EP3986843A1

EP3986843A1 - Metering device for withdrawing and dispensing a melt and method for producing the metering device

Info

Publication number: EP3986843A1
Application number: EP20734866.5A
Authority: EP
Inventors: Philipp Kolbe; Thomas Wamser; Anna-Lena SPENLER; Michael KÄMMLER
Original assignee: Schunk Kohlenstofftechnik GmbH
Current assignee: Schunk Kohlenstofftechnik GmbH
Priority date: 2019-06-21
Filing date: 2020-06-18
Publication date: 2022-04-27
Also published as: US20220315494A1; DE102019116844A1; WO2020254485A1; MX2021015299A; CN114026055B; CN114026055A

Abstract

The invention relates to a metering device (10) for withdrawing and dispensing a melt consisting of or containing an oxide fibre reinforced oxide ceramic composite material.

Description

description

Dosing device for removing and dispensing a melt as well as a method for manufacturing the dosing device

The invention relates to a metering device, preferably a metering crucible or container for vacuum-assisted metering, for withdrawing and dispensing a melt, preferably metal melt, in particular non-ferrous metal melt, in particular an aluminum melt or a melt containing aluminum.

The invention relates in particular to the field of processing molten metal, in particular molten non-ferrous metal, preferably aluminum melts, wherein the melt is sucked in by negative pressure and then e.g. is drained into a mold. A mouthpiece of a so-called dosing crucible is usually dipped into a liquid aluminum melt, with an oxide layer having to be pierced if necessary.

Appropriate dosing crucibles can be made from a monolithic ceramic such as aluminum titanate. Typical wall thicknesses are between 10 and 25 mm.

After dipping into the melt, it is sucked into the dosing crucible by negative pressure. Usual pressures are <800 mbar. After the crucible has been filled as desired, it is closed on the suction opening side by means of a plunger made, for example, of silicon carbide. The crucible is then pulled out of the melt with an automatable displacement device, preferably a robot arm, and aligned with a casting mold. The melt flows out as the plunger releases the opening and at the same time negative pressure is reduced to a certain extent.

The wall thickness and the high density of aluminum titanate (3.7 g / cm ³ ) have the disadvantage that the thermal shock resistance of the material is negatively affected. The crucible also takes a long time to heat up for large component volumes. There is a risk of the melt solidifying due to the heat dissipation.

The disadvantage of the known dosing crucibles is also that only moderate mechanical parameters with flexural strengths well below 80 MPa are achieved and a brittle fracture behavior and the mentioned low thermal shock resistance can be observed. Immersing the crucible creates a large thermal gradient along the axis and along the wall thickness. The desired thermal shock resistance is not achieved due to the unfavorably low thermal conductivity of aluminum titanate (second thermal shock parameter).

It can also be observed that the crucible material reacts with aggressive aluminum melts, which are processed, for example, in the refining or grain refinement or other alloy compositions, in particular alkali-containing melts that contain sodium or strontium additives. The reactions that occur in the process lead to successive destruction of the metering device and, in the case of strong corrosive / chemical attack, also to contamination of the melt.

Furthermore, it has been shown that the aluminum titanate shows an unfavorable wetting behavior, so that adhesions of solidified aluminum up to the plunger sticking to the dosing crucible can be determined. In this case, dismantling must take place in the cold state, so that the resulting abrasion can lead to wear and tear and destruction of the dosing crucible and plunger. The monolithic ceramic made of aluminum titanate is porous and riddled with cracks in order to improve the thermal shock behavior. The crucibles are produced by slip casting of particle-laden slips. The slip casting process has disadvantages in terms of component geometry or wall thickness. With the slip casting process, the wall thickness within the component cannot generally be varied. The maximum wall thickness is limited. The wall thickness is proportional to the root of the meal duration. During the casting process, gradients can form due to different particles. There are also disadvantages when sintering large-volume components. Furthermore, the shrinkage that occurs in large-volume components leads to considerable problems.

The present invention is based on the object of developing a metering device of the type mentioned at the outset in such a way that reproducible, rapid and precise metering of metal melts, in particular aluminum melts, without the formation of melt artifacts, contamination of the melt or air inclusions is possible, the metering device for a vacuum-assisted Casting method can be used and the metering device should be movable.

To achieve the object, the invention essentially provides that the metering device consists of or contains an oxide-fiber-reinforced oxide-ceramic composite material with an open porosity, in particular from 20% to 40%.

If necessary, the metering device consisting of the oxide-fiber-reinforced oxide-ceramic composite material can be coated or compacted on the surface. Surface side means inside or outside or both inside and outside.

For this purpose, it is provided in particular that the oxide fiber-reinforced oxide-ceramic composite material is coated at least in some areas, in particular on the outside, to form a preferably closed-pore layer. There is the option of using glass solder or organometallic compounds as the coating material.

In particular, the invention provides that a ceramic layer, a precursor-based layer or a glass-like layer is applied to the base body.

There is a possibility that the layer is applied by thermal spraying. The composite material contains oxide-ceramic fibers, preferably formed from at least one material from the group Al ₂ O3, SiO ₂ , ZrO ₂ , Y ₂ O ₃ , TiO ₂ , CaO, MgO, Y ₂ O ₃ stabilized ZrO2. Furthermore, it is provided that the composite material contains an oxide-ceramic matrix, preferably formed from at least one material from the group Al ₂ O ₃ , SiO ₂ , ZrO ₂ , Y ₂ O ₃ , TiO ₂ , CaO, MgO, Y ₂ O ₃ stabilized ZrO ₂ .

It is provided in particular that the matrix and the fibers consist of the same oxide-ceramic material or oxide-ceramic materials or contain this or these or that the main components of the matrix and the fibers match, for example consist of Al ₂ O ₃ .

It should be emphasized that the metal in the composite material and that of the melt or the main component of the melt should be the same.

By using the oxide-ceramic composite material, a non-brittle material is made available which has thermal shock resistance, sufficient mechanical strength and, regardless of the porosity, surprisingly the required vacuum tightness. There are no solidification processes or the formation of inhomogeneities. This increases the process reliability when processing the melt.

Furthermore, advantageous wetting and corrosion properties are found, particularly when dosing aluminum melt, if the metal of the oxide-ceramic composite material is aluminum, i.e. the fiber consists of Al ₂ O ₃ and the matrix also consists of Al ₂ O ₃ or essentially contains it. There is also good resistance to alkali-containing aluminum melts, so that the range of applications can be expanded.

The same metals prevent contamination of the melt from the material of the metering device or the crucible or the container. The use of the oxide-ceramic composite material results in a low component weight compared to the state of the art, so that the dosing process can be accelerated. There is also less wear and tear on the automatable displacement device or robot unit compared to the prior art, since smaller masses have to be moved.

The metering device itself can be produced from the oxide-ceramic fibers by winding fibers onto a tool that depicts the inner geometry of the metering device, or by using textile fabrics, braids, scrims. This results in particular advantages with regard to the geometry of the metering device, as a result of which structural improvements can be achieved.

The internal geometry is the same as the interior of the metering device into which the melt is sucked.

Ventilation options, attachment or integration of heating elements due to the thin wall thickness are possible. The thin wall thickness also offers the advantage that only a small amount of heat is extracted from the melt, so that it is possible to work at a lower melting temperature than in the prior art. This brings energetic advantages. Structures required for handling the metering device can be designed without any problems. Easy assembly is possible due to the low weight. In spite of this, simple manufacture is possible.

DE 10 2013 104 416 A1 relates to monolithic ceramics with mesh reinforcement that are used in construction and for armor plates. The ceramic can also be used for graphite reinforcement.

The subject of WO 2016/184776 A1 is a composite pipe that consists of two layers, one of which consists of non-porous monolithic oxide ceramic and one layer of oxide fiber composite ceramic.

A method for producing a component made of fiber-reinforced composite material can be found in DE 10 2010 055 221 A1. Oxide-ceramic composite materials which have oxide-ceramic fiber reinforcements are known. In this regard, reference is made to EP 2 848 509 A1 or DE 10 2016 007 652 A1, for example. Turbine blades and turbine blades of superheated steam turbines are described in DE 102017202 221 A1 as an application example of a corresponding material.

However, there is no use for areas in which vacuum-assisted work - such as with casting processes - is not found, especially against the background that, due to the porosity, one should assume that corresponding materials are unsuitable for vacuum processes. Surprisingly, however, it has been shown that reproducible, rapid and precise metering of non-ferrous metal melts is also possible when using the oxide-ceramic fiber-reinforced composite material used according to the invention.

Thin-walled dosing containers or crucibles can be produced from the porous oxide-fiber-reinforced oxide ceramic with additional components or add-on elements, the volumes being designed so that up to 50 kg of melt can be accommodated and transported without any problems.

The individual fiber filaments, which are brought together in particular as fiber bundles or rovings with several hundred individual filaments, should have a diameter between 5 mm and 20 mm, in particular between 10 mm and 12 mm. The density should preferably be between 2.0 g / cm ³ and 6.0 g / cm ³ , more preferably between 3.0 g / cm ³ and 4.0 g / cm ³ .

If the open porosity, i.e. the cavities of the metering device or its oxide-ceramic composite material, which are connected to each other and to the environment, are in the range between 20% and 40%, the range between 27% and 32% is preferred. Due to the open porosity, a low conductivity of the melting device of in particular less than 10 W / mK is achieved.

The wall thickness of the metering device, that is to say of the crucible or container, should preferably be between 1 mm and 20 mm, more preferably between 1 mm and 4 mm. The geometric design is arbitrary and can in particular be rotationally symmetrical.

The invention also includes that the metering device is designed as an insert for a metallic structure. This means that the metallic structure cannot be attacked by the melt, which could otherwise be destroyed.

In particular, it is provided that further components connected to the metering device are made from the same oxide-ceramic material as the metering device.

As mentioned, the metering device can be manufactured using winding technology or based on textile fiber semi-finished products such as woven fabrics, braids, scrims.

As mentioned, the invention does not exclude that a coating is additionally provided.

Single-layer or multi-layer layers or coating systems, preferably with thicknesses in the range between 50 mm and 2 mm, can be used as the coating in order to reduce the gas permeability. The structure of the base body, i.e. the oxide-ceramic composite material, should be retained as far as possible.

As a result of the coating, the composite material is basically infiltrated or modified only on the surface to a depth of 500 mm in order to enable good layer adhesion.

To reduce the gas permeability, the porosity of the layer or layers should be significantly lower than that of the base material.

In particular, it is provided that the layer or layers are closed-pore, preferably achieve at least a density of 97% of the theoretical density of the coating material. Theoretical density is to be understood as that density at which a body made from the material has no pores. The coating is intended to improve the gas tightness so that the metering device can be coated on the inside, that is to say on the melt side, or on the outside. A coating on the inside and outside is of course not excluded.

The coating material can preferably be identical to that of the base body, that is to say of the oxide-ceramic material.

The coating material can consist of crystalline and oxide-ceramic components.

Regardless of this, the coating material should be temperature resistant up to 1200 ° C and corrosion and abrasion resistant. The metering device can be coated on one or both sides, that is to say inside and outside. A coating can also be limited to certain areas.

Possible coating variants are e.g. the application of glass solder, precursor-based layers or thermal spraying.

With the so-called glass solders, a vitreous layer crystallizes on the substrate through a temperature treatment in the course of the layer production. The coating particles are coated with a slip e.g. applied by brushing. In this respect, reference is also made to the disclosure of DE 10 2014 106 560 B3 or EP 2 942 342 A1. With a corresponding application process using glass solder, a dense ceramic layer is formed.

In the case of precursor-based layers, liquid organometallic compounds can be used. The application takes place wet-chemically, for example by spraying or dipping. These compounds pyrolyze, ceramize and crystallize through a temperature treatment. The volume shrinkage during processing can be reduced by adding passive and active fillers. Passive fillers can be, for example, aluminum oxide, zirconium oxide. Active components in the layer would be A1, ZrSi ₂ , T1B ₂ . These oxidize in the course of the synthesis and there is an increase in volume. In thermal spraying, the coating particles are melted with the aid of a torch, such as a plasma jet or an electric arc, and applied to the substrate by a gas stream. The melted particles hit the substrate, flatten and solidify. When they hit, there is a mechanical interlocking between the substrate and the particle. No further temperature treatment is necessary.

Due to the thermomechanical and thermodynamic compatibility, the coating material used for thermal spraying should be one that corresponds to the substrate material, i.e. the composite material, with regard to the main components. If a composite material made of Al ₂ O ₃ and ZrO _{2 is} used, the particles should also consist of Al ₂ O ₃ and ZrO ₂ .

In thermal spraying, appropriate particles made from these materials are used. However, it is also possible to work reactively with aluminum, which oxidizes when the substrate material has Al ₂ O ₃ and ZrO ₂ as main components. The expansion for AI ₂ O ₃ fits e.g. YAG (Yttrium-Aluminum-Garnet) and Y2Si2O7 / YSiO ₅ .

A layer system can be applied that forms one layer overall. Layer systems are several individually differentiable layers of a layer. E.g. a layer system of bond coat for adhesion, TBC (thermal barrier coating) for thermal insulation and on the outside, i.e. on top, an EBC (environmental barrier coating) as corrosion protection. Every single layer has a special function. An expansion mismatch can also be reduced by using graded layers.

The depth of penetration can be varied depending on the coating process. The term penetration depth is also intended to express that there can be a transition area between the layer and the substrate. If organometallic precursors are used, they penetrate deeper into the substrate material and infiltrate it, with some reaction between the coating material and the substrate. During thermal spraying, the melted or partially melted particles hit the colder substrate surface, so that mechanical adhesion occurs. In this case, the depth of penetration is very small or only superficial adhesion can occur, so that practically no depth of penetration can be spoken of.

Regardless of how the coating is produced, the properties of the substrate material are retained. The coating has the advantage that embrittlement does not occur. The coating increases the gas tightness. The coating has a high hardness and offers abrasion and corrosion resistance.

In particular, the teaching according to the invention is characterized in that fiber reinforcements can be provided which are designed to be appropriate for the load. In particular, in the dispensing and therefore removal area of the metering device, thickenings can be provided in order to protect areas of increased stress.

The geometrical restrictions occurring according to the prior art when using monolithic ceramics are not given.

In particular, it is provided that a corresponding metering device is intended to process non-ferrous metal melts which consist of or contain Al, Si, Mg, Cu, Zn, Sn, Ti, Na, Sr, B, whereby aluminum melts or aluminum alloy melts should be mentioned in particular are.

The fiber reinforcement including the porous matrix leads to a significant increase in strength and damage tolerance compared to the monolithic ceramic that can be removed from the prior art. This leads to a quasi-ductile material behavior, which prevents brittle fracture and impacts or similar mechanical loads are classified as non-critical. For example, collisions when moving the dosing device, which can be caused by incorrect teaching of a robot, are less problematic. Surprisingly, the porosity of the composite material does not represent a technically relevant problem when the melt is sucked, held and metered by means of negative pressure. A high metering accuracy and exact quantity recording are possible. However, this does not exclude the possibility of an additional coating being provided.

In particular, when the fibers and the matrix consist of the same oxide as Al ₂ O ₃ , this means that, for example, in the case of aluminum melts and its alloys, corrosion of the material of the metering device is prevented and an extremely favorable wetting ratio occurs. Additions of zirconium oxide, for example, can be advantageous.

The invention is therefore also characterized in that the weight proportion of the additive or the matrix component zirconium oxide, which is optionally reinforced with yttrium oxide, is 5% to 30%, in particular 12% to 25%, of the oxide ceramic of the matrix.

The favorable wetting behavior prevents e.g. the closure such as the plunger, e.g. can consist of SiC or an oxide ceramic material such as that of the metering device, baked firmly to the metering device.

Wear is reduced. The cleaning effort is also reduced due to adherence that is difficult to remove and damage is avoided.

As mentioned above, changes in mass and structure do not fundamentally occur if aggressive, e.g. Alkali-containing aluminum fused alloys are traded, especially when the matrix and the reinforcing fibers consist of or contain aluminum oxide.

Wear is reduced and the service life is increased considerably.

Due to the lightweight construction resulting from the material, systems and robotics are less mechanically stressed and down-sizing is made possible. The travel time of the metering device can be reduced in comparison to the prior art and thus the overall process time can be reduced.

Another advantage of the lightweight construction is the heat and temperature insulation properties, which enables new processing options by means of low temperature drops, i.e. temperature drops in the melt. Energy savings can be achieved.

The manufacturing technique gives freedom of geometric design. Any complex geometries with undercuts can be implemented. The metering behavior can be improved by changing or adapting the geometry.

Due to the use of oxide-ceramic materials according to the invention, larger-volume crucibles can be produced in comparison with the prior art. The small wall thickness enables the melt to be tempered by heating and cooling elements that surround the metering device.

Furthermore, there is the possibility that the plunger is made hollow and thus sensors such as temperature sensors can be integrated in it.

The opening, that is to say the mouthpiece of the metering device, can be designed in such a way that melt droplets cannot adhere.

It is also possible to integrate sieve elements or filters to clean the melt.

The melt flow can be designed without interference if flow aids are formed inside the metering device, the negative shape of which is shown on the tool, on which the fiber bundles are wound or the flat fiber fabrics, scrims, braids are placed, which are previously impregnated with a slip containing oxide ceramic particles that form the matrix.

The invention is therefore also characterized by a method for producing a metering device, in particular a vacuum-assisted metering crucible or container, for withdrawing and discharging a melt, preferably metal melt, preferably non-ferrous metal melt, in particular an aluminum melt or a melt containing aluminum, comprising the process steps

Impregnation of an arrangement of oxide-ceramic fibers with a slip containing oxide-ceramic particles,

Winding or laying the impregnated arrangement of fibers on a tool that depicts the internal geometry of the metering device,

Drying of the arrangement laid or wound on the tool.

The arrangement is then removed from the tool, in particular removed from the mold or partially removed from the mold. Sintering then takes place. If necessary, the metering device produced in this way is reworked. In this case, one or more continuous fiber bundles or flat structures, in particular fiber scrims, fabrics or braids, are used as the arrangement.

In particular, it is provided that the drying process for forming a green body from the arrangement is carried out in a temperature range between 40.degree. C. and 250.degree. C., in particular between 80.degree. C. and 150.degree.

After drying and demolding or partial demolding, sintering takes place, in particular at a temperature between 1000 ° C and 1300 ° C, preferably between 1150 ° C and 1250 ° C.

Further details, advantages and features of the invention emerge not only from the claims, the features to be taken from them - individually and / or in combination - but also from the following description of preferred exemplary embodiments to be taken from the drawing and their explanations.

Show it:

1 shows a basic illustration of a metering device for removing and dispensing a melt with a separately drawn plunger, FIG. 2 shows a section of FIG. 1,

3 shows a variant of the illustration in FIGS. 2 and

4 shows a basic illustration of a winding process.

In the figures, purely by way of example, a metering device for removing and dispensing a melt, in particular a metal melt, is shown, which is also referred to as a metering crucible or container 10 and is referred to in the following simply as a metering crucible.

The dosing crucible 10 has on the withdrawal or delivery side a mouth opening 14 which can be closed by a plunger 12 and which merges into a conical and then hollow-cylindrical section 16, 18.

The outer diameter of the plunger 12, specifically in its distal section 20, corresponds to the inner diameter of the mouthpiece or the mouth opening 14. By axially adjusting the plunger 12, the mouth opening can consequently be closed or released. The dosing crucible 10 consists of a fiber-reinforced oxide-ceramic composite material made of the material or materials described above.

The porosity of the metering crucible 10 should in particular be between 27% and 32%. The plunger 12 can be made of the same material as the dosing crucible 10 or, e.g. consist of silicon carbide,

If the plunger 12 is made of an oxide-ceramic composite material, it can be hollow and e.g. Contain one or more sensors in order to control the process management and, if necessary, to control or regulate it.

The dosing crucible 10 is preferably produced using the winding technique, although prepregs, which can be placed on a tool that depicts the internal geometry of the dosing crucible 10, or a combination of these methods can also be used. Fiber bundles, so-called rovings, are wound onto the winding core, with the individual fiber filament diameters between 5 mm and 20 mm, in particular in the range between 10 mm and 12 mm. The density should be in the range between 2 g / cm ³ to 6 g / cm ^3, preferably between 2.5 g / cm ³ to 3.2 g / cm ^3.

Before being wound onto the winding core, the fiber bundles are passed through a slip and thus impregnated. The slip contains the ceramic particles that form the matrix of the composite body.

The proportion of ceramic particles can be 10% by volume to 50% by volume, in particular 20% by volume to 40% by volume, based on the total volume of the slip.

In particular, a water-based slip is used with preferably organic additives e.g. Polyols, polyvinyl alcohols or polyvinylpyrrolidones, dispersion binders, preferably styrene acrylate dispersions.

The slip can be at least 10 wt% to 20 wt%, preferably at least 24 wt%, e.g. 21-35% by weight, based on the total weight of the ceramic particles, glycerine.

A material from the group Al ₂ O ₃ , SiO ₂ , ZrO ₂ , Y ₂ O ₃ , TiO ₂ , CaO, MgO, and ZrO ₂ stabilized with Y ₂ O _{3 are used} as oxide ceramic both for the ceramic particles and for the fiber in question.

If an aluminum melt or an aluminum alloy melt is to be dosed with the dosing crucible 10, then Al ₂ O ₃ should be used as material both for the matrix, ie consequently the ceramic particles, and for the fiber. The slip can optionally contain additives such as ZrO ₂ , the proportion being between 5% and 30%, in particular between 12% and 25% in% by weight, of the total powder amount of the ceramic metal oxide. The proportion by volume of the ceramic particles should be 20 to 50% by volume based on the total volume of the slip.

The corresponding impregnated fiber bundles are then wound onto the winding core and then dried, in particular in the temperature range between 40 ° C and 250 ° C, preferably in the range between 80 ° C and 150 ° C. A body produced in this way is cut through and pulled off the winding core. This is followed by sintering in the temperature range between 1,000 ° C and 1,300 ° C, in particular between 1,150 ° C and 1,250 ° C. Possibly. post-processing takes place in order to then use the metering crucible 10 produced in this way.

The drying time depends on the temperature and is between 2 hours and 48 hours, preferably between 12 hours and 24 hours. Sintering takes place over a temperature / time curve with various holding stages and

-duration, the holding time at the maximum temperature should be between 5 minutes and 24 hours, preferably between 1 hour and 12 hours.

Due to the winding technology used, the geometry of the dosing crucible 10 can be changed to the desired extent as a function of the geometry of the winding core. This is illustrated in principle with reference to FIGS. 2 and 3. It is thus possible to vary the opening angle of the conical section 16 to the desired extent. In FIG. 2 the angle a1 is smaller than the angle a2 in FIG. 3. Furthermore, the length of the mouthpiece 14 can be varied, as a comparison of FIGS. 2 and 3 with regard to the sections S1, S2 makes clear. The length of the conical section 16 can also be varied (LI <L2).

There is also the possibility of varying the wall thickness of the component or of designing the end sections of the winding core in such a way that flow aids result in the interior of the cones, as is indicated purely in principle with reference to FIG. 3.

Ribs can thus be formed, preferably those which run in a spiral. Wave structures can also be concentric around the longitudinal axis of the dosing crucible be provided to run in order to influence the flow behavior of the melt to the desired extent.

In particular, it is provided that the fiber volume content of the metering device is 35% to 50%, preferably 32% to 42%.

The following is to be added in addition to the winding technique.

Winding processes are used to produce rotationally symmetrical parts. The internal geometry of the object is determined by the so-called winding core on which the fibers impregnated with the matrix are placed.

In the case of the winding core, a distinction is made between reusable, lost, meltable and separable cores. In the present case, the dosing crucibles are removed from the core so that the latter can be used again. Meltable cores are often used for smaller components and separable cores for components with larger diameters.

The winding is usually done with a winding machine that corresponds to that of a CNC lathe. The winding core is clamped at one of its ends on a three-jaw chuck and at the other end e.g. stored on a tailstock.

In order to wind rovings, that is to say fiber bundles, which for example can comprise 100 or more individual fibers, so-called filaments, on the winding core, these are unwound from a bobbin holder. The rovings can then pass deflection rollers, by means of which the tension of the rovings is adjusted via a resistor. The fiber bundle is then passed through a thread eye over further deflection rollers through a slip bath, the composition of which has been described above. After the fibers have been impregnated, they are centered by a thread eye via one or more other pulleys, which also determine the spring tension and the number of revolutions, winding speed and length of the used fiber strand, and are placed on the winding core, which is rotating. The thread tension is also of paramount importance. If this is too low, the fibers are not pressed onto the winding core to a sufficient extent. If the tension is too great, the slip cannot be sufficient get between the individual fiber filaments and the Ro vings can be torn off.

After the winding process, the wound fiber architecture is tied with tear-off fabric. This is used to create a uniform surface, compression by displacing excess slip and thus increasing the fiber volume content and also protects the component.

In the circumferential winding, which is also called radial winding, the rovings are laid in parallel, as can be seen from the present illustration in FIG. 4. In the case of cross-winding, the rovings are deposited from one pole cap, that is from one end to the other pole cap, that is to the other end, in order to obtain fiber reinforcement in the x and y directions. The winding angle is measured from the deposited fiber strand against the axis of rotation and influences the absorption of axial loads.

If a winding part has purely unidirectional circumferential windings, d. H. the angle a is about 90 °, the highest tensile strengths can be achieved in tangential orientation. If the winding angle is <45 °, more axial loads are absorbed. With reinforcement in the axial direction, i. H. small winding angles, the problem arises during production that it is no longer possible to fix the roving at the end of the body.

Various calculation programs are available for the coordination of the type of winding, winding angle, number of layers (fiber requirement). After the winding process, the wound fiber architecture is tied off with a tear-off fabric in order to achieve a uniform surface. Compression also takes place by displacing excess slip and thus an increase in the fiber volume content and also protects the component. This is followed by drying and the sintering process.

An exemplary embodiment follows:

First, oxide-ceramic prepregs are produced. For this purpose, fabric made of aluminum oxide fibers (> 99% Al ₂ O ₃ ) with an oxide ceramic particle is used impregnated with water-based slip. The filament diameter is 10-12 mm and the yarn count is 20,000 denier. The slip has a solids content of 30% by volume consisting of 80% by weight of Al ₂ O ₃ particles and 20% by weight of ZrO ₂ particles. The mean particle size is 1 mm. 2% by weight of polyacrylic acid are added as a dispersant. After the water content of the infiltrated fiber architecture has been reduced, the resulting prepreg can be processed by cutting it to size and placing it on a tool that reproduces the inner contour of the dosing crucible. Then the tool covered with the prepreg is clamped in a winding device. Then the aluminum oxide fiber rovings (> 99% Al ₂ O ₃ ) of yarn size 20,000 denier are guided from a bobbin holder over pulleys through an immersion bath and on the rotating one

Winding core deposited. The rovings are centered using a thread eye. The thread tension is in the range from 10 to 90 N and is set using the pulleys. The slip in the immersion bath has a solids content of 32% by volume of the ceramic particles based on the total volume of the slip, consisting of 80% Al ₂ O ₃ particles and 20% ZrO ₂ particles. The mean particle size is 1 mm. When

2% by weight of polyacrylic acid are added to the dispersant. The coiled fiber architecture of the molded composite material is consolidated by reducing the water content so that a green body is obtained. After drying, the wound fiber architecture can be removed from the core. Sintering then takes place at 1200 ° C. Rework can be done by turning, milling or grinding.

Claims

1. Dosing device (10), preferably dosing crucible or container for vacuum-assisted dosing, for removing and dispensing a melt, preferably metal melt, in particular non-ferrous metal melt, in particular aluminum melt or a melt containing aluminum,

characterized,

that the metering device (10) consists of or contains an oxide-fiber-reinforced oxide-ceramic composite material.

2. Dosing device according to claim 1,

characterized,

that the metering device (10) is provided on the inside and / or outside with at least one preferably closed-pore coating or is compacted.

3. Dosing device according to claim 1 or 2,

characterized,

that one or more layers of a thickness d of 50 mm £ d £ 2 mm are applied to the oxide fiber reinforced oxide ceramic composite material as the base body of the metering device (10).

4. Dosing device according to at least one of the preceding claims,

characterized,

that the coating has a density of at least 95%, preferably at least 97% of the theoretical density of the material from which the coating is made.

5. Dosing device according to at least one of the preceding claims

characterized,

that the composite material contains oxide-ceramic fibers, preferably formed from at least one material from the group Al ₂ O ₃ , SiO ₂ , ZrO ₂ , Y ₂ O ₃ , TiO ₂ , CaO, MgO, Y ₂ O ₃ stabilized ZrO ₂ .

6 dosing device according to at least one of the preceding claims,

characterized,

that the composite material contains an oxide ceramic matrix, preferably formed from at least one material from the group Al ₂ O ₃ , SiO ₂ , ZrO ₂ , Y ₂ O ₃ , TiO ₂ , CaO, MgO, Y ₂ O ₃ stabilized ZrO ₂ .

7. Dosing device according to at least one of the preceding claims,

characterized,

that the matrix and the fiber consist of or contain the same oxide-ceramic material or the same oxide-ceramic materials or that the main components of the oxide-ceramic materials match.

8. Dosing device according to at least one of the preceding claims,

characterized,

that the metal in the composite material and that of the melt or main component of the melt are the same.

9. Dosing device according to at least one of the preceding claims,

characterized,

that the matrix and the fiber consist of Al ₂ O ₃ or contain them as a main component.

10. Dosing device according to at least one of the preceding claims,

characterized,

that the open porosity of the metering device (10) or of the oxide-fiber-reinforced oxide-ceramic composite material is between 20% and 40%, in particular between 27% and 32%.

11. Dosing device according to at least one of the preceding claims,

characterized,

that the density p of the fibers is 2 g / cm ³ <p <6 g / cm ³ , in particular 3.0 g / cm ³ <p <4.0 g / cm ³ and / or the fiber diameter is 5 mm to 20 mm , particularly 10 mm to 12 mm.

12. Dosing device according to at least one of the preceding claims,

characterized,

that the metering device (10) has a metallic structure which is provided on the melt side with an inherently rigid body made of the oxide-ceramic composite material and introduced into the metering device.

13. Dosing device according to at least one of the preceding claims,

characterized,

that the metering device (10) is made from the oxide-ceramic fibers by winding fibers on a tool that depicts the inner geometry of the metering device and / or by using textile fabrics, braids, fabrics.

14. Dosing device according to at least one of the preceding claims,

characterized,

that the oxide-ceramic fibers consist of continuous fibers, in particular in the form of continuous fiber bundles, short fibers or a combination of these.

15. Dosing device according to at least one of the preceding claims,

characterized,

that the metering device (10) has a wall thickness W _{D of} 1 mm £ WD £ 20 mm, in particular 1 mm £ WD £ 3 mm.

16. Dosing device according to at least one of the preceding claims,

characterized,

that the metering device (10) has fiber reinforcements suitable for the load, in particular in the removal and delivery area.

17. Dosing device according to at least one of the preceding claims, characterized in that

that flow aids are formed on the inside of the metering device (10).

18. Dosing device according to at least one of the preceding claims,

characterized,

that the metering device (10) can be closed by a plunger (12) which consists of or contains a material from the group SiC, material of the matrix.

19. Dosing device according to at least claim 18,

characterized,

that the plunger (12) is hollow, with at least one sensor, such as a temperature sensor, preferably being arranged in the plunger.

20. A method for producing a metering device (10), such as a metering crucible or

-container for vacuum-assisted metering, for withdrawing and dispensing a melt, preferably metal melt, in particular non-ferrous metal melt, in particular aluminum melt or a melt containing aluminum, comprising at least the process steps

Winding or laying the impregnated arrangement of the fibers on a tool that depicts the inner geometry of the metering device (10), drying the arrangement placed or wound on the tool, removing the arrangement and sintering it.

21. The method according to claim 20,

characterized,

that the arrangement of the fibers at a temperature between 40 ° C and 250 "C, in particular between 80 ° C and 150 ° C, is dried.

22. The method according to at least claim 20 or 21,

characterized,

that the arrangement of the fibers is sintered at a temperature between 1,000 ° C. and 1,300 ° C., in particular between 1,150 "C and 1,250" C.

23. The method according to at least one of claims 20 to 22,

characterized,

that one or more continuous fiber bundles and / or flat fiber structures, in particular fiber scrims, woven fabrics or braids, are used as an arrangement.

24. The method according to at least claim 20,

characterized,

that the sintered and optionally reworked arrangement for producing the metering device (10) is coated at least in certain areas, in particular at least on the outside, to form a preferably closed-pore layer.

25. The method according to at least one of claims 20 to 24,

characterized,

that glass solder or organometallic compounds are used as coating material.

26. The method according to at least one of claims 20 to 24,

characterized,

that a ceramic layer, a precursor-based layer or a glass-like layer is applied to the base body.

27. The method according to at least one of claims 20 to 24,

characterized,

that the layer is applied by thermal spraying.

28. Use of a metering device (10) according to at least one of claims 1-19 for removing a melt, transporting the melt in the metering device (10) by a method and draining the melt into a casting mold.

29. Use according to claim 28,

characterized,

that the metal of the oxide-ceramic composite and the metal of the metal melt are the same.