EP1218128B1 - Continuous casting roll for metal strip comprising a cooling circuit - Google Patents

Description

Field of the invention

The invention relates to the continuous casting of metal strips, in particular aluminum or aluminum alloy. The invention particularly relates to a continuous metal strip casting roll cooling circuit in particular to reduce the oval (or false round) thermal appearing in said cylinders in use.

State of the art

As schematically illustrated in cross-section in FIG. Continuous casting of metal strip usually contains at least two cylinders (1A and 1B) identical face to face, separated by a space (or gap) E of the thickness of the metal strip to be produced and turning in the opposite direction one of the other. The metal (2) is fed, in the liquid state, on one side of the space with the aid of a injector (6), while the strip (3) leaves the other side at its nominal thickness Eo. The metal solidifies between the two cylinders, at what is known as the solidification front name (5).

With such a device, it is possible to produce strips ranging from a few centimeters thick to a few millimeters or less.

Figure 2 gives the general structure of a cylinder of the state of the art. The Figure 2a) corresponds to a cross-sectional representation in the area of rolling (20), that is to say in the part of the cylinder which comprises the hoop. The figure 2b) corresponds to a representation in longitudinal section along the plane of section I-I ' of Figure 2a).

A cylinder (1) typically comprises a cylindrical body (10) which in its part central, is surrounded by a band (11) intended to receive the molten metal and serving rolling the strip, and cooling means. It is indeed necessary to effectively cool the rolls during the rolling operation.

Cooling is usually done using a coolant, typically water, circulating in at least one cooling circuit (12) located inside the cylinder body (10). This circuit includes at least a first conduit (13) for supplying cold water (F) and at least one second conduit (14) for the evacuation of the heated water (C). These conduits present themselves essentially in the form of blind holes parallel to the axis (4) of the cylinder which open at one end, the other end being closed, and extending over the entire length of the band (11). A plurality of radial tubes (15, 16) more small diameter connects each duct (13, 14) to a corresponding manifold (17, 18) which takes the form of a groove located just below the inner surface of the hoop (11) and disposed parallel to the axis (4) of the cylinder. The collectors (17, 18) are connected to a plurality of annular channels (19) located just below the hoop (11) in a plane transverse to the axis (4) of the cylinder. Ring channels and collectors are generally machined at the peripheral surface of the cylinder body (10).

Each cold water supply duct (13, 131, 132) and the radial tubes (15, 151, 152) and the corresponding distribution manifold (17, 171, 172), constitute a cold water supply circuit. Similarly, each conduit for discharging the heated water (14, 141, 142) and the radial tubes (16, 161, 162) and the corresponding exhaust collector (18, 181, 182) constitute a evacuation circuit of the heated water. Figure 3 illustrates the alternation, in the sense periphery, manifolds for feeding and evacuating the cylinder bodies of the prior art (only a few annular channels (19) have been shown in order to lighten the figure). Typically, each radial tube simultaneously feeds 5 channels separate rings.

The cooling water is injected into the circuit via the water supply ducts cold (131, 132, ...), is distributed in distribution manifolds (171, 172, ...) by via the first radial tubes (151, 152, ...), comes into thermal contact with the collar at the right of the collectors (171, 172, ...) and the annular channels (19), thus ensuring its cooling, is then collected by collectors discharge (181, 182, ...) via the second radial tubes (161, 162, ...), and is evacuated through the exhaust ducts (141, 142, ...). Arrows of Figures 2a) and 2b) indicate the flow direction of the cooling fluid.

Usually, the cylinders comprise an identical number of circuits supplying cold water and circuits for discharging the heated water. The number of pairs of supply and discharge ducts is typically two, three or four. These ducts, and the corresponding channels, are arranged symmetrically in the cylinder body. The case illustrated in Figure 2 includes two pairs of circuits which are arranged alternately and which are shifted by 90 °. In the In the case of three or four pairs of circuits, the offset is respectively 60 ° or 45 °.

Problem

With the cooling circuits of the state of the art, there appear zones cold and hot in the fret and in the cylinder in the vicinity of the collectors and channels for supplying cold water and discharging heated water. This heterogeneity temperature, which can reach 4 ° C, causes dilations deformation of the cylinder called ovalization or false round. This fake round is translated by cyclic irregularities in the thickness of the cast metal strip and thereby alters the quality. This defect is all the more annoying that the cast strip is thin.

Temperature heterogeneity also modifies the heat exchange coefficient between the metal and the hoop, which produces a variation of the thickness even in the absence of deformation of the cylinder.

The plaintiff has therefore sought effective means, easy to achieve or implemented and inexpensive, which allow to eliminate or minimize the temperature differences in the cylinder, so as to improve the quality and regularity thickness of the casting tape.

In order to solve this problem, the applicant has proposed in the French application FR 2 723 014 (corresponding to the European patent application EP 694 356 and U.S. Patent No. 5,642,772), to periodically reverse the flow direction of the cooling fluid in the cylinder body, the fluid supply circuit cold becoming the evacuation circuit of the heated fluid and vice versa. The preamble to the attached claims is based on this document. This solution, which can significantly reduce the false circle without having to change the cylinders, however, requires adaptation of the external cooling circuit and of the operating mode of the machine. In particular, the transitional regime and / or the frequency of reversal of the flow direction depend on the nature of the alloy.

The applicant has therefore sought solutions that overcome the disadvantages of the prior art and which make it possible in particular to reduce, or even eliminate, the temperature heterogeneities and thickness variations of the band which in result, especially for cylinders of great length (≥ 2 meters).

Description of the invention

The continuous casting machine cylinder body according to the invention is suitable for carrying in its central part, called the rolling zone, a cylindrical hoop and comprises a cooling circuit, which circuit comprises at least one duct for supplying cooling fluid, at least one discharge pipe of the cooling fluid, at least one distribution manifold, at least one exhaust manifold, at least one distribution tube connecting each manifold to the corresponding conduit, and a plurality of annular channels connecting the collectors supply and discharge, said collectors and annular channels used to put the cooling fluid circulating in said circuit in contact with the inner surface of the hoop so as to cool it, and is characterized in that the collectors are arranged so as to produce an alternation, both in the direction periphery and in the longitudinal direction, of distribution manifolds and evacuation collectors.

The applicant has indeed had the idea to modify the internal cooling circuit cylinders so as to allow an alternation, preferably close, of the zones for the arrival of cold fluid F and zones for evacuating the heated fluid C, in the two directions of the surface of the hoop, that is to say both in the direction peripheral and in the longitudinal direction.

The plaintiff considers that this particular configuration of the circuit of cooling, which does not significantly increase manufacturing costs product, produces alternating cold and warm areas under the inner surface fret capable of promoting a significant reduction in temperature heterogeneity the outer surface of the hoop. The Applicant further assessed that, surprisingly, the use of a plurality of collectors leads to a greater high uniformity of coolant flow in the channels.

According to the preferred embodiment of the invention, the collectors are presented under the shape of grooves, the length of which is significantly less than the length Lf of the fret, which are aligned on equidistant generatrices angularly and which are connected to the supply and exhaust ducts so as to produce a regular network layout, or checkerboard, collectors.

The invention also relates to a continuous casting machine cylinder comprising a hoop and a cylinder body according to the invention.

The invention also relates to a continuous casting machine comprising at least a cylinder according to the invention.

The invention also relates to a method of cooling casting rolls continuously in which the direction of circulation of the fluid of cooling circulating in at least one cylinder of the invention.

figures

Figure 1 schematically shows the basic elements of a machine continuous casting.

Figure 2 illustrates a continuous casting machine cylinder of the prior art.

FIG. 3 represents flat, for a cylinder of the prior art, the part of the surface the cylinder body located under the hoop (rolling zone).

FIG. 4 is a flat representation, for a cylinder body according to the invention, of the part of the surface of the cylinder body located under the hoop (rolling zone).

FIG. 5 shows two cross sections of a cylinder body according to FIG. the invention passing through the distribution tubes (planes I-I 'and II-II' of Figure 4).

FIG. 6 represents two longitudinal sections of a cylinder body according to FIG. the invention (plans I-I 'and II-II' of Figure 5).

Detailed description of the invention

In order to simplify the text, elements with the same function, such as distribution manifolds and supply ducts, are also designated collectively by the generic references of Figure 6. Thus, for example, where no specific element is intended, the distribution manifolds (7101, 7102, 7103, ...) can be identified collectively by reference (70), the conduits (31, 32, 33, ...) can be identified collectively by the reference (30).

The continuous casting machine cylinder body (110) according to the invention is suitable for carry in its central part, said rolling zone (20), a cylindrical hoop (111) and comprises a cooling circuit (200), said circuit comprising at least a cooling fluid supply duct (30), at least one duct for discharging the cooling fluid (40), at least one distribution manifold (70), at least one exhaust manifold (80), at least one distribution tube (50, 60) connecting each collector to the corresponding conduit, and a plurality of channels annuli (90) connecting the supply and the evacuation manifolds, collectors and annular channels used to put the coolant which circulates in said circuit in contact with the inner surface of the ferrule (111) of coolant, and is characterized in that the collectors (70, 80) are arranged in such a way as to produce alternation, both in the peripheral and in the longitudinal direction, distribution manifolds (70) and collectors evacuation device (80).

In other words, the collectors are arranged under the surface of the hoop so as to be able to form, for example, sequences 70/80/70/80 ... both in the direction peripheral and in the longitudinal direction. In order to obtain this alternation, the number of distribution manifolds (70) is at least 2 and the number of collectors discharge (80) is at least 2.

In order to simplify the circuit, the number of supply and exhaust ducts is preferably even (and typically equal to 2, 4 or 6), which makes it possible, when the use, a number of supply ducts equal to the number of ducts discharge. In this way, the supply and exhaust ducts can be arranged alternately on a circle (in cross section); it is the same with collectors connected to them. The number Na of supply ducts (30) is preferably equal to the number Ne of exhaust ducts (40).

Preferably, the total number of collectors is an integer multiple M of the number total of ducts. More specifically, it is advantageous that the number of collectors of distribution is an integer multiple M of the number of supply ducts and that the number of evacuation collectors is the same integer multiple M of the number of exhaust ducts, where M is greater than or equal to 2. This choice makes it possible to simplify the design and practical realization of the cooling circuit. In that case, each supply duct can be connected to M separate distribution manifolds and each exhaust duct may be connected to M separate exhaust manifolds. For example, if the circuit includes three supply ducts and three ducts and if each duct is connected to 6 collectors (M = 6), then the number total of collectors will be 36.

The supply (30) and exhaust (40) conduits are separate and separate. The ducts are preferably in the form of substantially blind holes parallel to the axis (4) of the cylinder, which open at one end, the other end being closed, and which extend over substantially the entire length of the fret (111). It is also advantageous to distribute the conduits (30, 40) symmetrically around the axis (4) of the cylinder. The ducts (30, 40) are of preferably at the same distance from the axis (4). These provisions simplify in particular the manufacture of the cylinder body.

The circuit according to the invention may comprise any number of pairs of supply and exhaust ducts. In order to obtain homogeneity optimum temperature on the surface of the hoop, the circuit according to the invention preferably comprises at least two pairs of feed ducts and evacuated at an angle α equal to 360 ° / N, where N is the total number of ducts. For example, if the circuit includes three supply ducts and three exhaust ducts, then N will be equal to 6 and the angle α will be 60 °.

The collectors (70, 80) typically take the form of an elongate groove located just below the inner surface (113) of the hoop (111) and whose major axis is preferably substantially parallel to the axis (4) of the cylinder. The number of collectors each path, which is at least 2, is determined according to the the length of the hoop so as to allow efficient homogenization of the temperature at the outer surface (112) of the hoop.

The collectors (70, 80) are of much shorter length than the one (Lf) of the fret (111), and more precisely of length at most equal to about half of that of the fret. According to the preferred embodiment of the invention, the collectors (70, 80) have substantially the same length Lc.

The collectors (70, 80) are connected to a plurality of annular channels (90) located just below the surface of the hoop (111) in planes transverse to the axis (4) of the cylinder. These channels connect each distribution manifold (70) to at least one exhaust manifold (80) and circulate coolant in contact with the inner surface (113) of the hoop (111) so as to produce a efficient cooling thereof. The annular channels (90) are distributed under the surface of the hoop and are preferably equidistant in order to favor a more great homogeneity of cooling. The number of annular channels is less than 2.

The number and section of the distribution tubes (50, 60) are adjusted to ensure a satisfactory loss of load in the circuit, a satisfactory flow in the annular channels (90) and a specific (generally uniform) distribution of the cooling fluid along the hoop. The cross section of the tubes of For these reasons, the distribution (50, 60) is preferably smaller than that of the ducts.

According to the invention, the collectors advantageously form a regular network under the surface of the hoop (111), so that each distribution manifold (70) alternates with at least one exhaust manifold (80) in the longitudinal direction and in the peripheral direction. The regularity of the network allows a greater mastery of the homogeneity of the temperature.

In order to simplify the circuit manufacturing, the collectors are preferably arranged in linear rows along a generatrix of the cylinder, that is to say in queues longitudinal. In this case, the ducts (30, 40) are advantageously connected to collectors (70, 80) of different queues, and preferably connected only to collectors (70, 80) of adjacent queues. The number of collector queues (70, 80) is advantageously equal to the number of ducts (30, 40), which makes it possible to simplify the circuit according to the invention.

The number Nc of separate collectors of a queue, which is at least 2, is determined depending on the length of the hoop so as to allow homogenization effective temperature of the surface of said hoop. The length Lc of each collector will then be slightly less than Lf / Nc, where Lf is the length of the fret. In order to simultaneously ensure a smooth cooling of the hoop and a effective complementary mechanical support, the collectors of a line are preferably separated by a distance of between 5 and 25% of their length. The number of collectors per generator is typically 10 per linear meter.

The cooling fluid is injected into the circuit by the supply ducts in cold fluid (30) is distributed in distribution manifolds (70) by via the first distribution tubes (50), comes into thermal contact with the hoop (111) at the right of the collectors (70) and the annular channels (90), at the right of the inner surface (113) of the hoop (111), thus ensuring its cooling, is then collected by evacuation manifolds (80) via the second distribution tubes (60), and is evacuated through the exhaust ducts (40). energy heat absorbed by the hoop at its outer surface (112), when the continuous casting operation is thus transmitted to the cooling fluid and discharged outside the cylinder by the cooling circuit.

The invention is particularly suitable for casting rolls whose hoop has a thickness between 20 and 100 mm.

In order to increase the homogeneity of the temperature, the method of Continuous casting roll cooling may include the use of a cylinder according to the invention and a periodic inversion of the direction of circulation of the fluid in the cylinder circuit, that is to say that the supply ducts become periodically exhaust ducts and that the distribution manifolds also become periodically evacuation collectors, and vice versa, as described in the application FR 2 723 014.

Preferred embodiment of the invention

In the preferred embodiment of the invention, a particular case of which represented in FIGS. 4 to 6, the collectors (70, 80) extend only under a weak part of the hoop (111) (less than half its length) and the collectors are distributed on the surface of the cylinder body so as to form lines of collectors which are preferably aligned on a generator and which constitute a regular network of collectors. Collectors located on a generator are separated angularly at an angle α relative to those of the neighboring generator.

Figures 4 to 6 illustrate a cooling circuit comprising three ducts three alternating evacuation pipes and 20 collectors by file. The number of aligned collector queues is then equal to the total number of N = 6. In this case, for example, the separate collectors connected to the cold fluid supply duct (31) are the collectors (7101, 7102, 7103, ..., 7120), the separate manifolds connected to the cold fluid discharge duct (41) are collectors (8101, 8102, 8103, ..., 8120), etc. Distribution manifolds alternate with exhaust manifolds located on the same generator and on a neighboring generator. The angle α separating two rows of collectors is then 60 °.

Figure 4, which gives an unfolded view of the part of the body surface of cylinder located under the hoop (corresponding to the rolling zone (20)), shows the checkerboard layout of the supply and removal manifolds of cylinder according to the preferred embodiment of the invention. The letters F and C indicate the zones of arrival of cold fluid and discharge of fluid respectively warmed. In order to lighten the figures, only a few annular channels (90) have been illustrated. The arrows P and L respectively indicate the peripheral and longitudinal. The numbering of the references to the distribution manifolds (70) and evacuation (80) is matrix: the first digit (7 or 8) corresponds to the nature of the collector (supply or discharge), the second digit corresponds to the duct (30 or 40) to which the collector is connected, and the third and fourth digits correspond to the row i in which the collector is located. For example, the reference exhaust manifold 8302 is connected to the exhaust vent of reference 43 and is in the row i = 2.

FIG. 5 represents a cross-section of a cylinder body corresponding to this embodiment of the invention. Figures Sa) and 5b) correspond respectively to the sectional planes I-I 'and II-II' of Figure 4, and more generally to even (i = 2, 4, 6, ...) and odd (i = 1, 3, 5, ...) alternations of the collectors connected to each conduit (to the references that must be incremented accordingly, i.e., for example, reference 7101 of Figure 5b) will become the reference 7103 for the cut corresponding to i = 3, the reference 7105 for cutting corresponding to i = 5, etc.).

In this embodiment, the cooling circuit can be decomposed into identical slices (or sections), as shown in Figure 5, which are repeated along of the cylinder so as to produce an alternation of the pattern of the collectors. This configuration allows to connect, alternately, each supply duct or evacuation to corresponding collectors located on either side of it, to form a regular network. The fineness of the mesh of this network is determined by the number of collectors and conduits.

As shown in Figure 5, the ducts are then advantageously offset angularly with respect to the corresponding manifolds so as to be located at the same distance from all collectors to which they are connected. In this case, the tubes of distribution (50, 60), which connect the conduits (30, 40) to the collectors (70, 80), can be inclined at an angle β with respect to a radial axis passing through the duct or the corresponding collector.

FIG. 6 represents two longitudinal sections of a cylinder body according to FIG. preferred embodiment of the invention. These cuts correspond, respectively at the planes I-I 'of Figure 5a) and II-II' of Figure 5b). The arrows indicate the flow direction of the coolant.

In this embodiment, the collectors (70, 80) preferably have substantially the same length Lc, which makes it possible in particular to simplify the design of the circuit cooling.

The Applicant believes that, with such a configuration, temperature differences the surface of the hoop should remain below 0.5 ° C compared to the maximum temperature of this surface, which may be greater than 500 ° C. In the same conditions, but with a cooling circuit of the prior art, the gap maximum temperature is rather 4 ° C, which causes variations thickness of the 0.04 mm band due to the roundness of the cylinders.

The applicant also estimated the differences in flow between the channels in the case of typical cylinders comprising a hoop having a diameter of 1150 mm and a thickness of 80 mm, and a cooling circuit comprising three ducts three alternate discharge ducts substantially parallel to each other. the axis of the cylinder and angularly separated by 60 °, and six collectors arranged on 6 generators angularly separated by 60 °. In one case, corresponding to art of a cylinder comprising 17 radial tubes and 85 annular channels (ie 5 annular channels for each radial tube), and whose collectors typically have a length of 2050 mm, a depth of 10 mm, a width of 20 mm, the plaintiff considered that the flow of the channels close to the radial tubes was about twice that of the most distant channels of radial tubes. In typical configuration of the invention, as illustrated in FIGS. 4 to 6, which comprises on each of the 6 generators, 23 manifolds with a length of 75 mm, one depth of 8 mm and a width of 14 mm, which collectors are arranged in 6 generators, which includes 3 ring channels for each collector, the plaintiff considered that the debit was substantially the same in all channels.

Advantages of the invention

The invention is particularly advantageous for the manufacture of thin strips, that is to say for thicknesses less than 5 mm for which the false round of cylinder is all the more detrimental as the thickness is small.

The invention also has the advantage of providing more mechanical support uniformity of the fret by the presence of discontinuities in the collectors along it. This configuration improves the resistance to mechanical fatigue of the frets limiting the surface of the flexion zones.

Claims (15)

1. Roll body (110) for a continuous casting machine able, in its central part the so-called rolling zone, to carry a cylindrical shell (111) and comprising a cooling circuit (200), said circuit comprising at least one cooling liquid supply conduit (30), at least one cooling liquid evacuation conduit (40), at least one distribution collector (70), at least one evacuation collector (80), at least one distribution pipe (50, 60) connecting each collector to the corresponding conduit, and a plurality of ring channels (90) connecting the supply and evacuation collectors, said collectors and ring channels being used to place the cooling liquid circulating in said circuit in contact with the inner surface of the shell (111) such as to cool the shell, said body being characterized in that the collectors (70, 80) are arranged such as to produce both in the peripheral direction and in the longitudinal direction an alternation of distribution collectors (70) and evacuation collectors (80).
2. Body according to claim 1, characterized in that the total number of said conduits (30, 40) is even, preferably equal to 2, 4 or 6.
3. Body according to claim 1 or 2, characterized in that the total number of collectors (70, 80) is a whole multiple M of the total number of conduits (30, 40), M being 2 or more.
4. Body according to claim 3, characterized in that each supply conduit (30) is connected to M separate distribution collectors (70), and in that each evacuation conduit (40) is connected to M separate supply collectors (80).
5. Body according to claims 1 to 4, characterized in that the collectors (70, 80) are in the shape of elongated grooves.
6. Body according to claim 5, characterized in that the collectors (70, 80) are of substantially the same length Lc.
7. Body according to claim 5 or 6, characterized in that the major axis of the collectors (70, 80) is substantially parallel to the axis (4) of the roll.
8. Body according to any of claims 1 to 7, characterized in that the collectors (70, 80) form a regular network below the surface of the shell (111).
9. Body according to claims 1 to 8, characterized in that the collectors (70, 80) are arranged in longitudinal rows below the shell (111).
10. Body according to claim 9, characterized in that the supply conduits (30) and evacuation conduits (40) are respectively connected to distribution collectors (70) and evacuation collectors (80) in different rows.
11. Body according to claim 9 or 10, characterized in that the conduits (30, 40) are solely connected to collectors (70, 80) in adjacent rows.
12. Body according to any of claims 9 to 11, characterized in that the number of rows of collectors (70, 80) is equal to the total number of conduits (30, 40).
13. Roll of a continuous casting machine comprising a shell (111) and a body (110) according to any of claims 1 to 12.
14. Continuous casting machine comprising at least one roll according to claim 13.
15. Method for cooling continuous casting rolls characterized in that the direction of circulation of the liquid in the cooling circuit (200) of at least one roll according to claim 13 is periodically reversed.

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