Injection molding method for high-polishing titanium alloy plug housing

Abstract

The invention discloses a low-cost high-polishing titanium alloy plug housing injection molding method, and belongs to the technical field of metal injection molding. The method comprises the following steps: powder preparation, raw material weighing, internal mixing, granulation, injection molding, acid degreasing, thermal degreasing and vacuum sintering, and polishing. Titanium alloy powder used in the method is composite powder formed by adding 0-50 [mu] m non-spherical powder into 0-60 [mu] m spherical powder prepared through a plasma atomization method (PDPA). The cost of the non-spherical titanium powder is far lower than that of spherical titanium powder, and the production cost is relatively reduced by more than 80%; the 0-60 [mu] m spherical powder prepared by the plasma atomization method is high in powder permeability, and sintering densification is facilitated; the sintering shrinkage coefficient of the porous titanium alloy part with the complex shape prepared through vacuum sintering is accurately controlled to be 1.20-1.350, and extra shaping matched equipment is not needed; according to the high-polishing titanium alloy product part manufactured through the method, the density is larger than or equal to 4.45 g / cm < 3 >, the tensile strength is larger than or equal to 950 MPa, the elongation after fracture is larger than or equal to 12%, and the hardness is larger than or equal to 350 (HV).

Description

Technical Field

[0001] The present invention mainly relates to the technical field of injection molding manufacturing of aviation plug housings, and particularly relates to a method for injection molding manufacturing of high-efficiency and low-cost titanium alloy aviation plug housings. Background Art

[0002] Metal powder injection molding technology is a net shaping process formed by combining powder metallurgy technology and plastic injection molding technology, breaking through the limitations of traditional metal powder die pressing forming technology in product shape, and having the advantages of high raw material utilization rate, high production efficiency, and net shaping. However, there are certain problems and limitations in titanium alloy powder injection molding in aspects such as titanium alloy powder preparation, injection molding, debinding, and sintering process parameter control, mainly involving oxygen content control, deformation control, selection of binder, temperature control of injection molding and sintering, etc. For example, impurity elements (oxygen) dissolve in the matrix titanium at the sintering temperature, which will lead to a decline in the mechanical properties of the titanium alloy. Therefore, it is necessary to reduce the oxygen increase in each process such as powder making, debinding, and sintering; the shrinkage of the sintered part finished product compared to the injection-molded blank will be 10-18%. For the high-precision requirement of the aviation plug housing size accuracy of ±0.05mm, there are huge challenges in the selection of binder, injection mold design, debinding, and sintering temperature control. It is precisely these problems that have led to the non-industrialization of the production of high-precision injection-molded titanium alloy batch parts. Therefore, it is urgent to overcome the forming technical problems in titanium alloy metal powder injection molding, ensure the mechanical properties of titanium alloy and the dimensional accuracy of parts, and form the batch manufacturing ability of high-efficiency and low-cost titanium alloy aviation plug housings. Summary of the Invention

[0003] Object of the Invention: The object of the present invention is to overcome the technical problems in powder preparation, debinding, and sintering in the existing titanium alloy metal injection molding technology, and provide a method for injection molding manufacturing of high-efficiency and low-cost titanium alloy aviation plug housings. By controlling the oxygen content in the process and the temperature in the debinding and sintering processes, etc., the batch production of net-shaped titanium alloy aviation plug housings is realized, and the high-precision technical requirements of parts are ensured.

[0004] Technical Solution: The high-polishing titanium alloy plug housing injection molding method described in the present invention includes the following steps: S1: Powder Making: Prepare 0-30um titanium alloy spherical powder, with the powder particle size being 0-30um, add 0-30um non-spherical powder according to the proportion, and load it into a three-dimensional mixer to mix evenly to prepare a composite powder; the particle size of the composite powder is 0-30um, the tapped density is greater than 2.7g / cm3, the oxygen content of the powder is less than 0.2%, and the nitrogen content of the powder is less than 0.03%; S2: Kneading: Mix titanium alloy powder and molding binder in a gas-protected kneading and granulating machine in proportion for 1 - 2 h and then granulate to obtain titanium alloy injection feedstock; S3: Injection molding: Heat the feedstock to 160 - 180 °C and inject and fill it into the mold cavity to form a green compact; S4: Acid degreasing: Place the injection-molded green compact in a degreasing furnace and perform acid degreasing under an oxalic acid atmosphere. The acid degreasing temperature is 110 - 140 °C and the acid degreasing time is 7 - 10 h; S5: Thermal degreasing: Put the acid-degreased green compact into a vacuum furnace, evacuate it to below 1×10 -3 Pa for thermal degreasing. The thermal degreasing temperature is 300 - 650 °C and the thermal degreasing holding time is 5 - 12 h; S6: Sintering: After thermal degreasing, raise the temperature of the vacuum furnace to 1150 - 1250 °C, hold for 2 - 8 h, then lower the temperature of the blank to 400 - 600 °C, hold for 1 - 4 h, and then cool to 40 - 80 °C and take it out; S7: Post-treatment: Shape, sandblast, and machine the blank to obtain the finished plug housing.

[0005] Furthermore, as a preferred embodiment, the volume ratio of titanium alloy powder to binder added in step S2 is: 1:1 - 1.5:1.

[0006] Furthermore, as a preferred embodiment, the molding binder in step S2 is at least one of polyoxymethylene, paraffin wax, octadecyl acrylate, ethylene bisstearamide, ethylene-vinyl acetate copolymer, polyethylene, polypropylene, and BASF antioxidant.

[0007] Furthermore, as a preferred embodiment, the kneading temperature in step S2 is 170 °C - 180 °C, the kneading time is 1 h, and argon is used for protection in the kneading chamber; the specific operation is: preheat the composite powder to 180 °C, then add part of the molding binder. After the molding binder is completely melted, add the remaining molding binder and cool to 175 °C, continue kneading for 40 min to complete the kneading process; the granulating temperature after kneading is 180 °C.

[0008] Furthermore, as a preferred embodiment, the injection pressure in step S3 is 80 Mpa - 120 Mpa.

[0009] Furthermore, as a preferred embodiment, the acid feeding amount during acid degreasing in step S4 is 3.2 g / min - 7.5 g / min; During the sintering process in step S6, maintain the vacuum degree at 10 -3 -10 -1 Pa.

[0010] Furthermore, to improve the kneading effect, the atmosphere-protected kneading and pelletizing integrated machine used in the kneading process of step S2 is equipped with an atmosphere protection device. The atmosphere protection device is arranged above the kneading chamber of the kneader and includes a main box body, an operation door panel, an inert gas inlet device, and an oxygen content detection device. The bottom end and the rear part of the main box body are fixedly connected to the kneader. The operation door panel is connected and rotatable to the main box body through a single-side hinge. The inert gas inlet device is arranged above the main box body, and the oxygen content detection device is arranged at the upper and lower ends inside the main box body.

[0011] Furthermore, as a preferred embodiment, a one-way exhaust valve is provided at the upper end of the main box body. One end of the one-way exhaust valve is connected to the inside of the box body through a gas pipeline, and the other end is connected to a gas filtering device.

[0012] Furthermore, as a preferred embodiment, one end of the inert gas inlet device is connected to the inside of the main box body, and the other end is connected to an inert gas cylinder through an inert gas pipeline. A gas flow control valve is installed on the pipeline; one end of the oxygen content detection device is connected to the inside of the main box body, and the other end is connected to an oxygen content display through a signal transmission line. Beneficial effects

[0013] (1) The density of the titanium alloy antenna unit parts manufactured by using the method of the present invention is ≥4.38 g / cm 3 , the tensile strength is ≥850 MPa, and the elongation after fracture is ≥8%. The density and mechanical properties meet the weight reduction and usage requirements of the aviation plug housing; (2) The dimensional accuracy of the outer diameter of the aviation plug sintered by using this method is ±0.05 mm, and the dimensional accuracy of the outer contour is ±0.05 mm. The dimensional accuracy meets the complex structural requirements of the aviation plug housing.

[0014] (3) Calculated according to 50,000 parts, the manufacturing cycle of this method is shortened by more than 50% compared with the traditional machining and forming manufacturing cycle.

[0015] (4) Calculated according to 50,000 parts, the manufacturing cost of this method is reduced by more than 20% compared with the traditional machining and forming manufacturing cost.

[0016] (5) Calculated according to 50,000 parts, the material loss rate of this method is reduced by more than 60% compared with the traditional machining and forming manufacturing material loss rate.

[0017] (6) The titanium alloy aviation plug housing manufactured by this method breaks through the technical bottleneck of mass production of this product and is suitable for popularizing mass production in aviation plug products. Description of the drawings

[0018] Figure 1 It is a schematic diagram of the overall process of the solution of the present invention; Figure 2It is a schematic structural diagram of the atmosphere protection device in the solution of the present invention; Figure 3 It is a schematic structural diagram of the back of the atmosphere protection device; Figure 4 It is a partial schematic structural diagram of the box door of the atmosphere protection device; Figure 5 It is an enlarged view of area A of the atmosphere protection device; Figure 6 It is an enlarged view of area B of the atmosphere protection device; Wherein: 1. protection box; 2. box door; 3. transparent window; 4. glove port; 5. fixing ring; 6. groove; 7. sealing ring; 8. convex block; 9. installation mechanism; 91. through groove; 92. card slot; 93. retaining pin; 94. spring; 95. mounting ring; 96. mounting block; 97. pulling block; 10. first argon filling port; 11. vacuum pumping port; 12. second argon filling port; 13. oxygen content detector; 14. first exhaust port; 15. second exhaust port; 16. mounting seat. Specific embodiments

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0020] Embodiment 1: A high-polish titanium alloy plug cover injection molding method includes the following steps: S1: Powder preparation: Prepare 0-30um titanium alloy spherical powder with a powder particle size of 0-30um, add 0-30um non-spherical powder in proportion, and load it into a three-dimensional mixer to mix evenly to prepare a composite powder; the composite powder has a particle size of 0-30um, a tapped density greater than 2.7g / cm 3 , the oxygen content of the powder is less than 0.2%, and the nitrogen content of the powder is less than 0.03%; S2: Kneading: Knead the titanium alloy powder and the molding binder polyoxymethylene in proportion in an atmosphere-protected kneading and granulating all-in-one machine for 1-2h and then granulate to obtain titanium alloy injection feed; wherein, the volume ratio of titanium alloy powder to binder addition is: 1:1-1.5:1; the kneading temperature is 170°C-180°C, the kneading time is 1h, and argon is used for protection in the kneading chamber; the specific operation is: preheat the composite powder to 180°C, then add part of the molding binder, wait for all the molding binder to melt, then add the remaining molding binder, and cool down to 175°C, continue kneading for 40min to complete the kneading process; the granulation temperature after kneading is 180°C; S3: Injection molding: Heat the feedstock to 160 - 180 °C, inject and fill it into the mold cavity to form a green compact; the injection pressure is 80 - 120 Mpa; S4: Acid degreasing: Place the green compact obtained by injection molding in a degreasing furnace, and perform acid degreasing under an oxalic acid atmosphere. The acid degreasing temperature is 110 - 140 °C, and the acid degreasing time is 7 - 10 h; during the acid degreasing process, the acid feeding amount is 3.2 - 7.5 g / min; S5: Thermal degreasing: Put the acid - degreased green compact into a vacuum furnace, evacuate to below 1×10 -3 Pa for thermal degreasing. The thermal degreasing temperature is 300 - 650 °C, and the thermal degreasing holding time is 5 - 12 h; S6: Sintering: After thermal degreasing, raise the temperature of the vacuum furnace to 1150 - 1250 °C, hold for 2 - 8 h, then lower the blank temperature to 400 - 600 °C, hold for 1 - 4 h, and then cool to 40 - 80 °C and take out; during the sintering process, maintain the vacuum degree at 10 -3 -10 -1 MPa; S7: Post - treatment: Shape, sand - blast and machine - process the blank to obtain the finished plug housing.

[0021] In this project, the atmosphere - protected internal mixer granulator used in the mixing process of step S2 has an atmosphere - protection device. The atmosphere - protection device is arranged above the mixing bin of the internal mixer and includes a protection box 1. The front of the protection box 1 is hinged with a box door 2. A transparent window 3 is arranged on the box door 2. A glove port 4 is opened on the transparent window 3. A fixing ring 5 is fixedly connected inside the glove port 4. The fixing ring 5 contacts the transparent window 3. A groove 6 is opened inside the fixing ring 5. A sealing ring 7 is slidably connected inside the fixing ring 5. A convex block 8 is fixedly connected to the outside of the sealing ring 7. The convex block 8 is slidably connected in the groove 6. An installation mechanism 9 for quickly installing the sealing ring 7 is arranged on the transparent window 3; The installation mechanism 9 includes a through - slot 91, a card slot 92, a pin 93, a spring 94, an installation ring 95, an installation block 96, and a pulling block 97. A through - slot 91 is opened inside the fixing ring 5. A card slot 92 is opened inside the convex block 8. A pin 93 is slidably connected in the card slot 92. A spring 94 is sleeved outside the pin 93. An installation ring 95 is fixedly connected to the outside of the pin 93. An installation block 96 is fixedly connected to the transparent window 3. A pulling block 97 contacts the installation block 96.

[0022] By setting the cooperation of each component in the above - mentioned installation mechanism 9, the pin 93 can be pulled to slide into the through - slot 91, and then the convex block 8 fixed on the sealing ring 7 is placed into the groove 6 opened inside the fixing ring 5. Release the pin 93, and under the action of the spring 94, the pin 93 moves and slides into the card slot 92 opened inside the convex block 8, thus completing the installation of the sealing ring 7, which is convenient and fast.

[0023] One end of the spring 94 is fixedly connected to the mounting ring 95, and the other end of the spring 94 is fixedly connected to the mounting block 96.

[0024] During the process of the latch 93 sliding out of the card slot 92, the spring 94 will be squeezed. At this time, the spring 94 generates elastic force, and then under the elastic action of the spring 94, the latch 93 can be moved back to its original position.

[0025] The latch 93 is slidably connected within the mounting block 96, and a pull block 97 is fixedly connected to the latch 93.

[0026] During the movement of the latch 93, there is a groove in the mounting block 96 that matches its shape. At this time, the latch 93 can be guided through this groove to prevent the latch 93 from shifting during movement.

[0027] The through groove 91 communicates with the card slot 92, and a latch 93 is slidably connected within the through groove 91.

[0028] The communicating through groove 91 and card slot 92 enable the latch 93 to slide into the card slot 92 through the through groove 91 to limit the sealing ring 7.

[0029] The upper end of the protection box 1 is respectively provided with a first argon filling port 10 and a second argon filling port 12, the upper end of the protection box 1 is provided with a vacuum pumping port 11, and the upper end of the protection box 1 is provided with an oxygen content detector 13.

[0030] The glove port 4 is blocked by the sealing ring 7. At this time, the protection box 1 is evacuated through the vacuum pumping port 11 externally connected to a vacuum negative pressure pump, and then argon gas is filled into the protection box 1 through the first argon filling port 10 and the second argon filling port 12.

[0031] The back of the protection box 1 is respectively provided with a first exhaust port 14 and a second exhaust port 15, and the lower end of the protection box 1 is fixedly connected to a mounting seat 16.

[0032] When filling argon gas into the protection box 1, the air inside the protection box 1 can be discharged through the first exhaust port 14 and the second exhaust port 15, so as to keep the inside of the protection box 1 as a rare protective gas, which can protect the atmosphere inside the protection box 1. The oxygen content inside the box is monitored in real time through the oxygen content detector 13 to keep the oxygen content inside the box low and avoid the oxidation problem of titanium alloy powder during the internal mixing process caused by a relatively high oxygen content.

[0033] During specific use, the retaining pin 93 is pulled to slide it into the through slot 91, and then the convex block 8 fixed on the sealing ring 7 is placed into the groove 6 formed in the fixing ring 5. During the process of the retaining pin 93 sliding out of the card slot 92, the spring 94 will be compressed. At this time, the spring 94 generates an elastic force, and then under the elastic action of the spring 94, the retaining pin 93 can move back to its original position and slide into the card slot 92 formed in the convex block 8. At this time, the installation of the sealing ring 7 is completed. Then, a vacuum negative pressure pump is externally connected to the protection box 1 through the vacuum port 11 to evacuate the protection box 1. Then, argon gas is filled into the protection box 1 through the first argon filling port 10 and the second argon filling port 12, and the air in the protection box 1 is discharged through the first exhaust port 14 and the second exhaust port 15, so as to keep the inside of the protection box 1 as a rare protective gas, and the atmosphere in the protection box 1 can be protected.

[0034] The density of the titanium alloy component manufactured in this embodiment is ≥4.48 g / cm 3 , the tensile strength is ≥958 MPa, the elongation after fracture is ≥15%, and the density and mechanical properties meet the weight reduction and usage requirements of the aviation plug housing. The dimensional accuracy of the outer diameter of the sintered blank of the aviation plug is ±0.05 mm, and the dimensional accuracy of the outer contour is ±0.05 mm, and the dimensional accuracy meets the complex structural requirements of the aviation plug housing; calculated according to 50,000 parts, the manufacturing cycle of this method is shortened by 50% compared with the traditional machining forming manufacturing cycle; calculated according to 50,000 parts, the manufacturing cost of this method is reduced by 20% compared with the traditional machining forming manufacturing cost; calculated according to 50,000 parts, the material loss rate of this method is reduced by 60% compared with the traditional machining forming manufacturing material loss rate. This technology breaks through the technical bottleneck of mass production of this type of product and is suitable for popularizing mass production in aviation plug products.

[0035] As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as a limitation of the present invention itself. Various changes can be made in its form and details without departing from the spirit and scope of the present invention defined by the appended claims.

Claims

1. A method for injection molding a highly polished titanium alloy plug housing, characterized in that: It includes the following steps: S1: Powder preparation: Prepare titanium alloy spherical powder with a particle size of 0 - 60 μm. Add non-spherical powder with a particle size of 0 - 50 μm in proportion and mix them evenly in a three-dimensional mixer to prepare a composite powder. The particle size of the composite powder is 0 - 30 μm, and the tapped density is greater than 2.7 g / cm 3 , the oxygen content of the powder is less than 0.2%, and the nitrogen content of the powder is less than 0.03%; S2: Internal mixing: Mix titanium alloy powder and molding binder in a gas-protected internal mixing and granulating machine in proportion for 1 - 2 h and then granulate to obtain titanium alloy injection feedstock; S3: Injection molding: Heat the feedstock to 160 - 180 °C and inject and fill it into the mold cavity to form a green compact; S4: Acid degreasing: Place the injection-molded green compact in a degreasing furnace and perform acid degreasing under an oxalic acid atmosphere. The acid degreasing temperature is 110 - 140 °C and the acid degreasing time is 7 - 10 h; S5: Thermal debinding: Put the green compact after acid debinding into a vacuum furnace and evacuate it to a pressure below 1×10 -3 Pa for thermal debinding. The thermal debinding temperature is 300 - 650 °C, and the thermal debinding holding time is 5 - 12 h; S6: Sintering: After thermal degreasing, heat up the vacuum furnace to 1150 - 1250 °C, keep the temperature for 2 - 8 h, then cool the blank temperature to 400 - 600 °C, keep the temperature for 1 - 4 h, and then cool to 40 - 80 °C and take it out; S7: Post-treatment: Shape, sandblast, and machine the blank to obtain the finished plug housing.

2. The injection molding method of the highly polished titanium alloy plug housing according to claim 1, characterized in that: In step S2, the volume ratio of titanium alloy powder to binder addition is: 1:1 - 1.5:

1.

3. The injection molding method of the highly polished titanium alloy plug housing according to claim 2, characterized in that: The molding binder in step S2 is at least one of polyoxymethylene, paraffin wax, octadecyl acrylate, ethylene bisstearamide, ethylene-vinyl acetate copolymer, polyethylene, polypropylene, and BASF antioxidant.

4. The injection molding method of the highly polished titanium alloy plug cover according to claim 1, characterized in that: In step S2, the internal mixing temperature is 170 °C - 180 °C, the internal mixing time is 1 h, and argon is used for protection in the internal mixing chamber; the specific operation is: preheat the composite powder to 180 °C, then add part of the molding binder. After the molding binder is completely melted, add the remaining molding binder and cool down to 175 °C, continue internal mixing for 40 min to complete the internal mixing process; the granulating temperature after internal mixing is 180 °C.

5. The injection molding method of the highly polished titanium alloy plug housing according to claim 1, characterized in that: In step S3, the injection pressure is 80 Mpa - 120 Mpa.

6. The injection molding method of the highly polished titanium alloy plug housing according to claim 1, wherein: In step S4, the acid inlet amount during acid degreasing is 3.2 g / min - 7.5 g / min; During the sintering process in step S6, maintain the vacuum degree at 10 -3 -10 -1 Pa.

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