FR2749785A1 - SIDE SHUTTER SIDE FOR CONTINUOUS CASTING INSTALLATION OF METAL STRIPS BETWEEN TWO CYLINDERS - Google Patents

Abstract

The subject of the invention is a lateral closure face for an installation for the continuous casting of metal strips between two counter-rotating cylinders with parallel axes energetically cooled internally, of the type comprising a refractory wall clamped on at least part of its periphery by a belt. metal which is fixed to it and relative to which the active face of said refractory wall protrudes, characterized in that said refractory wall initially has a thickness (e + e ') such that it can be used for several castings after having undergone rectification of its active surface between each casting, and in that said metal belt is fragmented according to its thickness into several elements (8, 8 ', 8 ", 8"', 8 "") attached independently to said refractory wall and can be separated from one another between two castings.

Description

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  SIDE SHUTTERING SIDE FOR CASTING INSTALLATION

  CONTINUOUS METAL STRIPS BETWEEN TWO CYLINDERS

  The invention relates to the continuous casting of metals. More specifically, it relates to devices for the lateral confinement of liquid metal in the ingot molds of machines for the continuous casting of thin strips, in which the solidification of the liquid metal is ensured by the close side surfaces of two cylinders with horizontal parallel axes, energetically cooled internally. and rotated in

opposite senses.

  On this type of continuous casting machine called "casting between cylinders", whose industrial application to the casting of steel strips about 2 to 10 mm thick is currently in progress, the lateral confinement of the liquid metal in the casting space defined by the cylinders is provided by closure walls. They are applied against the flat ends of the cylinders, called "edges", by thrust members comprising for example jacks and springs. These closure walls are usually designated by the terms "side faces" or "small faces". Their central part intended to be in contact with liquid metal is made of refractory material, as is their peripheral part which rubs against the cylinders while gradually wearing out. It is also possible to design the installation in such a way that during the greatest possible part of the casting, the aim is to maintain the lateral face in the vicinity of the cylinders with minimal clearance between them, sufficiently weak so that the lateral tightness of the casting space is still assured. This minimizes wear by friction of the refractory wall, but it is periodically necessary to apply the wall strongly against the edges of the cylinders, in order to regenerate their interfaces and thus ensure their perfect regularity. The two central and peripheral parts of the lateral face can be formed by different refractory materials, in which case they are joined to one another by an insulating cement. The central part must above all have a strong thermal insulation power and resistance to corrosion by liquid steel, while the peripheral part must also be able to resist as best as possible the thermal shocks, the thermal gradients and the intense friction that 'it undergoes (permanently or temporarily) from the edges of the cylinders. One can also provide that the side face is made of a single piece, and therefore of a single type of refractory. Each side face as just described can, in addition, be mounted on an insulating refractory support plate, such as silica. The pushing members act on the side face either directly or via a metal plate to which the side face

is fixed.

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  Preferably, the refractory part of the lateral face is clamped over all, or only the major part, of its periphery by a metal belt (for example cast iron or steel) cooled or not which ensures the cohesion of the assembly ( when the refractory part of the lateral face has several elements) and increases its rigidity. When the lateral face is new, its "active face" (that which is intended to be in contact with the metal and the cylinders) must protrude with respect to the metal belt, over a thickness greater than the maximum wear normally suffered by the periphery of the side face during casting, so that the belt

  metal can never come into contact with the cylinders.

  The side faces are fundamental parts of the installation, and their construction must be carried out with great care to avoid any incident during casting. In the case of the relatively complex design which has been exposed where the refractory part comprises several elements, this construction takes time, both for the assembly and for the drying of the functional materials and their bonding materials. And this phase of the preparation of the machine must be repeated before each casting, since the side faces are designed to be used only once: only the metal belt can be recycled for

  subsequently constitute another lateral face. Another problem also arises.

  If it is expected that, during casting, the lateral face will wear to a maximum thickness of approximately 10 mm, it must be foreseen that its useful face protrudes by approximately 15 mm in relation to the face of the metal belt which will be turned towards the cylinders. We are thus assured, as we have already said, that even if the wear on the useful face is greater than expected, the metal belt will never rub against the edges of the cylinders. On the other hand, the lateral face proper is surrounded by the metal belt over a thickness which can be of the order of 10 mm, thickness to which may be added at least a part of that of the support plate. It can therefore be estimated that, in the construction example which has just been described, if a lateral face 25 mm thick is provided (not including the support plate), at least 15 mm of this thickness will not be used during casting, and they cannot be reused during a subsequent casting since they must be destroyed during the repair of the sealing device. The support plate itself can also no longer be reused. This refractory material is spent wasted, and we can consider that its cost unnecessarily strike the cost of a metal casting, all the more so than the hard refractory materials which usually constitute the peripheral part.

  from the side, such as the Sialon, are priced high.

  The object of the invention is to propose a new design of the lateral faces of a casting between cylinders which, without questioning the fundamental technological choices of the design which has just been described, provides a cost

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  significantly reduced in use, both in terms of surface preparation time

  lateral than in terms of quantities of refractory materials used.

  To this end, the subject of the invention is a lateral shutter face for installation for the continuous casting of metal strips between two counter-rotating cylinders with parallel axes energetically cooled internally, of the type comprising a refractory wall enclosed on at least part of its periphery by a metal belt which is fixed to it and relative to which the active face of said refractory wall projects, characterized in that said refractory wall initially has a thickness (e + e ') such that it can be used for several castings after having undergone a rectification of its active surface between each pouring, and in that said metal belt is fragmented according to its thickness into several elements (8, 8 ', 8 ", 8"', 8 "") fixed independently to said refractory wall and

  can be separated from each other between two flows.

  As will be understood, the invention consists in producing a refractory part of the lateral face of a significantly increased thickness compared to the usual lateral faces, so that it can be used during several successive castings, and at ensuring the rigidity and cohesion of this lateral face by means of a metal belt fragmented according to its thickness, comprising several superimposed elements which can be separated from each other. Thus, after each casting, it suffices to rectify by machining the active face of the lateral face and to remove the element which was

  closest to the cylinders to obtain a ready-to-use side obturation side.

  An appreciable time saving is thus achieved on the operation of repairing the lateral face. In addition, almost all of the refractory material initially constituting the side face is used over successive castings. Only the part which remains enclosed by the last element of the metal belt at the end of the last casting, as well as, possibly, the support plate, remain lost. This results in a substantial saving of material compared to the usual case described above, o

  this same loss of material occurs with each casting.

  The invention will be better understood on reading the description which follows, which

  assumes that the invention is applied to the casting of steel strips (carbon or stainless steel), and refers to the following figures: - Figure I which shows an example of lateral obturation face according to the prior art seen from the front and in perspective in FIG. 1a, and seen in cross section along Ib-Ib in FIG. 1b; FIG. 2 which shows an example of a lateral shutter face according to the invention, seen from the front and in perspective in FIG. 2a, seen in cross section along IIb-IIb in FIG. 2b;

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  The lateral refractory shutter face according to the prior art shown in FIG. 1 comprises a support plate 1 made of a refractory with high insulating properties, such as silica (it is invisible in FIG. 1a). It is on this support plate 1 that is exerted (directly or by means of a metal plate) the pushing force of the organs (jacks, springs, etc.) which maintain the lateral face in contact with the cylinders of casting. On this support plate 1 are mounted the elements whose external faces are intended, during casting, to be in contact with the liquid steel and / or the cylinders, and whose contour has substantially the same shape as the lateral section. of the casting space defined by the cylinders. These elements consist first of all of a core 2. This is made of a refractory material which is asked above all to have high insulating properties, in order to prevent large parasitic solidifications of liquid steel from occurring at his contact. It must also resist as well as possible the chemical attack by the liquid steel, and the mechanical wear caused by the movements of the liquid steel in the casting space. Dense or graphitized silica and alumina or zirconia, for example, are well suited for this use. In areas where the side face is intended to rub against the cylinders, the core 2 is surrounded by two inserts 3, 3 '. These are made of a refractory material such as Sialon, capable of resisting as well as possible the friction of the cylinders, attack by liquid steel (with which the inserts 3, 3 'are in contact on a part of their surface), and to thermal shocks and gradients. In the example shown, each insert 3, 3 'is in a single part, but it can also be provided that each of them is composed of several contiguous fractions. The locations 4, 4 ′ of the contours of the cylinders when the lateral face is in operation are shown in dotted lines in FIG. We see in this figure that the core 2 and the inserts 3, 3 'are interrupted slightly below the neck 5, that is to say at the level where the cylinders are closest to each other and where , normally, the steel completes its solidification. This guarantees that the liquid steel cannot escape from the casting space below the neck 5. The support plate 1, the core 2 and the inserts 3, 3 ′ are made integral by

  suitable bonding materials (refractory cement, concrete, glue ...).

  The lateral face as just described is enclosed over its entire perimeter (at least in the example described and shown here) by a metal belt 6 which has the function of ensuring the cohesion of the various parts of the refractory wall and the rigidity of the assembly, and is fixed to it by a layer of insulating concrete 7 continuous or discontinuous. In the example shown, the metal belt encloses both a portion of the thickness of the support face 1 and a portion of the thickness of the core 2 and the inserts 3, 3 '. By way of example, the core 2 and the inserts 3, 3 'are enclosed over a depth "e" of 10 mm, and protrude over a thickness "e" of 15 mm relative to the metal belt 6. L total initial thickness of the refractory part of the

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  lateral face (support plate I not included) is therefore equal to "e + e" '= 25 mm. It is expected that, after use of the lateral face during a single casting, the active face will have been worn by friction and corrosion to a maximum depth of about mm. The entire side face is then dismantled, and as we said, only the metal belt 6 is reusable. In the example of lateral face according to the invention represented in FIG. 2, the refractory part has the same overall structure as in the previous example, namely a core 2 surrounded by two inserts 3, 3 ', the whole being fixed on a support plate 1. However, according to the invention, the core 2 and the inserts 3, 3 'have been given a much greater thickness "e + e"', so that they can be used for several successive flows. As for the metal belt, it is fragmented according to its thickness into five superimposed elements 8, 8 ', 8 ", 8"', 8 "", which enclose the core 2 and the inserts 3, 3 'to a depth "e" . The first element 8 lets the refractory part protrude relative to it over a depth "e" "of the order of 15 mm, as in the previous example (corresponding to the sum of the 10 mm of maximum wear expected, plus a 5 mm safety margin). The last element 8 "" also encloses the support plate I over a part of its thickness, about 10 mm deep. The elements 8 to 8 "" are secured to each other in a removable manner by a device such as a set of bolts 9, 9 ', 9 ", 9"', 9 "" distributed over their periphery. For this purpose, the elements have on their front face (that which is intended to be turned towards the cylinders) recesses 10 serving as housings for the nuts (not shown) of the bolts 9 to 9 "", so that the nuts do not create extra thicknesses on said front face. Each of the elements 8 to 8 "" is fixed to the refractory part of the side face by a ring of concrete or cement jointing 11, 1 1 ', 1 1 ", 1 1" ", 1 1" ". It is important that these rings 11 to 11 "" are

  well separated, so that they can be destroyed independently of each other.

  Bolts 9 to 9 "" can also help fix the side face on its

  support members which ensure its application against the cylinders.

  The side face thus formed can be used in the following manner. After being preheated as usual (albeit for a longer time and / or with a higher power, since the refractory part is thicker than in the usual side faces), the side face is put in place, and a first casting is carried out. At the end of this first casting, the active face of the refractory part has undergone more or less regular wear which may reach, for example, 10 mm. A lateral face according to the previously described prior art should then be completely redone before its next use. But with the lateral face according to the invention, it suffices to rectify, for example by machining, the active faces of the core 2 and of the inserts 3, 3 ′ to give them a regular surface, then to remove the first element 8 from the belt

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  metallic by removing the bolts 9 to 9 "" and destroying the ring 11. The rods of the bolts 9 to 9 "" are replaced by shorter rods which do not exceed the front face of the second element 8 ', and we find thus a ready-to-use side face. In order to better ensure the cohesion of the entire side face during machining, provision may be made for a prior injection of glue through channels 12, 12 ', 12 ", 12"', 12 "" formed in the plate. support 1, which allow the glue to reach the interfaces of the various refractory parts. All of these operations for repairing the side face take approximately half an hour, while the complete repair of a side face according to the prior art which has been described takes at least four hours, without counting the multiple baking required. , and must be repeated between each use. After each new casting, we proceed to the repair of the side face of the same

way as before.

  Each of the first four elements 8 to 8 "'of the metal belt has a thickness of 10 mm, therefore substantially equal to the maximum wear by casting expected for the refractory of the side face. The fifth and last element 8" "has a greater thickness in the example shown, of the order of 25 to mm, since it must enclose the bases of the core 2 and of the inserts 3, 3 ′ as well as part of the support plate 1. Normally, such side face is intended to carry out five castings before its complete repair. But if during two or three successive castings the wear of the refractory was significantly lower than the expected 10 mm, it is possible that after machining the active face of the refractory the side face remains projecting by 15 mm or more in relation to the exposed metallic element. Under these conditions, it is not useful to remove this metallic element before the next casting, and the side face can therefore be used during

  at least one more pour than originally planned.

  As explained, this configuration according to the invention allows optimal use of the refractory of the lateral face since, ultimately, only the part which remains enclosed by the fifth metallic element 8 "" at the end of the last casting is lost. Total time spent preparing the side faces

  for the (at least) five castings planned is also considerably reduced.

  Of course, the numerical values which have been given for the number of elements 8 to 8 "" of the metal belt and their dimensions, as well as for the wear of the refractories, are only examples. They can be adapted to each particular use case of the invention. Similarly, the fixing of elements 8 to 8 "" each

  to others can be ensured by any device other than bolts.

  The overall design of the casting machine, and particularly of the support and application devices for the side faces, must, of course, take into account the fact that the thickness of the refractory part of the side faces is initially

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  more important than with the usual configurations, and is variable from one casting to another. This can lead, in particular, to an increase in the stroke of the organs

  thrust compared to usual configurations.

  The invention is, of course, also applicable to the case where the lateral face is devoid of support plate 1, as well as to the case where all of its refractory part is

  consisting of a single piece instead of a heart 2 and two inserts 3, 3 '.

  As a variant, provision may be made for the fragmented metal belt to enclose the refractory part only over part of its periphery, leaving its upper edge free, for example. It is then necessary to check whether, in the particular use case envisaged, the rigidity of the lateral face remains sufficient, but if this is the case, such a configuration

  facilitates the dismantling of elements 8 to 8 "" from the metal belt.

  It goes without saying that the invention can be applied to continuous casting between cylinders of metals other than steel.

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Claims (5)

  1) Sealing side face for installation for continuous casting of metal strips between two counter-rotating cylinders with parallel axes energetically cooled internally, of the type comprising a refractory wall enclosed on at least part of its periphery by a metal belt which is attached to it fixed and with respect to which the active face of said refractory wall protrudes, characterized in that said refractory wall initially has a thickness (e + e ') such that it can be used for several castings after having undergone a rectification of its active surface between each casting, and in that said metal belt is fragmented according to its thickness into several elements (8, 8 ', 8 ", 8"', 8 "") fixed independently to said refractory wall and being able to be separated each other between two flows. 2) lateral obturation face according to claim 1, characterized in that said refractory wall comprises a core (2) made of an insulating material and inserts (3,   3 ') made of a hard material intended to rub against the edges of said cylinders.   3) lateral obturation face according to claim 1 or 2, characterized in that said refractory wall is mounted on a support plate (1) made of an insulating refractory material, and in that said support plate (1) is at least partially   enclosed by one of the elements (8 "") of said metal belt.   4) lateral obturation face according to claim 3, characterized in that said support plate comprises orifices (12, 12 ', 12 ", 12"', 12 "") suitable for the injection of glue at the interfaces between the various refractory parts (1, 2, 3, 3 ') of said wall.   5) lateral shutter face according to one of claims 1 to 4, characterized   in that said elements (8, 8 ', 8 ", 8"', 8 "") of the metal belt are fixed to each other   to the others by bolts (9, 9 ', 9 ", 9"', 9 "").