Method for producing castings, molding sand and its use for carrying out said method

Abstract

The invention provides a method with which high-quality complex-shaped castings can be manufactured and with which, after the end of the casting process, the casting mould parts can be easily removed out of or from the casting without any risk. To achieve this the following steps are carried out: Manufacture of a mould material by mixing of a basic mould material, inert in comparison with the molten metal and pourable, which under heating expands less than quartz sand, and a binding agent, which under heating expands differently in comparison with the basic mould material, the manufacture of a casting mould part from the mould material, assembly of a casting mould making use of the casting mould part, pouring of the molten metal into the casting mould to form a casting, cooling of the casting over a solidification and cooling period, in which the casting mould part disintegrates self-actingly into fragments, removal of the fragments of the casting mould part from or out of the casting, and reprocessing of the fragments of the mould material to form a pourable basic mould material.

1 - 17  (canceled).  
     
     
         18 . A method for the manufacture of castings from a molten metal, in particular a molten light metal, comprising the following steps: 
 Manufacture of a casting mould part from the mould material, which is mixed from a pourable basic mould material which is inert in relation to the molten metal, exhibiting a proportion of synthetic mullite, which consists of particles of which the shape is essentially spherical, and an inorganic binding agent, wherein the thermal expansion behaviour of basic mould material and binding agent are adjusted to one another in such a way that the coefficient of thermal expansion of the molten metal lies above the coefficient of thermal expansion of the casting mould part manufactured from the mould material,    Assembling a casting mould making use of the casting mould part,    Pouring of the molten metal into the casting mould to form a casting,    Cooling of the casting over a solidification and cooling period, in which the casting mould part self-actingly disintegrates into fragments,    Removal of the fragments of the casting mould part from or out of the casting,    Reprocessing of the fragments of the mould material to form a pourable basic mould material.    
     
     
         19 . The method according to  claim 18 , wherein the manufacture of the casting mould part comprises the shooting of the mould material into a hollow mould formed in a core box, the preliminary hardening of the mould material shot into the core box to form the casting mould part by the application of heat, and the hardening of the casting mould part in a heating device arranged outside the core box.  
     
     
         20 . The method according to  claim 19 , wherein the heating device comprises a microwave heating.  
     
     
         21 . The method according to  claim 19 , wherein the casting mould part is sprayed with binding agent before the hardening.  
     
     
         22 . The method according to  claim 18 , wherein the reprocessing of the fragments of the mould material comprises the breaking of the fragments, the metal separation, the individualisation of grains, and/or dust extraction.  
     
     
         23 . A mould material for the manufacture of casting mould parts for the casting of molten metal, in particular of molten light metal, consisting of a mixture of a pourable basic mould material, inert in relation to the molten metal exhibiting a proportion of synthetic mullite, which consists of particles of which the shape is essentially spherical, and an inorganic binding agent mixed with the basic mould material, wherein the thermal expansion behaviour of the basic mould material and binding agent are adjusted to one another in such a way that the coefficient of thermal expansion of the molten metal in each case lies above the coefficient of thermal expansion of the casting mould part manufactured from the mould material.  
     
     
         24 . The mould material according to  claim 23 , wherein the binding agent expands differently when heated in comparison with the basic mould material.  
     
     
         25 . The mould material according to  claim 23 , wherein the binding agent is stable under the effect of the casting heat.  
     
     
         26 . The mould material according to  claim 23 , wherein the binding agent is a water glass binding agent.  
     
     
         27 . The mould material according to  claim 23 , wherein the basic mould material consists entirely of mullite.  
     
     
         28 . The mould material according to  claim 23 , wherein the molten metal is an aluminium melt.  
     
     
         29 . The mould material according to  claim 24 , wherein its thermal conductivity is lower than that of the metal which is to be cast.  
     
     
         30 . The method according to  claim 18  performed with a basic mould material formed in accordance with  claim 24 .  
     
     
         31 . The method according to  claim 30 , wherein the casting mould part is manufactured from the mould material is a casting core.  
     
     
         32 . The method according to  claim 31 , wherein the length (A,C) of the casting mould part is many times larger than its diameter (B,D).