A near-net-shape forming process and device for cylindrical parts with inner and outer ring ribs

Abstract

The present invention discloses a near-net-shape forming process and device for a cylindrical part with inner and outer ring ribs, which belongs to the technical field of metal plastic forming processing. The near-net-shape forming process includes the following steps: preparing titanium alloy powder; filling titanium alloy powder; preheating the mold and the powder as a whole; prepressing to form upper and lower outer ring ribs; radially pressing the cylinder and the inner ribs; taking out the titanium alloy green body; vacuum continuous sintering; and surface treatment. The integral forming of the titanium alloy cylindrical part with inner and outer ring ribs can be realized, and the axial pressing force and back pressure are provided by the floating die and the split punch to ensure the forming accuracy of the upper and lower outer ring ribs. The titanium alloy powder pre-filled in the die and preheated is pressed in the axial radial direction at high speed by the upper punch and the split punch with rib grooves to form a green body, and then the powder green body is sintered and densified by the continuous sintering process to realize the efficient near-net-shape forming of the complex structure, and solve the problems of high cost, long forming cycle, low material utilization rate and many welding joints of the traditional process method.

Description

Technical Field

[0001] The invention belongs to the technical field of metal plastic forming processing, and specifically relates to a near-net forming process and device for a cylindrical part with inner and outer ring ribs. Background Art

[0002] Titanium alloy cylindrical parts with ring ribs are high-performance, lightweight key load-bearing structural parts for aerospace, weapons and equipment, submarines or deep-sea exploration equipment. The titanium alloy cylinder section with inner and outer ring ribs is the basic component unit of the pressure hull and the supporting skeleton of the entire deep-sea submersible. It not only provides an installation base for the manned cabin, buoyancy blocks and various equipment, but also bears the weight of the entire submersible and the huge pressure (maximum 40 to 110 atmospheres) and low temperature (average 4°C) of the deep sea water during the process of lifting and recovery, mother ship loading and sinking to the seabed. Therefore, its design and manufacturing often determine the "bottom line" of the performance and safety of the submersible. Figure 1 As shown in the figure, the titanium alloy cylinder segment is generally made of lightweight and high-strength titanium alloys such as TC4, TC4ELI (low gap TC4 alloy), Ti80 and Ti62A. A single cylinder segment has a large number of annular thin-walled internal ribs, and thicker external ribs (or flanges) are used at the connection of the cylinder segments to further strengthen the overall structure. It is a typical complex structure of difficult-to-deform materials, which brings great challenges to its high-performance and high-precision forming and manufacturing.

[0003] The existing manufacturing method of titanium alloy cylindrical parts with inner and outer ring ribs is:

[0004] (1) Casting method: The cylinder 200 and the outer ring rib 300 (connecting ring) are manufactured separately. ① First, the titanium alloy ingot is subjected to primary processing (opening and forging for more than 10 times), and then the ring ingot is prepared by heating, upsetting and punching. The ring diameter is further expanded by heating and radial rolling, and finally the ring is prepared by machining; ② The 1 / 6 to 1 / 4 cylinder shell segment is prepared by hot die forging of the forged ingot after primary processing, or the titanium alloy forged ingot after primary processing is rolled multiple times to prepare the titanium alloy thick plate, and the thick plate is hot stamped to prepare the cylinder shell segment, and the shell segment is welded to form an integral cylinder segment, and finally the annular inner rib is machined; ③ The ring and the cylinder segment are assembled and welded. In the above process, the 200 cylinder can also be divided into annular basic units 100, and the same process can be used for separate manufacturing and assembly welding. (2) Powder metallurgy method: ① Titanium alloy powder is encapsulated and hot isostatically pressed to prepare a simple structure cylinder segment; ② Remove the encapsulation and machine the hot isostatically pressed titanium alloy cylinder to produce inner and outer ring ribs with precise dimensions; ③ Assemble and weld the cylinder segments with inner and outer ring ribs.

[0005] The existing process methods have the problems of long process steps and high costs. It is difficult to form the annular rib structure of the cylindrical shell by radial rolling, resulting in low material utilization (a large amount of machining). In addition, the radial rolling process of thin-walled and large-sized circular rings is prone to various forming defects such as cracking and loss of roundness. In addition, multi-section forgings are welded together, there are many welding joints, and it is difficult to control weld defects. The residual stress after welding is large, and the joint quality stability and fatigue life are poor, which seriously restricts the application of titanium alloy cylindrical parts with inner and outer annular ribs. Summary of the invention

[0006] The patent of the present invention provides a near-net forming process and device for cylindrical parts with inner and outer ring ribs, which can realize the integral forming of titanium alloy cylindrical parts with inner and outer ring ribs, and provide axial pressing force and back pressure through a floating die and a split punch to ensure the forming accuracy of the upper and lower outer ring ribs. The titanium alloy powder pre-filled in the die and preheated by the mold is pressed axially and radially at high speed by an upper punch and a split punch with rib grooves to form a blank, and then a continuous sintering process is used to sinter and densify the powder green body to realize efficient near-net forming of complex structures, and solve the problems of high cost, long forming cycle, low material utilization rate and many welding joints in traditional process methods.

[0007] In order to solve the above technical problems, a technical solution adopted by the present invention is:

[0008] A near-net-shape forming process for a cylindrical part with inner and outer ring ribs comprises the following steps:

[0009] S1. preparing titanium alloy powder;

[0010] S2, the upper outer ring rib pressing die moves upward, titanium alloy powder is filled in the cavity between the upper outer ring rib pressing die and the split punch and die, and the upper outer ring rib pressing die moves downward for assembly;

[0011] S3, preheating the mold and powder as a whole, and stopping heating after reaching the preset temperature;

[0012] S4, applying a preset axial pressing force to the upper outer ring rib pressing die, and the lower outer ring rib pressing die provides back pressure, respectively cooperating with the concave die to pre-press and form the upper and lower outer ring ribs;

[0013] S5, the upper outer ring rib pressing die is maintained under pressure, the upper punch is impacted downward at high speed to load, an outward radial force is applied to the split punch, the split punch moves radially outward at high speed, a radial pressing force is applied to the powder to perform high-speed warm pressing and forming;

[0014] S6, after the pressure is maintained for a preset time, the upper punch moves upward to apply an inward radial force to the split punch, the split punch retracts radially inward to reset, the base moves downward, the die opens, and the titanium alloy green billet is taken out;

[0015] S7, performing vacuum continuous sintering on the titanium alloy green body to obtain a final formed part;

[0016] S8. Perform surface treatment on the formed part to obtain a near-net-shape component.

[0017] Furthermore, the steps of preparing titanium alloy powder are specifically as follows:

[0018] S1.1. Place the titanium alloy powder prepared according to the preset composition in a ball mill, add anhydrous ethanol, and wet grind for 12 to 48 hours at a ball mill speed of 300 ± 50 r / min;

[0019] S1.2, place the wet-milled mixed powder in an oven for drying, the drying time is 12±1h, and the drying temperature is 60±5℃;

[0020] S1.3. The dried mixed powder is placed in a ball mill and dry-milled at 300±50r / min. After dry-milling, it is sieved through a 200-mesh sieve to obtain a uniformly mixed powder.

[0021] Furthermore, the preset temperature for preheating the mold and the powder as a whole is 250~300℃.

[0022] Furthermore, the preset axial pressing force applied to the upper outer ring rib pressing die is not less than 200t.

[0023] Furthermore, the loading speed of the upper punch for high-speed downward impact loading is 10-30 m / s.

[0024] Furthermore, vacuum continuous sintering is carried out in a vacuum sintering furnace, the titanium alloy green body efficient densification sintering temperature is 1000~1300℃, the holding time is 30~120min, and the dehydrogenation temperature is 400~600℃.

[0025] The present invention also provides a near-net-shape forming device for a cylindrical part with inner and outer ring ribs, comprising a base, a die, an upper outer ring rib pressing die, a lower outer ring rib pressing die, a split punch and an upper punch, wherein the base is fixedly arranged at the top end of the lifting mechanism, the die comprises two matched half-dies, the outer side of each half-die is connected to the output end of the horizontal positioning mechanism, a first back pressure mechanism is arranged at the bottom of the die, the lower outer ring rib pressing die is movably embedded in the bottom end of the die and a second back pressure mechanism is arranged at the bottom, the upper outer ring rib pressing die is movably embedded in the top end of the die and the top is connected to the output end of the pressing power mechanism, the upper punch is coaxially arranged in the die and the top is connected to the output end of the high-speed impact loading mechanism, and the split punch is arranged between the die and the upper punch and is located on the top surface of the lower outer ring rib pressing die;

[0026] The split punch comprises a plurality of split dies evenly distributed around the axis of the upper punch, and a filling die movably arranged between two adjacent split dies, and rib groove sections are correspondingly provided on the outer circumferential surfaces of the split dies and the filling die;

[0027] During the downward movement of the upper punch, each split mold and the filling mold are driven to move radially outward synchronously until the outer cylindrical surface of the filling mold is correspondingly connected with the outer cylindrical surfaces of the two adjacent split molds to form a complete cylindrical surface; during the upward movement of the upper punch, each split mold and the filling mold are driven to move radially inward synchronously until the outer cylindrical surfaces of the split molds are correspondingly connected to form a continuous cylindrical surface and the filling mold is located on the inner side of the split mold.

[0028] Furthermore, inclined slide rails are fixedly provided on the inner side walls of the split mold and the filling mold respectively, and a sliding block slidably matched with the slide rails is fixedly provided on the outer circumferential surface of the upper punch.

[0029] Furthermore, a die top stop ring and an inner die stop plate are slidably connected in the upper outer ring rib pressing die. The die top stop ring is located above the split punch. When the split die and the filling die are radially retracted, the inner die stop plate is inserted between the split die and the filling die, and the side wall of the inner die stop plate is in contact with the side wall of the split die.

[0030] Furthermore, vertically arranged and mutually engaged bending grooves are provided on the opposing sides of the two half molds.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] 1. The present invention adopts a process method of powder pressing and continuous sintering to prepare a titanium alloy cylindrical part with inner and outer ring ribs. The production process is simple, the manufacturing cost is significantly reduced, and the radial loading of the shaft is realized by combining the outer ring rib pressing punch, the floating die, the punch and the split punch with rib grooves. The structure with inner and outer ring ribs can be formed in a short process and with high precision, breaking through the limitation that traditional powder pressing is only suitable for forming short shaft parts with simple structures, realizing near-net forming with little or no cutting, and greatly improving the material utilization rate;

[0033] 2. In the pressing process of the present invention, a back pressure mechanism is arranged at the bottom of the concave die and the lower outer ring rib pressing die to make the concave die float, thereby improving the filling rate of the upper and lower outer ring rib forming areas, and utilizing the back pressure at the floating concave die to ensure the density of the lower outer ring rib pressing process;

[0034] 3. The pressing process of the present invention adopts high-speed warm pressing, which has fast forming speed, strong powder deformation ability, high filling rate of inner ring ribs under the action of inertial force, high density after pressing and forming, and good mechanical properties after sintering;

[0035] 4. The present invention can realize the integral forming of titanium alloy cylindrical parts with inner and outer ring ribs, reduce welds, avoid problems such as post-weld degradation and welding residual stress, improve the structural strength and fatigue life of components, and the overall structure of the equipment is simple, which is convenient for continuous production. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1It is a schematic diagram of the welding structure of a titanium alloy cylindrical part with inner and outer ring ribs in the prior art;

[0037] Figure 2 It is a schematic structural diagram of a titanium alloy cylindrical part with inner and outer ring ribs prepared by the process and device of the present invention;

[0038] Figure 3 It is a schematic diagram of the three-dimensional structure of the near-net-shape forming device of the present invention in the extrusion forming state;

[0039] Figure 4 It is a schematic diagram of the top view of the structure of the near-net-shape forming device of the present invention in the extrusion forming state;

[0040] Figure 5 for Figure 4 Schematic diagram of the cross-sectional structure at the AA position;

[0041] Figure 6 for Figure 5 Schematic diagram of the cross-sectional structure at the middle BB position;

[0042] Figure 7 It is a three-dimensional structural schematic diagram of the near-net-shape forming device of the present invention in a powder filling state;

[0043] Figure 8 It is a three-dimensional structural schematic diagram of the near-net-shape forming device of the present invention in a powder filling state;

[0044] Fig. 9 for Figure 8 Schematic diagram of the cross-sectional structure at the CC position;

[0045] Fig.10 for Fig. 9 Schematic diagram of the cross-sectional structure at the middle DD position;

[0046] Fig.11 It is a structural schematic diagram of the near-net-shape forming device of the present invention in a state where the upper outer ring rib pressing die is removed;

[0047] Fig.12 is one of the three-dimensional structural schematic diagrams of the split mold;

[0048] Fig.13 The second schematic diagram of the three-dimensional structure of the split mold;

[0049] Fig.14 is one of the three-dimensional structural schematic diagrams of the filling mold;

[0050] Fig.15 The second schematic diagram of the three-dimensional structure of the filling mold;

[0051] Fig.16 is a schematic diagram of the three-dimensional structure of the upper punch;

[0052] Fig.17 It is a three-dimensional structural schematic diagram of the upper punch and the split module assembly state;

[0053] Fig.18 It is a three-dimensional structural schematic diagram of the upper punch and the filling die assembly state;

[0054] Fig.19 It is a schematic diagram of the three-dimensional structure of the split mold and the filling mold in a synchronous radial outward movement state;

[0055] Fig. 20 It is a schematic diagram of the three-dimensional structure of the split mold and the filling mold in a synchronous radially retracted state;

[0056] Fig.21 One of the three-dimensional structural schematic diagrams of the upper outer ring rib pressing die;

[0057] Fig. 22 The second schematic diagram of the three-dimensional structure of the upper outer ring rib pressing die;

[0058] Fig.23 is a schematic diagram of the three-dimensional structure of the die top retaining ring;

[0059] Fig.24 It is a three-dimensional structural schematic diagram of the assembly state of the die top retaining ring and the upper outer ring rib pressing die;

[0060] Fig.25 is a schematic diagram of the three-dimensional structure of the in-mold material baffle plate;

[0061] Fig.26 This is an equivalent stress distribution diagram of the titanium alloy cylindrical part after forming of the present invention;

[0062] Fig. 27 This is the equivalent strain distribution diagram of the titanium alloy cylindrical part after forming of the present invention;

[0063] Fig.28 This is a density distribution diagram of the titanium alloy cylindrical part after forming.

[0064] In the figure: 1. base; 2. concave die; 3. upper outer ring rib pressing die; 31. countersunk groove; 32. first plug hole; 33. second plug hole; 4. lower outer ring rib pressing die; 5. split punch; 51. split die; 52. filling die; 53. first slide rail; 54. second slide rail; 6. upper punch; 61. first slider; 62. second slider; 7. first back pressure mechanism; 8. second back pressure mechanism; 9. die top stop ring; 91. plug rod; 92. limit ring; 10. in-die stop plate; 100. annular base unit; 200. cylinder; 300. outer ring rib. DETAILED DESCRIPTION

[0065] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0066] It should be noted that when a component is referred to as being "mounted on" another component, it may be directly on the other component or there may be a central component. When a component is considered to be "set on" another component, it may be directly set on the other component or there may be a central component at the same time. When a component is considered to be "fixed to" another component, it may be directly fixed on the other component or there may be a central component at the same time.

[0067] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "or / and" used herein includes any and all combinations of one or more of the related listed items.

[0068] The present invention provides a near-net-shape forming process and device for a cylindrical part with inner and outer ring ribs, which is used for Figure 2 The titanium alloy cylindrical part with inner and outer ring ribs shown is axially and radially high-speed warm pressing and continuous sintering to near-net shape, realizing low-cost, high-efficiency, integrated near-net shape manufacturing of complex thin-walled high-cylinder structures.

[0069] See also Figures 3 to 25 , a near-net-shape forming device for a cylindrical part with inner and outer ring ribs, comprising a base 1, a die 2, an upper outer ring rib pressing die 3, a lower outer ring rib pressing die 4, a split punch 5 and an upper punch 6. The base 1 is fixedly arranged on the top of a lifting mechanism (such as a workbench of a punching machine), and the lifting mechanism drives the base 1 to rise, so that the upper punch 6 above it is assembled in the die 2 and ensures the coaxial arrangement; the lifting mechanism drives the base 1 to descend, so that the split punch 5 in the recovered state is vertically drawn out from the formed part. The die 2 includes two mating half-dies, and the outer side of each half-die is connected to the output end of a horizontal positioning mechanism (such as a hydraulic press), so that the two half-dies can be quickly mated and separated, and the mating state can be kept stable. Preferably, a vertically arranged and mutually interlocking bending groove is opened on the mating side of the two half-dies to reduce the overflow of the titanium alloy powder in the forming cavity during the extrusion forming process. In this embodiment, the bending groove is two continuous reverse semi-arc grooves. The die 2 is a cylindrical shell structure that penetrates from top to bottom, and circular embedding grooves are provided on the top and bottom surfaces thereof. The upper outer ring rib pressing die 3 and the lower outer ring rib pressing die 4 are both circular plates, which are movably embedded in the upper and lower circular embedding grooves of the die 2 respectively.

[0070] The upper outer ring rib pressing die 3 is movably embedded in the top of the die 2 and the top is connected to the output end of the pressing power mechanism. In this embodiment, the pressing power mechanism adopts a two-stage hydraulic cylinder, the first-stage output is used for the upper outer ring rib pressing die 3 to open upward and assemble downward, and the second-stage output is used to apply a downward axial pressing force to the top of the upper outer ring rib pressing die 3. A first back pressure mechanism 7 is provided at the bottom of the die 2, and a lower outer ring rib pressing die 4 is movably embedded in the bottom end of the die 2 and a second back pressure mechanism 8 (such as a spring group) is provided at the bottom. A second back pressure mechanism 8 (such as a butterfly spring) is provided at the bottom of the lower outer ring rib pressing die 4, so that the die 2 and the lower outer ring rib pressing die 4 are both in a floating state. The elastic coefficient of the first back pressure mechanism 7 is smaller than that of the second back pressure mechanism 8, so that after the titanium alloy powder is filled in the upper and lower circular grooves, after the axial pressing force is applied to the upper outer ring rib pressing mold 3, the die 2 and the lower outer ring rib pressing mold 4 are both moved downward, and the bottom end of the die 2 is moved downward relative to the lower outer ring rib pressing mold 4, so that the top surface of the lower outer ring rib pressing mold 4 cooperates with the top surface of the circular groove below, and the powder between the two is axially pre-pressed, and the powder forms the lower outer ring rib; at the same time, the bottom surface of the upper outer ring rib pressing mold 3 cooperates with the bottom surface of the circular groove above, and the divided material between the two is axially pre-pressed to form the upper outer ring rib, thereby ensuring the density of the upper and lower outer ring ribs during the pressing process.

[0071] The upper punch 6 is coaxially arranged in the die 2 and the top is connected to the output end of the high-speed impact loading mechanism. The split punch 5 is arranged between the die 2 and the upper punch 6 and is located on the top surface of the lower outer ring rib pressing die 4. Specifically, the split punch 5 includes four split dies 51 evenly distributed around the axis of the upper punch 6, and a filling die 52 movably arranged between two adjacent split dies 51. Rib groove sections are correspondingly provided on the outer circumferential surfaces of the split dies 51 and the filling die 52. The cross-sectional shape of the split die 51 is a sector shape approximately equal to 1 / 4 of a circle, and the corresponding central angle is less than 90°. In this way, after the four split dies 51 are radially retracted to the limit position, the outer circumferential edges of the adjacent two split dies 51 are connected to each other to form a continuous approximately cylindrical surface. In this way, during the titanium alloy powder filling stage, the powder will not directly enter the interior of the split punch 5 from the connection between the two adjacent split dies 51, which will have an adverse effect on the horizontal movement of the split die 51 in the subsequent forming process. The cross-sectional profiles of the opposite sides of the two adjacent split molds 51 are both "V" shaped, so that after the outer circumferential edges of the two adjacent split molds 51 are connected to each other, a channel with a cross-sectional shape of two parallel sides and a "V" shaped top is formed between the opposite sides. The filling mold 52 is located in the channel, and its two side walls are respectively slidably fitted with the two parallel side walls of the channel, and the outer ends of the two side walls are provided with chamfered surfaces, which are parallel to the outer end side of the channel, such as Fig.10As shown. The outer wall of the filling mold 52 is an arc-shaped surface. When the four split molds 51 are synchronously moved radially outward, the outer cylindrical surfaces are connected to each other and form a vertical gap. After the four filling molds 52 are synchronously moved radially outward to the limit position, their outer walls are connected with the outer cylindrical surfaces of the two adjacent split molds 51 to form a complete cylindrical surface. The radius of the cylindrical surface is the same as the radius of the inner wall of the formed part. The rib groove sections on the split mold 51 and the filling mold 52 are also connected to each other to form a complete annular rib groove for forming each inner annular rib on the inner wall of the formed part. The chamfered surface of the filling mold 52 is also in contact with the outer end side surface of the channel, as shown in FIG. Figure 6 shown.

[0072] The upper punch 6 is arranged on the inner side of each split mold 51 and the filling mold 52, and drives the split mold 51 and the filling mold 52 to move outward and inward in a synchronous radial direction by transmitting power. During the synchronous radial outward movement, each split mold 51 and the filling mold 52 extrude the titanium alloy powder located between the concave mold 2 and the split punch 5 at a high speed, and utilizes the strong deformation ability of the powder and the high filling rate of the inner ring rib under the action of the inertial force, so that the powder is fully filled in the rib groove, and the density after pressing and forming is high. Specifically, during the downward movement of the upper punch 6, each split mold 51 and the filling mold 52 are driven to move outward in a synchronous radial direction until the outer circumferential surface of the filling mold 52 is correspondingly connected with the outer circumferential surfaces of the two adjacent split molds 51 to form a complete cylindrical surface; during the upward movement of the upper punch 6, each split mold 51 and the filling mold 52 are driven to retract in a synchronous radial direction until the outer circumferential surfaces of each split mold 51 are correspondingly connected to form a continuous cylindrical surface, and the filling mold 52 is located on the inner side of the split mold 51.

[0073] A first inclined slide rail 53 is fixedly provided on the inner side wall of the split mold 51, a second inclined slide rail 54 is fixedly provided on the inner side wall of the filling mold 52, and a first slider 61 slidably matched with the first slide rail 53 and a second slider 62 slidably matched with the second slide rail 54 are fixedly provided on the bottom end of the outer cylindrical surface of the upper punch 6. Since the split mold 51 and the filling mold 52 are alternately adjacent in the circumferential direction, the first slider 61 and the second slider 62 are also alternately distributed on the outer cylindrical surface of the upper punch 6. A dovetail groove guide slider structure is adopted between the two groups of sliders and the slide rails, so that a wedge-shaped surface transmission structure is formed between the upper punch 6 and each of the split molds 51 and the filling mold 52. Before synchronous radial outward movement, the outer side surface of the filling mold 52 is located inside the outer side surface of the split mold 51. After synchronous radial outward movement, the outer side surface of the filling mold 52 is connected with the outer side surface of the split mold 51. Therefore, the radial outward movement distance of the filling mold 52 is greater than the radial outward movement distance of the split mold 51. Correspondingly, the slope of the first slide rail 53 is greater than the slope of the second slide rail 54. The specific slopes of the two slide rails are calculated based on the vertical movement distance of the upper punch 6 and the horizontal movement distance of the filling mold 52 and the split mold 51.

[0074] Preferably, a die top stopper ring 9 is slidably connected in the upper outer ring rib pressing die 3, and the die top stopper ring 9 is located above the split punch 5, and is used to prevent the titanium alloy powder from entering the split punch 5 from the top free position of the split punch 5 when the titanium alloy powder is filled in the cavity between the upper outer ring rib pressing die 3, the split punch 5 and the concave die 2. Specifically, a sink 31 is provided on the bottom surface of the upper outer ring rib pressing die 3, and a plurality of first plug holes 32 are provided on the edge of the sink 31, which penetrate to the top surface of the upper outer ring rib pressing die 3. The vertical cross-section of the die top stopper ring 9 is in an "L" shape, and the vertical section is located outside the horizontal section, and the top of the vertical section is provided with a plug rod 91 matching the first plug hole 32. The outer circular surface of the vertical section of the die top stopper ring 9 is slidably fitted with the inner circular surface of the sink 31, and the plug rod 91 is movably plugged into the first plug hole 32. Before filling the titanium alloy powder, the upper outer ring rib pressing die 3 moves upward to the top of the die 2, and the die top stopper ring 9 stays on the split punch 5 under the action of its own gravity, and the outer circumferential surface of the vertical section of the die top stopper ring 9 is located outside the outer surface of the split punch 5. In the process of filling the titanium alloy powder into the forming cavity through the top edge of the die 2, the vertical section of the die top stopper ring 9 forms an isolation zone at the top of the split punch 5, and the titanium alloy powder will not enter the inside of the split punch 5 from the top empty position of the split punch 5. In the subsequent inner ring rib extrusion forming process, since the horizontal section of the die top stopper ring 9 is in sliding contact with the top surface of the split punch 5, it will not cause any interference to the horizontal movement of the split mold 51 and the filling mold 52. In order to prevent the die top stopper ring 9 from falling off from the upper outer ring rib pressing die 3 during the upward movement of the upper outer ring rib pressing die 3, the top ends of each plug-in rod 91 are also fixedly connected with a limit ring 92.

[0075] Further preferably, an in-mold material retaining plate 10 is slidably connected in the upper outer ring rib pressing die 3. Specifically, the cross-sectional shape of the in-mold material retaining plate 10 is "V"-shaped, and there are 4 in total. Four second plug-in holes 33 matching the cross-sectional shape of the in-mold material retaining plate 10 are provided on the upper outer ring rib pressing die 3, and the in-mold material retaining plate 10 is movably plugged into the second plug-in holes 33. A vertical positioning mechanism (such as a synchronous belt transmission mechanism) is provided on the top surface of the upper outer ring rib pressing die 3, which is used to drive the vertical lifting and positioning of the in-mold material retaining plate 10. When the split mold 51 and the filling mold 52 are in the radially retracted state, since the "V"-shaped channel formed by the adjacent positions of the two adjacent split molds 51 has a through area with the rib forming groove, during the titanium alloy powder filling process, the powder can easily enter the "V"-shaped channel through the through area, which is not conducive to subsequent extrusion forming. Therefore, before filling the titanium alloy powder, the mold inner material retaining plate 10 is inserted between the split mold 51 and the filling mold 52, and the side wall of the mold inner material retaining plate 10 is in contact with the side wall of the split mold 51. Fig.15As shown, the titanium alloy powder can be prevented from entering the split punch 5. In the subsequent process of heating and pre-pressing the internal titanium alloy powder to form the upper and lower outer ring ribs, the in-mold material retaining plates 10 are all in the aforementioned plug-in state. After the initial high-temperature extrusion, the titanium alloy powder no longer has the initial loose flow performance. At this time, the in-mold material retaining plates 10 are raised to the highest position by the vertical positioning mechanism until its bottom end is located above the top of the split punch 5, which will not cause motion interference to the subsequent synchronous radial outward movement of the split mold 51 and the filling mold 52. In order to facilitate the synchronous lifting and lowering of the four in-mold material retaining plates 10, the tops of the four in-mold material retaining plates 10 are commonly fixedly connected with a lifting connection ring, and the lifting connection ring is fixedly connected to the power output end of the vertical positioning mechanism.

[0076] A near-net-shape forming process for a cylindrical part with inner and outer ring ribs comprises the following steps:

[0077] S1. Prepare titanium alloy powder. The specific steps are:

[0078] S1.1. Place the titanium alloy powder prepared according to the preset composition in a ball mill, add anhydrous ethanol, and wet-mill for 12 to 48 hours at a ball mill speed of 300 ± 50 r / min.

[0079] S1.2, place the wet-milled mixed powder in an oven for drying, the drying time is 12±1h, and the drying temperature is 60±5℃;

[0080] S1.3. The dried mixed powder is placed in a ball mill and dry-milled at 300±50r / min. After dry-milling, it is sieved through a 200-mesh sieve to obtain a uniformly mixed powder.

[0081] In this embodiment, the titanium alloy powder is composed of Ti powder and AlV powder, wherein the Ti powder has a particle size of 50-100 μm and a mass fraction of 90%, the AlV powder has a particle size of 50-100 μm and a mass fraction of 10%, and the particle size of the mixed powder after ball milling is controlled to be no greater than 10 μm at D50. The amount of anhydrous ethanol added accounts for about 1 / 3 of the volume of the container, and the total volume of the titanium alloy powder and the steel balls after addition does not exceed 2 / 3 of the container.

[0082] S2, the upper outer ring rib pressing die 3 moves upward, and the titanium alloy powder prepared above is filled in the cavity between the upper outer ring rib pressing die 3, the split punch 5 and the die 2, and the upper outer ring rib pressing die 3 moves downward for assembly. This operation completes the natural filling of the titanium alloy powder in the forming cavity, ensuring that the powder fills the forming cavity completely. Since the upper outer ring rib pressing die 3 needs to complete the pressing of the upper and lower outer ring ribs in the subsequent steps, the top of the upper outer ring rib pressing die 3 is connected to the output end of the pressing power mechanism (such as a secondary hydraulic cylinder), and the primary output is used for the upper outer ring rib pressing die 3 to open upward and assemble downward, and the secondary output is used to apply a downward axial pressing force to the top of the upper outer ring rib pressing die 3.

[0083] S3. Preheat the mold and powder as a whole, and stop heating after reaching the preset temperature. In this embodiment, the preset temperature is 250~300℃. Twelve heating bodies are evenly distributed in the circumferential direction inside the die 2 to ensure the uniformity of heat distribution; a thermocouple is set every 120 degrees in the center of the cylinder, connected to the temperature feedback control system to ensure the reliability of heating. Preferably, a high-temperature resistant heat-insulating layer (such as asbestos) is set on the outside of the die 2 to reduce energy loss and ensure that the temperature environment in the mold is in a preset state during the forming process.

[0084] S4, the pressing power mechanism applies a preset axial pressing force to the upper outer ring rib pressing die 3, and the lower outer ring rib pressing die 4 provides a back pressure, and cooperates with the concave die 2 to pre-press and form the upper and lower outer ring ribs. In this embodiment, the preset axial pressing force applied to the upper outer ring rib pressing die is 200t, the bottom of the concave die 2 is provided with a first back pressure mechanism 7 (such as a spring group), and the bottom of the lower outer ring rib pressing die 4 is provided with a second back pressure mechanism 8 (such as a butterfly spring), so that the concave die 2 and the lower outer ring rib pressing die 4 are both in a floating state. The elastic coefficient of the first back pressure mechanism 7 is smaller than that of the second back pressure mechanism 8, so that after the axial pressing force is applied to the upper outer ring rib pressing die 3, the die 2 and the lower outer ring rib pressing die 4 both move downward, and the bottom end of the die 2 moves downward relative to the lower outer ring rib pressing die 4, thereby axially pre-pressing the powder between the two to form the lower outer ring rib; at the same time, the upper outer ring rib pressing die 3 axially pre-presses the divided material between its bottom surface and the top of the die 2 to form the upper outer ring rib, thereby ensuring the density of the upper and lower outer ring ribs during the pressing process.

[0085] S5, the upper outer ring rib pressing die 3 is kept under pressure, the upper punch 6 is impacted downward at high speed to load, an outward radial force is applied to the split punch 5, the split punch 5 is radially moved outward at high speed, and a radial pressing force is applied to the powder for high-speed warm pressing and forming. In this embodiment, the output end of the high-speed impact loading mechanism (such as an energy storage spring or a hydraulic hammer) is connected, and the loading speed of the upper punch 6 for high-speed downward impact loading is 10~30m / s. Each split mold 51 of the split punch 5 is radially moved outward at high speed at the same time, so as to extrude the powder between the outer wall of the split mold 51 and the inner wall of the die 2 at high speed, and utilize the strong deformation ability of the powder and the high filling rate of the inner ring rib under the action of inertial force, so that the powder is fully filled in the rib groove, and the density after pressing and forming is high. Since the impact loading speed is fast and the time is short, each filling mold 52 reaches the outermost limit position almost at the same time as the split mold 51, so the titanium alloy powder on the entire circumference of the outer side of the split punch 5 completes the axial extrusion forming almost synchronously, and the inner wall of the formed part is almost a complete and continuous cylindrical surface.

[0086] S6. After the pressure is maintained for a preset time, the upper punch 6 moves upward, exerts an inward radial force on the split punch 5, and the split punch 5 retracts radially to reset, the base 1 moves downward, the die 2 opens, and the titanium alloy green billet is taken out. In this embodiment, the die 2 includes two mating half-molds, and the outer side of each half-mold is connected to the output end of the horizontal positioning mechanism (hydraulic cylinder), which can realize the rapid mating and separation between the two half-molds, and keep the mating state stable. The lower part of the base 1 is lifted and lowered by a lifting mechanism (such as a workbench of a punching machine). After the base 1 is lowered, the formed green billet can be separated from the split punch 5, which is convenient for taking out the green billet; after the base 1 is raised, the split punch 5 can be accurately coaxially arranged in the die 2.

[0087] S7, vacuum continuous sintering the titanium alloy green body to obtain the final formed part. In this embodiment, vacuum continuous sintering is performed in a vacuum sintering furnace, the titanium alloy green body high efficiency densification sintering temperature is 1000-1300°C, the holding time is 30-120 minutes, and the dehydrogenation temperature is 400-600°C.

[0088] S8. Surface treatment is performed on the formed parts to obtain near-net-shaped components. Surface treatment mainly involves local machining and surface finishing of the inner and outer surfaces of the formed parts (especially the intersection of the mold) to obtain near-net-shaped components. Sampling tests are performed on different characteristic areas of the formed components, including testing the density using the Archimedes drainage method and testing the microstructure using metallographic microscopic analysis. The process parameters are adjusted based on the test results.

[0089] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0090] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A near-net forming process for a cylindrical part with inner and outer ring ribs, characterized in that: The following steps are involved: S1. preparing titanium alloy powder; S2, the upper outer ring rib pressing die moves upward, titanium alloy powder is filled in the cavity between the upper outer ring rib pressing die and the split punch and die, and the upper outer ring rib pressing die moves downward for assembly; S3, preheating the mold and powder as a whole, and stopping heating after reaching the preset temperature; S4, applying a preset axial pressing force to the upper outer ring rib pressing die, and the lower outer ring rib pressing die provides back pressure, respectively cooperating with the concave die to pre-press and form the upper and lower outer ring ribs; The bottom of the concave die is provided with a first back pressure mechanism, the lower outer ring rib pressing die is movably embedded in the bottom end of the concave die and the bottom is provided with a second back pressure mechanism, and the bottom of the lower outer ring rib pressing die is provided with a second back pressure mechanism, so that the concave die and the lower outer ring rib pressing die are both in a floating state; S5, the upper outer ring rib pressing die is maintained under pressure, the upper punch is impacted downward at high speed to load, an outward radial force is applied to the split punch, the split punch moves radially outward at high speed, a radial pressing force is applied to the powder to perform high-speed warm pressing and forming; S6, after the pressure is maintained for a preset time, the upper punch moves upward to apply an inward radial force to the split punch, the split punch retracts radially inward to reset, the base moves downward, the die opens, and the titanium alloy green billet is taken out; S7, performing vacuum continuous sintering on the titanium alloy green body to obtain a final formed part; S8. Perform surface treatment on the formed part to obtain a near-net-shape component.

2. The near-net-shape forming process of a cylindrical part with inner and outer ring ribs according to claim 1, characterized in that: The steps for preparing titanium alloy powder are specifically as follows: S1.

1. Place the titanium alloy powder prepared according to the preset composition in a ball mill, add anhydrous ethanol, and wet grind for 12 to 48 hours at a ball mill speed of 300 ± 50 r / min; S1.2, place the wet-milled mixed powder in an oven for drying, the drying time is 12±1h, and the drying temperature is 60±5℃; S1.

3. The dried mixed powder is placed in a ball mill and dry-milled at 300±50r / min. After dry-milling, it is sieved through a 200-mesh sieve to obtain a uniformly mixed powder.

3. The near-net-shape forming process of a cylindrical part with inner and outer ring ribs according to claim 1, characterized in that: The preset temperature for preheating the mold and powder as a whole is 250~300℃.

4. The near-net-shape forming process of a cylindrical part with inner and outer ring ribs according to claim 1, characterized in that: The preset axial pressing force applied to the upper outer ring rib pressing die is not less than 200t.

5. The near-net-shape forming process of a cylindrical part with inner and outer ring ribs according to claim 1, characterized in that: The loading speed of the upper punch for high-speed downward impact loading is 10~30m / s.

6. The near-net-shape forming process of a cylindrical part with inner and outer ring ribs according to claim 1, characterized in that: Vacuum continuous sintering is carried out in a vacuum sintering furnace. The efficient densification sintering temperature of the titanium alloy green body is 1000~1300℃, the holding time is 30~120min, and the dehydrogenation temperature is 400~600℃.

7. A near-net-shape forming device for a cylindrical part with inner and outer ring ribs, characterized in that: It includes a base, a die, an upper outer ring rib pressing die, a lower outer ring rib pressing die, a split punch and an upper punch. The base is fixedly arranged at the top of the lifting mechanism. The die includes two matched half-dies. The outer side of each half-die is connected to the output end of the horizontal positioning mechanism. The bottom of the die is provided with a first back pressure mechanism. The lower outer ring rib pressing die is movably embedded in the bottom end of the die and a second back pressure mechanism is provided at the bottom. The upper outer ring rib pressing die is movably embedded in the top end of the die and the top is connected to the output end of the pressing power mechanism. The upper punch is coaxially arranged in the die and the top is connected to the output end of the high-speed impact loading mechanism. The split punch is arranged between the die and the upper punch and is located on the top surface of the lower outer ring rib pressing die. The bottom of the concave die is provided with a first back pressure mechanism, the lower outer ring rib pressing die is movably embedded in the bottom end of the concave die and the bottom is provided with a second back pressure mechanism, and the bottom of the lower outer ring rib pressing die is provided with a second back pressure mechanism, so that the concave die and the lower outer ring rib pressing die are both in a floating state; The split punch comprises a plurality of split dies evenly distributed around the axis of the upper punch, and a filling die movably arranged between two adjacent split dies, and rib groove sections are correspondingly provided on the outer circumferential surfaces of the split dies and the filling die; During the downward movement of the upper punch, each split mold and the filling mold are driven to move radially outward synchronously until the outer cylindrical surface of the filling mold is correspondingly connected with the outer cylindrical surfaces of the two adjacent split molds to form a complete cylindrical surface; During the upward movement of the upper punch, each split mold and the filling mold are driven to synchronously retract radially inward until the outer circumferential surfaces of each split mold are correspondingly connected to form a continuous cylinder, and the filling mold is located on the inner side of the split mold.

8. The near-net-shape forming device for a cylindrical part with inner and outer annular ribs according to claim 7, characterized in that: Inclined slide rails are fixedly arranged on the inner side walls of the split mold and the filling mold respectively, and a sliding block slidably matched with the slide rails is fixedly arranged on the outer cylindrical surface of the upper punch.

9. The near-net-shape forming device for a cylindrical part with inner and outer annular ribs according to claim 7 or 8, characterized in that: A die top stop ring and an inner die stop plate are slidably connected in the upper outer ring rib pressing die. The die top stop ring is located above the split punch. When the split die and the filling die are radially retracted, the inner die stop plate is inserted between the split die and the filling die, and the side wall of the inner die stop plate fits with the side wall of the split die.

10. The near-net-shape forming device for a cylindrical part with inner and outer annular ribs according to claim 7 or 8, characterized in that: The sides of the two half molds facing each other are provided with vertically arranged bending grooves which are embedded with each other.

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