A device and method for realizing magnesium alloy injection molding

Abstract

The present invention discloses a device and method for realizing magnesium alloy injection molding, the device comprises an injection molding machine and a molding die, the injection molding machine comprises a screw injection mechanism, a hopper, a long nozzle, a movable mold fixing plate and a fixed mold fixing plate, the molding die comprises a movable mold frame, a movable mold core, a fixed mold frame and a fixed mold core, and is characterized in that: a feed port is provided at the center of the fixed mold core, and the two open ends of the feed port are respectively connected to the mold cavity and the injection end of the long nozzle, and a cooling jacket is provided on the injection end of the long nozzle. The present invention creatively allows semi-solid magnesium alloy materials to be directly fed from the long nozzle into the mold cavity through the feed port provided at the center of the fixed mold core, and no longer uses the flow channel method for feeding. It not only has the advantages of simple structure, less waste, low material loss, good product quality, short molding cycle, etc., but also has safe and environmentally friendly production, and has significant value in promoting the wide application of magnesium alloy injection molding technology in the industrial field.

Description

Technical Field

[0001] The invention relates to a device and a method for realizing magnesium alloy injection molding, and belongs to the technical field of magnesium alloy molding processing. Background Art

[0002] Magnesium alloy is a low-density alloy. Compared with other pure metal materials or alloy materials, and even compared with aluminum alloy, magnesium alloy is lighter. At the same time, magnesium alloy also has the advantages of strong vibration absorption, impact resistance, cutting performance and good wear resistance. Therefore, under the requirements of quality and environmental protection, it has become a mainstream trend to use magnesium alloy to make automobile dashboard frames, seats, steering column components, steering wheel cores, gearbox housings, engine suspensions, etc. and the shells and internal parts of electronic products. Magnesium alloy products have begun to be used in transportation, aerospace, military products, daily necessities and other fields, so the forming and processing technology of magnesium alloys has also received more and more attention.

[0003] Since the traditional magnesium alloy molding is die-casting, there are problems such as slow molding speed, low processing efficiency, and easy hole defects in the product. Therefore, the current research hotspot in this field is magnesium alloy injection molding technology. Magnesium alloy semi-solid injection molding technology, also known as thixoforming, refers to heating magnesium alloy particles or fragments to a partially molten state through the injection unit of the injection machine to form a solid-liquid coexistence state, that is, a semi-solid state, and then using a screw to shear (to make the original solid phase of the magnesium alloy become spherical to reduce the viscosity of the semi-solid alloy and improve its fluidity) and push the semi-solid slurry into the molding mold for injection molding. This molding technology is derived from plastic injection molding and applied to the molding process of magnesium alloys. However, the current method for magnesium alloy injection molding is to use runner feeding, that is, the nozzle of the injection molding machine is connected to the gate provided on the fixed mold core, and the semi-solid magnesium alloy is injected to the gate through the nozzle, and then transported from the gate to the cavity formed by the movable mold core and the fixed mold core through the main runner and the branch runner. This feeding structure not only leads to a large waste area, resulting in a great waste of molding materials, but also has many auxiliary runner systems, making the molding mold complex, large in size, and high in production cost. In particular, it leads to a large clamping force, making it difficult to produce large-sized products with existing specifications of injection molding machines.

[0004] Although the hot runner technology in the prior art, such as: a hot runner of a semi-solid injection molding mold of a magnesium alloy disclosed in CN201620215890.2, controls the metal liquid in the mold runner to be in a semi-molten state through the heating system on the hot runner, which can solve the problems of long main runner, large pressure loss in the main runner during the molding process, which is not conducive to product molding, and excessive waste, etc., there are still problems such as complex structure, high manufacturing cost, and inability to realize injection molding of large-size products; In addition, a magnesium alloy injection molding multi-point feeding system disclosed in the existing patent CN201620416882.4, by setting a splitter plate detachable from the fixed mold frame, a total feed port and 4 branch runners are set on the splitter plate to realize front multi-point feeding, although the patent can simplify the feeding structure to a certain extent, it needs to add a splitter plate, and the manufacturing cost is still high. The key is that the patent technology still has a runner. If the waste generated by the runner is to be truly reduced, the hot runner technology is still needed, otherwise there will still be runner waste problems and product quality problems. In other words, to date, the existing technology cannot simultaneously solve the problems existing in magnesium alloy injection molding, such as complex structure, large amount of waste, large waste of raw materials, poor product quality assurance, inability to produce products with large projection area and large casting weight using small tonnage machines, and long molding cycle, thus limiting the widespread application of magnesium alloy injection molding technology in the industrial field. Summary of the invention

[0005] In view of the above-mentioned problems existing in the prior art, the purpose of the present invention is to provide a device and method for realizing magnesium alloy injection molding which can simultaneously solve the problems existing in magnesium alloy injection molding, such as complex structure, large amount of waste, large waste of raw materials, poor product quality assurance, inability to produce products with large projection area and large casting weight using small tonnage machines, and long molding cycle, so as to promote the widespread application of magnesium alloy injection molding technology in the industrial field.

[0006] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:

[0007] A device for realizing magnesium alloy injection molding, comprising an injection molding machine and a molding die, wherein the injection molding machine comprises a screw injection mechanism, a hopper, a long nozzle, a movable mold fixing plate and a fixed mold fixing plate, and the molding die comprises a movable mold frame, a movable mold core, a fixed mold frame and a fixed mold core, wherein the movable mold frame is detachably fixedly connected to the movable mold fixing plate, the movable mold core is detachably fixedly connected to the movable mold frame, the fixed mold frame is detachably fixedly connected to the fixed mold fixing plate, the fixed mold core is detachably fixedly connected to the fixed mold frame, and the mold cavity formed by the movable mold core and the fixed mold core is adapted to the product to be molded; the invention is characterized in that: a feed port is provided at the center of the fixed mold core, two open ends of the feed port are respectively connected to the mold cavity and the injection end of the long nozzle, and a cooling jacket is provided on the injection end of the long nozzle.

[0008] In a preferred embodiment, the feed port is in a trumpet shape, wherein: the expanded end surface is located on the cavity surface of the fixed mold core, and the contracted end surface abuts against the injection end of the long nozzle.

[0009] In a further preferred embodiment, the longitudinal cross-section of the feed port is an isosceles trapezoid, the height of the isosceles trapezoid is 18 to 25 mm, and the base angle of the isosceles trapezoid is 60 to 75 degrees.

[0010] In a preferred embodiment, the cooling sleeve is fixed in the nozzle mounting hole of the fixed mold core through a nozzle positioning ring.

[0011] In a preferred embodiment, the cooling jacket is connected to an external cooling device via a condenser.

[0012] In a further preferred embodiment, the cooling device is a high pressure point cooler.

[0013] A method for realizing magnesium alloy injection molding, comprising the above-mentioned device, the method comprising the following steps:

[0014] a) feeding the magnesium alloy material into the hopper;

[0015] b) The heated molten magnesium alloy material is pushed to the long nozzle through the screw injection mechanism, and is directly injected into the mold cavity through the long nozzle and the feed port located in the center of the fixed mold core; when the material required for forming the magnesium alloy product is injected each time, the injection end of the long nozzle is immediately cooled by the cooling jacket;

[0016] c) After forming, the mold is opened, the magnesium alloy rough product is taken out and cooled to room temperature, and then the feed port blank formed on its outer surface is milled and polished to obtain a magnesium alloy finished product.

[0017] A preferred solution, step b), each time the cooling jacket uses tap water at room temperature to circulate for 16±2 seconds at a pressure of 15±3MPa to cool the ejection end of the long nozzle.

[0018] Compared with the prior art, the present invention has the following beneficial technical effects:

[0019] 1. The present invention creatively allows the semi-solid magnesium alloy material to be directly fed from a long nozzle into the feed port located at the center of the fixed mold core into the mold cavity, and no longer uses a runner to feed the material. This not only significantly simplifies the mold structure, but also eliminates the need for a complex heating and heat preservation system of hot runner technology, and also eliminates the need for a complex structure of multi-point feeding, which can significantly reduce the mold volume. According to calculations, when processing magnesium alloy products of the same size, the present invention can reduce the clamping force by 35%, and can achieve the production of products with a large projection area and a large casting weight using a small tonnage machine;

[0020] 2. Since the present invention is provided with a cooling jacket at the injection end of the long nozzle, it can ensure that the material required for each molding can be quickly and timely separated from the nozzle after injection, which not only makes it possible to feed without flow channel, but also can save materials to the greatest extent, so that the product material loss can be reduced by at least 118%, and the production cost is significantly reduced;

[0021] 3. Since the present invention has no runner feeding, the injection molding cycle can be significantly shortened, which not only improves the molding production efficiency, but also significantly improves the shrinkage deformation of the product, so that the magnesium alloy yield is significantly improved;

[0022] 4. Tests have shown that the tensile strength of the magnesium alloy product obtained by the device and method of the present invention can be increased by at least 18% compared with the prior art, the product has good performance, and has no defects in appearance;

[0023] To sum up, the present invention creatively adopts a runnerless feeding method to achieve magnesium alloy injection molding, which not only has the advantages of simple structure, less waste, low material loss, good product quality, and short molding cycle, but also has safe and environmentally friendly production. It has significant value in promoting the widespread application of magnesium alloy injection molding technology in the industrial field, and has produced obvious progress compared with the existing technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of the three-dimensional structure of a device for realizing magnesium alloy injection molding provided by an embodiment of the present invention;

[0025] Figure 2 is a schematic diagram of the longitudinal cross-sectional structure of a forming mold provided by an embodiment of the present invention;

[0026] Figure 3 is a schematic diagram of the transverse cross-sectional structure of a forming die provided in an embodiment of the present invention;

[0027] Figure 4 It is a schematic diagram of the connection structure between the long nozzle, the cooling jacket and the feed port in an embodiment of the present invention;

[0028] Figure 5 is a schematic diagram of the three-dimensional structure of the fixed mold core described in an embodiment of the present invention;

[0029] Figure 6 is a schematic structural diagram of a magnesium alloy crude product obtained in an embodiment of the present invention;

[0030] Figure 7 It is a schematic diagram of the three-dimensional structure of a device for realizing injection molding of magnesium alloy provided in a comparative example;

[0031] Figure 8 It is a three-dimensional structural schematic diagram of the fixed mold core provided for comparison;

[0032] Fig. 9 1 is a stress-strain curve diagram of the magnesium alloy products obtained in the embodiment and the comparative example.

[0033] The numbers in the figure are as follows: 1. Injection molding machine; 11. Screw injection mechanism; 12. Hopper; 13. Long nozzle; 131. Injection end of long nozzle; 14. Moving mold fixing plate; 15. Fixed mold fixing plate; 2. Molding mold; 21. Moving mold frame; 22. Moving mold core; 23. Fixed mold frame; 24. Fixed mold core; 3. Cavity; 4. Feed port; 41. Expanding end face; 42. Shrinking end face; 5. Cooling jacket; 6. Nozzle positioning ring; 7. Condenser; 8. Feed port blank; 01. Gate; 02. Main flow channel; 03. Branch flow channel. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings, specific embodiments and comparative examples.

[0035] Example

[0036] Please combine Figures 1 to 5 As shown, the present embodiment provides a device for realizing magnesium alloy injection molding, comprising an injection molding machine 1 and a molding mold 2, wherein the injection molding machine 1 comprises a screw injection mechanism 11, a hopper 12, a long nozzle 13, a movable mold fixing plate 14 and a fixed mold fixing plate 15, and the molding mold 2 comprises a movable mold frame 21, a movable mold core 22, a fixed mold frame 23 and a fixed mold core 24, wherein the movable mold frame 21 is detachably fixedly connected to the movable mold fixing plate 14 (for example, screw connection), and the movable mold core 22 is detachably fixedly connected to the movable mold frame 21 (for example, screw connection). For example: screw connection), the fixed mold frame 23 is detachably fixedly connected to the fixed mold fixing plate 15 (for example: screw connection), the fixed mold core 24 is detachably fixedly connected to the fixed mold frame 23 (for example: screw connection), and the cavity 3 formed by the movable mold core 22 and the fixed mold core 24 is adapted to the product to be formed; a feed port 4 is provided at the center of the fixed mold core 24, and the two open ends of the feed port 4 are respectively connected to the cavity 3 and the injection end 131 of the long nozzle, and a cooling jacket 5 is provided on the injection end 131 of the long nozzle.

[0037] In this embodiment, the feed port 4 is in a trumpet shape, wherein: the flared end face 41 is located on the cavity surface 31 of the fixed mold core 24, and the contracted end face 42 is in contact with the ejection end 131 of the long nozzle; and the longitudinal cross-section of the feed port 4 is an isosceles trapezoid, the height h of the isosceles trapezoid is 18 to 25 mm, and the base angle α of the isosceles trapezoid is 60 to 75 degrees.

[0038] The cooling jacket 5 is fixed in the nozzle mounting hole of the fixed mold core 24 through the nozzle positioning ring 6, and the cooling jacket 5 is connected to an external cooling device (not shown in the figure) through a condenser 7. The cooling device is preferably a high-pressure point cooler, for example: the high-pressure point cooler disclosed in Chinese utility model patent ZL2014205679866, which can realize fixed-point, timed and quantitative cooling and has the advantage of uniform cooling.

[0039] In addition, it should be pointed out that the injection molding machine 1 described in this patent is a known product purchased from outside, such as: Nippon Steel JSW-JLM series magnesium alloy injection molding machine, so it is not shown as a whole in the accompanying drawings because it does not involve relevant improvements.

[0040] The method for implementing magnesium alloy injection molding using the above device of this embodiment includes the following steps:

[0041] a) feeding the magnesium alloy material into the hopper 12;

[0042] b) The heated magnesium alloy material in a molten state is pushed to the long nozzle 13 through the screw injection mechanism 11, and is directly injected into the mold cavity 3 through the long nozzle 13 and the feed port 4 provided at the center of the fixed mold core 24; when the material required for forming the magnesium alloy product is injected each time, the injection end 131 of the long nozzle is immediately cooled by the cooling jacket 5;

[0043] c) After forming, open the mold and take out the magnesium alloy rough product (such as Figure 6 As shown in the figure, the blank is cooled to room temperature, and then the feed port blank 8 formed on its outer surface is milled and polished to obtain a magnesium alloy finished product.

[0044] As a preferred solution, in step b), the cooling jacket 5 uses tap water at room temperature to circulate for 16±2 seconds at a pressure of 15±3MPa each time to cool the ejection end 131 of the long nozzle. This can not only achieve timely separation between the feed port 4 and the ejection end 131 of the long nozzle, saving materials, but also avoid shrinkage holes and cracks on the product surface, thereby ensuring that the product appearance is flawless.

[0045] Comparative Example

[0046] See also Figure 7 and Figure 8 As shown, conventional magnesium alloy injection molding is achieved by feeding in a runner manner, and the feeding system includes a gate 01, a main channel 02 and multiple branch channels 03. The molten magnesium alloy material is injected into the gate 01 by a nozzle 13, then passes through the main channel 02 to multiple branch channels 03, and then injected into the cavity 3 by the branch channel 03.

[0047] It is known through experiments that: assuming that the rest of the structures are the same as those in the present embodiment, the magnesium alloy product with the same size (length and width are 65cm*17cm) and the same weight (490g) as the embodiment of the present invention is processed by the existing flow channel method, at least 1168g of material is required (including the loss of slag bag and flow channel), and the projected area of ​​the casting on the parting surface reaches 65cm*30cm; and because there is no loss of flow channel in the present invention, only 590g of material is required, and the projected area of ​​the casting on the parting surface is only 65cm*20cm; after the following calculation:

[0048] The calculation formula of the die-casting machine clamping force is: Flock ≥ K*Fmain, where: Flock- represents the clamping pressure of the die-casting machine; K- represents the safety factor, generally K = 1.1; Fmain- represents the main expansion force, the projected area of ​​the casting on the parting surface, including the area of ​​the pouring system, overflow, and exhaust system multiplied by the specific pressure (KN), that is: Fmain = A*P / 10, A- represents the projected area of ​​the casting on the parting surface, and P- represents the compaction pressure; therefore, the size of the clamping force required by the present invention is:

[0049] Flock = 65*20*60*1.1 / 10 = 8580KN, while the clamping force required for the comparative example is:

[0050] Flock=65*30*60*1.1 / 10=12870KN; it can be seen that the present invention can reduce the clamping force and can realize the production of products with large projection area and large casting weight by using a small tonnage machine.

[0051] In addition, the material loss of the present invention is: (590-490)*490*100%=20.5%, while the material loss of the comparative example is: (1168-490)*490*100%=138.4%; it can be seen that: compared with the prior art, the present invention can reduce material loss by 118%, which not only significantly saves costs, but also avoids the problem of recycling a large amount of magnesium alloy waste, and has significant energy-saving and environmental protection advantages.

[0052] Please see again Fig. 9 As shown by Fig. 9 It can also be seen that the tensile strength of the magnesium alloy product obtained using the present invention is 187.1 MPa, while the tensile strength of the magnesium alloy product obtained in the comparative example is 158.4 MPa. It can be seen that: compared with the prior art, the present invention can also increase the tensile strength of the obtained magnesium alloy product by at least 18%, and the product performance is good.

[0053] To sum up, the present invention creatively adopts a runnerless feeding method to achieve magnesium alloy injection molding, which not only has the advantages of simple structure, less waste, low material loss, good product quality, and short molding cycle, but also has safe and environmentally friendly production. It has significant value in promoting the widespread application of magnesium alloy injection molding technology in the industrial field, and has produced obvious progressive and unexpected technical effects compared to the existing technology.

[0054] Finally, it is necessary to point out here that the above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto, and any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A device for realizing injection molding of magnesium alloy, comprising an injection molding machine and a molding die, wherein the injection molding machine comprises a screw injection mechanism, a hopper, a long nozzle, a movable mold fixing plate and a fixed mold fixing plate, wherein the molding die comprises a movable mold frame, a movable mold core, a fixed mold frame and a fixed mold core, wherein the movable mold frame is detachably fixedly connected to the movable mold fixing plate, the movable mold core is detachably fixedly connected to the movable mold frame, the fixed mold frame is detachably fixedly connected to the fixed mold fixing plate, the fixed mold core is detachably fixedly connected to the fixed mold frame, and the cavity formed by the movable mold core and the fixed mold core is adapted to the product to be molded; characterized in that: A feed port is provided at the center of the fixed mold core, and the two open ends of the feed port are respectively connected with the cavity and the injection end of the long nozzle, and the feed port is in a trumpet shape, wherein: the expanded end face is located at the cavity surface of the fixed mold core, the contracted end face is abutted against the injection end of the long nozzle, and a cooling jacket is provided on the injection end of the long nozzle; the longitudinal section of the feed port is an isosceles trapezoid, the height of the isosceles trapezoid is 18 to 25 mm, and the base angle of the isosceles trapezoid is 60 to 75 degrees.

2. The device according to claim 1, characterized in that: The cooling sleeve is fixed in the nozzle mounting hole of the fixed mold core through a nozzle positioning ring.

3. The device according to claim 1, characterized in that: The cooling jacket is connected to an external cooling device through a condenser.

4. The device according to claim 3, characterized in that: The cooling device is a high pressure point cooler.

5. A method for realizing injection molding of magnesium alloy, comprising the device according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: a) feeding the magnesium alloy material into the hopper; b) The heated molten magnesium alloy material is pushed to the long nozzle through the screw injection mechanism, and is directly injected into the mold cavity through the long nozzle and the feed port located in the center of the fixed mold core; when the material required for forming the magnesium alloy product is injected each time, the injection end of the long nozzle is immediately cooled by the cooling jacket; c) After forming, the mold is opened, the magnesium alloy rough product is taken out and cooled to room temperature, and then the feed port blank formed on its outer surface is milled and polished to obtain a magnesium alloy finished product.

6. The method according to claim 5, characterized in that: In step b), each time the cooling jacket uses tap water at room temperature to circulate for 16±2 seconds at a pressure of 15±3 MPa to cool the ejection end of the long nozzle.

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