SU1766576A1 - Method for reagent activation of moulding and core sands - Google Patents

Abstract

Usage: foundry production with reagent activation of molding and core mixtures based on lignosulphonet binders. Essence; The method consists in mixing bulk flow materials, liquid lignosulfonig, urea group and ferrous sulfate crystalline hydrate at 10-60 ° C, followed by aging at this temperature to obtain uniform mixture properties in the whole mixture.

Description

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The invention relates to foundry, in particular, to methods of reagent activation of molding and core mixtures based on lignosulfonate binders.

The known method of improving the quality of molding and core mixtures made on lignosulfonate, introducing reagent-activating additives into it, including mixing refractory filler, water-soluble lignosulfonate and activators, such as caustic soda, sodium chloride, ammonium chloride, ammonium chloride, and the quality of your own bodywork. (see Magazine Foundry Production 1982 No. 5, pp. 14-15, Chudin Yu.G. and others. Improving the quality of the molding mixture by introducing activating additives).

The disadvantages of this method:

1) the use of these activating additives with the other components does not allow to obtain the desired anti-adhesion, therefore, the dry forms and rods of these mixtures are used with the use of a nonstick coating;

2) this method of activation of the mixtures leads to prolonged drying of the casting molds and cores (drying the control samples of the mixture is 30-60 minutes to obtain maximum dry strength).

The closest in technical essence and the achieved result to the proposed is the method of reagent activation of molding and core mixes.

ABOUT

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This is based on lignosulfonate binders, which includes mixing bulk materials with liquid lignosulfonate and urea activator, which reduces the wet and dry strength of the mixtures due to the decrease in viscosity of the lignosulfonate, the interaction with the reducing substances of the lignosulfonate and the formation of urea aldehyde, and the formation of a urea aldehyde resin and a reduction of the urea aldehyde content with a reducing urea aldehyde composition. high dry binding properties (see Foundry, 1975, No. 1, pp.4-6, N.H. Ivanov et al. Activated molding sands).

The disadvantages of this method:

1) this method of reagent activation of the mixture does not allow the use of dry forms and rods without a nonstick coating;

2) such activation does not provide mixtures of rapid moisture transfer, i.e., acquiring a high water-holding capacity, causes the need for prolonged drying of the molds and rods (drying of control samples is 30-40 minutes for maximum dry strength);

3) the reagent activation in this method is carried out under normal or close to normal conditions, which limits the activation process.

The aim of the invention is to manufacture molds and cores without a nonstick coating and to reduce the duration of heat curing.

The goal is achieved by the method of reagent activation of molding and core mixtures used for casting molds and cores to pry and dry, including mixing bulk materials, liquid technical lignosulfonates and urea, while mixing the components, the mixture additionally introduces crystalline hydrate of copper sulfate simultaneously with urea and liquid technical lignosulfonates. In this case, stirring is carried out at 10-60 ° C and the resulting mixture is maintained at this temperature until homogeneous properties are obtained in the whole volume of the mixture.

The following components are used to implement the method.

The technical density of 1.18-1.28 g / cm3 is used as liquid water-soluble lignosulfonates.

The bulk materials used are quartz sand, marshalite, ordinary molding clay and bentonite, spent molding and core sand, chamotte and magnesite powder.

The clay is applied either in powder or in the form of a water clay slurry.

The urea group contains urea or thiourea, or a combination of them in a lumpy, powdered, granular, or water soluble state. The amount of the urea group can be different depending on the requirements of the technological process, and the optimal one is 0.1–10.0% in terms of solid state.

Iron sulfate crystalline hydrate may be introduced into the mixture in a piecewise, powdered, granular, or water-soluble state. Its quantity depends on the requirements of production. Its preferred content is 0.003-5.0%, based on the solid state. Iron sulfate crystalline hydrate is introduced into the mixture in proportion to the content of the urea group. The larger the urea group in the mixture, the greater the content of ferrous sulfate crystalline hydrate. In order not to decrease the strength characteristics of dry forms and rods, it is necessary to observe the excess of the urea group content over the crystalline hydrate of blue vitriol.

Technological additives, such as kerosene, KO, USK, various oils that perform the functions of reducing the adhesion of mixtures to the rigging, can be added if there is a technological need.

The method of reagent activation of the mixtures is performed as follows.

At the temperature of components from 10 to 60 ° C, bulk materials, liquid lignosulfonate binder, urea group and ferrous sulfate crystalline hydrate are mixed together until a homogeneous state is formed in the mixture system. At the same time, the urea group and ferrous sulfate crystalline hydrate are introduced into the mixture either together with bulk materials or together with liquid lignosulfonate. When performing reagent activation below 10 ° Q, the process slows down, it does not fully proceed, which leads to prolonged preparation and technological unprofitability. When reagent activation is performed above 60 ° C, intensive moisture generation occurs when the mixture is stirred, the activation process does not have time to completely occur, and the mixture becomes non-technological.

The resulting mixture is kept at 10-60 ° C before using it to achieve uniform properties throughout the volume.

In the process of mixing the components of the mixture, interaction between them occurs, leading to a phase transformation, causing a highly active state of the system, reducing the duration of heat curing of casting molds and cores, as well as eliminating the use of nonstick coating of casting molds and cores to obtain a clean steel surface. the castings made vsyryu and dry.

The test results of this method of reagent activation of molding and core mixtures based on lignosulfonate binders and the prototype method are given in Tables 1 and 2. As can be seen from Tables 1 and 2, when introducing crystalline hydrate of vitriol less than 0.003%, it is not possible to obtain a clean surface steel castings. When you enter it more than 5%, the strength properties of the mixture in a heat-cured state are reduced, which makes it impossible to apply them to molds and rods of a responsible purpose. The heat curing of the molds and rods of these mixtures is carried out at 200-300 ° C.

The duration of exposure of the finished mixture to achieve uniform properties depends on its temperature: the higher the temperature, the shorter the duration of exposure.

The developed method of reagent activation allows the use of a reagent. The effect of reagent activation of the skis on the duration of warm curing.

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no-activatable mixtures for wet and dry forms, reduce the duration of heat cure by 1.5-5 times, ensure the clean surface of steel castings made on raw and dry casting molds and cores without the use of a nonstick coating, and expand carrying out the activation process at 10-60 ° C.

Claims (1)

DETAILED DESCRIPTION A method for the reagent activation of molding and core mixtures used for casting molds and cores, dry and dry, comprising mixing bulk materials, liquid technical lignosulfonates and urea, excluding that with the aim of reducing the cycle of making molds and rods without a nonstick coating by reducing the duration of heat curing, the mixture of hydrated sulphate of iron sulphate is added to the mixture while mixing the components, simultaneously with urea or with liquid technical lignosulfonates, while stirring is carried out at Te Mriepafype o f 10 to 60 ° C and the resulting mixture is kept at this temperature until homogeneous properties are obtained in the whole volume of the mixture. Table 1 2.8 2.5 0.5 0.6-1.5 The effect of reagent-activated mixtures on the surface quality of steel castings Table