RU1784609C - Thixotropic ceramic-concrete mixture for vibrational casting - Google Patents

Abstract

Usage: compositions of thixotropic ceramic concrete mixtures for vibrocasting, used for lining the outlet troughs, continuous continuous casting of steel. The inventive mixture contains a ceramic cementitious slurry with a pH of 10-10.5 based on high-alumina fireclay 28-30%, mullite chamotte fraction up to 10 mm 45-66.9%, a finely ground mixture of corundum and quartz in a stoichiometric ratio corresponding to the mullite, 5-25% and high alumina refractory powder with a content of alumina of 60% and magnesium oxide of 4-7%, 0.1-1.5%. Characteristics: the exposure time of the samples in the forms of 30-45 min, the compressive strength after hardening in the liquid glass solution of 68.6-79.5 I / mm2. 2 tab.

Description

FIELD OF THE INVENTION This invention relates to compositions of refractory thixotropic ceramic concrete mixtures for vibrocasting, used for lining exhaust gutters, continuous casting of steel, steel mill, for the manufacture of large-sized blocks and shaped products for various purposes.

Ceramic concrete mix is known, where a mullite suspension is used as a binder, and two fractions (10-15 and 1.6-2.5 mm) in a ratio of 3: 1 (by weight) as a filler scrap of MLO-62 products. The disadvantage of this mixture is the long exposure time of the products in the molds (24-36 hours).

Ceramic concrete mix is known, where high-alumina mixture is used as a binder in a cement slurry, and as a filler, the products MLO-62 are fractions of 5-15 mm with a component ratio of 40-55 and 60-65%, respectively

The disadvantage of this mixture is that the manufactured products must be kept in molds for 20-24 hours.

Also known is a ceramic concrete mixture based on a high-conductivity ceramic in a cement slurry (V KB C) from scrap products MLO-62 and aggregate of a similar chemical composition with grain size: 2.5-5.0; 5.0-10.0; 10.0-15.0 mm.

The disadvantage of this ceramic concrete mixture is the long exposure time of the product in molds - from 18 to 24 hours

Closest to the proposed solution is a thixotropic ceramic concrete mix for vibrolito of the following composition, wt.%:

Xj

00

about oh

High alumina ceramic in slurry suspension 28-30

Mullite aggregate fractions 10-0 mm 45-67 5 Fine-milled corundum-pre-quartz additive mullite stoichiometry, fractions less than 0.1 mm 5-25, Yu

The disadvantage of this thixotropic ceramic concrete mixture is the long exposure time of molded products in forms of 1.5-5 hours.

The thixotropic ceramic concrete mixture 15 has good mobility and is formed by vibrocasting at a moisture content of 7-9%. The structure formation of such a mixture in products made on its basis (loss of mobility and transition to solid state - 20) occurs when the content of kinetically free water in the casting system is reduced to 3-4%, the latter in the known compositions is achieved by using a porous filler with 25 large water absorption of 10-15%, while the exposure time of the product in the form until the end of its structural formation is determined by the duration of the process of absorbing an excess of 30 kinetically free water Fill the grains . The final hardening of the ceramic concrete mixture takes place after drying at 105-110 ° C, when durable water-resistant adhesive joints between solid particles are formed in it, due to polycondensation processes 35.

. The goal is to reduce the exposure time of products in the form, i.e. hardening of concrete mixture. 40

The goal is achieved in that the thixotropic ceramic-concrete mixture for vibrocasting, including high-alumina ceramic in a cement slurry, homogeneous with a cementitious aggregate and 45 finely ground corundum-quartz admixture of mullite stoichiometry, additionally contains high alumina refractory powder, 50% wt.

High Alumina

ceramic in thick

suspension 28-30

Mullite aggregate, fractions 10-0 mm 45-66.9 55

Fine-milled corundum quartz additive of mullite stoichiometry 5-25

Refractory powder

high alumina 0.1-1.5

The finely ground corundum quartz additive of mullite stoichiometry promotes the formation of a coagulation-thixotropic structure, which allows the products to be formed after 1.5-5.0 hours.

The incorporation of a high alumina refractory powder further reduces the setting time and accelerates the structure formation process. Perhaps this phenomenon is explained by the fact that the high-alumina powder, when interacting with water, forms hydrated neoplasms, and in particular A (OH) 3 in colloidal form, which precipitate on the activated surface of the suspension and aggregate particles, changing their electrosurface properties.

The combination of changes in the surface charge of a part of dispersed particles to the opposite, as well as the formation of hydrates A (OH) 3, which bound the remaining kinetically free water, significantly accelerates the process of coagulation-condensation structure formation. This, in turn, makes it possible to have durable products in 30-45 minutes and to remove products from the molds or remove the template, for example, when lining a steel ladle.

An example implementation of the invention.

A thixotropic ceramic concrete mixture for vibrocasting (composition 2, table 1) is obtained by mixing high alumina ceramic in a cement slurry of 28.0 wt.%, Finely ground corundum-quartz additive with mullite stoichiometry 5 wt.%, Mullite aggregate 66.5 wt.% And 0.5 wt. % powder of high-alumina refractory for air-hardening solutions, TK 14-8-294-78.

A high alumina ceramic cement slurry is obtained by wet grinding of chamotte, which is crushed waste, scrap of MLO-62 products with a fraction of 2.5-0 mm in a ball mill with ceramic lining, a volume of 100 l, corundum balls with a diameter of 20-30 mm. The grinding is carried out in an alkaline medium (addition of water glass) at a pH of 10.0-10.5 and is carried out in three stages; on the first, 50 material is loaded from the total amount of chamotte introduced with a ratio of W: T 1: 5. Before loading, grinding media, dry chamotte and water are heated to 70 ° C. The first charge is milled until the suspension sample passes completely through a 0.063 mm sieve. Then a second charge is carried out - 25 wt.% Chamotte, adjust the pH with liquid glass to a value of 10.5 and continue grinding to a residue on a sieve

0.063 mm - 7.0-7.5%. After that, the pH value is also adjusted with liquid glass to a value of 10.5 and the final third load of chamotte is made, and grinding is carried out to a sieve residue of 0.063 mm - 10-11%.

In order to obtain a finely ground corundum-lime mixture of mullite stoichiometry of a fraction of less than 0.1 mm, corundum TU 14-8-384-81 is introduced into the finished high alumina ceramic cementitious slurry; May 72.% - of the total weight of the additive and quartz sand GOST 25551-78; 28 wt.%. Additional grinding (milling of the additive) is carried out for two hours.

The resulting high alumina ceramic cementitious slurry containing a finely ground corundum-quartz mullite stoichiometry additive is stabilized by mechanical stirring in a mill drum without grinding media for six hours. In this case, a uniform distribution of finely ground corundum-quartz additive in the suspension volume occurs and thixotropy appears due to physicochemical processes.

The preparation of a thixotropic ceramic concrete mixture is carried out in a gravitational laboratory mixer by mixing together a high alumina slurry containing a finely ground corundum-quartz additive, a mullite aggregate and a high alumina refractory powder for four minutes.

The addition of a high alumina powder additive is carried out by mixing all other components in a mixer.

The finished mixture, with a moisture content of 8%, is poured into metal molds - cubes 70 mm in size, pre-lubricated with machine oil, and vibrated on a vibrating table with a frequency of 50 Hz and an amplitude of 0.70 mm for two minutes. After the cessation of vibration, the setting time of the ceramic-concrete mixture (transition to the solid state) is determined. This corresponds to the preservation of the geometric shape of the vibrocast samples after removal of the side walls. The extracted samples are dried in an oven at 110 ° C to a residual moisture content of 0.5-1.0% and then

subjected to impregnation in a solution of water glass with a density of 1.06 g / cm3 for 30 minutes, followed by drying.

Mixtures of compositions 1.3-8 (table 1) were prepared according to the above procedure.

For all samples was determined; the setting time (hardening) of the mixture according to GOST 310.3-76, the compressive strength after hardening in a liquid glass solution according to GOST 4071-80. The test results of all mixtures are shown in table 2.

In composition 7, they used: for the preparation of a suspension, synthetic mullite of the PMLTS-2.5 brand fry 14-8-450-83), and as a mullmite filler, crushed scrap of mullite products (fr. Up to 10 mm), TU 14-8- 438 -83.

Composition 8 used: for the preparation of a suspension of crushed scrap fr. up to 2 mm of mullite-corundum products based on fused mullite and corundum MKPG-88 (TU-8-439-83) with a mass fraction of over 88%, crushed scrap (fr. up to 10 mm) of MKPG-88 products is used as a mullite filler.

In comparison with the prototype, the use of the proposed composition of the thixotropic ceramic-concrete mixture allows to reduce the exposure time of products in forms by an average of 3.2 times; to increase the mechanical strength after exposure to liquid glass in an average of 1.1 times; to increase labor productivity due to the turnover of forms and reducing the time of the technological process of manufacturing products.

Claims (1)

SUMMARY OF THE INVENTION A thixotropic ceramic concrete mixture for vibrocasting, comprising 28-30% ceramic cement slurry with a pH of 10.0-10.5 based on high-alumina fireclay, 45-66.9% mullite chamotte fraction up to 10 mm and 5-25% fine-ground mixture corundum and quartz in a stoichiometric ratio corresponding to the mullite, characterized in that, in order to reduce the exposure time of the products in the molds, it additionally contains a high alumina refractory powder with an alumina content of 60% and magnesium oxide 4-7% in quantity 0.1-1.5%. Table 1 ijj I, u