MXPA97007339A - Method for obtaining vibrations in the walls of the crystallizer of an ingot mold by means of actuators and the relat device - Google Patents

Abstract

A method for obtaining vibrations in the walls of the crystallizer (11) in an ingot mold (810) by means of actuators, the ingot mold (10) including a channel element (13) for the circulation of cooling liquid, being the ingot mold (10) associated with a conventional oscillation system inducing on the crystallizer (11) vibrations of a small amplitude and a high frequency and acceleration, obtained by means of the excitation of an actuator (16) comprising an element of magnetostrictive alloy (18), configured in cooperation with at least one face of the crystallizer (119 itself, the element being in magnetostrictive alloy (18) associated with the element (19) to generate an electric field.) A device for obtaining vibrations in the crystallizer walls (11) of an ingot mold (10) by means of actuators, including the ingot mold (10) at least one channel (13) for the circulation of liquid or cooling, defined between an intermediate wall (12) and the external face of the crystallizer (11), the ingot mold (10) being associated with a conventional vertical oscillation system, in cooperation with at least one wall of the crystallizer (11). ), including at least one actuator (16) comprising an element (18) made of a manetostrictive alloy, associated with the element (19) to generate a magnetic field.

Description

METHOD FOR OBTAINING VIBRATIONS BN THE WALLS OF THE CRYSTALLIZER OF AN INGOT MOLD BY MEANS OF ACTUATORS AND THE RELATIVE DEVICE This invention relates to a method for obtaining vibrations in the walls of the crystallizer of an ingot mold by means of actuators, and also to the relative device, as stipulated in the respective main claims. The invention is applied in the field of continuous casting of ingots, chiggers, or plates of any type or section, in order to reduce friction between the molten product and the walls of the crystallizer, thereby allowing the speed to increase of the foundry, and reducing the risk of breakage in the skin of the product that is being formed. The crystallizers to which the invention can be applied are those having a thick wall, or a medium wall, or a thin wall, and also those for plates with short movable walls, to vary the width of the plate. The state of the art covers attempts to reduce the force required to extract the molten product from inside the crystallizer, and the problems related thereto. Because it is well known that the skin, as it solidifies, at least at the top of the crystallizer, tends to adhere to the walls, generating considerable friction during the extraction step. In order to facilitate the separation of the skin from the walls, the state of the art includes the generation of vertical mechanical oscillations on the mold of the ingot, which facilitate the extraction of the product, and consequently, make it possible to increase the speed of the casting, and improve the surface quality of the product that comes out of the crystallizer. It is also well known that, at the bottom of the crystallizer, the skin, which has now solidified, tends to separate from the walls, creating an air gap that causes a reduction in the heat exchange between the cooled wall and the wall. the solidified skin, and consequently, a reduction in the heat flow removed from the molten metal through the crystallizer wall. The present applicants, in their application for a European Patent Number EP-A-0686445, described the use of a thin walled crystallizer associated with a method for controlling deformations of the walls; In this invention, the pressure of the cooling fluid flowing in the transit channel adjacent to the side walls is regulated to compensate for the different shrinkage of the skin of the molten product along the crystallizer, in accordance with the type of steel and with the speed of casting. According to this document, the walls of the crystallizer take on an elastic quality, depending on the different pressures of the cooling liquid that flows inside them, in such a way that, in the first segment of the crystallizer, the negative thinning induced by the thermal field, and in the lower part of the crystallizer, it minimizes the air gap created between the solidified skin and the walls.These pressures are calculated in such a way as to obtain the desired deformation of the walls, and to be kept substantially constant , until the parameters of the casting are changed, particularly the type of steel and the speed of the casting The present applicants, with this invention, have set themselves the goal of 'obtaining a solution which can be applied substantially to any kind of crystallizer , that provides advantages by reducing the force required to extract the product, reducing the adhesion in between the skin and the walls, the reduction of the friction force between the crystallizer wall and the molten product, and also increase the surface quality and other advantages; for this purpose, the present applicants have designed, tested, and incorporated this invention.

This invention is stipulated and characterized in the respective main claims, while the dependent claims describe variants of the idea of the main mode. The purpose of the invention is to provide a method for obtaining the desired vibrations in the specific walls of the crystallizer by means of actuators, vibrations that will make it possible to reduce the friction between the crystallizer wall and the molten product, and consequently, will make it possible to reduce the force required to extract the molten product from the crystallizer. A further purpose of the invention is to obtain a consequent increase in the surface quality of the molten product thus obtained. Moreover, the invention encourages the separation of the metal in the upper part of the crystallizer, reducing friction due to adhesion, and also reducing the risk of deterioration in the surface of the molten product due to its scraping along the walls. According to the invention, in cooperation with at least one of the walls of the crystallizer, there are magnetostrictive actuators suitable for generating the desired vibrations of a small amplitude and a high frequency and acceleration on the walls with which they are associated.

The frequency, acceleration, and amplitude characteristics of the induced vibrations are such that they assist the continuous separation of the skin of the molten product from the crystallizer wall, as soon as the skin begins to adhere to the wall. Magnetostrictive materials have the property that they can suffer transient mechanical deformations if they are subjected to a magnetic field, or produce a magnetic field if they are subjected to mechanical deformation. In other words, these magnetostrictive materials represent, in the magnetic field, what piezoelectric materials represent in the electric field. Accordingly, the SP magnetostrictive alloy can be used efficiently to achieve actuators with a much higher performance than the acciiaries using piezoelectric materials. In particular, these actuators respond very quickly to stimuli, have a high energy density and low losses, are activated with low working voltages, and contain a high resistivity. A typical application of magnetostrictive actuators used in applications of the invention, is to obtain a force produced between 4 and 30 kN in a frequency range between 0.1 and 20 kHz with a maximum acceleration of 3,000 g, and a maximum displacement of approximately 0.2 mm , for a maximum supply current of approximately 145 A. Moreover, the size of these actuators is extremely small. The magnetostrictive actuators work on the principle that a rod made of a magnetostrictive alloy brought into contact, directly or by means of an intermediate oppression element, with the wall of the crystallizer, and subjected to a magnetic field, is mechanically deformed, and consequently, it induces a vibration in the wall itself. The walls of the crystallizer can be vibrated by means of these actuators in a plurality of different ways. One method is to apply a transverse excitation by means of the actuators, exploiting the elastic properties of the crystallizer, which is left free to vibrate. According to the shape of the crystallizer segment, the distribution of the actuators may be: an actuator for each wall or face of the crystallizer, or two actuators associated with the opposite faces of the crystallizer. According to a variant, there are groups of actuators configured along the axis of the crystallizer, and each group cooperates with one face thereof, in order to distribute the effect over the entire length of the crystallizer. In accordance with this solution, the excitation of the walls of the crystallizer is achieved by inducing vibrations that are coherent with the crystallizer's own frequencies. According to a variant, the excitation of the walls of the crystallizer is achieved by the induction of vibrations that are not coherent with the crystallizer's own frequencies. The solution of exciting the crystallizer's own frequencies is convenient from the point of view of saving energy, in which a small amount of energy is sufficient to obtain a considerable vibration effect. Still, from the mechanical point of view, it is possible to determine the deformation characteristics associated with the crystallizer's own frequencies, which better satisfy the vibration needs. In this case, it is possible to select the individual frequencies, or their linear combinations, which have nodes and antinodes in fixed and convenient positions for the casting process. According to this modality, it is also possible to excite the crystallizer with a series of its own frequencies, in such a way that the nodes and the antinodes do not remain fixed for a period of time, but create an effect of migration along the crystallizer .

According to the invention, the number and position of the actuators along the crystallizer are determined by the type and number of the crystallizer's own frequencies to be excited. According to a variant, there is a computerized system of supervision and retroactive intervention to obtain the induced vibration at the desired frequencies. The variant can be used where the own frequencies of the dristallizer are not induced when it is necessary to obtain a vibration located in the crystallizer, for example, when it is necessary to excite only the upper part of the crystallizer, where the adhesion of the molten product is greater. the crystallizer wall. According to this embodiment, the range of frequencies that can be used is between approximately 0.1 and approximately 20 kHz, while the maximum amplitude of the vibrations is approximately 0.20 millimeters. In a second embodiment of the invention, the magnetostrictive actuators are configured in such a way as to induce a transverse vibration in the crystallizer, which is restrained on the sides by elastic supports. In this embodiment, the crystallizer is anchored to the external wall of the mold of the ingot by means of elastic supports, which allow a rigid movement in one of the two directions transverse to the vertical, and perpendicular to the wall of the crystallizer itself. By using one or more magnetostrictive actuators suitably configured in contact with the wall of the crystallizer and transverse to it, it is possible to induce transverse vibrations on the crystallizer, in such a way as to make it oscillate as a rigid body. This solution has the advantage, from the mechanical point of view, that it does not stress the structure of the crystallizer directly, but that it discharges at least part of the stresses towards the suitably selected elastic system. In this case, the range of frequencies that can be used is between approximately 0.1 and approximately 20 kHz, while the maximum amplitude of the vibrations is approximately 0.08 millimeters. In accordance with a further embodiment of the invention, the magnetostrictive actuators are configured in such a way as to induce a vertical vibration on the crystallizer that overcomes the induced oscillations in a manner known in the state of the art, in the molds of ingots that contain the crystallizer. In this case, the magnetostrictive actuators constitute a system that causes a vertical oscillation of the crystallizer itself with respect to the mold of the ingot, which in turn is oscillating vertically in a known manner. The vertical oscillation induced on the crystallizer by the magnetostrictive actuators has high frequency parameters, for example, between approximately 1 and approximately 20 kHz, with an extremely small amplitude, of approximately 0.03 millimeters maximum. Considering the ingot-crystallizer mold system as a whole, a high frequency and low amplitude oscillation is obtained in this case, which is caused by the direct action of the magnetostrictive actuators on the crystallizer, modulated at a low frequency, until approximately 5 Hz, by the main oscillation of high amplitude, of up to 6 millimeters, generated on the ingot mold. The attached figures are given as a non-restrictive example, and show some preferred embodiments of the invention as follows: Figure 1 shows a partial section along a diagram of an ingot mold, where the method is applied to obtain vibrations according to the invention. Figure Ib shows an amplified detail A of the Piguaya la. Figure 2 shows an embodiment of the invention in the form of a diagram and partially in section throughout. Figure 3 shows the embodiment of Figure 2 in a cross section. Figures 4a and 4b show, in two embodiments, a variant of the invention. Figure 5 shows a further variant of the invention. Figures 6 and 7 show partially and in diagram form, two additional embodiments of the invention. The ingot mold 10 shown in Figure 1 comprises a crystallizer 11 inside which molten metal 23 is emptied by means of a nozzle 24 located below the meniscus 25. As already said, the crystallizer 11 may have stationary or movable walls, and the walls may be of a normal thickness or a thin thickness. Subsequently, the invention is shown using a crystallizer with stationary walls, but the invention can be easily transferred to a crystallizer with movable walls. In this case, the ingot mold 10 includes intermediate walls 12 configured outside the crystallizer 11, and defining with it, the channel 13, where the cooling liquid flows. The intermediate layer may be angled at right angles to the crystallizer 11, to achieve a transit channel 13 with a variable cross section according to the desired cooling parameters. The channel 13 is connected to an inlet 17a and an outlet 17b for the cooling liquid, and cooperates, outside the intermediate wall 12, with a chamber 14, for introducing / discharging the liquid, defined by an external wall 15. In this case, in cooperation with at least one face of the crystallizer 11, there is a magnetostrictive actuator 16, which includes at least one oppression element 116 located substantially in contact with the face of the crystallizer 11 .. The oppression element 116 is placed in contact with the wall of the crystallizer 11, passing through an opening made at least in the intermediate wall 12, and its back part is anchored, in this case, to the outer wall 15. According to a variant, the magnetostrictive actuator 16 is placed outside the outer wall 15, and the oppression element 116? passes through the walls 15 and 12. • In the embodiment shown in Figures 2 and 3, there is a magnetostrictive actuator 16 in correspondence with two opposite faces of the crystalliser 11, while, in the embodiment shown in Figure 6, they are the magnetostrictive actuators 16 in cooperation with the four faces of the crystallizer 11. The embodiment shown in Figure 7 includes several magnetostrictive actuators, in this case 16a and 16b, at different heights along the length of the crystallizer 11, in order to distribute its effect over a vast area i of the crystallizer 11, possibly with different functional parameters according to the different behavior of the molten product at different heights of the crystallizer 11. The magnetostrictive actuator 16 is composed, in the case shown in Figure Ib, of a rod 18 of magnetostrictive alloy configured coaxially with the oppression element 116, around which there is a bovine 19 which, when activated by the current passing through it, is suitable for inducing a field magnetic. When activated, according to the working parameters, this magnetic field causes controlled mechanical deformations of the magnetostrictive rod 18 such that generate, through the oppression element 116, a consequent vibration in the wall of the crystallizer 11. The magnetostrictive actuator 16 it also comprises a cooling circuit with water 22 for cooling the coils 19 during the operating cycle. In accordance with the embodiment shown in Figures la, Ib, 2, 3, 6, and 7, vibrations are induced on the crystallizer 11 in a transverse direction, in order to exploit the elastic properties thereof, since the crystallizer 11 itself is free. to oscillate. These vibrations, which act on the feeding parameters of the bovine 19, on the size of the magnetostrictive rod 18, on the length of the oppression element 116, and on other parameters, can be obtained, according to the need, by means of the excitation of the vibration frequencies of crystallizer 11, or not exciting these frequencies. In accordance with the embodiment shown diagrammatically in Figures 4a and 4b, the crystallizer 11 is limited, on one or more sides, to the rigid support 26 of the ingot mold 10, by means of the elastic supports 27. These elastic supports 27, according to their configuration, make it possible to move the crystallizer 11, in two directions, indicated by the reference numbers 28 and 29, respectively, in Figures 4a and 4b, transversely to the vertical, and at right angles to the wall of the crystallizer 11 itself. In this case, by exciting one or more magnetostrictive actuators 16, the crystallizer 11 is oscillated transversely as a rigid body, and still more, when at least part of the stresses are discharged on the elastic supports 27, and more generally on the crystallizer support system 11. In accordance with the additional embodiment shown in Figure 5, the magnetostrictive actuators are configured vertically on the crystallizer 11, in this case in cooperation with its lower part, and induce vertical oscillations on this base; these vertical oscillations, referenced by the number 20, overlap in the high amplitude and low frequency oscillations, references by the number 21, generated by the oscillation system of the ingot mold 10, which is known in the state of the art. According to a variant, the actuators 16 are configured to cooperate with the wall of the crystallizer 11 at a desired angle. In this case, a global system of vertical oscillation is obtained, which is generated by the magnetostrictive actuators 16, and which includes characteristics of small amplitude and high frequency and acceleration, modulated at a lower frequency by the system of vertical oscillation of the mold of ingot 10.

Claims (8)

1. A method for obtaining vibrations in the walls of the crystallizer (11) of an ingot mold (20), by means of actuators, the ingot mold (10) including a channel element (13) for the circulation of the cooling liquid, the ingot mold (10) being associated with a conventional vertical oscillation system, the method being characterized in that vibrations of small amplitude and high frequency and acceleration are induced on the crystallizer (11) by means of the excitation of an actuator (16) comprising an element made of a magnetostrictive alloy (18) configured in cooperation with at least one face of the crystallizer (11) itself, the magnetostrictive alloy element (18) being associated with an element (19) to generate an electric field. A method as in claim 1, wherein transverse vibrations are induced on the crystallizer (11), which are generated by the magnetostrictive actuators (16) configured at right angles to the longitudinal axis of the crystallizer (11), and associated with at least one face of the crystallizer (11). A method as in claim 1 or 2, wherein vertical vibrations are induced on the crystallizer (11), which are generated by the magnetostrictive actuators (16) which act parallel to the longitudinal axis of the crystallizer (11), and associated with the crystallizer (11). ' A method as in claim 1 or 2, wherein vertical vibrations are induced on the crystallizer (11), the vertical vibrations being generated by magnetostrictive actuators (16) acting at an angle with respect to the longitudinal axis of the crystallizer (11), and associated with the crystallizer (11). A method as in claim 1 or 2, wherein transverse vibrations are obtained, exploiting the elastic properties of the crystallizer (11), by means of the excitation of at least one magnetostrictive actuator (16) associated with one or more walls of the crystallizer ( eleven) . 6. A method as in any of the preceding claims, wherein the crystallizer (11) is free to oscillate. 7. A method as in claims 5 or 6, wherein the parameters with which the magnetostrictive actuator (16) is excited, induce in the crystallizer (11) its own vibration frequencies of the crystallizer (11) itself. A method as in claim 5, wherein the parameters with which the magnetostrictive drive (16) is excited, induce in the crystallizer (11) different frequencies from, and not coherent with, the vibration frequencies of the crystallizer (11) same. 9. A method as in any of claims 5 to 8 inclusive, wherein the range of frequencies that may be used, varies from about 0.1 to about 20 kHz, while the maximum amplitude of the vibrations of about 0.20 millimeters. A method as in any of the previous claims, wherein the transverse vibrations are obtained by the excitation of at least one magnetostrictive actuator (16) associated with at least one wall of the crystallizer (11), the crystallizer (11) being limited to support (26) of the ingot mold (10) by the elastic element (27), and being free to oscillate as a rigid body in one or the other of the two directions (28, 29) transverse to the vertical, and in Right angles to the crystallizer wall (11). Z.l. A method as in claim 10, wherein the range of frequencies that can be used varies from about 1 to about 20 kHz, while the maximum amplitude of the vibrations is about 0.20 millimeters. 1

2. A method as in any of the preceding claims, wherein the vertical vibrations generated by the magnetostrictive actuators (16) associated with the base of the crystallizer (11) are high frequency, included in a range between approximately 1 and approximately 20 kHz, and a limited amplitude of approximately 0.03 millimeters, and are modulated in low frequency by the vibration generated by the vertical oscillation system of the ingot mold (10). 1

3. A device for obtaining vibrations in the walls of a crystallizer (11) of an ingot mold (10), by means of actuators, including the ingot mold (10) at least one channel (13) for the circulation of liquid of cooling, defined between an intermediate wall (12) and the external face of the crystallizer (11), the ingot mold (10) being associated with a conventional vertical oscillation system, the device being characterized in that, in cooperation with at least one wall of the crystallizer (li), there is at least one actuator (16) comprising an element (18) made of a magneto-entree alloy associated with the element (9), to generate an electric field. A device as in claim 13, wherein the at least one magnetostrictive actuator (16) is configured transversely with respect to the wall of the crystallizer (11) (Figures la, Ib, 2, 3, 4, 6, 7) . 15. A device as in claim 13, wherein the at least one magnetostrictive actuator (16) is configured parallel to the vertical axis of the crystallizer (11), and cooperates with the crystallizer (11) itself. 16. A device as in any of claims 13 to 15 inclusive, wherein the magnetostrictive actuator (16) includes an oppression element (116) coaxial with the magnetostrictive alloy element (18), and configured in contact with the wall of the crystallizer (11), which passes through an opening made at least in the intermediate wall (12). A device as in any of claims 13 to 16 inclusive, wherein there is a plurality of magnetostrictive actuators (16a, 16b) configured at different heights along the crystallizer (11). 18. A device as in any of claims 13 to 16 inclusive, wherein there is a plurality of magnetostrictive actuators (16a, 16b) configured in different positions on the periphery of the crystallizer (11).