Casting sand cores and expansion control methods therefor
View Patent ↗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% Li 2 O, 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 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 including 2–5% of Li 2 O, 10–25% of TiO 2 , 15–25% of Al 2 O 3 , 10–20% of Fe 3 O 4 , and 60–70% of SiO2, 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.
2. The method of claim 1 wherein the amount of Fe 2 O 3 comprises about 1% by weight of red iron oxide.
3. The method of claim 2 comprising about 2.5% by weight of the lithia-containing material and wherein the core sand comprises a silica sand.
4. The method 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.
5. The method of claim 1 wherein the core-forming material contains about 1% by weight of a lithia-containing material.
6. The method of claim 1 wherein the step of uniformly mixing comprises 2% by weight of said lithia-containing material.
7. 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 comprising 2–5% of Li 2 O, 10–25% of TiO 2 , 15–25% of Al 2 O 3 , 10–20% of Fe 3 O 4 , and 60–70% of SiO2, 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.
8. The method of claim 7 wherein the amount of Fe 2 O 3 comprises about 1% by weight of red iron oxide.
9. The method of claim 8 wherein the lithia-containing material comprises about 1% by weight and wherein the core sand comprises lake sand.
10. The method of claim 7 wherein the lithia-containing material comprises about 1% to about 2.5% by weight.
11. The method of claim 10 wherein the lithia-containing material comprises about 2.5% by weight, and wherein the core sand comprises a silica sand.
12. The method of claim 7 comprising about 2% by weight of lithia-containing material and about 1.5% by weight of iron oxide (Fe 2 O 3 ).
13. The method of claim 7 wherein the lithia-containing materials is selected from a group consisting of .α.-spodumene, amblygonite, montebrasite, petalite, lepidolite, zinnwaldite, eucryptite and lithium carbonate.
14. The method of claim 7 wherein the Fe 2 O 3 comprises red iron oxide.
15. In a method of making a sand core for casting, comprising uniformly mixing together a core sand, an effective amount of core sand binder and an anti-veining material, and thereafter forming from the resulting mixture a sand core, the improvement wherein the anti-veining material comprises about 1% to about 3.5% by weight of a mixture including 2–5% of Li 2 O, 10–25% of TiO 2 , 15–25% of Al 2 O 3 , 10–25% of Fe 3 O 4 , and 60–70% of SiO 2 , and about 1.5% by weight of red iron oxide (Fe 2 O 3 ).