Method of preparing zirconium fused corundum and crystallizer for preparation thereof

FIELD: abrasive materials.

SUBSTANCE: invention is destined to provide high-strength corundum materials suited to manufacture of abrasive disks. Method of invention comprises preparing alumina-zirconium blend, fusing it from below and introducing reducer under surface of melt through the bed of blend in the second half-melting, tapping melt, and crystallization and cooling thereof. When being tapped and crystallized melt is protected against contact with air oxygen. Crystallizer contains metal vessel with upright metallic plates mounted inside the vessel with gaps between them. Crystallizer further has a holder to mount plate set. Outline of the lower part of plates follows outline of the vessel bottom. In the top part of each plate, V-shaped cut is made so that all cuts form together longitudinal groove to pour melt.

EFFECT: increased stability of physical structure on cooling, increased strength of grain and improved performance characteristics of abrasive tool, reduced laboriousness and material loss during crystallization operation, spared consumption of metallic reducer, and prolonged service time of crystallizer.

3 cl, 1 dwg, 1 tbl

 

The invention relates to the production of abrasive materials, in particular the production of high-strength refractory materials used for the manufacture of abrasive wheels.

Zirconium oxide includes aluminum oxide and zirconium oxide, the latter of which consists of phases with various modifications (see Aphesin and other Abrasive materials. Leningrad, "engineering", Leningrad branch, 1983, pagination 126-131).

A large number of high-temperature tetragonal modification of Zirconia having oxygen deficiency in the crystal lattice (ZrO1,96), results in high internal stresses in the material. High-temperature modification of zirconium dioxide is retained in a metastable state, which leads to high internal stresses, stacking to occur during operation of abrasive wheels high workloads, and causes cracking of the grain.

A method of obtaining zirconium oxide, selected as a prototype, comprising preparing a mixture of the oxides of aluminum and zirconium, its fusion with the introduction of the reductant, plums melt, crystallization and cooling (see ibid.).

Stabilization in the prototype is achieved by introducing reductant aluminum or carbon, resulting in a deficiency of oxygen ions is. However, this process leads to premature oxidation of the reducing agent with oxygen in the air during the entire melting and increases the consumption of reducing agent. Reducing agents, in addition to providing the necessary oxygen deficiency, is associated in the nitride dissolved in the melt of nitrogen, which causes crystallization increased gas porosity of the material. Nitrides are unstable compounds and prolonged contact with oxygen in the air are oxidized, that is, when the introduction of reducing agents before melting a significant part of the effect on the stabilization of the tetragonal phase of zirconium oxide and suppression of gas porosity disappears. When carbon black is used, the formation and secretion, causing increased gas porosity of the oxide.

Known mold to obtain zirconium oxide, selected as a prototype containing metal welded tank with hollow walls and placed inside the tank with a gap relative to each other parallel plates supported by brackets on the side shelf capacity. The tank is located on the wheeled undercarriage, movable on rails (see U.S. patent No. 4070796, 09 With 3/04 declared 27.12.71 published 31.01.78).

Spill the melt in the mold is carried out as follows: the container shall be placed so that p is pout, the gap between the parallel plates is opposite the filling hole of the furnace. This gap is filled with the melt, then the capacity of the slip on the rails and carry out filling the second gap, etc.

The disadvantages of the prototype mold:

- the complexity of the service (the need to ensure accurate movement and locking of the position of the vessel relative to the melting unit);

- loss of metal spatter, because the gap between the plates is quite small and the jet of the melt hits the upper ends of the plates when filling in each of the gaps;

- increased complexity of extracting each plate separately, as they are not connected with each other.

The challenges facing the creators of the complex of the invention:

- the stability of the physical structure upon cooling due to partial removal of internal stress of the material and, consequently, increase the strength of the grain and the improvement of the performance characteristics of the abrasive tool; reducing labor costs in the technology of production of zirconium oxide and losses of material during casting and solidification;

- saving of metal-reducing agents;

- increase the service life of the mould.

This is accomplished due to the fact that in a method of producing zirconium oxide, comprising preparing a mixture of the oxides of aluminum and zirconium, its fusion with the introduction of the reductant, plums races the lava, its crystallization and cooling, according to the invention the heat produced under the layer of the mixture, the reducing agent is injected under the surface of the melt through the layer of the charge in the second half melting, while in the process of casting and crystallization limit the contact of the material with oxygen.

The mold containing a metal container with vertical metal plates installed inside the tank with a gap relative to each other, according to the invention is equipped with a cartridge to install the entire set of plates, the contour of the lower part of the plate follows the contour of the bottom of the tank, and at the top of each plate is made V-neck, with cut-outs for all of the plates form a longitudinal tray for pouring of the melt.

In addition, the capacity of the mold is equipped with a water cooling system.

The invention provides:

- the preservation of the structure of the material without destroying it;

- reduction of internal stresses of the material at temperatures that exist in the technology and services abrasive wheels (0-200°).

When this stabilization structures, reduction of internal stresses while maintaining the optimum balance between high-temperature low-temperature tetragonal and monoclinic phases of Zirconia occurs when the limit contact is and the surface of the melt with oxygen (melting under a layer of charge), the introduction of the oxidant at the end of the melt through the layer of the charge under the surface of the melt, casting and crystallization while limiting the possibility of contact with air.

In addition, the introduction of the reducing agent in the second half of the melting provides the minimum gas porosity of the material, because the dissolved nitrogen is bound in the nitrides of aluminum, and the latter is not able to oxidize before the release of the melt is dissolved in the melt of nitrogen during crystallization is not allocated in the gas phase and does not form in the material gas pores.

The design of the mold also contributes to the achievement of these goals, namely execution on the upper ends of the plates, between which crystallized oxide, cut in the form of a tray promotes rapid pouring of the melt, ensuring minimal contact with air, and evenly spread (distribution) of the melt between the plates.

The thickness of the molded plates can be adjusted and selected in such a way as to ensure minimum energy consumption in crushing and obtain the maximum amount of grit desired fraction (10 to 1 mm).

The invention is illustrated by the drawing, which shows a mould.

The mold includes a water-cooled container 1 with a cylindrical bottom, placed on the carriage 2 to move in POS is the fill and discharge. Inside the container 1 placed the cartridge 3 with a set of parallel plates 4. At the top of each plate is made cutouts forming the groove 5 for the spreading of the melt. The lower contour of the plates 4 repeats the shape of the bottom of the tank 1.

As a result of implementation of the proposed method are zirconium oxide containing aluminum oxide and zirconium oxide, and zirconium oxide includes high-temperature phase and the low-temperature phase of ZrO2the ratio between within between 20:50-50:80. High-temperature phase has a tetragonal structure with high internal stresses and the low-temperature phase is monoclinic structure.

The process of melting the inventive zirconium oxide is illustrated by the following example.

Example.

In arc three-phase electric melting furnace with transformer capacity of 2000 kW downloaded 800 kg of a mixture of alumina and 75% with baddeleyite 25%. The content of Al2About3the alumina was 99.4%, the content of ZrO2in the baddeleyite - 98,7%.

Within 115 minutes melted 600 kg. of the Mixture, the remaining 200 kg, covered the mirror melt layer thickness of 150-200 mm

15 minutes before pouring into the melt under a layer of mixture introduced a special device 0.8 kg aluminum metal until it dissolves in the melt.

At the end of the melting furnace is lowered and filled what aspava the gap between the plates 4 of the mold, located in the center of the plate pack, then melt the chute 5, formed by the cutouts of the plates 4, spread over the entire length of the plate pack, consistently filling the remaining gaps (the gaps between adjacent plates). The casting time of 62 seconds.

Formed in the Central plate nastily shaped vessel with a melt depth of 20-30 mm Jet of the melt from the furnace, getting in this capacity, was not sprayed.

The thickness of the formed plates 8 mm, the crystallization 2,85 sec, cooling zakristallizuetsya plates of zirconium oxide without access of air between the plates to a temperature of 800° - within 3 minutes.

After cooling package steel plates together with the cassette 3 by a crane with a capacity of 8 tons was removed from the shell mold and unloaded plates of zirconium oxide in a special Bank, where the plates were cooled to ambient temperature in air. At a temperature of 880°and below the interaction of zirconium oxide with nitrogen and oxygen flows with an infinitesimal rate, oxidation of the surface of the material is not happening, not inducing additional stress.

The resulting material to grind and scattered on fractions. The fraction of grains with a size of 2500 μm in parallel with similar grain size obtained by the method-protot the PU, was subjected to x-ray analysis apparatus DRON-3 and dynamic tests, when the grain was thrown against a hard wall with a speed of 70 m/min, the Test was repeated ten times for each of the investigated grit. The results are given in the table.

Table
№№ p/pMaterial nameThe content of the tetragonal phase of ZrO2, %Share nerazrushaushsii grains, %
1.Selfthere - prototype81-100the 11.6
2.Selfthere by the present method28-4167,9
3.Selfthere firm Norton (USA)16-1963,4

Tested 1000 grains of 10 lots of 100 pieces. Shows the averaged results for all parties.

These tables show that selfthere of the proposed method in 5.8 times better resists dynamic loads, similar to those which it experiences in working in abrasive wheel than selfthere on the prototype method, and somewhat superior for these indicators selfthere firm Norton (USA).

1. A method of obtaining a zirconium oxide, comprising preparing a mixture of the oxides of aluminum and the circus is tion, its fusion with the introduction of the reductant, plums melt, crystallization and cooling, wherein the melting is performed under layer of the mixture, the reducing agent is injected under the surface of the melt through the layer of the charge in the second half melting, while in the process of casting and crystallization limit the contact of the material with oxygen.

2. The mold containing a metal container with vertical metal plates installed inside the tank with a gap relative to each other, characterized in that the mould is equipped with a cartridge to install the entire set of plates, the contour of the lower part of the plate follows the contour of the bottom of the tank, and at the top of each plate is made V-neck, with cut-outs for all of the plates form a longitudinal tray for pouring of the melt.

3. The mold according to claim 2, characterized in that the capacity of the mold is equipped with a water cooling system.



 

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FIELD: refractory industry, in particular manufacturing of refractory material for cladding of steel teeming ladles.

SUBSTANCE: claimed refractory material is obtained from refractory mass containing (mass %): <0.063 mm-grade corundum 16-20; 0.5-1.0 mm-grade periclase 4-12; graphite 6-10; metal aluminum 1-5; crystalline silicium 2-5; ethylene glycol 1.5-1.8; powdered phenol binder containing not more than 1.0 mass % of free phenol 2.7-3.3; and balance: 0.5-6 mm-grade corundum. Abovementioned <0.063 mm-grade corundum contains <0.020 mm grade in amount of 1-5 mass % or more based on total corundum mass.

EFFECT: refractory material with bulk stability, high mechanical strength and low oxidation susceptibility.

2 tbl

FIELD: refractory articles for manufacturing of ceramic units operating at 1800°C.

SUBSTANCE: claimed raw mixture contains (mass %): fused corundum of grade <0.05 mm 45-50; fused mullite of grade 0.4-1 mm 15-22; ethyl silicate 1-2: and additionally it contains fused corundum of grade 0.5-0.8 mm 20-25; fused mullite of grade 1.0-2.5 mm 5-8; and graphite 2-5. Method of present invention makes it possible to increase refractoriness up to 1900°C and simultaneously to decrease backing temperature to 1450-1550°C.

EFFECT: raw mixture for production of refractory articles with increased refractoriness.

2 tbl

FIELD: manufacturing refractory materials.

SUBSTANCE: refractory packing mass comprises, in mass %, 51-61 of grain corundum, 32-43 of the mixture of fine corundum and refractory clay, and 5.5-7.5 of orthophosphoric acid.

EFFECT: enhanced strength.

3 cl, 1 tbl

FIELD: metallurgy.

SUBSTANCE: proposed device includes cluster unit with blowing unit arranged inside it; it consists of coaxial parts molded from refractory materials in form of truncated cone or truncated pyramid; said parts are engageable with one another forming passages between them for delivery of inert gas; on side of larger base of blowing unit flange is provided with hole for delivery of inert gas. Formed between flange and blowing unit is cavity. Blowing unit combined with cluster unit includes cylindrical porous refractory insert located between working part of blowing unit and metal flange. In central part of its lower base there is spherical recess in form of segment for receiving inert gas; upper base has square seats forming gas distributing cavity before working part of blowing unit. Cylindrical metal envelope welded to metal flange has at last two external beads over circle or metal angles welded to it. Passages in working part of blowing unit are oriented in way of motion of gas or are formed by projections over entire length on one of engageable taper or trapezoidal components of blowing unit. Cluster unit and porous insert are made from refractory material of definite composition on base of mineral binder; working part of blowing unit is made from carbon-containing mass of definite composition on organic binder. Monoblock unit of cluster unit and blowing unit is molded in molding built-up molding rigging. Use is made of multi-stage manual pneumatic ramming at initial stage of molding and automatic vibration ramming at final stage for obtaining large blowing units, up to 500 mm in height. Monoblock thus molded is subjected to heat treatment at a temperature of 200-400°C.

EFFECT: enhanced reliability and safety; guaranteed capacity of unit; increased service life.

14 cl, 7 dwg

FIELD: manufacture of refractory materials of corundum composition; manufacture of articles for lining of different thermal units working at high temperatures.

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EFFECT: enhanced efficiency.

1 tbl, 4 ex

FIELD: non-iron metallurgy, in particular cladding of metal plunge.

SUBSTANCE: claimed refractory concrete contains (mass %): corundum mass 82-85; high-aluminous cement 4-5; electrical filter dust from silicium production 4-5; phosphoric acid 2-3; and water 3-4. Method for cladding manufacturing using the said concrete includes former installation into plunge; charging of refractory concrete into space between plunge internal wall and former, vibratory compaction, and two-step drying: at first at 20-250C for 5-7 days and then by graduated heating and drying. Namely, at first cladding is heated up to 1500C with rate of 6-80C/h and kept for 9-11 h; then cladding is heated up to 4000C with rate of 13-150C/h and kept for 14-16 h; then cladding is heated up to 6000C with rate of 20-220C/h and kept for 10-12 h. Cladding obtained by claimed method stands on silicium refining plunge up to 90 air thermal cycling.

EFFECT: cladding of improved strength.

2 cl, 4 tbl, 1 ex

FIELD: metallurgy, in particular equipment for steel treatment in liquid state.

SUBSTANCE: hydraulically cured bulk contains (mass %): high aluminous cement 2.5-5; alumina 18-25; modifying additive 1.5-3; and balance: electrocorundum. As modifying additive preliminary synthesized material containing 45-55 % of Al2O3 and 42-52 % of CaO is used.

EFFECT: refractory material sintered at 16000C with decreased opened porosity and increased mechanical strength.

2 tbl

FIELD: refractory industry, in particular corundum parts for ferrous and non-ferrous metallurgy.

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EFFECT: corundum-based articles with improved strength and heat resistance.

7 cl, 2 tbl

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EFFECT: improved cake quality.

1 tbl

FIELD: reworking of low-quality bauxites at high content of silica, iron, sulfur and carbonates into alumina by combined Bayer-sintering scheme.

SUBSTANCE: proposed method includes grinding bauxite in Bayer branch, concentration of it by removal of kaolinite and iron sands, leaching-out, thickening of pulp thus obtained, separation of aluminate solution from red mud, filtration of red mud immediately after thickening, hydrochemical processing of part of said mud for obtaining sodium hydroaluminate, decomposition of aluminate solution, calcination of aluminum hydroxide, evaporation of mother liquer at separation of circulating soda, organic admixtures and sulfates, thus obtaining circulating solution which is subjected to thorough evaporation for obtaining sodium hydroaluminate which is used in decomposition. Gallium is obtained from mother liquer after crystallization of sodium hydroaluminate. After separation of gallium, high-modulus solution is delivered for hydrochemical processing. Proposed method includes also preparation of charge in sintering branch from red mud at addition of alkaline, bauxite at silicon modulus below Bayer modulus of solid phase of separated kaolinite fraction, part of separated pulp after separation of iron sands, sintering of mud charge, leaching-out of sinter at simultaneous washing-out and separation of mud, delivery of aluminate solution to Bayer branch for leaching-out; proportioning of bauxite is performed for obtaining the caustic modulus in sinter not above 1.2.

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6 cl, 4 dwg, 1 tbl, 3 ex

FIELD: mining industry.

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3 cl, 4 dwg, 1 tbl

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