RU2167021C2 - Mixture for manufacture of casting molds and cores - Google Patents

Abstract

FIELD: metallurgy. SUBSTANCE: mixture contains the following components, wt. %: water glass, 5-7; sodium hydroxide (10-% aqueous solution), 0.5-1.0; hydrolytic resin (by-product of sulfuric acid lignin-containing raw materials), 1.2-2.0; refractory filler, the balance. EFFECT: increased strength of mixture and improved its knock-out. 2 tbl, 1 ex

Description

 The invention relates to metallurgy, in particular to compositions of molding and core mixtures.

 There are various compositions of mixtures for the manufacture of foundry molds and cores, however, each of which has its own advantages and disadvantages.

 A known mixture containing 4.5-5.5% liquid glass, 0.9-1.1% caustic soda, 0.8-1.0% extract of selective purification of oil distillers and refractory filler.

 This mixture has good strength and unsatisfactory knockout, therefore, requires improvement (see.with. N 627904 B 22 C 1/02, BI N 38, 1978).

 Such a mixture is known containing 84-88% refractory filler, 12-16% diatomite chips and 5.3-5.9% liquid glass (see A.S. N 648322 B 22 C 1/02, BI N 7, 1979 g.).

 This mixture has improved fluidity with reduced adherence to snap. However, knockability of the mixture leaves much to be desired.

 The closest in technical essence to the developed is a mixture of a. from. N 1411089 A1, B 22 C 1/00, 07.23.88, including refractory filler, 4.0-6.0% water glass, 0.5-1.5% sodium hydroxide, 0.8-1.2% hydrolysis resins (a by-product from sulphate hydrolysis of lignin-containing raw materials).

 However, this mixture is not without the drawbacks of the above mixtures.

 The technical result of this development is to increase the strength of the mixture and improve its knockability from castings.

This is achieved by the fact that the mixture for the manufacture of foundry molds and cores, including refractory filler, liquid glass, caustic soda and hydrolysis resin (a byproduct of sulfuric acid hydrolysis of lignin-containing raw materials), contains the above components in the following ratio, wt.%:
Caustic soda (10% aqueous solution) - 0.5-1.0
Hydrolysis resin (a by-product from lignin-containing raw materials, sulfuric acid) - From more than 1.2 to 2.0
Liquid glass - 5-7
Refractory Filler - Else
Example.

 To prepare the mixture, quartz sand KO2A of the Chaadaevsky quarry of the Penza region is used. Kneading by weight of quartz sand was 2.5-3.0 kg, liquid glass in the amount of 5.0-7.0%, 10% aqueous solution of caustic soda 0.5-1.0% was used as a binder. Hydrolysis resin in the range of 5-30% of the amount of water glass, i.e. 1.2-2.0%, wt.% In total by weight of the mixture. In total, 6 compositions of the core mixture were investigated. The main components remained constant, and the composition of the hydrolysis resin varied within 5, 10, 15, 20, 25, and 30% of the amount of water glass.

 The technology for preparing the core mixture: dry quartz sand was poured into the runners, then hydrolysis resin was supplied, the components were mixed in the dry state for 2-3 minutes, then liquid glass was supplied and stirring was carried out for 2 minutes, then a solution of liquid sodium was fed and mixing was carried out for 2 minutes.

 The prepared mixture, for the purpose of uniformity, was kneaded for 0.5 hours, after which standard samples were prepared for wet (cylindrical) and dry (eights) gas permeability strengths.

Samples were dried in an oven at a temperature of 200-250 ^o C for 15-20 minutes, while samples were purged with carbon dioxide in parallel with hardening.

 Rods with a diameter of 50 mm and a height of 70 mm were made in a standard core box from a mixture of conventional composition and from a test mixture with the addition of hydrolysis resin.

Studies were conducted simultaneously. The rods were installed in the experimental form, the size of the casting had the following dimensions: 260 x 120 x 60 mm. The molds were filled with gray cast iron at a temperature of 1300-1320 ^o C. After pouring, the molds were kept until the castings were completely cooled, then the rods from the castings — the samples were knocked out on a laboratory head. Knockout was determined by the number of strokes of the copra.

 The results of some studies are given in table. 1.

 Physico-chemical properties of core mixtures are given in table. 2.

 The strength of the crude samples increases in proportion to the increase in hydrolysis resin. The adherence of the mixture to the working surface of the core box increases, the gas permeability of the mixture is high and remains within acceptable limits. With an increase in the content of hydrolysis resin in the mixture, the gas-generating ability increases.

 The knockability of liquid-glass mixtures increases with an increase in the content of hydrolysis resin in the mixture and reaches the optimum, i.e. the core from the casting is knocked out together with the knockout of the mold, the knockability of the test mixture is close to the knockout of sand and tar.

 The action of the hydrolysis resin additive is based on the optimal combination of inorganic and organic materials. As can be seen from the table. 2, the use of a hydrolysis mixture in the range from more than 1.2 to 2.0% is justified and gives a positive effect.

 The use of a hydrolysis resin as a minimal additive to a liquid-glass mixture makes it possible to reduce the work of knocking out casting rods by a factor of 15–20.

Claims (1)

A mixture for the manufacture of foundry molds and cores, including a refractory filler, liquid glass, caustic soda and hydrolysis resin (a byproduct of sulfuric acid hydrolysis of lignin-containing raw materials), characterized in that the components are contained in the following ratio, wt.%:
Liquid glass - 5 - 7
Caustic soda (10% aqueous solution) - 0.5 - 1.0
Hydrolysis resin (a by-product of sulfuric acid lignin-containing raw materials) - From more than 1.2 to 2.0
Refractory Filler - Else

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