Precise hydraulic forming method and device for corrugated pipe

Abstract

The invention relates to a corrugated pipe precision hydraulic forming method and device.The method comprises the steps that the corrugated pipe precision hydraulic forming device with a forming cavity is obtained, a pipe blank is placed in the forming cavity, and the corrugated pipe precision hydraulic forming device comprises an upper sealing assembly, a plurality of mold pieces, a base plate and a lower sealing assembly; the upper sealing assembly, the multiple mold pieces and the lower sealing assembly are coaxially arranged, and the multiple mold pieces are arranged between the upper sealing assembly and the lower sealing assembly. Under the condition that the corrugated pipe precision hydraulic forming device is in the second state, the pressure control assembly controls the pressure in the pipe blank to be maintained at a second pressure value for at least 1 min, and the second pressure value is at least five times of the forming pressure value; and after forming is finished, all the mold pieces are attached, the shape and size of the corrugated pipe are stabilized through a method of maintaining pressure for a certain time, elastic resilience of the corrugated pipe is remarkably reduced, and the workload of the subsequent corrugated pipe shaping procedure is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of metal bellows manufacturing, and in particular to a bellows precision hydraulic forming method and device. Background Art

[0002] Bellows mechanical seals are widely used due to their excellent performance and high reliability, and can be used in working conditions such as high speed, high pressure, high temperature and low temperature. The existing bellows forming molds and forming methods can solve the problems of mold marks after forming and improve the dimensional accuracy of bellows to a certain extent. However, the existing mold design and forming process methods cannot meet the requirements for the use of sealed bellows in terms of dimensional control accuracy, and no method is given to control the shape accuracy and dimensional accuracy of the outer diameter waveform of the bellows. It is necessary to optimize the design of the existing forming molds and innovate the forming process to meet the strict requirements of the sealing bellows for dimensional tolerances. Summary of the invention

[0003] 1. Technical issues to be resolved In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a method and device for precision hydraulic forming of bellows, which solves the technical problem that the existing mold design and forming process methods cannot meet the use requirements of sealing bellows in terms of dimensional control accuracy, and do not provide a method for controlling the accuracy of the waveform shape and dimensional accuracy of the outer diameter of the bellows.

[0004] (II) Technical solution In order to achieve the above object, the main technical solutions adopted by the present invention include: In a first aspect, an embodiment of the present invention provides a method for precision hydraulic forming of a bellows.

[0005] An embodiment of the present invention provides a method for precision hydraulic forming of a bellows, the method comprising: Obtain a bellows precision hydraulic forming device having a forming cavity, and place a tube blank in the forming cavity, wherein the bellows precision hydraulic forming device comprises an upper sealing assembly, a plurality of die sheets, a backing plate, and a lower sealing assembly, wherein the upper sealing assembly, the plurality of die sheets, and the lower sealing assembly are coaxially arranged, and the plurality of die sheets are arranged between the upper sealing assembly and the lower sealing assembly, and backing plates having a thickness equal to a backing plate height value are selected and arranged on both sides of the die sheets, so that the bellows precision hydraulic forming device forms a first state; The internal pressure of the tube blank is controlled by the pressure control component so that the internal pressure of the tube blank reaches the forming pressure value, and the backing plate is removed when the internal pressure of the tube blank reaches the forming pressure value; When the backing plate is removed from the bellows precision hydraulic forming device, an axial pressure is applied to the bellows precision hydraulic forming device to move adjacent die sheets toward each other along their axes, and the internal pressure of the tube blank is controlled to maintain the forming pressure value until the die sheets are attached to each other, so that the bellows precision hydraulic forming device is formed into a second state; When the bellows precision hydraulic forming device is in the second state, the pressure control component controls the pressure in the tube blank to maintain the pressure at the second pressure value for at least 1 minute, wherein the second pressure value is at least 5 times the forming pressure value; The bellows precision hydraulic forming device is removed to obtain the bellows.

[0006] Optionally, the step of obtaining a pad height value of the pad includes: The pad height value is calculated based on the first real-time data and the pad height equation. The first real-time data includes the corrugated cavity peak radius, the corrugated cavity trough radius, the transition zone portion length and the mold thickness.

[0007] Alternatively, the pad height equation is: ; in, is the pad height value, is the radius of the corrugated cavity peak, is the radius of the corrugated cavity trough, is the length of the transition zone, is the die thickness.

[0008] Optionally, the step of obtaining the forming pressure value includes: The forming pressure value is obtained by calculation based on the second real-time data and the forming pressure equation, wherein the second real-time data includes the wall thickness of the bellows, the tensile strength of the material and the inner diameter of the bellows.

[0009] Optionally, the forming pressure equation is: ; in, The bellows forming pressure, is the wall thickness of the bellows, is the tensile strength of the material, is the inner diameter of the bellows.

[0010] In a second aspect, an embodiment of the present invention provides a bellows precision hydraulic forming device.

[0011] A bellows precision hydraulic forming device provided in an embodiment of the present invention is used to implement any forming method of the first aspect, comprising an upper sealing assembly, a plurality of die sheets and a lower sealing assembly coaxially arranged, and a gasket is arranged between adjacent die sheets; Among them, a forming cavity for carrying the tube blank to be pressed is formed inside the bellows precision hydraulic forming device; The pressure control component is communicated with the forming cavity and is used for controlling the internal pressure of the forming cavity.

[0012] Optionally, the upper sealing assembly further comprises: Upper sealing outer ring; The upper sealing cover is detachably mounted on the inner ring opening of the upper sealing outer ring.

[0013] Optionally, the lower sealing assembly comprises: Lower sealing outer ring; The lower sealing cover is detachably mounted on the inner ring opening of the lower sealing outer ring.

[0014] Optionally, the die comprises: A mold core, at least two mold cores form a full ring piece, and the inner ring opening of the full ring piece forms a corrugated mold cavity; The fixing ring is detachably mounted on the outer ring opening of the full ring piece and is used to fix the mold cores of the same group to each other.

[0015] Optionally, the pressure control assembly comprises: A low-pressure pump is connected to the forming cavity; A high-pressure pump is communicated with the forming cavity and is connected in parallel with the low-pressure pump; A first stop valve, connected in parallel with the low-pressure pump and the high-pressure pump, for controlling the connection between the forming cavity and the outside; A direct-acting relief valve is communicated with the forming cavity and is connected in parallel with the low-pressure pump, the high-pressure pump and the first stop valve; The second stop valve is arranged between the direct-acting relief valve and the high-pressure pump.

[0016] (III) Beneficial effects The beneficial effects of the present invention are as follows: a method and device for precision hydraulic forming of a bellows of the present invention, when the precision hydraulic forming device for the bellows is in the second state, the pressure control component controls the pressure in the tube blank to maintain the pressure at the second pressure value for at least 1 minute, wherein the second pressure value is at least 5 times the forming pressure value; after the forming is completed, the various mold pieces are fitted together, and the shape and size of the bellows are stabilized by maintaining the pressure for a certain period of time, which significantly reduces the elastic rebound of the bellows and reduces the workload of the subsequent bellows shaping process. Since the shape of the bellows is confined in the mold cavity, the holding pressure can be greater than the forming pressure without causing the outer diameter of the bellows to continue to increase or the bellows to rupture. Therefore, a pressure greater than the forming pressure can be used to maintain the pressure of the bellows, thereby improving the loose fit between the bellows and the mold caused by factors such as the type of bellows material and the structural form, so that the waveform can better fit the mold cavity to obtain the expected corrugated shape. At the same time, when designing the mold forming cavity, the thickness of the mold piece is appropriately adjusted, and the holding pressure and holding time are appropriately increased during pressure holding. This can solve the problems of titanium alloys, high-temperature alloys, corrosion-resistant alloys, etc. with relatively large yield strength, and more material springback after forming, resulting in forming difficulties and waveform size out-of-tolerance problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the process of the bellows precision hydraulic forming method of the present invention; Figure 2 It is a schematic diagram of the front cross-sectional structure of the first state of the bellows precision hydraulic forming device of the present invention; Figure 3 It is a schematic diagram of the front cross-sectional structure of the bellows precision hydraulic forming device of the present invention in the second state; Figure 4 A schematic diagram of the top view of the die piece of an embodiment of the bellows precision hydraulic forming device of the present invention; Figure 5 It is a schematic diagram of the front cross-sectional structure of a die piece of an embodiment of the bellows precision hydraulic forming device of the present invention; Figure 6 It is a schematic diagram of the main structure of the mold core of an embodiment of the bellows precision hydraulic forming device of the present invention; Figure 7 It is a schematic diagram of the front cross-sectional structure of a fixing ring of an embodiment of the bellows precision hydraulic forming device of the present invention; Figure 8 It is a schematic cross-sectional structure diagram of a tube blank according to an embodiment of the present invention; Fig. 9 for Figure 8 Schematic diagram of the enlarged structure of part A.

[0018] [Description of Reference Numerals] 200, forming cavity; 300, upper sealing assembly; 310, upper sealing outer ring; 320, upper sealing cover; 400, mold piece; 401, corrugated mold cavity; 410, mold core; 420, fixing ring; 500, gasket; 600, lower sealing assembly; 610, lower sealing outer ring; 620, lower sealing cover; 700, pressure control assembly; 710, low-pressure pump; 720, high-pressure pump; 730, first stop valve; 740, direct-acting relief valve; 750, second stop valve; 800, tube blank. DETAILED DESCRIPTION

[0019] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below in conjunction with the accompanying drawings through specific embodiments. Figure 2 The orientation is used as a reference.

[0020] In order to better understand the above technical solution, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a clearer and more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0021] First, see Figure 1 , which is a flow chart of a bellows precision hydraulic forming method provided in an embodiment of the present application, may specifically include: S110-S150.

[0022] S110, obtaining a bellows precision hydraulic forming device having a forming cavity 200, placing a tube blank 800 in the forming cavity 200, wherein the bellows precision hydraulic forming device comprises an upper sealing assembly 300, a plurality of mold pieces 400, a backing plate 500 and a lower sealing assembly 600, wherein the upper sealing assembly 300, the plurality of mold pieces 400 and the lower sealing assembly 600 are coaxially arranged, and the plurality of mold pieces 400 are arranged between the upper sealing assembly 300 and the lower sealing assembly 600, and the backing plate 500 having a thickness equal to the backing plate height value is selected and arranged on both sides of the mold piece 400, so that the bellows precision hydraulic forming device forms a first state; The step of obtaining the pad height value of the pad 500 includes: calculating based on first real-time data and a pad height equation to obtain the pad height value, the first real-time data including the corrugated cavity crest radius, the corrugated cavity trough radius, the transition zone portion length and the die thickness; The pad height equation is: (1); in, is the pad height value, is the radius of the corrugated cavity peak, is the radius of the corrugated cavity trough, is the length of the transition zone, is the die thickness.

[0023] S120, controlling the internal pressure of the tube blank 800 through the pressure control assembly 700 so that the internal pressure of the tube blank 800 reaches the forming pressure value, and removing the backing plate 500 when the internal pressure of the tube blank 800 reaches the forming pressure value; S130, when the backing plate 500 is removed from the bellows precision hydraulic forming device, axial pressure is applied to the bellows precision hydraulic forming device to move adjacent die pieces 400 along their axes toward each other, and the internal pressure of the tube blank 800 is controlled to maintain the forming pressure value until the die pieces 400 are attached to each other, so that the bellows precision hydraulic forming device is in the second state; The step of obtaining the forming pressure value includes: calculating based on the second real-time data and the forming pressure equation to obtain the forming pressure value, the second real-time data including the wall thickness of the bellows, the tensile strength of the material and the inner diameter of the bellows; The forming pressure equation is: (2); in, The bellows forming pressure, is the wall thickness of the bellows, is the tensile strength of the material, is the inner diameter of the bellows.

[0024] S140, when the bellows precision hydraulic forming device is in the second state, the pressure control assembly 700 controls the pressure in the tube blank 800 to maintain the pressure at a second pressure value for at least 1 minute, wherein the second pressure value is at least 5 times the forming pressure value; S150, dismantle the bellows precision hydraulic forming device to obtain the bellows.

[0025] According to the above content, the bellows precision hydraulic forming method first obtains a bellows precision hydraulic forming device with a forming cavity 200, wherein the bellows precision hydraulic forming device includes a coaxially arranged upper sealing component 300, a plurality of mold pieces 400 and a lower sealing component 600, wherein a pad 500 with a thickness equal to the pad height value is selected and arranged on both sides of the mold piece 400, so that the bellows precision hydraulic forming device forms a first state, and a forming cavity 200 is formed inside the bellows precision hydraulic forming device in the first state, and the forming cavity 200 is coaxially arranged with the upper sealing component 300, the plurality of mold pieces 400 and the lower sealing component 600, and the tube blank is placed in the forming cavity 200, wherein the upper sealing component 300 and the lower sealing component 600 are arranged at both ends of the forming cavity 200, and the interior of the tube blank 800 is sealed by the upper sealing component 300 and the lower sealing component 600, and when the bellows precision hydraulic forming device is in the first state, a pad space for placing the pad 500 is formed between adjacent mold pieces 400, and due to the upper sealing component The assembly 300 and the lower sealing assembly 600 are arranged on both sides of the plurality of mold pieces 400. Therefore, the mold piece 400, the upper sealing assembly 300 and the lower sealing assembly 600 also form a pad space for placing the pad 500. When the pad 500 is placed in the pad space, the pad 500 is in close contact with the mold piece 400, the upper sealing assembly 300 and the lower sealing assembly 600. The height of the pad 500 determines the outer diameter of the bellows and determines whether the bellows can be completely fitted with the forming cavity 200 after being formed. Therefore, the height of each pad 500 is and tolerances should be consistent, and the height of the pad is calculated according to formula (1); after the bellows precision hydraulic forming device forms the first state, the upper sealing component 300 is limited, the low-pressure pump 710 in the pressure control component 700 is started, and the inside of the tube blank 800 is quickly filled with liquid through the lower sealing component 600. The forming liquid is deionized water. After the inside of the tube blank 800 is filled with deionized water, the high-pressure pump 720 in the pressure control component 700 is started. The high-pressure pump 720 is started to make the pressure reach the forming pressure value. The forming pressure value is calculated according to formula (2);After the internal pressure of the tube blank 800 reaches the forming pressure value, the tube blank 800 expands and deforms, and fits tightly with the mold piece 400. In this state, the internal pressure of the tube blank 800 is unloaded through the pressure control component 700, and the pad 600 is removed at this time. Since the tube blank 800 expands and deforms at this time, the deformed tube blank 800 can keep the mold piece 400 and the upper sealing component 300 in the original position without moving. After removing the pad 600, the high-pressure pump 720 in the pressure control component 700 continues to punch into the tube blank 800 to the forming pressure value. At the same time, axial pressure is applied to the bellows precision hydraulic forming device through external equipment. For example, the bellows precision hydraulic forming device is placed vertically on a horizontal plane, and the lower sealing component 600 is abutted against the horizontal plane. At this time, applying axial pressure to the bellows precision hydraulic forming device is to apply compression force to the upper sealing component 300, so that the bellows tube blank 800 is compressed axially while expanding outward. During the axial compression process, the volume of the tube blank 800 gradually decreases, resulting in an increase in the internal pressure value of the tube blank 800. In order to stabilize the internal pressure of the tube blank 800 at the forming pressure value, the direct-acting relief valve 750 in the pressure control component 700 is started at this time. For example, the direct-acting relief valve 750 can achieve 10L / min overflow pressure regulation under a high pressure of 150MPa, and keep the pressure inside the tube blank 800 relative to the forming pressure value The fluctuation does not exceed 5% until several mold pieces 400 are attached to each other. At the same time, the upper sealing component 300 and the lower sealing component 600 are also tightly attached to the mold piece 400 at the same time. At this time, the tube blank 800 expands outward to completely fit with the forming cavity 200, so that the bellows precision hydraulic forming device is in the second state. In this state, the pressure control component 700 controls the pressure inside the tube blank 800 to maintain the pressure at the second pressure value for at least 1min, wherein the second pressure value is at least 5 times the forming pressure value, and the second pressure value is the holding pressure; After the pressure holding is completed, the pressure holding pressure is unloaded, the axial limit of the bellows precision hydraulic forming device is removed, and the upper sealing component 300, several mold pieces 400 and the lower sealing component 600 are removed in turn to obtain the formed bellows. Through this method, multiple corrugations can be formed at one time, and the ratio of the outer diameter to the inner diameter of the bellows can reach between 1.2 and 1.5. The size deviation and shape of the formed bellows are better than those of the bellows manufactured by the traditional hydraulic forming process, and no subsequent shaping or correction is required.

[0026] By combining engineering experience and finite element simulation analysis, the pressure control component 700 controls the pressure in the tube blank 800 to maintain the pressure at least 5 times the forming pressure value for at least 1 minute to address the change in bellows size caused by the elastic rebound of the bellows material after the forming pressure is unloaded. This can solve the problems of titanium alloys, high-temperature alloys, corrosion-resistant alloys, etc. with large yield strength, and more material rebound after forming, resulting in forming difficulties and waveform size out-of-tolerance.

[0027] like Figures 2 to 9 As shown, according to the second aspect of the embodiment of the present application, a bellows precision hydraulic forming device is proposed, which is used to implement the bellows precision hydraulic forming device described in any of the above methods, including the coaxially arranged upper sealing assembly 300, a plurality of the mold pieces 400 and the lower sealing assembly 600, and the pad 500 is arranged between adjacent mold pieces 400; wherein, the bellows precision hydraulic forming device has a forming cavity 200 for carrying the pressed tube blank 800; the pressure control assembly 700 is connected to the forming cavity 200, and is used to control the internal pressure of the forming cavity 200.

[0028] In this technical solution, the bellows precision hydraulic forming device includes a coaxially arranged upper sealing assembly 300, a plurality of mold pieces 400 and a lower sealing assembly 600. A pad 500 is arranged between adjacent mold pieces 400 to play a supporting and spacing role. In this device, a forming cavity 200 is formed inside the bellows precision hydraulic forming device for carrying a tube blank 800 to be formed. For example, the size and shape of the forming cavity 200 are set according to the specifications of the bellows to be formed, ensuring that the tube blank 800 can be accurately formed therein.

[0029] The pressure control component 700 is connected to the forming cavity 200, and its main function is to control the pressure inside the forming cavity 200. For example, the pressure control component 700 can adopt a combination of equipment such as a hydraulic pump, a pressure sensor and a control valve to ensure that the tube blank is subjected to appropriate pressure during the forming process by real-time monitoring and adjusting the pressure.

[0030] In actual operation, the tube blank 800 is first placed in the forming cavity 200, and then the pressure in the forming cavity 200 is gradually increased through the pressure control assembly 700. The upper sealing assembly 300 and the lower sealing assembly 600 ensure the sealing of the forming cavity 200 to prevent pressure leakage. The die 400 presses the tube blank 800 under the action of pressure, and the pad 500 ensures that the spacing between the die pieces is uniform, so that the bellows can be formed more accurately.

[0031] Exemplarily, the upper sealing component 300 and the lower sealing component 600 can be made of high-strength sealing materials to ensure good sealing performance under high pressure; the mold 400 can be made of wear-resistant materials to extend its service life; exemplary, the pressure sensor in the pressure control component 700 should have high precision and high response speed to provide timely and accurate feedback of pressure information.

[0032] like Figure 2 and Figure 3 As shown, in some examples, the upper sealing assembly 300 further includes: an upper sealing outer ring 310 ; and an upper sealing cover 320 detachably mounted on the inner ring opening of the upper sealing outer ring 310 .

[0033] In some examples, the lower sealing assembly 600 includes: a lower sealing outer ring 610 ; and a lower sealing cover 620 detachably mounted on an inner ring opening of the lower sealing outer ring 610 .

[0034] As can be seen from the above content, the upper sealing outer ring 310 and the upper sealing cover 320 form a seal on the inside of the tube blank 800 at the upper part of the tube blank 800 of the bellows, and the lower sealing outer ring 610 and the lower sealing cover 620 form a seal on the inside of the tube blank 800 at the lower part of the tube blank 800 of the bellows. At the same time, illustratively, the upper sealing outer ring 310 and the lower sealing outer ring 610 both have the function of a forming mold. The lower part of the upper sealing outer ring 310 has a half corrugated cavity 401, which forms a complete corrugated cavity 401 after being attached to the adjacent mold piece 400. The lower sealing outer ring 610 The upper part has a half corrugated cavity 401, which forms a complete corrugated cavity 401 after being bonded with the adjacent mold piece 400. The upper and lower parts of the mold piece 400 each have a half corrugated cavity 401, which forms a complete corrugated cavity 401 after being bonded with the adjacent mold piece 400, the upper sealing outer ring 310 or the upper sealing outer ring 610. A gasket 500 is placed in the gap between the adjacent mold pieces 400 or between the mold piece 400 and the upper sealing outer ring 310 or the lower sealing outer ring 610, and the gasket 500 is in close contact with the mold piece 400, the upper sealing outer ring 310 or the lower sealing outer ring 610.

[0035] like Figures 2 to 7 As shown, in some examples, the mold piece 400 includes: a mold core 410, at least two of the mold cores 410 form a full ring piece, and the inner ring mouth of the full ring piece forms a corrugated mold cavity 401; a fixing ring 420, which can be detachably installed on the outer ring mouth of the full ring piece, and is used to fix the mold cores 410 in the same group to each other.

[0036] In this technical solution, the mold piece 400 includes a mold core 410 and a fixing ring 420. The mold core 410 is the basic unit that constitutes the full ring piece. The two mold cores 410 fit tightly along the side walls to form a complete circle. The two semi-corrugated cavities 401 are symmetrically distributed on both sides of the mold core 410. The inner diameter of the mold core 410 is processed into a fillet, and the radius of the fillet is consistent with the radius of the trough of the bellows. In actual operation, according to the requirements of bellows of different specifications, an appropriate number of mold cores 410 can be selected to form a full ring piece to meet the forming requirements of bellows of different sizes and shapes.

[0037] The fixing ring 420 is detachably mounted on the outer ring opening of the full ring piece. The fixing ring 420 is used to fix the mold cores 410 of the same group to each other, ensuring that the mold cores 410 will not be relatively displaced during the hydraulic forming process, thereby ensuring the forming accuracy of the bellows. When it is necessary to replace a mold piece 400 of different specifications, the fixing ring 420 can be easily removed to replace the mold core 410 or the entire mold piece 400 assembly.

[0038] For example, the backing plate 500 has a rectangular or square cross section, and the length or height of the rectangle (side length of the square) is the difference between the single wave expansion length and the thickness of the mold 400, and two planes whose length or height of the backing plate 500 matches the difference are used as working planes; the corrugated tube blank 800 is a seamless tube with a longitudinal weld formed by welding a seamless tube or a plate or a strip, and can be one layer or multiple layers set together; Exemplarily, the chamfer radius at the inner diameter of the upper sealing outer ring 310, the lower sealing outer ring 610 and the semi-corrugated cavity 401 of the mold piece 400 is consistent with the radius of the trough of the bellows; the thickness of the mold core 410 is consistent with the wave pitch of the bellows, and after being fitted with the upper and lower adjacent mold cores 410, a complete corrugated cavity 401 can be formed; the fixing ring 420 and the mold core 410 are matched with a small gap, and after the forming pressure is unloaded, the fixing ring 420 can be separated from the mold core 410.

[0039] like Figure 2 As shown, in some examples, the pressure control component 700 includes: a low-pressure pump 710, which is connected to the forming cavity 200; a high-pressure pump 720, which is connected to the forming cavity 200 and is connected in parallel with the low-pressure pump 710; a first stop valve 730, which is connected in parallel with the low-pressure pump 710 and the high-pressure pump 720, and is used to control the connection between the forming cavity 200 and the outside; a direct-acting overflow valve 740, which is connected to the forming cavity 200 and is connected in parallel with the low-pressure pump 710, the high-pressure pump 720 and the first stop valve 730; and a second stop valve 750, which is arranged between the direct-acting overflow valve 740 and the high-pressure pump 720.

[0040] In this technical solution, the pressure control assembly 700 includes a low-pressure pump 710 , a high-pressure pump 720 , a first stop valve 730 , a direct-acting relief valve 740 , and a second stop valve 750 .

[0041] The first stop valve 730 is connected in parallel with the low-pressure pump 710 and the high-pressure pump 720 to control the connection between the forming cavity 200 and the outside. By controlling the opening and closing of the first stop valve 730, the pressure in the forming cavity 200 can be adjusted to be maintained or released.

[0042] The direct-acting relief valve 740 is connected to the forming chamber 200 and is connected in parallel with the low-pressure pump 710, the high-pressure pump 720 and the first stop valve 730. The direct-acting relief valve 740 can automatically open when the pressure exceeds the set value, thereby playing a safety protection role and preventing the pressure in the forming chamber 200 from being too high and damaging the equipment or affecting the quality of the bellows.

[0043] The second stop valve 750 is disposed between the direct-acting relief valve 740 and the high-pressure pump 720 to further control the communication between the high-pressure pump 720 and the direct-acting relief valve 740. In certain cases, the output pressure of the high-pressure pump 720 can be adjusted or the direct-acting relief valve 740 can be protected by operating the second stop valve 750.

[0044] The low-pressure pump 710 is connected to the forming cavity 200. In the initial stage, it can quickly transport liquid to the forming cavity 200 to meet the needs of the initial deformation of the tube blank 800. The high-pressure pump 720 is also connected to the forming cavity 200 and is connected in parallel with the low-pressure pump 710. When the tube blank 800 is filled with liquid, the high-pressure pump 710 is started to make the pressure in the tube blank 800 reach the bellows forming pressure, so that the bellows tube blank 800 expands and deforms and fits tightly with the mold piece 400. The position where the tube blank 800 expands and deforms can fix the mold piece 400. At this time, the internal pressure of the tube blank 800 is unloaded, and then the pad 500 is removed. The high-pressure pump 720 is started again to pressurize the inside of the bellows tube blank 800. When the pressure When the value reaches the forming pressure, the tube blank 800 expands radially, and at the same time, axial force is applied to the upper sealing component 300 to make the mold pieces 400 fit together. In this process, the tube blank 800 is limited by the mold forming cavity 800 during radial expansion and is completely fitted with the mold forming cavity 200. The internal volume of the tube blank 800 increases first and then decreases. The internal pressure of the tube blank 800 caused by this factor increases, and the excess forming liquid overflows from the direct-acting overflow valve 740 to maintain the stability of the forming pressure. After the mold pieces are fitted together, the second stop valve 750 in front of the direct-acting overflow valve 740 is closed to continue to pressurize the inside of the bellows tube blank 800, and the pressure in the tube blank 800 is controlled to maintain the second pressure value for at least 1 minute.

[0045] Example like Figures 4 to 9 As shown, Fig. 9 The metal bellows is made from the tube blank 800 through the bellows precision hydraulic device in the present technical solution. The inner diameter φ1 of the metal bellows is 65±0.2mm, the outer diameter φ2 of the bellows is 80.3±0.3mm, the wave pitch L1 is 5.08mm, the effective length L2 is 12.7±0.3mm, a double-layer structure is adopted, the single-layer wall thickness A1 is 0.12mm, the wave number is 3, and the forming pressure of the metal bellows is 4.5MPa.

[0046] Designed using Figure 4 and Figure 5 The mold piece 400 shown in the figure is designed to have a thickness of t=4.6mm, which is 90% of the wave pitch size, and a radius of the semi-corrugated cavity 401 of r1=R1.15, which is slightly smaller than the wave thickness fillet R1.39. The fillet at the inner diameter of the mold core is r2=R1.15, which is consistent with the wave valley radius. The inner diameter size of the mold cavity is processed to φ3, which is 80 +0.1mm, which improves the dimensional accuracy compared with the drawing requirement of φ80.3±0.3mm.

[0047] like Figures 4 to 7 The mold piece 400 is composed of a fixing ring 420 and a mold core 410. The two mold cores 410 are closely fitted along the side walls to form a complete circle, and the fixing ring 420 is assembled outside the mold core 410 with a small gap.

[0048] The forming method is as follows: Step 1: Follow Figure 2 , assemble the complete set of forming dies and the tube blank 800 to achieve sealing of the upper and lower ends of the tube blank 800; Step 2: Place the lower sealing assembly 600 on the equipment base, connect it to the external hydraulic system, and use a press to axially limit the upper sealing assembly 300; Step 3, close the first stop valve 730 and the second stop valve 750, start the low-pressure pump 710 to quickly fill the interior of the tube blank 800 with the forming liquid through the lower sealing assembly 600; Step 4, open the second stop valve 750, start the high-pressure pump 720 to make the pressure in the tube blank 800 reach 4.5 MPa, so that the corrugated tube blank 800 expands and deforms to fit closely with the mold piece 400, and the mold piece 400 can be fixed; Step 5, turn off the high pressure pump 720, unload the internal pressure of the tube blank 800, and remove the backing plate 500; Step 6, start the high-pressure pump 720 again to pressurize the inside of the corrugated tube blank 800. When the pressure value reaches 4.5 MPa, the tube blank 800 expands radially, and at the same time, axial pressure is applied to the upper sealing assembly 300 to make the mold pieces 400 fit together. In this process, the tube blank 800 is limited by the mold cavity 200 during the radial expansion process, and is completely fitted with the mold cavity 200. The internal volume of the tube blank 800 increases first and then decreases. The internal pressure of the tube blank 800 caused by this factor is increased, and the direct-acting overflow valve 740 overflows the excess forming liquid to keep the forming pressure stable; Step 7: After the mold pieces 400 are attached, close the second stop valve 750 and continue to pressurize the inside of the corrugated tube blank 800, the pressure value is 30MPa, and the pressure is maintained for 5 minutes. The mold pieces 400 are attached and the pressure is maintained as shown in the figure. Figure 2 As shown; Step 8: turn off the high-pressure pump 720, open the first stop valve 730 to unload the pressure, remove the mold, and obtain the metal bellows.

[0049] Using this embodiment, the outer diameter of the bellows after forming is φ80 -0.1 mm, effective length 13 -0.3 mm, the stiffness index and effective area index are 100% qualified, which greatly improves the forming accuracy and product quality.

[0050] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0051] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0052] In the present invention, unless otherwise clearly specified and limited, when a first feature is “on” or “below” a second feature, it may be that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Moreover, when a first feature is “above”, “above” or “above” a second feature, it may be that the first feature is directly above or obliquely above the second feature, or it may simply mean that the first feature is higher in level than the second feature. When a first feature is “below”, “below” or “below” a second feature, it may be that the first feature is directly below or obliquely below the second feature, or it may simply mean that the first feature is lower in level than the second feature.

[0053] In the description of this specification, the description of the terms "one embodiment", "some embodiments", "embodiment", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0054] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and deform the above embodiments within the scope of the present invention.

Claims

1. A bellows precision hydraulic forming method, characterized in that: The method comprises: Obtain a bellows precision hydraulic forming device having a forming cavity, and place a tube blank in the forming cavity, wherein the bellows precision hydraulic forming device comprises an upper sealing assembly, a plurality of die sheets, a backing plate, and a lower sealing assembly, wherein the upper sealing assembly, the plurality of die sheets, and the lower sealing assembly are coaxially arranged, and the plurality of die sheets are arranged between the upper sealing assembly and the lower sealing assembly, and the backing plate having a thickness equal to the backing plate height value is selected and arranged on both sides of the die sheet, so that the bellows precision hydraulic forming device forms a first state; Control the internal pressure of the tube blank by means of a pressure control component so that the internal pressure of the tube blank reaches a forming pressure value, and remove the backing plate when the internal pressure of the tube blank reaches the forming pressure value; When the backing plate is removed from the bellows precision hydraulic forming device, axial pressure is applied to the bellows precision hydraulic forming device to move adjacent die sheets toward each other along their axes, and the internal pressure of the tube blank is controlled to maintain the forming pressure value until the die sheets are attached to each other, so that the bellows precision hydraulic forming device is in the second state; When the bellows precision hydraulic forming device is in the second state, the pressure control component controls the pressure in the tube blank to maintain the pressure at the second pressure value for at least 1 minute, wherein the second pressure value is at least 5 times the forming pressure value; The bellows precision hydraulic forming device is removed to obtain the bellows.

2. The bellows precision hydraulic forming method according to claim 1, characterized in that: The step of obtaining the pad height value of the pad includes: The pad height value is calculated based on the first real-time data and the pad height equation. The first real-time data includes the corrugated cavity peak radius, the corrugated cavity trough radius, the transition zone portion length and the mold thickness.

3. The bellows precision hydraulic forming method according to claim 2, characterized in that: The pad height equation is: H = π(r1+r2)+2a-t; Among them, H is the height of the pad, r1 is the radius of the crest of the corrugated cavity, r2 is the radius of the trough of the corrugated cavity, a is the length of the transition zone, and t is the thickness of the mold.

4. The bellows precision hydraulic forming method according to claim 1, characterized in that: The steps for obtaining the forming pressure value include: The forming pressure value is obtained by calculation based on the second real-time data and the forming pressure equation, wherein the second real-time data includes the wall thickness of the bellows, the tensile strength of the material and the inner diameter of the bellows.

5. The bellows precision hydraulic forming method according to claim 4, characterized in that: The forming pressure equation is: Among them, p is the bellows forming pressure, h is the bellows wall thickness, σ b is the tensile strength of the material and d is the inner diameter of the bellows.

6. A bellows precision hydraulic forming device, used to implement the forming method according to any one of claims 1 to 5, characterized in that: It comprises the upper sealing assembly, a plurality of the mold pieces and the lower sealing assembly which are coaxially arranged, and the pad is arranged between the adjacent mold pieces; Wherein, the bellows precision hydraulic forming device has a forming cavity formed inside for carrying the formed tube blank; The pressure control component is communicated with the forming cavity and is used for controlling the internal pressure of the forming cavity.

7. The bellows precision hydraulic forming device according to claim 6, characterized in that: The upper sealing assembly also includes: Upper sealing outer ring; The upper sealing cover is detachably mounted on the inner ring opening of the upper sealing outer ring.

8. The bellows precision hydraulic forming device according to claim 6, characterized in that: The lower sealing assembly comprises: Lower sealing outer ring; The lower sealing cover is detachably mounted on the inner ring opening of the lower sealing outer ring.

9. The bellows precision hydraulic forming device according to claim 6, characterized in that: The mold piece comprises: A mold core, at least two of which form a full ring piece, and an inner ring opening of the full ring piece forms a corrugated mold cavity; The fixing ring is detachably mounted on the outer ring opening of the full ring piece and is used to fix the mold cores in the same group to each other.

10. The bellows precision hydraulic forming device according to claim 6, characterized in that: The pressure control assembly comprises: A low-pressure pump, connected to the forming cavity; a high-pressure pump, communicated with the forming cavity and connected in parallel with the low-pressure pump; a first stop valve, connected in parallel with the low-pressure pump and the high-pressure pump, for controlling the connection between the forming cavity and the outside; a direct-acting relief valve, connected to the forming cavity and connected in parallel with the low-pressure pump, the high-pressure pump and the first stop valve; The second stop valve is disposed between the direct-acting relief valve and the high-pressure pump.

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