A feed material for metal injection moulding, a method of preparing a feed material and a metal article

Abstract

The application relates to a feed for metal injection molding, a preparation method of the feed and a metal product, wherein the preparation method of the feed comprises the following steps: S1, obtaining the following components according to weight parts: 40-50 parts of Fe elements, 2-8 parts of Ni elements, 20-25 parts of Cr elements, 20-25 parts of Co elements, 2-8 parts of Mo elements, 2-8 parts of Cu elements, 0.1-3 parts of Si elements, 1-3 parts of Mn elements, mixing and then heating to melt the material, and then adopting a high-pressure water-gas combined atomization method to obtain mixed powder; S2, obtaining a forming agent; S3, preheating the mixed powder obtained in S1 under vacuum conditions, then adding the forming agent into the mixed powder for mixing, and then performing plasticizing extrusion granulation to prepare the feed. The feed can meet the size precision requirements of MIM injection, green compact degreasing sintering and related post-process machining, the existing MIM materials on the market cannot simultaneously meet the problem of high polishable hardness, and the obtained metal product has the comprehensive advantages of appearance and hardness.

Description

Technical Field

[0001] This invention relates to metal injection molding technology, and in particular to a feedstock for metal injection molding, a method for preparing the feedstock, and metal products. Background Technology

[0002] In recent years, smart wearable devices have developed rapidly and are updated quickly, especially with the advent of the 5G era, electronic devices are becoming increasingly popular. Based on our numerous successful cases, our clients not only require us to innovate in product functionality but also place higher demands on appearance.

[0003] Metal injection molding (MIM) is a process in which a mixture of metal powder and binder is injected into a mold, and then the binder is removed by debinding and sintering to obtain products with complex shapes and high precision, possessing physical, chemical, and mechanical properties close to those of forgings. This technology is suitable for the mass production of small, precision metal parts with complex three-dimensional shapes and special performance requirements.

[0004] The development of metal products has set performance requirements: firstly, a hardness value of over 200 HV is needed to prevent deformation; secondly, the appearance must achieve a high polishing grade of A1. Currently, none of the materials available on the market for MIM technology meet these requirements. This is because hardness and appearance are interrelated; products with higher hardness are more difficult to polish, making it harder to achieve an A1 grade appearance.

[0005] For example, the most commonly used material in metal injection molding is SUS 316L, which has a high density (7.9 g / cm³). 3 It has high fracture toughness and excellent polishing performance, but its disadvantage is low hardness, usually between 100HV and 160HV.

[0006] Co-Cr-Mo alloy (F75) is also widely used in metal injection molding technology. Its advantage is that it has high hardness, which can reach 250HV-320HV. Other properties are similar to SUS 316L. However, due to its dense layer, the polishing effect after sintering cannot reach A1 grade (standard: Ra<0.016μm).

[0007] Patent application CN111299590A discloses a preparation method for a high-gloss MIM 316L stainless steel watch case, including the following steps. S1: Mixing: Mixing is the core first-stage process for preparing metal injection molding products. It is a process of rotating and mixing metal powder and molding agent at a certain ratio under certain temperature conditions in a kneading and granulating machine for a certain period of time and temperature. After melting, it is extruded by a screw and cut into particles by a blade to obtain injection molding particle feed. During the entire mixing process, as the temperature continuously rises, the molding agent gradually changes from a solid state to a glass state → a high-elastic state → and finally a viscous flow state. The viscous flow state molding agent after heating and melting accompanies the continuous rotation of the mixer, and the viscous flow state molding agent and metal powder are mixed with each other. The enlarged state is that the surface of each monomer particle powder is uniformly coated with the viscous flow state molding agent;

[0008] S2: Molding: After the feed is heated and melted in the barrel of the injection machine, it is filled into the product mold cavity under the high-pressure and high-speed propulsion of the internal injection screw. Due to the small channels of the injection material flow path, nozzle, hot nozzle, and glue inlet, under friction and shear, the feed is extremely easy to decompose and generate a large amount of gas and carbide. The exhaust grooves of the product cavity cannot meet the discharge of a large amount of gas, and the cavity pressure becomes higher and higher. It is difficult for the feed to be evenly filled in the cavity, and finally defects such as uneven density, low density, and more carbides inside the product occur, seriously affecting the density after sintering of the product. The method of the present invention is that the injection channels are enlarged under the actual standard situation after existing mold flow analysis. The minimum cross-sectional area of all flow paths is enlarged by 1.5 times. After the flow paths are enlarged, it is beneficial to the flow of the feed. Due to the larger channels, the feed is not easy to decompose at high temperature and high speed during injection, and a high-density and uniform embryo can be easily obtained;

[0009] S3: Debinding: The formed watch case product is placed on an alumina ceramic plate and loaded into a catalytic debinding furnace. The debinding process parameters are: debinding temperature 110°C, nitrogen flow rate 5 L / min, nitric acid inlet amount 2 g / min, catalytic time 4 hours. After the equipment program runs to completion, the watch case product is taken out. The product weight loss ≥ 7.8% is qualified. The debinding rate of the existing production process is ≥ 7.2%. Because the debinding rate is low before sintering of the product, during the sintering process, the product is prone to incomplete removal of the molding agent. After the outer surface of the product is combined with liquid, the internal polymer cannot be discharged, resulting in being trapped inside. After continuous high-temperature sintering, the internal polymer molding agent that cannot be discharged is carbonized, and many sand holes and pores are formed inside the product after polishing;

[0010] S4: Sintering: The watch case product after qualified debinding is transferred into a powder metallurgy MIM sintering furnace for sintering. After the sintering program runs to completion, the watch case product is taken out, and the green density of the product is measured with a densitometer. The density of the sintered watch case product ≥ 7.95 g / cm 3 is qualified, and the measured product density value is 7.97 g / cm3 ;

[0011] S5: Post-processing: The post-processing method for watch case products is to first use a hemp wheel with polishing wax for roughing, then perform ultrasonic cleaning, and after cleaning and drying, take it out and use a cloth wheel with fine polishing wax to polish it to a high gloss effect.

[0012] The above method uses conventional 316L material for polishing to prepare stainless steel high-gloss watch cases, and the hardness can only reach 100HV-120HV, making it difficult to obtain materials with higher hardness. Summary of the Invention

[0013] The purpose of this invention is to overcome the limitations of existing metal injection molding feedstocks in meeting the requirements for product hardness and appearance. This invention provides a feedstock for metal injection molding. Through continuous exploration and learning from the advantages and disadvantages of feedstocks currently used in the industry, the inventors sought a new feedstock that could integrate the advantages of different materials. They finally obtained a feedstock with high density, high strength, high fracture toughness, and a hardness reaching 210HV-240HV, while also possessing excellent polishing properties. Based on this, the inventors used this new feedstock in a MIM molding process to form a dense polished layer with a hardness reaching 210HV. This meets the dimensional accuracy requirements of green body debinding and sintering, as well as related post-processing, overcoming the problem that existing MIM feedstocks on the market cannot simultaneously meet the requirements of high polishability and high hardness.

[0014] In this invention, the key component affecting performance in the feed is Fe / Ni element. If Fe / Ni is insufficient or absent, the product's hardness value will be lower than 210HV, and its Ra value after polishing will be greater than 0.016μm, failing to reach the A1 grade.

[0015] In this invention, during the preparation of the feed, it is necessary to control the mixing time to 50 minutes and the temperature to 195°C. If the mixing time is too short, the mixing will be uneven; if the mixing time is too long, the internal additive molecules will dissolve. If the mixing temperature is too low, the additives will not melt; if the mixing temperature is too high, the additives will decompose.

[0016] The specific plan is as follows:

[0017] A method for preparing feedstock for metal injection molding includes the following steps:

[0018] S1, according to the following components by weight: 40-50 parts Fe, 2-8 parts Ni, 20-25 parts Cr, 20-25 parts Co, 2-8 parts Mo, 2-8 parts Cu, 0.1-3 parts Si, 1-3 parts Mn, after mixing, heat to melt the material, and then use high-pressure water-air combined atomization method to obtain mixed powder;

[0019] S2, according to parts by weight, comprises the following components: 1-5 parts stearic acid, 2-10 parts photothermal stabilizer, 2-10 parts polymer wax, 3-15 parts high-density polyethylene, 1-5 parts polyethylene-acetic acid, 1-6 parts carnauba wax, and 65-90 parts polyoxymethylene. These are then mixed to obtain a molding agent.

[0020] S3, under vacuum conditions, the mixed powder obtained in S1 is preheated, and then the molding agent obtained in S2 is added to the mixed powder that has reached a predetermined temperature. The mixture is then mixed in a mixer, and the mixed material is fed into a granulator, plasticized, extruded, and granulated to obtain a feedstock for metal injection molding.

[0021] Furthermore, S1 contains the following components by weight: 43-47 parts Fe, 4-5 parts Ni, 20-23 parts Cr, 20-23 parts Co, 2-4 parts Mo, 3-5 parts Cu, 1-2 parts Si and 1-3 parts Mn.

[0022] Preferably, S1 contains the following components by weight: 44-46 parts Fe, 4-5 parts Ni, 21-23 parts Cr, 21-23 parts Co, 3-4 parts Mo, 4-5 parts Cu, 1-2 parts Si and 2-3 parts Mn.

[0023] More preferably, S1 contains the following components in parts by weight: 45 parts Fe, 4 parts Ni, 23 parts Cr, 22 parts Co, 4 parts Mo, 4 parts Cu, 2 parts Si, and 3 parts Mn.

[0024] Furthermore, the component obtained in S1 is a powder, preferably a powder that satisfies at least one of the following (1) to (3):

[0025] (1) D10 is in the range of 1μm to 3μm;

[0026] (2) D50 is between 7μm and 10μm;

[0027] (3) D90 is between 18μm and 22μm.

[0028] Furthermore, after mixing in S1, the mixture is heated to 1600-1800°C, preferably 1650-1750°C, and more preferably 1670-1730°C, to melt the material.

[0029] Furthermore, the following components are obtained in S2 by weight: 1 to 3 parts stearic acid, 2 to 7 parts photothermal stabilizer, 2 to 8 parts polymer wax, 4 to 12 parts high-density polyethylene, 1 to 4 parts polyethylene-acetic acid, 1 to 5 parts carnauba wax, and 68 to 88 parts polyoxymethylene.

[0030] Preferably, S2 contains the following components in parts by weight: 1 to 2.5 parts stearic acid, 3 to 6 parts photothermal stabilizer, 3 to 7 parts polymer wax, 5 to 10 parts high-density polyethylene, 1.5 to 3 parts polyethylene acetate, 2 to 4 parts carnauba wax, and 70 to 85 parts polyoxymethylene.

[0031] More preferably, S2 contains the following components in parts by weight: 2 parts stearic acid, 4 parts photothermal stabilizer, 5 parts polymer wax, 5 to 10 parts high-density polyethylene, 1.5 to 3 parts polyethylene acetate, 2 to 4 parts carnauba wax, and 70 to 85 parts polyoxymethylene.

[0032] Furthermore, the preheating mentioned in S3 refers to heating to 120±10℃ with a vacuum degree of 10-500Pa;

[0033] Preferably, the speed of the mixer is 15-35 r / min, the stirring time is 40-70 min, and the material is pre-agglomerated into a mud-like mass after mixing;

[0034] Preferably, the granulator has a pressure of 5 MPa-6 MPa and a temperature of 180℃-190℃.

[0035] Preferably, the granulation will yield a feed with the following particle size distribution:

[0036] (1) D10 is in the range of 1μm to 3μm;

[0037] (2) D50 is between 7μm and 10μm;

[0038] (3) D90 is between 18μm and 22μm.

[0039] The present invention also protects the feed prepared by the method for preparing feed for metal injection molding.

[0040] This invention also protects a metal product, which is obtained by injection molding a green blank containing the aforementioned feedstock, followed by degreasing, sintering, and polishing.

[0041] Furthermore, the method for preparing the metal article includes:

[0042] Injection molding: The feed material is injection molded at 100-150°C to obtain a green preform;

[0043] Degreasing and sintering: The green embryo is placed in a degreasing furnace, preferably an oxalic acid degreasing furnace, with an oxalic acid feed rate of 0.010-0.050 mL / min, a degreasing temperature of 120-125℃, and a degreasing time of 8-24 h. The green embryo is completely immersed in the degreasing solution. After degreasing, sintering is performed using a vacuum metal furnace at a temperature of 1340-1350℃ for 90-120 min. During the sintering process, the pressure is maintained at 0.5-4 MPa. It is preferable to use a corundum mullite support plate to place the sample during the sintering process.

[0044] Grinding and polishing: Grinding the sintered sample is preferred. The process route of fiber wheel / purple wax + hemp wheel / purple wax + thread wheel / white wax + thread wheel / green wax is preferred to obtain metal products.

[0045] Furthermore, the metal product has an appearance grade of A1 and a hardness of 210-240HV.

[0046] Beneficial effects:

[0047] In this invention, the feedstock used for metal injection molding has high fluidity, which can meet the requirements of MIM injection molding, facilitates material flow and fusion, and makes molding easier.

[0048] Furthermore, the feed of the present invention has good shape retention during the debinding and sintering of green embryos, thereby satisfying the support of the product during the debinding and sintering of green embryos and preventing the occurrence of cracks and other defects.

[0049] Furthermore, the feed material of the present invention has the characteristics of high polish and high hardness, so that it is not easy to deform during related post-processing, thereby meeting the accuracy requirements of the processing dimensions.

[0050] In summary, this invention overcomes the problem that existing MIM materials on the market cannot simultaneously meet the requirements of high polishability and hardness, and the resulting metal products have the combined advantages of appearance and hardness. Attached Figure Description

[0051] To more clearly illustrate the technical solution of the present invention, the accompanying drawings will be briefly described below. Obviously, the drawings described below only relate to some embodiments of the present invention and are not intended to limit the present invention.

[0052] Figure 1 This is a schematic diagram of the mixed powder preparation process provided by the present invention;

[0053] Figure 2 This is a schematic diagram of the feeding process for preparing metal injection molding provided by the present invention;

[0054] Figure 3 This is a product drawing provided in Embodiment 1 of the present invention;

[0055] Figure 4 This is a product drawing provided in Comparative Example 1 of the present invention;

[0056] Figure 5 This is a product drawing provided in Comparative Example 2 of the present invention. Detailed Implementation

[0057] The method for preparing feedstock for metal injection molding in this invention includes the following steps:

[0058] S1, as Figure 1 As shown, the following components were obtained by weight: 40-50 parts Fe, 2-8 parts Ni, 20-25 parts Cr, 20-25 parts Co, 2-8 parts Mo, 2-8 parts Cu, 0.1-3 parts Si, and 1-3 parts Mn. After mixing, the materials were heated to melt them, and then a high-pressure water-air combined atomization method was used to obtain a mixed powder.

[0059] S2, according to the following components in parts by weight: 1 to 5 parts stearic acid, 2 to 10 parts photothermal stabilizer, 2 to 10 parts polymer wax, 3 to 15 parts high-density polyethylene, 1 to 5 parts polyethylene-acetic acid, 1 to 6 parts carnauba wax, and 65 to 90 parts polyoxymethylene, which are then mixed to obtain a molding agent.

[0060] S3, as Figure 2 As shown, the mixed powder obtained in S1 is preheated under vacuum conditions, and then the molding agent obtained in S2 is added to the mixed powder that has reached a predetermined temperature. The mixture is then mixed in a mixer, and the mixed material is fed into a granulator, plasticized, extruded, and granulated to obtain a feedstock for metal injection molding.

[0061] Among them, the high-pressure water-air combined atomization method refers to the process in which high-speed airflow is accelerated through an atomizing nozzle, and the kinetic energy of the airflow is converted into the surface energy of small metal droplets. In this way, the metal flow is pulverized into small droplets, which then solidify into powder during subsequent flight.

[0062] Preferred embodiments of the present invention will now be described in more detail. While preferred embodiments of the present invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products. In the following embodiments, unless otherwise specified, "%" refers to weight percentage, and "parts" refers to parts by weight.

[0063] The following testing methods are included:

[0064] Hardness test: Take four areas of the product and measure 5 hardness values ​​in each area. Subtract the maximum and minimum values ​​and keep and record the remaining 3 values ​​in each area.

[0065] Polishing performance test: The inspector's vision is greater than 1.2. The inspection is carried out under a 220V / 50HZ 18 / 40W fluorescent lamp and a 220V / 50HZ 40W daylight lamp at a visual distance of 45±5cm. The surface is required to be free of pits, scratches and white spots.

[0066] Roughness was measured using a surface roughness meter, with a standard Ra ≤ 0.016 μm.

[0067] The main reagents used include:

[0068] The Fe and Ni elements used in the following examples are all elemental powders with particle sizes that meet the following distribution: D10 is 1μm to 3μm, D50 is 7μm to 10μm, and D90 is 18μm to 22μm.

[0069] Example 1

[0070] S1, the following components are obtained according to the following weight parts: 40 parts Fe, 2 parts Ni, 25 parts Cr, 25 parts Co, 2 parts Mo, 2 parts Cu, 1 part Si, and 3 parts Mn. After mixing, the materials are heated to melt them, and then a mixed powder is obtained by high-pressure water-air combined atomization method.

[0071] S2, according to the following components in parts by weight: 1 part stearic acid, 2 parts photothermal stabilizer, 2 parts polymer wax, 10 parts high-density polyethylene, 3 parts polyethylene-acetic acid, 1 part carnauba wax, and 80 parts polyoxymethylene, which are then mixed to obtain a molding agent.

[0072] S3. Under vacuum conditions, the mixed powder obtained in S1 is preheated to 120±10℃ and the vacuum degree is 200Pa. Then, the molding agent obtained in S2 is added to the mixed powder that has reached the predetermined temperature. The mixture is then mixed in a mixer at a speed of 15-35 r / min and a stirring time of 40-70 min. After mixing, the material is pre-agglomerated into a mud-like shape. The mixed material is then fed into a granulator, plasticized, extruded, and granulated. The pressure of the granulator is 5Mpa-6Mpa and the temperature is 180℃. The granulation yields a feedstock with the following particle size distribution: D10 is 1μm~3μm; D50 is 7μm~10μm; D90 is 18μm~22μm, which is used to prepare a feedstock for metal injection molding.

[0073] The following describes a method for preparing metal products after the feedstock is injection molded into a green preform, followed by degreasing, sintering, and polishing.

[0074] Injection molding: The feed material is injection molded at 100°C to obtain a green preform;

[0075] Degreasing and sintering: The green embryo is placed in a degreasing furnace using oxalic acid. The oxalic acid feed rate is 0.010 mL / min, the degreasing temperature is 120℃, and the degreasing time is 12 h. The green embryo is completely immersed in the degreasing solution. After degreasing, sintering is performed using a vacuum metal furnace at a temperature of 1340℃ for 90 min. The pressure is maintained at 2 MPa during the sintering process. It is preferable to use a corundum mullite support plate to place the sample during the sintering process.

[0076] Grinding and polishing: The sintered sample is ground using a process route of fiber wheel / purple wax + hemp wheel / purple wax + thread wheel / white wax + thread wheel / green wax to obtain metal products.

[0077] The metal products were tested, and the results are as follows:

[0078] Hardness test result: 220 HV;

[0079] Roughness test result: Ra = 0.012 μm.

[0080] Product image as shown Figure 3 As shown, the polishing grade is A1 and the hardness is 220HV.

[0081] Example 2

[0082] S1, the following components are obtained according to the following weight parts: 44 parts Fe, 4 parts Ni, 23 parts Cr, 23 parts Co, 3 parts Mo, 4 parts Cu, 2 parts Si and 3 parts Mn. After mixing, the mixture is heated to 1730℃ to melt the material, and then a mixed powder is obtained by high-pressure water-air combined atomization method.

[0083] S2, according to the following components in parts by weight: 2 parts stearic acid, 5 parts photothermal stabilizer, 8 parts polymer wax, 8 parts high-density polyethylene, 4 parts polyethylene-acetic acid, 2 parts carnauba wax, and 75 parts polyoxymethylene, which are then mixed to obtain a molding agent.

[0084] S3, under vacuum conditions, the mixed powder obtained in S1 is preheated, and then the molding agent obtained in S2 is added to the mixed powder that has reached a predetermined temperature. The mixture is then mixed in a mixer, and the mixed material is fed into a granulator, plasticized, extruded, and granulated to obtain a feedstock for metal injection molding.

[0085] The following describes a method for preparing metal products after the feedstock is injection molded into a green preform, followed by degreasing, sintering, and polishing.

[0086] Injection molding: The feed material is injection molded at 130°C to obtain a green preform;

[0087] Degreasing and sintering: The green embryo is placed in a degreasing furnace using oxalic acid. The oxalic acid feed rate is 0.050 mL / min, the degreasing temperature is 125℃, and the degreasing time is 10 h. The green embryo is completely immersed in the degreasing solution. After degreasing, sintering is performed using a vacuum metal furnace at a temperature of 1350℃ for 90 min. The pressure is maintained at 1 MPa during the sintering process. It is preferable to use a corundum mullite support plate to place the sample during the sintering process.

[0088] Grinding and polishing: The sintered sample is ground using a process route of fiber wheel / purple wax + hemp wheel / purple wax + thread wheel / white wax + thread wheel / green wax to obtain metal products.

[0089] Hardness test result: 230 HV;

[0090] Roughness test result: Ra = 0.011 μm.

[0091] Example 3

[0092] S1, according to the following components by weight: 46 parts Fe, 4 parts Ni, 21 parts Cr, 23 parts Co, 4 parts Mo, 5 parts Cu, 1 part Si and 2 parts Mn. After mixing, the mixture is heated to 1670℃ to melt the material, and then a mixed powder is obtained by high-pressure water-air combined atomization method.

[0093] S2, according to the following components in parts by weight: 5 parts stearic acid, 2 parts photothermal stabilizer, 2 parts polymer wax, 3 parts high-density polyethylene, 5 parts polyethylene-acetic acid, 6 parts carnauba wax, and 85 parts polyoxymethylene, which are then mixed to obtain a molding agent.

[0094] S3, under vacuum conditions, the mixed powder obtained in S1 is preheated, and then the molding agent obtained in S2 is added to the mixed powder that has reached a predetermined temperature. The mixture is then mixed in a mixer, and the mixed material is fed into a granulator, plasticized, extruded, and granulated to obtain a feedstock for metal injection molding.

[0095] The following describes a method for preparing metal products after the feedstock is injection molded into a green preform, followed by degreasing, sintering, and polishing.

[0096] Injection molding: The feed material is injection molded at 140°C to obtain a green preform;

[0097] Degreasing and sintering: The green embryo is placed in a degreasing furnace using oxalic acid. The oxalic acid feed rate is 0.010 mL / min, the degreasing temperature is 125℃, and the degreasing time is 8 hours. The green embryo is completely immersed in the degreasing solution. After degreasing, sintering is performed using a vacuum metal furnace at a temperature of 1350℃ for 120 minutes. The pressure is maintained at 1.5 MPa during the sintering process. It is preferable to use a corundum mullite support plate to place the sample during the sintering process.

[0098] Grinding and polishing: The sintered sample is ground using a process route of fiber wheel / purple wax + hemp wheel / purple wax + thread wheel / white wax + thread wheel / green wax to obtain metal products.

[0099] Hardness test result: 225HV;

[0100] Roughness test result: Ra = 0.016 μm.

[0101] Example 4

[0102] S1, according to the following components by weight: 44-46 parts Fe, 4-5 parts Ni, 21-23 parts Cr, 21-23 parts Co, 3-4 parts Mo, 4-5 parts Cu, 1-2 parts Si and 2-3 parts Mn, after mixing, heat to 1750℃ to melt the material, and then use high-pressure water-air combined atomization method to obtain mixed powder.

[0103] S2, according to the following components in parts by weight: 1 to 5 parts stearic acid, 2 to 10 parts photothermal stabilizer, 2 to 10 parts polymer wax, 3 to 15 parts high-density polyethylene, 1 to 5 parts polyethylene-acetic acid, 1 to 6 parts carnauba wax, and 65 to 90 parts polyoxymethylene, which are then mixed to obtain a molding agent.

[0104] S3, under vacuum conditions, the mixed powder obtained in S1 is preheated, and then the molding agent obtained in S2 is added to the mixed powder that has reached a predetermined temperature. The mixture is then mixed in a mixer, and the mixed material is fed into a granulator, plasticized, extruded, and granulated to obtain a feedstock for metal injection molding.

[0105] The following describes a method for preparing metal products after the feedstock is injection molded into a green preform, followed by degreasing, sintering, and polishing.

[0106] Injection molding: The feed material is injection molded at 110°C to obtain a green preform;

[0107] Degreasing and sintering: The green embryo is placed in a degreasing furnace using oxalic acid. The oxalic acid feed rate is 0.030 mL / min, the degreasing temperature is 120℃, and the degreasing time is 20 h. The green embryo is completely immersed in the degreasing solution. After degreasing, sintering is performed using a vacuum metal furnace at a temperature of 1345℃ for 120 min. The pressure is maintained at 4 MPa during the sintering process. It is preferable to use a corundum mullite support plate to place the sample during the sintering process.

[0108] Grinding and polishing: The sintered sample is ground using a process route of fiber wheel / purple wax + hemp wheel / purple wax + thread wheel / white wax + thread wheel / green wax to obtain metal products.

[0109] Hardness test result: 218HV;

[0110] Roughness test result: Ra = 0.013 μm.

[0111] Example 5

[0112] S1, the following components are obtained according to the following weight parts: 46 parts Fe, 5 parts Ni, 23 parts Cr, 23 parts Co, 3 parts Mo, 5 parts Cu, 2 parts Si and 2 parts Mn. After mixing, the mixture is heated to 1650℃ to melt the material, and then a mixed powder is obtained by high-pressure water-air combined atomization method.

[0113] S2, according to the following components in parts by weight: 4 parts stearic acid, 5 parts photothermal stabilizer, 6 parts polymer wax, 5 parts high-density polyethylene, 1 part polyethylene-acetic acid, 5 parts carnauba wax, and 70 parts polyoxymethylene, which are then mixed to obtain a molding agent.

[0114] S3, under vacuum conditions, the mixed powder obtained in S1 is preheated, and then the molding agent obtained in S2 is added to the mixed powder that has reached a predetermined temperature. The mixture is then mixed in a mixer, and the mixed material is fed into a granulator, plasticized, extruded, and granulated to obtain a feedstock for metal injection molding.

[0115] The following describes a method for preparing metal products after the feedstock is injection molded into a green preform, followed by degreasing, sintering, and polishing.

[0116] Injection molding: The feed material is injection molded at 100°C to obtain a green preform;

[0117] Degreasing and sintering: The green embryo is placed in a degreasing furnace using oxalic acid. The oxalic acid feed rate is 0.020 mL / min, the degreasing temperature is 122℃, and the degreasing time is 12 h. The green embryo is completely immersed in the degreasing solution. After degreasing, sintering is performed using a vacuum metal furnace at a temperature of 1350℃ for 100 min. The pressure is maintained at 3 MPa during the sintering process. It is preferable to use a corundum mullite support plate to place the sample during the sintering process.

[0118] Grinding and polishing: The sintered sample is ground using a process route of fiber wheel / purple wax + hemp wheel / purple wax + thread wheel / white wax + thread wheel / green wax to obtain metal products.

[0119] Hardness test result: 232HV;

[0120] Roughness test result: Ra = 0.015 μm.

[0121] Comparative Example 1

[0122] We purchased 316L feedstock from the market; the manufacturer is Huzhou Huijin Materials Technology Co., Ltd.

[0123] Metal products were prepared using 316L feedstock as described in Example 1. The product image is shown below. Figure 4 As shown, the polishing grade is A1 and the hardness is 120HV.

[0124] Comparative Example 2

[0125] Purchase feedstock F75 from the market; the manufacturer is Hunan Lide Electronic Slurry Co., Ltd.

[0126] Metal articles were prepared using feeder F75 according to Example 1, and the product image is shown below. Figure 5 As shown, the polishing grade is B2 and the hardness is 280VHV.

[0127] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0128] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0129] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A metal product, obtained by using a feedstock for metal injection molding, wherein a green preform is obtained through injection molding, followed by degreasing, sintering, and polishing, characterized in that: A method for preparing feedstock for metal injection molding includes the following steps: S1, the following components are obtained according to the following weight parts: 40-50 parts Fe, 4-8 parts Ni, 23-25 ​​parts Cr, 20-25 parts Co, 2-8 parts Mo, 2-8 parts Cu, 1-3 parts Si, and 1-3 parts Mn. After mixing, the materials are heated to melt, and then a high-pressure water-air combined atomization method is used to obtain a mixed powder. S2, according to parts by weight, comprises: 1-5 parts stearic acid, 2-10 parts photothermal stabilizer, 2-10 parts polymer wax, 3-15 parts high-density polyethylene, 1-5 parts polyethylene-acetic acid, 1-6 parts carnauba wax, and 65-90 parts polyoxymethylene. The mixture is then used to obtain a molding agent. S3, under vacuum conditions, the mixed powder obtained in S1 is preheated, and then the molding agent obtained in S2 is added to the mixed powder that has reached a predetermined temperature. The mixture is then mixed in a mixer, and the mixed material is fed into a granulator, plasticized, extruded, and granulated to obtain a feedstock for metal injection molding. The method for preparing the metal product includes: Injection molding: The feed material is injection molded at 100-150°C to obtain a green preform; Degreasing and sintering: The green embryo is placed in a degreasing furnace using oxalic acid. The oxalic acid feed rate is 0.010–0.050 mL / min, the degreasing temperature is 120–125℃, and the degreasing time is 8–24 h. The green embryo is completely immersed in the degreasing solution. After degreasing, sintering is performed using a vacuum metal furnace at a temperature of 1340–1350℃ for 90–120 min. During the sintering process, the pressure is maintained at 0.5–4 MPa. The sample is placed on a corundum-mullite sintering plate during the sintering process. Grinding and polishing: The sintered sample is ground using a process route of fiber wheel / purple wax + hemp wheel / purple wax + thread wheel / white wax + thread wheel / green wax to obtain metal products; the appearance grade of the metal products reaches A1 grade and the hardness is 210-240HV.

2. The metal article of claim 1, wherein: S1 contains the following components by weight: 43-47 parts Fe, 5 parts Ni, 23 parts Cr, 20-23 parts Co, 2-4 parts Mo, 3-5 parts Cu, 1-2 parts Si, and 1-3 parts Mn.

3. The metal article of claim 2, wherein: S1 contains the following components by weight: 44-46 parts Fe, 5 parts Ni, 23 parts Cr, 21-23 parts Co, 3-4 parts Mo, 4-5 parts Cu, 1-2 parts Si, and 2-3 parts Mn.

4. The metal article of claim 3, wherein: S1 contains the following components by weight: 45 parts Fe, 4 parts Ni, 23 parts Cr, 22 parts Co, 4 parts Mo, 4 parts Cu, 2 parts Si, and 3 parts Mn.

5. The article of claim 2, wherein: The component obtained in S1 is a powder that satisfies at least one of the following (1) to (3): (1) D10 is in the range of 1μm to 3μm; (2) D50 is between 7μm and 10μm; (3) D90 is between 18μm and 22μm.

6. The metal article of any of claims 1-4, wherein: After mixing in S1, heat to 1600-1800℃ to melt the material.

7. The metal article according to claim 5, characterized in that: After mixing in S1, heat to 1650-1750℃ to melt the material.

8. The metal article according to claim 6, characterized in that: After mixing in S1, heat to 1670-1730℃ to melt the material.

9. The metal article according to claim 1, characterized in that: S2 contains the following components in parts by weight: 1 to 3 parts stearic acid, 2 to 7 parts photothermal stabilizer, 2 to 8 parts polymer wax, 4 to 12 parts high-density polyethylene, 1 to 4 parts polyethylene acetate, 1 to 5 parts carnauba wax, and 68 to 88 parts polyoxymethylene.

10. The metal article according to claim 8, characterized in that: S2 contains the following components in parts by weight: 1 to 2.5 parts stearic acid, 3 to 6 parts photothermal stabilizer, 3 to 7 parts polymer wax, 5 to 10 parts high-density polyethylene, 1.5 to 3 parts polyethylene acetate, 2 to 4 parts carnauba wax, and 70 to 85 parts polyoxymethylene.

11. The metal article according to claim 9, characterized in that: S2 contains the following components in parts by weight: 2 parts stearic acid, 4 parts photothermal stabilizer, 5 parts polymer wax, 5 to 10 parts high-density polyethylene, 1.5 to 3 parts polyethylene acetate, 2 to 4 parts carnauba wax, and 70 to 85 parts polyoxymethylene.

12. The metal article according to any one of claims 1-4, characterized in that: The preheating mentioned in S3 refers to heating to 120±10℃ with a vacuum degree of 10-500Pa.

13. The metal article according to claim 11, characterized in that: The speed of the mixer is 15-35 r / min, the stirring time is 40-70 min, and the material is pre-agglomerated into mud after mixing.

14. The metal article according to claim 11, characterized in that: The granulator operates at a pressure of 5 MPa-6 MPa and a temperature of 180℃-190℃.

15. The metal article according to claim 11, characterized in that: The granulation process will yield a feed with the following particle size distribution: (1) D10 is in the range of 1μm to 3μm; (2) D50 is between 7μm and 10μm; (3) D90 is between 18μm and 22μm.

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