Metal injection molding process for pure copper material
By optimizing the pure copper powder and binder components and the three-stage thermal stripping process, the problems of insufficient density and thermal conductivity in pure copper processing were solved, and the forming of high-density, high-thermal conductivity copper products was achieved.
Patent Information
- Application Number
- CN202510805376.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-17
- Publication Date
- 2025-09-16
AI Technical Summary
Traditional pure copper processing technology is difficult to form complex thin-walled structures, the material waste rate is high, the copper powder is easily oxidized, resulting in difficulty in sintering and densification, the density and thermal conductivity of copper products are insufficient, and traditional binders have a lot of degreasing residue and high porosity.
Small-particle low-carbon and low-oxygen pure copper powder is used with an optimized binder component design, combined with oxalic acid catalytic degreasing and a three-stage stepped warm thermal desintering process. Hydrogen is introduced during the thermal desintering process to carry out redox reactions.
The density and thermal conductivity of copper products are improved, the porosity is reduced, the molding requirements of high density and complex structures are met, and the material cost is reduced.
Smart Images
Figure CN120644661A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of metal powder injection molding, in particular to a pure copper material metal injection molding process. Background Art
[0002] Pure copper materials are widely used in electronic heat dissipation, power transmission, and medical devices due to their excellent electrical and thermal conductivity, ductility, and corrosion resistance. Pure copper's electrical and thermal conductivity is second only to silver, and its cost is relatively low, making it the material of choice for high-end heat sinks, power transmission components, and medical devices. However, traditional pure copper processing technology faces significant challenges: due to the soft texture and easy deformation of pure copper, it is difficult to form complex thin-walled structures in mechanical processing, and the material waste rate is high. Moreover, with the miniaturization of electronic devices and the increase in power density, traditional pure copper processing technology can no longer meet the needs of precise heat dissipation structures (such as microchannels and ultra-thin fins).
[0003] Metal Injection Molding (MIM) combines the advantages of powder metallurgy and plastic injection molding. Metal powder and a binder are mixed into a feedstock, which is then injection-molded into complex part blanks. These are then degreased and sintered to produce near-net-shape products. MIM technology is particularly suitable for the mass production of small, complex structural parts, achieving material utilization rates exceeding 95%, significantly reducing the high cost of pure copper. However, the MIM process for pure copper has long faced technical bottlenecks: copper powder is easily oxidized (oxygen content > 0.5%), making sintering densification difficult. The density of copper products is typically less than 8.5 g / cm³, making it difficult to meet high-density requirements. Traditional binders produce a high level of residual degreasing, resulting in numerous pores and a thermal conductivity of less than 300 W / (m·K) in copper products. Furthermore, the poor fluidity of copper powder limits the ability to form ultra-fine structures. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide a pure copper material metal injection molding process, and the copper products prepared by the pure copper material metal injection molding process have the advantages of high density and high thermal conductivity.
[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a pure copper material metal injection molding process, comprising the following steps: Raw material preparation: weigh pure copper powder and binder. The weight percentage of each component in the pure copper powder is Fe≤0.1wt%, C≤0.02wt%, O≤0.15wt%, and Cu is the balance. The particle size specification of the pure copper powder is D 90 :22-24μm,D 50 :7-9μm,D 10: 2-4μm; the components of the binder are POM: 85%-88%, PE: 5%-6%, EVA: 2%-4%, SA: 3%-4%, PW: 1%-2%; Mixing and granulation: add the weighed pure copper powder into an internal mixer, heat it up and bake it, then add the weighed binder and knead it. After the pure copper powder and the binder are evenly mixed, cool it down, extrude it, and cut it into pieces to obtain block feed. Then, put the block feed into a granulator for extrusion and granulation to obtain granular injection feed. Injection sample: Put the granular injection feed into the injection machine hopper and inject it into the mold to obtain the copper green sample; Degreasing: The copper green body sample was degreased by using oxalic acid catalytic degreasing process to obtain a degreased green body sample; Thermal desintering: The degreased green sample is placed in a tubular furnace for thermal desintering. Hydrogen is introduced throughout the thermal desintering process. During the thermal desintering stage, the temperature is increased to 375-385 °C at a heating rate of 1 °C / min-2 °C / min and kept warm for 85-95 min; after the insulation is completed, the temperature is increased to 445-455 °C at a heating rate of 1 °C / min-2 °C / min and kept warm for 85-95 min; after the insulation is completed, the temperature is increased to 575-585 °C at a heating rate of 1.5 °C / min-2 °C / min and kept warm for 85-95 min.
[0006] The beneficial effects of the present invention are as follows: the metal injection molding process of pure copper materials adopts small-particle low-carbon and low-oxygen pure copper powder in combination with a binder component to design and optimize a feed with a higher flow rate, which reduces the porosity while meeting the requirements of injecting complex structure products, and is conducive to reducing the limitations of the application of the metal injection molding process of pure copper materials; the three-stage stepped warm desintering process is adopted, which can more completely remove the binder, thereby reducing the porosity and improving the density and thermal conductivity of the copper product; hydrogen is introduced throughout the hot desintering step, so that the copper oxide in the tubular furnace undergoes an oxidation-reduction reaction, allowing the degreased green body to be sintered densely, thereby greatly improving the density and thermal conductivity of the copper product. BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Figure 1 This is the metallographic image of the polished sintered sample of Example 1.
[0008] Figure 2 This is the metallographic image of the polished sintered sample of Example 2.
[0009] Figure 3 This is the metallographic image of the polished sintered sample of comparative example 1.
[0010] Figure 4 This is the metallographic image of the polished sintered sample of comparative example 2. DETAILED DESCRIPTION
[0011] To illustrate the technical content, achieved objectives and effects of the present invention in detail, the following description is given in conjunction with the embodiments and accompanying drawings.
[0012] A pure copper metal injection molding process comprises the following steps: Raw material preparation: weigh pure copper powder and binder. The weight percentage of each component in the pure copper powder is Fe≤0.1wt%, C≤0.02wt%, O≤0.15wt%, and Cu is the balance. The particle size specification of the pure copper powder is D 90 :22-24μm,D 50 :7-9μm,D 10 : 2-4μm; the components of the binder are POM: 85%-88%, PE: 5%-6%, EVA: 2%-4%, SA: 3%-4%, PW: 1%-2%; Mixing and granulation: add the weighed pure copper powder into an internal mixer, heat it up and bake it, then add the weighed binder and knead it. After the pure copper powder and the binder are evenly mixed, cool it down, extrude it, and cut it into pieces to obtain block feed. Then, put the block feed into a granulator for extrusion and granulation to obtain granular injection feed. Injection sample: Put the granular injection feed into the injection machine hopper and inject it into the mold to obtain the copper green sample; Degreasing: The copper green body sample was degreased by using oxalic acid catalytic degreasing process to obtain a degreased green body sample; Thermal desintering: The degreased green sample is placed in a tubular furnace for thermal desintering. Hydrogen is introduced throughout the thermal desintering process. During the thermal desintering stage, the temperature is increased to 375-385 °C at a heating rate of 1 °C / min-2 °C / min and kept warm for 85-95 min; after the insulation is completed, the temperature is increased to 445-455 °C at a heating rate of 1 °C / min-2 °C / min and kept warm for 85-95 min; after the insulation is completed, the temperature is increased to 575-585 °C at a heating rate of 1.5 °C / min-2 °C / min and kept warm for 85-95 min.
[0013] From the above description, it can be seen that the beneficial effects of the present invention are: the pure copper material metal injection molding process adopts small-particle low-carbon and low-oxygen pure copper powder in combination with a binder component to design and optimize a feed with a higher flow rate, which reduces the porosity while meeting the requirements of injecting complex structure products, and is conducive to reducing the limitations of the application of the pure copper material metal injection molding process; the three-stage stepped warm stripping process is adopted, which can more completely remove the binder, thereby reducing the porosity and improving the density and thermal conductivity of the copper product; hydrogen is introduced throughout the hot stripping and sintering step, so that the copper oxide in the tubular furnace undergoes an oxidation-reduction reaction, allowing the degreased green body to be sintered densely, thereby greatly improving the density and thermal conductivity of the copper product.
[0014] Furthermore, in the raw material preparation step, the powder loading is 53%-60%.
[0015] From the above description, it can be seen that determining the appropriate powder loading amount is beneficial to ensuring the fluidity of the feeding.
[0016] Furthermore, in the mixing and granulation step, the temperature is raised to 170-190° C., the powder is baked for 8-12 minutes, the kneading is performed for 40-60 minutes, and the temperature is lowered to 150-170° C. during the cooling step.
[0017] Furthermore, in the sample injection step, the injection pressure is 200-220 MPa, the injection speed is 30-40 mm / s, the holding pressure is 140-160 MPa, and the holding time is 1-3 s.
[0018] Furthermore, in the sample injection step, the mold temperature during injection is 95-110°C, and the barrel temperature is divided into five sections: the nozzle temperature is 185°C, the barrel head temperature is 180°C, the front temperature is 175°C, the middle temperature is 170°C, the rear temperature is 165°C, and the barrel inlet temperature is 55°C.
[0019] Furthermore, after degreasing, the relative degreasing rate of the degreased green sample is greater than or equal to 94%.
[0020] From the above description, it can be seen that the purpose of debinding is to remove most of the binder, while the remaining small amount of binder can support the debinded green sample to be placed in a tube furnace while maintaining a certain structural stability for thermal desintering.
[0021] Furthermore, in the degreasing step, the acid flow process is divided into three stages: the acid flow rate of the first stage is 2 g / min, and the time is 120 min; the acid flow rate of the second stage is 3.5 g / min, and the time is 300 min; the acid flow rate of the third stage is 1 g / min, and the time is 60 min.
[0022] From the above description, it can be seen that the three-stage oxalic acid catalytic degreasing can effectively remove POM from the binder.
[0023] Furthermore, the degreasing temperature in the degreasing step is 120°C.
[0024] Furthermore, in the thermal stripping and sintering step, in the thermal stripping stage, the temperature is increased to 380°C at a heating rate of 1°C / min-2°C / min, and kept warm for 90 minutes; after the insulation at 380°C is completed, the temperature is increased to 450°C at a heating rate of 1°C / min-2°C / min, and kept warm for 90 minutes; after the insulation at 450°C is completed, the temperature is increased to 580°C at a heating rate of 1.5°C / min-2°C / min, and kept warm for 90 minutes; in the sintering stage, the temperature is continued to be increased to 600-800°C at a heating rate of 1°C / min-3.5°C / min, and kept warm for 2-4 hours; after the insulation is completed, the temperature is increased to 1050-1080°C at a heating rate of 1°C / min-3.5°C / min, and kept warm for 3-6 hours, and then cooled to the predetermined cooling temperature at a cooling rate of 2°C / min-4°C / min, and then cooled to room temperature with the furnace.
[0025] As can be seen from the above description, the three-stage heating process during the thermal debinding stage effectively removes binder components with different melting points, resulting in a more complete debinding of the degreased green sample and significantly reducing debinding residue. During the sintering stage, a large-scale redox reaction between copper oxide and hydrogen occurs, reducing the copper oxide to metallic copper. This helps increase the density of the resulting copper product during the subsequent sintering process.
[0026] Furthermore, in the sintering stage, the process of raising the temperature to 600-800°C at a heating rate of 1°C / min-3.5°C / min specifically includes the steps of raising the temperature to 600°C at a heating rate of 1°C / min-2.5°C / min, keeping warm for 2 hours, and then raising the temperature to 800°C at a heating rate of 2.5°C / min-3.5°C / min, and keeping warm for 2 hours.
[0027] From the above description, it can be seen that the two-stage heating method is used to raise the furnace temperature to 600-800°C during the sintering stage, which is beneficial to further improve the tensile strength, density and thermal conductivity of the copper products, while reducing the carbon and oxygen content in the copper products.
[0028] Embodiment 1 of the present invention is a pure copper metal injection molding process, comprising the following steps: S1. Raw material preparation: Weigh 5 kg of fine pure copper powder and 0.64 kg of binder. Fine pure copper powder is prepared by water-gas combined atomization process. The weight percentage of each component of fine pure copper powder is Fe≤0.1wt%, C≤0.02wt%, O≤0.15wt%, and Cu is the balance. The particle size specification of fine pure copper powder is D 90 :22-24μm,D 50 :7-9μm,D 10: 2-4μm. The binder adopts a plastic-based formula, with the main ingredients including POM (polyoxymethylene): 85-88%, PE (polyethylene): 5-6%, EVA (ethylene-vinyl acetate copolymer): 2-4%, SA (stearic acid): 3-4%, PW (paraffin wax): 1-2%; the powder loading is 53%-60%.
[0029] S2. Mixing and granulation: Add the fine pure copper powder weighed in S1 into an internal mixer, heat it to 170-190°C, bake the powder for 10 minutes, add a binder, and knead for 40-60 minutes. After the fine pure copper powder and the binder are evenly mixed, cool it to 160°C, extrude it, cut it into block feed, and then put the block feed into a granulator for extrusion and granulation, and finally obtain granular injection feed.
[0030] S3. Injection Sample: The granular injection feed obtained in S2 was placed into the injection molding machine hopper and injected into the mold to obtain a copper green body sample. The mold temperature during injection was 95-110°C, and the barrel temperature was divided into five sections: nozzle temperature 185°C, barrel head temperature 180°C, front temperature 175°C, middle temperature 170°C, rear temperature 165°C, and barrel inlet temperature 55°C. The injection pressure was 278 MPa, the injection speed was 35 mm / s, the holding pressure was 150 MPa, and the holding time was 2 seconds.
[0031] S4, Debinding: The copper green body samples obtained in S3 were degreased using oxalic acid catalytic debinding at 120°C. The acidification process was divided into three stages: the first stage had an acid feed rate of 2 g / min for 120 min; the second stage had an acid feed rate of 3.5 g / min for 300 min; and the third stage had an acid feed rate of 1 g / min for 60 min. After debinding, the relative debinding rate of the copper green body samples exceeded 94%. The purpose of debinding was to remove most of the POM binder, while the remaining small amount of binder was sufficient to support the sample in the sintering furnace.
[0032] S5, Thermal Desintering: The debinding green sample from S4 was placed in a tubular furnace for thermal desintering. Hydrogen was introduced throughout the process at a flow rate of 150 ml / min. The furnace was flushed three times before starting the program. In the thermal desintering stage, the temperature was increased from room temperature to 380°C at a heating rate of 2°C / min and held for 90 min. After holding at 380°C, the temperature was increased to 450°C at a heating rate of 1°C / min and held for 90 min. After holding at 450°C, the temperature was increased to 580°C at a heating rate of 1.5°C / min and held for 90 min. At this point, the thermal debinding process was essentially complete, and the sintering process began. Continue to increase the temperature to 600℃ at a heating rate of 1℃ / min and keep it for 2h; after keeping it at 600℃, increase the temperature to 800℃ at a heating rate of 3℃ / min and keep it for another 2h; after keeping it at 800℃, increase the temperature to 1075℃ at a heating rate of 3℃ / min and keep it for 6h, then cool it to 600℃ at a cooling rate of 4℃ / min, and then cool it to room temperature with the furnace.
[0033] S5. Performance test: The sintered samples were tested for performance. The results are as follows: Tensile strength 208MPa, elongation 50%, hardness 45-50HV, density 8.78-8.80g / cm 3 , thermal conductivity 347.36w / ( ), the C content is 0.017wt%, and the O content is 0.018wt%. Figure 1 This is the metallographic image of the polished sintered sample of Example 1.
[0034] A second embodiment of the present invention is a metal injection molding process for pure copper material, comprising the following steps: S1. Raw material preparation: Weigh 5 kg of fine pure copper powder and 0.64 kg of binder. Fine pure copper powder is prepared by water-gas combined atomization process. The weight percentage of each component of fine pure copper powder is Fe≤0.1wt%, C≤0.02wt%, O≤0.15wt%, and Cu is the balance. The particle size specification of fine pure copper powder is D 90 :22-24μm,D 50 :7-9μm,D 10 : 2-4μm. The binder adopts a plastic-based formula, with the main ingredients including POM (polyoxymethylene): 85-88%, PE (polyethylene): 5-6%, EVA (ethylene-vinyl acetate copolymer): 2-4%, SA (stearic acid): 3-4%, PW (paraffin wax): 1-2%; the powder loading is 53%-60%.
[0035] S2. Mixing and granulation: Add the fine pure copper powder weighed in S1 into an internal mixer, heat it to 170-190°C, bake the powder for 10 minutes, add a binder, and knead for 40-60 minutes. After the fine pure copper powder and the binder are evenly mixed, cool it to 160°C, extrude it, cut it into block feed, and then put the block feed into a granulator for extrusion and granulation, and finally obtain granular injection feed.
[0036] S3. Injection Sample: The granular injection feed obtained in S2 was placed into the injection molding machine hopper and injected into the mold to obtain a copper green body sample. The mold temperature during injection was 95-110°C, and the barrel temperature was divided into five sections: nozzle temperature 185°C, barrel head temperature 180°C, front temperature 175°C, middle temperature 170°C, rear temperature 165°C, and barrel inlet temperature 55°C. The injection pressure was 278 MPa, the injection speed was 35 mm / s, the holding pressure was 150 MPa, and the holding time was 2 seconds.
[0037] S4, Debinding: The copper green body samples obtained in S3 were degreased using oxalic acid catalytic debinding at 120°C. The acidification process was divided into three stages: the first stage had an acid feed rate of 2 g / min for 120 min; the second stage had an acid feed rate of 3.5 g / min for 300 min; and the third stage had an acid feed rate of 1 g / min for 60 min. After debinding, the relative debinding rate of the copper green body samples exceeded 94%. The purpose of debinding was to remove most of the POM binder, while the remaining small amount of binder was sufficient to support the sample in the sintering furnace.
[0038] S5, Thermal Desintering: The debinding green sample from S4 was placed in a tubular furnace for thermal desintering. Hydrogen was introduced throughout the process at a flow rate of 150 ml / min. The furnace was flushed three times before starting the program. In the thermal desintering stage, the temperature was increased from room temperature to 380°C at a heating rate of 2°C / min and held for 90 min. After holding at 380°C, the temperature was increased to 450°C at a heating rate of 1°C / min and held for 90 min. After holding at 450°C, the temperature was increased to 580°C at a heating rate of 1.5°C / min and held for 90 min. At this point, the thermal debinding process was essentially complete, and the sintering process began. Continue to increase the temperature to 800℃ at a heating rate of 3.5℃ / min, and keep it at that temperature for 2h. After keeping it at 800℃, increase the temperature to 1060℃ at a heating rate of 3℃ / min, keep it at that temperature for 3h, and then cool it to 600℃ at a cooling rate of 4℃ / min, and then cool it to room temperature with the furnace.
[0039] S5. Performance test: The sintered samples were tested for performance. The results are as follows: Tensile strength 205.52MPa, elongation 49.92%, hardness 45-52HV, density 8.74-8.78g / cm 3 , thermal conductivity 341.45w / ( ), the C content is 0.021wt%, and the O content is 0.025wt%. Figure 2 This is the metallographic image of the polished sintered sample of Example 2.
[0040] Comparative Example 1: A pure copper metal injection molding process, comprising the following steps: S1. Raw material preparation: Weigh 5 kg of crude pure copper powder and 0.64 kg of binder. The crude pure copper powder is prepared by a water-gas combined atomization process. The weight percentage of each component of the crude pure copper powder is Fe≤0.1wt%, C≤0.02wt%, O≤0.15wt%, and Cu is the balance. The particle size specification of the crude pure copper powder is D 90 :28-30μm,D 50 :13-16μm,D 10 The adhesive uses a plastic-based formula, with the main ingredients including POM (polyoxymethylene): 85-88%, PE (polyethylene): 5-6%, EVA (ethylene-vinyl acetate copolymer): 2-4%, SA (stearic acid): 3-4%, PW (paraffin wax): 1-2%; the powder loading is 53%-60%.
[0041] S2. Mixing and granulation: Add the crude pure copper powder weighed in S1 into an internal mixer, heat it to 170-190°C, bake the powder for 10 minutes, add a binder, and knead for 40-60 minutes. After the crude pure copper powder and the binder are evenly mixed, cool it to 160°C, extrude it, cut it into block feed, and then put the block feed into a granulator for extrusion and granulation, and finally obtain granular injection feed.
[0042] S3. Injection Sample: The granular injection feed obtained in S2 was placed into the injection molding machine hopper and injected into the mold to obtain a copper green body sample. The mold temperature during injection was 95-110°C, and the barrel temperature was divided into five sections: nozzle temperature 185°C, barrel head temperature 180°C, front temperature 175°C, middle temperature 170°C, rear temperature 165°C, and barrel inlet temperature 55°C. The injection pressure was 278 MPa, the injection speed was 35 mm / s, the holding pressure was 150 MPa, and the holding time was 2 seconds.
[0043] S4, Debinding: The copper green body samples obtained in S3 were degreased using oxalic acid catalytic debinding at 120°C. The acidification process was divided into three stages: the first stage had an acid feed rate of 2 g / min for 120 min; the second stage had an acid feed rate of 3.5 g / min for 300 min; and the third stage had an acid feed rate of 1 g / min for 60 min. After debinding, the relative debinding rate of the copper green body samples exceeded 94%. The purpose of debinding was to remove most of the POM binder, while the remaining small amount of binder was sufficient to support the sample in the sintering furnace.
[0044] S5, Thermal Desintering: The debinding green sample from S4 was placed in a tubular furnace for thermal desintering. Hydrogen was introduced throughout the process at a flow rate of 150 ml / min. The furnace was flushed three times before starting the program. In the thermal desintering stage, the temperature was increased from room temperature to 380°C at a heating rate of 2°C / min and held for 90 min. After holding at 380°C, the temperature was increased to 450°C at a heating rate of 1°C / min and held for 90 min. After holding at 450°C, the temperature was increased to 580°C at a heating rate of 1.5°C / min and held for 90 min. At this point, the thermal debinding process was essentially complete, and the sintering process began. Continue to increase the temperature to 600℃ at a heating rate of 1℃ / min and keep it for 2h; after keeping it at 600℃, increase the temperature to 800℃ at a heating rate of 3℃ / min and keep it for another 2h; after keeping it at 800℃, increase the temperature to 1075℃ at a heating rate of 3℃ / min and keep it for 6h, then cool it to 600℃ at a cooling rate of 4℃ / min, and then cool it to room temperature with the furnace.
[0045] S5. Performance test: The sintered samples were tested for performance. The results are as follows: Tensile strength is 204.05MPa, elongation is 48.08%, hardness is 45-55HV, density is 8.65-8.70g / cm 3 , thermal conductivity 284.46w / ( ), the C content is 0.017wt%, and the O content is 0.037wt%. Figure 3 This is the metallographic image of the polished sintered sample of comparative example 1.
[0046] Comparative Example 2 is a metal injection molding process of pure copper material, comprising the following steps: S1. Raw material preparation: Weigh 5 kg of crude pure copper powder and 0.64 kg of binder. The crude pure copper powder is prepared by a water-gas combined atomization process. The weight percentage of each component of the crude pure copper powder is Fe≤0.1wt%, C≤0.02wt%, O≤0.15wt%, and Cu is the balance. The particle size specification of the crude pure copper powder is D 90 :28-30μm,D 50:13-16μm,D 10 The adhesive uses a plastic-based formula, with the main ingredients including POM (polyoxymethylene): 85-88%, PE (polyethylene): 5-6%, EVA (ethylene-vinyl acetate copolymer): 2-4%, SA (stearic acid): 3-4%, PW (paraffin wax): 1-2%; the powder loading is 53%-60%.
[0047] S2. Mixing and granulation: Add the crude pure copper powder weighed in S1 into an internal mixer, heat it to 170-190°C, bake the powder for 10 minutes, add a binder, and knead for 40-60 minutes. After the crude pure copper powder and the binder are evenly mixed, cool it to 160°C, extrude it, cut it into block feed, and then put the block feed into a granulator for extrusion and granulation, and finally obtain granular injection feed.
[0048] S3. Injection Sample: The granular injection feed obtained in S2 was placed into the injection molding machine hopper and injected into the mold to obtain a copper green body sample. The mold temperature during injection was 95-110°C, and the barrel temperature was divided into five sections: nozzle temperature 185°C, barrel head temperature 180°C, front temperature 175°C, middle temperature 170°C, rear temperature 165°C, and barrel inlet temperature 55°C. The injection pressure was 278 MPa, the injection speed was 35 mm / s, the holding pressure was 150 MPa, and the holding time was 2 seconds.
[0049] S4, Debinding: The copper green body samples obtained in S3 were degreased using oxalic acid catalytic debinding at 120°C. The acidification process was divided into three stages: the first stage had an acid feed rate of 2 g / min for 120 min; the second stage had an acid feed rate of 3.5 g / min for 300 min; and the third stage had an acid feed rate of 1 g / min for 60 min. After debinding, the relative debinding rate of the copper green body samples exceeded 94%. The purpose of debinding was to remove most of the POM binder, while the remaining small amount of binder was sufficient to support the sample in the sintering furnace.
[0050] S5, Thermal Desintering: The debinding green sample from S4 was placed in a tubular furnace for thermal desintering. Hydrogen was introduced throughout the process at a flow rate of 150 ml / min. The furnace was flushed three times before starting the program. In the thermal desintering stage, the temperature was increased from room temperature to 380°C at a heating rate of 2°C / min and held for 90 min. After holding at 380°C, the temperature was increased to 450°C at a heating rate of 1°C / min and held for 90 min. After holding at 450°C, the temperature was increased to 580°C at a heating rate of 1.5°C / min and held for 90 min. At this point, the thermal debinding process was essentially complete, and the sintering process began. Continue to increase the temperature to 800℃ at a heating rate of 3.5℃ / min, and keep it at that temperature for 2h. After keeping it at 800℃, increase the temperature to 1060℃ at a heating rate of 3℃ / min, keep it at that temperature for 3h, and then cool it to 600℃ at a cooling rate of 4℃ / min, and then cool it to room temperature with the furnace.
[0051] S5. Performance test: The sintered samples were tested for performance. The results are as follows: Tensile strength is 205.85MPa, elongation is 44.15%, hardness is 40-46HV, density is 8.62-8.67g / cm 3 , thermal conductivity 280.91w / ( ), the C content is 0.016wt%, and the O content is 0.029wt%. Figure 4 This is the metallographic image of the polished sintered sample of comparative example 2.
[0052] According to the first and second embodiments, the density of the copper products produced by the metal injection molding process of the pure copper material is greater than 8.7g / cm 3 , which can meet the high density requirements of copper products, the internal porosity of copper products is low, and the thermal conductivity of copper products is greater than 340 W / (m·K). Comparing Example 1 with Example 2, it can be seen that using a two-stage heating method to raise the furnace temperature to 600-800°C during the sintering stage can greatly improve the tensile strength, density, and thermal conductivity of copper products, while reducing the carbon and oxygen content in the copper products.
[0053] According to Example 1 and Comparative Example 1 or Example 2 and Comparative Example 2, when the processing steps and parameters remain unchanged, the density and thermal conductivity of the copper products made of coarse pure copper powder with a relatively coarse particle size decrease significantly, especially the density of the copper products is difficult to reach 8.7 g / cm 3 , it is difficult to meet high density requirements.
[0054] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention's description and drawings, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.
Claims
1. A pure copper material metal injection molding process, characterized in that: The steps include: Raw material preparation: weigh pure copper powder and binder. The weight percentage of each component in the pure copper powder is Fe≤0.1wt%, C≤0.02wt%, O≤0.15wt%, and Cu is the balance. The particle size specification of the pure copper powder is D 90 :22-24μm,D 50 :7-9μm,D 10 : 2-4μm; the components of the binder are POM: 85%-88%, PE: 5%-6%, EVA: 2%-4%, SA: 3%-4%, PW: 1%-2%; Mixing and granulation: add the weighed pure copper powder into an internal mixer, heat it up and bake it, then add the weighed binder and knead it. After the pure copper powder and the binder are evenly mixed, cool it down, extrude it, and cut it into pieces to obtain block feed. Then, put the block feed into a granulator for extrusion and granulation to obtain granular injection feed. Injection sample: Put the granular injection feed into the injection machine hopper and inject it into the mold to obtain the copper green sample; Degreasing: The copper green body sample was degreased by using oxalic acid catalytic degreasing process to obtain a degreased green body sample; Thermal desintering: The degreased green sample is placed in a tubular furnace for thermal desintering. Hydrogen is introduced throughout the thermal desintering process. During the thermal desintering stage, the temperature is increased to 375-385 °C at a heating rate of 1 °C / min-2 °C / min and kept warm for 85-95 min; after the insulation is completed, the temperature is increased to 445-455 °C at a heating rate of 1 °C / min-2 °C / min and kept warm for 85-95 min; after the insulation is completed, the temperature is increased to 575-585 °C at a heating rate of 1.5 °C / min-2 °C / min and kept warm for 85-95 min.
2. The pure copper material metal injection molding process according to claim 1, characterized in that: During the raw material preparation step, the powder loading is 53%-60%.
3. The pure copper material metal injection molding process according to claim 1, characterized in that: In the mixing and granulation step, the temperature is raised to 170-190°C, the powder is baked for 8-12 minutes, the kneading is carried out for 40-60 minutes, and the temperature is lowered to 150-170°C.
4. The pure copper material metal injection molding process according to claim 1, characterized in that: In the sample injection step, the injection pressure is 200-220 MPa, the injection speed is 30-40 mm / s, the holding pressure is 140-160 MPa, and the holding time is 1-3 s.
5. The pure copper material metal injection molding process according to claim 1, characterized in that: In the sample injection step, the mold temperature during injection is 95-110°C, and the barrel temperature is divided into five sections: nozzle temperature is 185°C, barrel head temperature is 180°C, front temperature is 175°C, middle temperature is 170°C, rear temperature is 165°C, and barrel inlet temperature is 55°C.
6. The pure copper material metal injection molding process according to claim 1, characterized in that: After degreasing, the relative degreasing rate of the degreased green sample is greater than or equal to 94%.
7. The pure copper material metal injection molding process according to claim 1, characterized in that: In the degreasing step, the acid flow process is divided into three stages: the acid flow rate of the first stage is 2 g / min and the time is 120 min; the acid flow rate of the second stage is 3.5 g / min and the time is 300 min; the acid flow rate of the third stage is 1 g / min and the time is 60 min.
8. The pure copper material metal injection molding process according to claim 1, characterized in that: The degreasing temperature in the degreasing step is 120°C.
9. The pure copper material metal injection molding process according to claim 1, characterized in that: In the thermal stripping and sintering step, in the thermal stripping stage, the temperature is increased to 380°C at a heating rate of 1°C / min-2°C / min, and kept warm for 90 minutes; after the 380°C insulation is completed, the temperature is increased to 450°C at a heating rate of 1°C / min-2°C / min, and kept warm for 90 minutes; after the 450°C insulation is completed, the temperature is increased to 580°C at a heating rate of 1.5°C / min-2°C / min, and kept warm for 90 minutes; in the sintering stage, the temperature is continued to be increased to 600-800°C at a heating rate of 1°C / min-3.5°C / min, and kept warm for 2-4 hours; after the insulation is completed, the temperature is increased to 1050-1080°C at a heating rate of 1°C / min-3.5°C / min, and kept warm for 3-6 hours, and then cooled to the predetermined cooling temperature at a cooling rate of 2°C / min-4°C / min, and then cooled to room temperature with the furnace.
10. The pure copper material metal injection molding process according to claim 9, characterized in that: In the sintering stage, the process of raising the temperature to 600-800°C at a heating rate of 1°C / min-3.5°C / min specifically includes the steps of raising the temperature to 600°C at a heating rate of 1°C / min-2.5°C / min, keeping it warm for 2 hours, and then raising the temperature to 800°C at a heating rate of 2.5°C / min-3.5°C / min, and keeping it warm for 2 hours.