Abstract: In a method of controlling a blast furnace wherein iron ore is reduced to form pig iron and there being at least one reactor used for heating a reducing gas which reducing gas is introduced to at least one tuyere, the improvement being the steps of adjusting the composition and the temperture of the reducing gas in order to control at least one of the following: coke rate, productivity of the blast furnace, temperature and/or silicon content of the pig iron, and temperature of the top gas. Preferably, the reactor is a plasma torch and the temperature of the reducing gas is in the range of 1500.degree.-2800.degree. C. The coke rate is predetermined at a value of 50-350 kg/mt of pig iron and preferably at 80-200 kg/mt of pig iron produced.

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: A sensor unit comprising two pyrometers arranged in respective chambers disposed side-by-side and open at one end, one chamber being substantially totally reflecting and the other substantially totally absorbing. Periodically, the unit is advanced to the immediate proximity of the product, the signals from the pyrometers are received after the response time of the pyrometers has elapsed, and then the unit is withdrawn to its initial position. The signals from the pyrometers are processed so as to provide a signal representing the emissivity of the product.

Abstract: A metallurgical product, e.g. wire rod emerging from a hot rolling mill, is subjected to controlled cooling by immersing it in a bath, e.g. an aqueous bath, kept at a given temperature. During immersion, the bath is stirred, e.g. mechanically or by means of a fluid. In a controlled cooling installation a cover arranged above the bath has a condenser for recovering vapor from the bath.

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: A tuyere for injecting hot reducing gases into a furnace is provided with an inlet pipe and a plasma oven whose gas outlet axis is inclined to the longitudinal axis of the tuyere. The angles which the outlet axis of the plasma oven and the inlet pipe form with the said longitudinal axis are such that the longitudinal axis is parallel to the vector sum of the amount of movement of the gases from the plasma oven and the inlet pipe respectively .

Abstract: A wet welding electrode, for manual arc welding underwater, has a coating containing at least one oxidizing agent such as iron oxide, for neutralizing the embrittling effect of nascent hydrogen, and its core contains at least one constituent, e.g. aluminum oxide, aluminum and nitrogen, or copper, which results in the presence of hardening components in the weld deposit.

Abstract: Metal strip is passed around a cylinder immersed in a bath of molten metal. Selection of one-sided or two-sided coating is made by selecting the position at which the strip enters and leaves the bath relative to the position at which the strip comes into and out of contact with the cylinder, by selecting the level of the bath surface or by moving an auxiliary roll.

Abstract: The invention relates to a method of protecting devices designed for the galvanization of metal products, in particular for the galvanization of continuous drive cylinders used when galvanizing sheet on a single surface. A surface layer of the cylinders is coated with one or more oxide, one or more silicate, one or more zirconate, one or more mixed inorganic compound. Examples of the oxides include Mg, Ca, etc. Examples of the silicates include Al etc. Examples of the zirconates include Mg etc. Examples of the mixed inorganic compounds include serpentines, amphiboles, silicon carbide. The oxides are applied directly to the cylinder surface to be formed "in situ", for example, by heating in air to approximately 1000.degree. C.

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: During each period in which electrical power is supplied to the electrodes one determines whether the weld is subject to flash, by means of an accelerometer on one of the electrode supports. The frequency of occurrence of flash indicates the quality of the welding operation.

Abstract: In order to improve the surface characteristics of steel structure, it is oposed according to the invention to make at least one roll of a rolling-mill with a motif or pattern of motifs. The invention also includes apparatus for marking the roll which includes means for driving the roll marking device itself from the roll so that proper synchronization between the movements of the roll and marking device is achieved.

Abstract: A continuous beam from a laser is divided into two intermittent beams by a reflecting disc with peripheral holes, rotating about an axis skew to the continuous beam. At least one of the intermittent beams is transmitted to a marking head having a lens which focuses the beam onto the surface of a roll. The roll is rotated and the marking head is moved along the roll, in synchronism with the rotation of the disc, so that a regular hexagonal lattice of microcavities is cut by the focused intermittent beam. The second intermittent beam may be used to cut microcavities in the roll or in a second roll or for other purposes.

Abstract: A telemetric optical-radiation laser transmitter 5 outside an aperture 2 sends a beam to a point 14 scanned over the charge surface 1, via a rotating assembly 7 of deflectors, one deflector 11 oscillating with a periodicity related to the rotation of the assembly. A telemetric receiver 19, sensitive to the radiation from the transmitter 5 in a selected wavelength range, receives radiation re-transmitted from the point 14 through an aperture 3. A thermometric receiver 6 receives thermal radiation from the point 14 along a path coinciding with the path of the transmitted optical radiation.

Abstract: In a continuous heat-treatment process, cold-rolled steel strip having a thickness of 0.05 to 1 mm, e.g. for producing tin plate, is heated to 650.degree.-850.degree. C. and held in this temperature range for more than 1 s. The strip is then quenched for less than 12 seconds in an aqueous bath at above 75.degree. C., the strip emerging at below 550.degree. C. Temperatures, times, and subsequent steps such as overaging and final cooling are chosen depending on the hardness desired.

Abstract: The internal surface of a continuous casting nozzle, e.g. for casting steel, is coated with a finely divided material, comprising anti-wetting compounds such as ZrO.sub.2, Cr.sub.2 O.sub.3, and boron nitride, constituting a coating which inhibits the deposition of non-metallic inclusions tending to block the nozzle.

Abstract: A metal product, such as a steel strip or a mill roll, is cooled by spraying a coolant towards a surface of the product travelling along a given path, by means of cooling apparatus comprising two hollow caissons arranged one inside the other and rigidly connected together to constitute a unit. The caissons cool the strip contained within a tunnel. The method is applied to the product surface and extends across the path of the product surface. Each caisson has a plurality of holes in a wall which is to face the product surface, each hole of the outer caisson being paired with a coaxially aligned hole of the inner caisson. A coolant sprayer is fixed in each pair of holes. Preferably, the sprayers are supplied with air from the inner caisson and water from the outer caisson, the water being atomized by the air. The path containing the prouduct is enclosed within a tunnel wherein ends of the tunnel are enclosed by continuous curtains of water which contact the product and effectively seal the ends of the tunnel.

Abstract: Continuously cooling a rolled metal product emerging from the last stand of a rolling mill by spraying a liquid coolant through at least one outlet orifice of at least one hollow housing onto a rolled product vertically downwardly in the form of a compact jet of liquid which does not include any gaseous constituents and all the molecules of which are at the same speed in a given cross-section transverse to the direction of the jet.

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: A rolled steel product is given an elastic limit of 500 to 1200 MPa by selection of a particular steel composition and a particular heat treatment. The steel contains 0.10-0.50% C, 0.90-1.50% Mn, and 0.10-0.45% Si, and optionally 0.20-0.70% Ni, 0.10-0.80% Cr, and 0.02-0.10% V. The heat treatment consists of surface quenching from above the austenitization temperature by means of a fluid, the heat remaining in the product being sufficient to temper the martensite and/or bainite in the quenched surface.