A large injection amount of spherulitic crystal magnesium alloy thixomolding process and equipment

Abstract

The application discloses a large-injection-amount globular crystal magnesium alloy thixotropic forming process, which adopts a process cooperation of continuous five-stage temperature control, shearing and injection to promote magnesium alloy into semi-solid globular crystal and forming; stage 1: melting; stage 2: near liquid phase; stage 3: short-time low supercooling; stage 4: semi-solid isothermal globular crystal transformation; stage 5: high-speed injection cooling forming; the application also discloses a large-injection-amount globular crystal magnesium alloy thixotropic forming equipment which comprises a first material homogenizing assembly, a cooling pipe assembly, a second shearing and injection assembly and a cavity assembly, and magnesium alloy sequentially passes through the first material homogenizing assembly, the cooling pipe assembly, the second shearing and injection assembly and the cavity assembly to complete product production. The application provides a large-injection-amount globular crystal magnesium alloy thixotropic forming process and equipment which are large in injection amount, uniform in globular crystal, good in process connectivity and suitable for high-performance large products.

Description

Technical Field

[0001] This invention relates to the field of materials synthesis, specifically to a thixotropic molding process and equipment for large-volume spherical crystalline magnesium alloys. Background Technology

[0002] In the context of dual carbon, lightweighting is an important trend in the development of high-end manufacturing. Magnesium alloys are currently the lightest metal structural materials available worldwide. Replacing materials such as steel and aluminum in the automotive and aerospace fields can effectively reduce carbon emissions. Moreover, magnesium is extremely abundant in nature and is a key lightweight material for future industrial development.

[0003] Among various magnesium alloy forming technologies, semi-solid forming technology is hailed as the most promising magnesium alloy forming technology of the 21st century due to its significant improvement in production safety and environmental friendliness. Semi-solid forming typically refers to controlling the alloy to an intermediate temperature between a liquid and a solid phase, while simultaneously transforming the microstructure into a slurry containing a uniformly distributed solid phase within the liquid phase under external force or internal induction. This slurry exhibits unique thixotropic mechanical behavior, including shear thinning and isothermal transient rheological characteristics, allowing for laminar flow filling to obtain highly dense parts. Obtaining an ideal slurry is a key aspect of semi-solid forming technology; the performance of semi-solid products requires not only specific temperature conditions but, more fundamentally, the microstructure conditions of the slurry. Currently, a relatively mature semi-solid forming process for magnesium alloys is the thixotropic injection molding method promoted and developed in Japan. This method integrates continuous shearing with a single screw, continuous heating, and injection into a single process, enabling low-oxidation forming of magnesium alloys and is already used in the production of small products such as laptop casings. However, for heavy automotive parts and similar components, the increased size and structural complexity, coupled with higher performance requirements, necessitate not only a significant increase in slurry injection volume but also ensuring that the spheroidal crystals within the slurry are sufficiently fine and uniform to achieve adequate filling capacity, mechanical properties, and corrosion resistance. Currently, traditional processes, limited by technological constraints, can only achieve semi-solid molding of magnesium products weighing less than 5 kg, hindering large-scale production. Therefore, there is an urgent need to develop new magnesium alloy thixotropic molding processes and equipment that offer larger injection volumes, uniform spheroidal crystals, better process continuity, and suitability for high-performance, large-component products.

[0004] A search revealed Chinese invention patent CN107671260A, which relates to a multi-station semi-solid injection molding machine. The invention states: "By setting two sets of semi-solid injection mechanisms to inject semi-solid magnesium alloy, the injection volume is effectively increased and the flow length ratio is reduced. This structure is suitable for applications requiring the production of thin-walled or thick-walled magnesium alloy products with high mass and high flow length ratio." This invention utilizes the traditional thixotropic injection molding method, increasing the injection volume by setting two injection mechanisms. However, its shortcomings include: non-fusion easily occurs at the junction of the two melt streams within the mold cavity, resulting in weak performance at that location; the mold requires two gates, which is not compatible with traditional molds in the industry; and the semi-solid slurry preparation still uses a single continuous heating method, limiting the control of spherical crystal morphology and easily leading to low filling capacity and product performance. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a large injection volume spherical magnesium alloy thixoforming process and equipment with large injection volume, uniform spherical crystals, good process connectivity, and suitable for high-performance large parts.

[0006] The technical solution adopted by the present invention to solve the above problems is: a large injection volume spherical crystalline magnesium alloy thixotropic molding process, which adopts a continuous five-stage temperature control, shearing and injection process to promote the magnesium alloy to transform into semi-solid spherical crystals and then to form them.

[0007] Stage 1: Melting. Using a first-stage material processing component, the magnesium alloy particles are rapidly heated and softened in a tunnel until they melt above the liquidus line. At the same time, under the extrusion and propulsion of the material processing screw, they gradually self-compact and maintain the liquefaction process without air entrainment.

[0008] Stage 2: Near-liquid phase. At the end of the first-stage material processing assembly, the magnesium alloy is kept at 10-30°C above the near-liquidity line for homogenization, so that the alloy structure is transformed into a pure liquid phase or a very low solid phase state.

[0009] Stage 3: Short-term low undercooling, using a cooling conduit assembly connected to the first-stage material assembly to provide short-term low undercooling conditions to the flowing magnesium melt, so that a large number of semi-solid primary crystals are rapidly generated in the near-liquid phase alloy structure.

[0010] Stage 4: Semi-solid isothermal spheroidal crystal transformation. A horizontal second-order shearing and injection assembly is used, which is connected to the cooling conduit assembly. It is used to provide semi-solid isothermal heat treatment and injection screw shearing to the low-cooled magnesium alloy, so that the solid phase in the semi-solid primary crystals in the magnesium alloy structure is penetrated and surrounded by the low-melting-point liquid phase, resulting in refinement and full spheroidization, transforming into spheroidal crystal semi-solid slurry.

[0011] Stage 5: High-speed injection cooling molding. The spherical semi-solid slurry with good thixotropic properties is injected under high pressure and high speed into the cavity assembly and cooled to form a dense magnesium alloy product.

[0012] Compared with the prior art, the advantages of the present invention are as follows:

[0013] 1. Precise control of the semi-solid spherical crystal slurry structure: A multi-stage temperature control and shear synergy are employed. In the first stage, magnesium particles are rapidly heated above the liquidus line, and the melt is self-compacted by a screw propulsion, thus preparing conditions for the formation of the supercooled solid phase. However, the temperature should not be too high, and should be stably controlled at 10-20℃ above the liquidus line, otherwise the magnesium alloy is prone to oxidation and material reflux. In the second stage, when the magnesium melt flows through the cooling conduit, the low supercooling promotes supercooled nucleation in the liquid phase structure, which quickly transforms into a melt containing a large amount of primary solid phase. However, the supercooling should not be too high, and should be controlled at 15-30℃ below the liquidus line, otherwise the high primary solid phase ratio can easily cause the melt to block in the conduit. In the third stage, the primary solid phase is heated a second time, and the semi-solid isothermal heat treatment promotes the rounding of grains. At the same time, the screw shearing action is used to refine and uniformly distribute the solid phase, resulting in a spherical crystal semi-solid slurry with excellent thixotropic properties.

[0014] 2. Large-volume magnesium alloy semi-solid pulping: The three-stage pulping method of this invention not only effectively improves pulping quality and efficiency, forming a series process and avoiding the problem of insufficient heating power of a single component; it also has good pulping monitoring and easy maintenance, clear functional zoning, and convenient operation when maintaining or replacing a single component.

[0015] As an improvement of this invention, in stage 1, the magnesium alloy uses a particle size between 0.5 and 5 mm and is kept dry. The magnesium alloy material needs to be selected with a semi-solid process window range of 50°C or higher. Through this improvement, the magnesium alloy particles with uniform particle size can be melted with a more precise temperature, avoiding excessively high melting temperatures that could cause oxidation and material backflow. Keeping it dry prevents water from vaporizing at high temperatures and forming bubbles in the first-stage material assembly, which would affect the density of the magnesium alloy. Selecting a semi-solid process window range of 50°C or higher ensures the machinability of the magnesium alloy. If the process window range is too small, the magnesium alloy is prone to oxidation and material backflow, or the initial solid phase ratio may be too high.

[0016] As an improvement of the present invention, in stage 2, the end temperature of the first-stage material preparation component is set to 10-20°C above the liquidus temperature of the magnesium alloy; the rotation speed of the material preparation screw is 100 r / min.

[0017] In stage 3, the low undercooling condition is 10-30°C below the liquidus temperature of the magnesium alloy.

[0018] In stage 4, the isothermal setting temperature of the second-order shear and injection components is 5-10℃ below the liquidus temperature, corresponding to a slurry solid phase ratio of 10-30%; the injection screw speed is 60r / min.

[0019] In stage 5, the mold temperature is 280℃ and the injection speed is 5m / s.

[0020] The technical solution adopted by this invention to solve the above problems is as follows: a large-volume spherical crystalline magnesium alloy thixotropic molding device, and a large-volume spherical crystalline magnesium alloy thixotropic molding process, including a first-stage material preparation assembly, a cooling conduit assembly, a second-stage shearing and injection assembly, and a cavity assembly. The magnesium alloy sequentially passes through the first-stage material preparation assembly, the cooling conduit assembly, the second-stage shearing and injection assembly, and the cavity assembly to complete product production. The first-stage material preparation assembly includes a material preparation channel, a material preparation screw, and a material preparation heater. The material preparation screw is located on the axis of the material preparation channel to propel the self-compacting liquid magnesium alloy and expel air. The material preparation screw simultaneously propels the magnesium alloy towards the cooling conduit assembly by rotation and axial movement. The material preparation heater is located outside the material preparation channel for heating. The material processing channel maintains its temperature above the liquidus line of the magnesium alloy. The cooling conduit assembly includes a cooling channel and a cryogenic heater. The cooling channel is connected to the material processing channel. The cryogenic heater is located outside the cooling channel to ensure that the cooling conduit assembly performs short-term low-subcooling operation. The first-stage material processing assembly is located above the second-stage shearing and injection assembly. The cooling conduit assembly is vertically arranged. The second-stage shearing and injection assembly includes an injection channel, an injection screw, and an injection heater. The injection channel is connected to the cooling channel. The injection screw is located on the axis of the injection channel for injecting magnesium alloy into the cavity assembly. The injection heater is used to heat the injection channel to ensure the solidity of the magnesium alloy slurry and ensure smooth injection.

[0021] Compared with the prior art, the advantages of the present invention are as follows:

[0022] 1. Precise control of the semi-solid spherical crystal slurry structure: A multi-stage temperature control and shear synergy are employed. In the first stage, magnesium particles are rapidly heated above the liquidus line, and the melt is self-compacted by a screw propulsion, thus preparing conditions for the formation of the supercooled solid phase. However, the temperature should not be too high, and should be stably controlled at 10-20℃ above the liquidus line, otherwise the magnesium alloy is prone to oxidation and material reflux. In the second stage, when the magnesium melt flows through the cooling conduit, the low supercooling promotes supercooled nucleation in the liquid phase structure, which quickly transforms into a melt containing a large amount of primary solid phase. However, the supercooling should not be too high, and should be controlled at 15-30℃ below the liquidus line, otherwise the high primary solid phase ratio can easily cause the melt to block in the conduit. In the third stage, the primary solid phase is heated a second time, and the semi-solid isothermal heat treatment promotes the rounding of grains. At the same time, the screw shearing action is used to refine and uniformly distribute the solid phase, resulting in a spherical crystal semi-solid slurry with excellent thixotropic properties.

[0023] 2. Large-volume magnesium alloy semi-solid pulping: The three-stage pulping method of this invention not only effectively improves pulping quality and efficiency, forming a series process and avoiding the problem of insufficient heating power of a single component; it also has good pulping monitoring and easy maintenance, clear functional zoning, and convenient operation when maintaining or replacing a single component.

[0024] 3. Continuous Storage of Semi-Solid Magnesium Alloy with Large Injection Volume: In the horizontally designed first-stage chemical mixing assembly of this invention, the chemical mixing screw is simultaneously connected to a hydraulic cylinder and a motor, enabling the chemical mixing screw to move and rotate axially during the mixing and melting process. When the injection channel is full, the chemical mixing screw continues to rotate during the injection process without stopping. The chemical mixing screw will retract to expand the storage space of the chemical mixing channel, and the molten material is temporarily stored in the chemical mixing channel. After the second-stage shearing and injection assembly finishes injection, the chemical mixing screw rotates and moves forward, using pressure to push the temporarily stored molten material into the second-stage shearing and injection assembly. This achieves continuous storage and injection operations for semi-solid magnesium alloy with large injection volume. The first-stage chemical mixing assembly continues to rotate, resulting in more uniform heating of the molten material, reducing the likelihood of premature solidification in certain areas, and ensuring a short cycle time, thus improving production efficiency and product qualification rate.

[0025] 4. Leveraging the performance advantages of semi-solid magnesium alloys: First, the process and equipment of this invention can control the magnesium alloy to contain more than 10% uniform spheroidal crystal semi-solid slurry. This slurry has good fluidity, and in the cooling conduit assembly, high-speed laminar flow filling ensures a significant reduction in porosity defects, enabling high-density forming of large magnesium alloy parts. Second, it gives the magnesium alloy product higher mechanical properties. The fine grains in the semi-solid solidification structure first promote the fine grain strengthening effect, while the spheroidal crystals are conducive to the coordinated plastic deformation of the alloy structure, improving the fracture elongation. Moreover, this semi-solid product can undergo T6 heat treatment without bubbling, and the final casting's comprehensive mechanical properties can be improved by more than 15% compared to traditional die casting. Third, it gives the magnesium alloy product higher corrosion resistance. On the one hand, the spheroidal crystal structure contains Mg... 17 Al 12 When the second phase is also refined, microgalvanic corrosion is reduced. On the other hand, the densified alloy structure can uniformly block the expansion of the surface corrosion layer, which greatly reduces the probability of pitting corrosion.

[0026] 5. The entire process of this invention is carried out in a closed cylinder and connecting parts, eliminating the risk of combustion and oxidation, ensuring good safety, and eliminating the need for a magnesium alloy melting furnace, resulting in low power consumption and cost. It is a green and environmentally friendly near-net-shape forming technology for magnesium alloys.

[0027] In another improvement of the present invention, the injection screw includes a screw section and a piston section. The piston section is in a movable sealing fit with the injection channel. The screw section is located between the piston section and the cavity assembly. The connection between the cooling channel and the injection channel is also located between the piston section and the cavity assembly. The injection screw simultaneously injects magnesium alloy towards the cavity assembly by rotating and moving axially. Through this improvement, utilizing the structural design of the screw section, when the magnesium alloy slurry flows into the second-order shear and injection assembly, as the screw section rotates, the magnesium alloy slurry moves forward along the spiral propulsion groove, avoiding immediate entry into the cavity assembly. The magnesium alloy slurry entering the second-stage shearing and injection assembly is covered, ensuring a first-in, first-out injection effect and preventing slurry accumulation in the assembly. This also ensures uniform heating of the slurry, guaranteeing the quality of the molding process. Furthermore, the screw design promotes forward flow of the slurry during screw rotation, preventing backflow towards the cooling conduit assembly. Simultaneously, the screw rotation during the second-stage shearing and injection assembly's reception of the slurry further facilitates the flow of the slurry. This design propels the magnesium alloy slurry towards the cavity assembly, preventing slurry retention and blockage. This reduces the need for one-way valves on the cooling duct assembly, lowering their production costs. Furthermore, the screw design allows the injection screw to inject the magnesium alloy slurry closer to the cavity assembly, resulting in more thorough injection and reduced secondary shearing and residue in the injection assembly. This facilitates efficient slurry utilization and subsequent cleaning. Simultaneously, the moving seal between the piston and the injection channel ensures complete slurry injection and prevents... To prevent magnesium alloy slurry from seeping or overflowing between the piston and the injection channel, the design aims to avoid this issue. While the piston may seep into the side furthest from the screw, the continuous movement of the piston and injection channel during long-term use inevitably compromises their tightness, leading to seepage and overflow. The screw's structural design reduces the pressure of the magnesium alloy slurry on the piston during injection, thus lowering the seepage pressure and reducing the required tightness of the fit between the piston and injection channel. This reduces the likelihood of seepage and overflow, improving the equipment's safety.

[0028] As an improvement of the present invention, the cooling channel is arranged perpendicular to the injection channel, and the injection channel is provided with a feed port connected to the cooling channel. The feed port is arranged along the rotation tangent direction of the screw section. Through this improvement, the second-stage shearing and injection components can receive magnesium alloy slurry more smoothly and faster, and the magnesium alloy slurry is less likely to form a vortex or accumulate at the feed port.

[0029] As an improvement of the present invention, the injection screw is further provided with an injection section, which is located at one end of the screw section near the cavity. A connecting rod is provided between the injection section and the screw section, and a check ring is movably sleeved on the connecting rod. The outer diameter of the connecting rod matches the inner diameter of the check ring. The connecting rod has multiple material passage grooves on its circumference for material passage. Through this improvement, the design of the check ring can prevent the backflow of magnesium alloy slurry. When magnesium alloy slurry is injected into the cavity assembly, the check ring moves towards the cavity assembly, and the magnesium alloy slurry... The material is injected sequentially through the gap between the check ring and the screw section and the feed groove. When the second-stage shearing and injection assembly receives the magnesium alloy slurry from the cooling duct assembly, the injection screw retracts. Due to the vacuum low pressure caused by the retraction, the magnesium alloy slurry will flow back. At this time, the check ring moves towards the screw section and blocks it to prevent the magnesium alloy slurry from flowing back. The outer diameter of the connecting rod matches the inner diameter of the check ring, which can ensure the coaxiality of the connecting rod and the check ring and ensure that the check ring will not swing or deviate during the movement, making the injection and material receiving process more stable.

[0030] As an improvement of the present invention, the injection section is provided with a guide groove designed along the axial direction, the check ring is provided with a guide block that cooperates with the guide groove, and the check ring is also provided with a stop block arranged in the same direction as the guide block. The stop block abuts against the injection section to form a material passage between the injection section and the check ring. The injection section is also provided with multiple material passage holes. Through the improved design of the guide groove and the guide block, the relative movement between the check ring and the injection head can be ensured to move along the axial direction without relative rotation, thus ensuring the synchronicity of the rotation of the injection head and the check ring. The design of the material passage hole can ensure the injection of magnesium alloy slurry during injection and avoid blockage between the injection head and the check ring. The design of the material passage hole can ensure the injection rate of magnesium alloy slurry and reduce material retention.

[0031] As an improvement of the present invention, a sealing ring is provided on the outer side of the check ring, the sealing ring is provided with an adjustment gap, and the check ring is provided with a mounting groove for mounting the sealing ring. The mounting groove is provided with a control hole. Through this improvement, the high pressure during injection can be used to expand the sealing ring by utilizing the pressure transmission of the control hole, thereby achieving a tight fit between the sealing ring and the injection channel. This ensures the sealing performance between the sealing ring and the injection channel during injection, preventing the alloy mixture fluid from flowing back through the gap between the check ring and the injection channel. When receiving the alloy mixture fluid, the pressure decreases, the sealing ring contracts, and a gap is formed between the sealing ring and the injection channel, preventing rotational and movement friction between the check ring and the injection channel.

[0032] As an improvement of the present invention, the control hole includes a first control hole and a second control hole. The first control hole is located at the end of the check ring near the injection head, and the second control hole is located at the end of the check ring away from the injection head. The first control hole is inclined from the inside out, from the injection head towards the spiral propulsion groove, and the second control hole is arranged radially along the connecting rod. Through this improvement, the design of the first control hole can make the pressure formed on the sealing ring more stable, without impact pressure, thereby avoiding instantaneous resistance of the sealing ring and ensuring the stability of the sealing ring. The second control hole is subjected to less impact and only needs to ensure the sealing effect of the sealing ring. Therefore, a radial design is adopted to reduce the pressure stroke and quickly achieve the sealing effect. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0034] Figure 2 This is a cross-sectional view of the connection structure between the feed inlet and the screw section of the present invention.

[0035] Figure 3 This is a schematic diagram of the cross-sectional structure of the connection between the feed inlet and the screw section of the present invention.

[0036] Figure 4 This is a schematic diagram of the connection structure between the injection section and the check ring of the present invention.

[0037] Figure 5 This is a schematic diagram of the cross-sectional structure of the connecting rod and the check ring of the present invention.

[0038] Figure 6 This is a schematic diagram of the injection unit and connecting rod structure of the present invention.

[0039] Figure 7 This is a schematic diagram of the anti-reverse ring structure of the present invention.

[0040] Figure 8 This is a cross-sectional schematic diagram of the connection structure between the injection section and the check ring of the present invention.

[0041] Figure 9 This is a process flow diagram of the present invention.

[0042] Figure 10 This is a pure liquid phase or extremely low solid phase grain diagram of the magnesium alloy slurry at the end of the first-stage material processing assembly of the present invention.

[0043] Figure 11 This is a diagram of the semi-solid primary crystal grains of the magnesium alloy slurry of the present invention in the cooling conduit assembly.

[0044] Figure 12 This is a diagram of the spheroidal semi-solid grains of the magnesium alloy slurry after spheroidization in a second-order shearing and injection assembly according to the present invention.

[0045] Figure 13 This is a diagram of the spheroidized semi-solid grains in Embodiment 1 of the present invention.

[0046] Figure 14 This is a diagram of the spheroidized semi-solid grains in Embodiment 2 of the present invention.

[0047] Figure 15 This is a diagram of the spheroidized semi-solid grains in Embodiment 3 of the present invention.

[0048] Figure 16 This is a diagram of the spheroidized semi-solid grains in Embodiment 4 of the present invention.

[0049] Figure 17 This is a semi-solid grain diagram of Comparative Example 1 of the present invention.

[0050] Figure 18 This is a semi-solid grain diagram of Comparative Example 2 of the present invention.

[0051] The diagram shows: 1. First-stage material processing assembly, 1.1. Material processing channel, 1.2. Material processing screw, 1.3. Material processing heater, 2. Cooling conduit assembly, 2.1. Cooling channel, 2.2. Low-temperature heater, 3. Second-stage shearing and injection assembly, 3.1. Injection channel, 3.1.1. Inlet, 3.2. Injection screw, 3.2.1. Screw section, 3.2.2. Piston section, 3.2.3. Injection section, 3.2.4. Connecting rod, 3.2.5. Material passage groove, 3.2.6. Guide groove, 3.2.7. Material passage hole, 3.3. Injection heater, 4. Cavity assembly, 5. Check ring, 5.1. Guide block, 5.2. Abutment block, 5.3. Material passage, 5.4. Sealing ring, 5.4.1. Adjustment gap, 5.5. Mounting groove, 5.6. First control hole, 5.7. Second control hole. Detailed Implementation

[0052] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0053] like Figure 1As shown, a high-volume injection spherical magnesium alloy thixotropic molding device includes a first-stage material preparation assembly 1, a cooling conduit assembly 2, a second-stage shearing and injection assembly 3, and a cavity assembly 4. The magnesium alloy is sequentially processed through the first-stage material preparation assembly 1, the cooling conduit assembly 2, the second-stage shearing and injection assembly 3, and the cavity assembly 4 to complete product production. The first-stage material preparation assembly 1 includes a material preparation channel 1.1, a material preparation screw 1.2, and a material preparation heater 1.3. The material preparation screw 1.2 is located on the axis of the material preparation channel 1.1 to propel the self-compacting liquid magnesium alloy and expel air. Simultaneously, the material preparation screw 1.2 propels the magnesium alloy towards the cooling conduit assembly 2 by rotation and axial movement. The material preparation heater 1.3 is located outside the material preparation channel 1.1 to heat the material preparation channel 1.1 and maintain the temperature of the material preparation channel 1.1 above the liquidus line of the magnesium alloy. The cooling conduit assembly 2 includes a cooling channel 2.1 and a cryogenic heater 2.2. The cooling channel 2.1 is connected to the slurry channel 1.1. The cryogenic heater 2.2 is located outside the cooling channel 2.1 to ensure that the cooling conduit assembly 2 performs short-term low-subcooling operation. The first-stage slurry assembly 1 is located above the second-stage shearing and injection assembly 3. The cooling conduit assembly 2 is vertically arranged. The second-stage shearing and injection assembly includes an injection channel 3.1, an injection screw 3.2, and an injection heater 3.3. The injection channel 3.1 is connected to the cooling channel 2.1. The injection screw 3.2 is located on the axis of the injection channel 3.1 for injecting magnesium alloy into the cavity assembly 4. The injection heater 3.3 is located outside the injection channel 3.1 to heat the injection channel 3.1, ensuring the solidity of the magnesium alloy slurry and ensuring the smoothness of the injection.

[0054] A hydraulic cylinder for driving the axial movement of the chemical feed screw 1.2 and a motor for driving the rotation of the chemical feed screw 1.2 are provided at the end of the feed screw 1.2 away from the cooling duct assembly 2.

[0055] The injection screw 3.2 includes a screw section 3.2.1 and a piston section 3.2.2. The piston section 3.2.2 is in a movable sealing fit with the injection channel 3.1. The screw section 3.2.1 is located between the piston section 3.2.2 and the cavity assembly 4. The connection between the cooling channel 2.1 and the injection channel 3.1 is also located between the piston section 3.2.2 and the cavity assembly 4. The injection screw 3.2 injects magnesium alloy into the cavity assembly 4 by rotating and moving axially. At the end of the injection screw 3.2 away from the cavity assembly 4, there is a hydraulic cylinder for driving the injection screw 3.2 to move axially and a motor for driving the injection screw 3.2 to rotate.

[0056] The injection screw 3.2 includes a screw section 3.2.1 and a piston section 3.2.2. The piston section 3.2.2 is in a movable sealing fit with the injection channel 3.1. The screw section 3.2.1 is located between the piston section 3.2.2 and the cavity assembly 4. The connection between the cooling channel 2.1 and the injection channel 3.1 is also located between the piston section 3.2.2 and the cavity assembly 4. The injection screw 3.2 injects magnesium alloy slurry towards the cavity assembly 4 by rotating and moving axially. The outer diameter of the screw section 3.2.1 is in clearance fit with the inner wall of the injection channel 3.1. The clearance fit means that the screw section 3.2.1 and the injection channel 3.1 maintain rotational space, but the gap is very small. The flow of magnesium alloy slurry through the gap is small, which allows the screw section 3.2.1 to advance more fully when injecting magnesium alloy slurry without causing wear on the screw section 3.2.1 and the injection channel 3.1.

[0057] like Figure 1-3 As shown, the first-stage material preparation assembly 1 and the second-stage shearing and injection assembly 3 are arranged horizontally, with the first-stage material preparation assembly 1 located above the second-stage shearing and injection assembly 3. The cooling conduit assembly 2 is arranged vertically, with the cooling channel 2.1 arranged perpendicular to the injection channel 3.1. The injection channel 3.1 is provided with an inlet 3.1.1 connected to the cooling channel 2.1, and the inlet 3.1.1 is arranged along the rotational tangent direction of the screw section 3.2.1.

[0058] The inner diameter of the thread at one end of the screw section 3.2.1 near the piston section 3.2.2 is tapered, that is, the inner radial direction of the thread towards the piston section 3.2.2 is increased, to ensure that the alloy mixture fluid flows towards the cavity assembly 4, and to better prevent overflow and seepage.

[0059] Compared to traditional injection pistons, the piston section 3.2.2 of this invention is shorter. In traditional injection pistons, to ensure the injection volume, the piston needs to complete the stroke required for the injection volume. The stroke length needs to ensure that the piston section 3.2.2 connects to the outlet of the cooling conduit assembly 2, thus requiring an increased length of the piston section 3.2.2. This prevents the outlet of the cooling conduit assembly 2 from directly connecting to the injection rear end of the piston section 3.2.2, which would cause the magnesium alloy slurry to flow directly to the injection rear end of the piston section 3.2.2, affecting the safety of the equipment. In contrast, the injection front end of this invention uses a screw section 3.2.1 structure. The injection length of the injection screw 3.2 can be utilized by the screw section 3.2.1 structure, allowing the magnesium alloy slurry to flow directly into the screw section 3.2.1 before being injected forward. Therefore, the piston section 3.2.2 does not need a long design; it only needs to ensure that the outlet of the cooling conduit assembly 2 is located at the injection front end of the piston section 3.2.2. This also reduces the fitting length between the piston section 3.2.2 and the injection channel 3.1, reducing wear length.

[0060] like Figure 1 As shown, a tapered hole is provided at the connection between the injection channel 3.1 and the cavity assembly 4. The tapered hole is conical, and its diameter decreases from the injection screw 3.2 toward the cavity assembly 4. A buffer through hole is also provided between the tapered hole and the molding cavity. During the injection of magnesium alloy slurry, the screw rotates to push the slurry, causing it to continuously move in a self-compacting manner. However, to ensure the molding quality of the product and prevent the formation of air bubbles in the magnesium alloy slurry, the hole diameter is reduced to expel any potential air bubbles from the slurry, thus ensuring the molding quality of the alloy. The design of the buffer through hole can stabilize the injection flow of the alloy mixture and ensure the uniformity of the alloy molding.

[0061] like Figure 1 , Figure 4-8 As shown, the injection screw 3.2 is also provided with an injection section 3.2.3, which is located at the end of the screw section 3.2.1 near the cavity. A connecting rod 3.2.4 is provided between the injection section 3.2.3 and the screw section 3.2.1. A check ring 5 is movably sleeved on the connecting rod 3.2.4. The outer diameter of the connecting rod 3.2.4 matches the inner diameter of the check ring 5. The connecting rod 3.2.4 has multiple material feeding grooves on its circumference for material feeding. 3.2.5 The injection part 3.2.3 is provided with a guide groove 3.2.6 designed along the axial direction. The check ring 5 is provided with a guide block 5.1 that cooperates with the guide groove 3.2.6. The check ring 5 is also provided with a stop block 5.2 arranged in the same direction as the guide block 5.1. The stop block 5.2 abuts against the injection part 3.2.3 to form a material passage 5.3 between the injection part 3.2.3 and the check ring 5. The injection part 3.2.3 is also provided with a plurality of material passage holes 3.2.7.

[0062] The outer side of the check ring 5 is provided with a sealing ring 5.4. The sealing ring 5.4 is provided with an adjustment gap 5.4.1. The two ends of the adjustment gap 5.4.1 have overlapping areas in the radial direction to prevent overflow. The check ring 5 is provided with a mounting groove 5.5 for mounting the sealing ring 5.4. The mounting groove 5.5 is provided with a control hole. The control hole includes a first control hole 5.6 and a second control hole 5.7. The first control hole 5.6 is located at the end of the check ring 5 near the injection head, and the second control hole 5.7 is located at the end of the check ring 5 away from the injection head. The first control hole 5.6 is inclined from the inside to the outside, from the injection head towards the spiral propulsion groove. The second control hole is arranged radially along the connecting rod 3.2.4.

[0063] like Figure 1 As shown, the first-stage material processing assembly 1 includes a feed funnel, and the outlet of the feed funnel is located at the end of the material processing screw 1.2 away from the cooling duct assembly 2.

[0064] like Figure 9As shown, a thixotropic molding process for high-volume spherical magnesium alloys employs a five-stage process of continuous temperature control, shearing, and injection to transform the magnesium alloy into semi-solid spherical crystals and then form it.

[0065] Stage 1: Melting. Using the first-stage material processing component 1, the magnesium alloy particles are rapidly heated and softened in a tunnel until they melt above the liquidus line. At the same time, under the extrusion and propulsion of the material processing screw 1.2, they gradually self-compact and maintain the liquefaction process without air entrapment.

[0066] Stage 2: Near-liquid phase. At the end of the first-stage material processing component 1, the magnesium alloy is kept at 10-30°C above the near-liquid phase line for homogenization, so that the alloy structure is transformed into a pure liquid phase or a very low solid phase state.

[0067] Stage 3: Short-term low undercooling, using cooling conduit assembly 2, connected to first-stage material assembly 1, to provide short-term low undercooling conditions to the flowing magnesium melt, so that a large number of semi-solid primary crystals are rapidly generated in the near-liquid phase alloy structure.

[0068] Stage 4: Semi-solid isothermal spheroidal crystal transformation. A horizontal second-order shearing and injection assembly 3 is connected to a cooling conduit assembly 2 to provide semi-solid isothermal heat treatment to the low-subcooled magnesium alloy and the shearing action of the injection screw 3.2, so that the solid phase in the semi-solid primary crystals in the magnesium alloy structure is penetrated and surrounded by the low-melting-point liquid phase, resulting in refinement and full spheroidization, transforming into spheroidal crystal semi-solid slurry.

[0069] Stage 5: High-speed injection cooling molding. The spherical semi-solid slurry with good thixotropic properties is injected under high pressure and high speed into the cavity assembly 4 and cooled to form a dense magnesium alloy product.

[0070] In stage 1, the magnesium alloy uses a particle size between 0.5 and 5 mm and is kept dry. The magnesium alloy material needs to be selected from those with a semi-solid process window range of above 50°C.

[0071] In stage 2, the end temperature of the first-stage material preparation component 1 is set to 10-20°C above the liquidus temperature of the magnesium alloy; the rotational speed of the material preparation screw 1.2 is 100 r / min, forming a mixture as shown in the figure. Figure 10 Magnesium alloy slurry with pure liquid phase or very low solid phase grain diagram shown;

[0072] In stage 3, the low undercooling condition is 10-30°C below the liquidus temperature of the magnesium alloy. Under short-term low undercooling conditions, a large number of semi-solid primary crystals are rapidly generated in the magnesium alloy slurry, such as... Figure 11 As shown, the solid fraction reaches 40-60%;

[0073] In stage 4, the semi-solid magnesium alloy slurry is uniformly fed into the second-stage shearing and injection assembly 3, where it is again subjected to isothermal heating. The isothermal setting temperature is 5-10°C below the liquidus temperature, and the injection screw 3.2 rotates at 60 r / min. At this point, under the combined action of shearing and semi-solid isothermal heat treatment, the primary solid phase is penetrated and surrounded by the low-melting-point liquid phase, resulting in refinement and full spheroidization, transforming into an equiaxed, uniform, and fine spherical semi-solid slurry. Figure 12 As shown, the solid fraction of the magnesium alloy slurry is between 10% and 30%.

[0074] In stage 5, the mold temperature is 280℃ and the injection speed is 5m / s.

[0075] This invention uses magnesium alloy raw materials in the form of millimeter-sized particles, including but not limited to grades such as AZ91 and AM60. The particles are heated to near the liquidus line via a first-stage material preparation component 1, and then rapidly generate a large number of primary crystals through a cooling conduit component 2. These primary crystals are then transformed into a fine, spherical, semi-solid slurry via a second-stage shearing and injection component 3. Finally, the slurry is injected into a cavity component 4 and cooled to form a large magnesium alloy part. This product exhibits uniform spherical crystals and few oxide inclusions, significantly improving its mechanical and corrosion resistance.

[0076] Example 1, as Figure 13 As shown:

[0077] Using AZ91 magnesium particles with dimensions of 1.2mm x 1.2mm x 4mm, the raw material is fed into the first-stage material preparation assembly 1 through a feeding funnel. Under the shearing action of the 1.2mm material preparation screw at 100r / min, the magnesium alloy particles are propelled forward, compressed, and rapidly heated to 605℃, transforming the microstructure into a pure liquid phase. Subsequently, the magnesium alloy slurry flows to the cooling conduit assembly 2, where a large number of semi-solid primary crystals are rapidly generated in the magnesium alloy microstructure under short-term low supercooling conditions at 575℃, with a solid phase ratio reaching 50%. Then, the magnesium alloy slurry is pushed into the second-stage shearing and injection assembly 3, where it is transformed into an equiaxed, uniform, and fine spherical semi-solid slurry under the combined action of semi-solid isothermal heat treatment at 590℃ and shearing. Afterward, it is injected from the front end of the second-stage shearing and injection assembly 3 into the cavity assembly 4 with a mold temperature of 280℃ for cooling and molding. The injection speed is selected as 5m / s to obtain a high-density, high-performance magnesium alloy part. It has excellent formability, with fine, spherical and uniformly distributed semi-solid grains, achieving a yield strength of 170MPa, a tensile strength of 280MPa, and an elongation of 7%.

[0078] Example 2, as Figure 14 As shown:

[0079] Using AZ91 magnesium particles with dimensions of 1.2mm x 1.2mm x 4mm, the raw material is fed into the first-stage material preparation assembly 1 through a feeding funnel. Under the shearing action of the 1.2mm material preparation screw at 100r / min, the magnesium alloy particles are propelled forward, compressed, and rapidly heated to 605℃, transforming the microstructure into a pure liquid phase. Subsequently, the magnesium alloy slurry flows to the cooling conduit assembly 2, where a large number of semi-solid primary crystals are rapidly generated in the magnesium alloy microstructure under short-term low supercooling conditions at 570℃, with a solid phase ratio reaching 60%. Then, the magnesium alloy slurry is pushed into the second-stage shearing and injection assembly 3, where it is transformed into an equiaxed, uniform, and fine spherical semi-solid slurry under the combined action of semi-solid isothermal heat treatment at 585℃ and shearing. Afterward, it is injected from the front end of the second-stage shearing and injection assembly 3 into the cavity assembly 4 with a mold temperature of 280℃ for cooling and molding. The injection speed is selected as 5m / s to obtain a high-density, high-performance magnesium alloy part. It has excellent formability, with fine, spherical and uniformly distributed semi-solid grains, achieving a yield strength of 165MPa, a tensile strength of 270MPa, and an elongation of 5.5%.

[0080] Example 3, as Figure 15 As shown:

[0081] AM60 magnesium particles with dimensions of 1.2mm x 1.2mm x 4mm are fed into the first-stage material preparation assembly 1 via a feed funnel. Under the shearing action of the 1.2mm material preparation screw at 100r / min, the magnesium alloy particles are propelled forward, compressed, and rapidly heated to 630℃, transforming the microstructure into a pure liquid phase. Subsequently, the magnesium alloy slurry flows to the cooling conduit assembly 2, where a large number of semi-solid primary crystals are rapidly generated in the magnesium alloy microstructure under short-term low supercooling conditions at 590℃, achieving a solid phase ratio of 60%. The magnesium alloy slurry is then pushed into the second-stage shearing and injection assembly 3, where it is transformed into an equiaxed, uniform, and fine spherical semi-solid slurry under the combined action of semi-solid isothermal heat treatment at 615℃ and shearing. Finally, it is injected from the front end of the second-stage shearing and injection assembly 3 into the cavity assembly 4 with a mold temperature of 250℃ for cooling and molding. The injection speed is selected as 5m / s to obtain a high-density, high-performance magnesium alloy part. The semi-solid grains are fine, fully spherical, and uniformly distributed, achieving a yield strength of 140 MPa, a tensile strength of 300 MPa, and an elongation of 15%.

[0082] Example 4, as Figure 16 As shown,

[0083] AM60 magnesium particles with dimensions of 1.2mm x 1.2mm x 4mm are fed into the first-stage material preparation assembly 1 via a feed funnel. Under the shearing action of the 1.2mm material preparation screw at 100r / min, the magnesium alloy particles are propelled forward, compressed, and rapidly heated to 630℃, transforming the microstructure into a pure liquid phase. Subsequently, the magnesium alloy slurry flows to the cooling conduit assembly 2, where a large number of semi-solid primary crystals are rapidly generated in the magnesium alloy microstructure under short-term low supercooling conditions at 602℃, with a solid phase ratio reaching 40%. The magnesium alloy slurry is then pushed into the second-stage shearing and injection assembly 3, where it is transformed into an equiaxed, uniform, and fine spherical semi-solid slurry under the combined action of semi-solid isothermal heat treatment at 620℃ and shearing. Finally, it is injected from the front end of the second-stage shearing and injection assembly 3 into the cavity assembly 4 with a mold temperature of 250℃ for cooling and molding. The injection speed is selected as 5m / s to obtain a high-density, high-performance magnesium alloy part. The semi-solid grains are fully spheroidized and uniformly distributed, achieving a yield strength of 144 MPa, a tensile strength of 300 MPa, and an elongation of 12%.

[0084] Compared with Example 1, such as Figure 17 As shown:

[0085] AZ91 magnesium particles with dimensions of 1.2mm x 1.2mm x 4mm were fed into the first-stage material preparation assembly 1 via a feed funnel. Under the shearing action of a 100r / min material preparation screw (1.2), the magnesium alloy particles were propelled forward, compressed, and rapidly heated to 605℃, transforming the microstructure into a pure liquid phase. The magnesium alloy slurry then flowed into the cooling conduit assembly 2, passing through it under non-supercooled conditions at 600℃, achieving a solid phase ratio of 10%. The magnesium alloy slurry was then pushed into the second-stage shearing and injection assembly 3, where it underwent semi-solid isothermal heat treatment at 590℃ and shearing. Finally, it was injected from the front end of the second-stage shearing and injection assembly 3 into the cavity assembly 4 at a mold temperature of 280℃ for cooling and molding. The injection speed was selected as 5m / s to obtain the magnesium alloy part. It is evident that coarse semi-solid dendritic structures still exist, causing the matrix to fracture and making it prone to brittle fracture. The yield strength is 155MPa, the tensile strength is 230MPa, and the elongation is 3%.

[0086] Comparative Example 2, such as Figure 18 As shown:

[0087] AZ91 magnesium particles with dimensions of 1.2mm x 1.2mm x 4mm are fed into the first-stage material preparation assembly 1 via a feed funnel. Under the shearing action of the 1.2mm material preparation screw at 100r / min, the magnesium alloy particles are propelled forward, compressed, and rapidly heated to 585℃, forming a semi-solid structure below the liquidus line. Subsequently, the magnesium alloy slurry flows to the cooling conduit assembly 2, where a short-term low-supercooling condition at 575℃ causes the formation of semi-solid primary crystals in the magnesium alloy slurry, achieving a solid phase ratio of 50%. The magnesium alloy slurry is then pushed into the second-stage shearing and injection assembly 3, where it undergoes a semi-solid isothermal heat treatment at 590℃ and shearing action. Finally, it is injected from the front end of the second-stage shearing and injection assembly 3 into the cavity assembly 4 at a mold temperature of 280℃ for cooling and molding. The injection speed is selected as 5m / s to obtain the magnesium alloy part. It is evident that the coarse semi-solid dendritic structure still exists, which causes the matrix to be fragmented and prone to stress concentration when subjected to deformation. The yield strength is 150 MPa, the tensile strength is 225 MPa, and the elongation is 2.8%.

[0088] Table 1

[0089]

[0090] The above description only illustrates the preferred embodiments of the present invention and should not be construed as limiting the scope of the claims. The present invention is not limited to the above embodiments, and variations in its specific structure are permitted. All modifications made within the scope of the independent claims of this invention are also within the scope of protection of this invention.

Claims

1. A large shot globular crystal magnesium alloy thixomolding process characterized by: The process employs a continuous five-stage temperature control, shearing, and injection process to transform magnesium alloy into semi-solid spherical crystals and shape them. It includes a first-stage material preparation component (1), a cooling conduit component (2), a second-stage shearing and injection component (3), and a cavity component (4). The magnesium alloy is sequentially processed through the first-stage material preparation component (1), the cooling conduit component (2), the second-stage shearing and injection component (3), and the cavity component (4) to complete product production. The first-stage material preparation component (1) includes a material preparation channel (1.1) and a material preparation screw (1. 2) and a chemical heating element (1.3), wherein the chemical screw (1.2) is located on the axis of the chemical channel (1.1) for advancing the self-compacting liquid magnesium alloy and venting air, and the chemical screw (1.2) simultaneously advances the magnesium alloy toward the cooling conduit assembly (2) by rotation and axial movement, and the chemical heating element (1.3) is located outside the chemical channel (1.1) for heating the chemical channel (1.1) and maintaining the temperature of the chemical channel (1.1) above the liquidus line of the magnesium alloy; Stage 1: Melting. Using a first-stage material processing component (1), the magnesium alloy particles are rapidly heated and softened in a tunnel until they melt above the liquidus line. At the same time, under the extrusion and propulsion of the material processing screw (1.2), they gradually self-compact and maintain the liquefaction without air entrainment. Stage 2: Near liquid phase, at the end of the first-stage material preparation component (1), the end temperature of the first-stage material preparation component (1) is set to 10-20℃ above the liquidus temperature of the magnesium alloy for homogenization, so that the alloy structure is transformed into a pure liquid phase or a very low solid phase state; the rotation speed of the material preparation screw (1.2) is 100r / min. Stage 3: Short-term low undercooling, using a cooling conduit assembly (2), the cooling conduit assembly (2) includes a cooling channel (2.1) and a low-temperature heater (2.2), the cooling channel (2.1) is connected to the material channel (1.1), the low-temperature heater (2.2) is located outside the cooling channel (2.1) to ensure that the cooling conduit assembly (2) performs short-term low undercooling operation, the first-stage material assembly (1) is located above the second-stage shearing and injection assembly (3), the cooling conduit assembly (2) is vertically arranged to provide short-term low undercooling conditions to the flowing magnesium melt, so that a large number of semi-solid primary crystals are rapidly generated in the near-liquid phase alloy structure, the low undercooling condition is 10-30℃ below the liquidus temperature of the magnesium alloy; Stage 4: Semi-solid isothermal spheroidal crystal transformation, using a horizontal second-order shearing and injection assembly (3). The isothermal setting temperature of the second-order shearing and injection assembly (3) is 5-10℃ below the liquidus temperature, corresponding to a slurry solid phase ratio of 10-30%. It is connected to the cooling conduit assembly (2) and is used to provide semi-solid isothermal heat treatment and shearing action of the injection screw (3.2) to the low-cooled magnesium alloy, so that the solid phase in the semi-solid primary crystals in the magnesium alloy structure is penetrated and surrounded by the low-melting-point liquid phase, resulting in refinement and full spheroidization, transforming into spheroidal semi-solid slurry; the second-order shearing and injection assembly (3) includes an injection channel (3.1), an injection screw (3.2) and an injection heater (3.3). The injection screw (3.2) rotates at 60 r / min. The injection channel (3.1) is connected to the cooling channel (2.1). The injection screw (3.2) is located on the axis of the injection channel (3.1) and is used to inject into the cavity assembly ( 4) Injection of magnesium alloy: The injection heater (3.3) is used to heat the injection channel (3.1) to ensure the solidity of the magnesium alloy slurry and the smoothness of the injection. The injection screw (3.2) includes a screw part (3.2.1) and an injection part (3.2.3) is also provided on the injection screw (3.2). The injection part (3.2.3) is located at one end of the screw part (3.2.1) near the cavity. The injection part (3.2.3) and the screw... A connecting rod (3.2.4) is provided between parts (3.2.1). A check ring (5) is movably sleeved on the connecting rod (3.2.4). The outer diameter of the connecting rod (3.2.4) matches the inner diameter of the check ring (5). Multiple material passage grooves (3.2.5) for material passage are provided on the circumference of the connecting rod (3.2.4). A sealing ring (5.4) is provided on the outer side of the check ring (5). An adjustment gap is provided on the sealing ring (5.4). 5.4.1) The check ring (5) is provided with a mounting groove (5.5) for installing a sealing ring (5.4). The mounting groove (5.5) is provided with a control hole. The control hole includes a first control hole (5.6) and a second control hole (5.7). The first control hole (5.6) is located at the end of the check ring (5) near the injection head, and the second control hole (5.7) is located at the end of the check ring (5) away from the injection head. The first control hole (5.6) is inclined from the inside to the outside, from the injection head to the spiral propulsion groove. The second control hole is arranged radially along the connecting rod (3.2.4). Stage 5: High-speed injection cooling molding. The spherical semi-solid slurry with good thixotropic properties is injected under high pressure and high speed and filled into the cavity assembly (4) for cooling molding. The mold temperature is 280℃ and the injection speed is 5m / s to form a dense magnesium alloy product.

2. A thixomolding process for large shot size globular crystal magnesium alloys according to claim 1, characterized in that: In stage 1, the magnesium alloy uses a particle size between 0.5 and 5 mm and is kept dry. The magnesium alloy material needs to be selected from those with a semi-solid process window range of above 50°C.

3. The thixotropic molding process for large-volume spherical magnesium alloys according to claim 1, characterized in that: The injection screw (3.2) includes a piston part (3.2.2), which is in a movable sealing fit with the injection channel (3.1). The screw part (3.2.1) is located between the piston part (3.2.2) and the cavity assembly (4). The connection between the cooling channel (2.1) and the injection channel (3.1) is also located between the piston part (3.2.2) and the cavity assembly (4). The injection screw (3.2) simultaneously injects magnesium alloy toward the cavity assembly (4) by rotating and moving axially.

4. The thixotropic molding process for large-volume spherical magnesium alloys according to claim 3, characterized in that: The cooling channel (2.1) is arranged perpendicular to the injection channel (3.1). The injection channel (3.1) is provided with a feed port (3.1.1) connected to the cooling channel (2.1). The feed port (3.1.1) is arranged along the rotational tangent direction of the screw section (3.2.1).

5. The thixotropic molding process for large-volume spherical magnesium alloys according to claim 1, characterized in that: The injection section (3.2.3) is provided with a guide groove (3.2.6) designed along the axial direction. The check ring (5) is provided with a guide block (5.1) that cooperates with the guide groove (3.2.6). The check ring (5) is also provided with a stop block (5.2) arranged in the same direction as the guide block (5.1). The stop block (5.2) abuts against the injection section (3.2.3) to form a material passage (5.3) between the injection section (3.2.3) and the check ring (5). The injection section (3.2.3) is also provided with a plurality of material passage holes (3.2.7).

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