A method for friction stir additive manufacturing of aluminum-steel composite structures

Abstract

A method for friction stir additive manufacturing of aluminum-steel composite structures, relating to the field of heterogeneous material joining, addresses the problems of high interfacial stress and low joint strength in the manufacturing of aluminum-steel composite structures. The method includes: mechanically grinding and cleaning the steel plate surface before additive manufacturing; preparing a mechanically interlocking structure on the surface to be composited; performing electrically driven silicon-magnesium co-infiltration on the steel plate surface with the mechanically interlocking structure; using friction stir additive manufacturing to deposit multiple layers of aluminum alloy to the required height; and using subtractive machining to obtain the transition joint of the aluminum-steel composite structure. This invention, through interfacial mechanical interlocking and silicon-magnesium co-infiltration metallurgical joining, alleviates the residual interfacial stress caused by the difference in thermal expansion coefficients between aluminum and steel, inhibits excessive diffusion between aluminum and steel, and avoids interfacial brittleness caused by excessive intermetallic compound formation. This invention can be applied not only to the manufacturing of aluminum-steel composite structures but also to the reliable manufacturing of aluminum-titanium composite structures, magnesium-steel composite structures, and others.

Description

Technical Field

[0001] This invention relates to the field of heterogeneous material joining technology, specifically to a method for friction stir additive manufacturing of an aluminum-steel composite structure. Background Technology

[0002] Aluminum-steel composite structures, as a typical example of dissimilar metal composite materials, are demonstrating unprecedented strategic value in contemporary industrial manufacturing. With the accelerated global energy structure transformation and the lightweighting of high-end equipment, the demand for aluminum-steel transition joints in key components such as pressurized pipelines in aerospace vehicles, anode steel claws in electrolytic aluminum smelting equipment, and battery trays in new energy vehicles is experiencing explosive growth. These composite structures organically combine the low density and high specific strength of aluminum alloys with the high stiffness and fatigue resistance of steel, achieving not only a significant weight reduction of 30%-50% but also overcoming the performance bottlenecks of single materials under extreme service environments. Taking the anode steel claws in electrolytic aluminum smelting equipment as an example, which must simultaneously withstand high-temperature environments of 250-350℃ and ultra-high current loads, the use of aluminum-steel transition structures can effectively ensure structural strength and energy savings.

[0003] Traditional aluminum-steel composite structure manufacturing technology has long been constrained by technical bottlenecks caused by differences in their physical and metallurgical properties. The lattice constants of aluminum and iron differ by as much as 28%, and in the molten state, Fe₄Al is readily formed. 13 Brittle intermetallic compounds such as Fe2Al5 are difficult to avoid in conventional fusion welding processes, causing the joint elongation to plummet to below 5%. Even with solid-state joining processes such as brazing and diffusion welding, technical challenges remain, including insufficient interfacial bonding strength and a narrow process window. More importantly, existing technologies are mostly limited to two-dimensional connections of simple-shaped parts, failing to meet the integrated manufacturing needs of modern engineering equipment for complex three-dimensional components. In the manufacturing of components with multi-chamber structures, such as the drive motor housing of new energy vehicles, traditional processes require separate machining of the aluminum heat sink and the steel load-bearing frame before secondary connection. This process separation not only reduces material utilization by more than 40% but also introduces residual stress during subsequent assembly, severely impacting the product's fatigue life.

[0004] Friction stir additive manufacturing (FSM) has opened up a new path for the breakthrough development of aluminum-steel composite structures. This technology achieves material deposition in a plastic flow state below the material's melting point through the large plastic deformation friction between a rotating stirring head and the metallic material. This solid-phase deposition characteristic effectively avoids elemental segregation defects during the welding process. More importantly, the intense plastic deformation generated by friction stir can form a unique mechanical interlocking structure at the interface of dissimilar materials, reconstructing the material's microstructure through a dynamic recrystallization process. Our team's preliminary experiments show that, under optimized process parameters, a 5-8 μm wide nano-transition layer can be formed at the aluminum / steel interface, with its microhardness gradient change reduced by more than 60% compared to traditional processes. While this mechanical interlocking mechanism significantly improves the interfacial bonding strength, relying solely on physical interlocking is still insufficient to meet the long-term service requirements under extreme load conditions. When the composite structure is subjected to alternating impact loads, microcracks may still initiate at the interface due to a lack of metallurgical bonding. This problem is particularly prominent under dynamic load conditions such as spacecraft propulsion systems.

[0005] Therefore, introducing a silicon-magnesium co-infiltration metallurgical bonding mechanism is expected to be a key breakthrough in overcoming existing technological bottlenecks. This binary co-infiltration mechanism constructs a gradient transition metallurgical bonding layer at the aluminum-steel interface, which is expected to alleviate interfacial stress. Simultaneously, combined with the mechanical interlocking structure design of the aluminum-steel interface, it can significantly improve the strength of the aluminum-steel composite structure. Against this backdrop, developing friction stir additive manufacturing technology based on interfacial mechanical interlocking and silicon-magnesium co-infiltration metallurgical bonding can not only overcome the technical barriers to high-performance bonding of dissimilar materials, but also promote end-to-end innovation in my country, from materials to manufacturing processes, in fields such as pressurized delivery pipelines for aerospace vehicles, anode steel claws for electrolytic aluminum smelting equipment, and battery trays for new energy vehicles. Summary of the Invention

[0006] To address the problems of high interfacial stress and low joint strength in the manufacturing of aluminum-steel composite structures, this invention proposes a friction stir additive manufacturing method for aluminum-steel composite structures.

[0007] The technical solution adopted by the present invention to solve the above problems is as follows:

[0008] The present invention discloses a method for friction stir additive manufacturing of an aluminum-steel composite structure, comprising the following steps:

[0009] Step 1: Perform mechanical grinding and cleaning on the surface 101 of the steel plate to be laminated before additive manufacturing;

[0010] Step 2: Prepare a mechanical interlocking structure 10101 on the surface to be composited 101, specifically including:

[0011] The steel plate 1 is placed in a space protected by an inert gas atmosphere, and a mechanical interlocking structure 10101 is made on the surface 101 of the steel plate by mechanical knurling or laser etching. The morphology of the mechanical interlocking structure 10101 is controlled by adjusting parameters such as knurling depth / number of times or laser power / defocusing amount / scanning path.

[0012] Step 3: Perform electro-driven silicon-magnesium co-permeation on the surface of a steel plate with a mechanical interlocking structure, specifically including:

[0013] A steel plate 1 with a mechanical interlocking structure is placed in a eutectic molten salt mixture of 42% KCl-58% MgCl2 (by mass fraction) protected by an inert gas atmosphere. Nano silica powder, auxiliary flux, reducing agent, etc. are added to the molten salt mixture. Pulsed electric drive is used to assist diffusion and infiltration with a carbon rod as the anode and the steel plate 1 as the cathode to achieve co-permeation of silicon and magnesium on the surface of the steel plate 10102.

[0014] Step 4: Using the friction stir additive manufacturing method, multi-layer aluminum alloy deposition is performed to the required height, specifically including:

[0015] The friction stir additive manufacturing method is used to deposit multiple layers of aluminum alloy 2 on the surface 101 of a steel plate until the desired aluminum-steel composite structure is obtained. The forming quality of the deposited aluminum alloy 2 is controlled by adjusting parameters such as feed rate, layer height, overlap between passes, rotation speed, and travel speed.

[0016] Step 5: Use machining to subtract materials to obtain the required aluminum-steel composite structure transition joint.

[0017] Furthermore, in step 1, the specific steps for grinding the steel plate surface 101 before additive manufacturing are as follows: use an angle grinder to mechanically grind the steel plate surface 101 until the surface reveals a metallic luster and is free of rust spots.

[0018] Furthermore, in step 1, the specific steps for cleaning the steel plate surface 101 before additive manufacturing are as follows: the steel plate surface 101 is wiped with anhydrous ethanol to remove oil stains, then alkaline washed in a 10% NaOH solution at 80-90°C for 10 minutes, then transferred to room temperature and acid washed with a 5% HF + 5% HCl solution for 2 minutes, and then dried after rinsing.

[0019] Furthermore, in step 2, the morphology formed by mechanical knurling or laser etching includes, but is not limited to, unidirectional grooves, multidirectional grooves, dot matrix, etc., and its structural feature size should be between 2 and 5 mm, and the depth is usually between 0.2 and 1.5 mm. The hardness of the mechanical knurling tool used should be significantly greater than that of the steel plate 1 used to manufacture the aluminum-steel composite structure.

[0020] Furthermore, in step 3, the amount of nano-silica powder added should be 5-20% (by mass fraction) of the eutectic molten salt mixture, and the auxiliary flux used may be, but is not limited to, MgF2, KF, etc., with an addition amount of 0.5-3.0% (by mass fraction). The reducing agent used may be selected from at least one of magnesium powder or silicon powder, with an addition amount of 1.0-5.0% (by mass fraction).

[0021] Furthermore, in step 3, the process parameters for pulsed electric drive assisted diffusion are: operating temperature 500–550℃, current density 50–200 mA / cm². 2 The pulse frequency is 50Hz, the duty cycle is 0.2 to 0.8, and the diffusion time is 1 to 5 hours.

[0022] Furthermore, in step 4, the tools used in friction stir additive manufacturing include a stirring head, a follower sleeve, and additive raw materials. The stirring head has a screw structure 301 with a rotation speed of 100–1200 rpm, and travels along the additive manufacturing path at a speed of 200–2000 mm / min to achieve multi-stage, multi-layer deposition. The follower sleeve is fitted onto the screw structure and does not rotate but travels synchronously with the stirring head; its working part forms a clearance fit with the screw. The additive raw materials, in the form of wires or rods, are fed into the gap between the extrusion screw structure and the working part of the follower sleeve through the feed hole on the follower sleeve. Under the action of the screw, the raw materials are extruded downwards and deposited into shape under the action of the follower sleeve's shoulder.

[0023] The beneficial effects of this invention are:

[0024] 1. This invention proposes a method for friction stir additive manufacturing of aluminum-steel composite structures. Through interfacial mechanical interlocking and silicon-magnesium co-infiltration metallurgical connection, since the thermal expansion coefficient of the silicon-magnesium co-infiltration layer is between that of aluminum and steel, it effectively alleviates the residual stress at the interface caused by the difference in thermal expansion coefficients of aluminum and steel, while suppressing excessive diffusion between aluminum and steel, and avoiding the interface brittleness caused by excessive formation of intermetallic compounds.

[0025] 2. This invention uses a 42% KCl-58% MgCl2 eutectic molten salt mixture as the reaction medium. Its working temperature is significantly lower than that of conventional NaCl-KCl eutectic molten salt, which effectively reduces the thermal damage to the base steel. This allows the prepared aluminum-steel composite structure to meet performance requirements without subsequent heat treatment, simplifying the process.

[0026] 3. The mechanical interlocking-metallurgical connection synergistic composite structure manufacturing method proposed in this invention has excellent process universality. It is not only suitable for the high-quality preparation of aluminum-steel composite structures, but can also be extended to the reliable connection of various heterogeneous material systems such as aluminum-titanium composite structures and magnesium-steel composite structures, and has broad application prospects. Attached Figure Description

[0027] Figure 1 This is a flowchart of a method for manufacturing an aluminum-steel composite structure using friction stir additive manufacturing, as described in this invention.

[0028] Figure 2 This is a schematic diagram of a method for manufacturing an aluminum-steel composite structure using friction stir additive manufacturing, as described in this invention.

[0029] Figure 3 This is a schematic diagram of the steel plate surface treatment structure of the friction stir additive manufacturing method for aluminum-steel composite structures according to the present invention.

[0030] Figure 4 This is a schematic diagram of the additive manufacturing tool used in the friction stir additive manufacturing method for an aluminum-steel composite structure as described in this invention.

[0031] In the figure, 1-steel plate, 101-steel plate surface, 10101-mechanical interlocking structure, 10102-silicon-magnesium co-diffusion metallurgical structure;

[0032] 2-Aluminum alloy;

[0033] 3-Stirring head, 301-Screw structure;

[0034] 4-Follower sleeve, 401-Feed hole, 402-Working part, 403-Shoulder;

[0035] 5-Additive manufacturing materials. Detailed Implementation

[0036] Specific implementation method one: Combining Figures 1 to 3 This embodiment describes a method for manufacturing an aluminum-steel composite structure using friction stir additive manufacturing. The specific method includes the following steps:

[0037] S1: Mechanical grinding and cleaning of the steel plate surface 101 used for making aluminum-steel composite structures before additive manufacturing;

[0038] S2: Place the steel plate 1 in a space protected by an inert gas atmosphere, and use mechanical knurling or laser etching to create a mechanical interlocking structure 10101 on the surface 101 of the steel plate. By adjusting parameters such as knurling depth / number of times or laser power / defocusing amount / scanning path, the morphology of the mechanical interlocking structure 10101 can be controlled.

[0039] S3: The steel plate 1 with mechanical interlocking structure is placed in a eutectic molten salt mixture of 42% KCl-58% MgCl2 (by mass fraction) protected by an inert gas atmosphere. Nano silica powder, auxiliary flux, reducing agent, etc. are added to the molten salt mixture. Pulsed electric drive is used to assist diffusion and infiltration with carbon rod as anode and steel plate 1 as cathode to achieve co-permeation of silicon and magnesium on the surface of steel plate 10102.

[0040] S4: Using the friction stir additive manufacturing method, multiple layers of aluminum alloy 2 are deposited on the surface 101 of the steel plate until the required aluminum-steel composite structure is obtained. The forming quality of the deposited aluminum alloy 2 is controlled by adjusting parameters such as feed rate, layer height, overlap between passes, rotation speed, and travel speed.

[0041] S5: The required aluminum-steel composite structure transition joint is obtained by machining and subtractive manufacturing.

[0042] Specific Implementation Method Two: Combining Figure 2 This embodiment describes an aluminum-steel composite structure friction stir additive manufacturing method. In step S1, the specific steps for grinding the steel plate surface 101 before additive manufacturing are as follows: the steel plate surface 101 is mechanically ground using an angle grinder until the surface shows a metallic luster and is free of rust spots.

[0043] Specific implementation method three: Combining Figure 2 This embodiment describes a method for manufacturing an aluminum-steel composite structure using friction stir additive manufacturing. The specific steps for cleaning the steel plate surface 101 before additive manufacturing in step S1 are as follows: The steel plate surface 101 is wiped with anhydrous ethanol to remove oil stains, then alkaline-washed in a 10% NaOH solution at 80-90°C for 10 minutes, subsequently transferred to room temperature and acid-washed with a 5% HF + 5% HCl solution for 2 minutes, and then dried after cleaning and rinsing.

[0044] Specific implementation method four: Combination Figure 3 This embodiment describes an aluminum-steel composite structure friction stir additive manufacturing method. In S2, the morphology formed by mechanical knurling or laser etching includes, but is not limited to, unidirectional grooves, multidirectional grooves, and dot matrix morphologies. The structural feature dimensions should be between 2 and 5 mm, and the depth is usually between 0.2 and 1.5 mm. The hardness of the mechanical knurling tool used should be significantly greater than that of the steel plate 1 used to manufacture the aluminum-steel composite structure.

[0045] Specific Implementation Method 5: In the aluminum-steel composite structure friction stir additive manufacturing method described in this implementation method, the amount of nano-silica powder added in S3 should be 5-20% (by mass fraction) of the eutectic molten salt mixture. The auxiliary flux used may be, but is not limited to, MgF2, KF, etc., and the amount added is usually 0.5-3.0% (by mass fraction). The reducing agent used may be, but is not limited to, magnesium powder, silicon powder, etc., and the amount added is usually 1.0-5.0% (by mass fraction).

[0046] Specific Implementation Method Six: In the friction stir additive manufacturing method for aluminum-steel composite structures described in this embodiment, the pulsed electric drive assisted diffusion temperature in step S3 should be set within the range of 500–550℃, and the current density should be 50–200 mA / cm². 2The pulse frequency is set to 50Hz, the duty cycle is 0.2 to 0.8, and the diffusion time is 1 to 5 hours to avoid the formation of a loose capping layer due to excessive precipitation.

[0047] Specific implementation method seven: Combining Figure 2 and Figure 4 This embodiment describes a friction stir additive manufacturing method for an aluminum-steel composite structure. The tools used in S4 comprise three parts: a stirring head 3, a follower sleeve 4, and additive raw material 5. The stirring head 3 rotates at 100-1200 rpm during the additive manufacturing process and travels along the additive manufacturing path at 200-2000 mm / min to achieve multi-layer deposition. The follower sleeve 4 does not rotate but travels synchronously with the stirring head 3. The stirring head 3 is equipped with an extrusion screw structure 301, which is clearance-fitted with the working part 402 of the follower sleeve. The additive raw material 5, in the form of wire or rod, is fed through the feed hole 401 on the follower sleeve into the gap between the extrusion screw structure 301 and the working part 402. Under the action of the screw 301, it is extruded downwards and deposited under the action of the follower sleeve shoulder 403. The feed rate, layer height, and overlap between passes should be designed to match the mass conservation relationship between the feed rate and the deposition amount.

[0048] Example

[0049] A method for friction stir additive manufacturing of an aluminum-steel composite structure, comprising the following steps:

[0050] S1: Select 30mm thick 304 austenitic stainless steel. First, use an angle grinder to mechanically grind its surface until the surface shows a metallic luster and is free of rust spots. Then, clean the surface by wiping the steel plate surface with anhydrous ethanol to remove oil stains. Then, wash it in 10% NaOH solution at 80-90℃ for 10 minutes. After that, transfer it to room temperature and acid wash it with 5% HF + 5% HCl solution for 2 minutes. After rinsing, dry it.

[0051] S2: In an argon protective atmosphere, a knurling knife with a grid knurling structure and a grid spacing of 2mm is used to knurl the surface of the stainless steel plate to a depth of 0.5mm.

[0052] S3: The mechanically knurled stainless steel plate is placed in a eutectic molten salt mixture of 42% KCl and 58% MgCl2 (by mass fraction) protected by an argon atmosphere. The molten salt mixture is further enriched with 150 g / L 10 nm silica powder, 75 g / L MgF2, 50 g / L KF, and 30 g / L 40 mesh magnesium powder, and mixed thoroughly. A pulsed electrically driven assisted diffusion process is performed using a carbon rod as the anode and the mechanically knurled stainless steel plate as the cathode, with a current density of 120 mA / cm². 2A silicon-magnesium co-diffusion layer was formed on the surface of a mechanically knurled stainless steel plate with a pulse frequency of 50Hz, a duty cycle of 0.5, and a diffusion time of 2 hours.

[0053] S4: Using the friction stir additive manufacturing method, multiple layers of aluminum alloy are deposited on the surface of the treated stainless steel plate. The aluminum alloy raw material is 6061 aluminum alloy wire with a diameter of 4mm. The additive layer height is 3mm (the first layer height is set separately to 0.5mm), the layer width is 30mm, the overlap width between passes is 5mm, the stirring head rotation speed is 1200rpm, the travel speed is 800mm / min, the wire feed rate is 4800mm / min, and the equivalent deposition rate is 9.77kg / h, until an aluminum alloy with a height of not less than 33mm is deposited on the surface of the stainless steel plate.

[0054] S5: The process involves machining and subtractive manufacturing to remove the steel plate area without aluminum alloy layer around the edges, and milling the aluminum alloy deposit layer until its height is 30mm, thus obtaining the final required aluminum-steel composite structure transition joint.

[0055] The aluminum-steel composite structure obtained by the above process is formed and quantified, without structural defects such as pores and cracks. The aluminum-steel composite uniaxial tensile specimens (with the interface located at the center of the gauge length of the tensile specimen) prepared according to GB / T 228.1-2021 and GB / T 228.2-2015 have a room temperature tensile strength of 188±5MPa and a high temperature tensile strength of 66±2MPa at 250℃.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent substitutions, and improvements made to the above embodiments without departing from the scope of the present invention, based on the technical essence of the present invention and within the spirit and principles of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A method for friction stir additive manufacturing of an aluminum-steel composite structure, characterized in that: The method includes the following steps: Step 1: Mechanically grind and clean the surface (101) of the steel plate (1) to be laminated before additive manufacturing; Step 2: Prepare a mechanical interlocking structure (10101) on the surface (101) of the steel plate to be laminated, specifically including: The steel plate (1) is placed in a space protected by an inert gas atmosphere. A mechanical interlocking structure (10101) is made on the surface (101) of the steel plate by mechanical knurling or laser etching. The morphology of the mechanical interlocking structure (10101) is controlled by adjusting the knurling depth / number of times or the laser power / defocusing amount / scanning path parameters. Step 3: Perform electrically driven silicon-magnesium co-permeation on the surface (101) of the steel plate with a mechanical interlocking structure, specifically including: A steel plate (1) with a mechanical interlocking structure is placed in a eutectic molten salt mixture of 42% KCl-58% MgCl2 protected by an inert gas atmosphere. Nano silica powder, auxiliary flux and reducing agent are added to the molten salt mixture. Pulse electric drive is used to assist diffusion by using a carbon rod as the anode and the steel plate (1) as the cathode to realize the silicon-magnesium co-diffusion metallurgical structure (10102) on the surface of the steel plate. Step 4: Using the friction stir additive manufacturing method, multi-layer aluminum alloy deposition is performed to the required height, specifically including: The friction stir additive manufacturing method is used to deposit multiple layers of aluminum alloy (2) on the surface (101) of a steel plate until the desired aluminum-steel composite structure is obtained. The forming quality of the deposited aluminum alloy (2) is controlled by adjusting the parameters of feeding rate, layer height, overlap between passes, rotation speed and travel speed. Step 5: Use machining to subtract materials to obtain the required aluminum-steel composite structure transition joint.

2. The method for manufacturing an aluminum-steel composite structure using friction stir additive manufacturing according to claim 1, characterized in that: In step 1, the specific steps for grinding the steel plate surface (101) before additive manufacturing are as follows: use an angle grinder to mechanically grind the steel plate surface (101) until the surface shows a metallic luster and is free of rust spots.

3. The method for manufacturing an aluminum-steel composite structure using friction stir additive manufacturing according to claim 1, characterized in that: In step 1, the specific steps for cleaning the steel plate surface (101) before additive manufacturing are as follows: the steel plate surface (101) is wiped with anhydrous ethanol to remove oil stains, then alkaline washed in 10% NaOH solution at 80-90℃ for 10 minutes, then transferred to room temperature and acid washed with 5% HF + 5% HCl solution for 2 minutes, and then dried after rinsing.

4. The method for manufacturing an aluminum-steel composite structure using friction stir additive manufacturing according to claim 1, characterized in that: In step 2, the morphology formed by mechanical knurling or laser etching includes, but is not limited to, unidirectional grooves, multidirectional grooves, and lattice morphology. The structural feature dimensions should be between 2 and 5 mm, and the depth is usually between 0.2 and 1.5 mm. The hardness of the mechanical knurling tool used should be significantly greater than that of the steel plate used to manufacture the aluminum-steel composite structure (1).

5. The method for manufacturing an aluminum-steel composite structure using friction stir additive manufacturing according to claim 1, characterized in that: In step 3, the amount of nano-silica powder added should be 5-20% of the eutectic molten salt mixture. The auxiliary flux used may be, but is not limited to, MgF2 or KF, and the amount added is 0.5-3.0%. The reducing agent used may be selected from at least one of magnesium powder or silicon powder, and the amount added is 1.0-5.0%.

6. The method for manufacturing an aluminum-steel composite structure using friction stir additive manufacturing according to claim 1, characterized in that: In step 3, the process parameters for pulsed electric drive assisted diffusion are: operating temperature 500–550℃, current density 50–200 mA / cm². 2 The pulse frequency is 50Hz, the duty cycle is 0.2 to 0.8, and the diffusion time is 1 to 5 hours.

7. The method for manufacturing an aluminum-steel composite structure using friction stir additive manufacturing according to claim 1, characterized in that: In step 4, the tools used in friction stir additive manufacturing include a stirring head (3), a follower sleeve (4), and additive raw material (5). The stirring head (3) is equipped with a screw structure (301) with a rotation speed of 100-1200 rpm, and moves along the additive manufacturing path at a speed of 200-2000 mm / min to achieve multi-layer deposition. The follower sleeve (4) is fitted on the screw structure (301). The follower sleeve (4) does not rotate but moves synchronously with the stirring head (3), and its working part (402) forms a clearance fit with the screw structure (301). The additive raw material (5), in the form of wire or rod, is fed into the gap between the extrusion screw structure (301) and the working part (402) of the follower sleeve through the feed hole (401) on the follower sleeve. Under the action of the screw, it is extruded downward and extruded and deposited into shape under the action of the follower sleeve shoulder (403).

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