CASTING CORE FOR CASTING MOULDS AND METHOD FOR THE PRODUCTION OF SAME

Abstract

The invention relates to a casting core for casting moulds, wherein the casting core comprises a central core and a core shroud arranged around the central core. The core shroud contains or consists of ceramic particles bound to a binder. The central core contains or consists of ceramic particles bound to a binder, wherein the ceramic particles of the central core contain or consist of at least one component, which exhibits, at a temperature in a range from 100° C. to 1500° C., a thermally induced phase transformation, and/or at least two components, the thermal expansion coefficients of which at 20° C. differ by at least 5.Math.10−6 K−1. The invention further relates to a method for producing the casting core according to the invention and the use of the casting core according to the invention.

Claims

1. A casting core for casting molds, comprising: an inner core; and an outer core located around the inner core; wherein the outer core includes multiple ceramic particles bound using a binder, wherein the inner core includes multiple ceramic particles bound using a binder, and wherein the ceramic particles of the inner core comprise at least one of: at least one component that has a thermally induced phase change at a temperature in a range of 100° C. to 1500° C., inclusive; or at least two components having coefficients of thermal expansion that, at 20° C., differ from one another by at least 5.Math.10.sup.−6K.sup.−1.

2. The casting core according to claim 1, wherein the multiple ceramic particles of the outer core are at least one of: of zircon sand particles, aluminosilicate particles, mullite particles, inorganic hollow microspheres, alumina particles, or mixtures thereof.

3. The casting core according to claim 1, wherein at least one of: the multiple ceramic particles of the outer core or the multiple ceramic particles of the inner core have a mean particle diameter of 0.5 μm to 500 μm, inclusive.

4. The casting core according to claim 1, wherein at least one of: the binder of the outer core or the binder of the inner core include at least one of: an inorganic binder, an organic binder, or a mixture thereof.

5. The casting core according to claim 1, wherein the at least one component that has a thermally induced phase change at a temperature in a range of 100° C. to 1500° C., inclusive, and is at least one of: quartz, cristobalite, or a mixture thereof.

6. The casting core according to claim 1, wherein the at least two components having coefficients of thermal expansion that, at 20° C., differ from one another by at least 5.Math.10.sup.−6K.sup.−1 comprise: at least one first component having a coefficient of thermal expansion in a range of 0.5.Math.10.sup.−6K.sup.−1 to 13.0.Math.10.sup.−6K.sup.−1, inclusive. at least one second component having a coefficient of thermal expansion in a range of 9.0.Math.10.sup.−6K.sup.−1 to 13.0.Math.10.sup.−6K.sup.−1, inclusive.

7. The casting core according to claim 6, wherein at least one of: the first component is at least one of, of amorphous silica, cordierite, or mixtures thereof, or the second component is at least one of, forsterite, magnesium oxide, or mixtures thereof.

8. The casting core according to claim 1, wherein the outer core and the inner core include multiple pores having a mean pore size of 1 μm to 50 μm, inclusive, and wherein the outer core has a lower porosity than the inner core.

9. The casting core according to claim 1, wherein the outer core has a thickness of 3 mm to 15 mm, inclusive.

10. The casting core according to claim 1, wherein the inner core has a diameter of 5 mm to 100 mm, inclusive.

11. A method for producing a casting core, the method comprising: producing a first aqueous ceramic suspension, the first aqueous ceramic suspension including multiple ceramic particles, a binder, and water; producing a second aqueous ceramic suspension, the second aqueous ceramic suspension including multiple ceramic particles, a binder, and water; solidifying the first aqueous ceramic suspension to form an inner core of the casting core; drying the solidified first aqueous ceramic suspension; solidifying the second aqueous ceramic suspension to form an outer core of the casting core; and drying the second aqueous ceramic suspension; wherein the ceramic particles of the first aqueous ceramic suspension include at least one of: at least one component that has a thermally induced phase change at a temperature in a range of between 100° C. and 1500° C., inclusive; or at least two components having coefficients of thermal expansion that, at 20° C., differ from one another by at least 5.Math.10.sup.−6K.sup.−1.

12. The method according to claim 11, further comprising: a) pouring the first aqueous ceramic suspension into a first casting mold which has a negative contour of the inner core of the casting core to be produced; b) solidifying the first aqueous ceramic suspension present in the first casting mold to form the inner core of the casting mold; c) removing the inner core of the casting core from the first casting mold; d) drying the inner core of the casting core; e) inserting the dried inner core of the casting core into a second casting mold which has the negative contour of the casting mold to be produced; f) pouring the second aqueous ceramic suspension into this second casting mold; g) solidifying the second aqueous ceramic suspension present in the second casting mold to form the outer core of the casting mold; h) removing the casting core comprising the inner core and the outer core is removed from the second casting mold; and i) drying the casting core.

13. The method according to claim 11, further comprising: a) solidifying the second aqueous ceramic suspension to form the outer core of the casting core, the outer core including a cavity for the inner core; b) drying the outer core of the casting core; filling the cavity in the outer core of the casting core with the first aqueous ceramic suspension; d) solidifying the first aqueous ceramic suspension present in the cavity of the outer core to form the inner core of the casting core; and e) drying the inner core.

14. (canceled)

15. The casting core according to claim 4, wherein the inorganic binder is at least one of: a phosphate binder, gypsum, cement, silica sols, sodium silicate, or another silicate binder.

16. The casting core according to claim 4, wherein the organic binder is at least one of: a protein binder, a phenolic resin, a furan resin, or another synthetic resin.

17. The casting core according to claim 9, wherein the outer core has a thickness of between 3 mm and 10 mm, inclusive.

18. The casting core according to claim 9, wherein the outer core has a thickness of between 3 mm and 7 mm, inclusive.

19. The casting core according to claim 10, wherein the inner core has a diameter of between 10 mm and 100 mm, inclusive.

20. The casting core according to claim 10, wherein the inner core has a diameter of between 15 mm and 100 mm, inclusive.

21. The method according to claim 11, wherein the solidifying and drying of the first aqueous ceramic suspension is performed prior to the solidifying and drying of the second aqueous ceramic suspension.

22. The method according to claim 11, wherein the solidifying and drying of the first aqueous ceramic suspension is performed after the solidifying and drying of the second aqueous ceramic suspension.

23. A casting core for casting mold, comprising: an outer core; and an inner core; wherein the outer core includes a first set of ceramic particles bound using a first binder, wherein the inner core includes a second set of ceramic particles bound using a second binder, wherein the second set of ceramic particles comprise at least one of: at least one component that has a thermally induced phase change at a temperature of between 100° C. and 1500° C., inclusive, or at least two components having coefficients of thermal expansion that, 20° C., differ from one another by at least 5.Math.10.sup.−6K.sup.−1, wherein the first set of ceramic particles are at least one of: zircon sand particles, aluminosilicate particles, mullite particles, inorganic hollow microspheres, alumina particles, or mixtures thereof, wherein at least one of the first set of ceramic particles or the second set of ceramic particles have a mean particle diameter of between 0.5 μm and 500 μm, inclusive, wherein at least one of the binder of the inner core or the binder of the outer core include at least one of an inorganic binder, an organic binder, or a mixture thereof, wherein the at least one component has a thermally induced phase change at a temperature in a range between 100° C. to 1500° C., inclusive, and wherein the at least one component is at least one of quartz, cristobalite, or a mixture thereof.

24. The casting core of claim 23, wherein the outer core and the inner core include multiple pores having a mean pore size between 1 μm to 50 μm, inclusive, and wherein the outer core has a lower porosity than the inner core.

Description

Exemplary Embodiment 1

[0074] An inorganic bound outer core is produced for use in aluminum casting using conventional/known methods, comprising a cavity for the inner core. The cavity is filled with a filler mixture made of 30 vol % SiO.sub.2 (mean particle size 75 μm), 30 vol % forsterite (mean particle size 90 μm), and 40 vol % cristobalite (sieve fraction 63 μm), and silicate binder, and is then dried up to 200° C.

Exemplary Embodiment 2

[0075] A sodium silicate-bound inner core having the following filler composition is produced: 25 vol % cordierite (mean particle size 250 μm), 25 vol % forsterite (mean particle size 150 μm), 40 vol % quartz powder (mean particle size 150 μm), and 10 vol % cristobalite (sieve fraction 63 μm). The formed inner core is cured (CO2), inserted into a mold having the geometry of the required core, and surrounded with an inorganically bound outer core, solidified, demolded, and dried.