A method for preparing ceramic corundum abrasive based on recycled alumina material

Abstract

This invention belongs to the field of abrasive preparation technology, specifically relating to a method for preparing ceramic corundum abrasive based on recycled alumina. It uses waste chips and slag from used alumina abrasives such as fused alumina or ceramic corundum as the main raw materials. Through six steps—degreasing, deironizing, desalting, grinding, drying, sintering, and crushing—the alumina component in the original abrasive is reused to prepare ceramic corundum abrasive with performance superior to fused white alumina, achieving the goal of reducing solid waste emissions and reusing resources. The recycled ceramic corundum abrasive prepared by this technology has low production costs, saves energy, requires less equipment investment, and is environmentally friendly.

Description

Technical Field

[0001] This invention belongs to the field of abrasive preparation technology, specifically relating to a method for preparing ceramic corundum abrasive based on recycled alumina. Background Technology

[0002] Alumina corundum abrasive is one of the most widely used abrasives in current industrial manufacturing. It possesses good mechanical properties, stable high-temperature grinding performance, is relatively simple to produce, and is significantly cheaper than diamond and silicon carbide abrasives, making it highly sought after in the processing of steel workpieces. Corundum abrasives have seen substantial development and play an irreplaceable role in many fields such as automotive manufacturing and aerospace. Currently, my country's alumina abrasives are mainly fused white corundum and brown corundum, manufactured using traditional electrofusion processes. Fused corundum is produced by melting bauxite at temperatures exceeding 3000℃ using an electric arc discharge to form α-shaped alumina crystals, which are then cooled in water or allowed to cool naturally before being crushed and graded. This method is energy-intensive, and the pouring of molten corundum requires skilled operation and carries high risks. The resulting corundum abrasive particles are mainly millimeter-sized aggregates, resulting in short grinding life due to transgranular fracture during grinding. The abrasive fragments formed after crushing form waste slag, becoming a type of industrial solid waste, and transportation and disposal incur additional costs.

[0003] Compared to fused alumina, ceramic alumina abrasives do not exhibit transgranular fracture. During grinding, the shedding of surface micro-particles creates a new grinding surface, resulting in excellent self-sharpening properties and a long service life. Furthermore, the shedding of surface micro-particles significantly reduces the heat generated during grinding, minimizing the risk of ablation on the workpiece. Based on these advantages, many domestic abrasive companies have invested in the research and development of ceramic alumina abrasives and have made significant progress. Examples include invention patents such as Qingdao Ruikel New Material Technology Co., Ltd. (CN 116789459 A), Shandong Panshi Alumina Co., Ltd. (CN115140754 B), and Hunan Joseph Technology Co., Ltd. (CN 113845356 B), which have developed ceramic alumina abrasives from different raw materials through various methods. However, regardless of whether it is fused alumina abrasive or ceramic alumina abrasive, their raw materials are all derived from natural minerals or processed products of natural minerals. They are both a consumption of non-renewable natural resources, and after use, they inevitably generate waste and slag, causing pollution and requiring special treatment. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing ceramic corundum abrasive based on recycled alumina material. This method uses recycled alumina abrasive (slag waste) as raw material, processes, sinters, and crushes it to produce a ceramic corundum abrasive with a service life longer than that of fused white corundum. The ceramic corundum abrasive prepared by this technology has low production costs, low energy consumption, low equipment investment, and is environmentally friendly, thus solving some waste and solid waste treatment problems.

[0005] This invention is achieved through the following technical solution:

[0006] A method for preparing ceramic corundum abrasive based on recycled alumina, characterized by comprising the following steps:

[0007] 1) Degreasing and iron removal treatment of recycled alumina materials;

[0008] 2) Remove soluble salts from the degreased and de-ironized alumina recycled material;

[0009] 3) Add additives to the degreased, deironized, and soluble salt-free recycled alumina material and grind it to obtain alumina powder;

[0010] 4) Dry and calcine the ground alumina powder;

[0011] 5) The calcined alumina coarse material is crushed and classified to obtain ceramic corundum abrasive.

[0012] The alumina recycled material of the present invention is recycled alumina abrasive slag, which may be derived from any one or a mixture of both of fused alumina abrasive (waste fused alumina abrasive after grinding) and ceramic alumina abrasive (waste residue and shavings of ceramic alumina abrasive).

[0013] Furthermore, when the iron content in the alumina recycled material of the present invention is not higher than 10%, the degreasing and iron removal process in step 1) involves placing the alumina recycled material into a high-temperature kiln, controlling the supply of natural gas and air to be 1:12 to 1:15 (referring to the volume ratio under the same pressure) during the kiln combustion heating process, and controlling the overall temperature of the kiln to be 950 to 1050°C, so that the oil in the alumina recycled material is completely burned and decomposed under high temperature and oxygen-rich conditions, and the iron in the alumina recycled material is converted into magnetic iron oxide, which is then separated by an electromagnet.

[0014] Furthermore, when the iron content in the recycled alumina material of the present invention is higher than 10%, pre-iron removal is performed using an electromagnet.

[0015] Furthermore, after iron removal, the total iron content in the recycled alumina of the present invention is less than 3%.

[0016] Furthermore, in step 2) of the present invention, the method of soaking and rinsing with tap water is used for desalination.

[0017] In this invention, the desalination process involves immersing the iron-removed alumina recycled material in tap water and repeatedly rinsing it with circulating water to dissolve soluble sodium salts, potassium salts, chlorides, sulfates, and other components in the alumina recycled material. Depending on the salt content of different batches of alumina recycled material, multiple rinsing processes can be performed.

[0018] Furthermore, the conductivity of the tap water after desalination and soaking is less than 0.2 S / m.

[0019] Furthermore, based on the weight of the degreased, deironized, and soluble salt-removed alumina recycled material, the additives added in step 3) by mass percentage are 1%~2% Cr2O3, 0.5%~1.5% Na3AlF6, and 3‰~5‰ Y2O3.

[0020] Additives are beneficial for low-temperature sintering and increasing toughness. Specifically, Na3AlF6 can reduce the difficulty of sintering during the calcination process, allowing calcination to be completed at a slightly lower temperature. The proportion of 0.5% to 1.5% is controlled because adding too much of the above substances is detrimental to the density of the sintered product. Cr2O3 and Y2O3 are beneficial for eliminating cracks at the Al2O3 interface during sintering to increase the toughness of the particles. At the same time, the light pink color of Cr2O3 in Al2O3 can mask the dark hue caused by trace amounts of Fe.

[0021] Furthermore, the particle size of the alumina powder after grinding in step 3) of the present invention is d50=1.0~1.5μm.

[0022] d50 refers to the particle size value corresponding to a cumulative distribution percentage of 50%. d50 is also known as median diameter or median particle size.

[0023] Furthermore, in step 4) of the present invention, the drying temperature is 60~80℃.

[0024] Furthermore, in step 4) of this invention, the calcination conditions are as follows: calcination at 900~1000℃ for 1 hour, then heating to 1450~1500℃ for another 2 hours, followed by natural cooling to room temperature.

[0025] The present invention employs a calcination process where the calcination is first carried out at 900~1000℃ for 1 hour, and then the temperature is raised to 1450~1500℃ for 2 hours. Compared with the traditional method of directly raising the temperature to 1450~1500℃ for calcination, there is a low-temperature holding process, which allows the particles to undergo a densification process, resulting in a product with better density and grinding life.

[0026] The present invention preferably uses a programmable temperature-controlled high-temperature furnace or a zone-controlled temperature tunnel kiln for calcination.

[0027] The main raw material used in the preparation of ceramic corundum abrasives in this invention is recycled alumina abrasive fragments, which can be derived from fused alumina abrasives or ceramic corundum abrasives. By using industrial waste that would otherwise require disposal costs as raw material for production, this invention solves some of the waste treatment problems, reduces production costs, and minimizes environmental pollution.

[0028] The beneficial effects of this invention are:

[0029] 1) Using recycled alumina as raw material reduces the cost of industrial waste disposal and production raw material costs, making it green, environmentally friendly, and sustainable;

[0030] 2) The iron removal process can recover a large amount of iron filings and iron oxides. These recyclables can be used as raw materials in the iron and steel metallurgy industry, which is environmentally friendly and also helps companies increase their revenue.

[0031] 3) The process is simple, with low restrictions on the residual amount of alumina recycled material after iron and salt removal, making it easy to start production and requiring less equipment investment.

[0032] Experiments have shown that the density of the ceramic corundum abrasive obtained by this invention can reach 3.75~3.85 g / cm³. 3 Its Vickers microhardness reaches Hv1800 or higher, and its grinding service life exceeds that of fused white fused alumina. Attached Figure Description

[0033] Figure 1 Flowchart of the preparation process of the ceramic corundum abrasive of the present invention;

[0034] Figure 2 The graph shows the change in the unbroken rate of fused white fused alumina over time during the wear resistance test.

[0035] Figure 3 The graph shows the change in the unbroken rate of the ceramic corundum abrasive prepared in Example 1 over time in the wear resistance test.

[0036] Figure 4 The graph shows the change in the unbroken rate of the ceramic corundum abrasive prepared in Example 2 over time in the wear resistance test.

[0037] Figure 5 The graph shows the change in the unbroken rate of the ceramic corundum abrasive prepared in Example 3 over time in the wear resistance test. Detailed Implementation

[0038] The present invention will be further described below with reference to the embodiments.

[0039] Example 1: The alumina recycled material in this example is fused corundum abrasive material discarded after grinding, with an iron content of less than 10%.

[0040] As Figure 1 shown: The preparation method of the ceramic corundum abrasive in this embodiment is as follows:

[0041] 1) Degreasing and iron removal treatment of alumina recycled materials with low iron content:

[0042] Burn the alumina recycled materials with iron content below 10% in a tunnel furnace with an oxidizing atmosphere. The fuel of the tunnel furnace is natural gas. Adjust the volume ratio of the supply flow rates of natural gas and air to be 1:12. Control the temperature of the gas flame in the furnace at 1000°C through the total flow rate. Burn the alumina recycled materials in the kiln for 25 minutes. Transfer the burned materials out of the tunnel furnace. After cooling, remove the iron oxides in the burned alumina with an electromagnet.

[0043] In this treatment step, while removing iron in the alumina recycled materials, organic substances such as oil stains are also removed by gas burning.

[0044] 2) Remove the soluble salts from the degreased and iron-removed alumina recycled materials:

[0045] Place the degreased and iron-removed alumina recycled materials in a water storage tank separated by an ultra-fine mesh. Soak them thoroughly with tap water to dissolve soluble sodium salts, potassium salts, chlorides, sulfates and other components in the alumina recycled materials. Open the valve at the bottom of the filter screen to make the soaking water flow into the water storage tank below. Measure the conductivity of the soaking water. If the conductivity is lower than 0.2 S / m, it is qualified.

[0046] Note: Depending on the source and batch of the alumina waste residue, its salt content is different, and multiple rinses can be carried out.

[0047] 3) Incorporate 1.5% of Cr2O3, 1.5% of Na3AlF6, and 5‰ of Y2O3 into the iron-removed, salt-removed and soluble-salt-removed alumina recycled materials by mass percentage. After adding water, carry out ball milling to obtain alumina powder with an average particle size d50 = 1.0 μm.

[0048] 4) After drying the ball-milled alumina slurry at 60°C to obtain agglomerated alumina block materials, directly transfer them to a high-temperature furnace for calcination. The calcination conditions are as follows: The furnace temperature rises from room temperature to 960°C in 3 hours; keep the temperature at 960°C for 1 hour; then rise from 960°C to 1470°C in 2 hours; stop heating after keeping the temperature at 1470°C for 2 hours, and naturally cool to room temperature.

[0049] 5) Crush and classify the calcined alumina coarse materials to obtain ceramic corundum abrasives with different particle sizes.

[0050] Example 2: The alumina recycled materials in this example are the waste residues and waste chips of ceramic corundum abrasives, and the iron content is higher than 10%.

[0051] like Figure 1 As shown: The preparation method of the ceramic corundum abrasive described in this embodiment includes the following steps:

[0052] 1) Degreasing and iron removal treatment for recycled alumina with high iron content:

[0053] Alumina recycled material with an iron content higher than 10% is first separated from the ferromagnetic substances using an electromagnet. The pre-removed alumina recycled material is then calcined in an oxidizing atmosphere in a tunnel furnace. The tunnel furnace is fueled by natural gas, with the natural gas to air supply volume ratio adjusted to 1:15. The total flow rate controls the furnace flame temperature to 1050℃, calcining the alumina recycled material for 30 minutes. After calcination, the material is transferred out of the tunnel furnace, cooled, and then the magnetic iron oxides in the calcined alumina are recovered again using an electromagnet.

[0054] 2) Remove soluble salts from the degreased and de-ironized alumina recycled material:

[0055] The degreased and de-ironized alumina recycled material is immersed in tap water and repeatedly rinsed with circulating water to dissolve the soluble salt components in the alumina slag. Depending on the salt content of different batches of alumina waste slag, multiple rinsings may be performed. After filtration, as the soluble salt decreases, the conductivity of the rinsing water also decreases. The filtered water is tested using a conductivity meter, and desalination is complete when the conductivity is below 0.2 S / m.

[0056] 3) The filtered alumina powder was mixed with 2% Cr2O3, 1% Na3AlF6 and 3‰ Y2O3 by mass percentage, and then ball-milled with water to obtain alumina powder with an average particle size d50=1.3μm.

[0057] 4) After the ball-milled alumina slurry is dried at 70℃ to obtain clumped alumina blocks, it is directly transferred to a high-temperature furnace for sintering. The calcination process is as follows: heat up to 1000℃ in 3 hours; hold at 1000℃ for 1 hour; then heat up from 1000℃ to 1500℃ for another 2 hours; hold at 1500℃ for 2 hours and then stop heating, allowing it to cool naturally to room temperature.

[0058] 5) The calcined alumina coarse material is crushed and classified to obtain ceramic corundum abrasives of different particle sizes.

[0059] Example 3: The alumina recycled material in this example is the waste residue and shavings of fused alumina abrasive and ceramic alumina abrasive discarded after grinding, with an iron content of less than 10%.

[0060] like Figure 1 As shown: The preparation method of the ceramic corundum abrasive described in this embodiment includes the following steps:

[0061] 1) Degreasing and iron removal treatment of alumina recycled materials with low iron content:

[0062] Burn the alumina recycled materials with iron content below 7% in a tunnel furnace with an oxidizing atmosphere. The fuel of the tunnel furnace is natural gas. Adjust the volume ratio of the supply flow rates of natural gas and air to 1:13. Control the temperature of the gas flame in the furnace at 1030°C through the total flow rate. Burn the alumina recycled materials in the kiln for 20 minutes. Transfer the burned materials out of the tunnel furnace. After cooling, remove the iron oxides in the burned alumina with an electromagnet.

[0063] This treatment step removes iron in the alumina recycled materials and also removes organic substances such as oil stains through gas burning.

[0064] 2) Remove soluble salts from the degreased and iron-removed alumina recycled materials:

[0065] Place the degreased and iron-removed alumina recycled materials in a water storage tank separated by a superfine mesh. Soak them thoroughly with tap water to dissolve soluble sodium salts, potassium salts, chlorides, sulfates, etc. in the alumina recycled materials. Open the valve at the bottom of the filter screen to let the soaking water flow into the water storage tank below. Measure the conductivity of the soaking water. If the conductivity is lower than 0.2 S / m, it is qualified.

[0066] Note: Depending on the source and batch of the alumina waste residue, its salt content is different, and multiple rinses can be carried out.

[0067] 3) Incorporate 1.0% Cr2O3, 0.5% Na3AlF6, and 3‰ Y2O3 into the iron-removed, salt-removed, and soluble-salt-removed alumina recycled materials by mass percentage, add water, and then carry out ball milling to obtain alumina powder with an average particle size d50 = 1.5 μm.

[0068] 4) After drying the ball-milled alumina slurry at 80°C to obtain a compacted alumina block material, directly transfer it to a high-temperature furnace for calcination. The calcination conditions are as follows: The furnace temperature is raised from room temperature to 900°C over 3 hours; hold at 900°C for 1 hour; then raise the temperature from 900°C to 1,450°C over 2 hours; stop heating after holding at 1,450°C for 2 hours, and naturally cool to room temperature.

[0069] 5) Crush and classify the calcined alumina coarse material to obtain ceramic corundum abrasives with different particle sizes.

[0070] Performance test and analysis:

[0071] 1. Abrasive density:

[0072] Test the densities of the ceramic corundum abrasives prepared in Example 1, Example 2, and Example 3 through a liquid hydrostatic balance, and the densities are 3.75 g / cm 3 、3.85 g / cm3 3.79 g / cm 3 Slightly smaller than dense white corundum without air bubbles (density 4.00 g / cm³). 3 ).

[0073] 2. Vickers microhardness:

[0074] As shown in Table 1, the micro Vickers hardness of the ceramic corundum abrasives prepared in Examples 1, 2, and 3, tested using a digital display micro Vickers hardness tester, is as follows:

[0075] Table 1

[0076]

[0077] As can be seen from Table 1, the hardness of the ceramic corundum abrasive prepared by the present invention is slightly lower than that of non-porous white corundum (Hv2200~Hv2300).

[0078] Test conditions: diamond indenter, load 1kg, holding time 15 seconds.

[0079] 3. Wear resistance test: The grinding life of the ceramic corundum abrasive prepared by this patent method was evaluated using the method proposed in invention patent CN 115140754 B, with electrofused white corundum abrasive of the same particle size as the standard reference. The test results are shown in Tables 2, 3, and 4.

[0080] Table 2: Comparison of Wear Resistance Tests between Ceramic Corundum Abrasive and Fused White Corundum Abrasive in Example 1

[0081]

[0082] Table 3: Comparison of Wear Resistance Tests between Ceramic Corundum Abrasive and Fused White Corundum Abrasive in Example 2

[0083]

[0084] Table 4: Comparison of Wear Resistance Tests between Ceramic Corundum Abrasive and Fused White Corundum Abrasive in Example 3

[0085]

[0086] like Figures 3-5 As shown: Plot the data from Tables 2, 3, and 4, perform curve fitting, and take the grinding time corresponding to a 50% integrity rate, such as... Figure 2As shown, the grinding time for 50% crushing of fused white fused alumina is 135.6 minutes. Under the same conditions, the ceramic fused alumina abrasive prepared in Example 1 requires 234.8 minutes to crush 50%, the ceramic fused alumina abrasive prepared in Example 2 requires 207.3 minutes to crush 50%, and the ceramic fused alumina abrasive prepared in Example 3 requires 216.2 minutes to crush 50%. All of these are significantly better than the grinding service life of fused white fused alumina.

[0087] In summary, the results show that the ceramic corundum abrasive obtained by the present invention through degreasing, de-ironizing, de-salting, adding calcining aids to recycled alumina material, followed by grinding, drying, and calcination, has better density, hardness, and grinding life than fused white corundum.

Claims

1. A method for preparing ceramic corundum abrasive based on recycled alumina, characterized in that, Includes the following steps: 1) The alumina recycled material is treated to remove oil and iron. The process involves placing the alumina recycled material into a high-temperature kiln, controlling the natural gas to air supply ratio at 1:12 to 1:15 during the kiln combustion heating process, and controlling the overall kiln temperature at 950 to 1050℃. This allows the oil in the alumina recycled material to be completely burned and decomposed under high-temperature and oxygen-rich conditions, and the iron in the alumina recycled material to be converted into magnetic iron oxides. These oxides are then separated by an electromagnet. After iron removal, the total iron content in the alumina recycled material is less than 3%. 2) Remove soluble salts from the degreased and de-ironized alumina recycled material; 3) Add additives to the degreased, deironized, and soluble salt-free alumina recycled material and grind it to obtain alumina powder. Based on the weight of the degreased, deironized, and soluble salt-free alumina recycled material, the additives added by mass percentage are 1%~2% Cr2O3, 0.5%~1.5% Na3AlF6, and 3‰~5‰ Y2O3. 4) Dry and calcine the ground alumina powder; 5) The calcined alumina coarse material is crushed and classified to obtain ceramic corundum abrasive.

2. The method for preparing ceramic corundum abrasive based on recycled alumina material according to claim 1, characterized in that, When the iron content in recycled alumina is higher than 10%, pre-iron removal is performed using an electromagnet.

3. The method for preparing ceramic corundum abrasive based on recycled alumina material according to claim 1, characterized in that, In step 2), the method of soaking and rinsing with tap water is used for desalination. After desalination, the conductivity of the soaked tap water is measured and is less than 0.2 S / m.

4. The method for preparing ceramic corundum abrasive based on recycled alumina material according to claim 1, characterized in that, Step 3) The particle size of the ground alumina powder is d50=1.0~1.5μm.

5. The method for preparing ceramic corundum abrasive based on recycled alumina material according to claim 1, characterized in that, Step 4) The drying temperature is 60~80℃.

6. The method for preparing ceramic corundum abrasive based on recycled alumina material according to claim 1, characterized in that, Step 4) The calcination conditions are: calcination at 900~1000℃ for 1 hour, then heating to 1450~1500℃ for another 2 hours, followed by natural cooling to room temperature.

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