A method of frictionally additive manufacturing

Abstract

The application relates to the technical field of friction blanking, and discloses a friction additive blanking method, which comprises the following steps: feeding a blank along the axial direction of a floating tool head into the cavity of a mold below the floating tool head; then pre-compacting the blank; rotating the floating tool head while pressing it downward along the axial direction; separating the floating tool head from the blank along the axial direction; repeating the above steps one or more times; and the ratio alpha (H2 / H1) of the total pressing amount H2 of the floating tool head to the height H1 of the blank is between 0.35 and 0.85. The prepared blank has high internal organization density and few defects.

Description

Technical Field

[0001] This invention relates to the field of friction preform technology, specifically a method for friction additive preform production. Background Technology

[0002] Currently, document CN201810235551.4 discloses a wire-filled friction stir additive manufacturing apparatus and method. The apparatus includes a stirring pin, a tool head, a filament, and a substrate. The tool head rotates and moves on the surface of the substrate to be additively processed, and the stirring pin pushes the filament through a through-hole in the tool head for wire filling. The specific steps are as follows: first, the stirring pin is inserted into the axial through-hole of the tool head and pushed until the tip of the filament contacts the inner wall of the tool head. Then, the stirring head, consisting of the tool head and the stirring pin, is placed on the surface of the substrate to be additively processed. The tip of the filament undergoes thermoplasticization under the friction of the axial through-hole wall inside the tool head, resulting in a single-layer or multi-layer material deposition in the additive processing area. Under heavy loads, the tool head rubs against the blank, causing severe plastic deformation, but it is impossible to obtain a high-performance blank with high density and few quality defects. Summary of the Invention

[0003] The purpose of this invention is to provide a method for friction additive manufacturing of preforms to solve the problem of low internal density of preforms.

[0004] To achieve the above objectives, the present invention provides a method for friction additive manufacturing of preforms, characterized by comprising the following steps:

[0005] Step 1: Feed the blank into the cavity of the mold below the floating tool head along the axial direction of the floating tool head;

[0006] Step 2: Pre-compact the billet;

[0007] Step 3: The floating tool head rotates while being pressed downward along the axial direction;

[0008] Step 4: The floating tool head moves axially upward away from the billet;

[0009] Step 5, repeat steps 1-4 once or multiple times.

[0010] Preferably, in step 3, the floating tool head has a rotation speed of 100 rpm to 3000 rpm, a pressing speed of 0.1 mm / min to 5 mm / min, and a preform height of 0.2 mm to 3 mm.

[0011] Before starting step 2, inert gas is introduced into the floating tool head to prevent oxidation of the billet until the preparation is complete.

[0012] To further improve the quality and yield of preforms, the additive manufacturing equipment used in this invention includes an upper mold frame, a rotating mechanism, a floating tool head, and a floating mechanism. The rotating mechanism rotates radially within the inner hole of the upper mold frame. The rotating mechanism drives the floating tool head below it to rotate radially via a transmission shaft. The upper mold frame does not rotate, and the rotating mechanism is axially fixed. The transmission shaft is axially separated from the rotating mechanism with a gap. The floating mechanism is sleeved on the outside of the transmission shaft. The transmission shaft and the floating tool head slide relative to each other axially under the drive of the floating mechanism.

[0013] The floating mechanism includes a hydraulic cylinder and a bidirectional thrust angular contact bearing. The bidirectional thrust angular contact bearing is sleeved on the outside of the drive shaft, and its inner ring rotates with the drive shaft. The hydraulic cylinder includes an annular cylinder body and an annular plunger. The outer ring of the bidirectional thrust angular contact bearing is fixedly connected to the inner side of the annular cylinder body. One end of the annular plunger is slidably connected to the annular cylinder body, and the other end is fixedly connected to the upper mold frame. The annular cylinder body slides axially relative to the hydraulic cylinder body only when the rated pressure set in the hydraulic cylinder is greater than the actual bearing capacity of the floating tool head.

[0014] Furthermore, the method for friction additive manufacturing specifically includes the following steps:

[0015] Step 1: Feed the blank with powder particle size of 100um~400um along the axial direction through the internal through holes of the upper mold frame, rotating mechanism, transmission shaft and floating tool head, and deliver the powder into the slot hole of the steel plate, with the initial working pressure value set in the hydraulic cylinder.

[0016] Step 2: Inert gas is introduced into the floating tool head for protection, and the floating tool head is controlled to apply axial loading to the billet along the axial direction, so as to promote the pre-compacting and forming of the material, and radial pressure is maintained to obtain the height of the preform.

[0017] Step 3: Control the floating tool head to apply axial load to the billet along the axial direction. At the same time, the rotating mechanism drives the floating tool head to rotate at high speed and maintain radial pressure. The floating tool head adjusts the axial load and relative position in real time according to the change in billet thickness.

[0018] Step 4: The floating tool head moves axially upward away from the billet;

[0019] Step 5, repeat steps 1-4 once or multiple times.

[0020] To further improve the density of the billet structure, the ratio of the total reduction H2 of the floating tool head to the preform height H1 is set to satisfy the following formula: 0.35 < H2 / H1 < 0.85.

[0021] The beneficial effects are as follows: This invention provides a method for preparing a billet through friction additive manufacturing. During the friction additive manufacturing process, the billet undergoes severe plastic deformation under the combined action of axial pressure and rotational friction pressure, ensuring the compaction of the billet's microstructure. Furthermore, by controlling the relationship between the total reduction of the friction additive manufacturing tool head and the height of the preform, high-performance billets with high microstructure and few quality defects can be obtained, which has wide application value in materials such as aluminum alloys, magnesium alloys, and alloy steels. Traditional rigid tool heads, when dealing with thick blanks, experience large real-time deformation, which can lead to situations where the rigid tool head cannot compress the blank, causing tool head vibration. This results in the actual deformation not reaching the designed deformation amount, leading to insufficient compaction, loose structure, and lack of plasticization within the blank. Internal defects such as voids and gaps can easily occur, affecting forming performance. This invention designs a floating tool head, which can adjust its real-time downward displacement, i.e., adjust the deformation amount in real time. If the feed rate is high, the floating tool head's compression automatically decreases to ensure sufficient deformation and achieve the desired plasticization of the blank. If the feed rate is low, the floating tool head's compression automatically increases to ensure compaction and plasticization of the blank, reducing internal defects and external flash, thus improving the overall quality of the blank. The ratio α = H2 / H1 of the total compression amount H2 of the floating tool head to the preform height H1 is 0.35–0.85. Under the same ratio α, reducing the preform height H1 is beneficial for achieving a denser blank structure. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the additive manufacturing equipment in Embodiment 1.

[0023] Figure 2 Metallographic image of the aluminum alloy billet structure in Example 1;

[0024] Figure 3 Metallographic image of the aluminum alloy billet structure in Example 2;

[0025] Figure 4 This is a schematic diagram showing the total reduction H2 of the floating tool head and the preform height H1 in Examples 1 and 2;

[0026] Figure 5 This is a schematic diagram for preparing multi-layered blanks.

[0027] Reference numerals: 1. Upper mold frame; 2. Rotation mechanism; 3. Floating tool head; 4. Floating mechanism; 5. Drive shaft; 6. Screw; 7. Bidirectional thrust angular contact bearing; 8. Annular cylinder; 9. Annular plunger; 10. Double-ended stud; 11. Drive key. Detailed Implementation

[0028] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. However, the present invention is not limited to these embodiments. Any improvements made to the present invention without departing from the principle of the present invention also fall within the protection scope of the claims of the present invention.

[0029] Example 1

[0030] like Figure 1 , 2 As shown in Figures 4 and 5, a method for friction additive manufacturing employs an additive manufacturing apparatus including an upper die holder 1, a rotating mechanism 2, a floating tool head 3, and a floating mechanism 4. The lower end face of the rotating mechanism 2 is inlaid with symmetrically distributed transmission keys 11. The transmission keys 11 are fixed to the rotating mechanism 2 by screws 6, and the transmission keys 11 drive the transmission shaft 5 to rotate. The transmission shaft 5 is axially separated from the rotating mechanism 2 with a gap. The floating tool head 3 is connected below the transmission shaft 5. The rotating mechanism 2 rotates radially within the inner hole of the upper die holder 1. The rotating mechanism 2 drives the floating tool head 3 below it to rotate radially via the transmission shaft 5. The upper die holder 1 does not rotate. Under the drive of external rotational force and axial movement, the rotating mechanism 2 rotates and moves axially. The transmission shaft 5 and the floating tool head 3 slide relative to each other axially under the influence of the floating mechanism 4.

[0031] Furthermore, the floating mechanism 4 includes a hydraulic cylinder and a bidirectional thrust angular contact bearing 7. The bidirectional thrust angular contact bearing 7 is sleeved on the outside of the transmission shaft 5, and its inner ring rotates with the transmission shaft 5. The hydraulic cylinder includes an annular cylinder body 8, an annular plunger 9, and a double-ended stud 10. The outer ring of the bidirectional thrust angular contact bearing 7 is fixedly connected to the inner side of the annular cylinder body 8. One end of the annular plunger 9 is slidably connected to the annular cylinder body 8, and the other end is fixedly connected to the upper mold frame 1 through the double-ended stud 10. Only when the rated pressure set in the hydraulic cylinder is greater than the actual load-bearing capacity of the floating tool head 3 will the moving annular cylinder body 8 slide axially relative to the floating tool head 3, thereby driving the floating tool head 3 to slide axially relative to the floating tool head 3 simultaneously through the bidirectional thrust angular contact bearing 7. When the rated pressure set in the hydraulic cylinder is less than the actual load-bearing capacity of the floating tool head 3, the transmission shaft 5 and the rotating mechanism 2 are tightly axially engaged, that is, the floating tool head 3 does not slide axially relative to the floating tool head 3.

[0032] A method for preparing a preform using friction additive manufacturing includes the following specific steps:

[0033] Step 1: The blank (7A04 aluminum alloy powder) is fed axially along the internal through hole of the upper mold frame 1, the rotating mechanism 2, the transmission shaft 5 and the floating tool head 3, and the powder is transported into the steel plate slot with an inner diameter of 40mm. The particle size of the blank is about 300um. The annular cylinder 8, the annular plunger 9 and the double-ended stud 10 in the floating tool head 3 form a hydraulic cylinder. The initial working pressure set in the hydraulic cylinder is 4.8MPa.

[0034] Step 2: Then, the floating tool head 3 contacts the material at a speed of 0.5 mm / min and presses the material downward along the axis to pre-compact the material. Hold the pressure for 6 seconds to obtain a preform height H1 of 2.6 mm.

[0035] Step 3: Control the floating tool head 3 to continue axial loading at a speed of 3 mm / min, while the tool head rotates at a high speed of 1000 rpm. The total pressing amount of the floating tool head 3 is 1.5 mm, and the pressure is held for 6 seconds. The ratio α (α=H2 / H1) of the total pressing amount H2 of the floating tool head 3 to the preform height H1 is 0.58, and the first layer of additive preform is obtained.

[0036] Step 4: The floating tool head 3 moves axially upward away from the billet;

[0037] Step 5: Repeat steps 1-4 above twice to obtain a blank with a total thickness of approximately 3.3 mm.

[0038] The billet has very few flash around its perimeter, good surface forming, and high internal density.

[0039] Example 2

[0040] like Figure 1 and 3 As shown, the additive manufacturing equipment used in Example 1 differs from that used in Example 1 in that the specific steps of the friction additive manufacturing method include:

[0041] Step 1: The billet (40Cr alloy steel powder) is fed axially along the through hole inside the upper mold frame 1, the rotating mechanism 2, the transmission shaft 5 and the floating tool head 3. The billet is transported into the slot of the steel plate with an inner diameter of 40mm. The particle size of the billet is about 100um. The annular cylinder 8, the annular plunger 9 and the double-ended stud 10 inside the floating tool head 3 form a hydraulic cylinder. The initial working pressure set in the hydraulic cylinder is 5.7MPa.

[0042] Step 2: Argon gas is introduced into the floating tool head 3 for protection. Then, the floating tool head 3 contacts the material at a speed of 0.5 mm / min and presses the material downward along the axis to pre-compact the material. The pressure is held for 10 seconds to obtain a preform height H1 of 1.5 mm.

[0043] Step 3: Control the floating tool head 3 to continue axial loading at a speed of 2 mm / min, while the floating tool head 3 rotates at a high speed of 1200 rpm. The total pressing amount of the tool head is 1 mm. After holding the pressure for 10 seconds, the ratio α (α=H2 / H1) of the total pressing amount H2 of the floating tool head 3 to the preform height H1 is 0.67, and the first layer of additive preform is obtained.

[0044] Step 4: The floating tool head 3 moves axially upward away from the billet;

[0045] Step 5: Repeat steps 1-4 above twice to obtain a blank with a total thickness of approximately 3 mm.

[0046] The billet has very few flash around its perimeter, good surface forming, and high internal density.

Claims

1. A method for preparing a preform using friction additive manufacturing, characterized in that, Includes the following steps: Step 1: Feed the blank into the cavity of the mold below the floating tool head (3) along the axial direction of the floating tool head (3); Step 2: Pre-compact the billet; Step 3, the floating tool head (3) rotates while pressing down axially. The rotation speed of the floating tool head (3) is 100rpm to 3000rpm, the pressing speed is 0.1mm / min to 5mm / min, and the preform height is 0.2mm to 3mm. The total pressing amount H2 of the floating tool head (3) and the preform height H1 are set to satisfy the following formula: 0.35<H2 / H1<0.85; Step 4, the floating tool head (3) moves axially upward away from the billet; Step 5, repeat steps 1-4 once or multiple times.

2. The method for preparing a preform through triboelectric additive manufacturing according to claim 1, characterized in that: Before starting step 2, inert gas is introduced into the floating tool head (3) for protection until the preparation is complete.

3. The method for preparing a preform through triboelectric additive manufacturing according to claim 2, characterized in that: The additive manufacturing equipment includes an upper mold frame (1), a rotating mechanism (2), a floating tool head (3), and a floating mechanism (4). The rotating mechanism (2) rotates radially within the inner hole of the upper mold frame (1). The rotating mechanism (2) drives the floating tool head (3) below it to rotate radially via a transmission shaft (5). The upper mold frame (1) does not rotate, and the rotating mechanism (2) is axially fixed. The transmission shaft (5) is axially separated from the rotating mechanism (2) with a gap. The floating mechanism (4) is sleeved on the outside of the transmission shaft (5). The transmission shaft (5) and the floating tool head (3) slide relative to each other axially under the drive of the floating mechanism (4). The floating mechanism (4) includes a hydraulic cylinder and a bidirectional thrust angular contact bearing (6). The bidirectional thrust angular contact bearing (6) is sleeved on the outside of the transmission shaft (5), and its inner ring rotates with the transmission shaft (5). The hydraulic cylinder includes an annular cylinder body (7) and an annular plunger (9). The outer ring of the bidirectional thrust angular contact bearing (6) is fixedly connected to the inner side of the annular cylinder body (7). One end of the annular plunger (9) is slidably connected to the annular cylinder body (7), and the other end is fixedly connected to the upper mold frame (1). The annular cylinder body (7) will only slide axially relative to the floating tool head (3) when the rated pressure set in the hydraulic cylinder is greater than the actual bearing capacity of the floating tool head (3).

4. The method for preparing a preform using triboelectric additive manufacturing according to claim 3, characterized in that: Step 1 specifically includes: feeding a blank with a powder particle size of 100um~400um through the through holes inside the upper mold frame (1), rotating mechanism (2), transmission shaft (5) and floating tool head (3) along the axial direction, and conveying the powder into the slot hole of the steel plate, with the initial working pressure value set in the hydraulic cylinder; Step 2 specifically includes: introducing inert gas into the floating tool head (3) for protection, controlling the floating tool head (3) to axially load the billet along the axial direction, causing the material to be pre-compacted and formed, and radially maintaining pressure to obtain the height of the preform; Step 3 specifically includes: controlling the floating tool head (3) to axially load the billet along the axial direction, while the rotating mechanism (2) drives the floating tool head (3) to rotate at high speed and radially maintain pressure, and the floating tool head (3) adjusts the axial bearing capacity and relative position in real time according to the change in billet thickness; Step 4 specifically includes: the floating tool head (3) moving upward along the axial direction away from the blank; Step 5 specifically includes: repeating steps 1-4 one or more times.

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