Core or foundry sand coated and/or mixed with water glass with a water content in the range of ≧ approximately 0.25% by weight to approximately 0.9% by weight

1. Core or foundry sand that can be used for producing cores and casting molds for casting of molten metals, comprising a basic molding material, a layer of an adhesive agent coating the basic molding material, and a layer of water glass lying over the adhesive agent layer, the core or foundry sand having a water content in the range of ≦ approximately 0.25% by weight to approximately 0.9% by weight in relation to the overall weight of the core or foundry sand.

2. The core or foundry sand according to claim 1 , wherein the water glass comprises at least one additive selected from the group consisting of flow improver, improvement agent for the casting surface, drying agent and separating agent.

3. The core or foundry sand according to claim 1 , wherein the basic molding material is selected from the group consisting of mineral and synthetic sands.

4. The core or foundry sand according to claim 1 , wherein the basic molding material has an average grain size of approximately 0.08 mm to approximately 0.5 mm.

5. The core or foundry sand according to claim 1 , wherein the basic molding material is selected from the group consisting of quartz sand, chrome ore sand, zircon sand, almost spherical sands and olivine sand.

6. The core or foundry sand according to claim 1 , wherein the adhesive agent is selected from hygroscopic bases and/or tensides.

7. The core or foundry sand according to claim 1 , wherein the adhesive agent comprises sodium hydroxide.

8. A method for producing a core or foundry sand according to claim 1 , comprising the steps of:

a) providing a basic molding material,

b) adding an adhesive agent and then adding water glass, and

c) drying the core or foundry sand so that the water content comes within the range of ≦ approximately 0.25% by weight to approximately 0.9% by weight in relation to the overall weight of the core or foundry sand.

9. The method according to claim 8 , further comprising homogenizing a mixture obtained after each of said adding steps.

10. The method according to claim 8 , wherein said step c) comprises introducing friction energy when mixing or heating.

11. The method according to claim 8 , wherein said step c) is implemented in a temperature range of ambient temperature up to 160° C. and for a period of time dependent upon mass of from 5 mins to 3 hrs.

12. The method according to claim 8 , wherein the core or foundry sand is filtered according to said step c).

13. The method according to claim 8 , wherein said step c) comprises applying a vacuum or negative pressure.

14. A method for producing a mold part of a casting mold for casting of molten metals, comprising:

a) providing a core or foundry sand according to claim 1 ,

b) pouring the core or foundry sand into a cavity for producing the mold part,

c) bringing the core or foundry sand into contact with at least one hardening agent before, during and/or after the pouring in said step b) and solidifying the mold part.

15. The method according to claim 14 , wherein said step c) comprises bringing the core or foundry sand into contact with water vapor.

16. The method according to claim 14 , wherein said step b) and said step c) are implemented simultaneously.

17. The method according to claim 14 , during at least one of said steps b) and c), further comprising heating the cavity for producing the mold part to a temperature in a range of from approximately 20° C. to approximately 160° C.

18. The method according to claim 17 , further comprising heating the cavity for producing the mold part during both of said steps b) and c).

19. The method according to claim 14 , further comprising heating, during at least one of said steps b) and c), the cavity for producing the mold part to a temperature in a range of 60 to 120° C.