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 2.5% LiO, 10-25% of TiO 2 , 15-25% Al 2 O 3 , 10-25% of Fe 3 O 4 , and 60-70% of SiO 2 mixed with about 1% by weight of Fe 2 O 3 , preferably red iron oxide.

1 . A sand core for metal casting, comprising less than 4% by weight of a lithia-containing material, about 1% or more by weight of Fe 2 O 3 , 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 Fe 2 O 3  comprises about 1% by weight of red iron oxide.  
     
     
         3 . The sand core of  claim 1  comprising equal amounts by weight of the lithia-containing material and Fe 2 O 3 , 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 1.0% to about 3.5% by weight of a lithia-containing material, about 1% by weight of Fe 2 O 3 , and the balance of core sand and a core sand binder.  
     
     
         6 . The mixture of  claim 5  wherein the amount of Fe 2 O 3  comprises about 1% by weight of red iron oxide.  
     
     
         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 . The mixture of  claim 5  comprising about 2% by weight of lithia-containing material and about 1.5% by weight of Black Rouge iron oxide (Fe 2 O 3 ).  
     
     
         11 . 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 Fe 2 O 3  as a core-forming material, and forming the core-forming material into a sand core.  
     
     
         12 . The method of  claim 11  wherein the core-forming material contains about 1% by weight of said lithia-containing material.  
     
     
         13 . (canceled)  
     
     
         14 . The method of  claim 11  wherein said lithia-containing material comprises 2% by weight and the Fe 2 O 3  comprises Black Rouge iron oxide.  
     
     
         15 . 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 4% by weight of a lithia-containing material and about 1% or more by weight of Fe 2 O 3  as a core-forming mixture and thereafter forming the core-forming mixture into a sand core.  
     
     
         16 . The method of  claim 15  wherein an anti-veining material comprises about 1% to about 3.5% by weight of the lithia-containing material and about 1% or more by weight of Fe 2 O 3 .  
     
     
         17 . The method of  claim 16  wherein the lithia-containing material is selected from a group consisting of .α.-spodumene, amblygonite, montebrasite, petalite, lepidolite, zinnwaldite, eucryptite and lithium carbonate.  
     
     
         18 . (canceled)  
     
     
         19 . The method of  claim 15  wherein the Fe 2 O 3  comprises red iron oxide.  
     
     
         20 . (canceled)  
     
     
         21 . A sand core for metal casting, comprising less than about 4% by weight of a lithia-containing material, an effective amount of Fe 2 O 3 , and the balance of core sand and a core sand binder, all formed into a sand core.  
     
     
         22 . The sand core of  claim 21 , wherein said effective amount of Fe 2 O 3  comprises from about 1% to about 3.5% by weight of Fe 2 O 3 .  
     
     
         23 . The sand core of  claim 21  wherein the amount of Fe 2 O 3  comprises about 1% of red iron oxide.  
     
     
         24 . The sand core of  claim 21  comprising equal amounts of the lithia-containing material and Fe 2 O 3 .  
     
     
         25 . The sand core of  claim 21  wherein said core sand comprises a silica sand and said lithia-containing material comprises about 2.5% by weight of the lithia-containing material.  
     
     
         26 . The sand core of  claim 21  wherein said lithia-containing material is selected from a group consisting of α.-spodumene, amblygonite, montebrasite, petalite, lepidolite, zinnwaldite, eucryptite and lithium carbonate.