EP0066524B1 - Process and apparatus for continuous casting with a grooved casting wheel - Google Patents

Abstract

A method and apparatus are set forth relating to casting of metals with a high melting point utilizing a casting wheel having a grooved rim into which liquid metal is introduced. The metal is sealed during solidification by means of movable flaps which move with the wheel during its rotation. Cooling device and device for positioning of the flaps are provided and the apparatus provides for manufacture of bars or strips of ferrous or non-ferrous metals which are free from sharp edges and burrs.

Description

The method and the device, which are the subject of the invention, relate most generally to the continuous casting of metals on wheels.

This method and this device allow the continuous casting of metals or alloys in the form of bars or strips. This process applies to a very wide range of metals or alloys. Although it can be used effectively for the casting of relatively low melting point metals such as aluminum, it is particularly suitable for the casting of high melting point metals such as copper and its alloys and, above all, all ferrous alloys, ordinary steels, alloys, stainless steels, refractory materials. It is also suitable for casting other metals or refractory alloys such as superalloys.

• Figure 1 dispositif connu de coulée continue sur roue avec fermeture de la jante par un ruban métallique sans fin.
• Figure 2 détail de la roue de la figure 1.
• Figure 3 ensemble comprenant le dispositif de la figure 1 et une installation de laminage continu qui lui est associée de façon connue.
• Figure 4 dispositif de coulée continue sur roue, également connu, dans lequel le ruban .métallique s'enroule sur des poulies de renvoi.
• Figure 5 dispositif de coulée continue sur roue avec fermeture de la jante par des volets suivant l'invention.
• Figure 6 vue de la jante de la roue de coulée et d'un volet, suivant l'invention, en position de fermeture.
• Figure 7 vue d'un volet, suivant l'invention, en position d'ouverture.
• Figure 8 détail d'un volet, suivant l'invention, en appui sur la jante de la roue de coulée.
• Figure 9 vue du mode d'accrochage suivant l'invention, des volets les uns aux autres.

The description and the figures below make it possible to better understand the characteristics of the process which is the subject of the invention.

• Figure 1 known device for continuous casting on a wheel with closure of the rim by an endless metal strip.
• Figure 2 detail of the wheel in Figure 1.
• Figure 3 assembly comprising the device of Figure 1 and a continuous rolling installation associated with it in known manner.
• Figure 4 continuous casting device on a wheel, also known, in which the metal strip is wound on idler pulleys.
• Figure 5 continuous casting device on wheel with closure of the rim by flaps according to the invention.
• Figure 6 view of the rim of the casting wheel and a flap, according to the invention, in the closed position.
• Figure 7 view of a flap, according to the invention, in the open position.
• Figure 8 detail of a flap, according to the invention, resting on the rim of the casting wheel.
• Figure 9 view of the method of attachment according to the invention, the flaps to each other.

The FR patent. 981 897 describes a continuous casting process on a wheel. Figures 1 and 2 allow us to understand the characteristics of this process which is now well known. A wheel (1), driven in rotation at slow speed by a motor not shown, comprises a hollow rim (2) in the groove (3) from which a supply device (4) makes it possible to introduce in (5) the liquid metal by means of a nozzle.

An endless metal ribbon (6) is wound on the casting wheel and on a free wheel (7) arranged in the same plane. This freewheel is mounted on an oscillating arm (8) which acts as a tensioner. The ribbon is thus pressed against the edges (9) of the rim of the wheel (1) and therefore prevents the metal cast in (5) from coming out of the groove. The rim is cooled by circulation of water in the space (10), which allows rapid solidification of the metal in the groove. This water is introduced by the axis of the wheel at (11) then sent into the space (10) through two diametrically opposite spokes (12) and (13). The water returns via two other spokes (14) and (15) and through the axis of the wheel at (16). The wheel turns in the direction of the arrow and the tightening of the metal strip on the rim is such that no noticeable slip occurs. The speed of solidification of the metal in the groove is relatively rapid and the solidified bar (17) is continuously extracted from the groove at the place where the metal strip peels off the rim to go and wind on the wheel (7) . It can be seen that the bar (17) thus formed continuously must be deflected with respect to the plane of symmetry of the rim (2) by an amount sufficient to allow it to come out of the space delimited by the wheels (1) and (7) and the ribbon (6) without hitting the latter. Such a deviation does not present any particular difficulties in the case of bars of small section made of a metal of limited hardness. On the other hand, it is more difficult to produce in the case of bars of large section or relatively wide strips, or even of hard metals or alloys.

FIG. 3 represents, still according to the teaching of the same patent cited above, the bar (17) extracted from the casting wheel (1) which is thus deflected from its outlet plane and then sent to a rolling installation continuous (18).

In order to remedy the drawback of this deviation from the bar, the FR. 1,178,580 proposes to circulate the tape or strip, which ensures the obturation of the rim, not on a single free wheel, playing the role of tensioner, but on, at least, two free wheels.

We see, in Figure 4, an arrangement proposed in this patent, in which the endless metal strip (19), which ensures the closure of the hollow rim (20) of the casting wheel (21), is wound on two return pulleys (22) and (23) and a tension pulley (24). Furthermore, support rollers (25) and (26) make it possible to improve the contact between the metal strip and the edges of the rim. In addition, to improve the cooling of the metal strip, a movable support (27) is provided with watering means (28) which project water onto the visible face of the strip.

Many modifications to the process of continuous casting on a wheel, which has just been described, have been proposed. However, experience has shown that, if this process adapts well to the continuous casting of metals with relatively low melting point, such as aluminum, it is much more difficult to implement in the case where it is desired casting much higher melting point metals such as copper or even steel. It then becomes increasingly difficult to ensure satisfactory cooling of the metal strip which ensures the closure of the rim. For reasons of mechanical characteristics, this strip is generally made of steel, and if its cooling is insufficient, it risks, on the one hand, being attacked by the liquid metal which comes into contact with it and, on the other hand, to lose by annealing part of its mechanical resistance characteristics. Furthermore, the alternating torsional forces to which this ribbon is subjected are a cause of transverse cracking, after a time which may be short and, finally, the watering of the ribbon on its external face; practically necessary in all cases, is not without risk. It may happen, in fact, that the water thus projected comes into contact with the liquid metal which is poured into the rim. There is then a risk of explosions occurring which in most cases cause the metal strip to rupture and can therefore seriously damage the casting wheel.

Finally, a serious defect of the products obtained by casting bars on a wheel rim, with sealing by metal tape, is the existence of two sharp angles on the solidified product at the place where the two edges of the tape are connected to the side walls. from the rim. These sharp angles are a cause of defects and, very often, it is necessary to subject the bar, which is extracted from the rim, to deburring before passing it through the rolling mill.

We then looked for the possibility of extending the applications of wheel casting to all kinds of metals or alloys and, in particular, to those with high melting point, overcoming the limitations currently imposed on the use of this casting method, in particular by means of sealing off the rim available.

In the case of document FR-A-2 317 032, a process for the continuous casting of metal alloys on a wheel without a groove is described, in which the space defined between a rotating wheel, a series of successive flaps cooled by water circulation enveloping part of the wheel and forming the opposite face of the mold, the other two faces being constituted by laterally retractable sectors to allow the flaps to be applied forcefully against the cast product . After casting, the flaps follow a separate trajectory. This grooved wheel device with retractable sectors is not suitable for the casting of metals or alloys with a high melting point, and the trajectory of its flaps represents a complication.

The device and method according to the invention make it possible to overcome the limitations and complications of the known prior art. This device, the characteristics of the preamble of claim 1 taking into account FR-A-2 317 032, makes it possible to achieve this objective by the characteristics mentioned in the characterizing part.

The device according to the invention consists of a casting wheel provided with a rim and means for closing off said rim over part of its periphery. Unlike the casting wheel of FR-A-2 317 032, the rim of the casting wheel of the invention has a groove. Its shutter means include, like the shutter means of the mold with movable walls of FR-A-2 317 032, a plurality of movable flaps substantially contiguous enveloping the product poured from the supply of liquid metal to the extraction of the solidified product. However, in a different manner, these movable flaps are pivotally mounted on the casting wheel so that each movable flap maintains a determined location along the rim during the rotation of the casting wheel. Thus, these movable shutter flaps fixed to the wheel accompany it permanently in its rotation. The closure means also include the means for opening and closing the flaps, means such that the flaps are in direct contact with the edges of the rim between the point of introduction of the liquid metal into the groove and a point close to the extraction point of the solidified metal bar or strip, and that the flaps are open, leaving the space located above the groove of the rim in the extraction zone of this solidified bar or strip.

These means for opening and closing the movable flaps comprise fixed ramps integral with the frame which supports the casting wheel

Preferably, the flaps comprise a means of cooling by internal circulation of water and, moreover, clamping means ensure that the flaps are pressed against the rim of the wheel with sufficient pressure. Finally, connecting means make it possible to secure the flaps together.

In much more detail, an embodiment of the device according to the invention will now be described.

FIG. 5 represents a casting wheel (29) driven by a motor, not shown, which rotates in the direction of the arrow and the rim (30) of which is fitted with movable flaps such as (31). As this figure shows, the flaps (31) are supported on the edges of the rim in an angular zone located between the point of introduction of the liquid metal into the groove by a supply means (32) up to a . point close to that where the solidified bar or strip (33) is extracted from the groove by a suitable means such as the guide rollers (34). Throughout the area which extends between the point of extraction of the solidified bar and the point of introduction of the liquid metal, the flaps are in the open position and arranged so as not to interfere with the operation of the means of extraction, and not to obstruct the passage of the solidified bar or strip which is generally directed towards reduction means for example by rolling, and not to obstruct the operation of the liquid metal supply means either .

An essential feature of the invention is that the movable flaps (31) permanently accompany the casting wheel in its rotation and that each of them maintains along the rim thereof, a determined location. Connecting hooks (35), shown schematically in Figure 5, maintain the flaps against each other, to avoid any leakage of liquid metal through a possible space between two adjacent flaps. Furthermore, as will be seen in detail below, a fixed ramp (36) surrounds the casting wheel throughout the angular region where the flaps must remain closed, and ensures the plating thereof on the rim flange by means of conventional clamping means.

FIG. 6 shows in detail an advantageous embodiment of the shutters according to the invention.

The casting wheel (29), which is shown in partial section along a plane parallel to the axis, comprises a rim (30) provided with a groove (37) intended to receive the liquid metal and to allow it to solidify. This rim is cooled by a circulation of water which takes place in a known manner in the annular space (38) and which is maintained by a system of arrival and departure of water, which is carried out for example through the 'axis of the wheel which is hollow and comprises in known manner, the necessary connections with the external network. The flap (39) is an assembly which is articulated by means of an arm (40) on the axis (41) which is itself fixed in a yoke rigidly connected to the structure of the casting wheel in the vicinity of the rim. The arm (40) is extended beyond the axis (41) by a lever (42) on which is fixed a roller (43).

We understand that by applying forces on the roller either upwards (arrow A) or downwards (arrow B), we act on the lever (41) which either keeps the flap (38) in contact with the edges of the rim (30) by its closure plate (45), or, on the contrary, raises it.

We see, Figure 7, the flap (39) in the open position, the space above the groove of the rim is then completely cleared, which allows to engage in this groove, in specific areas, means of extraction of the solidified bar or a means of introducing the metal or liquid alloy.

In practice, the opening and closing of each flap are caused for an angular position very well determined relative to the frame, as seen in Figure 7, by means of fixed ramps (44) integral with the frame on which is mounted the casting wheel. The profile of these ramps is designed to move the rollers (43) up or down according to the desired angle.

It is understood that it is absolutely necessary to obtain a tight closure of the throat to avoid any leakage of liquid metal which would be a cause of loss of metal and, above all, of surface defect. For this, it is possible, in a complementary manner, to improve the centering of the flaps relative to the rims and also to ensure, on the one hand, a tightening with sufficient pressure of the flap on the rim and, on the other hand , maintaining the successive flaps against each other by means of a connecting means such as hooks.

It can be seen in FIG. 8 that the closing plate (45) of the flap shown in section is centered relative to the rim (30) by means of centering pins, such as (46). These pins connected to the closure plate (45) penetrate at the time of the tilting of the flap, when it comes to bear on the rim (30), in housings such as (47) formed in this rim. In this way, the closure plate (45) is placed in a reproducible manner each time it comes to bear on the rim (30). Furthermore, in order to ensure constant tightening of this closure plate on the rim, an elastic tightening means is used.

As shown in the figure, each flap has a housing (48) inside which the closure plate is resiliently fixed by springs such as (49). At the top. the housing includes rollers such as (50). After closing each flap, in the vicinity of the filling point of the groove with liquid metal, the flaps engage in a space delimited by a fixed annular ramp (36) concentric with the wheel against which the rollers (50) come to roll . The distance between the ramp and the rim of the casting wheel is calculated so that the springs (49) are compressed by means of the rollers (50). The closure plate is thus applied against the rim with sufficient force. This embodiment makes it possible to absorb the expansions and possible excess thicknesses caused by liquid metal overflows.

As also shown in Figure 8, each closure plate is equipped with an internal cooling means (51). As water is most often used as a cooling fluid, it can be seen that the use of flaps articulated directly on the casting wheel allows an extremely easy supply of fluid from the wheel itself which, in turn, is supplied without difficulty thanks to fluid inlets and outlets at its axis.

As shown in Figures 6 and 8, the closure plate (45) has a double wall inside which water passages (51) are provided. Water inlet and outlet fittings (52) and (53) Figures 6, 7, 8 and 9 are connected by flexible connecting tubes, for example made of elastomer, symbolized at (54), to inlets and corresponding water outlets such as (55-56), formed on the lateral face of the casting wheel not far from the point of attachment of the tilting axis (41). The length of these connecting tubes is determined so as not to prevent tilting of the flap. Finally, a system for attaching the successive flaps to each other is shown in FIG. 9. It can be seen that each flap has a hook (57) articulated around an axis (58) which is capable of catching on a tenon ( 59). The opening and closing of the hook is controlled by a roller (60) which is raised or lowered by suitably arranged stops. The connecting means thus produced makes it possible to avoid leakage of liquid metal between the closure plates.

The use of shutters, of relatively small dimensions, and of compact structure, articulated separately on the casting wheel itself, allows the use of the most suitable metals for the closure plate to withstand direct contact with the metal to be poured. This will make it possible to use, for producing the closure plate, metals with high specific heat and / or high thermal conductivity, such as aluminum, magnesium, copper, silver or else certain alloys of these metals. Most often, it will be preferable to make the closure plate in the same metal as the rim, that is to say in many cases, in copper or in alloys with a high copper content. In many cases, only the face of the closure plate, which is in contact with the liquid metal, will be made of high conductivity metal. The second wall, or outer wall of the plate, can be made of a metal of much higher mechanical strength. Thanks to vigorous fluid cooling of the closure plate, practically no deformation is observed due to differential expansion phenomena. The dimensions of the closure plates are calculated so as to take account of the expansion of the rim during use in order to avoid leakage of liquid metal.

The embodiment provided for closing the casting wheel makes it possible to envisage a very significant modification of the profile of the bars or strips cast by this process. In fact, in conventional wheel casting with closing of the groove by a metal strip, the angle formed between the inner face of the metal strip and the side walls of the groove is approximately 80 °. This results from the need for a draft of about ten degrees to be able to get the bar out of the throat. In addition, there can be no rounding at the top of this angle which is therefore sharp. Furthermore, as the walls of the groove wear out, there is a risk of small infiltrations of liquid metal between the strip and the edge of the rim, which are an additional reason for deburring.

In the case, on the contrary, of the present invention, thanks to the rigidity of the closure plates which are practically undeformable, it is possible to give the face of these plates, which is opposite the rim, a profile complementary to that of the throat.

In Figure 8, we see such a closure plate (45) which has rounded (61) and (62) by which the bar which will be cast in the rim, will only have rounded edges and can therefore be laminated under conditions particularly favorable.

The connection between the closure plate and the rim is thus produced on the lateral faces of the bar and, thanks to the centering devices which are used, no relative transverse displacement of this closure plate is observed with respect to the rim .

The invention relates not only to the casting device which has just been described, but also to a method of casting on a wheel metals or alloys with a high melting point such as copper and its alloys, steels and other metals. or high melting point alloys.

This method allows, by closing the rim in the casting area, by means of flaps cooled by circulation of a fluid such as water, to obtain a very rapid solidification of the metals or alloys cast.

This thus reduces the risks of segregation and makes it possible to obtain particularly fine-grained cast metal structures. This process also makes it possible to obtain cast bars, the section of which does not have sharp angles, which avoids the risks of folds, and can even approach the round.

Different means for supplying liquid metal to the casting wheel can be envisaged depending on the case. It is possible, in particular, to use nozzles or else channels with a substantially constant level. In the case of the casting of oxidizable metals such as copper, the liquid metal supply means can be placed in a controlled atmosphere.

Claims (7)

1. Apparatus for continuously casting on a wheel, bars or strips with rounded edges of metal or alloy having a high melting point such as copper or steels, said apparatus comprising a casting wheel (29) provided with a rim (30) and closure means for the ingot casting mould formed on the periphery of said rim (30), means comprising a plurality of contiguous movable flaps (31, 39) enveloping the cast product from the feed of liquid metal to the point of extraction of the solidified product (33), characterised in that the rim (30) of the casting wheel (29) comprises a groove (37) serving as an ingot casting mould, that the movable flaps (31, 39) are mounted pivotably on the casting wheel (28) so that each flap (31, 39) remains in a given location along the rim (30) during the rotation of said casting wheel (29), and that the closure means for the groove (37) further include means for opening and closing the flaps (31, 39) comprising fixed ramps (36, 44) which are fixed with respect to the frame which supports the casting wheel, said means (36, 44) being such that said flaps (31, 39) bear directly against the edges of the rim (30) between the point of introduction of the liquid metal into the groove (37) and a point which is close to the point of extraction of the solidified bar or strip (33), and that said flaps (31, 39) are opened leaving clear the space which is above the groove (37) of the rim (30) in the region for extraction of said solidified bar or strip (33).

2. Apparatus according to claim 1 characterised in that each movable flap (31, 39) comprises a closure plate (45) which is centred with respect to the rim (30) by means of pins (46) connected to said closure plate (45), said pins (46) engaging into housings (47) provided in said rim (30) when said movable flaps (31, 39) are pivoted and come to bear against the rim (30).

3. Apparatus according to claim 2 characterised in that each flap (31, 39) comprises a casing (48) within which the closure plate (45) is resiliently fixed by springs (49) and rollers (50) fixed to the upper part of said casing (48), said rollers (50), when said flap (31, 39) has been closed, rolling against a fixed annular ramp (36) which is concentric with respect to the casting wheel (29).

4. Apparatus according to any one of claims 1 to 3 characterised in that the successive movable flaps (31, 39) are in hooking engagement with each other by way of connecting means which for each flap (31, 39) comprise a hook (57) pivoted about an axis (58), so disposed as to come into hooking engagement with a peg (59) of the adjacent flap, opening and closing of said hook (57) being controlled by a roller (60) connected to said hook (57), said roller (60) being raised or lowered by abutments..

5. Apparatus according to any one of claims 1 to 4 characterised in that each closure plate (45) comprises a double wall within which there are provided ducts (51) for circulating therein a cooling fluid such as water, fluid intake and discharge connections (52, 53) being connected to water intakes and outlets (55, 56) disposed on the side face of the casting wheel (29).

6. Apparatus according to any one of claims 1 to 5 characterised in that the face of each closure plate (45) which is towards the rim (30) is of a profile which is complementary to that of the groove (37) of said rim (30) with rounded portions (61, 62) by means of which the cast bar or strip produced with the casting wheel (29) will have rounded edges.

7. A process for continuously casting on a wheel bars or strips having rounded edges of metal or alloy having a high melting point such as copper or steels, wherein liquid metal or alloy is introduced into a casting cavity formed on the periphery of the rim (30) of a casting wheel (29) and wherein the ingot casting mould formed on the periphery of said rim (30) is closed in the metal or alloy casting and solidification region by means comprising a plurality of contiguous movable flaps (31, 39) which enclose the cast product from the feed of liquid metal to the point of extraction of the solidified product (33), characterised in that the movable flaps (31, 39) are mounted pivotably on the casting wheel (29) so that each flap (31, 39) remains in a given location along the rim (30) comprising a groove (37) during the rotation of the casting wheel (29) and that said groove (37) is closed, between the point of introduction of the liquid metal into said groove (37) and a point which is close to the point of extraction of the solidified metal or alloy, by applying the flaps (31, 39) against the edge of the rim (30) by means of fixed ramps (36, 44) which are fixed with respect to the frame which supports the casting wheel (29), and that, by pivotal movement of the flaps (31, 39) about an axis which is fixed with respect to the wheel, the space disposed above the groove (37) in the region of extraction of the solidified bar or strip (33) is cleared.

Images