FR2670216A1 - Plant for the production of steel in an electrical furnace - Google Patents

Abstract

Plant for the production of steel by melting iron scrap, comprising an electrical furnace, means for supplying iron scrap in the form of individual charges and means for placing above the furnace a charging receptacle containing a charge of iron scrap for pouring the latter into the tank, through a bottom opening, the whole being placed in a building including at least one area for receiving and picking up iron scrap and a production area. According to the invention the means for placing the charging receptacle above the furnace consist of a specific conveying device placed permanently between the receiving area and the melting area and provided with means for carrying and controlling the movement of the charging receptacle following a determined path and at a substantially constant level between a position for taking over the iron scrap and a position for pouring it.

Description

 The subject of the invention is an installation for producing a metal such as steel by melting, in an electric furnace, a ferrous material such as scrap.

 Electric arc furnaces have been used for a long time, and more and more, for the production of steel by melting scrap or other ferrous raw material, for example a pre-reduced ore.

 In general, an electric arc furnace comprises a melting tank limited by a refractory hearth surrounded by a side wall and closed at its upper part by a removable cover, the tank being associated with one or more connected electrodes to a power source. Each electrode is fixed to the end of an arm extending in overhang over the tank and penetrates vertically therein through the cover through an orifice provided for this purpose. The oven can be supplied with alternating current by means of three electrodes or alternatively with direct current. In this case, one or more electrodes crossing the vault are used, each associated with one or more electrodes placed in the hearth and connected to the current source, each by a return conductor. Of course, the oven is associated with a certain number of ancillary equipment such as electrical installations, means of loading with scrap and additives, means for evacuating molten steel and slag and smoke evacuation circuits. Often, to improve the efficiency of the furnace, provision is also made for preheating the scrap before it enters the furnace in an enclosure traversed by hot gases.

 This fairly complex set of expensive and bulky devices is placed in a building which generally includes a scrap reception and recovery area, possibly a preheating area, and a processing area.

 The raw scrap arrives in the reception area in one or more transport containers or "baskets". Each basket is taken up by a traveling crane, circulating over the entire installation, and is brought either directly above the oven, or into a preheating cell, in more sophisticated installations, the basket then being taken up by the traveling crane and transported above the tank.

Each basket is generally provided with an opening bottom consisting of two shells mounted to rotate each around a horizontal axis and which, moving away from one another, drop the scrap metal which pours into the oven bowl whose cover has been removed. To this end, the vault constituting the cover as well as the electrodes can be suspended from a gantry that can be moved horizontally or, preferably, from arms mounted to rotate around a vertical axis on a base placed next to the oven -
The production of steel generates a large volume of hot and dusty gases during the melting and refining phases and these fumes are captured by a pipe connected to an orifice in the vault and which discharges them outside after dusting.

Generally, the flue gases pass through a combustion chamber making it possible to burn the carbon monoxide and the other unburnt substances and to recover part of the dust entrained by the fumes. The burnt gases are sent to one or more scrap preheating cells awaiting loading.

 Of course, during loading, the cover must be opened and there is still a strong emission of fumes which are not captured. Steel and slag splashes can also occur when the scrap is poured into the tank.

 As such an installation produces, in addition, a significant noise, it is sought to isolate it as much as possible in order to reduce pollution both by smoke and by noise.

 To this end, it has been proposed to place the oven in a closed enclosure fitted out in the building, which makes it possible to reduce noise and to capture the fumes leaving the oven during loading, but the results obtained remain insufficient and, moreover, such an enclosure interferes with the transport of various materials and the movement of personnel.

 On the other hand, the transport by an overhead crane, above the various apparatuses, of baskets or other receptacles containing the scrap, in particular when it has been preheated, always presents a certain danger and the imprecision of the movements, whatever regardless of the skill of the bridge crane operator, it is necessary to respect fairly large safety distances, in three dimensions, so as not to risk striking the various devices and the rather complex circuits of gas circulation and electrical supply.

 The subject of the invention is improvements to installations for the production of steel in an electric oven which make it possible to remedy all of these drawbacks and, in particular, to reduce pollution, to improve safety and to allow automation of most of the operations.

 The invention therefore applies, in general, to an installation for producing steel by melting scrap comprising at least one electric furnace comprising a melting tank closed by a removable cover and at least one electrode connected to a source of current and capable of penetrating vertically into the tank by passing through the cover, means for supplying the scrap in the form of individual charges by means of at least one movable container and means of positioning au- above the furnace, after opening the lid, of a scrap loading container, the latter being provided with an opening bottom for the dumping of scrap in the tank, the assembly being placed in a building comprising a zone of scrap reception and recovery and a processing area.

 In accordance with the invention, the means for positioning the loading container above the oven consist of a specific transport member, permanently interposed between the receiving zone and the melting zone and provided with means for support and control of the movement of the loading container along a determined path and at a substantially constant level between a take-up position and a position for dumping the scrap.

 In a more sophisticated installation, comprising means for preheating each load of scrap before it is introduced into the furnace, by circulation of hot gases, the specific transport member determines the movement of the loading container between a position for taking charge of the preheated scrap and the pouring position in the oven.

 In a particularly advantageous embodiment, the member for transporting the loading container comprises at least one arm pivotally mounted about a vertical axis on a fixed base placed between the receiving zone and the processing zone and extending cantilevered to a free end provided with means for supporting the loading container, and means for controlling the rotation of said arm about its axis for the displacement of the loading container in an arc of circle between a pick-up position in the receiving area and the spill position in the oven bowl.

 Advantageously, the transport member is provided with means for controlling a vertical movement of limited magnitude of the loading container relative to the level of movement.

 Depending on the case, the loading container can be mounted either removably or permanently on the transport member.

 In a particularly advantageous embodiment, the loading container is provided, at its lower part, with a substantially sealed connection means with the oven bowl to channel the ascending gases towards the container placed above it in the spill position. This connecting means may consist of a skirt surrounding the lower part of the loading container and the base of which follows a profile corresponding substantially to that of the upper part of the tank. In this way, by slightly lowering the loading container after positioning above the tank, the base of the skirt is applied to the upper edge of the tank which is thus capped by the loading container.

 It should be noted that the means of connection of the loading container with the oven tank also serves to guide the scrap metal descending towards the oven tank.

 According to another particularly advantageous improvement, the loading container itself constitutes a scrap preheating chamber and is provided for this purpose with two orifices spaced apart in height and capable of being connected in a removable manner, in a preheating position, respectively on two pipes, one for the arrival of a stream of hot gases and the other for discharging said gases, said container being associated with means for detachably closing, at least in the preheating position, its two openings , respectively upper and lower.

 The preheating chamber can be removably mounted on the transport member. In this case, the enclosure, placed in a preheating position, is first connected to hot gas inlet and outlet pipes for the time necessary for preheating, then said pipes are disconnected and the enclosure is taken loaded by the overhead crane to be installed on the transport device. The loading of cold scrap can be carried out either in the preheating position, or in another position, in the reception area, for example.

 However, the preheating chamber can also be permanently mounted on the specific member for transporting the chamber between the two positions for taking over and pouring into the tank. In this case, the enclosure placed in the pick-up position is first loaded with cold scrap, normally by means of a basket, then its cover is closed and the enclosure is connected to fixed supply lines. and gas evacuation. After preheating, said pipes are disconnected, then the transport member moves the enclosure to the pouring position, above the tank, the closing vault of which is separated.

 The closing cover of the preheating chamber can be raised and moved apart before the latter is put into place in the discharge position, but it can also be maintained, the gas evacuation orifice then being connected in a removable manner on an oven smoke evacuation pipe.

 The use of a specific means of transporting the loading container between the reception area and the processing area makes it possible, in a particularly advantageous manner, to place the installation in a building comprising two adjacent parallel halls, respectively a preparation hall in which the reception area and, where applicable, the preheating means are placed, and a processing hall in which the oven is placed, the transport member being placed on the junction between the two halls for the passage of the loading container from one hall to another.

 However, the invention will be better understood from the more detailed description of certain embodiments given by way of example and shown in the accompanying drawings.

 Figure 1 is a schematic plan view of the entire installation.

 Figure 2 is a schematic view, in cross section, along II / II of Figure 1.

 Figure 3 is a schematic view, in cross section, along III / III of Figure 1.

 Figure 4 is a schematic plan view of an installation placed in a building with two adjacent halls.

 Figure 5 is an elevational view, in axial section, of a preheating chamber.

 Figure 6 which is a sectional view, according to VI / VI of Figure 4, shows the use of a loading container as a preheating chamber.

 Figure 7 and Figure 8 show respectively in elevation and in top view, the oven and the preheating chamber in the loading position.

 In Figures 1, 2 and 3, there is shown schematically the whole of a processing installation placed inside a building 1 comprising, in the example shown, a main hall 10 limited by posts 11 supporting an overhead crane 12 and covered by a roof 13.

 Inside hall 10, it is possible to define a zone A for receiving scrap, a zone B for preheating and a zone C for processing. Generally, the production of the metal requires additions which are prepared and stored in a zone D placed in hall 10 or in an annex hall.

 The electric oven 2, placed in the processing zone and shown in elevation in FIG. 3, comprises a tank 2 'consisting of a hearth 21 and a ferrule 22 and closed by a cover 23 through which at least passes an electrode 24 connected to a current source and penetrating vertically into the tank 2 ′ by passing through the cover 23.

As indicated in FIG. 1, the cover 23 consists of a vault suspended from the end of an arm 25 extending in overhang from a base 26 and mounted pivoting around a vertical axis so as to be able to spread the vault up to position 23 ′ shown in dotted lines in FIG. 1 and for which the tank is entirely released.

 Likewise, each electrode 24 is mounted at the end of an arm 27 also pivoting on the base 26 around a vertical axis.

 All these arrangements are conventional and do not need to be described in detail. In the example shown, the furnace 2 has a single electrode and therefore operates on direct current. it could also be provided with three electrodes and supplied with alternating current.

 The scrap which must be melted in the electric oven 2 arrives in the raw and cold state in the reception zone A, in one or more receptacles generally called "baskets". As seen in Figure 2, each basket 14 has the shape of a pocket open upwards and downwards, the lower orifice being closed by a bottom 15 consisting of two shells which can move apart one on the other by rotation around a horizontal axis.

 Before preparation, it is preferable to preheat the scrap charge and in this case the basket 14 can be placed in a preheating chamber consisting, in the example of Figure 1, of a closed chamber 3 into which opens a line 31 for hot gas inlet.

The latter come from a combustion chamber 32 receiving the gases produced in the oven during melting and refining and captured by a tube 33 connected to an orifice formed on the roof 23 of the oven. Indeed, these gases contain a high proportion of carbon monoxide which is thus eliminated with production of heat.

 To simplify the Figure, the circuit for circulating the preheating gases, which is easy to design, has not been shown in detail.

 The scrap is introduced into the furnace 1 by means of a loading container 4 in the manner shown in FIGS. 2 and 3.

 The loading container 4 is limited by a substantially cylindrical side wall 41 comprising an upper opening for the introduction from the top of a scrap load and a lower opening for spillage. The latter can be removably closed, by a bottom 42 usually consisting of two shells pivotally mounted around horizontal axes so as to be able to open or close. In addition, the container 4 is mounted on a support and transport member 5 which comprises an arm 51 extending in overhang from a base 52 placed next to the furnace 2 and rotatably mounted on the base 52 around an axis 50. At its free end, the arm 51 forms a fork 53 in which the container 4 engages.

 In this way, the axis 40 of the container 4 describes, by rotation of the arm 51, an arc centered on the axis 50, the latter being placed relative to the furnace 2 so that the axis 40 of the container 4 is placed, after rotation, in alignment with the axis 20 of the tank 2 'of the oven, in the position shown in Figure 3.

 Thus, when the scrap metal has been reheated in chamber 3, the basket 14 ′ is supported by the traveling crane 12 which, by longitudinal displacement, places it above the loading container 4 in the position of FIG. 2. The bottom 15 is open and the preheated scrap descends into the container 4. A rotation of the arm 51 is then commanded which places the container 4 above the tank 2 ', in the position of Figure 3. The bottom 42 is opened and the preheated scrap is poured into the oven. It can be seen that, thanks to the use of a specific member 5 for supporting and transporting the loading container 4, the latter moves over a well-defined path and at a constant level between two fixed positions, respectively the gripping position. under load shown in Figure 2 and the discharge position shown in Figure 3.

 We therefore know precisely the path traveled by the loading container 4 and the level of movement which is thus carried out in complete safety. The transport member 5 can indeed be installed so as not to hinder the movements around the furnace 2 and the various organs, in particular all the gas circulation pipes, can be positioned so as to remain apart at all times , of the transport member 5. In the example shown, the various devices are placed in alignment with one another inside a single hall 10, the support arm 51 rotating 1800 between the position of takeover and the dumping position. A whole side of the hall is thus freed in which the devices 6 for supplying additions from a certain number of hoppers 61 can be placed, in particular.

 In addition, when transporting the scrap baskets 14, the crane 12 does not exceed the preheating zone 3 and no longer has a crane 12 does not exceed the preheating zone 3 and no longer has to come to - above the oven, if not stopped, for maintenance. In this way, as can be seen in FIG. 3, when the scrap is loaded by the container 4, the entire space of the hall 10 above the oven is cleared and allows the free evacuation of the fumes which are guided by the container 4 to a hood 17 placed in the roof 13. One could even, possibly, lower the recovery hood to bring it closer to the oven. On the contrary, in conventional installations where a basket is brought directly above the oven by means of an overhead crane, the latter hinders the evacuation of the smoke towards the hood.

 However, the use of a rotary transport member between the two preheating and processing zones also makes it possible to arrange the installation, as shown in Figures 4 and 6, in two parallel halls, respectively a hall 10a where the receiving zone A, the preheating zone B and the zone D for preparing the addition elements are placed, and a hall 10b in which the furnace is placed only, on a completely unobstructed casting floor. All the handling of the baskets is thus carried out in hall 10a and hall lOb is provided with a traveling crane which is used only for maintenance.

 It will be noted that, as we know exactly the level of displacement of the container 4, the latter can be brought as close as possible to the tank 2 'of the oven to ensure the channeling of the rising smoke current as well as the guidance of the scrap metal descending into the tank from the oven 2.

 The invention also has another very important advantage.

In fact, the use of a specific transport member along a determined path and between two fixed positions for taking over and discharging makes it possible to fully automate all the loading operations, which is not possible when the we use an overhead crane.

 However, the invention also makes it possible to easily add to the tank, before or after the dumping of scrap metal, addition elements such as limestone, lime, coal, etc. These can be loaded, for example, at by means of the traveling crane 12, in a receiving hopper 62 from which they are directed to a set of hoppers 61 for storing the various addition elements. Advantageously, the arm 51 is provided with an auxiliary hopper 63 which is placed next to the loading container 4 and therefore comes to be placed with the latter above the oven, at a certain distance from the axis 20, in the position 63 'indicated by dotted lines in the Figure. This position being constant, the storage hoppers 61 can be associated with a loading member 6 which follows a determined path to arrive above the position of the hopper 63', the last section of the loading member 6 may consist of a chute 64 pivotally mounted so as to clear the space above the vault 23 to allow rotation thereof.

 As seen in FIGS. 2 and 3, the auxiliary hopper 63 is placed along the container 4 so as not to obstruct the opening of the shells 42.

According to another advantageous arrangement shown on the
Figure 6, an orifice 27 may be formed on the pipe 26 for discharging the fumes so as to open out above the tank 2 'of the oven. In this case, as indicated in FIG. 4, the member for loading the additions 6 can open out above the orifice 27 which makes it possible to pour the additions directly into the oven, without opening the cover 23.

 In the example shown, the loading container 4 is permanently fixed to the arm 51, but it can also be removably mounted. In this case, the container 4 is placed inside the preheating chamber 3, in place of the transport basket 14 'and is then taken up by the traveling crane 12 to be placed on the arm 51, in the fork 53.

 As already indicated, since the loading container follows a determined path and at a constant level, it can, in the pouring position shown in Figure 3, place it very close to the upper edge of the tank 2 'and perfectly centered on the axis 20 thereof. Therefore, the container 4 reduces the risk of steel splashes during the spill, its lower part being able to have the shape of a hopper to channel the scrap towards the center of the tank 2 ′ thereby reducing the risks of deposits on the edges of the sole 21 and the deterioration of the side wall 22.

 In addition, by being thus placed very close to the tank 2 ′, the container 4 collects the fumes and serves as a chimney for ascending guide of the gases towards the hood 17.

 This effect can be further improved by providing, at the base of the container 4, a substantially sealed connection means with the tank, according to the arrangement shown, by way of example, in FIG. 5.

 In this case, in fact, there is around the lower part of the container 4 a skirt 43 bounded by a metal wall 43 which surrounds the side wall 41 at a certain distance, so as to provide an annular space in which can be placed. , in the raised position, the shells 42 for closing the bottom of the container 4.

 At its upper part, the side wall 43 is connected to the wall 41 of the container 4 by a partition 44 which closes the annular space upwards. On the other hand, the skirt 43 opens widely downwards, through an orifice limited by a flange 45 placed at a level lower than that of the closing shells 42 and having, in horizontal section, a profile identical to that of the upper edge of the shell 22 of the tank 2 'of the oven 2.

 Often, the ferrule 22 is cylindrical and, in this case, the orifice 45 is given a circular profile of the same diameter.

 But it also happens that the ferrule 22 and the cover 23 are given an ovoid shape so as to cover the spout of the steel usually arranged on one side of the sole 21. In this case, the the lower orifice of the skirt 43 a circular section of the same diameter as the oven, but extending the flange 45 on one side, by a plate 46 capable of covering the oval part of the oven corresponding to the spout. Thus, when the container 4 is placed above the oven tank, the latter is completely covered by the base 45, 46 of the skirt 43 which can be placed a short distance from the upper edge of the side wall 22 of the tank 2 'and provides a substantially sealed guide of the gases towards the container 4 forming a chimney.

 In addition, one can provide on the transport member 5, a small amplitude adjustment of the height of the container 4. For example, the latter can rest on two short stroke cylinders 57 bearing on the two branches of the fork 53 and allowing the container to be raised or lowered. It is also possible to provide an articulation of the arm 51 on the base 52 around a horizontal axis by associating it with a jack allowing a certain height adjustment.

 In this way, when the arm 51 is pivoted to a constant level, the height of the container 4 can be adjusted to pass it a little above the tank, then the container 4 is lowered by applying the base 45, 46, of the skirt 43 on the upper edge of the tank 2 '. This ensures a practically sealed connection between the tank 2 'and the container 4.

 But Figure 5 shows another particularly advantageous improvement of the loading container 4, allowing the latter to be used as a preheating chamber.

 In this case, in fact, the container 4 is associated with means for detachably closing the two upper and lower openings and can be connected to a hot gas circulation circuit.

 In the examples shown in Figures 6 to 8, the container 4 can be closed, at its upper part, by a removable cover 7 and, at its lower part, by a closed base 34 formed on an auxiliary floor 18 and on which is put the container 4 in the preheating position. it thus constitutes a closed enclosure in which a stream of hot gases can be passed.

 To this end, as indicated in FIG. 5, the skirt 43 is provided with a lateral orifice provided with a tube 47 to which a supply pipe for hot gases which spread in the can be connected. annular space, passing between the shells 42 and the lower edge of the wall 41, the closure not being leaktight, rise in the container 4 by yielding their heat to the charge of scrap which is accumulated therein and escape by an orifice 71 formed in the cover 7.

 Such a hot gas circulation circuit has been shown diagrammatically in FIG. 6 which shows the entire installation in the preheating position.

 In this position, the oven 2 is in operation, the cover 23 being closed and the electrode 24 lowered. the transport member 5 is turned on the side opposite the oven 2 so as to place the loading container 4 above the floor 18 on the closed base 34, the latter having, in cross section, a profile identical to that of the side wall 22 of the tank 2 'of the oven and oriented symmetrically with respect to the pivot axis 20 of the transport member 5. As already indicated, the loading container 4 can advantageously rest on the arm of support 51 by means of jacks 54 which make it possible to control vertical displacement of small amplitude. Thus, after having brought the container 4 into the position of FIG. 6, it is lowered slightly by means of the jacks 54 to make it rest on the base 34, the skirt 43 thus being closed in a sealed manner. It will be noted that the jacks 54 make it possible to adjust the application pressure of the container 4 on the base 34, most of the load being supported by the arm 51.

 It has also been seen that the cover 23 of the oven 2 is provided with an orifice opening into a tube 26 to which can be removably connected, a pipe 33 for evacuating the fumes towards a combustion chamber 32. In particular advantageous, the combustion chamber 32 is placed below the floor 18 and the pipe 33 passes inside the base 52 for supporting the transport member 5. This reduces the length of the circuit which, moreover, is well protected. The gases produced by combustion escape to a dust removal and evacuation circuit via an outlet pipe 35 to which a pipe 31 passing through the floor 18 is connected in diversion and provided at its end with a removable seal 38.

 Valves 36 and 37 are placed respectively on the pipes 35 and 31, downstream of the bifurcation so as to direct the gases either directly to the dedusting or to the pipe 31.

 When the container 4 is placed on the base 34, in the preheating position shown in Figure 6, the tubing 47 is placed opposite the end of the bypass pipe 31 to which it can be connected by means of the seal 38. Likewise, in this position, the tubing 71 opening into the cover 7 is placed in front of a pipe 72 for discharging the gases towards the dedusting circuit and to which it can be connected by a removable joint 73.

 Thus, the fumes leaving the furnace via line 33 are directed towards the combustion chamber 32 and, depending on the position of the valves 36 and 37, the hot gases thus produced can be evacuated via the outlet line 35, either towards the outside, either to line 31 when the container 4 is in the preheating position. The skirt 43 being closed in a leaktight manner by the base 34, the gases rise inside the container 4, yielding their heat to the scrap charge and are evacuated towards the outside by the pipe 71 and the evacuation pipe. 72, which can be connected to line 35.

 When the furnace 2 must be replenished with scrap, the electrode 24 is reassembled and the pipe 33 is disconnected, which allows the opening of the cover 23. Likewise, the pipes 31 and 72 are disconnected from the pipes 47 and 71 respectively. The cover 7 is removed and, the container 4, thus freed, is placed by rotation of the transport member 5, above the tank 2 'of the oven in the position shown in Figures 7 and 8. The preheated scrap is then poured into the tank 2 '.

 In the arrangement shown in Figures 6 to 8, the cover 7 is suspended from an auxiliary arm 74 pivotally mounted about the axis 20, above the transport member 5, for example by means of cables suspension 75 which allow the cover to be raised or lowered 7.

 When the cover 7 is raised, the auxiliary arm 74 accompanies the movement of the arm 51 and of the container 4 but is stopped in the transverse position 7 ′ shown in FIG. 8 and it is left in this position when the container 4 is brought back in its preheating position 4 ′ after having discharged the charge of preheated scrap into the oven 2. The container 4 is thus opened upwards and there can be introduced a new charge of cold scrap contained in a basket 14 suspended from the bridge rolling. By rotation of the arm 74, the cover 7 is then brought back above the container 4 which has itself been lowered so as to rest on the base 34. The cover 7 is lowered on the side wall 41 and the supply lines 31 and discharge 72 of the hot gases. The container 4 is then in position for preheating the new charge.

 Of course, the invention is not limited to the details of the embodiments which have just been described, other improvements and other variants that can be imagined.

 Thus, if it is advantageous to place the combustion chamber 32 under the floor 18 to easily connect it to the preheating chamber 4 by circulating the hot gases from bottom to top, one could imagine other arrangements and a reverse direction of circulation, for example when the improvements according to the invention are adapted to an existing installation and it is desired to keep as far as possible the location of the means of production and circulation of hot gases.

 In addition, the cover 7 for closing the preheating chamber 4 could be held thereon in the pouring position, the tube 71 then being removably connected to a circuit for evacuating the fumes towards means of dusting.

 One could also simplify the loading of additions by placing on the transport member 5 several auxiliary hoppers such as 63, provided at their base with a removable closure and each containing the necessary quantity of an addition element. Thus, each hopper passing in turn, above the oven, would introduce the desired additions.

 Finally, the hot gas circulation circuits could be arranged otherwise, for example by vertically opening the pipe 31 in an orifice formed in the base 34 for closing the loading container 4.

 The reference signs, inserted after the technical characteristics mentioned in the claims, have the sole purpose of facilitating the understanding of the latter and in no way limit their scope.

Claims (19)

 1. Installation for producing a metal such as steel by melting a ferrous material such as scrap comprising - at least one electric furnace comprising a melting tank closed by a removable cover and at least one connected electrode to a source of current and capable of penetrating vertically into the tank through the cover, - means for supplying the scrap in the form of individual charges intended to be introduced one after the other into the oven, - at least a loading container comprising an upper opening for the introduction of a scrap load and a lower dumping opening closed by a removable bottom, - means for placing above a furnace, after opening the cover, a loading container containing a load of scrap metal for dumping it into the tank, by opening the bottom, - the assembly being placed in a building comprising at least one area e reception and recovery of scrap and a processing area,  characterized in that the means for placing the loading container above the oven consist of a specific transport member permanently interposed between the receiving zone and the melting zone and provided with support means and for controlling the movement of the loading container along a determined path and at a substantially constant level between a position for taking over and a position for dumping the scrap.  2. Installation according to claim 1, wherein each scrap load is preheated, before its introduction into the oven, by circulation of hot gases, characterized in that the specific transport member determines the movement of the loading container, according a fixed path, between a position for taking over the preheated scrap metal and the position for dumping into the oven.  3. Installation according to one of claims 1 or 2, characterized in that the member for transporting the loading container comprises at least one arm pivotally mounted about a vertical axis on a fixed base placed between the reception area and the working zone and extending in a cantilever fashion to a free end provided with means for supporting the loading container, and means for controlling the rotation of said arm around its axis for the movement of the container loading in an arc between the picking up position and the dumping position of the scrap in the oven tank.  4. Installation according to one of claims 1 to 3, characterized in that the transport member is provided with means for controlling a vertical movement of limited extent of the loading container relative to the level of movement.  5. Installation according to one of claims 1 to 4, characterized in that the loading container is removably mounted on the transport member.  6. Installation according to one of claims 1 to 4, characterized in that the loading container is permanently fixed to one transport member.  7. Installation according to claim 2, characterized in that the loading container is provided, at its lower part, with a substantially sealed connection means with the furnace tank for the upward guidance of the gases from the tank to the container placed above it in the spill position.  8. Installation according to claim 7, characterized in that the means of connection of the loading container with the tank is used for the downward guidance of the scrap to the tank.  9. Installation according to claim 7, characterized in that the connecting means between the tank and the container consists of a metal wall forming a skirt surrounding the lower part of the loading container and whose base follows a substantially corresponding profile to that of the upper part of the tank.  10. Installation according to claim 9, characterized in that, after displacement and positioning of the loading container above the tank, said container is slightly lowered so that the base of the skirt is applied on the edge top of the tank.  11. Installation according to one of the preceding claims, characterized in that the transport member is provided with at least one hopper for loading with addition products, integral in displacement with the loading container.  12. Installation according to claim 11, characterized in that the hopper is placed on the transport member so as to pass over the tank of the oven before or after the arrival of the loading container in the pouring position in an intermediate position for discharging the additions.  13. Installation according to one of the preceding claims, characterized in that the loading container constitutes an enclosure for preheating the scrap, said container being provided with two orifices spaced apart in height and capable of being connected in a removable manner, a preheating position, respectively on two pipes, one for the arrival of a stream of hot gases and the other for discharging said gases, and being associated with removable closing means, at least in the preheating position, of the two openings, respectively upper and lower.  14. Installation according to claim 13, characterized in that the means for closing the upper opening of the preheating chamber is a cover mounted on a support with a possibility of limited vertical displacement for its application on the chamber and its raising, and a possibility of horizontal displacement for its separation from the enclosure in the raised position.  15. Installation according to one of claims 13 and 14, characterized in that the preheating chamber is removably mounted on the specific transport and displacement member and can be moved, in the preheating zone, between a preheating position in which the enclosure is loaded with scrap and connected to the hot gas inlet and outlet pipes, and a positioning position on the specific transport member.  16. Installation according to one of claims 13 and 14, characterized in that the preheating chamber is permanently mounted on the specific transport member which controls the movement of the chamber between two fixed positions, respectively take-over and discharge and that, in the take-over position, the enclosure is first loaded with cold scrap then the cover is closed and the enclosure is connected to fixed inlet and outlet pipes gas, then the lines are disconnected and the transport member moves the enclosure to the discharge position.  17. Installation according to claim 16, characterized in that the cover is raised and moved away from the enclosure before the latter is placed in the pouring position.  18. Installation according to claim 16, characterized in that the upper connection orifice for the hot gas circulation circuit is formed on the cover and that, after disconnecting said orifice, the cover is maintained on the preheating chamber and, when the latter is placed in the pouring position in the tank, the orifice of the cover is removably connected to a smoke evacuation circuit.  19. Installation according to one of the preceding claims, characterized in that it is placed in a building comprising two adjacent parallel halls, respectively a preparation hall in which are placed the reception zone and the preheating zone, and a processing hall in which the oven is placed, the transport member being placed on the junction of the two halls for the passage of the loading container from one hall to another.