Method for preventing large deformation in isostatic cool pressing of large-diameter yttrium oxide disc

Abstract

The invention discloses a method for preventing large deformation in cold isostatic pressing of a large-diameter yttrium oxide disk, which comprises the following steps: S1, filling a powdery yttrium oxide material into a disk-shaped elastic mold, and pressing down to primarily form the powdery yttrium oxide material; s2, sealing the green body subjected to pre-pressing and preliminary forming in the step S1 in an elastic mold; s3, the elastic mold in the S2 is put into a high-pressure container of cold isostatic pressing equipment, pressure is applied to the elastic mold, and the pressure is increased in a two-stage gradient boosting mode; s4, releasing the pressure of the elastic mold subjected to pressure increasing and increasing twice in the step S3, wherein the rate is controlled to be smaller than or equal to 4 MPa / min during pressure releasing; s5, the elastic mold subjected to pressure relief in the S4 is demolded, and a demolded green body is placed in a constant-temperature platform for standing; and S6, directly drying or sintering the blank after standing in the step S5 to prepare the required large-diameter yttrium oxide disc. The technology is simple and convenient, large buckling deformation of the yttrium oxide disc in the cold isostatic pressing process can be effectively restrained, and the forming yield of the yttrium oxide disc is increased.

Description

Technical Field

[0001] The invention relates to the technical field of yttrium oxide disc processing, in particular to a method for preventing large deformation of large-diameter yttrium oxide discs during cold isostatic pressing. Background Art

[0002] Yttrium oxide discs are a high-performance ceramic material widely used in fields such as optics, electronics, semiconductors, and high-temperature industries, especially in semiconductors and optical coatings. However, large-diameter yttrium oxide discs (≥600 mm) are prone to warping and deformation after cold isostatic pressing (CIP) due to uneven stress distribution. Traditional methods rely on subsequent machining corrections, but this is costly and results in significant material loss. Existing technologies have attempted to improve plasticity by adjusting the binder ratio, but this cannot address the macroscopic deformation problem of large-sized blanks. Others have employed multi-layer gradient pressing, but this process is complex and has a low yield rate.

[0003] Therefore, it is necessary to provide a method for preventing large deformation during cold isostatic pressing of large-diameter yttrium oxide discs to solve the above problems. Summary of the Invention

[0004] In order to overcome the above-mentioned shortcomings, the purpose of the present invention is to provide a method for preventing large deformation during cold isostatic pressing of large-diameter yttrium oxide discs. The process is simple, can effectively suppress the large warping deformation of the yttrium oxide discs during the cold isostatic pressing process, and improve the yield rate of yttrium oxide disc forming.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: a method for preventing large deformation during cold isostatic pressing of large-diameter yttrium oxide disks, comprising the following steps: S1: Powdered yttrium oxide material is loaded into a disc-shaped elastic mold and pressed down to form a preliminary shape; pre-pressing is used to avoid the formation of holes or uneven density between the yttrium oxide materials in the elastic mold.

[0006] Among them, the elastic material of the elastic mold can withstand high pressure and can evenly transmit pressure. After the yttrium oxide material is filled into the elastic mold, the external pressing piece can further evenly transmit the pressure to the yttrium oxide material, so that it forms a preliminary formed pre-pressed blank. S2: sealing the pre-pressed and pre-formed green body in S1 in an elastic mold; S3: placing the elastic mold in S2 into a high-pressure container of a cold isostatic pressing device and applying pressure thereto in a two-stage gradient pressure-increasing manner; By applying pressure to the high-pressure container, the powder particles on the preliminarily formed green body are further tightly combined under uniform pressure, thereby ensuring the forming effect of the yttrium oxide disc.

[0007] During the manufacturing process of yttrium oxide discs, the main way to suppress their deformation is to fully release the stress.

[0008] Specifically, during cold isostatic pressing, the pressure on the blank in the elastic mold is first increased to a certain value and maintained for a certain period of time, during which part of the stress is released; then the blank in the elastic mold is continued to be pressurized to the set maximum pressure value, and maintained at this pressure for a certain period of time, so that the blank can release all stress and be completely shaped into the desired disc shape.

[0009] The two-step pressurization can effectively prevent the green body from slowly rebounding when it is subsequently taken out of the mold and placed.

[0010] S4: Depressurize the elastic mold that has been pressurized twice in S3, and control the rate during depressurization to be ≤4MPa / min; The pressure relief speed is controlled to be low during pressure relief. On the one hand, this can prevent the formed body from cracking due to a sudden drop in pressure in the mold; on the other hand, it can also prevent the yttrium oxide disc from warping due to sudden stress changes.

[0011] S5: demoulding the elastic mold that has been depressurized in S4, and placing the demoulded green body on a constant temperature platform for rest; After a long period of static treatment on the constant temperature platform, the residual stress on the blank is evenly released, further ensuring that the blank will not produce significant warping and deformation. The yield rate can be increased from 60% based on traditional methods to 95%.

[0012] S6: directly drying or sintering the green body after the standing in S5 to produce the desired large-diameter yttrium oxide disc.

[0013] Furthermore, the elastic mold described in S1 is made of polyisoprene.

[0014] Polyisoprene material is a polymer material made from the polymerization of isoprene monomers. It has excellent elasticity and good temperature resistance and tear resistance.

[0015] When it is made into a mold for use, the user can easily demold it, making it convenient for the staff to take out the blank in the mold, effectively improving the overall production efficiency of the yttrium oxide disc; its good temperature resistance and tear resistance make it have high tear strength when used as a mold in a certain low temperature or high temperature environment, and can withstand multiple demolding, so that the mold can be reused, thereby increasing the overall service life of the elastic mold of this material.

[0016] Furthermore, the two-stage gradient pressure boosting steps are: The first stage: pressurize to 60MPa at a rate of 15MPa / min; The second stage: pressurizing at a rate of 10 MPa / min to 150-180 MPa. This two-stage pressurization method is used to release the stress in the blank in two stages, avoiding the phenomenon of incomplete stress release and large warping caused by direct pressurization. This effectively suppresses the large warping deformation of the yttrium oxide disc during the cold isostatic pressing process.

[0017] Furthermore, the elastic mold needs to be pressure-maintained after each stage of gradient pressure increase. This not only allows sufficient time for the green body to release stress, but also ensures sufficient densification of the powder and the yield rate of the green body.

[0018] Furthermore, the holding time after the first stage of pressurization is 5 minutes, and the holding time after the second stage of pressurization is 20-30 minutes. By holding the pressure after the first and second stages of pressurization, sufficient time is reserved for stress release during the two pressurizations. Only when the stress is fully released can the warping deformation of the blank during the production process be effectively suppressed.

[0019] Furthermore, the surface flatness of the constant temperature platform selected in S4 is ≤0.02mm, the temperature is maintained at 25℃±2℃, the humidity in the constant temperature platform is maintained at 40%±5%, and the standing time of the blank is 48 hours. The temperature of the blank after demolding may be different from the ambient temperature. Direct exposure to the environment may cause thermal stress and cause deformation of the blank. Therefore, the constant temperature platform with a constant temperature and humidity environment provides an environment for the blank to finally release stress. The specific standing time allows the blank to gradually stabilize and the internal stress to be released, avoiding subsequent cracking or deformation.

[0020] Furthermore, the cold isostatic pressing equipment needs to fill a high-pressure container with a liquid medium before applying pressure, and the elastic mold is immersed in the high-pressure container.

[0021] Furthermore, the liquid medium used to fill the high-pressure container is water or oil.

[0022] Beneficial effects of the present invention: 1. The present invention adopts a two-stage pressure-increasing method during cold isostatic pressing to release the stress in the blank twice, thereby avoiding the phenomenon that the blank stress cannot be completely released due to direct pressure increase and thus causing large warping deformation. This effectively suppresses the large warping deformation of the yttrium oxide disc during the cold isostatic pressing process and improves the yield rate of yttrium oxide disc molding. 2. In the present invention, the green body after demoulding is immediately placed on a constant temperature platform to stand and release the residual stress again. The setting of the constant temperature platform avoids the sudden change of internal stress of the green body just demoulded due to temperature change, which affects its final molding and ensures the yield of yttrium oxide disc molding. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A cold isostatic pressing pressure-time curve diagram of an embodiment of the present invention; DETAILED DESCRIPTION The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more precise definition of the protection scope of the present invention.

[0024] In order to solve the problems in the existing technology, some improve the plasticity by adjusting the binder ratio, but cannot solve the macro deformation problem of large-sized green bodies; some adopt multi-layer gradient pressing, but the process is complicated and the yield rate is low. Figure 1 As shown, a method for preventing large deformation during cold isostatic pressing of a large diameter yttrium oxide disk in this embodiment includes the following steps: S1: Powdered yttrium oxide material is loaded into a disc-shaped elastic mold and pressed down to form a preliminary shape; pre-pressing is used to avoid the formation of holes or uneven density between the yttrium oxide materials in the elastic mold.

[0025] Among them, the elastic material of the elastic mold can withstand high pressure and can evenly transmit pressure. After the yttrium oxide material is filled into the elastic mold, the downward pressure of the external pressing part can further evenly transfer the pressure to the yttrium oxide powder material, so that the yttrium oxide powder material is tightly combined to form a preliminary formed yttrium oxide disc blank.

[0026] It should be noted that the above-mentioned pressing member is a prior art and its structure or shape is not limited, as long as it can apply pressure to the yttrium oxide powder material loaded into the elastic mold so that it is formed under the action of external force; In addition, the powdered yttrium oxide material needs to be screened, mixed or dried before filling to ensure that the yttrium oxide powder subsequently filled into the elastic mold has a uniform particle size distribution and is free of impurities.

[0027] S2: The pre-pressed and pre-formed green body in S1 is sealed in an elastic mold to prevent the liquid medium used in the subsequent cold isostatic pressing process from penetrating and affecting the production quality of the yttrium oxide discs; S3: The elastic mold in S2 is placed in a high-pressure container of a cold isostatic pressing device and pressure is applied thereto. The pressure is applied in a two-stage gradient pressure-increasing manner. By applying pressure to the high-pressure container, the powder particles on the initially formed body are further tightly combined under uniform pressure, thereby ensuring the forming effect of the yttrium oxide disc and making the structure of the yttrium oxide disc more stable after forming.

[0028] It should be noted that, during the manufacturing process of the yttrium oxide disc, the main way to suppress its deformation is to fully release the stress.

[0029] Specifically, during cold isostatic pressing, the elastic mold in the high-pressure container is pressurized, and the pressure on the blank in the elastic mold is first increased to a certain value and maintained for a certain time, during which part of the stress on the blank is released; then the blank in the elastic mold is continued to be pressurized to a set maximum pressure value, and under this pressure condition, it is set to be maintained for a certain time, during which the blank can fully release the internal stress for the second time, and then be completely shaped into the required disc-shaped structure with a small amount of warping deformation.

[0030] The two step-by-step pressurizations can effectively prevent the green body from slowly rebounding when it is subsequently taken out of the elastic mold and placed.

[0031] It should be noted that cold isostatic pressing equipment is an existing technology, and its function and working principle are already public. Cold isostatic pressing equipment with known mechanical structures on the market can be used to pressurize elastic molds filled with yttrium oxide powder materials. Therefore, its specific structure will not be described in detail here.

[0032] S4: Depressurize the elastic mold that has been pressurized twice in S3, and control the rate during depressurization to be ≤4MPa / min; The elastic mold must be depressurized before demolding after pressurization, and the depressurization speed must be controlled to be low. On the one hand, it can prevent the formed yttrium oxide disc from cracking due to the sudden drop in pressure in the elastic mold; on the other hand, it can also prevent the yttrium oxide disc from causing large warping deformation due to sudden stress changes.

[0033] S5: Demolding the elastic mold that has been depressurized in S4, and placing the demolded blank on a constant temperature platform for static rest. After a long period of static rest on the constant temperature platform, the last residual stress on the blank is evenly released, further ensuring that the blank will not produce significant warping deformation. The yield of yttrium oxide discs produced by the method of this application can be increased from 60% produced by traditional methods to 95%.

[0034] S6: The green body, after resting in S5, is directly dried or sintered to produce the desired large-diameter yttrium oxide disc. Depending on the material properties, the green body may also need to be dried or sintered at high temperature after resting in the constant temperature platform to further improve its overall strength and density.

[0035] In some embodiments, the green body is made of yttrium oxide powder material, and thus the yttrium oxide disc green body can be directly sintered after being left to stand.

[0036] It should be noted that before sintering, the yttrium oxide disc body needs to be machined or surface treated to achieve the required size and performance requirements of the final product. The specific machining and surface treatment methods are all existing technologies and will not be described in detail here.

[0037] In some embodiments, when preparing an yttrium oxide disc with a diameter of 610 mm and a thickness of 20 mm, the blank pre-pressed and sealed in an elastic mold is pressurized twice in a cold isostatic pressing device. First, the pressure is increased to 60 MPa at a rate of 15 MPa / min and kept warm for 5 minutes, and the internal stress is initially released within 5 minutes; then the pressure is increased to 160 MPa at a rate of 10 MPa / min and kept warm for 25 minutes, and the stress inside the blank is further released within 25 minutes of keeping warm; then the pressure is released and the mold is demolded, and the demolded yttrium oxide disc blank is immediately placed on a constant temperature platform and left to stand for 48 hours. The yttrium oxide disc produced through the above steps has a maximum surface flatness of 2.18 mm, which effectively suppresses its warping and deformation and can be directly sintered without subsequent correction.

[0038] In other embodiments, see the table below for comparative flatness data of yttrium oxide disks with a diameter of 630 mm produced by the traditional method and the steps described above in this application after cold isostatic pressing.

[0039]

[0040] It can be seen that the large-diameter yttrium oxide disk produced through the steps of this application can effectively suppress large deformation of its surface and can control the flatness within 2.5 mm.

[0041] In some embodiments, the elastic mold described in S1 is made of polyisoprene.

[0042] Polyisoprene material is a polymer material made from the polymerization of isoprene monomers. It has excellent elasticity and good temperature resistance and tear resistance.

[0043] When the elastic mold is made for use, the user can easily demould, making it convenient for the staff to take out the blank in the elastic mold, thereby effectively improving the overall production efficiency of the yttrium oxide disc; The elastic mold made of polyisoprene also has good temperature resistance and tear resistance, so that it has high tear strength when used as a mold in a certain low or high temperature environment. It can withstand multiple demolding, allowing the mold to be reused, thereby increasing the overall service life of the elastic mold of this material, eliminating the need for frequent mold replacement, and effectively reducing the company's production costs.

[0044] In some embodiments, the thickness of the elastic mold is set to 4-6 mm. A mold with a smaller thickness is more convenient for subsequent demoulding.

[0045] In some embodiments, the two-stage gradient pressurization step is: The first stage: pressurize to 60MPa at a rate of 15MPa / min; The second stage: pressurize to 150-180 MPa at a rate of 10 MPa / min.

[0046] The method of increasing pressure in two stages is adopted to release the stress in the blank twice, and the stress in the yttrium oxide disc blank is released completely twice as much as possible, avoiding the phenomenon that the yttrium oxide disc blank cannot be completely released due to the inability to release the stress directly when increasing pressure only once, thereby effectively suppressing the large warping deformation of the yttrium oxide disc during the cold isostatic pressing process.

[0047] After each stage of gradient pressure increase, the elastic mold needs to be pressure-maintained. This not only allows sufficient time for the yttrium oxide disc body to release stress, but also ensures that the yttrium oxide powder is fully densified, effectively improving the production yield of the yttrium oxide disc body.

[0048] The holding time after the first stage of pressurization is 5 minutes, and the holding time after the second stage of pressurization is 20-30 minutes. By holding the pressure after the first and second stages of pressurization, sufficient time is reserved for stress release during the two pressurizations. Only when the stress is fully released can the warping deformation of the blank during the production process be effectively suppressed.

[0049] The surface flatness of the constant temperature platform selected in S4 is ≤0.02mm, the temperature is maintained at 25℃±2℃, the humidity in the constant temperature platform is maintained at 40%±5%, and the blank is left standing for 48 hours. The temperature of the blank after demolding may be different from the ambient temperature. Direct exposure to the environment may cause thermal stress and deformation of the blank. Therefore, the constant temperature platform with a constant temperature and humidity environment provides an environment for the blank to finally release stress. The specific standing time allows the blank to gradually stabilize and release internal stress, avoiding subsequent cracking or deformation.

[0050] The cold isostatic pressing equipment needs to fill a high-pressure container with a liquid medium before applying pressure, and the elastic mold is immersed in the high-pressure container.

[0051] The liquid medium used to fill the high-pressure container is water or oil.

[0052] The above embodiments are only for illustrating the technical concept and features of the present invention. Its purpose is to enable people familiar with this technology to understand the content of the present invention and implement it. It cannot be used to limit the scope of protection of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preventing large deformation during cold isostatic pressing of large-diameter yttrium oxide disks, characterized in that: The following steps are involved: S1: Powdered yttrium oxide material is loaded into a disc-shaped elastic mold and pressed down to form a preliminary shape; S2: sealing the pre-pressed and pre-formed green body in S1 in an elastic mold; S3: placing the elastic mold in S2 into a high-pressure container of a cold isostatic pressing device and applying pressure thereto in a two-stage gradient pressure-increasing manner; S4: Depressurize the elastic mold that has been pressurized twice in S3, and control the rate during depressurization to be ≤4MPa / min; S5: demoulding the elastic mold that has been depressurized in S4, and placing the demoulded green body on a constant temperature platform for rest; S6: directly drying or sintering the green body after the standing in S5 to produce the desired large-diameter yttrium oxide disc.

2. The method for preventing large deformation during cold isostatic pressing of large-diameter yttrium oxide discs according to claim 1, characterized in that: The elastic mold described in S1 is made of polyisoprene.

3. The method for preventing large deformation during cold isostatic pressing of large-diameter yttrium oxide disks according to claim 1, characterized in that: The two-stage gradient pressurization steps are: The first stage: pressurize to 60MPa at a rate of 15MPa / min; The second stage: pressurize to 150-180 MPa at a rate of 10 MPa / min.

4. The method for preventing large deformation during cold isostatic pressing of large-diameter yttrium oxide disks according to claim 3, characterized in that: The elastic mold needs to maintain pressure after each stage of gradient pressure increase.

5. The method for preventing large deformation during cold isostatic pressing of large-diameter yttrium oxide disks according to claim 4, characterized in that: The holding time after the first stage of pressure boosting and pressurization is 5 minutes, and the holding time after the second stage of pressure boosting and pressurization is 20-30 minutes.

6. The method for preventing large deformation during cold isostatic pressing of large diameter yttrium oxide disks according to claim 1, characterized in that: The surface flatness of the constant temperature platform selected in S4 is ≤0.02 mm, the temperature is maintained at 25°C±2°C, the humidity in the constant temperature platform is maintained at 40%±5%, and the standing time of the blank is 48 hours.

7. The method for preventing large deformation during cold isostatic pressing of large diameter yttrium oxide discs according to claim 1, characterized in that: The cold isostatic pressing equipment needs to fill a high-pressure container with a liquid medium before applying pressure, and the elastic mold is immersed in the high-pressure container.

8. The method for preventing large deformation during cold isostatic pressing of large-diameter yttrium oxide disks according to claim 7, characterized in that: The liquid medium used to fill the high-pressure container is water or oil.

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