RU2206537C1 - Refractory concrete mixture - Google Patents

Abstract

FIELD: refractory materials. SUBSTANCE: refractory concrete mixture comprises 50-85 wt.-% of refractory filling agent based on aluminum oxide and 15-50 wt. -% of binding agent of the following composition, wt.-%: aluminum oxide-base refractory component, 84-97; sodium tripolyphosphate, 1.8-15.0; oxalic acid, 0.2-2.0. Oxalic acid in combination with sodium tripolyphosphate forms sol that promotes to friction decrease between particles and confers the enhanced fluidity to concrete solution and absence of chemically bound moisture ensures to intensify the rate of thermal treatment of lining concrete solution. EFFECT: improved properties of mixture. 1 tbl

Description

 The invention relates to the production of refractory solutions for the manufacture of linings, for example steel-pouring ladles, intermediate ladles and other units.

 Refractory concrete mixtures are known, including a refractory aggregate based on aluminum oxide, for example, a.s. USSR 673634, C 04 B 35/00 1979, a. from. USSR 555064, C 04 V 35/18 1977, a.s. USSR 876593, C 04 V 19/04, 1981.

 The closest in essence and coinciding features should be considered a refractory concrete mix according to a.s. USSR 673634, С 04 В 35/00 1979. It contains a refractory aggregate based on aluminum oxide and sodium tripolyphosphate.

The disadvantage of the prototype is that at speeds of temperature rise above 50 ^o / h does not provide the necessary set of strength of refractory concrete.

 The invention is aimed at reducing the heat treatment time of a refractory concrete lining.

 The technical result that is achieved by the invention is to accelerate the set of strength of refractory concrete when heated.

 To ensure this, the binder additionally contains oxalic acid in the composition, wt. %: refractory component based on alumina 84-97, sodium tripolyphosphate 1.8-15.0, oxalic acid 0.2-2.0 in the following ratio of components, wt.%: refractory aggregate based on alumina 50-85, the specified binder 15-50.

 Sodium tripolyphosphate, having low solubility in water, together with oxalic acid forms a sol, which helps to reduce friction between particles and gives greater fluidity to the concrete solution. When heated, a chemical interaction occurs with the formation of strong compounds at lower temperatures. A small amount of water and the absence of chemically bound moisture can intensify the speed of heat treatment of the concrete solution of the lining.

 When the content of oxalic acid is less than 0.2 wt.%, An insufficient amount of sol is formed to fluidize the refractory solution upon mixing with a minimum amount of water. As a result, it will be necessary to increase the amount of water, which reduces the density, increases the porosity of the lining and extends the time of its heat treatment. With an increase in oxalic acid content of more than 2.0 wt.%, The refractoriness of concrete decreases.

 When the content of the specified binder in the refractory concrete mixture is less than 15 wt. % refractory concrete mortar does not have the necessary fluidity, which requires an increase in water content and leads to an increase in the time of heat treatment of concrete. With an increase in the content of the specified binder more than 50 wt. % decreases refractoriness and the temperature of the onset of deformation under the load of refractory concrete.

 The invention is illustrated by the following examples.

To obtain a refractory concrete mixture, the following starting materials were used:
- corundum fr. 5-0 mm with an Al ₂ O ₃ content _of at least 97 wt.%;
- aluminum-magnesium spinel fr. 5-0 mm with a content of Al ₂ O ₃ 72 wt.%, MgO 26 wt.%;
- sodium tripolyphosphate according to GOST 3447.2-91, powder fr. less than 1 mm;
- oxalic acid, powder fr. less than 1 mm;
- a binder of the prototype: refractory clay 15, kaolin 15, dust from electrostatic precipitators of the drying drum 60, sodium tripolyphosphate 1,0; sulphite-yeast mash 9.

 Specific compositions of binders and refractory concrete mixtures are given in the table.

 To obtain a binder, a refractory component (corundum or aluminum-magnesium spinel), sodium tripolyphosphate and oxalic acid were simultaneously loaded into the ball mill in the stated ratios. Joint dry grinding of the components was carried out for 3 hours to obtain fractions of less than 50 microns.

 To obtain a refractory concrete mixture, the refractory aggregate (corundum or aluminum-magnesium spinel) was uniformly mixed with the obtained refractory binder in the stated proportions.

Refractory concrete mortar was prepared at the place of manufacture of the lining of the steel pouring ladle. To do this, 5 wt.% Water in excess of 100% was added to the refractory concrete mixture and mixed thoroughly until a fluid concrete was obtained, which was poured into the gap between the template and the reinforcing layer of the bucket. Then, the lining was dried for 6 hours using a gas burner, and after removing the template, it was heat treated to 1500 ^° C with a temperature rise rate of 100 ^° / h.

The properties of refractory concrete mixtures, depending on the heat treatment speed, were determined on samples with a size of 100x100x100 mm of the compositions shown in the table. After mixing with water, refractory concrete masses were poured into metal molds and subjected to vibration on a vibration table for 30 seconds. The samples poured into the molds were placed in a drying oven and dried at a temperature of 90 ^{° C.} for 2 hours. After this, the molds were broken and the samples were installed in a muffle furnace, where they were heat treated to a temperature of 1500 ^o С according to two modes: the first - when the temperature in the furnace was raised to 30 ^o / h, the second - 100 ^o / h. In heat-treated samples, the appearance and the following parameters were determined: compressive strength according to GOST 8462-85, open porosity according to GOST 4071.1-94, linear shrinkage or growth according to GOST 5402-81. The properties of the samples are given in the table.

As can be seen from the table, the properties of the samples of the patented compositions and the prototype at a heat treatment speed of 30 ^o / h are approximately the same. However, at a heat treatment speed of 100 ^o / h, the compressive strength of samples of patentable compositions is significantly higher, and open porosity is lower than that of samples of the prototype. The appearance of the samples of compositions 1, 2 did not change, while the prototype samples heated at a speed of 30 ^o / h had a network of cracks, and heated at a speed of 100 ^o / h, had cracks and fractures. This is evidenced by data on the growth of the material of the prototype, which leads to chips and destruction of the lining of the unit.

 Thus, the use of patented compositions of refractory concrete mixes allows to reduce the heat treatment time of refractory concrete for lining a metallurgical unit without affecting its thermomechanical characteristics.

Claims (1)

Refractory concrete mixture containing a refractory aggregate based on aluminum oxide and a binder in the form of a finely ground mixture of a refractory component based on aluminum oxide and sodium tripolyphosphate, characterized in that the binder additionally contains oxalic acid in the composition, wt.%:
Alumina based refractory component - 84 - 97
Sodium tripolyphosphate - 1.8 - 15.0
Oxalic acid - 0.2 - 2.0
in the following ratio of components, wt.%:
Alumina Refractory Aggregate - 50 - 85
Specified Binder - 15 - 50n

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