A large crankshaft segmented die forging process

Abstract

The present application belongs to the field of crankshaft processing, in particular to a large crankshaft segmented die forging process, which comprises the following steps: raw material preparation and inspection: raw material preparation and inspection work; blanking and secondary inspection: the raw material is processed into a specific size of φ310*2566, weight 1520kg, and the material after blanking is inspected again; primary heating and blank making, by using a 20,000-ton electric screw press, which is significantly smaller than the tonnage of normal integral die forging equipment, the present application successfully breaks through the limitation of large-tonnage equipment for producing large crankshafts, greatly reduces the equipment tonnage threshold for producing large crankshafts and shaft parts with a length of 3-4.5 meters, and enables more enterprises to participate in the production of such large crankshafts; in terms of cost investment, compared with a 40,000-ton die forging hydraulic press and a 35,000-ton electric screw press with the same forging tonnage, the investment is reduced by more than 1 times.

Description

Technical Field

[0001] This invention belongs to the field of crankshaft machining, specifically a segmented forging process for large crankshafts. Background Technology

[0002] In the production of large crankshafts, the manufacturing processes are mainly divided into two categories: casting plus machining and forging plus machining. Since forging can better guarantee the mechanical properties of the crankshaft, for crankshafts whose shape and size can be achieved by forging, the forging plus machining process is usually chosen.

[0003] In forging processes, there are two main methods for large crankshafts: upsetting and die forging. For large crankshafts longer than 3.0 meters, upsetting is mostly used. Market demand is high for large crankshafts with lengths between 3.0 and 4.5 meters. Currently, there are two main forging processes for these crankshafts: one is to use a 3700-5000 ton upsetting machine to upset each crankshaft individually; the other is to use a 100-ton-meter hammer (with a forging capacity equivalent to a 40,000-ton hydraulic forging press) for integral die forging.

[0004] However, these existing processes have obvious shortcomings:

[0005] When using an upsetting forging machine for upsetting, each crankshaft needs to be upset individually, resulting in low production efficiency. At the same time, the crankshaft forgings have a large allowance and low material utilization, leading to material waste and increased production costs.

[0006] When using a 100-ton-meter counter-hammer for production, the availability of only one such machine at China Erzhong Deyang Wanhang Die Forging Co., Ltd. severely limits the choices available to manufacturers, making it difficult to meet the large market demand for this type of large crankshaft. Conversely, using a 40,000-ton or larger die forging hydraulic press incurs extremely high fixed costs, and the limited number of companies possessing such large-tonnage equipment also severely restricts production, hindering the ability to flexibly respond to market demands.

[0007] Therefore, the present invention provides a segmented forging process for large crankshafts. Summary of the Invention

[0008] In order to overcome the shortcomings of the prior art, at least one technical problem raised in the background art is solved.

[0009] The technical solution adopted by this invention to solve its technical problem is: a segmented forging process for large crankshafts, which includes the following steps:

[0010] S1. Raw material preparation and inspection: Prepare raw materials and carry out inspection work;

[0011] S2. Blanking and Secondary Inspection: The raw materials are processed into specific dimensions of φ310×2566 and weigh 1520kg. The materials are then inspected again after blanking.

[0012] S3. Initial heating and billet preparation: Heat the qualified material to 1200±20℃ and hold for 120 minutes. Use a 3-ton free forging hammer and an anvil preheated to 250℃~350℃ to prepare the billet.

[0013] S4. Secondary heating and descaling: The material after blanking is heated a second time, and a high-pressure water descaling machine is used. The nozzle servo device runs at a speed of 380mm / s for 3390mm to remove the oxide scale on the surface of the material.

[0014] S5. Segmented final forging and trimming: Using an electric screw press, the small end and big end of the crankshaft are forged separately. The segmented final forging uses two single cavities with one end closed and the other end open, and both pre-forging and final forging are carried out in segmented die forging.

[0015] During final forging, the corresponding cavity is used, and the machine is hammered 4 times with energy parameters of 35%, 30%, 28%, and 27% respectively. The forging die is preheated to 250℃~350℃. The edges are then trimmed using a 3,000-ton hydraulic press and a trimming die.

[0016] S6. No phase change temperature compensation: Heat the material after trimming to 1225±20℃ and hold for 35~45min; repeat steps S4~S6 twice.

[0017] S7. High-temperature tempering and polishing inspection: After the crankshaft has been trimmed three times, it is kept at 660~700℃ for 300~360min and then air-cooled. The crankshaft after high-temperature tempering is then polished and inspected.

[0018] S8. Normalizing and mold correction: After the inspected and qualified crankshaft is kept at 900~940℃ for 240~360min, it is air-cooled and then the mold is corrected by hammering twice with 5% energy parameter using a 20,000-ton electric screw press.

[0019] S9. Quenching and shot blasting during tempering: Heat the crankshaft to 860~880℃, hold for 300~360min, then cool with water, and shot blast with 1.5~2.0mm shot for 15~45min.

[0020] S10. Pre-tempering and thermal correction after quenching: After shot blasting, the crankshaft is kept at 530~550℃ for 600~720 min and then air-cooled. A 300T hydraulic press is used to support the M1 and M9 main journals for thermal correction at an initial temperature of 500℃ and an ending temperature of 350℃.

[0021] S11. Tempering and magnetic particle inspection during quenching and tempering: After heat correction, the crankshaft is held at 550~580℃ for 600~720min, removed from the furnace at ≤400℃ and air-cooled. Magnetic particle inspection is performed according to the requirements of crankshaft forging using a magnetic particle inspection machine.

[0022] S12. Finished product inspection and warehousing: Crankshafts that pass the flaw detection are inspected and then put into storage.

[0023] Preferably, in step S5, the segmented die forging process uses a 20,000-ton electric screw press for large crankshaft die forging.

[0024] Preferably, the edge cutting in step S5 is an integral edge cutting, and the crankshaft is corrected by an integral thermal forming mold after integral edge cutting.

[0025] Preferably, in step S6, the temperature without phase change compensation is not lower than the Ar1 phase change end temperature when the crankshaft material is cooled.

[0026] The beneficial effects of this invention are as follows:

[0027] 1. The segmented die forging process for large crankshafts described in this invention, by using a 20,000-ton electric screw press, which has a significantly smaller tonnage than normal integral die forging equipment, successfully breaks through the limitation of large tonnage equipment in the production of large crankshafts, greatly lowers the equipment tonnage threshold for producing such large crankshafts and shaft parts with a length of 3 to 4.5 meters, and enables more companies to participate in the production of such large crankshafts;

[0028] In terms of cost, compared with large-scale die forging production equipment such as 40,000-ton hydraulic forging presses and 35,000-ton electric screw presses of the same forging tonnage, the investment is reduced by more than half, and the equipment cost in the production cost is reduced by more than 80%; compared with 100-ton-meter hammers, it also effectively reduces the investment pressure on enterprises in equipment.

[0029] 2. The segmented die forging process for large crankshafts described in this invention, through segmented die forging combined with innovative mold design, significantly improves the precision of forgings and can better meet the dimensional and shape precision requirements of large crankshafts;

[0030] In terms of material utilization and production efficiency, compared with the upsetting process, the material utilization rate of forgings has increased from 60% to over 80%, which greatly reduces material waste and lowers material costs; at the same time, the production cycle is shortened by 40%, which speeds up the output of products and improves the company's production efficiency and market responsiveness.

[0031] Furthermore, this process pioneers a new approach to large crankshaft forging by using smaller forging equipment instead of traditional large-tonnage die forging equipment, providing a more economical, efficient, and precise solution for the production of large crankshafts. Detailed Implementation

[0032] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0033] An embodiment of the present invention provides a segmented forging process for large crankshafts, the process comprising the following steps:

[0034] S1. Raw material preparation and inspection: Prepare raw materials and carry out inspection work;

[0035] S2. Blanking and Secondary Inspection: The raw materials are processed into specific dimensions of φ310×2566 and weigh 1520kg. The materials are then inspected again after blanking.

[0036] S3. Initial heating and billet preparation: Heat the qualified material to 1200±20℃ and hold for 120 minutes. Use a 3-ton free forging hammer and an anvil preheated to 250℃~350℃ to prepare the billet.

[0037] S4. Secondary heating and descaling: The material after blanking is heated a second time, and a high-pressure water descaling machine is used. The nozzle servo device runs at a speed of 380mm / s for 3390mm to remove the oxide scale on the surface of the material.

[0038] S5. Segmented final forging and trimming: Using an electric screw press, the small end and big end of the crankshaft are forged separately. The segmented final forging uses two single cavities with one end closed and the other end open, and both pre-forging and final forging are carried out in segmented die forging.

[0039] During final forging, the corresponding cavity is used, and the machine is hammered 4 times with energy parameters of 35%, 30%, 28%, and 27% respectively. The forging die is preheated to 250℃~350℃. The edges are then trimmed using a 3,000-ton hydraulic press and a trimming die.

[0040] S6. No phase change temperature compensation: Heat the material after trimming to 1225±20℃ and hold for 35~45min; repeat steps S4~S6 twice.

[0041] S7. High-temperature tempering and polishing inspection: After the crankshaft has been trimmed three times, it is kept at 660~700℃ for 300~360min and then air-cooled. The crankshaft after high-temperature tempering is then polished and inspected.

[0042] S8. Normalizing and mold correction: After the inspected and qualified crankshaft is kept at 900~940℃ for 240~360min, it is air-cooled and then the mold is corrected by hammering twice with 5% energy parameter using a 20,000-ton electric screw press.

[0043] S9. Quenching and shot blasting during tempering: Heat the crankshaft to 860~880℃, hold for 300~360min, then cool with water, and shot blast with 1.5~2.0mm shot for 15~45min.

[0044] S10. Pre-tempering and thermal correction after quenching: After shot blasting, the crankshaft is kept at 530~550℃ for 600~720 min and then air-cooled. A 300T hydraulic press is used to support the M1 and M9 main journals for thermal correction at an initial temperature of 500℃ and an ending temperature of 350℃.

[0045] S11. Tempering and magnetic particle inspection during quenching and tempering: After heat correction, the crankshaft is held at 550~580℃ for 600~720min, removed from the furnace at ≤400℃ and air-cooled. Magnetic particle inspection is performed according to the requirements of crankshaft forging using a magnetic particle inspection machine.

[0046] S12. Finished product inspection and warehousing: Crankshafts that pass the flaw detection are inspected and then put into storage.

[0047] In step S5, the segmented die forging process uses a 20,000-ton electric screw press for large crankshaft die forging.

[0048] The edge trimming in step S5 is a whole edge trimming. After the whole edge trimming, the crankshaft is corrected by the whole thermal forming mold.

[0049] In step S6, the temperature without phase change compensation is not lower than the Ar1 phase change end temperature when the crankshaft material is cooled.

[0050] Specifically,

[0051] A 20,000-ton electric screw press, with a significantly smaller tonnage than standard integral forging equipment, was adopted to replace traditional large-tonnage forging equipment. This equipment selection breaks through the dependence on large-tonnage equipment for the production of large crankshafts, greatly reducing the equipment tonnage limit for producing large crankshafts and shaft components with lengths of 3 to 4.5 meters, while significantly reducing equipment investment and production costs.

[0052] In terms of mold design, the traditional dual-cavity design for pre-forging and final forging of large crankshafts using integral die forging is abandoned. Instead, two single cavities are innovatively adopted. Each single cavity is closed at one end and open at the other, and it simultaneously performs pre-forging and final forging functions. Through this segmented die forging design, the small and large ends of the crankshaft can be precisely forged in stages, which not only expands the number of companies capable of producing large crankshafts with high market demand, but also improves the precision of the forgings.

[0053] In the process flow, the forging process is combined with non-phase transformation heating at a temperature not lower than the Ar phase transformation temperature of the crankshaft material (such as heating to 1225±20℃ and holding for 35~45min in step S6) to ensure that the die forging is completed under the specified heating temperature and to guarantee the quality stability of the forging. After the overall edge trimming is completed, the die forging process is finished. Subsequently, the crankshaft is corrected using an overall hot forming die to further ensure the shape and dimensional accuracy of the crankshaft.

[0054] Compared to upsetting, this segmented die forging process, through precise die design and process control, increases the material utilization rate of forgings from 60% to over 80% and shortens the production cycle by 40%, demonstrating significant advantages in improving material utilization efficiency and production efficiency.

[0055] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A segmented forging process for large crankshafts, characterized in that, The process includes the following steps: S1. Raw material preparation and inspection: Prepare raw materials and carry out inspection work; S2. Blanking and Secondary Inspection: The raw materials are processed into specific dimensions of φ310×2566 and weigh 1520kg. The materials are then inspected again after blanking. S3. Initial heating and billet preparation: Heat the qualified material to 1200±20℃ and hold for 120 minutes. Use a 3-ton free forging hammer and an anvil preheated to 250℃~350℃ to prepare the billet. S4. Secondary heating and descaling: The material after blanking is heated a second time, and a high-pressure water descaling machine is used. The nozzle servo device runs at a speed of 380mm / s for 3390mm to remove the oxide scale on the surface of the material. S5. Segmented final forging and trimming: Using an electric screw press, the small end and big end of the crankshaft are forged separately. The segmented final forging uses two single cavities with one end closed and the other end open, and both pre-forging and final forging are carried out in segmented die forging. During final forging, the corresponding cavity is used, and the machine is hammered 4 times with energy parameters of 35%, 30%, 28%, and 27% respectively. The forging die is preheated to 250℃~350℃. The edges are then trimmed using a 3,000-ton hydraulic press and a trimming die. S6. No phase change temperature compensation: Heat the material after trimming to 1225±20℃ and hold for 35~45min; repeat steps S4~S6 twice. S7. High-temperature tempering and polishing inspection: After the crankshaft has been trimmed three times, it is kept at 660~700℃ for 300~360min and then air-cooled. The crankshaft after high-temperature tempering is then polished and inspected. S8. Normalizing and mold correction: After the inspected crankshaft is kept at 900~940℃ for 240~360min, it is air-cooled and then the mold is corrected by hammering it twice with 5% energy parameter using a 20,000-ton electric screw press. S9. Quenching and shot blasting during tempering: Heat the crankshaft to 860~880℃, hold for 300~360min, then cool with water, and shot blast with 1.5~2.0mm shot for 15~45min. S10. Pre-tempering and thermal correction after quenching: After shot blasting, the crankshaft is kept at 530~550℃ for 600~720 min and then air-cooled. A 300T hydraulic press is used to support the M1 and M9 main journals for thermal correction at an initial temperature of 500℃ and an ending temperature of 350℃. S11. Tempering and magnetic particle inspection during quenching and tempering: After heat correction, the crankshaft is held at 550~580℃ for 600~720min, removed from the furnace at ≤400℃ and air-cooled. Magnetic particle inspection is performed according to the requirements of crankshaft forging using a magnetic particle inspection machine. S12. Finished product inspection and warehousing: Crankshafts that pass the flaw detection are inspected and then put into storage.

2. The segmented forging process for large crankshafts according to claim 1, characterized in that: In step S5, the segmented die forging process uses a 20,000-ton electric screw press to forge large crankshafts.

3. The segmented forging process for large crankshafts according to claim 1, characterized in that: The edge trimming in step S5 is an integral edge trimming, and the crankshaft is corrected by an integral thermal shaping mold after integral edge trimming.

4. The segmented forging process for large crankshafts according to claim 1, characterized in that: In step S6, the temperature without phase change compensation is not lower than the Ar1 phase change end temperature when the crankshaft material is cooled.