Speaking of sodium silicate sand, is actually a variety of silicate (sodium silicate, potassium silicate, lithium silicate, etc.) aqueous solution of the general term. Below, we will understand the casting process of sodium silicate sand.

1. Sodium sodium silicate glass is prepared by wet method for casting:

After NaOH solution and quartz powder or silica sand are heated to about 160 degrees in a high pressure (0.5~ 0.7mpa) thermal reaction kettle with agitator and vacuum filtration or evaporation concentration, the finished sodium silicate glass can be prepared, namely: mSiO2+2NaOH=Na2O. MSiO2 +H2O

The modulus M of sodium water glass obtained by wet method is usually less than 3, which can meet the requirements of foundry. The energy consumption of this process is relatively low. In recent years, in order to solve the problem of short service time of water glass, low modulus is often used. The water glass of 0# xkhjsprolongs the usable time of the water glass sand, each factory has made its own factory standard according to the specific conditions. At present, many small and medium sized water glass factories supply foundries. They usually purchase bulk or powder solid sodium silicate raw materials from large sodium silicate production plants, and then heat and dissolve the solid sodium silicate raw materials for processing to produce water glass for foundry.

It should be noted that the foundry industry also advocates the use of high quality water glass. In general, the adoption of high-quality sodium silicate and high-quality raw sand can greatly reduce the amount of sodium silicate, not only will not increase the manufacturing cost of casting, but also solve the problem of poor collapsibility of sodium silicate sand will get twice the result with half the effort.

2. Performance parameters of sodium silicate glass

(1) modulus

It's the molar ratio of SiO2 to Na2O
M= mass of SiO2 / mass of Na2O
M= (SiO2 mass fraction /Na2O mass fraction) *1.033
R#xkhks# silicon-base ratio #xkhjs#=SiO2 mass fraction /Na2O mass fraction

The modulus is determined by the composition of solid sodium silicate, which has great influence on the properties of sodium silicate.

(2) density

Can indirectly indicate the concentration of sodium silicate in sodium silicate or solid sodium silicate content. The higher the density, the higher the content of solid sodium silicate. Can Be expressed by baume degree Be:
The relationship between baume degree and density: rho #xkhks#g/cm3#xkhjs#
Rho =144.3/#xkhks#144.3- baume xkhjs#;
Baume degree = 144.3-144.3 / rho

The above indicates that density is positively correlated with baume degree, that is, the higher the density is, the higher the baume degree is. In fact, the relationship between modulus and density is mostly inversely changing, but there is no fixed relationship.

(3) impurity content

Pure sodium sodium sodium silicate appears as a colorless, viscous liquid that contains impurities such as iron trioxide, aluminum trioxide, and calcium oxide, and can be gray, green, or even black. In addition, sodium sodium sodium silicate also contains impurity salt, sodium chloride, sodium sulfate, sodium carbonate, etc. The sodium silicate impurity density and viscosity of sodium silicate, hardening speed, bond strength, aging, has obvious adverse effects, such as surface tension, therefore, should try to reduce the impurity content of sodium silicate, to reduce the amount of the addition of sodium silicate, and improve the bonding strength of sodium silicate sand breakup sex has great significance.

(4) properties of sodium water glass

Sodium sodium silicate is a complex dispersion system, which has the properties of both ionic solution and colloidal solution. The properties of the solution are determined by the modulus of the water glass: when M is less than 2, it is a pure ionic solution with almost no colloidal ions. When M is greater than 2, silica colloidal particles begin to appear in the solution, and the proportion of colloidal particles increases with the increase of modulus. When M=4, the sodium sodium sodium silicate glass is basically silica solated. Therefore, the high modulus sodium silicate is easy to coagulate and unstable, which has both weak electrophoresis and dinzel effect, and the properties of colloidal solution. In the water glass solution, the phenomenon of spontaneous colloidal polymerization is called "aging".

3. Adjustment method of sodium water glass modulus and density

(1) reduce modulus: add sodium hydroxide (caustic soda);
(2) improve modulus: add hydrochloric acid or ammonium chloride;
(3) modulo adjustment: two kinds of high and low modulus water glass are used to adjust the modulus.
Above is sodium silicate sand sodium silicate casting process.