High-performance and high-utilization-rate MIM titanium alloy feeding circulation method

Abstract

The invention discloses a high-performance and high-utilization-rate MIM titanium alloy feeding circulation method. The method comprises the following steps that firstly, titanium alloy powder and a first binder are mixed together; 2, a second binder, a drainage opening material and the raw feed obtained through mixing are evenly mixed and subjected to extrusion granulation, the mass ratio of the raw feed to the drainage opening material is larger than or equal to 1: 1, and the second binder comprises 0.1 wt% of zinc stearate and 0.5 wt%-5 wt% of polyformaldehyde; 3, injecting the granular injection feed to obtain a green body; 4, degreasing the green body to obtain a brown blank; 5, performing a thermal degreasing process and a sintering process on the brown blank to obtain a titanium alloy sintered part; 6, cutting a drainage opening material of the titanium alloy sintered part; and repeating the steps 1-6. According to the high-performance and high-utilization-rate MIM titanium alloy feeding circulation method, the feeding circulation utilization of the high-performance MIM titanium alloy is achieved by controlling the specific proportion mixing of the original feeding material and the drainage opening material and adding a proper amount of the second binder. The titanium alloy feed is high in repeated utilization rate, and the material performance of a circulating product is excellent.

Description

Technical Field

[0001] This invention relates to the field of metal powder injection molding technology, and in particular to a high-performance and high-utilization MIM titanium alloy feeding cycle method. Background Technology

[0002] Metal Injection Molding (MIM) has become a key technology in precision manufacturing due to its advantages in producing complex and high-precision parts. Titanium alloys have a wide range of applications thanks to their excellent specific strength, corrosion resistance, and biocompatibility; however, titanium alloy products are difficult to CNC machine and are costly. MIM technology for titanium alloys is a near-net-shape forming process with high material utilization and reduced secondary processing. It is suitable for the efficient molding of complex titanium alloy parts, such as those used in consumer electronics, automotive parts, aerospace, and medical device components.

[0003] Metal injection molding typically produces sprue material (recycled material) in addition to the finished product. Sprue material mainly refers to the molding material from the gates and runners outside the product. Recycling and reusing sprue material is a technical strategy to reduce material waste, lower costs, and improve environmental benefits.

[0004] MIM titanium alloys typically employ a multi-component plastic-based first binder system, with polyoxymethylene (POM) as the primary first binder and polyethylene (PE) as the skeleton first binder. Other micro-component first binders (including ethylene-vinyl acetate (EVA), stearic acid (SA), and paraffin wax (PW)) are prone to volatilization. To ensure feed uniformity and injection molding performance, the mixing and injection process temperatures must be maintained at approximately 180-200°C. This inevitably leads to the continuous thermal degradation of low-melting-point components. As the number of cycles increases, the integrity of the first binder coating is compromised, resulting in a continuous increase in the specific surface area of ​​the titanium powder. This leads to a continuous increase in the oxygen content of the sintered parts, ultimately resulting in a decrease in the performance of the recycled titanium alloy material, a low feed cycle count, and high production costs, especially for small products with a large amount of sprue material.

[0005] Therefore, designing a suitable feeding cycle method and improving closed-loop management of feeding are crucial to ensuring efficient use of resources. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a high-performance and high-utilization MIM titanium alloy feeding and recycling method.

[0007] To solve the above-mentioned technical problems, the present invention adopts a high-performance and high-utilization MIM titanium alloy feeding and recycling method, comprising the following steps: Step 1: Weigh out titanium alloy powder and the first binder, put the titanium alloy powder and the first binder into a mixer and mix them, then crush them with a crusher to obtain small pieces of raw material; Step 2: The second binder, the sprue material of the titanium alloy sintered part, and the original feed material obtained in Step 1 are put into the granulator as granulation raw materials, mixed evenly, and extruded into granules to obtain granular injection feed; wherein, the mass ratio of the original feed material to the sprue material of the titanium alloy sintered part is ≥1:1, and the second binder includes 0.1wt% zinc stearate and 0.5wt%~5wt% polyoxymethylene; Step 3: Place the granular injection feed obtained in Step 2 into the injection hopper and inject it into the drawing rod mold to obtain a titanium alloy green billet. Step four: Degrease the titanium alloy green billet obtained in step three to obtain a titanium alloy brown billet. Step 5: The titanium alloy blank obtained in Step 4 is subjected to hot degreasing and sintering processes in sequence, and then cooled in the furnace to obtain the titanium alloy sintered part. Step 6: Cut the sprue material of the titanium alloy sintered part obtained in Step 5, and crush the sprue material into granules using a crusher; Repeat steps one through six, and in each cycle, the sprue material for the titanium alloy sintered part in step two uses the granular sprue material obtained in step six of the previous cycle.

[0008] The beneficial effects of this invention are as follows: This high-performance and high-utilization MIM titanium alloy feeding recycling method achieves the recycling of high-performance MIM titanium alloy feedstock by controlling the specific mixing ratio of the original feedstock and the sprue material and adding an appropriate amount of second binder. This results in a high reusability rate of the titanium alloy feedstock, excellent material properties of the recycled products, and solves key bottlenecks in the process stability and mechanical properties of titanium alloys. It also improves the utilization rate of titanium alloy MIM feedstock, providing reliable technical support for its large-scale application in high-end fields. Attached Figure Description

[0009] Figure 1 This is a flowchart of a high-performance and high-utilization MIM titanium alloy feeding cycle method according to Embodiment 1 of the present invention. Detailed Implementation

[0010] To explain in detail the technical content, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0011] Please refer to Figure 1 A high-performance and high-utilization MIM titanium alloy feeding and recycling method, characterized by comprising the following steps: Step 1: Weigh out titanium alloy powder and the first binder, put the titanium alloy powder and the first binder into a mixer and mix them, then crush them with a crusher to obtain small pieces of raw material; Step 2: The second binder, the sprue material of the titanium alloy sintered part, and the original feed material obtained in Step 1 are put into the granulator as granulation raw materials, mixed evenly, and extruded into granules to obtain granular injection feed; wherein, the mass ratio of the original feed material to the sprue material of the titanium alloy sintered part is ≥1:1, and the second binder includes 0.1wt% zinc stearate and 0.5wt%~5wt% polyoxymethylene; Step 3: Place the granular injection feed obtained in Step 2 into the injection hopper and inject it into the drawing rod mold to obtain a titanium alloy green billet. Step four: Degrease the titanium alloy green billet obtained in step three to obtain a titanium alloy brown billet. Step 5: The titanium alloy blank obtained in Step 4 is subjected to hot degreasing and sintering processes in sequence, and then cooled in the furnace to obtain the titanium alloy sintered part. Step 6: Cut the sprue material of the titanium alloy sintered part obtained in Step 5, and crush the sprue material into granules using a crusher; Repeat steps one through six, and in each cycle, the sprue material for the titanium alloy sintered part in step two uses the granular sprue material obtained in step six of the previous cycle.

[0012] As can be seen from the above description, the beneficial effects of this invention are as follows: This high-performance and high-utilization MIM titanium alloy feeding recycling method achieves the recycling of high-performance MIM titanium alloy feedstock by controlling the specific mixing ratio of the original feedstock and the sprue material and adding an appropriate amount of second binder. This results in a high reusability rate of the titanium alloy feedstock, excellent material properties of the recycled products, solves the key bottlenecks in the process stability and mechanical properties of titanium alloys, improves the utilization rate of titanium alloy MIM feedstock, and provides reliable technical support for its large-scale application in high-end fields.

[0013] Furthermore, the particle size of the titanium alloy powder satisfies: D10=5~7μm, D50=8~13μm, D90=15~23μm.

[0014] Furthermore, in the titanium alloy powder, the weight percentage of Al is 6wt%~7wt%, the weight percentage of V is 3wt%~4.5wt%, the weight percentage of Fe is ≤0.3wt%, the weight percentage of C is ≤0.08wt%, the weight percentage of O is ≤0.18wt%, and Ti is the balance.

[0015] Furthermore, the first adhesive in step one comprises: 85wt%~88wt% polyoxymethylene, 4wt%~7wt% polyethylene, 2wt%~4wt% ethylene-vinyl acetate, 2wt%~4wt% zinc stearate, 1wt%~2wt% paraffin wax, and 0.5wt%~1wt% antioxidant B215.

[0016] Furthermore, in step one, the titanium alloy powder accounts for 51.2 vol% to 63.2 vol%, the first binder accounts for 36.8 vol% to 48.8 vol%, and the OSF shrinkage rate is 1.165 to 1.250.

[0017] Furthermore, in step two, the rotor speed of the internal mixer is 40 rpm to 200 rpm, the mixing time is 1 h to 5 h, and the temperature is 160℃ to 250℃.

[0018] Furthermore, in step two, the granulation temperature is 175℃~185℃, the extrusion speed is 10Hz~100Hz, the feeding speed is 5Hz~100Hz, and the cutting speed is 5Hz~100Hz; the particle size of the granular injection feed is 3mm, and the particle length is 2mm~4mm.

[0019] Furthermore, in the three steps, the injection mold temperature is 80℃~120℃, the feeding heating temperature is 160℃~230℃, the injection pressure is 80MPa~250MPa, and the holding time is 5s~20s.

[0020] Furthermore, the degreasing method in step four is oxalic acid-catalyzed degreasing, with a degreasing temperature of 80℃~250℃ and a degreasing time of 5h~25h.

[0021] Furthermore, the thermal degreasing process in step five is specifically as follows: heat up to 250℃~350℃ and hold for 0.5h~2h; heat up to 400℃~500℃ and hold for 0.5h~2h; heat up to 550~650℃ and hold for 0.5h~2h; the sintering process in step five is specifically as follows: heat up to 800~900℃ and hold for 0.5h~2h; heat up to 1000~1250℃ and hold for 1~15h.

[0022] Please refer to Figure 1 Embodiment 1 of the present invention is: a high-performance and high-utilization MIM titanium alloy feeding and recycling method, comprising the following steps: Step 1: Weigh out the first binder and a certain mass of commercially available spherical titanium alloy powder prepared by gas atomization. The particle size of the titanium alloy powder meets the following requirements: D10 = 5~7μm, D50 = 8~13μm, D90 = 15~23μm. In the titanium alloy powder, the weight percentage of Al is 6wt%~7wt%, V is 3wt%~4.5wt%, Fe is ≤0.3wt%, C is ≤0.08wt%, O is ≤0.18wt%, and Ti is the balance. The first binder consists of: 88wt% polyoxymethylene (POM), 5wt% polyethylene (PE), 3wt% ethylene-vinyl acetate (EVA), 2wt% zinc stearate (SA-Zn), 1wt% paraffin wax (PW), and 1wt% antioxidant B215. The volume ratio of the titanium alloy powder to the first binder meets the following requirements: titanium alloy powder accounts for 58 vol%, and the first binder accounts for 42%. Titanium alloy powder and the first binder were loaded into an argon atmosphere internal mixer according to the specified loading amount and mixed. The rotor speed of the internal mixer was 180 rpm, the mixing time was 3 hours, and the temperature was 180℃. The raw material was then crushed by a crusher to obtain small pieces of raw material.

[0023] Step two involves uniformly mixing the second binder, the sprue material of the titanium alloy sintered part, and the original feedstock obtained in step one in a granulator, followed by extrusion granulation to obtain granular injection feedstock. The mass ratio of the original feedstock to the sprue material of the titanium alloy sintered part is 1:1. The second binder comprises 0.1 wt% zinc stearate and 2 wt% polyoxymethylene. The granulation temperature is 200℃, the extrusion speed is 20 Hz, the feeding speed is 10 Hz, and the cutting speed is 10 Hz. The particle size and length of the granular injection feedstock are 3 mm.

[0024] Step 3: The granular injection feed obtained in Step 2 is placed into the injection hopper and injected into the drawing rod mold to obtain a titanium alloy green billet. The injection mold temperature is 100℃, the feed heating temperature is 200℃, the injection pressure is 200MPa, and the holding time is 10s.

[0025] Step four involves degreasing the titanium alloy green billet obtained in step three to obtain a titanium alloy brown billet. The degreasing method uses oxalic acid catalytic degreasing at a temperature of 120℃ for 5–12 hours. Specifically, the degreasing time can be selected according to the thickness of the product, with the relationship between thickness and time being 1–3 hours per mm.

[0026] Step 5: The brown embryo obtained in Step 4 is subjected to a thermal degreasing process and a sintering process. The thermal degreasing process specifically involves: heating to 300℃ at a rate of 4℃ / min in an argon atmosphere, followed by holding at that temperature for 2 hours; heating to 450℃ at a rate of 4℃ / min in an argon atmosphere, followed by holding at that temperature for 2 hours; and heating to 600℃ at a rate of 4℃ / min in an argon atmosphere, followed by holding at that temperature for 2 hours. The thermal degreasing process is performed under negative pressure. The sintering process specifically involves: heating to 850℃ at a rate of 4℃ / min, followed by holding at that temperature for 2 hours (vacuum firing during this stage); heating to 1100℃ at a rate of 4℃ / min (partial pressure sintering during this stage), followed by holding at that temperature in an argon atmosphere for 4 hours (partial pressure sintering during this stage). Finally, the embryo is cooled in the furnace to obtain the titanium alloy sintered part PB1-1.

[0027] Step 6: Cut the sprue material of the titanium alloy sintered part PB1-1 obtained in Step 5, and crush the sprue material into granules using a crusher. Repeat steps one through six, and in each cycle, use the granular sprue material obtained in step six of the previous cycle for the titanium alloy sintered parts from step two. Repeat this process a total of six times to obtain titanium alloy sintered parts PB1-2, PB1-3, PB1-4, PB1-5, PB1-6, and PB1-7 in sequence.

[0028] Example 2: A feeding and circulation method for MIM titanium alloys, comprising the following steps: Step 1: Weigh out the first binder and a certain mass of commercially available spherical titanium alloy powder prepared by gas atomization. The particle size of the titanium alloy powder meets the following requirements: D10 = 5~7μm, D50 = 8~13μm, D90 = 15~23μm. In the titanium alloy powder, the weight percentage of Al is 6wt%~7wt%, V is 3wt%~4.5wt%, Fe is ≤0.3wt%, C is ≤0.08wt%, O is ≤0.18wt%, and Ti is the balance. The first binder consists of: 88wt% polyoxymethylene (POM), 5wt% polyethylene (PE), 3wt% ethylene-vinyl acetate (EVA), 2wt% zinc stearate (SA-Zn), 1wt% paraffin wax (PW), and 1wt% antioxidant B215. The volume ratio of the titanium alloy powder to the first binder meets the following requirement: titanium alloy powder volume ratio is 58vol%, and the first binder volume ratio is 42vol%. Titanium alloy powder and the first binder were loaded into an argon atmosphere internal mixer according to the specified loading amount and mixed. The rotor speed of the internal mixer was 180 rpm, the mixing time was 3 hours, and the temperature was 180℃. The raw material was then crushed by a crusher to obtain small pieces of raw material.

[0029] Step two involves uniformly mixing the second binder, the sprue material of the titanium alloy sintered part, and the raw feedstock obtained in step one in a granulator, followed by extrusion granulation to obtain granular injection feedstock. The mass ratio of the raw feedstock to the sprue material of the titanium alloy sintered part is 1:1. The second binder comprises 0.1 wt% zinc stearate and 5 wt% polyoxymethylene. The granulation temperature is 200℃, the extrusion speed is 20 Hz, the feeding speed is 10 Hz, and the cutting speed is 10 Hz. The particle size and length of the granular injection feedstock are 3 mm.

[0030] Step 3: The granular injection feed obtained in Step 2 is placed into the injection hopper and injected into the drawing rod mold to obtain a titanium alloy green billet. The injection mold temperature is 100℃, the feed heating temperature is 200℃, the injection pressure is 200MPa, and the holding time is 10s.

[0031] Step four involves degreasing the titanium alloy green billet obtained in step three to obtain a titanium alloy brown billet. The degreasing method uses oxalic acid catalytic degreasing at a temperature of 120℃ for 5–12 hours. Specifically, the degreasing time can be selected according to the thickness of the product, with the relationship between thickness and time being 1–3 hours per mm.

[0032] Step 5: The brown embryo obtained in Step 4 is subjected to a thermal degreasing process and a sintering process. The thermal degreasing process specifically involves: heating to 300℃ at a rate of 4℃ / min in an argon atmosphere, followed by holding at that temperature for 2 hours; heating to 450℃ at a rate of 4℃ / min in an argon atmosphere, followed by holding at that temperature for 2 hours; and heating to 600℃ at a rate of 4℃ / min in an argon atmosphere, followed by holding at that temperature for 2 hours. The thermal degreasing process is performed under negative pressure. The sintering process specifically involves: heating to 850℃ at a rate of 4℃ / min, followed by holding at that temperature for 2 hours (vacuum sintering during this stage); heating to 1100℃ at a rate of 4℃ / min (partial pressure sintering during this stage), followed by holding at that temperature in an argon atmosphere for 4 hours (partial pressure sintering during this stage). Finally, the embryo is cooled in the furnace to obtain the titanium alloy sintered part PB2-1.

[0033] Step 6: Cut the sprue material of the titanium alloy sintered part PB2-1 obtained in Step 5, and crush the sprue material into granules using a crusher. Repeat steps one through six, and in each cycle, use the granular sprue material obtained in step six of the previous cycle for the titanium alloy sintered parts from step two. Repeat this process a total of six times to obtain titanium alloy sintered parts PB2-2, PB2-3, PB2-4, PB2-5, PB2-6, and PB2-7 in sequence.

[0034] Example 3: A feeding and circulation method for MIM titanium alloys, comprising the following steps: Step 1: Weigh out the first binder and a certain mass of commercially available spherical titanium alloy powder prepared by gas atomization. The particle size of the titanium alloy powder meets the following requirements: D10 = 5~7μm, D50 = 8~13μm, D90 = 15~23μm. In the titanium alloy powder, the weight percentage of Al is 6wt%~7wt%, V is 3wt%~4.5wt%, Fe is ≤0.3wt%, C is ≤0.08wt%, O is ≤0.18wt%, and Ti is the balance. The first binder consists of: 88wt% polyoxymethylene (POM), 5wt% polyethylene (PE), 3wt% ethylene-vinyl acetate (EVA), 2wt% zinc stearate (SA-Zn), 1wt% paraffin wax (PW), and 1wt% antioxidant B215. The volume ratio of the titanium alloy powder to the first binder meets the following requirement: titanium alloy powder volume ratio is 58vol%, and the first binder volume ratio is 42vol%. Titanium alloy powder and the first binder were loaded into an argon atmosphere internal mixer according to the specified loading amount and mixed. The rotor speed of the internal mixer was 180 rpm, the mixing time was 3 hours, and the temperature was 180℃. The raw material was then crushed by a crusher to obtain small pieces of raw material.

[0035] Step two involves uniformly mixing the second binder, the sprue material of the titanium alloy sintered part, and the raw feedstock obtained in step one in a granulator, followed by extrusion granulation to obtain granular injection feedstock. The mass ratio of the raw feedstock to the sprue material of the titanium alloy sintered part is 1:1. The second binder comprises 0.1 wt% zinc stearate and 0.5 wt% polyoxymethylene. The granulation temperature is 200°C, the extrusion speed is 20 Hz, the feeding speed is 10 Hz, and the cutting speed is 10 Hz. The particle size and length of the granular injection feedstock are 3 mm.

[0036] Step 3: The granular injection feed obtained in Step 2 is placed into the injection hopper and injected into the drawing rod mold to obtain a titanium alloy green billet. The injection mold temperature is 100℃, the feed heating temperature is 200℃, the injection pressure is 200MPa, and the holding time is 10s.

[0037] Step four involves degreasing the titanium alloy green billet obtained in step three to obtain a titanium alloy brown billet. The degreasing method uses oxalic acid catalytic degreasing at a temperature of 120℃ for 5–12 hours. Specifically, the degreasing time can be selected according to the thickness of the product, with the relationship between thickness and time being 1–3 hours per mm.

[0038] Step 5: The brown embryo obtained in Step 4 is subjected to a thermal degreasing process and a sintering process. The thermal degreasing process specifically involves: heating to 300℃ at a rate of 4℃ / min in an argon atmosphere, followed by holding at that temperature for 2 hours; heating to 450℃ at a rate of 4℃ / min in an argon atmosphere, followed by holding at that temperature for 2 hours; and heating to 600℃ at a rate of 4℃ / min in an argon atmosphere, followed by holding at that temperature for 2 hours. The thermal degreasing process is performed under negative pressure. The sintering process specifically involves: heating to 850℃ at a rate of 4℃ / min, followed by holding at that temperature for 2 hours (vacuum sintering during this stage); heating to 1100℃ at a rate of 4℃ / min (partial pressure sintering during this stage), followed by holding at that temperature in an argon atmosphere for 4 hours (partial pressure sintering during this stage). Finally, the embryo is cooled in the furnace to obtain the titanium alloy sintered part PB3-1.

[0039] Step 6: Cut the sprue material of the titanium alloy sintered part PB3-1 obtained in Step 5, and crush the sprue material into granules using a crusher. Repeat steps one through six, and in each cycle, use the granular sprue material obtained in step six of the previous cycle for the titanium alloy sintered parts obtained in step two. Repeat this process a total of 6 times to obtain titanium alloy sintered parts PB3-2, PB3-3, PB3-4, PB3-5, PB3-6, and PB3-7 in sequence.

[0040] Comparative Example 1: A feeding and circulation method for MIM titanium alloy, comprising the following steps: Step 1: Weigh out the binder and a certain mass of commercially available spherical titanium alloy powder prepared by gas atomization. The particle size of the titanium alloy powder meets the following requirements: D10 = 5~7μm, D50 = 8~13μm, D90 = 15~23μm. In the titanium alloy powder, the weight percentage of Al is 6wt%~7wt%, V is 3wt%~4.5wt%, Fe is ≤0.3wt%, C is ≤0.08wt%, O is ≤0.18wt%, and Ti is the balance. The first binder consists of: 88wt% polyoxymethylene, 5wt% polyethylene, 3wt% ethylene-vinyl acetate, 2wt% zinc stearate, 1wt% paraffin wax, and 1wt% antioxidant B215. The volume ratio of the titanium alloy powder to the first binder meets the following requirement: titanium alloy powder 58vol%, first binder 42vol%. Titanium alloy powder and the first binder were loaded into an argon atmosphere internal mixer according to the specified loading amount and mixed. The rotor speed of the internal mixer was 180 rpm, the mixing time was 3 hours, and the temperature was 180℃. The raw material was then crushed by a crusher to obtain small pieces of raw material.

[0041] Step two: The raw feed obtained in step one is placed into a granulator, mixed evenly, and extruded into granules to obtain granular injection feed. The granulation temperature is 200℃, the extrusion speed is 20Hz, the feeding speed is 10Hz, and the cutting speed is 10Hz. The particle size of the granular injection feed is 3mm, and the particle length is 3mm.

[0042] Step 3: The granular injection feed obtained in Step 2 is placed into the injection hopper and injected into the drawing rod mold to obtain a titanium alloy green billet. The injection mold temperature is 100℃, the feed heating temperature is 200℃, the injection pressure is 200MPa, and the holding time is 10s.

[0043] Step four involves degreasing the titanium alloy green billet obtained in step three to obtain a titanium alloy brown billet. The degreasing method uses oxalic acid catalytic degreasing at a temperature of 120℃ for 5–12 hours. Specifically, the degreasing time can be selected according to the thickness of the product, with the relationship between thickness and time being 1–3 hours per mm.

[0044] Step 5: The brown embryo obtained in Step 4 is subjected to a thermal degreasing process and a sintering process. The thermal degreasing process specifically involves: heating to 300℃ at a rate of 4℃ / min in an argon atmosphere, followed by holding at that temperature for 2 hours; heating to 450℃ at a rate of 4℃ / min in an argon atmosphere, followed by holding at that temperature for 2 hours; and heating to 600℃ at a rate of 4℃ / min in an argon atmosphere, followed by holding at that temperature for 2 hours. The thermal degreasing process is performed under negative pressure. The sintering process specifically involves: heating to 850℃ at a rate of 4℃ / min, followed by holding at that temperature for 2 hours (vacuum firing during this stage); heating to 1100℃ at a rate of 4℃ / min (partial pressure sintering during this stage), followed by holding at that temperature in an argon atmosphere for 4 hours (partial pressure sintering during this stage). Finally, the embryo is cooled in the furnace to obtain the titanium alloy sintered part R0 (i.e., R0 is made from pure raw materials).

[0045] Step 6: Cut the sprue material of the titanium alloy sintered part R0 obtained in Step 5, and crush the sprue material into granules using a crusher; Repeat steps one through six, with step two in each cycle using the granulated sprue material obtained in step six of the previous cycle as the granulation raw material. Repeat this process a total of seven times to obtain titanium alloy sintered parts R1, R2, R3, R4, R5, R6, and R7 in sequence.

[0046] Comparative Example 2: A feeding and circulation method for MIM titanium alloy, comprising the following steps: Step 1: Weigh out the binder and a certain mass of commercially available spherical titanium alloy powder prepared by gas atomization. The particle size of the titanium alloy powder meets the following requirements: D10 = 5~7μm, D50 = 8~13μm, D90 = 15~23μm. In the titanium alloy powder, the weight percentage of Al is 6wt%~7wt%, V is 3wt%~4.5wt%, Fe is ≤0.3wt%, C is ≤0.08wt%, O is ≤0.18wt%, and Ti is the balance. The first binder consists of: 88wt% polyoxymethylene, 5wt% polyethylene, 3wt% ethylene-vinyl acetate, 2wt% zinc stearate, 1wt% paraffin wax, and 1wt% antioxidant B215. The volume ratio of the titanium alloy powder to the first binder meets the following requirement: titanium alloy powder 58vol%, first binder 42vol%. Titanium alloy powder and the first binder were loaded into an argon atmosphere internal mixer according to the specified loading amount and mixed. The rotor speed of the internal mixer was 180 rpm, the mixing time was 3 hours, and the temperature was 180℃. The raw material was then crushed by a crusher to obtain small pieces of raw material.

[0047] Step 2: The sprue material from the titanium alloy sintered part and the raw feed material obtained in Step 1 are fed into a granulator, mixed evenly, and extruded to obtain granulated injection feed. The mass ratio of the raw feed material to the sprue material from the titanium alloy sintered part is 1:1. The granulation temperature is 200℃, the extrusion speed is 20Hz, the feeding speed is 10Hz, and the cutting speed is 10Hz. The particle size and length of the granulated injection feed are 3mm.

[0048] Step 3: The granular injection feed obtained in Step 2 is placed into the injection hopper and injected into the drawing rod mold to obtain a titanium alloy green billet. The injection mold temperature is 100℃, the feed heating temperature is 200℃, the injection pressure is 200MPa, and the holding time is 10s.

[0049] Step four involves degreasing the titanium alloy green billet obtained in step three to obtain a titanium alloy brown billet. The degreasing method uses oxalic acid catalytic degreasing at a temperature of 120℃ for 5–12 hours. Specifically, the degreasing time can be selected according to the thickness of the product, with the relationship between thickness and time being 1–3 hours per mm.

[0050] Step 5: The brown embryo obtained in Step 4 is subjected to a thermal degreasing process and a sintering process. The thermal degreasing process specifically involves: heating to 300℃ at a rate of 4℃ / min in an argon atmosphere, followed by holding at that temperature for 2 hours; heating to 450℃ at a rate of 4℃ / min in an argon atmosphere, followed by holding at that temperature for 2 hours; and heating to 600℃ at a rate of 4℃ / min in an argon atmosphere, followed by holding at that temperature for 2 hours. The thermal degreasing process is performed under negative pressure. The sintering process specifically involves: heating to 850℃ at a rate of 4℃ / min, followed by holding at that temperature for 2 hours (vacuum sintering during this stage); heating to 1100℃ at a rate of 4℃ / min (partial pressure sintering during this stage), followed by holding at that temperature in an argon atmosphere for 4 hours (partial pressure sintering during this stage). Finally, the embryo is cooled in the furnace to obtain the titanium alloy sintered part PB4-1.

[0051] Step 6: Cut the sprue material of the titanium alloy sintered part PB4-1 obtained in Step 5, and crush the sprue material into granules using a crusher. Repeat steps one through six, and in each cycle, use the granular sprue material obtained in step six of the previous cycle for the titanium alloy sintered parts from step two. Repeat this process a total of six times to obtain titanium alloy sintered parts PB4-2, PB4-3, PB4-4, PB4-5, PB4-6, and PB4-7 in sequence.

[0052] Comparative Example 3: A feeding and circulation method for MIM titanium alloy, comprising the following steps: Step 1: Weigh out the first binder and a certain mass of commercially available spherical titanium alloy powder prepared by gas atomization. The particle size of the titanium alloy powder meets the following requirements: D10 = 5~7μm, D50 = 8~13μm, D90 = 15~23μm. In the titanium alloy powder, the weight percentage of Al is 6wt%~7wt%, V is 3wt%~4.5wt%, Fe is ≤0.3wt%, C is ≤0.08wt%, O is ≤0.18wt%, and Ti is the balance. The first binder consists of: 88wt% polyoxymethylene, 5wt% polyethylene, 3wt% ethylene-vinyl acetate, 2wt% zinc stearate, 1wt% paraffin wax, and 1wt% antioxidant B215. The volume ratio of the titanium alloy powder to the first binder meets the following requirement: titanium alloy powder accounts for 58 vol%, and the first binder accounts for 42 vol%. Titanium alloy powder and the first binder were loaded into an argon atmosphere internal mixer according to the specified loading amount and mixed. The rotor speed of the internal mixer was 180 rpm, the mixing time was 3 hours, and the temperature was 180℃. The raw material was then crushed by a crusher to obtain small pieces of raw material.

[0053] Step 2: The second binder, the sprue material of the titanium alloy sintered part, and the raw feed material obtained in Step 1 are fed into a granulator, mixed uniformly, and extruded to granulate, resulting in granular injection feed. The mass ratio of the raw feed material to the sprue material of the titanium alloy sintered part is 1:2. The second binder comprises 0.1 wt% zinc stearate and 2 wt% polyoxymethylene. The granulation temperature is 200℃, the extrusion speed is 20 Hz, the feeding speed is 10 Hz, and the cutting speed is 10 Hz. The particle size and length of the granular injection feed are 3 mm.

[0054] Step 3: The granular injection feed obtained in Step 2 is placed into the injection hopper and injected into the drawing rod mold to obtain a titanium alloy green billet. The injection mold temperature is 100℃, the feed heating temperature is 200℃, the injection pressure is 200MPa, and the holding time is 10s.

[0055] Step four involves degreasing the titanium alloy green billet obtained in step three to obtain a titanium alloy brown billet. The degreasing method uses oxalic acid catalytic degreasing at a temperature of 120℃ for 5–12 hours. Specifically, the degreasing time can be selected according to the thickness of the product, with the relationship between thickness and time being 1–3 hours per mm.

[0056] Step 5: The brown embryo obtained in Step 4 is subjected to a thermal degreasing process and a sintering process. The thermal degreasing process specifically involves: heating to 300℃ at a rate of 4℃ / min in an argon atmosphere, followed by holding at that temperature for 2 hours; heating to 450℃ at a rate of 4℃ / min in an argon atmosphere, followed by holding at that temperature for 2 hours; and heating to 600℃ at a rate of 4℃ / min in an argon atmosphere, followed by holding at that temperature for 2 hours. The thermal degreasing process is performed under negative pressure. The sintering process specifically involves: heating to 850℃ at a rate of 4℃ / min, followed by holding at that temperature for 2 hours (vacuum sintering during this stage); heating to 1100℃ at a rate of 4℃ / min (partial pressure sintering during this stage), followed by holding at that temperature in an argon atmosphere for 4 hours (partial pressure sintering during this stage). Finally, the embryo is cooled in the furnace to obtain the titanium alloy sintered part PB5-1.

[0057] Step 6: Cut the sprue material of the titanium alloy sintered part PB5-1 obtained in Step 5, and crush the sprue material into granules using a crusher. Repeat steps one through six, and in each cycle, use the granular sprue material obtained in step six of the previous cycle for the titanium alloy sintered parts from step two. Repeat this process a total of six times to obtain titanium alloy sintered parts PB5-2, PB5-3, PB5-4, PB5-5, PB5-6, and PB5-7 in sequence.

[0058] The titanium alloy sintered parts from Examples 1, 2, 3, Comparative Examples 1, 2, and 3 were subjected to performance tests, and the test results are shown in Table 1 below:

[0059] Table 1 As described above, Examples 1, 2, and 3 all employ a technical scheme that mixes the original feedstock with the sprue feedstock (mass ratio of 1:1), and simultaneously adds 0.1 wt% zinc stearate and 0.5 wt%~5 wt% polyoxymethylene (POM). The main difference lies in the amount of POM added: Example 1 uses 2 wt% POM, Example 2 uses 5 wt% POM, and Example 3 uses 0.5 wt% POM. After 7 cycles, the melt flow index (MFR) of PB1-1 in Example 1 was 890, the melt flow index (MFR) of PB2-7 in Example 2 was 932, and the melt flow index (MFR) of PB3-7 in Example 3 was 840. Example 2, with the highest amount of POM added, had the highest melt flow index, indicating the best flow rate. The material properties (yield strength and elongation) of PB1-1, PB2-7, and PB3-7 did not differ significantly.

[0060] Example 1 and Comparative Example 1 use different feed cycle methods. Example 1 uses a mixture of original feedstock and sprue (mass ratio 1:1), with 0.1 wt% zinc stearate and 2 wt% polyoxymethylene added as binders for recycling; Comparative Example 1 uses iterative injection molding with pure sprue. After the 7th cycle, the titanium alloy sintered part PB1-7 obtained in Example 1 still maintains a high melt flow index (MFR) of 890, which is better than the MFR of 420 for the titanium alloy sintered part R7 obtained in Comparative Example 1 after the 7th cycle. A melt flow index (MFR) within a suitable range is beneficial for injection molding. The titanium alloy sintered part PB1-7 obtained using the MIM titanium alloy feed cycle method of Example 1 has a yield strength of 955.4 MPa and an elongation of 11.1%, meeting the requirements for high-performance titanium alloys. However, the yield strength of the titanium alloy sintered part R7 obtained by the MIM titanium alloy feeding cycle method in Comparative Example 1 is 948.3 MPa and the elongation is 7.1%. Its performance is significantly different from that of the titanium alloy sintered part made from pure raw materials. This is mainly because the oxygen content in the powder increases with the number of cycles, which leads to a decrease in performance. Specifically, the oxygen content of the titanium alloy sintered part PB1-7 is 0.312%, while the oxygen content of the titanium alloy sintered part R1 is 0.368%.

[0061] Both Example 1 and Comparative Example 2 use an iterative cyclic injection method with the original feedstock and sprue material. The main difference is that Comparative Example 2 did not add 0.1 wt% zinc stearate and 2 wt% polyoxymethylene. Because Comparative Example 2 did not add a specific proportion of a second binder during the cyclic mixing, the melt flow index (MFR) of the titanium alloy sintered part PB4-7 obtained using the MIM titanium alloy feeding cyclic method of Comparative Example 2 (MFR=680) was lower than that of the titanium alloy sintered part PB1-7 obtained using the MIM titanium alloy feeding cyclic method of Example 1 (MFR=890). The yield strength of the titanium alloy sintered part PB4-7 was 936.4 MPa, and the elongation was 9.7%, significantly lower than the yield strength (955.4 MPa) and elongation (11.1%) of the titanium alloy sintered part PB4-7. The addition of 0.1 wt% zinc stearate and 2 wt% polyoxymethylene during the cyclic mixing process helps maintain a high melt flow index (MFR) in the feed. Meanwhile, the addition of a second binder during granulation in Example 1 supplements the decomposition of zinc stearate and polyoxymethylene, preventing the oxidation of the exposed titanium alloy powder.

[0062] Both Example 1 and Comparative Example 3 use a cyclical feeding method involving the ratio of raw feedstock to sprue material, with the addition of 0.1 wt% zinc stearate and 2 wt% polyoxymethylene (POM). However, the mass ratio of raw feedstock to sprue material differs. In Example 1, the ratio is 1:1, while in Comparative Example 3, it is 1:2, indicating a larger mass of sprue material added. The melt flow index (MFR) of the titanium alloy sintered part PB5-7 obtained using the MIM titanium alloy feeding cycle method in Comparative Example 3 is lower than that of the titanium alloy sintered part PB1-7 obtained using the MIM titanium alloy feeding cycle method in Example 1 (MFR=890). This suggests that a higher raw feedstock ratio (MFR) results in a higher MFR, and also indicates that the sprue material undergoes decomposition of POM and other binders during injection molding, leading to lower fluidity compared to the raw feedstock. The yield strength of the titanium alloy sintered part PB5-7 in Comparative Example 3 is 943.6 MPa and the elongation is 7.5%, which is significantly lower than the yield strength (955.4 MPa) and elongation (11.1%) of the titanium alloy sintered part PB1-7. Therefore, it is necessary to strictly control the ratio of raw feed to sprue material and add as little sprue material as possible for feeding and recycling.

[0063] In summary, the high-performance and high-utilization MIM titanium alloy feeding recycling method provided by this invention achieves the recycling of high-performance MIM titanium alloy feedstock by controlling the specific mixing ratio of the original feedstock and the sprue material and adding an appropriate amount of second binder. This results in a high reusability rate of the titanium alloy feedstock, excellent material properties of the recycled products, and solves key bottlenecks in the process stability and mechanical properties of titanium alloys. It also improves the utilization rate of titanium alloy MIM feedstock, providing reliable technical support for its large-scale application in high-end fields.

[0064] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention's specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A high performance and high utilization rate MIM titanium alloy feed cycle method, characterized in that, The method comprises the following steps: Step one, weigh the titanium alloy powder and the first binder, put the titanium alloy powder and the first binder into a mixer to mix, and then crush the mixture with a crusher to obtain small pieces of raw feedstock; Step two, put the second binder, the water nozzle material of the titanium alloy sintered part, and the raw feedstock obtained in step one into a granulator as granulation raw materials, uniformly mix and extrude granulation to obtain granular injection feedstock; wherein the mass ratio of the raw feedstock to the water nozzle material of the titanium alloy sintered part is ≥1:1, and the second binder comprises 0.1wt% zinc stearate and 0.5wt%-5wt% polyformaldehyde; Step three, put the granular injection feedstock obtained in step two into an injection feed bin and inject it into a stretching rod mold to obtain a titanium alloy green body; Step four, perform a debinding treatment on the titanium alloy green body obtained in step three to obtain a titanium alloy brown body; Step five, sequentially perform a hot debinding process and a sintering process on the titanium alloy brown body obtained in step four, and then cool in the furnace to obtain a titanium alloy sintered part; Step six, cut the water nozzle material of the titanium alloy sintered part obtained in step five, and make the water nozzle material into a granular shape by using a crusher; Repeat steps one to six, and use the granular water nozzle material obtained in step six of the previous cycle as the water nozzle material of step two in each cycle.

2. The high performance and high utilization rate MIM titanium alloy feedstock recycling method according to claim 1, characterized in that, The particle size of the titanium alloy powder satisfies D10=5-7μm, D50=8-13μm, and D90=15-23μm.

3. The high performance and high utilization rate MIM titanium alloy feedstock recycling method according to claim 1, characterized in that, In the titanium alloy powder, the weight percentage of Al is 6wt%-7wt%, the weight percentage of V is 3wt%-4.5wt%, the weight percentage of Fe is ≤0.3wt%, the weight percentage of C is ≤0.08wt%, the weight percentage of O is ≤0.18wt%, and Ti is the balance.

4. The high performance and high utilization rate MIM titanium alloy feedstock recycling method according to claim 1, characterized in that, The first binder in step one comprises 85wt%-88wt% polyformaldehyde, 4wt%-7wt% polyethylene, 2wt%-4wt% ethylene-vinyl acetate, 2wt%-4wt% zinc stearate, 1wt%-2wt% paraffin wax, and 0.5wt%-1wt% antioxidant B215.

5. The high performance and high utilization rate MIM titanium alloy feedstock recycling method according to claim 1, characterized in that, In step one, the proportion of the titanium alloy powder is 51.2vol%-63.2vol%, and the proportion of the first binder is 36.8vol%-48.8vol%.

6. The high performance and high utilization rate MIM titanium alloy feedstock recycling method according to claim 1, characterized in that, The rotor speed of the mixer in step two is 40rpm-200rpm, the mixing time is 1h-5h, and the temperature is 160℃-250℃.

7. The high performance and high utilization rate MIM titanium alloy feedstock recycling method according to claim 1, characterized in that, In step two, the granulation temperature is 175℃-185℃, the extrusion speed is 10Hz-100Hz, the feeding speed is 5Hz-100Hz, and the cutting speed is 5Hz-100Hz; the particle size of the granular injection feedstock is 3mm, and the particle size length is 2mm-4mm.

8. The high performance and high utilization rate MIM titanium alloy feedstock recycling method according to claim 1, characterized in that, In step three, the injection mold temperature is 80℃-120℃, the feed heating temperature is 160℃-230℃, the injection pressure is 80MPa-250MPa, and the holding pressure time is 5s-20s.

9. The high performance and high utilization rate MIM titanium alloy feedstock recycling method according to claim 1, characterized in that, The debinding method in step four is oxalic acid catalytic debinding, the debinding temperature is 80℃-250℃, and the debinding time is 5h-25h.

10. The high performance and high utilization rate MIM titanium alloy feedstock recycling method according to claim 1, characterized in that, The heat debinding process in the fifth step is specifically: heating to 250-350 DEG C, holding for 0.5-2 h; heating to 400-500 DEG C, holding for 0.5-2 h; heating to 550-650 DEG C, holding for 0.5-2 h; the sintering process in the fifth step is specifically: heating to 800-900 DEG C, holding for 0.5-2 h; heating to 1000-1250 DEG C, holding for 1-15 h.

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