EP0694356B1 - Method and apparatus for correcting the crown of the rolls in continuous casting of metal strips - Google Patents

Abstract

The cooling of two counter-rotating strip casting rolls, which tend to become oval as a result of unequal cooling of their circumferences and consists of a roll body (1) and a cylindrical shell (2), involves introducing cooling fluid through axial inlet channels (3) passing through radial channels (4) into longitudinal collector grooves (5) and then into circumferential cooling grooves next to the shell (2), through collector grooves (7) and radial channels (8) to reach the outlet channels (9), and leave the roll. By means of a pipe and three-way valve system, the flow direction of cooling fluid is periodically reversed so that the roles of the axial channels (3) and (9) are exchanged. <IMAGE>

Description

TECHNICAL AREA

The invention relates to a method and a device for correcting thermal ovalization (or runout) appearing on cylinders continuous metal strip casting.

STATE OF THE ART

A continuous metal strip casting machine generally contains two identical cylinders located face to face, separated by a space of the thickness of the metal strip to be produced and turning in the opposite direction one of the other.

The liquid metal is fed on one side of the space while the strip comes out on the other side at its nominal thickness.

It is possible to produce with such a device bands ranging from a few centimeters thick to a few millimeters or less.

Figures 1 (longitudinal section) and 2 (cross section) give the general structure of a cylinder.

It includes in (1) a cylinder body (central part) which is surrounded a hoop (2) which receives the molten metal and is used for rolling the bandaged. Therefore it is necessary to cool the whole.

Cooling is usually carried out using a cooling (generally water) circulating in at least one circuit inside the cylinder body (1).

This circuit includes at least one cold water supply hole (3), under shape of a tube drilled in the cylinder body (1), parallel to its axis, opening to the outside by one of its ends, the other being closed, and extending to the right of the hoop (2) over its entire width.

A plurality of smaller diameter tubes (4) connect each hole supply (3) to a distribution manifold (5) sort of groove located under the hoop (2) and substantially parallel to the supply tube (3); each collector supplies water to a cooling device proper comprising a network of small channels (5) machined to the peripheral surface of the cylinder body (1) and located under the hoop in a transverse plane; the water circulates there and comes into thermal contact with the hoop and ensures its cooling.

After the water has heated up, it is removed using a identical to the power supply. It includes (see part low of fig. 1 and fig. 2) a water drain collector (7) hot, a plurality of small diameter tubes (8) connecting it to the tube evacuation (9).

Usually a cylinder body has two or three or four water supply circuits and as many drainage circuits interconnected by the channels (6) of the cooling device. The reciprocal arrangement of the cold and hot water circuits is good visible in particular in fig. 2 which represents the case of 2 circuits. We see their interconnection and their alternate and offset arrangement one relative to the other by 90 °. The arrows illustrate the meaning of water circulation. In the case of three or four circuits, the offset is 60 ° or 45 °

Thus the cold water arriving in one of the distribution collectors (5), is then distributed in the cooling channels (6) located on the on the other side of the collector (5), heats up and is evacuated by the collectors (7) which thus collect water from two collectors distribution (5) located on either side.

A cooling device of this type is described in the patent FR-A-2 217 098. It shows a cylinder comprising a core (1) surrounded a hoop (7), the whole being cooled by a circulation of water in channels (2, 3, 4, 6) formed in said core (1) and opening into grooves (5) located at the core-hoop interface.

With such an arrangement of the cooling circuits, it appears cold and hot zones in the hoop and the cylinder in the vicinity cold water collectors and tubes and water evacuation hot.

This heterogeneity of temperature which can reach 4 ° C causes dilations causing a deformation of the cylinder called ovalization or false round.

This false round will result in cyclic irregularities of the thickness of the cast metal strip and therefore alter its quality; this defect is all the more troublesome the thinner the strip is cast.

It is therefore advisable to eliminate or minimize these temperature differences. to improve the quality and regularity of thickness of the strip casting. Also the Applicant has sought a method and a device aimed at reducing temperature differences in the cylinder which is effective and easy to carry out or to implement and inexpensive.

DESCRIPTION OF THE INVENTION

In a first aspect, the invention is a method of cooling continuous rolls of metal strip using a fluid, said metal cylinders comprising a cylinder body and a metallic hoop consisting essentially of a tube or an envelope metallic, the inner face of which surrounds said body, the other face used to receive liquid metal and to produce the strip by cooperation of two cylinders, said cylinder body comprising at minus a cooling circuit leading to the outside of the body cylinder by two inlet / outlet ends and comprising at least one cold fluid supply device (usually water), a actual cooling device where the fluid is in contact thermal with the underside of the hoop and a device evacuation of the heated fluid in contact with the hoop, characterized in which we periodically reverse the direction of circulation of the fluid in the cylinder body, the cold fluid supply device becoming the hot fluid evacuation device and vice versa.

The invention is particularly suitable for cylinders having the configuration described above using fig. 1 and 2, their body of cylinder with two or three or four feed devices cold water alternated with as many hot water evacuation devices, these devices being offset by 90 ° (two devices), by 60 ° (three devices) or 45 ° (four devices) and connected by a device proper cooling.

Continuous strip casting generally takes place between two cylinders identical, reversing the direction of the coolant according to the invention is advantageously practiced on the two cylinders. Such a process is also applicable to casting on a single cylinder by example, film casting.

The process according to the invention is particularly advantageous when one runs thin strips for example from 1 to 12 mm thick, or even more thin, specifically in the usual range of thickness from 5 to 12 mm where the process is very efficient, or even in the area of the weak thicknesses for example from 1 to 5 mm for which a cylinder runout is all the more harmful as the thickness is low. It is particularly suitable for casting aluminum strip or its alloys.

The frequency of reversing the direction of water circulation must be set in depending on the characteristics of the installation, for example diameter of cylinders, coolant flow etc ...

With the process of the invention, a better smoothing of the temperature heterogeneities in cylinders using frets thick, for example between 20 and 100 mm.

It is better to have supply and evacuation devices identical fluid.

So we manage to limit the maximum temperature difference in a cylinder at a few fractions of ° C, which practically eliminates completely runout and thus improve the consistency of thickness cast tapes.

By way of illustration, the method according to the invention has been applied to a 8 mm thick aluminum strip continuous casting installation, on cylinders with an outside diameter of 96 cm, the hoop of which had a 8 cm thick, and having an internal cooling circuit identical to that given in fig. 1 and 2.

In the absence of a reversal of the direction of the cooling water, it has been measured in normal operation during casting a maximum deviation temperature of 4 ° C, which caused variations in thickness of the 0.04 mm casting strip due to the runout of the cylinders.

After operating with reverse direction of the coolant a the frequency of every 5 minutes and with the same rate as previously, variations in strip thickness were obtained negligible flow (not measurable).

• un bassin tampon contenant ledit fluide,
• au moins une pompe en soutirant le fluide et alimentant un circuit de fluide
• ledit circuit de fluide comprenant une première vanne à trois voies dont une première voie V1 est alimentée par la pompe, optionnellement par l'intermédiaire d'un débimètre B, une deuxième voie V2 est reliée d'une part à une des extrémités dudit circuit de refroidissement d'autre part à une première voie W1 d'une deuxième vanne à trois voies W, une troisième voie V3 est reliée d'une part à l'autre extrémité dudit circuit de refroidissement d'autre part à une deuxième voie W2 de la vanne W, la troisième voie W3 de W étant reliée à un conduit d'évacuation du fluide chaud.

A second aspect of the invention is a device making it possible to invert the direction of circulation of the cooling fluid in at least one cylinder intended for continuous casting, generally of metal strip as described above, that is to say that is to say containing at least one fluid cooling circuit located inside said cylinder, said circuit located in the cylinder opening to the outside at two ends, characterized in that said device comprises:

• a buffer tank containing said fluid,
• at least one pump by withdrawing the fluid and supplying a fluid circuit
• said fluid circuit comprising a first three-way valve, a first channel V1 of which is supplied by the pump, optionally by means of a flow meter B, a second channel V2 is connected on the one hand to one end of said circuit of cooling on the other hand to a first channel W1 of a second three-way valve W, a third channel V3 is connected on the one hand to the other end of said cooling circuit on the other hand to a second channel W2 of the valve W, the third channel W3 of W being connected to a pipe for discharging the hot fluid.

The buffer tank can receive the hot fluid if it is large sufficient to cool it or if it has a autonomous cooling device.

It appears that the valve V is assigned to supply the cylinder with cold fluid, while the valve W is assigned to the evacuation of the fluid warmed up.

The simultaneous operation of the three-way valves makes it possible to reverse the direction of circulation of the fluid in the cylinder without modifying the circuit fluid from the pump and discharge to the basin.

These maneuvers can advantageously be automated or managed by microprocessor, computer ... etc ...

When the casting machine has two cylinders (upper and lower), you can connect the cold fluid supply circuit to the second cylinder in diversion on track V2 or W1 of the valves respective V and W already supplying cold fluid to the first cylinder. Similarly, the hot fluid evacuation circuit can be connected to said second cylinder in diversion on track V3 or W2 of the valves respective V and W which already collect the hot fluid from the first cylinder.

But to have more flexibility of adjustment it is better to use for the second cylinder, a circuit identical to that supplying the first cylinder, these two circuits can be mounted bypass on the pump discharge.

FIG. 3 illustrates a device according to the invention for a casting machine comprising two cylinders: C (upper cylinder), D (lower cylinder).
C1, C2 and D1, D2 represent the input / output ends, interchangeable during the reversal of direction of the fluid, of the fluid cooling circuit located inside each of the cylinders C and D respectively.

• en R, le bassin tampon de fluide de refroidissement,
• en P1 et P2, deux pompes de soutirage branchées en parallèle,
• en A des vannes d'arrêt,
• en V et W les vannes trois voies avec leurs voies respectives V1, V2, V3, W1, W2, W3 ; en particulier on voit que V1 est branchée sur le refoulement des pompes P par l'intermédiaire d'un débimètre D isolé par deux vannes d'arrêt (ce débit-mètre peut être court-circuité par un circuit S), que V2 et W1 sont reliées au point d'entrée/sortie C2 de C tandis que V3 et W2 sont reliées au point d'entrée sortie C1 et que W3 est relié à l'évacuation du fluide qui retourne au bassin R ;
• en V' et W' les repères correspondant au cylindre D ; ils ont les mêmes significations et fonctions que pour le cylindre C.

We also see:

• in R, the cooling fluid buffer tank,
• in P1 and P2, two withdrawal pumps connected in parallel,
• at A stop valves,
• in V and W the three-way valves with their respective channels V1, V2, V3, W1, W2, W3; in particular we see that V1 is connected to the discharge of pumps P via a flow meter D isolated by two stop valves (this flow meter can be short-circuited by a circuit S), that V2 and W1 are connected to the entry / exit point C2 of C while V3 and W2 are connected to the exit entry point C1 and that W3 is connected to the discharge of the fluid which returns to the basin R;
• in V 'and W' the marks corresponding to cylinder D; they have the same meanings and functions as for cylinder C.

Claims (11)

1. Process for cooling rolls for the continuous casting of metal strip by means of a fluid, said metal rolls comprising a roll body (1) and a metal shell (2) consisting essentially of a metal tube or casing of which the internal face surrounds said roll body (1), the other face receiving liquid metal and producing the strip by cooperation of two rolls, said roll body (1) comprising at least one cooling circuit opening at the exterior of the roll body through two inlet/outlet ends and comprising at least one cold fluid supply device, an actual cooling device where the fluid is in thermal contact with the lower face of the shell and a device for the discharge of the fluid which is heated on contact with the shell, characterised in that the direction of circulation of said fluid in the roll body is periodically reversed, the device for the supply of cold fluid becoming the device for the discharge of hot fluid and vice versa.
2. Process according to Claim 1, characterised in that the cold fluid supply device comprises at least one fluid supply tube (3) pierced in the roll body (1) parallel to its axis and opening at the exterior through one of its ends, a plurality of smaller diameter tubes (4) connecting the supply tube (3) to a distributing manifold (5) substantially parallel to said tube (3) and located beneath the shell (2), a cooling device comprising a network of small channels (6) machined at the peripheral surface of the roll body (1) in a plane transversal to its axis and allowing the fluid to make thermal contact with the shell (2), a fluid discharge device identical to said supply device and comprising in succession a discharge manifold (7) connected to a plurality of small diameter tubes (8) themselves connected to a discharge tube (9) opening at the exterior, said cooling device connecting the distributing manifold (5) and the discharge manifold (7).
3. Process according to Claim 2, characterised in that the roll body (1) comprises two fluid supply devices and two discharge devices in alternation and offset by 90°, connected by the cooling devices (6).
4. Process according to Claim 2, characterised in that the roll body (1) comprises three fluid supply devices and three discharge devices in alternation and offset by 60°, connected by the cooling devices (6).
5. Process according to Claim 2, characterised in that the roll body (1) comprises four fluid supply devices and four discharge devices in alternation and offset by 45°, connected by the cooling devices (6).
6. Device for circulating the coolant circulating in at least one roll intended for continuous casting containing at least one cooling circuit, said circuit opening at the exterior through two inlet/outlet ends, in particular suited to put into practice the process according to anyone of claims 1 to 5, characterised in that it comprises a device for reversing the direction of circulation of the coolant.
7. Device according to claim 6, characterised in that it comprises a buffer basin (R), containing said fluid, at least one pump (P) extracting the fluid from it and supplying a fluid circuit comprising a first three-port valve of which a first port V1 is supplied by the pump, a second port V2 is connected on the one hand to one of the ends of said cooling circuit and on the other hand to a first port W1 of a second three-port valve W, a third port V3 is connected on the one hand to the other end of said cooling circuit, and on the other hand to a second port W2 of the valve W, the third port W3 of W being connected to a hot fluid discharge conduit.
8. Device according to Claim 7 characterised in that it comprises two casting rolls of which the inlet/outlet ends of the cooling circuit of each of them branch respectively from the ports V2 or W1 on the one hand and V3 and W2 on the other hand.
9. Device according to Claim 7, characterised in that it comprises two casting rolls, the first being connected to the circuits comprising the three-port valves V and W as mentioned in Claim 4, the second being connected to a second identical circuit comprising three-port valves V' and W', the two said circuits being branched from the output of the pump.
10. Device according to any one of Claims 7 to 9, characterised in that the three-port valves are manipulated simultaneously and are preferably automated.
11. Device according to any one of Claims 7 to 10, characterised in that the cooling circuit of a roll is the one described in Claims 1 to 5.

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