Foundry insert and method of production

Abstract

The invention relates to a cast insert (1) comprising: - a wall (2) essentially formed of a liquid phase sintered refractory metal alloy; - a cavity (3) formed by the wall (2); - at least one cooling duct (4) distinct from the cavity (3) and at least partially configured within the cavity (3) and / or at least partially configured within the wall (2), wherein the wall (2) has a wall thickness (t) that can be defined by the normal distance between a point of the wall (2) facing the cavity (3) and a point on the outer surface (A) of the wall (2), and the wall thickness (t) is at least partially less than 25% of the diameter (D) of the cast insert (1).

Description

Technical Field

[0001] This invention relates to a casting insert and a method for producing the casting insert. Background Technology

[0002] In the context of this invention, casting inserts are understood to be components used with molds, particularly molds for metal die casting.

[0003] For example, this includes so-called inserts, gate bushings, cooling inserts, and core pins.

[0004] The aforementioned components are characterized by their ability to withstand high corrosion and thermal stress. In particular, cast inserts are used to remove locally amplified heat from the casting.

[0005] Although the mold itself is usually made of hot-worked steel, for casting inserts, materials with higher thermal conductivity than the steel used for the mold are also used.

[0006] For example, casting inserts made of tungsten or molybdenum-based alloys have been proposed. Tungsten heavy metal alloys or TZM molybdenum alloys are particularly suitable because of their high thermal conductivity and resistance to molten metal.

[0007] The cast insert can be configured for active cooling. For this purpose, cooling conduits are installed in the solid cast insert, through which coolant circulates.

[0008] According to existing technology, cooling channels are typically formed by drilling. An inclined profile can be achieved through a cross-shaped hole that is subsequently sealed with a plug. More geometrically complex cooling channel profiles can be achieved by first introducing recesses within the component half of a cast insert and then joining the component half together to form a finished cast insert. Summary of the Invention

[0009] One object of the present invention is to provide an improved casting insert and a method of production.

[0010] In particular, this casting insert and method are designed to achieve a more economical use of materials. Furthermore, it aims to enable particularly advantageous heat dissipation and / or heat storage.

[0011] This objective is achieved by the casting insert according to the invention and the method for producing the casting insert according to the invention.

[0012] Advantageous embodiments are defined in other advantageous improvements.

[0013] The casting insert according to the present invention comprises:

[0014] - Cast insert walls, which are essentially formed from a liquid-phase sintered refractory metal alloy.

[0015] - A cavity, formed by cast insert walls.

[0016] - At least one cooling conduit, which is different from the cavity, and is at least partially constructed within the cavity and / or at least partially constructed within the wall of the cast insert.

[0017] The cast insert wall has a wall thickness defined by the normal distance between a point on the cast insert wall facing the cavity and a point on the outer surface of the cast insert wall, and the wall thickness is at least partially less than 25% of the diameter of the cast insert.

[0018] A cast insert is provided that meets thermal, mechanical, and chemical requirements while utilizing materials in a particularly advantageous manner.

[0019] The material that forms the wall of the cast insert is called the cast insert wall material.

[0020] The cavity formed by the cast insert wall means that, in the cast insert according to the invention, the cast insert forms a shell; therefore, the cast insert is not entirely made of the material forming the cast insert wall (cast insert wall material). Thus, the cast insert is a hollow body having at least one cooling conduit and optional support structure. This does not mean that, in all exemplary embodiments, the cavity of the cast insert is completely devoid of material. Rather, the cavity can be completely or partially filled by filling it with a filler material different from the cast insert wall material.

[0021] In all cases, the portion of the cast insert that comes into contact with the melt during use will have a closed cast insert wall. Conversely, the portion of the cast insert away from this side can have an open construction.

[0022] The wall thickness of the cast insert is at least partially less than 25% of the diameter of the cast insert, preferably partially less than 20%, and more preferably partially less than 10% of the diameter.

[0023] This shows that the structure of the cast insert is thin-walled. The lower limit of the wall thickness is essentially derived from the requirement for mechanical and / or chemical resistance of the cast insert wall. In particular, the wall thickness is at least 2% of the diameter of the cast insert, more preferably at least 5% of the diameter of the cast insert. In absolute terms, the wall thickness is preferably at least 1 mm, more preferably at least 2 mm.

[0024] The wall thickness can be defined by the normal distance between the point on the wall of the cast insert facing the cavity and the point on the outer surface of the cast insert.

[0025] Preferably, in the longitudinal section passing through the cast insert, the wall thickness along at least 50%, preferably at least 80%, of the cast insert wall is less than 25%, preferably less than 20%, and more preferably less than 10% of the cast insert diameter. This defined longitudinal section is provided to show the wall thickness in a manner that reflects the actual distance.

[0026] According to further improvements, the average wall thickness is less than 25% of the diameter of the cast insert, preferably less than 20%, and particularly preferably less than 10%. Of course, relatively large wall thicknesses can be set locally, but on average, there are relatively small wall thicknesses.

[0027] To assess wall thickness, the corresponding portion of the cast insert wall is considered to protrude into the mold when the cast insert is in use. In other words, when mounted in the mold, the ratio forms the wall thickness only at those locations where the cast insert wall forms an outer surface relative to the melt.

[0028] This excludes any reinforcements, collars, etc., primarily used to receive the mold.

[0029] Similarly, no supporting structure is included in the ratio formation.

[0030] The advantage of thin-walled properties is primarily the need to use less of the relatively expensive wall material, i.e., refractory metal alloys, to form the cast insert. Beyond this economic consideration, in the case of thin walls, a larger volume of the cast insert can be filled with filler material, which, for example, possesses particularly suitable thermal conductivity or other properties. This property can be utilized to a greater extent at a larger volume ratio compared to the case of thick-walled cast inserts where the filler material accounts for a smaller volume proportion.

[0031] The construction according to the invention means that only as much material as is needed to achieve the required heat dissipation, the required heat storage, and the material required to resist the melt is used to form the cast insert wall.

[0032] This contrasts with solid cast inserts known in the prior art. Therefore, cast inserts according to the prior art are made almost entirely of the material that comes into contact with the melt during use.

[0033] This invention allows for material-saving manufacturing of cast inserts produced in a single piece. Compared to existing technologies, the advantages of this cast insert include:

[0034] - Improved heat dissipation and cooling pipe implementation with increased degrees of freedom relative to spatial profile and cross-sectional shape.

[0035] - Cool only when needed.

[0036] - When using materials with practically high heat capacity, the heat storage capacity is reduced.

[0037] In particular, this can reduce cycle time in applications (e.g., in die casting, especially in aluminum die casting).

[0038] According to the invention, the cast insert wall material is essentially formed of a liquid-phase sintered refractory metal alloy. The term "essentially" herein means that the cast insert wall material comprises at least 80 vol.% (volume percentage) of a liquid-phase sintered refractory metal alloy, preferably greater than 90 vol.%, more preferably greater than 95 vol.%, and particularly completely comprises it.

[0039] In the context of this application, refractory metals are understood to be metals of Group 4 (titanium, zirconium, and hafnium), Group 5 (vanadium, niobium, and tantalum), and Group 6 (chromium, molybdenum, and tungsten) of the periodic table, as well as rhenium. Refractory metal alloys are alloys of the aforementioned elements having at least 50 at.% (atomic percentage).

[0040] Of particular interest are tungsten heavy metal alloys containing tungsten and one or more elements selected from the group consisting of nickel, iron, copper and molybdenum, and liquid-phase sinterable molybdenum-based alloys containing molybdenum and one or more elements selected from the group consisting of nickel, copper and tungsten.

[0041] The minimum content of tungsten in tungsten heavy metal alloys or molybdenum in liquid-phase sinterable molybdenum-based alloys is preferably at least 85 wt.%, particularly at least 87 wt.%.

[0042] These elements are also referred to below by abbreviations of their element symbols (W, Mo, Cu, etc.).

[0043] Liquid-phase sintering means that the powder metallurgy production of cast inserts is carried out in the presence of a molten phase. Furthermore, this is associated with the advantageous low porosity of the cast insert wall material. It needs to be clarified that in tungsten heavy metals and liquid-phase sinterable molybdenum-based alloys, tungsten or molybdenum itself typically does not melt.

[0044] Therefore, the wall material of the cast insert is formed from a composite material consisting of refractory metal particles and a binder phase surrounding the particles.

[0045] In particular, the following refractory metal alloy compositions are preferred:

[0046]

[0047] Table 1: Examples of suitable tungsten heavy metal alloys. and It is a registered trademark of PLANSEE SE.

[0048] Alloys D185 and D2M have proven particularly advantageous for use with molten aluminum because they have a low proportion of Fe-Ni binder phase that is eroded by liquid aluminum.

[0049] Also suitable are molybdenum-based liquid-phase sinterable refractory metal alloys. Particularly suitable are molybdenum alloys with a molybdenum content of approximately 90 wt.%, a nickel content of 3 wt.% to 7 wt.%, a copper content of 1 wt.% to 6 wt.%, and an iron content of 0.5 wt.% to 2 wt.%.

[0050] Examples of compositions selected for this purpose include:

[0051] Mo content [wt.%] Ni content [wt.%] Cu content [wt.%] Fe content [wt.%] 90 6.66 1.67 1.67 90 4 5.1 0.9 90 3.34 6.0 0.66

[0052] Table 2: Examples of suitable liquid-phase sinterable molybdenum alloys (selected).

[0053] Due to density ratios, the binder phase content in these examples of liquid-phase sinterable molybdenum alloys is approximately 12.5 vol.%.

[0054] The examples mentioned here should not be construed as limiting.

[0055] A particular advantage of the cast inserts according to the invention is that the relatively expensive refractory metal alloys are primarily present in the cast inserts only at locations dependent on the chemical, mechanical, and / or thermal properties of these alloys. Specifically, these are the portions of the cast insert walls exposed to the melt during use.

[0056] The economic advantage of using molybdenum alloys lies in their lower cost per volume compared to tungsten heavy metal alloys.

[0057] At least one cooling conduit may be at least partially constructed within the cavity and / or at least partially constructed within the cast insert wall.

[0058] This means that the variant firstly includes at least one cooling conduit completely constructed within the cavity. Furthermore, at least one cooling conduit may be completely constructed within the cast insert wall. Further, at least one cooling conduit may extend partially within the cast insert wall and partially within the cavity, spaced apart from the cast insert.

[0059] Of course, two or more cooling pipes may also be provided, wherein the above-mentioned conditions relating to the construction are at least partially within the cavity and / or at least partially within the wall of the cast insert, at least one cooling pipe is applied, and preferably all cooling pipes are applied.

[0060] Cooling conduits that are at least partially constructed within the cavity mean that they are at least partially spaced from the cast insert wall. Correspondingly, the cooling channels are at least partially constructed as tubes with cooling conduit walls. In other words, the cooling conduits here have walls at least partially different from the "self" of the cast insert wall. This type of cooling conduit can be particularly advantageously produced by additive manufacturing processes.

[0061] The cooling conduit can also be at least partially constructed within the cast insert wall. This means that the cooling conduit can be completely or partially surrounded by the cast insert wall. In this variation, the wall of the cooling conduit is at least partially formed by the wall of the cast insert. This describes the possibility of alternatively or additionally forming the cooling conduit on or within the cast insert wall. This means that the cooling conduit can alternatively or additionally be constructed as a layer spaced apart from the cast insert wall to form an integral part of the cast insert wall.

[0062] This, for example, allows for the arrangement of cooling pipes in portions particularly close to the outer surface of the cast insert.

[0063] This allows for advantageous heat dissipation from the areas of the cast insert walls under specific thermal stress.

[0064] This type of cooling conduit can also be advantageously produced by additive manufacturing processes. For example, in the case of a layer-by-layer construction of cast inserts, no material and / or removable placeholder can be placed at the location of the free conduit cross-section of the cooling conduit described below.

[0065] In particular, on the end face of the casting insert facing the melt, that is, in the area that extends further into the mold, the distance between the cooling channel and the outer surface of the casting insert can be smaller than the distance in the area that extends closer into the mold.

[0066] The at least one cooling conduit is configured to guide the cooling medium through a cast insert in a defined manner. The cooling medium is typically water, oil, or an emulsion.

[0067] Therefore, unnecessary material accumulation is avoided. Furthermore, the construction according to the invention allows for greater freedom in the spatial arrangement of the cooling pipes, as these cooling pipes do not need to follow the cast insert walls.

[0068] Typically, at least one cooling conduit is constructed such that a cooling medium guided therein can flow through a cast insert. Therefore, it usually has an inlet section and an outlet section. The cooling medium is introduced into the cast insert through the inlet section, flows through the cast insert, and exits the cast insert through the outlet section. In simple cases, the profile of the cooling conduit can be approximately U-shaped and lies essentially in a plane.

[0069] When the cooling channels have a preferably at least partially spiral profile, more intense and uniform heat removal is achieved. Furthermore, it is advantageous that the cooling channels follow the outer contour of the cast insert in a substantially spiral shape, such that the cooling channels extend at a substantially uniform spacing with the outer contour. This further contributes to uniform heat removal.

[0070] At least one cooling duct can be configured to have at least a partial change in cross-section. For example, it is conceivable that the free-flow cross-section of the cooling duct is partially narrowed or that its cross-sectional shape is varied. Thus, heat transfer can be adapted to localized needs.

[0071] In the case of cast inserts with relatively low or small heat output requirements, such as in the case of so-called cooling fingers, it is sufficient to implement the cooling conduit simply as a blind orifice. In this case, there are no separate inflow and outflow sections; instead, the cooling medium must enter and exit through the cooling conduit implemented as a blind orifice. In this case, cooling is achieved through so-called impact cooling at the bottom of the cooling conduit.

[0072] Preferably, a support structure can be provided there, which is configured to connect the cast insert wall and at least one cooling conduit. A case is described herein in which at least one cooling conduit is spaced apart from the cast insert wall by a material connection (i.e., the support structure).

[0073] The supporting structure serves for the mechanical stability and placement of the cooling conduits. This allows for the construction of slender, thin-walled cooling conduits while maintaining mechanical robustness. A cavity is preserved between the cooling conduits and the cast insert walls. This makes it possible to fill the cavity between the cooling conduits and the cast insert walls with additional material.

[0074] More preferably, the support structure can be configured as separate beams and / or ribs.

[0075] This defines the preferred scenario, in which the cooling pipes are supported by a lattice structure of support structure, which is in the form of separate beams and / or ribs.

[0076] The supporting structure can be constructed, for example, as a three-dimensional frame.

[0077] Advantageously, the support structure is designed to be so sparse that the gap between the cooling channels and the cast insert walls can be filled with filler material. This filler material can be achieved, for example, through back casting.

[0078] Preferably, the support structure is formed of the same material as the wall of the cast insert.

[0079] This section describes a preferred scenario where the support structure and the cast insert walls are made of the same material.

[0080] In particular, the support structure transitions from the cast insert wall to the wall of the cooling pipe in one piece.

[0081] More preferably, one or more cooling pipes are also made of the same material as the wall of the cast insert.

[0082] In particular, the cast insert walls, support structures, and cooling channels are made of the same material, namely a liquid-phase sintered refractory metal alloy.

[0083] As a result, for example, when additively manufacturing cast inserts, the material does not need to be changed during the manufacturing process. The walls, support structures, and cooling channels of the cast insert can advantageously be formed from the same material.

[0084] Preferably, the cast insert wall is produced by an additive manufacturing process, particularly preferably by a binder-based additive manufacturing process. This makes it particularly advantageous to reproduce the typically complex shapes of the cast insert. Therefore, the additive manufacturing approach is advantageous only for the production of cast insert walls.

[0085] Additional advantages are gained when at least one cooling conduit and optional support structure are produced, in addition to the cast insert walls, via additive manufacturing processes, particularly preferably via binder-based additive manufacturing processes. This allows for the simultaneous production of the structure. Furthermore, complex shapes can be advantageously achieved for at least one cooling conduit.

[0086] Therefore, in particularly preferred cases, the cast insert walls, support structures, and cooling channels are integrally produced by additive manufacturing processes, particularly preferably by binder-based additive manufacturing processes.

[0087] In the case of layer-by-layer construction in additive manufacturing, the areas of cast insert walls, support structures, and cooling channels can be laid out simultaneously in one layer. In this particularly preferred case, the cast insert walls, support structures, and cooling channels transition to each other in a seamless manner.

[0088] In addition, cooling pipes can be introduced into the cavity separately, for example, in the form of prefabricated pipes.

[0089] Preferably, the cavity between the cast insert wall and at least one cooling conduit is configured to contain at least partially a filler formed of a filler material different from the material of the cast insert wall (cast insert material).

[0090] This describes a preferred configuration in which the cast insert is at least partially filled with a filler material different from the wall material of the cast insert. The filler is preferably back-cast. For example, the cavity is back-cast with copper or a copper alloy.

[0091] In particular, the filler material has higher thermal conductivity than the wall material. This increases the heat output that can be removed through the cast insert.

[0092] Advantageously, in such composite materials, appropriate materials are used according to their strength: for example, the cast insert walls exposed to the melt are formed of refractory metal alloys, while the filler can be provided by materials with particularly high thermal conductivity.

[0093] Furthermore, the infill material provides mechanical stability to the cast insert, which is advantageous. The walls of the cast insert can have a relatively thin construction because they are supported internally by the infill material. This also contributes to the efficient use of material.

[0094] The filler material preferably has a thermal conductivity of at least 200 W / mK, more preferably at least 300 W / mK, and particularly preferably at least 350 W / mK.

[0095] Copper and copper alloys are particularly suitable as filler materials because copper has good compatibility and high thermal conductivity with refractory metal alloys sintered in the liquid phase.

[0096] Due to its good compatibility with refractory metal alloys, a tight bond is formed between the cast insert wall and the filler, resulting in good heat transfer.

[0097] It is particularly advantageous to construct a diffusion zone between the filler material and the refractory metal alloy.

[0098] The present invention relates in particular to casting inserts for molten light metals (especially molten aluminum).

[0099] Particularly preferred is that the cast insert wall is at least partially produced by an additive manufacturing process, particularly by a binder-based additive manufacturing process. A particularly preferred embodiment is described herein, wherein the cast insert is at least partially produced by an additive manufacturing process, particularly preferably by a binder-based additive manufacturing process. The term "binder-based" refers to the treatment of the metal powder used for the additive structure with at least one organic binder component. Specifically, known binder-based additive manufacturing processes include:

[0100] Fine-grain printing is performed using raw material filaments, selective laser sintering (SLS) is performed using raw material particles / powders, and photolithography is performed by spraying mixed, pre-alloyed, or granulated metal powders with raw materials and binders.

[0101] The structural features discussed can be advantageously achieved through binder-based additive manufacturing processes. Advantages of additive manufacturing include, for example, the absence of bonding zones. In binder-based additive manufacturing, a green compact is first produced, which retains its cohesion through a binder component. The metallic components are then metallurgically bonded by sintering.

[0102] For the selection of materials (liquid-phase sintered refractory metal alloys) for the casting inserts according to the invention, the production route via a binder-based additive manufacturing process is particularly advantageous, as will be explained in more detail below.

[0103] Particularly preferably, the cast insert walls, cooling channels, and optional support structures are manufactured integrally using an additive manufacturing process. In other words, the entire cast insert is preferably manufactured using an additive manufacturing process, particularly a binder-based additive manufacturing process. In many cases, it is economically advantageous to eliminate the need for surface finishing.

[0104] In addition to the advantageous ability to produce complex geometries (such as undercuts), monolithic manufacturing offers structural advantages, such as the continuous material bonding between casting insert walls, cooling channels, and optional support structures. The monolithic nature contributes to good heat dissipation and mechanical stability.

[0105] It will be apparent to those skilled in the art that casting inserts can be produced using additive manufacturing processes. In particular, there are microstructural and / or macroscopic differences between additively constructed parts and conventionally produced parts. For example, those skilled in the art can identify manufacturing pathways on untreated external areas or internal walls by so-called layer lines or increased roughness. These structures can also be scaled up in a controlled manner, for example, to alter the inner walls of cooling conduits in terms of flow.

[0106] In addition to differences in microstructure, there are also significant features related to the complexity of the manufacturable structure and / or thin-wall properties.

[0107] Furthermore, in the existing sintering bonding process, defects are usually present in the bonding zone.

[0108] Also seeking protection is a method for producing cast inserts. This is a binder-based additive manufacturing method. Examples of binder-based additive manufacturing methods include, in particular, filament printing with raw material filaments, selective laser sintering (SLS) with raw material particles or powders, and photolithography using raw material or binder to spray mixed, pre-alloyed, or granulated metal powders.

[0109] The method according to the present invention includes the following steps:

[0110] - Provides a powder containing a liquid-phase sinterable refractory metal alloy and at least one organic binder component.

[0111] - Producing a green blank by additively constructing at least a portion of the wall of a cast insert from powder treated with at least one organic binder component.

[0112] - The green bodies produced in this way are debonded to obtain palm blanks.

[0113] - Sinter the brown blank in the presence of at least a temporary liquid phase to obtain a metal blank for casting inserts.

[0114] -Optionally, the blank can be finished to obtain a casting insert.

[0115] First, a powder comprising a liquid-phase sinterable refractory metal alloy and at least one organic binder component is provided. Providing this powder may mean treating the metal powder into a plasticizer using at least one organic binder component.

[0116] For example, the material can be obtained through vigorous mechanical mixing and kneading and / or extrusion and / or granulation and / or milling. Plasticizers can be applied in various forms. For filament printing, raw material filaments are produced; for selective laser sintering (SLS), raw material granules or powders are provided; for photolithography processes, raw material blocks are typically used.

[0117] Alternatively, in the case of adhesive spraying, the organic adhesive components are coated in situ onto the metal powder, that is, during layer-by-layer construction.

[0118] Liquid-phase sinterable refractory metal alloys can be introduced as a mixture of pre-alloyed powders or elemental powders or a mixture of pre-alloyed powders.

[0119] The following are specifically recommended compositions: tungsten heavy metal alloys comprising tungsten and one or more elements selected from the group consisting of nickel, iron, copper and molybdenum, and liquid-phase sinterable molybdenum-based alloys comprising molybdenum and one or more elements selected from the group consisting of nickel, iron, copper and tungsten.

[0120] Additive manufacturing processes result in the production of green blanks that form cast insert walls layer by layer. The cast insert walls produced thereby at least partially form the following external contour of the green blank.

[0121] A particular advantage of additive manufacturing is that it allows for the production of complex external and / or internal geometries that would otherwise be very laborious to manufacture using conventional processes, if required. Cooling conduits can be advantageously produced, for example, by eliminating material in cast insert walls or by forming a closed cross-section within the cavity.

[0122] Additive structures are achieved, for example, by filament printing using raw material filaments, SLS using raw material particles / powders, or photolithography using mixed or pre-alloyed or granular metal powders or binders.

[0123] The applicant’s experiments demonstrate that binder-based additive manufacturing processes are particularly well-suited for the use of liquid-phase sinterable refractory metal alloys.

[0124] Laser or electron beam melting processes, typically used for weldable materials such as steel, are disadvantageous for composite materials such as liquid-phase sinterable refractory metal alloys. The localized high input heat of the high-energy beam can, for example, evaporate the low-melting-point phase while the melting point of the high-melting-point phase is far from being reached.

[0125] Another characteristic of binder-based additive manufacturing processes is the presence of a green compact after layer-by-layer construction. The green compact comprises metal powder and at least one organic binder component. Typically, two or more binder components are used. Compositions comprising a thermoplastic polymer and at least one plasticizer are particularly advantageous. Additives are also typically added, for example as lubricants or to adjust viscosity.

[0126] Thermoplastic polymers are particularly selected from polyurethanes, polyamides, polyvinylpyrrolidone, polyacrylates, polyolefins, or mixtures thereof.

[0127] Plasticizers can be esters or mixtures of esters.

[0128] Suitable commercially available adhesive compositions are disclosed, for example, in European Patent Specification EP 3167101(B1).

[0129] The green body is mechanically robust and, for example, can be easily processed. This is another advantage of the adhesive-based approach.

[0130] Debinding is carried out chemically, chemically / thermally, or thermally alone. Debinding removes organic components that are primarily used to modulate rheology and processability.

[0131] The polymer "backbone" between the powder particles remains, providing sufficient mechanical stability for the brown preform obtained after debinding. Another advantage of debinding is the reduction of organic load encountered during the sintering step. In the case of the polyamide example above, debinding is preferably carried out using chemical methods, such as with acetone. The polyamide bridges between the metal particles remain. The preform after debinding is referred to as the brown preform.

[0132] The brown blank is then sintered in the presence of at least a temporary liquid phase to obtain a metal blank for casting inserts.

[0133] Sintering in the presence of at least a temporary liquid phase can mean, as exemplified by MoCu or WCu alloys, that the low-melting-point element (Cu in this case) exists in molten form, wetting and eventually binding with the higher-melting-point powder particles (Mo or W in this case).

[0134] This could also mean that, due to a thermally induced process, a low-melting-point phase forms, and the Mo or W particles partially dissolve initially. This latter process is referred to in the literature as true liquid-phase sintering. For example, known tungsten heavy metal alloys function through this mechanism.

[0135] In conjunction with this invention, both methods should be understood as sintering in the presence of at least a temporary liquid phase.

[0136] Depending on whether a finished part with the final dimensions has been obtained after sintering, or whether further dimensional changes are required, net-shape or near-net-shape manufacturing can be referenced.

[0137] Optional finishing processes for the blank include mechanical rework, surface treatment, blasting, sandblasting, or finishing.

[0138] However, finishing may not be necessary at all. In this case, the blank obtained in the optional steps prior to finishing is already a finished casting insert.

[0139] This method enables the production of cast inserts with complex internal three-dimensional extended cooling channels, where material is consumed only in areas where material is required in the following applications.

[0140] The cast insert wall is particularly preferably produced in such a manner that the wall thickness of the cast insert is at least partially less than 25% of the diameter of the cast insert, and particularly less than 20%. As described above, this characteristic describes the thin-walled nature of the cast insert. The description of the thin-walled nature of the cast insert also applies to this section related to the method.

[0141] The construction of thin-walled casting inserts is particularly advantageous through additive manufacturing processes because, unlike machining, only the material actually required for the final shape needs to be used.

[0142] According to one variation, a separately configured cooling conduit is metallurgically joined to the cast insert thus produced. Specifically, a suitably formed steel pipe can, for example, be inserted into the sintered cast insert and, for example, bonded to the wall of the cast insert by back casting with a filler material. This variation allows for the economical and efficient production of cast inserts with simple geometries.

[0143] However, preferably, at least one cooling conduit is also manufactured simultaneously with the cast insert wall via an additive manufacturing process. Therefore, the at least one cooling conduit is integrally constructed with the cast insert wall.

[0144] It is also possible to simultaneously produce a support structure connecting the cast insert wall and at least one cooling conduit. This is particularly relevant when at least one cooling conduit is intended to be at least partially spaced from the cast insert wall. The support structure ensures the placement and mechanical stability of the cooling conduit operating in this manner.

[0145] It is particularly advantageous to simultaneously produce cast insert walls, cooling channels, and optional support structures. In this way, the advantages of additive manufacturing processes are particularly advantageously utilized.

[0146] In a further improvement, the cavity may be at least partially filled with a filler material that is different from the material of the cast insert wall, as discussed in more detail above.

[0147] Production Example:

[0148] The metal powder used is DENSIMET D185 powder.

[0149] The nominal chemical composition of the metal powder is 97 wt.% tungsten, 2 wt.% nickel and 1 wt.% iron.

[0150] The d50 particle size is between 6-8 μm.

[0151] Powders are treated with a polyamide-based thermoplastic binder containing plasticizers and additives to form raw material filaments. The filler content is approximately 55 vol.%. Polyamide-based binders have proven particularly effective for refractory metals.

[0152] Polyamides ensure good thermoplastic processing properties of the raw materials, while plasticizers regulate rheological properties. Additives are used for lubrication and viscosity adjustment.

[0153] Green bodies are constructed layer by layer using raw material filaments on a filament printer.

[0154] The resulting green body is then chemically debonded in acetone.

[0155] The resulting brown blank is sintered at approximately 1550°C in an H2 atmosphere to obtain the finished casting insert.

[0156] Finally, the inlays are cast with a copper backing.

[0157] Filling the cast insert with filler material is a preferred embodiment.

[0158] Further advantages and utility of the present invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0159] Figure 1 A cast insert according to a first exemplary embodiment is shown;

[0160] Figure 2 A cast insert according to another exemplary embodiment is shown;

[0161] Figure 3 A cast insert according to another exemplary embodiment is shown;

[0162] Figure 4 A cast insert according to another exemplary embodiment is shown;

[0163] Figures 5a-5bA photograph of the cast insert (sample part) is shown;

[0164] Figures 6a-6c A schematic diagram of the cast insert is shown;

[0165] Figures 7a-7c A cross-sectional schematic diagram of the cast insert is shown;

[0166] Figures 8a-8c The image shown is a surface scanning electron microscope (SEM) image magnified 50 times.

[0167] Figures 9a-9c The image shown is a surface scanning electron microscope (SEM) image magnified 100x.

[0168] Figures 10a-10c The image shown is a surface scanning electron microscope (SEM) image magnified 250 times.

[0169] Figures 11a-11b A cross-section of the body formed from tungsten heavy metal is shown;

[0170] Figure 12 The sequence of methods for producing cast inserts is shown. Detailed Implementation

[0171] Figure 1 A cross-section of a cast insert according to a first exemplary embodiment is schematically shown.

[0172] The cast insert 1 includes a cast insert wall 2 formed of a refractory metal alloy sintered in the liquid phase, which forms a shell and surrounds the cavity 3. A cooling conduit 4 is constructed within the volume defined by the cast insert wall 2 (cavity 3). Therefore, the cooling conduit 4 is a separate unit from the cavity 3.

[0173] Cooling conduit 4 is a conduction device for the cooling medium. The term "cooling channel" in connection with this application, depending on the specific circumstances, refers to the free conduit cross-section of the conduction device for the cooling medium (in the case of its layer within the cast insert wall 2) or the entire solid conduction device, that is, wherein the cooling conduit wall has a certain wall thickness and a conduit cross-section defined by the cooling conduit wall.

[0174] In this exemplary embodiment, the cooling conduit 4 is constructed as a tubular conduction device. The arrows indicate the inflow and outflow directions of the cooling medium. Of course, two or more cooling conduits 4 can also be constructed. As shown in this example, at least one cooling conduit 4 may protrude from the cavity 3 or terminate flush with the opening side of the cast insert 1.

[0175] The free pipe cross-section of the cooling pipe 4 is formed by the pipe wall of the cooling pipe 4, in contrast to an exemplary embodiment in which the cooling pipe 4 extends at least partially into the cast insert wall 2. In the latter case, the free pipe cross-section is at least partially constructed in the cast insert wall 2.

[0176] In this example, the cooling conduit 4 is held by a support structure 5 and connected to the cast insert wall 2 via this support structure. The support structure 5 is preferably in the form of a grid structure including beams and / or ribs.

[0177] The support structure 5 has the function of holding and stabilizing the cooling pipes 4 in the desired position. Advantageously, the support structure 5 is an open design, which allows the support structure 5, or more precisely, the hollow space network formed by the support structure 5, to be fully permeable.

[0178] In this exemplary embodiment, an optional preferred variant is shown, according to which the cast insert 1 is at least partially filled with a filler 6 that is different from the wall material of the cast insert. The filler 6 is particularly composed of a material having a higher thermal conductivity than the wall material of the cast insert. A filler 6 formed of copper or a copper alloy is particularly suitable. In this case, the filler 6 can be easily produced by back casting.

[0179] The cast insert 1 is particularly preferably integral, i.e., a single piece. This means that the cast insert wall 2, cooling conduit 4, and support structure 5 are materially transitioned to each other. The cast insert wall 2, cooling conduit 4, and support structure 5 are specifically formed from the same material (cast insert material) and have already been produced together in the additive manufacturing process.

[0180] Specifically, the cast insert 1 has been produced using a filament printing method (fused deposition modeling or fused filament fabrication) of raw material filaments. This method is capable of producing complex part geometries with hollow spaces and undercuts. Binder-based additive manufacturing processes are particularly advantageous for liquid-phase sinterable refractory metal alloys.

[0181] When the cast insert 1 is used, the cast insert protrudes into the mold 9 (not shown in more detail here). Optionally, a shoulder or flange 8 may be formed on the cast insert 1 to provide a support surface, sealing surface, and / or mounting possibility for the mold 9. Preferably, the shoulder or flange 8 is integrally constructed with the cast insert 1 from the cast insert wall material.

[0182] In use, the casting insert 1 is exposed to the molten metal M at its outer surface A. The surface of the casting insert 1 typically represents the outer contour of the workpiece in this manner. Through the casting insert 1, heat can be extracted from the molten metal M located in the mold 9 in a reinforced manner. In this way, the properties of the part produced in the mold 9 can be positively influenced. Particularly advantageous is the near-net-surface-shape profile of the cooling conduit 4. Due to the variable distance between the cooling conduit 4 and the outer surface A of the casting insert 1, localized cooling can be affected.

[0183] In the area where the casting insert 1 protrudes into the mold 9 when in use, in other words, in the area far from the cooling medium inlet, the distance between the cooling pipe 4 and the outer surface A can be set to be smaller than the distance in the area near the cooling medium inlet.

[0184] The cross-sectional variations in the cooling pipe 4 can also be configured in a particularly concise manner using the additive manufacturing process discussed, thereby affecting heat transfer.

[0185] The cast insert 1 shown here is cylindrical. It can also be produced in any other desired shape. The cast insert 1 has a diameter D and a wall thickness t of the cast insert wall 2. The cast insert 1 has a thin-walled construction. In this example, the wall thickness t is approximately 1 / 12 of the diameter D, or approximately 8%.

[0186] The wall thickness t can be defined as the normal distance between the point on the cast insert wall 2 facing the cavity 3 and the point on the outer surface A of the cast insert 2.

[0187] According to the present invention, the wall thickness t is set to be at least partially less than 25% of the diameter D of the cast insert 1.

[0188] The wall thickness t of the cast insert 1 of the present invention is preferably less than 25% of the diameter D on average. More preferably, the wall thickness t is less than 20% of the diameter D on average, and even more preferably less than 10% of the diameter D. To evaluate the wall thickness t, the corresponding portion of the cast insert wall 2 is considered to protrude into the mold during use. Parts mainly used for fastening purposes, such as shoulders or flanges 8, are not included in the calculation.

[0189] The thin-walled characteristic means that casting insert wall material, i.e., refractory metal alloy, can be saved. Besides economic considerations, in the case of the variation with filler 6, this is also advantageous for accommodating more filler material and arranging it particularly close to the outer surface A of the casting insert 1 exposed to the melt. The thin-walled characteristic is also advantageous when the casting insert 1 exhibits low thermal mass, either wholly or partially. For example, in the case of short cycle times, it may be desirable for the casting insert 1 to have minimal thermal inertia.

[0190] This can be advantageously achieved by constructing the cast insert 1 as thin-walled and / or at least partially hollow. The phrase "at least partially hollow" means that the cast insert 1 does not contain material filler at least partially. This can be advantageously achieved in a defined manner by an additive manufacturing process.

[0191] When deviating from the basic cylindrical shape, equivalent characteristic variables such as wall thickness t and diameter D can be defined to classify thin-walled properties.

[0192] To define the characteristic wall thickness t, the average wall thickness of the cast insert wall 2 in the area actually exposed to the melt when the cast insert 1 is used is used.

[0193] The characteristic diameter D can be defined by the diameter of the smallest enclosed cylinder surrounding the portion of the cast insert 1 that is actually exposed to the melt when the cast insert 1 is in use. The ratio of wall thickness t to diameter D can therefore also be determined for any deviation of the cylindrical shape of the cast insert 1.

[0194] It should be reiterated that the thin-walled characteristic does not mean that the cast insert 1 must be hollow. It can contain the entire filler 6. Rather, the thin-walled characteristic means that the cast insert wall 2, formed of a refractory metal alloy, is only the same thickness required for sealing and resistance to the melt.

[0195] Figure 2 A cross-section of a cast insert 1 according to another exemplary embodiment is shown. Reference numerals are as follows. Figure 1 The allocation is in the middle, so it will not be explained further.

[0196] The difference in the exemplary embodiment shown here is that the cooling conduit 4 extends partially within the cast insert wall 2.

[0197] Therefore, the cooling conduit 4 can be guided in a particularly near-net-shape manner. This method, also known as "conformal cooling," promotes uniform heat dissipation through the cast insert 1.

[0198] Figure 3 A cross-section of a cast insert 1 according to another exemplary embodiment is shown. Here, with Figure 2 In contrast, the example in the middle does not have a support structure 5 configured, but instead the cooling pipe 4 is partially constructed within the cast insert wall 2 and extends partially within the cavity 3.

[0199] The cooling conduit 4 is integrally constructed with the cast insert wall 2. Optional filler 6 is also shown in this example.

[0200] Figure 4 A cross-section of the cast insert 1 according to another exemplary embodiment is shown. Here, the cooling conduit 4 extends within the cavity 3 without the support structure 5. The cooling conduit 4 may also be manufactured separately from the cast insert wall 2.

[0201] It is conceivable, for example, that the cooling conduit 4 is configured as a pipe and connected to the cast insert wall 2 by a suitable device and / or filler 6. The cooling conduit 4 is thus not integrally constructed with the cast insert wall 2.

[0202] However, as further explained above, it is preferable to produce the cast insert wall 2 having at least one cooling pipe 4 integrally by an additive manufacturing process.

[0203] Figure 5a A photograph of the cast insert 1 in the form of a sample component is shown. The view is directed towards the inlet and outlet openings of the cooling conduit 4. Inside the cast insert 1, a lattice-like support structure 5 constructed within the cavity 3 can be seen; these support structures house the cooling conduit 4. The cast insert 1 is produced by filament printing using raw material filaments formed from a tungsten heavy metal alloy. The cast insert wall 2, the support structure 5, and the cooling conduit 4 are correspondingly integrally constructed.

[0204] Figure 5b It shows Figure 5a A photograph of the cast insert 1, in which most of the cavity 3 contains a filler 6 of a different material than the cast insert wall 2. Here, the filler 6 is made of copper, which has been introduced into the cast insert 1 via back casting. This variation has particularly advantageous characteristics in terms of achievable heat dissipation. Furthermore, the filler 6 also forms the cooling conduits 4 and provides mechanical support for the thin-walled cast insert wall 2.

[0205] Figures 6a to 6c The perspective structure of the cast insert 1 is shown in various views, each with a semi-transparent visualization. The cooling conduit 4 extends in a spiral manner, wherein the distance between the cooling conduit 4 and the outer surface a of the cast insert 1 decreases with increasing distance from the cooling medium inlet region (in... Figure 6a In this context, the area corresponds to the lower edge of the image. In other words, the cooling conduit 4 extends within a portion of the casting insert 1, which protrudes further into the mold 9 (not shown here) during use of the casting insert 1, closer to the outer surface A than in the inlet region of the cooling medium.

[0206] Figure 6b The cast insert 1 is shown from another viewing direction. The support structure 5, constructed in the form of ribs, can be seen. Section P is also shown, with a plane normal to which extends perpendicularly to the longitudinal axis L of the cast insert 1, and section P encompassing the longitudinal axis L.

[0207] Figure 6c The casting insert 1 is shown, with its viewing direction at its end face, which protrudes into the mold (not shown here) during use. The thin-walled structure of the casting insert wall 2 can be seen in the figure.

[0208] Figures 7a to 7c It shows the way Figures 6a to 6c The schematic longitudinal cross-section of the cast insert 1 shown is generated by rotating section P about the longitudinal axis L.

[0209] exist Figure 7a In the middle, section P is located through the support structure 5.

[0210] exist Figure 7b In the middle, the cross section extends between the supporting structures 5, thus revealing the cavity 3 formed by the cast insert wall 2.

[0211] Figure 7c The outline of cooling pipe 4 is schematically shown (no cross-sectional view).

[0212] Figures 8a-8c , Figures 9a-9c and Figures 10a-10c Scanning electron microscope images of various surfaces of tungsten heavy metal samples are shown. Each series was taken at the same magnification.

[0213] In the first column ( Figure 8a , Figure 9a , Figure 10a In the image, the polished surfaces of tungsten heavy metal are magnified and displayed. These surfaces can be observed, for example, in cast inserts produced in conventional manufacturing.

[0214] In the second column ( Figure 8b , Figure 9b , Figure 10b In the image, the surface of a tungsten heavy metal produced by selective laser sintering (SLS) of the raw material particles is magnified and displayed. The surface is in a sintered state. Slight undulations on the surface can be seen, originating from the texture of the raw material particles.

[0215] In the third column ( Figure 8c , 9c In 10c), the surface of tungsten heavy metal was displayed with increased magnification by filament printing using raw material filaments.

[0216] The surface is in a sintered state. Slight wavy features can be seen on the surface, which originate from the fine filaments of the raw material placed there.

[0217] therefore, Figure 8b , Figure 9b , Figure 10b and Figure 8c , Figure 9c , Figure 10c The surface that can be observed on the unfinished cast insert 1 produced according to the present invention is shown.

[0218] Those skilled in the art can obtain instructions on the production method based on the surface characteristics of the sintered surface.

[0219] In particular, conclusions regarding the production process are possible regarding those portions of the cast insert 1 according to the invention that have not undergone any subsequent surface treatment.

[0220] Figure 11a A cross-section of the polished surface of a matrix formed from tungsten heavy metal is shown. Cut tungsten particles within the metal binder phase matrix are visible. For example, the cut particles are indicated by block arrows.

[0221] Figure 11b A cross-section of the unprocessed sintered surface of a matrix formed from tungsten heavy metal is shown. Flattened tungsten particles aggregated within the metal binder phase matrix can be seen.

[0222] like Figure 11b As shown, without further processing, a surface without cut particles can be observed on the cast insert 1 produced according to the present invention.

[0223] Figure 12 The sequence of methods for producing casting insert 1 by means of filament printing variation using raw material filaments is schematically shown.

[0224] Here, in the first step (I), the metal powder P of the liquid-phase sinterable refractory metal alloy is treated with binder Bi and other organic components to obtain a plastic-treated raw material F, which is further treated to obtain raw material filaments FF.

[0225] Raw material filaments are fine threads, usually produced by extrusion, formed from raw material substances, and are typically flexible, for example, they can be wound on a spool.

[0226] In the next step (II), the raw material filaments are extruded through a heated nozzle onto a movable worktable. The (filament) printing process is carried out layer by layer according to the previously generated layer model to form the green body G to be produced, and in a manner that allows the applied raw material trajectories to merge with each other.

[0227] Based on the expected shrinkage coefficient during sintering and any necessary finishing measures, the green blanks of the following casting insert 1 in the X, Y, and Z directions are too large.

[0228] Obtain the green blank G of the following casting insert 1.

[0229] In the debinding step (III), most of the organic adhesive is removed. Chemical debinding is shown here. Alternatively, thermal or catalytic debinding can also be performed.

[0230] Then, in step (IV), the resulting brown blank B is sintered in the presence of at least a temporary liquid phase.

[0231] In step (V), a metal blank R for casting insert 1 is obtained.

[0232] Fine finishing can be performed at will.

Claims

1. A cast insert (1) comprising: - a cast insert wall (2) essentially formed of a liquid phase sinterable refractory metal alloy, - a cavity (3) formed by the cast insert wall (2), - at least one cooling duct (4) distinct from the cavity (3) and at least partially configured within the cavity (3), wherein the cast insert wall (2) has a wall thickness (t) defined by the normal distance between a point of the cast insert wall (2) facing the cavity (3) and a point on the outer surface (A) of the cast insert wall (2), and the wall thickness (t) is at least partially less than 25% of the diameter (D) of the cast insert (1).

2. The cast insert (1) according to claim 1, wherein configured with a support structure (5) connecting the cast insert wall (2) and the at least one cooling duct (4).

3. The cast insert (1) according to claim 2, wherein The support structure (5) is configured in the form of separate beams and / or ribs.

4. The casting insert (1) according to claim 2 or 3, wherein The support structure (5) is formed of the same material as the cast insert wall (2).

5. The casting insert (1) according to claim 1 or 2, wherein The at least one cooling duct (4) is formed of the same material as the cast insert wall (2).

6. The casting insert (1) according to claim 1 or 2, wherein The at least one cooling duct (4) has at least partially a helical profile.

7. The cast insert (1) according to claim 1 or 2, wherein The at least one cooling duct (4) exhibits at least partially a cross section variation.

8. The cast insert (1) according to claim 1 or 2, wherein The cavity (3) between the cast insert wall (2) and the at least one cooling duct (4) contains at least partially a filler (6) formed of a filler material distinct from the material of the cast insert wall (2).

9. The cast insert (1) according to claim 8, wherein The filler material is selected from the group comprising copper and copper alloys.

10. The cast insert (1) according to claim 1 or 2, wherein At least one portion of the cast insert wall (2) is produced by an additive manufacturing process.

11. The cast insert (1) according to claim 1 or 2, wherein The cast insert wall (2) and the at least one cooling duct (4) are produced integrally by an additive manufacturing process.

12. A method of producing a cast insert (1) according to any one of claims 1 to 11, the method comprising the steps of: - providing a powder (P) of a liquid phase sinterable refractory metal alloy and at least one organic binder component, - producing a green body (G) by additive building at least one portion of a cast insert wall (2) from the powder (P) treated with at least one organic binder component, - debinding the green body (G) produced in this way to obtain a brown body (B), - sintering the brown body (B) in the presence of a liquid phase at least temporarily to obtain a metal blank (R) of a cast insert (1).

13. The method of claim 12, wherein, comprising the further step of finishing the blank (R) to obtain the cast insert (1).

14. The method of claim 12, wherein, At least one portion of a cooling duct (4) is also produced by additive building simultaneously to the production of at least one portion of a cast insert wall (2).

15. The method of claim 12, 13, or 14, wherein, A support structure (5) at least partially connecting the cast insert wall (2) and the cooling duct (4) is produced by additive building simultaneously.

16. The method according to claim 12, 13 or 14, comprising at least partially filling the cavity (3) with a filler material distinct from the material of the cast insert wall (2).

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