SK280995B6 - Apparatus for twin-roll continuous casting - Google Patents

Abstract

Apparatus for continuous casting between twin rolls (1, 2) with parallel axes, defining between them and with two fixed lateral walls (3) a casting space for a molten metal, each lateral wall (3) comprising at least one lateral part (6), placed against the plane end front surface of one of the rolls (1, 2), and consisting of a disc portion (6) with an external diameter equal to that of the said adjacent roll (1, 2), and a central part, opposite the said casting space, made from an insulating refractory material. The said disc portion (6) is produced from a material which has characteristics of thermal conductivity and mechanical strength which are greater than those of the said refractory material and is a frustoconical disc portion whose face (7) with the greatest radius of curvature is located towards the roll (6), and whose frustoconical surface (8) is in contact with the insulating material of the said central part (12).

Description

Technical field

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a continuous casting device between two cylinders with parallel axes which define between each other and between two fixed side walls a casting space for molten metal, each side wall comprising at least one side portion opposite the planar face of one of a portion of a conical disk having a larger diameter equal to the diameter of the adjacent cylinder; and a central portion located opposite said casting space of refractory insulating material.

BACKGROUND OF THE INVENTION

It is known that in this metal casting method one of the problems is the limitation of the liquid metal introduced into the casting space defined between the rollers at the ends of the rollers. One solution to this problem is the use of rigid side walls maintained in close alignment against the rollers, and in particular against the end surfaces of their end regions. In order to prevent the solidification of the molten metal on contact with these walls and to form an edge of the solidified metal which would prevent the casting edges from forming correctly, it is known to use these side walls of sufficiently insulating material to avoid or limit this solidification. To date, such a refractory insulating material has generally insufficient mechanical properties to be kept in contact with the movable rollers without causing rapid wear.

In order to solve this problem, it has been proposed in French Patent No. 2636259 to provide side walls on which only the central region is formed of insulating material. Two metal tongues, located on either side of this material, enter slightly between the rollers and observe their curvature. In addition to improved mechanical resistance, these tongues promote sealing between the rollers and the side walls, since the skins of the stiffened metal extend on these fixed tongues, along the edges of the skids sliding, closing the contact area between the cylinder and the side walls.

In French patent application 89 08086 of the same Applicant, a side wall comprising at least one side part, for example a metal part, has been provided against a planar face surface of a cylinder and whose face facing the face lies in an extension of the cylinder surface and attaches to the front portion of said wall as it is rearwardly displaced therefrom with respect to the side portion so that a cavity extending the side casting space is formed in the wall.

It is an object of the present invention to provide another, more advantageous solution to the problem.

SUMMARY OF THE INVENTION

The invention solves the problem by providing a continuous casting device between two cylinders with parallel axes defining a casting space for molten metal between each other and between two fixed side walls, each side wall comprising at least one side portion positioned opposite the planar front surface of one a cylindrical portion of a conical disk having a larger diameter equal to the diameter of the adjacent cylinder, and a central portion opposed to said casting space of a refractory insulating material, said core portion being formed of a material having a thermal a conductivity and a mechanical resistance higher than the refractory insulating material of the central portion, that the front surface with a greater radius of curvature of said conical disk portion is positioned against the front surface of the cylinder and that the conical surface is in contact with the central portion.

According to a preferred embodiment of the present invention, the angle (α) formed by the larger diameter front surface and the conical surface of the conical disk portion lies in the range of 5 to 85 °.

According to another preferred embodiment of the present invention, the refractory insulating material is fibrous alumina.

According to a further preferred embodiment of the present invention, the central part is formed from several layers of materials with increasing mechanical resistance from the layer placed facing the casting space, to the last layer.

According to another preferred embodiment of the present invention, the conical disk portions are formed from a material selected from the group consisting of cast iron, steel, copper, molybdenum or alloys thereof.

According to another preferred embodiment of the present invention, the conical surface of the portion of the conical discs comprises roughening.

According to a further preferred embodiment of the present invention, the parts of the conical discs are coated with material or formed in the region of their front surface of a larger diameter from a material with high mechanical strength at high temperatures.

According to another preferred embodiment of the present invention, said material is zirconium.

According to a further preferred embodiment of the present invention, the disc parts are provided with means for cooling by circulating a cooling fluid.

According to a further preferred embodiment of the present invention, the parts of the conical discs are provided in the area adjacent to the gap between the roll, provided with a recess filled with refractory insulating material.

According to a further preferred embodiment of the present invention, the recess is formed over the entire width of the portion of the roll to form a direct contact of said insulating material with the roll over the entire height of said recess.

According to a further preferred embodiment of the present invention, the recess is formed on a portion of the width of the roll portion leaving the tapered portion of the portion of the roll in contact with the roller to prevent direct contact of said insulating material with the roller at the height of said recess.

According to a further preferred embodiment of the present invention, the central part is provided with a projection 15 penetrating between the rollers.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated in the drawings, wherein FIG. 1 is a partial sectional plan view of the device according to the invention, taken along a horizontal plane, FIG. 2 is a front view in the direction of the arrow F in FIG. 1, FIG. Figures 3a, 3b and 3c show the formation of a central part of the side wall near the roll gap at the start of casting; 4 is a schematic front view of a side wall during casting; FIG. 5 is a section along line V-V of FIG. 4, FIG. Fig. 6 is a side elevational view of a first embodiment of the invention; 7a, 7b are sectional views at levels a and b of FIG. 6.

SK 280995 Β6 fig. 8 is a side view of a side wall according to a second embodiment of the invention; FIG. 9a and 9b are sectional views at levels a and b of FIG. 8, FIG. 10 is a partial cross-sectional view of another variant of the invention of a casting device between two rollers which are axially displaceable from one another; and FIG. 11 is an enlarged detail of a central wall region with several layers of refractory insulating material.

DETAILED DESCRIPTION OF THE INVENTION

The continuous casting device between two rollers, shown partly in FIG. 1, comprises two rollers 1 and 2 with parallel horizontal axes and are rotatable and two side walls 3 for limiting the casting space located at the ends of the rollers 1, 2 against their front surfaces 4,5.

The side wall 3 shown in FIG. 1 in cross-section in a horizontal plane passing through the axes of the rollers 1, 2 and FIG. 2, shown in elevation, comprises two lateral portions 6, each of which is formed by a cone-shaped disc portion whose largest diameter is equal to the diameter of the cylinders 1, 2 so that the face 7 of the disc portions has the greatest radius of curvature the cylinder 1, 2 and the edge 9 of the inclined edge formed by the conical surface 8 and the face 7 of these parts of the discs lie opposite the edge formed by the edge of the cylindrical surface 10 of the corresponding cylinder 1,2.

In FIG. 2, the rollers 1,2 are shown only by the contour 10 'of their cylindrical surface and it is clear that this contour 10' coincides with the edge 9 of the slanted edge of the roll portions.

Edge angle, t. j. the angle of the base portion of the cone-shaped discs is from 5 to 85 °, preferably about 30 °.

The parts of the roll forming the side portions 6 of the side wall 3 are made of a material which has good mechanical properties, is resistant to wear and preferably has a low coefficient of friction to limit the forces resulting from the possible friction of the rollers 1, 2 on the roll portions. For example, they can be made of cast iron, steel, copper and friction lubrication can be reduced.

It should also be noted that the mechanical resistance of the material forming part of the disks makes it possible to avoid their disruption upon contact of the solidifying liquid metal with them by using a refractory insulating material. The wear process is stopped or at least severely limited and metal ingress between the roll and cylinder parts is prevented.

The side portions 6 may also be coated or formed near the edge 9 of a material having a particularly high mechanical resistance at high temperature and preferably with a low tendency to attack molten metal to be cast and inert to contact with liquid steel to prevent rupture of the edges 9 of the wheel portions or anchoring of the cast metal in the case of contacting the molten metal during casting with said edges 9. For example, it is possible to use a ceramic coating such as zirconium on a metal substrate or also on a ceramic substrate or to form part of a roll in monolithic piece of ceramics or composite ceramics or use an antioxidant coating.

In addition, these parts of the discs may be cooled, for example by circulating coolant in channels 11 formed in the parts of the discs, and the cooling thus formed should be sufficient to maintain the region adjacent the edge at a temperature lower than the temperature at which disturbance can occur. caused cooling of the cast metal.

Between the two parts of the disc 6 in the central part of the side wall 3, a refractory insulating material 12 is placed in close contact with the conical surfaces 8 of the parts of the disks 6. This central part of the refractory insulating material is retained parts of discs 6 fixed.

In order to improve the attachment of the refractory insulating material to the parts of the rolls 6, and in particular near the gap between the rollers 1, 2, their conical surface is provided with roughening, e.g.

Finally, the central part 12 comprises a projection 15 with respect to the plane of the faces 7 of the disc parts, which penetrates between the rollers 1,2.

The refractory insulating material has a thermal conductivity of less than 0.35 W / m.K, i.e. it should be sufficiently insulating to prevent the metal from solidifying on contact with it and have good dimensional stability at various temperature changes. It is possible to use a fibrous refractory material, for example a composite material of alumina fibers impregnated with a zirconium gel, for example a commercial type designated Procelite or Procal.

For a better understanding of the advantages of the side wall of the invention, the scheme of FIG. 3 show the development of this wall at the beginning of the casting.

Fig. 3a shows to a larger extent the central region of the side wall before the start of casting in a plane slightly above the gap between the rolls. Thus, there is shown a wall and a protrusion 15 which slightly enters between the rollers 1,2.

After a relatively short casting time, the cast metal 22 has worn the refractory material, removed the protrusion 15 and hollowed out the middle portion as shown in FIG. 3b.

As the casting is continued, the metal continues to remove the refractory material to form a circular cross-section cavity 16 therein. The rigid cortex 17, which is then formed in the cavity, is attached to the refractory insulating material to form a solid corrugated metal.

The rigid bark 17 occupies a greater space in the refractory material than that which is at the same level between the rollers 1, 2. This increase is due to the particular design of the side walls according to the invention, in particular because the parts of the rolls 6 are conical.

Moreover, this enlargement of the rigid crust 17 causes the edges of the casting to maintain a width approximately equal to the general width of the article. Obviously, the edges of the final product are obtained starting from the metal during solidification, which is displaced simultaneously with the metal flowing between the rollers in a vertical trough formed by a rigid bark that is rigid with respect to the side wall.

It is further evident that once the solid crust has been formed, it protects the refractory insulating material from direct contact with the molten metal and prevents its wear and tear, which makes it possible to stabilize the process for continued casting.

It will further be appreciated that the metal crust 23 solidified by contact with the rollers 1,2 and displacing them is not associated with the rigid crust 16.

In FIG. 4 and 5 show a side wall in the casting mode at the level of the horizontal section along the line VV above the gap between the rollers 1, 2. They show a V-shaped cavity resulting from wear of the refractory insulating material of the metal crust 23. The depth and width of the wear marks 18 increase downwards until they are joined to form the cavity 16 shown in FIG. 3 c as a solid crust 17.

SK 280995 Β6

It should further be noted that the formation and stability of the rigid cortex results from the thermal stability that is formed between the cast metal and the various components of the apparatus, in particular the side wall.

For this reason, the refractory insulating material with which the liquid metal is brought into contact at the start of the casting must be highly insulating to avoid premature solidification of the metal between the edges of the rollers 1, 2. It is desirable that the stiff bark once formed is as stable as possible. . For this purpose, it is possible to form the central part of the wall in the form of one piece of the composite shown in FIG. 11 and made up of several layers 12a, 12b, 12c of different refractory materials arranged vertically, whose mechanical resistance increases and the thermal insulation decreases, starting from the plane of the face 7 of the roll parts towards the support plate 13. By this measure from the first contact of the molten metal with the refractory insulating material, while, after the rigid cortex has been formed, the depressing of the central portion causes the rigid cortex to reach layers of greater mechanical resistance which limit its progress and provide better persistence upon reaching the steady state.

The last layer or carrier plate 13 itself constitutes a security plate to eliminate any risk of molten metal leakage in the event of a rupture of the solid crust. They may be formed, for example, from a hard material which is not deformed by stretching, for example silica.

According to one embodiment of the invention shown in FIG. 6 and 7, the disc portions have a recess 19 at their lower part adjacent to the spacing between the rollers 1, 2 for being pushed to the bottom of the side wall, said recess being terminated by an extension 20 corresponding to the refractory insulating material contained in the presence of the end faces of the rollers 1, 2 at the height of this recess 19. The presence of an insulating material softer than the material of the roll parts causes the edges of the product to unfold beyond the influence of the rollers 1, 2 solidified near the gap. The layer thickness at the gap level and at the edges of the rollers can thus be limited, thus preventing the said edges from being broken.

The height of the recess above the gap will preferably be close to the arc length of 2 ° measured at the circumference of the rollers 1,2.

According to another variant of the invention shown in FIG. 8 and 9, the roll portions are not provided with recesses in the same area as previously in a portion of their width, leaving the weakened portion 21 of the roll in contact with the rollers 1, 2, avoiding direct contact of the refractory material with the rollers 1, 2 in large part.

Finally, these recesses allow the eventual larger width of the edge of the article to pass into the refractory material, which could occur if the thickness of the rigid crust is increased too temporarily.

In FIG. 10 is a cross-sectional view at the gap level of application of the invention in the case of casting between two rollers axially displaced from one another, for example in a device allowing the casting of variable width products by the axial displacement of rollers 1,2.

In this case, the side wall is not symmetrical as in the examples given with respect to the median plane P of the device parallel to the axes of the cylinders 1, 2. This wall 30 is formed by the side where it contacts the face of the cylinder 1; 10, in the same manner as in the above examples, and includes a portion of the cone-shaped disc 6 'mounted on the support plate 13' and a central portion 12 'of refractory insulating material. The other side of the wall 30, see the upper part of FIG. 10 is formed by a tongue 31 positioned against the cylindrical surface of the roll 2 ', for example of the same material as the part of the roll 6', this tongue also having an edge conforming to the curvature of the roll 2 'and equally fastened to the support plate 13'. The refractory insulating material 12 'fills the space between the part of the roll 6' and the metal tongue 31.

This side wall is equivalent to that which in a variant is adapted to the cylinders axially displaced, according to the French patent application No. 89 08086, from which detailed information can be obtained and to which the principle of the wall according to the present invention has been transferred.

It will be appreciated that the particular arrangement of FIG. 10 allows the cylinder 2 'to be axially displaced relative to the cylinder 1' and the wall 30, allowing the casting width to be varied.

Obviously, in this variant, the rigid bark, which is formed in a manner similar to that explained above, is not symmetrical with respect to the P plane, but is deflected towards the side of the portion of the roll 6 ', causing the shape of the article slightly bent relative to the general the product plane. This obvious error is not serious, since the product strips are subsequently separated after casting, for example by shearing. Conversely, in this case, the separation of the belts can be facilitated.

The invention is not limited by the described examples, variations are possible without departing from the spirit of the invention.

Claims (13)

PATENT CLAIMS An apparatus for continuously casting between two cylinders with parallel axes defining a casting space for molten metal between each other and between two fixed side walls, each side wall comprising at least one side portion opposed to the planar front surface of one of the cylinders and formed by a portion a conical disc having a larger diameter equal to the diameter of the adjacent cylinder and a central portion located opposite said casting space of a refractory insulating material, characterized in that said conical disc portion (6) is formed of a material having thermal conductivity and mechanical resistance higher than the refractory insulating material of the central portion (12), that the face (7) with a greater radius of curvature of said portion of the conical disk (6) is positioned against the face (5) of the cylinder (1, 2) and that the conical surface (8) is in contact with the central part (12). Apparatus according to claim 1, characterized in that the angle (α) between the larger diameter face (7) and the conical surface (8) of the conical disc portion (6) lies in the range of 5 to 85 °. Device according to claim 1, characterized in that the refractory insulating material is fibrous alumina. Device according to claim 1, characterized in that the central part (12) is formed of a plurality of layers (12a, 12b, 12c) of materials with increasing mechanical resistance from the layer (12a) facing the casting space to the last layer (12a). 12c). Apparatus according to claim 1, characterized in that the parts of the conical discs (6) are formed from a material selected from the group consisting of cast iron, steel, copper, molybdenum or alloys thereof. A device according to claim 1, characterized in that the conical surface (8) of the cone disc parts comprises roughening (14). Device according to claim 1, characterized in that the parts of the conical discs are coated EN 280995 Β6 material or formed in the region of their front surface (7) of larger diameter from a material with high mechanical strength at high temperatures. 8. The apparatus of claim 7, wherein said material is zirconium. Apparatus according to claim 1, characterized in that the parts of the disc are provided with means for cooling the coolant circuit. Apparatus according to claim 1, characterized in that the conical disk portions are provided with a recess (19) filled with a refractory insulating material (20) in the region adjacent to the roll gap. Apparatus according to claim 10, characterized in that the recess (19) is formed by the bee width of a portion of the roll for direct contact of said insulating material (20) with the roll over the entire height of said recess (19). Apparatus according to claim 10, characterized in that the recess (19) is formed on a portion of the width of the roll portion leaving the tapered portion (21) of the roll portion in contact with the roll to prevent direct contact of said insulating material (20) with the roll at the height of said recess (20). Device according to claim 1, characterized in that the central part (12) is provided with a projection (15) penetrating between the rollers.