SU761111A1 - Lining mixture for producing casting double-layer mould - Google Patents

Description

The invention relates to foundry, namely the manufacture of double-layer casting molds.

It is known that during the show process a mixture containing a refractory filler and an ethyl silicate binder ι is used for the facing layer ι [1]. The specified facing mixture has a low gas permeability and high mechanical strength, which complicates the cleaning of castings from the remnants of the facing layer, and ethyl silicate binder is expensive and scarce.

Closest to the described invention by its technical essence and the achieved result is a facing mixture for the manufacture of two-layer casting molds containing a refractory filler, an organic binder (fasteners PRS, MP or SB) and bentonite * [2). 20

This mixture does not have the necessary fluidity, which does not allow its pressing or pouring into the cavity formed by the model equipment and counterplate, or into the cavity formed by 25 model equipment and the supporting layer in the manufacture of two-layer casting molds, and the presence of bentonite in its composition creates favorable conditions for sintering the mixture under the influence of the temperature poured into 30

2

the shape of the metal, in connection with which its strength increases, when heated and, accordingly, the energy consumption increases when cleaning castings from the remnants of the facing layer.

The aim of the invention is to increase the fluidity of the mixture, reducing the residual strength of the cladding layer after casting the mold with liquid metal and the complexity of cleaning castings from the remnants of the cladding layer.

To achieve this goal, the facing mixture for the manufacture of casting two-layer forms, curable by heat drying, including a refractory filler and an organic binder, additionally contains a diluent selected from the group of aqueous or non-aqueous solvents in the following ratio of ingredients, weight. %:

Organic binder. 4-5 Thinner 11-13

Refractory filler Rest

As an organic binder, the facing mixture according to the invention may contain sulphite-alcohol bard (PRS) or sulphite-yeast brew (RRT), then it contains water as a diluent.

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As an organic binder, the facing mixture may also contain a KO binder (solution in white spirit bottoms from the distillation of synthetic fatty acids), then it contains white spirit or kerosene, or gasoline, or a solvent 646 as a diluent.

Instead of the KO binder, other casting binders can be used, which are completely insoluble in water or only soluble in it, for example, binder P, PT, SB, SP, etc.

When the content of the diluent in the composition of the facing mixture is below the lower limit, the mixture has a lower fluidity, which makes filling the cavity between the supporting layer and the model difficult if there is a gap between them of 3-4 mm affects the quality of the finished facing layer.

The mixture is prepared by mixing the components in a laboratory mixer, made similar to the mod unit. 661. used to prepare refractory coatings for investment casting. A diluent and a binder are fed into the agitator tank, stirred for 3-5 minutes, and then quartz sand is introduced.

The resulting prepared mixture by free pouring or pressing in at low pressures (2-3 kgf / cm ² ) is fed into the cavity formed by the model and the supporting layer of the mold.

For drying, the formed facing layer is preliminarily dehydrated or the removal of excess organic diluent by blowing, vacuuming or pressing, after which the moisture content of the facing layer does not exceed 6%, while the mixture loses its mobility, which allows all subsequent operations: removal from 4

loformes from the model plate, transportation and drying.

When used as a binder of an aqueous solution of sulfite-alcohol 5 bards, the drying temperature is 160–180 ° C, the drying time is 30–60 minutes. The moisture content of the coating layer after drying is 0.2–0.5%. When used as a binder solution KO on white spirit Yu, the drying temperature is 160–180 ° C, the duration is 15–20 min. The moisture content of the coating layer after drying is 0.2–0.3%.

With an optimal content of liquid components (4% PRS or KO and 12% 15 of solvent), the mixture shrinks after drying to 0.7–1.0%, which ensures the production of castings corresponding to 6–7 accuracy classes of GOST 1855–71 (machine forming rods).

20 The implementation of the process of forming a facing layer using the proposed facing mixture does not require complex technical means, thereby significantly reducing capital costs, eliminating the need for scarce and expensive thermosetting resins, ethyl silicate and similar binders, improves sanitary and hygienic working conditions due to

30 exemptions from the production of substances harmful to human health, the cost of cleaning castings from the cladding remains is reduced.

In tab. 1 shows the compositions of facing blends No. 1-3 according to the invention and No. 4 according to a known technical solution [2].

Properties of mixtures No. 1-4 are given in Table. 2

40 Thus, the proposed facing mixture has a fluidity sufficient to fill the gap of 3-4 mm between the model and the base layer of the form. This allows to obtain a facing layer.

4 5 to 5-7 times thinner than with use

Table I

Name Content of ingredients, weight. %, in mixtures №: ingredients one 2 3 four Quartz sand KO ₂ 81—86 81—86 81—86 92.5—94.0 PRS 3-6 - - 1.0-1.5 KO - 3-6 3-6 - Water 11—13 - - - White spirit or kerosene, or gasoline - 11—13 - - Solvent 646 - - 11—13 - Bentonite - - - 5-6

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table 2

five

Property Name Property indicators for mixtures №№ one 2 3 four The fluidity of the mixture on the spreading cone stroypnil, cm 1.1-4.0 1.5-4.5 1.5-4.5 missing Compressive strength, kgf / cm ² * - - - 0.5-0.6 Gas permeability, units 105–120 105-120 105-120 not less than 100 Humidity,% ** 14-18 14-13 14-18 5-6 Residual compressive strength after heating to 800 ° C and cooling, kgf / cm ² 1-3 1-3 1-3 5-6

* Facing the mixture according to the invention acquires the strength in the raw state after removing the excess diluent by vacuuming, blowing air, etc.

** When using non-aqueous diluents, the humidity is conditionally determined by the content in the mixture of this non-aqueous diluent.

mixtures according to the known technical solution (2].

In addition, due to the continuous heating of a thin layer of the facing mixture during pouring and the lack of sintering effect of bentonite, the residual strength of the mixture is significantly reduced and, accordingly, the complexity of its removal from the casting is reduced.

Claims (3)

Claim 1. Facing the mixture for the manufacture of two-layer casting molds, curable by heat drying, including a refractory filler and an organic binder, characterized in that, in order to increase the mixture's fluidity, reduce the residual strength of the facing layer after casting the mold 2 / scrap and the complexity of cleaning the casting from the remnants of the cladding layer, it additionally contains a diluent selected from the group of aqueous or non-aqueous solvents, with the following ratio of ingredients: 5 dents, weight. %: Organic binder 4-5 Thinner 11-13 Refractory filler Rest 5 2. Facing mixture in π. 1, characterized in that as the organic binder it contains sulfite-alcohol bard or sulfite-yeast mash, and as a diluent - U water. 3. Facing mixture in π. 1, characterized in that as an organic binder it contains a keeper (KO) - solution in white spirit bottoms 15 residues from the distillation of synthetic fatty acids, and as a diluent - white spirit or kerosene, or gasoline, or solvent 646.