RU2000286C1 - Method for manufacture of rammed refractories - Google Patents

Abstract

The invention relates to the production of refractories and can be used in the manufacture of a protective liner for the reaction chamber of an apparatus designed to extract aluminum from a metal feed by distillation through volatile subhalides of aluminum or other purposes. Usage: the material is moistened with water in a ratio of 100: (8-10), then a solution of phosphoric acid with a density of 1.38 g / cm in a ratio of T: G 100: (16-21) is introduced. The mass of material thus prepared is packed into bulk forms, dried in air, and subjected to heat treatment to strengthen the printed material. The finished printed material can withstand heating up to 2000-2100 ° C without deformation, has a compressive strength of 180-245 kg / cm and is chemically resistant to the reaction medium MgF2 + 2AI 2AIF + Md carried out at a temperature of 1580-1700 ° C; S 73

Description

The invention relates to the production of refractory products and can be used in the manufacture of protective linings for reaction chambers in thermal apparatuses for the extraction of aluminum from alloys and other metal raw materials by distillation through volatile aluminum subhalides.

The use of phosphoric acid as a binder is known. This acid is used in the manufacture of printed articles from quartz clay, mullite-corundum and corundum masses with the introduction of it in terms of phosphorus oxide (PaOs) in an amount of from 1 to 3.5 wt.%.

The technical solution closest to this is a method of obtaining

refractory products, including mixing aluminum nitride with a phosphate binder in the required ratio, pressing the blanks and polymerizing at 80-100 ° C for 3 hours 2.

However, mixing dry with phosphoric acid causes their rapid interaction and rapid uneven hardening.

An object of the invention is to increase strength and chemical resistance.

This is achieved by the fact that in the method of manufacturing printed refractory products from aluminum nitride, comprising preparing a mixture of aluminum nitride with phosphoric acid, stuffing the mixture into volumetric forms, drying the packings in air O O O O

Yu

00

about

about

: heat treatment, aluminum nitride is mixed with water with respect to i Ж 1) 0 (0 10) and an aqueous solution oi rr.j) is introduced; hydrophoric acid with a density of 1.38, /, and; about wearing T: F 100: (16-21).

And the lripodonic recipe above is solid, unflappable. G is porked in weight units; g, 1 liquid - G - in the corresponding, different units (cm, dm m.

OyuiHccii, the invention is explained in the following description of process details

Due to wetting, it occurs as a muffling of the intense reaction of the interaction of the material with the binder. The introduction of more water to moisten the material than indicated in the recipe (8 K) o.ed.) leads to a decrease in the strength of hermetically sealed packings and even to cracking of the surface of the products; : n.:uee quantity - makes it difficult to change the number of links. The interaction between the .in g MP .-. Puminium mass and the orthophosphorus ... i i.-Logo gi is determined by the presence in g, "of a certain amount of Al20z: for k:,:, i Al20j and НзР04 aluminum is formed FTT connection.

The density of an aqueous solution of acid - 1 ZR was chosen experimentally. With such a density, the convenience of operation is ensured. D, undiluted acid is difficult to operate because of the small amounts necessary for its introduction and uniform mixing with the material. A greater dilution of the acid also negatively affects the quality of the packing, making it more friable, porous, and weak after heat treatment.

In terms of solid oxide (PaOb), the binder content is in the range of 21-16 units. an aqueous solution of orthophosphate acid with a density of 1.38 will be 8.08-10.35 wt.% in an anhydrous mixture of material

Violation of the quantitative content of the binder (16-21 volume units) towards an increase in its batch size during heat treatment of the packing leads to an increase in the volume of the mass — crawling out of the mold or formation of a cap (depending on the amount of excess binder), a decrease in the bond below the interval of decreasing the strength of the printed product (for example, when entering an acid solution in the amount of 16.0 cm, the compressive strength of the sample after calcination at 282 kg / cm2, and when entering 12.0 cm3 - 89 kg / m2).

The strength of the refractory product is characterized by a compressive strength ranging from 100-200

g

kg / cm - for products with a disguised reference.

Empirically, we had a mouth for those obtained by pressing (without

5 at a specific pressure of 1250 kg / cm, which were processed at 900 and 1100 ° C; the specific pressure was crushed at 140 and 260 kg / cm. Samples obtained using

Yu solution within 16-21 ob. strength was shown after heat treatment at 1000 ° C, respectively, 280-34 after heat treatment at 1900 180-245 kg / cm. Reached by

15, the strengths for printed aluminum oxide samples are not inferior to standard refractory products are considered satisfactory. tenacity ceramic products for

20 refractory (1580-1780 ° С), high-temperature (1770-2000 ° С) and of the highest tendency (over 2000 ° С). Nitride packings withstood treatment within the range of 1800-2100 ° С without

25 cts, therefore highly refractory can be evaluated.

Heat treatment of samples at 1000 ° C was carried out without a protective apron, higher in vacuum or under protection

30 on, since at high rates, aluminum nitride is oxidized in the atmosphere. During heat treatment, right or slightly higher, the right water was removed - free and bound,

35 juice strips 2100 ° C), phosphorus oxide was removed outside the bond, which was obtained by analysis of heat-treated samples. In them the content f

40 was of the order of 0.02%; Visual excretion (phosphorus compound was observed as haze

Thus, heat treatment 45 relieves the samples of the previously introduced binder, which was first necessary to ensure the strength of the samples that, at high temperatures of 50 pax, the role of the hardener is played by the sintering of nitride itself, and aluminum bonding is positive because the main mater, in the absence of an impurity, becomes more resistant 55 (and negative, chemically resistant - increases the pore mass.

Volumetric weight of crude gaskets with in the range of 2.2-2.3 g / cm, proc

kg / cm2 for a range of products, up to 500-700 at 1900-2000 ° С - 1.74-1.74 g / cm1

g

kg / cm - for products for emergency use.

Empirically, we have established for those obtained by pressing (without binding)

at a specific pressure of 1250 kg / cm and heat-treated samples at 900 and 1100 ° C, the specific crushing pressure is 140 and 260 kg / cm, respectively. Packing samples obtained using a binder

solution in the range of 16-21 ob. (cm, strength was shown after heat treatment at 1000 ° C, respectively 280-340 kg / cm2, after heat treatment at 19001980 ° C - 180-245 kg / cm. Achieved indicators

5, the strengths for printed samples of aluminum nitride are not inferior to the standards of a common refractory product and can be considered satisfactory. In terms of fire resistance, ceramic products are divided into:

0 refractory (1580-1780 ° С), highly refractory (1770-2000 ° С) and higher refractoriness (over 2000 ° С). Aluminum nitride packings withstood heat treatment in the range of 1800–2100 ° С without deformations5, therefore, they can be evaluated as highly refractory.

Heat treatment of packing samples up to 1000 ° C was carried out without a protective atmosphere, higher in vacuum or under argon protection, since at high temperatures, aluminum nitride is oxidized in the air. During heat treatment at 105 ° C or slightly higher, almost all water was removed — free and bound; with high-temperature gaskets (1800–2100 ° C), phosphorus oxide introduced into the binder was removed, which is confirmed by analysis of heat-treated samples. They contain phosphorus

0 was on the order of 0.02%. Visually, gas evolution (phosphorus compound) was observed in the form of haze.

Thus, the high temperature 5 heat treatment removes the packing samples from the previously applied binder, which is necessary at first to ensure the strength of the samples. It can be assumed that, at high temperatures, the role of a hardener is played by the beginning sintering of aluminum nitride itself. Binding is of both positive importance, because the main material, in the absence of impurities, becomes more fire resistant (and chemically resistant), and negative increases the porosity of the packed mass.

The volumetric weight of the raw gaskets is in the range of 2.2-2.3 g / cm, calcined

at 1900-2000 ° С - 1.74-1.74 g / cm1

In order to obtain the samples necessary for further tests, they were prepared by packing in graphite cylindrical cups. Raw packings in glasses were dried for 2–3 days in air and a day — two were kept in an oven at 105 ° С, then, together with a glass, they were calcined for 1 h at 1000 ° С, freed from graphite shells and a final high-temperature was carried out. (1800-2100 ° C) calcination.

The main application of the nitride aluminum packing being developed was for the manufacture of protective linings for reaction chambers of furnaces for distilling aluminum through aluminum subfluoride (AIF) from aluminum metal feed. Along with the production of printed linings on the side, its molding and heat treatment could be carried out in the furnace itself. Ceramic, graphite, metal can be used for the forming shells of the packing. After the low-temperature heat treatment stage, they are removed, since after drying at 105 ° C, the packings acquire sufficient strength (240-290 kg / cm2). Further heat treatment of the printed lining should be carried out according to a schedule of a gradual rise in temperature under a vacuum or protective argon atmosphere. Other uses for aluminum nitride printed products may appear, where a different, lower temperature heat treatment level will be satisfactory.

Heat-treated (at 1900 ° C and above) packed samples were tested in the reaction medium (MgF2 + 2AI 2AIF Md) of the process of distillation of aluminum through subfluoride, where MgF2 and AI are in the liquid state through subfluoride, where MgF2 and AI are TC in the liquid state, AIF and MD — vapor form.

To carry out this reaction, temperatures in the range of 1580-1700 ° C are necessary; the process is carried out under a protective atmosphere of argon. The samples were kept in the reaction melt at 1580–1640 ° С for 3 h and passed the test — they did not deform, did not crack, but added about 76% in weight due to the saturation of the pores of the packed mass with magnesium fluoride salt. For comparison, prefabricated samples tested at the same time (compression) were added an average weight of 26%. The increased porosity of the packings is explained by the fly over during calcination of the binder and water. Perhaps the removal of phosphorus from the packing favored the preservation of the chemical resistance of the samples. The presence of magnesium fluoride in the pores of the packing is neutral to the chemical resistance of aluminum nitride. The compressive strength of the samples after testing in the reaction was about 280 kg / cm

Example 1. Take 100 g of powder of aluminum nitride, 21 cm (ml) of an aqueous solution of NZRO density of 1.38 g / cm and 10 cm (ml) of water. The aluminum nitride powder is mixed with 10 cm of water, then 21 cm3 of an acid solution is uniformly distributed into the moistened mass of the material. The resulting composition is filled by hand tampering into cylindrical graphite cups (with an inner diameter and a height of up to 25 mm, wall thickness 2.5 mm). Volumetric weight of crude stuffed mass is 2.287 g / cm3. The beaten forms are kept for 3 days in air and 2 days in an oven at 105 ° C.

After drying, the samples were calcined at 1000 ° С with a b-rhino at this temperature for 1 h. After that, the packing samples were freed from the graphite shell and subjected to high-temperature firing at 1900-1980 ° С for 1 hour under vacuum. Volumetric weight after firing - 1.74 g / cm. sample strength - 245 kg / cm. The phosphorus content in the sample was 0.019%. The packing was tested for chemical resistance. The samples withstood the test, retained their shape, but were saturated with magnesium fluoride, the bulk density became 3.06 g / cm. The strength of the sample was 280 kg / cm2.

PRI me R 2. The components of the printed composition: 100 g of powder of aluminum nitride, 16 cm of an aqueous solution of phosphoric acid with a density of 1.38 g / cm and 8 cm of water. The starting aluminum nitride powder was uniformly moistened with 8 cm of water, then 16 cm of an aqueous acid solution was introduced into the material. The resulting wetted binder composition was manually tamped into graphite cups (with inner diameters and 25 mm high). The packings were kept in air for 3 days. After that, they were dried in an oven at 105 ° С for 2 days (the drying time depends on the load weight of the samples). Subsequent laying of packing samples at 1000 ° C and 1-hour exposure led to the following indicators: bulk density - 1.93 g / cm3, strength 282 kg / cm2. Samples calcined at 1000 ° С after being freed from graphite cups were subjected to high-temperature firing in vacuum at a temperature of 1900– 2000 ° C for 1 h. After such firing, the bulk density became 1.794 g / cm, the crushing strength was 179 kg / cm2, the content phosphorus in the sample amounted to 0.02%.

The heat-treated material was tested for chemical resistance, bulk density became 3.11 g / cm. The printed material tested in the reaction medium showed a strength of 274 kg / cm2.

Claims (1)

SUMMARY OF THE INVENTION A method of manufacturing a printed refractory product, comprising preparing a mixture of aluminum nitride with a phosphate binder, molding, drying in air, heat treatment, characterized in that the phosphate binder is an aqueous solution of orthophosphoric acid with a density of 1.38 g / cm3, and first aluminum nitride is mixed with water in a ratio of 100: (8-10), after which the indicated phosphoric acid solution is introduced in a ratio of T: W 100: (16-21).