High-precision thick-walled cylinder forming method and auxiliary tooling

Abstract

The application discloses a high-precision thick-wall cylinder forming method and an auxiliary tool, and ingeniously solves the problem of high precision requirement of the thick-wall cylinder by using a plate rolling machine, and avoids the problem of wrong edge of ring seam welding; the method comprises the following steps: reserving a pre-bending straight edge when the thick-wall cylinder is rolled; adopting a twice jointing mode to perform a jointing operation on the cylinder; performing a stress relief heat treatment, and performing a roundness correction by using the temperature of the heat treatment; performing a stainless steel overlay welding on the inner wall of the cylinder; and adjusting the ovality of the end of the cylinder by using an adjustable supporting device, so that the end of the cylinder meets the requirements of the ring seam assembly and the wrong edge.

Description

Technical Field

[0001] This invention relates to the field of thick-walled cylinder forming technology for pressure vessels used in petroleum, chemical, and nuclear power industries, and specifically to a high-precision thick-walled cylinder forming method and auxiliary tooling. Background Technology

[0002] In order to save manufacturing costs, some thick-walled cylinders of large pressure vessels used in petroleum, chemical, and nuclear power plants are now made by rolling plates instead of forgings. However, rolled cylinders are prone to the following defects:

[0003] The cylinder body requires high forming precision and the inner wall of the cylinder needs to be integrally welded with stainless steel. Deformation after welding causes misalignment when assembling with the head, which cannot meet the product's welding precision requirements.

[0004] Existing methods for rolling cylinders include two main approaches: One is the center diameter unfolding and rounding method, which involves unfolding the material according to its center diameter and then rounding any unrolled edges after welding. This method is primarily suitable for thin-walled cylinders. However, for thick-walled cylinders, sharp angles may exist at the weld seam, affecting subsequent assembly. Furthermore, the rounding process uses strong pressure, which can negatively impact weld quality and poses a risk of weld cracking. The other method is the die pre-bending method, where after unfolding the material to its center diameter, specialized dies and a hydraulic press are used to pre-bend both ends of the cylinder to the final diameter. This method is suitable for thick-walled cylinders, but its applicability is limited by cylinder size, requiring different dies and thus less versatility. Additionally, the use of a hydraulic press makes die pre-bending costly.

[0005] Based on the existing technology and the precision requirements of thick-walled pressure vessels, the inventors have conducted in-depth research on thick-walled cylinder forming methods and auxiliary devices, with the aim of designing a high-precision thick-walled cylinder forming method and auxiliary tooling that can solve the above problems. Summary of the Invention

[0006] To overcome the above problems, the inventors conducted intensive research and designed a high-precision thick-walled cylinder forming method and auxiliary tooling. This method cleverly solves the problem of high precision requirements for thick-walled cylinders by utilizing a plate rolling machine, while avoiding the problem of misaligned edges in circumferential welding. The steps of this method are as follows: a pre-bent straight edge is reserved during the rolling of the thick-walled cylinder; a two-stage joining method is used to join the cylinder; stress-relieving heat treatment is performed, and the roundness is corrected using the temperature of this heat treatment; stainless steel is overlaid on the inner wall of the cylinder. Due to the deformation caused by forming and welding, the roundness of the end does not meet the requirements of machining and assembly. An adjustable support device is then used to adjust the ellipticity of the cylinder end to meet the requirements of misaligned edges in circumferential welding, thus completing the invention.

[0007] Specifically, the purpose of this invention is to provide a high-precision thick-walled cylinder forming method, which includes the following steps:

[0008] Step 1: When cutting thick-walled cylinders, leave a pre-bent straight edge;

[0009] Step 2: Use a two-stage joining method to join the plates to obtain the cylinder;

[0010] Step 3: Perform stress-relieving heat treatment on the cylinder and use the temperature of this heat treatment to round the cylinder.

[0011] Step 4: Weld stainless steel onto the inner wall of the cylinder, and then use an adjustable support device to adjust the ellipticity of the cylinder end to meet the requirements of misaligned edge assembly of the circumferential seam.

[0012] In step 1, when the thick-walled cylinder is cut, after unfolding according to the middle diameter, pre-bent straight edges are reserved at both ends, and the width of the pre-bent straight edges is greater than or equal to twice the thickness of the cylinder wall.

[0013] Preferably, the material cutting size is controlled such that the difference between the diagonals of the board is no more than 2mm.

[0014] Step 2 includes the following sub-steps:

[0015] Sub-step 2-1: Use a heavy-duty plate rolling machine to perform initial rolling and forming of the plate; wherein, when the two ends of the plate are pre-bent during the initial rolling, template 1 is used to measure the inner arc radius of the plate near the longitudinal seam after the initial rolling and pre-bending, and the inner arc radius is controlled to be consistent with the inner radius of the cylinder after forming.

[0016] Sub-step 2-2: Measure the dimensions of the initially rolled sheet and calculate the sheet elongation;

[0017] Sub-steps 2-3: Remove the pre-bent straight edges of the plate; wherein, based on the inner circumference of the end cap to be welded to the cylinder as required, and according to the plate elongation and expected cylinder size, process the removal of the straight edge allowance according to the positive tolerance of the cylinder size, and process the longitudinal seam bevel of the cylinder.

[0018] Sub-steps 2-4: The sheet metal is joined into a cylinder on the plate rolling machine. The misalignment of the longitudinal seam is adjusted by welding door-shaped plates to both ends of the cylinder. Then, with the cooperation of the plate rolling machine, the decoration of the longitudinal seam is completed.

[0019] Sub-steps 2-5: longitudinal seam welding of the cylinder, followed by non-destructive testing.

[0020] In sub-step 2-1, before the initial roll forming, the expected longitudinal seam positions are marked on both ends of the sheet metal according to the expected cylinder size.

[0021] The area near the longitudinal seam is a board area at least 300 mm wide, including the longitudinal seam.

[0022] One end of the template is an arc surface, and the radius of the arc surface is consistent with the inner radius of the formed cylinder; thus, the template can be attached to the inner wall of the board, and the initial rolling degree of the board can be judged by observing the adhesion between the template and the inner wall of the board.

[0023] In step 3, heat treatment is used to eliminate the thermal stress caused by welding on the cylinder. After heat treatment, the cylinder is air-cooled. When the temperature is cooled to below 150 degrees Celsius, the cylinder is rounded using a heavy-duty plate rolling machine.

[0024] Preferably, after the cylinder is rounded, a non-destructive test is performed on the longitudinal seam of the cylinder.

[0025] During the rounding process, the temperature of the cylinder is controlled between 38 degrees Celsius and 150 degrees Celsius.

[0026] In step 4, the adjustable support device includes an annular support plate 2, the inner diameter of which is larger than the outer diameter of the cylinder, and is sleeved on the outside of the cylinder.

[0027] Multiple jacks 3 are provided between the support plate 2 and the cylinder, and the axial direction of the jacks all points to the axis of the cylinder.

[0028] The jacks are evenly distributed around the cylinder. Preferably, there are 16 jacks, and each jack is individually controlled, which can provide different forces to each jack according to the shape requirements.

[0029] The present invention also provides an auxiliary tooling for high-precision thick-walled cylinder forming, the tooling including a template 1 and an adjustable support device;

[0030] The template 1 is used to check the inner radius of the board in a timely manner when the board is initially rolled and pre-bent at both ends.

[0031] The adjustable support device is used to adjust the ellipticity of the cylinder end to meet the requirements of misaligned edge assembly of the circumferential seam.

[0032] The beneficial effects of this invention include:

[0033] (1) According to the high-precision thick-walled cylinder forming method and auxiliary tooling provided by the present invention, the method effectively solves the roundness and edge angle problems required by the high-precision cylinder by reserving a pre-bent straight edge in the cylinder and adding a heat treatment process before rounding, and at the same time solves the longitudinal seam quality problem of the cylinder.

[0034] (2) According to the high-precision thick-walled cylinder forming method and auxiliary tooling provided by the present invention, the adjustable support device is used to cleverly connect the cylinder and the jack together, which solves the problems of cylinder end deformation and circumferential bevel machining after the inner wall of the cylinder is welded, and effectively ensures the circumferential assembly of the cylinder and the head, solves the problem of misalignment of thick-walled containers, which not only ensures product quality, but also improves the efficiency of cylinder assembly and welding. Attached Figure Description

[0035] Figure 1This paper presents an overall logic diagram of the high-precision thick-walled cylinder forming method in this application.

[0036] Figure 2 This is a schematic diagram of the structure when measuring the inner arc radius of the initial roll of the sheet metal after pre-bending using a template in sub-step 2-1 of this application;

[0037] Figure 3 This diagram shows the structure of the adjustable support device installed on the cylinder.

[0038] Figure Labels

[0039] 1-Sample

[0040] 2-Support plate

[0041] 3-jack

[0042] 4-Sheet

[0043] 5-Pre-bend straight edge

[0044] 6-Longitudinal seam Detailed Implementation

[0045] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Through these descriptions, the features and advantages of the present invention will become clearer and more apparent.

[0046] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0047] The high-precision thick-walled cylinder forming method provided by the present invention, such as Figure 1 As shown, the method includes the following steps:

[0048] Step 1: When cutting thick-walled cylinders, leave a pre-bent straight edge;

[0049] Preferably, in step 1, when the thick-walled cylinder is cut, after unfolding according to the middle diameter, a pre-bent straight edge 5 is reserved at both ends. The width of the pre-bent straight edge is greater than or equal to twice the wall thickness of the cylinder. The thick-walled cylinder mentioned in this application refers to a cylinder with a wall thickness of 80mm or more.

[0050] Preferably, the material cutting size is controlled so that the difference between the diagonals of the plates is no more than 2mm. Strict control of the material cutting size provides a material basis for obtaining a high-precision cylinder.

[0051] Step 2: Use a two-stage joining method to join the plates to obtain the cylinder;

[0052] Step 2 includes the following sub-steps:

[0053] Sub-step 2-1 involves using a heavy-duty plate rolling machine to initially roll and form the sheet 4. During the initial pre-bending of both ends of the sheet, template 1 is used to measure the inner radius of the pre-bent sheet near the longitudinal seam 6. This inner radius is controlled to be consistent with the inner radius of the formed cylinder, thereby controlling the edge angle at the longitudinal seam. This initial pre-bending can be repeated multiple times at both ends of the sheet based on the measurement results. Figure 2 As shown;

[0054] Sub-step 2-2: Measure the dimensions of the initially rolled sheet and calculate the sheet elongation. Since the pre-bending process stretches or compresses the sheet, the circumferential dimensions of the sheet will change. Obtaining the sheet elongation can provide a more accurate data basis for subsequent sheet cutting.

[0055] Sub-steps 2-3: Remove the pre-bent straight edges of the plate; wherein, based on the inner circumference of the end cap to be welded to the cylinder as required, and according to the plate elongation and expected cylinder size, process the removal of the straight edge allowance according to the positive tolerance of the cylinder size, and process the longitudinal seam bevel of the cylinder.

[0056] Sub-steps 2-4 involve joining the sheet metal into a cylindrical shape on a plate rolling machine, adjusting the misalignment of the longitudinal seam by welding door-shaped plates to both ends of the cylindrical shape, and then completing the finishing of the longitudinal seam with the assistance of the plate rolling machine; the finishing is called spot welding.

[0057] Sub-steps 2-5: longitudinal seam welding of the cylinder, followed by non-destructive testing.

[0058] Preferably, in sub-step 2-1, before the initial roll forming, the expected longitudinal seam 6 positions are marked on both ends of the sheet metal according to the expected cylinder size; that is, as shown in... Figure 2 As shown, there are two longitudinal seam locations;

[0059] The area near the longitudinal seam is a board area at least 300 mm wide, including the longitudinal seam. More preferably, the area near the longitudinal seam includes board areas at least 100 mm wide on each side of the longitudinal seam.

[0060] Preferably, one end of the template 1 is an arc surface, and the radius of the arc surface is consistent with the inner radius of the formed cylinder; thus, the template can be attached to the inner wall of the board, and the initial rolling degree of the board can be judged by observing the adhesion between the template and the inner wall of the board.

[0061] Preferably, in sub-steps 2-4, the portal plate is a plate-shaped metal block that can bear a sufficiently large force. The portal plate is pushed along the axis of the cylinder by a jack or hydraulic cylinder. The portal plate then pushes and squeezes the side of the cylinder where it is located, thereby adjusting the longitudinal seam misalignment of the cylinder. When the longitudinal seam misalignment meets the expectation, it is spot welded and fixed.

[0062] Step 3: Perform stress-relieving heat treatment on the cylinder and use the temperature of this heat treatment to round the cylinder.

[0063] In step 3, heat treatment is used to eliminate the thermal stress generated by welding on the cylinder. After heat treatment, the cylinder is air-cooled. When the temperature is cooled to below 150 degrees Celsius, the cylinder is rounded using a heavy-duty plate rolling machine.

[0064] Preferably, after the cylinder is rounded, a non-destructive test is performed on the longitudinal seam of the cylinder.

[0065] Preferably, during the rounding process, the temperature of the cylinder is controlled between 38 degrees Celsius and 150 degrees Celsius. Performing the rounding process within this temperature range improves rounding efficiency and yields a cylinder structure with higher roundness. However, excessively high temperatures can easily cause changes in material properties, affecting the final cylinder performance; conversely, excessively low temperatures will result in poor rounding results and reduced work efficiency.

[0066] Step 4: Stainless steel is overlaid on the inner wall of the cylinder. Due to the deformation caused by forming and welding, the roundness of the end does not meet the requirements of machining and assembly. Then, an adjustable support device is used to adjust the ellipticity of the cylinder end, which effectively ensures the processing of the cylinder circumferential seam bevel, and at the same time ensures that the cylinder and the end cap meet the requirements of circumferential seam assembly misalignment.

[0067] In step 4, the adjustable support device includes an annular support plate 2, the inner diameter of which is larger than the outer diameter of the cylinder, and is sleeved on the outside of the cylinder.

[0068] Multiple jacks 3 are provided between the support plate 2 and the cylinder, and the axial direction of the jacks all points to the axis of the cylinder.

[0069] Preferably, the jacks are evenly distributed around the cylinder. Preferably, there are 16 jacks, and each jack is individually controlled, which can provide different forces to each jack according to the shape requirements.

[0070] The present invention also provides an auxiliary tooling for high-precision thick-walled cylinder forming, characterized in that the tooling includes a template 1 and an adjustable support device;

[0071] The template 1 is used to check the inner radius of the board in a timely manner when the board is initially rolled and pre-bent at both ends.

[0072] The adjustable support device is used to adjust the ellipticity of the cylinder end to meet the requirements of misaligned edge assembly of the circumferential seam.

[0073] Example

[0074] The pressure vessel cylinder of a nuclear power project is rolled. The cylinder has a wall thickness of 78mm, a length of 4000mm, and an inner diameter of 3500mm. After rolling, stainless steel is welded onto its inner wall.

[0075] The rolling and forming process specifically includes the following steps:

[0076] Step 1: When cutting the thick-walled cylinder, pre-bent straight edges are reserved at both ends; the width of the pre-bent straight edges is approximately 300mm.

[0077] Furthermore, the difference in diagonal of the boards obtained by measuring and controlling the cutting process should not exceed 2mm.

[0078] Step 2 involves a two-stage joining process to join the sheet metal to obtain the cylinder; specifically, this includes:

[0079] Sub-step 2-1 involves using a heavy-duty plate rolling machine to initially roll the sheet metal; specifically, during the initial rolling and pre-bending of both ends of the sheet metal, the following method is used... Figure 2 The inner arc radius of the plate after initial rolling and pre-bending near the longitudinal seam 6 is measured using template 1, and this inner arc radius is controlled to be consistent with the inner radius of the formed cylinder; the area near the longitudinal seam refers to the plate area with a width of 150mm on each side of the longitudinal seam.

[0080] Sub-step 2-2: Measure the dimensions of the initially rolled sheet and calculate the sheet elongation;

[0081] Sub-steps 2-3: Remove the pre-bent straight edges of the board material;

[0082] Sub-steps 2-4: The sheet metal is joined into a cylinder on the plate rolling machine. The misalignment of the longitudinal seam is adjusted by welding door-shaped plates to both ends of the cylinder. Then, with the cooperation of the plate rolling machine, the decoration of the longitudinal seam is completed.

[0083] Sub-steps 2-5: longitudinal seam welding of the cylinder, followed by non-destructive testing.

[0084] Step 3: Perform stress-relieving heat treatment on the cylinder. After heat treatment, air-cool the cylinder. When the temperature drops below 150 degrees Celsius, use a heavy-duty plate rolling machine to round the cylinder.

[0085] After the cylinder is rounded, a non-destructive test is performed on the longitudinal seam of the cylinder.

[0086] Step 4: Stainless steel is overlaid on the inner wall of the cylinder. Due to forming and welding deformation, the end roundness does not meet the machining and assembly requirements. Then, it is reused... Figure 3 The adjustable support device shown adjusts the ellipticity of the cylinder end, effectively ensuring the processing of the cylinder circumferential seam bevel, while also ensuring that the welding of the cylinder and the end cap meets the requirements for misaligned circumferential seam assembly.

[0087] After completing the above operations, the product cylinder was obtained. The dimensional accuracy of the cylinder was measured from all angles. The roundness at both ends of the cylinder was less than 6mm, indicating that the dimensional data fully met the design requirements. Furthermore, it could be quickly welded to the end cap, and the weld quality was good, meeting the design requirements.

[0088] As can be seen from the above embodiments, the high-precision thick-walled cylinder forming method and auxiliary tooling provided in this application can quickly and reliably obtain rolled pressure vessels with the expected dimensions and performance.

[0089] The present invention has been described above with reference to preferred embodiments; however, these embodiments are merely exemplary and illustrative. Various substitutions and modifications can be made to the present invention based on these embodiments, all of which fall within the scope of protection of the present invention.

Claims

1. A high-precision thick-walled cylinder forming method, characterized in that, The method includes the following steps: Step 1: When cutting the thick-walled cylinder, a pre-bent straight edge is reserved. Specifically, after unfolding according to the middle diameter, pre-bent straight edges are reserved at both ends. The width of the pre-bent straight edge is greater than or equal to twice the thickness of the cylinder wall. Control the cutting size so that the difference between the diagonals of the plates is not greater than 2mm. Step 2 involves a two-stage joining process to join the sheet metal to obtain the cylinder; Step 2 includes the following sub-steps: Sub-step 2-1: Use a heavy-duty plate rolling machine to perform initial rolling and forming of the plate; wherein, when the two ends of the plate are pre-bent during the initial rolling, a template (1) is used to measure the inner arc radius of the plate after the initial rolling and pre-bending near the longitudinal seam, and the inner arc radius is controlled to be consistent with the inner radius after the cylinder is formed; the two ends of the plate can be pre-bent repeatedly based on the measurement results; the area near the longitudinal seam is a plate area with a width of at least 300mm including the longitudinal seam. One end of the template is an arc surface, and the radius of the arc surface is consistent with the inner radius of the formed cylinder; thus, the template can be attached to the inner wall of the board, and the initial rolling degree of the board can be judged by observing the adhesion between the template and the inner wall of the board. Sub-step 2-2: Measure the dimensions of the initially rolled sheet and calculate the sheet elongation. Since the pre-bending process stretches or compresses the sheet, the circumferential dimensions of the sheet will change. Obtaining the sheet elongation can provide a more accurate data basis for subsequent sheet cutting. Sub-steps 2-3: Remove the pre-bent straight edges of the plate; wherein, based on the inner circumference of the end cap to be welded to the cylinder as required, and according to the plate elongation and expected cylinder size, process the removal of the straight edge allowance according to the positive tolerance of the cylinder size, and process the longitudinal seam bevel of the cylinder. In sub-steps 2-4, the sheet metal is joined into a cylinder on a plate rolling machine. The longitudinal seam misalignment is adjusted by welding gate-shaped plates to both ends of the cylinder. With the cooperation of the plate rolling machine, the longitudinal seam is finished. The gate-shaped plate is a plate-shaped metal block that can bear a large enough force. The gate-shaped plate is pushed along the axis of the cylinder by a jack or hydraulic cylinder. The gate-shaped plate then pushes and squeezes the side of the cylinder where it is located, thereby adjusting the longitudinal seam misalignment of the cylinder. When the longitudinal seam misalignment meets the expectation, it is spot welded to fix it. Sub-steps 2-5: longitudinal seam welding of the cylinder, non-destructive testing; Step 3: Perform stress-relieving heat treatment on the cylinder and use the temperature of this heat treatment to round the cylinder; eliminate the thermal stress on the cylinder caused by welding through heat treatment. After heat treatment, air-cool the cylinder. When the temperature drops below 150 degrees Celsius, round the cylinder using a heavy-duty plate rolling machine; during the rounding process, the temperature of the cylinder is controlled between 38 degrees Celsius and 150 degrees Celsius. After the cylinder is rounded, a non-destructive test is performed on the longitudinal seam of the cylinder. Step 4: Weld stainless steel onto the inner wall of the cylinder, and then use an adjustable support device to adjust the ellipticity of the cylinder end to meet the requirements of misaligned edge assembly of the circumferential seam. In step 4, the adjustable support device includes an annular support plate (2), the inner diameter of which is larger than the outer diameter of the cylinder, and is sleeved on the outside of the cylinder; Multiple jacks (3) are provided between the support plate (2) and the cylinder, and the axial direction of the jacks all points to the axis of the cylinder. The jacks are evenly distributed around the cylinder, and there are 16 jacks. Each jack is individually controlled, and different forces can be provided to each jack according to the shape requirements.

2. The high-precision thick-walled cylinder forming method according to claim 1, characterized in that, In sub-step 2-1, before the initial roll forming, the expected longitudinal seam positions are marked on both ends of the sheet metal according to the expected cylinder size.

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