Integrated forming method of high-strength stainless steel bent pipe for liquid rocket engine

Abstract

An integrated forming method of a high-strength stainless steel bent pipe for a liquid rocket engine comprises the steps that a seamless high-strength stainless steel pipe serves as a blank, liquid filling forming is conducted on the interior of a pipe blank raw material through a hydraulic forming machine and a determined mold, meanwhile, axial thrust is applied to the two ends of the pipe blank, and the bent pipe with a certain three-dimensional shape and forming precision is obtained; and one-time forming of the high-strength stainless steel bent pipe is achieved. According to the method, a traditional bent pipe forming method of a liquid rocket engine based on a half-pipe tailor-welding scheme is broken through, the problems that half-pipe tailor-welding bent pipes are poor in forming precision, low in welding seam strength, large in residual stress and the like are solved, one-time forming of multiple bent pipes is achieved, the size consistency, the bearing strength and the production efficiency of the bent pipes are greatly improved, and the production cost is reduced. And reliable connection of the general assembly pipeline of the high-performance liquid rocket engine is ensured.

Description

Technical Field

[0001] The present invention relates to an integrated forming method for high-strength stainless steel bent pipes used in liquid rocket engines, belonging to the field of advanced manufacturing technology. Background Art

[0002] The high-strength stainless steel bent pipes used in liquid rocket engines are responsible for transporting propellants and work in extremely harsh environments of high temperature, high pressure and vibration. The bent pipes are required to have high strength and precise geometric dimensions. High-strength stainless steel materials have high yield strength and large yield ratio. Due to the compact structure of liquid rocket engines, the bending radius of the bent pipes is smaller than the pipe orifice diameter. Conventional presses cannot integrally form high-strength stainless steel bent pipes, and only the method of semi-pipe welding can be used for processing, which has problems such as weak weld strength, poor dimensional accuracy and low production efficiency, resulting in greater difficulty in the space assembly of the engine. Therefore, it is urgent to introduce a new forming method for high-strength stainless steel bent pipes of liquid rocket engines. Summary of the Invention

[0003] The technical problem solved by the present invention is: overcoming the deficiencies of the prior art, providing an integrated forming method for high-strength stainless steel bent pipes used in liquid rocket engines, solving the problems of weak weld strength and poor dimensional accuracy of the bent pipes brought by the semi-pipe welding forming method, reducing the difficulty of the space assembly of the engine, realizing the one-time forming of multiple bent pipes, and improving the production efficiency.

[0004] The technical solution of the present invention is: an integrated forming method for high-strength stainless steel bent pipes used in liquid rocket engines, comprising: Preparing a mold; the mold includes an upper die holder, a lower die holder, an upper die, a lower die, a left punch and a right punch; the upper die holder is used to connect and fix the upper die to a hydroforming machine, and the lower die holder is used to connect and fix the lower die to a hydroforming machine; the upper die and the lower die are designed according to the pipe diameter, bending radius and bending angle of the bent pipe and are consistent with the outer contour of the bent pipe; a closed cavity is formed between the upper die and the lower die; the left punch and the right punch are provided with a sealing device and a fluid filling joint, and before fluid filling, the left punch and the right punch are used to press and seal the pipe blank in the cavity; Installing the mold in a matching manner with the hydroforming machine, including: installing the upper die holder and the lower die holder on the workbench of the hydroforming machine; installing the left punch and the right punch on the hydraulic system of the hydroforming machine; controlling the hydroforming machine to raise the upper die holder, placing the pipe blank on the lower die; controlling the hydroforming machine to make the left punch and the right punch press the pipe blank; controlling the hydroforming machine to fill the pipe blank with fluid so that the fluid enters the inside of the pipe blank from the left punch and the right punch; Successively performing fluid filling, fluid filling bending and high-pressure shaping on the pipe blank by using the hydroforming machine and the determined mold to complete the integrated forming; After the forming is completed, separating the pipe blank, the hydroforming machine and the mold to obtain the formed bent pipe.

[0005] Furthermore, the liquid filling, liquid-filled bending, and high-pressure shaping include: Controlling the hydraulic forming machine to pressurize the liquid inside the tube blank; Controlling the hydraulic forming machine to move the upper die holder downward so that the upper die applies force to the tube blank. At the same time, controlling the hydraulic forming machine to adjust the liquid pressure inside the tube blank. The tube blank is subjected to the pressure of the upper die and the internal liquid pressure and is formed into a bent tube with a surplus, completing the integrated forming.

[0006] Furthermore, after the forming is completed, separating the tube blank, the hydraulic forming machine, and the mold includes: Controlling the hydraulic forming machine to relieve the internal liquid pressure of the bent tube with a surplus, and then pumping out the internal liquid of the bent tube with a surplus; Controlling the hydraulic forming machine to retract the left punch and the right punch from both ends of the bent tube with a surplus, and then raising the upper die holder to take out the bent tube with a surplus from the lower die.

[0007] Cutting off the surplus section in the bent tube with a surplus to obtain a bent tube.

[0008] Furthermore, the yield strength of the high-strength stainless steel material of the bent tube is not less than 600 MPa, and the yield ratio is not less than 0.7; the ratio of the bending radius R of the bent tube to the outer diameter D of the tube orifice is not greater than 1.

[0009] Furthermore, the tube blank is installed between the upper die and the lower die, and the tube blank is tightly pressed and sealed in the cavity through the sealing devices on the left punch and the right punch.

[0010] Furthermore, after the tube blank undergoes the liquid filling process, the inner cavity of the tube blank is filled with a liquid medium, so that the inner cavity of the tube blank is under the action of internal pressure support.

[0011] Furthermore, after the tube blank is filled with pressure liquid, under the support of internal pressure, the hydraulic forming machine applies a vertical pushing force and an axial pushing force to the mold to complete the liquid-filled bending of the tube blank.

[0012] Furthermore, the tube blank is attached to the upper die and the lower die through the internal cavity liquid pressure to complete the high-pressure shaping and obtain a bent tube that meets the preset size and process parameter range.

[0013] Furthermore, after forming, after maintaining the pressure for a preset duration, first release the vertical mold pressing force, then gradually remove the liquid in the inner cavity of the tube blank, and separate the mold after the internal cavity pressure of the tube blank is completely released.

[0014] Furthermore, at least 3 bent tubes are made from one tube blank through one-time forming.

[0015] The advantages of the present invention compared with the prior art are: The integrated forming method of high-strength stainless steel elbow for liquid rocket engine provided by the present invention is based on the fluid high-pressure forming technology, and uses seamless high-strength stainless steel pipe for integral forming, which solves the problem of integral forming of high-strength stainless steel elbow, eliminates the weld seam generated by the semi-pipe welding forming method, and improves the overall strength of the elbow parts; the integrated forming method of elbow provided by the present invention can achieve precise forming of elbow dimensions, greatly improve the forming dimension consistency and part interchangeability of the elbow, and reduce the difficulty of engine space assembly; the integrated forming method of elbow provided by the present invention can realize one-time forming of multiple elbows, and greatly improve the production efficiency of the elbow. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered as limiting the present invention. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings: Figure 1 is a schematic structural diagram of a high-strength stainless steel elbow; Figure 2 is a schematic structural diagram of a high-strength stainless steel tube blank; Figure 3 is a schematic diagram of one-time forming of multiple high-strength stainless steel elbows; Figure 4 is a schematic structural diagram of a forming die; Figure 5 is a schematic diagram of the forming of a high-strength stainless steel elbow; Figure 6 is a schematic diagram of the forming of a high-strength stainless steel elbow. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] In order to better understand the above technical solutions, the technical solutions of the present invention will be described in detail below with reference to the drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solutions of the present invention, rather than limitations on the technical solutions of the present invention. Without conflict, the technical features in the embodiments of the present invention and the embodiments can be combined with each other.

[0018] The following further describes in detail an integrated forming method of a high-strength stainless steel elbow for a liquid rocket engine provided by an embodiment of the present invention with reference to the accompanying drawings of the specification. The specific implementation manner may include: Prepare the mold; the mold includes an upper die holder, a lower die holder, an upper die, a lower die, a left punch, and a right punch; the upper die holder is used to connect and fix the upper die to the hydroforming machine, and the lower die holder is used to connect and fix the lower die to the hydroforming machine; the upper die and the lower die are designed according to the pipe diameter, bending radius, and bending angle of the bent pipe, and are consistent with the outer contour of the bent pipe; a closed cavity is formed between the upper die and the lower die; the left punch and the right punch are provided with a sealing device and a fluid filling joint. Before fluid filling, the left punch and the right punch are used to press and seal the pipe blank in the cavity. Install the mold in a matching manner with the hydroforming machine, including: installing the upper die holder 4 and the lower die holder 10 on the workbench of the hydroforming machine; installing the left punch 8 and the right punch 7 on the hydraulic system of the hydroforming machine; controlling the hydroforming machine to raise the upper die holder 4, and placing the pipe blank 6 on the lower die 9; controlling the hydroforming machine to make the left punch 8 and the right punch 7 press the pipe blank 6; controlling the hydroforming machine to fill the pipe blank 6 with fluid, so that the fluid enters the inside of the pipe blank 6 from the left punch 8 and the right punch 7. Use the hydroforming machine and the determined mold to sequentially perform fluid filling, fluid filling bending, and high-pressure shaping on the pipe blank to complete integrated forming; the high-pressure shaping pressure is 350 - 480 MPa. After forming, separate the pipe blank, the hydroforming machine, and the mold to obtain the formed bent pipe.

[0019] In the solution provided by the embodiment of the present invention, for a certain liquid rocket engine bent pipe, such as Figure 1 shown, the material of the bent pipe is high-strength stainless steel S-03, the yield strength of high-strength stainless steel S-03 is 700 - 800 MPa, and the compressive strength is 980 - 1100 MPa. The outer diameter D of the pipe orifice of the bent pipe is 106 mm, the wall thickness t is 8 mm, the bending angle is 90°, the bending radius R is 90 mm, and the ratio of the bending radius R to the outer diameter D of the pipe orifice is 0.85.

[0020] The implementation steps are as follows: Step 1: Preparation Figure 2 Prepare the pipe blank shown, the outer diameter d of the pipe blank is 103 mm, and the wall thickness t0 is 8.5 mm.

[0021] Step 2: Refer to Figure 4 , connect and install the upper die holder 4 and the upper die 5, and connect and install the lower die holder 10 and the lower die 9.

[0022] Step 3: Continue to refer to Figure 4 , install the upper die holder 4 and the lower die holder 10 on the hydroforming machine; install the left punch 8 and the right punch 7 on the hydroforming machine.

[0023] Step 4: Continue to refer to Figure 4 , control the hydroforming machine to raise the upper die holder 4, and place the pipe blank 6 on the lower die 9.

[0024] Step 5: Refer toFigure 5 , control the hydroforming machine to make the left punch 8 and the right punch 7 press the tube blank 6.

[0025] Step 6: Continue to refer to Figure 5 , control the hydroforming machine to fill the tube blank 6 with liquid, so that the liquid enters the inside of the tube blank 6 from the left punch 8 and the right punch 7.

[0026] Step 7: Continue to refer to Figure 5 , control the hydroforming machine to pressurize the liquid inside the tube blank 6.

[0027] Step 8: Continue to refer to Figure 5 , control the hydroforming machine to make the upper die holder 4 move downward, so that the upper die 5 applies force to the tube blank 6. At the same time, control the hydroforming machine to adjust the liquid pressure inside the tube blank 6. The tube blank 6 is formed into a bent tube 11 with a margin under the action of the pressure of the upper die 5 and the internal liquid pressure.

[0028] Step 9: Continue to refer to Figure 5 , control the hydroforming machine to remove the internal liquid pressure of the bent tube 11 with a margin, and then extract the internal liquid of the bent tube 11 with a margin.

[0029] Step 10: Refer to Figure 6 , control the hydroforming machine to retract the left punch 8 and the right punch 7 from both ends of the bent tube 11 with a margin, and then raise the upper die holder 4 to take out the bent tube 11 with a margin from the lower die 9.

[0030] Step 11: Refer to Figure 3 , cut off the margin sections 2 and 3 in the bent tube 11 with a margin to obtain 3 bent tubes 1.

[0031] Furthermore, liquid filling, liquid filling bending and high-pressure shaping include: Control the hydroforming machine to pressurize the liquid inside the tube blank; Control the hydroforming machine to make the upper die holder move downward, so that the upper die applies force to the tube blank. At the same time, control the hydroforming machine to adjust the liquid pressure inside the tube blank. The tube blank is formed into a bent tube with a margin under the action of the pressure of the upper die and the internal liquid pressure, completing the integrated forming.

[0032] In a possible implementation manner, separating the tube blank, the hydroforming machine and the mold after the forming is completed includes: Control the hydroforming machine to remove the internal liquid pressure of the bent tube with a margin, and then extract the internal liquid of the bent tube with a margin; Control the hydroforming machine to retract the left punch and the right punch from both ends of the bent tube with a margin, and then raise the upper die holder to take out the bent tube with a margin from the lower die; Cut off the margin section in the bent tube with a margin to obtain a bent tube.

[0033] Optionally, in a possible implementation, the yield strength of the high-strength stainless steel material of the elbow is not less than 600 MPa, and the yield ratio is not less than 0.7; the ratio of the bending radius R to the outer diameter D of the pipe orifice of the elbow is not greater than 1.

[0034] In a possible implementation, the tube blank is installed between the upper die and the lower die, and the tube blank is tightly pressed and sealed in the cavity through the sealing devices on the left punch and the right punch.

[0035] Furthermore, during the liquid filling process of the tube blank, the inner cavity of the tube blank is filled with a liquid medium, so that the inner cavity of the tube blank is under the action of internal pressure support.

[0036] In a possible implementation, after the tube blank is filled with pressurized liquid, under the support of internal pressure, a vertical pushing force and an axial pushing force are applied to the die by a hydroforming machine to complete the hydroforming and bending of the tube blank.

[0037] In a possible implementation, the tube blank fits with the upper die and the lower die through the internal cavity liquid pressure to complete high-pressure shaping, and an elbow meeting the preset size and process parameter range is obtained.

[0038] Furthermore, after forming, after maintaining the pressure for a preset duration, first release the pressing force of the vertical die, then gradually remove the liquid in the inner cavity of the tube blank, and separate the die after the pressure in the inner cavity of the tube blank is completely released.

[0039] By the method of the present invention, at least 3 elbows can be made from one tube blank through one-time forming.

[0040] In summary, the present invention overcomes the deficiencies of the prior art, provides an integrated forming method for high-strength stainless steel elbows for liquid rocket engines, solves the problem of integral forming of high-strength stainless steel elbows, eliminates the welds generated by half-tube welding and forming, realizes the precise forming of the elbow size, improves the consistency of the formed elbow size and the interchangeability of parts, reduces the difficulty of engine space assembly. At the same time, the one-time forming of multiple elbows is realized, and the production efficiency of the elbows is greatly improved.

[0041] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these changes and modifications.

[0042] The content not detailedly described in the specification of the present invention belongs to the well-known technology of those skilled in the art.

Claims

1. An integrated forming method for a high-strength stainless steel elbow used in a liquid rocket engine, characterized in that, Including: Preparing a mold; The mold includes an upper die holder, a lower die holder, an upper die, a lower die, a left punch, and a right punch; the upper die holder is used to connect and fix the upper die to a hydroforming machine, and the lower die holder is used to connect and fix the lower die to a hydroforming machine; the upper die and the lower die are designed according to the pipe diameter, bending radius, and bending angle of the bent pipe, and are consistent with the outer contour of the bent pipe; a sealed cavity is formed between the upper die and the lower die; the left punch and the right punch are provided with sealing devices and fluid filling joints. Before fluid filling, the left punch and the right punch are used to press and seal the pipe blank in the cavity. Installing the mold in a matching manner with the hydroforming machine, including: installing the upper die holder and the lower die holder on the workbench of the hydroforming machine; installing the left punch and the right punch on the hydraulic system of the hydroforming machine; controlling the hydroforming machine to raise the upper die holder and place the pipe blank on the lower die; controlling the hydroforming machine to make the left punch and the right punch press the pipe blank; controlling the hydroforming machine to fill the pipe blank with fluid so that the fluid enters the interior of the pipe blank from the left punch and the right punch. Using the hydroforming machine and the determined mold to sequentially perform fluid filling, fluid-filled bending, and high-pressure shaping on the pipe blank to complete integrated forming. After forming is completed, separating the pipe blank, the hydroforming machine, and the mold to obtain the formed bent pipe.

2. The integrated forming method of a high-strength stainless steel elbow for a liquid rocket engine according to claim 1, characterized in that, The fluid filling, fluid-filled bending, and high-pressure shaping include: Controlling the hydroforming machine to pressurize the fluid inside the pipe blank. Controlling the hydroforming machine to move the upper die holder downward so that the upper die applies force to the pipe blank, and at the same time controlling the hydroforming machine to adjust the fluid pressure inside the pipe blank. The pipe blank is subjected to the pressure of the upper die and the internal fluid pressure and is formed into a bent pipe with a margin to complete integrated forming.

3. An integrated forming method for a high-strength stainless steel elbow for a liquid rocket engine according to claim 1, characterized in that, The separating the pipe blank, the hydroforming machine, and the mold after forming is completed includes: Controlling the hydroforming machine to relieve the internal fluid pressure of the bent pipe with a margin, and then pumping out the internal fluid of the bent pipe with a margin. Controlling the hydroforming machine to retract the left punch and the right punch from both ends of the bent pipe with a margin, and then raising the upper die holder to take out the bent pipe with a margin from the lower die. Cutting off the margin section in the bent pipe with a margin to obtain the bent pipe.

4. An integrated forming method for a high-strength stainless steel elbow used in a liquid rocket engine according to claim 1, characterized in that, The yield strength of the high-strength stainless steel material of the bent pipe is not less than 600 MPa, and the yield ratio is not less than 0.7; the ratio of the bending radius R of the bent pipe to the outer diameter D of the pipe orifice is not greater than 1.

5. An integrated forming method for a high-strength stainless steel elbow for a liquid rocket engine according to claim 1, characterized in that, The pipe blank is installed between the upper die and the lower die, and the pipe blank is pressed and sealed in the cavity through the sealing devices on the left punch and the right punch.

6. An integrated forming method for a high-strength stainless steel elbow for a liquid rocket engine according to claim 1, characterized in that After the pipe blank undergoes the fluid filling process, the inner cavity of the pipe blank is filled with a fluid medium, so that the inner cavity of the pipe blank is under the action of internal pressure support.

7. An integrated forming method for a high-strength stainless steel elbow for a liquid rocket engine according to claim 1, characterized in that, After the pipe blank is filled with pressure fluid, under the internal pressure support, a vertical pushing force and an axial pushing force are applied to the mold by the hydroforming machine to complete the fluid-filled bending of the pipe blank.

8. An integrated forming method for a high-strength stainless steel elbow for a liquid rocket engine according to claim 1, characterized in that, The pipe blank is attached to the upper die and the lower die through the internal cavity fluid pressure to complete high-pressure shaping and obtain a bent pipe that meets the preset size and process parameter range.

9. An integrated forming method for a high-strength stainless steel elbow used in a liquid rocket engine according to claim 1, characterized in that, After forming, after maintaining the pressure for a preset time, first release the vertical mold pressing force, then gradually remove the fluid in the inner cavity of the pipe blank, and separate the mold after the internal pressure of the pipe blank is completely released.

10. An integrated forming method for a high-strength stainless steel elbow for a liquid rocket engine according to claim 1, characterized in that, One pipe blank is formed into no less than 3 bent pipes through one-time forming.

Images