Injection molding process for water-soluble degreased metal powder

Abstract

The invention discloses a water-soluble degreased metal powder injection molding process, which belongs to the technical field of metal powder injection molding, and comprises the following steps: pre-drying metal powder; the preparation method comprises the following steps: weighing the following raw materials in parts by weight: 40-60 parts of polyethylene glycol, 0-15 parts of high-density polyethylene, 0-30 parts of polypropylene, 10-30 parts of polymethyl methacrylate, 0-5 parts of polyformaldehyde, 0-7 parts of ethylene-vinyl acetate copolymer, 1-5 parts of stearic acid, 0-10 parts of dioctyl phthalate and 0-10 parts of maleic anhydride grafted polypropylene; performing mixing; dicing is performed; injection molding; degreasing is conducted; performing drying; and sintering. By optimizing a mixed binder formula and a feed preparation process, the fluidity stability of the feed is effectively improved, the feed is prevented from being adhered in a screw rod of an injection molding machine, the continuous and smooth charging barrel feeding and mold filling processes are ensured, the forming interruption or equipment cleaning frequency caused by the feeding problem is reduced, and the production efficiency is improved. And the batch production requirement of metal powder injection molding is met.

Description

Technical Field

[0001] This invention relates to the field of metal powder injection molding technology, and more specifically to a water-soluble degreased metal powder injection molding process. Background Technology

[0002] Metal powder injection molding (MIM) technology, as a near-net-shape forming technology, has significant advantages in the mass production of three-dimensional complex-shaped products. Debinding is a key step in the MIM process, and its rationality and stability directly affect subsequent sintering processes and the quality of the final product.

[0003] To avoid the shortcomings of traditional degreasing processes, water-soluble degreasing (water-based degreasing) has gradually become one of the research directions of MIM degreasing technology due to its potential environmental protection and safety characteristics. However, the application of water-soluble degreasing in the MIM field is currently limited in scope, with only a few manufacturers in a few regions attempting it. Furthermore, the water-soluble degreasing raw materials prepared with reference to existing technologies are prone to sticking to the screw during the injection stage, interfering with the molding process, and producing green bodies with weak strength and high brittleness, leading to degreasing failure or product scrap. As a result, the formulation and supporting processes of water-soluble degreasing have always been difficult to promote.

[0004] Based on this, the present invention designs a water-soluble degreased metal powder injection molding process to solve the above problems. Summary of the Invention

[0005] To address the aforementioned shortcomings of existing technologies, this invention provides a water-soluble degreased metal powder injection molding process, comprising the following steps: S1: Select 100-120 parts of metal powder and pre-dry them to obtain pretreated metal powder; S2: Weigh the raw materials; 40-60 parts polyethylene glycol, 0-15 parts high-density polyethylene, 0-30 parts polypropylene, 10-30 parts polymethyl methacrylate, 0-5 parts polyoxymethylene, 0-7 parts ethylene-vinyl acetate copolymer, 1-5 parts stearic acid, 0-10 parts dioctyl phthalate, and 0-10 parts maleic anhydride-grafted polypropylene. S3: The raw materials weighed in S2 are premixed at 80-100℃, then heated to 130-160℃ for mixing, and cooled to room temperature to obtain a mixed binder; S4: Mix the pretreated metal powder and the mixed binder at a volume ratio of 45-55:48-57 at 150-190℃, granulate at 20-40℃ and dry to obtain feed pellets. S5: Add the feed pellets to the injection molding machine, control the temperature in gradient zones at 160-200℃, and the mold temperature at 45-65℃. After cooling, demold to obtain the green body. S6: Pre-dry the green body at 65-85℃ to obtain a pretreated green body. Immerse the pretreated green body in deionized water at 35-50℃ for 1.5-3.5h, continue to raise the temperature to 55-75℃ and stir for 2.5-5.5h, continue to raise the temperature to 75-95℃ and stir for 1.5-4.5h to obtain a degreased green body, and rinse it. S7: Dry the rinsed degreased green body to obtain a dried green body. Under an inert atmosphere, first heat the green body to 220-320℃ and hold it at that temperature. Then, continue to heat the green body to 550-620℃ and hold it at that temperature to obtain a hot degreased green body. S8: Heat the hot degreased green body to 1280-1350℃ at 10-15℃ / min, hold for 2-6 hours, and cool to room temperature to obtain a sintered green body.

[0006] Furthermore, S1 specifically involves selecting 100-120 parts of metal powder with a D90 of 10-30 μm, drying the metal powder at 50-70℃ and 0.05-0.09 MPa for 1-2 hours to obtain pretreated metal powder.

[0007] Furthermore, S3 specifically involves: premixing the raw materials weighed in S2 at 80-100℃ and 20-40 r / min for 5-10 minutes, then heating to 130-160℃ and mixing at 30-60 r / min for 25-40 minutes, and cooling to room temperature to obtain a mixed binder.

[0008] Furthermore, S4 specifically involves: mixing pretreated metal powder and mixed binder at a volume ratio of 45-55:48-57 at 150-190℃ and 70-110r / min for 35-60min, pelletizing at 20-40℃, and drying at 60-80℃ for 2-4h to obtain feed pellets.

[0009] Furthermore, S5 specifically involves: adding feed pellets into the injection molding machine, setting the barrel temperature to 160-180℃ in zone 1, 170-190℃ in zone 2, and 180-200℃ in zone 3, while maintaining the mold temperature at 45-65℃, the injection pressure at 90-160MPa, the holding pressure at 60-110MPa, the holding time at 25-70s, the injection rate at 30-60mm / s, and demolding after cooling for 10-30s to obtain the green body.

[0010] Furthermore, S6 specifically involves: pre-drying the green billet at 65-85℃ and 35%-55% relative humidity for 1.5-3.5 hours to obtain a pretreated green billet; immersing the pretreated green billet in deionized water at 35-50℃ and stirring at 15-35 r / min for 1.5-3.5 hours; continuing to raise the temperature to 55-75℃ and stirring for 2.5-5.5 hours; continuing to raise the temperature to 75-95℃ and stirring for 1.5-4.5 hours, changing the deionized water every 25-35 minutes during this period to obtain a degreased green body; rinsing the degreased green body with room temperature deionized water for 2-5 minutes.

[0011] Furthermore, S7 specifically involves: drying the rinsed degreased blank at 55-75℃ and 0.06-0.095MPa for 2.5-6.5h to obtain a dried blank; heating the dried blank to 220-320℃ at 2-4℃ / min under an argon atmosphere and holding it at that temperature for 30-60min; then further heating it to 550-620℃ at 5-7℃ / min and holding it at that temperature for 60-120min to obtain a hot degreased blank.

[0012] Compared with the prior art, the beneficial effects of this invention are as follows: 1. This invention effectively improves the flowability and stability of the feed by optimizing the mixed binder formulation and the feed preparation process (standardizing the premixing and mixing temperature and speed, and controlling the drying after pelleting), avoiding the adhesion of the feed in the screw of the injection molding machine, ensuring continuous and smooth feeding of the barrel and filling of the mold, reducing the frequency of molding interruption or equipment cleaning caused by feeding problems, and adapting to the mass production needs of metal powder injection molding.

[0013] 2. This invention enhances the binding and adhesion of the binder to metal powder through a suitable binder combination. It adopts a standardized pre-treatment before degreasing and a segmented water-soluble degreasing process to avoid the reduction of green body compressive strength and structural integrity due to rapid water evaporation and excessive dissolution of binder during the degreasing process. This reduces the breakage rate of green body during the degreasing stage, lowers the risk of product scrap, and improves the production qualification rate. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0015] Example 1: This example provides a water-soluble degreased metal powder injection molding process, including: S1: Select 100 parts of metal powder with D90 of 10-30μm (316L powder purchased from Qinghe County Chaoneng Alloy Materials Co., Ltd.), dry the metal powder at 50℃ and 0.05MPa for 1-2h to obtain pretreated metal powder. S2: Weigh the raw materials; 40 parts polyethylene glycol (PEG600 / PEG2000 / PEG4000 / PEG8000 / PEG20000 in a molar ratio of 2:3:1:0.5:1), 30 parts polypropylene (purchased from Suzhou Xindezhi New Material Co., Ltd., grade R370Y), 10 parts polymethyl methacrylate (purchased from Dongguan Chengyuhui New Material Co., Ltd., model PMMA-CM-205), 2 parts polyoxymethylene (purchased from Shanghai Yuanfeng Plastic Technology Co., Ltd., grade MC270-01), 4 parts ethylene-vinyl acetate copolymer (purchased from Guangzhou Hongcheng Plastic Co., Ltd., grade EVA1520), 1 part stearic acid (purchased from Shanghai Shengyue International Trade Co., Ltd., model 1801), 4 parts dioctyl phthalate (purchased from Changzhou Senlang Chemical Co., Ltd., CAS No. 117-81-7), and 5 parts maleic anhydride-grafted polypropylene (purchased from Dongguan Yingxiang Plastic Raw Materials Co., Ltd., grade AT2937). S3: The raw materials weighed in S2 are premixed at 80℃ and 20r / min for 5min, then heated to 130℃ and mixed at 30r / min for 25min, and cooled to room temperature for later use to obtain the mixed binder; S4: Mix the pretreated metal powder and the mixed binder at a volume ratio of 45:48 at 150℃ and 70r / min for 35min, cut into pellets (2-5mm) at 20℃, and dry at 60℃ for 2h to obtain feed pellets. S5: Add the feed pellets to the injection molding machine. The temperature of the barrel is 160-180℃ in zone 1, 170-190℃ in zone 2, and 180-200℃ in zone 3. The mold temperature is 45℃, the injection pressure is 90MPa, the holding pressure is 60MPa, the holding time is 25s, the injection rate is 30mm / s, and the mold is demolded after cooling for 10s to obtain the green body. S6: Pre-dry the green body at 65℃ and 35% relative humidity for 1.5h to obtain a pretreated green body. Immerse the pretreated green body in deionized water at 35℃, stir at 15r / min, degrease for 1.5h, continue to raise the temperature to 55℃, stir for 2.5h, continue to raise the temperature to 75℃, stir for 1.5h, and replace the deionized water every 25min during the process to obtain a degreased green body. Rinse the degreased preform with room temperature deionized water for 2 minutes; S7: The rinsed degreased blank is dried at 55℃ and 0.06MPa for 2.5h to obtain a dried blank. The dried blank is heated to 220℃ at 2℃ / min under an argon atmosphere and held for 30min. Then, the temperature is increased to 550℃ at 5℃ / min and held for 60min to obtain a hot degreased blank. S8: Heat the hot degreased green body to 1280℃ at 10℃ / min, hold for 2 hours, and cool to room temperature to obtain a sintered green body.

[0016] Example 2: This example provides a water-soluble degreased metal powder injection molding process, including: S1: Select 120 parts of metal powder with D90 of 10-30μm (316L powder purchased from Qinghe County Chaoneng Alloy Materials Co., Ltd.), and dry the metal powder at 70℃ and 0.09MPa for 1-2h to obtain pretreated metal powder. S2: Weigh the raw materials; 40-60 parts polyethylene glycol (PEG600 / PEG2000 / PEG4000 / PEG8000 / PEG20000 in a molar ratio of 4:5:1.5:1.3:1), 15 parts high-density polyethylene, 30 parts polymethyl methacrylate, 5 parts polyoxymethylene, 7 parts ethylene-vinyl acetate copolymer, 5 parts stearic acid, 10 parts dioctyl phthalate, and 10 parts maleic anhydride-grafted polypropylene; S3: The raw materials weighed in S2 are premixed at 100℃ and 40r / min for 10min, then heated to 160℃ and mixed at 60r / min for 40min, and cooled to room temperature for later use to obtain the mixed binder; S4: Mix the pretreated metal powder and the mixed binder at a volume ratio of 55:57 at 190℃ and 110r / min for 60min, cut into pellets (2-5mm) at 40℃, and dry at 80℃ for 4h to obtain feed pellets. S5: Add the feed pellets to the injection molding machine. The temperature of the barrel is 160-180℃ in zone 1, 170-190℃ in zone 2, and 180-200℃ in zone 3. The mold temperature is 65℃, the injection pressure is 160MPa, the holding pressure is 110MPa, the holding time is 70s, the injection rate is 60mm / s, and the green body is demolded after cooling for 30s. S6: Pre-dry the green body at 85℃ and 55% relative humidity for 3.5h to obtain a pretreated green body. Immerse the pretreated green body in 50℃ deionized water, stir at 35r / min, degrease for 3.5h, continue to raise the temperature to 75℃, stir for 5.5h, continue to raise the temperature to 95℃, stir for 4.5h, and change the deionized water every 35min during the process to obtain a degreased green body. Rinse the degreased preform with room temperature deionized water for 5 minutes; S7: The rinsed degreased blank is dried at 75℃ and 0.095MPa for 6.5h to obtain a dried blank. The dried blank is heated to 320℃ at 4℃ / min under an argon atmosphere and held for 60min. Then, the temperature is increased to 620℃ at 7℃ / min and held for 120min to obtain a hot degreased blank. S8: Heat the hot degreased green body to 1350℃ at 15℃ / min, hold for 6 hours, and cool to room temperature to obtain a sintered green body.

[0017] Example 3: This example provides a water-soluble degreased metal powder injection molding process, including: S1: Select 108 parts of metal powder with D90 of 10-30μm (316L powder purchased from Qinghe County Chaoneng Alloy Materials Co., Ltd.), dry the metal powder at 55℃ and 0.07MPa for 2h to obtain pretreated metal powder. S2: Weigh the raw materials; 40-60 parts polyethylene glycol (PEG600 / PEG2000 / PEG4000 / PEG8000 / PEG20000 in a molar ratio of 3:4:1.2:1:1), 13 parts high-density polyethylene, 25 parts polypropylene, 18 parts polymethyl methacrylate, 6 parts ethylene-vinyl acetate copolymer, 3 parts stearic acid, 8 parts dioctyl phthalate, and 8 parts maleic anhydride-grafted polypropylene; S3: The raw materials weighed in S2 are premixed at 95℃ and 25r / min for 7min, then heated to 145℃ and mixed at 45r / min for 30min, and cooled to room temperature for later use to obtain the mixed binder; S4: Mix the pretreated metal powder and the mixed binder at a volume ratio of 48:51 at 170℃ and 90r / min for 40min, cut into pellets (2-5mm) at 35℃, and dry at 75℃ for 3h to obtain feed pellets. S5: Add the feed pellets to the injection molding machine. The temperature of the barrel is 160-180℃ in zone 1, 170-190℃ in zone 2, and 180-200℃ in zone 3. The mold temperature is 49℃, the injection pressure is 120MPa, the holding pressure is 95MPa, the holding time is 60s, the injection rate is 45mm / s, and the mold is demolded after cooling for 27s to obtain the green body. S6: Pre-dry the green body at 72℃ and 50% relative humidity for 2 hours to obtain a pretreated green body. Immerse the pretreated green body in deionized water at 45℃, stir at 25r / min, degrease for 3 hours, continue to raise the temperature to 65℃, stir for 4 hours, continue to raise the temperature to 80℃, stir for 3 hours, and change the deionized water every 30 minutes to obtain a degreased green body. Rinse the degreased preform with room temperature deionized water for 3 minutes; S7: The rinsed degreased blank is dried at 62℃ and 0.085MPa for 4h to obtain a dried blank. The dried blank is heated to 300℃ at 3℃ / min under an argon atmosphere and held for 45min. Then, the temperature is increased to 600℃ at 6℃ / min and held for 80min to obtain a hot degreased blank. S8: Heat the hot degreased green body to 1300℃ at 12℃ / min, hold for 5 hours, and cool to room temperature to obtain a sintered green body.

[0018] Example 4: This example provides a water-soluble degreased metal powder injection molding process, including: S1: Select 115 parts of metal powder with D90 of 10-30μm (17-4PH powder purchased from Qinghe County Chaoneng Alloy Materials Co., Ltd.), and dry the metal powder at 62℃ and 0.08MPa for 1.5h to obtain pretreated metal powder. S2: Weigh the raw materials; 48 parts polyethylene glycol (PEG600 / PEG2000 / PEG4000 / PEG8000 / PEG20000 in a molar ratio of 3:4:1.2:1:1), 10 parts high-density polyethylene, 20 parts polypropylene, 25 parts polymethyl methacrylate, 4 parts polyoxymethylene, 4 parts stearic acid, 5 parts dioctyl phthalate, and 5 parts maleic anhydride-grafted polypropylene; S3: The raw materials weighed in S2 are premixed at 82℃ and 30r / min for 8min, then heated to 142℃ and mixed at 50r / min for 32min, and cooled to room temperature for later use to obtain the mixed binder; S4: Mix the pretreated metal powder and the mixed binder at a volume ratio of 47:52 at 163℃ and 101r / min for 55min, cut into pellets (2-5mm) at 30℃, and dry at 77℃ for 4h to obtain feed pellets. S5: Add the feed pellets to the injection molding machine. The temperature of the barrel is 160-180℃ in zone 1, 170-190℃ in zone 2, and 180-200℃ in zone 3. The mold temperature is 52℃, the injection pressure is 150MPa, the holding pressure is 100MPa, the holding time is 60s, the injection rate is 45mm / s, and the mold is demolded after cooling for 18s to obtain the green body. S6: Pre-dry the green body at 67℃ and 42% relative humidity for 2 hours to obtain a pretreated green body. Immerse the pretreated green body in deionized water at 40℃, stir at 22r / min, degrease for 3 hours, continue to raise the temperature to 66℃, stir for 4 hours, continue to raise the temperature to 78℃, stir for 3 hours, and replace the deionized water every 31 minutes to obtain a degreased green body. Rinse the degreased preform with room temperature deionized water for 5 minutes; S7: The rinsed degreased blank is dried at 70℃ and 0.09MPa for 4h to obtain a dried blank. The dried blank is heated to 280℃ at 3℃ / min under an argon atmosphere and held for 40min. Then, the temperature is increased to 600℃ at 6℃ / min and held for 100min to obtain a hot degreased blank. S8: Heat the hot degreased green body to 1294°C at 12°C / min, hold for 5 hours, and cool to room temperature to obtain the sintered green body.

[0019] Example 5: This example provides a water-soluble degreased metal powder injection molding process, including: S1: Select 108 parts of metal powder with D90 of 10-30μm (17-4PH powder purchased from Qinghe County Chaoneng Alloy Materials Co., Ltd.), dry the metal powder at 66℃ and 0.09MPa for 2h to obtain pretreated metal powder. S2: Weigh the raw materials; 53 parts polyethylene glycol (PEG600 / PEG2000 / PEG4000 / PEG8000 / PEG20000 in a molar ratio of 3:4:1.2:1:1), 9 parts high-density polyethylene, 21 parts polypropylene, 13 parts polymethyl methacrylate, 2 parts polyoxymethylene, 5 parts ethylene-vinyl acetate copolymer, and 4 parts stearic acid; S3: The raw materials weighed in S2 are premixed at 92℃ and 35r / min for 8min, then heated to 144℃ and mixed at 52r / min for 38min, and cooled to room temperature for later use to obtain the mixed binder; S4: The pretreated metal powder and the mixed binder are mixed at a volume ratio of 47:52 at 169℃ and 88r / min for 51min. After being pelletized (2-5mm) at 40℃, the pellets are dried at 70℃ for 4h to obtain feed pellets. S5: Add the feed pellets to the injection molding machine. The temperature of the barrel is 160-180℃ in zone 1, 170-190℃ in zone 2, and 180-200℃ in zone 3. The mold temperature is 61℃, the injection pressure is 120MPa, the holding pressure is 100MPa, the holding time is 50s, the injection rate is 50mm / s, and the mold is demolded after cooling for 22s to obtain the green body. S6: Pre-dry the green body at 73℃ and 45% relative humidity for 3 hours to obtain a pretreated green body. Immerse the pretreated green body in deionized water at 47℃, stir at 30 r / min, degrease for 3.5 hours, continue to raise the temperature to 74℃, stir for 5 hours, continue to raise the temperature to 92℃, stir for 2 hours, and change the deionized water every 30 minutes to obtain a degreased green body. Rinse the degreased preform with room temperature deionized water for 5 minutes; S7: The rinsed degreased blank is dried at 71℃ and 0.09MPa for 6h to obtain a dried blank. The dried blank is heated to 310℃ at 4℃ / min under an argon atmosphere and held for 55min. Then, the temperature is increased to 620℃ at 7℃ / min and held for 105min to obtain a hot degreased blank. S8: Heat the hot degreased green body to 1320℃ at 15℃ / min, hold for 5 hours, and cool to room temperature to obtain a sintered green body.

[0020] Comparative Example 1: The difference between this comparative example and Example 1 is that the raw material ratio in S2 is as follows: 20 parts polyethylene glycol (PEG600 / PEG2000 / PEG4000 / PEG8000 / PEG20000 in a molar ratio of 2:3:1:0.5:1), 60 parts polypropylene, 3 parts polymethyl methacrylate, 8 parts polyoxymethylene, 12 parts ethylene-vinyl acetate copolymer, 0.3 parts stearic acid, 15 parts dioctyl phthalate, and 20 parts maleic anhydride-grafted polypropylene.

[0021] Comparative Example 2: The difference between this comparative example and Example 1 is that S6 is specifically: the green body is immersed in deionized water at 75°C, stirred at 15 r / min, and degreased for 7.5 h to obtain a degreased green body; the degreased green body is rinsed with room temperature deionized water for 2 min.

[0022] Comparative Example 3: The difference between this comparative example and Example 1 is that the raw material ratio of Comparative Example 1 is followed while degreasing is performed in the manner of Comparative Example 2.

[0023] Experimental Example 1: According to GB / T 41329-2022, the feed pellet flowability (s / 50g) was tested. Experimental Example 2: According to GB / T 6525-2019, the compressive strength (MPa) of the green body at 480℃ was tested. The results are shown in the table below:

[0024] As shown in the table above, the feed flowability of Examples 1-5 is highly consistent, indicating that the set binder formulation and process are compatible. Polyethylene glycol, as the main water-soluble binder, can adjust the viscosity of the feed in the molten state by adjusting its multiple molecular weight ratios (PEG600-20000). Stearic acid, as a lubricant, can reduce the frictional resistance between the feed and the equipment screw. The standardized mixing and drying process avoids the formation of air bubbles or uneven composition inside the feed particles, ultimately ensuring stable flowability.

[0025] Comparative Example 1 suffered from an imbalance in the binder formulation, which led to an increase in the melt viscosity of the feed and a decrease in fluidity. Comparative Example 2 did not change the formulation, but omitted the pre-drying of the green body and the gradient temperature degreasing steps, resulting in a decrease in fluidity. Comparative Example 3 combined the above two defective factors, resulting in the worst feed fluidity, which confirms the key influence of the synergistic effect of the binder formulation and the gradient temperature degreasing process on fluidity.

[0026] The strength of all three in Examples 1-3 remains at a high level of around 531 MPa. The key lies in the compatibility of the adhesive formulation and the degreasing process, which ensures stable compressive strength. Comparative Example 1 showed a decrease in strength due to an imbalance in the binder formulation. Comparative Example 2, due to the omission of pre-drying and the use of a single high-temperature degreasing process, experienced a further decrease in strength in the initial stage of degreasing due to rapid evaporation of moisture and rapid dissolution of the binder. Comparative Example 3, with its combination of formulation imbalance and abnormal degreasing, became the group with the lowest strength among the 316L groups, demonstrating the importance of both formulation and process specifications for the structural integrity of the green body.

[0027] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A water-soluble degreased metal powder injection molding process, characterized in that, Includes the following steps: S1: Select 100-120 parts of metal powder and pre-dry them to obtain pretreated metal powder; S2: Weigh the raw materials; 40-60 parts polyethylene glycol, 0-15 parts high-density polyethylene, 0-30 parts polypropylene, 10-30 parts polymethyl methacrylate, 0-5 parts polyoxymethylene, 0-7 parts ethylene-vinyl acetate copolymer, 1-5 parts stearic acid, 0-10 parts dioctyl phthalate, and 0-10 parts maleic anhydride-grafted polypropylene. S3: The raw materials weighed in S2 are premixed at 80-100℃, then heated to 130-160℃ for mixing, and cooled to room temperature to obtain a mixed binder; S4: Mix the pretreated metal powder and the mixed binder at a volume ratio of 45-55:48-57 at 150-190℃, granulate at 20-40℃ and dry to obtain feed pellets. S5: Add the feed pellets to the injection molding machine, control the temperature in gradient zones at 160-200℃, and the mold temperature at 45-65℃. After cooling, demold to obtain the green body. S6: Pre-dry the green body at 65-85℃ to obtain a pretreated green body. Immerse the pretreated green body in deionized water at 35-50℃ for 1.5-3.5h, continue to raise the temperature to 55-75℃ and stir for 2.5-5.5h, continue to raise the temperature to 75-95℃ and stir for 1.5-4.5h to obtain a degreased green body, and rinse it. S7: Dry the rinsed degreased green body to obtain a dried green body. Under an inert atmosphere, first heat the green body to 220-320℃ and hold it at that temperature. Then, continue to heat the green body to 550-620℃ and hold it at that temperature to obtain a hot degreased green body. S8: Heat the hot degreased green body to 1280-1350℃ at 10-15℃ / min, hold for 2-6 hours, and cool to room temperature to obtain a sintered green body.

2. The water-soluble degreased metal powder injection molding process according to claim 1, characterized in that, S1 specifically involves selecting 100-120 parts of metal powder with a D90 of 10-30 μm, drying the metal powder at 50-70℃ and 0.05-0.09 MPa for 1-2 hours to obtain pretreated metal powder.

3. The water-soluble degreased metal powder injection molding process according to claim 1, characterized in that, S3 specifically involves: premixing the raw materials weighed in S2 at 80-100℃ and 20-40 r / min for 5-10 minutes, then heating to 130-160℃ and mixing at 30-60 r / min for 25-40 minutes, and cooling to room temperature to obtain a mixed binder.

4. The water-soluble degreased metal powder injection molding process according to claim 1, characterized in that, S4 specifically involves mixing pretreated metal powder and a mixed binder at a volume ratio of 45-55:48-57 at 150-190℃ and 70-110r / min for 35-60 minutes, pelletizing at 20-40℃, and then drying at 60-80℃ for 2-4 hours to obtain feed pellets.

5. The water-soluble degreased metal powder injection molding process according to claim 1, characterized in that, S5 specifically involves: adding feed pellets into the injection molding machine, setting the barrel temperature to 160-180℃ in zone 1, 170-190℃ in zone 2, and 180-200℃ in zone 3, while maintaining the mold temperature at 45-65℃, the injection pressure at 90-160MPa, the holding pressure at 60-110MPa, the holding time at 25-70s, the injection rate at 30-60mm / s, and demolding after cooling for 10-30s to obtain the green blank.

6. The water-soluble degreased metal powder injection molding process according to claim 1, characterized in that, S6 specifically involves: pre-drying the green billet at 65-85℃ and 35%-55% relative humidity for 1.5-3.5 hours to obtain a pretreated green billet; immersing the pretreated green billet in deionized water at 35-50℃ and stirring at 15-35 r / min for 1.5-3.5 hours; continuing to raise the temperature to 55-75℃ and stirring for 2.5-5.5 hours; and continuing to raise the temperature to 75-95℃ and stirring for 1.5-4.5 hours, changing the deionized water every 25-35 minutes during this period to obtain a degreased green body; rinsing the degreased green body with room temperature deionized water for 2-5 minutes.

7. The water-soluble degreased metal powder injection molding process according to claim 1, characterized in that, S7 specifically involves drying the rinsed degreased blank at 55-75℃ and 0.06-0.095MPa for 2.5-6.5 hours to obtain a dried blank. The dried blank is then heated to 220-320℃ at 2-4℃ / min under an argon atmosphere and held for 30-60 minutes. The temperature is then further increased to 550-620℃ at 5-7℃ / min and held for 60-120 minutes to obtain a hot degreased blank.

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