RU2227079C2 - Molding sand for making dispensable casting molds amd process for preparing it - Google Patents

Abstract

FIELD: foundry, namely manufacture of dispensable casting molds at making castings of cast iron, steel, aluminum. SUBSTANCE: molding sand contains, mass%: bentonite, 7 - 8%; industrial-grade carbon, 0.01 -0.5; water, 7.0; surface active matter such as monoalkyl ether of polyethylene glycol on base of primary aliphatic alcohols, 0.0005 - 0.025; refractory filler, the balance. Industrial-grade carbon is preliminarily treated with surface active matter. Water, refractory filler and bentonite are added to prepared suspension and agitated in edge- runner mill for 10 - 15 min. Industrial-grade carbon has optimal fraction size and linear structure of aggregated particles. Due to treatment by means of surface active matter such carbon has hydrophilic properties providing uniform distribution of it in molding sand. EFFECT: enhanced strength, gas permeability, burning-prevention properties of molding sand with reduced gas generating capability. 2 cl, 2 tbl, 3 ex

Description

The invention relates to the field of foundry, namely, to obtain molding sand-clay or sand-bentonite mixtures used for the manufacture of single casting molds for the production of castings from cast iron, steel, aluminum.

The known composition of the molding mixture for the manufacture of single casting molds, including components in the following ratio,%:

Bentonite 5.0-10.0

Ground coal 0.05-5.0

Water 2.0-3.5

10% Aqueous solution of alkyl polyglycol ether 0.05-0.30

Refractory filler

and a method for its production (USSR Author's Certificate No. 850251, B22C 1/02, 1979) according to which bentonite, ground coal, refractory filler, water and a 10% aqueous solution of an alkyl polyglycol ether - a product of the interaction of liquid alcohol with ethylene oxide are mixed and mixed within 10 minutes

The disadvantage of this composition is the high content of surfactants, which contributes to the formation of burns on the castings and the increased gas content of the molds when they are filled with metal.

Closest to the invention is the composition of the molding sand for the manufacture of single casting molds, in which bentonite, carbon black from anthracene oil, refractory filler and water are mixed in the following ratio of components,%:

Bentonite 8.0-10.0

Carbon black from anthracene oil 1.0-2.0

Water 3.0-5.0

Refractory filler

and a method for its production (USSR patent No. 804368, B22C 1/02, 1/16, 1989), which consists in mixing bentonite with carbon black from anthracene oil, a refractory filler and water at a temperature of 20 ° C.

The disadvantage of this composition is: low compressive strength, high gas content, instability of strength properties, hydrophobic surface of carbon black causes an uneven distribution of its particles in bentonite, which contributes to instability of strength properties and low strength. In addition, a relatively large percentage of the introduced carbon black contributes to the increased gas content of the material of the molding composition.

The objective of the invention is the development of the composition of the molding mixture, providing increased strength properties, gas permeability, non-stick properties and reduce gas production.

The technical result is achieved by the fact that the raw mixture for the manufacture of single casting molds containing refractory filler, bentonite, a carbon-containing additive and water, contains carbon black P-161 treated with a surfactant solution in the following ratio of components,% as a carbon-containing additive:

Bentonite 7.0-8.0

Carbon black 0.01-0.5

Water 7.0

Surfactant OS 20 - monoalkyl ether of polyethylene glycol

based on primary fatty alcohols 0.0005-0.025

Refractory filler

The molding mixture for the manufacture of single casting molds is prepared as follows: carbon black P-161 in concentrations from 0.01 to 0.5% is mixed with 0.2-5.4% aqueous surfactant solution. Then bentonite, a refractory filler and water are added and mixed for 10-15 minutes in the runners.

Pretreatment of P-161 carbon black with an aqueous surfactant solution gives the surface hydrophilic properties and promotes a uniform distribution of carbon black in the composition. The carbon black of the selected brand has an optimal dispersion (Ssp = 165 m ² / g for low-temperature adsorption of argon) and a linear structure of particle aggregates for mixing with bentonite. The use of this technique increases the strength characteristics by 1.4-1.6 times while maintaining good knockability of the molds after their pouring with metal. A small percentage of surfactants introduced into the composition does not affect its gas content.

The invention is illustrated by the following tables: table 1 shows the corresponding composition of the molding sand, table 2 explains the properties of the proposed molding sand. The properties of the mixtures were evaluated by the following parameters: σ _SJ - compressive strength, MPa; G - gas permeability.

Example 1. Take 0,022 g of surfactant (OS 20), dissolved in 10 g of water. 0.01% (0.437 g) of P-161 grade carbon black is introduced into the resulting solution. The prepared suspension is mixed with 300 g of bentonite, 340 g of water and a refractory filler in runners for 10-15 minutes.

Example 2. Take 1,08 g of surfactant (OS 20), dissolved in 20 g of water. 0.5% (21.7 g) of P-161 grade carbon black is introduced into the resulting solution. The prepared suspension is mixed with 342 g of bentonite, 340 g of water and a refractory filler in runners for 10-15 minutes.

Example 3. Take 0.152 g of surfactant (OS 20), dissolved in 15 g of water. 0.07% (3.038 g) of P-161 grade carbon black is introduced into the resulting solution. The prepared suspension is mixed with 321 g of bentonite, 340 g of water and a refractory filler in runners for 10-15 minutes.

Claims (2)

1. The molding mixture for the manufacture of single casting molds, including bentonite, a carbon-containing additive, a refractory filler, water, characterized in that carbon black P-161 is used as a carbon-containing additive, pre-treated with an aqueous solution of a surface-active substance (surfactant) - monoalkyl ether polyethylene glycol based on primary fatty alcohols, in the following ratio of components, wt.%: Bentonite 7.0-8.0 Carbon black P-161 0.01-0.5 Water 7.0 Surfactant 0.0005-0.025 Refractory filler 2. A method of obtaining a molding mixture, comprising mixing bentonite, carbon black, a refractory filler and water, characterized in that the suspension is preliminarily prepared from an aqueous solution of a surfactant — polyethylene glycol monoalkyl ether based on primary fatty alcohols and P-161 carbon black — add it to the remaining components and mix for 10-15 minutes in the runners.