level, a distance calculator for calculating 9 for each ultrasound emitter 5 its distance to the aqueous solution level and a power controller for controlling the power 10 of the at least one ultrasound emitter 5 and at least an impermeable closable opening 11 on at least a lateral side of the tank through which the at least one ultrasound emitter 5 can pass.

There is provided a liquid removal device that removes liquid attached to a surface of a steel sheet, the device including a slit nozzle that jets gas to the surface of the sheet, the slit nozzle being installed so as to jet gas from a downstream side toward an upstream side in a movement direction of the sheet that moves relatively to the slit nozzle and being configured in a manner that a jet angle θ, a back face inclination angle β, and a back face length L of a nozzle back face of the slit nozzle satisfy, β+θ≥60° and L≥20mm, and a gap h between a jetting port of the slit nozzle and the sheet, a slit width d, and nozzle pressure P.sub.n of the slit nozzle satisfy the following relationship: P.sub.n≥2.0×10.sup.10(h/d).sup.0.6{1/(1+exp(β+θ−58)+1}.sup.−4L.sup.−7.

A 780 MPa-grade ultra-high reaming steel having high surface quality and high performance stability, and a manufacturing method therefor. The ultra-high reaming steel comprises the following components in percentage by weight: 0.03-0.08% of C, Si≤0.2%, 0.5-2.0% of Mn, P≤0.02%, S≤0.003%, 0.01-0.08% of Al, N≤0.004%, 0.05-0.20% of Ti, 0.1-0.5% of Mo, Mg≤0.005%, O≤0.0030%, and the remainder being Fe and other inevitable impurities. The ultra-high reaming steel of the present invention achieves matching between good structure homogeneity and performance homogeneity and excellent strength, plasticity, and ultra-high reaming rate; the ultra-high reaming steel has yield strength greater than or equal to 750 MPa, tensile strength greater than or equal to 780 MPa, an elongation A50 greater than or equal to 15%, and a reaming rate greater than or equal to 70%; moreover, appearance of red iron scales on the surface of a steel plate can be avoided, thereby improving the surface quality of pickled high-strength steel; the ultra-high reaming steel can satisfy user requirements well, and can be applied to parts of passenger vehicle chassis components such as a control arm and an auxiliary frame, which require high strength and thinning.

A 980 MPa-grade full-bainite ultra-high hole expansion steel and a manufacturing method therefor. The hole expansion steel has the following chemical compositions in percentage by weight: 0.05-0.10% of C, Si≤2.0%, 1.0-2.0% of Mn, P≤0.02%, S≤0.003%, 0.02-0.08% of Al, N≤0.004%, 0.1-0.5% of Mo, 0.01-0.05% of Ti, O≤0.0030%, the remainder being Fe, and other inevitable impurities. The ultra-high hole expansion steel in the present invention has yield strength ≥800 MPa, tensile strength ≥980 MPa, and a hole expansion rate up to 60% or more, and can be applied in the parts of chassis components such as a control arm and an auxiliary frame, which require high strength thinning and complex forming, of passenger vehicles.

Process and device for cooling a steel strip (1) running through the cooling section (2) of a continuous line, whereby cooling is achieved by projecting the strip with an aqueous solution of formic acid with a concentration of formic acid between 0.1% and 6%, and preferably between 0.5% and 2%.

To prevent over-pickling during pickling pause, shorten the time required to switch between pickling operation and pickling pause, and heat acid solution efficiently, a pickling device includes: a pickling tank for storing acid solution and for pickling a steel strip by allowing the steel strip to travel therethrough while the steel strip is immersed in the acid solution; a heat exchanger for heating the acid solution in the pickling tank; a circulation tank for storing the acid solution, provided separately from the pickling tank; an acid-solution circulation device configured to circulate the acid solution between the pickling tank and the circulation tank; a control device configured to withdraw the steel strip from the acid solution; and a guide plate disposed in the pickling tank and configured to guide the acid solution circulated in the pickling tank by the acid-solution circulation device to the heat exchanger.