Abstract: At the outlet of the finishing stand of a rolling mill, a cooling apparatus is arranged to surface quench only the outer layer of the flat face of a steel section by a cooling fluid. The cooling conditions are adjusted so that, at the outlet of the cooling zone, the unquenched parts of the section are at a temperature still sufficiently high to temper the quenched face, and so that the austenite is transformed into ferrite and carbides in the unquenched parts of the section.

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 After the strip has been withdrawn from the bath, oxide is eliminated from at least part of the surface of the strip, e.g., from one or both faces, by removal of the oxide or by reduction of the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: Cooling apparatus for cooling metal sections comprises a series of sprayers for simultaneously spraying a mixture of liquid and gas. Each sprayer has a gas inlet at one end and a mixture outlet at the other end. One or more liquid inlets are provided between two distinct peripheral shoulders. An elongate gas-supply manifold has outlet orifices adapted to seat the gas-inlet-side shoulders of the respective sprayers in a gas-tight manner. An elongate liquid-supply manifold has outlet orifices adapted to seat the mixture-outlet-side shoulders of the respective sprayers in a liquid-tight manner.

Abstract: Steel wire rod leaving the last stand of a rolling mill is quenched to between 850.degree. C and a temperature corresponding to the nose of the curve representing the start of the transformation of austenite to ferrite-pearlite plotted with respect to time and temperature. The wire rod is then subjected to a second cooling while in the form of loose turns passing along a given path. The variation of the temperature of the wire rod along this path is observed, and the position is detected at which a temperature increase occurs owing to recalescence. At this position the wire rod is subjected to supplementary cooling.

Abstract: In the rolling mill the temperature of the product is reduced to between Ac.sub.3 and Ac.sub.3 + 150.degree. C before it enters the finishing stands. The product emerging from the finishing stands is quenched to provide a surface layer of martensite and/or bainite. Subsequently the heat of the core of the product is allowed to raise the temperature of the surface layer to between 450.degree. and 750.degree. C, so that the quenched layer is tempered.

Abstract: Steel rod or bar at the exit of the finishing stand of a hot rolling mill is superficially quenched, so that the surface layer of the rod or bar is given a bainitic or martensitic structure. Immediately after quenching, the core of the rod or bar is at about 850.degree. C and, therefore, still austenitic. Subsequent air cooling allows the austenite to transform to ferrite and carbides, while the surface layer is tempered by the heat transferred to it from the core.