Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
  • B22D11/0622—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars formed by two casting wheels
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
  • B22D11/0637—Accessories therefor
  • B22D11/068—Accessories therefor for cooling the cast product during its passage through the mould surfaces
  • B22D11/0682—Accessories therefor for cooling the cast product during its passage through the mould surfaces by cooling the casting wheel
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
  • B22D11/001—Continuous casting of metals, i.e. casting in indefinite lengths of specific alloys
  • B22D11/003—Aluminium alloys

Definitions

• the invention relates to the continuous casting of metal strip, in particular aluminum or aluminum alloy.
• the invention relates very particularly to a circuit for cooling cylinders of continuous metal strip casting, in particular making it possible to reduce the thermal ovalization (or runout) appearing in said cylinders during use.
• a continuous metal strip casting machine generally contains at least two identical cylinders (1A and 1B) located face to face, separated by a space (or air gap) E of the thickness of the metal strip to be produced and rotating in opposite directions to each other.
• the metal (2) is fed, in the liquid state, on one side of the space using an injector (6), while the strip (3) comes out on the other side at its thickness rated Eo.
• the metal solidifies between the two cylinders, at what is known as the solidification front (5).
• bands ranging from a few centimeters thick to a few millimeters or less can be produced.
• Figure 2 gives the general structure of a cylinder of the state of the art.
• Figure 2a) corresponds to a cross-sectional representation in the rolling zone (20), that is to say in the part of the cylinder which comprises the hoop.
• FIG. 2b) corresponds to a representation in longitudinal section along the section plane II 'in FIG. 2a).
• a cylinder (1) typically comprises a cylindrical body (10) which, in its central part, is surrounded by a hoop (11) intended to receive the molten metal and used for rolling the strip, and cooling means. It is indeed necessary to effectively cool the rolls during the rolling operation.
• the cooling is usually carried out using a cooling fluid, typically water, circulating in at least one cooling circuit (12) located inside the cylinder body (10).
• This circuit comprises at least a first conduit (13) intended for the supply of cold water (F) and at least a second conduit (14) intended for the discharge of the heated water (C).
• These conduits are essentially in the form of blind holes parallel to the axis (4) of the cylinder which open at one of its ends, the other end being closed, and which extend over the entire length of the hoop (11) .
• a plurality of smaller diameter radial tubes (15, 16) connects each conduit (13, 14) to a corresponding manifold (17, 18) which takes the form of a groove located just below the internal surface of the hoop (11 ) and arranged 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.
• the annular channels and the manifolds are generally machined on the peripheral surface of the cylinder body (10).
• each cold water supply duct (13, 131, 132), as well as the radial tubes (15, 151, 152) and the corresponding distribution manifold (17, 171, 172), constitute a supply circuit. in cold water.
• Figure 3 illustrates the alternation, in the peripheral direction, of the supply and discharge manifolds of the cylinder bodies of the prior art (only a few annular channels (19) have been shown in order to lighten the figure).
• each radial tube simultaneously feeds 5 separate annular channels.
• the cooling water is injected into the circuit by the cold water supply pipes (131, 132, ...), is distributed in distribution manifolds (171, 172, %) via first radial tubes (151, 152, ...), comes into thermal contact with the hoop in line with the collectors (171, 172, ...) and annular channels (19), thus ensuring its cooling, is then collected by evacuation collectors (181, 182, %) via the second radial tubes (161, 162, ...), then is evacuated by the evacuation conduits (141, 142, ... ).
• the arrows in FIGS. 2a) and 2b) indicate the direction of circulation of the cooling fluid.
• the cylinders comprise an identical number of circuits for supplying cold water and circuits for discharging heated water.
• the number of pairs of inlet and outlet pipes is typically two, three or four. These conduits, and the corresponding channels, are arranged symmetrically in the body of the cylinder.
• the case illustrated in FIG. 2 comprises two pairs of circuits which are arranged alternately and which are offset by 90 °. In the case of three or four pairs of circuits, the offset is respectively 60 ° or 45 °.
• the heterogeneity of temperature also changes the effective heat exchange coefficient between the metal and the hoop, which produces a variation in thickness even in the absence of deformation of the cylinder.
• the Applicant has therefore sought effective means, easy to make or implement and inexpensive, which make it possible to eliminate or minimize the temperature differences in the cylinder, so as to improve the quality and regularity of thickness of the casting tape.
• the cylinder body of a continuous casting machine is capable of carrying in its central part, called the rolling zone, a cylindrical hoop and comprises a cooling circuit, which circuit comprises at least one fluid supply pipe for cooling, at least one coolant discharge duct, at least one distribution manifold, at least one discharge manifold, at least one distribution tube connecting each manifold to the corresponding duct, and a plurality of annular channels connecting the supply and discharge collectors, said collectors and annular channels serving to bring the coolant circulating in said circuit into contact with the inner surface of the hoop so as to cool it, and is characterized in that the manifolds are arranged so as to produce an alternation, both in the peripheral direction and in the longitudinal direction, of distribution manifolds and discharge collectors.
• the Applicant has indeed had the idea of modifying the internal cooling circuit of the cylinders so as to allow alternation, preferably close together, of the cold fluid arrival zones F and of the discharge zones of the heated fluid C, in the two directions of the hoop surface, that is to say both in the peripheral direction and in the longitudinal direction.
• the Applicant considers that this particular configuration of the cooling circuit, which does not significantly increase the manufacturing costs of the product, produces an alternation of cold and hot zones under the interior surface of the hoop capable of promoting a significant reduction in temperature heterogeneity. the outer surface of the hoop.
• the Applicant has also evaluated that, surprisingly, the use of a plurality of collectors results in greater uniformity of the flow rate of the cooling fluid in the channels.
• the collectors are in the form of grooves, the length of which is significantly less than the length Lf of the hoop, which are aligned on generators equidistant angularly and which are connected to the conduits d 'supply and evacuation so as to produce a regular network, or even checkerboard, arrangement of the collectors.
• the subject of the invention is also a cylinder of a continuous casting machine comprising a hoop and a cylinder body according to the invention.
• the invention also relates to a continuous casting machine comprising at least one cylinder according to the invention.
• the invention also relates to a method of cooling continuous casting cylinders in which the direction of circulation of the cooling fluid circulating in at least one cylinder of the invention is periodically reversed.
• Figure 1 shows schematically the basic elements of a continuous casting machine.
• FIG. 2 illustrates a cylinder of a continuous casting machine of the prior art.
• FIG. 3 shows flat, for a cylinder of the prior art, the part of the surface of the cylinder body situated under the hoop (rolling zone).
• FIG. 4 shows flat, for a cylinder body according to the invention, the part of the surface of the cylinder body located under the hoop (rolling zone).
• FIG. 5 represents two cross sections of a cylinder body according to the invention passing through the distribution tubes (planes I-I 'and II-II * of FIG. 4).
• Figure 6 shows two longitudinal sections of a cylinder body according to the invention (planes I-I 'and II-II' of Figure 5).
• the elements having the same function are also collectively designated by the generic references of FIG. 6.
• the distribution manifolds (7101, 7102, 7103, ...) can be identified collectively by the reference (70)
• the supply conduits (31, 32, 33, ...) can be identified collectively by the reference (30).
• the body (110) of a continuous casting machine cylinder according to the invention is capable of carrying in its central part, called the rolling zone (20), a cylindrical hoop (111) and comprises a cooling circuit (200), said circuit comprising at least one coolant supply conduit (30), at least one coolant discharge conduit (40), at least one distribution manifold (70), at least one discharge manifold ( 80), at least one distribution tube (50, 60) connecting each manifold to the corresponding conduit, and a plurality of annular channels (90) connecting the supply and discharge collectors, said collectors and annular channels serving to place the cooling fluid which circulates in said circuit in contact with the internal surface of the hoop (111) so as to cool it, and is characterized in that the collectors (70, 80) are arranged so as to produce alternation, at the time in the peripheral direction and in the longitudinal direction, distribution manifolds (70) and discharge collectors (80).
• the collectors are arranged under the surface of the hoop so that they can form, for example, sequences 70/80/70/80 ... both in the peripheral direction and in the longitudinal direction.
• the number of distribution collectors (70) is at least equal to 2 and the number of evacuation collectors (80) is at least equal to 2.
• the number of supply and discharge conduits is preferably even (and typically equal to 2, 4 or 6), which makes it possible to have, during use, a number of conduits supply equal to the number of exhaust ducts.
• the supply and discharge conduits can be arranged alternately on a circle (in cross section); the same is true of the collectors connected to them.
• the number Na of supply conduits (30) is preferably equal to the number Ne of evacuation conduits (40).
• the total number of collectors is an integer multiple M of the total number of conduits. More specifically, it is advantageous that the number of collectors distribution system is an integer multiple M of the number of supply conduits and the number of evacuation manifolds is the same integer multiple M of the number of evacuation conduits, where M is greater than or equal to 2.
• M is greater than or equal to 2.
• the supply (30) and discharge (40) conduits are distinct and separate.
• the conduits are preferably in the form of blind holes substantially parallel to the axis (4) of the cylinder, which open at one of its ends, 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 conduits (30, 40) are preferably at the same distance from the axis (4).
• the circuit according to the invention can comprise any number of pairs of supply and discharge conduits.
• the circuit according to the invention preferably comprises at least two pairs of supply and exhaust pipes offset by an angle ⁇ equal to 360 ° / N , where N is the total number of conduits. For example, if the circuit includes three supply conduits and three discharge conduits, then N will be equal to 6 and the angle ⁇ will be 60 °.
• the collectors (70, 80) typically take the form of an elongated groove situated just below the internal surface (113) of the hoop (111) and the major axis of which is preferably substantially parallel to the axis (4) of the cylinder .
• the number of separate collectors connected to each conduit, which is at least equal to 2 is determined according to of the length of the hoop so as to allow efficient homogenization of the temperature on the external surface (112) of the hoop.
• the collectors (70, 80) are of length much shorter than that (Lf) of the hoop (111), and more precisely of length at most equal to about half that of the hoop. According to the preferred embodiment of the invention, the collectors (70, 80) have substantially the same length Le.
• the manifolds (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 discharge manifold (80) and circulate the cooling fluid in contact with the interior surface (113) of the hoop (111) so as to produce efficient cooling. of it.
• the annular channels (90) are distributed under the surface of the hoop and are preferably equidistant in order to promote greater homogeneity of the cooling.
• the number of annular channels is at least equal to 2.
• the number and the section of the distribution tubes (50, 60) are adjusted so as to ensure a satisfactory pressure drop in the circuit, a satisfactory flow in the annular channels (90) and a specific (generally uniform) distribution of the cooling along the hoop.
• the cross section of the distribution tubes (50, 60) is, for these reasons, preferably less than that of the conduits.
• 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 discharge collector (80) in the longitudinal direction and in the peripheral direction.
• the regularity of the network allows greater control of the temperature uniformity.
• the collectors are preferably arranged in linear rows along a generatrix of the cylinder, that is to say in rows longitudinal.
• the conduits (30, 40) are advantageously connected to collectors (70, 80) of different lines, and preferably connected only to collectors (70, 80) of adjacent lines.
• the number of rows of collectors (70, 80) is advantageously equal to the number of conduits (30, 40), which simplifies the circuit according to the invention.
• the number Ne of separate collectors of a line is determined as a function of the length of the hoop so as to allow effective homogenization of the temperature at the surface of said hoop.
• the length Le of each collector will then be slightly less than Lf / Ne, where Lf is the length of the hoop.
• the collectors in a row are preferably separated by a distance of between 5 and 25% of their length approximately.
• the number of collectors per generator is typically 10 per linear meter.
• the coolant is injected into the circuit through the cold fluid supply conduits (30), is distributed in distribution manifolds (70) via the first distribution tubes (50), comes into thermal contact with the hoop (111) in line with the collectors (70) and the annular channels (90), in line with the interior surface (113) of the hoop (111), thus ensuring its cooling, is then collected by evacuation collectors (80) via the second distribution tubes (60), then is evacuated by the evacuation conduits (40).
• the thermal energy absorbed by the hoop at its outer surface (112), during the continuous casting operation, is thus transmitted to the cooling fluid and evacuated outside the cylinder by the cooling circuit.
• the invention is particularly suitable for casting rolls the hoop of which has a thickness of between 20 and 100 mm.
• the method of cooling the continuous casting cylinders can comprise the use of a cylinder according to the invention and a periodic reversal of the direction of circulation of the fluid.
• the supply conduits periodically become discharge conduits and that the distribution manifolds also periodically become discharge collectors, and vice versa, as described in the application FR 2,723,014.
• the manifolds (70, 80) extend only under a small part of the hoop (11 1) (less than the half its length) and the collectors are distributed over the surface of the cylinder body so as to form rows of collectors which are preferably aligned on a generator and which constitute a regular network of collectors.
• the collectors located on a generator are angularly separated by an angle ⁇ with respect to those of the neighboring generator.
• Figures 4 to 6 illustrate a cooling circuit comprising three supply conduits, three discharge conduits arranged alternately, and 20 collectors per line.
• the separate collectors connected to the cold fluid supply conduit (31) are the collectors (7101, 7102, 7103, ..., 7120)
• the separate manifolds connected to the cold fluid discharge duct (41) are the manifolds (8101, 8102, 8103, ..., 8120), etc.
• Distribution manifolds alternate with exhaust manifolds located on the same generator and on a neighboring generator.
• the angle ⁇ separating two rows of collectors is then 60 °.
• FIG. 4 which gives a deployed view of the part of the surface of the cylinder body situated under the hoop (corresponding to the rolling zone (20)), shows the checkerboard arrangement of the supply and discharge collectors of the cylinder body according to the preferred embodiment of the invention.
• the letters F and C indicate respectively the cold fluid inlet and heated fluid discharge zones.
• annular channels (90) In order to lighten the figures, only a few annular channels (90) have been illustrated.
• the arrows P and L respectively indicate the peripheral directions and longitudinal.
• the numbering of the references to the distribution (70) and evacuation (80) collectors is matrix: the first digit (7 or 8) corresponds to the nature of the collector (supply or evacuation), the second digit corresponds to the conduit (30 or 40) to which the collector is connected, and the third and fourth digits correspond to row i in which the collector locates it.
• the cooling circuit can be broken down into identical slices (or sections), as illustrated in FIG. 5, which are repeated along the cylinder so as to produce an alternation of the pattern of the collectors.
• This configuration makes it possible to connect, alternately, each supply or discharge conduit to corresponding collectors situated on either side of it, so as to form a regular network. The fineness of the mesh of this network is determined by the number of collectors and conduits.
• the conduits are then advantageously offset angularly with respect to the corresponding collectors so as to be located at the same distance from all the collectors to which they are connected.
• the distribution tubes (50, 60) which connect the conduits (30, 40) to the collectors (70, 80), can be inclined by an angle ⁇ relative to a radial axis passing through the conduit or the corresponding collector.
• FIG. 6 represents two longitudinal sections of a cylinder body according to the preferred embodiment of the invention. These sections correspond, respectively, to the planes II 'of FIG. 5a) and II-IT of FIG. 5b). The arrows indicate the direction of circulation of the coolant.
• the collectors (70, 80) preferably have substantially the same length Le, which in particular makes it possible to simplify the design of the cooling circuit.
• the Applicant considers that, with such a configuration, the temperature differences of the surface of the hoop should remain less than 0.5 ° C. with respect to the maximum temperature of this surface, which can be greater than 500 ° C. Under the same conditions, but with a cooling circuit of the prior art, the maximum temperature difference is rather 4 ° C., which causes variations in the thickness of the strip of 0.04 mm attributable to the runout. cylinders.
• the Applicant has also estimated the flow differences 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 supply ducts and three ducts of d 'alternate evacuation, substantially parallel to the cylinder axis and angularly separated by 60 °, and six collectors arranged on 6 generators angularly separated by 60 °.
• a cooling circuit comprising three supply ducts and three ducts of d 'alternate evacuation, substantially parallel to the cylinder axis and angularly separated by 60 °, and six collectors arranged on 6 generators angularly separated by 60 °.
• FIGS. 4 to 6 which comprises, on each of the 6 generators, 23 collectors with a length of 75 mm, a depth of 8 mm and a width 14 mm, which collectors are arranged in rows on the 6 generators, and which includes 3 annular channels for each collector, the plaintiff estimated that the flow was roughly the same in all channels.
• the invention is particularly advantageous for the manufacture of thin strips, that is to say for thicknesses less than 5 mm for which the runout of the cylinder is all the more detrimental the lower the thickness.
• the invention also has the advantage of providing a more uniform mechanical support for the hoop by the presence of discontinuities in the collectors along the latter. This configuration improves the resistance to mechanical fatigue of the frets by limiting the surface of the bending zones.

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• 1999
  • 1999-10-06 FR FR9912655A patent/FR2799399B1/fr not_active Expired - Lifetime
• 2000
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