RU2222409C1 - Silicate binding agent - Google Patents

Abstract

FIELD: foundry; manufacture of shell forms on investment patterns. SUBSTANCE: the invention is dealt with manufacture of shell forms on investment patterns and may be used in foundry. Silicate binding contains in mass %: silica - 65-75, polyacrylamide - 0.005-0.015, a defoamer - 0.015- 0.1, surface-active material - 0.05-0.85, desalted water - the rest. Usage of polyacrylamide together with the defoamer and surface-active material in the silicate binding composition allows to increase strength and quality of foundry shell forms. EFFECT: the invention provides manufacture of molding with the quality surface. 3 ex

Description

 The invention relates to the production of binders based on silica sol and can find application in foundry in the manufacture of shell molds in investment casting.

 A known suspension, including, wt.%: Silica sol - 41.0-44.0, ethyl silicate - 1.1-2.0, sulfanol - 0.05-0.06, butanol - 0.3-0.6, dusty quartz - 51.0-51.5 and water (RF patent 2185260, CL 22 C 1/16, publ. 2002.07.20).

 A known suspension for the manufacture of shell molds for investment castings, including, wt.%: Basic silica 34.3-29.75, ethyl silicate 0.7-5.25, surfactant 0.1-6.2 and refractory filler - the rest (RF patent 2191656, class B 22 C 1/16, publ. 2002.10.27 - prototype).

 Known suspensions do not provide the necessary strength of the calcined shell forms, which does not allow them to be used for the manufacture of all layers of shell forms. In addition, the surface of the obtained castings does not always turn out to be of high quality.

 The invention solves the problem of increasing the strength of the calcined shell forms obtained using a binder.

The problem is solved in that the silicate binder, including silica sol and a surfactant, according to the invention additionally contains polyacrylamide, antifoam and desalted water, in the following ratio, wt.%:
Silica sol - 65-75
Polyacrylamide - 0.005-0.015
Defoamer - 0.015-0.1
Surfactant - 0.05-0.85
Desalted Water - The Rest.

 Signs of the invention are the qualitative and quantitative composition of the claimed binder.

 The binder is a colloidal solution of high-modulus sodium silicate - silica with a thickener, stabilized by a surfactant.

The binder has the following properties: appearance - a slightly yellow liquid without visible impurities, mass fraction of silicon dioxide - 20-22%, density at a temperature of 20 ^o C, 1.133-1.138 g / cm ³ , pH value - 9.5-12 , kinematic viscosity - not more than 10 mm ³ / s, wetting angle - not more than 90 ^o , foam falling time - 10-15 s.

 Binder is used in the manufacture of investment casting molds.

The following materials are used to prepare the binder:
- silica sol - colloidal sodium silicate (TU 2145-001-43811938-97) with a mass fraction of silicon dioxide of 26.6-30.8%, a mass fraction of sodium oxide of 0.36-0.85%, a silicate module of 35-65 and a density at 20 ^o With 1,185-1,205 g / cm ³ ;
- polyacrylamide with a mass fraction of the main component of at least 90%;
- defoamer 139-282 (TU 6-02-1-529-86) - liquid polymethylsiloxane;
- defoamer PGKO-1001 - liquid polymethylsiloxane;
- desalted water with a pH of not less than 6.2, hardness not more than 0.006 mg equiv / l and electrical conductivity of the order of 1 Ohm • mm ² / m;
- surfactant sulfonol (STP 00204872-15-96P) with a mass fraction of sodium alkylbenzenesulfonates of at least 30%;
- surfactant bis (alkylpolyoxyethylene) phosphate oxyphos KD-6 (TU 6-02-1148-78) with a density at 20 ^o With 1.0-1.1 g / cm ³ .

The process of obtaining a binder consists of the following stages:
- preparation of a working solution of a surfactant;
- preparation of a working solution of polyacrylamide;
- preparation of a binder;
- structure formation.

 Working solutions of a surfactant and polyacrylamide are prepared by dissolving them in demineralized water. A solution of a surfactant is prepared by dissolving it in demineralized water to a concentration of 7.4-12.75%. A solution of polyacrylamide is prepared by dissolving it in demineralized water to a concentration of 0.038-0.042%.

 In the preparation of the binder, silica is first charged to the reactor. Then, with the stirrer operating, a solution of polyacrylamide is introduced. The contents are mixed for 25-35 minutes. After that, when the stirrer is working, a solution of a surfactant is loaded into the reactor. All mixed for 25-35 minutes. Lastly, with a working stirrer, an antifoam is added. The contents are mixed for 25-35 minutes.

 Structuring is carried out in the reactor at an exposure time of 15-20 hours. After that, check the density, viscosity, wettability.

 The use of a polyacrylamide binder together with an antifoam and a surfactant allows to obtain shell forms characterized by high strength and quality. Castings made in molds are even, smooth, without roughness and smudges, i.e. defect-free surface.

Case Studies
Example 1. Prepare a binder, including, wt.%:
Silica sol - 65
Polyacrylamide - 0.005
Defoamer - 139-282 - 0.015
Surfactant oxyphos KD-6 - 0.05
Desalted water - 34.93
Example 2. Prepare a binder, including, wt.%:
Silica sol - 70
Polyacrylamide - 0.01
Antifoam - 139-282 - 0.05
Surfactant sulfonol - 0.4
Desalted water - 29.54
Example 3. Prepare a binder, including, wt.%:
Silica Sol - 75
Polyacrylamide - 0.015
Defoamer - ПГКО-1001 - 0,1
Surfactant oxyphos KD-6 - 0.85
Desalted water - 24,035
A binder is prepared by mixing the components as described above. The required amount of pulverized silica is introduced into the finished binder and applied in layers to the sample model, each layer is sprinkled with a coarse fraction of the filler and each layer is dried at a temperature of 25-30 ^o C, air humidity 45-50% and blowing 1-3 m / s. The drying time of the facing layer is 2-3 hours, the subsequent layers up to 4-5 hours to a residual moisture content of the shell of not more than 2%. Using the prepared 5-layer samples, the model mass is melted and calcined for 30 minutes at a temperature of 850 ^o C.

 The bending strength of shell specimens is determined. The bending strength of non-calcined samples after smelting the model mass in boiling water is 0.8-1.0 MPa according to the prototype, according to examples 1-3 it is 2.3-3.4 MPa. The bending strength of the calcined samples after smelting the model mass in boiling water is 2.2-2.5 MPa according to the prototype, according to examples 1-3 it is 3.0-5.5 MPa.

 Application of the proposed binder will increase the strength of products made on its basis, improve their quality.

Claims (1)

Silicate binder, including silica sol and a surfactant, characterized in that it further comprises polyacrylamide, antifoam and desalted water in the following ratio, wt.%: Silica sol 65-75 Polyacrylamide 0.005-0.015 Defoamer 0.015-0.1 Surfactant 0.05-0.85 Demineralized water