Casting core for casting molds and method for the production thereof

Patent metadata

Field	Value
Publication number	US-11794236-B2
Application number	US-201917277712-A
Country	US
Kind code	B2
Filing date	Sep 19, 2019
Priority date	Sep 19, 2018
Publication date	Oct 24, 2023
Grant date	Oct 24, 2023

Abstract

The present invention relates to a casting core for casting molds, wherein the casting core contains or consists of ceramic particles bound with a silica sol. The casting core has a pore structure, in which the average pore size of the pores increases at least in sections from the outside to the inside in the casting core. The present invention also relates to a method for producing the casting core according to the invention and to the use of the casting core according to the invention.

First claim

The invention claimed is:

1. A casting core for casting molds, the casting core comprising ceramic particles bound with a silica sol, wherein the casting core has a pore structure comprising pores, and an average pore size of the pores increases at least in sections from an outside to an inside in the casting core: wherein the casting core comprises a core center, which contains ceramic particles bound with a silica sol, and at least one core shroud which is arranged around the core center and which contains ceramic particles bound with a silica sol, wherein the core center has a pore structure in which the average pore size of the pores increases from the outside to the inside in the casting core, wherein the at least one core shroud has a pore structure in which the average pore size of the pores increases from the outside to the inside in the casting core, and wherein the average pore size of the pores in an outer region of the core center is less than the average pore size of the pores in an inner region of the core shroud.

2. The casting core according to claim 1 , wherein the average pore size of the pores increases from the outside to the inside in the casting core and at least one of (1) the average pore size of the pores in an outer region of the casting core is 3 μm to 20 μm, and (2) the average pore size of the pores in an inner region of the casting core is 100 μm to 1500 μm.

3. The casting core according to claim 1 , wherein the ceramic particles are inorganic ceramic particles selected from a group consisting of mullite particles, zircon sand particles, silica sand particles, aluminosilicate particles, inorganic hollow spheres, aluminum oxide particles, and mixtures thereof.

4. The casting core according to claim 1 , wherein the ceramic particles have an average particle diameter of from 0.5 μm to 300 μm.

5. The casting core according to claim 1 , wherein the silica sol is selected from a group consisting of waterglass, colloidal nanosols and mixtures thereof.

6. The casting core according to claim 1 , wherein the silica sol is present in a form of particles with an average particle diameter of from 8 nm to 40 nm.

7. The casting core according to claim 1 , wherein at least one of (1) the average pore size of the pores in an outer region of the core center and in an outer region of the core shroud is 3 μm to 20 μm, and (2) the average pore size of the pores in an inner region of the core center and in an inner region of the core shroud is 100 μm to 1500 μm.

8. The casting core according to claim 1 , wherein at least one of the following:
a composition of the core center differs from a composition of the core shroud;
the core shroud has a higher packing density than the core center;
a material of the ceramic particles contained in the core center differs from a material of the ceramic particles contained in the core shroud; and
the average particle diameter of the ceramic particles contained in the core center differs from the average particle diameter of the ceramic particles contained in the core shroud.

9. The casting core according to claim 1 , wherein the casting core is at least one of infiltrated and coated with at least one of (1) at least one wash; and (2) at least one reinforcing component.

10. A method for producing the casting core according to claim 1 , the method comprising:
a) producing a plurality of aqueous, ceramic suspensions, each comprising ceramic particles, a silica sol as binder, and water;
b1) pouring a first of the produced aqueous, ceramic suspensions into a first casting mold having a negative contour of a core center of the casting core;
c1) subjecting the first of the produced aqueous, ceramic suspension arranged in the first casting mold to a first cold treatment, and thereby freezing and solidifying the first aqueous, ceramic suspension to form a core center of the casting core;
d1) removing the core center of the casting core in a frozen state from the first casting mold;
b2) inserting the core center of the casting core into a second casting mold having a negative contour of at least one portion of the casting core, and then pouring a second of the produced aqueous, ceramic suspensions into the second casting mold;
c2) subjecting the second of the produced aqueous, ceramic suspension arranged in the second casting mold to a second cold treatment, and thereby freezing and solidifying the second aqueous, ceramic suspension to form at least one portion of a core shroud of the casting core;
d2) removing the at least one portion of the casting core comprising the core center and the at least one portion of the core shroud in the frozen state from the second casting mold and then drying the at least one portion of the casting core comprising the core center and the at least one portion of the core shroud.

11. The method according to claim 10 , wherein after step d2), steps b2), c2) and d2) are repeated at least once.

12. The method according to claim 10 , wherein one of the following:
in step d1) the core center of the casting core is removed in the frozen state from the first casting mold and is then dried, and in step b2) the dried core center of the casting core is inserted into the second casting mold; and
in step d1) the core center of the casting core is removed in the frozen state from the first casting mold, and in step b2) the frozen core center of the casting core is inserted into the second casting mold.

13. The method according to claim 10 , wherein at least one of the following:
a composition of the first aqueous, ceramic suspension differs from a composition of the second aqueous, ceramic suspension;
the second aqueous, ceramic suspension has a higher solids content than the first aqueous, ceramic suspension;
the second aqueous, ceramic suspension has a higher packing density than the first aqueous, ceramic suspension;
a material of the ceramic particles of the first aqueous, ceramic suspension differs from a material of the ceramic particles of the second aqueous, ceramic suspension; and
the average particle diameter of the ceramic particles of the first ceramic suspension differs from the average particle diameter of the ceramic particles of the second ceramic suspension.

14. The method according to claim 10 , wherein at least one of (1) during the first cold treatment, the first aqueous, ceramic suspension is cooled at a rate of 0.1 K/min to 15 K/min to a temperature≤−10 degrees Celsius; and (2) during the second cold treatment, the second aqueous, ceramic suspension is cooled at a rate of 0.1 K/min to 15 K/min to a temperature≤−10 degrees Celsius.

15. The method according to claim 10 , wherein the casting core is at least one of infiltrated and coated with at least one of (1) at least one wash and (2) at least one reinforcing component following step d2).

16. A method for casting one or more components comprising using the casting core according to claim 1 .

Assignees

• Fraunhofer Ges Forschung

Inventors

• Busse Matthias
• Soltmann Christian
• Stumm Lukas
• Wöstmann Franz-Josef

Classifications

• B22C1/186 Primary

  contaming ammonium or metal silicates, silica sols · CPC title

• B22C9/106

  Vented or reinforced cores · CPC title

• B22C9/126

  Hardening by freezing · CPC title

• B22C3/00

  Selection of compositions for coating the surfaces of moulds, cores, or patterns · CPC title

• B22C9/10

  Cores; Manufacture or installation of cores {(breaker cores B22C9/084)} · CPC title