INORGANIC WATER-SOLUBLE BINDER SYSTEM

1 . A composition for making a core for use in a molding or metal casting process, the composition comprising:

a particulate refractory material; and

a binder composition comprising:

1 to 15 wt % of at least one alkali metal silicate:

0.125 to 10 wt % of potassium carbonate; and

0.5 to 10 wt % of at least one pozzolanic additive

wherein the binder composition ranges are relative to the weight of the particulate refractory material.

2 . The composition according to claim 1 , wherein the binder comprises 1.625 to 35 wt % relative to the weight of the particulate refractory material.

3 . The composition according to claim 1 , wherein the binder composition is an inorganic binder composition.

4 . The composition according to claim 1 , wherein the at least one alkali metal silicate comprises sodium silicate and potassium silicate.

5 . The composition according to claim 1 , wherein the at least one alkali metal silicate is in aqueous solution and has a solids content of between 30 and 50 wt %.

6 . The composition according to claim 1 , wherein the at least one pozzolanic additive has a D50 particle diameter of no more than 20 μm.

7 . The composition according to claim 1 , wherein the at least one pozzolanic additive comprises silica fume.

8 . The composition according to claim 1 , wherein the potassium carbonate comprises 1 to 6 wt %, relative to the weight of the particulate refractory material.

9 . The composition according to claim 1 , further comprising a surfactant, and optionally, wherein the surfactant is sodium ethyl hexyl sulphate.

10 . (canceled)

11 . A core for use in a molding or metal casting process comprising the composition according to claim 1 .

12 . The core of claim 11 , wherein the core is coated with a surface coating, and optionally, wherein the surface coating comprises boron nitride, silicate, titania, alumina, zirconia, alumina, aluminum silicates, or mixtures thereof.

13 . A mold comprising the core of claim 11 , wherein the mold is for producing an article by metal casting and the core is for defining an internal cavity of the article.

14 . A method for producing an article by high pressure die casting or semi-solid casting, the method comprising the steps of:

(i) mixing a composition according to claim 1 to form a mixture;

(ii) molding and hardening the mixture to produce a core in the shape of an internal cavity of the article;

(iii) assembling the core with a mold for high pressure die casting or semi-solid casting, such that the mold and the core together define a casting cavity;

(iv) injecting molten or semi-solid metal into the casting cavity until the cavity is filled;

(v) cooling and solidifying the molten or semi-molten metal to form the article, the core being contained within the internal cavity of the article;

(vi) removing the article containing the core from the mold; and

(vii) removing the core from the internal cavity by flushing out with water.

15 . The use of a composition according to claim 1 in a molding process or a metal casting process.