Axle roll-forging process

Abstract

Disclosed in the present invention is an axle roll-forging process, comprising performing two-pass precision roll-forging on a heated metal blank having a square cross section, and then performing forming. The present invention effectively improves the quality of an axle forging, thereby reducing the rejection rate, obtaining a blank having good shape, size and surface quality, and overcoming the defects such as forging folding and insufficient filling caused by the blank forming shape problem; the trend of metal fibers is consistent with the shape of the forging due to continuous local deformation in the roll-forging process, and the metallographic structure is uniform and compact and has high mechanical performance, such that a forging having good mechanical performance can be obtained; and in addition, because the cycle time of a roll-forging machine is stable, and the temperature consistency of the roll-forging blank is good, a forging product having a stable size can be obtained easily.

Description

Axle roll forging process Technical Field

[0001] The present invention relates to the technical field of axle processing, in particular to a roll forging process for an axle used in rail transportation. Background Art

[0002] At present, there are two methods for producing rail transit axles at home and abroad: free forging and radial forging.

[0003] 1) Free forging: Slow forging speed, low production efficiency, low material utilization, large forging allowance, high noise levels (greater than 100dB during forging), causing significant pollution to the production environment and a poor working environment. 2) Radial forging: The forging effect of axles is poor, and cracks often appear on the ends after forging. The degree of automation is low, the noise level is high, and the working environment is poor. The core equipment, the radial forging machine, currently needs to be imported, resulting in relatively high equipment costs and a large investment in supporting facilities. It also requires a high level of technical expertise and professional talent.

[0004] Summary of the Invention

[0005] The purpose of the present invention is to address the defects of the current free forging and radial forging processes and provide a roll forging process for rail transit axles. The process adopts a two-pass roll forging forming process, utilizes roll forging to continuously locally form the workpiece, and directly forms rail transit axles, thereby improving axle production efficiency and material utilization, and reducing equipment investment costs and the amount of subsequent machining of the axle.

[0006] The technical solution adopted to achieve the purpose of the present invention is:

[0007] An axle roll forging process, in which a heated metal blank with a square cross section is subjected to two passes of precision roll forging and then formed.

[0008] In some embodiments, after the workpiece is subjected to a first roll forging process on a first roll forging die, the workpiece is rotated 90 degrees about its axis and subjected to a second roll forging process on a second roll forging die to form the workpiece.

[0009] In some embodiments, the width of the single-pass roll forging die is the same as that of the second-pass roll forging die, the width of the groove of the single-pass roll forging die at the widest position is 450 mm, and the width of the groove at the widest position after the single-pass roll forging die is rotated 90 degrees around its own axis is 250 mm.

[0010] In some embodiments, the sector angle of the groove of the single-pass roll forging die is smaller than the sector angle of the groove of the second-pass roll forging die.

[0011] In some embodiments, the sector angle of the groove of the one-pass roll forging die is 165 degrees.

[0012] In some embodiments, the sector angle of the groove of the two-pass roll forging die is 220 degrees.

[0013] In some embodiments, the groove of the first-pass roll forging die has the same shape as the groove of the second-pass roll forging die, and the shape of the groove is adapted to the outer shape of the axle for rail transit.

[0014] In some embodiments, the metal blank is a blank with rounded corners at the four corners of the outer surface.

[0015] In some embodiments, a medium frequency heating furnace is used to heat the metal blank to a required temperature.

[0016] In some embodiments, after the heated metal blank with a square cross-section is subjected to two passes of precision roll forging and then formed, a heat treatment step is also included.

[0017] The axle roll forging process of the present invention performs two passes of precision roll forging and then forms a heated metal blank with a square cross section, effectively improving the quality of axle forgings, reducing the scrap rate, obtaining blanks with good shape, size and surface quality, and avoiding defects such as folding and insufficiency of forgings caused by blank shape problems. Moreover, the continuous local deformation during the roll forging process makes the direction of the metal fibers consistent with the shape of the forging, and the metallographic structure is uniform, dense, and has high mechanical properties, which is conducive to obtaining forgings with good mechanical properties. In addition, since the beat of the roll forging machine is stable, the temperature consistency of the roll forging blank is good, which is conducive to obtaining forging products with stable dimensions. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG1 is a flow chart of an axle roll forging process according to an embodiment of the present invention.

[0019] FIG2 is a schematic front view of an axle roll forging blank according to an embodiment of the present invention.

[0020] FIG3 is a side view of an axle roll forging blank according to an embodiment of the present invention.

[0021] FIG4 a is a schematic diagram of an axle roll forging blank after cutting according to an embodiment of the present invention.

[0022] FIG4 b is a schematic diagram of an axle roll forging blank after a single roll forging according to an embodiment of the present invention.

[0023] FIG4 c is a schematic diagram of an axle roll forging blank after two roll forging passes according to an embodiment of the present invention.

[0024] FIG5 a is a schematic top view of a single-pass roll forging die according to an embodiment of the present invention.

[0025] FIG5 b is a schematic diagram of the structure in FIG5 a from another perspective.

[0026] FIG6 a is an axonometric diagram of a one-pass roll forging die according to an embodiment of the present invention.

[0027] FIG6 b is a schematic diagram of the structure in FIG6 a from another perspective.

[0028] FIG7 a is a schematic top view of a two-pass roll forging die according to an embodiment of the present invention.

[0029] FIG7 b is a schematic diagram of the structure in FIG7 a from another perspective.

[0030] FIG8 a is an axonometric diagram of a two-pass roll forging die according to an embodiment of the present invention.

[0031] FIG8 b is a schematic diagram of the structure in FIG8 a from another perspective.

[0032] FIG9 is a schematic diagram of a one-pass roll forging die according to an embodiment of the present invention corresponding to the AA position in FIG12 .

[0033] FIG10 is a schematic diagram of a one-pass roll forging die corresponding to the BB position in FIG12 according to an embodiment of the present invention.

[0034] FIG11 is a schematic diagram of a one-pass roll forging die corresponding to the CC position in FIG12 according to an embodiment of the present invention.

[0035] FIG12 is a diagram showing the roll forging simulation results of an RE2B axle processed according to an embodiment of the present invention.

[0036] FIG13 is a cross-sectional view of the structure in FIG8a at a position corresponding to line AA.

[0037] FIG14 is a cross-sectional view of the structure in FIG8a at a position corresponding to line BB.

[0038] FIG15 is a cross-sectional view of the structure in FIG8a at a position corresponding to line CC.

[0039] FIG16 is a schematic diagram of the journal end face of the RE2B axle forging processed by the present invention from one perspective.

[0040] FIG17 is a schematic diagram of the journal end face of the RE2B axle forging processed by the present invention from another perspective. DETAILED DESCRIPTION

[0041] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0042] As shown in Figure 1, the axle roll forging process in an embodiment of the present invention first heats a square cross-section metal blank to be processed. The heated square cross-section metal blank is then precision roll-forged in two passes through a roll forging machine to form a roll forging. The purpose of heating the metal blank before roll forging is to improve the metal's plasticity and reduce its resistance to deformation, thereby increasing its forgeability. This facilitates metal flow and forming, and ensures that the roll forging has good microstructure and mechanical properties.

[0043] Among them, the metal blank is formed after two passes of precision roll forging. After the workpiece is roll forged once on a single roll forging die, the workpiece is rotated 90 degrees around its axis and roll forged twice on a second roll forging die to form it. After two passes, the roll forging of an axle is completed. The workpiece is extended in the axial direction by roll forging, and the groove on the roll forging die rotates and extrudes the surface of the workpiece to form the required shape on the surface of the workpiece. For example, the surface of the axle roll forging forms a cylindrical axle with a large diameter and a small diameter, as shown in Figures 4a to 4c.

[0044] The present invention adopts two roll forging passes to directly form the axle roll forging, has a simple production process, effectively improves the quality of the axle forging, can reduce the scrap rate, obtains the blank with good shape, size and surface quality, avoids the defects of forging folding, insufficiency and the like caused by blank shape problems, and the continuous local deformation during the roll forging process makes the direction of the metal fiber consistent with the shape of the forging, the metallographic structure is uniform and dense, and the mechanical properties are high, which is conducive to obtaining forgings with good mechanical properties; in addition, since the beat of the roll forging machine is stable, the temperature consistency of the roll forging blank is good, which is conducive to obtaining forging products with stable dimensions.

[0045] Before roll forging an axle, the corresponding roll forging die must be designed. Given the original blank dimensions and the final hot forging drawing, the groove dimensions of the first-pass roll forging die are determined, followed by the groove dimensions of the second-pass roll forging die. The die is then designed, and the workpiece is roll forged using the roll forging die. The first-pass roll forging die corresponds to the slots at lines AA, BB, and CC in Figure 12. As shown in Figures 9-11, the groove depths at these three locations are 150mm, 205mm, and 173mm, respectively, with radii of 301.6mm, 200mm, and 241.3mm, respectively.

[0046] Among them, the width of the first-pass roll forging die is the same as that of the second-pass roll forging die, which is the distance between the left and right sides of the roll forging die shown in Figures 4a-4c and Figures 6a-6b. For example, it is 600 mm. The groove sector angle of the first-pass roll forging die is smaller than the groove sector angle of the second-pass roll forging die. For example, the groove sector angle of the first-pass roll forging die is 165 degrees, and the groove sector angle of the second-pass roll forging die is 220 degrees.

[0047] The groove of the primary roll forging die has the same shape as the groove of the secondary roll forging die, and the shape of the groove is adapted to the outer shape of the rail transit axle. More preferably, the width of the groove on the circumferential surface of the primary roll forging die is greater than the width of the groove of the secondary roll forging die. As shown in Figures 5a-5b, 6a-6b, 7a-7b, and 8a-8b, the width of the groove at its widest point in the primary roll forging die is 450 mm. After the primary roll forging die is rotated 90 degrees about its axis, the width of the groove at its widest point is 250 mm.

[0048] In an embodiment of the present invention, the square blank is a metal blank with rounded corners on the four corners of the outer surface, as shown in 1, its length is 1290 mm, and the width of the four sides is the same, all 250 mm, as shown in Figures 2 and 3. The square blank can be made of aluminum alloy material or metal or alloy material.

[0049] Among them, during production, before roll forging, a medium frequency heating furnace is used to heat the metal billet to the required temperature, such as 1150℃~1180℃, and then it is sent to the roll forging machine. Through the previous two passes of precision roll forging, the roll forging of the axle is formed. Through roll forging, the workpiece is extended in the axial direction, and the groove on the roll forging die is rotated to extrude the surface of the workpiece to form the required shape on the surface of the workpiece. For example, the surface of the axle roll forging forms a roll forging with a large diameter and a small diameter, as shown in Figures 4a to 4c.

[0050] Among them, in an embodiment of the present invention, after the heated metal billet with a square cross-section is subjected to two passes of precision roll forging and then formed, a subsequent heat treatment step (including one normalizing and one tempering; the normalizing holding zone is set at 830°C to 870°C, the tempering holding zone is set at 520°C to 560°C, the normalizing is 480 to 560 minutes, and the tempering is 480 minutes) is included, that is, the two-pass roll forging part is subjected to subsequent heat treatment. Through the subsequent heat treatment process, the microstructure inside the workpiece can be changed, or the chemical composition on the surface of the workpiece can be changed, thereby imparting or improving the performance of the workpiece. The process includes heating, insulating and cooling the material in a solid state to obtain the expected structure and performance, and ultimately the grain of the roll forging is refined, the ultrasonic flaw detection is qualified, and the product quality is guaranteed.

[0051] Furthermore, after the subsequent heat treatment process is completed, an inspection step is included to check whether the roll forgings produced are qualified. If they are qualified, they are taken off the line to the next process, including ultrasonic testing, etc.

[0052] After the inspection is completed, qualified workpieces need to undergo subsequent machining, which includes one or more of trimming, punching, and correction, to ultimately achieve the final shape of the product.

[0053] 12 , 13 , 14 and 15 , the present invention uses numerical simulation software to perform numerical simulation analysis on the forming process. From the simulation results, it can be seen that the axle roll forgings of the present invention have regular shapes, smooth transitions, and are free of defects such as burrs and folds. The cross-sections of the journal, wheel seat and axle body are analyzed respectively, and it can be seen that the roundness of the cross-section of each part is good, which is consistent with the effect of the axles actually produced by roll forging.

[0054] As shown in Figures 16 and 17, the present invention uses precision roll forging technology to create a smooth axle neck end surface without noticeable bumps or petal-shaped shapes. After forging, the train axle forging will be free of crack defects. In contrast, on-site photos of axle end surfaces produced using a rapid forging hydraulic press show noticeable pits and petal-shaped shapes.

[0055] The axle roll forging process of the present invention performs two passes of precision roll forging on a square blank with a square cross section after heating and then forms the blank, thereby effectively improving the quality of the axle forging, reducing the scrap rate, obtaining a blank with good shape, size and surface quality, and avoiding defects such as folding and underfilling of the forging caused by problems with the blank shape. Moreover, the continuous local deformation during the roll forging process makes the direction of the metal fiber consistent with the shape of the forging, and the metallographic structure is uniform, dense, and has high mechanical properties, which is conducive to obtaining forgings with good mechanical properties. In addition, since the beat of the roll forging machine is stable, the temperature consistency of the roll forging blank is good, which is conducive to obtaining forging products with stable dimensions.

[0056] The basic principles, main features and advantages of the present invention are shown and described above. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention.

[0057] The embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being defined by the appended claims rather than the foregoing description, and all changes that come within the meaning and range of equivalents of the claims are therefore intended to be embraced therein.

[0058] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. Axle roll forging process for rail transit, characterized in that: The heated metal blank with a square cross section is formed by two passes of precision roll forging.

2. The rail transit axle roll forging process according to claim 1, characterized in that: After the workpiece is subjected to a first-pass roll forging process on the first-pass roll forging die, the workpiece is turned 90 degrees along its axial direction and subjected to a second-pass roll forging process on the second-pass roll forging die to be formed.

3. The rail transit axle roll forging process according to claim 2, characterized in that: The width of the first-pass roll forging die is the same as that of the second-pass roll forging die. The maximum width of the groove of the first-pass roll forging die is 450 mm, and the width dimension is 250 mm after rotating 90 degrees.

4. The rail transit axle roll forging process according to claim 2, characterized in that: The sector angle of the groove of the first-pass roll forging die is smaller than the sector angle of the groove of the second-pass roll forging die.

5. The rail transit axle roll forging process according to claim 4, characterized in that: The sector angle of the groove of the one-pass roll forging die is 165 degrees.

6. The rail transit axle roll forging process according to claim 5, characterized in that: The sector angle of the groove of the two-pass roll forging die is 220 degrees.

7. The rail transit axle roll forging process according to claim 2, characterized in that: The groove shape of the first-pass roll forging die is the same as that of the second-pass roll forging die, and the shape of the groove is adapted to the outer shape of the axle for rail transit.

8. The rail transit axle roll forging process according to claim 1, characterized in that: The metal blank is a blank with rounded corners at the four corners of the outer surface.

9. The rail transit axle roll forging process according to claim 1, characterized in that: The metal blank is heated to a required temperature by a medium frequency heating furnace.

10. The rail transit axle roll forging process according to claim 1, characterized in that: After the heated metal blank with a square cross section is subjected to two passes of precision roll forging and then formed, a heat treatment step is also included.

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