Anti-veining additive for the production of casting molds and cores

Abstract

The present invention belongs to the field of the additives for molding sands used in the manufacture of casting molds and cores. More specifically, the present invention relates to an additive to prevent veining in the manufacture of metal parts, to a molding sand comprising said additive, to a core or mold prepared from said molding sand and to a metal part prepared by means of using one of said cores or molds.

1 . An additive for molding sands comprising hollow alumina silicate microspheres between 90-99% of the total weight of the additive and a flux between 1-10% of the total weight of the additive. 
     
     
         2 . The additive according to  claim 1 , wherein the hollow alumina silicate microspheres have an alumina content of between 15-45% by weight. 
     
     
         3 . The additive according to  claim 1 , wherein the flux is an alkaline or alkaline-earth element carbonate. 
     
     
         4 . The additive according to  claim 3 , wherein the alkaline or alkaline-earth element carbonate is a lithium carbonate or a strontium carbonate. 
     
     
         5 . (canceled) 
     
     
         6 . A molding sand comprising between 90% and 99% by weight of sand and between 1-10% by weight of an additive according to  claim 1 . 
     
     
         7 . The molding sand according to  claim 6 , wherein the sand is a silica sand with a silica content greater than 95% by weight. 
     
     
         8 . (canceled) 
     
     
         9 . A method for preparing a casting mold or core which comprises:
 a) mixing a molding sand according to  claim 6  with a binding resin,   b) introducing the mixture of a) in a mold to form a core or mold,   c) contacting said core or mold with a curing catalyst, and   d) separating the core or mold once it has hardened.   
     
     
         10 . Casting core or mold comprising a sand according to  claim 1 . 
     
     
         11 . A method for preparing metal castings which comprises:
 a) inserting a core or mold according to  claim 10  in a casting device,   b) pouring the metal in liquid state in said device,   c) allowing the metal poured in the casting device to cool and solidify, and   d) separating the metal part from the casting device.   
     
     
         12 . The method according to  claim 11  wherein the metal part is made of ferric or non-ferric metals. 
     
     
         13 . The method according to  claim 12 , wherein the ferric metal is grey, nodular cast iron or steel. 
     
     
         14 . The method according to  claim 12 , wherein the non-ferric metal is copper, bronze, tin. 
     
     
         15 . A metal part obtained by the method of  claim 11 .