Forging method with centrifuge spindle gradient deformation and gradient cooling collaborative control

Abstract

The application discloses a forging method for gradient deformation and gradient cooling collaborative control of a centrifuge spindle, and the method comprises the following steps: setting a differentiated target forging ratio according to the sectional size of each section; sequentially performing local upsetting in the order of a large-diameter section, then a middle section, and finally a small-diameter section, and setting a heat insulation baffle between the sections and controlling temperature by standing; adopting a mandrel to elongate to a design size and controlling a reduction amount to compensate for deviation; after forging, implementing partitioned differentiated slow cooling, adopting a combined heat preservation cover for the large-diameter section, adopting a fiber blanket for wrapping the middle section, and naturally cooling the small-diameter section; and monitoring temperature in real time in the whole process and cooperatively regulating and controlling heat supplementing and cooling parameters. The application solves the problem of uneven performance caused by large grain size difference and uneven cooling of the variable cross-section spindle, and realizes full-length organization homogenization and defect rate reduction of the spindle.

Description

Technical Field

[0001] This invention relates to the field of metal plastic forming technology, specifically to a forging method for coordinated control of gradient deformation and gradient cooling of a centrifuge spindle. Background Technology

[0002] As the core rotating component of high-speed rotary equipment, the centrifuge spindle's density, grain uniformity, and metal flow line integrity directly determine the equipment's operational safety and lifespan. Therefore, it places extremely high demands on the precision and control level of the forging process.

[0003] Traditional processes for processing long-shaft forgings with significant cross-sectional differences often face technical challenges, such as the difficulty in precisely matching the deformation amounts of each section, leading to severe grain size inhomogeneity, and the inability of the overall cooling method after forging to adapt to the heat dissipation characteristics of different sections, resulting in differences in microstructure and properties, and internal stress deformation. In particular, the existing technology separates the forging and cooling processes and lacks differentiated gradient control methods based on spatial dimensions, making it difficult to solve the problems of mixed grains and early failure caused by the mismatch between the large-diameter and small-diameter sections during deformation energy storage and cooling phase transformation. Summary of the Invention

[0004] This invention aims to solve the technical problems in the prior art for forging centrifuge spindles with variable cross-sections, such as the difficulty in accurately matching the deformation of each section, resulting in severe uneven grain size; the inability of the overall cooling method after forging to adapt to the heat dissipation characteristics of different cross-sections, leading to differences in microstructure and internal stress deformation; the disconnect between the forging and cooling processes; and the lack of differentiated gradient control methods based on spatial dimensions. To this end, this invention provides a forging method for coordinated control of gradient deformation and gradient cooling of centrifuge spindles.

[0005] To address the aforementioned technical problems, this invention provides a forging method for the coordinated control of gradient deformation and gradient cooling of a centrifuge spindle, comprising the following steps: S1. Pre-setting of segmented target forging ratios: Based on the design cross-sectional dimensions and material recrystallization critical deformation of the large-diameter section, intermediate transition section, and small-diameter section of the centrifuge spindle, differentiated target forging ratios are set for the large-diameter section, the intermediate transition section, and the small-diameter section, respectively. The target forging ratio of the large-diameter section is greater than that of the intermediate transition section, and the target forging ratio of the intermediate transition section is greater than that of the small-diameter section. S2. Segmented Local Upsetting and Thermal Balance Control: The heated billet is locally upset in the order of the large diameter segment, the intermediate transition segment, and the small diameter segment. After each segment is partially upset, a temporary heat insulation baffle is placed between the segment and the adjacent segment, and the segment is left to stand for 30 to 60 seconds until the deformation heat generated by the segment is fully dissipated and the temperature difference between the surface temperature of the segment and the surface temperature of the adjacent segment does not exceed 50 degrees Celsius. Then, the next segment is partially upset, so that the actual forging ratio of each segment falls within the preset deviation range of its corresponding target forging ratio. S3. Mandrel Lengthening and Deviation Compensation: After local upsetting of each section, a mandrel lengthening process is used to lengthen each section to the design size, controlling the reduction amount in each pass to ensure that the deviation between the final actual forging ratio and the target forging ratio of each section is controlled within ±5%. When the actual forging ratio of a section is more than 3% lower than the target value, a light pressing is added in the next pass of the section, and the reduction amount of the light pressing is 5% to 8% of the current height of the section. When the actual forging ratio of a section is more than 3% higher than the target value, the reduction amount of the section is reduced in subsequent passes. S4. Differentiated Gradient Cooling in Different Zones: After forging, differentiated cooling is implemented in different zones according to the cross-sectional dimensions of the large-diameter section, the intermediate transition section, and the small-diameter section. The large-diameter section is covered with a combined insulation cover for slow cooling, with a cooling rate controlled at 20 to 35 degrees Celsius per hour. The combined insulation cover is removed after cooling to 550 degrees Celsius ± 20 degrees Celsius. The intermediate transition section is wrapped with an aluminosilicate ceramic fiber blanket for slow cooling, with a cooling rate controlled at 40 to 55 degrees Celsius per hour. The aluminosilicate ceramic fiber blanket is removed after cooling to 600 degrees Celsius ± 20 degrees Celsius. The small-diameter section is naturally cooled in the air, and no active ventilation equipment is installed within 2 meters of the surface of the small-diameter section. S5. Full-process collaborative monitoring: During the forging stage, an infrared thermometer is used to monitor the surface temperature of each section in real time. When the surface temperature of a certain section is lower than the minimum allowable forging temperature of that section, the forging operation of that section is suspended and local reheating is performed. During the cooling stage, thermocouples are used in conjunction with a multi-channel temperature recorder to monitor the temperature of each section in real time. The coverage of the combined heat preservation cover or the number of wrapping layers of the aluminosilicate ceramic fiber blanket is adjusted according to the monitoring data. The temperature monitoring data of the forging stage and the cooling stage are continuously recorded, which together constitute a complete temperature time series from the start of forging to the end of cooling, realizing full-process collaborative control.

[0006] Furthermore, in step S1, the diameter of the large-diameter section is not less than 300 mm, and the target forging ratio of the large-diameter section is not less than 4.0; the diameter of the intermediate transition section is between 150 mm and 300 mm, and the target forging ratio of the intermediate transition section is not less than 3.5; the diameter of the small-diameter section is less than 150 mm, and the target forging ratio of the small-diameter section is not less than 3.0.

[0007] Furthermore, in step S2, the specific operation of the local upsetting is as follows: by changing upsetting anvils of different sizes in sections, pressure is applied only to the billet area corresponding to the section; the single pressing amount of local upsetting of each section does not exceed 15% of the original height of the billet of the section, and is completed in two to three times, with pressure held for three to five seconds after each pressing.

[0008] Furthermore, in step S3, the amount of reduction per pass during the mandrel drawing process is controlled to be between 8% and 12%.

[0009] Furthermore, in step S4, the combined heat preservation cover is a semi-enclosed structure, with a steel plate outer shell lined with aluminum silicate ceramic fiber cotton, and a ventilation gap at the bottom; the distance between the bottom of the combined heat preservation cover and the surface of the large diameter section is adjustable, and the adjustable range of the distance is 50 to 150 mm.

[0010] Furthermore, the combined heat preservation cover is equipped with an electrically or pneumatically driven lifting and adjusting mechanism. The lifting and adjusting mechanism is connected to the multi-channel temperature recorder. The lifting and adjusting mechanism automatically calculates the current cooling rate based on the real-time temperature data fed back by the thermocouple, and automatically adjusts the position of the combined heat preservation cover after comparing it with the target cooling rate.

[0011] Furthermore, in step S5, the local heating operation is as follows: a medium-frequency induction heating device is used to locally heat the section with insufficient surface temperature. During heating, ceramic fiber baffles are covered on the surface of adjacent sections, and the duration of each heating operation does not exceed 2 minutes.

[0012] Furthermore, in step S5, the operation of using thermocouples in conjunction with a multi-channel temperature recorder to monitor the temperature of each segment in real time during the cooling stage is as follows: a blind hole with a depth of 5 to 8 mm is opened on the surface of each segment, a K-type thermocouple is inserted into the blind hole and fixed with high-temperature resistant putty, the K-type thermocouple is connected to the multi-channel temperature recorder through a compensating wire, and the temperature data of each segment is automatically recorded every 5 minutes until the temperature of each segment drops below 400 degrees Celsius.

[0013] Furthermore, in step S5, the minimum allowable forging temperature is: not less than 1000 degrees Celsius for the large diameter section, not less than 950 degrees Celsius for the intermediate transition section, and not less than 900 degrees Celsius for the small diameter section.

[0014] Furthermore, in step S5, the infrared thermometer is a handheld infrared thermometer, which measures the surface temperature of each section before each forging operation.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention solves the problems of difficult precise control of deformation in different sections of a variable cross-section spindle in traditional processes, which leads to large differences in grain size and severe mixed grains, by setting segmented target forging ratios and segmented local upsetting operations. By setting differentiated target forging ratios for different cross-sectional sizes and using segmented upsetting anvils for local upsetting, it ensures that the large-diameter section obtains sufficient deformation to break up the as-cast structure, while avoiding overheating or excessively fine grains in the small-diameter section due to concentrated deformation. This keeps the grain size difference between different sections of the spindle within one grade, significantly improving the fatigue strength and impact resistance of the material.

[0016] By placing temporary heat insulation baffles after each section of local upsetting is completed and allowing it to stand still to wait for thermal equilibrium, the problem of uneven temperature field caused by excessive heat transfer from the deformation generated by intense plastic deformation to adjacent sections can be solved. This measure, combined with the operation sequence of large-diameter sections first and then small-diameter sections, ensures that the large-diameter sections maintain a suitable temperature during the subsequent elongation process, while avoiding the small-diameter sections from becoming too cold due to excessive waiting time. This ensures that each section deforms within the optimal temperature range, laying the foundation for obtaining a uniform microstructure.

[0017] By using a deviation compensation mechanism during the spindle elongation process, the problem of the actual forging ratio deviating from the target value due to equipment precision or material inhomogeneity during forging can be solved. The actual forging ratio is monitored in real time, and dynamic compensation is performed by adjusting the light pressure or reducing the amount of reduction when the deviation exceeds the threshold. The deviation between the final actual forging ratio and the target value of each section is strictly controlled within ±5%, which further ensures the consistency of the degree of deformation throughout the entire length of the spindle.

[0018] By using zoned differential gradient slow cooling, the problems of uneven cooling rate, high internal stress, and significant differences in microstructure and properties caused by large differences in the cross-sectional dimensions of each section in traditional integral cooling methods can be solved. For the large-diameter section, intermediate transition section, and small-diameter section, a combined heat preservation cover, ceramic fiber blanket wrapping, and natural cooling are used respectively, and the cooling rate and termination temperature of each section are precisely controlled so that each section has a similar degree of supercooling at the phase transformation critical point, effectively avoiding the generation of white spots, ensuring that the nucleation rate and growth rate of pearlite transformation tend to be consistent, and controlling the hardness fluctuation within ±15HB along the entire length of the spindle.

[0019] By implementing full-process collaborative monitoring and forging-cooling connection control, the problems of fragmented forging and cooling processes and lack of real-time data support in traditional processes, which prevent targeted adjustment of process parameters, can be solved. By using infrared temperature measurement and thermocouples to continuously record the temperature time series from the start of forging to the end of cooling, and by performing local heating when the temperature is insufficient or automatically / manually adjusting the heat preservation measures during the cooling stage, closed-loop precise control of forging temperature and cooling rate is achieved. This significantly reduces the forging defect rate such as overheating, burning, and cracking, improves the ultrasonic flaw detection pass rate, and greatly reduces the amount of deformation after forging due to improved cooling uniformity, simplifying the subsequent straightening process. Attached Figure Description

[0020] Figure 1 This is a process flow diagram of the forging method for coordinated control of gradient deformation and gradient cooling of centrifuge spindle according to the present invention.

[0021] Figure 2 This is a schematic diagram of the target forging ratio distribution of each section of the main shaft in this invention.

[0022] Figure 3 This is a schematic diagram of the spindle partitioned differential cooling system in this invention.

[0023] Figure 4 This is a comparison diagram of the grain size differences between the embodiments and comparative examples of this invention. Detailed Implementation

[0024] The technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0025] See Figure 1 This invention proposes a forging method for coordinated control of gradient deformation and gradient cooling of centrifuge spindle, the method comprising the following steps: First, the segmented target forging ratio presetting step S1 is executed; based on the design cross-sectional dimensions of the large-diameter section, intermediate transition section and small-diameter section of the centrifuge spindle and the critical deformation amount of material recrystallization, differentiated target forging ratios are set respectively, wherein the target forging ratio of the large-diameter section is greater than that of the intermediate transition section, and the target forging ratio of the intermediate transition section is greater than that of the small-diameter section, so as to ensure that each section can obtain sufficient plastic deformation to refine the grains.

[0026] Secondly, the segmented local upsetting and heat balance control step S2 is executed; the heated billet is locally upset sequentially in the order of large diameter segment, intermediate transition segment, and finally small diameter segment. After each segment is partially upset, a temporary heat insulation baffle is placed between the segment that has just completed the local upsetting operation and the adjacent segment, and the segment is left to stand for 30 to 60 seconds. When the deformation heat generated by the intense plastic deformation of the segment that has just completed the local upsetting operation is fully dissipated, and the temperature difference between the surface temperature of the segment that has just completed the local upsetting operation and the surface temperature of the adjacent segment does not exceed 50 degrees Celsius, the next segment of local upsetting operation is then carried out, so that the actual forging ratio of each segment falls within the preset deviation range of its corresponding target forging ratio.

[0027] Next, the mandrel drawing and deviation compensation step S3 is executed. After the local upsetting of each section is completed, the mandrel drawing process is used to draw each section to the design size. During the drawing process, the reduction amount of each pass is strictly controlled. Through real-time monitoring and feedback adjustment, the deviation between the final actual forging ratio of each section and the target forging ratio is controlled within ±5%. When it is detected that the actual forging ratio of a certain section is more than 3% lower than the target value, light pressure compensation is added in the next pass. When the actual forging ratio is more than 3% higher than the target value, the reduction amount of subsequent passes is reduced to achieve high-precision dimensional and microstructure control.

[0028] Subsequently, the zoned differential gradient slow cooling step S4 is executed; after forging, zoned differential cooling is implemented according to the cross-sectional dimensions of each segment, such as... Figure 3 As shown, specifically, for the large-diameter section with a larger cross-section, a combined insulation cover is used for slow cooling, controlling the cooling rate at 20 to 35 degrees Celsius per hour, until it cools to 550 degrees Celsius ± 20 degrees Celsius, after which the combined insulation cover is removed; for the intermediate transition section, an aluminosilicate ceramic fiber blanket is used for slow cooling, controlling the cooling rate at 40 to 55 degrees Celsius per hour, until it cools to 600 degrees Celsius ± 20 degrees Celsius, after which the insulation layer is removed; for the small-diameter section, it is allowed to cool naturally in the air, and it is ensured that no active ventilation equipment is installed within 2 meters of the surface of the small-diameter section to avoid the small-diameter section cooling too quickly.

[0029] Finally, the full-process collaborative monitoring step S5 is executed. During the forging stage, an infrared thermometer is used to monitor the surface temperature of each section in real time. When the temperature of a certain section is lower than the minimum allowable forging temperature, the operation of that section is paused and local reheating is performed. During the cooling stage, thermocouples are used in conjunction with a multi-channel temperature recorder to monitor the temperature of each section in real time. The coverage of the combined heat preservation cover or the number of wrapping layers of the aluminosilicate ceramic fiber blanket is dynamically adjusted according to the monitoring data. The temperature monitoring data of the forging stage and the cooling stage are continuously recorded, which together constitute a complete temperature time series from the start of forging to the end of cooling, thereby realizing the full-process collaborative control of the forging and cooling process.

[0030] The above-mentioned collaborative control method can effectively eliminate the mixed crystal phenomenon in traditional processes, significantly improve the uniformity of grain size in each section of the spindle, improve the consistency of microstructure and properties, and reduce the forging defect rate, providing reliable technical support for the high-quality manufacturing of large centrifuge spindles.

[0031] In some implementations, step S1 specifically involves the presetting of segmented target forging ratios. In step S1, the differentiated target forging ratios for the large-diameter segment, the intermediate transition segment, and the small-diameter segment are calculated and set according to the design cross-sectional dimensions of each segment of the centrifuge spindle and the critical recrystallization deformation of the material used.

[0032] The calculation of the target forging ratio λ follows the formula ,in The original cross-sectional area of ​​the blank segment is given. The final design cross-sectional area of ​​the forging segment is given by the above forging ratio calculation formula, which can quantify the required degree of deformation for each segment to ensure that the internal as-cast structure of the metal is fully broken and refined.

[0033] Specifically, for the large-diameter segment, the design diameter of the large-diameter segment is usually not less than 300 mm. Considering the large cross-sectional size and high deformation resistance of the large-diameter segment, in order to ensure sufficient deformation penetration to refine the grains, the target forging ratio of the large-diameter segment is set to not less than 4.0. Preferably, the target forging ratio of the large-diameter segment can be set between 4.0 and 4.5.

[0034] For the intermediate transition section, the design diameter of the intermediate transition section is usually between 150 mm and 300 mm. The intermediate transition section serves as a transition area connecting the large diameter section and the small diameter section. The target forging ratio of the intermediate transition section is set to be no less than 3.5. Preferably, the target forging ratio of the intermediate transition section can be set between 3.5 and 4.0.

[0035] For the small diameter segment, the design diameter of the small diameter segment is usually less than 150 mm. Since the cross-section of the small diameter segment is small, deformation is relatively easy to concentrate. In order to avoid excessively fine grains or overheating, the target forging ratio of the small diameter segment is set to not less than 3.0. Preferably, the target forging ratio of the small diameter segment can be set between 3.0 and 3.5.

[0036] Figure 2 A schematic diagram showing the correspondence between the target forging ratio and the cross-sectional size of each section of the spindle is presented. As can be seen from the figure, the target forging ratio decreases in a stepwise manner as the cross-sectional size decreases. The above gradient setting is intended to balance the deformation energy storage of each section, laying the foundation for obtaining a uniform microstructure in the future.

[0037] Before performing segmented local upsetting, a preliminary overall upsetting pretreatment step is included; the steel ingot heated to 1150 degrees Celsius to 1250 degrees Celsius is placed on a forging press for preliminary overall upsetting. The upsetting ratio of the preliminary overall upsetting step is controlled between 1.5 and 2.0. Through preliminary overall upsetting, the cross-section of the billet can be uniformly increased and the height reduced, eliminating the porosity defects inside the steel ingot, and providing sufficient operating space and a uniform billet base for subsequent segmented local upsetting.

[0038] In some implementations, the segmented local upsetting operation in step S2 aims to achieve a grain refinement effect that matches the cross-sectional size of each segment of the spindle through differentiated deformation control. Specifically, the billet after preliminary overall upsetting is transferred to a forging manipulator, and local upsetting is performed sequentially in the order of large-diameter segment first, then intermediate transition segment, and finally small-diameter segment. The design of the above sequence takes into account the heat dissipation characteristics of different cross-sectional segments: the large-diameter segment has a large cross-section and large heat capacity but relatively slow heat dissipation, so prioritizing upsetting with high deformation is beneficial to utilizing the heat storage of the large-diameter segment itself; the small-diameter segment has a small cross-section and fast heat dissipation, so arranging it last can shorten the waiting time of the small-diameter segment at high temperature and avoid forging difficulties or cracks caused by excessive temperature drop.

[0039] When performing local upsetting, the upsetting anvil of different sizes is replaced in sections. The operator selects an upsetting anvil of the corresponding width to replace the original anvil according to the target cross-sectional size and deformation requirements of the current section to be processed. By replacing the upsetting anvil, it is ensured that the pressure is concentrated on the current billet area to be processed, while the adjacent sections are not stressed or only suffer a small amount of elastic deformation, thereby achieving true local deformation control and avoiding unnecessary plastic flow in non-target areas.

[0040] To achieve precise thermal balance control and prevent excessive axial conduction of deformation heat, a temporary heat insulation baffle is immediately placed between the section that has just completed the local upsetting operation and the adjacent unprocessed section after each section is completed. The temporary heat insulation baffle can be made of ceramic fiber board or other high-temperature resistant heat insulation materials to block the rapid transfer of heat from the high-temperature deformation zone to the low-temperature zone. After placing the heat insulation baffle, wait for 30 to 60 seconds to allow the deformation heat generated by the intense plastic deformation of the section that has just completed the local upsetting operation to dissipate fully. During this period, monitor the surface temperature of the section that has just completed the local upsetting operation and the surface temperature of the adjacent section. When the temperature difference between the two does not exceed 50 degrees Celsius, remove the heat insulation baffle and proceed with the next section of local upsetting operation. The above thermal balance measures effectively avoid abnormal grain growth caused by local overheating or thermal stress concentration caused by excessive temperature difference.

[0041] Regarding the control of deformation parameters for local upsetting, the single reduction amount of local upsetting in each segment shall not exceed 15% of the original height of the billet in that segment. In order to ensure that the deformation fully penetrates into the core of the billet and improves the internal density, local upsetting is completed in two to three stages. After each reduction, the pressure is maintained for three to five seconds for holding pressure, and then the load is unloaded. The above-mentioned process of multiple small reductions combined with holding pressure helps to refine the grains and eliminate internal defects.

[0042] To monitor in real time and ensure that the actual forging ratio meets the preset target, end-face positioning marks are pre-set at the boundaries of each section of the billet. Clear marking points are punched onto the end face of the billet using a punching method. These marks serve as the operational benchmark for each local upsetting and subsequent drawing process, defining the processing range of each section. After each section's local upsetting is completed, a portable laser rangefinder is used to measure the actual outer diameter and height of the section that just completed the local upsetting operation. Based on the measurement data, the forging ratio is calculated using the formula. The actual forging ratio of the segment that has just completed the local upsetting operation is calculated, and the actual forging ratio is compared with the target forging ratio set in step S1 in real time. If the deviation is found to exceed the allowable range, targeted micro-adjustments are made in the subsequent mandrel drawing process to compensate for the deviation, thereby ensuring the uniformity of the final product's performance.

[0043] In some embodiments, the mandrel elongation process described in step S3 aims to further extend the various sections of the billet after local upsetting to the designed dimensions, while precisely controlling the final forging ratio of each section. The mandrel elongation process is usually carried out on a forging manipulator or hydraulic press in conjunction with a mandrel. During the elongation process, in order to balance the deformation penetration depth and production efficiency, the reduction amount in each pass is strictly controlled between 8% and 12%. The selection of the above reduction amount range is based on the plastic deformation law of the material: if the reduction amount is too small, the deformation is difficult to penetrate to the core of the billet, which can easily lead to uneven internal structure; if the reduction amount is too large, it may cause surface cracks or equipment overload. Through the accumulation of multiple passes and small deformations, the grains can be effectively refined and the metal flow line distribution can be improved.

[0044] In practice, after each drawing pass is completed, the operator must immediately measure the actual cross-sectional dimensions of the current drawing section and calculate the actual forging ratio of the current drawing section based on its current height. The system will then compare the actual forging ratio calculated in real time with the target forging ratio set in step S1 to execute a dynamic deviation compensation mechanism. The core of this mechanism is to adjust the process parameters of subsequent passes according to the direction and magnitude of the deviation to ensure final accuracy.

[0045] When the actual forging ratio of a certain segment is found to be more than 3% lower than the target value, it indicates that the deformation of that segment is insufficient, and there is a risk of inadequate grain refinement. In this case, a light pressing operation is added in the next pass of that segment as a compensation measure. The reduction amount of the light pressing is set to 5% to 8% of the current height of the segment. This small amount of additional deformation is sufficient to make up for the previous deficiency, while avoiding stress concentration or sudden temperature drop caused by a single large deformation. To facilitate understanding of the above light pressing compensation mechanism, an example is given: If the actual forging ratio of the intermediate transition segment (target forging ratio 3.6) is found to be more than 3% lower than the target value after a certain drawing pass, a light pressing operation is added in the subsequent drawing pass, with a reduction amount of approximately 6% of the current height of that segment, so that the cumulative deformation amount returns to the target range.

[0046] Conversely, when the actual forging ratio of a certain segment is detected to be more than 3% higher than the target value, it indicates that the segment is deformed excessively, which may result in excessive grain breakage or energy waste. In this case, the reduction amount of the segment is actively reduced in subsequent passes. For example, the originally planned 10% reduction amount is adjusted to 6% to 8%, or a smaller finishing reduction amount is used when approaching the target size to prevent dimensional deviations and performance degradation.

[0047] Through the above real-time monitoring and dynamic adjustment, the deviation between the final actual forging ratio and the target forging ratio of each section is strictly controlled within ±5%. The above high-precision control is crucial to ensuring the performance consistency of the centrifuge spindle throughout its entire length.

[0048] In some implementations, the partitioned differential gradient slow cooling in step S4 specifically includes differentiated cooling control strategies for the large-diameter section, the intermediate transition section, and the small-diameter section.

[0049] For the large-diameter section, a combined insulation cover is used for slow cooling. This combined insulation cover is a semi-enclosed structure. Its main structure includes a steel plate outer shell and aluminum silicate ceramic fiber cotton lining the steel plate outer shell. The steel plate outer shell provides structural support and external protection, while the aluminum silicate ceramic fiber cotton serves as the main insulation medium, reducing heat radiation and convective heat dissipation. A ventilation gap is provided at the bottom of the combined insulation cover, located between the bottom edge of the insulation cover and the surface of the large-diameter forging section, to regulate airflow. The cooling rate is controlled by the airflow. The distance between the bottom of the combined insulation cover and the surface of the large-diameter section is an adjustable parameter, ranging from 50 mm to 150 mm. By adjusting the distance, the size of the ventilation gap can be changed, thereby precisely controlling the actual cooling rate of the large-diameter section. The target cooling rate of the large-diameter section is controlled at 20 to 35 degrees Celsius per hour. When the temperature of the large-diameter section cools to 550 degrees Celsius ± 20 degrees Celsius, the combined insulation cover is removed, and then the section is allowed to cool naturally in the air.

[0050] In some embodiments, the combined heat preservation cover is equipped with a lifting and adjusting mechanism. This mechanism can drive the entire heat preservation cover to move up and down to adjust the height of the bottom ventilation gap in real time. The lifting and adjusting mechanism can be selected as an electric push rod or a cylinder driven mechanism. The control accuracy of the lifting and adjusting mechanism can reach ±5 mm. Through the lifting and adjusting mechanism, the position of the heat preservation cover can be dynamically adjusted according to the real-time monitored temperature data. When the measured cooling rate is higher than the target range, the heat preservation cover is driven to move downward to reduce the ventilation gap; when the measured cooling rate is lower than the target range, the heat preservation cover is driven to move upward to increase the ventilation gap.

[0051] For the intermediate transition section, an aluminosilicate ceramic fiber blanket is used for slow cooling. In specific operation, the number of wrapping layers is determined according to the target cooling rate of the intermediate transition section, usually three to five layers. The aluminosilicate ceramic fiber blanket has good flexibility and high temperature resistance, and can closely adhere to the outer surface of the intermediate transition section to form a uniform heat insulation layer. In this embodiment, the target cooling rate of the intermediate transition section is controlled at 40 to 55 degrees Celsius per hour. When the temperature of the intermediate transition section cools to 600 degrees Celsius ± 20 degrees Celsius, the aluminosilicate ceramic fiber blanket is removed, and then it is transferred to the air for natural cooling.

[0052] For the small-diameter segment, natural cooling in the air is adopted. To avoid the cooling rate of the small-diameter segment exceeding the reasonable range due to excessive heat dissipation, industrial fans or other active ventilation equipment shall not be installed within 2 meters of the surface of the small-diameter segment. By limiting the disturbance of the ambient airflow, it is ensured that the small-diameter segment dissipates heat at a relatively stable rate. In this embodiment, the measured cooling rate of the small-diameter segment is about 65 degrees Celsius per hour. The above cooling rate helps to avoid excessive internal stress in the small-diameter segment while ensuring the completion of the tissue transformation.

[0053] The determination of the target range of cooling rate for each section is based on the following: within the above cooling rate range, the pearlitic phase transformation of medium carbon alloy steels such as 42CrMoA can be completed under controllable conditions, effectively avoiding the generation of white spots, while ensuring the uniformity of microstructure in each section. Due to the large cross-sectional size and slow heat dissipation of the large diameter section, a thicker insulation layer (such as an insulation cover with an inner lining thickness of not less than 100 mm) and a smaller ventilation gap are required to maintain a lower cooling rate. The middle section has a moderate cross-sectional size and achieves a moderate cooling rate by wrapping it with multiple layers of ceramic fiber blankets. The small diameter section has a small cross-section and fast heat dissipation, and can meet the cooling requirements without additional insulation measures. The above-mentioned differentiated cooling regime for each section matches the aforementioned gradient deformation process, and together achieves the uniformity of microstructure and properties throughout the entire length of the spindle.

[0054] In some implementations, to further improve the accuracy and response speed of cooling rate control, the combined heat preservation cover is equipped with an electrically or pneumatically driven lifting adjustment mechanism, which is connected to the multi-channel temperature recorder to form a closed-loop automatic control system.

[0055] Specifically, the lifting adjustment mechanism may include one or more of an electric push rod, a cylinder, or a hydraulic cylinder. The driving accuracy of the lifting adjustment mechanism can reach ±5 mm. The output end of the electric push rod or cylinder is fixedly connected to the top or side wall of the combined heat preservation cover, and is used to drive the combined heat preservation cover to move in the vertical direction, thereby changing the ventilation gap distance between the bottom of the combined heat preservation cover and the surface of the large diameter section.

[0056] In terms of control logic, the multi-channel temperature recorder receives real-time temperature data from the K-type thermocouple inserted into the large-diameter blind hole. The control system automatically calculates the current actual cooling rate based on the temperature data recorded at preset time intervals (e.g., every 10 minutes). Subsequently, the system compares the calculated actual cooling rate with the preset target cooling rate (e.g., 20 to 35 degrees Celsius per hour).

[0057] When the measured cooling rate is higher than the upper limit of the target cooling rate, it indicates that the heat dissipation is too fast. At this time, the lifting and adjusting mechanism drives the combined heat insulation cover to move closer to the surface of the large-diameter section, reducing the distance between the bottom of the combined heat insulation cover and the surface of the large-diameter section, thereby narrowing the ventilation gap, reducing the air convection heat transfer efficiency, and slowing down the cooling rate. Conversely, when the measured cooling rate is lower than the lower limit of the target cooling rate, it indicates that the heat dissipation is too slow. At this time, the lifting and adjusting mechanism drives the combined heat insulation cover away from the surface of the large-diameter section, increasing the distance between the bottom of the combined heat insulation cover and the surface of the large-diameter section, thereby widening the ventilation gap, enhancing the air convection heat transfer efficiency, and accelerating the cooling rate.

[0058] Through the above-mentioned closed-loop automatic adjustment mechanism, precise and stable control of the cooling rate of the large-diameter section can be achieved, avoiding fluctuations in tissue properties caused by lag or error in manual adjustment. Preferably, the control accuracy of the lifting adjustment mechanism is ±5 mm, which is sufficient to meet the needs of fine adjustment of the cooling rate and ensure the uniformity of the temperature field of the large-diameter section during the slow cooling process.

[0059] In some implementations, step S5 involves the coordinated monitoring of the entire process of forging and cooling stages, aiming to ensure that the thermal history of each section of the spindle is within a controllable range during deformation and phase transformation through continuous temperature data acquisition and feedback control.

[0060] During the forging stage, a handheld infrared thermometer is used to monitor the surface temperature of each section in real time. Before each forging operation, the operator measures the surface temperature of the large-diameter section, the intermediate transition section, and the small-diameter section respectively. Based on the material properties and the differences in cross-sectional dimensions, the minimum allowable forging temperature thresholds for each section are set: the minimum allowable forging temperature for the large-diameter section is not lower than 1000 degrees Celsius, the minimum allowable forging temperature for the intermediate transition section is not lower than 950 degrees Celsius, and the minimum allowable forging temperature for the small-diameter section is not lower than 900 degrees Celsius. When the surface temperature of a certain section is detected to be lower than the minimum allowable forging temperature corresponding to that section, the forging operation of that section is immediately suspended to prevent the increase in plastic deformation resistance or the generation of forging cracks due to excessively low temperature.

[0061] For sections with insufficient temperature, localized reheating is implemented using medium-frequency induction heating equipment. This equipment enables rapid and precise heating of specific areas. During localized reheating, to prevent excessive heat diffusion to adjacent unheated sections and thus affecting the uniformity of the overall temperature field, ceramic fiber baffles are placed on the surfaces of adjacent sections as temporary insulation. The duration of each reheating session is strictly controlled, not exceeding 2 minutes. The goal of the reheating is to raise the temperature of the insufficient sections to the suitable forging range of 1050 to 1150 degrees Celsius, after which forging operations continue. The combination of segmented monitoring and precise localized reheating effectively maintains the deformation capacity of each section in its optimal plastic state.

[0062] During the cooling phase, the temperature monitoring method is changed from non-contact infrared thermometry to contact thermocouple monitoring to improve the accuracy of long-term low-temperature monitoring. The specific operation is as follows: after the forging is hoisted to the cooling area, blind holes with a depth of 5 to 8 mm are opened on the surface of the large-diameter section, the intermediate transition section and the small-diameter section respectively. K-type thermocouples are inserted into the blind holes and fixed with high-temperature resistant putty to ensure that the thermocouple probes are in good contact with the forging substrate and are not easy to fall off. Each K-type thermocouple is connected to a multi-channel temperature recorder through a compensating wire to realize synchronous acquisition of the temperature of each section. The multi-channel temperature recorder is set to automatically record the temperature data of each section every 5 minutes. The recording process continues until the temperature of each section of the spindle drops below 400 degrees Celsius.

[0063] To achieve seamless integration and data continuity between the forging and cooling processes, a temperature monitoring program for the cooling stage is initiated after the final forging is completed but before the forging has cooled to below 900 degrees Celsius. Thus, the infrared temperature measurement data at the beginning of forging and the thermocouple data recorded during the cooling stage together constitute a complete temperature and time sequence from high-temperature forging to the end of low-temperature phase transformation. This continuous data is not only used to monitor in real time whether the cooling rate deviates from the target range (such as 20 to 35 degrees Celsius per hour or 40 to 55 degrees Celsius per hour), but also serves as a basis for adjusting the coverage of the combined insulation cover or the number of layers of aluminosilicate ceramic fiber blanket, ensuring the precise execution of the gradient cooling regime.

[0064] Example 1 Taking a centrifuge spindle made of 42CrMoA material and with a total length of 2500 mm as an example, the forging is carried out; the spindle is distributed along the axial direction with a large diameter section, an intermediate transition section and a small diameter section, wherein the large diameter section has a diameter of 380 mm and a length of 400 mm, the intermediate transition section has a diameter of 220 mm and a length of 1200 mm, and the small diameter section has a diameter of 140 mm and a length of 900 mm.

[0065] First, a 42CrMoA steel ingot with a diameter of 500 mm is selected. After removing the riser and the ingot tail, it is heated in a bogie-type heating furnace. The heating regime is set as follows: heat to 850 degrees Celsius at a heating rate of no more than 150 degrees Celsius per hour and hold for 2 hours; then heat to 1200 degrees Celsius ± 10 degrees Celsius at a heating rate of no more than 200 degrees Celsius per hour and hold for 4 hours to ensure that the temperature inside and outside the billet is uniform and reaches a suitable initial forging temperature.

[0066] Next, the heated steel ingot is initially upset on a 5000-ton hydraulic press, with an upsetting ratio controlled at 1.8. After upsetting, the billet height is approximately 55% of the original height. The billet is then placed on a forging manipulator, and partial upsetting is performed sequentially, starting with the large-diameter section, followed by the intermediate transition section, and finally the small-diameter section. After each section is partially upset, a temporary heat insulation baffle is placed between the section and the adjacent section, and the section is allowed to stand for 40 seconds. The next section is only started when the surface temperature difference between the section and the adjacent section does not exceed 50 degrees Celsius. For the large-diameter section, a target forging ratio of 4.2 is set, and partial upsetting is performed in two stages, with a single reduction of 12% of the original height of the large-diameter section. After each pressing, the pressure was held for 4 seconds, and the actual forging ratio was measured to be 4.15. For the intermediate transition section, the target forging ratio was set at 3.6, and it was completed in two stages, with each pressing amount being 10% of the original height of the intermediate transition section. The actual forging ratio was measured to be 3.58. For the small diameter section, the target forging ratio was set at 3.1, and it was completed in two stages, with each pressing amount being 8% of the original height of the small diameter section. The actual forging ratio was measured to be 3.08. The deviation between the actual forging ratio and the target value for each section was controlled within ±5%. During the local upsetting process, a handheld infrared thermometer was used to monitor the surface temperature of each section. The temperatures of the three sections were 1160 degrees Celsius, 1120 degrees Celsius, and 1080 degrees Celsius, respectively, all of which were higher than their respective minimum allowable forging temperatures, and no additional heating was required.

[0067] Next, the mandrel drawing process is used to draw each section to the design size. A total of 4 drawing passes are performed, with the reduction amount in each pass controlled at 12%, 10%, 9%, and 8%, respectively. The actual cross-sectional dimensions are measured after each pass to ensure that the final dimensional accuracy and forging ratio deviation meet the requirements. Taking Example 1 as an example, the spindle undergoes 4 drawing passes, with the reduction amount in each pass set at 12%, 10%, 9%, and 8%, respectively. After each pass, dimensional verification and feedback adjustment are performed. Finally, the actual forging ratios of the large-diameter section, the intermediate transition section, and the small-diameter section are stabilized at 4.15, 3.58, and 3.08, respectively. Compared with their respective target values ​​of 4.2, 3.6, and 3.1, the deviations are all within the allowable range, thereby achieving the homogenization of the overall mechanical properties of the spindle.

[0068] After forging, differentiated gradient slow cooling is immediately initiated. For the large-diameter section, a combined insulation cover is used, with an insulation layer thickness of 120 mm and the inner wall of the insulation cover 80 mm from the surface of the forging. The combined insulation cover is equipped with an electric push rod driven lifting and adjustment mechanism and is connected to a thermocouple signal connected to a multi-channel temperature recorder. During the first 30 minutes after cooling begins, the temperature is recorded every 10 minutes, and the actual cooling rate is calculated to be 28 degrees Celsius per hour, which is within the target range of 20 to 35 degrees Celsius per hour. After slow cooling to 550 degrees Celsius, the insulation cover is removed and the section is allowed to air cool naturally. For the intermediate transition section, a three-layer aluminum silicate ceramic fiber blanket is wrapped, with a target cooling rate of 45 to 50 degrees Celsius per hour. After calibration, the actual cooling rate is 47 degrees Celsius per hour. After cooling to 600 degrees Celsius, the insulation layer is removed and the section is air cooled. For the small-diameter section, natural air cooling is performed within 2 meters of the surface of the small-diameter section without any active ventilation equipment. The measured cooling rate is approximately 65 degrees Celsius per hour.

[0069] Testing revealed that the grain size of each segment of the spindle prepared in this embodiment was: grade 7.5 for the large-diameter segment, grade 8 for the intermediate transition segment, and grade 8 for the small-diameter segment. The grain size difference between each segment was less than one grade. Ultrasonic testing showed that the spindle was qualified, with no internal defects such as white spots or cracks. Hardness distribution testing showed that the hardness of the large-diameter segment was 268 to 275 HB, the intermediate transition segment was 265 to 278 HB, and the small-diameter segment was 270 to 276 HB. The overall hardness fluctuation was less than ±15 HB. Furthermore, the spindle straightness was controlled within 0.4 mm per meter. Figure 4 The comparison of grain size detection results for each segment of the spindle in this embodiment is shown, which intuitively reflects the uniformity of grain size.

[0070] Comparative Example 1 Comparative Example 1 adopted the same segmented local upsetting process as Example 1, which achieved gradient deformation control. However, after forging, it did not adopt zoned differential cooling, but was naturally cooled in the air as a whole. The test results showed that the grain size difference of each segment reached 2.5 to 3 levels (6 levels for the large diameter segment, 7.5 levels for the intermediate transition segment, and 8.5 levels for the small diameter segment). The hardness fluctuation was ±35HB, and ultrasonic testing found 3 white spot defects. The above data were derived from the average value of 12 batches of historical production records under the same production conditions.

[0071] Comparative Example 2 Comparative Example 2 adopted the traditional integral forging process, that is, without segmented control of the forging ratio, but after forging, the zoned differential cooling system of Example 1 was adopted. The test results showed that the grain size difference of each segment was 2 to 2.5 (6.5 for the large diameter segment, 7 for the intermediate transition segment, and 8 for the small diameter segment), and the hardness fluctuation was ±28HB. The above data were derived from the average value of 8 batches of historical production records under the same production conditions.

[0072] By comparing Example 1 with Comparative Examples 1 and 2, it can be seen that neither gradient deformation alone (as in Comparative Example 1) nor gradient cooling alone (as in Comparative Example 2) can simultaneously achieve highly uniform grain size, low hardness fluctuation, and high flaw detection pass rate. Although Comparative Example 1 establishes a uniform dislocation structure during the deformation stage, the lack of matching during the cooling stage leads to non-uniform phase transformation that disrupts the uniformity of the microstructure and causes white spots. Although Comparative Example 2 achieves differentiated control during the cooling stage, the large differences in energy storage in each segment during the deformation stage mean that the cooling measures are insufficient to fully compensate for the inherent non-uniformity of the deformation stage. Only when gradient deformation and gradient cooling work together can a uniform energy storage state be established during the deformation stage and the aforementioned uniformity be maintained during the cooling stage until the phase transformation is complete. This results in grain size differences being controlled to less than one level, hardness fluctuations being controlled to less than ±15 HB, and the ultrasonic flaw detection pass rate being increased to over 98%, which is significantly better than the prior art.

[0073] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A forging method for coordinated control of gradient deformation and gradient cooling of a centrifuge spindle, characterized in that, Includes the following steps: S1. Pre-setting of segmented target forging ratios: Based on the design cross-sectional dimensions and material recrystallization critical deformation of the large-diameter section, intermediate transition section, and small-diameter section of the centrifuge spindle, differentiated target forging ratios are set for the large-diameter section, the intermediate transition section, and the small-diameter section, respectively. The target forging ratio of the large-diameter section is greater than that of the intermediate transition section, and the target forging ratio of the intermediate transition section is greater than that of the small-diameter section. S2. Segmented Local Upsetting and Thermal Balance Control: The heated billet is locally upset in the order of the large diameter segment, the intermediate transition segment, and the small diameter segment. After each segment is partially upset, a temporary heat insulation baffle is placed between the segment and the adjacent segment, and the segment is left to stand for 30 to 60 seconds until the deformation heat generated by the segment is fully dissipated and the temperature difference between the surface temperature of the segment and the surface temperature of the adjacent segment does not exceed 50 degrees Celsius. Then, the next segment is partially upset, so that the actual forging ratio of each segment falls within the preset deviation range of its corresponding target forging ratio. S3. Mandrel Lengthening and Deviation Compensation: After local upsetting of each section, a mandrel lengthening process is used to lengthen each section to the design size, controlling the reduction amount in each pass to ensure that the deviation between the final actual forging ratio and the target forging ratio of each section is controlled within ±5%. When the actual forging ratio of a section is more than 3% lower than the target value, a light pressing is added in the next pass of the section, and the reduction amount of the light pressing is 5% to 8% of the current height of the section. When the actual forging ratio of a section is more than 3% higher than the target value, the reduction amount of the section is reduced in subsequent passes. S4, zoned differentiated gradient slow cooling; After forging, differentiated cooling is implemented based on the cross-sectional dimensions of the large-diameter section, the intermediate transition section, and the small-diameter section. The large-diameter section is covered with a combined heat-insulating cover for slow cooling, with a cooling rate controlled at 20 to 35 degrees Celsius per hour. The heat-insulating cover is removed after cooling to 550 degrees Celsius ± 20 degrees Celsius. The intermediate transition section is wrapped with an aluminosilicate ceramic fiber blanket for slow cooling, with a cooling rate controlled at 40 to 55 degrees Celsius per hour. The aluminosilicate ceramic fiber blanket is removed after cooling to 600 degrees Celsius ± 20 degrees Celsius. The small-diameter section is naturally cooled in air, and no active ventilation equipment is installed within 2 meters of the surface of the small-diameter section. S5. Full-process collaborative monitoring: During the forging stage, an infrared thermometer is used to monitor the surface temperature of each section in real time. When the surface temperature of a certain section is lower than the minimum allowable forging temperature of that section, the forging operation of that section is suspended and local reheating is performed. During the cooling stage, thermocouples and multi-channel temperature recorders are used to monitor the temperature of each segment in real time. The coverage of the combined heat preservation cover or the number of wrapping layers of the aluminosilicate ceramic fiber blanket are adjusted according to the monitoring data. Temperature monitoring data of the forging stage and the cooling stage are continuously recorded, which together constitute a complete temperature time series from the start of forging to the end of cooling, realizing the coordinated control of the whole process.

2. The forging method for coordinated control of gradient deformation and gradient cooling of centrifuge spindle according to claim 1, characterized in that, In step S1, the diameter of the large-diameter section is not less than 300 mm, and the target forging ratio of the large-diameter section is not less than 4.0; the diameter of the intermediate transition section is between 150 mm and 300 mm, and the target forging ratio of the intermediate transition section is not less than 3.5; the diameter of the small-diameter section is less than 150 mm, and the target forging ratio of the small-diameter section is not less than 3.

0.

3. The forging method for coordinated control of gradient deformation and gradient cooling of centrifuge spindle according to claim 1, characterized in that, In step S2, the specific operation of the local upsetting is as follows: by changing upsetting anvils of different sizes in sections, pressure is applied only to the billet area corresponding to the section; the single pressing amount of local upsetting of each section does not exceed 15% of the original height of the billet of the section, and is completed in two to three times, with pressure held for three to five seconds after each pressing.

4. The forging method for coordinated control of gradient deformation and gradient cooling of centrifuge spindle according to claim 1, characterized in that, In step S3, the reduction amount per pass during the mandrel drawing process is controlled between 8% and 12%.

5. The forging method for coordinated control of gradient deformation and gradient cooling of centrifuge spindle according to claim 1, characterized in that, In step S4, the combined heat insulation cover is a semi-enclosed structure, with a steel plate outer shell lined with aluminum silicate ceramic fiber cotton, and a ventilation gap at the bottom; the distance between the bottom of the combined heat insulation cover and the surface of the large diameter section is adjustable, and the adjustable range of the distance is 50 to 150 mm.

6. The forging method for coordinated control of gradient deformation and gradient cooling of centrifuge spindle according to claim 5, characterized in that, The combined heat preservation cover is equipped with an electric or pneumatically driven lifting and adjusting mechanism. The lifting and adjusting mechanism is connected to the multi-channel temperature recorder. The lifting and adjusting mechanism automatically calculates the current cooling rate based on the real-time temperature data fed back by the thermocouple, and automatically adjusts the position of the combined heat preservation cover after comparing it with the target cooling rate.

7. The forging method for coordinated control of gradient deformation and gradient cooling of centrifuge spindle according to claim 1, characterized in that, In step S5, the local heating operation is as follows: a medium-frequency induction heating device is used to locally heat the section with insufficient surface temperature. During heating, ceramic fiber baffles are covered on the surface of adjacent sections. The duration of each heating operation does not exceed 2 minutes.

8. The forging method for coordinated control of gradient deformation and gradient cooling of centrifuge spindle according to claim 1, characterized in that, In step S5, the operation of using thermocouples in conjunction with a multi-channel temperature recorder to monitor the temperature of each segment in real time during the cooling stage is as follows: a blind hole with a depth of 5 to 8 mm is opened on the surface of each segment, a K-type thermocouple is inserted into the blind hole and fixed with high-temperature resistant putty, the K-type thermocouple is connected to the multi-channel temperature recorder through a compensating wire, and the temperature data of each segment is automatically recorded every 5 minutes until the temperature of each segment drops below 400 degrees Celsius.

9. The forging method for coordinated control of gradient deformation and gradient cooling of centrifuge spindle according to claim 1, characterized in that, In step S5, the minimum allowable forging temperature is: not less than 1000 degrees Celsius for the large diameter section, not less than 950 degrees Celsius for the intermediate transition section, and not less than 900 degrees Celsius for the small diameter section.

10. The forging method for coordinated control of gradient deformation and gradient cooling of centrifuge spindle according to claim 1, characterized in that, In step S5, the infrared thermometer is a handheld infrared thermometer, which measures the surface temperature of each section before each forging operation.

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