EP4387941A1 - Barbotine céramique destinée à la coulée de précision basée sur une suspension capillaire - Google Patents

Barbotine céramique destinée à la coulée de précision basée sur une suspension capillaire

Info

Publication number
EP4387941A1
EP4387941A1 EP22765428.2A EP22765428A EP4387941A1 EP 4387941 A1 EP4387941 A1 EP 4387941A1 EP 22765428 A EP22765428 A EP 22765428A EP 4387941 A1 EP4387941 A1 EP 4387941A1
Authority
EP
European Patent Office
Prior art keywords
ceramic
ceramic slip
slip
phase
investment casting
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP22765428.2A
Other languages
German (de)
English (en)
Inventor
Moritz Weiss
Norbert Willenbacher
Wolf WEDEL
David Menne
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Karlsruher Institut fuer Technologie KIT
Original Assignee
Karlsruher Institut fuer Technologie KIT
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Karlsruher Institut fuer Technologie KIT filed Critical Karlsruher Institut fuer Technologie KIT
Publication of EP4387941A1 publication Critical patent/EP4387941A1/fr
Pending legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C9/00—Moulds or cores; Moulding processes
    • B22C9/02—Sand moulds or like moulds for shaped castings
    • B22C9/04—Use of lost patterns
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
    • B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
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    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/10—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on aluminium oxide
    • C04B35/111—Fine ceramics
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Definitions

  • the present invention relates to a ceramic slip for investment casting based on a capillary suspension and a method for producing at least one ceramic mold or at least one investment casting component using the ceramic slip. Furthermore, the present invention relates to the use of the ceramic slip according to the invention for the production of ceramic casting cores and other porous molded bodies.
  • Investment casting is a casting process for the production of metallic components, which is characterized by attention to detail, dimensional accuracy and excellent surface properties.
  • the conventional investment casting process essentially comprises the following steps: Creation of prototypes (positive models) of the respective components, e.g. made of wax or a polymer, mounting several positive models on a model cluster (e.g.
  • a wax tree which also includes the gating system with the feed channels to the casting mould, repeated immersion of the model cluster in a ceramic slip, sanding of the ceramic layer after each immersion step and drying of the respective one sanded ceramic layer, melting the positive model out of the ceramic mold, burning out the ceramic mold, pouring the molten metal into the ceramic mold, removing the ceramic mold after the metal has solidified, cutting off and polishing the finished metal body (https://- www.richterformmaschine.com/ratgeber/ investment casting process/).
  • Slurry, sanding and drying are carried out according to conventional methods Casting process repeated about 6 - 12 times until a total layer thickness of approx. 5 - 8 mm is reached.
  • the drying time between the individual layers is approx. 3 - 8 hours; after the last layer the mold is completely dried for 12 - 24 hours.
  • the drying times vary depending on the composition of the ceramic slip and the thickness of the layer applied. In addition, drying systems are used, which means that drying times can be shortened.
  • the shell mold should have the following properties in order to be used in investment casting: the shape of the positive model must be reproduced exactly, the green part must be sufficiently stable for the positive model to be melted out and then burned out, the fired ceramic mold must not break when the metal is poured in and the air displaced by the metal in the mold during casting must be able to escape through the mold shell, ie. the shell mold must have high permeability. Finally, after the metal has solidified, the mold shell must be removable in such a way that the casting is not damaged.
  • the first layer is decisive for the shape accuracy, here a slip mixed with fine flour as well as a fine sand is usually used. Due to the smaller particles, filigree elements of a positive model can be imaged more reliably. How many layers are applied in this way depends on the geometry and the standards of the caster. For the following layers, the flour and sand used become coarser, which also results in a thicker layer.
  • refractory materials used to make ceramic slips are: silica, zircon, various aluminosilicates, and alumina. Binders used to hold the refractory in place include: ethyl silicate, colloidal silica, and sodium silicate (https://en.wikipedia.org/wiki/- Investment_casting).
  • US20030192667A2 discloses a method for investment casting which comprises preparing a refractory water-based slurry by mixing a binder, a refractory material and a quantity of water-insoluble organic fibers and applying one or more layers of this slurry to a positive model. It has been found that each layer of slurry so formed is surprisingly thick and that only a relatively short drying time is required for each layer, yielding a shell of desirable thickness relatively quickly can be built up with just a few dive cycles. These positive effects can be attributed to increased viscosity and better green part stability of the material used.
  • US4996084A describes a water-based slurry comprising colloidal silica, a latex adhesive, ammonium alginate, a wetting agent, ground zircon, alumina or glass matte and an anti-foaming agent.
  • the slurries presented in US4996084A allow drying times of 4 - 6 hours between the individual immersion steps.
  • EP0638379A2 covers a water-based binder for use in an investment casting slurry.
  • the binder contains a mixture of a colloidal silica sol and at least one latex polymer.
  • the latex polymer is preferably an acrylic latex or styrene-butadiene polymer, which reduces the processing time between dips in the manufacture of the investment casting shell mold by, for example, lowering the gel point of the colloidal silica sol.
  • the binder is combined with at least one refractory powder selected from aluminosilicates, fused silica, quartz silicate, alumina, zircon, and zirconia.
  • filler materials such as clay minerals and other ceramics are added to an investment casting slurry.
  • the slurry comprises a main portion with a finely divided material consisting of silicon dioxide, aluminum silicate, aluminum oxide and zircon, the material having as uniform a particle diameter as possible and a uniform spatial expansion of the particles.
  • the slurry contains a minor proportion of one or more finely divided materials that are plate-like, needle-like or tubular structures, in a concentration sufficient to reduce the drainage time of the slurry after application to an investment casting pattern.
  • Uniform coatings with strengths comparable to fiber-reinforced slurries can be achieved with the composition of EP1789240A2, with a higher component quality being achieved in comparison to fiber-reinforced slurries.
  • a capillary suspension is understood to mean a three-phase system "solid-liquid-liquid", which includes particles and, due to different polarities, immiscible liquids.
  • the first liquid (primary liquid) which dominates in terms of volume is called the main phase or primary phase
  • the second only a small amount of added liquid (secondary liquid) is referred to as the second phase or secondary phase.
  • Liquid phases are also to be understood as materials that are in the molten state, such as molten polymers and waxes.
  • Capillary forces can lead to the formation of a particulate gel in the capillary suspension, which encompasses a particle network that spans the sample, regardless of whether the secondary phase wets the particles better or worse than the primary phase.
  • two types of capillary suspensions are distinguished.
  • the secondary phase wets the solid particulate phase better than the continuous primary phase and forms capillary bridges between the particles.
  • this is referred to as the "capillary state”.
  • the particles form clusters around small volumes of the secondary phase (E. Koos et al., Soft Matter 2012, 8, 3988-3994; E. Koos et al., Science 2011, 331, 897-900).
  • the particle network held together by capillary forces is largely stable and no sedimentation occurs.
  • the The gel-like substance obtained can be formed into a shaped body, which can be sintered after removing the primary and secondary phases. These particle networks also do not collapse when the primary phase is separated from the suspension.
  • the flexible capillary bridges in capillary suspensions make it possible to compensate for drying stresses arising in the particle network and thus to reduce crack formation.
  • the intrinsic rheological properties of capillary suspensions with a high yield point and strong shear-thinning behavior are ideal for use as a coating material (M. Schneider et al., ACS Appl. Mater. Interfaces 2017, 9, 11095-11105; M.nos et al. , Journal of the European Ceramic Society 2019, 39, 5, 1887-1892).
  • EP2729431A1 describes a method for producing a porous ceramic using a capillary suspension, comprising the following steps: dispersing 2 to 40 percent by volume of a particulate solid selected from oxides, carbides, nitrides and phosphates in 50 to 97.99 percent by volume of a liquid non-polar primary phase and subsequent admixture of 0.01 to 10 percent by volume of a liquid polar secondary phase to the resulting suspension of particulate solid and liquid primary phase, in each case based on the total volume of the suspension, the primary phase and the secondary phase being immiscible with one another, removing the primary phase and the secondary phase from the suspension to obtain a solid, and sintering the obtained solid to form a porous ceramic.
  • the porous ceramic has a porosity of 10 to 80% and an average pore size d 50 of 0.1 to 100 ⁇ m.
  • EP3385244A1 describes a method for producing a porous, defect-free sintered body without the formation of cracks and deformations, based on a pasty capillary suspension.
  • the porous sintered body obtained by the method has a porosity in the range from 30 to 80% and an average pore size in the range from 0.5 to 50 ⁇ m.
  • the procedure includes the following steps:
  • the present invention is based on the object of a ceramic slip for investment casting based on a Provide a capillary suspension with which it is possible to produce at least one ceramic mold or at least one investment casting component with a significant reduction in the overall production time, with the at least one ceramic mold to be produced from the ceramic slip being intended to have significantly increased stability.
  • the invention describes a ceramic slip based on a capillary suspension with an advantageous slip composition which is improved over the prior art and is characterized by a high proportion of solids. Furthermore, a method is described for producing at least one ceramic mold for investment casting with the ceramic slip according to the invention or at least one investment casting component with the aid of this ceramic mold.
  • capillary suspensions are the ability of the particle network to compensate for the drying stresses that occur during the drying of the at least one ceramic mold in the investment casting process by means of the flexible capillary bridges and to reduce cracking. Furthermore, the rheological properties of capillary suspensions, such as the high yield point and the strong shear-thinning behavior, are ideal for coating complex geometries (undercuts) with an increased layer thickness to be achieved. Thanks to the shear-thinning behavior, the capillary suspension becomes thin when stirred, for example, which means that filigree geometries can be achieved from the slip. With a correspondingly high yield point, ie the minimum stress to make a material flow, the layer thickness per dip is increased.
  • the ceramic slip according to the invention comprises a particulate phase, a primary phase containing a polar primary liquid, and a secondary phase containing a secondary liquid that is immiscible with the primary liquid, with either the primary phase or the secondary phase or both the primary phase and the secondary phase containing at least one binder .
  • the particulate phase comprises 10-70% by volume of ceramic particles, based on the overall composition of the ceramic slip, with an average particle size of 0.1-150 ⁇ m. All types of particles suitable for investment casting can be used for the particulate phase.
  • Preferred ceramic particles for the particulate phase are oxides, silicates, carbides, nitrides or phosphates. Refractory materials such as zirconium(IV) silicate, zirconium(IV) oxide, aluminum(III) oxide, aluminosilicates (various combinations of Al2O3 and SiO2) or silica (SiO2) are particularly preferred.
  • the particulate phase consists of Al2O3, since Al2O3 can easily be recycled for a ceramic slip after the method according to the invention has been carried out.
  • the polar primary liquid of the primary phase is selected from water, aqueous polysaccharide solutions, aqueous polyhydric alcohol solutions, aqueous polymer solutions or molten polar polymers.
  • Water, aqueous glycerol solutions, aqueous sucrose solutions, polyethylene glycol (PEG), polyvinyl alcohol (PVA) or polyvinyl pyrrolidone (PVP) or aqueous solutions of polyethylene glycol (PEG), polyvinyl alcohol (PVA) or polyvinyl pyrrolidone (PVP) are preferably used.
  • Water, aqueous sucrose solutions, polyvinylpyrrolidone or an aqueous solution are particularly preferred
  • the proportion of the primary liquid is 15 - 81% by volume on the overall composition of the ceramic slip.
  • the secondary liquid is non-polar and immiscible with the primary liquid.
  • the secondary liquid is selected from oils, melted waxes or melted non-polar polymers. Paraffin waxes, carnauba waxes, montan waxes, polyethylene waxes, polypropylene waxes, polyamide waxes, paraffin oils, silicone oils, mineral oils, phthalates or aliphatic hydrocarbons are preferably used.
  • the proportion of the secondary liquid is 1 - 15% by volume, based on the overall composition of the ceramic
  • the at least one binder is preferably selected from colloidal silica, tetraethyl orthosilicate (TEOS), zirconium(IV) acetate, ammonium zirconium(IV) carbonate, geopolymers, bentonite, carboxymethyl cellulose (CMC), polyurethanes, polyacrylic acid, polytetra - fluoroethylene, rubber, alginate or resin.
  • TEOS tetraethyl orthosilicate
  • CMC carboxymethyl cellulose
  • polyurethanes polyacrylic acid
  • polytetra - fluoroethylene rubber
  • alginate or resin alginate or resin
  • the at least one binder particularly preferably comprises a colloidal silica suspension with 1-50% by weight of silica particles with a particle size of 1-100 nm.
  • the proportion by volume of the binder is 0.25 - 74% by volume, based on the overall composition of the ceramic slip.
  • the binder is contained only in the primary phase. In another embodiment, the binder is contained only in the secondary phase. In a further embodiment, the binder is contained both in the primary phase and in the secondary phase.
  • both the primary phase and the secondary phase contain colloidal silica as a binder.
  • the fibers are selected, for example, from needle coke, graphite, fibers containing camphor,
  • Nylon fibers Nylon fibers, rice husks or carbon fibers
  • the polymers are selected, for example, from polyvinyl alcohol (PVA),
  • PEG Polyethylene glycol
  • polysaccharides polysaccharides or latex as
  • the ceramic in another embodiment, the ceramic
  • additives added as stabilizers to slip. These additives are selected from dispersing aids such as surfactants (e.g., surfactants), e.g., surfactants, e.g., surfactants
  • Polysorbate 20 electrolytes, acids or bases as electrostatic stabilizers or defoamers.
  • Defoamers are, for example, Remet AF-XL, Burst 100, Remet
  • Foamaway from Remet the company's FoamS t a r ® defoamers
  • Ceramic mold for investment casting or . for the production of at least one investment casting component using the ceramic slip according to the invention based on a capillary suspension comprises the following steps:
  • model cluster with the ceramic slip 5 drying of the respective layer of ceramic slip formed on the at least one positive model in step D);
  • the material for the production of at least one positive model of the investment casting component is selected from waxes, thermoplastics and polymers with a melting point of 30 - 350 °C, such as polystyrene, phenolic resins, epoxy resins, polyester resins, ABS (acrylonitrile butadiene styrene) resins, paraffin waxes , filled and unfilled investment casting waxes (e.g. RomoCast from Romonta GmbH), polylactides, acrylonitrile-butadiene-styrene copolymers or high-impact polystyrene.
  • waxes such as polystyrene, phenolic resins, epoxy resins, polyester resins, ABS (acrylonitrile butadiene styrene) resins, paraffin waxes , filled and unfilled investment casting waxes (e.g. RomoCast from Romonta GmbH), polylactides, acrylonitrile-butadiene-st
  • the at least one positive model is in step D) by dipping in the ceramic slip and by moving the cluster of models in the ceramic slip or by moving the ceramic slip, z. B. by stirring, coated all around.
  • the ceramic slip becomes flowable under the shearing induced in this way, so that even complex geometries with undercuts can be completely coated become.
  • the layer thickness of a layer of ceramic slip applied by the method according to the invention is 0.3-3 mm.
  • the layer on the at least one positive model is then dried in step E) before the next layer is applied.
  • the drying time of the layer of ceramic slip is approx. 0.5-5 hours without technical aids, a drying time of approx. 2 hours is preferred.
  • technical dryers are additionally used for drying the layer. This reduces the drying time of the respective layer of ceramic slip to 5 - 30 minutes.
  • the coating of the at least one positive model is carried out according to step F) by repeated immersion in the ceramic slip and by subsequent drying of the respectively applied layer.
  • the number of repetitions depends on the component and the exact composition. As a rule, at least 2 repetitions are necessary to create a stable ceramic mold.
  • the at least one ceramic mold produced by the process according to the invention generally has a total layer thickness of 1.5-20 mm, and the total time for producing the at least one ceramic mold according to the invention is usually 12-48 hours.
  • the positive model is removed from the at least one ceramic mold in step G).
  • the positive model is melted out by heating.
  • the melting out takes place under normal pressure at 400-1100° C. or in another embodiment under pressure in a steam autoclave (5-12 bar, 120-250° C.).
  • step H the at least one ceramic mold is fired at 700-1200° C. for 20-180 minutes.
  • step I the molten investment casting material is poured into the at least one ceramic mold.
  • the at least one ceramic mold is preheated to 500-1200° C. before the molten investment casting material is poured in.
  • the investment casting material contained in the at least one ceramic mold is cooled.
  • the at least one ceramic mold is removed in step K) and the desired at least one investment casting component is obtained by separating the at least one investment casting component from the pattern cluster. Any remaining residues of the ceramic mold are then removed from the at least one precision cast component.
  • the at least one ceramic mold can be separated mechanically as well as chemically.
  • the ceramic mold is first mechanically destroyed with a high-frequency compressed air hammer, followed by blasting of the precision cast component with an abrasive material. If there are still remains of the ceramic mold on the at least one investment casting component, chemical baths are used, for example a 25% sodium hydroxide solution.
  • the at least one ceramic mold produced by the method according to the invention has a high open porosity of 30-75% and a high permeability/air permeability of IO -16 - 10 -10 m 2 , it dries without cracks and has sufficient green part stability with flexural strength of the green part from 0.1 - 10 MPa.
  • the open porosity is determined with a density measurement according to the Archimedean principle and the DIN EN 993-1 test method.
  • the open porosity describes the volume ratio of open pores to the total volume of the porous body in percent.
  • the permeability is calculated according to Sint Test standards (SPN) DIN 30911-6 measured.
  • SPN Sint Test standards
  • the flexural strength is determined using the 4-point bending test according to DIN EN 843-1.
  • the at least one ceramic mold sintered according to the invention has a high mechanical stability with a flexural strength of 0.5-50 MPa and goes through the dewaxing process without defects.
  • the layer formation process of the at least one ceramic mold is expanded to include a sanding step.
  • ceramic mold formation consists of repetitions of dipping and coating, sanding and drying. This increases the layer thickness and the drying speed of the individual layers.
  • the invention can also be combined with ceramic slurries from the prior art. In this way, different slips can be used for the first layers and the subsequent layers.
  • the ceramic slip according to the invention can also be used for gypsum casting.
  • the model is coated with the slip and dried as a "block".
  • the ceramic slip according to the invention can also be used to produce ceramic cores for investment casting or other casting processes, such as sand casting.
  • the ceramic slip according to the invention is used as a precursor for a ceramic casting core.
  • the ceramic slip according to the invention represents an advantage over the prior art due to the water-based, relatively simple production, low-shrinkage and crack-free drying and the open pore structure.
  • Cast cores are used to create cavities in cast products.
  • the ceramic slip according to the invention is shaped, dried and then sintered.
  • the sintered ceramic core is built into the positive model.
  • the positive model is then subjected to the precision casting shaping process as usual.
  • the casting core is then destroyed mechanically or chemically.
  • the open porosity of the casting core produced with the ceramic slip according to the invention is of great advantage in the investment casting process when the casting core is mechanically or chemically detached. If the casting core is to be chemically dissolved out, the acid used can quickly spread over the entire core, for example.
  • the fired/sintered casting core according to the invention is inserted into the finished positive model or the ceramic slip according to the invention is injected or poured through an opening into the cavity of the positive model, dried there without cracks and with low shrinkage and fired after the coating.
  • the direct filling of the positive model with the ceramic slip according to the invention offers great added value, especially in the case of very complex geometries that are otherwise only produced by divided cores and manual work.
  • the ceramic slip according to the invention can be used with all common shaping processes for suspensions (e.g. slip casting, extrusion, 3D printing, injection molding) can be combined.
  • suspensions e.g. slip casting, extrusion, 3D printing, injection molding
  • the rheological properties may have to be adjusted.
  • the ceramic slip according to the invention meets all the requirements for shell formation or casting core formation in investment casting and represents an improvement over state-of-the-art ceramic slips:
  • the ceramic slip according to the invention has very good rheological properties, which lead to reduced crack formation in the ceramic mold to be produced or the casting core to be produced, and a correspondingly low viscosity, so that positive models with complex geometries and undercuts are also reliably coated or investment cast components with complex geometries can be produced.
  • the yield point of the ceramic slip composition according to the invention is in the range of 40-3000 Pa, preferably 60-100 Pa, with the slip exhibiting strong shear-thinning behavior.
  • the typical microstructure of the particle network of the capillary suspension used in the method according to the invention offers a large, free layer surface and allows the ceramic slip to dry relatively evenly and quickly. On the one hand, this accelerates the production of ceramic shells or casting cores and, on the other hand, reduces the complexity of the process to a few process steps.
  • the high solids content of the ceramic slip according to the invention reduces the shrinkage potential, so that only a small, homogeneous shrinkage takes place during the production of a ceramic mold or a casting core, and the binder ensures very good stability.
  • the application of a crack-free and thicker ceramic layer allows a reduction in the Coating cycles and thus a reduction in the shell formation time in investment casting from 10 days to 0.5 - 2 days.
  • the sanding process per ceramic layer to be built up can be omitted due to the high solids content of the ceramic slip composition according to the invention and the dust and particle pollution for man and machine in the factories is greatly reduced. Furthermore, the formation of skins can be accelerated if no technical dryer is used.
  • the properties of the ceramic slip mentioned lead to a reduction in the energy requirement in a precision casting process and to an increase in productivity and flexibility.
  • the ceramic slip according to the invention has a high long-term stability and can be stored for days to months without constant stirring.
  • the ceramic slip according to the invention based on a capillary suspension is therefore used in investment casting, plaster casting, sand casting or artificial casting, in the production of high-performance components, for example made of metals or metal alloys, or in tooth replacement methods.
  • the ceramic slip according to the invention based on a capillary suspension is suitable for the production of casting cores, coatings, bone replacement materials, sintering aids, refractory materials, thermal insulators, insulators for electrical heating elements, turbine blade diffusion coatings, electrolytes, body protection products, abrasion-resistant nozzles or moisture sensors .
  • Figure 1 is a positive wax model of an investment cast component to be produced according to Example 5 (Figure 1, left image), the positive wax model coated 3 times with a ceramic slip according to the invention ( Figure 1, middle image) and the finished investment cast component made of cast iron according to the invention after knocking off the according to the invention ceramic mold produced ( Figure 1, right image) to see.
  • FIG. 2 left image, shows a cross section of a coated positive wax model with alternating uncolored and colored layers of a ceramic slip according to the invention.
  • a pinch of graphite powder was added to part of the ceramic slip in the final mixing step.
  • a piece of wax was then alternately coated with the inventive ceramic slip without graphite powder and the inventive ceramic slip with graphite powder.
  • the layer thickness of the individual layers can be seen clearly in FIG. FIG. 2, right image, shows a cut open ceramic mold produced according to the invention with the differently colored layers.
  • Figure 3 shows a cross section of a coated positive wax model with alternating uncolored and colored layers of a ceramic slip according to the invention.
  • FIG. 3 shows a temperature profile used for firing the ceramic slip according to the invention.
  • the ceramic slip was formed into bars measuring 50 ⁇ 12 ⁇ 5 mm using a perforated plate and then fired at 900° C. for 2 h, following the temperature profile in FIG. 3 (Example 1).
  • FIG. 4 shows a positive wax model (left) for a radial compressor and the radial compressor made of tin (right) produced with the aid of the ceramic slip according to the invention according to example 11 and the positive wax model.
  • FIG. 5 shows a positive wax model for a fir tree structure and the positive wax model coated with the ceramic slip according to the invention (left) and the fir tree structure made of tin (right) using the ceramic slip according to Example 11 and the positive wax model.
  • FIG. 6 shows a positive wax model for a radial compressor and the positive wax model coated with the ceramic slip according to the invention (left) and the radial compressor made of tin (right) using the ceramic slip according to Example 12 and the positive wax model.
  • FIG. 7 shows a positive wax model for a filigree
  • FIG. 8 shows a printed positive model made of PLA for a centrifugal compressor (left) and the centrifugal compressor made of tin (right) produced with the aid of the ceramic slip according to Example 13 and the positive model.
  • FIG. 9 shows three casting cores produced according to Example 14 in different shapes.
  • FIG. 10 shows three casting cores produced according to Example 15 in different shapes.
  • FIGS. 11 and 12 show larger, crack-free ceramics which were slip-cast using the ceramic slip produced according to Example 5, dried at room temperature and then fired and sintered.
  • FIG. 13 shows a crack-free ceramic made from ⁇ -Al 2 O 3 produced according to example 7.
  • Example 1 Production of a ceramic slip according to the invention:
  • the cooled beams had an open and continuous porosity of 54% (Archimedes' principle, DIN EN 993-1), a permeability of 1.8 x IO -14 m 2 (according to DIN 30911-6) and a flexural strength of 4 MPa ( 4-point bending test according to DIN EN 843-1).
  • Table 1 lists further ceramic slip compositions according to the invention.
  • Table 1 Example compositions for ceramic slips according to the invention. All percentages by volume relate to the respective overall composition of the ceramic slip:
  • a handmade wax positive model in a T-shape made of paraffin wax (FIG. 1, left image) was coated at intervals of 2 hours by dipping into a ceramic slip according to the invention and turning in the ceramic slip according to the invention and subsequent drying. This process was repeated 3-4 times.
  • a coated piece of wax is shown in Figure 1, middle panel.
  • the ceramic mold was dewaxed at 120° C. and normal pressure in a drying cabinet. Liquid cast iron at a temperature of 1450° C. was then poured into the cold ceramic mold produced according to the invention.
  • the investment cast component obtained after cooling and knocking off the ceramic mold is shown in FIG. 1, right-hand image.
  • Cast wax positive models made of paraffin wax were coated at intervals of 2 hours by dipping in a ceramic slip according to the invention and turning in the ceramic slip according to the invention and subsequent drying. This process was repeated 3-4 times. After the last layer had dried for a total of 4 hours, the ceramic molds were dewaxed in a pressure cooker at 120 °C and 1.2 bar. The ceramic molds were then fired at 900°C for 2 hours. The preheated ceramic molds were filled with liquid tin at a mold temperature of 350 °C. This operation was performed with different geometries carried out. Corresponding images are shown in FIG. 4 for 2 centrifugal compressors and in FIG. 5 for a Christmas tree.
  • Wax positive models made from industrial wax for investment casting were coated at intervals of 2 hours by dipping in the ceramic slip produced according to Example 5 and turning in the ceramic slip produced according to Example 5 and then drying. This process was repeated 3-4 times. After the last layer had dried for a total of 4 hours, the ceramic molds were dewaxed at 160° C. and 1.2 bar in a pressure cooker. The ceramic molds were then fired at 900°C for 2 hours. The preheated ceramic molds were filled with liquid tin at a mold temperature of 350 °C. This process was carried out with different geometries. Corresponding images are shown in FIG. 6 for a centrifugal compressor and in FIG. 7 for a filigree finger structure.
  • FIG. 8 shows a radial compressor made of PLA and the metal component produced according to the method. Production of casting cores:
  • the ceramic slip produced according to Example 5 was poured into an angular mold, dried, processed if necessary and then fired at 1200° C. for 2 hours. The ceramics could then be successfully used as casting cores. The cores could be easily removed from the solidified metal component.
  • 3 forms are shown as an example.
  • the ceramic slip produced according to Example 6 is ideally suited for the 3D printing process.
  • the ceramic slip was printed in different geometries onto a 90 °C hot cordierite plate and then sintered at 1400 °C for 2 hours.
  • the ceramics produced have an open porosity of 45% and a compressive strength of 70 MPa.
  • Figure 10 shows some 3D-printed ceramic components as an example. Among other things, this process is suitable for producing complex casting cores.
  • Example 17 With their microstructure, they are suitable, for example, for use as refractory materials, insulating materials or as sinter bases.
  • Example 17 With their microstructure, they are suitable, for example, for use as refractory materials, insulating materials or as sinter bases.
  • the resulting ceramic consists of a single material ( ⁇ -Al 2 O 3 in this example). This composition also dries without cracks (FIG. 13).
  • the ceramic slip produced according to Example 7 is suitable for 3D printing using the binder jetting method. In this process, a thin layer is applied and dried. A binding agent (often a resin) is then applied to the desired areas with a print head. The next layer is then applied and again selectively glued. Once the desired geometry has been printed, the unbonded material is rinsed off, leaving the 3D printed part. The challenge in this process is the crack-free drying of water-based slip formulations.
  • the barium titanate-based ceramic slip produced according to Example 8 was sintered at 1150° C. for 2 hours.
  • the resulting ceramic has a total open porosity of 50%.
  • Barium itanate is known in particular as "energy harvesting material” and is used, among other things, as a sensor.
  • the ceramic slip based on kieselguhr produced according to Example 9 was sintered at 1150° C. for 2 hours and has a completely open porosity of 65%. These ceramics are ideal for use in a soil moisture sensor. Devices and methods:
  • Dissolver stirrer Dissolver stirrer with a diameter of 40 mm.
  • Drying cabinet VT 6060 M, Thermo Scientific.
  • ZrSiO 4 powder Zirconium Silicate Micro 20 TDS, Alkroko GmbH
  • Barium titanate powder Commercial grade barium titanium oxide (BT), 99% (metals basis), Alfa Aesar
  • Diatomaceous earth powder Celite® Standard Super Cel®, VWR International GmbH

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  • Organic Chemistry (AREA)
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Abstract

La présente invention se rapporte à un barbotine céramique destinée à la coulée de précision basée sur une suspension capillaire, et à un procédé de fabrication d'au moins un moule céramique ou d'au moins un composant coulé avec précision à l'aide de la barbotine céramique. La présente invention se rapporte également à l'utilisation de la barbotine céramique selon l'invention pour la fabrication de noyaux coulés en céramique et d'autres corps moulés poreux. La barbotine céramique comprend une phase particulaire, une phase principale qui contient un liquide principal polaire, et une phase secondaire qui contient un liquide secondaire qui n'est pas miscible avec le liquide principal ; soit la phase primaire, soit la phase secondaire, soit la phase principale et la phase secondaire contenant en outre au moins un liant ; la proportion de la phase particulaire étant comprise entre 10 et 70 % en volume, la proportion du liquide principal étant comprise entre 15 et 81 % en volume, la proportion du liquide secondaire étant comprise entre 1 et 15 % en volume et la proportion du liant étant comprise entre 0,25 et 74 % en volume, chacune étant basée sur la composition totale de la barbotine céramique.
EP22765428.2A 2021-08-20 2022-08-10 Barbotine céramique destinée à la coulée de précision basée sur une suspension capillaire Pending EP4387941A1 (fr)

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DE102021121622.2A DE102021121622A1 (de) 2021-08-20 2021-08-20 Keramischer Schlicker für den Feinguss auf Basis einer Kapillarsuspension
PCT/EP2022/072410 WO2023020905A1 (fr) 2021-08-20 2022-08-10 Barbotine céramique destinée à la coulée de précision basée sur une suspension capillaire

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US3017677A (en) * 1959-07-20 1962-01-23 Jr Herbert Greenewald Composition and method of forming ceramic cores
US4996084A (en) 1989-06-30 1991-02-26 Pfizer Hospital Products Group, Inc. Colloidal silica water based slurry system for investment casting shell backup coats
DE4116609A1 (de) * 1991-01-19 1992-07-23 Thyssen Industrie Verfahren zur herstellung von keramischen schalen als giessform
US5824730A (en) 1993-08-13 1998-10-20 Remet Corporation Fast processing water based binder system
CN1250360C (zh) * 1999-08-25 2006-04-12 邓特斯普里国际公司 壳模粘合剂组合物和方法
ES2245683T3 (es) 2000-03-17 2006-01-16 Daniel James Duffey Molde de fusion a la cera perdida.
DE10043202A1 (de) 2000-09-01 2002-03-28 Epcos Ag Keramikschlicker, Verfahren zur Herstellung einer keramischen Grünfolie und Verwendung des Verfahrens
US20060054057A1 (en) 2004-09-16 2006-03-16 Doles Ronald S Filler component for investment casting slurries
DE102005028721B4 (de) 2005-06-20 2008-07-10 Heraeus Kulzer Gmbh Verwendung von Pasten und Verfahren zur Destabilisierung von Schlickern in der keramischen Formgebung
DE102011106834B3 (de) 2011-07-07 2012-09-20 Karlsruher Institut für Technologie Verfahren zur Herstellung einer porösen Keramik und eines porösen polymeren Werkstoffes sowie damit erhältliche Keramiken und Werkstoffe
US10953460B2 (en) 2016-10-10 2021-03-23 3M Innovative Properties Company Method of making investment casting mold
EP3385244B1 (fr) 2017-04-07 2023-01-18 Karlsruher Institut für Technologie Procédé de fabrication de corps fritté poreux à base de suspensions capillaires sous forme de pâte
WO2020150039A1 (fr) * 2019-01-14 2020-07-23 Corning Incorporated Mélanges de lots de matières céramiques crues comprenant une émulsion inverse et procédés de formation d'un corps céramique

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