CN1192833C - Apparatus for supplying molten metal to ingot mold for continuous casting and method of use thereof - Google Patents

Abstract

The invention concerns an equipment comprising an immersed nozzle (6) with outlets in the main casting plane (P) differentiated by their output direction into at least two categories (7, 8) associated to two mutually opposite inductors (14, 15) on each large surface (22) of the casting ingot mould forming an air gap circumscribed at the nozzle and producing a through magnetic field covering the outlets of at least one category (7), means being provided to adjust the intensity of the field or for moving it so as to be able to modify the distribution among the outlets of the total flow rate of molten metal. In particular, when the method is implemented, it enables to add at all times the fraction of metal flow heading towards the free surface (9) relative to the main surface, oriented towards the base of the ingot mould. The invention is advantageously used for continuous casting of steel slabs.

Description

Apparatus for supplying molten metal to ingot mold for continuous casting and method of use thereof

technical field

This invention relates to the continuous casting of metals, especially steel. In particular, the present invention relates to the technique of injecting molten metal from above into an ingot mold for continuous casting, and more precisely, to the application of a magnetic field to the ingot mold in order to alter the flow of the molten metal as it enters the ingot mold Technology.

Background technique

It is known that the application of magnetic fields to ingot molds for continuous casting can increase the output of casting equipment, while maintaining or even improving the metallurgical properties of the resulting cast product, provided that electromagnetic interactions are properly manipulated. In fact, it has been proven that the hydrodynamic eddies produced by the recirculation flow are detrimental in terms of the eddy currents inside the ingot mold when the casting speed is increased, especially when casting products of elongated cross-section, such as slabs and the like. will be very, very strong.

It should be noted that when casting slabs continuously, molten metal is injected into the ingot mold from a tundish (répartiteur) placed at a distance The spout openings of the ingots lead substantially to the main casting face parallel to the broad face below the free surface of the molten steel in the ingot mould, which is generally covered with a liquid layer of dynamic slag.

It can be determined that once the casting speed reaches about 1 m/min to 1.5 m/min, the velocity of the liquid metal flow at the sprue outlet is as high as several meters per second. The resulting recirculation flow in the ingot mold violently agitates the metal-slag interface. Undulations in the free surface of the metal being cast lead to irregular solidification of the first shell of the casting, which is known to be the source of harmful and even serious nuisance defects (bubbles, spalling, etc.) on the finished product. In addition, the overlying slag fragments may be rolled into the ingot mold and even into the center of the casting, thereby reducing the purity of the resulting solidified metal.

Steel manufacturers currently have two main solutions to the problems created by these hydrodynamic fluctuations: one is to use efficient electromagnetic hydrodynamic devices suitable for continuous casting of metals; the other is to focus on casting the pouring tube itself Geometry.

Electromagnetic actuators with static or traveling magnetic fields developed for this purpose are able to influence the return flow of liquid metal in the ingot mould, after it has flowed from the pouring tube, so as to slow down or speed up said flow, or to make said flow Symmetrical on both sides of the buried pouring tube.

Electromagnetic brakes were therefore first developed in that, at a predetermined height in the interior space of the ingot mould, a transverse magnetic field is applied which generates a braking force (pull) inside the moving metal as it passes through this area. Plath force). For this purpose, it has been proposed to place a magnetic pole on each wide face of the ingot mold, which is designed as an electromagnet with a coiled, projecting pole, which either has a The shape of the block between the narrow end faces of the ingot moulds (EP-A-0040383), either in the form of a single horizontal rod extending over the entire width of the wide face (WO 92/12814) or two spaced apart in the height direction The shape of parallel rod rods placed in the ground (WO 96/26029, WO 98/53936). Whichever geometry is used, the purpose is the same: On the one hand, together with the counter-poles of opposite polarity placed oppositely on the other side of the ingot mould, a transverse magnetic field is generated, the effect of which is to slow down said rise to the free liquid level. An overly intense flow, on the other hand, can also distribute the main flow of liquid metal flowing downwards better over the entire cross-section of the ingot mold.

In order to give this type of technology greater adjustment flexibility, it has been proposed to use no static magnetic field but a traveling magnetic field, which is known to have the property of driving the metal flow in its motion (EP-A-0 151648, WO 83 /02079, and JP-B-1 534 702). Two inductors with a horizontally running magnetic field (conductors oriented vertically) are placed on each broad face of the ingot mold on either side of a buried pouring tube with side spouts, and between said pouring tube and the between the narrow end faces of the ingot mould, so that as soon as the molten metal enters the region of the ingot mould, the traveling magnetic field resists it. It is thus possible to accelerate (or decelerate, depending on the direction of relative movement given by the traveling magnetic field) the liquid metal supply flow of the ingot mould, by simply adjusting the induction The operating parameters of the device, such as the initial supply of current intensity, or pulse frequency, and the sliding speed of the magnetic field.

It should be noted that such traveling magnetic fields are typically generated, if necessary, by inductors of the "polyphase linear motor stator" type (typically two- or three-phase) with winding coils in multiple independent phases, and will induce The receptacles are placed facing each other on the wide face of the ingot mould, thus parallel to the main casting face (FR-A-2,324,395; FR-A-2,324,397). Each coil is respectively connected to a different phase of the multi-phase power supply in an appropriate connection sequence to ensure that the magnetic field moves along the active surface of the inductor in a direction perpendicular to the conductor in a desired manner.

This time, in order to overcome the observed phenomenon of propagation of undulations on the free surface from one narrow face of the ingot mold to the other, it has also been proposed that by means of a movable magnet whose position can be adjusted mechanically ( plot magnétique), or by means of two adjacent fixed magnets (EP-A-0,832,704; JP-A-03275256), which are fixed relative to each other in their respective effects on the moving metal, the molten metal flowing into the ingot mold The flow is more symmetrical in the areas on both sides of the sprue.

Another type of solution consists in optimizing the geometry of the embedded part of the pouring tube for casting, in particular the outlet opening for the molten metal. Its purpose is always the same: to control the distribution of the flow of liquid metal into the ingot mould.

Such solutions can be found, for example, with a pouring tube of the "box" type (US-A-464,698; JP-A63,76753), the embedded part of which is generally bulb-shaped, similar to a painter's brush or to that of a watering can. The flat head, and its embedded part, may be considered to fulfill the stated function.

These pouring tubes are sufficiently wide open downwards to facilitate the outflow in the main casting plane of the casting stream at a lower velocity but over a larger flow cross section. Its main characteristic is that it is desirable to feed the liquid metal to the ingot mold with a uniform flow - close to the ideal flow of the so-called "plug flow". In said "plug flow", the velocity gradient between any two points in a cross-section approaches zero, and the cross-section rapidly approaches as closely as possible the section of the ingot mould. The box-shaped pouring tube came to be widely used in industry, especially in continuous casting plants for thin slabs. In fact, the metal recirculation in the direction of the free surface of the metal being cast is in fact greatly reduced, and, in this connection, if desired, additional openings can be provided in the upper or side parts of the box for enabling the melting The metal streamlines are fanned out upwards to ensure a regular supply of heat to the free surface, which is known to be necessary for a good casting process.

Among such solutions there are also certain straight pouring tubes with two different sets of side openings oriented in the main casting plane and parallel to the wide face of the ingot mould. Outlets opening at the bottom end of the sprue stem generally convey downwardly said main flow of metal to be removed from the ingot mould. The other outlet is opened in the upper part to deliver an auxiliary metal flow to provide heat to the free surface by a uniform but small flow of "fresh" molten metal having a high enthalpy just entering the ingot mould. get. The relatively low cost of such pouring tubes is of great economic advantage for wearing parts that require frequent refurbishment.

This means that the geometry of the pouring tube structure, whether straight or box-shaped, must be fixed and can thus only be optimized for a single function mode of the casting operation, or for a specific shape of the casting. Therefore, such solutions do not appear to be suitable for the unavoidable, intentional or unintentional changes and modifications in modern continuous casting equipment, such as changes in casting speed, changes in casting shape, etc...

Electromagnetic actuators (brakes, accelerators, symmetrizers) are flexible in nature and therefore better able to accommodate such changes. However, they are not optimized for any particular mode of operation. Once the liquid metal enters the ingot mould, they control the flow of the liquid metal and act sometimes as an accelerator and sometimes as a fluid retarder. However, in contrast to some of the sprues described above, they are completely incapable of distributing the flow of molten metal between the high region (towards the free surface) and the low region (towards removal from the casting) of the ingot mould. Furthermore, they are relatively expensive in terms of investment costs as well as the cost of electrical energy consumption, and they involve complex and economically burdensome modifications in the ingot mold technology in which they are used.

Contents of the invention

It is an object of the present invention to provide a steel manufacturer with an apparatus for supplying molten metal to ingot molds for continuous casting which can easily and quickly and accurately adjust the distribution of the flow of incoming metal between the high and low areas of the ingot mold .

To this end, an object of the present invention is to propose a device for supplying molten metal to an ingot mold of a continuous casting plant for products of rectangular cross-section, such as slabs, characterized in that the device comprises:

- a submerged sprue with a molten metal outlet located, or approximately located, in said main casting plane parallel to the wide face of the ingot mould, said outlet having a direction in the direction of outflow They can be divided into at least two different types;

- a set of induction units placed on the wide face of the ingot mold, which is used to generate two opposite magnetic poles, which are placed oppositely on both sides of the main casting face and are substantially limited in Transmitting a transverse magnetic field covering at least one orifice of said type in the magnetic gap in the area of the pouring tube;

-- and magnetic field strength adjustment means for adjusting the relative strength of said magnetic field at the place covering said type of outflow opening with respect to another type of outflow opening, so that between all outflow openings of said pouring tube Change the distribution of the total flow of molten metal.

According to an alternative embodiment, the induction unit is an electromagnetic unit comprising at least one electromagnet.

According to another alternative embodiment, said induction unit comprises: an inductor of the "traveling magnetic field" type with a plurality of phase coils, placed oppositely on both sides of said main casting surface; an associated power supply, which supplies each The coils are respectively supplied with direct current; and the means for adjusting the relative strength of the magnetic fields comprise means for moving the position of the poles within the magnetic gap of the electromagnetic unit.

It is conceivable to use inductors (electromagnets or "traveling field" type inductors) on only one side of the ingot mold, but with a loss of effective electromagnetic power. In any case, according to the invention, the magnetic poles of the inductor should always transmit a magnetic field perpendicular to the wall of the ingot mold against which the inductor is mounted. Otherwise, the desired effect cannot be obtained. Therefore, if two inductors are placed facing each other, the magnetic poles facing each other have opposite polarities, so that a transverse magnetic field can be generated, that is to say, the magnetic field lines of the transverse magnetic field connect the two magnetic poles and extend perpendicularly through the main casting The main casting surface in which the metal stream flowing from the outflow of the pouring tube located in the magnetic gaps of the two inductors is spread out.

The magnetic pole of an inductor can be defined as the area of the active surface of the inductor where the generated magnetic field is the strongest. In the case of an electromagnet, the poles are typically the ends of the raised, coiled ferromagnetic metal body that characterizes the device. In the case of inductors of the "traversing magnetic field" type with multiple phase coils, the poles have no fixed physical representation connected to a given ferromagnet of the yoke, but, in accordance with the alternating current (AC) phase current supplied to the conductor Instantaneous strength and phase difference, the magnetic poles can move on the active face of the inductor. It can likewise be said that the magnetic field "covers" the outflow opening of the pouring tube when the outflow opening is located in a region of the interior of the ingot mold in which the electromagnetic induction caused by the magnetic field is at a maximum.

Having presented these details, it should be understood that it is easy to vary the magnetic field in the region of the spout of the pouring tube which is covered by the magnetic field, according to the invention (with respect to the effects which may be applied to other spouts), by suitably adjusting the Field strength can be achieved. This effect can be achieved by changing (decreasing or increasing) the magnetic field strength without changing the magnetic pole position of the transmission magnetic field, or by changing the position of the magnetic pole on the wide surface of the ingot mold while maintaining its magnetic field strength. If the two types of outflow openings are so far apart on the pouring tube box in relation to the size and separation distance of the magnetic poles used, that the magnetic induction values in the respective areas may differ considerably, whereas e.g. If the field strength is greatest near the outflow outlet, then the first alternative operation described above may be preferred. In contrast, the second variant of implementation described above is better suited to the situation that will no doubt be frequently encountered: all outflow openings are covered, and only moving poles can create a sufficient field difference between them to effectively Reach the desired effect of the present invention.

Of course, in the case of electromagnets, this can be achieved by mounting the electromagnets movably on a frame connected to the casting equipment, wherein the casting equipment is equipped with such that the magnetic poles are placed in the cast iron housing said electromagnets. A device that moves on the surface of an ingot mold and enables it to stop at a selected point.

In some cases it may also be beneficial to divide the induction unit into two induction parts which are placed side by side on the same face of the ingot mould, each thus controlling said flow opening on one side of the pouring tube. outlet, and is independent of the outflow opening on the other side.

Regardless of which alternative embodiment is adopted, it is undoubtedly clear that the basic idea of the invention consists in using a magnetic field approximately as a non-substantial plug valve for the passage provided by the outflow opening of a type of pouring tube in order to vary The outflow of another type of outflow port. Since the supply flow rate is constant, or because in each case, said supply flow rate is rarely affected by the magnetic field effect, the magnetic field action directly acting on the outlet of one type of flow as described here has that change in the two types of flow. The effect of the proportional distribution of the total flow among the outlets. In this way, a buried pouring tube with variable geometry and constant shape is realized.

Preferably, the magnetic field covers the main outlet, that is, the outlet where the molten metal flows out the most (generally the outlet facing downward), because the magnetic field effect on the main outlet changes the outflow flow less than that on the metal flow. The outflow port is more sensitive. In the remainder of the description, for the sake of clarity, it will be assumed that the magnetic field covers the downwardly facing main flow outlet.

It should also be understood that in the preferred embodiment of the invention the invention employs a transverse magnetic field which is movable in the height direction at the pour tube region but which is generated by a fixed induction unit: a pair of of the inductors, all of the "horizontal magnetic field linear motor stator" type, they are matched to each other so that their phases are opposite, and each inductor thus generates a magnetic field whose flux lines are oriented in the same direction (obtaining the so-called "transverse" suitable conditions for the magnetic field), but the phase coils of the magnetic field are connected to separate DC power supplies and can be adjusted independently of each other. As is known, this type of induction unit can generate magnetic poles of opposite polarity, ie a transverse static magnetic field, which can be located at the desired location within the magnetic gap. The change of pole position is achieved by simply adjusting the operating parameters of the power supply element, ie in practice the amperage of the supplied current to selectively energize the induction coils. This adjustment can be done instantaneously during the casting process, if required, away from the casting equipment, in a manner which is completely safe for the operator and in a manner which is obvious, that is to say, without affecting the casting operation. Normal processes generate disturbances, even the smallest ones. It should be noted that the structure of such an inductor is already well known and used in continuous casting as a device for moving molten metal along the height of the ingot mold (for example the aforementioned patents FR-A-2,324,395; FR-A-2,324,397). The use in slabs is also well known.

It is therefore another object of the present invention to propose a method of operating the above-mentioned preferred device and which consists in adjusting the The strength of the magnetic field.

Description of drawings

With reference to the accompanying drawings, the present invention will be better understood, and other aspects of the present invention and its advantages will be clearer through the following description as a non-limiting embodiment, in the accompanying drawings:

- Figure 1 shows schematically an ingot mold for continuous casting of steel slabs from the front, sectioned vertically in the main casting plane, on top of which there is an ingot mold according to the invention with only one surface per ingot mold face A molten metal supply apparatus having an alternate embodiment of an inductor;

- Figure 2, as an illustration of Figure 1, schematically shows the structure of a known type of flat panel inductor, which can be adapted to implement the invention and which is connected for this purpose to a DC power supply;

- Figure 3 is a schematic view, which is a vertical section along the vertical plane R-R of Figure 1, and which shows the mode of operation of the "transverse magnetic field" of the present invention viewed from the side of the ingot mold;

- Figure 4 is a schematic view, which is a horizontal cross-sectional view along the horizontal plane Q-Q of Figure 1, and which shows the mode of operation of the "transverse magnetic field" of the present invention viewed along the casting axis;

- Figure 5 is a schematic view similar to Figure 1 but showing an alternative embodiment of the invention having two inductors juxtaposed per ingot mold face.

Detailed ways

In these drawings, the same components are denoted by the same reference numerals.

An ingot mold 1 made of copper or an alloy of copper, which is sufficiently cooled by circulating water on its outer wall, receives from its upper part a certain amount of molten metal 2 which flows in the form of semi-finished iron and steel metallurgical products 3 to Bottom, the article is set here as a steel slab. When leaving the casting mould, the center 4 of the slab is still liquid, but the periphery 5 of the slab has solidified due to its contact with the cooled inner wall of the casting mould, as the slab advances along the casting axis S and passes the The slab is completely cooled during the next step of the casting plant, in particular by spraying water directly on its surface. The pouring of "new" metal into the ingot mold is carried out through a buried pouring tube 6, the top of which (not shown) is fixed around a casting port, which is placed in a tundish On the bottom, the tundish is placed above and at a distance from the ingot mould, while the bottom of the pouring tube 6 is buried in the ingot mould. The bottom of the pouring tube comprises outflow openings 7 , 8 which open below the free surface 9 of the liquid metal covered by the slag layer 10 . As shown, these spouts oriented to the main casting plane are of two different types:

-- Main outlet 7, which slopes downwards and injects most of the steel quantity, which is supplied to the ingot mold by jets 11 in all directions along the main casting plane (the plane shown), and generally flows to the bottom of the ingot mold .

- the second outflow port 8, which is located at the top, inclined upwards, and in this direction injects the rest of the metal quantity through the jet 12, which supplies the supplementary heat required by the surface 9 to avoid the meniscus (solidification) Corners, etc...) appear to breed and solidify

It should be noted that by "main casting plane" is meant the vertical mid-plane P which passes through the casting axis S at the center of the ingot mould, and which is parallel to the wide face 22 of the ingot mould. In this case, Figures 1 and 5 are precisely within the main casting plane P. Another similar surface parallel to the narrow side 13 of the ingot mold is designated as the second casting surface. Figures 3a and 3b are inside the second casting face.

The law of conservation of fluid "matter" determines that the liquid metal flowing out from the bottom of the ingot mold is equal to all the liquid metal flowing into the ingot mold through the pouring pipe 6. Since the discharge velocity V is a casting parameter which, for a given cross-section of the product 3, determines the inflow and thus the velocity of the liquid metal from the pouring tube. As mentioned above, if the casting equipment is highly productive (the threshold value of the discharge velocity V is about 1.5 m/min), the unavoidable circulation in the ingot mold will quickly reach a large level, and the inevitable reason This is because there is a large difference between the discharge speed and the speed at which the metal is ejected from the pouring tube, which is one hundred times faster than the discharge speed. The free surface 9 is strongly disturbed by the strongly turbulent recirculation flow mixed with the metal jet reflected by the narrow face 13 of the ingot mold. This perturbation is harmful and should be reduced or even eliminated. However, this attenuation should not affect the heat flow carried by the jets 12 to the free surface 9 . Just as the operating conditions of continuous casting machines are primarily of a "transient" nature, especially due to changes in casting speed, therefore, between the free surface that needs to be flat and quiet and the free surface that needs to be heated by "new" molten metal from the pouring tube Achieving the desired balance between the two has almost always been a problem.

This is why the invention introduces an induction unit on the wide face 22 of the ingot mold, consisting of a pair of electromagnetic inductors 14, 15 located opposite the ends of the pouring tube. These two inductors are used in cooperation to each generate magnetic poles facing each other and of opposite polarity, thereby forming a transverse magnetic field perpendicular to the wide face 22 . As shown in FIGS. 1 and 3 , the transverse magnetic field is located at "M" in the lower part of the magnetic gap, thereby "covering" the spout 7 of the type located at the bottom end of the pouring tube 6 body. However, these inductors are designed so that their poles move together within the magnetic gap. Here the movement is in the height direction of the ingot mould, since the electrical conductors 16...17' are placed in the horizontal direction. The combined movement of the magnetic poles of the inductor by a distance of approximately 10 cm or 15 cm results in a corresponding movement of the transverse magnetic field within the magnetic gap and thus an associated change in the local magnetic conditions in the area of the different outflow openings 7 and 8 of the pouring tube . As a result, the amount of metal flowing out of the two types of outlets is redistributed as desired with no or little change in the total amount. Thus, as shown in Figure 3, M represents the initial low position of the magnetic field within the magnetic gap and N represents the final high position reached after moving vertically a distance "d" in the direction of the outlet 8 carrying the metal stream upwards.

The movement of the magnetic field is obtained by means of a pair of inductors of the "electromagnet" type, provided with a protruding pole which acts as a support on which to wind the wire, and which is movably mounted on a On the frame connected to the casting equipment. Therefore, in this embodiment, physical movement of the sensing unit is required.

Where prevailing conditions permit, it is preferred to use a magnetic field that moves within a fixed magnetic gap. It will be appreciated that this is possible with an induction unit which, as shown in Figure 2, consists of two inductors of the "traveling magnetic field" type with multiple phase coils placed within the width of the ingot mold The two sides of the face 22 face each other. The inductor shown here is a "linear motor stator" type flat inductor with two phases (and thus two phase coils). Its conductors are straight copper strips (barre) 16, 16', 17, 17', the number of which is four, and they are placed horizontally in parallel with each other at intervals. Each coil consists of two copper strips connected in series-opposition so that current flows through them in opposite directions. The connected strips may be directly adjacent copper strips, such as 17 and 16' and 16 and 17' (inductors with adjacent poles), or may be interleaved copper strips, as shown, such as 16 and 16' and 17 and 17' (inductor with distributed poles), and there is no difference.

However, no matter what configuration is chosen, each phase coil must be connected to a separate DC (or rectified) power source, independent of the other coils' power supplies. For convenience, the power supplies shown with reference numerals 18, 19 in Fig. 2 have a common neutral terminal (neutre). They may be integrated in a power supply unit 20 with means 21a and 21b which automatically adjust the intensity of current delivered by each individual power source 18, 19, thus making it possible, for example, to pass the maximum current intensity through one of the coils , while simultaneously deactivating the other coils (zero amperage) and vice versa, all adjusted at once. In this case, the flat panel inductor 14 (15) can no longer produce a traveling magnetic field as usual, but produces a static magnetic field. As long as the current intensity in the two coils is appropriately changed, the magnetic poles of the static magnetic field are released. It can move on the active surface of the sensor in a direction perpendicular to the conductor. Also, if desired, a more detailed description of this type of inductor and both traveling and static field modes of operation can be found in the applicant's published International PCT application WO 99/30856.

As shown in Figure 3, the low position "M" of the poles corresponds to a maximum current in the coils 16, 16' supplemented by zero current in the coils 17, 17'. Conversely, the high position "N" in Fig. 3 corresponds to: the current in the coils 17, 17' is maximum, supplemented by the current in the coils 16, 16' being zero. It is clear that by combining said current intensities with the aid of the adjusting means 21 equipped with the power supply 20, it is possible to adjust the magnetic poles of the inductor to any position between these two extreme positions.

As can be seen more clearly in FIG. 4 , the paired two panel inductors 14 , 15 are constructed in such a way that their magnetic poles facing each other have opposite polarity. Therefore, at any point within the magnetic gap between the two inductors, the magnetic field of one inductor is superimposed on the induced magnetic field of the other. The structure is of the "transverse field" type: as indicated by the direction of the arrow B, the magnetic field lines connect the two magnetic poles of the inductor and pass perpendicularly through the main casting plane P and thus also perpendicularly to the direction of the molten metal ejected from the pouring tube.

From another perspective, this type of structure can be found in Figure 3. The transverse magnetic field generated by the magnetic poles of each inductor 14, 15 can move a certain distance "d" along the height direction from the low position "M" until the high position "N", at which the direction of the main outlet 7 The magnetic braking effect of the steel flow is the largest, and at the high position "N", the magnetic effect on the main outlet 7 is weakened, while the magnetic braking effect on the second outlet 8 is enhanced.

It is obvious that the invention is not limited to the exemplified embodiments described above, but it extends to many variants or equivalents within the scope defined in accordance with the appended claims.

In fact, it will be appreciated that although the present invention uses a sprue with outlet openings on the main casting face, the sprue can also be provided with other outlet openings at other locations, such as diagonally at the corners of the ingot mould. direction. In fact, the greater the degree to which the outlet jet direction is orthogonal to the magnetic field lines, the more pronounced the effect of the invention, because the effect of this electromagnetic effect is proportional to the vector product of the magnetic field and the jet velocity vector at the exit of the pouring tube orifice .

Also, although the gist of the invention is primarily to better control the heat supplied to the free surface by the molten metal entering the ingot mould, the gist of the invention is therefore also preferably focused on those equipped with one part facing down and the other part facing up. On the pouring pipe of the outflow port, but the present invention is also generally applicable to the pouring pipe in which the various outflow ports are not all in the same direction. In fact, as long as the two orifices differ, even by a small difference, such as only a few degrees in angular direction, the invention will work scrupulously. But its applicability is that the two outlets are far enough apart from each other that the transverse magnetic field can cover one outlet but not the other; or it can at least cover both outlets with an induction value such that, At the same moment, there is a significant difference in the induction values at the two outlets. In fact, it is evident that the possibility of a difference in field strength between two points in the interior space of the ingot mold for continuous casting of elongated products is the basis of the original design idea of the invention.

Thus, although the invention can be used to good effect in the case of the above-mentioned "box"-shaped pouring pipe, the invention can also be used for straight pouring pipes, it is important that the buried pouring pipe for casting has a different flow Outlets, at least two types of orifices generally directed upwards and downwards, said orifices eject a stream of molten metal flowing parallel to the broad face of the ingot mould. In other words, the invention can also be used, for example, in sprue pipes with side outflow openings that differ up and down on the struts of the sprue pipe.

On the other hand, the above implicitly assumes that the magnetic field strength B remains constant. However, as already pointed out, the magnetic field strength B also changes considerably when the supplied current strength changes, and the magnetic field itself can also move simultaneously or individually in the magnetic gap.

Likewise, as shown in Figure 5, the inductor 14 (and of course the inductor 15) can be divided into two identical parts 14a and 14b which are placed side by side on the same face of the ingot mould, and arranged in rows. On both sides of the casting axis S, in addition the pouring tube for casting is typically located in the center of the casting axis S. In this way, mutually independent lateral regions of the pouring tube are “covered” by the magnetic field, so that the metal streams 11 , 12 escaping from these regions can be selectively acted upon. By adjusting the sensor parts 14a and 14b autonomously, the symmetry of the fluid in the ingot mold can be optimized, since it can be intervened at the moment it flows out of the pouring tube. Of course, this result is obtained as a supplement to the optimum effect of the invention, by adjusting the magnetic poles of each inductor part 14a and 14b in the height direction, which can always distribute the total flow of metal between the different outlets of the pouring tube . In this variant, each inductor is partially powered by its own dedicated power supply (not shown), so that the different heights of the magnetic poles can be adjusted as desired on each inductor, and the current flowing through them can also be changed separately. current intensity.

On the other hand, instead of an inductor of the "walking field" type, not only electromagnets as described above, but also natural or industrial permanent magnets can be used.

In addition, the "DC power supply" mentioned in the specification should be understood not only to add a structurally independent power supply, but also to add a single multi-phase power supply with two or three phases and adjustable frequency. Set to zero frequency for DC. Such polyphase power supplies are well known. It is a polyphase power supply of the kind with inverters with adjustable clipping (hachage) thresholds, and it is commonly used to start those electric motors with rotating or moving fields. The operation of supplying the coils of the inductor 14 from this source in a coil-to-coil manner consists of: setting the inverter at zero frequency; making this adjustment at selected times so that the phases The current intensity at this moment is the desired current intensity in the coils connected to those.

It should also be noted that although the preferred field of application of the invention is the continuous casting of steel slabs, for which the invention was originally designed, the invention is also applicable to the continuous casting of metals in general, and in particular to the continuous casting of thin slabs. casting.

Claims (12)

1. Equipment for supplying molten metal to ingot molds for continuous casting equipment for products of rectangular cross-section, comprising: - a buried pouring tube (6) equipped with molten metal outflow openings located, or approximately, in the main casting plane (P) parallel to the wide face of the ingot mould, said outflow openings being in the outflow direction , which can be divided into at least two different types of outlets (7, 8); and - a set of induction units (14, 15) positioned facing the wide face of the ingot mold in order to generate thereon two magnetic poles of opposite polarity, said magnetic poles being placed facing each other on either side of said main casting face (P) ; Characterized in that said induction unit (14, 15) has a magnetic gap substantially surrounding said pouring tube (6) and conveys at least one type of outflow covering said different types of outflow openings (7, 8) (7) the transverse magnetic field; and Said device comprises means (20, 21) for adjusting the relative strength of said magnetic field for adjusting said magnetic field at a place covering said type of outflow opening (7) relative to another type of outflow opening ( 8) relative strength, making it possible to vary the distribution of the total flow of molten metal between all outlets of said pouring tube (6). 2. The device of claim 1, wherein the induction unit is an electromagnetic unit comprising at least one electromagnet. 3. The apparatus as claimed in claim 2, characterized in that said induction unit comprises: an inductor (14, 15) of the "traveling magnetic field" type with a plurality of phase coils, placed oppositely on said main casting the two sides of the plane (P); and an associated power supply, which supplies direct current to each of said coils respectively; and means (20, 21) for adjusting the relative strength of said magnetic fields are included in the magnetic gap of said electromagnetic unit A device that moves the position of a magnetic pole. 4. The device according to claim 1, characterized in that said induction unit consists of at least one permanent magnet. 5. Apparatus as claimed in claim 2 or 3, characterized in that said means for adjusting the relative strength of said magnetic fields comprises a means for varying the current strength of the current supplied to said induction unit. 6. Apparatus as claimed in claim 2 or 4, characterized in that the means for adjusting the relative strength of the magnetic fields comprises a movable assembly which slides the magnet or electromagnet. 7. Apparatus according to claim 3, characterized in that the means for changing the position of the magnetic poles within the magnetic gap consists of separately adjusting the direct current supplied separately to each phase coil of the inductor (14, 15) The current intensity of the device constitutes. 8. Device according to claim 1, characterized in that said induction unit comprises on each side of the main casting surface (P) two similar bodies (14a, 14b) placed side by side on both sides of the casting axis. 9. Apparatus according to claim 1, characterized in that said buried pouring tube is a type in the main casting surface (P) equipped with a downward main flow outlet (7) towards the bottom of the ingot mold and towards its The pouring pipe of the upper second outlet (8) on the top. 10. Apparatus according to claim 9, characterized in that said buried pouring tube is a straight pouring tube. 11. Method of operating an apparatus for supplying molten metal to an ingot mold of a continuous casting apparatus for products of rectangular cross-section as claimed in claim 1, characterized in that the adjustment by the magnetic pole position of the induction unit is adjusted by the The relative strength of the magnetic field generated by the poles of the sensing unit. 12. Method of operating an apparatus for supplying molten metal to an ingot mold of a continuous casting apparatus for products of rectangular cross-section according to claim 1, characterized in that by varying the current intensity of the current supplied to said induction unit The relative strength of the magnetic field generated by the magnetic poles of the induction unit is adjusted.

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