RU2410349C1 - Method of producing molten-cast comsilite ctc material for lining non-ferrous metallurgy thermal units - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: proposed method comprises preparing mix material by mixing quartz sand powder, metallurgical magnesite, alumina- and fluorine-containing components, smelting of produced mix material, pouring the melt into die, melting, removing casting from die, annealing and cooling. Said alumina- and fluorine-containing components represent aluminium fluoride or magnesium fluoride, and, additionally, potash, taken in the following ratio, wt %: quartz sand - 23.8-38.9, metallurgical magnesite - 15.2-29.4 refractory clay 4.3-31.5 fluoride-containing component - 17.1-18.9, and potash - 15.2-16.8. In preparing mix material, pelletising is additionally performed to produce granules with diametre of 5-20 mm of plastic mass obtained by adding water to aforesaid mix. Granules are dried, annealed at 800-900°C, fused at 1450-1500°C, and cooled down at the rate of 35-45°C/h.

EFFECT: expanded operating performances of proposed lining.

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Description

The invention relates to the field of building materials and can be used in the manufacture of cast material for lining thermal units for working with aggressive environments, melts, mainly for melting non-ferrous metals.

From the existing level of technology there is a known method for producing molten cast material for lining thermal units, including preparing a mixture by mixing sand, magnesite, clay, alumina and a fluorine-containing component, melting the resulting mixture at 1500-1550 ° C, producing castings, annealing them and cooling (SU 649669 publ. 03.03.1979).

The closest analogue to the claimed invention is a method for producing fused-cast material for lining thermal units of non-ferrous metallurgy, including preparing the mixture by mixing powdered quartz sand, metallurgical magnesite, alumina and potassium silicofluoride, in an amount, crushed by a hammer mill and runners before passing through a sieve providing, for example, the content, g: potassium fluoride 27, alumina 13, magnesium oxide 29, silicon oxide 36, melting the resulting mixture at a temperature e 1500-1600 ° C, pouring the melt into the mold, exposure of 3-15 minutes demolding, annealing at a temperature of 750-800 ° C and cooling in the furnace to a temperature of 150-200 ° C, then - to normal temperature. (Collection of scientific works and articles "Problems of stone casting", Malyavin AG Technological modes of manufacturing shaped castings from fluorosilicate melts, Kiev, Naukova dumka, 1975, issue 342 3).

The disadvantage of this method is the low temperature limit of the operation of the lining of the obtained material.

The technical result of the invention is the expansion of the temperature range of the lining.

The specified technical result is achieved by the fact that in the method for producing fused-cast material for lining thermal units of non-ferrous metallurgy, which includes preparing the mixture by mixing powdered quartz sand, metallurgical magnesite, alumina-containing and fluorine-containing components, melting the resulting mixture, pouring the melt into the mold, holding, extracting the casting from forms, annealing and cooling, refractory clay is used as an alumina-containing component, f - as a fluorine-containing component aluminum toride or magnesium fluoride, and additionally potash, in the following ratio of components, wt.%:

quartz sand 23.8-38.9 metallurgical magnesite 15.2-29.4 fire-clay 4.3-31.5 fluorine-containing component 17.1-18.9 potash 15.2-16.8

during the preparation of the charge, additional pelletizing is carried out to obtain granules with a diameter of 5-20 mm of plastic mass obtained by adding water to the mixture of these components, and drying the granules, annealing at a temperature of 800-900 ° C, melting at a temperature of 1450-1500 ° C, cooling - at a speed of 35-45 ° C / hour.

The preparation of the mixture includes the following operations: dosage of the components — weighing, mixing the components of the mixture, which can be carried out in a closed mixer, moistening to obtain a plastic mass — was carried out in closed runners, the formation of a pelletized mixture with the formation of balls - granules with a diameter of 5-20 mm and their drying. It is possible to use defective products, sprues, and fluorophlogopite casting profits, for which they are crushed in a jaw crusher and the resulting product is melted together with a fresh charge, adding it to the last by simple mixing with a pelletized charge. In this case, the content of fluorophlogopite casting waste is 10-20% in relation to the fresh pelletized charge. Powder materials - potash, sand, fluorine-containing components were mixed with kaolin powder. Water was added to the resulting mixture until a plastic mass was obtained, from which granules with a diameter of 5-20 mm were rolled out, which were dried and used as such to be loaded into crucibles during melting. The technology for producing the melt from the pelletized charge does not differ from the technology for melting the powder mixture, but dusting and spilling of the material are excluded, and a lower rate of fluorine volatilization is visually noted, the temperature of the fluorophlogopite melt is 1450-1550 ° С. The molds are poured with a continuous stream when the melt temperature reaches 1430 ° -1450 ° C. Under the conditions of melting the charge in an electric arc furnace, the melt formation is forced, the duration of the entire melting weighing 100-150 kg is about 1 hour. Therefore, the fluorine loss under real melting conditions is not high and the formation of the required material structure is stable. The use of refractory clay, which allows pelletizing the charge mixture, also helps to reduce fluoride losses when using aluminum fluoride. Conducted control experiments showed that with the same temperature and time parameters of the melting as the powder mixture, the formation of mica-crystalline material in the case of using pelletized mixture is more successful. Crystallites in the form of spherulites are formed with a diameter of 5-10 mm. Cast samples have a zonal structure, consisting of three zones: the cortical zone, the intermediate zone and the inner zone.

The cortical zone has a dense fine-crystalline structure, the intermediate one is composed of elongated columnar mica crystals, and the inner one consists of equiaxed crystallites. The color of the synthesized material is yellowish. In the case of the use of metallurgical magnesite powder containing impurities of iron and other elements, the fused-cast material is obtained a darker blackish-gray color, however, in this case, it is mainly represented by fluorophlogopite crystals. X-ray phase analysis of the samples of synthesized materials showed that they are composed mainly of the mineral phase, corresponding to the indices for potassium fluorophlogopite.

The use of magnesium fluoride, which is a more thermally stable compound in comparison with aluminum fluoride, provides a decrease in fluorine losses during melting of a charge with magnesium fluoride and, therefore, this charge is more environmentally friendly.

The use of pelletized calcined (dried) mixture creates the prerequisites for changing the traditional technology of preparation of the mixture and the process of obtaining the melt in an arc furnace. This improves environmental conditions for the production of fluorophlogopite castings by eliminating the dusting of the charge during loading into the smelting furnace and during the smelting process, as well as by reducing fluorine losses during melt formation.

For casting, it is recommended to use sand-clay one-time molds with a dried, heated surface, graphite and metal permanent molds, heated to a predetermined temperature of 200-500 ° C. It is also advisable to use foundry molds and cores from liquid-filled self-hardening molding mixtures based on quartz sand and sodium liquid glass, which are widely used in foundry production of metals and alloys, as well as in the manufacture of shaped castor casting.

The main technical indicators of the synthesized mica crystals were determined.

These indicators include: density of materials, compressive strength, thermal coefficient of linear expansion, heat resistance, expressed in the number of thermal shocks (heat exchange) until cracks appear when samples are cooled from a temperature of 900 ° C and subsequent cooling in running water with a temperature of 20 ° C, melting point.

The density of the materials was determined by the standard method on samples of size (10 × 10 × 10) mm. The density of mica crystals for potassium fluorophlogopite, depending on the type of raw materials, was (2.65-2.85) g / m ³ .

The compressive strength was determined on cubes with a rib value of 5 mm. Samples were ground before testing to ensure parallel support faces. The compressive strength was 80-100 MPa.

The thermal coefficient of linear expansion for different materials was (11-11.5) · 10 ^-7 deg ^-1 within the temperature range from 0 ° C to 1000 ° C, i.e. in the indicated temperature range the increase in linear dimensions will be 0.1%.

The heat resistance of the materials was tested on cubes with 12 mm ribs during cyclic heating to 900 ° C and rapid cooling in cold water. The cubes of the material, after cooling in water, were dried and placed in a furnace for reheating, where they were kept at 900 ° С for 15 min for complete heating, and then dumped into water. Samples of all fused-cast mica crystals withstood more than 200 thermal cycles and did not collapse due to the appearance or formation of cracks.

The melting temperature was determined on samples in the form of plates 20 × 20 × 5 mm in size, which were placed on a substrate of refractory material and heated until softening and melting of the samples were noted, the melting point of sodium fluorophlogopite was about 1200 ° C, and potassium fluorophlogopite synthesized using magnesium fluoride or aluminum fluoride exceeded 1380 ° C.

The composition of the mixture and the test results are shown in tables 1 and 2

Table 1 The composition of the charge No. Component Content, wt.% Code of composition F-Mgl Code of composition F-Agl Magnesium fluoride 17/8 Aluminum fluoride 18/0 3 Potash 15/4 15/5 four Metallurgical Magnesite 16/0 25/5 5 Quartz sand 23/8 36/5 6 Fire-clay 27/0 4/5 Total weight 100.0% 100.0%

table 2 Test results Name of indicator F-Agle F-Mgl Strength under compression, MPa, not less than: - at a temperature of 20 ° C 80 95 Bending strength, MPa, not less than: - at a temperature of 20 ° C 17 twenty Density, g / cm ³ 2.75-2.85 2.80-2.90 Open porosity,% 0.6 0.6 Thermal stability, water heat exchange, not less 200 200 Softening start temperature, ° С, not lower 1380 1380 Electrical resistivity at 1000 ° С, Ohm · cm 1.2 · 10 ⁶ 1.2 · 10 ⁶ Thermal coefficient of linear expansion,% 0.1 0.1

Claims (1)

A method of producing a molten cast material for lining thermal units of non-ferrous metallurgy, including preparing a mixture by mixing powdered quartz sand, metallurgical magnesite, alumina and fluorine-containing components, melting the resulting mixture, pouring the melt into the mold, holding, extracting the cast from the mold, annealing and cooling, characterized in that use refractory clay as an alumina-containing component, aluminum fluoride or magnesium fluoride as a fluorine-containing component, and additional potash in the following ratio of components, wt.%:
quartz sand 23.8-38.9 metallurgical magnesite 15.2-29.4 fire-clay 4.3-31.5 fluorine-containing component 17.1-18.9 potash 15.2-16.8
during the preparation of the charge, additional pelletizing is carried out to obtain granules with a diameter of 5-20 mm of plastic mass obtained by adding water to the mixture of these components, and drying the granules, annealing at a temperature of 800-900 ° C, melting at a temperature of 1450-1500 ° C, cooling at a speed 35-45 ° C / h.