Method for three-roller staggered distance precision spinning of variable wall thickness out-of-round stepped cylinder

Abstract

A three-roller staggered distance precision spinning method for a variable wall thickness cylinder with an outer step is disclosed. By determining the positional relationship between the radial gap of the three rollers and the axial feed distance, the high-precision spinning of the step part of the cylinder with large gradient variable wall thickness is realized. At the same time, the adjustment method and basis of the diameter expansion amount, the pass thinning amount, the roller gap and the staggered distance are given to realize the high-precision forming of the thin-walled and thick-walled straight cylinder. Finally, the high-precision forming control of the full size of the variable wall thickness cylinder with a step is ensured. By using the characteristics of multi-roller staggered reverse spinning, combined with the traditional high-strength steel cylinder power spinning forming method, the high-precision reverse spinning of the full size of the medium diameter variable wall thickness cylinder with an outer step is realized, which provides technical support for the high-precision spinning of the same structure cylinder and other diversified structure cylinders. The present application has the characteristics of simple process, strong operability and conformity to the actual production process, and can mass-produce the ultra-high strength steel variable wall thickness cylinder with an outer step.

Description

Technical Field

[0001] This invention relates to the field of metal processing technology, specifically to a variable wall thickness cylindrical tube with external steps and its ultra-high precision reverse rotation machining method. Background Technology

[0002] Variable-wall thickness stepped thin-walled rotary bodies are a common type of metal cylindrical structure, widely used in various fields due to their unique structural characteristics. The forming processes for this cylinder include rolling and welding, casting, machining, and spinning. Traditional machining and casting methods struggle to guarantee the required microstructure and properties, while rolling and welding reduce the overall performance and increase the weight of the component. High-intensity spinning, however, enables integrated forming, ensuring forming accuracy and enhancing microstructure and properties, making it an effective method for producing variable-wall thickness stepped thin-walled metal cylinders. With continuous technological advancements, the processing accuracy requirements for metal rotary cylinders are becoming increasingly stringent. In the spinning manufacturing field, the straightness of the inner and outer surfaces of variable-wall thickness stepped thin-walled cylinders is a key focus. Precise forming of the tapered connecting step between the thin-walled and thick-walled sections has always been a critical quality challenge for this type of product. Ensuring high-precision forming of this structure significantly impacts the overall component's shape and position accuracy and stability, further enhancing its reliability.

[0003] Limited by a combination of factors such as process parameters, tooling and mold structure, spinning equipment processing capacity, and large gradient changes in product wall thickness, the wall thickness reduction and spinning force of this type of product change drastically at the step. The metal deformation and flow are often unstable, and the step accuracy is poor. This often manifests as serious quality problems such as protruding ridges on the outer surface, grooves on the inner surface, large wall thickness deviation, out-of-tolerance slope and length, and poor axial straightness. This is especially true for medium-diameter cylinders, where the control of the step conical surface accuracy is even more difficult.

[0004] Patent CN 110405040 B, "A Reverse Spinning Method for Ultra-High Strength Steel Outer Step Thin-Walled Cylindrical Body," introduces a reverse spinning process for forming a thin-walled cylindrical body with an outer step by adjusting processing parameters; Patent CN 112474983A, "A Thin-Walled Cylinder with an Outer Annular Boss and Its Spinning Process," introduces a forward spinning method for a thin-walled cylinder with an outer annular boss; neither of the above patents provides a method for high-precision forming of the conical surface of the transition section of the outer step cylindrical body. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, such as poor accuracy of the inner and outer surfaces of the steps, difficulty in controlling the axial length of the conical surface, poor material flowability, and instability under stress, a three-wheel staggered precision spinning method for externally stepped cylinders with variable wall thickness is proposed.

[0006] The outer circumferential surface of the variable-wall thickness stepped cylinder proposed in this invention is stepped, creating a boss in the middle of the cylinder's length, forming a thick-walled section. Both ends of this boss are thin-walled sections of the cylinder, designated as the first and second thin-walled sections, respectively. The outer diameter of the thin-walled section is 950±0.50 mm, and the wall thickness is 3.5±0.20 mm. The wall thickness of the thick-walled section is 8±0.20 mm. The two ends of the thick-walled section transition to the thin-walled section via conical surfaces. These conical surfaces are divided into an outwardly expanding conical surface and an inwardly converging conical surface. The sum of the length of the thick-walled section and the lengths of the conical surfaces at both ends of the thick-walled section is 560 mm, and the projected length of each conical surface is 20±1.0 mm. The total length of the cylinder is 1800 mm.

[0007] Its characteristic is that the specific process is as follows:

[0008] Step 1, Tooling preparation:

[0009] The spinning process is divided into two passes. A three-wheel CNC high-power spinning machine is selected, and the three wheels are used for staggered reverse spinning.

[0010] The tooling preparation includes the preparation of the spinning die and the spinning wheel. Install the spinning mandrel and the spinning wheel; vertically mount the spinning blank onto the mandrel.

[0011] The three rotating wheels used in the reverse spinning process are all double-cone angle rotating wheels with an angle of attack α = 25° and a radius R of 6mm. The three rotating wheels are evenly distributed 120° circumferentially along the spun blank, axially staggered, and arranged in the axial sequence of rotating wheel A, rotating wheel B, and rotating wheel C. Rotating wheel A is the closest to the main shaft of the equipment, while rotating wheels B and C are arranged sequentially away from the main shaft. The axial offset Z between rotating wheels A and B is [missing information]. AB =10mm, axial misalignment Z between wheel B and wheel C BC =8mm.

[0012] Step 2, preparation of the spinning blank;

[0013] Ultra-high strength steel ring forgings are used. The ring forging blanks are solution treated to ensure that the hardness of the annealed forging blanks is HB≤205 and the grain size is greater than or equal to grade 4.

[0014] Step 3: Set the spinning parameters for each pass:

[0015] Each pass includes a first pass and a second pass; each pass is a large-thinning continuous high-intensity spinning process.

[0016] The spinning parameters for each pass include the blank thinning rate, the gap during linear spinning of the three spinning wheels in each pass, the gap during spinning of the conical cylindrical surface of the three spinning wheels in each pass, and the feed ratio.

[0017] The specific process for determining the thinning rate of the blank in the spinning parameters for each pass is as follows:

[0018] The thinning rate of the blank is determined based on the wall thickness of the final formed cylinder. The wall thickness of the final formed cylinder includes the wall thickness t3 of the thick-walled section and the wall thickness t1 of the thin-walled section. The thinning rate of the blank is (t0-t1) / t0. The thinning process of the blank is t0—t3—t1, where t0 is the original wall thickness of the blank.

[0019] Among the spinning parameters for each pass, the specific process for determining the gap during linear spinning with three spinning wheels in each pass is as follows:

[0020] The linear spinning gap of each roller in each pass is determined by formula (1).

[0021]

[0022] Among them, t A t B t C These represent the radial clearance values ​​for rollers A, B, and C, respectively, and Δt is the wall thickness difference before and after each deformation pass. f Z represents the material springback amount per pass, f is the feed ratio per pass, and t is the wall thickness before deformation per pass. For a single spin pass, t = t0. AB Z is the axial misalignment between wheel A and wheel B. BC It is the axial misalignment between wheel B and wheel C.

[0023] Among the spinning parameters for each pass, the specific process for determining the gap between the three spinning wheels when spinning the conical cylindrical surface in each pass is as follows: during the spinning process of forming the conical cylindrical surface, the gap between each spinning wheel is a dynamic process, so that the gap between each spinning wheel is determined by t. A or t B or t C The value is changed to be the same as the wall thickness of the thick-walled section.

[0024] In each spinning pass, the spindle speed is 40±10 r / min. The determined feed ratios are: for the first spinning pass, the feed rate is 60±10 mm / min and the feed ratio is 1.5; for the second spinning pass, the feed rate is 50±10 mm / min and the feed ratio is 1.25.

[0025] Step 4: Determine the machining path for each spinning pass:

[0026] The machining path for one spinning pass: The three spinning wheels perform straight machining along the outer circumferential surface of the blank according to the determined machining parameters.

[0027] The processing path of two-pass spinning: Based on the structural characteristics of the formed cylinder, the two-pass spinning process includes thin-walled section forming - outward expansion cone surface forming - thick-walled section forming - inward convergence cone surface forming - thin-walled section forming.

[0028] The specific process for determining the coordinate points of the wall thickness variation of the spun blank in the two-pass spinning process is as follows:

[0029] Taking the center point of the final spin end section as the origin of the Z-axis, the coordinate points of the wall thickness variation of the spin-formed blank are determined by formula (2) based on the principles of reverse spinning and equal volume forming.

[0030]

[0031] In the formula, B6' is one end face of the cylinder, and in spinning, B6' is the starting point of spinning for each spinning wheel; B1' is the other end face of the cylinder, and in spinning, B1' is the ending point of spinning for each spinning wheel. B6' is also the starting point of the first thin-walled section, and B5' is the ending point of the first thin-walled section. In spinning, all three spinning wheels feed linearly in the (-0, +x) direction according to the cylinder's dimensions. B5' is also the starting point of the expanding conical surface in spinning, and B4' is the ending point of the expanding conical surface. In spinning, all three spinning wheels feed linearly in the (-0, +x) direction according to the cylinder's dimensions. B4' is also the starting point of the thick-walled section, and B3' is the ending point of the thick-walled section. In spinning, all three spinning wheels feed linearly in the (-0, x) direction according to the cylinder's dimensions, based on the set parameters. B3' is the starting point of the inward-convex conical surface, and B2' is the ending point of the inward-convex conical surface. During spinning, all three spinning wheels feed in the (-0, -x) direction according to the dimensions of the cylinder. B2' is also the starting point of the second thin-walled section, and B1' is also the ending point of the second thin-walled section. During spinning, the three spinning wheels feed linearly in the (-0, x) direction according to the set parameters and the dimensions of the cylinder.

[0032] In the formula: L1 is the axial length of the second thin-walled section of the cylinder; L2 is the axial projection length of the outer conical surface of the cylinder, L4 is the axial projection length of the inner conical surface of the cylinder, L2=L4; L3 is the axial length of the thick-walled section of the cylinder.

[0033] In the two-pass spinning process, the specific process for determining the machining path of each spinning wheel in the conical surface machining is as follows:

[0034] The expanding and contracting conical surfaces are each divided into 5 segments, and the start and end points of each segment are determined by formula (3):

[0035]

[0036] In the formula: Z1~Z6 are the start and end points of each segment, respectively; θ is the angle of the spinning path of each spinning wheel; t A1 Let t be the clearance value of wheel A at point Z1.B1 Let t be the clearance value of wheel B at point Z1. C1 t is the clearance value of the C-roller at point Z1; A2 Let t be the clearance value of wheel A at point Z2. B2 Let t be the clearance value of wheel B at point Z2. C2 t is the clearance value of the C-roller at point Z2; A3 Let t be the clearance value of wheel A at point Z3. B3 Let t be the clearance value of wheel B at point Z3. C3 t is the clearance value of the C-roller at point Z3; A4 Let t be the clearance value of wheel A at point Z4. B4 Let t be the clearance value of wheel B at point Z4. C4 t is the clearance value of the C-roller at point Z4; A5 Let t be the clearance value of wheel A at point Z5. B5 Let t be the clearance value of wheel B at point Z5. C5 The clearance value of the C-roller at point Z5; t A6 Let t be the clearance value of wheel A at point Z6. B6 Let t be the clearance value of wheel B at point Z6. C6 This is the clearance value of the C-rotor at point Z6.

[0037] Step 5, Spinning processes in each pass:

[0038] One-pass high-intensity spinning process: A three-wheel staggered reverse spinning method is used. Based on the calculation method for the thinning rate of the spun blank, the total thinning rate for this pass is determined to be 30%–40%. The three wheels perform one-pass high-intensity spinning on the spun blank according to the set process parameters.

[0039] Two-pass high-intensity spinning: A three-wheel staggered reverse spinning method is used. Based on the calculation method for the thinning rate of the spun blank, the total thinning rate for this two-pass process is determined to be 34%–55%. The three wheels perform two-pass high-intensity spinning on the spun blank according to the set process parameters.

[0040] This completes the process of machining a variable wall thickness cylinder with an external step using a three-rotor staggered spinning process.

[0041] This invention utilizes the characteristics of multi-rotor staggered reverse spinning and combines it with the traditional high-strength steel cylinder strong spinning forming method to propose a precision reverse spinning processing method for cylinders with variable wall thickness and external steps. This method can achieve high-precision reverse spinning within the full size range of medium-diameter cylinders with variable wall thickness and external steps.

[0042] Based on the dimensions of the cylinder to be processed and the proposed process plan, a spinning blank was designed and prepared. A spinning process plan and route for the variable-wall thickness cylinder with external steps were formulated. Precision spinning deformation of the variable-wall thickness cylinder with external steps was performed, ultimately achieving high-precision spinning forming of the variable-wall thickness cylinder with external steps. This provides a new general solution and technical support for the high-precision processing of similar spun cylinders and other diverse structural cylinders.

[0043] This invention proposes a machining path calculation method for variable-wall-thickness stepped cylinders by determining the positional relationship between the radial clearance of the three rotary wheels and the axial feed distance, achieving ultra-high precision machining of the stepped sections of cylinders with large gradient variable-wall-thickness. Simultaneously, it provides methods for adjusting the thinning amount per pass, rotary wheel clearance, and offset, achieving high-precision forming of both thin-walled and thick-walled straight cylindrical sections. Ultimately, this ensures high-precision forming control of the entire dimension of the variable-wall-thickness stepped cylinder.

[0044] The present invention provides a high-precision variable wall thickness stepped cylinder. The wall thickness, diameter and form and position accuracy of the straight section of the cylinder all meet the design requirements. The appearance quality and form and position accuracy of the inner and outer surfaces at the cylinder step are greatly improved. The slope of the outer surface of the step is consistent and the length is consistent. The inner surface has a smooth transition. The axial straightness fully meets the requirements and there are no obvious tool marks.

[0045] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0046] 1. This invention clarifies a high-precision reverse spinning method for variable wall thickness strip outer stepped cylinders. This method combines the plastic forming characteristics of materials and the principle of reverse spinning, and provides a high-precision spinning control method for variable wall thickness strip outer stepped cylinders from multiple aspects and dimensions, such as controlling the radial clearance and axial misalignment clearance of the spinning wheel throughout the entire process, determining the key points of the final spinning pass, and determining the segmented spinning program of the stepped conical surface.

[0047] 2. In response to the problems of poor accuracy in existing conical surface forming, this invention innovatively proposes to utilize the principles of calculus and adopt a segmented processing program to dynamically adjust the gap between the three rotating wheels with axial feed. This invention provides specific calculation formulas, which can ensure that the material is subjected to relatively balanced stress during the forming process of the conical segment, which conforms to the actual production process and has good adaptability.

[0048] 3. The method proposed in this invention is simple in process, easy to operate, and can be used for mass production of ultra-high strength steel variable wall thickness cylindrical tubes with external steps. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of a cylindrical structure.

[0050] Figure 2 This is a schematic diagram of the blank structure.

[0051] Figure 3This is an axial distribution diagram of the wheel misalignment of the present invention.

[0052] Figure 4 This is a schematic diagram of the coordinate points of the wall thickness variation of the spinning blank during the second spinning process.

[0053] Figure 5 This is a schematic diagram showing the lengths of each segment in the variation of the wall thickness of the spun blank.

[0054] Appendix Figure 6 This is a schematic diagram of the machining path of the three rotary wheels when machining a stepped conical surface.

[0055] Figure 7 This is a schematic diagram of the structure of the cylinder obtained in the embodiment.

[0056] Figure 8 This is a schematic diagram of the blank structure in the embodiment.

[0057] Figure 9 This is a flowchart of the present invention.

[0058] In the diagram: 1. Second thin-walled section; 2. Inward conical surface; 3. Thick-walled section; 4. Outward conical surface; 5. First thin-walled section; 6. A-wheel; 7. B-wheel; 8. C-wheel; 9. C-wheel machining path; 10. B-wheel machining path; 11. A-wheel machining path. Detailed Implementation

[0059] This embodiment uses a three-wheel vertical CNC high-power spinning machine to perform two consecutive spinning processes on a medium-diameter variable-wall thickness cylinder with an external step. The outer circumferential surface of the processed cylinder is stepped, creating a boss in the middle of the cylinder's length, forming a thick-walled section 3. Both ends of this boss are thin-walled sections of the cylinder, namely the first thin-walled section 5 and the second thin-walled section 1. The outer diameter of the thin-walled section is Φ950±0.50mm, and the wall thickness is 3.5±0.20mm. The wall thickness of the thick-walled section is 8±0.20mm. The two ends of the thick-walled section transition to the thin-walled section via conical surfaces. These conical surfaces are divided into an outwardly expanding conical surface 4 and an inwardly converging conical surface 2. The sum of the length of the thick-walled section and the lengths of the conical surfaces at both ends of the thick-walled section is 560mm, and the projected length of each conical surface is 20±1.0mm. The total length of the cylinder is 1800mm.

[0060] The spinning process in this embodiment is divided into two passes. The specific process is as follows:

[0061] Step 1, Tooling preparation:

[0062] Based on the dimensions and spinning pressure of the medium-diameter variable wall thickness cylindrical tube with external steps to be processed, a three-wheel CNC high-power spinning machine is selected, and the three wheels are used for staggered reverse spinning to form the tube.

[0063] Spinning Die: The spinning die adopts existing technology. The die material is Cr12MoV, which has good hardenability during spinning; the outer diameter of the spinning die is Φ942.90mm, and the length of the spinning working part is 1200mm. The outer diameter of the core die satisfies D<(D 设计公差范围最小内径 -0.20).

[0064] Spinning wheels: A three-wheel staggered reverse spinning forming method is adopted. The three spinning wheels have the same geometric parameters, all being double-cone angle spinning wheels with a spinning wheel angle of attack α = 25° and a spinning wheel radius R of 6mm. The three spinning wheels are evenly distributed 120° around the circumference of the spinning blank, and are axially staggered and arranged in the axial sequence of spinning wheel A, spinning wheel B, and spinning wheel C. Spinning wheel A is the spinning wheel closest to the main shaft of the equipment, and spinning wheels B and C are arranged sequentially away from the main shaft of the equipment. The axial offset Z between spinning wheels A and B is Z. AB =10mm, axial misalignment Z between wheel B and wheel C BC =8mm.

[0065] After installing the spinning mandrel and spinning wheel, apply sufficient lubricating oil evenly to the inner wall of the blank and the working surface of the mandrel. Then, vertically lift the spinning blank and place it onto the mandrel.

[0066] When installing the core mold and rotating wheel, the circular runout of the core mold should not exceed 0.05.

[0067] Step 2, Preparation of the spinning blank:

[0068] The external dimensions of the spinning blank are determined based on the material properties, the determined process thinning route, and the thinning rate per pass, following the principle of constant volume.

[0069] The variable wall thickness cylindrical spinning blank with external steps in this invention is made of ultra-high strength steel ring forging. The ring forging blank is subjected to solution treatment and annealing treatment. The forging is then machined to obtain a spinning blank that meets the design dimensions. The hardness is required to be HB≤205 and the grain size is greater than or equal to level 4.

[0070] Step 3: Set the spinning parameters for each pass:

[0071] Each pass includes a first pass and a second pass; each pass is a large-thinning continuous high-intensity spinning process.

[0072] The process employs a three-wheel staggered spinning method, consisting of a spinneret A, a spinneret B, and a spinneret C. The three spinnerets are evenly distributed around the circumference of the mandrel to ensure balanced force distribution, while being staggered along the axial direction of the mandrel to achieve large thinning deformation in a single pass.

[0073] I. Determine the thinning rate of the blank. The thinning rate of the blank is determined based on the wall thickness of the final formed cylinder. The wall thickness of the final formed cylinder includes the wall thickness t3 of the thick-walled section and the wall thickness t1 of the thin-walled section. The thinning rate of the blank is (t0-t1) / t0. The thinning process of the blank is t0—t3—t1, where t0 is the original wall thickness of the blank.

[0074] II. Determine the clearance during linear spinning of the three spinning wheels in each pass.

[0075] The linear spinning gap of each roller in each pass is determined by formula (1).

[0076]

[0077] Among them, t A t B t C These represent the radial clearance values ​​for rollers A, B, and C, respectively, and Δt is the wall thickness difference before and after each deformation pass. f Z represents the material springback amount per pass, f is the feed ratio per pass, and t is the wall thickness before deformation per pass. For a single spin pass, t = t0. AB Z is the axial misalignment between wheel A and wheel B. BC It is the axial misalignment between wheel B and wheel C.

[0078] Ⅲ Determine the clearance when the three rotary wheels spin the conical cylindrical surface in each pass.

[0079] During the spinning process of forming a cylindrical conical surface, the gap between each spinning wheel is a dynamic process, causing the gap between each spinning wheel to change from t to... A or t B or t C The value is changed to be the same as the wall thickness of the thick-walled section.

[0080] IV. Determine the feed ratio. The feed ratio is the ratio of feed rate to spindle speed. The spindle speed is 40±10 r / min; for a single pass spinning, the feed rate is 60±10 mm / min; the feed ratio is determined to be 1.5. For a two-pass spinning, the feed rate is 50±10 mm / min; the feed ratio is determined to be 1.25.

[0081] Step 4: Determine the machining path for each spinning pass:

[0082] The machining path for one spinning pass: The three spinning wheels perform straight machining along the outer circumferential surface of the blank according to the determined machining parameters.

[0083] The two-pass spinning process, based on the structural characteristics of the formed cylinder, includes thin-walled section forming—outward-expanding conical surface forming—thick-walled section forming—inward-convex conical surface forming—thin-walled section forming. When determining the two-pass spinning process path:

[0084] I. Determine the coordinate points where the wall thickness of the spun blank changes during the two-pass spinning process. The specific process is as follows:

[0085] Taking the center point of the final spin end section as the origin of the Z-axis, the coordinate points of the wall thickness variation of the spin-formed blank are determined by formula (2) based on the principles of reverse spinning and equal volume forming.

[0086]

[0087] In the formula, B6' is one end face of the cylinder, and in spinning, B6' is the starting point of spinning for each spinning wheel; B1' is the other end face of the cylinder, and in spinning, B1' is the ending point of spinning for each spinning wheel. B6' is also the starting point of the first thin-walled section, and B5' is the ending point of the first thin-walled section. In spinning, all three spinning wheels feed linearly in the (-0, +x) direction according to the cylinder's dimensions. B5' is also the starting point of the expanding conical surface in spinning, and B4' is the ending point of the expanding conical surface. In spinning, all three spinning wheels feed linearly in the (-0, +x) direction according to the cylinder's dimensions. B4' is also the starting point of the thick-walled section, and B3' is the ending point of the thick-walled section. In spinning, all three spinning wheels feed linearly in the (-0, x) direction according to the cylinder's dimensions, based on the set parameters. B3' is the starting point of the inward-convex conical surface, and B2' is the ending point of the inward-convex conical surface. During spinning, all three spinning wheels feed in the (-0, -x) direction according to the dimensions of the cylinder. B2' is also the starting point of the second thin-walled section, and B1' is also the ending point of the second thin-walled section. During spinning, the three spinning wheels feed linearly in the (-0, x) direction according to the set parameters and the dimensions of the cylinder.

[0088] In this embodiment, Z B1’ =Z1=150mm, Z B2’ =368.75mm, Z B3’ =383.1mm, Z B4’ = 903.1mm, Z B5’ = 917.45mm, Z B6’ =1241.2mm.

[0089] In the formula: L1 is the axial length of the second thin-walled section of the cylinder; L2 is the axial projection length of the outer conical surface of the cylinder, L4 is the axial projection length of the inner conical surface of the cylinder, L2=L4; L3 is the axial length of the thick-walled section of the cylinder.

[0090] II. Determine the machining path of each rotary wheel in the conical surface machining.

[0091] The expanding and contracting conical surfaces are each divided into multiple segments. In this embodiment, they are divided into 5 segments. The start and end points of each segment are determined by formula (3):

[0092]

[0093] In the formula: Z1~Z6 are the start and end points of each segment, respectively; θ is the angle of the spinning path of each spinning wheel; t A1 Let t be the clearance value of wheel A at point Z1. B1 Let t be the clearance value of wheel B at point Z1. C1 t is the clearance value of the C-roller at point Z1; A2 Let t be the clearance value of wheel A at point Z2. B2 Let t be the clearance value of wheel B at point Z2. C2 t is the clearance value of the C-roller at point Z2; A3 Let t be the clearance value of wheel A at point Z3. B3 Let t be the clearance value of wheel B at point Z3. C3 t is the clearance value of the C-roller at point Z3; A4 Let t be the clearance value of wheel A at point Z4. B4 Let t be the clearance value of wheel B at point Z4. C4 t is the clearance value of the C-roller at point Z4; A5 Let t be the clearance value of wheel A at point Z5. B5 Let t be the clearance value of wheel B at point Z5. C5 The clearance value of the C-roller at point Z5; t A6 Let t be the clearance value of wheel A at point Z6. B6 Let t be the clearance value of wheel B at point Z6. C6 This is the clearance value of the C-rotor at point Z6.

[0094] In this embodiment, the coordinates of the start and end points of each segment on the Z-axis are as follows: Z1 = 8.8, Z2 = 13.4, Z3 = 15.2, Z4 = 16, Z5 = 26, Z6 = 34.

[0095] In this embodiment, t A1 =6.2, t B1 =4.4, t C1 =2.7; t A2 =7.2, t B2 =4.4, t C2 =2.7; t A3 =7.6, t B3 =4.8, t C3 =2.7; t A4 =8,t B4 =5.0, t C4 =2.9; t A5 =8,t B5 =8,t C5 =5.1; t A6 =t B6 =t C6 =8.

[0096] Step 5, Spinning processes in each pass:

[0097] One-pass high-intensity spinning process: A three-wheel staggered reverse spinning method is used. Based on the calculation method for the thinning rate of the spun blank, the total thinning rate for this pass is determined to be 30%–40%. The three wheels perform one-pass high-intensity spinning on the spun blank according to the set process parameters.

[0098] In this embodiment, the total thinning rate of a single heavy-duty spinning process is 38.5%, which means a thinning amount of 5 mm per pass. The spindle speed is 40±10 r / min, and the feed rate is 60±10 mm / min. The processing parameters for one pass are shown in Table 1.

[0099] Table 1. Processing parameters for one pass

[0100] First round mm 5 0.8 11.02 9.05 7.2 10 8

[0101] Two-pass high-intensity spinning: A three-wheel staggered reverse spinning method is used. Based on the calculation method for the thinning rate of the spun blank, the total thinning rate for this two-pass process is determined to be 34%–55%. The three wheels perform two-pass high-intensity spinning on the spun blank according to the set process parameters.

[0102] In this embodiment, the total thinning rate of the two-pass high-strength spinning process is 34.6%, that is, the thinning amount per pass is 4.5 mm, the spindle speed is 40±10 r / min, and the feed rate is 50±10 mm / min. The two-pass processing parameters are shown in Table 2.

[0103] Table 2. Second-pass processing parameters

[0104] Second round mm 4.5 0.8 6.20 4.40 2.7 10 8

[0105] This completes the process of machining a variable wall thickness cylindrical tube with an external step using a three-rotor staggered spinning process.

Claims

1. A three-wheel staggered precision spinning method for a variable-wall thickness outer stepped cylinder, wherein the outer circumferential surface of the variable-wall thickness outer stepped cylinder is stepped, forming a boss in the middle of the cylinder's length, creating a thick-walled section; both ends of the boss are thin-walled sections of the cylinder, namely a first thin-walled section and a second thin-walled section; the outer diameter of the thin-walled section is 950±0.50mm, and the wall thickness is 3.5±0.20mm; the wall thickness of the thick-walled section is 8±0.20mm; both ends of the thick-walled section transition to the thin-walled section via conical surfaces; the conical surfaces are divided into an outwardly expanding conical surface and an inwardly converging conical surface; the sum of the length of the thick-walled section and the lengths of the conical surfaces at both ends of the thick-walled section is 560mm, and the projected length of each conical surface is 20±1.0mm; the total length of the cylinder is 1800mm; Its features are, The specific process is as follows: Step 1, Tooling preparation: The spinning process is divided into two passes. A three-wheel CNC high-power spinning machine is selected, and the three wheels are used for staggered reverse spinning. The tooling preparation includes the preparation of the spinning die and the spinning wheel; the installation of the spinning mandrel and the spinning wheel; and the vertical mounting of the spinning blank onto the mandrel. Step 2, preparation of the spinning blank; Ultra-high strength steel ring forging blanks are used; the ultra-high strength steel ring forging blanks are subjected to solution treatment so that the hardness of the annealed ultra-high strength steel ring forging blanks is HB≤205 and the grain size is greater than or equal to level 4; Step 3: Set the spinning parameters for each pass: Each pass includes a first pass and a second pass; each pass is a large-thinning continuous high-intensity spinning process. The spinning parameters for each pass include the blank thinning rate, the gap during linear spinning of the three spinning wheels in each pass, the gap during spinning of the cylindrical conical surface of the three spinning wheels in each pass, and the feed ratio. In the spinning parameters for each pass, the specific process for determining the blank thinning rate is as follows: the blank thinning rate is determined based on the wall thickness of the final formed cylinder; the wall thickness of the final formed cylinder includes the wall thickness t3 of the thick-walled section and the wall thickness t1 of the thin-walled section; the blank thinning rate is (t0-t1) / t0; the blank thinning process is t0—t3—t1, where t0 is the original wall thickness of the blank; The specific process for determining the gap during linear spinning of the three spinning wheels in each pass, as described in the setting of spinning parameters for each pass, is as follows: The linear spinning gap of each roller in each pass is determined by formula (1); Among them, t A t B t C These represent the radial clearance values ​​for rollers A, B, and C, respectively, and Δt is the wall thickness difference before and after each deformation pass. f Z represents the material springback amount per pass, f is the feed ratio per pass, t is the wall thickness before deformation per pass, and when spinning per pass, t = t0; AB Z is the axial misalignment between wheel A and wheel B. BC It is the axial misalignment between wheel B and wheel C; α is the angle of attack of the wheels; Step 4: Determine the machining path for each spinning pass: The machining path for one spinning pass: the three spinning wheels process in a straight line along the outer circumferential surface of the blank according to the determined machining parameters; The processing path of two-pass spinning: Based on the structural characteristics of the formed cylinder, the two-pass spinning process includes thin-walled section forming - outward expanding conical surface forming - thick-walled section forming - inward conical surface forming - thin-walled section forming; Step 5, spinning processes in each pass: One-pass high-intensity spinning process: a three-wheel staggered reverse spinning forming method is adopted; according to the calculation method of the thinning rate of the spinning blank, the total thinning rate of this pass is determined to be 30% to 40%; the three wheels perform one-pass high-intensity spinning process on the spinning blank according to the set process parameters; Two-pass high-intensity spinning: a three-wheel staggered reverse spinning forming method is adopted; according to the calculation method of the thinning rate of the spinning blank, the total thinning rate of the two passes is determined to be 34% to 55%; the three wheels perform two-pass high-intensity spinning on the spinning blank according to the set process parameters; This completes the process of machining a variable wall thickness cylindrical tube with an external step using a three-rotor staggered spinning process.

2. The three-wheel staggered precision spinning method for variable wall thickness outer stepped cylinders as described in claim 1, characterized in that, The three rotating wheels used in the staggered reverse spinning forming process are all double-cone angle rotating wheels with an angle of attack α = 25° and a radius R of 6mm. The three rotating wheels are evenly distributed 120° circumferentially along the spinning blank, axially staggered, and arranged in the axial sequence of rotating wheel A, rotating wheel B, and rotating wheel C. Rotating wheel A is the closest to the main shaft of the equipment, while rotating wheels B and C are arranged sequentially away from the main shaft. The axial offset Z between rotating wheels A and B is [missing information]. AB =10mm, Axial misalignment Z between wheel B and wheel C BC =8mm.

3. The three-wheel staggered precision spinning method for variable wall thickness outer stepped cylinders as described in claim 1, characterized in that, In setting the spinning parameters for each pass, the specific process for determining the gap between the three spinning wheels when spinning the cylindrical conical surface in each pass is as follows: during the spinning process of forming the cylindrical conical surface, the gap between each spinning wheel is a dynamic process, so that the gap between each spinning wheel is determined by the radial gap value t of spinning wheel A. A Or the radial clearance value t of the B-roller B Or C-roller radial clearance value t C The value is changed to be the same as the wall thickness of the thick-walled section.

4. The three-wheel staggered precision spinning method for variable wall thickness outer stepped cylinders as described in claim 1, characterized in that, In each spinning pass, the spindle speed is 40±10 r / min; the determined feed ratio is: for the first spinning pass, the feed rate is 60±10 mm / min and the feed ratio is 1.5; for the second spinning pass, the feed rate is 50±10 mm / min and the feed ratio is 1.

25.

5. The three-wheel staggered precision spinning method for variable wall thickness outer stepped cylinders as described in claim 1, characterized in that, In the two-pass spinning process, the specific process for determining the coordinate points of the wall thickness change of the spinning blank is as follows: taking the center point of the final spinning end section as the origin of the Z-axis, and based on the principles of reverse spinning and equal volume forming, the coordinate points of the wall thickness change of the spinning blank are determined by formula (2). In the formula, B6' is one end face of the cylinder, and in spinning, B6' is the starting point of spinning for each spinning wheel; B1' is the other end face of the cylinder, and in spinning, B1' is the ending point of spinning for each spinning wheel; B6' is also the starting point of the first thin-walled section, and B5' is the ending point of the first thin-walled section. In spinning, all three spinning wheels feed linearly in the direction (-0, x) according to the dimensions of the cylinder; B5' is also the starting point of the expanding conical surface in spinning, and B4' is the ending point of the expanding conical surface. In spinning, all three spinning wheels feed linearly in the direction (-0, x) according to the dimensions of the cylinder. The three rotary wheels feed in the (-0, x) direction according to the set parameters and the dimensions of the cylinder; B4' is also the starting point of the thick-walled section, and B3' is the ending point of the thick-walled section. During the spinning process, the three rotary wheels feed in a straight line in the (-0, x) direction according to the set parameters and the dimensions of the cylinder; B3' is also the starting point of the inward conical surface, and B2' is the ending point of the inward conical surface. During the spinning process, the three rotary wheels feed in a straight line in the (-0, x) direction according to the set parameters and the dimensions of the cylinder; B2' is also the starting point of the second thin-walled section, and B1' is also the ending point of the second thin-walled section. During the spinning process, the three rotary wheels feed in a straight line in the (-0, x) direction according to the set parameters and the dimensions of the cylinder. In the formula: L1 is the axial length of the second thin-walled section of the cylinder; L2 is the axial projection length of the outer conical surface of the cylinder; L4 is the axial projection length of the inner conical surface of the cylinder; L2=L4; L3 is the axial length of the thick-walled section of the cylinder.

6. The three-wheel staggered precision spinning method for variable wall thickness outer stepped cylinders as described in claim 1, characterized in that, In the two-pass spinning process, the specific process for determining the machining path of each spinning wheel in the conical surface machining is as follows: the outward-expanding conical surface and the inward-convex conical surface are each divided into 5 segments, and the start and end points of each segment are determined by formula (3). （3） In the formula: Z1~Z6 are the start and end points of each segment, respectively; θ is the angle of the spinning path of each spinning wheel; t A1 Let t be the clearance value of wheel A at point Z1. B1 Let t be the clearance value of wheel B at point Z1. C1 t is the clearance value of the C-roller at point Z1; A2 Let t be the clearance value of wheel A at point Z2. B2 Let t be the clearance value of wheel B at point Z2. C2 t is the clearance value of the C-roller at point Z2; A3 Let t be the clearance value of wheel A at point Z3. B3 Let t be the clearance value of wheel B at point Z3. C3 t is the clearance value of the C-roller at point Z3; A4 Let t be the clearance value of wheel A at point Z4. B4 Let t be the clearance value of wheel B at point Z4. C4 The clearance value of the C-roller at point Z4; t A5 Let t be the clearance value of wheel A at point Z5. B5 Let t be the clearance value of wheel B at point Z5. C5 The clearance value of the C-roller at point Z5; t A6 Let t be the clearance value of wheel A at point Z6. B6 Let t be the clearance value of wheel B at point Z6. C6 This is the clearance value of the C-rotor at point Z6.

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