Method for producing fused zirconia solid spheres by titration method

Abstract

The invention relates to the technical field of inorganic non-metallic materials, in particular to a method for producing electric melting zirconium oxide solid spheres by using a titration method. The method comprises the following steps: uniformly mixing zirconium oxide powder and a stabilizer to form a mixed raw material; and preparing a consumable electrode by adopting the mixed raw material, then melting the end part of the consumable electrode into zirconium oxide melt, and dripping to form the electric melting zirconium oxide solid ball. The method comprises the following steps: melting the end part of a consumable electrode to form a zirconium oxide solution, gathering the zirconium oxide solution into liquid drops with a certain size under the action of surface tension, and naturally dropping from the tail end of the electrode under the action of gravity to prepare the electric melting zirconium oxide solid sphere. The preparation method is short in technological process, and the prepared product is good in sphericity degree, high in density and uniform in chemical component.

Description

A method for producing fused zirconia solid spheres using titration Technical Field

[0001] This invention relates to the field of inorganic non-metallic materials technology, specifically to a method for producing fused zirconia solid spheres using titration. Background Technology

[0002] Fused zirconia is widely used as a refractory material, ceramic pigment, advanced abrasive, and surface sand material in the foundry industry due to its high melting point, high chemical stability, low thermal conductivity, and excellent wear resistance. Solid zirconia balls, as an ideal ceramic grinding media and refractory aggregate, require high standards for sphericity, density, and uniformity of chemical composition.

[0003] Currently, the main methods for producing zirconia spheres are: extrusion spheroidization: zirconia powder is mixed with a binder, extruded into strips, and then cut and spheroidized. Spheres produced by this method have poor sphericity, a wide size distribution, and are prone to internal defects, affecting their service life.

[0004] Compression molding: This method uses a mold to compress and shape powder. It is inefficient, causes significant mold wear, and is prone to uneven density for large spheres.

[0005] Spray granulation method: such as Chinese invention patent with publication number CN110171970A, zirconium salt solution is sprayed and pyrolyzed to generate spherical powder, but the resulting powder is mostly hollow or porous with low density, which cannot meet the requirements of high-performance grinding media.

[0006] Electrofusion method: This method involves melting raw materials at high temperatures in an electric arc furnace and then cooling them to obtain high-density zirconia. However, traditional electrofused zirconia produces irregular particles after crushing, making it difficult to directly obtain spherical products. To obtain spheres, the electrofused zirconia blocks typically need to be crushed and ground again, and then sphericalized using the powder forming process described above. This process is lengthy, energy-intensive, and the product performance is limited by the secondary forming process.

[0007] Therefore, developing a method for directly and continuously preparing high-density (density ≥99.0%, corresponding to actual true density: ≥5.90 g / cm³) and high sphericity (true sphericity >95%) fused zirconia solid spheres has significant industrial application value. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a method for producing fused zirconia solid spheres by titration, so as to directly and continuously prepare high-density, high-sphericity fused zirconia solid spheres.

[0009] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a method for producing fused zirconia solid spheres using titration, comprising the following steps: uniformly mixing zirconia powder with a stabilizer to form a mixed raw material; preparing a consumable electrode using the mixed raw material; and then, under the protection of an inert gas, melting the end of the consumable electrode into molten zirconia and dripping it to form a fused zirconia solid sphere.

[0010] The beneficial effects of this invention are as follows: This invention prepares fused zirconia solid spheres by melting the end of a consumable electrode to form a molten zirconia solution, which, under the action of surface tension, aggregates into droplets of a certain size and drips naturally from the end of the electrode under the action of gravity. This preparation method has a short process flow and produces products with good sphericity, high density, and uniform chemical composition. Detailed Implementation

[0011] To explain in detail the technical content, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments.

[0012] A method for producing fused zirconia solid spheres using titration includes the following steps: uniformly mixing zirconia powder with a stabilizer to form a mixed raw material; preparing a consumable electrode using the mixed raw material; and then, under inert gas protection, melting the end of the consumable electrode into molten zirconia and dripping it to form a fused zirconia solid sphere.

[0013] As described above, the beneficial effects of this invention are as follows: This invention prepares fused zirconia solid spheres by melting the end of a consumable electrode to form a zirconia melt. Under the influence of surface tension, this solution aggregates into droplets of a certain size, which then drip naturally from the electrode end under gravity. This preparation method is a one-step process with a simplified procedure, combining melting and forming into one step. Solid spheres are obtained directly from the cooled molten droplets, eliminating the lengthy steps of crushing, grinding, pressing, and sintering in traditional processes, thus significantly reducing energy consumption and production costs. Because it involves direct cooling from the molten state, the resulting zirconia spheres have a density close to the theoretical density, are free of pores and defects, and have a highly uniform chemical composition. The spheres, naturally formed by surface tension, have extremely high sphericity (true sphericity > 95%), a smooth surface, and excellent product performance.

[0014] Furthermore, the stabilizer is at least one of yttrium oxide, calcium oxide, and magnesium oxide.

[0015] As described above, adding stabilizers allows zirconia to maintain its tetragonal or cubic crystal phase at room temperature, preventing material cracking due to volume changes caused by crystal transformation, thereby improving the material's stability and reliability. The addition of stabilizers significantly improves the material's mechanical properties, such as plasticity, toughness, and strength. During the electrofusion process, the addition of stabilizers helps reduce the material's porosity.

[0016] Furthermore, the amount of stabilizer added accounts for 3 to 10% of the total mass of the mixed raw materials.

[0017] As can be seen from the above description, both excessively high and low stabilizer content may cause some adverse changes in the electrical and mechanical properties of the material.

[0018] Furthermore, the specific preparation method of the consumable electrode is as follows: the mixed raw materials are pressed into rods or blocks to serve as consumable electrodes.

[0019] As can be seen from the above description, the preparation method is simple and convenient.

[0020] Furthermore, the consumable electrode is placed in an electric arc furnace, and under the protection of an inert gas, the high temperature generated by the electric arc melts the end of the consumable electrode into molten zirconium oxide.

[0021] Furthermore, the electric arc current of the electric arc furnace is 800~1200A, and the consumable electrode is fed at a constant speed of 5~8mm / min.

[0022] As can be seen from the above description, by controlling the arc current and the feed speed, the size of the droplets can be stably controlled, thereby achieving controllable production of product particle size and narrow particle size distribution.

[0023] Furthermore, as the molten zirconia drips, it passes through the cooling medium to form solid fused zirconia spheres.

[0024] As described above, when molten zirconia drips, it passes through the cooling medium, causing it to cool rapidly and improving the sphericity of the fused zirconia solid spheres.

[0025] Furthermore, the cooling medium is a flowing inert gas.

[0026] As can be seen from the above description, melting and cooling under an inert atmosphere can effectively prevent the phase transformation and contamination of zirconium oxide.

[0027] Furthermore, the inert gas is argon or nitrogen.

[0028] Furthermore, the flow rate of the cooling medium is 8~12 m / s.

[0029] As can be seen from the above description, by controlling the flow rate and temperature of the cooling medium, the cooling rate of the sphere can be adjusted, thereby optimizing its microstructure and phase composition.

[0030] Furthermore, the particle size of the fused zirconia solid spheres is 0.5~10 mm.

[0031] As described above, the collected zirconia spheres are sieved to obtain products with the desired particle size range.

[0032] Furthermore, the fused zirconia solid spheres are polished.

[0033] As can be seen from the above description, polishing can be performed optionally to remove surface burrs.

[0034] In the following examples, the zirconia powder has a purity greater than 99.5%, and the inert gas has a purity of not less than 99.99%.

[0035] Embodiment 1 of the present invention is a method for producing fused zirconia solid spheres using a titration method, the specific steps of which are as follows: S1: 95 kg of zirconia powder and 5 kg of yttrium oxide are mixed in a V-type mixer for 4 hours to form a mixed raw material; S2: The mixed raw material is pressed into a cylindrical consumable electrode with a diameter of 30 mm under a pressure of 200 MPa; S3: The consumable electrode is installed in a vacuum arc furnace and evacuated to a vacuum of 1×10⁻⁶. -2 After Pa, argon gas is introduced to -0.05MPa. After arc ignition, the arc current is controlled at 800A and the voltage at 40V. At the same time, the consumable electrode is fed at a constant speed of 5mm / min, so that the end of the consumable electrode melts into zirconia melt. The molten zirconia melt drips under the action of gravity, passes through the argon gas flowing at a flow rate of 10m / s, and quickly solidifies into solid spheres, falling into the rotating water-cooled copper collection tray at the bottom. S4: The collected spheres are graded through a standard sieve, and products with a particle size range of 1.8~2.2mm are selected. They are then lightly polished with a drum polisher to obtain a final product with a smooth surface and high sphericity.

[0036] Embodiment 2 of the present invention is: a method for producing fused zirconia solid spheres using titration, the specific steps of which are as follows: S1: 92 kg of zirconia powder and 8 kg of calcium oxide are mixed in a V-type mixer for 4 hours to form a mixed raw material; S2: the mixed raw material is pressed into a cylindrical consumable electrode with a diameter of 50 mm under a pressure of 200 MPa; S3: the consumable electrode is installed in a vacuum arc furnace and evacuated to a vacuum of 1×10⁻⁶. -2 After Pa, argon gas is introduced to -0.05MPa. After arc ignition, the arc current is controlled at 1200A and the voltage at 40V. At the same time, the consumable electrode is fed at a constant speed of 8mm / min, so that the end of the consumable electrode melts into zirconia melt. The molten zirconia melt drips under the action of gravity, passes through the argon gas flowing at a flow rate of 10m / s, and quickly solidifies into solid spheres, falling into the rotating water-cooled copper collection tray at the bottom. S4: The collected spheres are graded through a standard sieve, and products with a particle size range of 4.5~5.5mm are selected. They are then lightly polished with a drum polisher to obtain a final product with a smooth surface and high sphericity.

[0037] Embodiment 3 of the present invention is: a method for producing fused zirconia solid spheres using titration, the specific steps of which are as follows: S1: 90 kg of zirconia powder, 5 kg of yttrium oxide, and 5 kg of calcium oxide are mixed in a V-type mixer for 4 hours to form a mixed raw material; S2: the mixed raw material is pressed into a sphere with an end face area of ​​500 mm² under a pressure of 200 MPa. 2 The block shape serves as a consumable electrode; S3: The consumable electrode is installed in a vacuum arc furnace and evacuated to 1×10⁻⁶. -2 After Pa, nitrogen gas is introduced to -0.05MPa. After arc ignition, the arc current is controlled at 1200A and the voltage at 40V. At the same time, the consumable electrode is fed at a constant speed of 8mm / min, so that the end of the consumable electrode melts into zirconia melt. The molten zirconia melt drips under the action of gravity, passes through the nitrogen gas flowing at a flow rate of 8m / s, and quickly solidifies into solid spheres, which fall into the rotating water-cooled copper collection tray at the bottom. S4: The collected spheres are graded through a standard sieve, and products with a particle size range of 0.5~0.6mm are selected. They are then lightly polished with a drum polisher to obtain a final product with a smooth surface and high sphericity.

[0038] Embodiment 4 of the present invention is a method for producing fused zirconia solid spheres using titration, the specific steps of which are as follows: S1: Mixing 97 kg of zirconia powder and 3 kg of magnesium oxide in a V-type mixer for 4 hours to form a mixed raw material; S2: Pressing the mixed raw material into spheres with an end face area of ​​1000 mm² under a pressure of 200 MPa. 2 The rod-shaped electrode serves as a consumable electrode; S3: The consumable electrode is installed in a vacuum arc furnace and evacuated to 1×10⁻⁶. -2 After Pa, argon gas is introduced to -0.05MPa. After arc ignition, the arc current is controlled at 1000A and the voltage at 40V. At the same time, the consumable electrode is fed at a constant speed of 7mm / min, so that the end of the consumable electrode melts into zirconia melt. The molten zirconia melt drips under the action of gravity, passes through the argon gas flowing at a flow rate of 12m / s, and quickly solidifies into solid spheres, which fall into the rotating water-cooled copper collection tray at the bottom. S4: The collected spheres are graded through a standard sieve, and products with a particle size range of 9.8~10mm are selected. They are then lightly polished with a drum polisher to obtain a final product with a smooth surface and high sphericity.

[0039] The first comparative example of the present invention is as follows: The only difference between the first comparative example and the first example is that the flow rate of the cooling medium is 15 m / s.

[0040] The second comparative example of the present invention is as follows: The only difference between the second comparative example and the first example is that the flow rate of the cooling medium is 5 m / s.

[0041] The final products of Examples 1-4 and Comparative Examples 1 and 2 were tested, and the test results are shown in Table 1.

[0042] Table 1

[0043] As shown in Table 1, the fused zirconia solid spheres produced by the method of this invention have a bulk density ≥ 5.8 g / cm³. 3 It has a sphericity of ≥97% and its main phase is stable cubic zirconium oxide.

[0044] In summary, the method for producing fused zirconia solid spheres using titration provided by the present invention has the following advantages: 1. It combines the melting and forming processes into one, directly obtaining solid spheres by cooling molten droplets, which simplifies the process and greatly reduces energy consumption and production costs.

[0045] 2. Melting and cooling under an inert atmosphere effectively prevents phase transformation and contamination of zirconia. With the addition of stabilizers, the final product is a stable cubic or tetragonal zirconia.

[0046] 3. Direct cooling from molten droplets results in zirconia spheres with a density close to the theoretical density and extremely high sphericity.

[0047] 4. By controlling the arc current and feed rate, the size of the droplets can be stably controlled.

[0048] 5. By controlling the flow rate and temperature of the cooling medium, the cooling rate of the sphere can be adjusted, thereby optimizing its microstructure and phase composition.

[0049] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made using the present invention specification, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for producing fused zirconia solid spheres using titration, characterized in that, Includes the following steps: Zirconia powder and stabilizer are uniformly mixed to form a mixed raw material; a consumable electrode is prepared using the mixed raw material, and then the end of the consumable electrode is melted into molten zirconia under inert gas protection and dripped to form a solid fused zirconia sphere.

2. The method for producing fused zirconia solid spheres using titration according to claim 1, characterized in that, The stabilizer is at least one of yttrium oxide, calcium oxide, and magnesium oxide.

3. The method for producing fused zirconia solid spheres using titration according to claim 1, characterized in that, The amount of stabilizer added is 3-10% of the total mass of the mixed raw materials.

4. The method for producing fused zirconia solid spheres using titration according to claim 1, characterized in that, The specific preparation method of the consumable electrode is as follows: the mixed raw materials are pressed into rods or blocks to serve as consumable electrodes.

5. The method for producing fused zirconia solid spheres using titration according to claim 1, characterized in that, The consumable electrode is placed in an electric arc furnace, and under the protection of an inert gas, the high temperature generated by the electric arc melts the end of the consumable electrode into molten zirconium oxide.

6. The method for producing fused zirconia solid spheres using titration according to claim 1, characterized in that, As the molten zirconia drips, it passes through the cooling medium to form a solid fused zirconia sphere.

7. The method for producing fused zirconia solid spheres using titration according to claim 6, characterized in that, The cooling medium is a flowing inert gas.

8. The method for producing fused zirconia solid spheres using titration according to claim 7, characterized in that, The inert gas is argon or nitrogen.

9. The method for producing fused zirconia solid spheres using titration according to claim 6, characterized in that, The flow rate of the cooling medium is 8~12 m / s.

10. The method for producing fused zirconia solid spheres using titration according to claim 1, characterized in that, The particle size of the fused zirconia solid spheres is 0.5~10mm.

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