The present disclosure relates to a workpiece cleaning device and a cleaning method. The workpiece cleaning device comprises: a frame (1); and a plurality of cleaning tanks disposed on the frame (1) side by side, comprising a molten salt cleaning tank (2) for cleaning a workpiece with molten salt, a first rinsing tank (5) for rinsing the workpiece cleaned with the molten salt, a de-rusting cleaning tank (6) for cleaning the workpiece rinsed in the first rinsing tank (5) with a de-rusting agent, a second rinsing tank (7) for rinsing the workpiece cleaned with the de-rusting agent, and an anti-rust cleaning tank (8) for cleaning the workpiece rinsed in the second rinsing tank (7) with anti-rust liquid, which are sequentially disposed from upstream to downstream in terms of procedure.

A pickling process of a metallic strip is provided including the steps of: passing said metallic strip through at least a pickling bath being at a temperature between 1 and 100° C., applying an alternating current, having a current density of 1x10.sup.2 to 1x10.sup.5 A.m.sup.−2 of unit surface of said metallic strip to said metallic strip passing through said at least one pickling bath.

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 roll 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 and estimator for estimating 8 the aqueous solution level, a calculator for calculating 9 for each ultrasound emitter 5 its distance to the aqueous solution level and a 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.

A steel sheet with excellent surface quality, and a manufacturing method therefor are provided. The present invention provides a pickled steel sheet with excellent surface quality, comprising, by wt %, carbon (C) in an amount greater than or equal to 0.05% and less than 0.4%, 0.5% or less of silicon (Si) (excluding 0%), 0.05% or less of phosphorus (P), 0.03% or less of sulfur (S), 0.01% or less of boron (B), 0.1-2.5% of manganese (Mn) and/or chromium (Cr), and the balance of iron (Fe) and inevitable impurities, wherein the average thickness of an internal oxide layer and/or a tantalum layer, which are formed on the surface layer of the steel sheet, is 1-10 μm, and the standard deviation of the thickness of the internal oxide layer and/or the tantalum layer in the length direction of the steel sheet is 2 μm or less.

Provided are a high-carbon steel sheet having good surface quality and a manufacturing method therefor. The present invention provides a high-carbon pickled steel sheet having good surface quality, the steel sheet containing, in weight %, 0.4% or more and less than 1.2% of carbon (C), 0.5% or less (excluding 0%) of silicon (Si), 0.05% or less of phosphorus (P), 0.03% or less of sulfur (S), 0.1 to 2.5% of at least one of manganese (Mn) and chromium (Cr), and the balance of iron (Fe) and inevitable impurities, wherein the average thickness of an internal oxide layer and/or a decarburized layer formed in a surface layer portion of the steel sheet is 1 to 10 μm and the standard deviation of the thickness of the internal oxide layer and/or the decarburized layer in the length direction of the steel sheet is 2 μm or less.

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.

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.

A pickling installation for applying a pickling treatment to a metal strip in continuous movement, the pickling treatment using an acid solution, the pickling installation including: a plurality of cascading treatment tanks among which at least one treatment tank includes a spray/injection section for spraying/injecting the acid solution on the metal strip; and collection means for retrieving the sprayed acid solution after use and redirecting the sprayed acid solution to each spray/injection section. The at least one treatment tank has a first header in front of a first face of the metal strip and a second header in front of a second face of the metal strip. In a first treatment tank configuration, each of the first header and the second header have an internal flat surface intended to be parallel respectively to first and second faces of metal strip, and at a distance thereof.