Segmented die forging process for large crankshaft

Abstract

The invention belongs to the field of crankshaft machining, and particularly relates to a large crankshaft segmented die forging process which comprises the following steps: raw material preparation and inspection: raw materials are prepared, and inspection work is carried out; blanking and secondary inspection are conducted, specifically, the raw materials are machined to be in the specific size of phi 310 * 2566 and the weight of 1520 kg, and the blanked materials are inspected again; according to the method, the tonnage of the 20,000-ton electric screw press is greatly reduced compared with that of normal integral die forging equipment, so that the limitation of large-tonnage equipment for producing large crankshafts is successfully broken through, and the tonnage threshold of the equipment for producing the large crankshafts with the lengths of 3-4.5 m and shaft parts is greatly reduced; more enterprises are enabled to have the ability to participate in the production of the large crankshafts; and in the aspect of cost input, compared with large die forging production equipment such as a die forging hydraulic press of more than 40 thousand tons and an electric screw press of 3.5 thousand tons with the same forging and pressing tonnage, the investment is reduced by more than one time.

Description

Technical Field

[0001] The invention belongs to the field of crankshaft processing, in particular to a large crankshaft segmented die forging process. Background Art

[0002] In the field of large crankshaft production, its manufacturing process is mainly divided into two categories: casting and machining, and forging and machining. Since the forging process can better ensure the mechanical properties of the crankshaft, forging and machining is usually selected for crankshafts whose shapes and dimensions can be achieved by forging.

[0003] In the forging process, there are two main methods for large crankshafts: upsetting and die forging. Large crankshafts longer than 3.0 meters are mostly produced using upsetting. Market demand is for large crankshafts between 3.0 and 4.5 meters in length. Currently, there are two main forging production processes: one uses a 3,700-5,000-ton upsetting press to upset each crank individually; the other uses a 100-ton-meter hammer (with a forging capacity equivalent to a 40,000-ton die forging hydraulic press) for integral die forging.

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

[0005] When using an upsetting machine for upsetting, each crankshaft needs to be upset one by one, resulting in low production efficiency. At the same time, the crankshaft forging has a large margin and low material utilization, resulting in material waste and increased production costs.

[0006] When using a 100-ton-meter counter-blow hammer for production, only one unit, owned by China Second Heavy Industries' Deyang Wanhang Die Forging Company, severely limited manufacturers' options and made it difficult to meet the high market demand for such large crankshafts. Furthermore, the high fixed costs associated with using a hydraulic die forging press of 40,000 tons or more, coupled with the limited availability of such large-capacity equipment, also severely constrained production and hindered flexible response to market demand.

[0007] To this end, the present invention provides a large crankshaft segmented die forging process. Summary of the Invention

[0008] In order to make up for the deficiencies of the prior art, at least one technical problem raised in the background technology is solved.

[0009] The technical solution adopted by the present invention to solve the technical problem is: a large crankshaft segmented die forging process described in the present invention includes the following steps:

[0010] S1. Raw material preparation and inspection: prepare raw materials and conduct inspection;

[0011] S2. Cutting and secondary inspection: Process the raw materials into specific dimensions of φ310×2566 and weight 1520kg, and inspect the cut materials again;

[0012] S3. Initial heating and blanking: Heat the qualified materials to 1200±20℃ and keep them warm for 120min. Use a 3-ton open die forging hammer with anvil preheated to 250℃~350℃ to make blanks.

[0013] S4, secondary heating and descaling: The material after blanking is secondary heated, and the surface oxide scale of the material is removed by using a high-pressure water descaling machine with the nozzle servo device running 3390mm at a speed of 380mm / s;

[0014] S5. Segmented final forging and trimming: Use an electric screw press to perform final forging on the small and large ends of the crankshaft. The segmented final forging is performed using two single cavities with one end closed and the other open, with both pre-forging and final forging being performed simultaneously.

[0015] During final forging, the corresponding cavity is used and hammered four times with energy parameters of 35%, 30%, 28%, and 27% in sequence. The forging die is preheated to 250℃~350℃; trimming is performed using a 3,000-ton hydraulic press and a trimming die.

[0016] S6, non-phase change heating: heat the trimmed material to 1225±20℃ and keep warm for 35~45min; repeat S4~S6 steps twice;

[0017] S7. High-temperature tempering and grinding inspection: After three trimmings, the crankshaft is kept at 660-700°C for 300-360 minutes and then air-cooled. The crankshaft after high-temperature tempering is then ground and inspected.

[0018] S8. Normalizing and die calibration: Keep the crankshaft that has passed the inspection at 900-940°C for 240-360 minutes, then air-cool it. Use a 20,000-ton electric screw press to hammer twice at 5% energy parameters to calibrate the die.

[0019] S9. Quenching and shot blasting during quenching and tempering: heat the crankshaft to 860-880°C, keep it warm for 300-360 minutes, then water-cool it. Use a shot blasting machine to blast with 1.5-2.0 mm pellets for 15-45 minutes.

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

[0021] S11. Tempering and magnetic particle inspection during quenching and tempering: Keep the crankshaft after thermal correction at 550-580℃ for 600-720min, remove it from the furnace and air-cool it at ≤400℃, and use a magnetic particle inspection machine to perform magnetic particle inspection according to the requirements of the crankshaft forgings;

[0022] S12. Finished product inspection and warehousing: The crankshafts that have passed the NDT are inspected and put into storage after passing the inspection.

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

[0024] Preferably, the trimming in step S5 is integral trimming, and after the integral trimming, the crankshaft is corrected by an integral heat shaping die.

[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 the present invention are as follows:

[0027] 1. The large crankshaft segmented die forging process described in this invention utilizes a 20,000-ton electric screw press, a significantly smaller machine than conventional monolithic die forging equipment. This process successfully overcomes the limitation of large-tonnage equipment required for large crankshaft production, significantly lowering the equipment tonnage threshold for producing such large crankshafts and shaft components with lengths of 3 to 4.5 meters, allowing more companies to participate in the production of such large crankshafts.

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

[0029] 2. The segmented die forging process for large crankshafts described in this invention significantly improves the precision of forgings through the segmented die forging process combined with innovative die design, and can better meet the requirements for dimensional and shape accuracy 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%, greatly reducing material waste and lowering material costs. At the same time, the production cycle has been shortened by 40%, accelerating product output and improving the company's production efficiency and market responsiveness.

[0031] In addition, this process has opened up a new path for forging large crankshafts by using smaller tonnage 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 DESCRIPTION

[0032] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0033] A large crankshaft segmented die forging process according to an embodiment of the present invention comprises the following steps:

[0034] S1. Raw material preparation and inspection: prepare raw materials and conduct inspection;

[0035] S2. Cutting and secondary inspection: Process the raw materials into specific dimensions of φ310×2566 and weight 1520kg, and inspect the cut materials again;

[0036] S3. Initial heating and blanking: Heat the qualified materials to 1200±20℃ and keep them warm for 120min. Use a 3-ton open die forging hammer with anvil preheated to 250℃~350℃ to make blanks.

[0037] S4, secondary heating and descaling: The material after blanking is secondary heated, and the surface oxide scale of the material is removed by using a high-pressure water descaling machine with the nozzle servo device running 3390mm at a speed of 380mm / s;

[0038] S5. Segmented final forging and trimming: Use an electric screw press to perform final forging on the small and large ends of the crankshaft. The segmented final forging is performed using two single cavities with one end closed and the other open, with both pre-forging and final forging being performed simultaneously.

[0039] During final forging, the corresponding cavity is used and hammered four times with energy parameters of 35%, 30%, 28%, and 27% in sequence. The forging die is preheated to 250℃~350℃; trimming is performed using a 3,000-ton hydraulic press and a trimming die.

[0040] S6, non-phase change heating: heat the trimmed material to 1225±20℃ and keep warm for 35~45min; repeat S4~S6 steps twice;

[0041] S7. High-temperature tempering and grinding inspection: After three trimmings, the crankshaft is kept at 660-700°C for 300-360 minutes and then air-cooled. The crankshaft after high-temperature tempering is then ground and inspected.

[0042] S8. Normalizing and die calibration: Keep the crankshaft that has passed the inspection at 900-940°C for 240-360 minutes, then air-cool it. Use a 20,000-ton electric screw press to hammer twice at 5% energy parameters to calibrate the die.

[0043] S9. Quenching and shot blasting during quenching and tempering: heat the crankshaft to 860-880°C, keep it warm for 300-360 minutes, then water-cool it. Use a shot blasting machine to blast with 1.5-2.0 mm pellets for 15-45 minutes.

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

[0045] S11. Tempering and magnetic particle inspection during quenching and tempering: Keep the crankshaft after thermal correction at 550-580℃ for 600-720min, remove it from the furnace and air-cool it at ≤400℃, and use a magnetic particle inspection machine to perform magnetic particle inspection according to the requirements of the crankshaft forgings;

[0046] S12. Finished product inspection and warehousing: The crankshafts that have passed the NDT are inspected and put into storage after passing the inspection.

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

[0048] The trimming in step S5 is integral trimming, and after the integral trimming, the crankshaft is corrected by an integral heat shaping die.

[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, significantly smaller than standard integral die forging equipment, was used to replace traditional large-tonnage die forging equipment. This equipment choice eliminated the reliance on large-tonnage equipment for large crankshaft production, significantly lowering the equipment tonnage requirement for producing these large crankshafts and shaft components with lengths ranging from 3 to 4.5 meters, while also significantly reducing equipment investment and production costs.

[0052] The die design abandons the traditional dual-cavity design for pre-forging and final forging of large crankshafts in a single die forging process, adopting two single cavities. Each cavity is closed at one end and open at the other, and performs both pre-forging and final forging functions. This segmented die forging design enables precise forging of the crankshaft's small and large ends in stages, expanding the number of companies capable of producing these large crankshafts, which are in high demand, while also improving the precision of the forgings.

[0053] During the forging process, the forging process is accompanied by a non-phase-change supplementary heating temperature (e.g., heating to 1225±20°C and holding for 35-45 minutes in step S6) that is no lower than the crankshaft material's Ar phase transition temperature. This ensures that the die forging is completed within the specified heating cycle and guarantees the quality and stability of the forging. The die forging process is completed after integral trimming, and the crankshaft is subsequently corrected using an integral hot-forming die to further ensure the crankshaft's shape and dimensional accuracy.

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

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

Claims

1. A large crankshaft segmented die forging process, characterized in that: The process includes the following steps: S1. Raw material preparation and inspection: prepare raw materials and conduct inspection; S2. Cutting and secondary inspection: Process the raw materials into specific dimensions of φ310×2566 and weight 1520kg, and inspect the cut materials again; S3. Initial heating and blanking: Heat the qualified materials to 1200±20℃ and keep them warm for 120min. Use a 3-ton open die forging hammer with anvil preheated to 250℃~350℃ to make blanks. S4, secondary heating and descaling: The material after blanking is secondary heated, and the surface oxide scale of the material is removed by using a high-pressure water descaling machine with the nozzle servo device running 3390mm at a speed of 380mm / s; S5. Segmented final forging and trimming: Use an electric screw press to perform final forging on the small and large ends of the crankshaft. The segmented final forging is performed using two single cavities with one end closed and the other open, with both pre-forging and final forging being performed simultaneously. During final forging, the corresponding cavity is used and hammered four times with energy parameters of 35%, 30%, 28%, and 27% in sequence. The forging die is preheated to 250℃~350℃; trimming is performed using a 3,000-ton hydraulic press and a trimming die. S6, non-phase change heating: heat the trimmed material to 1225±20℃ and keep warm for 35~45min; repeat S4~S6 steps twice; S7. High-temperature tempering and grinding inspection: After three trimmings, the crankshaft is kept at 660-700°C for 300-360 minutes and then air-cooled. The crankshaft after high-temperature tempering is then ground and inspected. S8. Normalizing and die calibration: Keep the crankshaft that has passed the inspection at 900-940°C for 240-360 minutes, then air-cool it. Use a 20,000-ton electric screw press to hammer twice at 5% energy parameters to calibrate the die. S9. Quenching and shot blasting during quenching and tempering: heat the crankshaft to 860-880°C, keep it warm for 300-360 minutes, then water-cool it. Use a shot blasting machine to blast with 1.5-2.0 mm pellets for 15-45 minutes. S10, pre-tempering and thermal correction after quenching: the shot blasted crankshaft is kept at 530-550℃ for 600-720min and then air-cooled. A 300T hydraulic press is used to support the M1 and M9 main journals for thermal correction at a starting temperature of 500℃ and an ending temperature of 350℃. S11. Tempering and magnetic particle inspection during quenching and tempering: Keep the crankshaft after thermal correction at 550-580℃ for 600-720min, remove it from the furnace and air-cool it at ≤400℃, and use a magnetic particle inspection machine to perform magnetic particle inspection according to the requirements of the crankshaft forgings; S12. Finished product inspection and warehousing: The crankshafts that have passed the NDT are inspected and put into storage after passing the inspection.

2. A large crankshaft segmented die forging process according to claim 1, characterized in that: In step S5, the segmented die forging process uses a 20,000-ton electric screw press to perform die forging of a large crankshaft.

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

4. The large crankshaft segmented die forging process 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.