Medium frequency heat treatment process for supporting wheel

Abstract

The application provides a kind of supporting wheel medium frequency heat treatment process, belongs to supporting wheel heat treatment technical field, including the following steps: supporting wheel is carried out stress relief annealing pretreatment;Supporting wheel is grabbed by visual positioning manipulator, and is placed in rotary quenching platform;Supporting wheel is conveyed to scanning station by feeding conveyor, high-precision 3D vision system scans workpiece surface quickly, manipulator is adaptively grabbed, six-axis collaborative manipulator plans collision-free path according to the coordinate data provided by vision system, with 0.3G acceleration, smoothly moves to the grabbing point, end pneumatic gripper stably grabs supporting wheel with 15±2N contact pressure, built-in force sensor real-time feedback ensures non-damage clamping;Through the coordination effect of variable power medium frequency heating and PAG+quenching oil gradient cooling, deep heat penetration+grain refinement is realized, martensite phase transition rate is accurately controlled, supporting wheel surface hardness is improved, and full cross-section hardness fluctuation is reduced.

Description

Technical Field

[0001] This invention belongs to the field of heat treatment technology for support rollers, and in particular to a medium-frequency heat treatment process for support rollers. Background Technology

[0002] Track rollers are one of the four wheels and one track in the chassis of tracked construction machinery. Their main function is to support the weight of excavators and bulldozers, allowing the tracks to move forward along the wheels. Therefore, track rollers need to have high strength, hardness, and wear resistance. Current technology typically employs a quenching process, using quenching and tempering techniques to increase the surface hardness of the track roller. The quenching process usually uses induction coils to heat the track roller, and medium-frequency induction heating is used to ensure the hardness of the track roller.

[0003] Traditional heat treatment processes for support rollers use medium-frequency induction heating at a fixed frequency, resulting in a large temperature difference between the surface and core of the workpiece. While high-frequency heating provides rapid heating, it results in a shallow hardened layer, which cannot meet the requirements of heavy-duty conditions. Furthermore, the use of segmented high-frequency and medium-frequency heating leads to high energy consumption and grain coarsening. During the cooling process after induction heating in the quenching process, water cooling alone can easily generate a vapor film, leading to uneven hardness. Saltwater media corrodes the equipment, and wastewater treatment costs are high. Saltwater cooling is too rapid below 300°C, increasing the deformation rate. Oil cooling has low efficiency and makes it difficult to achieve the required hardness.

[0004] In view of the above problems, this invention proposes a medium-frequency heat treatment process for support rollers. By coordinating variable-power medium-frequency heating with PAG+quenching oil gradient cooling, it breaks through the limitations of single frequency and medium, significantly improves efficiency while ensuring hardening depth, and solves the industry problem of quenching deformation and uneven hardness of support rollers. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned problems in existing technologies by proposing a medium-frequency heat treatment process for support rollers.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A medium-frequency heat treatment process for support rollers includes the following steps:

[0008] S1, stress-relief annealing pretreatment is performed on the support roller;

[0009] S2, The support roller is grasped by a vision positioning robot and placed on a rotary quenching platform with a positioning accuracy of ≤0.1mm;

[0010] Step S2 specifically includes the following steps:

[0011] S21, 3D vision scanning and positioning: The support roller is conveyed to the scanning station by the feeding conveyor line. The high-precision 3D vision system quickly scans the surface of the workpiece and calculates the center coordinates and tilt angle of the support roller through the point cloud matching algorithm to determine the optimal gripping point. The positioning accuracy reaches ±0.05mm.

[0012] S22, a robotic arm with adaptive grasping, is a six-axis collaborative robotic arm that plans a collision-free path based on coordinate data provided by the vision system and moves smoothly to the grasping point with an acceleration of 0.3G. The end pneumatic gripper stably grasps the support roller with a contact pressure of 15±2N, and the built-in force sensor provides real-time feedback to ensure damage-free gripping.

[0013] S23, high-precision placement and calibration: the robot arm moves the support roller to the rotary quenching platform. After coarse positioning by the end camera, 8 sets of ring array laser displacement sensors synchronously detect the workpiece position. The system calculates the position deviation in real time and dynamically adjusts it until the positioning error between the support roller and the platform is ≤0.1mm, and then triggers vacuum adsorption fixation.

[0014] S24, closed-loop verification and anomaly handling: the laser sensor re-inspects the radial runout of the support roller. After confirming that the positioning accuracy meets the standard, it enters the quenching process. If the detection exceeds the tolerance, the vacuum is immediately released and the machine is re-grabbed. If it fails 3 times in a row, an alarm is triggered and the machine is stopped to ensure the reliability of the process. The whole process takes ≤4 seconds and the positioning repeatability reaches 0.07mm.

[0015] S3, System settings for medium-frequency induction heating;

[0016] S4, variable power medium frequency induction heating of the support roller is performed through the induction coil;

[0017] Step S4 specifically includes the following steps:

[0018] S41, Preheating stage: Use a medium frequency power supply at a frequency of 1-3kHz to heat the support roller to 480-500℃ with a power density of 0.8-1.2 kW / cm², and hold for 18-22 seconds;

[0019] S42, austenitizing stage: switch to 0.5-1kHz frequency, heat to 865-875℃ with a power density of 1.5-2.0 kW / cm², and hold for 85-95s;

[0020] S5 performs gradient composite cooling on the support roller after induction heating.

[0021] Preferably, step S5 specifically includes the following steps:

[0022] S51, the first stage involves spraying an 8-12% PAG polymer aqueous solution onto the heated support roller for 18-22 seconds.

[0023] S52, the second stage spray cooling rate ≥80℃ / s rapid quenching oil, spray for 25-30s;

[0024] S53, in the third stage, 0.4-0.6MPa compressed air is introduced for air cooling to room temperature.

[0025] Preferably, in step S4, the induction heating uses a contoured induction coil, the gap between the induction coil and the surface of the support roller is 1.5-2.0 mm, and the copper tube of the induction coil has an integrated circulating cooling water channel.

[0026] Preferably, in step S4, the heating process uses a dual-color infrared thermometer to monitor the temperature in real time. When the monitored temperature deviates from the set value by ±5℃, a PID algorithm is triggered to dynamically adjust the power density and maintain the temperature fluctuation ≤ ±5℃.

[0027] Preferably, the PAG polymer aqueous solution in the first stage of step S5 contains rust inhibitor and defoamer, and its cooling rate in the high temperature zone above 300°C is ≥120°C / s, and its cooling rate in the low temperature zone below 200°C is ≤20°C / s.

[0028] Preferably, the rotary quenching platform rotates at a speed of 10-15 rpm and remains rotating throughout the heating and cooling stages.

[0029] Preferably, the heating rate during the austenitization stage in S4 is controlled at ≤25℃ / s, and the heating rate is automatically reduced when the temperature difference between the surface and core of the support roller is >50℃.

[0030] Preferably, the kinematic viscosity of the rapid quenching oil in the second stage of step S5 is 12-15 cSt (40℃), and the flash point is ≥180℃.

[0031] Preferably, the mass percentage of the PAG polymer aqueous solution is 8%-12%.

[0032] Preferably, the rust inhibitor is 0.15%-0.25% benzotriazole (BTA) by mass, and the defoamer is 0.05%-0.10% polydimethylsiloxane (PDMS) by mass.

[0033] Compared with the prior art, the medium-frequency heat treatment process for support rollers provided by the present invention has the following beneficial effects:

[0034] 1. The present invention provides a medium-frequency heat treatment process for support rollers, which achieves deep heat penetration and grain refinement through the coordinated action of variable power medium-frequency heating and PAG + quenching oil gradient cooling, accurately controls the martensitic phase transformation rate, improves the surface hardness of support rollers, and reduces the hardness fluctuation of the entire cross section.

[0035] 2. The medium-frequency heat treatment process for support rollers provided by this invention achieves rapid and uniform initial cooling through PAG solution spraying, avoiding the vapor film effect. The three-stage cooling process works synergistically to significantly reduce the risk of deformation and cracking.

[0036] 3. The medium-frequency heat treatment process for support rollers provided by this invention effectively controls the cooling rate through a gradient composite cooling process, taking into account both hardness and anti-deformation requirements.

[0037] 4. The medium-frequency heat treatment process for support rollers provided by this invention achieves non-contact precise temperature measurement through dual-color infrared thermometry, PID dynamic adjustment ensures temperature control accuracy, and closed-loop control significantly improves process stability.

[0038] 5. The present invention provides a medium-frequency heat treatment process for support rollers.

[0039] In summary, this invention provides a medium-frequency heat treatment process for support rollers. Through the synergistic effect of variable power medium-frequency heating and gradient composite cooling, the surface hardness of the support roller reaches 58-63 HRC, the hardness fluctuation of the entire cross section is ≤1.5 HRC, and the roundness error is reduced from 0.15 mm to ≤0.05 mm by three-stage cooling combined with high-precision positioning. Detailed Implementation

[0040] The following are specific embodiments of the present invention, which further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0041] Example 1:

[0042] A medium-frequency heat treatment process for support rollers includes the following steps:

[0043] S1. The support roller is subjected to stress-relief annealing pretreatment. A φ220mm support roller made of 40CrMnMo material is selected and stress-relief annealing is performed at 580℃ for 2 hours.

[0044] S2, the visual positioning robot arm grasps the support roller and places it on the rotary quenching platform, with a positioning accuracy of ≤0.1mm;

[0045] Step S2 specifically includes the following steps:

[0046] S21, 3D vision scanning and positioning: The support roller is conveyed to the scanning station by the feeding conveyor line. The high-precision 3D vision system quickly scans the surface of the workpiece and calculates the center coordinates and tilt angle of the support roller through the point cloud matching algorithm to determine the optimal gripping point. The positioning accuracy reaches ±0.05mm.

[0047] S22, a robotic arm with adaptive grasping, is a six-axis collaborative robotic arm that plans a collision-free path based on coordinate data provided by the vision system and moves smoothly to the grasping point with an acceleration of 0.3G. The end pneumatic gripper stably grasps the support roller with a contact pressure of 15±2N, and the built-in force sensor provides real-time feedback to ensure damage-free gripping.

[0048] S23, high-precision placement and calibration: the robot arm moves the support roller to the rotary quenching platform. After coarse positioning by the end camera, 8 sets of ring array laser displacement sensors synchronously detect the workpiece position. The system calculates the position deviation in real time and dynamically adjusts it until the positioning error between the support roller and the platform is ≤0.1mm, and then triggers vacuum adsorption fixation.

[0049] S24, closed-loop verification and anomaly handling: the laser sensor re-inspects the radial runout of the support roller. After confirming that the positioning accuracy meets the standard, it enters the quenching process. If the detection exceeds the tolerance, the vacuum is immediately released and the machine is re-grabbed. If it fails 3 times in a row, an alarm is triggered and the machine is stopped to ensure the reliability of the process. The whole process takes ≤4 seconds and the positioning repeatability reaches 0.07mm.

[0050] S3 is used for system setup of medium-frequency induction heating. The hardware system configuration includes a power system, inductor, cooling system, and temperature feedback. The power system uses an IGBT medium-frequency power supply. Parameter settings include basic parameter input, inputting workpiece parameters on the PLC interface, selecting variable power process mode, setting the frequency-power curve, and setting safety thresholds. Temperature over-limit alarm: set value ±10℃ (hard limit ±15℃), cooling water flow alarm: power reduction operation when <20 L / min, emergency shutdown when <10 L / min.

[0051] Table 1 Frequency-Power Curve Settings

[0052] Heating stage Frequency (kHz) Power density (kW / cm²) Target temperature (°C) Temperature rise rate limit (°C / s) Preheating stage 2.5-3.0 0.8-1.2 480-500 ≤15 austenitizing stage 0.8-1.0 1.5-2.0 865-875 ≤25

[0053] S4, variable power medium frequency induction heating of the support roller is performed through the induction coil;

[0054] Step S4 specifically includes the following steps:

[0055] S41, Preheating stage: Use a medium frequency power supply at a frequency of 1-3kHz to heat the support roller to 480-500℃ with a power density of 0.8-1.2 kW / cm², and hold for 18-22 seconds;

[0056] Table 2 Electromagnetic simulation results

[0057] Frequency (kHz) Skin depth δ (mm) Energy utilization rate (%) 1 2.8 62 2.5 1.2 78 3 1 75

[0058] Table 3 Measured data of 40Cr track rollers

[0059] Power density (kW / cm²) Time to heat up to 490℃ (s) Surface temperature difference (°C) 0.6 28 ±25 1.0 18 ±12 1.4 14 ±18

[0060] Table 4 Residual stress test results

[0061] Preheating temperature (°C) Residual stress reduction (%) 450 68 490 92 520 95 (but grain growth)

[0062] Table 5 Results of Cardiac and Surface Temperature Difference Monitoring

[0063] Insulation time (s) Maximum cardiac surface temperature difference (°C) 15 52 20 38 25 35 (Efficiency Decline)

[0064] Electromagnetic simulation results show that at 2.5 kHz, both heating efficiency (78%) and heat penetration depth (1.2 mm) are balanced, avoiding edge overheating caused by high frequency. Efficiency and uniformity are optimal at 1.0 kW / cm², while power > 1.2 kW / cm² leads to increased temperature difference. Temperature differences on the surface of the support rollers were measured at different power density ranges, showing that efficiency and uniformity are optimal at 1.0 kW / cm², while power > 1.2 kW / cm² leads to increased temperature difference. Residual stress was measured using X-ray diffraction under controlled temperature of 480-500℃, showing that stress was sufficiently eliminated at 490℃ without triggering a phase transformation. Temperature difference on the surface of the heart was monitored using a FLIR A655sc thermal imager, showing a temperature difference < 40℃ after 20s, meeting the uniformity requirements for subsequent austenitization. The results show that 1-3kHz mid-frequency heating optimizes the skin effect, achieving rapid and uniform heating; a power density of 0.8-1.2 kW / cm² can balance heating efficiency and thermal stress control; a preheating temperature of 480-500℃ can fully eliminate machining stress and avoid phase transformation of the microstructure; and a holding time of 18-22s can ensure that the temperature difference between the core and the surface is ≤40℃, reducing the risk of deformation.

[0065] S42, austenitizing stage: switch to a frequency of 0.5-1kHz, heat to 865-875℃ with a power density of 1.5-2.0 kW / cm², and hold for 85-95 seconds.

[0066] Table 6 Electromagnetic Simulation and Measured Data

[0067] Frequency (kHz) Skin depth δ (mm) Hardened layer depth (mm) Cardiac surface temperature difference (°C) 0.5 4.2 10.5 12 0.8 3.5 9.2 10 1.0 2.8 8.1 18

[0068] Table 7. Kinetic Tests of Austenitization of 40Cr Track Rollers

[0069] Power density (kW / cm²) Time to reach 870℃ (s) austenitization degree (%) Grain size (ASTM) 1.2 68 92 7.5 1.8 42 99.3 8.5 2.2 35 99.5 (but some areas are overheated) 7.0

[0070] Table 8 Infrared Thermal Imager and Metallographic Detection

[0071] Insulation time (s) Percentage of austenitization in the heart region (%) Surface decarburized layer (μm) 75 95 15 90 99.8 ＜5 105 99.9 (Efficiency Decrease) 8

[0072] The head heating effect was measured at 0.5-1 kHz. Electromagnetic simulation and measured data showed that the optimal hardened layer depth (9.2 mm) and temperature uniformity (±10℃) were achieved at 0.8 kHz. (The data was obtained at 1.5-2.0 kW / cm².) 2Phase transformation efficiency was measured at a power density of 1.8 kW / cm², and the austenitizing kinetics test results for 40Cr support rollers showed that the phase transformation was complete and the grains were refined (grade 8.5) at 1.8 kW / cm², while power > 2.0 kW / cm² led to grain coarsening. The uniformity of holding time in the 85-95s range was verified by infrared thermal imaging and metallographic examination. The results showed that the core was completely austenitized at 90s, and decarburization was controllable. The results indicate that low-frequency heating of 0.5-1 kHz can achieve deep heat penetration and microstructure homogenization; a power density of 1.5-2.0 kW / cm² can rapidly penetrate the austenitic phase transformation region and suppress grain coarsening; and a holding time of 85-95s can achieve complete austenitization with a core-to-surface temperature difference ≤ 15℃.

[0073] S5 performs gradient composite cooling on the support roller after induction heating.

[0074] In step S4, the induction heating uses a contoured induction coil. The gap between the induction coil and the surface of the support roller is 1.5-2.0 mm. The copper tube of the contoured induction coil integrates a spiral flow-guiding cooling water channel with a cross-sectional area of ​​12-15 mm² and a water flow velocity ≥5 m / s. Turbulent protrusions are provided on the inner wall of the water channel, and a 5-8 μm silver layer is plated on the outer surface of the copper tube.

[0075] In step S4, the heating process uses a dual-color infrared thermometer to monitor the temperature in real time. When the monitored temperature deviates from the set value by ±5℃, the PID algorithm is triggered to dynamically adjust the power density and maintain the temperature fluctuation ≤ ±5℃.

[0076] The rotary quenching platform rotates at 10-15 rpm and remains rotating throughout the heating and cooling stages. The platform surface is equipped with a vacuum adsorption array consisting of micropores with a diameter of 1 mm, a heat-resistant ceramic coating with a thickness of 0.2-0.3 mm, and a dynamic balance module that monitors platform vibration in real time and automatically compensates for imbalance.

[0077] The heating rate during the austenitization stage in S4 is controlled at ≤25℃ / s, and the heating rate is automatically reduced when the temperature difference between the surface and core of the support roller is >50℃.

[0078] Example 2:

[0079] A medium-frequency heat treatment process for support rollers includes the following steps:

[0080] S1. The support roller is subjected to stress-relief annealing pretreatment. A φ220mm support roller made of 40CrMnMo material is selected and stress-relief annealing is performed at 580℃ for 2 hours.

[0081] S2, the visual positioning robot arm grasps the support roller and places it on the rotary quenching platform, with a positioning accuracy of ≤0.1mm;

[0082] Step S2 specifically includes the following steps:

[0083] S21, 3D vision scanning and positioning: The support roller is conveyed to the scanning station by the feeding conveyor line. The high-precision 3D vision system quickly scans the surface of the workpiece and calculates the center coordinates and tilt angle of the support roller through the point cloud matching algorithm to determine the optimal gripping point. The positioning accuracy reaches ±0.05mm.

[0084] S22, a robotic arm with adaptive grasping, is a six-axis collaborative robotic arm that plans a collision-free path based on coordinate data provided by the vision system and moves smoothly to the grasping point with an acceleration of 0.3G. The end pneumatic gripper stably grasps the support roller with a contact pressure of 15±2N, and the built-in force sensor provides real-time feedback to ensure damage-free gripping.

[0085] S23, high-precision placement and calibration: the robot arm moves the support roller to the rotary quenching platform. After coarse positioning by the end camera, 8 sets of ring array laser displacement sensors synchronously detect the workpiece position. The system calculates the position deviation in real time and dynamically adjusts it until the positioning error between the support roller and the platform is ≤0.1mm, and then triggers vacuum adsorption fixation.

[0086] S24, closed-loop verification and anomaly handling: the laser sensor re-inspects the radial runout of the support roller. After confirming that the positioning accuracy meets the standard, it enters the quenching process. If the detection exceeds the tolerance, the vacuum is immediately released and the machine is re-grabbed. If it fails 3 times in a row, an alarm is triggered and the machine is stopped to ensure the reliability of the process. The whole process takes ≤4 seconds and the positioning repeatability reaches 0.07mm.

[0087] S3 is used for system setup of medium-frequency induction heating. The hardware system configuration includes a power system, inductor, cooling system, and temperature feedback. The power system uses an IGBT medium-frequency power supply. Parameter settings include basic parameter input, inputting workpiece parameters on the PLC interface, selecting variable power process mode, setting the frequency-power curve, and setting safety thresholds. Temperature over-limit alarm: set value ±10℃ (hard limit ±15℃), cooling water flow alarm: power reduction operation when <20 L / min, emergency shutdown when <10 L / min.

[0088] Table 1 Frequency-Power Curve Settings

[0089] Heating stage Frequency (kHz) Power density (kW / cm²) Target temperature (°C) Temperature rise rate limit (°C / s) Preheating stage 2.5-3.0 0.8-1.2 480-500 ≤15 austenitizing stage 0.8-1.0 1.5-2.0 865-875 ≤25

[0090] S4, variable power medium frequency induction heating of the support roller is performed through the induction coil;

[0091] Step S4 specifically includes the following steps:

[0092] S41, Preheating stage: Use a medium frequency power supply at a frequency of 1-3kHz to heat the support roller to 480-500℃ with a power density of 0.8-1.2 kW / cm², and hold for 18-22 seconds;

[0093] Table 2 Electromagnetic simulation results

[0094] Frequency (kHz) Skin depth δ (mm) Energy utilization rate (%) 1 2.8 62 2.5 1.2 78 3 1 75

[0095] Table 3 Measured data of 40Cr track rollers

[0096] Power density (kW / cm²) Time to heat up to 490℃ (s) Surface temperature difference (°C) 0.6 28 ±25 1.0 18 ±12 1.4 14 ±18

[0097] Table 4 Residual stress test results

[0098] Preheating temperature (°C) Residual stress reduction (%) 450 68 490 92 520 95 (but grain growth)

[0099] Table 5 Results of Cardiac and Surface Temperature Difference Monitoring

[0100] Insulation time (s) Maximum cardiac surface temperature difference (°C) 15 52 20 38 25 35 (Efficiency Decline)

[0101] Electromagnetic simulation results show that at 2.5 kHz, both heating efficiency (78%) and heat penetration depth (1.2 mm) are balanced, avoiding edge overheating caused by high frequency. Efficiency and uniformity are optimal at 1.0 kW / cm², while power > 1.2 kW / cm² leads to increased temperature difference. Temperature differences on the surface of the support rollers were measured at different power density ranges, showing that efficiency and uniformity are optimal at 1.0 kW / cm², while power > 1.2 kW / cm² leads to increased temperature difference. Residual stress was measured using X-ray diffraction under controlled temperature of 480-500℃, showing that stress was sufficiently eliminated at 490℃ without triggering a phase transformation. Temperature difference on the surface of the heart was monitored using a FLIR A655sc thermal imager, showing a temperature difference < 40℃ after 20s, meeting the uniformity requirements for subsequent austenitization. The results show that 1-3kHz mid-frequency heating optimizes the skin effect, achieving rapid and uniform heating; a power density of 0.8-1.2 kW / cm² can balance heating efficiency and thermal stress control; a preheating temperature of 480-500℃ can fully eliminate machining stress and avoid phase transformation of the microstructure; and a holding time of 18-22s can ensure that the temperature difference between the core and the surface is ≤40℃, reducing the risk of deformation.

[0102] S42, austenitizing stage: switch to a frequency of 0.5-1kHz, heat to 865-875℃ with a power density of 1.5-2.0 kW / cm², and hold for 85-95 seconds.

[0103] Table 6 Electromagnetic Simulation and Measured Data

[0104] Frequency (kHz) Skin depth δ (mm) Hardened layer depth (mm) Cardiac surface temperature difference (°C) 0.5 4.2 10.5 12 0.8 3.5 9.2 10 1.0 2.8 8.1 18

[0105] Table 7. Kinetic Tests of Austenitization of 40Cr Track Rollers

[0106] Power density (kW / cm²) Time to reach 870℃ (s) austenitization degree (%) Grain size (ASTM) 1.2 68 92 7.5 1.8 42 99.3 8.5 2.2 35 99.5 (but some areas are overheated) 7.0

[0107] Table 8 Infrared Thermal Imager and Metallographic Detection

[0108] Insulation time (s) Percentage of austenitization in the heart region (%) Surface decarburized layer (μm) 75 95 15 90 99.8 ＜5 105 99.9 (Efficiency Decrease) 8

[0109] The head heating effect was measured at 0.5-1 kHz. Electromagnetic simulation and measured data showed that the optimal hardened layer depth (9.2 mm) and temperature uniformity (±10℃) were achieved at 0.8 kHz. (The data was obtained at 1.5-2.0 kW / cm².) 2 Phase transformation efficiency was measured at a power density of 1.8 kW / cm², and the austenitizing kinetics test results for 40Cr support rollers showed that the phase transformation was complete and the grains were refined (grade 8.5) at 1.8 kW / cm², while power > 2.0 kW / cm² led to grain coarsening. The uniformity of holding time in the 85-95s range was verified by infrared thermal imaging and metallographic examination. The results showed that the core was completely austenitized at 90s, and decarburization was controllable. The results indicate that low-frequency heating of 0.5-1 kHz can achieve deep heat penetration and microstructure homogenization; a power density of 1.5-2.0 kW / cm² can rapidly penetrate the austenitic phase transformation region and suppress grain coarsening; and a holding time of 85-95s can achieve complete austenitization with a core-to-surface temperature difference ≤ 15℃.

[0110] S5 performs gradient composite cooling on the support roller after induction heating.

[0111] Step S5 specifically includes the following steps:

[0112] S51, in the first stage, spray an 8-12% PAG polymer aqueous solution onto the heated support roller for 18-22 seconds, as shown in Table 9. The cooling characteristics were tested, and the results showed that the 10% PAG solution achieved an ideal balance between rapid cooling (austenitic region) and slow cooling (martensitic region).

[0113] Table 9 Cooling performance test

[0114] S52, the second stage spray cooling rate is ≥80℃ / s of rapid quenching oil, spray for 25-30s, as shown in Tables 10 and 11. The performance of the quenching oil and the uniformity of the structure were tested. The results showed that the workpiece hardness was the best when the rapid quenching oil was used. The difference in core / surface hardness and the content of retained austenite were both reduced compared with that of oil cooling alone.

[0115] Table 10 Comparison of Quenching Oil Performance

[0116] Table 11 Tissue homogeneity test

[0117] S53, in the third stage, 0.4-0.6MPa compressed air is introduced for air cooling to room temperature.

[0118] Table 12 Residual Stress Detection

[0119] The above test data shows that PAG solution spraying (8-12%) reduces deformation by 60% compared to pure water cooling, optimizes the vapor film stage, and achieves rapid and uniform cooling; rapid quenching oil (≥80℃ / s) increases hardness by 3-5 HRC compared to ordinary quenching oil, can accurately control the martensitic phase transformation rate, and reduce the risk of cracking; compressed air cooling saves 30% of subsequent cleaning costs compared to oil cooling, indicating that it can eliminate residual stress and avoid oil contamination.

[0120] In step S4, the induction heating uses a contoured induction coil. The gap between the induction coil and the surface of the support roller is 1.5-2.0 mm, and the copper tube of the induction coil has an integrated circulating cooling water channel.

[0121] The PAG polymer aqueous solution in the first stage of step S5 contains rust inhibitors and defoamers. Its cooling rate in the high-temperature zone above 300℃ is ≥120℃ / s, and its cooling rate in the low-temperature zone below 200℃ is ≤20℃ / s.

[0122] The kinematic viscosity of the rapid quenching oil in the second stage of step S5 is 12-15 cSt (40℃), and the flash point is ≥180℃.

[0123] The mass percentage of PAG polymer aqueous solution is 8%-12%.

[0124] The rust inhibitor is 0.15%-0.25% benzotriazole (BTA) by mass, and the defoamer is 0.05%-0.10% polydimethylsiloxane (PDMS) by mass.

[0125] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A medium-frequency heat treatment process for support rollers, characterized in that, Includes the following steps: S1, stress-relieving annealing pretreatment is performed on the support roller, and the support roller is a φ220mm support roller made of 40CrMnMo material; S2, The support roller is grasped by a vision positioning robot and placed on a rotary quenching platform with a positioning accuracy of ≤0.1mm; Step S2 specifically includes the following steps: S21, 3D vision scanning and positioning: The support roller is conveyed to the scanning station by the feeding conveyor line. The high-precision 3D vision system quickly scans the surface of the workpiece and calculates the center coordinates and tilt angle of the support roller through the point cloud matching algorithm to determine the optimal gripping point. The positioning accuracy reaches ±0.05mm. S22, a robotic arm with adaptive grasping, is a six-axis collaborative robotic arm that plans a collision-free path based on coordinate data provided by the vision system and moves smoothly to the grasping point with an acceleration of 0.3G. The end pneumatic gripper stably grasps the support roller with a contact pressure of 15±2N, and the built-in force sensor provides real-time feedback to ensure damage-free gripping. S23, high-precision placement and calibration: the robot arm moves the support roller to the rotary quenching platform. After coarse positioning by the end camera, 8 sets of ring array laser displacement sensors synchronously detect the workpiece position. The system calculates the position deviation in real time and dynamically adjusts it until the positioning error between the support roller and the platform is ≤0.1mm, and then triggers vacuum adsorption fixation. S24, closed-loop verification and anomaly handling: the laser sensor re-inspects the radial runout of the support roller. After confirming that the positioning accuracy meets the standard, it enters the quenching process. If the detection exceeds the tolerance, the vacuum is immediately released and the machine is re-grabbed. If it fails 3 times in a row, an alarm is triggered and the machine is stopped to ensure the reliability of the process. The whole process takes ≤4 seconds and the positioning repeatability reaches 0.07mm. S3, System settings for medium-frequency induction heating; S4, variable power medium frequency induction heating of the support roller is performed through the induction coil; Step S4 specifically includes the following steps: S41, Preheating stage: Use a medium frequency power supply at a frequency of 1-3kHz to heat the support roller to 480-500℃ with a power density of 0.8-1.2 kW / cm², and hold for 18-22 seconds; S42, austenitizing stage: switch to 0.5-1kHz frequency, heat to 865-875℃ with a power density of 1.5-2.0 kW / cm², and hold for 85-95s; S5, gradient composite cooling of the support roller after induction heating; S51, the first stage involves spraying an 8-12% PAG polymer aqueous solution onto the heated support roller for 18-22 seconds. S52, the second stage spray cooling rate ≥80℃ / s rapid quenching oil, spray for 25-30s; S53, in the third stage, 0.4-0.6MPa compressed air is introduced for air cooling to room temperature.

2. The medium-frequency heat treatment process for a support roller as described in claim 1, characterized in that, In step S4, the induction heating uses a contoured induction coil. The gap between the induction coil and the surface of the support roller is 1.5-2.0 mm, and the copper tube of the induction coil has an integrated circulating cooling water channel.

3. The medium-frequency heat treatment process for a support roller as described in claim 1, characterized in that, In step S4, the heating process uses a dual-color infrared thermometer to monitor the temperature in real time. When the monitored temperature deviates from the set value by ±5℃, the PID algorithm is triggered to dynamically adjust the power density and maintain the temperature fluctuation ≤ ±5℃.

4. The medium-frequency heat treatment process for a support roller as described in claim 1, characterized in that, The PAG polymer aqueous solution in the first stage of step S5 contains rust inhibitors and defoamers, and its cooling rate in the high-temperature zone above 300℃ is ≥120℃ / s, and its cooling rate in the low-temperature zone below 200℃ is ≤20℃ / s.

5. The medium-frequency heat treatment process for a support roller as described in claim 1, characterized in that, The rotary quenching platform rotates at a speed of 10-15 rpm and remains rotating throughout the heating and cooling stages.

6. The medium-frequency heat treatment process for a support roller as described in claim 1, characterized in that, The heating rate during the austenitization stage in S4 is controlled at ≤25℃ / s, and the heating rate is automatically reduced when the temperature difference between the surface and the core of the support roller is >50℃.

7. The medium-frequency heat treatment process for a support roller as described in claim 1, characterized in that, In step S5, the kinematic viscosity of the rapid quenching oil at 40°C in the second stage is 12-15 cSt, and the flash point is ≥180°C.

8. The medium-frequency heat treatment process for a support roller as described in claim 4, characterized in that, The rust inhibitor is 0.15%-0.25% benzotriazole (BTA) by mass, and the defoamer is 0.05%-0.10% polydimethylsiloxane (PDMS) by mass.