A sintering process

Abstract

The application relates to the technical field of workpiece sintering, and particularly discloses a sintering process. The sintering process introduces a separator between two workpieces with the same shrinkage ratio before sintering; when sintering a workpiece with a suspended surface, the separator is a high-temperature-resistant ceramic sheet, a workpiece with the same shrinkage ratio is placed below the workpiece with the suspended surface, and then the high-temperature-resistant ceramic sheet is placed between the workpiece with the suspended surface and the workpiece with the same shrinkage ratio as a supporting and separating component; when sintering two matched assembly parts with a size deviation of 0.05-0.1 mm, the separator is a high-temperature-resistant particle coating with a granularity of <500, and the high-temperature-resistant particle coating is coated on the matched interface of the assembly parts. The workpiece size deviation obtained by adopting the sintering process is 0.05-0.1 mm, the problem of uneven sintering shrinkage of the workpiece is solved, and the assembly precision of the workpiece is improved.

Description

Technical Field

[0001] This application relates to the field of workpiece manufacturing technology, and more specifically, to a sintering process. Background Technology

[0002] Metal injection molding sintering is a novel metal powder forming technology developed based on plastic injection molding. This technology is used to manufacture small-sized parts with more complex shapes that are difficult to mold using compression molding. It combines the advantages of powder metallurgy and injection molding and is widely used in the mass production of precision parts. However, the metal injection molding sintering process suffers from uneven shrinkage due to the product's structure, local density, and thickness instability. This can result in difficulty in achieving the design dimensional requirements, especially for two or more tightly assembled parts and assemblies. During the sintering process, some parts of the workpiece may be suspended, which can easily lead to breakage of these suspended parts during sintering. Furthermore, shrinkage can cause downward deformation due to gravity, resulting in insufficient assembly accuracy.

[0003] In related technologies, in order to improve the assembly accuracy of workpieces, the workpiece is placed directly under the conformal ceramic block. However, the ceramic block is generally 1-2 times larger than the workpiece, making it impossible to fit the workpiece tightly. Furthermore, when the workpiece shrinks during sintering, the ceramic sheet cannot shrink. In addition, the workpiece itself may have different thicknesses, resulting in large density differences and inconsistent shrinkage, which still easily leads to deformation and makes it difficult to meet the assembly accuracy required for actual use. Summary of the Invention

[0004] To address the problem of uneven shrinkage during sintering and improve the assembly accuracy of workpieces, this application provides a sintering process.

[0005] In a first aspect, this application provides a sintering process, which adopts the following technical solution: A sintering process, the sintering process comprising introducing a separator between two workpieces with the same shrinkage ratio before sintering.

[0006] By adopting the above technical solution, two workpieces with the same shrinkage ratio are sintered simultaneously during the sintering process. The two workpieces have the same shrinkage ratio. In order to prevent the two workpieces from sticking together during sintering, a separator is introduced in the middle, which solves the problem of uneven shrinkage during the sintering of the components and improves the assembly accuracy of the workpieces.

[0007] Preferably, the separator is a high-temperature resistant ceramic sheet. A workpiece with the same shrinkage ratio is placed below the workpiece with the suspended surface, and then the high-temperature resistant ceramic sheet is placed between the workpiece with the suspended surface and the workpiece with the same shrinkage ratio as a support and separator.

[0008] By adopting the above technical solution, when sintering workpieces with suspended surfaces, the traditional sintering process, where the height of the supporting ceramic sheet is the height after product shrinkage, easily causes the blank to be suspended, resulting in the ceramic sheet not shrinking while the workpiece shrinks. During the shrinkage process, it is prone to risks such as breakage, cracking, deformation, and collapse due to the influence of gravity. To solve this problem, a supporting workpiece with the same shrinkage ratio is placed below the workpiece with the suspended surface, and then a high-temperature resistant ceramic sheet is placed between the workpiece with the suspended surface and the supporting workpiece with the same shrinkage ratio as a supporting isolation component. The two workpieces shrink simultaneously and evenly, solving the problem of uneven shrinkage during workpiece sintering and improving the assembly accuracy of the workpiece.

[0009] This process has a wide range of applications and can be used for sintering various workpieces with suspended surfaces, such as... Figure 1-3 Workpieces that are assembled together can also be applied to, for example Figure 4-5 Non-assembled workpieces with suspended surfaces injection molded.

[0010] Preferably, the thickness of the high-temperature resistant ceramic sheet is the difference between the height of the workpiece's suspended surface and the height of the workpiece supported below with the same shrinkage ratio.

[0011] Preferably, when two matching components have a sintering size deviation of 0.05-0.1mm, the separator is a high-temperature resistant particle coating with a mesh size of ≥500, and the high-temperature resistant particle coating is applied to the interface of the component fitting. The high-temperature resistant particulate coating comprises the following raw materials in parts by weight: 80-90 parts of high-temperature resistant particles, 5-10 parts of flow aid, and 5-10 parts of adhesion inhibitor.

[0012] By employing the above technical solution, a high-temperature resistant particulate coating is applied to the mating interface of two fitting components, allowing the two sets of components to be assembled together. Because the materials are identical, the shrinkage ratios of the two sets of components are perfectly matched during shrinkage, and they restrain each other during shrinkage, thus improving the assembly accuracy of the components. Furthermore, using this method to sinter the components can also improve sintering efficiency; see details below. Figure 6-8 .

[0013] In this high-temperature resistant granular coating, the high-temperature resistant particles provide a physical support framework, while the flow aid fills the gaps between the particles. This allows the coating to form a uniform film during application and, at high temperatures, transform into a low-residue substance, preventing adhesion of residues that could affect surface quality. The mating interfaces can naturally detach or form a weak bond, improving component separation performance and sintered surface cleanliness. The adhesion inhibitor forms a low surface energy film on the coating surface, ensuring that the mating interfaces of the two sets of components are free from adhesion and easily separated after sintering, forming a high-precision assembly structure.

[0014] The high-temperature resistant particles are controlled to be larger than 500 mesh to improve their filling, isolation and flowability at the interface, and avoid local support instability or insufficient gap filling caused by coarse sand particles.

[0015] Preferably, the high-temperature resistant particles can be any one of ceramic sintered sand, zircon sand, white alumina corundum sand, and mullite sand.

[0016] When the high-temperature resistant particles used in this application are selected from any one of ceramic sintered sand, zircon sand, white alumina corundum sand, or mullite sand, they can improve the workpiece precision to varying degrees.

[0017] By adopting the above technical solution, the high-temperature resistant particles can be selected from any one of ceramic sintered sand, zircon sand, white alumina corundum sand, and mullite sand. Among them, ceramic sintered sand is selected because it has high high-temperature stability, which can avoid chemical reaction with the surface of the components and block "chemical bonding". The hydroxyl content of ceramic sintered sand is suitable for the chemical anchoring requirements of the adsorbent, which can ensure the bonding force and prevent the adsorbent from premature cross-linking and agglomeration due to excessive activity, making it more suitable as a high-temperature resistant particle.

[0018] Preferably, the flow aid can be any one or more of fumed silica, nano-calcium carbonate, and talc.

[0019] The flow aid in the sintered sand coating of this application can be any one or more of fumed silica, nano calcium carbonate, and talc. When any one of fumed silica, nano calcium carbonate, and talc is selected as the flow aid, the assembly accuracy of the components can be improved to varying degrees.

[0020] Preferably, the flow aid is a mixture of fumed silica, nano-calcium carbonate, and talc; the mass ratio of fumed silica, nano-calcium carbonate, and talc is 2:1:1.

[0021] By adopting the above technical solution, the flow aid, fumed silica, can form a steric hindrance effect to block the agglomeration of sintered sand particles. Nano-calcium carbonate can fill the gap between fumed silica and sintered sand, reduce the contact area between particles, and further improve fluidity. Talc powder has a flake structure that can form a "lubricating film" on the particle surface, reduce sliding friction, and at the same time improve the toughness of the coating, preventing the coating from falling off and the two sets of accessories from sticking together when they are attached.

[0022] Preferably, the adhesion inhibitor can be any one or more of zinc stearate, polytetrafluoroethylene micro powder, and modified silicone oil.

[0023] The adhesion inhibitor in the sintered sand coating of this application can be any one or more of zinc stearate, polytetrafluoroethylene micro powder, and modified silicone oil. Moreover, the use of any one of zinc stearate, polytetrafluoroethylene micro powder, and modified silicone oil as the adhesion inhibitor can improve the assembly accuracy of the components to varying degrees.

[0024] Preferably, the adsorption inhibitor is a mixture of zinc stearate and polytetrafluoroethylene micro powder; the mass ratio of zinc stearate to polytetrafluoroethylene micro powder is 1:(1-3).

[0025] By adopting the above technical solution, polytetrafluoroethylene (PTFE) micropowder provides a core low surface energy, forming a hydrophobic and oleophobic lubricating layer on the coating surface, fundamentally reducing the adhesion between the components and the coating. However, PTFE micropowder is prone to agglomeration. Zinc stearate can improve the dispersibility of PTFE micropowder, forming a continuous low surface energy layer, avoiding "local high surface energy areas" caused by PTFE micropowder agglomeration, and further improving the assembly accuracy of components.

[0026] In summary, this application includes at least one of the following beneficial technical effects: (1) When sintering a workpiece with a suspended surface, this application places a support workpiece with the same shrinkage ratio below the workpiece with the suspended surface, and then places a high-temperature resistant ceramic sheet as a support and isolation component between the workpiece with the suspended surface and the support workpiece with the same shrinkage ratio. When sintering two matching parts with a sintering dimensional deviation of 0.05-0.1mm, a high-temperature resistant particle coating of <500 mesh is applied to the mating interface, and the dimensional deviation is only 0.09-0.1mm, which can improve the assembly accuracy of the workpiece.

[0027] (2) This application uses a mixture of fumed silica, nano calcium carbonate and talc as a flow aid for sintered sand coating and controls the ratio of the three to make the dimensional deviation of the assembly parts 0.07mm, which further improves the assembly accuracy of the assembly parts.

[0028] (3) This application uses a mixture of zinc stearate and polytetrafluoroethylene micro powder as an adsorption inhibitor for sintered sand coating and controls the ratio of the two to make the dimensional deviation of the assembly parts 0.05mm, which further improves the assembly accuracy of the assembly parts. Attached Figure Description

[0029] Appendix Figure 1 First set of accessory parts Appendix Figure 2 Assembly diagram of the first set of component parts Appendix Figure 3 Schematic diagram of the first set of accessory parts being introduced into the ceramic sheet. Appendix Figure 4 Schematic diagrams of two types of workpieces Appendix Figure 5 Schematic diagram of two types of workpieces introduced into ceramic sheets Appendix Figure 6 Second set of accessory parts Appendix Figure 7 The second set of accessory parts are coated with sintered sand paint. Appendix Figure 8 Schematic diagram of the assembly of the second set of component parts after being coated with sintered sand paint. Detailed Implementation

[0030] The present application will be further described in detail below with reference to specific embodiments.

[0031] The following raw materials used in this application are all commercially available products and are intended to fully disclose the raw materials used in this application. They should not be construed as limiting the source of the raw materials. Specifically: high-temperature resistant particles, made from ceramic sintered sand, with a particle size of 500 mesh; flow aid, fumed silica, with an effective content of 99.8% and a particle size of 50 nm, nano-calcium carbonate, with a particle size of 50 nm, talc powder, with a particle size of 50 nm; adhesion inhibitor, zinc stearate, with an effective content of 99.5%, and polytetrafluoroethylene micro powder, with a particle size of 3 μm.

[0032] Example 1: The sintering process of Example 1 includes the following steps: Using powder metallurgy sintering, powder metallurgy is mixed, pressed, and then fed into a pre-set mold to form a blank door hinge workpiece. A support workpiece with the same shrinkage ratio is placed below the blank door hinge workpiece with a suspended surface. Then, a high-temperature resistant ceramic sheet is placed between the workpiece with the suspended surface and the support workpiece with the same shrinkage ratio as a support and isolation component. Sintering is performed at 1300℃ for 2 hours, followed by air cooling and polishing to obtain the first door hinge workpiece. The thickness of the high-temperature resistant ceramic sheet is 0.5 mm. See details below. Figure 1-3 .

[0033] Example 2: The sintering process of Example 2 includes the following steps: Using powder metallurgy sintering, powder metallurgy is mixed, pressed, and then fed into a pre-set mold to form a blank workpiece. A support workpiece with the same shrinkage ratio is placed below the blank workpiece with a suspended surface. Then, a high-temperature resistant ceramic sheet is placed between the workpiece with the suspended surface and the support workpiece with the same shrinkage ratio as a support and isolation component. Sintering is performed at 1300℃ for 2 hours, followed by air cooling and polishing to obtain the first door shaft workpiece. See details below. Figure 4-5 .

[0034] Example 3: The sintering process in Example 3 differs from that in Example 1 in that the separator is a high-temperature resistant particle coating, and the high-temperature resistant particles are selected from ceramic sintered sand. The high-temperature resistant particle coating is applied to the mating interface of two matching components; see details. Figure 6-8 .

[0035] The high-temperature resistant particulate coating comprises the following raw materials in parts by weight: 85g of ceramic sintered sand with a particle size of 500 mesh, 7g of fumed silica (flow aid), and 8g of polytetrafluoroethylene micro powder (adhesion inhibitor). The remaining steps are the same as in Example 1.

[0036] Example 4 The sintering process of Example 4 differs from that of Example 3 in that the flow aid is a mixture of fumed silica, nano-calcium carbonate and talc, and the amounts of fumed silica, nano-calcium carbonate and talc are 3.5g, 1.75g ​​and 1.75g, respectively. The remaining steps are the same as those of Example 3.

[0037] Examples 5-9 The sintering process of Examples 5-9 differs from that of Example 4 in that the adhesion inhibitor is a mixture of zinc stearate and polytetrafluoroethylene micro powder. The amounts of zinc stearate and polytetrafluoroethylene micro powder are 5.3g and 2.7g, 4g and 4g, 2.6g and 5.4g, 2g and 6g, and 1.6g and 3.4g, respectively. The remaining steps are the same as those in Example 4.

[0038] Comparative Example 1 The powder metallurgy component sintering process of Comparative Example 1 is as follows: the component is placed directly on the shaped ceramic block for sintering, and the remaining steps are the same as in Example 1.

[0039] Performance testing The workpieces obtained in Examples 1-9 and Comparative Example 1 were tested using the following methods. The specific test results are shown in Table 1.

[0040] Dimensional deviation: The actual dimensions of the assembly parts are measured using calipers. Based on the dimensions marked on the design drawings, the difference between the actual dimensions and the dimensions marked on the design drawings is calculated, which is the dimensional deviation.

[0041] Table 1. Detection results for different workpieces

[0042] The test results in Table 1 show that the dimensional deviation of the workpiece prepared by the sintering process of this application is 0.05-0.1 mm, which solves the problem of uneven sintering shrinkage of the workpiece and improves the assembly accuracy of the workpiece.

[0043] According to the workpiece performance tests in Examples 1-2 and Example 3, it was found that the sintering process of placing a support blank workpiece with the same shrinkage ratio under the workpiece with the suspended surface in Example 1, and then placing a high-temperature resistant ceramic sheet as a support and isolation component between the workpiece with the suspended surface and the support workpiece with the same shrinkage ratio, as well as the application of high-temperature resistant particle coating to the mating interface of two matching components, can improve the workpiece assembly accuracy to varying degrees.

[0044] According to the workpiece performance tests of Examples 3 and 4, the dimensional deviation of the workpiece in Example 4 was 0.07 mm, which was lower than that in Example 3. This indicates that when the flow aid in the high-temperature resistant particulate coating is a mixture of fumed silica, nano-calcium carbonate and talc, and the mass ratio of fumed silica, nano-calcium carbonate and talc is 2:1:1, it is more conducive to improving the assembly accuracy of the workpiece.

[0045] According to the performance test of the workpieces in Examples 5-9, the dimensional deviation of the accessories in Examples 6-8 was 0.05mm, which was lower than that in Examples 5 and 9. This indicates that when the adsorption inhibitor in the sintered sand coating is a mixture of zinc stearate and polytetrafluoroethylene micro powder, and when the mass ratio of zinc stearate to polytetrafluoroethylene micro powder is 1:(1-3), it is more conducive to improving the assembly accuracy of the workpiece.

[0046] According to the performance tests of the components in Examples 1-3 and Comparative Example 1, the dimensional deviation of the components in the comparative example group was 0.2 mm, which was significantly higher than that in Examples 1-2. This indicates that the effect of introducing a separator between the workpieces before sintering to improve the workpiece accuracy is far greater than placing the workpiece directly on the ceramic block. This proves that the sintering process of this application can significantly improve the assembly accuracy of the workpiece.

[0047] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A sintering process, characterized in that, The sintering process includes introducing a separator between two workpieces with the same shrinkage ratio before sintering.

2. The sintering process according to claim 1, characterized in that, The separator is a high-temperature resistant ceramic sheet. A workpiece with the same shrinkage ratio is placed below the workpiece with the suspended surface, and then the high-temperature resistant ceramic sheet is placed between the workpiece with the suspended surface and the workpiece with the same shrinkage ratio as a support and separator.

3. The sintering process according to claim 2, characterized in that, The thickness of the high-temperature resistant ceramic sheet is the difference between the height of the workpiece's suspended surface and the height of the workpiece supported below with the same shrinkage ratio.

4. The sintering process according to claim 1, characterized in that, When two matching components have a sintering size deviation of 0.05-0.1mm, the separator is a high-temperature resistant particle coating with a mesh size of ≥500, which is applied to the interface of the component fitting. The high-temperature resistant particulate coating comprises the following raw materials in parts by weight: 80-90 parts of high-temperature resistant particles, 5-10 parts of flow aid, and 5-10 parts of adhesion inhibitor.

5. The sintering process according to claim 4, characterized in that, The high-temperature resistant particles can be any one of ceramic sintered sand, zircon sand, white alumina corundum sand, or mullite sand.

6. The sintering process according to claim 4, characterized in that, The flow aid can be any one or more of fumed silica, nano-calcium carbonate, and talc.

7. The sintering process according to claim 4, characterized in that, The flow aid is a mixture of fumed silica, nano-calcium carbonate, and talc; the mass ratio of fumed silica, nano-calcium carbonate, and talc is 2:1:

1.

8. The sintering process according to claim 4, characterized in that, The adhesion inhibitor can be any one or more of zinc stearate, polytetrafluoroethylene micro powder, and modified silicone oil.

9. The sintering process according to claim 4, characterized in that, The adhesion inhibitor is a mixture of zinc stearate and polytetrafluoroethylene micro powder; the mass ratio of zinc stearate to polytetrafluoroethylene micro powder is 1:(1-3).

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