阅读说明：本技术 用于铸模的铸芯及其生产方法 (Casting core for casting mould and production method thereof ) 是由 F-J·沃斯特曼 L·施图姆 C·索尔特曼 M·布塞 于 2019-09-19 设计创作，主要内容包括：本发明涉及一种用于铸模的铸芯,该铸芯包括芯心和围绕该芯心设置的芯套。芯套包含或由通过粘结剂粘合的陶瓷颗粒组成。芯心包含通过粘结剂粘合的陶瓷颗粒以及一个或多个占位符元素。占位符元素至少部分地可热分解。本发明还涉及一种用于生产根据本发明的铸芯的方法以及根据本发明的铸芯的用途。(The invention relates to a casting core for a casting mould, comprising a core and a core jacket arranged around the core. The core sleeve comprises or consists of ceramic particles bonded by a binder. The core includes ceramic particles bonded by a binder and one or more placeholder elements. The placeholder elements are at least partially thermally decomposable. The invention also relates to a method for producing a casting core according to the invention and to the use of a casting core according to the invention.)

1. A casting core for a casting mould, the casting core comprising a core and a core jacket arranged around the core, the core jacket comprising or consisting of ceramic particles bonded by a binder, and the core comprising ceramic particles bonded by a binder and additionally one or more placeholder elements, the one or more placeholder elements being at least partially thermally decomposable.

2. The casting core according to claim 1, wherein the ceramic particles of the core jacket and/or the ceramic particles of the core are selected from the group consisting of: quartz sand particles, zircon sand particles, aluminosilicate particles, mullite particles, hollow inorganic spheres, alumina particles, and mixtures thereof.

3. The casting core according to claim 1 or 2, characterized in that the ceramic particles of the core jacket and/or the ceramic particles of the core have an average particle diameter of 0.5 μ ι η to 500 μ ι η.

4. The casting core according to any of claims 1 to 3, wherein the binder of the core jacket and/or the binder of the core is selected from the group consisting of:

inorganic binders, preferably silicate binders, such as silica sol and water glass, phosphate binders, gypsum, cement,

an organic binder, preferably a plastic resin, a protein binder, and

-mixtures thereof.

5. The casting core according to any of claims 1 to 4, characterized in that the one or more placeholder elements are at least partially thermally decomposable from a temperature in the range of 300 ℃ to 1500 ℃, preferably from a temperature in the range of 400 ℃ to 1400 ℃, particularly preferably from a temperature in the range of 500 ℃ to 1300 ℃.

6. The casting core according to any of claims 1 to 5, wherein the one or more placeholder elements are combustible, preferably combustible to be residue-free.

7. The casting core of any of claims 1 to 6, wherein the one or more placeholder elements are selected from the group consisting of: wood foam elements, polymer foam elements, polystyrene spheres, polymer particles, and mixtures thereof.

8. The casting core according to any of claims 1 to 7, characterized in that the core consists of ceramic particles bonded by the binder and the one or more placeholder elements.

9. The casting core according to any of claims 1 to 8, wherein the core sheath and the core have pores with an average pore diameter of 1 μm to 50 μm, the core sheath having a lower porosity than the core.

10. The casting core according to any of claims 1 to 9, characterized in that the thickness of the core jacket is 3 to 15mm, preferably 3 to 10mm, particularly preferably 3 to 7 mm.

11. The casting core according to any of claims 1 to 10, characterized in that the diameter of the core is 5mm to 100mm, preferably 10mm to 100mm, particularly preferably 15mm to 100 mm.

12. A method for producing a casting core according to any one of claims 1 to 11,

a) mixture of a first aqueous ceramic suspension comprising ceramic particles, a binder and water and one or more placeholder elements

Is produced and then poured into a first mould having the negative profile of the core to be produced, or

-is produced in a first mould having a negative profile of the core to be produced,

the one or more placeholder elements are at least partially thermally decomposable,

b) the mixture in the first casting mold is solidified to form a core of the casting core,

c) the core of the core is removed from the first mould and subsequently dried,

d) inserting the core of said core after drying into a second mould having the negative profile of the core to be produced, subsequently pouring a second aqueous ceramic suspension comprising ceramic particles, a binder and water into this second mould,

e) the second ceramic suspension in the second casting mold is solidified to form a core jacket of the casting core,

f) the casting core including the core and the core sleeve is removed from the second casting mold and then dried.

13. Method according to claim 12, characterized in that in step a) a mixture of a first aqueous ceramic suspension comprising ceramic particles, a binder and water and a plurality of placeholder elements, preferably polystyrene spheres, is produced and subsequently poured into a first casting mould having the negative profile of the core to be produced.

14. Method according to claim 12, characterized in that in step a) a mixture of a first aqueous ceramic suspension comprising ceramic particles, a binder and water and a placeholder element, preferably a wood or polymer foam element, is produced in a first casting mould having the negative contour of the core of the casting core to be produced, the placeholder element is first cut into the shape of the core and placed in the first casting mould, and subsequently the placeholder element is wetted by and/or poured around the first aqueous ceramic suspension.

15. Use of a casting core according to any of claims 1 to 11 in a method for casting one or more components.

Technical Field

The invention relates to a casting core for a casting mould, comprising a core and a core jacket arranged around the core. The core sleeve comprises or consists of ceramic particles bonded by a binder. The core includes ceramic particles bonded by a binder, and additionally one or more placeholder elements. The placeholder elements are at least partially thermally decomposable. The invention relates, in addition to a method for producing a casting core according to the invention, to the use of a casting core according to the invention.

Background

When casting a part in a mould, a casting core (or core) is used, so that any cavity to be provided in a subsequent part remains free of casting material when the mould is filled. For this purpose, the core must have the necessary strength and must remain dimensionally stable during the casting process. It is necessary to prevent the melt from being injected into the core under high pressure during the casting process. In order to obtain a good casting surface, additional requirements are placed on the core material. Here, minimal wetting between the melt and the core, and a smooth, chemically suitable surface are advantageous. In particular, in the case of cores for the production of complex internal molds, good decomposability is required to ensure that the core material is removed from the part after casting.

For the production of the casting core, the refractory filler (e.g. quartz sand, zircon sand, aluminosilicates, but also inorganic hollow spheres) and the organic binder (e.g. synthetic resins, protein binders) or inorganic binder (silicate binders, phosphate binders) are usually brought into the desired shape, the hardening of which can be effected by cold or hot methods, respectively. The shaping may be carried out by pressing, core firing or casting. The surface of the core may be improved by sizing. During the casting process, the thermal decomposition of the organic binder weakens the core structure, enabling the core material to be removed from the casting, however, this is also associated with the emission of environmental toxic gases. In addition, these gases can cause errors in the casting. In the case of thick-walled parts, the result may be that the heat introduced is not sufficient to sufficiently decompose the binder inside the core to make the mold easy to remove. Gas evolution is also problematic for the casting process. The commonly used core sand cannot be reused and must be disposed of as special waste. In the case of inorganic binder systems, in addition to sufficient core strength, good removability from the mold must also be provided. Heat introduction must loosen the structure and sintering must be excluded. Furthermore, as noted above, conventional cores are only suitable for sand casting, chill casting, and low pressure casting. They cannot be used for pressure casting.

Disclosure of Invention

On this basis, the object of the invention is to indicate a casting core which on the one hand remains dimensionally stable during the casting process and on the other hand can be easily removed from the cast component after the casting process.

This object is achieved with respect to the casting core by the features of patent claim 1 and with respect to the method for manufacturing such a casting core by the features of patent claim 12. Patent claim 15 points out the possibility of use of the casting core according to the invention. Accordingly, the dependent patent claims represent advantageous developments.

According to the present invention, a casting core for a casting mold is specified, the casting core comprising a core and a core jacket arranged around the core. The core sleeve comprises or consists of ceramic particles bonded by a binder. The core includes ceramic particles bonded by a binder, and additionally one or more placeholder elements. The one or more placeholder elements are at least partially thermally decomposable.

The casting core according to the invention advantageously comprises a plurality of sections, namely an inner section, a core and an outer section, a core jacket. As a result of this core construction with a core sleeve and a core in contact with the melt, the casting core according to the invention is optimally adapted to the different requirements during and after the casting process. Due to the presence of the thermally decomposable placeholder elements in the core, the core may become unstable due to thermal stresses, as a result of which removal of the core from the casting is simplified. The removal of the casting core is simplified because, due to the introduction of heat during the casting process, for example at a temperature in the range of 300 ℃ to 1500 ℃, the placeholder element or elements is/are thermally decomposed, i.e. for example burnt or greatly volume-contracted, as a result of which the material cohesion of the core is weakened. In other words, where the previous placeholder element or elements were located, a gap or cavity is created, and thus the core becomes porous or unstable. This instability simplifies the removal of the casting core. However, since the thermally decomposable placeholder elements are only disposed in the core, and not in the core sleeve, the core sleeve or the casting core has a dense and mechanically strong surface adapted to be in contact with the melt during the casting process, and thus the casting core remains dimensionally stable during the casting process.

Because of the core structure, which is formed by the core sleeve and the core in contact with the melt, the functionality of the material composition can be adapted to the opposing requirements in the different core regions. Thus, in the core sleeve, filler or ceramic particles having small interactions with the melt may be used. Additionally, in the core sleeve, a lower porosity and a higher mechanical strength may also be provided. The thermal properties can be selected by the filler used in the core sleeve such that, depending on the casting temperature and the heat introduced, a temporary counteracting destabilization of the core is achieved. Due to this decoupling, high process reliability and good casting quality can be achieved. The thermally decomposable placeholder elements reduce the amount of inorganic filler or ceramic particles that must be disposed of if necessary and reduce the weight of the core.

Preferred embodiments of the casting core according to the invention are distinguished by the fact that the ceramic particles of the core jacket and/or the ceramic particles of the core are selected from the group consisting of: quartz sand particles, zircon sand particles, aluminosilicate particles, mullite particles, hollow inorganic spheres, alumina particles, and mixtures thereof.

By selecting the filler or ceramic particles used in the core sleeve, the thermal properties can be influenced such that depending on the casting temperature and the heat introduced, a temporarily counteracted destabilization of the core is achieved. Thus, in this way, the rate of temperature rise in the core and thus the onset of failure of the cohesion of the material in the core can be adjusted via the thermal properties of the core sleeve. Therefore, during filling of the mold, an increase in pressure resistance of the casting core is ensured, and after sufficient heat is introduced into the core, destabilization of the core is generated.

According to a further preferred embodiment of the casting core according to the invention, the ceramic particles of the core jacket and/or the ceramic particles of the core have an average particle diameter of 0.5 μm to 500 μm. The average particle size can be determined, for example, by laser diffraction.

Furthermore, it is preferred that the binder of the core sleeve and/or the binder of the core is selected from the group consisting of:

inorganic binders, preferably silicate binders, such as silica sol and water glass, phosphate binders, gypsum, cement,

an organic binder, preferably a plastic resin, a protein binder, and

-mixtures thereof.

A further preferred embodiment of the casting core according to the invention is characterized in that the placeholder elements are at least partially thermally decomposable from (or at) a temperature in the range of 300 ℃ to 1500 ℃, preferably from (or at) a temperature in the range of 400 ℃ to 1400 ℃, preferably from (or at) a temperature in the range of 500 ℃ to 1300 ℃.

The feature that the placeholder element is at least partially thermally decomposable at a temperature in the range of 300 ℃ to 1500 ℃ should thus be understood as a decomposition or partial decomposition of the placeholder element from any temperature in the range of 300 ℃ to 1500 ℃. For example, one or more placeholder elements may decompose from a temperature of 800 ℃, meaning that the one or more placeholder elements are thermally decomposable at a temperature ≧ 800 ℃. The thermal decomposition may be, for example, combustion, e.g., partial combustion or residue-free combustion, of one or more placeholder elements.

Preferably, the placeholder elements are thermally decomposable or completely thermally decomposable from (or at) a temperature in the range of 300 ℃ to 1500 ℃.

It is also possible that the placeholder elements are thermally decomposable over the entire temperature range of 300 ℃ to 1500 ℃.

Furthermore, it is preferred that the placeholder elements are combustible, preferably combustible to be residue free.

A further preferred embodiment of the casting core according to the invention is distinguished by the fact that the placeholder elements are selected from the group consisting of: wood foam elements, polymer foam elements, polystyrene spheres, polymer particles, and mixtures thereof.

According to a further preferred embodiment, the core consists of ceramic particles bonded by means of a binder and also placeholder elements.

A further preferred embodiment is characterized in that the core sleeve and the core have pores with an average pore diameter of 1 μm to 50 μm, the porosity of the core sleeve being lower than the porosity of the core. The average pore size and/or porosity may be determined, for example, by mercury porosimetry.

Furthermore, it is preferred that the core sleeve has a thickness of 3mm to 15mm, preferably 3mm to 10mm, particularly preferably 3mm to 7 mm. Via the thickness of the core sleeve, the rate of temperature rise in the core and thus the onset of failure of the cohesion of the material in the core can be regulated. Therefore, an increase in pressure resistance of the core during filling of the mold is ensured, and after heat is sufficiently introduced into the core, destabilization of the core is generated.

According to a further preferred embodiment, the core has a diameter of 5mm to 100mm, preferably 10mm to 100mm, particularly preferably 15mm to 100 mm.

Additionally, the present invention relates to a method for producing a casting core according to the present invention, wherein,

a) mixture of a first aqueous ceramic suspension comprising ceramic particles, a binder and water and one or more placeholder elements

Is produced and then poured into a first mould having the negative profile of the core to be produced, or

Is produced in a first mould having the negative profile of the core to be produced,

the placeholder elements are at least partially thermally decomposable (preferably from or at a temperature in the range of 300 ℃ to 1,500 ℃),

b) the mixture in the first mold is solidified to form a core of the core,

c) the core of the core is removed from the first mould and subsequently dried,

d) the core of the core after drying is inserted into a second casting mould having the negative profile of the core to be produced, and a second aqueous ceramic suspension comprising ceramic particles, a binder and water is subsequently poured into this second casting mould,

e) the second ceramic suspension in the second casting mould is solidified to form a core jacket of the casting core,

f) the casting core including the core and the core sleeve is removed from the second mold and then dried.

For example, inorganic binders based on gypsum, cement, phosphate or silica may be used. The water glass-based binder may be supplied with carbon dioxide gas after forming. The water glass reacts with the formation of colloidal silicic acid and sodium carbonate, thus solidifying the suspension, forming the corresponding part of the casting core. In the case of suspensions with water glass or colloidal silica sols as binders, curing can also be achieved by shifting the pH to the neutral range (for example by addition of acid) or by drying. After forming, excess water and binding water must be removed, which can separate at the casting temperatures required for the metal melt, thereby affecting the casting quality. This is done by drying. If the required drying temperature is higher than the temperature resistance of the placeholder elements used, partial thermal decomposition of the placeholder elements already starts during the drying process and the porosity or instability of the core increases.

The drying in steps c) and f) is preferably carried out at a temperature of from 50 ℃ to 300 ℃, particularly preferably from 90 ℃ to 200 ℃, and/or for a duration of from 0.1 to 10 hours, preferably from 0.5 to 5 hours, particularly preferably from 1 to 3 hours. The drying may be performed in a plurality of steps, for example, a low temperature is selected in the first drying step and a high temperature is selected in the second drying step.

In metal casting, the positioning and retention of the core in the mould by the core marking and core mounting is standard and therefore common knowledge to a person skilled in the art. This may also occur in the present invention or in the method according to the present invention. Preferably, between step c) and step d), the dried core is thus provided with core markings (for positioning the core in the second casting mould). The core marking then enables a precise positioning of the core in the second casting mould during the insertion of the dry core of the casting core into the second casting mould, so that the core then has a corresponding desired position in the finished core.

A preferred variant of the method according to the invention is distinguished by producing, in step a), a mixture of a first aqueous ceramic suspension comprising ceramic particles, a binder and water and a plurality of placeholder elements (preferably polystyrene spheres), and subsequently pouring the mixture into a first casting mould having a negative profile of the core to be produced.

A further preferred variant of the method according to the invention is characterized in that in step a) a mixture of a first aqueous ceramic suspension comprising ceramic particles, a binder and water and placeholder elements (preferably of wood or polymer foam elements) is produced in a first casting mould having the negative contour of the core of the casting core to be produced, the placeholder elements are first cut into the shape of the core and placed in the first casting mould, and subsequently the placeholder elements are wetted by and/or poured around the first aqueous ceramic suspension.

Additionally, the invention relates to the use of a casting core according to the invention in a method for casting one or more components.

The invention is intended to be described in more detail with reference to the examples that follow, without limiting the invention to the specific embodiments and parameters shown herein.

Detailed Description

Example 1

Core materials based on phosphate binders were produced as follows: 60% phosphate binder "Wiroveste" (BEGO) and 40% quartz flour were added to the water until a flowable consistency was obtained. Reticulated foam (polyether-based Dryfeel, pore size 15ppi, Eurofoam) was cut into core shapes, placed into molds, and then infiltrated and poured around the core material produced. After curing has begun, the part is removed from the mold. The core was dried (excess water removed at 90 c followed by one hour at 180 c) and placed in a dividable mold that imaged the core geometry. The core material is poured around the core. After curing and removal from the mold, the core was dried at a temperature of 180 ℃ for one hour.

Example 2

50% by volume of polystyrene spheres were stirred into a ceramic mass consisting of 88.5% phosphate binder "Wirovett" (BEGO) and 11.5% demineralized water and poured into a mould for the core. The cured part is removed from the mold, placed into a separable mandrel, and the following ceramic mass is poured around: 40% mullite (Symulox M72K 0, Nabaltec, average particle size between 7 and 15 μ M) and 60% phosphate binder "Wirovest" (BEGO) were stirred in water until a flowable mass was obtained. After curing, the core is removed from the mold and dried at 100 ℃.