Abstract: A device for exchanging heat with a flat product moving in front of the device that includes a device for placing at least one plenum chamber under gaseous pressure, the plenum chamber having on a front face several blades forming a duct for the ejection of the gas towards a surface of the flat product, the blades being superimposed upon one another in the direction of movement of the flat product and constituting an outlet orifice for the gas extending in the direction of the width of the flat product. The plenum chamber has a width in the direction of the width of the flat product sufficient to allow the evacuation of the gas on both sides of the plenum chamber.

Abstract: The continuous steel-sheet heat-treatment plant comprises, in sequence, a zone in which the sheet is heated to a temperature above the recrystallization temperature, a zone in which the sheet is held at this temperature for more than 30 seconds, a rapid cooling zone, an optional overaging zone, and a final cooling zone. The rapid cooling zone has devices for spraying a cooling fluid and a tank containing an aqueous bath at above 75.degree. C.

Abstract: Steel sheet is subjected to a thermal treatment as a result of which an oxide layer is formed. The sheet is pickled by contact with an organic acid solution (formic acid), containing at least 50 mg/l of iron, at a pH of 1.5 to 4 and at a temperature above a minimum value T.sub.m given by T.sub.m =20+(pH-1.5)32.

Abstract: Metal sheet (cold-rolled steel sheet) contaminated with rolling oil is heated at a temperature higher than its recrystallization temperature in a naked flame furnace, e.g. of the incomplete combustion type. The heated sheet is then rapidly cooled by contact with an aqueous medium. The resulting sheet has considerably improved suitability for phosphate coating and painting, compared with sheet which is annealed after alkaline degreasing. The sheet is preferably treated with formic acid.

Abstract: Steel strip is dipped in a molten metal bath (e.g. Al-Zn) maintained at above 500.degree. C., cooled to solidify the metal coating, and then cooled to below 475.degree. C. by an intense and rapid cooling operation which does not impair the flatness of the strip, e.g. immersion in a hot aqueous bath or spraying a mist. Before hot-dipping, the steel strip is preferably recrystallisation annealed and cooled to a temperature not lower than that of the molten metal bath.

Abstract: Metal strip, particularly steel strip, is heated to above 250.degree. C. and quenched in a phosphating bath, at 80.degree. C. or more, containing one or more phosphates of the type Me (H.sub.2 PO.sub.4).sub.n, where Me=Zn, Ni, Mn, or an alkali metal, at a concentration of 1 to 20 g/l.

Abstract: Steel strip is first heated to a predetermined temperature suitable for imparting desired properties to the strip and is then immersed in an aqueous bath maintained at substantially its boiling temperature. The composition of the aqueous bath is preferably adjusted to ensure the formation of an oxide film on the entire surface of the strip. After the strip has been withdrawn from the bath, oxide is eliminated from at least part of the surface of the strip, e.g., from one or both faces, by removal of the oxide or by reduction of the oxide. Simultaneously or subsequently, the strip is heated to a given temperature, e.g., 420.degree.-550.degree. C., maintained at this temperature, and immersed at this temperature in molten zinc.

Abstract: Cold-rolled steel strip is heated to a temperature higher than its recrystallization temperature, preferably faster than 4.degree. C/s. The strip is then held for more than 30 seconds. The strip is then cooled by immersion in an aqueous bath maintained at substantially its boiling temperature within a temperature range of 80.degree.-150.degree. C.