Method for preparing low-cost plastic-based titanium alloy feedstock for metal powder injection molding

Abstract

The present invention provides a low-cost plastic-based titanium alloy feed for metal powder injection molding and a preparation method thereof. The invention comprises the following steps: mixing coarse powder and fine powder, and mismatching fine-particle-size and coarse-particle-size titanium alloy powders to obtain an optimized powder with high tap density, low oxygen content, and a particle size distribution obeying a normal distribution; and regulating the feed components and selecting a preparation method to obtain a low-cost plastic-based feed with good powder dispersibility, compatibility, and encapsulation, high density, and strong fluidity.

Description

Technical Field

[0001] The present invention relates to the technical field of titanium alloy powder injection molding, and in particular to a method for preparing a low-cost plastic-based titanium alloy feedstock for metal powder injection molding. Background Art

[0002] Titanium and titanium alloys, as high-quality lightweight metal structural and functional materials, have the advantages of low density, high specific strength, low elastic modulus, good biocompatibility, excellent corrosion resistance, and good heat resistance. However, titanium alloys have low thermal conductivity, severe work hardening, and low processing efficiency, making traditional processing methods such as ingot metallurgy (forging, rolling, extrusion, drawing, stamping and spinning, etc.), casting or powder metallurgy very difficult and costly to process. Metal powder injection molding (MIM) technology has a series of excellent characteristics such as high precision, uniform structure, excellent performance, and low production cost. It makes up for the difficulties of traditional processing and is the best choice for the future processing method of complex and precise small titanium alloy components.

[0003] At present, most metal materials used in MIM are stainless steel and low-alloy steel, while the application of titanium and titanium alloy materials in its technology is extremely rare. The main reason is that the particle size of the raw powder used in MIM titanium alloy needs to be less than 45μm to obtain a higher sintering density. At the same time, the product has a large shrinkage problem, which makes it difficult to control the product size. In addition, due to the current level of titanium alloy powder making technology, the output of spherical powder with a particle size range below 45μm is low, resulting in high prices. The medium-sized particle size powder (75-100μm) with higher output and lower price is ignored by the MIM process due to its low sintering density. Summary of the Invention

[0004] The purpose of the present invention is to address the deficiencies of the existing technology and provide a low-cost plastic-based titanium alloy feed for metal powder injection molding and a preparation method thereof. By mismatching fine-particle size and coarse-particle size titanium alloy powders, an optimized powder with high tap density, low oxygen content, high specific surface area, and a particle size distribution that obeys a normal distribution is obtained; and then, by regulating the feed components and selecting the preparation method, a low-cost plastic-based feed with good powder dispersibility, compatibility and encapsulation, high density, and strong fluidity is obtained.

[0005] A first aspect of the present invention relates to a method for preparing a low-cost plastic-based titanium alloy feedstock for metal powder injection molding, comprising the following steps:

[0006] S1. Mixing a first titanium alloy powder and a second titanium alloy powder under an argon protective atmosphere to obtain a mixed titanium alloy powder; wherein the particle size of the first titanium alloy powder is larger than that of the second titanium alloy powder, thereby forming a mismatch between the coarse particle size and the fine particle size titanium alloy powder;

[0007] S2. Under vacuum conditions, in a protective atmosphere, after setting preheating conditions, add the antioxidant BTA and the mixed titanium alloy powder into an internal mixer, and stir and preheat;

[0008] S3. After preheating, the internal mixer continues to heat up to the first internal mixing temperature, adjusts the stirring speed and time, adds the shape retaining agent polyoxymethylene (POM) and the first skeleton agent, and obtains the first internal mixing material;

[0009] S4, after the internal mixer continues to heat up to the second internal mixing temperature, the stirring speed and time are adjusted, and the dispersant and the second framework agent are added to the first internal mixing material to obtain a second internal mixing material;

[0010] S5, after the internal mixer continues to heat up to the third internal mixing temperature, the stirring speed and time are adjusted, and the lubricant and the third skeleton agent are added to the second internal mixing material to obtain a third internal mixing material;

[0011] S6. After the set granulation conditions are met, the third densely mixed material is granulated to obtain the required feed.

[0012] In an optional embodiment, the first titanium alloy powder needs to meet the following conditions:

[0013] The particle size range is (75-100) μm, the largest particle does not exceed 135 μm, the particles with a particle size greater than 100 μm do not exceed 2%, and the particles with a particle size less than 75 μm do not exceed 3%. The flowability is 24s / 50g and the tap density is 2.83g / cm 3 , solid powder loading was 64%.

[0014] In an optional embodiment, the second titanium alloy powder needs to meet the following conditions:

[0015] The particle size range is (0-45) μm, the largest particle does not exceed 50 μm, the particle size greater than 45 μm does not exceed 2%, and the tap density is 3.03 g / cm 3 , solid powder loading was 68%.

[0016] In an optional embodiment, the mass ratio of the first titanium alloy powder to the second titanium alloy powder is (50-80):(20-50), the mixing time is (5-15) h; the tap density of the mixed titanium alloy powder is (2.84-3.11) g / cm 3 , the powder loading amount is (64~70)%.

[0017] In an optional embodiment, the mass percentages of the components in the feed are: mixed titanium alloy powder (82-86)%, shape retaining agent (10-15)%, skeleton agent (1-5)%, lubricant (0.02-2)%, dispersant (0.01-0.2)%, and antioxidant (0.01-0.2)%.

[0018] In an optional embodiment, the shape retaining agent is polyoxymethylene (POM).

[0019] In an optional embodiment, the first framework agent is polypropylene, the second framework agent is polyethylene, and the third framework agent is ethylene acrylic acid copolymer.

[0020] In an optional embodiment, the lubricant is paraffin, the dispersant is ethylene bisstearamide, and the antioxidant is benzotriazole.

[0021] In an optional embodiment, in step S3, the first banburying temperature is (155-185)°C, the banburying time is (8-18) min, and the screw speed is (5-10) rpm.

[0022] In the step S4, the second banburying temperature is (170-200)° C., the banburying time is (15-20) min, and the screw speed is (15-20) rpm.

[0023] In the step S5, the third banburying temperature is (180-200)°C, the banburying time is (25-35) min, and the screw speed is (20-25) rpm.

[0024] A second aspect of the present invention relates to a low-cost plastic-based titanium alloy feedstock for metal powder injection molding prepared by the aforementioned method.

[0025] Compared with the prior art, the present invention has the following significant beneficial effects:

[0026] The method for preparing low-cost plastic-based titanium alloy feedstock for metal powder injection molding of the present invention uses titanium alloy aerosolized powders of two different particle sizes, coarse and fine, as raw materials. By mismatching the fine particle size and the coarse particle size powder, the maximum tap density is obtained, thereby effectively reducing the shrinkage rate of the MIM sintered product and controlling the product dimensional accuracy. At the same time, due to the mismatch between the fine particle size powder and the coarse particle size powder, the contact area between the powders can be obtained to a greater extent, thereby facilitating the improvement of the MIM sintering density.

[0027] After obtaining a mixed powder that meets the requirements, polyoxymethylene with a thermoplastic low-molecular chain is added to this powder. This can greatly help improve the fluidity of the powder at a certain temperature, thereby improving the filling properties of the feed. The polyoxymethylene is combined with a small amount of a high-temperature skeleton agent with a large molecular chain. Combined with the powder's high tap density and good shape retention, it can maintain a relatively high dimensional accuracy of the degreased blank after catalytic debinding of the injection blank, preventing it from collapsing, deformation and other defects.

[0028] The addition of lubricant improves the wettability between irregular powder and polyoxymethylene and skeleton agent, which helps the binder to fully and completely wrap the powder surface and avoid powder agglomeration.

[0029] The addition of the antioxidant BTA has two functions: first, it covers the powder surface and has an oxygen-suppressing effect; second, it prevents the decomposition products of the polymer binder at high temperatures from corroding the titanium alloy powder. Furthermore, the addition reaction between BTA and polyoxymethylene prevents the hydrogen atoms in BTA from detaching from the binder, thereby keeping the entire binder environment in a neutral state. This overcomes the defect of BTA being soluble in water and having a weak acidity. At the same time, the derivatives obtained from the reaction also alleviate the irritating odor caused by BTA.

[0030] In this way, by regulating and optimizing the alloy powder, combined with the regulation of feed components and multiple graded mixing preparation processes, a low-cost plastic-based feed with good powder dispersibility, compatibility and encapsulation, high density and strong fluidity is obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a laser particle size distribution diagram of the mixed titanium alloy powder of Example 1 of the present invention.

[0032] Figure 2 This is a laser particle size distribution diagram of the mixed titanium alloy powder of Example 2 of the present invention.

[0033] Figure 3 This is a laser particle size distribution diagram of the mixed titanium alloy powder of Example 3 of the present invention.

[0034] Figure 4 This is a laser particle size distribution diagram of the mixed titanium alloy powder of Example 4 of the present invention.

[0035] Figure 5 This is a laser particle size distribution diagram of the mixed titanium alloy powder of Example 5 of the present invention.

[0036] Figure 6 This is a laser particle size distribution diagram of the mixed titanium alloy powder of Example 6 of the present invention.

[0037] Figure 7 This is a laser particle size distribution diagram of the 0-45 μm titanium alloy powder of Comparative Example 1 of the present invention.

[0038] Figure 8 This is a laser particle size distribution diagram of the 75-100 μm titanium alloy powder of Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0039] In order to better understand the technical content of the present invention, specific embodiments are given and described below with reference to the accompanying drawings.

[0040] Various aspects of the present invention are described in this disclosure with reference to the accompanying drawings, in which a number of illustrative embodiments are shown. The embodiments of the present disclosure are not necessarily intended to be comprehensive. It should be understood that the various concepts and embodiments described above, as well as those described in more detail below, can be implemented in any of a number of ways.

[0041] Since titanium alloy spherical powder (particle size ≤ 45μm) is expensive, and low-cost coarse-particle powder (particle size ≥ 45μm) has the problem of low sintering density, and in order to reduce the cost of titanium alloy powder injection molding and increase the scope of use of titanium alloy in MIM, the present invention designs and prepares low-cost high-density feed, adopts a part of coarse-particle powder (75-100μm) as raw material, and solves a series of problems such as low powder loading amount and high feed binder ratio caused by low tap density of coarse powder, large shrinkage rate and high porosity of MIM titanium alloy parts, so as to finally obtain titanium alloy MIM products that meet daily needs and open up the application prospects of low-cost coarse-particle titanium alloy powder in MIM.

[0042] In an exemplary embodiment of the present invention, a method for preparing a low-cost plastic-based titanium alloy feedstock for metal powder injection molding is provided, comprising the following steps:

[0043] S1. Mixing a first titanium alloy powder and a second titanium alloy powder under an argon protective atmosphere to obtain a mixed titanium alloy powder; wherein the particle size of the first titanium alloy powder is larger than that of the second titanium alloy powder, thereby forming a mismatch between the coarse particle size and the fine particle size titanium alloy powder.

[0044] S2. Under vacuum conditions, in a protective atmosphere, after setting preheating conditions, add the antioxidant BTA and the mixed titanium alloy powder into an internal mixer, and stir and preheat.

[0045] S3. After preheating, the internal mixer continues to heat up to the first internal mixing temperature, adjusts the stirring speed and time, adds the shape retaining agent polyoxymethylene POM and the first skeleton agent, and obtains the first internal mixing material.

[0046] S4. After the internal mixer continues to heat up to the second internal mixing temperature, the stirring speed and time are adjusted, and the dispersant and the second skeleton agent are added to the first internal mixing material to obtain a second internal mixing material.

[0047] S5. After the internal mixer continues to heat up to the third internal mixing temperature, the stirring speed and time are adjusted, and the lubricant and the third skeleton agent are added to the second internal mixing material to obtain the third internal mixing material.

[0048] S6. After the set granulation conditions are met, the third densely mixed material is granulated to obtain the required feed.

[0049] In an optional embodiment, the first titanium alloy powder needs to meet the following conditions:

[0050] The particle size range is (75-100) μm, the largest particle does not exceed 135 μm, the particles with a particle size greater than 100 μm do not exceed 2%, and the particles with a particle size less than 75 μm do not exceed 3%. The flowability is 24s / 50g and the tap density is 2.83g / cm 3 , solid powder loading was 64%.

[0051] In an optional embodiment, the second titanium alloy powder needs to meet the following conditions:

[0052] The particle size range is (0-45) μm, the largest particle does not exceed 50 μm, the particle size greater than 45 μm does not exceed 2%, and the tap density is 3.03 g / cm 3 , solid powder loading was 68%.

[0053] The above particle size range means that more than 80% of the powder size is within the defined range.

[0054] In an optional embodiment, the coarse and fine powders are screened through a 165-mesh to 300-mesh sieve, thereby effectively controlling the particle size range of the powder. The production process of the powder particle size range classification is simple, low-cost, and suitable for batch production.

[0055] In an optional embodiment, the mass ratio of the first titanium alloy powder to the second titanium alloy powder is (50-80):(20-50), and the powder mixing time is (5-15) hours.

[0056] The present invention uses titanium alloy aerosol powder with two different particle sizes, coarse and fine, as raw materials. The spherical powder ensures good fluidity of the powder and a small shrinkage rate. The optimization of the ratio of the coarse and fine powders and the mixing time ensures that the titanium alloy powder has a high tap density and a lower oxygen content than the fine powder. The particle size content of oversized and undersized particles in the coarse powder and the fine powder is controlled to effectively ensure the fluidity and bulk density of the powder, thereby obtaining an optimized powder with high tap density, low oxygen content, and a particle size distribution that obeys a normal distribution.

[0057] The closer the particle size distribution of the mixed powder is to a unimodal normal distribution, the more uniform the mixed powder is and the more uniform the corresponding feeding is.

[0058] In a preferred embodiment, the tap density of the mixed titanium alloy powder is (2.84-3.11) g / cm 3 , the powder loading is (64-70)%, corresponding to a relatively high density of the MIM product.

[0059] In an optional embodiment, the mass percentages of the components in the feed are: mixed titanium alloy powder (82-86)%, shape retaining agent (10-15)%, skeleton agent (1-5)%, lubricant (0.02-2)%, dispersant (0.01-0.2)%, and antioxidant (0.01-0.2)%.

[0060] In an optional embodiment, the shape retaining agent is polyoxymethylene (POM), and the added amount accounts for (12-15)% of the total feed mass.

[0061] In an optional embodiment, the first skeleton agent is a high-temperature skeleton agent, preferably polypropylene PP, the second skeleton agent is a high-temperature skeleton agent, preferably polyethylene HDPE, and the third skeleton agent is a low-temperature skeleton agent, preferably ethylene acrylic acid copolymer EAA; the total addition amount of the skeleton agents accounts for (1-2)% of the total feed mass.

[0062] It should be understood that the first framework agent, the second framework agent and the third framework agent are in any proportion, and those skilled in the art can adjust them according to actual conditions. It is only necessary to ensure that the total addition amount of the three accounts for (1-2)% of the total feed mass, and no further limitation is made here.

[0063] In an optional embodiment, the lubricant is paraffin wax (WAX), and the total addition amount accounts for (0.02-0.50)% of the total feed mass. The dispersant is ethylene bis stearamide (EBS), and the addition amount accounts for (0.01-0.16)% of the total feed mass. The antioxidant is benzotriazole (BTA), and the addition amount accounts for (0.05-0.1)% of the total feed mass.

[0064] In an optional embodiment, in step S2, the preheating conditions are: pressure 0.5 MPa, argon flow rate 20 L / min, oxygen content less than 1000 ppm, and temperature (140-150) ° C; the stirring conditions are: stirring time (14-23) min, and screw speed (5-7) rpm.

[0065] In an optional embodiment, in step S3, the first banburying temperature is (165-180)°C, the banburying time is (9-18) min, and the screw speed is (8-10) rpm.

[0066] In an optional embodiment, in step S4, the second banburying temperature is (180-210)°C, the banburying time is (15-20) min, and the screw speed is (15-19) rpm.

[0067] In an optional embodiment, in step S5, the third banburying temperature is (180-210)°C, the banburying time interval is (30-35) min, and the screw speed interval is (20-25) rpm.

[0068] In an optional embodiment, in step S6, the granulation conditions are: the argon pressure is 0.5 MPa; the double wrist temperature in the granulator is (170-185) ° C, and the double wrist speed is (10-15) rpm; the extrusion die temperature is (140-160) ° C, and the feed screw speed is (10-15) rpm; the pelletizer blade speed is (750-800) rpm.

[0069] In another exemplary embodiment of the present invention, a low-cost plastic-based titanium alloy feed for metal powder injection molding prepared by the aforementioned method is provided; by mismatching the powder, not only can the sintering density of the coarse-particle powder be improved, the performance be optimized, and the commercial application of the MIM titanium alloy be promoted, but also the production cost of the MIM titanium alloy can be reduced, and powders of different particle size ranges of the titanium alloy are fully utilized, and the storage cost of a large amount of coarse-particle powder is reduced, which has a broader application prospect.

[0070] In order to make the purpose and advantages of the feed preparation scheme more clear, the embodiments of the present invention are described in further detail below.

[0071] The coarse powder properties used in the following examples and comparative examples are as follows: particle size range is (75-100) μm, the largest particle does not exceed 135 μm, particles with a particle size greater than 100 μm do not exceed 2%, particles with a particle size less than 75 μm do not exceed 3%, flowability is 24 s / 50 g, and tap density is 2.83 g / cm 3 , solid powder loading was 64%.

[0072] The properties of fine powder are as follows: particle size range is (0~45)μm, the largest particle does not exceed 50μm, the particle size larger than 45μm does not exceed 2%, and the tap density is 3.03g / cm 3 , solid powder loading was 68%.

[0073] Example 1

[0074] The spherical TC4 titanium alloy mixed powder (denoted as #1-TC4 powder) was mixed with coarse and fine powders (the mass ratio of fine powder to coarse powder was 2:8) for 15 hours using a double cone mixer with an argon protective atmosphere. The mixture was placed in an electronic mixing oven, set to 70°C, and kept warm for 1 hour. The properties of the #1-TC4 powder are shown in Table 1.

[0075] Table 1 (0-45): (75-100) = 2:8, #1-TC4 powder properties

[0076]

[0077] Combine Figure 1 From Table 1, it can be seen that the tap density of #1-TC4 powder is 2.96 g / cm3 , which is between the tap density of coarse powder and fine powder, and the oxygen content is 900ppm, which meets the preparation requirements of the MIM process. The particle size distribution shows a bimodal normal distribution with obvious gradient distribution characteristics.

[0078] Weigh according to the mass percentage of binder to powder of 84:16, take 5kg of dried #1-TC4 powder and 0.95kg of binder, of which 0.95kg of binder components are distributed as follows: polyoxymethylene POM 0.79kg, high-temperature skeleton agent PP 0.03kg, high-temperature skeleton agent HDPE 0.08kg, low-temperature skeleton agent EAA 0.01kg, dispersant EBS 0.01kg, antioxidant BTA 0.005kg, paraffin WAX 0.01kg.

[0079] Put all the weighed raw materials into the internal mixer, seal the internal mixer, and introduce argon gas with a pressure of 0.5 MPa and a flow rate of 20 L / min to purge the internal mixer. At the same time, set the temperature of the internal mixer to 145°C for preheating. When the temperature reaches 145°C and the oxygen content in the mixing chamber is stable at ≤1000ppm, put #1-TC4 powder and BTA into the internal mixer at the same time for stirring and preheating. The screw speed is 6 rpm and mixing is carried out for 18 minutes.

[0080] Then raise the temperature to 165°C, add POM and PP, lower the pressure hammer, rotate the screw at 12 rpm, and mix for 12 minutes; continue to raise the temperature to 180°C, add high-temperature skeleton agent HDPE and dispersant EBS, lower the pressure hammer, rotate the screw at 18 rpm, and mix for 20 minutes; maintain the temperature at 180°C, add low-temperature skeleton agent EAA and paraffin WAX, and set the die head temperature in the granulator to 170°C during this process and preheat.

[0081] The mixed material was quickly transferred to the pelletizer with an argon pressure of 0.5 MPa. The temperature of the double wrists in the pelletizer was 175°C, the speed of the double wrists of the screw was 10 rpm, the temperature of the extrusion die was 150°C, the speed of the feed screw was 10 rpm, and the speed of the pelletizer blade was 750 rpm. The feed material had a particle size of ≤3 mm and a density of 2.61 g / cm 3 .

[0082] Example 2

[0083] The spherical TC4 titanium alloy powder (denoted as #2-TC4 powder) was mixed with coarse and fine powders (the mass ratio of fine powder to coarse powder was 3:7) for 15 hours using a double cone mixer with an argon protective atmosphere. The mixture was placed in an electronic mixing oven, set to 70°C, and kept warm for 1 hour. The properties of the #2-TC4 powder are shown in Table 2.

[0084] Table 2 (0-45): (75-100) = 3:7, #2-TC4 powder properties

[0085]

[0086] Combine Figure 2 From Table 2, we can see that the tap density of #2-TC4 powder is 3.11 g / cm 3 , which is higher than the tap density of fine powder, the oxygen content is 900ppm, which meets the preparation requirements of MIM process, and the particle size distribution conforms to the normal distribution characteristics.

[0087] Weigh according to the mass percentage of binder to powder of 86:14, take 5kg of dried #2-TC4 powder and 0.81kg of binder, of which 0.81kg of binder components are distributed as follows: polyoxymethylene POM 0.67kg, high-temperature skeleton agent PP 0.02kg, high-temperature skeleton agent HDPE 0.07kg, low-temperature skeleton agent EAA 0.01kg, dispersant EBS 0.008kg, antioxidant BTA 0.004kg, and paraffin WAX 0.008kg.

[0088] Place all weighed raw materials into an internal mixer, seal the mixer, and introduce argon gas at a pressure of 0.5 MPa and a flow rate of 20 L / min to purge the internal mixer. At the same time, set the temperature of the internal mixer to 145°C for preheating. When the temperature reaches 145°C and the oxygen content in the mixing chamber is stable at ≤1000 ppm, place #2-TC4 powder and BTA into the internal mixer at the same time for stirring and preheating. The screw speed is 6 rpm and mixing is carried out for 18 minutes.

[0089] Then raise the temperature to 165°C, add POM and PP, lower the pressure hammer, rotate the screw at 12 rpm, and mix for 12 minutes; continue to raise the temperature to 180°C, add high-temperature skeleton agent HDPE and dispersant EBS, lower the pressure hammer, rotate the screw at 18 rpm, and mix for 20 minutes; maintain the temperature at 180°C, add low-temperature skeleton agent EAA and paraffin WAX, and set the die head temperature in the granulator to 170°C during this process and preheat.

[0090] The mixed material was quickly transferred to the pelletizer with an argon pressure of 0.5 MPa. The temperature of the double wrists in the pelletizer was 175°C, the speed of the double wrists of the screw was 10 rpm, the temperature of the extrusion die was 150°C, the speed of the feed screw was 10 rpm, and the speed of the pelletizer blade was 750 rpm to obtain a feed material with a particle size of ≤3 mm. The density of the feed material was 2.72 g / cm 3

[0091] Example 3

[0092] The spherical TC4 titanium alloy powder (denoted as #3-TC4 powder) was mixed with coarse and fine powders (the mass ratio of fine powder to coarse powder was 4:6) for 15 hours using a double cone mixer with an argon protective atmosphere. The mixture was placed in an electronic mixing oven, set to 70°C, and kept warm for 1 hour. The properties of the #3-TC4 powder are shown in Table 3.

[0093] Table 3 (0-45): (75-100) = 4:6, #3-TC4 powder properties

[0094]

[0095] Combine Figure 3 From Table 3, it can be seen that the tap density of #3-TC4 powder is 3.08 g / cm 3 , higher than the tap density of fine powder, the oxygen content is 1000ppm, which meets the preparation requirements of MIM process, and the particle size distribution shows a bimodal normal distribution with obvious gradient distribution characteristics.

[0096] Weigh according to the mass percentage of binder to powder of 85:15, take 5kg of dried #2-TC4 powder and 0.86kg of binder, of which the 0.86kg binder components are distributed as follows: polyoxymethylene POM 0.71kg, high-temperature skeleton agent PP 0.03kg, high-temperature skeleton agent HDPE 0.08kg, low-temperature skeleton agent EAA 0.01kg, dispersant EBS 0.009kg, antioxidant BTA 0.004kg, and paraffin WAX 0.009kg.

[0097] Place all weighed raw materials into an internal mixer, seal the mixer, and introduce argon gas at a pressure of 0.5 MPa and a flow rate of 20 L / min to purge the internal mixer. At the same time, set the temperature of the internal mixer to 145°C for preheating. When the temperature reaches 145°C and the oxygen content in the mixing chamber is stable at ≤1000ppm, place #3-TC4 powder and BTA into the internal mixer at the same time for stirring and preheating. The screw speed is 6 rpm and mixing is carried out for 18 minutes.

[0098] Then raise the temperature to 165°C, add POM and PP, lower the pressure hammer, rotate the screw at 12 rpm, and mix for 12 minutes; continue to raise the temperature to 180°C, add high-temperature skeleton agent HDPE and dispersant EBS, lower the pressure hammer, rotate the screw at 18 rpm, and mix for 20 minutes; maintain the temperature at 180°C, add low-temperature skeleton agent EAA and paraffin WAX, and set the die head temperature in the granulator to 170°C during this process and preheat.

[0099] The mixed material was quickly transferred to the pelletizer with an argon pressure of 0.5 MPa. The temperature of the double wrists in the pelletizer was 175°C, the speed of the double wrists of the screw was 10 rpm, the temperature of the extrusion die was 150°C, the speed of the feed screw was 10 rpm, and the speed of the pelletizer blade was 750 rpm to obtain a feed material with a particle size of ≤3 mm. The density of the feed material was 2.65 g / cm 3 .

[0100] Example 4

[0101] The spherical TC4 titanium alloy powder (denoted as #4-TC4 powder) was mixed with coarse and fine powders (the mass ratio of fine powder to coarse powder was 5:5) for 15 hours using a double cone mixer with an argon protective atmosphere. The mixture was placed in an electronic mixing oven, set to 70°C, and kept warm for 1 hour. The properties of the #4-TC4 powder are shown in Table 4.

[0102] Table 4 (0-45): (75-100) = 5:5, powder properties of #4-TC4 powder

[0103]

[0104] Combine Figure 4 From Table 4, we can see that the tap density of #4-TC4 powder is 3.03 g / cm 3 , which is equivalent to the tap density of fine powder, the oxygen content is 1000ppm, which meets the preparation requirements of the MIM process, and the particle size distribution conforms to the normal distribution characteristics.

[0105] Weigh according to the mass percentage of binder to powder of 85:15, take 5 kg of dried powder and 0.91 kg of binder, of which 0.91 kg of binder components are distributed as follows: polyoxymethylene POM 0.76 kg, high-temperature skeleton agent PP 0.03 kg, high-temperature skeleton agent HDPE 0.08 kg, low-temperature skeleton agent EAA 0.01 kg, dispersant EB S 0.009 kg, antioxidant BTA 0.005 kg, and paraffin WAX 0.009 kg.

[0106] Place all weighed raw materials into an internal mixer, seal the mixer, and introduce argon gas at a pressure of 0.5 MPa and a flow rate of 20 L / min to purge the internal mixer. At the same time, set the temperature of the internal mixer to 145°C for preheating. When the temperature reaches 145°C and the oxygen content in the mixing chamber is stable at ≤1000 ppm, place #4-TC4 powder and BTA into the internal mixer at the same time for stirring and preheating. The screw speed is 6 rpm and mixing is carried out for 18 minutes.

[0107] Then raise the temperature to 165°C, add POM and PP, lower the pressure hammer, rotate the screw at 12 rpm, and mix for 12 minutes; continue to raise the temperature to 180°C, add high-temperature skeleton agent HDPE and dispersant EBS, lower the pressure hammer, rotate the screw at 18 rpm, and mix for 20 minutes; maintain the temperature at 180°C, add low-temperature skeleton agent EAA and paraffin WAX, and set the die head temperature in the granulator to 170°C during this process and preheat.

[0108] The mixed material was quickly transferred to the pelletizer with an argon pressure of 0.5 MPa. The temperature of the double wrists in the pelletizer was 175°C, the speed of the double wrists of the screw was 10 rpm, the temperature of the extrusion die was 150°C, the speed of the feed screw was 10 rpm, and the speed of the pelletizer blade was 750 rpm to obtain a feed material with a particle size of ≤3 mm. The density of the feed material was 2.64 g / cm 3 .

[0109] Example 5

[0110] The spherical TC4 titanium alloy powder (denoted as #5-TC4 powder) was mixed with coarse and fine powders (the mass ratio of fine powder to coarse powder was 3:7) in a double cone mixer with an argon protective atmosphere for 5 hours and placed in an electronic mixing oven, set to 70°C, and kept warm for 1 hour. The properties of #5-TC4 powder are shown in Table 5.

[0111] Table 5 (0-45): (75-100) = 3:7, powder properties of #5-TC4 powder

[0112]

[0113]

[0114] Combine Figure 5 From Table 5, it can be seen that the tap density of #5-TC4 powder is 3.02 g / cm 3 , which is equivalent to the tap density of fine powder, the oxygen content is 800ppm, which meets the preparation requirements of the MIM process, and the particle size distribution shows a bimodal normal distribution with obvious gradient distribution characteristics.

[0115] Weigh according to the mass percentage of binder to powder of 85:15, take 5 kg of dried powder and 0.88 kg of binder, of which 0.88 kg of binder components are distributed as follows: polyoxymethylene POM 0.73 kg, high-temperature skeleton agent PP 0.03 kg, high-temperature skeleton agent HDPE 0.08 kg, low-temperature skeleton agent EAA 0.01 kg, dispersant EBS 0.009 kg, antioxidant BTA 0.004 kg, and paraffin WAX 0.009 kg.

[0116] Place all weighed raw materials into an internal mixer, seal the mixer, and introduce argon gas at a pressure of 0.5 MPa and a flow rate of 20 L / min to purge the internal mixer. At the same time, set the temperature of the internal mixer to 145°C for preheating. When the temperature reaches 145°C and the oxygen content in the mixing chamber is stable at ≤1000 ppm, place #5-TC4 powder and BTA into the internal mixer at the same time for stirring and preheating. The screw speed is 6 rpm and mixing is carried out for 18 minutes.

[0117] Then raise the temperature to 165°C, add POM and PP, lower the pressure hammer, rotate the screw at 12 rpm, and mix for 12 minutes; continue to raise the temperature to 180°C, add high-temperature skeleton agent HDPE and dispersant EBS, lower the pressure hammer, rotate the screw at 18 rpm, and mix for 20 minutes; maintain the temperature at 180°C, add low-temperature skeleton agent EAA and paraffin WAX, and set the die head temperature in the granulator to 170°C during this process and preheat.

[0118] The mixed material was quickly transferred to the pelletizer with an argon pressure of 0.5 MPa. The temperature of the double wrists in the pelletizer was 175°C, the speed of the double wrists of the screw was 10 rpm, the temperature of the extrusion die was 150°C, the speed of the feed screw was 10 rpm, and the speed of the pelletizer blade was 750 rpm to obtain a feed material with a particle size of ≤3 mm. The density of the feed material was 2.69 g / cm 3 .

[0119] Example 6

[0120] The spherical TC4 titanium alloy powder (denoted as #6-TC4 powder) was mixed with coarse and fine powders (the mass ratio of fine powder to coarse powder was 3:7) for 10 hours using a double cone mixer with an argon protective atmosphere. The mixture was placed in an electronic mixing oven, set to 70°C, and kept warm for 1 hour. The properties of the #6-TC4 powder are shown in Table 6.

[0121] Table 6 (0-45): (75-100) = 3:7, powder properties of #6-TC4 powder

[0122]

[0123] Combine Figure 6 From Table 6, it can be seen that the tap density of #6-TC4 powder is 2.97 g / cm 3 , which is between the tap density of coarse powder and fine powder, and the oxygen content is 900ppm, which meets the preparation requirements of the MIM process. The particle size distribution shows a slight bimodal distribution. Combining Examples 2 and 5, it is found that the longer the mixing time, the more uniform the powder is, and it tends to the standard normal distribution.

[0124] Weigh according to the mass percentage of binder to powder of 84:16, take 5 kg of dried powder and 0.95 kg of binder, of which 0.95 kg of binder components are distributed as follows: polyoxymethylene POM 0.79 kg, high-temperature skeleton agent PP 0.03 kg, high-temperature skeleton agent HDPE 0.08 kg, low-temperature skeleton agent EAA 0.01 kg, dispersant EBS 0.01 kg, antioxidant BTA 0.005 kg, and paraffin WAX 0.01 kg.

[0125] Place all weighed raw materials into an internal mixer, seal the mixer, and introduce argon gas at a pressure of 0.5 MPa and a flow rate of 20 L / min to purge the internal mixer. At the same time, set the temperature of the internal mixer to 145°C for preheating. When the temperature reaches 145°C and the oxygen content in the mixing chamber is stable at ≤1000 ppm, place #6-TC4 powder and BTA into the internal mixer at the same time for stirring and preheating. The screw speed is 6 rpm and mixing is carried out for 18 minutes.

[0126] Then raise the temperature to 165°C, add POM and PP, lower the pressure hammer, rotate the screw at 12 rpm, and mix for 12 minutes; continue to raise the temperature to 180°C, add high-temperature skeleton agent HDPE and dispersant EBS, lower the pressure hammer, rotate the screw at 18 rpm, and mix for 20 minutes; maintain the temperature at 180°C, add low-temperature skeleton agent EAA and paraffin WAX, and set the die head temperature in the granulator to 170°C during this process and preheat.

[0127] The mixed material was quickly transferred to the pelletizer with an argon pressure of 0.5 MPa. The temperature of the double wrists in the pelletizer was 175°C, the speed of the double wrists of the screw was 10 rpm, the temperature of the extrusion die was 150°C, the speed of the feed screw was 10 rpm, and the speed of the pelletizer blade was 750 rpm. The feed material had a particle size of ≤3 mm. The density of the feed material was 2.63 g / cm 3 .

[0128] Comparative Example 1

[0129] Fine powder ((0-45) μm) TC4 single titanium alloy powder (denoted as #7-TC4 powder) was placed in an electronic mixing oven, set to 70°C, and kept warm for 1 hour. The properties of #7-TC4 powder are shown in Table 7.

[0130] Table 7 Powder properties of single (0-45) μm TC4, #7-TC4 powder

[0131]

[0132] Combine Figure 7From Table 7, it can be seen that the #7-TC4 powder is a single TC4 powder with a particle size distribution range of 0-45 μm, and its oxygen content is 1100 ppm. It can be seen that the oxygen content of the fine-particle powder is relatively high, and the particle size distribution is uniform, which conforms to the normal distribution.

[0133] Weigh according to the mass percentage of binder to powder of 85:15, take 5kg of dried #7-TC4 powder and 0.88kg of binder, of which the 0.88kg binder components are distributed as follows: polyoxymethylene POM 0.73kg, high-temperature skeleton agent PP 0.03kg, high-temperature skeleton agent HDPE 0.08kg, low-temperature skeleton agent EAA 0.01kg, dispersant EBS 0.009kg, antioxidant BTA 0.004kg, and paraffin WAX 0.009kg.

[0134] Place all weighed raw materials into an internal mixer, seal the mixer, and introduce argon gas at a pressure of 0.5 MPa and a flow rate of 20 L / min to purge the internal mixer. At the same time, set the temperature of the internal mixer to 145°C for preheating. When the temperature reaches 145°C and the oxygen content in the mixing chamber is stable at ≤1000ppm, place #7-TC4 powder and BTA into the internal mixer at the same time for stirring and preheating. The screw speed is 6 rpm and mixing is carried out for 18 minutes.

[0135] Then raise the temperature to 165°C, add POM and PP, lower the pressure hammer, rotate the screw at 12 rpm, and mix for 12 minutes; continue to raise the temperature to 180°C, add high-temperature skeleton agent HDPE and dispersant EBS, lower the pressure hammer, rotate the screw at 18 rpm, and mix for 20 minutes; maintain the temperature at 180°C, add low-temperature skeleton agent EAA and paraffin WAX, and set the die head temperature in the granulator to 170°C during this process and preheat.

[0136] The mixed material was quickly transferred to the pelletizer with an argon pressure of 0.5 MPa. The temperature of the double wrists in the pelletizer was 175°C, the speed of the double wrists of the screw was 10 rpm, the temperature of the extrusion die was 150°C, the speed of the feed screw was 10 rpm, and the speed of the pelletizer blade was 750 rpm. The feed material had a particle size of ≤3 mm. The density of the feed material was 2.75 g / cm 3 .

[0137] Comparative Example 2

[0138] Coarse powder (75-100 μm) TC4 single titanium alloy powder (denoted as #8-TC4 powder) was placed in an electronic mixing oven, set to 70°C, and kept warm for 1 hour. The properties of #8-TC4 powder are shown in Table 8.

[0139] Table 8 Powder properties of single (75-100) μm TC4, #8-TC4 powder

[0140]

[0141] Combine Figure 8 From Table 8, it can be seen that the #8-TC4 powder is a single TC4 powder with a particle size distribution range of 75-100 μm, and its oxygen content is 770 ppm. It can be seen that the oxygen content of the coarse-particle powder is relatively low, and the particle size distribution is also uniform, which conforms to the normal distribution.

[0142] Weigh according to the mass percentage of binder to powder of 82:18, take 5 kg of dried powder and 1.04 kg of binder, of which the components of 1.04 kg of binder are distributed as follows: polyoxymethylene POM 0.86 kg, high-temperature skeleton agent PP 0.03 kg, high-temperature skeleton agent HDPE 0.09 kg, low-temperature skeleton agent EAA 0.02 kg, dispersant EBS 0.01 kg, antioxidant BTA 0.005 kg, and paraffin WAX 0.01 kg.

[0143] Place all weighed raw materials into an internal mixer, seal the mixer, and introduce argon gas at a pressure of 0.5 MPa and a flow rate of 20 L / min to purge the internal mixer. At the same time, set the temperature of the internal mixer to 145°C for preheating. When the temperature reaches 145°C and the oxygen content in the mixing chamber is stable at ≤1000 ppm, place #6-TC4 powder and BTA into the internal mixer at the same time for stirring and preheating. The screw speed is 6 rpm and mixing is carried out for 18 minutes.

[0144] Then raise the temperature to 165°C, add POM and PP, lower the pressure hammer, rotate the screw at 12 rpm, and mix for 12 minutes; continue to raise the temperature to 180°C, add high-temperature skeleton agent HDPE and dispersant EBS, lower the pressure hammer, rotate the screw at 18 rpm, and mix for 20 minutes; maintain the temperature at 180°C, add low-temperature skeleton agent EAA and paraffin WAX, and set the die head temperature in the granulator to 170°C during this process and preheat.

[0145] The mixed material was quickly transferred to the pelletizer with an argon pressure of 0.5 MPa. The temperature of the double wrists in the pelletizer was 175°C, the speed of the double wrists of the screw was 10 rpm, the temperature of the extrusion die was 150°C, the speed of the feed screw was 10 rpm, and the speed of the pelletizer blade was 750 rpm. The feed material had a particle size of ≤3 mm. The density of the feed material was 2.59 g / cm 3 .

[0146] It can be seen from Examples 1-6 that by adjusting the ratio of powders with particle size distributions of 0-45 and 75-100 μm, a set of optimal processes with the lowest oxygen content of the mixed powder, the highest tap density, and the largest prepared feed density was determined. When the mass ratio of the two particle size distributions of 75-100 μm and 0-45 μm is (50-80):(20-50), a double-conical mixing well with an argon protective atmosphere is used for mixing for (5-15) hours, which can ensure that the feeding meets the requirements. The final MIM titanium alloy parts have the smallest shrinkage rate and the lowest oxygen content, thereby achieving the purpose of controllable size and performance.

[0147] Comparative Examples 1 and 2 are feed preparations using a single powder. The tap density of the 0-45 μm powder and the density of the corresponding feed have optimal values, while the oxygen content of the 75-100 μm powder has an optimal value, and the cost of the powder with this particle size distribution is only 50% of that of the fine powder. Compared with Example 2, the tap density, oxygen content, and density of the corresponding feed obtained by mixing coarse and fine powders in the present invention can meet the requirements, and under the condition of similar feed characteristics, the cost of MIM titanium alloy raw materials can be saved by about 35%.

[0148] While the present invention has been disclosed above with reference to preferred embodiments, this is not intended to limit the present invention. Persons skilled in the art will readily appreciate that various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A method for preparing low-cost plastic-based titanium alloy feedstock for metal powder injection molding, characterized in that: The following steps are involved: S1. Mixing a first titanium alloy powder and a second titanium alloy powder under an argon protective atmosphere to obtain a mixed titanium alloy powder; wherein the particle size of the first titanium alloy powder is larger than that of the second titanium alloy powder, thereby forming a mismatch between the coarse particle size and the fine particle size titanium alloy powder; The particle size of the first titanium alloy powder is in the range of 75 to 100 μm, the largest particle does not exceed 135 μm, the particles with a particle size greater than 100 μm do not exceed 2%, and the particles with a particle size less than 75 μm do not exceed 3%; The particle size of the second titanium alloy powder ranges from 0 to 45 μm, the largest particle does not exceed 50 μm, and the particles with a particle size greater than 45 μm do not exceed 2%; S2. Under vacuum conditions, in a protective atmosphere, after setting preheating conditions, add the antioxidant BTA and the mixed titanium alloy powder into an internal mixer, and stir and preheat; S3. After preheating, the internal mixer continues to heat up to the first internal mixing temperature, adjusts the stirring speed and time, adds the shape retaining agent polyoxymethylene (POM) and the first skeleton agent, and obtains a first internal mixing material; wherein the first skeleton agent is polypropylene; S4, after the internal mixer continues to heat up to the second internal mixing temperature, the stirring speed and time are adjusted, and the dispersant and the second framework agent are added to the first internal mixing material to obtain a second internal mixing material; wherein the second framework agent is polyethylene; S5, after the internal mixer continues to heat up to the third internal mixing temperature, the stirring speed and time are adjusted, and the lubricant and the third framework agent are added to the second internal mixing material to obtain a third internal mixing material; wherein the third framework agent is ethylene acrylic acid copolymer; S6. After the set granulation conditions are met, the third densely mixed material is granulated to obtain the required feed; The mass percentages of the components in the feed are: 82-86% of mixed titanium alloy powder, 10-15% of a shape retaining agent, 1-5% of a skeleton agent, 0.02-2% of a lubricant, 0.01-0.2% of a dispersant, and 0.01-0.2% of an antioxidant.

2. The method for preparing low-cost plastic-based titanium alloy feedstock for metal powder injection molding according to claim 1, characterized in that: The first titanium alloy powder must meet the following conditions: The fluidity is 24s / 50g and the tap density is 2.83g / cm 3 , solid powder loading was 64%.

3. The method for preparing low-cost plastic-based titanium alloy feedstock for metal powder injection molding according to claim 1, characterized in that: The second titanium alloy powder must meet the following conditions: The tap density is 3.03g / cm 3 , solid powder loading was 68%.

4. The method for preparing low-cost plastic-based titanium alloy feedstock for metal powder injection molding according to claim 1, characterized in that: The mass ratio of the first titanium alloy powder to the second titanium alloy powder is 50-80:20-50, and the mixing time is 5-15 hours. The tap density of the mixed titanium alloy powder is 2.84-3.11 g / cm 3 , the powder loading is 64~70%.

5. The method for preparing low-cost plastic-based titanium alloy feedstock for metal powder injection molding according to claim 1, characterized in that: The lubricant is paraffin, and the dispersant is ethylene bisstearamide.

6. The method for preparing low-cost plastic-based titanium alloy feedstock for metal powder injection molding according to claim 1, characterized in that: In step S3, the first banburying temperature is 155-185° C., the banburying time is 8-18 min, and the screw speed is 5-10 rpm; In step S4, the second banburying temperature is 170-200° C., the banburying time is 15-20 min, and the screw speed is 15-20 rpm; In step S5, the third banburying temperature is 180-200° C., the banburying time is 25-35 min, and the screw speed range is 20-25 rpm.

7. A low-cost plastic-based titanium alloy feedstock for metal powder injection molding prepared by the method according to any one of claims 1 to 6.

Images