High-efficiency and low-cost forging die repairing method

Abstract

The invention belongs to the technical field of forging die repairing, and particularly relates to a high-efficiency and low-cost forging die repairing method which comprises the following steps: carrying out air gouging treatment on a fatigue forging die to be repaired, and carrying out polishing and comprehensive flaw detection on an impression of the forging die to be repaired after air gouging treatment; carrying out preheating and heat preservation treatment on the forging die to be repaired after flaw detection, and carrying out profiling surfacing on the forging die to be repaired after heat preservation treatment by adopting a profiling welding robot; carrying out tempering treatment on the to-be-repaired forging die subjected to profiling surfacing; the impression of the to-be-repaired forging die subjected to tempering treatment is machined, the machining process comprises the two stages of surface hard layer machining and overall machining, the surface hard layer machining adopts a reverse milling mode, and the overall machining adopts a clockwise milling mode; and the machined impression of the to-be-repaired forging die is subjected to overall polishing treatment, and the repaired forging die is obtained.

Description

Technical Field

[0001] This invention belongs to the field of forging die repair technology, specifically relating to a high-efficiency and low-cost forging die repair method. Background Technology

[0002] In the current equipment manufacturing industry, forging die forming technology has become the mainstream manufacturing process due to its significant advantages of stable quality, high production efficiency, and relatively low cost. As a key tool in the metal forming process, the performance of forging dies directly determines the quality and production efficiency of forgings.

[0003] However, in the actual use of forging dies, due to the influence of various complex working conditions such as high temperature, high pressure, friction, and impact, the dies are prone to wear, cracks, deformation, and other damage. This damage not only affects the quality of the forgings, leading to an increase in scrap rate, but also reduces production efficiency and increases production costs.

[0004] To maintain normal production, companies often need to maintain a large reserve of molds as backups. This is especially true for complex or high-precision forgings, where several sets of molds are often required for repeated repairs to ensure production needs are met. However, mold repair is no easy task. How to improve repair efficiency and reduce repair costs while ensuring repair quality has become a major challenge for companies.

[0005] Currently, most existing mold repair methods involve complete welding, which involves welding the damaged parts of the mold and then restoring it to its original size and shape through machining. However, this repair method requires re-welding the entire mold cavity, which is time-consuming, material-intensive, costly, and has a long repair cycle, making it difficult to meet the needs of enterprises for high-efficiency and low-cost production. Summary of the Invention

[0006] In view of this, the present invention provides a high-efficiency and low-cost method for repairing forging dies, so as to solve the technical problems of long repair cycles and high costs in existing die repair methods.

[0007] To achieve the above objectives, this application adopts the following approach:

[0008] A highly efficient and low-cost method for repairing forging dies includes the following steps:

[0009] S10. Perform air gouging on the forging die to be repaired after fatigue to remove the fatigue layer around the die cavity and in the depth direction of 20-25mm, and groove at the crack until the crack disappears.

[0010] S20. Grind the cavity of the forging die to be repaired after air gouging until the surface shows a metallic luster;

[0011] S30. Conduct a comprehensive flaw detection inspection on the cavity of the forging die to be repaired after grinding. If cracks or defects are found, continue to groove at the cracks or defects until the cracks or defects are completely eliminated.

[0012] S40. The forging die to be repaired after flaw detection is preheated and kept warm, and a contour welding robot is used to perform contour welding on the forging die to be repaired after the heat preservation treatment.

[0013] S50. Tempering treatment is performed on the forging die to be repaired after contour welding;

[0014] S60. The cavity of the forging die to be repaired after tempering is machined, including two stages: surface hardening and overall machining. The surface hardening is carried out by reverse milling, and the overall machining is carried out by climb milling.

[0015] S70. The die cavity of the forging die to be repaired after processing is polished as a whole to obtain the repaired forging die.

[0016] Preferably, step S40 specifically includes the following steps:

[0017] S41. Based on the forging mold to be repaired, establish a real mold cavity, and then add a preset machining allowance around the real mold cavity to form a contour welding control dimension model.

[0018] S42. Model the die cavity of the forging mold to be repaired after air gouging to form a contour welding blank model;

[0019] S43. Import the contour welding control dimension model and the contour welding blank model into the CAM software system simultaneously;

[0020] S44. Based on geometric features, optimize the welding torch posture by setting and planning the path using CAM software, and generate executable welding torch trajectory code;

[0021] S45. Based on the generated welding torch trajectory code, perform reachability checks and collision detection to ensure the welding process is safe and reliable;

[0022] S46. Convert the safe and reliable welding torch trajectory into specific controller code, transmit it to the robot via DNC network or mobile USB flash drive, and use the robot to perform contour welding.

[0023] Preferably, the machining parameters for the reverse milling method are: rotational speed 800-1000 r / min, depth of cut 1-2 mm, and feed rate 800-1200 mm / min.

[0024] Preferably, the machining parameters for the climb milling method are: rotational speed 2000-6000 r / min, depth of cut 0.3-0.8 mm, and feed rate 2500-4000 mm / min.

[0025] Preferably, the diameter of the tool used for machining the surface hard layer is ≥25mm, the blade thickness is ≥5mm, and the blade radius is ≥0.5mm.

[0026] Preferably, thermal expansion tools are used for deeper parts during the overall machining process.

[0027] Preferably, the preset machining allowance is 8mm-10mm.

[0028] Preferably, the step of "preheating the forging mold to be repaired after flaw detection" to 200℃-300℃ and holding it at that temperature for 2h-3h.

[0029] Preferably, the "tempering treatment of the forging die to be repaired after contour welding" includes the following steps:

[0030] S51. After performing contour welding on the forging die to be repaired, heat the forging die to be repaired to 450°C and keep it at that temperature for more than 4 hours. After keeping it at that temperature, slowly cool it to 150°C.

[0031] S52. The forging mold to be repaired, after slow cooling, is heated to 550°C and held at that temperature for more than 8 hours. After holding at that temperature, it is then slowly cooled to 150°C.

[0032] S53. Repeat step S52.

[0033] In the aforementioned high-efficiency, low-cost forging die repair method, the forging die to be repaired after fatigue is first subjected to air gouging to remove damaged material. The die cavity of the air-gouged forging die is then ground and inspected for flaws to ensure comprehensive repair. After flaw inspection, the forging die is preheated and kept at a constant temperature to prevent cracks during welding. Then, a contour welding robot is used to perform contour welding on the heat-treated forging die. Contour welding only welds the damaged pits and grooves, significantly reducing the amount of welding compared to full welding, shortening the repair cycle, reducing material consumption, and saving repair costs. Finally, the forging die after contour welding is tempered to eliminate… Thermal stress improves the performance of the repaired forging die. The die cavity of the forging die to be repaired after tempering is processed in two stages: surface hardening and overall machining. Surface hardening is performed using conventional milling, while overall machining is performed using climb milling. In conventional milling, the tool starts cutting from the relatively soft inner material and gradually contacts the hard surface layer. Since the inner layer is relatively soft, this avoids direct contact between the tool and the surface hard layer, thus extending tool life and reducing repair costs. In overall machining, climb milling is used. In climb milling, the cutting thickness gradually decreases, the cutting force changes relatively little, the working process is relatively stable, the cutting force is more stable, the power consumption is lower, and the machining efficiency is improved. Detailed Implementation

[0034] To facilitate understanding of this application, a more comprehensive description will be provided below, along with preferred embodiments. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0036] In one specific embodiment, a high-efficiency, low-cost method for repairing forging dies includes the following steps:

[0037] S10. Perform air gouging on the forging die to be repaired after fatigue to remove the fatigue layer around the die cavity and in the depth direction of 20-25mm, and groove at the crack until the crack disappears.

[0038] S20. Grind the cavity of the forging die to be repaired after air gouging until the surface shows a metallic luster;

[0039] S30. Conduct a comprehensive flaw detection inspection on the cavity of the forging die to be repaired after grinding. If cracks or defects are found, continue to groove at the cracks or defects until the cracks or defects are completely eliminated.

[0040] S40. The forging die to be repaired after flaw detection is preheated and kept warm, and a contour welding robot is used to perform contour welding on the forging die to be repaired after the heat preservation treatment.

[0041] S50. Tempering treatment is performed on the forging die to be repaired after contour welding;

[0042] S60. The cavity of the forging die to be repaired after tempering is machined, including two stages: surface hardening and overall machining. The surface hardening is carried out by reverse milling, and the overall machining is carried out by climb milling.

[0043] S70. The die cavity of the forging die to be repaired after processing is polished as a whole to obtain the repaired forging die.

[0044] When repairing a fatigued forging die with damaged areas, the operator must locate the areas requiring repair (such as cracks, fissures, or wear dents) during forging. Then, using carbon arc gouging, a regular groove with a depth and width of 20-25mm is carved along the edge and bottom of the damaged area to completely remove all fatigue and damaged material. If visible cracks remain, the grooving continues along the crack direction until the cracks are completely eliminated. The surface of the forging die after gouging will be covered with an oxide layer and impurities. Grinding exposes the metal's natural color, providing a clean and active surface for subsequent flaw detection and welding. Next, a comprehensive inspection of the ground area can be performed using methods such as magnetic particle testing (MT) or penetrant testing (PT). These methods can reveal micro-cracks invisible to the naked eye. Once discovered, the defect is regrooved (20-25mm deep and wide) to ensure all potential problems are completely eliminated. Then, using a contour welding robot and welding wire, and following a pre-programmed 3D mold model, multi-layer, multi-pass automated contour welding is performed in the cleaned groove to fill in missing metal, achieving cost reduction and efficiency improvement. Before welding, the mold must be preheated and kept at a constant temperature to prevent welding cracks. The welding process generates significant internal stress; therefore, the welded mold needs to be placed in a heating furnace for tempering to relieve stress, stabilize the structure, and prevent deformation or cracking during subsequent use. The roughened surface after welding then needs to be machined to the final mold cavity shape and size. Since the surface of the weld overlay is usually very hard, reverse milling (the tool rotation direction is opposite to the feed direction) is used to machine the hardened surface layer. During reverse milling, the tool starts cutting from the relatively soft inner material and gradually contacts the hard surface layer. Because the inner layer is relatively soft, this avoids direct contact between the tool and the hard surface layer, thus extending tool life. The entire process employs climb milling, where the cutting thickness gradually decreases, resulting in relatively small changes in cutting force and a smoother working process. This leads to more stable cutting force, lower power consumption, and improved machining efficiency. Finally, the entire die cavity is polished to reduce surface roughness. A smooth die cavity reduces friction during forging, facilitates demolding, and improves the surface quality of the forging.

[0045] In the aforementioned high-efficiency, low-cost forging die repair method, the forging die to be repaired after fatigue is first air-gouged to remove damaged material. The die cavity after air-gouging is then ground and inspected for flaws to ensure comprehensive repair. After flaw inspection, the forging die is preheated and kept warm to prevent cracks during welding. Then, a contour welding robot is used to perform contour welding on the warmed die. Contour welding only welds the damaged pits and grooves, significantly reducing the amount of welding compared to full welding, shortening the repair cycle, reducing material consumption, and saving repair costs. Next, the forging die after contour welding is tempered to eliminate thermal stress and improve the performance of the repaired forging die. The die cavity of the tempered forging die undergoes two stages: surface hardening and overall machining. Surface hardening uses climb milling, while overall machining uses conventional milling to extend tool life and reduce repair costs. The use of conventional milling in the overall machining process improves machining efficiency.

[0046] In one specific embodiment, S40 specifically includes the following steps:

[0047] S41. Based on the forging mold to be repaired, establish a real mold cavity, and then add a preset machining allowance around the real mold cavity to form a contour welding control dimension model.

[0048] S42. Model the die cavity of the forging mold to be repaired after air gouging to form a contour welding blank model;

[0049] S43. Import the contour welding control dimension model and the contour welding blank model into the CAM software system simultaneously;

[0050] S44. Based on geometric features, optimize the welding torch posture by setting and planning the path using CAM software, and generate executable welding torch trajectory code;

[0051] S45. Based on the generated welding torch trajectory code, perform reachability checks and collision detection to ensure the welding process is safe and reliable;

[0052] S46. Convert the safe and reliable welding torch trajectory into specific controller code, transmit it to the robot via DNC network or mobile USB flash drive, and use the robot to perform contour welding.

[0053] First, based on the original design drawings of the forging die to be repaired or using 3D scanning technology, a digital model that perfectly matches the intact die cavity is created in the computer. Then, based on this digital model, a dimension is uniformly expanded outward (peripheral) and in depth, i.e., a preset machining allowance. The resulting slightly larger model is the "contour welding control dimension model," which represents the ideal state after welding but before finishing. The actual damaged area of ​​the die after air gouging and grinding is scanned using a 3D scanner to obtain accurate 3D point cloud data reflecting the current shape of the pit, and a "contour welding blank model" is generated accordingly. This model accurately reflects the size and shape of the "cavity" that needs to be filled. The two models are simultaneously imported into computer-aided manufacturing (CAM) software, which automatically calculates the volume difference between the two models. This volume difference is the precise amount of metal to be welded. Subsequently, the operator sets welding parameters (such as speed and oscillation) in the software, which automatically plans the optimal path (trajectory) for the welding torch to fill the volume, while optimizing the angle (attitude) of the welding torch, generating executable welding torch trajectory code. The virtual-verified and secure welding torch trajectory code is converted into code that the robot controller can recognize, and then transmitted to the robot on site via network or USB flash drive. The robot then strictly follows this digital instruction to perform precise contour welding on the mold.

[0054] Through precise comparison of the "target model" and the "current situation model" and the robot's accurate execution, the robot automatically and accurately fills the groove with welding material, with the shape and allowance controlled just right.

[0055] In a preferred embodiment, the reverse milling method employs machining parameters of low rotational speed (800r / min-1000r / min), large depth of cut (1mm-2mm), and low feed rate (800mm / min-1200mm / min).

[0056] In another preferred embodiment, the climb milling method employs parameters of high rotational speed (2000r / min-6000r / min), small depth of cut (0.3mm-0.8mm), and high feed rate (2500mm / min-4000mm / min).

[0057] The surface hardness of the forging die to be repaired is very high after welding. It is considered to remove the hard surface layer first and then process the whole die. This can greatly reduce the cost of tools. In a preferred embodiment, the tool used for processing the hard surface layer has a diameter of ≥25mm, a blade thickness of ≥5mm, and a blade radius of ≥0.5mm. For the deeper parts during the whole die processing, a thermal expansion tool is used.

[0058] In one specific embodiment, the preset machining allowance is 8mm-10mm.

[0059] In one specific embodiment, the "preheating of the forging mold to be repaired after flaw detection" is performed to 200℃-300℃ and held at that temperature for 2h-3h.

[0060] In a preferred embodiment, the "tempering treatment of the forging die to be repaired after conformal welding" includes the following steps:

[0061] S51. After performing contour welding on the forging die to be repaired, the forging die to be repaired is heated to 450°C and held at that temperature for more than 4 hours. After holding at that temperature, it is slowly cooled to 150°C. Heating the die to 450°C and holding it at that temperature for a long time can greatly eliminate residual stress. Moreover, tempering at 450°C is exactly the tempering temperature range of martensite, which can decompose it into tempered troostite or tempered sorbite with better toughness, thereby improving the toughness of this area and reducing the risk of cracking.

[0062] S52. The forging mold to be repaired, after slow cooling, is heated to 550°C and held at that temperature for more than 8 hours. After holding, it is slowly cooled to 150°C. The higher temperature of 550°C allows for more complete atomic diffusion, eliminating the remaining stress after the first tempering and achieving a stress-stable state.

[0063] S53. Repeat step S52.

[0064] The following specific experimental examples further illustrate the technical solution and effects of the present invention. It should be noted that the following experimental examples are only for further explanation of the present invention and do not limit the technical solution of the present invention.

[0065] Example

[0066] Prepare the forging die to be repaired. After fatigue, the forging die is air-gouged to remove the fatigue layer around the die cavity and up to 25mm in depth. The die cavity is then ground until a metallic luster appears. A comprehensive flaw detection inspection is performed on the ground die cavity. If cracks or defects are found, grooving is continued at the cracks or defects until they completely disappear. A contour welding robot is used to perform contour welding on the flaw-detected forging die. Before welding, the forging die is preheated to 250℃ and held at that temperature for 3 hours. After contour welding, the forging die is heated to 450℃ and held for at least 4 hours, then slowly cooled to 150℃. The forging die to be repaired is heated to 550℃ and held at that temperature for more than 8 hours, then slowly cooled to 150℃. The slowly cooled forging die is then heated again to 550℃ and held at that temperature for more than 8 hours, then slowly cooled to 150℃. The die cavity of the tempered forging die is machined, including two stages: surface hardening and overall machining. The surface hardening is performed using climb milling, and the overall machining is performed using conventional milling. The parameters for climb milling are: rotation speed 900 r / min, depth of cut 2 mm, feed rate 1000 mm / min; the parameters for conventional milling are: 4600 r / min, depth of cut 0.5 mm, feed rate 3200 mm / min. The machined die cavity is then polished to obtain the repaired forging die.

[0067] Comparative Example

[0068] Prepare a forging die with the same degree of damage as the forging die to be repaired in the embodiment. The existing method is to fully overlay the die with welding, that is, to overlay the damaged parts of the die with welding, and then restore it to its original size and shape through machining.

[0069] The time and cost of repairing the forging die to be repaired in the above embodiments and comparative examples are shown in Table 1.

[0070] Table 1 Comparison of Data from Examples and Comparative Cases

[0071] As can be seen from the data in Table 1 above, the method provided in this application for repairing forging dies in the embodiments can significantly shorten the processing time, reduce tooling costs, improve processing efficiency, and save processing costs compared with the method in the comparative examples.

[0072] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions should all be covered within the scope of protection of the present invention.

Claims

1. A high-efficiency, low-cost method for repairing forging dies, characterized in that, Includes the following steps: S10. Perform air gouging on the forging die to be repaired after fatigue to remove the fatigue layer around the die cavity and in the depth direction of 20-25mm, and groove at the crack until the crack disappears. S20. Grind the cavity of the forging die to be repaired after air gouging until the surface shows a metallic luster; S30. Conduct a comprehensive flaw detection inspection on the cavity of the forging die to be repaired after grinding. If cracks or defects are found, continue to groove at the cracks or defects until the cracks or defects are completely eliminated. S40. The forging die to be repaired after flaw detection is preheated and kept warm, and a contour welding robot is used to perform contour welding on the forging die to be repaired after the heat preservation treatment. S50. Tempering treatment is performed on the forging die to be repaired after contour welding; S60. The cavity of the forging die to be repaired after tempering is machined, including two stages: surface hardening and overall machining. The surface hardening is carried out by reverse milling, and the overall machining is carried out by climb milling. S70. The die cavity of the forging die to be repaired after processing is polished as a whole to obtain the repaired forging die.

2. The high-efficiency, low-cost forging die repair method according to claim 1, characterized in that, S40 specifically includes the following steps: S41. Based on the forging mold to be repaired, establish a real mold cavity, and then add a preset machining allowance around the real mold cavity to form a contour welding control dimension model. S42. Model the die cavity of the forging die to be repaired after air gouging to form a contour welding blank model; S43. Import the contour welding control dimension model and the contour welding blank model into the CAM software system simultaneously; S44. Based on geometric features, optimize the welding torch posture by setting and planning the path using CAM software, and generate executable welding torch trajectory code; S45. Based on the generated welding torch trajectory code, perform reachability checks and collision detection to ensure the welding process is safe and reliable; S46. Convert the safe and reliable welding torch trajectory into specific controller code, transmit it to the robot via DNC network or mobile USB flash drive, and use the robot to perform contour welding.

3. The high-efficiency, low-cost forging die repair method according to claim 1, characterized in that, The machining parameters for the reverse milling method are: rotational speed 800-1000 r / min, depth of cut 1-2 mm, and feed rate 800-1200 mm / min.

4. The high-efficiency, low-cost forging die repair method according to claim 1, characterized in that, The machining parameters for the climb milling method are: rotational speed 2000-6000 r / min, depth of cut 0.3-0.8 mm, and feed rate 2500-4000 mm / min.

5. The high-efficiency, low-cost forging die repair method according to claim 1, characterized in that, The diameter of the tool used for machining the surface hard layer is ≥25mm, the blade thickness is ≥5mm, and the blade radius is ≥0.5mm.

6. The high-efficiency, low-cost forging die repair method according to claim 1, characterized in that, During the overall machining process, thermal expansion tools are used for deeper parts.

7. The high-efficiency, low-cost forging die repair method according to claim 2, characterized in that, The preset machining allowance is 8mm-10mm.

8. The high-efficiency, low-cost forging die repair method according to claim 1, characterized in that, The process of "preheating the forging mold to be repaired after flaw detection" to 200℃-300℃ and holding it at that temperature for 2h-3h.

9. The high-efficiency, low-cost forging die repair method according to claim 1, characterized in that, The "tempering treatment of the forging die to be repaired after conformal welding" includes the following steps: S51. After performing contour welding on the forging die to be repaired, heat the forging die to be repaired to 450°C and keep it at that temperature for more than 4 hours. After keeping it at that temperature, slowly cool it to 150°C. S52. The forging mold to be repaired, after slow cooling, is heated to 550°C and held at that temperature for more than 8 hours. After holding at that temperature, it is then slowly cooled to 150°C. S53. Repeat step S52.

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