DE102018121847A1 - Process for metal die casting with lost core - Google Patents

Abstract

In a method for producing metallic workpieces (12) using the die casting method, with the following method steps:
A core (18) which has at least one core element (8) containing at least 5% plastic is introduced into a die casting mold (101) and held in a predetermined position in the die casting die,
A workpiece (12) is produced by introducing metal into the die-casting mold in the die-casting process, casting around the core and cooling the metal,
The core is removed from the workpiece (12) and destroyed in the process, the invention proposes,
• that the core element has a geometry such that so-called filigree structures (14) are created in the workpiece (12),
wherein metallic elements are created which protrude with a thickness or diameter of at most 5 mm into a cavity (108) created by the core element,
or the length of the cavity (108) is more than 7 times larger than its smallest cross-sectional dimension,
• and that the core element (8) is removed from the workpiece (12) without demolding.

Description

The invention relates to a method according to the preamble of claim 1.

From the DE19635920A1 a generic method is known. Cores made of thermoplastic material with an irregularly shaped wall are used, which is thicker than in other areas where they are exposed to higher temperature or mechanical loads during the casting process. Under the influence of the molten metal flowing into the mold during the die-casting process, the plastic core softens, but maintains sufficient inherent stability so that it can be pulled out of the still warm workpiece. Here, a narrow time window must be observed in which the core has a certain degree of strength, because in order to be able to transmit a tensile force, the core must be pulled out before it melts too much and has too little strength, and it must on the other hand, be pulled out before it cools down too much and begins to solidify again, since it then has too great a strength and pulling is no longer possible due to buildup on the metallic casting and / or even the smallest undercuts.

In the generic method, the core is pulled out of the workpiece in one piece. The core is deformed for the purpose of demolding and destroyed in that it is no longer suitable for a second, repeated use. The process of drawing also limits the design of the core cavity to geometries that do not impede the drawing of the core, e.g. B. The geometry must be free of larger undercuts or of metallic structures protruding into the core, which are created in the workpiece. The core can be pulled after the workpiece has cooled as soon as the workpiece has sufficient dimensional stability. In particular, the pulling of the core is not waited until the workpiece has completely cooled and has reached room temperature, for example, since then the core would also have regained strength that makes it impossible to pull the core.

Furthermore, cores are known from practice, which are based on salts such as. B. sodium chloride or sodium carbonate are formed and are referred to as salt cores. They have a higher temperature stability than the generic plastic cores, and they can be easily removed from the workpiece by opening or breaking them up. Due to the strong shrinkage in their manufacture, their porosity and their brittleness, or their ceramic behavior, and the corresponding sensitivity to breakage, salt cores only allow limited shapes. In particular, for rod-shaped salt cores, for example, which can run in a straight line or curved, have a round or polygonal cross section, and which can serve to create a bore or a fluid channel in a workpiece, that their length is 7 times their diameter or should not exceed a comparable cross-sectional dimension. In practice, this length to cross-section ratio of 7: 1 has been found to be the limit up to which the salt core can be used in the die casting process without causing damage to the salt core due to the pulse-like loading during the casting process.

Accordingly, no more complex geometries or particularly fine structures can be achieved with the salt cores, since the mentioned ratio of 7: 1 would be exceeded at least in some areas and therefore the required stability of the core would not be guaranteed. Because of their brittleness, machining of the salt cores - for example to create defined, fine structures or smooth surfaces - is not possible in practice with the demands placed on series production. The salt cores are therefore usually produced in a casting process. This requires special casting machines or special casting processes that deviate from standardized machines and processes, such as those used for. B. can be used for the injection molding plastic cores mentioned above.

From the DE 10 2011 076 905 A1 Salt cores are known which are produced by a dry pressing process or by core shooting. The core is made from a powder that can contain binders. Since the core is made from a powder and not from the melt, these methods are very limited in their geometric design, especially if cores are to be produced in three-dimensional space. The powder does not flow and therefore cannot be compressed in every direction, as is possible with cores from the melt. Furthermore, the cores are reinforced with an infiltrate so that they are suitable for use in die casting.

The invention has for its object to improve a generic method in such a way that workpieces with a highly complex internal structure can be manufactured as inexpensively as possible.

This object is achieved by a method according to claim 1. Advantageous configurations are described in the subclaims. A component produced by this method is described in claim 16.

The proposal according to the invention provides that a core element is used which contains at least 5% by weight of plastic. Thus, in contrast to salt cores, the production of the core element can be carried out using economically more advantageous methods, that is to say with a mechanical device and method such as is available or known in many companies. Possible manufacturing processes are casting processes, sintering processes, 3D printing, extrusion of extruded or plate profiles, as well as the processing of semi-finished products, e.g. Machined pipes or tubes or rods or plates that are bent or deformed under the influence of heat.

The core element is particularly preferably produced by injection molding, since it can also be used to produce complex structures in an economical manner. From a plastic content of 5% by weight in particular, the flowability of the core material required for injection molding is achieved. As a result, a complex shape of the core element can be produced in injection molding due to the homogeneous pressure distribution, particularly in three-dimensional space. No other core manufacturing process is known which could produce the core with the material described in a manner which is advantageous for the process and free of shaping in three-dimensional space.

Core manufacturing processes that produce the core from free-flowing material are limited here by the shape due to the force distribution. In other core production processes, such as the hot chamber die casting process, which produce cores from the liquid melt of the core material, as is known to the person skilled in the field of salt cores, or in known sintering processes, the resulting core is brittle and or has a high shrinkage and / or can be infiltrated through parts of the melt, so that these cores sometimes require a further processing step, such as a sheathing with another material.

Furthermore, it is proposed according to the proposal that a core element has such a geometry with projections and indentations that it cannot be pulled out of the workpiece. This gives the design of the workpiece considerable design freedom for the location and design of the core cavities, so that highly complex geometries such. B. can be realized by flow channels within a workpiece. In particular, flow channels can be optimized to the requirements of the respective component, so that flows e.g. can be guided with low pressure loss, turbulence can be avoided, the merging and splitting of flows can be improved, and the flow channel does not have to have any draft angles and thus unnecessary cross-sectional changes obstructing the flow. In the same way, it is also possible for workpieces such as filters, mixers, catalysts or other applications that are obvious to the person skilled in the art, e.g. with a surface structure that creates as much turbulence as possible. Since the removal of the core element in the proposed method does not depend on the geometry of the core in such a way that it can be pulled out, undercuts, cross-sectional changes in a flow channel, e.g. for an optimized inflow of functional components such as heat exchangers, but also small geometries for optimizing the flow, as is the case with a "golf ball surface" or for other advantages that are apparent to the expert.

The core element mentioned can form a section of a core composed of two or more elements. These two or more elements can consist of the same or different materials. It is not necessary for every core element to be a core element according to the invention, it is sufficient if there is a core element according to the invention. For example, only a part of the core for which a filigree structure is provided can be formed by a core element according to the invention, and the rest of the core can be formed in a conventional manner known from the prior art. However, a core element can also form the entire core in one piece. In the following, the term core is often used as a representative, whereby the statements made also apply to a core element, which only forms a section of a core, unless the context indicates otherwise.

The core can also itself contain elements made of a second material, which can also be embedded in the core element, for example. It is conceivable, for example, that metallic pins are provided in one or more core elements as assembly aids for assembling a core, or elements that serve as a core brand. The elements can also be removed when the core is removed later, or can remain in the workpiece. It is thus also possible for the core to be produced by injection molding or extrusion-coating an arbitrarily shaped first semifinished product with the core composition according to the invention, ie by forming the core element according to the invention thereon. After the coring, the semi-finished product remains in the workpiece. In the sense of the registration is as inventive The core element understood only the core mass according to the invention, irrespective of whether further (core) elements not according to the invention are provided thereon or therein.

It is also conceivable that the core is essentially hollow or has cavities in some areas. Channels can also be formed in the core, which e.g. can be flowed through by a coolant during a casting process. In the case of a soluble core, a coolant must be selected in which the core is insoluble, e.g. an oil for a water-soluble core.

Furthermore, the core as a whole or in some areas can also be provided with a functional layer which can remain on the workpiece or diffuse into the casting material during casting and / or can form an intermetallic phase on the workpiece wall in order, for example, to to implement corrosion protection.

It is also proposed, according to the proposal, to implement a geometry in the core cavity of the workpiece, also called the cavity, which is referred to in the context of the present proposal as a so-called “filigree structure”. The structure of the metal workpiece to be created is particularly important, so that it can be a structure which is formed by the metal material of the workpiece or which is surrounded as a cavity or cavity by the metal material of the workpiece. Due to the interaction between the core and the workpiece, this means that a filigree structure of a cavity in the workpiece, surrounded by the metal, requires a correspondingly shaped core.

The term filigree structure is understood in the context of the present proposal as an embodiment of the workpiece in which either metallic areas of the workpiece with a thickness or a diameter of at most 5 mm protrude into the cavity, for example ribs, connecting webs, knobs or the like. , or in which the cavity at least in sections has a ratio of the smallest cross-sectional dimension to length which is less than 1: 7, so that the length of the cavity is at least in sections more than seven times greater than its smallest cross-sectional dimension, e.g. B. with a round cross-section its diameter or e.g. with a rectangular cross-section the shorter side length or e.g. in the case of a polygonal cross-section, the smallest dimension from height, diagonal or side length. Thus, with the proposed method, component geometries can be realized in the workpiece that are not possible with a salt core due to the problem of mechanical stability. Even the plastic cores, which are known from the generic method, typically do not allow filigree structures, since if the ratio of the smallest cross-sectional dimension to length is 1: 7, the pull-out resistance when pulling the core is so great that a breakage of the core cannot be ruled out and complete removal of the core cannot be guaranteed in a series production process. As a result, a ratio of the smallest cross-sectional dimension to length of 1: 7 has been the limit for the geometry of cores that are to be produced in series production - and in the area of automobile production, especially in large series production - so far.

In the case of a flow channel with a round channel cross-section, for example, the diameter of the flow channel denotes the cross-sectional dimension of the core cavity, i.e. the cavity. In the case of rectangular or otherwise deviating cross-sections of the core cavity, in which, for example, a height and a width can be determined, the smaller dimension of these cross-sectional dimensions determines the relevant dimension, which is related to the length of the core cavity in order to use the ratio of 1: 7 to define a design as a filigree structure. As is readily apparent to those skilled in the art, the ratio does not have to relate to the complete core cavity (envelope) and, accordingly, not to the entire core; Within the scope of the present proposal, it is also considered to be a filigree structure if the core cavity has at least one partial section with the ratio mentioned less than 1: 7 and the core accordingly has a core element with this geometry.

With the proposed method, it is also possible to produce other, not filigree, geometries, for example also geometries with a ratio of cross-section to length in the range of 1. These geometries are difficult to produce due to the shrinkage, especially with larger-sized cores, what with the The method according to the proposal is not the case to the extent that the method according to the invention is also particularly suitable for this.

Finally, it is proposed that the core be removed from the workpiece without demolding. In the context of the present proposal, demolding means that the core is removed from the core cavity in one piece with a certain geometry, for example by moving corresponding elements of the casting mold in the manner of a slide or the like, or by removing the core from a core cavity of the workpiece can be pulled out.

Rather, it is proposed that such demolding does not take place, but rather that the core is removed from the core cavity by converting at least the plastic portion into an unbound state. An unbound state is understood to mean that the plastic at least predominantly changes into another state of matter, ie the originally solid plastic, or its components are predominantly liquid or gaseous in the unbound state. For example, the plastic itself can change the state of matter through a temperature-induced phase transition from the solid phase in which the core is initially present to another, in particular liquid or gaseous phase. For the purposes of the invention, the disintegration of the plastic into a liquid or gaseous mixture of substances, ie for example in smoke, is also understood as a change in the state of matter. It can be provided that the core alone is transferred to the unbound state and removed from the cavity. However, it can also be provided to bring the core into the unbound state by combining it with other substances, for example by dissolving the plastic portion in a liquid or gaseous medium, and then the material of the core and the material of the other substance together from the Remove core cavity.

Partial or complete dissolution of the core can be achieved by means of a chemical or physical solvent. In the context of the invention, it is also understood as a solution if chemical reactions occur between the plastic and the solvent, so that the reaction products form a mixture with the remaining solvent, which is predominantly in the unbound state, i.e. for example a solution or an emulsion, or else a suspension or an aerosol.

The plastic is thus in an unbound state if the plastic itself is in a liquid or gaseous state or its components are in a predominantly liquid or gaseous mixture.

The core is consequently broken up into a multitude of small components - possibly down to the molecular level - in order to remove it from the core cavity. This can be, for example, a mechanical breakup, for example if the core is exposed to a certain radiation, possibly in connection with vibrations. In particular, it has been found in initial tests that, depending on the material used, the core is advantageously pyrolytic, i.e. can be removed by thermal decomposition, which ensures reliable, residue-free removal of the core. Alternatively, it can be provided that the core is removed from the workpiece by melting. The melting can be used, for example, to deliberately leave a residue of the core material on the surface of the core cavity, so that a surface coating of the core cavity can be effected, for example in order to protect the metal material used from the influence of aggressive fluids which are caused by the core cavity during flow later use of the workpiece.

Furthermore, initial tests have shown that the core can also advantageously be removed from the workpiece without residue or can be rinsed out using a chemical or physical solvent. The complete core element does not necessarily have to be loosened here, because it can be sufficient to at least bring about an unbound state of the plastic. The thermal stress on the workpiece, which acts on the workpiece in the event of pyrolytic or enamel removal of the core, can be avoided by dissolving or rinsing out the core.

• Beispielsweise kann erstens vorgesehen sein, dass zuerst der Kunststoffanteil des Kerns pyrolysiert wird und anschließend ein Salzanteil des Kerns in Wasser aufgelöst wird.

A combination of different procedures for removing the core is possible, as will be explained using three examples:

• For example, it can first be provided that the plastic portion of the core is pyrolyzed first and then a salt portion of the core is dissolved in water.

Or secondly, a combination of different processes can take place in that initially only the plastic is “destroyed”, eg. B. by a transition to a liquid or gaseous state, and then a filler of the core such. B. rinsed the salt or talc from the core cavity. The filler itself does not have to be soluble, but can also form any mixture with the flushing medium.

Or thirdly, a combination of different methods can take place in that the core has an outer cladding layer as the core element, which has a geometry causing the undercuts and which, as described above, is broken up into small components and removed from the core cavity. The proposed method is therefore only applied to this outer core element. After removal of this outer covering layer, there is a rest of the core, which can now be removed in one piece, e.g. B. can be pulled, as known from the prior art. This combination may reduce the time required that would otherwise be required for the complete breakdown of the entire core into small components.

In the context of the present proposal, it is provided that an element is created by the injection molding process, which is referred to as the “core element”. The use of injection molding is particularly advantageous because the core element is produced with a significantly lower shrinkage than is known from the melt in the case of salt core casting processes. It can be the complete core to be inserted into the die. However, it can also be just one of two or more elements that are initially connected to one another in order to create the core with its final geometry. It is not necessary for all parts of the core to be removable in accordance with the invention without demolding; it is sufficient if at least one core element is of such a nature.

For example, by gluing several core elements, a complex geometry of the core can be achieved without having to machine the core to an undesirably large extent, apart from the possible finishing operations typical of injection molding, such as the removal of sprues, burrs or the like Gluing several core elements can use core elements that can be the same or different with regard to their geometry and / or their materials. Ideally, the adhesive itself can be removed without demolding so that residue-free removal is possible in a simple manner. With a suitable plastic in the material of the core elements, these can also be bonded to one another by heating the contact surfaces without the addition of a separate adhesive. The core elements also do not necessarily have to be glued, in principle any type of non-positive, positive or material connection is also suitable.

However, it can be provided that the core element, which is initially produced by the injection molding process, is subsequently reworked, in particular post-machined, in order to obtain the finally desired geometry of this core element. In particular, if only a single core element is to form the core later, such a reworking of the core can be economically advantageous compared to the production of a core from a plurality of individual core elements to be connected to one another. Post-processing can take place in particular in the contact area with the workpiece to be formed, i.e. e.g. create structures in the core element through post-processing, which are later mapped in the workpiece.

The core elements, which can be produced by injection molding, can consist partially or in particular entirely of a plastic, such as Bakelite, epoxies or thermosets, in particular made of a thermoplastic such as a polyamide, an acrylate, styrene, lactide, ethylene, propylene, acetate or an alcohol, in particular a polyvinyl alcohol or a mixture of these plastics. In addition to the good processability of these plastics, they also have advantages with regard to their later removability from the core cavity, and for example the thermoplastics can also be reused under certain conditions. Polyvinyl alcohol is also problem-free in terms of environmental pollution and advantageous in that it can be released into the waste water.

The proposed method can advantageously be used if the workpiece is produced in a cold chamber or hot chamber die casting process, and in particular in a high pressure casting process. High-pressure casting is understood to mean a pressure casting process in which the pressures greater than 30 bar, in particular greater than 100 bar, are used. The person skilled in the art can see that the method can also be used in low-pressure casting at pressures below 30 bar.

The method is particularly advantageous in high-pressure casting at a casting pressure of more than 100 bar, since there is typically a high bending stress on the core and the proposed core element has a particularly good bending strength compared to. a core element with a lower plastic content or a higher brittleness. Since the core element is cast very quickly within a few milliseconds at a high casting pressure, the plastic cannot soften or lose strength during this time, as could possibly be the case at a lower casting speed; This ensures good dimensional stability of the core element, especially at a high casting speed or a high casting pressure.

The method is particularly advantageous when the workpiece is produced using the aluminum high-pressure casting method, that is to say a molten aluminum alloy is introduced into the mold at a pressure of 250 bar or more. The casting pressure can preferably be 500 bar or higher, particularly preferably 700 bar or higher. The high pressure can ensure that the metal flows completely into all areas of the mold cavity, so that the filigree structures mentioned can be reliably produced even in series production with the shortest possible cycle times. The high pressure causes furthermore, that the die-casting mold can be filled completely within a few milliseconds, i.e. within fractions of a second and typically within less than 1/10 second, so that the temperature exposure to the basically temperature-sensitive core, which contains plastic, is limited to a very short time can be until the metal on the outer surfaces of the workpiece, or at the interface of the workpiece and core, begins to solidify and has sufficient dimensional stability. If the core then softens and can no longer guarantee dimensional stability, the metallic workpiece has achieved sufficient dimensional stability to prevent undesired deformation of the workpiece.

The metal, which can be any castable metal or alloy known to the person skilled in the art, in particular not iron metal such as copper, zinc, brass, magnesium or aluminum, which is advantageously introduced into the die-casting mold at a temperature of more than 380 ° C. In particular if an aluminum alloy is used as the material and the metal is processed in high-pressure aluminum casting with pressures of more than 250 bar, a flow behavior of the aluminum melt is ensured by a temperature of more than 500 ° C., which enables the desired filigree structures to be produced .

In particular, it has been found in initial tests that, given pressures of more than 500 bar and temperatures ranging from 550 to 650 ° C, when the aluminum alloy flows into the die casting mold, the core has sufficient mechanical and thermal stability has to survive the casting process undamaged and thus not endanger the desired later geometry of the workpiece due to defects in the core.

It can advantageously be provided that the core element contains thermally stable but soluble fillers in addition to the plastic. This can be a salt, for example. On the one hand, this improves the temperature resistance of the core, and on the other hand, the salt or a comparable filler can support the destruction of the core, namely the breaking up into a large number of small components. For example, if it is a water-soluble salt such as sodium chloride (NaCl), the salt can be dissolved by water.

The use of halogen-free salts, such as e.g. Sodium carbonate proven as a salt: This is also water-soluble and prevents reactions with the plastic, which could occur in the case of sodium chloride, for example, and which could lead to water-insoluble residues in the core cavity.

If the salt components in the core element prevent the individual plastic areas from being connected to core elements, the salt element can be broken up into a large number of small particles by dissolving the salt, which can then be washed out of the core cavity. Preferably, however, the plastic material can form a kind of matrix within a core element, in which the salt portion is embedded, so that the individual plastic areas are all connected to one another. In this way, the mechanical stability - for example the vibration and shock resistance - of the core element can be considerably improved, so that mechanical damage to the core during the die casting process can be avoided if the melt flows into the mold and acts on the core within fractions of a second in the high pressure casting process . Due to the high mechanical stability, the core can be manufactured with a particularly fine geometry and small cross-sections without fear of the core breaking during the casting process.

In the first attempts, the use of polyvinyl alcohol (PVAL) for the plastic material of a core element has proven itself. The polyvinyl alcohol is water-soluble, so that a completely water-soluble core element can be created in connection with a water-soluble salt, such as the sodium carbonate mentioned. In particular, if several core elements are joined together to form a core and a water-soluble adhesive is used, the entire core can be rinsed out of the core cavity without residue using water.

Other possible fillers for the fillers already mentioned include chalk and talcum, as well as other salts and fillers that are apparent to those skilled in the art. Mixtures of different salts and / or fillers and / or plastics can also be used.
In addition to water, organic solvents, in particular glycols, can also be used as solvents in order to remove a core element from the core cavity. The solvents can be used at room temperature or at elevated temperature, for example in order to optimize the solubility and improve the economy of the process.

With a sufficiently high proportion of the plastic in the core material, in particular from the proposed proportion of 5% by weight, it can be used to remove the core element suffice if only the plastic changes to an unbound state, so that the binding of the filler in the core element is released, so that the filler can be rinsed out, for example, without having to be pyrolyzed or chemically or physically dissolved, rather it is sufficient to have one To create dispersion.

The method is particularly suitable for the production of machine parts with filigree structures, complex undercuts or, for example, also integrated cooling channels. The method can e.g. Especially for the production of engine parts such as engine housings, gearbox housings or cylinder crankcases, turbine blades with fine structures or hollow structures, tools with integrated cooling channels, e.g. for contour cooling, or other complex components, which today otherwise only involve a particularly large number of process steps or complex processes such as the selective laser Sintering can be produced, applied.

The proposed method can advantageously be used for producing a workpiece which has one or more flow channels optimized for the use of the workpiece. For example, an optimization can relate to the flow resistance in the flow channel, i.e. minimizing pressure loss or avoiding turbulence. For this purpose, for example, sharp edges or deflections can be avoided (“sharp” is understood in particular if the radius of the edge or deflection is smaller than the cross-sectional diameter of the channel in the plane spanning the radius) or other known methods from fluid mechanics are used . However, optimization can also relate, for example, to a cross-sectional configuration or surface structuring to improve the heat transport between the workpiece and a fluid, e.g. by creating a large or specially structured wall surface.

The proposed method can be used particularly advantageously to produce a heat exchanger. For example, it is known from the field of internal combustion engines to use heat exchangers in which coolant and oil are passed through two separate flow channels of the heat exchanger. In particular, such heat exchangers are often designed as plate heat exchangers, a plurality of plates being arranged at a distance from one another and alternately a flow channel for the oil and a flow channel for the cooling fluid running between two adjacent plates. The assembly of such a heat exchanger from a large number of individual plates is complex on the one hand and, on the other hand, due to the large number of separation points, represents a multitude of sources of error in the form of potential leaks. According to the proposed method, such a plate heat exchanger can be produced as a single cast component, so that the both mentioned disadvantages of a heat exchanger in terms of assembly and in terms of tightness can be eliminated.

In particular, if the heat exchanger is to be connected to other components of an engine periphery anyway, it can be provided according to the proposal that the heat exchanger is not an independent, for. B. cuboid element, but rather to manufacture with other components in the form of a highly complex integrated component. In this way, potential leakage points can be reduced due to the further elimination of flange connections and the effort in the later assembly of the workpiece produced can be reduced. The advantages with regard to the degrees of freedom in the geometric configuration can also be used, thereby producing an improved product, in particular with regard to its use of installation space and with regard to a pressure loss when flowing through it, for example by means of a surface structuring which is particularly suitable for this.

• 1 schematisch die Herstellung eines Kernelements in mehreren Schritten,
• 2 die Herstellung eines metallischen Werkstücks im Aluminium-Hochdruckgussverfahren unter Verwendung des Kerns von 1,
• 3 + 4 Kernelemente zur Herstellung eines Plattenwärmetauschers,
• 5 - 7 die Anordnung einer Mehrzahl der Kernelemente zur Herstellung eines Plattenwärmetauschers,
• 8 - 10 Ansichten auf das Werkstück zur Herstellung eines Plattenwärmetauschers,
• 11 den aus diesem Werkstück hergestellten montagefertigen Plattenwärmetauscher.
• 12 zeigt ein Modul zur Aufnahme eines Filtereinsatzes sowie mit dem in dem Modul angeordneten Wärmetauscher von 11, und
• 13 ein Werkstück mit einem aus drei Kernelementen gebildeten Kern mit Einlegern.

The present proposal is explained in more detail below on the basis of the purely schematic representations. It shows

• 1 schematically the production of a core element in several steps,
• 2nd the production of a metallic workpiece in the aluminum high pressure casting process using the core of 1 ,
• 3rd + 4 core elements for the production of a plate heat exchanger,
• 5 - 7 the arrangement of a plurality of the core elements for producing a plate heat exchanger,
• 8th - 10th Views of the workpiece for the manufacture of a plate heat exchanger,
• 11 the ready-to-install plate heat exchanger made from this workpiece.
• 12th shows a module for receiving a filter insert and with the heat exchanger arranged in the module of 11 , and
• 13 a workpiece with a core formed from three core elements with inserts.

In 1 is an injection mold 1 shown, the one side of the nozzle shown as the upper mold 2nd and an ejector side shown as the lower mold half 3rd has, the nozzle side 2nd and the Ejector side 3rd a cavity 4th enclose. A flowable core material 5 is present as a compound and in the present example consists of polyvinyl alcohol, as a plastic component and sodium carbonate (Na ₂ CO ₃ ) as a salt component. The salt content is preferably more than 40% by weight. This initial situation for the production of a core 18th is in 1 shown on the far left as the first process step.

On the right, it can be seen that by means of an injection unit 6 , which is indicated here as a pressure piston, the core material 5 through a feed channel 7 into the injection mold 1 has been injected so that the core material 5 now the cavity 4th and the feed channel 7 fills out. In the cavity 4th forms the core material 5 now one from a single core element 8th formed core 18th .

In the third process step shown on the right, the injection mold is used 1 opened by the nozzle side 2nd and the ejector side 3rd be moved apart so that now the core element 8th from the injection mold 1 can be removed after it has cooled sufficiently and solidified accordingly, so that it remains dimensionally stable.

In the process step shown on the far right 1 it can be seen that the core element 8th for the production of a ready-to-use core 18th on the one hand from a sprue 9 has been separated, which is the core material 5 which is in the feed channel 7 is frozen. Furthermore, the core is by machining 18th with two wells 10th has been provided, namely in the form of holes that the core 18th Push through completely and have a diameter of 1 mm each. Except for these wells 10th points the nucleus 18th also a head start 11 on.

Depending on the form and shape, the wells mentioned can 10th can also be shown in the injection molding itself, which represent a filigree structure as described above, which may have depressions and / or elevations, the depressions being able to pass through the workpiece (holes), but not necessarily.

2nd shows the use of this core element thus produced 8th as the core 18th in the manufacture of a workpiece 12th , again in several steps from left to right. A casting mold is here as a die casting mold 101 designed and has a nozzle side 102 and an ejector side 103 on that a cavity 104 enclose. In the cavity 104 is the core 18th arranged. A flowable metallic material 105 , in the example the melt of an aluminum alloy, is located directly outside the die casting mold 101 .

The next step shows that the liquid metal 105 by means of an injection unit 106 into the die-casting mold under high pressure 101 has been injected and the cavity 104 as well as the feed channel 107 fills in and the core 18th surrounds. The metal is also in the holes, i.e. in the recesses 10th of the core 18th poured in.

In the work step shown next to it on the right is the die casting mold 101 been separated by the nozzle side 102 and the ejector side 103 have been moved apart, so that now a metallic workpiece 12th can be removed from the mold. The core 18th is still inside the workpiece 12th . Due to its geometry, it cannot get out of the workpiece 12th be demolded.

As the last manufacturing step in the manufacture of the finished workpiece 12th is in on the far right 2nd shown that a sprue 109 made of metal from the workpiece 12th has been removed and the core material 5 of the core 18th has been broken up into many small, schematically indicated components. Inside the workpiece 12th now remains a cavity 108 back that previously the core 18th had filled out. In particular, this creates a filigree structure 14 inside the workpiece 12th created by pens 14 ' with a diameter of 1 mm inside the workpiece 12th have been created, namely as material from the material 105 the aluminum alloy, which is in the recesses 10th of the core element 8th had poured in.

In that the core 18th consisted of polyvinyl alcohol and sodium carbonate, he could use only water from the workpiece 12th detached and completely dissolved.

Depending on the core material used, the coring can take place pyrolytically or by dissolving the core material in a solvent. It is also conceivable that a biodegradable plastic, such as a starch-based plastic, is destroyed by a chemical or biological process (e.g. decomposition by bacteria). Mechanical effects can also be used, e.g. B. by spray lances or other processes damaging or damaging the core. The different ways to remove the core 18th can be used alone or in combination with one another: for example, a core can be removed by loosening the core 18th done in a liquid, e.g. B. in a water bath, and combined in the form of an ultrasonic bath with a mechanical effect.

3rd shows a core element 8th , which is used to create a cavity in a workpiece 108 in shape a flow channel 21 to create, which is to be flowed through by oil, so that this core element is identified with the designation 8ö. The core element 8ö has the dimensions 10cm x 3cm, a thickness of 2mm and has a large number of depressions 10th in the form of bores with a diameter of 1 mm, and in the form of curved slots penetrating the core element 8ö. Furthermore, the core element 8ö has two molded pipe sockets 15 on, each a through hole penetrating the core element 8ö 16 surround.

4th shows another core element 8th which has a flow channel 21 for water in the workpiece, so that in the following this core element as the core element 8w referred to as. Here too has the core element 8w the dimensions 10cm x 3cm, a thickness of 2mm, and has a variety of wells 10th on, which are designed in the form of curved slots with a width of 1 mm. Through holes 16 are provided on the one hand where the two pipe sockets on the core element 8ö 15 are arranged, and on the other hand also within four pipe sockets 15 which is on the outer edge of the core element 8w are located.

The different geometries of the core element 8o, also called the oil core, and the core element, also called the water core 8w are selected in such a way that, on the one hand, they enable intensive heat transfer for the respective flow medium and, on the other hand, pressure losses in the respective flow channel 21 keep as low as possible; for example, the channels through which water is to flow are wider in the exemplary embodiment shown than the channels through which oil is to flow.

5 shows the alternating and still pulled apart arrangement of core elements 8ö and 8w one above the other.

6 shows the arrangement of 5 , with the core elements 8ö and 8w now forming a core 18th forming package are composed. The core 18th is arranged over the lower part of a die casting tool. This is with six guide pins 17th provided which the pipe socket 15 of the core elements 8ö and 8w record plate pack formed.

In 7 is the arrangement of this core designed as a plate package 18th shown in the die casting tool. An upper tool half, which in 7 can now be seen on the guide pins 17th be lowered, and then, under high pressure, a liquid aluminum alloy is brought into the tool and encloses it as a plate package of the core elements 8th formed core 18th .

8th shows the workpiece produced in this way 12th .

9 shows the workpiece 12th in an embodiment that is not ready for use, in which the top housing wall of the workpiece is used for illustration 12th is removed and so a look at one as a flow channel 21 trained cavity 108 , namely an oil channel 21ö is released after all the core elements 8ö and 8w from the workpiece 12th have been removed. The wells 10th of the core element 8ö have to design a variety of filigree structures 14 in the form of pimples 14 " and two curved webs 14 '" led, on the one hand, the flow of oil through the oil channel 21ö optimize and on the other hand maximize the heat exchanger surface.

10th shows a perspective view of another section through the workpiece 12th the 8th or the 9 , where in 10th a flow channel 21 , namely a water channel 21 w of the workpiece 12th is exposed. It can be seen that the undulating or curved depressions 10th of the core element 8w to corresponding filigree structures 14 in the form of curved webs 14 "' in the water channel 21w have led.

11 shows the workpiece 12th in a machined form, in which there is now a ready-to-install heat exchanger 20th forms: The four outer through holes 16 are omitted, and only the two middle through holes 16 have remained, namely as the inlet and outlet of the heat exchanger 20th connected to an oil line. The two long sides of the workpiece 12th have been machined to such an extent that not only the through holes arranged there 16 are eliminated, but also the two longitudinal side walls of the workpiece 12th have been removed. Accordingly, lie on the two opposite longitudinal sides of the heat exchanger 20th Water channels 21 free so that the heat exchanger 20th water or cooling fluid of an internal combustion engine can flow through transversely to its longitudinal direction and oil can flow through in its longitudinal direction.

12th shows a module 22 which has a filter cup 23 has, which serves to hold a replaceable filter insert and which with a separate, in 12th not shown, cover can be closed. The filter cup closes at the bottom 23 to a housing 24th of the heat exchanger 20th on. The heat exchanger 20th is in this case 24th used, the housing by a in 12th lid, also not shown, is closed in a liquid-tight manner and then water can flow through it. This Housing cover of the housing 24th allows connection of the mentioned oil line, so that inside the housing 24th the heat exchanger 20th both water and oil can flow through.

In the illustrated embodiment of the 12th is the heat exchanger 20th formed by a single component, so that the assembly and sealing of a large number of individual plates is not necessary. The creation of filigree structures within the heat exchanger 20th , as is made possible by the proposed production method, can deviate from that in 12th illustrated embodiment can be used to further integrate functions in the module 20th to enable. A higher level of integration means that the same functions with even more compact dimensions of the module 22 be made possible, or that with the same dimensions, the module can have a higher performance, for example a higher heat exchanger performance.

For example, the module designed as a cast part can be provided 22 holding the filter cup 23 and the housing 24th has as a single integrated casting, further develop in that this one casting also the heat exchanger 20th forms so that the heat exchanger 20th does not have to be installed as a separate component. For example, ribs can be provided 25th that the module 22 has anyway, and / or the filter cup 23 to be double-walled and to be provided with flow channels inside, so that in the module 22 shown space, the heat exchanger 20th requires can be significantly reduced.

13 shows the section through a further embodiment of a workpiece 12th with an inner core 18th that consists of three core elements 8a , 8b , 8c is formed and in the workpiece 12th a cavity 108 generated in the form of an optimized flow channel. Here are just the core elements 8a and 8b formed from a core composition according to the invention and the core element 8c is designed as a steel pin, which is used when removing the core 18th from the workpiece 12th just out of the cavity 108 can be pulled out. The core element 8c can thus be used to manufacture another core 18th be reused.

The core element 8b has a diameter D which is less than 1/7 the length L of the core element 8b and therefore in the cavity 108 of the workpiece 12th a delicate structure 14 trains.

The core element 8a has inlays 19th which can be formed, for example, from a metal, preferably from the same metal as the workpiece 12th . The depositors 19th be in the making of the core 18th into the core element 8a inserted and remain after removal of the core 18th from the workpiece 12th in the workpiece 12th . The depositors 19th can there, for example, an increase in the flow resistance in the 13 cause the upper portion of the flow channel or be provided as a filter for particles.

Reference list

1

Injection mold

2nd

Nozzle side of the injection mold

3rd

Ejector side of the injection mold

4th

Injection mold cavity

5

Core material

6

Injection unit of the injection mold

7

Injection mold feed channel

8th

Core element ( 8a , 8b , 8c) 8ö = for oil, 8w = for water

9

Sprue core element

10th

deepening

11

head Start

12th

workpiece

14

filigree structure / 14 ' Pen, 14 " Pimples, 14 '" web

15

Pipe socket

16

Through holes

17th

Guide pins

18th

core

19th

Depositor

20th

Heat exchanger

21

Flow channel

22

module

23

Filter cup

24th

casing

25th

Ribs

101

Die casting mold

102

Nozzle side of the die casting mold

103

Ejector side of the die casting mold

104

Die casting cavity

105

Metallic material

106

Injection unit of the die casting mold

107

Feed channel of the die casting mold

108

cavity

109

Sprue of the workpiece

D

diameter

L

length

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 19635920 A1 [0002]
• DE 102011076905 A1 [0006]

Claims (19)

Method for producing metallic workpieces (12) using the die casting method, with the following method steps: • A core (18) which has at least one core element (8) containing at least 5% plastic is introduced into a die casting mold (101) and in a predetermined position held in the die casting mold (101), • a workpiece (12) is produced by inserting metal in the die casting process into the die casting mold (101), the core (18) is thereby cast over, and the metal is cooled, • the core (18) removed from the workpiece (12) and the core element (8) destroyed, characterized in that • the core element (8) has a geometry such that so-called filigree structures (14) are created in the workpiece (12), wherein metallic elements are created which protrude with a thickness or diameter of at most 5 mm into a cavity (108) created by the core element (8), or the length of the cavity (108) more than 7-fa ch is larger than its smallest cross-sectional dimension, • and that the core element (8) is removed from the workpiece (12) without demolding. Procedure according to Claim 1 characterized in that the core element (8) is produced by injection molding. Procedure according to Claim 1 or 2nd characterized in that the plastic contained in the core element (8) is placed in an unbound state to remove the core element (8). Method according to one of the preceding claims, characterized in that the core (18) has an outwardly projecting projection (11) and / or an indentation (10) projecting into the core in such a way that a during the casting process of the workpiece (12) pulling out the core (18) from the workpiece (12) preventing undercut. Method according to one of the preceding claims, characterized in that the workpiece (12) is produced in the high-pressure casting process. Method according to one of the preceding claims, characterized in that the core element (8) contains a salt. Procedure according to Claim 6 , characterized in that the core element (8) contains a halogen-free salt. Method according to one of the preceding claims, characterized in that the core element (8) contains polyvinyl alcohol as plastic. Method according to one of the preceding claims, characterized in that the core element (8) is first produced by the injection molding process, and is then reworked in the contact area to the workpiece in order to create the final core element geometry. Procedure according to Claim 9 , characterized in that an undercut is created by the post-processing in the contact area to the workpiece. Method according to one of the preceding claims, characterized in that the core element (8) is connected to one or more further core elements (8) in order to create the core (18). Method according to one of the preceding claims, characterized in that the core (18) is removed pyrolytically from the workpiece (12). Procedure according to one of the Claims 1 to 11 , characterized in that the core (18) is removed from the workpiece (12) by melting. Procedure according to one of the Claims 1 to 11 , characterized in that the core (18) is removed from the workpiece (12) by mixing with an auxiliary. Procedure according to Claim 14 , characterized in that the core (18) is removed from the workpiece (12) by mixing with a solvent as an auxiliary. Workpiece (12) produced in a method according to one of the preceding claims, wherein the workpiece (12) has at least one flow channel (21) optimized for the use of the workpiece. Workpiece (12) after Claim 16 The at least one flow channel (21) is optimized to guide a flow with little pressure loss and / or low turbulence. Workpiece (12) after Claim 17 , wherein the flow channel (21) is free of sharp edges or deflections. Workpiece (12) according to one of the Claims 16 to 18th , the workpiece (12) forming a heat exchanger (20), and wherein the heat exchanger (20) has two separate flow channels (21ö, 21w) for two heat transfer fluids, and at least one of the two flow channels (21ö, 21w) is formed by a core cavity.

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