RU2549026C1 - Refractory gasketing compound - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: compound contains the following components, wt %: clay powder 7-15, water 2.8-4.2, polyatomic alcohol 2.8-4.2 and moulding sand is the rest.

EFFECT: improving the durability of a refractory gasketing compound.

7 cl, 2 tbl

Description

The invention relates to the field of foundry, and in particular to compositions of molding materials used for sealing welding forms, in particular welding forms for aluminothermic welding of joints of rail lashes and joints of turnouts on public and non-public railways, subway tracks, crane and tram tracks.

Currently, various foundry mixtures are known in the foundry industry. Among them, sand mixtures occupy a leading place, which provide a wide range of castings from a variety of alloys in a single and mass production. Quartz sand is used as a filler in such mixtures, and refractory clay and bentonite are used as a binder (See Foundry technology: Molding and core mixtures. Edited by S.S. Zhukovsky, A.N. Boldin and others. Bryansk, BSTU, 2002, p. 9). Sand mixtures are distinguished by the availability and relative low cost of the starting components, the ability to provide the required level of technological properties of the mixtures, as well as environmental safety. Therefore, such mixtures are widely used as refractory sealing mixtures for sealing welding forms during aluminothermic welding.

Quartz sand used in foundry in the Russian Federation is called molding, its and properties are regulated by GOST 2138-91. According to the aforementioned GOST, foundry sand based on quartz with a silica content of at least 93-98% is used for foundry, depending on the sand group. Refractory foundry molding clays are used as a binder in sand molding mixtures (See Foundry technology: Molding and core mixtures. Edited by S.S. Zhukovsky, A.N. Boldin et al. Bryansk, BSTU, 2002, p. 33 ) and bentonite clays (bentonite) (See Foundry technology: Molding and core mixtures. Edited by S. S. Zhukovsky, A. N. Boldin and others. Bryansk, BSTU, 2002, p. 43).

Compositions of sand-bentonite molding mixtures for foundry production (See Foundry technology: Molding and core mixtures. Edited by S. S. Zhukovsky, A. N. Boldin and others. Bryansk, BSTU, 2002, pp. 102-125) and compositions of sand-clay molding sand for foundry (See Foundry technology: Molding and core mixtures. Edited by S.S. Zhukovsky, A.N. Boldin et al. Bryansk, BSTU, 2002, pp. 149-152 ) contain a working mixture and fresh ingredients.

The technology of aluminothermic welding of rails involves carrying out work directly on the road, that is, at the place of work without removing the rails. Therefore, the reverse mixture in the composition of refractory sealing mixtures, as a rule, is not used. For sealing welding forms during aluminothermic welding of rails, a refractory sealing mixture is used, prepared in advance under production conditions on the appropriate stationary equipment from fresh components.

The closest to the claimed invention in composition and purpose is the refractory sealing mixture described in the patent of the Republic of Slovenia No. SK282419, priority dated February 13, 1997, “Sealing mixture for aluminothermic welding of rails” (“Zmes na utesnenie foriem pri aluminotermickom zvarani kolajnfe”).

According to the claims, the refractory sealing mixture contains molding sand, which is used as quartz sand with a particle size of from 0.6 to 0.2 mm, powder clay and water in the following proportions, wt.%:

Quartz sand  78-85% Powder clay  11-16% Water  4-6%

The disadvantage of this known refractory sealing mixture is its low survivability, especially at low temperatures. The survivability of a sealing mixture is understood as the time after which the composition loses its formability properties (See P. A. Borsuk, A. M. Lyass. Liquid self-hardening mixtures. M., Mechanical Engineering, 1979, p. 174).

As mentioned above, aluminothermic welding technology allows welding directly on the way. However, for countries with a cold climate, such as Russia, Finland, Sweden, Canada, etc., the use of known refractory sealing mixtures at low temperatures requires its storage at positive temperatures and the use of additional equipment to heat the mixture in case of freezing. If these factors are not given due attention, then during storage, transportation to the place of work and some expectation of such mixtures to be used on site during work, there is a high risk of the formation of frozen lumps in the mixture that cannot be loosened without additional heating of the mixture. The presence of lumps in the mixture (as well as any heterogeneities), in turn, can lead to local friability and leaks in the process of mold compaction, which will lead to subsequent leakage of termite metal when pouring molds.

The technology of aluminothermic rail welding involves the participation of a small number of specialists, and the need to use additional equipment significantly reduces the mobility of the welder group, increases its numerical strength, and increases the cost of work.

In addition, work on aluminothermic welding of rails is carried out, as a rule, in the “window” mode, i.e. in tight time frames when each technological operation is scheduled per minute. Therefore, specialists conducting aluminothermic welding of rails should not be distracted by adjusting the quality of the sealing mixture, and also, if possible, pay as little attention to the condition of the materials, their control and adjustment (the maximum elimination of the influence of the human factor): the sealing mixture should be high-quality in everything temperature range at which welding can be performed.

For Russia, this is especially true in view of the large length of railways and the remoteness of some sections from settlements, which does not allow transporting refractory sealing mixture at positive temperatures to the place of work in the autumn-winter time.

Increasing the survivability of the sealing mixture at positive temperatures is relevant when working in the summer, when the temperature at the work site can reach 30-40 ° C and higher.

Known refractory sealing mixtures under the influence of both high and low temperatures lose their properties and are practically unsuitable for high-quality work on aluminothermic welding of rails.

The present invention is the creation of a refractory sealing mixture for aluminothermic welding, with increased survivability at both positive and negative ambient temperatures at the place of work.

The task in a refractory sealing mixture containing foundry sand, powder clay and water is achieved by the fact that polyhydric alcohol is introduced into the composition, and the components are taken in the following proportions, wt.%:

Powder clay 7-15% Water 2.8-4.2% Polyhydric alcohol 2.8-4.2% Molding sand rest.

Various versions of the inventive sealing mixture are possible:

- bentonite can be used as powder clay;

- as polyhydric alcohol, for example, glycerin, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol can be used.

The technical result is to increase the survivability of the refractory sealing mixture for aluminothermic welding.

Specialists know the use of liquids with a low freezing point in various mixtures at low temperatures. For example, in RF patent No. 2406706, Composition for obtaining casts in trasology, priority from 07.20.2009. a gypsum mixture is described in which a liquid with a reduced freezing temperature is added (in one embodiment, 20-52 parts of ethylene glycol or propylene glycol antifreeze are added). However, in this known mixture, in contrast to the present invention, the survivability of the mixture, on the contrary, is extremely small. The authors of the mentioned patent set themselves the task of non-freezing and quick setting of the mixture at low temperatures. In the case of the invention, the opposite task is to increase the survivability of the refractory sealing mixture, both at negative and at positive temperatures.

In addition, the known solution proposes to use almost any liquid with a low freezing point, including the use of aqueous solutions of isopropyl, methyl, ethyl alcohols, or ethylene glycol or propylene glycol antifreeze.

A liquid with a low freezing point is also used to solve the problem of the present invention, but by no means is it suitable in completely different proportions. So, for example, the use of aqueous solutions of isopropyl, methyl or ethyl alcohols in the inventive refractory sealing mixture, on the contrary, reduces survivability and cannot be used to achieve the claimed technical result.

Survivability tests were conducted on nine different embodiments of the proposed refractory sealant mixture.

During the tests, the following parameters were measured:

- time (h) during which the volatiles are reduced by 1% at a temperature of + 20 ° C;

- survivability of the mixture at a temperature of + 20 ° C, h;

- the survivability of the mixture at a temperature of -5 ° C, h;

- survivability of the mixture at a temperature of -10 ° C, h;

- the survivability of the mixture at a temperature of -15 ° C, h;

The test results are shown in table 1 below.

To compare the inventive refractory sealing mixture with known analogues, the applicant conducted the same tests for 3 variants of the refractory sealing mixture according to patent SK282419 (prototype). The test results are shown in table 2 below.

From the data of tables 1 and 2 with the test results shows that the survivability of the inventive refractory sealing mixture is significantly higher than the known analogues. So, for example, at a temperature of -10 ° C, the survivability of the claimed mixture is tens of times higher than that of a known analogue, and hundreds of times at a temperature of -5 ° C!

The inventive refractory sealing mixture is prepared as follows. The components are taken according to a given proportion, the components are mechanically mixed until a homogeneous composition is formed. The order of introduction of the components may be different. Mechanical mixing of the components of the refractory sealing mixture can be carried out using roller-type runners, mixers and other mixing equipment.

According to the tests, the highest survivability at low temperatures has a refractory sealing mixture containing 86% of foundry sand, 7% of bentonite, 2.8% of water, 4.2% of propylene glycol. As can be seen from the data of table 1, at a temperature of -10 ° C, the survivability of such a refractory sealing mixture is 200 hours, which is up to 100 times higher than the survivability of the known refractory sealing mixture described in patent SK282419. And at positive temperatures, according to the tests, it is preferable to use the following composition: foundry sand 86%, bentonite 7%, water 2.8%, glycerol 4.2%.

Claims (7)

1. Refractory sealing mixture containing molding sand, powder clay and water, characterized in that it additionally contains polyhydric alcohol in the following ratio, wt.%:
Powder clay 7-15 Water 2.8-4.2 Polyhydric alcohol 2.8-4.2 Molding sand rest. 2. The refractory sealing mixture according to claim 1, characterized in that it contains bentonite as a powder clay. 3. The refractory sealing mixture according to claim 1 or 2, characterized in that it contains glycerol as a polyhydric alcohol. 4. Refractory sealing mixture according to claim 1 or 2, characterized in that it contains ethylene glycol as a polyhydric alcohol. 5. Refractory sealing mixture according to claim 1 or 2, characterized in that it contains propylene glycol as a polyhydric alcohol. 6. Refractory sealing mixture according to claim 1 or 2, characterized in that it contains diethylene glycol as a polyhydric alcohol. 7. Refractory sealing mixture according to claim 1 or 2, characterized in that it contains triethylene glycol as a polyhydric alcohol.