Electric porcelain dry forming ceramic trimming tool and preparation method thereof

Abstract

The application belongs to the technical field of ceramic materials, and particularly relates to a ceramic trimming tool for dry forming of electric porcelain and a preparation method thereof. The preparation method of the ceramic trimming tool for dry forming of electric porcelain adopts spherical alpha alumina powder with different particle sizes for particle grading, mixes the spherical alpha alumina powder with yttrium stabilized zirconium oxide powder as ceramic powder, and adopts a surface modifier to perform surface modification treatment on the ceramic powder. The surface modification treatment is performed on the ceramic powder according to the proportion of 88-92 wt.% of the surface modification treatment ceramic powder, 5-8 wt.% of an organic plasticizer, and 0.5-5 wt.% of a sintering aid to prepare a feedstock. Injection molding, extraction dewaxing, drying, and sintering are sequentially performed to obtain the ceramic trimming tool. The ceramic trimming tool for dry forming of electric porcelain is prepared by using a one-time sintering process, has low size shrinkage, a regular shape, sharp edges, and reduces the difficulty of grinding process. Meanwhile, the ceramic trimming tool has good wear resistance and bending strength, and has a long service life.

Description

Technical Field

[0001] This invention belongs to the field of ceramic materials technology, specifically relating to a ceramic trimming tool for dry forming of electrical porcelain and its preparation method. Background Technology

[0002] A ceramic trimming knife for dry forming of electrical porcelain is a ceramic cutting tool used in the trimming process during the dry forming of electrical porcelain. In use, the ceramic trimming knife is bonded and fixed to a metal shank and installed on a CNC trimming machine to cut the dry-formed ceramic blank to obtain electrical porcelain products of the corresponding specifications. The ceramic blanks used in dry forming are generally pressed into shape by an isostatic press under a pressure of 110 MPa. They have high hardness, high rigidity, and strong cutting resistance, which places high demands on the ceramic trimming knife's shape regularity, cutting edge sharpness, and wear resistance.

[0003] Currently, the main forming methods for ceramic trimming knives used in dry forming of electrical porcelain are slip casting and pressure forming. Both methods involve first firing the ceramic blank, then grinding the blade, followed by a second firing. For example, patent CN115784754A uses a two-stage firing process, placing the grinding step between the bisque firing and sintering stages. By controlling the dimensional shrinkage of the blank after bisque firing, the densification of the blank is controlled, reducing the wear of the grinding wheel during the grinding process. However, these production methods cannot achieve mass production or continuous operation, and the resulting ceramic trimming knives also suffer from irregular shapes and dull blades.

[0004] Furthermore, patent CN109485393A discloses an alumina ceramic that can be used in ceramic chopping knives. This invention significantly improves the bending strength, wear resistance, and hardness of alumina ceramics by adding spherical chromium oxide and zirconia to spherical alumina and performing atmospheric pressure sintering and isostatic pressing sintering processes. However, this alumina ceramic requires the addition of a large amount of forming agent during the forming process and also needs to undergo atmospheric pressure sintering and isostatic pressing sintering. Significant dimensional shrinkage occurs during forming and preparation. When used to process ceramic chopping knives, grinding is required. However, this alumina ceramic has a hardness exceeding 2000 HV and a very high density, greatly increasing the difficulty of grinding and the wear of the grinding wheel during grinding. In addition, the high price of chromium oxide also significantly increases the cost of the product. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a ceramic trimming knife for dry forming of electrical porcelain. It is prepared using a one-time firing process, resulting in low dimensional shrinkage, regular shape, sharp blade, good wear resistance and bending strength, and long service life. This invention also provides its preparation method.

[0006] The method for preparing the ceramic trimming tool for dry forming of electrical porcelain according to the present invention includes the following steps:

[0007] (1) Feed preparation: After melting the binder, add plasticizer and surfactant, mix evenly to obtain organic plasticizer; add surface-modified ceramic powder and sintering aid to the melted organic plasticizer, mix and obtain feed;

[0008] (2) Injection molding: The feed material is injection molded to obtain a preform;

[0009] (3) Extraction and dewaxing: The molded green body is placed in a dewaxing agent at 45-85℃ for extraction and dewaxing for 5-10 hours to obtain a dewaxed green body;

[0010] (4) Drying and sintering: Dry the dewaxed blank and keep it at 1480-1620℃ for 1-5 hours to sinter it and obtain a ceramic trimming knife.

[0011] In step (1), the feed composition is: 88-92 wt.% of surface-modified ceramic powder, 5-8 wt.% of organic plasticizer, and 0.5-5 wt.% of sintering aid.

[0012] In step (1), the surface-modified ceramic powder is a ceramic powder modified by a surface modifier. The surface modification process of the ceramic powder is as follows: the ceramic powder is added to a high-speed mixer and mixed evenly. Then, the surface modifier is added and the mixture is stirred for 0.5-1h. Finally, the mixture is sieved through a 30-mesh sieve to obtain the surface-modified ceramic powder.

[0013] Preferably, the ceramic powder consists of 75-90 wt.% spherical α-alumina powder and 10-25 wt.% yttrium-stabilized zirconium oxide powder; wherein the spherical α-alumina powder comprises 40-50 wt.% spherical α-alumina powder with a median particle size of 0.2 ≤ < 0.5 μm, 30-50 wt.% spherical α-alumina powder with a median particle size of 0.5 ≤ < 1.0 μm, and 10-20% spherical α-alumina powder with a median particle size of 1.0 ≤ < 1.5 μm.

[0014] Further preferably, the spherical α-alumina powder has a purity ≥99.9%. The yttrium-stabilized zirconia powder is 3Y zirconia powder with a median particle size of 0.3-1.0 μm and a purity ≥99.5%.

[0015] Preferably, the surface modifier is one or more of aluminate coupling agents, aluminum-zirconium coupling agents, and zirconate coupling agents; the amount of surface modifier is 0.5-5% of the mass of ceramic powder.

[0016] In step (1), the organic plasticizer consists of 80-85 wt.% binder, 5-15 wt.% plasticizer, and 5-10 wt.% surfactant.

[0017] Preferably, the binder is one or more of the following: paraffin wax, microcrystalline wax, polymethyl methacrylate, polyoxymethylene, polyvinyl chloride, high-density polyethylene resin, ABS resin, and EVA resin.

[0018] Preferably, the plasticizer is one or more of glycerol, dioctyl phthalate (DOP), polyethylene glycol 6000, and polyethylene glycol 8000.

[0019] Preferably, the surfactant is one or more of beeswax, oleic acid, stearic acid, vegetable oil, and Tween 80.

[0020] The preparation method of the organic plasticizer is as follows: the binder is added to a stainless steel crucible and melted at a melting temperature of 180-200℃. After the binder is completely melted, the plasticizer and surfactant are added, and the temperature is kept at 180-200℃ for no less than 30 minutes to obtain the organic plasticizer.

[0021] In step (1), the sintering aid is one or more of rare earth oxides, titanium oxide, magnesium oxide, calcium carbonate, strontium oxide, strontium carbonate, and chromium oxide.

[0022] In step (2), the molding pressure is 5-10 MPa and the molding temperature is 110-150℃.

[0023] In step (3), any commercially available dewaxing agent can be used, the main component of which is an alkane compound.

[0024] In step (4), the drying temperature is 60-80℃ and the drying time is 4-10h, preferably drying in an oven.

[0025] In step (4), during sintering, the temperature is increased to 1480-1620℃ at a heating rate of 0.8-5℃ / min, and the holding time is 1-5h. It is preferred to sinter in a sintering furnace.

[0026] The present invention also provides a ceramic trimming knife prepared by the above preparation method.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] (1) The raw materials of the present invention are spherical α-alumina powder with different particle sizes for particle size distribution, and the surface of ceramic powder is modified by surface modifier, which significantly increases the amount of ceramic powder added during the feeding preparation process and greatly reduces the amount of organic plasticizer added. The reduction of the amount of organic plasticizer can reduce the shrinkage rate of the green body during the molding and cooling process, thereby avoiding cracking of the green body during molding and improving the molding qualification rate. At the same time, the reduction of organic content in the green body can significantly shorten the degreasing time, thereby reducing the firing shrinkage rate, and finally obtaining a high-performance ceramic trimming knife with low shrinkage, high precision and low deformation.

[0029] (2) The present invention uses a surface modifier to modify ceramic powder, forming an organic molecular layer on the powder surface, enhancing the interfacial compatibility between inorganic powder and organic resin, improving the dispersibility of powder in organic binder, and significantly reducing the amount of organic plasticizer. At the same time, the surface modifier can be converted into alumina and zirconium oxide after the green body is sintered, improving the density of sintered products.

[0030] (3) The present invention adopts the extraction dewaxing method, and the main binder components in the green body are removed by extraction, which can greatly reduce the volatilization time of organic matter during sintering. Furthermore, the mixture after extraction can be reused after distillation, thus reducing production costs. The present invention adopts the injection molding and one-time sintering process, and the ceramic trimming knife prepared has a regular shape, sharp blade, and good wear resistance. Detailed Implementation

[0031] The present invention will be further described below with reference to the embodiments. Unless otherwise specified, the raw materials used in the embodiments are all commercially available conventional raw materials; unless otherwise specified, the process methods used in the embodiments are all conventional methods in the art.

[0032] The spherical α-alumina powder used in the examples has a purity of ≥99.9%; the yttrium-stabilized zirconium oxide powder used is 3Y zirconium oxide powder with a median particle size between 0.3-1.0 μm and a purity of ≥99.5%.

[0033] The dewaxing agent used in the examples is the 320 type environmentally friendly dewaxing agent produced by Shenzhen Yougongrong Company.

[0034] Example 1

[0035] A method for preparing a ceramic trimming tool for dry forming of electrical porcelain includes the following steps:

[0036] (1) Feed preparation:

[0037] By weight percentage, 50% paraffin wax and 30% high-density polyethylene resin are added to a stainless steel crucible and melted at a temperature between 180-200℃. After the paraffin wax and high-density polyethylene resin have completely melted, 15% dioctyl phthalate and 5% stearic acid are added and the mixture is kept at 180-200℃ for at least 30 minutes to obtain an organic plasticizer.

[0038] By mass percentage, the ceramic powder consists of 75% spherical α-alumina powder and 25% yttrium-stabilized zirconium oxide powder. Among the spherical α-alumina powder, 50 wt.% has a median particle size of 0.2 ≤ median particle size < 0.5 μm, 40 wt.% has a median particle size of 0.5 ≤ median particle size < 1.0 μm, and 10 wt.% has a median particle size of 1.0 ≤ median particle size < 1.5 μm. The above ceramic powder is added to a high-speed mixer at a particle-to-particle ratio of 1:2 and stirred for 3 hours. Then, 5% zirconate ester coupling agent by mass of the ceramic powder is added and stirred for another hour. Finally, the mixture is sieved using a 30-mesh sieve to obtain surface-modified ceramic powder.

[0039] By mass percentage, 7% of organic plasticizer is melted, and then 88% of surface-modified ceramic powder and 5% of sintering aid (magnesium oxide and calcium oxide in a mass ratio of 1:1) are added and mixed to obtain the feedstock.

[0040] (2) Injection molding: Preheat the injection molding machine to 120°C, add the prepared feed into the hopper of the injection molding machine for injection molding, and the molding pressure is 8MPa to obtain the molded preform;

[0041] (3) Extraction and dewaxing: The molded green body is placed in a dewaxing agent at 60°C for extraction and dewaxing for 8 hours to obtain a dewaxed green body;

[0042] (4) Drying and sintering: The dewaxed blank is dried in an oven at 70°C for 8 hours, and then placed in a sintering furnace. The temperature is raised to 600°C at a rate of 1°C / min, and then raised to 1550°C at a rate of 5°C / min. The temperature is held for 3 hours to sinter the blank and obtain a ceramic trimming knife.

[0043] Example 2

[0044] A method for preparing a ceramic trimming tool for dry forming of electrical porcelain includes the following steps:

[0045] (1) Feed preparation:

[0046] By weight percentage, 50% microcrystalline wax and 35% polymethyl acrylate are added to a stainless steel crucible and melted at a temperature between 180-200℃. After the polymethyl acrylate is completely melted, 10% polyethylene glycol 6000 and 5% beeswax are added and kept at 180-200℃ for no less than 30 minutes to obtain an organic plasticizer.

[0047] By mass percentage, the ceramic powder consists of 85% spherical α-alumina powder and 15% yttrium-stabilized zirconium oxide powder. Spherical α-alumina powder with a median particle size of 0.2 ≤ median < 0.5 μm accounts for 40 wt.%, spherical α-alumina powder with a median particle size of 0.5 ≤ median < 1.0 μm accounts for 50 wt.%, and spherical α-alumina powder with a median particle size of 1.0 ≤ median < 1.5 μm accounts for 10 wt.%. The above ceramic powder is added to a high-speed mixer at a particle-to-particle ratio of 1:1. After mixing for 2 hours, 3% (by mass) of aluminum-zirconium coupling agent is added, and mixing continues for another hour. The mixture is then sieved using a 30-mesh sieve to obtain surface-modified ceramic powder.

[0048] By mass percentage, 8% of organic plasticizer is melted, and then 91.5% of surface-modified ceramic powder and 0.5% of sintering aid (calcium carbonate and strontium carbonate in a mass ratio of 1:1) are added and mixed to obtain the feedstock.

[0049] (2) Injection molding: Preheat the injection molding machine to 150°C, add the prepared feed into the hopper of the injection molding machine for injection molding, and the molding pressure is 5MPa to obtain the molded preform;

[0050] (3) Extraction and dewaxing: The molded green body is placed in a dewaxing agent at 45°C for extraction and dewaxing for 10 hours to obtain a dewaxed green body;

[0051] (4) Drying and sintering: The dewaxed blank is dried in an oven at 80°C for 4 hours, and then placed in a sintering furnace. The temperature is raised to 580°C at a rate of 1.5°C / min, and then raised to 1480°C at a rate of 5°C / min. The temperature is held for 5 hours to sinter the blank and obtain a ceramic trimming knife.

[0052] Example 3

[0053] A method for preparing a ceramic trimming tool for dry forming of electrical porcelain includes the following steps:

[0054] (1) Feed preparation:

[0055] By weight percentage, 50% paraffin wax, 20% high-density polyethylene resin, and 15% ABS resin are added to a stainless steel crucible and melted at a temperature between 180-200℃. After the high-density polyethylene resin has completely melted, 5% glycerol, 5% stearic acid, and 5% beeswax are added and kept at 180-200℃ for no less than 30 minutes to obtain an organic plasticizer.

[0056] By mass percentage, the ceramic powder consists of 90% spherical α-alumina powder and 10% yttrium-stabilized zirconium oxide powder. Among the spherical α-alumina powder, 50 wt.% has a median particle size of 0.2 ≤ median particle size < 0.5 μm, 30 wt.% has a median particle size of 0.5 ≤ median particle size < 1.0 μm, and 20 wt.% has a median particle size of 1.0 ≤ median particle size < 1.5 μm. The above ceramic powder is added to a high-speed mixer at a particle-to-particle ratio of 1:2 and stirred for 4 hours. Then, 1% aluminate coupling agent by mass of the ceramic powder is added, and stirring is continued for 0.5 hours. Finally, the mixture is sieved using a 30-mesh sieve to obtain surface-modified ceramic powder.

[0057] By mass percentage, 5% of organic plasticizer is melted, and then 92% of surface-modified ceramic powder and 3% of sintering aid (chromium oxide, strontium oxide and lanthanum oxide in a mass ratio of 1:1:1) are added and mixed to obtain the feedstock;

[0058] (2) Injection molding: Preheat the injection molding machine to 110°C, add the prepared feed into the hopper of the injection molding machine for injection molding, and the molding pressure is 10MPa to obtain the molded preform;

[0059] (3) Extraction and dewaxing: The molded green body is placed in a dewaxing agent at 85°C for extraction and dewaxing for 5 hours to obtain a dewaxed green body;

[0060] (4) Drying and sintering: The dewaxed blank is dried in an oven at 60°C for 10 hours, and then placed in a sintering furnace. The temperature is raised to 620°C at a rate of 0.8°C / min, and then raised to 1620°C at a rate of 5°C / min. The temperature is held for 1 hour to obtain a ceramic trimming knife.

[0061] Comparative Example 1

[0062] The only difference between this comparative example and Example 1 is that all the spherical α-alumina powder used is spherical α-alumina powder with a median particle size of 0.5 ≤ median particle size < 1.0 μm; in addition, in order to achieve an injection molding effect similar to that of Example 1, the feed composition of this comparative example is: 12.5 wt.% organic plasticizer, 82.5 wt.% surface-modified ceramic powder, and 5 wt.% sintering aid.

[0063] Comparative Example 2

[0064] The only difference between this comparative example and Example 1 is that all the spherical α-alumina powder used is spherical α-alumina powder with a median particle size of 0.2 ≤ median particle size < 0.5 μm; in addition, in order to achieve an injection molding effect similar to that of Example 1, the feed composition of this comparative example is: 15 wt.% organic plasticizer, 80 wt.% surface-modified ceramic powder, and 5 wt.% sintering aid.

[0065] Comparative Example 3

[0066] The only difference between this comparative example and Example 1 is that ceramic powder without surface modification treatment is used; in addition, in order to achieve an injection molding effect similar to that of Example 1, the feed composition of this comparative example is: 14 wt.% organic plasticizer, 81 wt.% ceramic powder, and 5 wt.% sintering aid.

[0067] Comparative Example 4

[0068] The only difference between this comparative example and Example 1 is that thermal degreasing is used instead of extraction dewaxing. The thermal degreasing process is as follows: the molded blank is placed in a degreasing furnace, heated to 100°C, held for 30 minutes, heated to 230°C, held for 450 minutes, heated to 650°C, held for 350 minutes, and then cooled to room temperature in the furnace.

[0069] Comparative Example 5

[0070] The only difference between this comparative example and Example 1 is that no sintering aid is added; instead, the sintering aid is replaced with an equal mass of surface-modified ceramic powder.

[0071] The ceramic trimming knives prepared in each embodiment and comparative example were subjected to performance tests. The test methods were as follows: the density of the products was tested using the Archimedes' water displacement method; the bending strength of the products was tested using the three-point bending method; the Vickers hardness of the samples was tested using a Vickers hardness tester; the product dimensions were measured using vernier calipers and the dimensional shrinkage rate was calculated as follows: dimensional shrinkage rate = (dimensional size before sintering - dimensional size after sintering) / dimensional size before sintering × 100%; the service life was measured as the number of identical ceramic parts that a single ceramic trimming knife could process. The test results are shown in Table 1.

[0072]

[0073] As shown in Table 1, the ceramic trimming knives prepared in Examples 1-3 of this invention have low dimensional shrinkage, high density, and also possess high bending strength and hardness, resulting in a long service life. Comparative Example 1 used only spherical α-alumina powder with a larger particle size, while Comparative Example 2 used only spherical α-alumina powder with a smaller particle size. To achieve injection molding effects similar to Example 1, the amount of organic plasticizer added needed to be increased accordingly, and the dimensional shrinkage of the ceramic trimming knife increased significantly, while the bending strength, fracture toughness, and hardness also decreased. Comparative Example 3 used ceramic powder without surface modification treatment. To achieve injection molding effects similar to Example 1, the amount of organic plasticizer added also needed to be increased accordingly. Simultaneously, the dimensional shrinkage of the ceramic trimming knife increased significantly, and the bending strength, fracture toughness, and hardness decreased significantly. Comparative Example 4 used thermal degreasing instead of extraction dewaxing, which increased the degreasing time. During thermal degreasing, cracking and deformation of the product were easily caused, resulting in reduced mechanical properties, decreased regularity and sharpness, and a shortened service life for the obtained ceramic trimming knife. Comparative Example 5, without the addition of sintering aids, showed a significant decrease in product density, a marked decline in mechanical properties such as bending strength, fracture toughness, and hardness, and a shorter service life.

Claims

1. A method for preparing a ceramic trimming tool for dry forming of electrical porcelain, characterized in that: Includes the following steps: (1) Feed preparation: After melting the binder, add plasticizer and surfactant, mix evenly to obtain organic plasticizer; add surface-modified ceramic powder and sintering aid to the melted organic plasticizer, mix and obtain feed; (2) Injection molding: The feed material is injection molded to obtain a preform; (3) Extraction and dewaxing: The molded green body is placed in a dewaxing agent at 45-85℃ for extraction and dewaxing for 5-10 hours to obtain a dewaxed green body; (4) Drying and sintering: Dry the dewaxed blank and keep it at 1480-1620℃ for 1-5 hours to sinter it and obtain a ceramic trimming knife; In step (1), the feed composition is: 88-92 wt.% surface-modified ceramic powder, 5-8 wt.% organic plasticizer, and 0.5-5 wt.% sintering aid; The surface-modified ceramic powder is a ceramic powder modified with a surface modifier; the surface modifier is one or more of aluminate coupling agents, aluminum-zirconium coupling agents, and zirconate coupling agents. The surface modification process of the ceramic powder is as follows: the ceramic powder is added to a high-speed mixer and mixed evenly. Then, a surface modifier is added and the mixture is stirred for 0.5-1 hour. The mixture is then sieved through a 30-mesh sieve to obtain the surface-modified ceramic powder. The ceramic powder consists of 75-90 wt.% spherical α-alumina powder and 10-25 wt.% yttrium-stabilized zirconium oxide powder; of the spherical α-alumina powder, 40-50 wt.% are spherical α-alumina powder with a median particle size of 0.2 ≤ median < 0.5 μm, 30-50 wt.% are spherical α-alumina powder with a median particle size of 0.5 ≤ median < 1.0 μm, and 10-20% are spherical α-alumina powder with a median particle size of 1.0 ≤ median < 1.5 μm.

2. The method for preparing the ceramic trimming tool for dry forming of electrical porcelain according to claim 1, characterized in that: The purity of the spherical α-alumina powder is ≥99.9%; the yttrium-stabilized zirconia powder is 3Y zirconia powder with a median particle size of 0.3-1.0 μm and a purity of ≥99.5%.

3. The method for preparing the ceramic trimming tool for dry forming of electrical porcelain according to claim 1, characterized in that: The amount of surface modifier used is 0.5-5% of the mass of ceramic powder.

4. The method for preparing a ceramic trimming tool for dry forming of electrical porcelain according to claim 1, characterized in that: In step (1), the organic plasticizer consists of 80-85 wt.% binder, 5-15 wt.% plasticizer, and 5-10 wt.% surfactant.

5. The method for preparing a ceramic trimming tool for dry forming of electrical porcelain according to claim 1, characterized in that: The binder is one or more of the following: paraffin wax, microcrystalline wax, polymethyl methacrylate, polyoxymethylene, polyvinyl chloride, high-density polyethylene resin, ABS resin, and EVA resin; The plasticizer is one or more of the following: glycerol, dioctyl phthalate, polyethylene glycol 6000, and polyethylene glycol 8000; The surfactant is one or more of beeswax, oleic acid, stearic acid, vegetable oil, and Tween 80.

6. The method for preparing a ceramic trimming tool for dry forming of electrical porcelain according to claim 1, characterized in that: In step (1), the sintering aid is one or more of rare earth oxides, titanium oxide, magnesium oxide, calcium carbonate, strontium oxide, strontium carbonate, and chromium oxide.

7. The method for preparing a ceramic trimming tool for dry forming of electrical porcelain according to claim 1, characterized in that: In step (2), the molding pressure is 5-10 MPa and the molding temperature is 110-150℃.

8. The method for preparing a ceramic trimming tool for dry forming of electrical porcelain according to claim 1, characterized in that: In step (4), the drying temperature is 60-80℃ and the drying time is 4-10h; During sintering, the temperature is increased to 1480-1620℃ at a heating rate of 0.8-5℃ / min, and held for 1-5 hours in a sintering furnace.

9. A ceramic trimming knife for dry forming of electrical porcelain, characterized in that: It is prepared by the preparation method according to any one of claims 1-8.

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