EP0811446A1 - Mould for strand casting - Google Patents

Abstract

The mould for continuous casting of bolts and bars with homogeneously distributed primarily solidified particles consisting of individual degenerated dendrites is provided with an electromagnetic stirrer (80). Its characteristic features include: a) the inner surfaces (64, 74, 56) of the mould zones (60, 70, 52) are respectively bounded by elements (62, 72, 54); b) at least the inner surface (64) of the element (62) has a coefficient of heat conduction which is low in comparison with that of the material being cast; c) the mould element (72) is provided with means for introduction of a lubricating agent into the mould space (10); d) the mould element (54) serves for shaping the cast material, and has a coefficient of heat conduction comparable with that of the cast material; e) the stirrer (80) at least partially covers all three mould zones. Also claimed is a method for casting bolts or bars with thixotropic properties.

Description

The present invention relates to a mold for the continuous continuous casting of billets or bars with solid particles which are homogeneously distributed and primarily solidified therein and which consist of individual degenerate dendrites, the mold having an electromagnetic stirring device. The invention further relates to a process for the continuous production of billets or bars with thixotropes Properties in their further processing using the mold according to the invention.

Chill molds of the type mentioned at the outset for the production of ingots or bolts as starting material for their further processing by, for example, forging, die casting or extrusion in the thixotropic state are known, for example, from the patent DE 30 06 618.

In continuous casting, the inner walls of the molds exposed to the continuous casting material are subject to high abrasion. In addition, the continuous casting places a high temperature and pressure load on the mold, so that the mold can lose its optimal shape due to thermal and mechanical influences in the course of its use in order to achieve the desired bar or bolt shape. In order to achieve constant product quality, the metal bolts or bars used as the raw material must always have the same cross-sectional dimensions. Due to the required high dimensional accuracy of the ingots used as primary material, the previously known molds have to be replaced as a whole at short production intervals, which - due to the necessary replacement of the mold from the continuous casting device - results in a high expenditure of time, material and costs .

With the molds known from the prior art, it is possible to produce bolts or bars with a fine-grained casting structure with thixotropic properties during their further processing; in the edge region of the bolts or bars, however, a relatively thick edge shell made of dendritic material is formed, which can have a disruptive effect on the further processing of such starting materials.

Another disadvantage of the molds known from the prior art is their limited usability. DE 30 06 618, for example, to prevent the metal melt from overflowing due to the stirring process caused by the magnetic field of the stirring device, describes the use of a cover which partially closes off the mold at the top. However, such a device is only suitable for vertically mounted molds.

The object of the present invention is therefore to provide a mold which avoids the disadvantages described above and allows the continuous casting of metals or metal alloys for the cost-effective production of bolts or bars with a fine-grained microstructure with thixotropic properties over the entire bar or bolt cross section during further processing. Another object of the present invention is to provide a method for the production of bolts or bars with thixotropic properties during their further processing by means of a mold according to the invention.

According to the invention, the problem relating to the mold is achieved in that the mold has a modular structure and the mold cavity enclosed by it has three sequentially arranged mold zones with a common concentric mold longitudinal axis, and each of the three mold zones is delimited by the inner wall of a corresponding mold element, the first Mold element has an inlet opening for introducing continuous casting material, and at least the inner wall of the first mold element has a low thermal conductivity compared to the continuous casting material, the second mold element has means for introducing lubricant into the mold cavity, the third mold element describes the shaping mold area and at least its inner wall has one has comparable thermal conductivity to the continuous casting material, and the electromagnetic stirring device is such that its stirring effect is at least partially se includes all three mold zones, as well as the entire solidification zone of the continuous casting material.

In the mold according to the invention, the inner wall of the third mold zone is particularly exposed to high abrasion, i.e. that this mold area in particular is exposed to high temperature and pressure loads during continuous casting. It is now essential that the mold according to the invention enables the supply of lubricant, as a result of which the sliding of the continuous casting material on the inner wall of the third mold zone is considerably improved in precisely this critical mold area. This greatly reduces the thermal and mechanical stress, and thus the abrasion of the inner wall of the third mold zone. Consequently, the mold according to the invention allows the production of bolts or bars with constant product quality.

The supply of lubricant also increases the shear rate caused by the electromagnetic stirring device in the edge zone of the continuous casting material, as a result of which the dendrites forming there can be sheared off better, so that the bolts or bars also in the edge zone contribute to a fine-grained casting structure with thixotropic properties have their further processing. The better sliding of the continuous casting material on the inner wall of the third mold element also enables the stirring power to be reduced at constant shear rates, especially in the edge region of the continuous casting material that is critical for shearing off the dendrites, as a result of which, for example, the electromagnetic stirring device can be made smaller and more energy-saving. The shear rate is understood to mean the ratio of the speed difference .DELTA.v of two layers flowing past one another to their distance .DELTA.h perpendicular to the direction of flow. The term shear rate is therefore synonymous with the shear gradient or the speed gradient.

The electromagnetic stirring device is preferably dimensioned in such a way that a magnetic field can be set which generates a shear rate between 10 and 450 s ^-1 , the magnetic field being very preferably set in such a way that the shear rate in the continuous casting material is between 10 and 180 s ^-1 .

The mold cavity of the mold according to the invention, in particular its third mold zone, can have any cylindrical or frustoconical shape, in particular any rotationally symmetrical shape. In this context, the term cylindrical shape is understood to mean any hollow space which arises from the displacement of a flat surface area delimited by a closed curve parallel to itself by a certain distance. However, a cylindrical cavity is preferred, which is created by displacing a flat area delimited by a closed curve at right angles to the area. The cross section of the mold cavity, in particular that of the third mold zone, is preferably circular, but can also have a different cross-sectional shape, for example a polygonal or, in particular, a rectangular cross-sectional area.

The diameter of the third mold zone depends, for example, on the desired final diameter of the bolts or bars; for example, it is 3 to 20 cm, expediently 4 to 15 cm and preferably between 6 and 15 cm.

In a preferred embodiment of the mold according to the invention, the cross section of the inner wall of the first mold element on the side adjacent to the second mold zone is larger than the cross section of the inlet opening. Very preferably, the inner wall of the first mold element, starting from the cross section adjacent to the second mold zone, has a cross section which tapers continuously towards the inlet opening. This special configuration of the first mold zone means that The stirring effect of the electromagnetic stirring device against the inlet opening is reduced in such a way that essentially no rotation of the inserted continuous casting material caused by the electromagnetic stirring device takes place in the inlet opening itself.

The diameter of the inlet opening, as well as the diameter of the cross-sectional area of the first mold zone adjacent to the second mold zone, depend, for example, on the dimensions of the continuous casting material feed, on the shape of the first mold zone and on the desired final diameter of the bolt or ingot. The inlet opening is preferably circular and has a diameter of typically 4 to 5 cm. The diameter of the cross-sectional area of the first mold zone adjacent to the second mold zone is, for example, 3 to 19 cm, advantageously 4 to 14 cm, preferably between 6 and 14 cm and in particular between 10 and 11 cm.

The first mold element, in particular its inner wall exposed to the continuous casting material, is preferably made of ceramic. In addition, the inner wall of the first mold element is particularly preferably essentially pore-free. It is also essential for the first mold zone that at least the inner wall delimiting this zone has a low thermal conductivity compared to the continuous casting material.

In a further preferred embodiment, the cross-sectional area of the first mold zone that is in contact with the second mold zone is smaller than any cross-sectional area of the second mold zone. However, the cross-sectional area of the third mold zone adjacent to the second mold zone is particularly preferably smaller than any cross-sectional area of the second mold zone, but is larger than the cross-sectional area of the first mold zone adjacent to the second mold zone. These preferred developments of the mold according to the invention form an annular cavity for receiving lubricant emerging from the second mold element, and in addition the hot continuous casting material has no direct thermal and mechanical contact with the inner wall of the second mold element, so that firstly the inner wall of the second mold element is not clogged by, for example, any continuous casting material that has solidified on the inner wall for outflowing lubricant, and secondly, the thermal load on the second mold element is low.

The second mold element preferably consists of one, or the second mold element contains an annular body. This ring-shaped body preferably consists of highly porous, temperature-resistant material, the porosity expediently being such that lubricant can diffuse through the porous material. Especially this ring-shaped body is made of graphite or ceramic. The width of the annular body is, for example, between 0.1 to 5 mm, expediently 0.2 to 3 mm, preferably between 0.3 to 2 mm, and in particular between 0.5 to 0.8 mm.

In a further preferred embodiment of the second mold element, this consists of or contains an annular body made of fluffy, felt-like or sponge-like material, preferably containing chemically stable, non-flammable mineral fibers, the mineral fibers in particular up to 62.3% by weight of Al ₂ O ₃ and contain up to 37.2 wt .-% SiO ₂ . Such annular bodies expediently have a high ductility. The width of the ring-shaped body in the relaxed state is, for example, 0.5 to 5 mm, advantageously 0.8 to 3 mm and preferably between 0.8 to 1.5 mm. In the installed, ie compressed, state, the width of such an annular body is, for example, 0.1 to 2 mm, expediently 0.1 to 1 mm, preferably 0.1 to 0.5 mm and in particular between 0.15 and 0.3 mm.

The third mold element preferably consists of two hollow body elements which are concentric with respect to the longitudinal axis of the mold, one element, the inner sleeve, lying inside with respect to the longitudinal mold axis and laterally delimiting the third mold zone, and the other element, the support body, lying outside with respect to the longitudinal axis of the mold and receiving the inner sleeve, wherein the inner sleeve and the support body are releasably connected to each other by inserting the inner sleeve into the support body. The inner sleeve forms the element that is subject to high abrasion and contamination. The two-part design of the third mold element allows the dirty mold part to be easily removed for easier cleaning without having to remove the entire mold from the continuous casting device, and thus enables considerable cost savings compared to the use of molds known from the prior art. In this preferred embodiment of the third mold element, the support body preferably has the coolant and lubricant feeds which are mechanically complex to produce.

Further advantageous and preferred embodiments of the mold according to the invention relating to the further developments described in the further dependent claims.

The mold according to the invention thus has various mold elements with different functions, the individual mold elements having an optimized function.

The mold according to the invention is suitable for the horizontal or vertical continuous casting of metal alloys for the production of bolts or bars with primarily solid solid particles which are homogeneously distributed therein and which consist of individual degenerate dendrites. Such bolts or bars serving as primary material show thixotropic properties after they have been heated to a temperature which lies between the corresponding solidus and liquidus temperature of the metal alloy. In the thixotropic state, the metal alloys of such bolts or bars contain the re-developed dentritic, primarily solid particles in a matrix of liquid metal surrounding them. In order to achieve good casting, forging, rolling and finished part properties, for example, bolts or ingots that are processed further in the thixotropic state preferably have a homogeneously distributed, fine and isotropic grain, the degenerate dendrites preferably showing a globulistic shape. Due to the special design of the mold according to the invention, it is also particularly suitable for continuous horizontal continuous casting.

The use of the mold according to the invention is not restricted to the production of bolts or bars of a specific material. However, preferred materials are aluminum, magnesium, copper, steel, and their alloys, and excellent results can be achieved in particular in the case of light metals and very particularly preferably in the case of aluminum and magnesium alloys, which can also be fiber or particle-reinforced, for example.

The object directed to the method is achieved according to the invention in that continuous casting material is introduced into the inlet opening of the first mold element and is successively passed through the first, second and third mold zone, and the electromagnetic stirring device generates a magnetic field rotating about the longitudinal axis of the mold in such a way that Continuous casting material on the one hand experiences no stirring effect in the area of the first mold zone close to the inlet opening, on the other hand at least in the area of the first mold zone close to the second mold zone, and in the second and third mold zones, as well as in the entire solidification zone of the continuous casting material, so that it is stirred vigorously dendrites forming are sheared off, and the entire inner surface of the third mold element is continuously lubricated, the continuous casting material on the inner wall of the third mold element is subjected to primary cooling, so that the bolt or ingot emerging from the mold is in solid form at least in its outer edge zone, and the bolt or ingot is further cooled after it emerges from the mold by secondary cooling by means of coolant.

The method according to the invention is preferably used for the production of bolts or bars with homogeneously distributed, solidified primary particles which consist of individual degenerate, for example globulistically degenerate, dendrites.

The method according to the invention is particularly suitable for the horizontal or vertical continuous casting of aluminum, magnesium, zinc, copper, steel and their alloys. The process is particularly suitable for the continuous casting of aluminum or magnesium alloys. Regarding aluminum and its alloys, aluminum of all purity levels as well as all commercially available aluminum alloys can be used. Particularly suitable alloys are AlSi, AlSiMg, AlSiCu, AlMg, AlCuTi and AlCuZnMg alloys.

The molten continuous casting material is stirred by an electromagnetic stirring device, which generates a magnetic field rotating about the longitudinal axis of the mold. Stirring is preferably carried out by means of a stator of a multi-pole, for example two, four, or in particular six-pole induction motor.

Further advantages, features and details of the invention result from the following description of preferred exemplary embodiments, and with reference to FIGS. 1 and 2.

Figure 1 shows a schematic longitudinal section through a mold according to the invention.

Figure 2 shows a schematic longitudinal section through a preferred embodiment of the third mold element.

FIG. 1 schematically shows a longitudinal section through a modular continuous casting mold according to the invention with three mold elements 62, 72, 54 joined tightly together, which in their entirety delimit the mold cavity 10 laterally. The individual mold elements 62, 72, 54 are joined to one another in such a way that no continuous casting material can escape between their contact surfaces during the continuous casting.

The inlet opening 11 of the mold according to the invention for introducing the continuous casting material is located in the first mold element 62. The outlet opening 14 for the exit of the bolt or ingot from the mold according to the invention is located in the third mold element 54. The mold cavity located between the inlet 11 and outlet opening 14 10 is divided into three sequentially arranged mold zones 60, 70, 52.

The cross-sectional area of the first mold zone 60 adjoining the second mold zone 70 is larger than the cross-sectional area of the inlet opening 11, the cross-sectional area of the first mold zone 60 continuously decreasing towards the inlet opening 11, starting from the cross section adjacent to the second mold zone 70. The first mold element 62 thus resembles an inverted nozzle, in which the continuous casting material is introduced through the nozzle opening.

The shape of the first mold zone 60, together with the arrangement of the electromagnetic stirring device 80, reduces the rotation of the continuous casting material caused by the stirring device 80 at the inlet opening 11. The length of the first mold zone 60 is determined by its task, namely the formation of one for the prevention of the dendrite growth in the third mold zone 52 necessary rotation of the continuous casting material, the continuous casting material being essentially rotation-free after passing through the inlet opening 11. The continuous casting material in the first mold zone 60 is thus virtually rotation-free at the inlet opening 11 and is brought against the second mold zone 70 by the electromagnetic stirring device 80 to achieve the rotation required to prevent dendrite growth.

The continuous casting material is only shaped in the third mold zone 52. Thus, in order to prevent the continuous casting material from solidifying in the edge region of the first mold zone 60, at least the inner wall 64 of the first mold element 62 must have good thermal insulation.

The second mold zone 70 adjoining the first mold zone 60 is laterally delimited by the inner wall 74 of the second mold element 72. The second mold element 72 is formed by a hollow cylindrical or ring-shaped element whose inner diameter is larger than that of the cross-sectional area of the first mold zone 60 adjoining the second mold zone 70. This avoids direct contact of the continuous casting material with the inner wall 74 of the second mold element 72. In addition, this configuration of the second mold element 72 enables the formation of a cavity between the continuous casting material and the inner wall 74 for receiving lubricant, thereby ensuring a radially uniform distribution of the lubricant and a small reservoir formation of lubricant in this cavity. During the continuous casting process, the lubricant located in this cavity adjacent to the inner wall 74 is continuously captured by the continuous casting material flowing past, so that a thin film of lubricant is formed between the continuous casting material and the inner wall 56 of the third mold element 54.

In order to achieve a uniform supply of lubricant through the second mold element 72 during the entire continuous casting process, the diffusion properties of the second mold element 72 must be essentially independent of the temperature.

The third mold zone 52 adjoining the second mold zone 70 toward the outlet opening 14 forms the shaping region of the mold cavity 10. The third mold zone 52 is delimited laterally by the inner wall 56 of the third mold element 54.

The third mold element 54 and thus also its inner wall 56 is cooled by means of coolant, as a result of which cooling and thus solidification of the continuous casting material results in the edge region of the continuous casting material. In order to ensure sufficient cooling of the third mold element 54, it contains a second annular coolant chamber 32 which is fed by a first annular coolant chamber 22. The first 22 and the second 32 coolant chambers are connected to one another by a coolant distributor ring 26. This configuration of the cooling system allows heat to be dissipated radially from the continuous casting material as uniformly as possible. In order to further cool the continuous casting material after it has emerged from the outlet opening 14, the third mold element 54 contains radially uniformly distributed secondary coolant channels 24, which are connected to the second coolant chamber 32. In order to make the primary cooling of the continuous casting material as efficient as possible, the second coolant chamber 32 is located as close as possible to the inner wall 56 of the third mold element 54. In addition, the third mold element 54 has a high thermal conductivity, which is at least comparable to that of the continuous casting material.

The third mold element 54 shown in FIG. 1 consists of two hollow cylindrical mold parts 20, 30, which have a common concentric longitudinal axis that coincides with the longitudinal axis m of the mold.One mold part, the inner sleeve 30, is located inside the longitudinal axis m of the mold and delimits the third mold zone 52 laterally. The other mold element, the supporting body 20, lies outside with respect to the longitudinal axis of the mold and receives the inner sleeve 30 in its cavity. The inner sleeve 30 and the support body 20 are detachably connected to one another by inserting the inner sleeve 30 into the support body 20. In addition, the inner sleeve 30 on the side facing the support body 20 and the support body 20 on the side facing the inner sleeve 30 are such that, by inserting the inner sleeve 30 into the support body 20, an annular second coolant chamber 32 concentric with respect to the longitudinal axis m of the mold for the admission of coolant, as well as an annular cavity, the lubricant distributor ring 40, which is concentric with respect to the longitudinal axis m of the mold. The lubricant distributor ring 40 is connected to the second mold element 72 via lubricant channels 42.

The three mold elements 62, 72, 54 are fixed to a front plate 82 by means of fastening elements 84, 86. The first 84 and the second 86 fastening element contain at least one lubricant supply 91 for the supply of lubricant from an external lubricant supply (not shown) into the third mold element 54, and at least one coolant supply 87 for the supply of coolant from an external coolant supply (not shown) into the third mold element 54. The lubricant 91 and the coolant supply 87 point in a region remote from the inlet opening 11, ie in the first fastening element 84 and in a part of the second fastening element 86, a part 88, 92 which runs essentially parallel to the longitudinal axis m of the mold and in a region close to the inlet opening 11, i.e. in the second fastening element 86, a radially outwardly extending part (90, 94). This configuration of the coolant and lubricant feeds 87, 91 enables a lubricant and coolant feed which is arranged offset with respect to the inlet opening 11, so that the lubricant and coolant can be introduced into the third mold element 54 without expensive precautions in the electromagnetic stirring device 80.

The introduction of the lubricant from the lubricant supply 91 into the third mold element 54 takes place via at least one lubricant filling channel 43 located in the support body 20. The coolant is introduced from the coolant supply 87 into the third mold element 54 via at least one coolant channel 21 located in the support body 20.

The inner wall 56 of the third mold element 54 is such that the third mold zone 52 has a cylindrical shape with the mold longitudinal axis m as the concentric longitudinal axis. The cross-sectional area of the cylindrical third mold zone 52 has a diameter that is smaller than the diameter of the second mold zone, but larger than the diameter of the cross-sectional area of the first mold zone 60 adjacent to the second mold zone 70. As a result, the continuous casting material slides from the first mold zone 60 in the third mold zone 52 without touching the inner wall 74 of the second mold element 72.

The electromagnetic stirring device 80 is designed and arranged with respect to the mold elements 62, 72, 54 in such a way that its stirring action is part of the first mold zone 60, the entire second mold zone 70 and the entire third mold zone 52, and the entire liquid part of the continuous casting material after the outlet of the bolt or ingot captured from the outlet opening 14. The entire third mold zone 52 and the region of the ingot emerging from the outlet opening 14, in which part of the interior of the ingot is still in the liquid state of aggregation, denotes the solidification zone. It is essential for the design and positioning of the electromagnetic stirring device 80 that its stirring action is set such that, on the one hand, the continuous casting material has the shear rate necessary for shearing off the dendrites at the latest when reaching the second mold zone, and on the other hand the stirring action at the inlet opening 11 is reduced to such an extent that that the continuous casting material when entering the mold, ie in the entry-side area of the first mold zone 60, does not experience any significant stirring effect.

FIG. 2 shows two mold parts of the third mold element 54 which are detachably connected to one another. The two mold parts are the support body 20 and the inner sleeve 30, both of which have a concentric central axis which coincides with the mold longitudinal axis m. The two mold parts 20, 30 each have a cross section that is rotationally symmetrical with respect to the longitudinal axis of the mold. The annular inner sleeve 30 serves to shape the continuous casting material and thus represents that part of the mold which is exposed to high abrasion and contamination. The ring-shaped support body 20 accommodates the inner sleeve 30 in its essentially cylindrical cavity and gives the third mold element 54 the mechanical stability necessary for continuous casting.

The two-part construction of the third mold element 54 thus allows only the inner sleeve 30, which is subject to high abrasion or contamination, to be replaced. In addition, the two-part construction of the third mold element 54 allows the inner sleeve 30 to be removed for easier cleaning without having to remove the entire third mold element 54 or even the entire mold from the continuous casting device and thus enables considerable cost savings compared to the use of those known from the prior art Molds.

The support body 20 can be made of any material that provides the third mold element 54 with sufficient mechanical and thermal strength and sufficient dimensional stability. Metals or metal alloys are expedient and in particular aluminum or its alloys are used. The carrier body 20 very preferably consists of AlMgSi alloys.

The inner sleeve 30 preferably consists of aluminum or its alloys, or copper or its alloys. The inner sleeve 30 very preferably consists of AlMgSi alloys. In a further preferred embodiment of the inner sleeve 30, it consists of aluminum or an aluminum alloy and has a graphite layer or a graphite ring on the surface 46 directed against the third mold zone 52.

The dimensions of the third mold zone 52 depend, for example, on the desired final dimensions of the bolts or bars. The length of the third mold zone 52 or the length of the inner sleeve 30 is, for example, 2 to 20 cm, advantageously 2 to 10 cm and preferably between 3 and 6 cm. The length of the support body 20 is, for example, 3 to 25 cm, advantageously 3 to 15 cm and preferably between 4 and 8 cm. The outer diameter of the support body 20 is not critical per se; it is, for example, 8 to 25 cm, advantageously 9 to 20 cm and preferably between 11 and 18 cm.

The support body 20 contains an annular, first coolant chamber 22 which is concentric with respect to the mold axis m and is connected to the inflow-side surface of the support body 20 by at least one coolant channel 21 for introducing the coolant into the first coolant chamber 22.

The inner sleeve 30 and the support body 20 are designed such that, after the two mold elements 20, 30 have been joined between the inner sleeve 30 and the support body 20, an annular, second coolant chamber 32, which is concentric with respect to the longitudinal axis m of the mold, is formed, which with the first coolant chamber 22 via a coolant -Distributor ring 26 is connected.

The coolant distributor ring 26 represents a metal ring designed as a separate mold element with a multiplicity of through bores 27, two adjacent through bores 27, viewed in cross section, each enclosing the same central angle with respect to the mold axis m. The support body 20 has on its side facing the mold cavity an annular groove-shaped recess which is concentric with respect to the mold axis m and which at least partially has an annular connection opening with the first coolant chamber 22. The annular groove-shaped recess serves to receive the coolant distributor ring 26 provided with through bores 27. The annular groove-shaped recess and the coolant distributor ring 26 are designed such that the coolant distributor ring 26 fits positively into the annular groove-shaped recess of the support body 20, ie the inner surface of the coolant distributor ring 26 is flush with the inner surface 16 of the support body 20. To insert a coolant distributor ring 26 consisting of a metal ring provided with through bores 27 into the annular groove-shaped recess, the coolant distributor ring 26 can be separated at one point, for example, so that the coolant distributor ring 26 can be elastically deformed for insertion into the annular groove-shaped recess.

The inner sleeve 30 has, on the side facing the support body 20, an annular groove-shaped recess with respect to the longitudinal axis of the mold, which in cooperation with the side of the support body 20 facing the mold cavity 10 forms an annular cavity, the lubricant distributor ring 40, for receiving lubricant. The lubricant distributor ring 40 is connected to a lubricant filling channel 43 embedded in the carrier body 20. The lubricant distributor ring 40 thus serves for the radial distribution of the lubricant flowing in through the lubricant filling channel 43. This lubricant distribution ring 40 is also connected to the inflow-side end face 48 of the inner sleeve 30 via a plurality of lubricant channels 42 let into the inner sleeve 30, so that the lubricant located in the lubricant distribution ring 40 through the radially, for example uniformly, distributed lubricant channels 42 in the on the inflow side End face 48 of the inner sleeve 30 located lubricant outlet ring 41 can flow. The lubricant channels 42 are preferably arranged such that, viewed in a mold cross section, two adjacent lubricant channels 42 each include the same central angle with respect to the longitudinal axis m of the mold. In the lubricant outlet ring 41, the lubricant is again radially evenly distributed and thus evenly delivered to the second mold element 72.

The lubricant distributor ring 40 formed from the annular groove-shaped recess of the inner sleeve 30 and the inner surface 16 of the support body 20 is sealed on the inflow side 12 and outlet side 14 with annular sealing means 44, which come to lie between the inner sleeve 30 and the support body 20, that is to say on both sides that for formation of the lubricant distributor ring 40 necessary, annular groove-shaped recess of the inner sleeve 30, the inner sleeve can have parallel, parallel to the mold axis, further annular groove-shaped recesses which run parallel to the lubricant distributor ring 40 and which - for example together with corresponding recesses in the support body 20 - for receiving annular sealants 44, such as Sealing rings.

The support body 20 has a cylindrical inner surface 16 on the side facing the mold cavity, onto which an annular rib 18 directed against the mold cavity 10 is formed on the outlet-side end 14. The inner sleeve 30 has a hollow cylindrical part 34 with an annular flange 36 integrally formed on the inflow end 12, the annular flange 36 being directed against the support body 20. The annular flange 36 contains the lubricant channels 42 and the annular groove-shaped recesses required for the creation of the lubricant distributor ring 40, the lubricant outlet ring 41 and the receptacles for receiving the sealing means 44. The hollow cylindrical part 34 of the inner sleeve 30 has a further annular groove-shaped recess, the stop 39, in the outlet-side region 14 on the side directed towards the supporting body. This serves for the positive reception of the outer area of the annular rib 18 of the support body 20, which protrudes against the mold cavity 10.

The joining of the two mold elements 20, 30 expediently takes place by inserting the inner sleeve 30 into the support body 20, the annular stop 39 lying in the outlet-side region of the inner sleeve 30 positively engaging in the outer region of the annular rib 18 of the support body projecting against the mold cavity 10 20 takes hold. When the mold elements 20, 30 are pushed into one another, the hollow cylindrical part 34 of the inner sleeve 30 comes to lie on the annular rib 18 and the annular flange 36 lies on the cylindrical inner surface 16 of the supporting body 20, so that the annular one enclosed by the inner sleeve 30 and the supporting body 20 Cavity forms the second coolant chamber 32. The height of the flange 36 and the height of the annular rib 18 are selected such that the inner surface 46 of the inner sleeve 30 represents a straight cylindrical surface, the cylinder axis of which coincides with the longitudinal axis m of the mold.

The hollow cylindrical part 34 of the inner sleeve 30 serves the primary cooling of the continuous casting material flowing through the mold cavity 10 and consequently has - due to the good heat dissipation from the continuous casting material to the coolant - preferably a thin wall thickness. Preferably, at least the hollow cylindrical part 34 of the inner sleeve 30 consists of a good heat-conducting material, preferably copper, copper alloys, aluminum or aluminum alloys. Hollow cylindrical parts 34 made of aluminum or aluminum alloys are further preferred, which have a graphite ring on the side facing the mold cavity.

The annular rib 18 of the supporting body 20 furthermore has a multiplicity, for example 40 to 60, of secondary coolant channels directed obliquely at the billets emerging from the mold 24, which are connected to the second coolant chamber 32 and are used for secondary cooling by means of coolant application to the bolt or ingot after it has left the outlet opening 14.

The inner sleeve 30 also has on its inner surface 46 grooves 50 running parallel to the mold axis m, the grooves 50 expanding conically in the direction of the outlet opening 14 with regard to their groove depth and groove width. These grooves 50 essentially serve to guide the lubricant in the outlet-side region of the inner wall 56 of the third mold element 54, i.e. they are used to distribute the lubricant evenly. So that the lubricant does not flow to a significant extent through the grooves 50 without forming a film of lubricant evenly distributed over the inner surface 46, the grooves 50 incorporated into the inner sleeve only begin in the direction of flow of the continuous casting material after a certain distance, for example 1/4 to 1 / 3 corresponds to the length of the inner sleeve 30.

The inflow end face 48 of the inner sleeve 30 is set back with respect to the inflow end face of the support body 20, so that this creates a cavity, the recess 28, for the positive reception of the first (62) and second (72) mold elements.

Claims (20)

Mold for the continuous continuous casting of bolts or bars with homogeneously distributed, solidified primary particles, which consist of individual degenerate dendrites, the mold having an electromagnetic stirring device (80),
characterized in that
the mold is of modular construction and the mold cavity (10) enclosed by it has three sequentially arranged mold zones (60, 70 52) with a common concentric mold longitudinal axis (m), and each of the three mold zones through the inner wall (64, 74, 56) one corresponding mold element (62, 72, 54) is limited, the first mold element (62) having an inlet opening (11) for introducing continuous casting material, and at least the inner wall (64) of the first mold element (62) has a low thermal conductivity compared to the continuous casting material the second mold element (72) has means for introducing lubricant into the mold cavity (10), the third mold element (54) describes the shaping mold area and at least its inner wall (56) has a thermal conductivity comparable to that of the continuous casting material, and the electromagnetic stirring device ( 80) is such that its stirring effect at least partially includes all three mold zones (60, 70, 52), as well as the entire solidification zone of the continuous casting material. Chill mold according to claim 1, characterized in that the cross-section of the inner wall (64) of the first mold element (62) on the side adjacent to the second mold zone (70) is larger than the cross-section of the inlet opening (11). Chill mold according to claim 2, characterized in that the inner wall (64) of the first mold element (62), starting from the cross section adjacent to the second mold zone (70), has a cross section which tapers continuously towards the inlet opening (11) Chill mold according to one of claims 1 to 3, characterized in that the cross-sectional area of the first mold zone (60) adjacent to the second mold zone (70) is smaller than any cross-sectional area of the second mold zone (70). Chill mold according to one of claims 1 to 4, characterized in that the cross-sectional area of the third chill zone (52) adjacent to the second chill zone (70) is smaller than any cross-sectional area of the second mold zone (70), but is larger than that of the second mold zone (70) adjacent cross-sectional area of the first mold zone (60). Chill mold according to one of claims 1 to 5, characterized in that the first mold element (62) consists of ceramic, preferably at least the inner wall (64) of which is essentially non-porous. Chill mold according to one of claims 1 to 6, characterized in that the second mold element (72) contains or consists of an annular body made of highly porous, temperature-resistant material, the porosity being such that lubricant can diffuse through the porous material. Chill mold according to claim 7, characterized in that the annular body consists of graphite or ceramic. Mold according to one of claims 1 to 6, characterized in that the second mold element (72) contains an annular body made of fluffy, felt-like or sponge-like material or consists of such an annular body. Chill mold according to claim 9, characterized in that the annular body of the second mold element (72) consists of chemically stable, incombustible mineral fibers containing up to 62.3% by weight Al ₂ O ₃ and up to 37.2% by weight SiO ₂ . Chill mold according to one of claims 1 to 10, characterized in that the third mold element (54) has at least one coolant chamber (22, 32) for primary cooling of its inner wall (56), and means (24) for secondary, uniform application of coolant to the surface of the bolt or ingot after it emerges from the mold cavity (10), the means (24) preferably consisting of a plurality of secondary coolant channels (24) which are connected on the one hand to the coolant chamber (32) and on the other at an angle to the Surface of the bolt or ingot emerging from the mold are directed. Mold according to one of claims 1 to 11, characterized in that the mold has fastening elements (84, 86) for holding the mold elements (54, 62, 72), which has a coolant supply (87) for supplying coolant to the third Contain mold element (54), wherein the coolant supply (87) in a region remote from the inlet opening (11) has a part (88) running essentially parallel to the longitudinal axis (m) of the mold and in a region close to the inlet opening (11) a part running radially outwards Has part (90), and the radially outwardly extending part (90) with respect to the electromagnetic stirring device (80) is arranged offset towards the inlet opening (11). Chill mold according to one of claims 1 to 12, characterized in that the third mold element (54) on its contact surface with the second mold element (72) has an annular groove-shaped recess, the lubricant outlet ring (41), concentric with respect to the longitudinal axis of the mold (m), for the supply of lubricant in the second mold element (72), and means (40, 42, 43) for the supply of lubricant into the lubricant outlet ring (41). Chill mold according to claim 13, characterized in that the chill mold has fastening elements (84, 86) for holding the chill mold elements (54, 62, 72), which contain at least one lubricant supply (91) for the supply of lubricant into the third mold element (54) The lubricant supply (91) has a part (92) running essentially parallel to the longitudinal axis (m) of the mold in a region remote from the inlet opening (11) and a part (94) running radially outwards in a region close to the inlet opening (11) , and the radially outward-extending part (94) with respect to the electromagnetic stirring device (80) is arranged offset toward the inlet opening (11). Chill mold according to one of claims 1 to 14, characterized in that the third mold element consists of an inner sleeve (30) and a support body (20), the inner sleeve (30) and the support body (20) having a common concentric longitudinal axis, which with the longitudinal axis of the mold (m) coincides, and the inner sleeve (30) lies on the inside with respect to the longitudinal axis of the mold (m) and laterally delimits the third mold zone (52), and the support body (20) lies on the outside with respect to the longitudinal axis of the mold (m) and the inner sleeve (30 ), the inner sleeve (30) and the support body (20) being detachably connected to one another by pushing the inner sleeve (30) into the support body (20), and the inner sleeve (30) on the side facing the support body (20) and / or the support body (20) on the side facing the inner sleeve (30) is such that, by inserting the inner sleeve (30) into the support body (20), a longitudinal axis (m ) concentric, annular coolant chamber (32) for receiving coolant. Chill mold according to one of claims 1 to 15, characterized in that the inner wall (56) of the third mold element (54) has lubricant guide means (50) on its surface (46), which preferably run parallel to the longitudinal axis of the mold (m). Chill mold according to claim 16, characterized in that the lubricant guiding means (50) represent grooves (50) running parallel to the chill axis (m), which flow side only after a distance of 1/4 to 1/3 of the length of the third chill zone (52 ) begin and preferably expand conically with respect to their groove depth and groove width in the direction of the outlet opening (14) of the third mold zone (52). Use of the mold according to at least one of claims 1 to 17 for the continuous horizontal continuous casting of bolts or bars with homogeneously distributed, primarily solidified particles which consist of individual degenerate dendrites. Process for the continuous production of bolts or bars with thixotropic properties in their further processing by continuous casting of continuous casting material with a mold according to one of claims 1 to 17,
characterized in that
Continuous casting material is introduced into the introduction opening (11) of the first mold element (62) and is successively passed through the first (60), second (70) and third (52) mold zone, and the electromagnetic stirring device (80) about the mold longitudinal axis (m) rotating magnetic field generated in such a way that the continuous casting material on the one hand experiences no stirring effect in the area of the first mold zone (60) close to the inlet opening (11), on the other hand at least in the area of the first mold zone (60) close to the second mold zone (70), and in the second (70) and third (52) mold zones, and in the entire solidification zone of the continuous casting material is stirred vigorously so that dendrites forming during the solidification are sheared off and the entire inner surface (46) of the third mold element (54) is continuously lubricated, the continuous casting material on the inner wall (56) of the third mold element (54) is subjected to primary cooling, so that the bolt or ingot emerging from the mold is present in solid form at least in its outer edge zone, and the bolt or ingot is cooled further after it has left the mold by secondary cooling by means of coolant. A method according to claim 19, characterized in that the stirring is carried out by means of a stator of a multi-pole, for example two, four, or in particular six-pole induction motor.

Images