MXPA99007511A - Feeder of molten metal for moulds of continuous casting machines - Google Patents

Abstract

La presente invención proporciona un dispositivo alimentador de metal fundido para moldes de máquinas de colada continua que comprende un cuerpo cilíndrico (1) dentro del cual un conducto (5) de salida principal del metal fundido que viene desde la artesa refractaria se forma al cual se conecta al cuerpo cilíndrico (1) por medio de empalme frustocónico (2) formado integralmente con el cuerpo cilíndrico (1) en el extremo superior del mismo, caracterizado en que el extremo libre (3) del cuerpo cilíndrico (1) es de una forma sustancialmente frustopiramidal y tiene una pluralidad de salida (7, 8, 9, 10, 11) que se comunican con el conducto principal de salida (5).

Description

FUEL METAL FEED DEVICE FOR MOLDS OF CONTINUOUS MACHINE DESCRIPTION OF THE INVENTION The present invention relates to a feeder device of molten metal for molds of continuous casting machines of products of small thickness, and more precisely, to a feeder device of molten metal for molds in continuous casting machines which is suitable for feeding the molten metal in the mold in a uniform manner and transversely to the mold itself. Cast metal continuous casting machines are known which comprise a mold delimited by a pair of cylindrical counter-rotating rollers with horizontal axes and which are or are not in the same horizontal plane, and by two lateral containing end members that contact with the portions end of the rollers. The rollers are generally metallic and are cooled inside by circulating a coolant under pressure (water, for example) are separated to allow continuous casting from the mold of a solidified body REF .: 31104 that has a thickness of a width approximately equal to the length of the rollers where the solidification takes place. Additionally, the mold described in this manner is provided to be fed by a feeder device of molten metal connected to a refractory tundish above the mold. Up to now a great effort has been made by the great installers and steel manufacturers to solve the several problems related to the continuous casting of thin thicknesses of steel alloys, in particular stainless and magnetic steel, the quality of which depends, between other things, of the superficial perfection of the body of the cast piece. In fact, among the most important causes of surface infectiousness in a continuously cast product is the lack of uniformity in the distribution of the molten metal in the mold. This lack of uniformity causes differences in the temperature and flow of material, which in turn has an influence on the cooling rate and the thickness of the product of the cast as well as its structure and surface homogeneity.

In particular, changes in material flow and temperature lead to the following problems: a) surface undulation, which determines a non-horizontal curve of the points where the solidification begins with the subsequent lack of uniformity in the temperatures of the casting product stimulates the increase in surface defectivity, that is, the increase in the density of cracks and surface roughness; b) the inhomogeneous distribution of the temperature in the mold, or that causes longitudinal oscillations in the thickness, also called depressions. The problems mentioned above are perceived much more in the case of continuous casting of thin products. In fact, given the small dimensions of the molds, it is difficult to control the flow and related turbulence as well as the temperature distribution. Different methods and devices have been designed for this purpose. In NL-A-8801101 a pyramid frust is applied at the bottom of an immersion tube, but the walls of the tube do not diverge from each other downwards in the lower portion thereof. In JP-A-03027847 a submerged nozzle is described in which the walls of the lower portion converge downwards. Patent EP 515 075 illustrates a method and an apparatus for the continuous casting of thin metal products. According to the aforementioned patent, the apparatus includes a feeder device for molten metal to the mold comprising an inlet conduit for the molten metal which extends to an outlet opening of the molten metal. The feeder device is characterized in that the conduit has a curved lateral surface suitable for eliminating possible turbulences and discontinuities of the molten metal flow in the mold below it. The solution seems on the one hand, too complex from a mechanical point of view, in view of the need to make the refractory trough connect in an integral manner to a landfill and a split plunger. On the other hand, it does not show good functional requirements, such as the simplicity in the construction of the feeder device, the high reliability, and the easy operation, the ease in preheating the heating device both when it is mounted and when it is out of line and the possibility of moving it, while it is hot, for the operation. The present invention overcomes all the disadvantages mentioned above. In fact, it is the object of the present invention to provide a molten metal feeder device for continuous casting machine molds comprising a cylindrical body, within which a main outlet duct of the molten metal coming from the refractory tundish is formed to which connects the cylindrical body by means of a frustoconical joint, formed integrally with the cylindrical body at the upper end thereof, characterized in that the free end of the cylindrical body is of a frustopyramidal shape with at least two sloping walls that they diverge from each other downwards, and that has a plurality of outputs communicating with the main outlet conduit. Furthermore, according to the present invention, the free end of the cylindrical body has at least two inclined walls that form an angle with the longitudinal axis of the feeder device comprised between 10 ° and 45 °.

Additionally, according to the present invention, at least two outlets of the plurality of outlets have their longitudinal axis that forms an angle with the longitudinal axis of the feeder device comprised between 0 ° and 95 °, and preferably between 65 ° and 95 °. °. Additionally, in accordance with the present invention, the base of the frusto-pyramidal free end of the feeder device may be flat or convex. Additionally, according to the present invention, at least a portion of the longitudinal axis of the plurality of outlets and the longitudinal axis of the feeder device are in the same plane. According to the present invention, when at least two outputs of the plurality of outputs have their longitudinal axes forming an angle with the longitudinal axis of the feeder device comprised between 0 ° and 90 ° each of the longitudinal axes is in an orthogonal plane with the plane containing the longitudinal axes of the remaining outputs and the feeder device. Additionally, according to the present invention the feeder device optionally has the base of its free end that has at least one outlet in the form of a slit. Additionally, according to the present invention, the feeder device is characterized in that it is made of refractory material selected from the group comprising: silicon dioxide, graphite alumina and graphite alumina coated with zirconium. The present invention relates to the use of the feeder device according to claims 11 and 13. The present invention will be illustrated in greater detail in the following by a description of the various preferred embodiments thereof, given as a non-limiting example and with reference to the attached drawings.

Figure 1 is a longitudinal cross-sectional view of a first embodiment of the feeding device, according to the present invention; Figure 2 is a plan view of the bottom of the feeder device of Figure 1; Figure 3 is a cross-sectional, side and longitudinal view of the feeder device of Figure 1; Figure 4 is a longitudinal cross-sectional view of a second embodiment of the feeder device according to the present invention; Figure 5 is a plan view of the bottom of the feeder device of Figure 4; Figure 6 is a longitudinal cross-sectional view of a third embodiment of the feeder device according to the present invention; Figure 7 is a plan view of the bottom of the feeder device of Figure 6; Y Figures 8, 9 and 10 are cross-sectional, longitudinal, planar views of the bottom and longitudinal side views, respectively, of a fourth embodiment of the feeder device according to the present invention.

Now with reference to Figure 1, a cross-sectional, longitudinal view of the feeder device of the present invention is shown according to a first embodiment. The feeder device has a cylindrical body 1 and at the upper end thereof a frustoconical splice 2 of individual piece is formed for correction to a refractory tundish above this (not shown in the Figure). The free end of the feeder device has a portion 3, of a frustopiramidal shape, integral with the cylindrical body 1 and a base 4 of convex shape. The frusto-pyramidal portion 3 has two inclined walls 3a and two substantially vertical walls 3b (not shown in the Figure and illustrated in greater detail below). A main outlet duct 5 is formed for the molten metal inside the cylindrical body 1. The main duct 5 communicates upwards with the outside through an opening 6, and downwards with a plurality of outlets (later described in more detail) communicating outwards. The plurality of outlets is constituted by a pair of openings 7 arranged asymmetrically and having their longitudinal axes forming an angle a with the longitudinal axis of the feeder device. Below each opening 7, two openings 8 and 9 are respectively formed, having a smaller diameter than the openings 7. The openings 8 and 9 have their longitudinal axes forming an angle β and?. respectively, with the longitudinal axis of the feeder device. Additionally, an additional opening 10 is formed in the center of the base 4, which has the same diameter compared to the openings 8 and 9, and is arranged vertically. Additionally, in the portion where two openings 7 are formed, two additional openings 11 are formed (only one of which is shown in the Figure), and having a diameter substantially equivalent to openings 8, 9 and 10, these openings 11 that give the walls 3b of the free end 3 and therefore orthogonally to the walls 3a. In the same way as in the openings 7, also the openings 11 form an angle with the longitudinal axis of the feeder device. Referring now to Figure 2, a plan view of the bottom of the feeder device of Figure 1 is shown. As can best be pointed out, the axes of the openings 1, 8, 9 and 10 are all in the same plan that also contains the longitudinal axis of the feeder device. With reference to Figure 3, a longitudinal cross-sectional view and a side view of the feeder device of Figure 1 are shown. As can best be pointed out, the openings 11 are formed in the walls 3b and have their longitudinal axes at an angle. a with the longitudinal axis of the feeder device and its diameter is substantially equal to the diameter of the openings 8, 9 and 10. Referring now to Figures 4 and 5, a cross-sectional, longitudinal view and a plan view are shown. bottom, respectively, of a second embodiment of the feeder device of the present invention. For the sake of simplicity, the same portions have the same numbers and therefore, their description is omitted since it was previously described. As can be better pointed out in the Figures, the base 4 shows an individual output 12 that is split. Similar to the previous embodiment, the opening 12 is in the same plane as the axes of the openings 7 and the longitudinal axis of the feeder device. Additionally, the openings 7 form an angle a with the longitudinal axis of the feeder device. Referring now to Figures 6 and 7, there is shown a cross-sectional, longitudinal view and a plan view of the bottom, respectively, and a third embodiment of the feeding device of the present invention. For the safety of simplicity, the same portions have the same numbers and, therefore, their description is omitted since it was previously described. As can best be pointed out in the Figures, the base 4 of the free end 3 of the feeder device is flat and has opening pairs 7, 8 and 9 having its longitudinal axes forming angles a, d,,, respectively, with the longitudinal axis of the feeder device. Additionally, an additional opening 10 is formed in the center of the vertically arranged base 4, which has the same diameter compared to the diameter of the openings 8 and 9. It is necessary to specify that, as can be pointed out from the previous Figures, The shape of the cross section of the openings can be circular, elliptical, rectangular, square or polygonal or any other. The arrangement of the openings however is symmetrical in comparison to the longitudinal axis of the feeder device. The direction of the longitudinal axes of each opening pair 7 can be horizontal, inclining downwards or upwards. The number of openings for each wall of the free end, ie the walls 3a and 3b, can be individual and can also be multiple (two, three, four, etc.). the openings 11 with dimensions smaller or equal than the side openings 7 can be provided in the two side walls 3b. In this way, the flow of metal is facilitated. Additionally, the lower openings 8, 9 and 10 can be of different form and number. The lower portion of the feeder device can be curved or flat. The adoption of one or another solution is related on the one hand to * necessary guarantees of resistance that the manufacture must have and on the other hand to the adequate length of the conduits in order to guide the flow. Referring now to Figures 8, 9 and 10, a fourth embodiment of the feeder device according to the present invention is shown. This fourth mode corresponds to an optimal dimensioning of the feeder device. For the dimensioning of the cross sections and lengths of the feeder device, calculations have been made using numeric simulations with a code Thermofluid calculation commercial echanical (PHOENICS of Cham) which utilizes the known formulas of the thermodynamics and therefore not illustrated later for purposes of clarity and simplicity.

According to what was illustrated in the Figures, a table is given illustrating the optimal sizing of the feeder device, in a non-dimensional parametric form.

Table 1 Total height of the power supply device H Height of the frustopyramidal end portion H2 = 0.355 H Height of the lateral openings starting H3 = 0.127 H from below Height of the lower openings starting H4 = 0.101 H from below Height of the frustoconical joint H5 = 0.065 H Height of vertical edge of splice H6 = 0.040 H Height of frustoconical junction within H7 = 0.027 H main conduit Equivalent diameter of main conduit Di 0.087 H Equivalent outside diameter of the body B = 0.137 H cylindrical Width of the lower end of the cylindrical body L = 0.300 H Thickness of the free end of the cylindrical body Bi = 0.125 H Equivalent diameter of the end portion B2 = 0.064 H of the main duct Inner diameter of the frustoconical junction B3 = 0.118 H Equivalent diameter of the lateral outputs D2 = 0.057 H Equivalent diameter of the lower outputs D3 = 0.022 H Radius of curvature of the convex base R2 = 0.250 H Radius of curvature of the end edge R2 = 0.032 H lower Once the optimum sizing is obtained, a prototype was created and tested on a scale model of 1: 1 in a mold and which has been used water as the work fluid. Liquid steel has been chosen as the reference metal fluid. The experimental tests refer to a flow of approximately 10 m3 / h of molten metal with an average flow velocity in the main duct of approximately 1.4 m / s. Additionally, the feeder of molten metal of the present invention device is suitable to be preheated to a temperature of T ?? qu su - 600 ° C and r is Tüquido TlíqUldo the temperature at which begins to solidify the molten metal. Additionally, the feeder device according to the present invention is suitable for feeding a submerged in the bath of molten metal and at a depth equal to a stay between 5 and 120 mm starting from the highest outlet of the feeder pan.

The performance of the feeder device constituted in this way has been compared to a cylindrical feeder device of two outputs with horizontal axis. This performance refers to the level of thermal uniformity, the uniform distribution of the liquid metal, the surface undulation, the flow of hot metal in the side plates and the flow of surface metal. The comparison is given in the following table. Table 2 alal: is the ratio of the maximum difference in temperature in the orthogonal direction between the feeder device of the present invention and the reference case; (b): is the ratio of the standard deviation of the temperature gradient along the longitudinal direction between the feeder device of the present invention and the reference case; (c): is the ratio between the average height of the corrugations that occur with the feeder device of the present invention and the average height of the corrugations that occur in the reference case; (dl: is the ratio of the area of the side walls moistened by the steel to a temperature equal to or greater than the solid temperature increased by 75% by the solid-liquid solidification interval with the feeder device of the present invention and the total area of the lateral retaining wall, therefore, it is compared standardized to the reference case, (e): it is the ratio of the average residence time of the liquid metal in the upper surface around the feeder device (which is the area that has the lower level of the molten metal flow) between a feeder device of the present invention and the reference case As can be noted, the table shows the best performance obtainable with the new feeder device according to the present invention compared to one of reference under the terms of thermal uniformity, surface ripple and metal flow in the upper surface. it is not limited to the modalities described above, but includes any alternative modality within the scope of the appended claims.

It is noted that in relation to this date, the best method known by the applicant to carry out the present invention, is the conventional one for the manufacture of the objects to which it refers.

Having described the invention as above, the content of the following is claimed as property:

Claims (13)

1. Cast metal feeding device for continuous casting machine molds, comprising a cylindrical body within which a main outlet duct is formed for the molten metal coming from a refractory tundish, to which the cylindrical body is connected by means of a frustoconical junction, formed integrally with the cylindrical body at the upper end thereof, characterized in that the lower end of the cylindrical body is of a frustopyramidal shape with at least two sloping walls that diverge from each other downwards and have a plurality of outlets that are communicate with the main outlet conduit.

2. The molten metal feeder device for continuous casting machine molds according to claim 1, characterized in that each inclined wall forms an angle with the longitudinal axis of the feeder device comprised between 10 ° and 45 °.

3. The molten metal feeding device for continuous casting machine molds according to claim 1 or 2, characterized in that at least two outputs of the plurality of output have their longitudinal axes forming an angle with the longitudinal axis of the feeding device comprised between 0 ° _ and 95 °.

4. The molten metal feeder device for continuous casting machine molds according to claim 3, characterized in that the angle is between 65 ° and 95 °.

5. The feeder device of molten metal for molds of continuous casting machines according to any of the preceding claims, characterized in that the ratio between the entrance area and the sum of the exit areas is comprised between 0.4 and 1.1, and in more preferred, between 0.6 and 0.8.

6. The molten metal feeder device for continuous casting machine molds according to any of the preceding claims, wherein the frusto-pyramidal lower end has a flat base.

7. The molten metal feeder device for continuous casting machine molds according to any of claims 1 to 5, characterized in that the frusto-pyramidal lower end has a convex base.

8. The molten metal feeder device for continuous casting machine molds according to any of the preceding claims, characterized in that at least a portion of the longitudinal axes of the plurality of outputs and the longitudinal axis of the feeder device are in the same plane.

9. The molten metal feeding device for continuous casting machine molds according to any of claims 1 to 7, characterized in that at least two outputs of the plurality of outlets have their longitudinal axes forming an angle with the longitudinal axis of the feeder device included between 0 ° and 90 ° and each of the longitudinal axes of at least two outputs are in a plane orthogonal to the plane containing the longitudinal axes of the remaining outputs of the feeder device.

10. The molten metal feeder device for continuous casting machine molds according to any of claims 1 to 5, characterized in that the base of the bottom end of substantially frustopyramidal shape has at least one outlet in a split shape.

11. The molten metal feeder device for continuous casting machine molds according to any of the preceding claims, further characterized in that it is made of a refractory material selected from a group comprising: silicon dioxide, graphite alumina and graphite alumina coated with zirconium.

12. The use of the molten metal feeder device for continuous casting machine molds according to any of the preceding claims, wherein the feeder device is preheated to a temperature comprised between? Liquid _ 600 ° C and? Iquids, the temperature being liquid to which the molten metal begins to solidify.

13. The use of the molten metal feeder device for continuous casting machine molds according to any of the preceding claims 1 to 11, wherein the feeder device for feeding the mold is partially submerged in the molten metal bath and at a depth equal to a distance between 5 and 120 mm starting from the highest outlet of the feeder device.