Abstract: Installation for preparing metal billets for extrusion, comprising a furnace (1) heating a metal bloom (4), having an elongate receptacle (10), means of heating the bloom and means (3) of pushing the bloom out of the receptacle along a longitudinal axis of movement, and a shear (2) cutting the bloom into billets of a length suitable for extrusion, comprising a pair of rear jaws (5) mounted in a fixed frame (21) and at least one front jaw (65) mounted so as to slide, transversely relative to the axis of movement of the bloom, along the rear jaws (5) and on the opposite site to the furnace (1) and associated with means (66) of controlling, as a result of sliding, the shearing of a specific length of the bloom (4).

Abstract: At an installation comprising a roll stand having at least one roll of the variable camber type, comprising a fixed support and a casing carried by at least three jacks and rotationally movable about the support, the pressure of the fluid in each of the jacks (14), the position of the pistons of these jacks, the speed of rotation of the roll, and the flatness and thickness of the flat product are measured. The position of one of the jacks (14b) is controlled by the thickness measurement. The pressure in the other jacks (14a, 14c, 14d, 14e) is controlled by the pressure in the one jack (14b). The positions of the end jacks (14a and 14e) are compared and the pressure in the jacks (14) is modified in order to bring the tilt of the roll to a suitable value. The deformation of the fixed support is calculated and the shape of the generatrix of contact of the roll is determined. The pressure in the jacks (14) is modified in order to bring the generatrix to a reference shape.

Abstract: The invention relates to an acid pickling tank for metal strips with a width equal to or greater than 0.50 meter.The tank incorporates an external supporting structure (1) and a metal casing (3) coating internally with rubber (6). The rubber layer (6) is lined internally with large slabs (10a, 10b) of a natural rock of volcanic origin, which has a total SiO.sub.2 and Al.sub.2 O.sub.3 content greater than 60%, a porosity of between 6 and 30% and a relative density of less than 3. At most three slabs (10b) are placed side by side along the width of the tank and at most one slab (10a) is placed along its height. The minimum dimensions of a slab (10a or 10b) are 0.50.times.0.50 meter.The invention is applicable in particular to the pickling of strips of hot-rolled metal sheets.

Abstract: A direct-current arc furnace has a vessel with a floor and a cover, at least two vault electrodes projecting down into the vessel through the cover, and a hearth electrode exposed in the vessel generally in the floor below the vault electrodes. A scrap-metal charge is melted in this furnace by first energizing the vault electrodes with direct-current voltage of opposite polarity while displacing them downward through the charge from an upper position spaced relatively far from the hearth electrode to a lower position spaced relatively close to the hearth electrode and thereby passing an electric current through the charge to melt the charge and form a puddle of molten metal on the floor of the vessel at the hearth electrode.

Abstract: Electric arc furnace of the type comprising a bottom structure (1, 2) comprising the floor, a top structure (3) connected to the bottom structure by supporting columns (5), and cooled removable panels (6) filling the space between the two structures. Each of the removable panels and their supporting structures are provided with associated, separable hinge structures (15, 16, 17, 18) disposed on each panel and on its supporting structures in such manner that the panel can open outwards by rotation about its hinges.

Abstract: Hydraulic safety device for the mechanism for closing up the rolls of a rolling mill, comprising an hydraulic safety valve (20) which is accommodated directly inside the jack (1) for closing up the mill rolls and which automatically reduces the pressure of the fluid in the control chamber (12) as soon as the stroke of the body (11) of the jack reaches a predetermined limiting position.

Abstract: A system which permits the measurement, during operation, of the arc voltage electrodes having an upper metal portion (4) cooled by circulating water. The system employs an electrical instrumentation-cable (16) attached to a piece (5) for fixing the graphite consumable portion (3) of the electrode. This cable runs along the axis of the metal portion (4) and then inside one of the water-supply pipes (11), terminating at an electronic box (14) which converts the incoming measurement signal into a light wave.

Abstract: An electric arc furnace comprising at least one pair of electrodes extending through the roof of the furnace for the creation of electric arcs between each of the electrodes and the charge to be melted, and a source for applying direct current to each of said pairs of electrodes, respectively of different polarities. Preferably the furnace contains also an electric probe extending through the bottom of the furnace to determine the potential of the molten charge and means for adjusting the vertical position of each electrode for maintaining the potential difference between each electrode and the molten charge at a predetermined value.

Abstract: A process and device for drawing tubes by extrusion of a metal billet (4) placed in a receptacle (50) within which ramming of the billet (4) is carried out by first pushing the latter against a ramming insert (63) closing the receptacle (50), then perforating the billet by means of an axial mandrel (7), and finally replacing the ramming insert (63) in the axis of the receptacle (50) by an insert (65) holding a die. Drawing is carried out by extrusion of the billet. During ramming of the billet (4), a boss (41) is formed on the face of the latter turned towards the ramming insert (63) which is inscribed within an orifice (66) in the die and which has a plane face centered on an axis diverging from the drawing axis. The ramming insert (63) is provided for this purpose with an impression (8) which has recessed the desired shape.