RU2122535C1 - Refractory material and method of making same - Google Patents

Abstract

FIELD: steel making, more specifically linings of chemical equipment operating at elevated temperatures in aggressive media. SUBSTANCE: refractory material comprises (wt parts): 0.0010-98.00 aluminium oxide; 0.0010-98.00 magnesium oxide; 0.0010-40.00 calcium oxide; 0.0001-60.00 zirconium oxide; 0.0010-25.00 silicon oxide; 0.0010-30.00 titanium and/or chromium oxide; 0.0010-70.00 silicon carbide; 1.0000-70.000 graphite; and 0.0010-20.00 pyrocarbon. In preparing refractory material, mixture components are mixed, and the mixture thus formed is molded, dried and fired in two stages, second stage being carried out in lower unsaturated and/or saturated hydrocarbons to obtain material comprising pyrocarbon. EFFECT: highly dense refractory material having higher thermal stability and reduced wettability with respect to molten metals and slags. 3 cl, 2 tbl

Description

 The invention relates to the production of refractory materials and, more specifically, to a high-density refractory material and a method for its production. Refractory materials are widely used in industry at various sites of steelmaking, for lining chemical equipment operating at elevated temperatures in aggressive environments.

 Refractory materials based on a high-alumina dense granular filler — chamotte and ligaments of refractory clay in the amount of 10–20% are known (Strelov K.K., Mamykin P.S. Refractory technology. - M.: Metallurgy, 1978, p. 254). Although the materials have good physical and mechanical characteristics, they are characterized by increased reactivity with respect to molten metals and slags, as well as low thermal stability, which reduces the service life.

One of the possible solutions to reduce the reactivity of refractory materials is to introduce carbon into its composition. So in accordance with Japanese patent application N 3141157, class. C 04 B 35/66, 06/17/91 a refractory designed for lining a blast furnace contains, wt.%: Β-Al ₂ O ₃ 10-80; C 5-25 and SiC 15-85. 2-10% sintering agent and 1-5% antioxidant are added to 100% of this mixture. The material has low thermal conductivity, increased resistance to alkalis, oxidation, abrasion and cracking. In addition, the refractory is characterized by increased wettability with respect to the environments in which it is operated, as well as insufficient thermal stability due to low thermal conductivity.

In the composition of a monolithic refractory containing zirconium carbide (Japanese Patent Application No. 01051381, class C 04 B 35/66, 02.27.89), graphite is introduced to reduce wettability. This refractory is characterized by increased corrosion resistance to molten cast iron and resistance to cracking at high temperatures. The material contains, wt.%: Zirconium carbide powder with a particle size of 44 μm 3-30; Al ₂ O ₃ , MgO or CaO 40-80, silicon carbide and / or silicon metal 2-5, alumina or phosphate binder 0.5-5, finely ground graphite the rest. The material is relatively porous, which does not allow its wettability to be reduced by molten metals and slags, and therefore it is quite reactive with respect to them. In addition, the high content of zirconium carbide in the refractory, making it resistant to cracking, significantly increases its cost.

 A known method of obtaining a refractory material having increased corrosion resistance to molten cast iron, as well as erosion and cracking. The method is carried out by adding water to raw materials prepared by mixing finely divided silicon carbide or silicon metal, aluminum oxide, magnesium or calcium with graphite and an alumina or phosphate binder. The resulting mass is formed by known methods, dried and receive the above refractory material. The resulting refractory material is not sufficiently dense in structure, it is quite well wetted by molten metals, as a result of which a relatively high reactivity with respect to these metals is manifested. The specified method does not allow to obtain a high-density refractory material.

 Thus, the object of the invention was to obtain a high-density refractory material with increased thermal stability and reduced cost and wettability with respect to molten metals and slags, as well as a method for producing such a material.

 The problem is solved due to the fact that the refractory material, including aluminum and magnesium oxides, silicon carbide and graphite, additionally contains oxides of calcium, zirconium and silicon, at least one of the oxides of titanium, chromium and pyrocarbon, in the following ratio, wt.h .: alumina 0.0010-98.00; magnesium oxide 0.0010-98.00; calcium oxide 0.0010-40.00; zirconium oxide 0.0001-60.00; silica 0.0010-25.00; titanium and / or chromium oxide 0.0010-30.00; silicon carbide 0.0010-70.00; graphite 1.0000-70.00; pyrocarbon 0.0010-20.00.

 The formulated problem is also solved due to the fact that calcium oxides are additionally introduced into the raw material mixture in the method for producing refractory material, including aluminum and magnesium oxides, silicon carbide and graphite, including mixing the components of the mixture, molding the resulting mixture, subsequent drying and calcining of the molded mass, zirconium and silicon, at least one of the oxides of titanium, chromium, firing the molded mass is carried out in two stages and its second stage is carried out in an environment of lower unsaturated and / or saturated hydrocarbons to obtain m material including pyrolytic carbon.

 The refractory material of the above composition has low porosity of the surface layer and wettability by molten metals and slags, as well as reduced reactivity with respect to the environments in which it is operated. The material is relatively inexpensive and is characterized by increased heat resistance.

 The following examples of specific performance explain, but do not limit the present invention.

 Examples 1-6. To prepare the refractory material, the oxides of aluminum, magnesium, calcium, zirconium, silicon, and also chromium or titanium oxide, graphite and silicon carbide are mixed in accordance with the compositions given in the claims. The mass is molded, the resulting preforms are subjected to primary calcination at 2000 K. The calcined refractory material is subjected to repeated calcination in methane at a temperature of 1700K. The specific compositions of refractories after the first and second stages of firing are shown in table 1.

 Samples of refractory materials are tested for slag and metal resistance. To determine metal and slag resistance, a suspended sample of the test refractory material in the form of a cylinder with a diameter of 50 mm is kept for 6 hours in molten slag of metallurgical production or metal at a temperature of 2000K, constantly rotating at a speed of 60 rpm. After the specified time, the sample is removed from the molten slag or metal and weighed. The metal and slag resistance of the refractory is judged by the change in the mass of the sample during the test. The smaller the relative change in mass after the test, the more resistant the material is to the respective media. The test results of samples of refractory materials for metal-slag resistance are given in Table 2.

 As can be seen from the data in Table 2, the relative mass change after tests for slag and metal resistance of the materials obtained in accordance with the invention (columns 3 and 5), in all cases is significantly less than that of control samples containing the same components, with the exception of pyrocarbon (columns 2 and 4). At the same time, metal and slag resistance increases on average by 30-40%.

 This is achieved by obtaining a high-density structure of the refractory, which results in reduced wettability, which is manifested in increased metal and slag resistance. Such a change in the structure of the material during pyroconsolidation leads to a decrease in the coefficient of linear thermal expansion by about 10 times and, as a consequence, to an increase in its thermal stability.

 For the implementation of the present invention using conventional equipment for forming the initial mass, subsequent drying and the first stage of firing the molded workpiece. The preparation of pyro-compacted high-density refractories is carried out in industrial electric vacuum furnaces.

 Thus, to obtain high-density refractories in accordance with the present invention does not require special equipment and significant capital costs.

Claims (1)

1. Refractory material, including aluminum and magnesium oxides, silicon carbide and graphite, characterized in that the material additionally contains oxides of calcium, zirconium and silicon, at least one of the oxides of titanium, chromium and pyrocarbon in the following mass ratio of components, parts by weight .:
Alumina - 0.0010 - 98.00
Magnesium Oxide - 0.0010 - 98.00
Calcium oxide - 0.0010 - 40.00
Zirconia - 0.0001 - 60.00
Silica - 0.0010 - 25.00
Titanium and / or chromium oxide - 0.0010 - 30.00
Silicon Carbide - 0.0010 - 70.00
Graphite - 1.0000 - 70.00
Pyrocarbon - 0.0010 - 20.00
2. A method of obtaining a refractory material, including aluminum and magnesium oxides, silicon carbide and graphite, comprising mixing the components of the mixture, molding the resulting mixture, subsequent drying and calcining of the molded mass, characterized in that the oxides of calcium, zirconium and silicon are additionally introduced into the raw material mixture, at least one of the oxides of titanium, chromium, the firing of the molded mass is carried out in two stages, and its second stage is carried out in an environment of lower unsaturated and / or saturated hydrocarbons to obtain a material including pyrocarbon d.

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