Abstract A method is described for producing a dry flowable blended sand and using this sand in making a casting mold. The blended sand is prepared by mixing a refractory particle, such as silicious sand, with an alkali metal silicate solution, such as a sodium silicate solution of at least 40 percent (weight) solids content whose SiO2 to Na2O molar ratio has previously been adjusted with NaOH solution of at least 40 percent (weight) solids content to a molar ratio of 0.7 to 1.1 to thereby precipitate and deposit crystalline alkali metal silicate on the surface of said refractory particle, and thereafter blending the thus treated refractory particle with a powder of silicon, silicon alloy such as ferrosilicon, silicide such as calcium silicide or a mixture thereof, pouring the blended sand into a molding frame and allowing it to harden therein. The precipitation and deposition of the alkali metal silicate from solution is hastened by the addition of an alcohol such as methanol, or metal salt such as NaCl to the alkali metal silicate solution.
The process of claim 1, wherein the alkali metal silicate solution is a sodium silicate solution.
Claim 2
Dependent Claim
81 words
The process of claim 1, wherein 100 parts of the solution of silicate of alkali metal contain from about 2 percent to about 5 percent of Na2SiO3 whose molar ratio of SiO2 to Na2O is from about 0.7 to about 1.1, all of said parts and percents being by weight; from about 1 percent to about 4 percent by weight of coagulation assistant is employed; and from about 0.1 percent to about 1.0 percent by weight of crystallization promotor is employed.
Claim 3
Dependent Claim
63 words
The process of claim 1, wherein the solution of sodium silicate is prepared by adding sufficient NaOH in an aqueous solution of at least 40 percent by weight to solids, to a solution of water-glass having a SiO2 to Na2O molar ratio of about 2 to about 3.5 to thereby change said SiO2 to Na2O molar ratio to about 0.7 to about 1.1.
Claim 4
Dependent Claim
32 words
The process of claim 4, wherein the molding frame is heated to a temperature at least above the melting point of the crystalline sodium silicate prior to pouring the blended mixture therein.
Claim 5
Dependent Claim
21 words
The process of claim 5, wherein the crystalline sodium silicate is substantially Na2SiO3.9H2O having a melting point of about 47* C.
Claim 6
Dependent Claim
12 words
The process of claim 6, wherein the promoter is a lower alkanol.
Claim 7
Dependent Claim
35 words
A process according to claim 7 in which the refractory particles comprise silicious sand, and the aqueous solution of alkali metal silicate comprises a solution obtained by addition of aqueous sodium hydroxide to water glass.
Claim 8
Dependent Claim
31 words
The process of claim 6, in which sodium chloride is added to the mixture of aqueous solution of alkali metal silicate and refractory particles to assist deposition of the alkali silicate.
Claim 9
Dependent Claim
32 words
The process of claim 6, in which sodium aluminate is added to the mixture of aqueous solution of alkali metal silicate and refractory particles to assist deposition of the alkali metal silicate.