A high-precision rolling and cutting method for metal pipes and a model for strictly controlling angle defects with variable pitch

Abstract

This invention relates to a high-precision rolling and cutting method for metal tubes and a model for strictly controlling corner defects using variable pitch, within the field of metal deformation. Specifically, it relates to a high-precision rolling and cutting method for metal tubes and a model for strictly controlling corner defects using variable pitch, comprising the following steps: A cutter with a rectangular cross-section and a gradually decreasing pitch is spirally wound around the surface of a cylindrical roll. The cutter width... W The three rolls obtained in the first step are uniformly distributed in parallel space at 120-degree angles to each other. The three-dimensional space between the three rolls and the mandrel located inside the metal tube billet is the deformation zone. This invention uses a variable pitch rolling model to clarify the quantitative relationship between arbitrary radial reduction and axial extension. By gradually reducing the pitch of the cutter on the roll surface, the axial extension deformation is reduced, thereby improving the fill of the pass and achieving the function of strictly controlling the corner loss, which greatly improves the geometric dimensional accuracy of the bearing ring after cutting. At the same time, the cutting speed can be increased by adjusting the roll speed, thereby increasing the productivity.

Description

Technical Field

[0001] This invention relates to the field of metal deformation, specifically to a high-precision rolling and cutting method for metal tubes and a model for strictly controlling corner defects by varying pitch. Background Technology

[0002] Common methods for cutting metal pipes along their cross-sections in industrial production include cutting stationary pipes using static shearing machines or sawing machines, and cutting moving pipes online using flying shears or flying saws. The geometric accuracy of the cut cross-section and metal loss are major drawbacks. Furthermore, for materials with high toughness and plasticity, the resistance, deformation, and heat generated during cutting are significant, resulting in relatively poor machinability.

[0003] Spiral roll forming is a special rolling technology with advantages such as high production efficiency, high material utilization, good product quality, and low noise. It is particularly suitable for forming periodically complex rotating cross-section parts, such as spheres, fins, and variable cross-section shafts. However, due to the different forming characteristics of different product types, specialized research is required. With the increasing maturity of numerical simulation technology, opportunities have arisen for in-depth exploration, especially in the forming of hollow cross-section components.

[0004] In their paper "Numerical Simulation and Analysis of Inclined Threaded Anchor Rods", Chao Guoliang et al. analyzed the stress-strain distribution law of hollow threaded anchor rods. However, they found that during the spiral rolling process, due to metal flow, the inner wall of the tube would expand internally. Sun Tangping et al. used DEFORM-3D technology to obtain the three-dimensional stress-strain distribution characteristics of steel circular finned tubes; Chen Qiquan et al. analyzed the strain distribution law during the rolling process of integral steel high-spiral finned tubes; Zhang Lin et al. studied the motion relationship between the rolls and the rolled piece and the axial and tangential velocity distribution law in the deformation zone during the skew rolling process of integral spiral high-finned tubes; Ni Junyi used DEFORM-3D to simulate the rolling process of external thread anchor bolts and analyzed the influence of different process parameters on the inner and outer diameters and wall thickness of the rolled piece. Janusz Tomczak et al. proposed a rolling process for ball-head pins using a spiral die and verified its feasibility through numerical calculations and experimental results.

[0005] The aforementioned hollow tube forming process is all related to the compression of the outer diameter of the round tube and the reduction of the wall thickness. If the tube wall is smaller than the cutting depth of the spiral protrusion of the roll, it is possible to cut the hollow tube through a plastic deformation process in which the wall thickness of the round tube gradually decreases. This is especially suitable for the rapid cutting of bearing rings and other materials according to the bearing height, which can improve production efficiency and save costs. Gao Xin et al. explored this aspect in "Numerical Simulation and Analysis of Inner Ring Blanks of Skew Rolled Tapered Roller Bearings" and Li Zhi et al. in "Numerical Simulation and Analysis of Spiral Pass Skew Rolling Forming of Bearing Ring Blanks". However, there are problems such as the gradual reduction of the outer diameter of the tube and the unevenness of the inner wall; and the forming process along the axial length of the tube wall. The filling degree of the cavity corners on the outer surface of the tube is not ideal, and almost 30°~60° of missing corners are present. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a high-precision rolling and cutting method for metal tubes, which can significantly improve the filling degree of the cavity corners on the outer surface of the tube, thereby increasing production efficiency and cutting accuracy, as well as a model for strictly controlling corner defects using variable pitch.

[0007] This invention discloses a high-precision rolling and cutting method for metal tubes, comprising the following steps: The first step is roll design. A cutter with a rectangular cross-section and gradually decreasing pitch is spirally wound on the surface of a cylindrical roll. The cutter width... W Remain unchanged; The second step is to construct the deformation zone. The three rolls obtained in the first step are evenly distributed in space at 120 degrees to each other. The three-dimensional space between the three rolls and the mandrel located inside the tube blank is the deformation zone. The third step is rolling and cutting. The metal tube blank is fitted onto the mandrel, with the outer diameter of the mandrel being equal to the inner diameter of the metal tube. It is fed into the deformation zone from one end. The rolls rotate around their central axes, driving the metal tube blank to move spirally forward toward the other end of the deformation zone. During this process, the cutters on the rolls bite into the metal tube blank and gradually cut into it. The tube is allowed to spread freely between the rolls, and the inner diameter is restricted by the internal mandrel and no longer decreases. The metal tube blank is gradually cut, and the cut surface gradually expands from the outer surface of the metal tube blank inward until the metal tube blank is cut off. The spiral line at the center of the side of the cutter facing the roll is an Archimedean spiral. With the center of the transverse circular tangent where the thread begins as the origin of the coordinate system, any point on the spiral line of the roll's base cylindrical surface is designated as the radial axis (x-axis), tangential axis (y-axis), and axial axis (z-axis). The starting position... θ =0, corresponding to the coordinates of the point (R,0,0), and the coordinates of the point (x,y,z) at any time and any position satisfy the following formula: In the formula: i —Number of cutter rotations, 1≤i≤n, where n is the total number of rotations; T i —Pitch of the i-th turn of the helix, mm; T 0 —Initial pitch, mm; R —Relative radius of the roll base circle, mm; θ —The angle of blade rotation at any given moment, in degrees; Δ T i —Reduction in pitch per turn, mm; Z i，θ —The position of the cutter's rotation angle θ in the z-direction at any given time during the i-th cutter rotation; Furthermore, the variable pitch rolling model is satisfied during the metal tube cutting process: In the formula, R The base circle radius of the roll is in mm; W The width of the cutter is in mm; L The length of the single-circle cutter development line, in mm; d The outer diameter of the metal tube blank is in mm; s The thickness of the metal tube blank is in mm; β The helix angle; α is the lateral width expansion coefficient; i For the number of cutter turns, n is the maximum number of cutter rotations. The axial extension is expressed in mm. The pitch change of the cutter is expressed in mm. For the first cutting knife i Coil compression amount, mm; For the first i Set the cutting height to any position on the circle; and Cutting height at 180° intervals; Tool height H Increasing according to the Archimedean spiral; V The volume pressed down by the cutter along the thickness of the metal tube blank, in mm. 3 ; V1 represents the volume of metal flowing axially along the metal tube blank when the cutter bites into it, in mm. 3 ; V 2 represents the volume of metal expanding laterally along the metal tube blank when the cutter bites into it, in mm. 3 ; ξ represents the roundness of the cross-section; the closer this value is to 1.0, the rounder the cross-section. When V - (V1 + V2) = 0, When the cutter on the roll bites into the metal tube blank, the metal tube blank undergoes compression deformation, while the outer diameter remains unchanged and the cross-section is straight.

[0008] Preferably, the metal tube blank has an outer diameter of 50mm-150mm and a wall thickness of 10mm-30mm. During the rolling process, the initial helix angle is 2.3°-6°, the initial pitch is 25mm-150mm, and the pitch reduction rate is 10%-30%.

[0009] Preferably, the metal tube blank is a GCr15 metal tube blank or a tubular blank of carbon steel or alloy steel.

[0010] Preferably, all three rollers are active rollers.

[0011] A model for strictly controlling corner defects using variable pitch screw threads, the model being: In the formula, R The base circle radius of the roll is in mm; W The width of the cutter is in mm; L The length of the single-circle cutter development line, in mm; d The outer diameter of the metal tube blank is in mm; s The thickness of the metal tube blank is in mm; β The helix angle; α is the lateral width expansion coefficient; i For the number of cutter turns, n is the maximum number of cutter rotations. The axial extension is expressed in mm. The pitch change of the cutter is expressed in mm. For the first cutting knife i Coil compression amount, mm; For the first i Set the cutting height to any position on the circle; and Cutting height at 180° intervals; Tool height H Increasing according to the Archimedean spiral; V The volume pressed down by the cutter along the thickness of the metal tube blank, in mm. 3 ; V 1 represents the volume of metal flowing axially along the metal tube blank when the cutter bites into it, in mm. 3 ; V 2 represents the volume of metal expanding laterally along the metal tube blank when the cutter bites into it, in mm. 3 ; ξ represents the roundness of the cross-section; the closer this value is to 1.0, the rounder the cross-section. When V - (V1 + V2) = 0, When the cutter on the roll bites into the metal tube blank, the metal tube blank undergoes compression deformation, while the outer diameter remains unchanged and the cross-section is straight.

[0012] This invention utilizes a variable pitch rolling model to clarify the quantitative relationship between arbitrary radial reduction and axial extension. By gradually reducing the pitch of the cutters on the roll surface, axial extension deformation is reduced, thereby improving the roll fill and achieving strict control over corner loss, significantly improving the geometric dimensional accuracy of the bearing ring after cutting. Simultaneously, the cutting speed can be increased by adjusting the roll speed, thus improving productivity. Attached Figure Description

[0013] Figure 1 This is a schematic diagram illustrating the rolling principle of the present invention.

[0014] Figure 2 For metal tube blanks subjected to the first i A schematic diagram of the instantaneous state of the circular cutter.

[0015] Figure 3 This is a schematic diagram of the equivalent strain distribution during the rolling deformation process of the present invention and a comparative example.

[0016] Figure 4 This is a comparative analysis diagram showing the corner defects of the metal tube blanks during the second to third rolling processes in this invention and the comparative example.

[0017] Figure 5 This is a schematic diagram illustrating the variation of rolling force during the rolling process of metal tube blanks in this invention and comparative examples.

[0018] Figure 6 This is a schematic diagram illustrating the variation of rolling torque during the rolling process of metal tube blanks in this invention and comparative examples.

[0019] Reference numerals: 1-roll, 2-metal tube blank, 3-mandrel, 4-cutter.

[0020] This invention discloses a high-precision rolling and cutting method for metal tubes, comprising the following steps: The first step is the design of roll 1. A cutter 4 with a rectangular cross-section and gradually decreasing pitch is spirally wound on the surface of the cylindrical roll 1. The width of cutter 4 is... W Remain unchanged; The second step is to construct the deformation zone. The three rolls 1 obtained in the first step are evenly distributed in space at 120 degrees to each other. The three-dimensional space between the three rolls 1 and the mandrel 3 located inside the tube blank is the deformation zone. The third step is rolling and cutting. The metal tube blank 2 is fitted onto the mandrel 3. The outer diameter of the mandrel 3 is equal to the inner diameter of the metal tube. It is fed into the deformation zone from one end of the deformation zone. The rollers 1 rotate around their central axis, driving the metal tube blank 2 to move spirally forward toward the other end of the deformation zone. During this process, the cutter 4 on the rollers 1 bites into the metal tube blank 2 and gradually cuts into the metal tube blank 2. The tube is allowed to spread freely between the rollers 1. The inner diameter is restricted by the inner mandrel 3 and no longer decreases. The metal tube blank 2 is gradually cut. The cut surface gradually expands from the outer surface of the metal tube blank 2 inward until the metal tube blank 2 is cut off. The spiral line at the center of the side of the cutter 4 facing the roll 1 is an Archimedean spiral. With the center of the transverse circular tangent where the thread starts as the origin of the coordinate system, any point on the spiral line of the base cylindrical surface of the roll 1 is designated as the radial axis (x-axis), tangential axis (y-axis), and axial axis (z-axis). The starting position... θ =0, corresponding to the coordinates of the point (R,0,0), and the coordinates of the point (x,y,z) at any time and any position satisfy the following formula: In the formula: i —Number of cutter rotations, 1≤i≤n, where n is the total number of rotations; T i —Pitch of the i-th turn of the helix, mm; T 0 —Initial pitch, mm; R —Radius of the base circle of roll 1, mm; θ —The cutting blade rotates at any given time by 4 degrees; Δ T i —Reduction in pitch per turn, mm; Z i，θ —The position of the cutter at any given moment during the i-th rotation, representing the z-axis position of the 4th rotation angle θ; Furthermore, the variable pitch rolling model is satisfied during the metal tube cutting process: In the formula, R The radius of the base circle of roll 1 is in mm; W The width of the cutter is 4 mm; L The length of the unfolded line of a single-circle cutter (4mm); d The outer diameter of the metal tube blank is 2 mm; s The wall thickness of the metal tube blank is 2 mm; β The helix angle; α is the lateral width expansion coefficient; i For the number of cutter turns, n is the maximum number of cutter rotations. The axial extension is expressed in mm. The pitch change of cutter 4 is expressed in mm; For the 4th cutter i Coil compression amount, mm; For the first i Cut the blade at any position with a height of 4. and Cutting blades at 180° intervals, 4mm height; Tool height H Increasing according to the Archimedean spiral; V The volume of material pressed down by the cutter 4 along the wall thickness direction of the metal tube blank 2 is measured in mm. 3 ; V 1 represents the volume of metal flowing axially along the metal tube blank 2 when the cutter 4 bites into it, in mm. 3 ; V 2 represents the volume of metal expanding laterally along the metal tube blank 2 when the cutter 4 bites into it, in mm. 3 ; ξ represents the roundness of the cross-section; the closer this value is to 1.0, the rounder the cross-section. When V - (V1 + V2) = 0, When the cutter 4 on the roll 1 bites into the metal tube blank 2, the metal tube blank 2 undergoes compression deformation, with the outer diameter remaining unchanged and the cross-section straight.

[0021] For metal tube blanks with an outer diameter of 50mm-150mm and a wall thickness of 10mm-30mm, the initial helix angle during rolling is 2.3°-6°, the initial pitch is 25mm-150mm, and the pitch reduction rate is 10%-30%.

[0022] Metal tube blank 2 is GCr15 metal tube blank 2, or it can be a carbon steel tube blank or an alloy steel tube blank.

[0023] All three rollers are driven rollers.

[0024] A model for strictly controlling corner defects using variable pitch screw threads, the model being: In the formula, R The radius of the base circle of roll 1 is in mm; W The width of the cutter is 4 mm; L The length of the unfolded line of a single-circle cutter (4mm); d The outer diameter of the metal tube blank is 2 mm; s The wall thickness of the metal tube blank is 2 mm; β The helix angle; α is the lateral width expansion coefficient; i For the number of cutter turns, n is the maximum number of cutter rotations. The axial extension is expressed in mm. The pitch change of cutter 4 is expressed in mm; For the 4th cutter i Coil compression amount, mm; For the first i Cut the blade at any position with a height of 4. and Cutting blades at 180° intervals, 4mm height; Tool height H Increasing according to the Archimedean spiral; V The volume of material pressed down by the cutter 4 along the wall thickness direction of the metal tube blank 2 is measured in mm. 3 ; V 1 represents the volume of metal flowing axially along the metal tube blank 2 when the cutter 4 bites into it, in mm. 3 ; V2 represents the volume of metal expanding laterally along the metal tube blank 2 when the cutter 4 bites into it, in mm. 3 ; When V - (V1 + V2) = 0, that is When the cutter 4 on the roll 1 bites into the metal tube blank 2, the metal tube blank 2 undergoes compression deformation, with the outer diameter remaining unchanged and the cross-section straight.

[0025] like Figure 2 As shown, since the rolling process mainly involves reduction and elongation deformation, and the width expansion deformation is very small, α can be considered as a decimal less than 0.05. To obtain a straight cut surface and strictly control the occurrence of corner defects, i.e., when V - (V1 + V2) = 0... The reduction in pitch. At this point, the pressed-down metal does not extend axially. =0, all compression deformation has occurred. The reduction in pitch can be calculated from the above formula. The cut surface is horizontal and vertical, with no missing corners. Cutting processes that meet these conditions can obtain a cut surface with a constant outer diameter and a straight cross-section.

[0026] Based on the established variable pitch bore design model, a rigid-plastic finite element model was established using SIMUFACT numerical analysis software. The spiral protruding cutter 4 of the three active drive rollers can achieve cumulative pressing and cutting of the tube, the base cylindrical surface of the roll 1 can restrict the outward expansion of the tube, and the internal mandrel 3 can constrain the inward expansion of the inner surface of the metal tube blank 2.

[0027] To compare and analyze the rationality of the variable pitch model, this invention is compared with the constant pitch rolling and cutting method with the same initial pitch that remains unchanged. This invention is referred to as [insert abbreviation here]. Taking the cutting of a metal tube blank 2 with a diameter of 40mm and a wall thickness of 3.5mm as an example, the material is GCr15, the rotation speed of roll 1 during rolling is 50r / min, the base circle diameter of roll 1 is 216mm, the initial rolling temperature is 720 degrees Celsius, the single-turn cutter 4 has a reduction rate of 25%, the initial helix angle is 2.3°, the width of cutter 4 is 4mm, the initial pitch is 25mm, the pitch reduction rate is 19.6%, and the friction coefficient is 1.0.

[0028] The equivalent strain diagram during the rolling process of this invention and the comparative example, i.e., the constant pitch rolling and cutting method with the same initial pitch, is shown in the figure below. Figure 3 (b) and Figure 3As shown in (a), by comparison, the forward distance of the metal tube blank 2 during the same rolling time shows that after 1.0s of rolling time, the metal tube blank 2 basically achieves stable biting and enters the stable rolling stage. For the same rolling time of 2s, the forward distance of the metal tube blank 2 along the axial direction in the two rolling methods are as follows: the forward distance of the metal tube blank 2 along the axial direction in the comparative example is 30.7mm, and the forward distance of the metal tube blank 2 along the axial direction in the present invention is 35.2mm. This shows that the present invention has a higher rolling speed and faster efficiency than the comparative example.

[0029] In the present invention and comparative examples, the enlarged geometry of the metal tube blank 2 during the second and third rolling passes is as follows: Figure 4 As shown. Figure 4 In the process, after the cutting tool is pressed down, there is an area on the cut surface of the metal tube where the metal is not completely filled; this area is called a missing corner area. For example... Figure 4 (a) The unfilled area is both long and high, measuring 8.5 mm in length and 1.9 mm in height, with axial and radial cut-off rates of 34% and 5%, respectively. The cut-off rate is defined as the cut-off amount divided by the base value. The axial base value is the bearing ring width, and the radial base value is the bearing ring outer diameter. In this embodiment, the axial base value is 25 mm, and the radial base value is 40 mm. The present invention is used for rolling and cutting, as shown... Figure 4 (b) shows that only 1.1mm×1.4mm corners were not filled, with missing corner rates of 4% and 4% respectively, proving that the present invention can significantly improve the filling degree of the hole and the missing corner phenomenon after the metal tube blank 2 is cut can be significantly suppressed.

[0030] like Figure 5 and Figure 6 As shown, the rolling pressure gradually increases. Based on the average pressure comparison, the present invention has a pressure of 15.2 kN, while the comparative example has 21.7 kN. The fluctuation of the rolling torque exhibits a similar regularity to the change in rolling force. The average rolling torque of the present invention is 914.4 N•m, while that of the comparative example is 844.4 N•m. While improving the accuracy of the cut bearing ring cross-section, the present invention, compared to the comparative example, reduces the rolling force and slightly increases the rolling torque.

Claims

1. A high-precision rolling and cutting method for metal tubes, characterized in that, Includes the following steps: The first step is the roll design. A cutter with a rectangular cross-section and a gradually decreasing pitch is spirally wound on the surface of the cylindrical roll, while the cutter width W remains constant. The second step is to construct the deformation zone. The three rolls obtained in the first step are evenly distributed in space at 120 degrees to each other. The three-dimensional space between the three rolls and the mandrel located inside the metal tube blank is the deformation zone. The third step is rolling and cutting. The metal tube blank is fitted onto the mandrel, the outer diameter of which is equal to the inner diameter of the metal tube. It is fed into the deformation zone from one end. The rolls rotate around their central axis, driving the metal tube blank to move forward spirally toward the other end of the deformation zone. During this process, the cutter on the roll bites into the metal tube blank and gradually cuts into it. The metal tube blank is gradually cut, and the cut surface gradually expands from the outer surface of the metal tube blank inward until the metal tube blank is cut off. The spiral line at the center of the side of the cutter facing the roll is an Archimedean spiral. With the center of the transverse circular tangent where the thread begins as the origin of the coordinate system, any point on the spiral line of the roll's base cylindrical surface is designated as the radial axis (x-axis), tangential axis (y-axis), and axial axis (z-axis). The starting position... The corresponding point coordinates are (R, 0, 0), and the coordinates of any position at any time are (x, y, z), satisfying the following formula: Where: i — number of cutter turns, 1≤i≤n, n is the total number of turns; T i —Pitch of the i-th turn of the helix, mm; T0—Initial pitch, mm; R—radius of the roll base circle, mm; —The angle of blade rotation at any given moment, in degrees; ΔT i —Reduction in pitch per turn, mm; —The position of the cutter's rotation angle θ in the z-direction at any given time during the i-th cutter rotation; Furthermore, the variable pitch rolling model is satisfied during the metal tube cutting process: In the formula, W is the width of the cutter, in mm; L i The length of the unfolded line of the i-th cutter ring, in mm; d is the outer diameter of the metal tube blank, in mm; d' is the minimum outer diameter of the pipe at the notched corner of the cut surface, in mm; s represents the wall thickness of the metal tube blank, in mm; β i Let be the spiral angle of the i-th turn; α is the lateral width expansion coefficient; The axial extension of the i-th ring is in mm; Let be the pitch change of the cutter in the i-th turn, in mm; The cutting depth in the i-th rotation of the cutter, in mm; The height of the cutter at any position in the i-th cycle; and Cutting height at 180° intervals; The tool height H increases in an Archimedean spiral pattern. V represents the volume pressed down by the cutter along the wall thickness of the metal tube blank, in mm. 3 ; V1 is the volume of metal flowing axially along the metal tube blank when the cutter bites into it, in mm. 3 ; V2 is the volume of metal expanding laterally along the metal tube blank when the cutter bites into it, in mm. 3 ; ξ represents the roundness of the cross-section; the closer this value is to 1.0, the rounder the cross-section. When V - (V1 + V2) = 0 When the cutter on the roll bites into the metal tube blank, the metal tube blank undergoes compression deformation, while the outer diameter remains unchanged and the cross-section is straight.

2. The high-precision rolling and cutting method for metal tubes as described in claim 1, characterized in that, The metal tube blank has an outer diameter of 50mm-150mm and a wall thickness of 10mm-30mm. During the rolling process, the initial helix angle is 2.3°-6°, the initial pitch is 25mm-150mm, and the pitch reduction rate is 10%-30%.

3. The high-precision rolling and cutting method for metal tubes as described in claim 1, characterized in that, The metal tube blank is GCr15 metal tube blank or tubular blank of carbon steel or alloy steel.

4. The high-precision rolling and cutting method for metal tubes as described in claim 3, characterized in that, All three rollers are driven rollers.

5. A method for constructing a variable pitch, strictly controlled corner-cutting model, characterized in that, The model is as follows: In the formula, R is the base circle radius of the roll, in mm; W represents the blade width, in mm; L is the length of the single-circle cutter development line, in mm; d is the outer diameter of the metal tube blank, in mm; s represents the wall thickness of the metal tube blank, in mm; β is the helix angle; α is the lateral width expansion coefficient; i is the number of cutter rotations. n is the maximum number of cutter rotations. The axial extension is expressed in mm. The pitch change of the cutter is expressed in mm. The cutting depth in the i-th rotation of the cutter, in mm; The height of the cutter at any position in the i-th cycle; and Cutting height at 180° intervals; The tool height H increases in an Archimedean spiral pattern. V represents the volume pressed down by the cutter along the wall thickness of the metal tube blank, in mm. 3 ; V1 is the volume of metal flowing axially along the metal tube blank when the cutter bites into it, in mm. 3 ; V2 is the volume of metal expanding laterally along the metal tube blank when the cutter bites into it, in mm. 3 ; ξ represents the roundness of the cross-section; the closer this value is to 1.0, the rounder the cross-section. When V - (V1 + V2) = 0 When the cutter on the roll bites into the metal tube blank, the metal tube blank undergoes compression deformation, while the outer diameter remains unchanged and the cross-section is straight.

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