Molding materials for non-ferrous casting
View Patent ↗A molding material mixture for producing casting molds for metal processing, particularly for non-ferrous metals, such as aluminum or magnesium, is intended to reduce problems such as metal-mold reaction and/or shrinkage porosity defect. The free-flowing refractory molding material in the molding material mixture is coated with a mixture of inorganic salts exhibiting a eutectic melting point in the range of about 400 C to about 500 C, particularly in the range of about 420 C to about 460 C. Preferably this coating occurs by contacting the inorganic salt mixture with the molding material mixture at a temperature between 500 C and 700 C, in a manner that maintains the free-flowing nature of the coated product. One mixture of inorganic salts that is used is a mixture consisting of, by weight: 74% potassium fluoroborate; 15% potassium chloride; and 12% potassium fluoride. This mixture has a eutectic melting point of 420 C.
1. A molding material mixture for producing casting molds for metal processing comprising:
a free-flowing refractory molding material; and
a binder, provided as a two-component system that is mixed and cured at the time of use, wherein the refractory molding material has been coated with a mixture of inorganic salts exhibiting a eutectic melting point in the range of 400° C. to 500° C.
2. The molding material mixture of claim 1 , wherein the free-flowing refractory molding material comprises a molding sand.
3. The molding material mixture of claim 1 , wherein the two-component binder system is an epoxy-acrylic binder that is cured with sulfur dioxide gas.
4. The molding material mixture of claim 1 , wherein the mixture of inorganic salts is a mixture of three inorganic salts.
5. The molding material mixture of claim 4 , wherein each of the inorganic salts in the mixture has a Group IA cation.
6. The molding material mixture of claim 5 , wherein the Group IA cation of at least one of the inorganic salts is potassium.
7. The molding material mixture of claim 6 , wherein the Group IA cation of each of the inorganic salts is potassium.
8. The molding material mixture of claim 5 , wherein each of the inorganic salts in the mixture has, as an anion, either a halide anion or a fluorine complex of boron or titanium.
9. The molding material mixture of claim 8 , wherein each of the inorganic salts in the mixture has fluorine as an anion.
10. The molding material mixture of claim 5 , wherein each of the inorganic salts in the mixture has an individual melting point that is greater than 500° C. and at least two of the inorganic salts has an individual melting point that is greater than 700° C.
11. The molding material mixture of claim 1 , wherein the mixture of inorganic salts is a mixture consisting of, by weight:
74% potassium fluoroborate;
15% potassium chloride; and
12% potassium fluoride, wherein the mixture has a eutectic melting point of 420° C.
12. The molding material mixture of claim 1 , wherein the mixture of inorganic salts is a mixture consisting of, by weight:
59% potassium fluoride;
29% lithium fluoride; and
12% sodium fluoride, wherein the mixture has a eutectic melting point of 460° C.
13. The molding material mixture of claim 1 , wherein the mixture of inorganic salts is a mixture consisting of, by weight:
50% potassium fluoroborate;
47% potassium hexafluorotitanate; and
3% potassium chloride, wherein the mixture has a eutectic melting point of 420° C.
14. A method of preparing a refractory molding material for use in producing casting molds for metal processing, comprising the steps of:
obtaining a free-flowing refractory molding mixture;
obtaining a mixture of inorganic salts exhibiting a eutectic melting point in the range of 400° C. to 500° C.;
contacting the refractory molding mixture with the mixture of inorganic salts at a temperature in the range of 500° C. to 700° C., such that the refractory molding mixture is coated with the mixture of inorganic salts and remains free flowing; and
cooling the coated refractory molding mixture to ambient temperature.
15. The method of claim 14 , wherein the mixture of inorganic salts is contacted with the refractory molding mixture in an amount of 0.3% to 0.4% by weight.
16. The molding material of claim 1 , wherein the eutectic melting point of the mixture of inorganic salts is in the range of 420° C. to 460° C.
17. The molding material mixture of claim 2 , wherein the mixture of inorganic salts is a mixture of three inorganic salts.
18. The molding material mixture of claim 3 , wherein the mixture of inorganic salts is a mixture of three inorganic salts.
19. The molding material mixture of claim 17 , wherein each of the inorganic salts in the mixture has a Group IA cation.
20. The molding material mixture of claim 18 , wherein each of the inorganic salts in the mixture has a Group IA cation.
21. The molding material mixture of claim 19 , wherein the Group IA cation of at least one of the inorganic salts is potassium.
22. The molding material mixture of claim 21 , wherein the Group IA cation of each of the inorganic salts is potassium.
23. The molding material mixture of claim 20 , wherein the Group IA cation of at least one of the inorganic salts is potassium.
24. The molding material mixture of claim 23 , wherein the Group IA cation of each of the inorganic salts is potassium.
25. The molding material mixture of claim 19 , wherein each of the inorganic salts in the mixture has as an anion either a halide anion or a fluorine complex of boron or titanium.
26. The molding material mixture of claim 25 , wherein each of the inorganic salts in the mixture has fluorine as an anion.
27. The molding material mixture of claim 20 , wherein each of the inorganic salts in the mixture has as an anion either a halide anion or a fluorine complex of boron or titanium.
28. The molding material mixture of claim 27 , wherein each of the inorganic salts in the mixture has fluorine as an anion.
29. The molding material mixture of claim 19 , wherein each of the inorganic salts in the mixture has an individual melting point that is greater than 500° C. and at least two of the inorganic salts has an individual melting point that is greater than 700° C.
30. The molding material mixture of claim 20 , wherein each of the inorganic salts in the mixture has an individual melting point that is greater than 500° C. and at least two of the inorganic salts has an individual melting point that is greater than 700° C.
31. The molding material mixture of claim 2 , wherein the mixture of inorganic salts is a mixture consisting of, by weight:
74% potassium fluoroborate;
15% potassium chloride; and
12% potassium fluoride, wherein the mixture has a eutectic melting point of 420° C.
32. The molding material mixture of claim 2 , wherein the mixture of inorganic salts is a mixture consisting of, by weight:
59% potassium fluoride;
29% lithium fluoride; and
12% sodium fluoride, wherein the mixture has a eutectic melting point of 460° C.
33. The molding material mixture of claim 2 , wherein the mixture of inorganic salts is a mixture consisting of, by weight:
50% potassium fluoroborate;
47% potassium hexafluorotitanate; and
3% potassium chloride, wherein the mixture has a eutectic melting point of 420° C.
34. The molding material mixture of claim 3 , wherein the mixture of inorganic salts is a mixture consisting of, by weight:
74% potassium fluoroborate;
15% potassium chloride; and 12% potassium fluoride,
wherein the mixture has a eutectic melting point of 420° C.
35. The molding material mixture of claim 3 , wherein the mixture of inorganic salts is a mixture consisting of, by weight:
59% potassium fluoride;
29% lithium fluoride; and 12% sodium fluoride,
wherein the mixture has a eutectic melting point of 460° C.
36. The molding material mixture of claim 6 , wherein the mixture of inorganic salts is a mixture consisting of, by weight:
50% potassium fluoroborate;
47% potassium hexafluorotitanate; and 3% potassium chloride,
wherein the mixture has a eutectic melting point of 420° C.