Abstract: Cold-rolled steel sheet or strip (e.g. containing max. 0.15% C., max. 0.60% Mn, max. 0.020% Si, and 0.001-0.050% B) is heated to a temperature higher than its recrystallization temperature and then cooled by immersion in an aqueous bath at above 75.degree. C.The cooling by immersion consists of two successive stages, in the first of which cooling occurs at a rate of 25.degree.-180.degree. C./s to 200.degree.-425.degree. C., the product of the cooling rate v in .degree. C./s times the sheet or strip thickness e in mm being greater than 25, and in the second of which v is 90.degree.-500.degree. C./s and v times e is at least 35. Optionally a further annealing or overageing step comprises holding at 275.degree.-525.degree. C. for 30-250 s.

Abstract: A steel section 6 to 40 mm thick, emerging from a hot rolling mill at 1000.degree. to 800.degree. C. is surface quenched for 2 to 6 seconds at a cooling rate of the order of 1.5 to 5 MW/m.sup.2. During subsequent self-tempering of the quenched surface by heat from the remainder, the section tends to an equalization temperature of 500.degree. to 700.degree. C.

Abstract: The profile of a surface of an object is determined by scanning the line of intersection of this surface and a given plane transverse to the object. A radiation transmitter provides a transmitting beam, and a radiation receiver provides a receiving beam. Deflection means causes scanning movement of one or both of the beams so that a zone of intersection of the beams scans along a predetermined line and a detector in the receiver receives radiation transmitted from a source in the transmitter and reflected by the surface of the object. The deviation of the actual line of intersection from the predetermined line is determined from data supplied by the detector at a plurality of positions along the line of intersection.

Abstract: Wire rod is subjected to a cooling operation while emerging from a hot rolling mill. The rod is first cooled to a temperature of 850.degree. to 650.degree. C. and is then kept at substantially this temperature for a time sufficient for austenite to be transformed into ferrite. The rod is then cooled to a temperature of 625.degree. to 400.degree. C., and is kept at substantially this temperature, or allowed to cool slowly, for a time not shorter than 15 seconds and sufficiently long to permit precipitation of carbon in the form of carbides.

Abstract: A continuous casting process, in which the upper surface of the molten metal in the mold is covered by a protective powder, is controlled. The acceleration spectrum of the mold is recorded and compared with an ideal spectrum corresponding to optimum quality of the ingot skin. Any difference observed between the two spectra is taken up by modifying a parameter having an effect on the ingot quality at the time at which it is formed in the mold.

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: Waste water from coke ovens is purified by passing the waste water and a stripping fluid through a stripping column in counterflow. Non-volatile ammonium compounds are removed in one region of the column, phenolic compounds are removed in another region, and volatile ammonium compounds are removed in yet another region. The region in which phenolic compounds are removed is disposed at such a location that no ammoniacal vapor can traverse it. An acid and a strong base are fed laterally into the column at two different levels.

Abstract: Liquid and gaseous phases are contacted in a column having a plurality of perforated plates spaced one above another. Each plate undergoes rotational or translational movement while at least one of its faces is subjected to a cleaning operation.

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: 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.