Vacuum high-pressure smelting and impregnating process for graphite products and application thereof

Abstract

The application belongs to the technical field of graphite product impregnation, and particularly relates to a vacuum high-pressure smelting impregnation process for graphite products and application. The process comprises the following steps: firstly, loading the graphite product into a crucible, vacuumizing, preheating the graphite product crucible, wherein the preheating is performed by heating to 800 DEG C at a power of 30KW+ / -10KW, then heating to 1150+ / -50 DEG C at a power of 50KW+ / -5KW, and finally adjusting the temperature to 1220-1280 DEG C and keeping for 20-30 min. Then, alloy smelting is performed under vacuum to obtain an alloy melt; the alloy melt is poured into the preheated graphite product crucible under vacuum; and after pouring is completed, pressure impregnation is performed to obtain the product. After the specific impregnation treatment, the material performance of the graphite product is significantly improved, and the mechanical strength is improved and the open porosity is reduced.

Description

Technical Field

[0001] This invention belongs to the field of graphite product impregnation technology, specifically relating to a vacuum high-pressure melting and impregnation process for graphite products and its application. Background Technology

[0002] When carbon graphite products are impregnated with high-melting-point alloys in an atmospheric environment, the air is compressed during the pressurization process, generating a strong reaction force inside the product. Therefore, after depressurization, some of the molten alloy already impregnated in the carbon graphite product is inevitably expelled, ultimately leading to defects within the material. Furthermore, if carbon graphite products are not subjected to a vacuum process, the unexpelled gas in the core of the material can easily form an isobaric layer, disrupting the overall isotropy of the material.

[0003] Chinese invention patent application CN202311307551.8 discloses a vacuum metal impregnation method, which includes the following steps: S1, placing metal into a graphite crucible, closing the molten metal inlet pipe and the molten metal return pipe, turning on the power to the heating element, and melting the metal; S2, placing the graphite product to be impregnated into a graphite frame; then suspending the graphite frame onto a placement platform, sealing the container, evacuating, and heating with infrared radiation; S3, opening the molten metal inlet pipe, and simultaneously pressurizing the molten metal surface with nitrogen gas through a pressurization system; S4, after impregnation, closing the molten metal inlet pipe, restoring to atmospheric pressure, opening the molten metal inlet pipe, and allowing the molten metal to flow back into the graphite crucible; S5, closing the molten metal inlet pipe, selecting a suitable cooling curve according to the performance requirements of the final product, and removing the frame after cooling, taking out the impregnated graphite product, and placing it in a filler to prevent oxidation; this invention can perform metal impregnation more effectively.

[0004] Chinese invention patent application 201611020844.8 discloses a continuous hot isostatic pressing (HIP) impregnation method for preparing high-impregnation-weight carbon-copper composite materials. First, the components are proportioned according to the required properties. Then, copper ingots are melted in a crucible under vacuum. A tooling system is used to immerse the carbon material to be impregnated into the molten copper, and argon gas is introduced to control the pressure inside the furnace. After impregnation, part of the pressure is released, maintaining a stable pressure. The tooling system is then controlled to slowly lift the impregnated carbon-copper composite material from the molten copper in the crucible. Simultaneously, the molten copper in the impregnating material cools and solidifies during the slow ascent. After solidification, the pressure is reduced to atmospheric pressure, and the impregnated carbon-copper composite material is quickly removed under argon gas and transferred to an argon-filled glove box for further cooling to room temperature. This method ensures complete retention of the molten copper in the carbon-copper composite material, meets the requirements for rapid impregnation of high-impregnation-weight carbon-copper composite products, exhibits excellent impregnation uniformity, and allows for continuous operation.

[0005] Existing technologies have conducted some research on graphite product impregnation techniques and achieved certain results, but there are still problems such as the easy formation of defects inside carbon graphite products and the need to further improve the material properties. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a vacuum high-pressure melting and impregnation process for graphite products.

[0007] To achieve the objectives of this invention, the following technical solution is adopted:

[0008] A vacuum high-pressure melting and impregnation process for graphite products includes the following steps:

[0009] (1) Place the graphite product into the crucible, evacuate the vacuum, and preheat the graphite product crucible.

[0010] (2) The alloy is melted under vacuum to obtain an alloy melt;

[0011] (3) Under vacuum conditions, the alloy melt is poured into a preheated graphite crucible for casting;

[0012] (4) After casting, pressure impregnation is applied to obtain the product.

[0013] Preferably, the preheating in step (1) is to heat to 800°C with a power of 30KW±10KW, then heat to 1150±50°C with a power of 50KW±5KW, and finally adjust the temperature to 1220-1280°C and hold for 20-30 minutes.

[0014] Preferably, the vacuum degree after evacuation in step (1) is 100-300 Pa.

[0015] Preferably, the smelting in step (2) involves heating to 800℃±60℃ with a power of 20KW±10KW, and then rapidly heating to 1100℃±50℃ with a power of 55KW±5KW.

[0016] Preferably, the alloy in step (2) is a copper / tin alloy, and the mass ratio of copper to tin is 70-75:8-15.

[0017] Preferably, the vacuum condition in step (3) is no higher than 1000 Pa; the casting time is 8-10 s.

[0018] Preferably, after casting is completed in step (4), the vacuum degree is reduced to 0 MPa; the pressure is increased to 20-40 MPa in step (4).

[0019] Preferably, the pressurization in step (4) is to pressurize to 16 MPa at a rate of 0.2 ± 0.05 MPa / s, and then pressurize to 30-40 MPa at a rate of 0.4 ± 0.05 MPa / s.

[0020] Preferably, in step (4), the pressure is increased to 30-40 MPa and then maintained for 1-3 minutes.

[0021] The second objective of this invention is to provide a graphite composite material obtained by the aforementioned vacuum high-pressure melting and impregnation process.

[0022] Another objective of this invention is to provide the application of the above-mentioned vacuum high-pressure melting and impregnation process in the preparation of graphite composite materials.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] (1) This invention improves the penetration and diffusion of the impregnation material by changing the vacuum level and the duration of vacuum in the sealed container, allowing the copper alloy to penetrate more fully into the micropores of the solid material. The internal pores of the solid material are filled by the impregnation material, thus improving its mechanical strength. Furthermore, within the vacuum level range of this invention, this range can effectively prevent the interference of oxygen and impurities in the air on the melting process, while ensuring that the molten liquid can enter the graphite product uniformly, avoiding the formation of pores and defects. Excessive or insufficient vacuum has a non-negligible impact on porosity and strength properties.

[0025] (2) This invention has studied and explored the preheating procedure of graphite products and the heating gradient of alloy melting, which reduces the defects that may be generated in graphite during subsequent melting (such as porosity, cracks, etc.), improves the functionality and stability of the alloy, and improves the mechanical strength and other properties of graphite products.

[0026] (3) This invention utilizes a specific pressure rate for impregnation, resulting in a more uniform distribution of the alloy liquid within the graphite product, thereby improving the impregnation effect. While excessively fast impregnation can increase production efficiency, the impregnating liquid tends to accumulate on the surface, leading to voids and cracks in the graphite product. To ensure that all pores and gaps within the workpiece are filled with the alloy liquid and to avoid defects caused by uneven impregnation, the inventors first apply pressure at a specific rate to fill the large pores with the impregnating liquid. Then, the pressure rate is appropriately increased to 0.4 MPa / s, which overcomes the capillary resistance in the graphite product. After pressure-holding impregnation treatment, the impregnating agent can penetrate into the tiny pores inside the graphite product and bond tightly with the graphite material, thereby improving the mechanical strength of the graphite product, reducing the open porosity, and forming a uniform and dense composite material. Detailed Implementation

[0027] The present invention will be further described below with reference to specific embodiments. The raw materials used in the following embodiments are all commercially available conventional raw materials. The alloy used in the following embodiments is a copper-tin alloy with a mass ratio of 70-75:8-15, supplied by Zigong Huagang Wear-Resistant Materials Co., Ltd.

[0028] Example 1:

[0029] The vacuum high-pressure melting and impregnation process for graphite products involves the following steps:

[0030] (1) Put the graphite product into the crucible, evacuate the vacuum, and complete the preparation when the vacuum degree is lower than 255Pa. Start preheating the graphite product crucible. Preheating is done by heating to 800℃ with 30KW power, then heating to 1150℃ with 50KW power, and finally manually adjusting the temperature to 1220℃ and holding for 20min.

[0031] (2) Melt the alloy under vacuum conditions (same as step (1)). Heat the alloy to 800°C with 20KW power and then rapidly heat it to 1100°C with 55KW power to ensure that the alloy is in a slightly boiling state and does not produce boiling explosion. The alloy is directly purchased and belongs to copper / tin alloy. The copper to tin mass ratio is required to be 75:15. The supplier is Zigong Huagang Wear-resistant Materials Co., Ltd.

[0032] (3) Under vacuum conditions (same as step (1)), the alloy melt is poured into a preheated graphite crucible for casting, paused for 9 seconds, and the casting is completed.

[0033] (4) After casting, remove the vacuum condition from the graphite product crucible, apply pressure for impregnation, pressurize to 16 MPa at a rate of 0.2 MPa / s, and then pressurize to 30 MPa at a rate of 0.4 MPa / s, holding the pressure for 3 minutes. After impregnation, pour the alloy into a preheated graphite crucible, pour the impregnated product into a post-impregnation filler tank, and cool it with filler for protection.

[0034] Example 2

[0035] The vacuum high-pressure melting and impregnation process for graphite products involves the following steps:

[0036] (1) Put the graphite product into the crucible, evacuate the vacuum, and complete the preparation work when the vacuum degree is 120Pa. Start by raising the temperature to 800℃ with 20KW power, then raise it to 1100℃ with 45KW power, and then change the manual temperature control to 1250℃ to start timing and preheat the graphite product crucible for 30 minutes.

[0037] (2) The alloy is melted under vacuum conditions (same as step (1)). The melting is carried out by heating to 740°C with 10KW power and then rapidly heating to 1050°C with 50KW power to obtain the alloy melt. The alloy is directly purchased and belongs to copper / tin alloy. The supplier is Zigong Huagang Wear-resistant Materials Co., Ltd.

[0038] (3) Under vacuum conditions (same as step (1)), the alloy melt is poured into a preheated graphite crucible for casting, paused for 8 seconds, and the casting is completed.

[0039] (4) After casting, remove the vacuum condition from the graphite product crucible and apply pressure for impregnation. The pressure is increased to 16 MPa at a rate of 0.25 MPa / s, and then to 40 MPa at a rate of 0.45 MPa / s, and held for 1 minute. After impregnation, pour the alloy into the preheated graphite crucible, pour the impregnated product into the post-impregnation filler tank, and cool it with the filler for protection.

[0040] Example 3

[0041] The vacuum high-pressure melting and impregnation process for graphite products involves the following steps:

[0042] (1) Put the graphite product into the crucible, evacuate the vacuum, and complete the preparation work when the vacuum degree is 200Pa. Start preheating the graphite product crucible. Preheat to 800℃ with 40KW power, then heat to 1200℃ with 55KW power, and finally adjust the temperature to 1280℃ and hold for 30min.

[0043] (2) The alloy is melted under vacuum conditions (same as step (1)). The melting is to heat the alloy to 860°C with 30KW power and then rapidly heat it to 1150°C with 60KW power to obtain the alloy melt. The alloy is directly purchased and is a copper / tin alloy. The supplier is Zigong Huagang Wear-resistant Materials Co., Ltd.

[0044] (3) Under vacuum conditions (same as step (1)), the alloy melt is poured into a preheated graphite crucible for casting, paused for 10 seconds, and the casting is completed.

[0045] (4) After casting, remove the vacuum condition from the graphite product crucible, apply pressure for impregnation, pressurize to 16 MPa at a rate of 0.2 MPa / s, and then pressurize to 30 MPa at a rate of 0.4 MPa / s, holding the pressure for 3 minutes. After impregnation, pour the alloy into a preheated graphite crucible, pour the impregnated product into a post-impregnation filler tank, and cool it with filler for protection.

[0046] Comparative Example 1

[0047] The difference between this comparative example and Example 1 is that the vacuum degree in step (2) is 50 Pa, while the other conditions are the same as in Example 1.

[0048] Comparative Example 2

[0049] The difference between this comparative example and Example 1 is that the vacuum degree in step (3) is 500 Pa, while the other conditions are the same as in Example 1.

[0050] Comparative Example 3

[0051] The difference between this comparative example and Example 1 is that the melting conditions in step (2) are different, specifically, the temperature is raised to 1100°C with a power of 40KW.

[0052] Comparative Example 4

[0053] The difference between this comparative example and Example 1 is that the melting conditions in step (2) are different. Specifically, the temperature is raised to 800°C with a power of 55KW and to 1100°C with a power of 20KW.

[0054] Comparative Example 5

[0055] The difference between this comparative example and Example 1 is that the pressurization conditions in step (4) are different. Specifically, the pressure is increased to 12 MPa at a rate of 0.1 MPa / s, and then increased to 30 MPa at a rate of 0.3 MPa / s, and held for 3 minutes.

[0056] Experimental Test

[0057] The properties of impregnated graphite composite materials were tested using the method JB / T8133.1-2013, and the results are shown in Table 1.

[0058] Table 1

[0059]

[0060] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included within the scope of the technical solution of the present invention.

Claims

1. A vacuum high-pressure melting and impregnation process for graphite products, characterized in that, Includes the following steps: (1) Place the graphite product into the crucible, evacuate the vacuum, and preheat the crucible; (2) The alloy is melted under vacuum to obtain an alloy melt; (3) Cast the alloy melt into a preheated crucible under vacuum conditions; (4) After casting, pressure impregnation is applied to obtain the final product; The preheating in step (1) is to heat to 800°C with a power of 30kW±10kW, then heat to 1150±50°C with a power of 50kW±5kW, and finally adjust the temperature to 1220-1280°C and hold for 20-30 minutes. The vacuum degree after evacuation in step (1) is 100-300 Pa; the vacuum conditions in steps (2)-(3) are the same as the vacuum degree after evacuation in step (1); The pressurization in step (4) is to pressurize to 16 MPa at a rate of 0.2 ± 0.05 MPa / s, and then pressurize to 30-40 MPa at a rate of 0.4 ± 0.05 MPa / s; The smelting in step (2) involves heating to 800℃±60℃ with a power of 20kW±10kW, and then rapidly heating to 1100℃±50℃ with a power of 55kW±5kW.

2. The vacuum high-pressure melting and impregnation process according to claim 1, characterized in that, The alloy mentioned in step (2) is a copper / tin alloy with a copper to tin mass ratio of 70-75:8-15.

3. The vacuum high-pressure melting and impregnation process according to claim 1, characterized in that, The casting time in step (3) is 8-10 seconds.

4. The vacuum high-pressure melting and impregnation process according to claim 1, characterized in that, After casting is completed in step (4), the vacuum degree is reduced to 0 MPa; the pressure is increased to 20-40 MPa as described in step (4).

5. The vacuum high-pressure melting and impregnation process according to claim 4, characterized in that, After pressurizing to 30-40 MPa as described in step (4), maintain the pressure for 1-3 minutes.

6. A graphite composite material obtained by the vacuum high-pressure melting and impregnation process according to any one of claims 1-5.

7. The application of the vacuum high-pressure melting and impregnation process according to any one of claims 1-5 in the preparation of graphite composite materials.

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