To prevent over-pickling of a steel strip during pickling pause, and shorten the time required to switch between pickling operation and pickling pause, 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 unit configured to circulate the acid solution between the pickling tank and the acid-solution storage tank; and a control device configured to control the acid-solution circulation device to maintain a liquid level of the acid solution in the pickling tank at a level below a traveling height of the steel strip.

A pickling apparatus includes a plurality of pickling tanks in which a scale of a steel plate is removed while the steel plate is advanced and sequentially dipped; an intermediate spraying unit, disposed between a pickling tank at the front end and a pickling tank at the rear end, for spraying a pickling solution onto the steel plate; and a pickling solution supply means configured to provide a pickling solution of a concentration used in the pickling tank at the rear end to the intermediate spraying unit, wherein a wringer roll disposed between the plurality of pickling tanks is removed.

Continuous annealing equipment (1) including a cleaning device (11, 12) for performing a cleaning treatment on a steel strip (S) and an annealing device (12) for performing an annealing treatment on the steel strip (S) comprises an exhaust gas passage (31, 41) through which an exhaust gas discharged from the annealing device (12) flows, a solution circulation passage (32, 51) through which a cleaning solution used in the cleaning device (11, 12) circulates, and a heat exchanger (53) which forms a part of the solution circulation passage (32, 51) and contacts with the exhaust gas.

The present invention is a washing assembly having at least one washing chamber at which at least one sheet metal passing through for producing copper-coated double-layer steel pipe. The washing assembly comprises at least one pair of wiper pair accommodated by the washing chamber.

A device and a method for depositing undissolved materials, in particular undissolved silicon compounds, from a pickling fluid in a pickling plant. A pickling circuit of the pickling plant has a pickling tank for pickling metal strips, a return line between the pickling tank and a circuit tank, a circulation pump for circulating a main volume flow of pickling fluid from the pickling tank, and a heating device arranged in a pressure line between the circuit tank and the pickling tank. The device includes a flocculation device for introducing at least one flocculant into the main volume flow, and a deposition device in the circuit tank and preferably designed as an inclined clarifying device, for the sedimentation of undissolved materials directly from the main volume flow. When pickling silicon-containing steel strips (electrical steel strips), an at least two-stage flocculation can be carried out using two or more mixing zone containers.

A pickling apparatus includes a plurality of pickling tanks in which a scale of a steel plate is removed while the steel plate is advanced and sequentially dipped; an intermediate spraying unit, disposed between a pickling tank at the front end and a pickling tank at the rear end, for spraying a pickling solution onto the steel plate; and a pickling solution supply means configured to provide a pickling solution of a concentration used in the pickling tank at the rear end to the intermediate spraying unit, wherein a wringer roll disposed between the plurality of pickling tanks is removed.

A pickling apparatus for pickling a strip of metal being conveyed is equipped with: a pickling tank for storing an acid solution; a surrounding part disposed in the pickling tank so as to surround the strip immersed in the acid solution in the pickling tank; and an oxidant supply part for supplying a liquid oxidant toward an inside of the surrounding part.

To prevent over-pickling of a steel strip during pickling pause, and shorten the time required to switch between pickling operation and pickling pause, 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 unit configured to circulate the acid solution between the pickling tank and the acid-solution storage tank; and a control device configured to control the acid-solution circulation device to maintain a liquid level of the acid solution in the pickling tank at a level below a traveling height of the steel strip.

A method for pickling a steel plate having a first steel plate portion and a second steel plate portion which is connected to a tail end of the first steel plate portion and which requires a longer time for pickling than the first steel plate portion when pickled under the same condition includes: a step of pickling the steel plate by immersing the steel plate in an acid solution in at least one pickling tank while conveying the steel plate; a step of circulating the acid solution, through a circulation line connected to any of the at least one pickling tank, between the pickling tank and an oxidizing device disposed in the circulation line; a step of oxidizing Fe.sup.2+ in the acid solution to Fe.sup.3+ by the oxidizing device using a gaseous oxidant; and a feeding start step of, upon switching from pickling of the first steel plate portion to pickling of the second steel plate portion, starting feeding of a liquid oxidant for oxidizing Fe.sup.2+ in the acid solution to Fe.sup.3+ to any of the at least one pickling tank or to the circulation line.

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.