Method for improving rolling deformation uniformity of end face of ring piece through reversing rotation of conical roller

Abstract

The invention relates to the technical field of metal plastic forming, and discloses a method for improving the rolling deformation uniformity of the end face of a ring piece through reversing rotation of a conical roller. Secondly, end face rolling forming is conducted, specifically, on one hand, a conical roller of rolling equipment rotates around a conical shaft at the rotating speed of omega, on the other hand, the conical roller moves downwards at the speed V till the conical roller abuts against the upper end face of the annular blank, downward rolling is conducted on the upper end face of the annular blank, and meanwhile the annular blank and an annular mold are driven to rotate; when the downward feeding amount of the conical roller reaches the step length H of the conical roller, the conical roller stops moving downwards and continues to rotate around the axis of the conical roller at the rotating speed of omega; then changing the rotating direction of the conical roller, rotating at the rotating speed of omega, and simultaneously moving downwards at the speed V; and 3, demolding and taking. The rotation direction of the conical roller in the end face rolling process is alternately changed, and the internal stress and strain field distribution of the ring blank is changed, so that the overall deformation uniformity is improved.

Description

Technical Field

[0001] The invention relates to the technical field of metal plastic forming, and in particular to a method for improving the rolling deformation uniformity of a ring end face by utilizing the reverse rotation of a tapered roller. Background Art

[0002] Rings are widely used, fundamental components. Among the various proposed ring forming methods, ring rolling is the preferred method for forming seamless rings in high-tech fields such as aerospace and nuclear energy, due to its high quality, high efficiency, and material, labor, and energy savings. However, with the increasing demand for lightweight, integrated, and compact products, ring shapes are becoming increasingly complex, making traditional ring rolling increasingly difficult. "End face rolling" is a new ring forming method proposed to address the bottleneck of existing ring rolling technology in forming special-shaped rings. Chinese patent application number: 202311865866.4 discloses an end face rolling forming method for large-taper special-section rings: it uses a single tapered roller to perform "axial" local and progressive rolling on the upper end of the ring blank, and at the same time combines it with a driven rotatable annular lower die to realize ring forming. It can obtain special-section special-section rings with large tapers, "L" shapes, "T" shapes, and small aspect ratios that are difficult to complete with traditional ring forming methods, and has good forming quality, high efficiency, labor-saving and energy-saving, and easy operation.

[0003] The plastic forming process often generates residual stress due to reasons such as uneven deformation, which has an adverse effect on the subsequent processing, assembly and service of the workpiece. In particular, when the residual stress exceeds the critical value, it will not only cause large deformation of the workpiece, but may even cause cracking. In recent years, a lot of research has been done on the formation mechanism, analysis, testing and control of residual stress in plastic forming. However, due to the complexity of the problem, it is still impossible to achieve a comprehensive reduction of residual stress. End rolling, as a new ring forming method, adopts a continuous local plastic deformation mechanism to achieve ring forming, and there is also a problem of residual stress caused by uneven deformation. Excessive residual stress will have an adverse effect on the dimensional stability, fatigue and other mechanical properties of the ring, as well as corrosion resistance. Therefore, how to improve the uniformity of end rolling deformation and effectively control the generation of residual stress has become an important part of ensuring part accuracy, service performance and structural reliability. Summary of the Invention

[0004] The present invention aims to provide a method for improving the uniformity of deformation of the end face of a ring by reversing the rotation of a tapered roller, so as to solve the problem of unsatisfactory workpiece accuracy and service performance caused by residual stress during ring rolling in the prior art.

[0005] To achieve the above object, the present invention adopts the following technical solution: a method for improving the uniformity of rolling deformation of the end face of a ring by using the reverse rotation of a tapered roller, comprising the following steps: Step 1: Ring blank making: Use round bar stock to make ring blank; Step 2: End face rolling: The conical roller of the rolling equipment rotates around the conical axis at a speed of ω on the one hand, and moves downward at a speed of V on the other hand until it contacts the upper end face of the ring blank, and begins to roll the upper end face of the ring blank downward, while driving the ring blank and the ring die to rotate; when the downward feed amount of the conical roller reaches the step length △H of the conical roller, it stops moving downward and continues to rotate around its own axis at a speed of ω; then the conical roller changes its rotation direction and rotates at a speed of ω, while moving downward at a speed of V; Step 3: De-mould and remove the parts. Preferably, as an improvement, in step 2, after the tapered roller changes its rotation direction and the downward feed amount reaches △H, it stops moving downward again and continues to rotate around its own axis at a speed of ω; then changes its rotation direction again and moves downward at a speed V; Repeat the above steps until the total downward feed amount of the tapered roller reaches the preset downward feed displacement H, the tapered roller stops moving downward, continues to rotate at a speed of ω, and then stops rotating.

[0006] Preferably, as an improvement, in step 2, the step length ΔH is 1-5% of the displacement H.

[0007] Preferably, as an improvement, in step 2, after the tapered roller stops moving downward, it continues to rotate around its own axis at a speed of ω for 3 to 4 turns.

[0008] Preferably, as an improvement, in step 2, the annular blank is heated to a preset temperature T before end face rolling.

[0009] Preferably, as an improvement, the preset temperature T is 450° C., the rotation speed ω is 35 rpm, and the pressing speed V is 1 mm / s.

[0010] Preferably, as an improvement, in step 2, before end face rolling, the annular blank is placed on an annular die below the tapered roller and positioned.

[0011] The principles and advantages of this solution are as follows: In actual application, during the end face rolling process, the conical roller continuously rotates around its own axis while simultaneously moving downward and rolling the ring blank, using friction at the contact interface to drive the ring blank to rotate; the ring blank material at the front end of the conical roller rotates to the rear end of the conical roller after rolling, resulting in different degrees of deformation of the ring blank material at the front and rear ends of the conical roller, and the ring blank material at the front end may accumulate, while the ring blank material at the rear end may "slip back." If the conical roller always rotates in the same direction, the ring blank will also rotate in the same direction, and the continuous local plastic deformation of the ring blank will always proceed in the same direction. The internal deformation of the ring blank will be uneven in the radial, axial, and circumferential directions. This unevenness will continue to accumulate as the end face rolling progresses, resulting in large residual stresses within the part. Based on this, the inventors creatively proposed changing the deformation mode by reversing the cone rollers. By alternating the cone roller rotation direction at different stages of end face rolling, the continuous local plastic deformation direction of the ring blank is changed, avoiding the accumulation of deformation unevenness at the front and rear ends of the cone rollers, and changing the deformation state of the ring blank in the radial, axial, and circumferential directions, thereby achieving the purpose of improving the uniformity of the overall deformation of the ring and reducing residual stress. During the technical research and development stage, how to set the actual rolling process parameters that can be used, such as cone roller speed, step size, displacement, cone roller pressing (feed) speed, etc., is the key point of the research and development of this technical solution. Among them, the cone roller pressing (feed) speed has the greatest impact on the uniformity of residual stress. By comprehensively considering the internal stress of the blank, the existing equipment parameters and conditions, and the cost, the optimal cone roller speed, step size, displacement, and feed speed were determined.

[0012] The beneficial effect of this technical solution is that: by alternately changing the rotation direction of the tapered roller during the rolling process of the end face of the ring blank and combining it with a specific tapered roller downward feed step, this technical solution can change the internal stress, strain field distribution and evolution behavior of the ring blank, thereby improving the uniformity of the overall deformation of the ring. It is also simple and easy to operate with low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic diagram of improving the uniformity of rolling deformation of the end face of a ring by using the reverse rotation of a tapered roller in an embodiment of the present invention.

[0014] Figure 2 This is a schematic structural diagram of the AA7075 end face rolled ring blank in Example 1 of the present invention.

[0015] Figure 3 This is a diagram showing the finite element simulation results of the end face rolling of the ring blank in Example 1 of the present invention.

[0016] Figure 4The figures are comparative diagrams of cross-sectional stress distribution of ring end faces rolled according to Example 1 of the present invention and Comparative Examples 1-3, wherein (a) to (d) are simulation results without reverse rotation of the tapered roller, and (e) to (h) are simulation results with reverse rotation of the tapered roller.

[0017] Figure 5 This is a comparison diagram of the equivalent residual stress distribution of the cross section of the ring parts after end face rolling in Example 1 of the present invention and Comparative Examples 1-3.

[0018] The reference numerals in the drawings of the specification include: tapered roller 1 , annular blank 2 , and mold 3 . DETAILED DESCRIPTION

[0019] The following is further described in detail through specific embodiments, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the technical means used in the following embodiments are conventional means well known to those skilled in the art; the experimental methods used are all conventional methods; and the materials, reagents, etc. used are all commercially available.

[0020] The embodiment is basically as shown in the attached Figure 1 A method for improving the uniformity of rolling deformation of the end face of a ring by using the reverse rotation of a tapered roller comprises the following steps: Step 1: Ring blank making According to the ring forging drawing, determine the blanking weight and blanking specifications, and use round bars to make ring blanks.

[0021] Step 2: End face rolling 1) Based on the material, shape, and size of the ring, and in accordance with the process requirements of hot forging and end rolling, determine the heating temperature T of the ring blank 2 and the feed motion parameters of the tapered roller 1, including the rotation speed ω and the pressing speed V; 2) According to the axial height difference between the ring blank 2 and the ring forging diagram, the displacement H and step length ΔH of the tapered roller downward feed are set; the step length ΔH is set to 1 to 5% of the displacement H, that is, the value range of ΔH is 1% H to 5% H; 3) Set the tapered roller feed motion parameters on the control panel of the end face rolling equipment; 4) Heat the ring blank 2 to temperature T, and use the manipulator to place the ring blank 2 on the ring mold 3 below the tapered roller, and complete the positioning at the same time; 5) Start the end face rolling equipment. The tapered roller 1 rotates around the tapered axis at a speed of ω and moves downward at a speed of V until it contacts the upper end face of the ring blank 2. It then begins to roll the upper end face of the ring blank 2 downward, while simultaneously driving the ring blank 2 and the ring die 3 to rotate. When the downward feed amount of the tapered roller 1 reaches △H, it stops moving downward and continues to rotate around its own axis at a speed of ω for 3 to 4 turns; then, the tapered roller 1 changes its rotation direction and rotates at a speed of ω while moving downward at a speed of V; When the tapered roller 1 reaches the downward feed amount of △H, it stops moving downward again and continues to rotate around its own axis at a speed of ω for 3 to 4 circles; then it changes the direction of rotation and moves downward at a speed of V; Repeat the above steps until the total downward feed amount of the tapered roller 1 reaches the displacement H, the tapered roller stops moving downward, continues to rotate at the speed of ω for 3 to 4 circles, and then stops rotating.

[0022] Step 3: The tapered roller 1 moves upward, leaving the upper end face of the ring blank 2, and performs demoulding and removal, completing the end face rolling operation.

[0023] Example 1 This embodiment uses Figure 2 The material shown is AA7075 ring blank as an example.

[0024] A method for improving the uniformity of rolling deformation of a ring end face by using a tapered roller to reverse the rotation direction comprises the following steps: Step 1: Ring blank making According to the ring forging drawing, determine the blanking weight and blanking specifications, and use round bars to make ring blanks.

[0025] Step 2: End face rolling 1) According to the material, shape and size of the ring, and in accordance with the process requirements of hot forging and end rolling, the heating temperature T of the AA7075 ring blank is determined to be 450°C, the rotation speed ω of the tapered roller is determined to be 35 RPM, and the pressing speed V is determined to be 1 mm / s; 2) According to the axial height difference between the ring blank and the ring forging, the downward displacement of the tapered roller is set to H = 32 mm, and the step length △H of the tapered roller downward feed is set to 1 mm.

[0026] 3) Set the tapered roller feed motion parameters on the control panel of the end face rolling equipment; 4) Heat the ring blank to 450°C, and use the manipulator to place the ring blank on the ring die under the tapered roller and complete the positioning at the same time; 5) Start the end face rolling equipment. The conical roller rotates around the conical axis at a speed of ω = 35 RPM. On the other hand, it moves downward at a speed of V = 1 mm / s until it contacts the upper end face of the ring blank. It then begins to roll the upper end face of the ring blank downward, while driving the ring blank and the ring die to rotate. When the tapered roller reaches a downward feed of 1 mm, it stops moving downward and continues to rotate around its own axis at a speed of 35 RPM for 3 to 4 turns; then, the tapered roller changes its rotation direction and rotates at a speed of 35 RPM while moving downward at a speed of 1 mm / s; When the tapered roller reaches a downward feed of 1 mm, it stops moving downward again and continues to rotate around its own axis at a speed of 35 RPM for 3 to 4 turns; then it changes its direction of rotation and moves downward at a speed of 1 mm / s; Repeat the above steps until the total downward feed of the tapered roller reaches a displacement of H = 32 mm. The tapered roller stops moving downward and continues to rotate at a speed of 35 RPM for 3 to 4 turns before stopping.

[0027] Step 3: The tapered roller moves upward, leaving the upper end face of the ring blank, to demould and remove the piece, completing the end face rolling operation.

[0028] Example 2 The difference between this comparative example and Example 1 is that: in this example, the downward feeding step length ΔH of the tapered roller is 0.5 mm.

[0029] Example 3 The difference between this comparative example and Example 1 is that: in this example, the downward feeding step length ΔH of the tapered roller is 1.5 mm.

[0030] Comparative Example 1 The difference between this comparative example and Example 1 is that in this comparative example, the tapered roller does not reverse its rotation.

[0031] Comparative Example 2 The difference between this comparative example and Example 1 is that in this comparative example, the downward feeding step length ΔH of the tapered roller is 0.2 mm.

[0032] Comparative Example 3 The difference between this comparative example and Example 1 is that in this comparative example, the downward feeding step length ΔH of the tapered roller is 2 mm.

[0033] Experimental Example 1 Numerical simulations were performed on the end-face rolling process of the aforementioned ring blanks to compare the deformation and residual stress changes in the rings. The simulations were performed in Simufact Forming software, using the relevant parameters of AA7075 from the software's material library. The stress state of the rings was numerically transferred to simulate the "rolling-unloading-rolling" cycle with alternating rotation of the tapered rollers.

[0034] Figure 3 The finite element simulation results of the equivalent stress distribution during end face rolling of AA7075 ring blanks are shown. The conical rollers do not undergo reversing rotation. Figure 4The figure shows the comparison of the residual stress distribution of the cross section of the ring end face when the conical roller is rolled with and without reversing rotation. Among them, (a) to (d) are the simulation results of the conical roller without reversing rotation, and (e) to (h) are the simulation results of the conical roller reversing rotation with a downward feed step length of △H=0.5mm. As can be seen from the figure, the equivalent stress of the ring cross section increases slightly after reversing rotation, but the distribution uniformity is greatly improved. Figure 4 The circumferential residual stress distribution of (b) and (f) shows that the value has decreased, and the stress state of outer ring compression and inner ring tension has changed to uniform tensile stress. Figure 4 The radial residual stress distribution of (c) and (g) shows that the value is significantly reduced, and the residual stress distribution has no significant change. Figure 4 The axial residual stress distribution in (d) and (h) shows that the value increases slightly, and the tensile stress area in the core is transformed into a compressive stress distribution.

[0035] Experimental Example 2 To further quantify the magnitude and uniformity of residual stress, the average residual stress and residual stress variance were calculated at uniformly distributed tracking points around the circumference. The results are shown in Table 1. It can be seen that the mean of the equivalent residual stress increases after commutation, but the variance of the equivalent stress decreases significantly, indicating a more uniform distribution of the equivalent stress. From the perspective of stress in all three directions, the mean increases, the variance of the circumferential stress decreases, and the variances of the radial and axial stresses increase, indicating that commutation can improve the uniformity of the circumferential residual stress.

[0036] Table 1 Changes in residual stress values before and after commutation

[0037] Experimental Example 3 Comparison of equivalent residual stress distribution of the cross section of the ring end face after rolling of Examples 1-3 and Example 1. In Example 1, the tapered roller has a downward feed step length ΔH of 1mm, in Example 2, the tapered roller has a downward feed step length ΔH of 0.5mm, and in Example 3, the tapered roller has a downward feed step length ΔH of 1.5mm. In Example 1, the tapered roller does not reverse rotation (ΔH is 0). The results are shown in Figure 2. Figure 5 As shown in the figure, the results show that reversing rotation has a significant impact on the redistribution of equivalent stress. When the step length ΔH is 0.5mm and 1mm, the cross-sectional equivalent stress distribution is more uniform. When ΔH is 1.5mm, a larger residual stress is generated at the lower end of the inner diameter. Therefore, within a certain feed step length, reversing rotation can homogenize the residual stress distribution across the ring cross section, but exceeding a certain step length limit will reduce the residual stress uniformity.

[0038] The above is only an embodiment of the present invention, and the common knowledge such as the specific technical solutions and / or characteristics in the solution are not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the description can be used to interpret the content of the claims.

Claims

1. A method for improving the uniformity of rolling deformation of the end face of a ring by using the reverse rotation of a tapered roller, characterized in that: The steps include: Step 1: Ring blank making: Use round bar stock to make ring blank; Step 2: End face rolling: The conical roller of the rolling equipment rotates around the conical axis at a speed of ω on the one hand, and moves downward at a speed of V on the other hand until it contacts the upper end face of the ring blank, and begins to roll the upper end face of the ring blank downward, while driving the ring blank and the ring die to rotate; when the downward feed amount of the conical roller reaches the step length △H of the conical roller, it stops moving downward and continues to rotate around its own axis at a speed of ω; then the conical roller changes its rotation direction and rotates at a speed of ω, while moving downward at a speed of V; Step 3: De-mould and remove the parts.

2. The method of improving the uniformity of rolling deformation of the end face of a ring by using the reverse rotation of a tapered roller according to claim 1, characterized in that: In step 2, after the tapered roller changes its rotation direction and the downward feed reaches △H, it stops moving downward again and continues to rotate around its own axis at a speed of ω; then it changes its rotation direction again and moves downward at a speed of V; Repeat the above steps until the total downward feed amount of the tapered roller reaches the preset downward feed displacement H, the tapered roller stops moving downward, continues to rotate at a speed of ω, and then stops rotating.

3. The method of improving the uniformity of rolling deformation of the end face of a ring by using the reverse rotation of a tapered roller according to claim 2, characterized in that: In step 2, the step length △H is 1~5% of the displacement H.

4. The method of improving the uniformity of rolling deformation of the end face of a ring by using the reverse rotation of a tapered roller according to claim 3, characterized in that: In step 2, after the tapered roller stops moving downward, it continues to rotate around its own axis at a speed of ω for 3 to 4 turns.

5. The method of improving the uniformity of rolling deformation of the end face of a ring by using the reverse rotation of a tapered roller according to claim 4, characterized in that: In step 2, the ring blank is heated to a preset temperature T before end face rolling.

6. The method of improving the uniformity of rolling deformation of the end face of a ring by using the reverse rotation of a tapered roller according to claim 5, characterized in that: The preset temperature T is 450° C., the rotation speed ω is 35 rpm, and the pressing speed V is 1 mm / s.

7. The method of improving the uniformity of rolling deformation of the end face of a ring by using the reverse rotation of a tapered roller according to claim 6, characterized in that: In step 2, before end face rolling, the ring blank is placed on the ring die below the tapered roller and positioned.

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