A heat treatment process method for reducing the deformation of a crankshaft

Abstract

The present application relates to the technical field of heat treatment process of internal combustion engine crankshaft, and particularly relates to a heat treatment process method for reducing deformation of crankshaft. The heat treatment process method comprises quenching, tempering, primary stress relief, secondary stress relief and nitriding in sequence. During quenching, the temperature is raised to 850 DEG C-870 DEG C for 2.5h-3.5h, and then kept for 5h-6h, and then pre-cooled for 3.5min-5min after discharging, and then cooled for 5min-6.5min. During tempering, the temperature is raised to 610 DEG C-630 DEG C, and then kept for a predetermined time, and then cooled. During primary stress relief, the temperature is raised to 580 DEG C-600 DEG C, and then kept for a predetermined time, and then cooled. During secondary stress relief, the temperature is raised to 570 DEG C-590 DEG C, and then kept for a predetermined time, and then cooled. During nitriding, the temperature is raised to 510 DEG C-530 DEG C, and then kept for a predetermined time, and then slowly cooled in the furnace and then air-cooled after discharging. The present application solves the problems of large deformation before and after quenching and tempering of the crankshaft with increased Ni and V elements, and large runout of the crankshaft after nitriding.

Description

Technical Field

[0001] This invention relates to the field of heat treatment technology for internal combustion engine crankshafts, and more particularly to a heat treatment process method for reducing crankshaft deformation. Background Technology

[0002] The internal combustion engine industry is a crucial sector within the machinery industry. Internal combustion engines are the primary power source for equipment such as automobiles, agricultural machinery, construction machinery, ships, diesel locomotives, geological and oil drilling rigs, military equipment, general machinery, and mobile and backup power stations. The crankshaft is a core component of the internal combustion engine, primarily bearing the impact loads from the connecting rods and the torsional loads from its own high-speed rotation. It must also withstand the wear and tear of prolonged high-speed operation, significantly impacting the engine's reliability and lifespan.

[0003] A certain model of crankshaft is made of 42CrMoA, whose main material composition is C, Si, Mn, and Cr. To improve its mechanical properties to meet the requirements of different internal combustion engine models, Ni and V elements were added to the original alloy. While the performance was significantly improved after adding these alloying elements, the internal stress also increased, resulting in a greater overall deformation. Specifically, the new crankshaft shortened by more than 5mm before and after tempering, exceeding the requirements of machining technology, leading to insufficient machining allowance and making further processing impossible. Furthermore, the residual stress formed during tempering and machining was released during nitriding, causing the crankshaft runout to exceed tolerances and failing to meet assembly requirements. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a heat treatment process for reducing crankshaft deformation, thereby solving the problems of large deformation before and after tempering and large crankshaft runout after nitriding when Ni and V elements are added.

[0005] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0006] A heat treatment process for reducing crankshaft deformation includes quenching, tempering, primary stress relief, secondary stress relief, and nitriding. During quenching, the temperature is raised to 850℃-870℃ for 2.5-3.5 hours, held for 5-6 hours, pre-cooled for 3.5-5 minutes after removal from the furnace, and then cooled for 5-6.5 minutes. During tempering, the temperature is raised to 610℃-630℃, held for a predetermined time, and then cooled. During primary stress relief, the temperature is raised to 580℃-600℃, held for a predetermined time, and then cooled. During secondary stress relief, the temperature is raised to 570℃-590℃, held for a predetermined time, and then cooled. During nitriding, the temperature is raised to 510℃-530℃, held for a predetermined time, then slowly cooled in the furnace before being air-cooled.

[0007] Preferably, the blank is forged and normalized before quenching, heated to 880°C for 2 hours and held for 5 hours. After being taken out of the furnace, the blank is hot-corrected, and then cooled in water when the temperature of the normalized crankshaft drops below 300°C.

[0008] Preferably, the quenching is carried out in a continuous production process, with the temperature raised to 850℃-870℃ in 2.5h-3.5h, held for 5h-6h, pre-cooled for 3.5 minutes-5 minutes after being taken out of the furnace, and then cooled with a 5%-5.5% concentration water glass aqueous solution for 5 minutes-6.5 minutes.

[0009] Preferably, during quenching, the furnace loading temperature is <800℃, the temperature is raised to 860℃ in 3 hours, held for 5.5 hours, pre-cooled for 3.5 minutes after being removed from the furnace, and then cooled in a 5.1% concentration water glass aqueous solution for 5.5 minutes.

[0010] Preferably, during tempering, the temperature is raised to 620°C in 3 hours, held for 5 hours, and then air-cooled to room temperature in a pit after being taken out of the furnace.

[0011] Preferably, after tempering, the correction is performed by pressing open each connecting rod neck one by one, and adjusting the stop according to the runout value and direction.

[0012] Preferably, during the first stress relief, the temperature is raised to 590°C in 10 hours, held for 10 hours, and then slowly cooled in the furnace to below 200°C before being removed and air-cooled.

[0013] Preferably, during the secondary stress relief process, the temperature is raised to 580°C in 10 hours, held for 10 hours, and then slowly cooled in the furnace to below 200°C before being removed and air-cooled.

[0014] Preferably, during nitriding, the temperature is raised to 520°C in 10 hours, held at that temperature for 16 hours, and then slowly cooled in the furnace to below 200°C before being removed and air-cooled.

[0015] Preferably, nickel and vanadium elements are added to the crankshaft.

[0016] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages:

[0017] This invention proposes a heat treatment process for a novel crankshaft with added nickel and vanadium, which reduces the deformation in the length direction of the crankshaft after tempering, meets the requirements of subsequent machining processes, and the runout at the center measured by two-point support after nitriding is less than 0.12mm.

[0018] Advantages of additional aspects of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the surface hardness detection position after normalizing according to an embodiment of the present invention;

[0021] The distances or dimensions between parts have been exaggerated to show their positions; the diagram is for illustrative purposes only. Detailed Implementation

[0022] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0023] As described in the background section, a certain type of crankshaft is made of 42CrMoA, whose main material composition is C, Si, Mn, and Cr, as shown in Table 1 below:

[0024] Table 1. Composition (%) of a typical crankshaft

[0025]

[0026] A performance test bar (journey diameter 195mm) was taken at a distance of 7.5mm from the surface. The performance requirements are shown in Table 2.

[0027] Table 2 Performance Requirements for Ordinary Crankshafts

[0028] Rm(MPa) ReH(MPa) A(％) Z(％) Akv2(J) ≥900 ≥650 ≥12 ≥45 ≥27

[0029] The composition of the crankshaft after adding Ni and V elements is shown in Table 3 below:

[0030] Table 3. Composition (%) of the crankshaft after adding nickel and vanadium

[0031]

[0032] Besides Ni and V, the contents of Si and Mn also increased slightly. Performance test bars (journey diameter 195 mm) were taken at a distance of 32.5 mm from the surface, and the performance requirements are shown in Table 4 below:

[0033] Table 4. Crankshaft performance requirements after adding Ni and V elements.

[0034] Rm(MPa) ReH(MPa) A(％) Z(％) Akv2(J) ≥900 ≥650 ≥12 ≥45 ≥27

[0035] The ordinary crankshaft (hereinafter referred to as the original crankshaft) and the new model crankshaft (hereinafter referred to as the new crankshaft) have the same size but different composition, different sampling positions for performance test bars, and are applicable to different internal combustion engine models.

[0036] The chemical composition of the new crankshaft steel should meet the requirements of Table 3, with a C deviation of ±0.01%. C segregation should be less than 0.03% at the same location on different bars from the same heat, and from 1 / 2R to the surface of the same cross-section of the same bar. C segregation should not exceed 0.04% at the riser end and bottom end of the same bar. If compositional segregation exists in the raw materials, the crankshaft body will have a hardness deviation after quenching and tempering, resulting in significant differences in residual stress at different parts during subsequent processing, and affecting the final deformation after nitriding.

[0037] The original crankshaft did not include the requirement that "the carbon segregation at the same position on different bars in the same heat (steelmaking furnace) is less than 0.03%", and occasionally there will be a large difference in carbon content between two crankshafts that are quenched and tempered in the same furnace.

[0038] The new crankshaft with added elements had dimensions of 1656 + 1.2 mm before tempering. After tempering, its length shortened by more than 5 mm, exceeding the machining technical requirements (minimum 1651 mm), resulting in insufficient machining allowance and making subsequent processing impossible. Furthermore, the residual stress formed during tempering and machining was released during nitriding, causing crankshaft runout to exceed tolerances and failing to meet assembly requirements.

[0039] To address the aforementioned technical problems, this invention proposes a heat treatment process for reducing crankshaft deformation in new crankshafts with added nickel and vanadium. This method reduces the deformation along the length of the crankshaft after tempering, thereby meeting the dimensional requirements of subsequent semi-finishing and ultimately controlling the crankshaft runout after nitriding to below 0.12 mm.

[0040] S100 forging normalizing and billet hot straightening:

[0041] The crankshaft blank manufacturing process involves forging and normalizing (holding at 880℃ for 5 hours), hot straightening of the blank, and accelerated cooling in water after the normalized crankshaft temperature drops to a certain range. The normalizing process refines the requirements for crankshaft placement and spacing to ensure uniform cooling of all parts of the crankshaft, resulting in a uniform grain size. It also includes increasing the testing of surface hardness after normalizing, with the testing locations as follows: Figure 1 As shown, the left end is the shock absorber end, the right end is the flywheel end, and the mark 'a' is the test position. The required hardness range is 230-270 HB, and the difference between the highest and lowest points is <30 HB.

[0042] The original crankshaft specifications did not include requirements for surface hardness after normalizing. After normalizing, new stresses will be generated, with significant differences in stress across different parts. During quenching and heating, once the stress is fully released, the crankshaft will undergo some deformation, most notably a change in length. Since the crankshaft is inside the quenching furnace at this time, it's impossible to measure its length after austenitization; therefore, the only option is to minimize this effect. (Example: For rework of other crankshaft models, normalizing is required before rework. Before normalizing, the length difference between two crankshafts is 1mm; after normalizing, the difference becomes 4mm. This demonstrates the change in crankshaft length after stress release. The same principle applies to this case. Theoretically, normalizing stress is less than tempering stress, but it still has some impact.)

[0043] S200 quenching:

[0044] S201 rough machining:

[0045] Before quenching, rough machining is performed. After rough machining, the length meets the requirements of the quenching and tempering process (1656mm + 1.2mm), and the surface roughness of the journal does not exceed Ra12.5. After milling, the connecting rod journal is not allowed to have obvious tool-connecting steps, and the tool-connecting table should not be close to the root of the connecting rod journal. For example, the distance from the root of the connecting rod diameter should not be less than 15mm.

[0046] The original crankshaft did not include the requirement that "after milling the connecting rod journal, there should be no obvious tool-connecting step, and the tool-connecting table should not be close to the root of the connecting rod journal".

[0047] During quenching, the root of the connecting rod neck is a stress concentration area, and this requirement is also to reduce stress. This is a requirement for surface quality, but it also affects the process.

[0048] S202 quenching:

[0049] The addition of Ni and V to 42CrMoA significantly improves hardenability and reduces the hardness difference between the core and the surface. However, the corresponding structural stress also increases, which is the main cause of deformation after tempering.

[0050] Quenching process: The process is carried out in a continuous production mode. The temperature is raised to 850℃-870℃ in 2.5h-3.5h, held for 5h-6h, pre-cooled for 3.5 minutes-5 minutes after being taken out of the furnace, and then cooled with a 5%-5.5% concentration water glass aqueous solution for 5 minutes-6.5 minutes.

[0051] In the original crankshaft quenching process: continuous production is adopted, with full power heating to 850℃-870℃, holding at that temperature for a total of 8-9.5 hours, pre-cooling for 2.5-5 minutes after exiting the furnace, and then cooling with a 4%-4.5% concentration water glass aqueous solution for 5.5-6.5 minutes.

[0052] The total processing time for the new crankshaft remains unchanged, but the heating time is increased to reduce thermal stress. The pre-cooling time after the crankshaft exits the furnace is increased to further reduce the surface temperature and thermal stress. Increasing the concentration of the quenching fluid reduces the cooling rate of the crankshaft during quenching, thus reducing thermal and phase transformation stresses. The quenching cooling time is reduced to decrease the structural stress generated during quenching. The concentration of the water glass quenching fluid is strictly controlled between 5.0% and 5.5%, and the initial temperature of the quenching fluid must be between 45℃ and 55℃ to reduce the cooling rate in the martensitic transformation zone.

[0053] S300 tempering:

[0054] Heat to 620℃ in 2.5-3.5 hours, hold for 4.5-5.5 hours, and then air-cool to room temperature in a pit after being taken out of the furnace.

[0055] Original crankshaft quenching process: Full power heating to 590℃, holding for 7-9 hours, and then air cooling to room temperature in a pit after being taken out of the furnace.

[0056] Due to the influence of Ni and V, tempering at 620℃ is required to meet the performance requirements of the drawings, and a higher tempering temperature can better eliminate phase transformation stress and thermal stress.

[0057] S400 calibration:

[0058] The crankshaft length and runout were checked. For shafts shortened by 5mm or more, a 500T press was used to press open each connecting rod journal (connecting rod journal width 116mm) one by one, and the stops were adjusted according to the runout value and direction. The stop size was φ60×116+0.5. For shafts with the required length, only straightening and heat setting were performed. The crankshaft length was then rechecked; after pressing in the stops, the length must be greater than 1653mm.

[0059] A 200KW pit-type resistance furnace was used for heat setting at 600℃, and the furnace was held for 6-8 hours before air cooling. A 500T press was used to remove the blocks from each connecting rod and inspect them: the crankshaft length must be ≥1651mm and the runout ≤6mm.

[0060] The original crankshaft calibration process only addressed runout, not length. The improved calibration process can also serve as a solution for crankshafts with out-of-tolerance dimensions. The original solution for resolving out-of-tolerance crankshafts was normalizing followed by readjustment of parameters and tempering, essentially rework.

[0061] S500 stress relief in one step:

[0062] S501 Semi-finishing:

[0063] Before stress relief, a semi-finishing process is performed. After the semi-finishing, there is still a 3mm machining allowance before nitriding. At this point, the crankshaft is stress-relieved.

[0064] S502 stress relief in one step:

[0065] Heat to 590℃ in 10-12 hours, hold for 10 hours, then slowly cool to below 200℃ in the furnace before air cooling.

[0066] The original crankshaft stress relief process involved heating to 560℃ over 10-12 hours, holding at that temperature for 10 hours, then slowly cooling in the furnace to below 200℃ before air cooling. Higher temperatures resulted in better elimination of residual stress; at 590℃, the surface stress elimination rate was approximately 50%, and at 540-560℃, it was approximately 42%-45%.

[0067] S600 Secondary Stress Relief:

[0068] S601 one-time finishing:

[0069] Before the second stress relief, a finishing process is performed. After the first finishing process, there is still a 1mm machining allowance before nitriding.

[0070] S602 Secondary Stress Relief:

[0071] Heat to 580℃ in 10-12 hours, hold for 10 hours, then slowly cool in the furnace to below 200℃ and air cool.

[0072] The original crankshaft underwent only one stress relief process, without any finishing or secondary stress relief. After stress relief, it was directly machined to the nitriding dimension. The new crankshaft process separates finishing and stress relief into two separate processes, reducing machining stress and effectively eliminating residual stress.

[0073] S700 nitriding:

[0074] S701 secondary finishing:

[0075] Before nitriding, a second finishing process is performed. After the second finishing process, the machining allowance before nitriding is still 0mm.

[0076] S702 nitriding:

[0077] Nitriding process: The temperature is raised to 520℃ in 10-12 hours, held for 16 hours, and then slowly cooled in the furnace to below 200℃ before being air-cooled. The ammonia flow rate is 3-4 m³ / h during the heating and cooling stages, and 4-5 m³ / h during the holding stage. Liquid ammonia is vaporized in a gas-phase tank, dried, and then introduced into the furnace. 100-120 g of NH₄Cl catalyst is mixed evenly with 22 kg of other catalysts, loaded into a container, and placed at the bottom of the nitriding furnace.

[0078] When the original crankshaft is cooled to below 350°C, compressed air is passed between the furnace body and the furnace tank to accelerate the cooling process. Then, it is slowly cooled with the furnace to below 200°C before being removed and air-cooled.

[0079] The new crankshaft process eliminates the need for compressed air, thus slowing down the cooling rate.

[0080] The tempering temperature, heat setting temperature, primary stress relief temperature, secondary stress relief temperature, and nitriding temperature are decreased sequentially to ensure that the crankshaft performance does not change and no new stress is generated.

[0081] This invention improves the raw material composition, structure, machining, tempering, stress relief and nitriding processes. The length of the crankshaft after tempering and correction meets the requirements of subsequent machining processes, and the runout of the middle section measured by two-point support (V-bolt supports the main journals at both ends of the crankshaft, and the upper generatrix measurement method) after nitriding is less than 0.12mm.

[0082] To make the technical solutions provided by the embodiments of the present invention clearer, an example is used to illustrate the heat treatment process provided by the embodiments of the present invention.

[0083] The new crankshaft is designated T220424, and its chemical composition is shown in Table 5 below:

[0084] Table 5. Material Composition of T220424 Crankshaft

[0085]

[0086] S100 forging normalizing and billet hot straightening:

[0087] The temperature was raised to 880℃ in 2 hours and held for 5 hours. After being removed from the furnace, the blank was hot-corrected. When the temperature of the normalized crankshaft dropped below 300℃, it was accelerated cooled in water. The surface hardnesses were 237HB, 245HB, and 259HB, respectively.

[0088] S200 quenching:

[0089] S201 Rough Machining: After rough machining of the crankshaft, the surface roughness of the journal does not exceed Ra12.5, and after milling of the connecting rod journal, there is no obvious tool-jointing step, and the appearance quality meets the requirements.

[0090] S202 quenching process: furnace loading temperature < 800℃, heating to 860℃ in 3 hours, holding for 5.5 hours, pre-cooling for 3.5 minutes after removal from the furnace, and cooling in a 5.1% concentration water glass aqueous solution for 5.5 minutes.

[0091] S300 tempering:

[0092] Tempering process: Heat to 620℃ in 3 hours, hold for 5 hours, and then air cool to room temperature in a pit after being taken out of the furnace.

[0093] S400 calibration:

[0094] Calibration Process: The crankshaft length and runout were checked. The length was 1653mm, and the runout was 8mm, exceeding the process requirement of 6mm. Straightening was performed only until it reached 3.5mm. A 200KW pit-type resistance furnace was used for heat setting at 600℃, held for 6 hours, and then air-cooled. After remeasurement, the runout was 5mm, meeting the requirements.

[0095] S500 stress relief in one step:

[0096] The temperature is raised to 590℃ in 10 hours, held for 10 hours, and then slowly cooled to below 200℃ before being removed from the furnace and air-cooled.

[0097] S600 Secondary Stress Relief:

[0098] Secondary stress relief process: Heat to 580℃ in 10 hours, hold for 10 hours, then slowly cool in the furnace to below 200℃ and air cool.

[0099] S700 nitriding:

[0100] Nitriding process: The temperature is raised to 520℃ in 10 hours, held for 16 hours, and then slowly cooled in the furnace to below 200℃ before being air-cooled. The ammonia flow rate is 3.5 m³ / h during the heating and cooling stages, and 4.5 m³ / h during the holding stage. Liquid ammonia is vaporized in a gas-phase tank, dried, and then introduced into the furnace. 100-120 g of catalyst (NH₄Cl) is mixed evenly with 22 kg of quartz sand, loaded into a container, and placed at the bottom of the nitriding furnace.

[0101] The final test results of this embodiment are shown in Table 6 below:

[0102] Table 6 Test Results of T220424 Crankshaft

[0103] Axis number Length before conditioning Length after conditioning After conditioning, it bounces. The middle part jumps after nitriding T220424 1656mm 1653mm 5mm 0.07mm

[0104] Comparative Example

[0105] The chemical composition of the crankshaft is shown in Table 7 below:

[0106] Table 7 Original Crankshaft Material Composition

[0107]

[0108] S100 forging normalizing and billet hot straightening:

[0109] The temperature is raised to 880℃ in 2 hours and held for 5 hours. After being taken out of the furnace, the blank is hot-corrected. When the temperature of the normalized crankshaft drops below 300℃, it is cooled in water to accelerate cooling.

[0110] S200 quenching:

[0111] S201 Rough Machining: After rough machining of the crankshaft, the surface roughness of the journal does not exceed Ra12.5, and the appearance quality meets the requirements.

[0112] S202 quenching process: furnace loading temperature < 800℃, full power (approximately 1.5h) to heat to 860℃, hold for 7.5h, pre-cool for 3min after removal from the furnace, and cool in a 4.6% concentration water glass aqueous solution for 5.5min.

[0113] S300 tempering:

[0114] Tempering process: Heat to 590℃ at full power, hold for 7.5 hours, and then air cool to room temperature in a pit after being taken out of the furnace.

[0115] S400 calibration:

[0116] Calibration Process: The crankshaft length and runout were checked. The length was 1653mm, exceeding the minimum requirement of 1651mm. The runout was 8mm, exceeding the process requirement of 6mm, so only straightening was performed. The straightening was reduced to 3mm, and then heat-setting was carried out using a 200KW pit-type resistance furnace at 600℃ for 6 hours, followed by air cooling. After remeasurement, the runout was 3.5mm, meeting the requirements.

[0117] S500 stress relief:

[0118] The furnace is heated to 560℃ in 10 hours, held at that temperature for 10 hours, and then slowly cooled to below 200℃ before being removed from the furnace and air-cooled.

[0119] S700 nitriding:

[0120] Nitriding process: Heat to 520℃ in 10 hours, hold for 16 hours, and when the temperature drops below 350℃, accelerate cooling by introducing compressed air between the furnace body and the furnace tank. Allow to cool slowly in the furnace until below 200℃, then remove and air-cool. Ammonia flow rate is 3.5 m³ / h during the heating and cooling stages. 3 / h, ammonia flow rate during the heat preservation stage: 4.5m³ / h 3 / h. Liquid ammonia is vaporized in a gas phase tank, dried, and then introduced into the furnace. 100g of catalyst NH4Cl is mixed evenly with 22kg of quartz sand, loaded into a container, and placed at the bottom of the nitriding furnace.

[0121] The final test results of this embodiment are shown in Table 8 below:

[0122] Table 8 Crankshaft Inspection Results

[0123] Axis number Length before conditioning Length after conditioning After conditioning, it bounces. The middle part jumps after nitriding T200103 1656mm 1650mm 3.5mm 0.11mm

[0124] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A heat treatment process for reducing crankshaft deformation, characterized in that, The process includes, in sequence, quenching, tempering, primary stress relief, secondary stress relief, and nitriding; During quenching, heat to 850℃-870℃ for 2.5-3.5 hours, hold for 5-6 hours, pre-cool for 3.5-5 minutes after removal from the furnace, and then cool for 5-6.5 minutes. During tempering, heat to 610℃-630℃, hold for a predetermined time, and then cool. During the first stress relief, heat to 580℃-600℃, hold for a predetermined time, and then cool. During the second stress relief, heat to 570℃-590℃, hold for a predetermined time, and then cool. During nitriding, heat to 510℃-530℃, hold for a predetermined time, then slowly cool with the furnace before air cooling. Before quenching, the blank is forged and normalized. The temperature is raised to 880℃ in 2 hours and held for 5 hours. After taking it out of the furnace, the blank is hot-corrected. When the temperature of the normalized crankshaft drops below 300℃, it is cooled in water.

2. The heat treatment process for reducing crankshaft deformation as described in claim 1, characterized in that, The quenching process is carried out in a continuous production manner, with the temperature raised to 850℃-870℃ in 2.5h-3.5h, held for 5h-6h, pre-cooled for 3.5 minutes-5 minutes after being taken out of the furnace, and then cooled with a 5%-5.5% concentration water glass aqueous solution for 5 minutes-6.5 minutes.

3. The heat treatment process for reducing crankshaft deformation as described in claim 2, characterized in that, During quenching, the furnace loading temperature is <800℃, the temperature is raised to 860℃ in 3 hours, held for 5.5 hours, pre-cooled for 3.5 minutes after being taken out of the furnace, and then cooled in a 5.1% concentration water glass aqueous solution for 5.5 minutes.

4. The heat treatment process for reducing crankshaft deformation as described in claim 1, characterized in that, During tempering, the temperature is raised to 620℃ in 3 hours, held for 5 hours, and then air-cooled to room temperature in a pit after being taken out of the furnace.

5. The heat treatment process for reducing crankshaft deformation as described in claim 1, characterized in that, After tempering, the linkage necks are pressed open one by one, and the stops are adjusted according to the runout value and direction.

6. The heat treatment process for reducing crankshaft deformation as described in claim 1, characterized in that, During the first stress relief process, the temperature is raised to 590℃ in 10 hours, held for 10 hours, and then slowly cooled to below 200℃ before being removed from the furnace and air-cooled.

7. The heat treatment process for reducing crankshaft deformation as described in claim 1, characterized in that, During the second stress relief process, the temperature is raised to 580℃ in 10 hours, held for 10 hours, and then slowly cooled in the furnace to below 200℃ before being removed and air-cooled.

8. The heat treatment process for reducing crankshaft deformation as described in claim 1, characterized in that, During nitriding, the temperature is raised to 520℃ in 10 hours, held at that temperature for 16 hours, and then slowly cooled in the furnace to below 200℃ before being removed and air-cooled.

9. The heat treatment process for reducing crankshaft deformation as described in claim 1, characterized in that, Nickel and vanadium were added to the crankshaft.

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