Title of Invention

LIQUID COOLED MOULD FOR CONTINUOUS CASTING OF METALS

Abstract

The invention concerns a liquid-cooled mould for the continuous casting of metals, comprising mould plates (1) out of copper or a copper alloy, which are clamped to support plates (2)at the back, by means of a number of bolts (6). The bolts (6) have bolt heads (12) in the region of the rear side (9) of the support plates (2) facing away from the mould plates (1). A linking arrangement (13) enabling relative movements between the mould plate (1) and the support plates (2) is incorporated between the bolt head (12) and the support plate (2) with two linking members (14, 15), between which a sliding element (18) is embedded safely.

Full Text

The invention relates to a liquid-cooled mould for the continuous casting of metals. A continuous casting mould for metals is known from DE 195 81 604 T1 in which a uniformly thick mould plate made of copper or copper alloy is connected to a support plate made of steel by means of a number of bolts. A bending and tensile stress that cannot be overlooked, is created In the bolts due to the thermally-Induced elongation of the mould plates in the casting process, especially in the case of short bolts. A failure of the welding joints, in the case of welded bolts, or an overstraining of the threads, in the case of screwed bolts, can occur, depending on the way the bolts are fixed to the mould plate. In extreme case, even cracks can be formed in the mould plate. In order to avoid this, a sliding arrangement is provided in DE 195 81 604 T1 between the bolted mould plate and the support plate, so that the mould plate can move relative to the support plate in three dimensions. This is achieved by using sliding fixing medium and by over-dimensioning the through-holes in the support plate. A lateral or two-dimensional movement of the bolts and consequently of the mould plate is possible. In addition to this measure, discshaped split washers are suggested, preferably in stacked arrangement, in order to maintain the initial stressing force of the bolt even at high temperatures. The split washers serve additionally as a linking arrangement with a degree of freedom, namely as a sliding seat, from the point of view of transmission technique. There is an inherent disadvantage with this solution in that a considerable static friction arises between the resilient elements due to the use of steel split washers. Due to the multiple contact surfaces between the split washers as well as between the support plate and the mould plate, the static frictions add up, so that a stress-free relative movement of the mould plate is not possible. 2 Proceeding from this, the problem of the invention is based upon improving liquid-cooled mould for continuous casting of metals to the effect that the static friction between the support plate and the mould plate is reduced and a uniform expansion of the mould plate against the support plate is possible. The invention aims to solve this problem. According to the invention, a linking arrangement is provided between the bolt head and the backside of the support plate with linking members, which are attached respectively to one of the components mentioned, in which the linking members have sliding surfaces facing each other, between which a sliding element is incorporated safely. Linking arrangements as per the invention are supports, which enable a lateral movement of the bolt in a through-hole of the support plate, made bigger than the bolt diameter and with that permit an essentially parallel relative movement between the mould plate and the support plate. A sliding element as per the invention is that element which is suitable for reducing the static friction and/or the sliding friction between the sliding surfaces. A sliding surface or a sliding member is attached, fixed at least indirectly to the support plate, while the corresponding sliding suri'ace or the corresponding sliding member makes a relative movement, preferably lateral to the longitudinal axis of the bolt. The sliding element is particularly configured in the shape of a ring and inserted in the bolt and thus held safely between the sliding members. The sliding element can be taken up as a separate component between the sliding members. 3 According to another embodiment, it is possible that the sliding element is made as sliding coating, which is permanently joined at least to one of the sliding surfaces. That is, only one of the sliding surfaces or both the sliding surfaces can be provided with a sliding coating. The sliding coating is suitable for reducing the static friction value and/or the sliding friction value between the linking members and that eases the relative movement of the bolt against the support plate. Sliding coatings, which contain polytetrafluoroethylene(PTFE), are considered especially suitable for the purpose. The static and sliding friction values can be greatly reduced by the use of PTFE as against the comparable metallic sliding surfaces. It is considered advantageous if the static friction value between the sliding surfaces is less than 0.1. According to the invention, it is possible to achieve static friction values of even less than 0.04 between the sliding surfaces, especially with the use of PTFE containing sliding coatings. The indicated static friction values refer respectively to the dry friction between the sliding surfaces. Obviously, according to the invention, it is also possible to provide additional lubricants between the sliding surfaces to reduce the friction in this way. Particularly, solid lubricants also can be used. Under this are implied, e.g., compounds with layered grid structure, like graphite, molybdenum sulphide, dichalcogenides, metallic halogenides, graphitic fluoride, hexagonal boron nitrite. Furthermore, oxide and fluoride compounds of the transition and alkaline earth metals come under solid lubricants, besides soft metals like lead as well as polymers, especially fluorine containing plastics like PTFE. Besides permanent or temporary sliding elements are joined to the sliding surfaces in the form of solid lubricants, with which the sliding surfaces are 4 aligned parallel to each other, it is also possible to provide mechanical sliding elements for sliding surfaces which are not parallel to each other, with whose assistance a relative movement is made possible. For this, it is planned according to another preferred embodiment, the sliding surfaces of the sliding members are shaped concave and remain respectively in contact with a rocking disk with spherical dome-shaped surface. The rocking disk serves in this case as sliding element between the sliding surfaces. The rocking disk is in a ring -shape configuration and has spherical dome-shaped surfaces turned towards the sliding surfaces. An angular movement of the rocking disk takes place with a relative movement of the sliding members, which moves freely within the concave sliding surfaces. The sliding surfaces are configured as conical socket in another embodiment. While a conical socket enables a better force transmission and guidance of the rocking disk, only a linear guide is given between the rocking disk and the linking member by a conical socket. A linear guide has the advantage of small contact surfaces and, with suitable material mating, also small frictional forces. Rocking disks in two units, can be used especially conveniently, since these are usable as standard units. These types of rocking disks are also designated as hemispherical section disks and have a spherical dome- shaped surface and an annular flat radial surface. Two of these hemispherical section disks can serve as half-disks of the rocking disk, in which the half-disks are used between the linking members with their radial surfaces turned towards each other and the spherical dome-shaped surfaces facing outwards. It is obvious that, according to the invention, the rocking disk can also be made in one piece with the respective spherical dome-shaped surface facing outwards. 5 A sufficient elastic force of the bolts is essential for a secure connection between the mould plates and the support plates. The necessary initial stressing force must be maintained even with strong thermal fluctuations. In addition, it has to be observed that not only lateral movements with reference to the bolt's longitudinal axis, but also slight changes in the direction of the longitudinal axis, according to the position of the rocking disk, occur with the use of a rocking disk. That is, the distance of the linking members vary depending on the position of the rocking disk. Hence, it is useful for the sliding coatings and necessary for the rocking disk to incorporate at least one resilient element between the bolt head and the backside of the support element for the constant stability of the bolt connection. For this, both split washers as well as elastomers, like, for example, rubber, can serve as resilient element, which can be provided both between the bolt head and the first linking member as well as between the second linking member and the support plate. It is obviously also possible to provide several resilient elements in stacked arrangement in order to be able to compensate for thermal-induced large changes in length and to maintain the initial stressing force of the bolt connection. However, besides the sliding surfaces in the region of the bolting arrangement, a number of additional contact surfaces are still present on the backside of the mould plate and the side of the support plate facing it. Depending on the normal forces applied by the bolts, substantial frictional forces have to be reckoned within the joint between the mould plate and the support plate, which have to be countered by incorporating a sliding medium between the contact surfaces of the mould plate and the support plate moving parallel to each other. Although the material pair steel - copper already has a low sliding friction value, this can be further reduced by additional measures. In this case. 6 preferably solid lubricants are used, which are joined permanently with the respective contact surfaces of the mould plate and/or support plate. The sliding media are preferably coatings. These can be polymer coatings, especially based on PTFE, or also flat sliding elements, like sliding disks or sliding rings, with which the static friction value between the contact surfaces can be reduced preferably to a value less than 0.1. According to the invention, it is obvious that only those regions of the mould are equipped with sliding medium or sliding elements that reduce friction value, in which a relative movement is also desired. For a definite expansion of the mould plate, it can be appropriate, for example^ to bolt the middle region of the mould plate fixed with the support plate, so that a uniform, thermally stress-free expansion of the mould plate, proceeding from this region is possible. The present invention provides a liquid-codied mould for the continuous casting of metals, comprising mould plates made of copper or a copper alloy, which are clamped at the back to support plates by means of a number of bolts, in which the bolts have bolt heads arranged in the region of the rear side of the support plates facing away from the mould plates and linking arrangements, enabling relative movements between the mould plates and the support plates, are incorporated between the bolt heads and the back sides, characterized in that, the linking arrangements comprise firstly a linking member attached to the bolt head and secondly a linking member attached to the back side of the support plate respectively with sliding surfaces facing each other, in which a sliding element is provided to reduce the static and/or sliding friction between the sliding surfaces of the sliding members. -7- BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS The invention is explained in detail below based on the embodiments represented in the drawings. They show: Figure 1 a portion of a mould plate connected to a support plate through a bolt in section; Figure 2 the bolt of figure 1 including a linking arrangement, in enlarged perspective view and Figure 3 a bolt with an additional form of execution of the linking arrangement, in perspective view. 7A Figure 1 shows the cross section of the joining area of a copper or copper alloy mould plate 1 , which is fixed to the back of a support plate 2 The support plate 2 can be an adapter plate as well as a component of a water reservoir, not shown in detail. In this embodiment, a coolant slit 3 is formed through which the coolant flows. This extends between platform bases 4, arranged at a distance from each other, which project island-like from the coolant side 5 of the mould plate 1. A bolt 6 is screwed centrally in the platform base 4 shown. The bolt 6 is fixed in a threaded insert 7 in the platform base 4. The bolt 6 passes via a through-hole 8 in the support plate 2 with play. The diameter of the through-hole 8 is enlarged into a cylindrical countersunk bore 10 in the direction towards the backside 9 of the support plate 2. The elastic force applied via the bolt head 12 arranged in the countersunk bore 10 acts upon the bottom surface 11 of the countersunk bore 10 extending in the radial direction below the insertion of a linking arrangement 13 on the support plate 2. The linking arrangement is a sliding seat, which enables a thermally-induced movement of the mould plate 1,diagonally to the longitudinal axis LA of the bolt 6. A relative movement is basically possible only if the diameters of the through-hole 8 and the bolt 6 are different. In addition, the linking arrangement serves to reduce the static friction between the support plate 2, serving to a certain extent as a fixed bearing and the mould plate 1, functioning as a moveable bearing. Corresponding to that, the linking arrangement 13 has firstly an upper sliding member 14 attached to the bolt head 12 and secondly a lower sliding member 15 attached to the backside 9 or the floor of the bore 11 in the backside 9, which functions as a fixed bearing (figure 2). The linking members 14, 15 are shaped as ring targets respectively and the bolt 6 passes through them centrally. In this case, the diameter D of the upper linking member 14 functioning as the moving bearing 8 is smaller than the external diameter D1 of the lower linking member 15. By this, a lateral movement of the upper linking member 15 is possible without any sideways hindrance. The diameter D1 of the lower linking member 15 is determined by the diameter D2 of the countersunk bore 10, so that the linking member 15 cannot be moved sideways within the countersunk bore 10 except for the usual tolerances. Thereby, the linking member 15 fulfils its function as the fixed bearing. For reducing the static friction and the sliding friction, the sliding surfaces 16, 17 of the linking members 14, 15 facing each other are matched one against the other in such a way that the static friction value is less than 0.1. For this, in the embodiment illustrated in figure 2, the upper linking member 14 is provided with a PTFE-coating on its sliding surface 16, which consequently is held as sliding element 18 between the sliding surfaces 16, 17 accomplished safely by the bolt 6. The sliding surface 17 of the lower linking member is matched to the PTFE-coating in such a way that its surface has a low roughness. Hence, a metallic ring target with polished, hardened or ground surface can be used as linking member 15. A supporting disc 19 of the same diameter is arranged above the linking member 14, which is arranged below a single-piece radial collar 20 formed as a unit with the bolt head 12. The supporting disk 19 can optionally be inserted below the bolt head 12 in order to transmit the elastic force of the screw connection optimally to the linking arrangement 13 lying below it. The supporting disc 19 can also be formed as a unit with the bolt head 12. The bolt head 12 itself can be formed both as a unit with the bolt 6, that is be a screw head, or also be set up as a nut on a stud provided with threads. The bolt 6 itself can be integrally joined or form-fitted to the mould plate 1. 9 A resilient element 21 is connected below the lower linking member 15 in the direction to the bottom of the bore 11 of the countersunk bore 10. This can, for example, be a ring target out of elastomer matenal, like e.g. rubber. Also several resilient elements 21 can be provided in stacked arrangement. It is planned to provide the contact surfaces 22, 23 between the mould plate 1 with a sliding material as an additional measure for the reduction of friction between the mould plate 1 and the support plate 2. In this embodiment, the contact surfaces 22, 23 are in the region of the platform base 4. A flat solid lubricant, for example, can be incorporated here. This means, the support plate remains in contact with the mould plate in the connecting area, exclusively through sliding elements and sliding material, so that the effective prevailing static friction value is respectively reduced. Figure 3 shows an additional form of execution of the linking arrangement. In this case, again a bolt 6' made as screw 23 passes through a linking arrangement 24 centrally. In its construction from top to bottom, first of all a ring-shaped resilient element 21' is arranged below the bolt head 2', on which a second ring-shaped resilient element 21" follows. A steel disc, preferably hardened, connects here as upper linking member 25, incorporated with a cone opening downwards. The link member 25 functions to some extent as a conical socket. The lower linking member 26 is provided with a conical seat pointing in the direction of the bolt head 12' in an inverse configuration. That is, the sliding surfaces of the linking member 25, 26, not visible in detail in the illustration of the figure 4, are configured in the shape of a curved surface of a truncated cone. A rocking disc 27 is arranged between the linking members 25, 26, whose surfaces 28, 29, pointing in the direction of the linking members 25, 26, are shaped as a spherical dome and acts as a linear guide with the conical socket of the linking members 25, 26. 10 In this embodiment, tine rocking disc 27 consists of an upper half-disc 29 and a lower half-disc 30. The half-discs 29, 30 are configured identically and are reversed with their plain radial surfaces lying against each other. This means, that the rocking disc 27 is seated in the conical sockets of the linking members 25, 26, freely moveable , a relative movement of the upper linking member 25 and, with that, of the bolt 6' takes place against the lower linking member 26 functioning as a fixed bearing. The relative movement in this case, counterbalances not only possible angular movements between the linking members 25, 26, but especially also a lateral movement, diagonal to the longitudinal axis of the screw bolt 6'. However, a height compensation is required within the linking arrangement 24 for a pure lateral movement due to the given geometry. However, the height movement of the upper linking member 25 against lower linking member 26 amounts to only a fraction of the side movement. It has been shown that, for a sideways movement of about 3 mm, the height movement lies around 0.1 mm. The height movement can be compensated via the resilient elements 21', 21" maintaining the prestress. 11 12 13 WE CLAIM 1. Liquid-cooled mould for the continuous casting of nnetals, connprising nnould plates (1) nnade of copper or a copper alloy, which are clamped at the back to support plates (2) by means of a number of bolts (6, 6'), in which the bolts (6, 6') have bolt heads (12, 12') arranged in the region of the rear side (9) of the support plates (2) facing away from the mould plates (1) and linking arrangements (13, 24), enabling relative movements between the mould plates (1) and the support plates (2), are incorporated between the bolt heads (12, 12') and the back sides (9,11), characterized in that the linking arrangements (13, 24) comprise firstly a linking member (14, 25) attached to the bolt head (12, 12') and secondly a linking member (25, 26) attached to the back side (9, 11) of the support plate (2) respectively with sliding surfaces (16, 17) facing each other, in which a sliding element (18; 27) is provided to reduce the static and/or sliding friction between the sliding surfaces (16, 17) of the sliding members (14, 15,25,26). 2. Liquid-cooled mould as claimed in claim 1, wherein the sliding element (18) is a sliding coating, permanently joined with at least one of the sliding surfaces (16). 3. Liquid-cooled mould as claimed in claim 2, wherein a component of the sliding coating is polytetrafluoroethylene (PTFE) . 4. Liquid-cooled mould as claimed in claim 2 or 3, wherein the static friction value (|jo) between the sliding surfaces is less than or equal to 0.1. 14 Liquid-cooled mould as claimed in claim 4, wherein the static friction value (?|o) between the sliding surfaces is less than or equal to 0.04. Liquid-cooled mould as claimed in claim 1 to 5, wherein the sliding surfaces of the sliding members (25, 26) are concave shaped and remain in contact with a rocking disk (27) with spherical dome-shaped surface (28). Liquid-cooled mould as claimed in claim 6, wherein the concave sliding surfaces are configured as conical socket. Liquid-cooled mould as claimed in claim 6 or 7, wherein the rocking disk (27) is divided into an upper disk-half (29) and a lower disk-half (30) with one-sided spherical dome-shaped surface (28) for each of them. Liquid-cooled mould as claimed in any one of claims 6 to 8, wherein, at least one resilient element (21, 21', 21") is incorporated between the bolt head (12, 12') and the back side (9, 11) of the support plate (2). Liquid-cooled mould as claimed in any one of claims 1 to 9, wherein, a sliding medium is incorporated between the contact surfaces (22, 23) of the mould plate (1) and the support plate (2) moving parallel to each other. Liquid-cooled mould as claimed in claim 10, wherein, the sliding medium is a permanently joined layer with the respective contact surfaces (22, 23) of the mould plate (1) and/or the support plate (2). 15 Liquid-cooled mould as claimed in claim 11, wherein, a component of the sliding coating is polytetrafluoroethylene (PTFE). Liquid-cooled mould as claimed in any one of claims 10 to 12, wherein, flat sliding elements are arranged between the contact surfaces (22, 23) of the mould plate (1) and the support plate (2) moving parallel to each other. Liquid-cooled mould as claimed in claims 10 to 13, wherein, the static friction value (?o) between the contact surfaces (22, 23) is less than or equal to 0.1. A liquid cooled mould, substantially as herein described, particularly with reference to the accompanying drawings. 16 The invention concerns a liquid-cooled mould for the continuous casting of metals, comprising mould plates (1) out of copper or a copper alloy, which are clamped to support plates (2)at the back, by means of a number of bolts (6). The bolts (6) have bolt heads (12) in the region of the rear side (9) of the support plates (2) facing away from the mould plates (1). A linking arrangement (13) enabling relative movements between the mould plate (1) and the support plates (2) is incorporated between the bolt head (12) and the support plate (2) with two linking members (14, 15), between which a sliding element (18) is embedded safely.

Documents:

00435-kol-2003-abstract.pdf

00435-kol-2003-claims.pdf

00435-kol-2003-correspondence.pdf

00435-kol-2003-description(complete).pdf

00435-kol-2003-drawings.pdf

00435-kol-2003-form-1.pdf

00435-kol-2003-form-18.pdf

00435-kol-2003-form-2.pdf

00435-kol-2003-form-3.pdf

00435-kol-2003-form-5.pdf

00435-kol-2003-g.p.a.pdf

00435-kol-2003-leter patent.pdf

00435-kol-2003-priority document others.pdf

00435-kol-2003-reply f.e.r.pdf

435-kol-2003-granted-abstract.pdf

435-kol-2003-granted-claims.pdf

435-kol-2003-granted-description (complete).pdf

435-kol-2003-granted-drawings.pdf

435-kol-2003-granted-form 2.pdf

435-kol-2003-granted-specification.pdf

435-kol-2003-priority document.pdf

435-kol-2003-translated copy of priority document.pdf