Rotary backward extrusion forming method for weakly textured, equiaxed fine-grained aluminum alloy cylindrical members

Abstract

The application relates to a rotary backward extrusion forming method of a weak-texture equiaxed fine-grain aluminum alloy cylindrical member. The technical problem that the weak-texture equiaxed fine-grain aluminum alloy cylindrical member cannot be prepared by the existing processing means is solved. The technical scheme is as follows: the rotary backward extrusion forming method has the forming step that: 1) the outer diameter of the cylindrical blank is Phi 190-270 mm, the center through hole diameter is Phi 40-120 mm, the height is 100-180 mm, and the top of the cylinder is provided with a transition concave table; 2) firstly, the cylindrical blank and the die are preheated, the male die, the male die pad, the female die, the female die pad and the cylindrical blank are put into a box-type heating furnace to be preheated at 460-480 DEG C for 12-24 hours, after the preheating is completed, the male die pad, the male die, the female die and the female die pad are installed and fixed on a rotary extrusion machine, and then the preheated cylindrical blank is pressed into the female die; 3) rotary backward extrusion forming is carried out, and finally an aluminum alloy cylindrical member with a bottom thickness of about 25-30 mm, a height of 250-350 mm and a wall thickness of 13-16 mm is formed.

Description

Technical Field

[0001] This invention belongs to the field of metal plastic processing technology, specifically relating to a rotary reverse extrusion forming method for a weakly textured equiaxed fine-grained aluminum alloy cylindrical component. Background Technology

[0002] Hot-deformed aluminum alloys come in many varieties, mainly including sheets, extruded bars, and wheel rims. Sheets are characterized by a fibrous structure (approximately 20-50 µm wide) and strong deformation texture, which leads to limitations in their strength and toughness, as well as significant anisotropy in quasi-static and fatigue properties. Research results on hot-deformed extruded 7075 aluminum alloy bars show that these bars exhibit a distinct fibrous structure, with elongated grains (approximately 20-100 µm wide); simultaneously, these extruded bars possess relatively strong... <111> Deformed texture and relatively weak <001> Recrystallization texture leads to significant anisotropy in the quasi-static and fatigue mechanical properties. Hot deformation methods for aluminum alloy rims (cylindrical parts) mainly include forging and spinning. However, aluminum alloy rims easily form strong deformation textures and coarse fibrous structures during hot deformation (the fiber width of existing produced rims is approximately 20-40µm). Large cold deformation annealing can form equiaxed fine grains in aluminum alloys, but dynamic recovery is generally dominant; for larger workpieces, cold deformation is generally not feasible due to the large deformation force. In summary, existing hot-deformed aluminum alloy components all exhibit coarse fibrous structures, necessitating the development of a new deformation technology that can form a weakly textured equiaxed fine-grained structure to improve the strength and toughness of hot-deformed aluminum alloys and reduce their anisotropy in mechanical properties.

[0003] Researchers have proposed a novel rotary reverse extrusion deformation method by combining traditional reverse extrusion deformation and rotational deformation, and have conducted related studies using a thermal simulation testing machine. Unlike the smooth cylindrical punch of traditional reverse extrusion, the punch in rotary reverse extrusion deformation has through grooves or segmented grooves, which can induce more shear deformation in the metal. Numerical simulation studies of rotary reverse extrusion cylindrical parts from solid billets show that rotation introduces an eddy current velocity field; microstructure evolution characteristics show that with the increase of the number of rotations, the range of fine-grained regions in the wall and bottom gradually increases, while the texture is weakened, but the thickness of the large plastic deformation region caused by rotation itself is only a few hundred micrometers.

[0004] High-pressure torsion is a method for preparing fine-grained bulk materials using severe plastic deformation (SPD) technology. It uses compression torsion to deform disc-shaped billets to obtain fine and ultrafine grains. This shows that rotational loading is beneficial for forming equiaxed fine-grained structures, which cannot be achieved by other plastic processing methods. However, the alloys prepared by this compression-rotation loading method are small in size and are in the form of thin sheets with a thickness of only about 1 mm. This is because the area far from the contact surface of rotational extrusion cannot be violently agitated to achieve large plastic deformation. Therefore, this method cannot be used to prepare large-sized parts.

[0005] The above research shows that it is impossible to obtain a thick, weakly textured, equiaxed fine-grained microstructure using solid blanks and rotary reverse extrusion, and high-pressure torsion technology cannot be used to prepare large-sized parts. Summary of the Invention

[0006] The purpose of this invention is to solve the technical problem that existing processing methods cannot prepare weakly textured equiaxed fine-grained aluminum alloy cylindrical components, and to provide a rotary reverse extrusion forming method for weakly textured equiaxed fine-grained aluminum alloy cylindrical components.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0008] A rotary reverse extrusion forming method for a weakly textured equiaxed fine-grained aluminum alloy cylindrical component, wherein the forming steps are as follows:

[0009] 1) The outer diameter of the cylindrical blank is Φ190-270mm, the diameter of the central through hole is Φ40-120mm, and the height is 100-180mm. The top of the cylinder has a transitional concave platform to facilitate engagement with the fan-shaped boss below the punch.

[0010] 2) First, the cylindrical billet and the die are preheated. Before extrusion deformation, the punch, punch pad, die and die pad, and cylindrical billet are placed in a box furnace and preheated at 460-480℃ for 12-24 hours. After preheating, the punch pad and punch are installed on the upper worktable of the rotary extruder, and the die and die pad are installed and fixed on the lower rotary worktable of the rotary extruder. Then, the preheated cylindrical billet is pressed into the die with several vertical rib grooves to prevent the cylindrical billet from rotating relative to the die.

[0011] 3) Rotary reverse extrusion forming: During the rotary reverse extrusion process, the punch first moves downward to contact the cylindrical blank. Then, the rotating worktable rotates, causing the die to rotate while the punch continues to move downward. The extrusion speed is selected as 0.8~1.2 mm / s, the total number of rotations is 9~11, the rotation speed is 0.3-0.6 rad / s, and the total downward distance of the punch is 100~150 mm. As the rotary extrusion proceeds, the metal on the inner surface of the cylindrical blank rotates towards the central through-hole, which gradually closes, and the bottom of the cylinder is gradually thickened. As the rotary extrusion continues, the metal on the outer surface of the cylindrical blank flows upward along the sidewall of the punch for rotary reverse extrusion deformation, ultimately forming a blank with a bottom thickness of approximately 25~30 mm and a height of 250-350 mm. Aluminum alloy cylindrical components with a wall thickness of 13-16 mm and a diameter of 1 mm; wherein the inner side of the cylinder wall and the bottom of the cylinder forms a weakly textured equiaxed fine grain region with an average grain size of 3-5 μm and a thickness of more than 7 mm; its texture intensity weakens from the initial maximum texture intensity of 12-14 to 1-2, and the outer side of the cylinder wall and the bottom of the cylinder are composed of fine fibrous crystals and coarse fibrous crystals, respectively.

[0012] Furthermore, the cylindrical blank is an aluminum alloy cylindrical blank with a through hole in the center.

[0013] The beneficial effects of this invention are:

[0014] This invention utilizes hollow blanks and forging equipment to produce cylindrical components (bottom thickness 30mm, diameter 200mm, wall thickness 15mm, height 330mm). The maximum thickness of the weakly textured equiaxed fine-grained zone on the inner side of the bottom can reach approximately half the overall wall thickness (about 7.5mm). This solves the technical problem that existing processing methods cannot produce weakly textured equiaxed fine-grained aluminum alloy cylindrical components. Therefore, the advantages of this invention are:

[0015] (1) The grain refinement effect is significantly improved, and the microstructure uniformity is excellent. This invention uses a pre-fabricated hollow billet with a fan blade-shaped punch and a concave die with vertical rib grooves to achieve a dual-coupled large strain effect of closed-hole upsetting deformation and rotational shear deformation, effectively breaking through the technical bottleneck of limited rotational reverse extrusion deformation of traditional solid billets. After forming, a weakly textured equiaxed fine-grained region with an average grain size of 3~5μm is formed on the inner side of the cylinder wall and bottom, and the thickness of the weakly textured equiaxed fine-grained region is greater than 7mm. Its texture strength has been significantly weakened, from the previous initial maximum texture strength of 12~14 to 1~2. The outer side of the cylinder wall and bottom is composed of fine fibrous crystals and coarse fibrous crystals, respectively. This completely solves the problem that existing hot working processes cannot prepare weakly textured equiaxed fine-grained aluminum alloy cylindrical components.

[0016] (2) The mechanical properties are fully optimized. After testing, the yield strength, tensile strength and elongation of the equiaxed fine grain zone of the inner side of the cylinder wall and bottom of the aluminum alloy cylindrical component prepared by the present invention are 570~590 MPa, 610~650 MPa and 20%~30%, respectively. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the rotary reverse extrusion die of the present invention;

[0018] Figure 2 This is a schematic diagram of the structure of the punch of the present invention;

[0019] Figure 3 This is a schematic diagram of the structure of the concave mold of the present invention;

[0020] Figure 4 This is a schematic diagram of the structure of the blank of the present invention;

[0021] Figure 5 This is a schematic diagram of the aluminum alloy cylindrical component structure after forming according to the present invention;

[0022] Figure 6 These are metallographic images of the inner equiaxed fine grain region of the cylinder wall and bottom of the aluminum alloy cylindrical component after forming according to the present invention.

[0023] Figure 7 These are metallographic images of the fine fibrous crystalline region on the outer side of the cylinder wall and bottom of the aluminum alloy cylindrical component after forming according to the present invention.

[0024] Figure 8 These are metallographic images of the outer wall and coarse fibrous crystalline region of the aluminum alloy cylindrical component after forming according to the present invention;

[0025] In the diagram: 1—punch pad; 2—punch; 3—ejector plate; 4—ejector rod; 5—die; 6—ejector block; 7—die pad; 8—ejector rod; 9—blank; 10—formed part; 11—boss; 12—vertical rib groove. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0027] like Figures 1-5 As shown in this embodiment, a rotary reverse extrusion forming method for a weakly textured equiaxed fine-grained aluminum alloy cylindrical component includes the following forming steps:

[0028] 1) The outer diameter of the cylindrical blank 9 is Φ200mm, the diameter of the central through hole is Φ90mm, and the height is 170mm. The top of the cylinder has a transitional recess to facilitate engagement with the fan-shaped boss 11 below the punch.

[0029] 2) First, the cylindrical billet and die are preheated. Before extrusion forming, the punch 2, punch pad 1, die 5, die pad 7, and cylindrical billet 9 are placed in a box furnace and preheated at 460-480℃ for 12-24 hours. After preheating, the punch pad 1 and punch 2 are installed on the upper worktable of the rotary extruder, and the die 5 and die pad 7 are installed and fixed on the lower rotary worktable of the rotary extruder. Then, the cylindrical billet 9 is pressed into the die 5, which has several vertical rib grooves, to prevent relative rotation between the cylindrical billet 9 and the die 5. For the specific assembly of the die, see [link to die assembly instructions]. Figure 1 ;

[0030] 3) Rotary reverse extrusion forming is performed. During the rotary reverse extrusion process, the punch 2 first moves downward to contact the cylindrical blank 9. Then, the rotating worktable rotates, causing the die 5 to rotate, while the punch 2 continues to move downward. The extrusion speed is selected as 0.8~1.2 mm / s, the total number of rotations is 9~11, the rotation speed is 0.3-0.6 rad / s, and the total downward distance of the punch 2 is 100~150 mm. As the rotary extrusion proceeds, the metal on the inner surface of the cylindrical blank rotates and converges towards the central through hole, which gradually closes, and the bottom of the cylinder is gradually thickened. As the rotary extrusion continues, the metal on the outer surface of the cylindrical blank flows upward along the side wall of the punch for rotary reverse extrusion deformation, finally forming a blank with a bottom thickness of about 25~30 mm and a height of 250-350 mm. Aluminum alloy cylindrical components with a wall thickness of 13-16 mm and a diameter of 1 mm; wherein the inner side of the cylinder wall and the bottom of the cylinder forms a weakly textured equiaxed fine grain region with an average grain size of 3-5 μm and a thickness of more than 7 mm; its texture intensity is weakened from the maximum texture intensity of 12-14 in the initial state to 1-2, and the outer side of the cylinder wall and the bottom of the cylinder is composed of fine fibrous crystals and coarse fibrous crystals, respectively.

[0031] Figures 6-8 These are metallographic images of the wall and bottom of the prepared aluminum alloy cylindrical component, taken using a Carl Zeiss Axio Imager. A2m upright metallographic microscope at 200x magnification. Figure 6 The image shows the metallographic images of the inner side of the cylinder wall and bottom. It can be seen from the image that the prepared aluminum alloy cylindrical component has an equiaxed fine grain structure with a grain size of approximately 3~5μm. Figure 7 The image shows the metallographic region of the fine fibrous crystalline area on the outer side of the cylinder wall and bottom, with a grain morphology of fine fibrous structure. Figure 8 The image shows the metallographic pattern of the coarse fibrous crystalline region on the outer side of the cylinder wall and bottom. The grain morphology is the same as that of the original microstructure.

[0032] Furthermore, the cylindrical blank 9 is an aluminum alloy cylindrical blank with a through hole in the center.

[0033] In the above embodiments, the outer diameter of the cylindrical blank can be selected between Φ190-270mm, the diameter of the central through hole can be selected between Φ40-120mm, and the height can be selected between 100-180mm. Specific Implementation

[0034] This invention uses 7075 aluminum alloy as the blank. The blank has an outer diameter of Φ200mm, a central through hole diameter of Φ90mm, and a height of 170mm. The extrusion speed is selected as 1mm / s, the number of rotations is 10, and the rotation speed is 0.5rad / s. Using the rotary reverse extrusion forming method of this invention, a large-size 7075 aluminum alloy fine-grained cylindrical component with a bottom thickness of 25mm, a cylinder height of 300mm, and a wall thickness of 15mm is finally formed.

[0035] The specific embodiments described above are merely examples to clearly illustrate the present invention and are not intended to limit the implementation of the present invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above description, and these obvious variations or modifications derived from the spirit of the present invention are still within the protection scope of the present invention.

Claims

1. A rotary reverse extrusion forming method for a weakly textured equiaxed fine-grained aluminum alloy cylindrical component, the forming steps of which are: 1) The outer diameter of the cylindrical blank is Φ190-270mm, the diameter of the central through hole is Φ40-120mm, and the height is 100-180mm. The top of the cylinder has a transitional recess to facilitate the fitting of the fan-shaped boss below the punch. 2) First, the cylindrical billet and the die are preheated. Before extrusion deformation, the punch, punch pad, die and die pad, and cylindrical billet are placed in a box furnace and preheated at 460-480℃ for 12-24 hours. After preheating, the punch pad and punch are installed on the upper worktable of the rotary extruder, and the die and die pad are installed and fixed on the lower rotary worktable of the rotary extruder. Then, the preheated cylindrical billet is pressed into the die with several vertical rib grooves to prevent the cylindrical billet from rotating relative to the die. 3) Rotary reverse extrusion forming: During the rotary reverse extrusion process, the punch first moves downward to contact the cylindrical blank. Then, the rotating worktable rotates, causing the die to rotate while the punch continues to move downward. The extrusion speed is selected as 0.8~1.2 mm / s, the total number of rotations is 9~11, the rotation speed is 0.3-0.6 rad / s, and the total downward distance of the punch is 100~150 mm. As the rotary extrusion proceeds, the metal on the inner surface of the cylindrical blank rotates towards the central through-hole, which gradually closes, and the bottom of the cylinder is gradually thickened. As the rotary extrusion continues, the metal on the outer surface of the cylindrical blank flows upward along the sidewall of the punch for rotary reverse extrusion deformation, ultimately forming a blank with a bottom thickness of approximately 25~30 mm and a height of 250-350 mm. Aluminum alloy cylindrical components with a thickness of 13-16 mm and a wall thickness of 13-16 mm; wherein the inner side of the cylinder wall and the bottom of the cylinder forms a weakly textured equiaxed fine grain region with an average grain size of 3-5 μm and a thickness of more than 7 mm; its texture intensity is weakened from the maximum texture intensity of 12-14 in the initial state to 1-2, and the outer side of the cylinder wall and the bottom of the cylinder is composed of fine fibrous crystals and coarse fibrous crystals, respectively.

2. The rotary reverse extrusion forming method for a weakly textured equiaxed fine-grained aluminum alloy cylindrical component according to claim 1, characterized in that: The cylindrical blank is an aluminum alloy cylindrical blank with a through hole in the center.

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