RU2288804C2 - Sand for making casting cores - Google Patents

Abstract

FIELD: casting processes and equipment, namely sands for producing casting cores for aluminum castings and for thin-wall castings of cast iron.

SUBSTANCE: sand contains refractory filler such as quartz sand and binder such as solution with density 1.2 -1.3 g/cm³ of polystyrene in toluene at next relation of ingredients (mass. p.): refractory filler, 95 -96; solution of polystyrene in toluene, 4 - 5.

EFFECT: improved strength and knocking out capability of sand.

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Description

The invention relates to foundry, in particular to the manufacture of foundry cores for aluminum castings and thin-walled castings from cast iron.

A technical solution is known, adopted by the applicant for the prototype (Molding materials and mixtures / S.P. Doroshenko, V.P. Avdokushin, K. Rusin, I. Matsaszek. - K .: Vyshka school. 1990; Prague. SNLT, 1990. p. .263), in which the core mixture is prepared from a refractory filler and a binder - polyvinyl alcohol.

This mixture has good strength properties (2.2-2.4 MPa per gap) and is characterized by good knockability. However, this mixture has insufficient non-stick resistance, especially when casting iron castings, and also has increased hygroscopicity, which leads to softening of finished products from this mixture during storage.

The above disadvantages are eliminated by the claimed invention, the essence of which is as follows. A mixture for the manufacture of foundry rods, including a refractory filler, for example quartz sand, and a binder, contains as a binder a solution with a density of 1.2-1.3 g / cm ³ polystyrene in toluene in the following ratio of components (in parts by weight): refractory filler 95-96, a solution of polystyrene in toluene 4-5.

New in the claimed technical solution is that the mixture for the manufacture of foundry rods as a binder contains a solution with a density of 1.2-1.3 g / cm ³ polystyrene in toluene in an amount of 4-5 wt. hours

The technical result achieved by the implementation of the invention is to increase the tensile strength of the mixture in the dry state to 2.5-2.9 MPa, the complete absence of burn on castings from cast iron, ideal knockability, because after pouring the metal, the polystyrene binder burns out, which leads to complete softening of the mixture, and finished products from a mixture with a polystyrene binder during storage are not softened.

The density of the polystyrene solution in toluene was selected empirically. When the density of the polystyrene solution in toluene is more than 1.3 g / cm ^3, uniform distribution of the binder in the refractory filler (for example, quartz sand) is difficult, and the density of the polystyrene solution in toluene less than 1.2 g / cm ³ increases the consumption of the solvent — toluene. The content of the refractory filler and binder in the mixture was also selected empirically. Less than 4 parts by weight a binder leads to less than 2.4 MPa of the tensile strength of the mixture and increased crumbling. The content of the binder is more than 5 parts by weight leads to a slight increase in the tensile strength of the mixture, but this increases the gas content of the mixture. Thus, the most optimal is a mixture with a content of 95-96 wt.h. refractory filler, which may be quartz sand, and 4-5 wt.h. a solution of polystyrene in toluene.

A mixture for the manufacture of foundry cores is prepared as follows. Prepared quartz sand (washed, dried, etc.) in an amount of 95-96 mass parts is mixed with a previously prepared binder solution with a density of 1.2-1.3 g / cm ³ polystyrene in toluene in an amount of 4-5 mass parts in runners . The finished mixture is fed to the core section for the manufacture of foundry cores.

The characteristics of the claimed mixture and mixture of the prototype are presented in the table.

Table. Indicator A mixture using a polystyrene binder A mixture with polyvinyl alcohol as a binder Gas permeability 230-265 220-270 The tensile strength after drying at a temperature of 220-240 ° C, MPa 2.5-2.9 2.2-2.4 The tensile strength after drying at a temperature of 220-240 ° C and storage 72 hours, MPa 2.5-2.9 1.5-2.0 Knockout after pouring, the mixture crumbles good Casting surface (cast iron) no burn there are traces of burning in thermal units

In the inventive mixture, a polystyrene solution is used as a binder, which can be prepared from used polystyrene packaging using toluene as a solvent, a common and inexpensive solvent, which makes this binder a widely available and inexpensive material that reduces the cost of the mixture and solves the problem of recycling polystyrene packaging.

Using the proposed mixture for the manufacture of rods in comparison with the prototype allows to provide a number of technical and economic advantages:

- increases the strength of the mixture after drying;

- the mixture does not soften during storage;

- completely no burning on cast iron castings;

- after pouring and cooling the metal, the mixture is completely softened;

- promotes the disposal of polystyrene products.

Claims (1)

A mixture for the manufacture of foundry cores, including refractory filler - quartz sand and a binder, characterized in that it contains as a binder a solution with a density of 1.2-1.3 g / cm ³ polystyrene in toluene in the following ratio of components, parts by weight: Refractory filler 95-96 A solution of polystyrene in toluene 4-5