Ceramic microcrystalline grinding wheel

Abstract

The present application relates to a kind of ceramic microcrystalline grinding wheel, by ceramic microcrystalline abrasive and low-temperature sintering binder composition;The sintering temperature of the low-temperature sintering binder with the ceramic microcrystalline abrasive is 800~1000 ℃.The low-temperature sintering binder of the present application has the characteristics of low sintering temperature, so that the ceramic microcrystalline grinding wheel prepared has excellent grinding performance, can improve the dressing cycle of grinding wheel, greatly improves the service life of grinding wheel.

Description

Technical Field

[0001] This invention relates to the field of abrasives and grinding tools, and more particularly to a ceramic microcrystalline grinding wheel. Background Technology

[0002] The grinding wheel manufacturing industry is a traditional industry, dating back more than 100 years. It is an essential component of the industrial sector and is often referred to as the "teeth" of industry. With the emergence of more and more difficult-to-grind materials, the commonly used abrasives such as brown fused alumina, white fused alumina, chromium fused alumina, and single-crystal fused alumina are no longer sufficient to meet the processing requirements of new materials. Emerging ceramic microcrystalline fused alumina, due to its microcrystalline structure, has the characteristics of high toughness and strong self-sharpening properties, making it particularly suitable for processing difficult-to-grind materials. It offers high processing efficiency and is less likely to burn the workpiece, making it a current research hotspot.

[0003] The quality of a grinding wheel primarily depends on the performance of the binder itself, as well as the wettability, thermal expansion coefficient compatibility, and bond strength between the binder and abrasive particles. Therefore, binder selection is a crucial factor in obtaining high-quality grinding wheels. For ceramic microcrystalline abrasives, conventional high-temperature binders (generally referring to binders sintered at temperatures above 1100℃) cannot be used to manufacture grinding wheels. This is because when the microcrystalline structure of ceramic microcrystalline abrasives is held at temperatures above 1100℃ for more than 4 hours, the original microcrystals gradually grow, leading to a significant decrease in performance. Furthermore, conventional ceramic grinding wheel binders are composed of materials such as clay, feldspar, and glass powder. Due to variations in quality, these substances cannot guarantee uniform product quality and are no longer suitable for modern automated grinding processes with preset machining parameters.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a ceramic microcrystalline grinding wheel.

[0006] The technical solution adopted in this invention is as follows:

[0007] This invention provides a ceramic microcrystalline grinding wheel, which is composed of ceramic microcrystalline abrasive and a low-temperature sintering binder;

[0008] The sintering temperature of the low-temperature sintering binder and the ceramic microcrystalline abrasive is 800-1000℃.

[0009] The present invention proposes a ceramic microcrystalline grinding wheel. The low-temperature sintering binder has the characteristic of low sintering temperature, which makes the resulting ceramic microcrystalline grinding wheel have excellent grinding performance, can improve the grinding wheel dressing cycle, and significantly improve the service life of the grinding wheel.

[0010] Preferably, the ceramic microcrystalline abrasive is ceramic microcrystalline corundum.

[0011] Preferably, the low-temperature sintering binder is composed of the following raw materials by mass percentage: 40-60% SiO2, 10-20% Al2O3, 9-20% B2O3, 9-21% alkali metal oxide (M1)2O, and 1.5-2% alkaline earth metal oxide (M2)O, wherein M1 is Li, Na, and K, and M2 is Ca or Mg.

[0012] More preferably, the SiO2 is derived from quartz powder;

[0013] The Al2O3 is derived from Al(OH)3;

[0014] The B2O3 is derived from H3BO3;

[0015] The Li, Na and K are derived from Li2CO3, Na2CO3 and K2CO3, respectively;

[0016] The Ca or Mg is derived from CaCO3 or MgCO3, respectively.

[0017] More preferably, the molar percentage of Al2O3 is 8-12%;

[0018] The molar percentage of B2O3 is 11.5% to 18.1%.

[0019] More preferably, the boron anomalous coefficient of the low-temperature sintering binder is between 0 and 0.15, the boron anomalous coefficient being the ratio of total free oxygen to the molar percentage of B2O3, the total free oxygen being the sum of the free oxygen provided by each oxide, and the free oxygen provided by each oxide being the product of the free oxygen coefficient of the oxide and the molar percentage of the oxide.

[0020] Preferably, the mass percentage of the low-temperature sintering binder is 15-25%. Detailed Implementation

[0021] To better understand the above technical solutions, exemplary embodiments of the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a clearer and more thorough understanding of the present invention and to fully convey the scope of the invention to those skilled in the art.

[0022] This invention provides a ceramic microcrystalline grinding wheel, which is composed of ceramic microcrystalline abrasive and a low-temperature sintering binder;

[0023] The sintering temperature of the low-temperature sintering binder and the ceramic microcrystalline abrasive is 800-1000℃.

[0024] In this invention, for example, the sintering temperature can be any value among 800℃, 830℃, 860℃, 890℃, 920℃, 950℃, 980℃, and 1000℃, but is not limited to those listed above. Furthermore, this invention does not impose any particular limitation on the preparation method of the ceramic microcrystalline grinding wheel. For example, ceramic microcrystalline abrasive and a low-temperature sintering binder are mixed in a certain proportion, pressed into a blank, sintered at 800–1000℃, and then cooled to obtain the final product.

[0025] In a preferred embodiment of the present invention, the ceramic microcrystalline abrasive is ceramic microcrystalline corundum. In the present invention, the grain size of ceramic microcrystalline corundum is less than 1 μm, the abrasive grains have high strength, and it has micro-fragmentation properties. Grinding wheels prepared with it as abrasive have good self-sharpening properties, do not clog, have good toughness, and low wear.

[0026] In a preferred embodiment of the present invention, the low-temperature sintering binder is composed of the following raw materials by mass percentage: 40-60% SiO2, 10-20% Al2O3, 9-20% B2O3, 9-21% alkali metal oxide (M1)2O, and 1.5-2% alkaline earth metal oxide (M2)O, wherein M1 is Li, Na, and K, and M2 is Ca or Mg.

[0027] This invention provides a high-strength, low-melting-point low-temperature sintering binder by studying the composition and dosage of basic low-temperature sintering binders. SiO2 in the formulation of this invention is the most important network former in glass, ensuring the basic hardness and strength of the binder; however, the SiO2 content should not be too high, otherwise the melting point of the binder will be too high. Al2O3 can improve the strength and heat resistance of glass, but Al2O3 should not be excessive, otherwise it will increase the melting point of the binder. B2O3 can significantly reduce the melting point of glass, while also providing sufficient O2 content. 2+ In some cases, the [BO4] structural units are incorporated into the spatial network structure of the glass to improve its strength. However, insufficient B2O3 leads to a high melting point, while excessive B2O3, without sufficient O2, can cause problems. 2+In certain conditions, it will enter the glass network in a layered structure of [BO3], which will reduce the glass strength. Among alkali metal oxides, Li2O can reduce the coefficient of thermal expansion, improve chemical stability, act as a flux, improve production efficiency, and improve alkali resistance in glass. Na2O and K2O mainly reduce the melting point of glass, enhance the heat resistance and chemical stability of glass, and improve the stress resistance of glass. However, their content should not be too high, otherwise it will reduce the mechanical strength, chemical stability, and thermal stability of glass. The preferred amounts of Li2O, Na2O, and K2O are 3-7%, respectively. Among alkaline earth metal oxides, CaO mainly reduces the high-temperature viscosity of glass, promotes the melting and clarification of glass melt, and increases the chemical stability and mechanical strength of glass. However, excessive CaO may lead to problems such as increased crystallization tendency of glass, reduced thermal stability, and increased annealing temperature. MgO plays a similar role to CaO, which will not be elaborated here. In addition, the low-temperature sintering binder used in this invention belongs to the sodium-calcium-silicon glass system, with a linear expansion coefficient of 8.2 × 10⁻⁶. -6 / ℃, which is similar to the coefficient of thermal expansion of abrasive ceramic microcrystalline corundum (8.4×10⁻⁶ in the range of room temperature to 1000℃). -6 The low-temperature sintering binder of this invention has a low coefficient of thermal expansion (°C) and good compatibility. At the same time, the main phases of the binder are SiO2, Al2O3 and B2O3, which are inorganic non-metals, the main component of the abrasive Al2O3. They do not repel each other and have good compatibility.

[0028] In a more preferred embodiment of the present invention, SiO2 is derived from quartz powder;

[0029] Al2O3 originates from Al(OH)3;

[0030] B2O3 originates from H3BO3;

[0031] Li, Na and K are derived from Li2CO3, Na2CO3 and K2CO3, respectively;

[0032] Ca or Mg originates from CaCO3 or MgCO3, respectively.

[0033] In this invention, there are no particular limitations on the preparation method of the low-temperature sintering binder. For example, the raw materials are weighed and sieved according to the source and amount of the above-mentioned formula components (quartz powder through a 600-mesh sieve, Al(OH)3 through a 320-mesh sieve, H3BO3 through a 120-mesh sieve, Li2CO3 through an 800-mesh sieve, Na2CO3 and K2CO3 through a 220-mesh sieve, and CaCO3 through a 600-mesh sieve). After all the raw materials are mixed evenly, they are heated to 1300°C in a glass melting furnace. The molten glass flows into a water tank filled with water for water quenching. After the water quenching, the glass fragments are dried and ball-milled in a ball mill until they pass through a 220-mesh sieve to obtain the low-temperature sintering binder.

[0034] In a more preferred embodiment of the present invention, the molar percentage of Al2O3 is 8-12%;

[0035] The molar percentage of B2O3 is 11.5%–18.1%.

[0036] The hardness and strength of glass mainly depend on its chemical composition and structure. Generally, network-forming ions increase glass strength, while network-external ions decrease it. However, boron anomalies and boron-aluminum anomalies are equally important in the strength-composition relationship. When Al2O3 and B2O3 are both transformed into tetrahedral [AlO4] and [BO4] to participate in network formation, the network structure is denser than that composed solely of [SiO4], resulting in the best mechanical properties of the glass. Too much or too little free oxygen will lead to a decrease in the mechanical properties of the glass. Specifically, Al2O3 is a spatial network intermediate. In the presence of excess free oxygen, it changes from coordination 6 to coordination 4 and enters the network. Its network component [AlO4] preferentially enters the network than [BO4]. Therefore, in Li... + Na + K + Ca 2+ Mg 2+ When providing free oxygen, [AlO4] is supplied preferentially, and then excess free oxygen is supplied to B2O3, causing the layered [BO3] to be converted into [BO4] and enter the network structure. When there is insufficient free oxygen, B2O3 cannot be completely converted into [BO4] and enter the spatial network, thus reducing the mechanical properties of the binder; conversely, when there is too much free oxygen, it will break the network, also reducing the mechanical properties of the binder. In this invention, by further screening the molar percentage range of Al2O3 and B2O3, it is beneficial to meet the requirements of the boron anomaly and boron-aluminum anomaly principles, resulting in a binder with better performance.

[0037] In a more preferred embodiment of the present invention, the boron anomalous coefficient of the low-temperature sintering binder is between 0 and 0.15. The boron anomalous coefficient is the ratio of total free oxygen to the molar percentage of B2O3. The total free oxygen is the sum of the free oxygen given by each oxide, and the free oxygen given by each oxide is the product of the free oxygen coefficient of the oxide and the molar percentage of the oxide.

[0038] By analyzing the effects of various chemical components in glass and combining this with the network structure theory of glass, the inventors introduced the theory of free oxygen ions and used the boron anomalous coefficient as a criterion to further simplify the steps for obtaining the optimal formulation ratio. The inventors discovered that the boron anomalous coefficient must be between 0 and 0.15. First, the total free oxygen in the glass system must be greater than 0; otherwise, insufficient free oxygen in the glass system will result in a higher melting point. Simultaneously, according to the boron anomalous theory, only after the free oxygen supply [AlO4] provided by alkali metal and alkaline earth metal oxides is satisfied will there be excess free oxygen to supply B2O3, causing the layered structure of [BO3] to convert to [BO4] and enter the network structure. Under this condition, the boron anomalous coefficient gradually increases, indicating an increase in the amount converted to [BO4], and the strength of the glass also increases accordingly. However, the glass strength begins to decrease after the boron anomalous coefficient reaches its extreme value of 0.15. The ability of each oxide to provide free oxygen is measured by the free oxygen coefficient K, as shown in Table 1.

[0039] Table 1

[0040]

[0041]

[0042] In a preferred embodiment of the present invention, the mass percentage of the low-temperature sintering binder is 15-25%. In this invention, controlling the amount of low-temperature sintering binder and ceramic microcrystalline abrasive is beneficial for improving the wettability, compatibility of thermal expansion coefficients, and bonding strength between the binder and abrasive particles, resulting in a ceramic microcrystalline grinding wheel with superior overall performance.

[0043] Example 1

[0044] A ceramic microcrystalline grinding wheel, by mass percentage, is composed of 80% ceramic microcrystalline abrasive (ceramic microcrystalline corundum) and 20% low-temperature sintering binder;

[0045] The sintering temperature of the low-temperature sintering binder and the ceramic microcrystalline abrasive is 960℃.

[0046] The low-temperature sintering binder is composed of the following raw materials in the following mass percentages: 55% SiO2, 18% Al2O3 (molar percentage of 11.43%), 12.5% ​​B2O3 (molar percentage of 11.56%), 3% Li2O, 6.5% Na2O, 3% K2O, and 2% CaO.

[0047] SiO2 is derived from quartz powder;

[0048] Al2O3 originates from Al(OH)3;

[0049] B2O3 originates from H3BO3;

[0050] Li2O, Na2O, and K2O are derived from Li2CO3, Na2CO3, and K2CO3, respectively;

[0051] CaO originates from CaCO3.

[0052] The boron anomalous coefficient is the ratio of total free oxygen to the molar percentage of B₂O₃. Total free oxygen is the sum of the free oxygen values ​​given by each oxide, and the free oxygen value given by each oxide is the product of the free oxygen coefficient of the oxide and the molar percentage of the oxide. In this embodiment, the boron anomalous coefficient is 0.09; see Table 2 for specific calculations.

[0053] Table 2

[0054]

[0055]

[0056] The low-temperature sintering binder is prepared by the following method: raw materials are weighed according to the source and amount of the formula components and sieved (quartz powder through a 600-mesh sieve, Al(OH)3 through a 320-mesh sieve, H3BO3 through a 120-mesh sieve, Li2CO3 through an 800-mesh sieve, Na2CO3 and K2CO3 through a 220-mesh sieve, and CaCO3 through a 600-mesh sieve). All raw materials are mixed evenly and heated to 1300℃ in a glass melting furnace. The molten glass flows into a water-filled pool for water quenching. After water quenching, the glass fragments are dried and ball-milled in a ball mill until they pass through a 220-mesh sieve to obtain the low-temperature sintering binder.

[0057] Example 2

[0058] The difference between this embodiment and Embodiment 1 lies in the amount of raw materials used in the low-temperature sintering binder. The low-temperature sintering binder is composed of the following raw materials by mass percentage: 55% SiO2, 18.5% Al2O3 (molar percentage 11.75%), 12.5% ​​B2O3 (molar percentage 11.56%), 3% Li2O, 6% Na2O, 3% K2O, and 2% CaO. The remaining steps remain unchanged.

[0059] The boron anomalous coefficient in this embodiment is 0.017. For the specific calculation, please refer to Table 3.

[0060] Table 3

[0061] mass percentage (wt%) 55 18.5 2 6 3 3 12.5 100 molecular weight 60 102 56 62 94 30 70 number of moles 0.92 0.18 0.04 0.10 0.03 0.10 0.18 1.54 mole percentage % 59.36 11.75 2.31 6.27 2.07 6.48 11.56 Free oxygen coefficient -1.0 0.7 1.0 1.0 0.3 Free oxygen -0.117 0.016 0.063 0.021 0.019 0.002 Boron anomalous coefficient 0.017

[0062] Example 3

[0063] The difference between this embodiment and Embodiment 1 lies in the amount of raw materials used in the low-temperature sintering binder. The low-temperature sintering binder is composed of the following raw materials by mass percentage: 51.5% SiO2, 14.8% Al2O3 (molar percentage 9.40%), 19.5% B2O3 (molar percentage 18.04%), 3% Li2O, 6% Na2O, 3.2% K2O, and 2% CaO. The remaining steps remain unchanged.

[0064] The boron anomalous coefficient in this embodiment is 0.146. For the specific calculation, please refer to Table 4.

[0065] Table 4

[0066]

[0067]

[0068] Comparative Example 1

[0069] The difference between this comparative example and Example 1 lies in the amount of raw materials used in the low-temperature sintering binder. The low-temperature sintering binder is composed of the following raw materials by mass percentage: 55% SiO2, 19.5% Al2O3 (molar percentage 12.38%), 12.5% ​​B2O3 (molar percentage 11.56%), 3% Li2O, 6% Na2O, 2% K2O, and 2% CaO. The remaining steps remain unchanged.

[0070] The boron anomalous coefficient for this comparative example is -0.10 (total free oxygen < 0), and the specific calculation is shown in Table 5.

[0071] Table 5

[0072] mass percentage (wt%) 55.0 19.5 2.0 6.0 2.0 3.0 12.5 100.0 molecular weight 60 102 56 62 94 30 70 Number of moles 0.92 0.19 0.04 0.10 0.02 0.10 0.18 1.54 mole percentage % 59.36 12.38 2.31 6.27 1.38 6.48 11.56 Free oxygen coefficient -1.0 0.7 1.0 1.0 0.3 Free oxygen -0.124 0.016 0.063 0.014 0.019 -0.01 Boron anomalous coefficient -0.10

[0073] Based on the boron anomalous coefficients of Examples 1-3 and Comparative Example 1, the performance of the low-temperature sintering binders prepared by each formulation is as follows: Example 3 > Example 1 > Example 2 > Comparative Example 1. According to the free oxygen theory, the boron anomalous coefficient of Comparative Example 1 is <0 (i.e., total free oxygen <0), indicating insufficient free oxygen, resulting in a high melting point and insufficient mechanical properties in the glass system, making it unsuitable for the preparation of low-temperature sintering binders. Although the boron anomalous coefficient of Example 2 is >0, the value is relatively small, indicating that the amount of B2O3 supplied to convert it into [BO4] and enter the glass network structure is too small. Although the performance of the prepared low-temperature sintering binder is better than that of Comparative Example 1, the improvement is not significant enough. The boron anomalous coefficients of Examples 2 and 3 are close to 0.15, indicating that most of the B2O3 is converted into [BO4] and enters the glass network structure. The performance of the prepared low-temperature sintering binders can meet the actual requirements. Among them, the boron anomalous coefficient of Example 3 is closest to 0.15, therefore, the performance of the low-temperature sintering binder prepared in Example 3 is the best.

[0074] The low-temperature sintering binder of Example 3 was subjected to sintering experiments and grinding wheel performance tests, and the results are recorded in Tables 6-9.

[0075] (1) Low-temperature sintering binder melting experiment

[0076] Test method: Weigh 0.5g of the low-temperature sintering binder powder from Example 3, and... The tablets were pressed into shape in a mold and placed on an Al2O3 plate for sintering tests. The temperature profiles are shown in Table 6.

[0077] Table 6

[0078] heating 20℃ 960℃ 6 hours Insulation 960℃ 960℃ 4 hours Cooling 960℃ Natural cooling

[0079] The equivalent diameter after melting, as measured by the above method, is: The good flowability indicates that the low-temperature sintering binder of Example 3 of the present invention has good wetting properties for ceramic microcrystalline corundum.

[0080] (2) Testing of the manufacturing performance of ceramic microcrystalline grinding wheels

[0081] Test method: Products of the following specifications were manufactured according to the formula of Example 3 and the conventional grinding wheel production process. The product dimensions were outer diameter 183 mm × thickness 18 mm × inner diameter 33 mm. Five grinding wheels of each specification were produced. After the sample grinding wheels were manufactured, the grinding wheel density and sandblasting hardness were tested and compared with the standard. The grinding wheel dimensions were measured to examine the shrinkage performance of the grinding wheel manufacturing. The results are shown in Table 7.

[0082] Table 7

[0083]

[0084] As can be seen from the results in Table 7, the sintering density, sandblasting hardness and shrinkage performance of the ceramic microcrystalline grinding wheel prepared according to Example 3 meet the requirements of grinding wheel manufacturing, which also shows that the low-temperature sintering binder of Example 3 of the present invention has good manufacturing performance.

[0085] (3) Customer testing of ceramic microcrystalline grinding wheels

[0086] Test method: Ceramic microcrystalline grinding wheels were manufactured using conventional production methods according to the formula in Example 3 for customer testing. The wheel dimensions were 280 mm outer diameter × 160 mm thickness × 115 mm inner diameter. The results are recorded in Tables 8 and 9.

[0087] Table 8

[0088]

[0089] Table 9

[0090]

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A ceramic microcrystalline grinding wheel, characterized in that, It is composed of ceramic microcrystalline abrasive and low-temperature sintering binder; The sintering temperature of the low-temperature sintering binder and the ceramic microcrystalline abrasive is 800~1000℃; The low-temperature sintering binder is composed of the following raw materials by mass percentage: 40~60% SiO2, 10~20% Al2O3, 9~20% B2O3, 9~21% alkali metal oxide (M1)2O, and 1.5~2% alkaline earth metal oxide (M2)O, wherein M1 is Li, Na and K, and M2 is Ca or Mg; The molar percentage of Al2O3 is 8-12%; The molar percentage of B2O3 is 11.5% to 18.1%; The boron anomalous coefficient of the low-temperature sintering binder is between 0 and 0.

15. The boron anomalous coefficient is the ratio of total free oxygen to the molar percentage of B2O3. The total free oxygen is the sum of the free oxygen provided by each oxide. The free oxygen provided by each oxide is the product of the free oxygen coefficient of the oxide and the molar percentage of the oxide.

2. The ceramic microcrystalline grinding wheel as described in claim 1, characterized in that, The ceramic microcrystalline abrasive is ceramic microcrystalline corundum.

3. The ceramic microcrystalline grinding wheel as described in claim 1, characterized in that, The SiO2 is derived from quartz powder; The Al2O3 is derived from Al(OH)3; The B2O3 is derived from H3BO3; The Li, Na and K are derived from Li2CO3, Na2CO3 and K2CO3, respectively; The Ca or Mg is derived from CaCO3 or MgCO3, respectively.

4. The ceramic microcrystalline grinding wheel as described in claim 1, characterized in that, The mass percentage of the low-temperature sintering binder is 15-25%.

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