Casting sand cores and expansion control methods therefor

Abstract

Thermal expansion of sand cores and the formation of vein defects during metal casting operations can be substantially eliminated, with substantially reduced costs, by using an anti-veining material comprising less than about 4% by weight of a lithia-containing material, and at least about 1% by weight of ferric oxide (Fe 2 O 3 ), said anti-veining material preferably comprising about 1% to about 3.5% by weight of a lithia-containing material and about 1% by weight of ferric oxide.

What is claimed is:  
     
         1 . A sand core for metal casting, comprising less than about 4% by weight of a lithia-containing material, at least about 1% by weight of ferric oxide, and the balance of core sand and a core sand binder, all formed into a sand core.  
     
     
         2 . The sand core of  claim 1  wherein the amount of ferric oxide comprises about 1% by weight.  
     
     
         3 . The sand core of  claim 2  comprising equal amounts by weight of the lithia-containing material and ferric oxide, and wherein the core sand comprises lake sand.  
     
     
         4 . The sand core of  claim 2  comprising about 2.5% by weight of the lithia-containing material and wherein the core sand comprises a silica sand.  
     
     
         5 . A mixture for forming a sand core, comprising about 1.5% to about 3.5% by weight of a lithia-containing material, at least about 1% by weight of ferric oxide, and the balance of core sand and a core sand binder.  
     
     
         6 . The mixture of  claim 5  wherein the amount of ferric oxide comprises about 1% by weight.  
     
     
         7 . The mixture of  claim 5  wherein the lithia-containing material comprises about 1% to about 2.5% by weight.  
     
     
         8 . The mixture of  claim 7  wherein the lithia-containing material comprises about 2.5% by weight, and wherein the core sand comprises a silica sand.  
     
     
         9 . The mixture of  claim 6  wherein the lithia-containing material comprises about 1% by weight and wherein the core sand comprises lake sand.  
     
     
         10 . A method of making a sand core for casting, comprising uniformly mixing together a core sand, an effective amount of binder, about 1% to about 3.5% by weight of a lithia-containing material, and about 1% by weight of ferric oxide as a core-forming material, and forming the core-forming material into a sand core.  
     
     
         11 . The method of  claim 10  wherein the core-forming material contains about 1% by weight of a lithia-containing material.  
     
     
         12 . The method of  claim 10  wherein the lithia-containing material is the VEINSEAL® 14000 product of Industrial Gypsum, Inc.  
     
     
         13 . A method of making a sand core for casting, comprising uniformly mixing together a core sand, an effective amount of core sand binder, an anti-veining material comprising less than about 4% by weight of a lithia-containing material and at least about 1% by weight of ferric oxide as a core-forming mixture and thereafter forming the core-forming mixture into a sand core.  
     
     
         14 . The method of  claim 13  wherein an anti-veining material comprises about 1% to about 3.5% by weight of the lithia-containing material and at least about 1% by weight of ferric oxide.  
     
     
         15 . The method of  claim 14  wherein the lithia-containing materials is selected from a group consisting of. .-spodumene, amblygonite, montebrasite, petalite, lepidolite, zinnwaldite, eucryptite and lithium carbonate.