Method for preparing degassing rotor by using silicon oxynitride-beta-silicon carbide composite ceramic

Abstract

The invention discloses a method for preparing a degassing rotor by using silicon oxynitride-beta-silicon carbide composite ceramic. The method comprises the following steps: burdening, ball-milling, preparing ceramic slurry, aging the prepared ceramic slurry, spray-drying, preparing ceramic powder, and controlling the water content to be below 1%; putting the homogenized ceramic powder into an isostatic pressing die, sealing the isostatic pressing die, putting the isostatic pressing die into an isostatic pressing machine, pressing a green body of the degassing rotor rotating rod, taking out the formed green body, simultaneously releasing stress of the ceramic green body, placing the green body for a circle, and then machining the green body; the homogenized ceramic powder is pressed into a degassing rotor impeller green body, and the degassing rotor impeller green body is machined; and sintering the ceramic. The gap degassing rotor can better adapt to the complex working condition of gap degassing in the aluminum die-casting industry, the working efficiency and quality of the degassing rotor are effectively improved, and wide application and development of the gap degassing technology in the aluminum die-casting industry are promoted.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum processing industry manufacturing, and in particular to a method for preparing a gap degassing rotor for aluminum die casting industry by using silicon oxynitride-β-silicon carbide composite ceramics. Background Art

[0002] The degassing rotor in the aluminum die-casting industry is a key component in the purification of aluminum liquid. Its performance directly affects the degassing effect and the quality of aluminum products. The existing gap degassing rotors in the aluminum die-casting industry have the following problems: At present, the degassing rotors used in the gap are usually made of graphite materials, which have a large thermal expansion coefficient, low strength, poor anti-oxidation performance, poor stability in high-temperature use environments, unsatisfactory degassing effects, and a short service life, generally 15-30 days; at the same time, the anti-oxidation performance is poor, and it is easily oxidized and corroded in the aluminum liquid, affecting the quality of the aluminum liquid. The stripping performance with the aluminum liquid is poor, which will cause aluminum liquid residue, not only causing a waste of raw materials, but also may affect the quality of subsequent products; Silicon nitride ceramic degassing rotors cannot meet the requirements for intermittent degassing in the aluminum die-casting industry due to their thermal shock resistance.

[0003] Degassing rotors made of traditional graphite materials have a short service life, unsatisfactory degassing effect, and poor production stability in the aluminum die-casting industry, which increases the company's production and operation costs and weakens the company's market competitiveness.

[0004] Therefore, those skilled in the art are committed to providing a method for preparing a degassing rotor using silicon oxynitride-β-silicon carbide composite ceramics that can effectively solve the above technical problems. Summary of the invention

[0005] In view of the above-mentioned defects in the prior art, the technical problem to be solved by the present invention is to provide a method for preparing a degassing rotor using silicon oxynitride-β-silicon carbide composite ceramics, which can effectively solve the above-mentioned technical problems.

[0006] To achieve the above object, the present invention provides a method for preparing a degassing rotor using silicon oxynitride-β-silicon carbide composite ceramics, comprising: S1) Ingredients, ball milling Add silicon oxynitride, β-silicon carbide, α-alumina, mineralizer, dispersant, binder, and alcohol into a stirred mill and ball mill for 20-25 hours to prepare a ceramic slurry; S2) Spray powdering The prepared ceramic slurry is aged and degassed for 20-25 hours, and then spray-dried to prepare ceramic powder, with the moisture content being controlled below 1%; S3) Isostatic dry pressing and lathe processing Load the homogenized ceramic powder into an isostatic pressing mold, seal it, place it in an isostatic press, apply pressure up to 200 MPa to press the green body of the degassing rotor shaft, take out the formed green body, put it into a drying oven at 40 - 55 °C to dry, and at the same time make the ceramic green body release stress. After placing it for one week, carry out machining; Press the homogenized ceramic powder into the green body of the degassing rotor impeller, and process the green body of the degassing rotor impeller; S4) Sintering of ceramics Heat up at a rate of 30 - 60 °C per hour, hold the temperature at 300 - 400 °C for 4 - 8 hours, then continue to heat up to 1650 - 1685 °C, hold the temperature for 3 - 5 hours, turn off the power supply, and cool naturally to room temperature.

[0007] Furthermore, in the S1), the ball milling time is 24 hours.

[0008] Furthermore, in the S2), the defoaming time is 24 hours, and spray drying is carried out through a spray drying tower to make ceramic powder that meets the particle size grading.

[0009] Furthermore, in the S3), the sealing method is to tie it tightly with a rubber band for sealing; The temperature in the drying oven is 50 °C; The specific machining is to machine the green body of the degassing rotor with a CNC precision engraving machine according to the design dimensions of the degassing rotor impeller; The specific process of pressing the homogenized ceramic powder into the green body of the degassing rotor impeller is to press it through a 500 - ton dry pressing molding machine; The specific process of processing the green body of the degassing rotor impeller is to machine it with a CNC precision engraving machine according to the design dimensions of the degassing rotor impeller.

[0010] Furthermore, in the S4), the holding time is 6 hours; continue to heat up to 1680 °C and hold the temperature for 4 hours.

[0011] Furthermore, after the S4), it also includes post - processing and detection of the silicon oxynitride - β - silicon carbide composite ceramic degassing rotor; use a grinding machine to machine each component of the fired degassing rotor to the pre - designed dimensions, assemble, detect the concentricity of the product, and after passing the detection, package and store in the warehouse.

[0012] Furthermore, for silicon oxynitride: select self - propagating high - temperature synthesis silicon oxynitride powder with a particle size D50 less than 3 microns and a silicon oxynitride content of not less than 98%; For silicon carbide: select β - silicon carbide powder synthesized by chemical vapor deposition with a particle size D50 less than 2 microns and a β - silicon carbide purity greater than 99%.

[0013] For alumina: select α - alumina powder with a particle size D50 less than 1 micron and a purity of 99.9%; Dispersant: Ammonium polyacrylate 9300 is selected. Binder: PVB is selected.

[0014] Furthermore, the mineralizer selects rare earth elements such as yttrium oxide, cerium oxide, and lanthanum oxide; the particle size is controlled below 1 micron.

[0015] Furthermore, the batching and ball milling specifically include: 70 - 80 parts of silicon oxynitride powder, 15 - 20 parts of β-silicon carbide powder, 1 - 3 parts of α-aluminum oxide, 1 - 5 parts of sintering aid, 1 part of dispersant, 2 parts of binder PVB, and 100 - 150 parts of ethanol are added to the stirring mill according to the formula ratio, ball milled for 24 hours, and taken out of the mill for aging after reaching the particle size control index.

[0016] Furthermore, the batching and ball milling specifically include: 55 - 70 parts of silicon oxynitride, 20 - 35 parts of β-silicon carbide powder, 1 - 5 parts of α-aluminum oxide, 1 - 5 parts of sintering aid, 1 part of dispersant, 2 parts of binder PVB, and 100 - 150 parts of alcohol are added to the stirring mill according to the formula ratio, ball milled for 24 hours, and taken out of the mill for aging after reaching the particle size control index.

[0017] The beneficial effects of the present invention are: 1) The present invention uses silicon oxynitride-β-silicon carbide composite ceramic material to manufacture an interstitial degassing rotor, which is a global first. Currently, no other enterprises have launched similar products, having unique innovation. 2) The thermal expansion coefficient of the silicon oxynitride-β-silicon carbide composite ceramic material is about 1.8, only half of that of silicon nitride, and its thermal shock resistance is significantly better than that of silicon nitride ceramics. This characteristic makes it more stable in actual interstitial use, with a service life exceeding 1 year, more than 10 times that of the graphite degassing rotor. At the same time, the oxidation resistance of the silicon oxynitride-β-silicon carbide composite ceramic material and its peeling performance from the aluminum liquid are far superior to those of graphite materials, and it can better adapt to the complex working conditions of intermittent use in the aluminum die-casting industry, effectively improving the working efficiency and quality of the degassing rotor for rotary degassing. 3) Currently, there are many challenges in the production of large-sized products of silicon oxynitride-β-silicon carbide composite ceramic materials globally. The present invention has successfully overcome the problem of high-temperature decomposition of silicon oxynitride by optimizing process links such as formula, firing, ball milling, and molding, and by selecting micron-scale high-purity self-propagating powder produced by the Technical Institute of Physics and Chemistry, Chinese Academy of Sciences. The prepared product has a flexural strength of about 300 - 500 MPa and a thermal shock resistance of 1200 °C, fully meeting the performance requirements of the interstitial degassing use conditions in the domestic aluminum die-casting industry. Description of the Drawings

[0018] Figure 1This is a schematic diagram of the three-dimensional structure of the degassing rotor. DETAILED DESCRIPTION

[0019] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: In the description of the present invention, it should be noted that the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0020] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "setting", and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0021] like Figure 1 As shown, the degassing rotor comprises a degassing rotor rod 1, and two ends of the degassing rotor rod 1 are respectively provided with a degassing rotating disc 2 and a degassing rotor metal connecting flange.

[0022] Example 1 A method for preparing a degassing rotor using silicon oxynitride-β-silicon carbide composite ceramics, comprising: S1) Ingredients, ball milling Silicon oxynitride, β-silicon carbide, α-alumina, various mineralizers, dispersants, binders, and alcohol are added to a stirring mill in a certain proportion and ball-milled for 20-25 hours to prepare a uniform ceramic slurry; in this embodiment, the ball-milling time is 24 hours.

[0023] Among them, silicon oxynitride: self-propagating synthetic silicon oxynitride powder is selected, the particle size D50 is less than 3 microns, and the silicon oxynitride content is not less than 98%; Silicon carbide: β-silicon carbide powder synthesized by vapor deposition method is selected, with a particle size D50 of less than 2 microns and a β-silicon carbide purity of more than 99%.

[0024] Alumina: α-alumina powder is used, with a particle size D50 of less than 1 micron and a purity of 99.9%; Dispersant: ammonium polyacrylate 9300; Binder: Select PVB; The mineralizer selects rare earth elements such as yttrium oxide, cerium oxide, and lanthanum oxide; the particle size is controlled below 1 micron; Furthermore, 70-80 parts of silicon oxynitride powder, 15-20 parts of β-silicon carbide powder, 1-3 parts of α-aluminum oxide, 1-5 parts of sintering aids (including rare earth elements such as yttrium oxide, cerium oxide, and lanthanum oxide), 1 part of dispersant, 2 parts of binder PVB (calculated by dry powder, prepared as a 10% solution), and 100-150 parts of ethanol are added to the stirring mill according to the formula ratio and ball milled for 24 hours. After reaching the particle size control index, the milled material is aged.

[0025] S2) Spray powder making The prepared ceramic slurry is aged and degassed for 20-25 hours, then spray-dried to make ceramic powder meeting the particle size grading, and the moisture content is controlled below 1%; In this embodiment, preferably, the degassing time is 24 hours, and spray drying is carried out through a spray drying tower to make ceramic powder meeting the particle size grading.

[0026] S3) Isostatic dry pressing and lathe processing The homogenized ceramic powder is loaded into an isostatic pressing mold, sealed, placed in an isostatic press, pressurized to 200 MPa to press the green body of the degassing rotor shaft, the formed green body is taken out and dried in a drying room at 50 °C, while the ceramic green body slowly releases stress. After being placed for one week, machining is carried out; the homogenized ceramic powder is pressed into the green body of the degassing rotor impeller, and the green body of the degassing rotor impeller is processed; In this embodiment, the sealing method is to tightly tie and seal with a rubber band; The temperature in the drying room is 50 °C; The specific machining is to machine the green body of the degassing rotor with a CNC precision engraving machine according to the design dimensions of the degassing rotor impeller; The specific process of pressing the homogenized ceramic powder into the green body of the degassing rotor impeller is to press through a 500-ton dry pressing machine; The specific process of processing the green body of the degassing rotor impeller is to machine it with a CNC precision engraving machine according to the design dimensions of the degassing rotor impeller.

[0027] S4) Sintering of ceramics The sintering of silicon oxynitride-β-silicon carbide composite ceramics is the key of the whole process. The temperature is slowly increased at a rate of 50 °C per hour, and the heating rate is slowed down at 300-400 °C to ensure the degumming of the silicon oxynitride ceramic riser. It is kept warm at 300-400 °C for 4-8 hours, then continues to heat up to 1650-1685 °C and is kept warm for 3-5 hours. Then the power is turned off and it is naturally cooled to room temperature.

[0028] In this embodiment, the heat preservation time is 6 hours; then continue to heat up to 1680 °C and keep the temperature for 4 hours.

[0029] In addition, after S4), it also includes post-processing and inspection of the silicon oxynitride-β-silicon carbide composite ceramic degassing rotor; there may be certain dimensional deviations in the fired silicon oxynitride-β-silicon carbide composite ceramic degassing rotor, and post-processing is required. Use a grinding machine to process each component of the fired degassing rotor to the pre-designed size, assemble it, inspect the concentricity of the product, and package it into the warehouse after passing the inspection.

[0030] Embodiment 2 Others are the same as Embodiment 1, the difference is: In S1), 55 - 70 parts of silicon oxynitride, 20 - 35 parts of β-silicon carbide powder, 1 - 5 parts of α-aluminum oxide, 1 - 5 parts of sintering aids (including rare earth elements such as yttrium oxide, cerium oxide, and lanthanum oxide), 1 part of dispersant, 2 parts of binder PVB (calculated based on dry powder, prepare a 10% solution), and 100 - 150 parts of alcohol are added to the stirring mill according to the formula ratio and ball milled for 24 hours. After reaching the particle size control index, take it out of the mill and let it age.

[0031] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations according to the concept of the present invention without creative labor. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field of the present invention based on the concept of the present invention through logical analysis, reasoning, or limited experiments on the basis of the prior art should be within the protection scope determined by the claims.

Claims

1. A method for preparing a degassing rotor using silicon oxynitride-β-silicon carbide composite ceramics, characterized in that: include: S1) Ingredients, ball milling Add silicon oxynitride, β-silicon carbide, α-alumina, mineralizer, dispersant, binder, and alcohol into a stirred mill and ball mill for 20-25 hours to prepare a ceramic slurry; S2) Spray powdering The prepared ceramic slurry is aged and degassed for 20-25 hours, and then spray-dried to prepare ceramic powder, with the moisture content being controlled below 1%; S3) Isostatic dry pressing and lathe processing The homogenized ceramic powder is loaded into an isostatic pressing mold, which is sealed and placed in an isostatic press. The press is pressurized to 200 MPa to press the degassing rotor rod green body. The formed green body is taken out and placed in a drying room at 40-55°C for drying. At the same time, the ceramic green body is stress-released. After being placed for one week, it is machined. Pressing the homogenized ceramic powder into a degassing rotor impeller green body, and processing the degassing rotor impeller green body; S4) Sintering of ceramics Raise the temperature at a rate of 50°C per hour and keep it at 300-400°C for 6 hours. Then continue to raise the temperature to 1650-1685°C, keep it for 3-5 hours, and cool to room temperature.

2. The method for preparing a degassing rotor using silicon oxynitride-β-silicon carbide composite ceramic according to claim 1, characterized in that: In S1), the ball milling time is 24 hours.

3. The method for preparing a degassing rotor using silicon oxynitride-β-silicon carbide composite ceramics as claimed in claim 2, characterized in that: In the above S2), the degassing time is 24 hours, and the powder is spray-dried in a spray drying tower to produce a ceramic powder with a particle size distribution.

4. The method for preparing a degassing rotor using silicon oxynitride-β-silicon carbide composite ceramics as claimed in claim 3, characterized in that: In said S3), the sealing method is to seal by tying with a rubber band; The temperature in the drying room is 50°C; The machining specifically includes machining the degassing rotor green body according to the design size of the degassing rotor impeller by using a CNC engraving machine; The step of pressing the homogenized ceramic powder into a degassing rotor impeller green body is specifically performed by pressing the green body through a 500-ton dry pressing machine; The degassing rotor impeller green body is specifically processed by using a CNC engraving machine according to the design size of the degassing rotor impeller.

5. The method for preparing a degassing rotor using silicon oxynitride-β-silicon carbide composite ceramics as claimed in claim 4, characterized in that: In the step S4), the heat preservation time is 6 hours; the temperature is further raised to 1680° C. and kept for 4 hours.

6. The method for preparing a degassing rotor using silicon oxynitride-β-silicon carbide composite ceramics as claimed in claim 5, characterized in that: After the above S4), it also includes post-processing and testing of the silicon oxynitride-β-silicon carbide composite ceramic degassing rotor; the fired degassing rotor components are processed to the pre-designed size by a grinder, assembled, and tested for concentricity, and packaged and stored after passing the test.

7. The method for preparing a degassing rotor using silicon oxynitride-β-silicon carbide composite ceramics according to claim 1, The characteristics are as follows: silicon oxynitride: self-propagating synthesized silicon oxynitride powder is selected, the particle size D50 is less than 3 microns, and the silicon oxynitride content is not less than 98%; Silicon carbide: β-silicon carbide powder synthesized by vapor deposition method, with a particle size D50 of less than 2 microns and a β-silicon carbide purity of more than 99%; Alumina: α-alumina powder is used, with a particle size D50 of less than 1 micron and a purity of 99.9%; Dispersant: ammonium polyacrylate 9300; Adhesive: PVB is selected.

8. The method for preparing a degassing rotor using silicon oxynitride-β-silicon carbide composite ceramics as claimed in claim 7, characterized in that: The mineralizer is selected from rare earth elements such as yttrium oxide, cerium oxide and lanthanum oxide; and the particle size is controlled to be below 1 micron.

9. The method for preparing a degassing rotor using silicon oxynitride-β-silicon carbide composite ceramics as claimed in claim 8, characterized in that: The ingredients and ball milling specifically include: Add 70-80 parts of silicon oxynitride powder, 15-20 parts of β-silicon carbide powder, 1-3 parts of α-alumina, 1-5 parts of sintering aid, 1 part of dispersant, 2 parts of binder PVB, and 100-150 parts of ethanol into a stirred mill according to the formula ratio, and ball mill for 24 hours. After the particle size control index is reached, the mill is aged.

10. The method for preparing a degassing rotor using silicon oxynitride-β-silicon carbide composite ceramics as claimed in claim 8, characterized in that: The ingredients and ball milling specifically include: Add 55-70 parts of silicon oxynitride, 20-35 parts of β-silicon carbide powder, 1-5 parts of α-alumina, 1-5 parts of sintering aid, 1 part of dispersant, 2 parts of binder PVB, and 100-150 parts of alcohol into a stirred mill according to the formula ratio, and ball mill for 24 hours. After the particle size control index is reached, the mill is aged.

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