Abstract: Industrially pure oxygen is blown into molten pig iron surmounted by a layer of slag in a converter by means of at least one tuyere located below the upper surface of the molten metal. Input and output parameters are monitored and input parameters are controlled in order to obtain steel of a desired quality (e.g. composition and/or temperature). The intensity of sound emitted by the converter (e.g. in the range of from 20 to 50 Hz) is measured while the oxygen is blown in. The instant at which the intensity undergoes a sudden and considerable decrease is detected. From that instant, only that amount of oxygen is blown in which is necessary and sufficient to provide the steel with the desired quality at the end of the refining operation.

Abstract: The surface temperature of a body is measured by receiving thermal radiation from a given zone of the surface of the body along a given optical path by means of a sighting instrument. At least that part of the optical path which is adjacent the instrument is protected by means of a shield. The given zone is subjected to a scraping operation.

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: A device for inspecting the interior of an enclosure comprises an instrument which receives radiation from the interior of the enclosure through an orifice at one end of the instrument. A screen located immediately in front of the instrument has an opening in register with the orifice. Compressed gas is passed between the instrument and the screen and escapes through the opening. The surface of the screen remote from the instrument is cleaned periodically or continuously, e.g. by scraping, at least around the opening.

Abstract: Volatile compounds are desorbed from an aqueous liquid containing ammonia, by means of a stripping column. The aqueous liquid is supplied to the upper part of the column and a gaseous mixture including free oxygen is blown into the lower part of the column. Sodium hydroxide and/or calcium hydroxide is supplied to an intermediate part of the column at a plurality of levels. A gaseous mixture including ammonia is withdrawn from the top of the column. The pH and the temperature of the aqueous liquid are measured at a plurality of levels in the column. The flow rate of the aqueous liquid and the flow rate and temperature of the gaseous mixture blown in and of the hydroxide are controlled so that the pH of the aqueous liquid, at least in a predetermined zone of the column, is at least 11.

Abstract: A method of measuring a dimension of a body, the method comprising: direcg a beam of optical rays towards each of two points on the surface of the body at opposite sides of the body; forming rays reflected from the said points into two distinct reflected beams; directing the reflected beams towards a common plane by means of an optical system which causes the two resulting images to follow two respective straight lines, during displacement, two rows of photodiodes being arranged along the two respective straight lines; subjecting both rows of photodiodes to continuous and synchronized electronic scanning; starting a time counter when the scanning of one row of photodiodes detects a photodiode illuminated by an image; and stopping the counter when the scanning of the other row of photodiodes detects a photodiode illuminated by the other image, the time interval registered by the counter being representative of the said dimension.

Abstract: The permeability of a mixture to be agglomerated is measured by means of at east one permeability-measuring device situated upstream of a mixer directly preceding a feed hopper feeding an agglomerating apparatus. Water is added to the mixture in the mixer. The measured permeability value is utilized to influence the quantity of water added in the mixer by means of an automatic feed-forward regulating loop so as to obtain a given permeability at the output of the mixer. The feed-forward loop may be combined with a feedback regulating loop.

Abstract: A metal strand is cast by a continuous casting machine. The strand passes through a series of secondary cooling zones. The rate at which coolant is supplied to each zone is varied by means of valves which are controlled in accordance with the casting speed so as to maintain a desired thermal profile for the temperature along the surface of the strand.

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.

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: Industrially pure oxygen is blown into molten pig iron in a converter by means of at least one tuyere located below the upper surface of the molten metal. A quantity (such as amplitude, frequency, acceleration, or speed) characterizing movement of the converter is measured continuously while the oxygen is blown in. An instant at which this quantity undergoes a sudden and considerable decrease is detected. From that instant onwards, the amount of oxygen necessary and sufficient to provide the steel with a desired quality is blown in. The required amount of oxygen is determined from an empirical relationship between the amount of oxygen blown in after the instant and either the phosphorus content of the steel or the iron content of the slag.

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.

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: A measuring or sampling probe is to be lowered to a desired depth in a molten metal. The probe is mounted on a probe carrier which can be lowered and raised. A contact detector, which emits a control signal when the detector comes into contact with the upper surface of the molten metal, is fixed on the probe carrier at a distance above the probe.

Abstract: A measuring or sampling probe is to be lowered to a desired depth in molten metal. The probe is mounted on a tiltable elongate probe-carrier which can be lowered and raised. The probe-carrier is telescopic, its length being adjustable between given limits.

Abstract: A liquid fuel or other liquid is supplied to a supply line which communicates with an injection conduit opening out into a receptacle such as a steelmaking converter. The supply line includes a non-return valve which allows the liquid to pass only when its pressure exceeds a given critical pressure. A gas is introduced into the supply line downstream of the non-return valve at a pressure which is hgher than the critical pressure and which is sufficient to prevent any material in the receptacle from penetrating into the injection conduit.

Abstract: A combustible bed of ore is formed on a sinter grate, which may form part of a sinter strand. Holes are pierced through the bed before ignition. Combustion-supporting gas is passed through the ignited bed to cause a combustion front to pass through the bed. The bed can be pierced by piercing members carried by a reciprocal frame on a carriage moving parallel to the sinter strand.

Abstract: The apparatus includes a machine for subjecting a test-piece of superplastic material to a tensile test using a mobile member entraining one end of the test-piece and exerting traction on the test-piece. The mobile member is subjected to successive displacements whose speed and duration are controlled. The force applied to the test-piece and its length are measured as a function of time.