SU1713711A1 - Method of preparation of circulating sand mixture - Google Patents

Abstract

The invention can be used to prepare molding compounds for any type of production. The purpose of the invention is to expand the technological capabilities of the method by disposing of dust-like waste from foundries. The proposed method consists in the fact that the mixed components of the refreshment are moistened, then mixed with the plasticizer and introduced into the used mixture with the resulting composition adjusted to the desired humidity. A part of the refreshment components is used in the form of sludge in an amount of 0.1-4.0% of the amount of the mixture, and the pre-moistening of the refreshment composition is carried out by introducing the sludge into the dry components mixed together. 1 tab.

Description

The invention relates to foundry, in particular, to methods for preparing molding sands.

A known method of preparing molding materials and mixtures, which consists in the fact that the previously prepared components: sand, clay and coal dust, are pre-mixed in a separate mixer. and then fed to the main mixer for mixing with the used mixture and obtaining the final molding mixture, wherein the moisture adjustment is carried out by supplying water to the main mixer after mixing the refresh and used mixtures in a dry state after some time. After preparation, the mixture is kept for at least 1 hour before use (Aksenov, I., Foundry Equipment. - M., Mashinostroenie, 1977. P.24B-249).

However, with the known method of preparing sand-clay mixtures, the highly unproductive losses of dry components, as well as equipment wear due to the abrasive effect of dry materials. In addition, the fouling of 4o-clay, which is part of the mixture, should acquire optical strength and plastic properties upon swelling after interacting with water for a certain time (approximately 1 h), which requires the use of large-volume ready-mix bins. Due to the fact that in conditions of continuous mass production, the use of such bunkers is almost impossible due to high capital costs for bunkers and inefficient use of space, as well as a significant overrun of the mixture, in casting shops of mass mass production, technological properties are not calculated. the amount of refreshing additives, and at their obviously high consumption, which is also associated with a significant overrun of fresh materials. In addition, in mass production, the mixing time of the components in the mixer is limited, which leads to a decrease in the mixing efficiency, i.e. at a given mixing cycle, the mixture does not reach the maximum strength and technological characteristics, because of which a deliberately inflated amount of refreshing components is introduced into the mixture.

The closest to the proposed technical essence and the achieved results is the method of preparation of molding materials and mixtures {1 according to which the preparation of the mixture is carried out as follows. Molding clay, ground coal, technological additives (for example, extrusive starch-containing reagent and soda ash) are mixed (for example, in a single pneumatic system), and then simultaneously fed into a screw mixer. In parallel, a refractory filler and water are fed into the screw mixer in an amount equal to the amount of 20-25% of the content of molding clay and 0.60, 7% of the refractory filler. The plasticizer is last added. After mixing is completed in a screw mixer, the mixture is held in a settling bunker for 20-30 minutes.

When using this method of preparation, remnants of a core mixture containing a refractory filler, having a shell of a tergoreactive binder, with which dry or low-moisture components of the mixture are poorly combined and do not form a water-clay membrane system, get into the mixture, due to which mixing efficiency is significantly reduced. e. at a given mixing cycle, the nb mixture achieves optimum strength and technological characteristics, due to which a deliberately inflated amount of refreshing components is introduced into the mixture.

The aim of the invention is to expand the technological capabilities of the method of preparing circulating molding sands by disposing of dust-like waste from foundries.

For this purpose, the refreshment composition is moistened with a wet dust collection system sludge in an amount of 0.1-4.0% by weight of the spent mixture.

The used sludge contains in its composition the following ingredients (in terms of dry state), may.%:

Bentonite40-50

Coal dust 15-20

Kvartseva dust 5-10.

Fireclay, cokeExtra

This method of preparing wetting mixtures by introducing a wet dust collection system into the refreshing sludge composition is not known in the technical literature. The proposed method

0 meets the criterion of significant differences. .

According to the invention, the preparation

the mixture is carried out as follows.

Molding clay, ground coal ,.

5 technological additives (for example, extrusive starch-containing reagent and soda ash) are mixed (for example, in a single pneumatic system), and then simultaneously fed into auger

0 mixer. In parallel, a refractory filler is supplied to the screw mixer, as well as water and part of the refreshing additives in the form of sludge from wet dust removal systems in an amount of 0.1-4.0% of the mixture quantity. AT

5, the last plasticizer is added. After completion of mixing in a screw mixer, the mixture is kept in a settling bin for 10-20 minutes. During the pre-mixing process, the molding clay swells as a result of its interaction with soda ash in the presence of water (wet activation). At the same time, the clay envelops the grain base to form

5 uniformly distributed structure. When using sludge, this process is intensified due to the fact that up to 70% of the active components in the swollen state are contained in the sludge. it

0 permits a significant acceleration of the distribution process of the clay sheath on a grain basis to a uniform film state. The plasticizer, introduced last, wraps the grain

5 base, non-obstruction of the swelling of the molding clay. In addition, with the introduction into the main mixer of a pre-mixed refreshing composition containing sludge, significant

0 an increase in the efficiency of mixing by averaging the composition of the mixture. At the same time, the consumption of fresh molding materials is significantly reduced, and the dust content in the areas of mixed preparation is reduced.

Example. A mixture consisting of 5% refreshment and 95% waste mix is produced in two ways: according to known and proposed. In the first case, sand, coal and molding clay (bentonite) are mixed and fed simultaneously to the mixer. At the same time, extrusive starch-containing reagent, soda ash and plasticizer SKT-10 are dosed into it. Water is fed to the mixer through a separate pipeline.

In the second case, molding clay, extrusive starch-containing p6i gent, ground coal and calcined soda are fed into a single pneumatic system in which they are mixed. Then, the resulting composition is fed into a screw mixer, mixed in it with a refractory filler (sand) and part of water and refreshing drains in the form of sludge for 10 minutes and then mixed with plasticizer SKT-10 for 1-2 minutes.

The finished mixture is kept in a storage hopper according to a known method for 20-30 minutes, and according to the proposed method for 10-20 minutes, then fed to the main mixer for mixing with the used mixture and finishing in humidity;

The mixtures are tested immediately after leaving the main blender at a preliminary shutter speed of 10 and 25 minutes.

When holding the refreshing mixture in the settling bunker for more than 20 minutes, the moisture content of the mixture decreases below the allowable values due to evaporation of moisture, resulting in increased dustiness and the appearance of unproductive losses of fresh molding materials, while keeping the mixture less than Yumin, the strength properties of the mixture reach sufficient values.

The Unmixing process in the main mixer lasts 1, 3, 5 and 10 minutes,

  , - ,. ...: Three main indicators are evaluated: the wet compressive strength of the specimen, the fracture strength of the specimen in the wet state, and the tensile strength of the specimen in the moisture condensation zone. All indicators are evaluated by hotel methods. The test results are given in the table.

As can be seen from the table (the strength characteristics of the mixture made by the proposed method significantly exceed the results obtained with the known method.

The use of this method of preparation allows dbstich optimal strength characteristics of the finished mixture almost twice as fast as in the known method, 410 allows, in terms of flow mass production, save a significant amount of fresh molding materials, increase the efficiency of the mixing process, i.e. Significantly reduce energy consumption for the mix-prepared processes:

Formula 3 and 3d breasts. Method of preparing circulating molding mixtures, including mixing the components of the refreshing composition, moistening it, mixing with a plasticizer, sticking and entering into the used mixture, in order to expand technological capabilities By disposing of powder waste from foundries, wetting of the refreshing composition is carried out with sludge from the Wet Dust Collection System in an amount of 0.1-, 0% by weight of the used molding sand.

Table continuation

Claims (1)

Claim A method of preparing reverse molding sand mixtures, including mixing the components of the refreshing composition, moisturizing it, mixing it with a plasticizer, aging and introducing it into the waste mixture, such as to expand technological capabilities by utilizing dusty waste foundries, moisturizing the refreshing composition is carried out by the slurry of a wet dust collection system in an amount of 0.1-4.0% by weight of the spent molding mixture. Indicators In the manufacture of the prototype With the proposed method of preparation with exposure for min with exposure for min. 10 25 10 25 The compressive strength of the sample in the wet state (MPa) at the mixing time, min 1 3 5 The tensile strength of the sample on a chip in the wet state (MPa) 0.08. 0.12 0.18 0.10 0.18 0.20 0.10 0.14 0.20 0.13 0.20 0.20 Table continuation Indicators In the manufacture of the prototype With the proposed method of preparation with exposure for min with exposure for min 10 25 10 25 with mixing time, min 1 0,021 0,025 0,028 0,036 3 0.032 0.047 0,044 0.052 5 0,047 0.056 0.052 0.058 The tensile strength of the sample in the zone of moisture condensation (MPa) during mixing, min 1 0.0023 0.0025 V 0.0034 0.0039 3 0.0033 0.0037 0.0043. 0.0047 5 0.0045 0.0049 0.0049 0.0050