White corundum grinding material and preparation method thereof

Abstract

The invention relates to the technical field of white corundum abrasive materials, in particular to a white corundum abrasive material and a preparation method thereof.The preparation method comprises the steps of raw material mixing and bonding, blank pressing, drying, sintering, cooling, smashing and screening, the prepared white corundum abrasive material is high in single-particle compressive strength and breaking strength, impact strength and grinding performance are enhanced, and the service life of the white corundum abrasive material is prolonged. And the machining quality and the machining efficiency of grinding machining are greatly improved. In addition, the manufacturing process is simple, the equipment cost is low, the cost performance is high, and wide application prospects are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of white fused alumina abrasives, and particularly relates to a white fused alumina abrasive and a preparation method thereof. Background Art

[0002] An abrasive is a material that plays a cutting role in grinding, lapping, and polishing. Abrasives can be mainly divided into two categories: natural abrasives and artificial abrasives. When used for grinding, abrasives need to have a relatively high hardness and good corrosion resistance, workability, stability, hydrophilicity, and toughness. The higher the hardness of the abrasive, the better the wear resistance, and at the same time, the better the cutting performance; the greater the toughness of the abrasive, the higher the grinding efficiency, but excessive toughness will instead affect the self-sharpening of the abrasive; the hydrophilicity of the abrasive is an important factor determining the firmness of the combination between the abrasive and the binder, and the hydrophilic value of the abrasive is related to its variety, particle size, particle shape, surface cleanliness, and surface porosity.

[0003] White fused alumina is a high-strength abrasive sintered from alumina powder, with an alumina content of 98.5 wt%. The coarse-grained white fused alumina is bluish-white, and the whiteness gradually increases as the particle size becomes finer. The hardness of white fused alumina is higher than that of brown fused alumina, its chemical properties are stable, it can withstand high temperatures above 1800 °C, it has good self-sharpening, but its toughness is poor, and the abrasive grains are easy to break. It is suitable for grinding high-hardness steels such as hardened steel, high-speed steel, and alloy steel. In addition, due to the micro-edge structure of white fused alumina, it can also be used for mirror grinding. With the continuous development of science and technology, in order to meet the technical requirements of high-speed, heavy-load, and precision grinding, new challenges have been posed to the mechanical properties such as grinding performance, toughness, and hardness of ceramic corundum abrasives. Summary of the Invention

[0004] In view of the problems existing in the background art, the present invention provides a white fused alumina abrasive and a preparation method thereof, which are achieved through the following technical solutions:

[0005] Including the following steps:

[0006] Step a: Mix white fused alumina, binder, and copper powder with the same particle size in proportion, add them to a ball mill, sieve them, and then add them to a molding machine and stir evenly to obtain a molding material;

[0007] Step b: Place the molding material in a rectangular mold of 20×10×5 mm and compact it in a press, maintaining a pressure of 70 MPa for two minutes;

[0008] Step c: Place the compacted blank in a vacuum drying oven for drying;

[0009] Step d: Then put it into a resistance furnace for sintering, take it out after cooling to room temperature;

[0010] Step e: After crushing and screening, the white fused alumina abrasive can be obtained.

[0011] As a preferred embodiment of the present invention, in step a, the ratio of white fused alumina: binder: copper powder is 85:3:12.

[0012] As a preferred embodiment of the present invention, the binder is selected from one or more of epoxy resin, amino resin, and sodium carboxymethyl cellulose.

[0013] As a preferred embodiment of the present invention, the particle size of the white fused alumina in step a is 300 μm.

[0014] As a preferred embodiment of the present invention, the ball milling time in step a is 2 - 3 hours, and after ball milling, it is sieved through a 150 - mesh sieve.

[0015] As a preferred embodiment of the present invention, the drying condition in step c is drying at 80°C for 20 - 24 hours.

[0016] As a preferred embodiment of the present invention, the sintering condition in step d is heating in segments according to a certain heating curve:

[0017] In the first stage, it is heated from room temperature to 100 - 250°C at a rate of 5 - 10°C / minute and calcined for 1 - 1.5 hours;

[0018] In the second stage, it is heated from 100 - 250°C to 550 - 600°C at a rate of 10 - 15°C / minute and calcined for 1 - 2 hours;

[0019] In the third stage, it is heated from 550 - 600°C to 750 - 850°C at a rate of 10 - 15°C / minute and calcined for 0.5 - 1 hour.

[0020] As a preferred embodiment of the present invention, the particle size of the white fused alumina abrasive obtained after crushing and sieving in step e is 200 - 250 μm.

[0021] Compared with the existing technology, the advantages of the present invention are:

[0022] The flexural strength reflects the ability of the stacked abrasive spline to resist external forces. On the premise of ensuring the grinding requirements, the higher the compressive strength, the better the shape retention and grinding efficiency of the stacked abrasive wheel. The flexural strength of the samples obtained in the present invention is 28 - 33 MPa. Generally, a high grinding ratio can improve the grinding efficiency of the grinding wheel, reduce the dressing times of the grinding wheel, and lower the grinding cost. The grinding ratio of the samples prepared in the present invention is between 2.5 and 3.2, meeting the requirements in actual production. Epoxy resin is selected as the binder, and the sintering conditions are as follows: in the first stage, it is heated from room temperature to 150 °C at a rate of 5 - 10 °C per minute and calcined for 1.5 hours; in the second stage, it is heated from 150 °C to 550 °C at a rate of 10 - 15 °C per minute and calcined for 1 hour; in the third stage, when it is heated from 550 °C to 800 °C at a rate of 10 - 15 °C per minute, the properties of the white fused alumina abrasive are the best. In addition, the preparation process of the present invention is simple, the equipment cost is low, the cost performance is high, and it has broad application prospects. Detailed Embodiments

[0023] In order to make the application, technical solutions and advantages of the present invention clearer and more understandable, the content of the present invention will be described in detail in combination with specific embodiments. It should be understood that the embodiments are only used to illustrate the present invention, rather than limiting the protection scope of the present invention. Any simple improvement to the preparation method of the present invention under the premise of the inventive concept belongs to the protection scope of the present invention.

[0024] Example 1;

[0025] Mix white fused alumina with a particle size of 300 μm, amino resin, and copper powder in a ratio of 85:3:12, ball mill for 2 - 3 hours, pass through a 150 - mesh sieve after ball milling, and then add it to a molding machine and stir evenly to obtain a molding material; place the molding material in a 20×10×5 mm cuboid mold and press the blank in a press, maintaining a pressure of 70 MPa for two minutes; place the pressed blank in a vacuum drying oven and dry it at 80 °C for 20 - 24 hours; then put it into a resistance furnace for sintering. In the first stage, it is heated from room temperature to 100 - 250 °C at a rate of 5 - 10 °C per minute and calcined for 1 - 1.5 hours; in the second stage, it is heated from 100 - 250 °C to 550 - 600 °C at a rate of 10 - 15 °C per minute and calcined for 1 - 2 hours; in the third stage, it is heated from 550 - 600 °C to 750 - 850 °C at a rate of 10 - 15 °C per minute and calcined for 0.5 - 1 hour to obtain a white fused alumina abrasive spline. Take it out after cooling to room temperature; after crushing and screening, 200 - 250 μm white fused alumina abrasive can be obtained.

[0026] Example 2;

[0027] Mix white fused alumina with a particle size of 300 μm, epoxy resin, and copper powder in a ratio of 85:3:12, ball mill for 2 hours, pass through a 150-mesh sieve after ball milling, add to a molding machine and stir well to obtain a molding material; place the molding material in a 20×10×5 mm rectangular mold and press it in a press, maintaining a pressure of 70 MPa for two minutes; place the pressed blank in a vacuum drying oven and dry it at 80 °C for 24 hours; then put it into a resistance furnace for sintering. In the first stage, raise the temperature from room temperature to 100 °C at a rate of 5-10 °C per minute and calcine for 1 hour; in the second stage, raise the temperature from 100 °C to 550 °C at a rate of 10-15 °C per minute and calcine for 1 hour; in the third stage, raise the temperature from 550 °C to 750 °C at a rate of 10-15 °C per minute and calcine for 0.5 hour to obtain a white fused alumina abrasive sample bar. Take it out after cooling to room temperature; break it and sieve it to obtain 200-250 μm white fused alumina abrasive.

[0028] Example 3;

[0029] Mix white fused alumina with a particle size of 300 μm, epoxy resin, and copper powder in a ratio of 85:3:12, ball mill for 2 hours, pass through a 150-mesh sieve after ball milling, add to a molding machine and stir well to obtain a molding material; place the molding material in a 20×10×5 mm rectangular mold and press it in a press, maintaining a pressure of 70 MPa for two minutes; place the pressed blank in a vacuum drying oven and dry it at 80 °C for 20 hours; then put it into a resistance furnace for sintering. In the first stage, raise the temperature from room temperature to 150 °C at a rate of 5-10 °C per minute and calcine for 1.5 hours; in the second stage, raise the temperature from 150 °C to 550 °C at a rate of 10-15 °C per minute and calcine for 1 hour; in the third stage, raise the temperature from 550 °C to 800 °C at a rate of 10-15 °C per minute and calcine for 1 hour to obtain a white fused alumina abrasive sample bar. Take it out after cooling to room temperature; break it and sieve it to obtain 200-250 μm white fused alumina abrasive.

[0030] Example 4;

[0031] Mix white fused alumina with a particle size of 300 μm, sodium carboxymethyl cellulose, and copper powder in a ratio of 85:3:12, ball mill for 3 hours, pass through a 150-mesh sieve after ball milling, add to a molding machine and stir well to obtain a molding material; place the molding material in a 20×10×5 mm rectangular mold and press it in a press, maintaining a pressure of 70 MPa for two minutes; place the pressed blank in a vacuum drying oven and dry it at 80 °C for 20 hours; then put it into a resistance furnace for sintering. In the first stage, raise the temperature from room temperature to 250 °C at a rate of 5-10 °C per minute and calcine for 1.5 hours; in the second stage, raise the temperature from 250 °C to 600 °C at a rate of 10-15 °C per minute and calcine for 2 hours; in the third stage, raise the temperature from 600 °C to 800 °C at a rate of 10-15 °C per minute and calcine for 1 hour to obtain a white fused alumina abrasive sample bar. Take it out after cooling to room temperature; break it and sieve it to obtain 200-250 μm white fused alumina abrasive.

[0032] Example 5;

[0033] Mix white fused alumina with a particle size of 300 μm, epoxy resin, amino resin, sodium carboxymethyl cellulose, and copper powder in a ratio of 85:3:12, ball mill for 3 hours, pass through a 150-mesh sieve after ball milling, add to a molding machine and stir evenly to obtain a molding material; place the molding material in a 20×10×5 mm rectangular mold and press in a press, maintaining a pressure of 70 MPa for two minutes; place the pressed blank in a vacuum drying oven and dry at 80 °C for 22 hours; then put it into a resistance furnace for sintering. In the first stage, heat from room temperature to 250 °C at a rate of 5-10 °C per minute and calcine for 1.5 hours; in the second stage, heat from 250 °C to 600 °C at a rate of 10-15 °C per minute and calcine for 2 hours; in the third stage, heat from 600 °C to 850 °C at a rate of 10-15 °C per minute and calcine for 1 hour to obtain a white fused alumina abrasive sample bar. Take it out after cooling to room temperature; after crushing and screening, 200-250 μm white fused alumina abrasive can be obtained.

[0034] Example 6;

[0035] Single particle compressive strength test

[0036] Take 40 abrasive samples from Examples 1-5 each, use the DP-1 type single particle compressive strength tester of Shenzhen Xiangmin Instrument Equipment Co., Ltd. to measure the load value (N) when they are broken under static pressure respectively, and calculate the average value of these 40 particles, that is, the single particle compressive strength of the abrasive can be obtained.

[0037] Table 1 Average compressive strength of white fused alumina abrasive obtained from experiments

[0038] Serial number Average compressive strength N Example 1 38.3 Example 2 39.3 Example 3 41.1 Example 4 42.3 Example 5 41.2

[0039] The single particle compressive strength is an important index to measure the performance of the abrasive, which reflects the ability of the abrasive to resist external pressure and breakage under the action of impact force. It can be seen from the above table that with the change of sintering conditions, as the sintering time and temperature increase, the single particle compressive strength increases, but when the temperature continues to rise above 800 °C, the single particle compressive strength will no longer increase.

[0040] Flexural strength test

[0041] In this experiment, the national standard GB / T 9341-2008 is adopted, and the three-point flexure method is used with an electronic universal testing machine to test the flexural strength of the stacked abrasive sample bars under different heat preservation times.

[0042] Table 2 Flexural strength test results

[0043]

[0044] The flexural strength reflects the ability of the stacked abrasive spline to resist external forces. On the premise of ensuring the grinding requirements, the higher the compressive strength, the better the shape retention and grinding efficiency of the stacked abrasive grinding wheel. Under the sintering conditions of Example 3, the sample obtained has the highest flexural strength.

[0045] Impact strength test

[0046] The samples prepared in each example were subjected to an impact experiment, and the results are shown in Table 3.

[0047] Table 3 Impact strength test results

[0048] Serial number <![CDATA[Impact strength KJ / m 2 > Example 1 1.96 Example 2 2.03 Example 3 2.13 Example 4 1.98 Example 5 2.01

[0049] Grinding performance test

[0050] White fused alumina abrasive, phenolic resin binder and additives were mixed in a weight ratio of 75:20:5 to make a resin-bonded white fused alumina grinding wheel. Under the conditions of 5% water-based emulsion, 0.5 mm·min -1 feed rate, 0.5 MPa working pressure, 4 m·min -1 workpiece rotation speed, a grinding experiment was carried out on a M2011 type grinding machine. A grinding ratio tester (ZH10693, GHITEST, China) was used to test the grinding ratio of the resin-bonded white fused alumina grinding wheel at different grinding wheel speeds.

[0051] Table 4 Grinding table experiment test results

[0052] Serial number Grinding ratio Example 1 2.9 Example 2 2.6 Example 3 3.2 Example 4 2.5 Example 5 2.8

[0053] As can be seen from the above table, the grinding ratio in Example 4 is the highest.

[0054] In summary, the above are only the preferred examples of the present invention, and there is no any form of limitation to the present invention; any equivalent changes made by those skilled in the art within the scope of the technical solution of the present invention by using the disclosed technical content, such as some changes, modifications and evolutions, are regarded as the equivalent examples of the present invention; at the same time, any equivalent changes, modifications and evolutions made to the above embodiments according to the essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing white corundum abrasive, characterized in that: The following steps are involved: Step a: white corundum, a binder and copper powder of the same particle size are mixed in proportion, ball-milled and sieved, added into a molding machine and stirred evenly to obtain a molding material; Step b: placing the molding material in a 20×10×5 mm rectangular parallelepiped mold and pressing the blank in a press, maintaining a pressure of 70 MPa for two minutes; Step c: drying the green compact in a vacuum drying oven; Step d: then put it into a resistance furnace for sintering, and take it out after cooling to room temperature; Step e: crush and screen to obtain white corundum abrasive.

2. The method for preparing a white corundum abrasive according to claim 1, characterized in that: In the step a, white corundum: binder: copper powder = 85:3:

12.

3. The method for preparing a white corundum abrasive according to claim 1, characterized in that: The binder is selected from one or more of epoxy resin, amino resin and sodium hydroxymethyl cellulose.

4. The method for preparing a white corundum abrasive according to claim 1, characterized in that: The particle size of the white corundum in step a is 300 μm.

5. The method for preparing a white corundum abrasive according to claim 1, characterized in that: The ball milling time in step a is 2 to 3 hours, and the product is sieved with a 150-mesh sieve after ball milling.

6. The method for preparing a white corundum abrasive according to claim 1, characterized in that: The drying condition in step c is drying at 80° C. for 20 to 24 hours.

7. The method for preparing a white corundum abrasive according to claim 1, characterized in that: The sintering conditions in step d are to increase the temperature in stages according to a certain temperature increase curve: The first stage is to heat the temperature from room temperature to 100-250°C at a rate of 5-10°C / min and calcine for 1-1.5 hours; The second stage is to increase the temperature from 100-250°C to 550-600°C at a rate of 10-15°C / min and calcine for 1-2 hours; The third stage is to increase the temperature from 550-600°C to 750-850°C at a rate of 10-15°C / min, and calcine for 0.5-1 hour.

8. The method for preparing a white corundum abrasive according to claim 1, characterized in that: The particle size of the white corundum abrasive obtained after crushing and screening in step e is 200-250 μm.

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