System and method for optimizing heat treatment process of large gear of rotary kiln

Abstract

The invention belongs to the technical field of gear heat treatment, and discloses a rotary kiln large gear heat treatment process optimization system and method. The method comprises the following steps: carrying out normalizing forging on a pre-selected material twice to obtain a grain-refined pre-selected material, processing the grain-refined pre-selected material to obtain a gear, and carrying out vacuum nitriding treatment on the naturally cooled gear to obtain a first gear; carrying out gradient quenching treatment on the first gear to obtain a second gear; the second gear is subjected to carburizing treatment and isothermal tempering treatment, and a third gear is obtained; presetting a scanning range, a scanning step length and a scanning speed, and collecting an X-ray diffraction pattern, neutron diffraction data and an eddy current signal on the surface of the third gear; stress can be effectively eliminated, tempering and other process parameters are dynamically adjusted, the whole heat treatment process is in an accurate and controllable state, and gear performance is comprehensively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of gear heat treatment, and more specifically, to an optimization system and method for the heat treatment process of large gears in rotary kilns. Background Art

[0002] In the traditional gear heat treatment process during carburizing heat treatment, it is difficult to effectively control the deformation of gears, which directly affects the accuracy, strength, noise, and service life of gears. Even if a gear grinding process is added after carburizing, the deformation will still reduce the accuracy grade of the gears. There are many factors affecting the deformation during carburizing heat treatment, including metallurgical factors of gear materials, preliminary heat treatment, carburizing process, and quenching. Moreover, the traditional process has relatively single means for stress elimination and lacks a real-time detection and feedback mechanism to optimize process parameters, making it difficult to meet the requirements of modern industry for high-precision and high-performance large gears.

[0003] Chinese patent application with publication number CN116162782A discloses a heat treatment processing technology for escape wheels used in mechanical watches: Step 1, heat the gear to 750 ± 10 °C and hold for 2 - 3 h; then continue to heat to 930 ± 10 °C and hold for 4 - 5 h; Step 2, cool the gear to AC3 - 10 °C and hold for 4 - 5 h; Step 3, cool the gear to AC1 - 10 °C and hold for 5 - 6 h; Step 4, quickly cool the gear to BS - 10 °C and hold for 1 - 2 h; Step 5, quickly heat the gear to AC1 - 10 °C and hold for 5 - 6 h; Step 6, air-cool the gear to 650 ± 10 °C and hold for 4 - 5 h; Step 7, quickly cool the gear to 400 ± 10 °C, then slowly cool to 200 °C, and take it out of the furnace and air-cool to room temperature. This invention heats up to 930 ± 10 °C in stages and holds to make the austenite grains of the gear forging blank completely equiaxed after recrystallization of the structure, completely cutting off the tissue heredity and basically eliminating the processing stress generated during forging.

[0004] Although the above method can meet most scenarios, through research and practical application of the above method and the existing technology, it is found that the above method and the existing technology have at least the following partial defects:

[0005] The pertinence of stress elimination is insufficient, and the elimination means are single; there is a lack of a real-time detection and feedback mechanism to optimize process parameters.

[0006] In view of this, the present invention proposes an optimization system and method for the heat treatment process of large gears in rotary kilns to solve the above problems. Summary of the Invention

[0007] In order to overcome the above defects of the prior art and to achieve the above object, the present invention provides the following technical solution: An optimization method for the heat treatment process of large gears in rotary kilns, including the following steps:

[0008] The preselected material is subjected to normalizing forging twice to obtain a preselected material with refined grains. The preselected material with refined grains is processed to obtain a gear. The gear after natural cooling is subjected to vacuum nitriding treatment to obtain a first gear;

[0009] The first gear is subjected to gradient quenching treatment to obtain a second gear;

[0010] The second gear is subjected to carburizing treatment and isothermal quenching treatment to obtain a third gear;

[0011] A preset scanning range, scanning step size and scanning speed are set, and the X-ray diffraction pattern, neutron diffraction data and eddy current signal on the surface of the third gear are collected;

[0012] Feature extraction is performed on the X-ray diffraction pattern, neutron diffraction data and eddy current signal to obtain X-ray diffraction features, neutron diffraction features and eddy current features; the X-ray diffraction features, neutron diffraction features and eddy current features are spliced to obtain a feature vector;

[0013] The feature vector is used as the input of the parameter prediction model to obtain the tempering temperature and tempering time. The third gear is subjected to isothermal tempering treatment according to the obtained tempering temperature and tempering time to obtain a fourth gear;

[0014] The fourth gear is strengthened by a multi-field coupling stress elimination process to obtain a fifth gear;

[0015] The tooth profile data of the fifth gear is collected, and the fifth gear is finish-machined by a deformation compensation cutting strategy to obtain a large rotary kiln gear.

[0016] Further, the method for obtaining the third gear includes:

[0017] The second gear is placed in a carburizing furnace and heated to 920 - 940 °C at a rate of 10 - 15 °C / min, and then held for carburizing for 4 - 6 h; during the holding for carburizing, the carbon content in the carburizing furnace is 1.0% - 1.2%. After the holding for carburizing is completed, the carburizing furnace is opened, and the second gear is transferred to an isothermal quenching furnace at 280 - 350 °C for isothermal salt bath within 8 - 10 s and held for 2 h; after the holding is completed, the second gear is taken out and naturally cooled to room temperature to obtain the third gear.

[0018] Further, the method for obtaining the X-ray diffraction features includes:

[0019] The position of each diffraction peak, the intensity value corresponding to the highest point of each diffraction peak, and the full width at half maximum of each diffraction peak are extracted from the X-ray diffraction pattern, that is, the diffraction peak width corresponding to half of the intensity value corresponding to the highest point of the diffraction peak; the position of the diffraction peak corresponds to the diffraction angle of At a position, calculate the intensity ratio of adjacent diffraction peaks to obtain the peak intensity ratio; calculate the grain size of the third gear through the Scherrer formula; calculate the residual stress corresponding to different azimuth angles; splice the peak intensity ratio, grain size, and residual stress as the X-ray diffraction characteristics.

[0020] Furthermore, the method for obtaining neutron diffraction characteristics includes:

[0021] Extract the diffraction peak displacements of a preset crystal plane at different depths from the neutron diffraction data, calculate to obtain the lattice strain; calculate the internal stress according to Hooke's law; splice the lattice strain and internal stress as the neutron diffraction characteristics;

[0022] The method for obtaining eddy current characteristics includes:

[0023] Obtain the current in the eddy current signal, as well as the current corresponding to the eddy current signal with changes in phase and amplitude, calculate the crack depth; calculate the crack size; splice the crack depth and crack size as the eddy current characteristics.

[0024] Furthermore, the method for obtaining the fourth gear includes:

[0025] Put the third gear into a heating furnace, raise the furnace temperature of the heating furnace to the tempering temperature at a heating rate of 5 - 10 °C / min and hold for the corresponding tempering time, take out the third gear from the heating furnace, and naturally cool it to room temperature in the air to obtain the fourth gear.

[0026] Furthermore, the method for obtaining the second gear includes:

[0027] Place the first gear in a quenching furnace, raise the furnace temperature of the quenching furnace to 860 °C at a rate of 10 - 15 °C / min and hold for 1.5 - 2 h. After the holding is completed, transfer the first gear to a quenching tank filled with polymer quenching liquid within 5 - 10 s; adjust the flow rate of the circulation pump of the quenching tank filled with polymer quenching liquid to 600 - 800 L / min, adjust the flow rate of the polymer quenching liquid so that the cooling rate of the first gear is 80 - 100 °C / s; until the temperature of the first gear drops to 495 - 550 °C, transfer the first gear to a quenching tank filled with water-based coolant within 3 - 5 s; adjust the flow rate of the circulation pump of the quenching tank filled with water-based coolant to 300 - 500 L / min, adjust the flow rate of the water-based coolant so that the cooling rate of the first gear is 30 - 50 °C / s until the temperature of the first gear drops to 190 - 210 °C to obtain the second gear.

[0028] Furthermore, the method for obtaining the fifth gear includes:

[0029] Step 1: Demagnetize the fourth gear with a pulsed electromagnetic field having a frequency of 1 kHz and a magnetic field strength of 1.5 T for 5 min;

[0030] Step 2: Perform impact treatment on the root fillet of the fourth gear for 10 minutes using high-frequency ultrasonic waves with a frequency of 20 kHz and an amplitude of 80 μm, and set the impact energy density to 15 J / cm²; simultaneously apply an alternating circular magnetic field with a frequency of 50 Hz and a magnetic field strength of 0.8 T.

[0031] Step 3: Perform impact treatment on the fourth gear for 5 minutes using a Nd:YAG laser with a wavelength of 1064 nm and an energy density of 10 J / cm² to obtain the fifth gear.

[0032] Furthermore, the method for obtaining a large rotary kiln gear includes:

[0033] Use a laser scanning probe to measure the tooth profile of the fifth gear. The probe scans along the tooth profile of the fifth gear to obtain the tooth profile data of the fifth gear. Compare the tooth profile data of the fifth gear with the pre-designed tooth profile data, calculate the tooth profile error data, and based on the plasma-assisted cutting method, perform finish machining on the fifth gear according to the tooth profile error data. During the finish machining process, at preset time intervals, use the laser scanning probe to scan and measure the tooth profile of the fifth gear being machined, compare the measured tooth profile data of the fifth gear with the pre-designed tooth profile data, and calculate the tooth profile error compensation data.

[0034] Furthermore, the method for performing finish machining on the fifth gear based on the plasma-assisted cutting method according to the tooth profile error data includes:

[0035] Mix Ar and H₂ in a ratio of 5:1 - 10:1 to obtain a mixed gas. Introduce the mixed gas into a plasma generator, and the plasma generator ionizes the mixed gas to generate plasma. Adjust the plasma generator to make the temperature of the plasma 110 - 130 °C, and inject the plasma into the cutting area at an injection pressure of 0.12 MPa; control the cutting tool to perform cutting on the fifth gear according to the tooth profile error data at a preset cutting speed, preset feed rate, preset cutting depth, preset rake angle, preset clearance angle, and preset edge radius.

[0036] The method for obtaining the tooth profile error compensation data includes:

[0037] Take the heat treatment process parameters and machining process parameters as the input of the deformation compensation model to obtain the tooth profile error data. Calculate the difference between the tooth profile error data and the actually measured tooth profile error data, and take the difference as the tooth profile error compensation data. Compensate the tooth profile of the fifth gear according to the tooth profile error compensation data; the heat treatment process parameters include the heating rate, furnace temperature, and holding time during the gear heat treatment process; the machining process parameters include the plasma mixing ratio, temperature, injection pressure, cutting speed, feed rate, cutting depth, and the rake angle, clearance angle, and edge radius of the cutting tool.

[0038] Furthermore, the method for obtaining the preselected material with refined grains includes:

[0039] Put the preselected material into a heating furnace, raise the furnace temperature of the heating furnace to 890 °C at a heating rate of 5 - 10 °C / min and then hold for 4 h, take out the preselected material from the heating furnace, and naturally cool it to room temperature in the air; then put the preselected material into the heating furnace again, raise the furnace temperature of the heating furnace to 850 °C at a heating rate of 5 - 10 °C / min and then hold for 3 h, take out the preselected material from the heating furnace, and naturally cool it to room temperature in the air to obtain the preselected material with refined grains.

[0040] Furthermore, the method for obtaining the first gear includes:

[0041] Put the gear after natural cooling into a vacuum furnace with a pressure of 10 - 100 Pa, introduce nitrogen into the vacuum furnace until the pressure in the vacuum furnace reaches 500 - 1000 Pa, raise the furnace temperature of the heating furnace to 520 °C at a heating rate of 5 - 10 °C / min and then hold for 8 h. After the holding is completed, wait for the furnace temperature of the heating furnace to drop to room temperature, close the introduced nitrogen, and take out the gear in the heating furnace to obtain the first gear.

[0042] The heat treatment process optimization system for the large-scale gear of a rotary kiln, implementing the heat treatment process optimization method for the large-scale gear of a rotary kiln, includes:

[0043] Material pretreatment module: Perform two normalizing forging operations on the preselected material to obtain the preselected material with refined grains, process the preselected material with refined grains to obtain a gear, place the gear in the air for natural cooling, and perform vacuum nitriding treatment on the gear after natural cooling to obtain the first gear;

[0044] Heat treatment module: Perform gradient quenching treatment on the first gear to obtain the second gear; perform carburizing treatment and isothermal quenching treatment on the second gear to obtain the third gear;

[0045] Detection and optimization module: Preset the scanning range, scanning step size, and scanning speed, collect the X-ray diffraction pattern, neutron diffraction data, and eddy current signal on the surface of the third gear; perform feature extraction on the X-ray diffraction pattern, neutron diffraction data, and eddy current signal to obtain X-ray diffraction features, neutron diffraction features, and eddy current features; splice the X-ray diffraction features, neutron diffraction features, and eddy current features to obtain a feature vector; use the feature vector as the input of the parameter prediction model to obtain the tempering temperature and tempering time, and perform isothermal tempering treatment on the third gear according to the obtained tempering temperature and tempering time to obtain the fourth gear;

[0046] Post-treatment module: Perform strengthening treatment on the fourth gear through a multi-field coupling stress elimination process to obtain the fifth gear;

[0047] Finishing module: Collect the tooth profile data of the fifth gear, and perform finishing on the fifth gear through a deformation compensation cutting strategy to obtain a large rotary kiln gear.

[0048] Technical effects and advantages of the heat treatment process optimization system and method for the large rotary kiln gear of the present invention:

[0049] Through the collaborative action of multiple processes, the present invention significantly improves the performance of the large rotary kiln gear; by normalizing and forging twice, the grains of the gear are refined, strengthening the material basis of the gear; through vacuum nitriding, gradient quenching and carburizing treatment, the wear resistance and toughness of the gear are improved; based on the precise regulation of tempering parameters based on multi-modal detection data, stress is effectively eliminated; through the collection of multi-source data such as X-ray diffraction patterns, after feature extraction and model operation, a real-time detection and feedback mechanism is constructed to dynamically adjust process parameters such as tempering, making the process fully accurately controllable and comprehensively improving the gear performance; also through multi-field coupling stress elimination and deformation compensation finishing, the dimensional accuracy and fatigue life are further improved, meeting the requirements of the complex working conditions of the rotary kiln. Brief Description of the Drawings

[0050] Figure 1 It is a schematic flow chart of the heat treatment process optimization method for the large rotary kiln gear of the present invention;

[0051] Figure 2 It is the X-ray diffraction pattern of the third gear of the present invention;

[0052] Figure 3 It is a schematic flow chart of the method for obtaining the fifth gear of the present invention;

[0053] Figure 4 It is a block diagram of the heat treatment process optimization system for the large rotary kiln gear of the present invention;

[0054] Figure 5 It is a schematic diagram of the interface of the heat treatment process optimization system for the large rotary kiln gear of the present invention. Detailed Embodiments

[0055] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0056] Embodiment 1

[0057] Please refer to Figure 1 As shown, the heat treatment process optimization method for the large rotary kiln gear in this embodiment includes the following steps:

[0058] The preselected material is subjected to two normalizing forging operations to obtain a preselected material with refined grains. The preselected material with refined grains is processed to obtain a gear. The gear after natural cooling is subjected to vacuum nitriding treatment to obtain the first gear. The natural cooling process of the gear is relatively slow, which can enable the internal structure of the gear to transform uniformly, avoiding thermal stress generated by rapid cooling. During the cooling process, the atoms inside the preselected material have sufficient time to rearrange, further eliminating the residual stress remaining in the previous processing and heat treatment processes, making the internal stress distribution of the gear more uniform.

[0059] The method for obtaining the preselected material with refined grains includes:

[0060] Put the preselected material into a heating furnace, raise the furnace temperature of the heating furnace to 890 °C at a heating rate of 5 - 10 °C / min and hold for 4 h, take out the preselected material from the heating furnace, and naturally cool it to room temperature in the air; then put the preselected material into the heating furnace again, raise the furnace temperature of the heating furnace to 850 °C at a heating rate of 5 - 10 °C / min and hold for 3 h, take out the preselected material from the heating furnace, and naturally cool it to room temperature in the air to obtain the preselected material with refined grains; during the process of subjecting the preselected material to two normalizing forging operations, plastic deformation occurs in the metal, which can eliminate the residual stress formed inside the original preselected material due to casting, etc. During normalizing forging, rapid heating and cooling cause recrystallization of the internal structure of the preselected material, further eliminating the stress generated by forging, refining the grains, laying a good tissue foundation for subsequent processing, and reducing the possibility of generating new stress during subsequent processing.

[0061] The method for obtaining the first gear includes:

[0062] Put the gear after natural cooling into a vacuum furnace with a pressure of 10 - 100 Pa, introduce nitrogen into the vacuum furnace until the pressure inside the vacuum furnace reaches 500 - 1000 Pa, raise the furnace temperature of the heating furnace to 520 °C at a heating rate of 5 - 10 °C / min and hold for 8 h. After the holding is completed, wait for the furnace temperature of the heating furnace to drop to room temperature, close the introduced nitrogen, and take out the gear in the heating furnace to obtain the first gear. The vacuum environment reduces adverse factors such as oxidation. During the nitriding process, nitrogen atoms diffuse into the gear surface, forming a nitrided layer, which generates compressive stress on the gear surface, offsetting part of the internal tensile stress to a certain extent, and can improve the fatigue strength and stress corrosion resistance of the gear; nitriding the tooth surface of the gear can also form a high-hardness diffusion layer on the surface of the gear, providing a substrate for subsequent laser composite strengthening.

[0063] The first gear is subjected to gradient quenching treatment to obtain the second gear;

[0064] The method for obtaining the second gear includes:

[0065] Place the first gear in a quenching furnace. Raise the furnace temperature of the quenching furnace to 860 °C at a rate of 10 - 15 °C / min and hold for 1.5 - 2 h. After the holding is completed, transfer the first gear to a quenching tank filled with polymer quenching liquid within 5 - 10 s; adjust the flow rate of the circulation pump of the quenching tank filled with polymer quenching liquid to 600 - 800 L / min, and adjust the flow rate of the polymer quenching liquid so that the cooling rate of the first gear is 80 - 100 °C / s; until the temperature of the first gear drops to 495 - 550 °C, transfer the first gear to a quenching tank filled with water-based coolant within 3 - 5 s; adjust the flow rate of the circulation pump of the quenching tank filled with water-based coolant to 300 - 500 L / min, and adjust the flow rate of the water-based coolant so that the cooling rate of the first gear is 30 - 50 °C / s until the temperature of the first gear drops to 190 - 210 °C to obtain the second gear. Gradient quenching enables different parts of the gear to obtain different cooling rates, forming a hardened layer with a certain depth on the surface while maintaining good toughness inside. The formation of the hardened layer generates compressive stress on the surface, which can effectively offset part of the working stress and improve the load-bearing capacity of the gear. At the same time, by controlling the quenching process parameters, excessive quenching stress caused by too fast quenching cooling rate can be avoided, preventing the gear from deforming or cracking.

[0066] Carry out carburizing treatment and austempering treatment on the second gear to obtain the third gear;

[0067] The method for obtaining the third gear includes:

[0068] Put the second gear into a carburizing furnace, raise the temperature to 920 - 940 °C at a rate of 10 - 15 °C / min, and then hold for carburizing for 4 - 6 h; during the holding for carburizing, the carbon content in the carburizing furnace is 1.0% - 1.2%. After the holding for carburizing is completed, open the carburizing furnace and transfer the second gear to an austempering furnace at 280 - 350 °C for austempering salt bath within 8 - 10 s and hold for 2 h; after the holding is completed, take out the second gear and let it cool naturally to room temperature to obtain the third gear. Carburizing treatment increases the carbon content on the gear surface. During subsequent quenching and tempering processes, compressive stress is formed on the surface, improving the wear resistance and fatigue strength of the tooth surface. Austempering is maintained at a certain temperature for a period of time to fully transform the quenched structure, further eliminate the quenching stress, stabilize the structure, and improve the dimensional stability of the gear.

[0069] Preset the scanning range, scanning step size, and scanning speed, and collect the X-ray diffraction pattern, neutron diffraction data, and eddy current signal on the surface of the third gear; the X-ray diffraction pattern can be collected by a high-precision XRD device, specifically referring to Figure 2; Neutron diffraction data can be obtained by contacting a professional institution equipped with neutron diffraction experimental equipment, transporting the gear sample to the experimental site, and installing it in the neutron beam irradiation area for acquisition according to the standard process; Eddy current signals can be obtained by using a high-resolution eddy current array detection device; These data reflect information such as the internal organizational structure and residual stress of the gear. By analyzing the X-ray diffraction pattern, neutron diffraction data, and eddy current signals, information such as the grain size and lattice distortion of the gear can be obtained, and then the subsequent tempering and other process parameters can be optimized, such as determining more appropriate tempering temperature and time, to improve the performance and quality of the gear.

[0070] Feature extraction is performed on the X-ray diffraction pattern, neutron diffraction data, and eddy current signals to obtain X-ray diffraction features, neutron diffraction features, and eddy current features; The X-ray diffraction features, neutron diffraction features, and eddy current features are spliced to obtain a feature vector; The feature vector integrates information obtained by multiple detection methods and covers various features such as the organizational structure and residual stress of the gear. Using this as the input provides a rich data basis for constructing an accurate parameter prediction model, enabling the model to more accurately predict process parameters such as tempering temperature and time, thereby optimizing the heat treatment process of the gear and improving the gear performance.

[0071] The methods for obtaining X-ray diffraction features include:

[0072] The position of each diffraction peak, the intensity value corresponding to the highest point of each diffraction peak, and the full width at half maximum of each diffraction peak are extracted from the X-ray diffraction pattern, that is, the diffraction peak width corresponding to half of the intensity value corresponding to the highest point of the diffraction peak; The position of the diffraction peak corresponds to the diffraction angle of the position, calculate the intensity ratio of adjacent diffraction peaks to obtain the peak intensity ratio; The grain size of the third gear is calculated by the Scherrer formula ; Among them, is the Scherrer constant, generally taken as 0.89; is the X-ray wavelength; is the full width at half maximum; is the diffraction angle, that is, the angle between the incident X-ray and the crystal plane; Calculate the residual stress corresponding to different azimuth angles ; Among them, is the elastic modulus; is the Poisson's ratio; is the azimuth angle; The peak intensity ratio, grain size, and residual stress are spliced as the X-ray diffraction features.

[0073] The methods for obtaining neutron diffraction features include:

[0074] Extract the diffraction peak displacement of the preset crystal plane at different depths from the neutron diffraction data and calculate the lattice strain ; Among them, is the diffraction peak displacement; is the diffraction angle in the stress-free state; the internal stress is calculated according to Hooke's law ; The lattice strain and the internal stress are spliced as the neutron diffraction characteristics.

[0075] The methods for obtaining eddy current characteristics include:

[0076] Obtain the current in the eddy current signal , and the current corresponding to the eddy current signal whose phase and amplitude change , calculate the crack depth ; where and are calibration coefficients obtained by experimental fitting; calculate the crack size ; where is the material resistivity; is the excitation frequency; is the vacuum permeability; is the relative permeability; the crack depth and the crack size are spliced as the eddy current characteristics.

[0077] Taking the eigenvector as the input of the parameter prediction model, the tempering temperature and the tempering time are obtained. According to the obtained tempering temperature and tempering time, the third gear is subjected to isothermal tempering treatment to obtain the fourth gear. Isothermal tempering according to the tempering temperature and time obtained from the parameter prediction model can more accurately eliminate the internal residual stress of the gear and make the structure more stable. By precisely controlling the tempering process, the internal stress distribution of the gear can be effectively adjusted, the residual stress can be reduced to an appropriate level, and the fatigue life and dimensional stability of the gear can be improved; the parameter prediction model is calculated based on the multi-source data eigenvector, changing the traditional way of setting the tempering process parameters by experience, and realizing the precise optimization of the tempering process parameters. The tempering temperature and time determined according to the actual internal state of the gear can better meet the performance requirements of the gear and improve the scientificity and reliability of the heat treatment process.

[0078] The training method of the parameter prediction model includes:

[0079] Pre-collect Q groups of training data. The training data includes the eigenvector, as well as the tempering temperature and the tempering time corresponding to the eigenvector.

[0080] The parameter prediction model is trained using training data. The feature vector is used as the input of the parameter prediction model, and the tempering temperature and tempering time are used as the output of the parameter prediction model. The stochastic gradient descent method is adopted, and the weights and biases of the parameter prediction model are adjusted through the backpropagation algorithm to minimize the error between the prediction result and the actual result of the parameter prediction model; a loss function is set, and the loss function is the mean square error; when the value of the loss function reaches convergence, the training of the parameter prediction model is stopped, and the parameter prediction model corresponding to when the value of the loss function reaches convergence is used as the trained parameter prediction model.

[0081] The method for obtaining the fourth gear includes:

[0082] Put the third gear into a heating furnace, raise the furnace temperature of the heating furnace to the tempering temperature at a heating rate of 5 - 10 °C / min and hold for the corresponding tempering time, take out the third gear from the heating furnace, and naturally cool it to room temperature in the air to obtain the fourth gear.

[0083] The fourth gear is strengthened by a multi - energy - field coupling stress relief process to obtain the fifth gear; the multi - energy - field coupling stress relief process eliminates magnetostrictive stress through pulsed electromagnetic field demagnetization, and the high - frequency ultrasonic impact and alternating ring - shaped magnetic field act synergistically to induce dislocation slip and grain boundary migration, further eliminating residual stress, making the internal stress distribution of the gear more uniform, and greatly improving the fatigue strength and anti - deformation ability of the gear.

[0084] Refer to Figure 3 , the method for obtaining the fifth gear includes:

[0085] Step 1: Demagnetize the fourth gear for 5 min using a pulsed electromagnetic field with a frequency of 1 kHz and a magnetic field strength of 1.5 T;

[0086] Step 2: Impact the root fillet of the fourth gear with high - frequency ultrasound with a frequency of 20 kHz and an amplitude of 80 μm for 10 min, and set the impact energy density to 15 J / cm²; simultaneously apply an alternating ring - shaped magnetic field with a frequency of 50 Hz and a magnetic field strength of 0.8 T;

[0087] Step 3: Impact the fourth gear with a Nd:YAG laser with a wavelength of 1064 nm and an energy density of 10 J / cm² for 5 min to obtain the fifth gear.

[0088] Collect the tooth profile data of the fifth gear, and perform finish machining on the fifth gear through a deformation compensation cutting strategy to obtain a large rotary kiln gear. During the finish machining process of the deformation compensation cutting strategy, by optimizing the cutting parameters and adjusting the tool path, the additional stress generated by the cutting force is reduced. At the same time, the deformation that may occur during the previous heat treatment and machining processes is compensated, avoiding stress concentration caused by deformation, further improving the dimensional accuracy and surface quality of the gear, and making the stress distribution of the gear more uniform during operation; according to the collected tooth profile data, the cutting process parameters are adjusted in real time, such as cutting speed, feed rate, cutting depth, etc., as well as the selection of tools. Through the deformation compensation strategy, the machining accuracy of the gear can be precisely controlled, ensuring that the tooth profile, tooth direction and other parameters of the gear meet the design requirements, improving the transmission smoothness and load-bearing capacity of the gear, and optimizing the final link of the entire gear manufacturing process.

[0089] The method for obtaining a large rotary kiln gear includes:

[0090] Use a laser scanning probe to measure the tooth profile of the fifth gear. The probe scans along the tooth profile of the fifth gear to obtain the tooth profile data of the fifth gear. Compare the tooth profile data of the fifth gear with the pre-designed tooth profile data, calculate the tooth profile error data, and perform finish machining on the fifth gear based on the plasma-assisted cutting method according to the tooth profile error data. During the finish machining process, at preset time intervals (such as 100 ms), use a laser scanning probe to scan and measure the tooth profile of the fifth gear being machined once, compare the measured tooth profile data of the fifth gear with the pre-designed tooth profile data, and calculate the tooth profile error compensation data.

[0091] The method for performing finish machining on the fifth gear based on the plasma-assisted cutting method according to the tooth profile error data includes:

[0092] Mix Ar and H2 in a ratio of 5:1 - 10:1 to obtain a mixed gas. Introduce the mixed gas into a plasma generator, and the plasma generator ionizes the mixed gas (such as through a high-frequency electric field or a radio-frequency electric field, etc.) to generate plasma. Adjust the plasma generator so that the temperature of the plasma is 110 - 130 °C, and inject the plasma into the cutting area at an injection pressure of 0.12 MPa; control the cutting tool to cut the fifth gear according to the tooth profile error data at a preset cutting speed, preset feed rate, preset cutting depth, preset rake angle, preset clearance angle and preset edge radius; for example, the preset cutting speed is 120 m / min, the preset feed rate is 0.15 mm / r, the preset cutting depth is 0.5 mm, control the rake angle of the cutting tool to be 10°, the clearance angle to be 8°, and the edge radius to be 0.02 mm, and cut the fifth gear according to the tooth profile error data.

[0093] The method for obtaining the tooth profile error compensation data includes:

[0094] Take the heat treatment process parameters and machining process parameters as the inputs of the deformation compensation model, obtain the tooth profile error data, calculate the difference between the tooth profile error data and the actually measured tooth profile error data, take the difference as the tooth profile error compensation data, and perform compensation machining on the tooth profile of the fifth gear according to the tooth profile error compensation data; the heat treatment process parameters include the heating rate, furnace temperature, and holding time during the gear heat treatment; the machining process parameters include the plasma mixing ratio, temperature, injection pressure, cutting speed, feed rate, cutting depth, and the rake angle, clearance angle, and edge radius of the cutting tool.

[0095] The training method of the deformation compensation model includes:

[0096] Pre-collect M groups of deformation compensation data, where the deformation compensation data includes heat treatment process parameters, machining process parameters, and tooth profile error data.

[0097] Take the heat treatment process parameters and machining process parameters as the inputs of the deformation compensation model, take the corresponding tooth profile error data as the output of the deformation compensation model, continuously adjust the weights and biases of the model through the backpropagation algorithm to minimize the error between the predicted tooth profile error data of the deformation compensation model and the actual tooth profile error data; use the mean squared error as the loss function to train the deformation compensation model until the sum of the errors reaches convergence and stop training; take the deformation compensation model corresponding to when the sum of the errors reaches convergence as the trained deformation compensation model.

[0098] Based on the preparation processes of the above gears, prepare a large rotary kiln gear, and take the average value of the performance of the first gear - fifth gear during the preparation process. The specific test data can be referred to Table 1:

[0099] Table 1 Performance index data of different gears

[0100]

[0101] As can be seen from the above table:

[0102] For the first gear: The volume expansion of the nitrided layer of the first gear generates an initial compressive stress (-215.32 MPa), which can offset the peak tensile stress (such as up to 350 MPa for the third gear) that may be generated by subsequent gradient quenching and carburizing, reducing the risk of overall stress imbalance. If nitriding is omitted, the tensile stress after quenching of the second gear may rise from 287.45 MPa to over 350 MPa, increasing the cracking probability. Refining the grains (17.50 μm) enhances the toughness base of the material, making the stress distribution more uniform during subsequent heat treatment (such as gradient quenching), and avoiding stress concentration caused by coarse grains (when the grains of the traditional process are 50 - 60 μm, the stress gradient can reach over 200 MPa).

[0103] For the second gear: The surface martensite of the second gear (hardness 59.20 HRC) provides wear resistance, and the core bainite (impact toughness 47.50 J) retains impact resistance, achieving a balance between strength and toughness compared to traditional single-liquid quenching (fully martensite, toughness ≤ 35 J). The impact toughness is increased by 35.7%, enabling the gear to withstand the starting impact load of the rotary kiln (tooth root fracture is prone to occur in the traditional process). The surface tensile stress (287.45 MPa) is deliberately retained to reserve space for the subsequent superposition of compressive stress in the carburized layer (about 30% of the tensile stress can be offset after carburizing), avoiding the over-limit of a single process stress (such as directly generating 350 MPa tensile stress on the zero-stress substrate during carburizing, with higher risk).

[0104] For the third gear: After carburizing, the surface carbon content of the third gear reaches 1.1%, and the hardness after quenching is 61.85 HRC (traditional process ≈ 59 HRC), with the wear resistance increased by 20%, suitable for high-wear working conditions (such as gear meshing in the rotary kiln). Isothermal quenching reduces the amount of retained austenite (from 30% to 15%), and the dimensional stability is improved (the deformation amount is reduced by 30% compared to direct quenching). The peak tensile stress of 350 MPa generated by the martensite transformation in the carburized layer far exceeds the fatigue strength threshold of the material (≈ 250 MPa), and it must be eliminated through dynamic tempering (traditional fixed tempering can only be reduced to above 150 MPa, still higher than the safety threshold). If the third gear is directly used, the fatigue life is 72.6% lower than that of the fifth gear, proving that tempering is the "stress-saving link".

[0105] For the fourth gear: Through precise temperature (535.2 °C, 14.8 °C lower than the traditional 550 °C) and time (2.3 h, extended by 15%) during dynamic tempering, the tensile stress is reduced by 78.4% and transformed into a compressive stress-dominated state (75.50 MPa), offsetting the tensile stress of the working load (such as the tooth surface tensile stress ≈ 50 MPa during gear meshing). The compressive stress state extends the fatigue crack initiation time from 500 h (for the third gear) to 1200 h (for the fifth gear), verifying that "stress type determines life". Tempered martensite replaces quenched martensite, and the dispersion degree of carbides is improved (the grain size is calculated to be 15.50 μm by the Scherrer formula), increasing the impact toughness from 43.20 J (for the third gear) to 76.30 J, solving the "hard and brittle contradiction" of the traditional process.

[0106] For the fifth gear: Ultrasonic impact introduces a peak compressive stress layer of -300 MPa (depth 0.5 mm) at the tooth root, and laser shock superimposes a deep compressive stress (1 - 2 mm), making the surface comprehensive compressive stress reach -82.75 MPa. Traditional process stress elimination methods (such as shot peening and tempering) can usually only reach -30 to -50 MPa, greatly reducing the risk of tooth root bending fatigue. The fatigue life is increased from 0.78×10 7 cycles of the third gear to 2.85×10 7Next, directly prove that "stress optimization is the core driving force for life improvement". The stress equalization after dynamic tempering (gradient ≤ 50 MPa) provides a stable base for finish machining. Combined with laser scanning compensation (such as fine-tuning the cutting depth by 0.005 mm), the tooth profile error is reduced from 0.065 mm (for the third gear) to 0.0125 mm, reaching ISO Class 1 accuracy, avoiding the cyclic error of the traditional process of "heat treatment deformation - gear grinding correction - secondary stress".

[0107] Example 2

[0108] Please refer to Figure 4 as shown in the figure. The heat treatment process optimization system for large gears of a rotary kiln described in this example includes:

[0109] Material pretreatment module: The preselected material is subjected to two normalizing forging processes to obtain preselected material with refined grains. The preselected material with refined grains is processed to obtain gears, and the gears are placed in the air for natural cooling. The gears after natural cooling are subjected to vacuum nitriding treatment to obtain the first gear;

[0110] Heat treatment module: The first gear is subjected to gradient quenching treatment to obtain the second gear; the second gear is subjected to carburizing treatment and isothermal quenching treatment to obtain the third gear;

[0111] Detection and optimization module: The scanning range, scanning step size, and scanning speed are preset, and the X-ray diffraction pattern, neutron diffraction data, and eddy current signal on the surface of the third gear are collected; feature extraction is performed on the X-ray diffraction pattern, neutron diffraction data, and eddy current signal to obtain X-ray diffraction features, neutron diffraction features, and eddy current features; the X-ray diffraction features, neutron diffraction features, and eddy current features are spliced to obtain a feature vector; the feature vector is used as the input of the parameter prediction model to obtain the tempering temperature and tempering time, and the third gear is subjected to isothermal tempering treatment according to the obtained tempering temperature and tempering time to obtain the fourth gear;

[0112] Post-treatment module: The fourth gear is strengthened through a multi-field coupling stress elimination process to obtain the fifth gear;

[0113] Finish machining module: The tooth profile data of the fifth gear is collected, and the fifth gear is finish machined through a deformation compensation cutting strategy to obtain the large gear of the rotary kiln.

[0114] Refer to Figure 5 , the mixing ratio of Ar to H2 in the plasma is 7:1, the plasma temperature is set at 120 °C, and the injection pressure is 0.12 MPa. Real-time status monitoring shows that the current plasma status is normal, the temperature is 125 °C, the gas flow rate is 2.5 L / min, and the system pressure is the same as the injection pressure, which is 0.12 MPa. At the same time, the system prompts that the plasma parameters are in the optimal working range.

[0115] The current cutting parameters are set as follows: the cutting speed is 150 m / min, the feed rate is 0.2 mm / rev, the cutting depth is 2.5 mm, the rake angle is 15°, the clearance angle is 8°, and the edge radius is 0.8 mm. The system prompts that the current cutting depth is close to the warning value and it is recommended to adjust appropriately.

[0116] The current tooth profile error is 0.015 mm and the compensation effect reaches 85%.

[0117] The temperature change trend graph shows that from 8 am to around 2 pm, the temperature is basically stable near 120 °C with small fluctuations, and the system is in a relatively stable state.

[0118] As described above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the said claims.

[0119] Finally: The above is only the preferred embodiment of the present invention and is not used to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. Optimization method for heat treatment process of large gears in rotary kilns, characterized in that, The method includes the following steps: Subject the preselected material to normalizing forging twice to obtain a preselected material with refined grains, machine the preselected material with refined grains to obtain a gear, and perform vacuum nitriding treatment on the gear after natural cooling to obtain a first gear; Perform gradient quenching treatment on the first gear to obtain a second gear; Perform carburizing treatment and isothermal quenching treatment on the second gear to obtain a third gear; Preset the scanning range, scanning step size and scanning speed, and collect the X-ray diffraction pattern, neutron diffraction data and eddy current signal on the surface of the third gear; Extract features from the X-ray diffraction pattern, neutron diffraction data and eddy current signal to obtain X-ray diffraction features, neutron diffraction features and eddy current features; splice the X-ray diffraction features, neutron diffraction features and eddy current features to obtain a feature vector; Use the feature vector as the input of the parameter prediction model to obtain the tempering temperature and tempering time, and perform isothermal tempering treatment on the third gear according to the obtained tempering temperature and tempering time to obtain a fourth gear; Perform strengthening treatment on the fourth gear through a multi-field coupling stress elimination process to obtain a fifth gear; Collect the tooth profile data of the fifth gear, and perform finish machining on the fifth gear through a deformation compensation cutting strategy to obtain a large rotary kiln gear.

2. The optimization method for the heat treatment process of large gears of a rotary kiln according to claim 1, wherein The method for obtaining the third gear includes: Put the second gear into a carburizing furnace, heat it up to 920-940°C at a rate of 10-15°C / min, and keep it for carburizing for 4-6 hours; during the carburizing process, the carbon content in the carburizing furnace is 1.0%-1.2%. After the carburizing is completed, open the carburizing furnace, transfer the second gear to an isothermal quenching furnace at 280-350°C within 8-10 seconds for isothermal salt bath, and keep it for 2 hours; after the heat preservation is completed, take out the second gear and let it cool naturally to room temperature to obtain the third gear.

3. The optimization method for the heat treatment process of large gears of rotary kilns according to claim 1, characterized in that The method for obtaining the X-ray diffraction features includes: The position of each diffraction peak, the intensity value corresponding to the highest point of each diffraction peak, and the full width at half maximum of each diffraction peak, that is, the diffraction peak width corresponding to half of the intensity value corresponding to the highest point of the diffraction peak, are obtained by extraction from the X-ray diffraction pattern; the position of the diffraction peak corresponds to the diffraction angle of the position, the intensity ratio of adjacent diffraction peaks is calculated to obtain the peak intensity ratio; the grain size of the third gear is calculated by the Scherrer formula; the residual stress corresponding to different azimuth angles is calculated; the peak intensity ratio, the grain size, and the residual stress are spliced as the X-ray diffraction characteristics.

4. The optimization method for the heat treatment process of large gears of a rotary kiln according to claim 1, characterized in that, The method for obtaining the neutron diffraction features includes: Extract the diffraction peak displacements of preset crystal planes at different depths from the neutron diffraction data, calculate to obtain the lattice strain; calculate the internal stress according to Hooke's law; splice the lattice strain and the internal stress as the neutron diffraction features; The method for obtaining the eddy current features includes: Obtain the current in the eddy current signal and the current corresponding to the eddy current signal with changed phase and amplitude, calculate the crack depth; calculate the crack size; splice the crack depth and the crack size as the eddy current features.

5. The optimized method for the heat treatment process of large gears of a rotary kiln according to claim 1, characterized in that, The method for obtaining the fourth gear includes: Put the third gear into a heating furnace, heat the furnace temperature of the heating furnace to the tempering temperature at a heating rate of 5-10°C / min and keep it for the corresponding tempering time, take out the third gear from the heating furnace, and let it cool naturally in the air to room temperature to obtain the fourth gear.

6. The optimized method for the heat treatment process of the large gear of the rotary kiln according to claim 1, characterized in that The method for obtaining the second gear includes: Place the first gear in a quenching furnace, raise the furnace temperature of the quenching furnace to 860°C at a rate of 10 - 15°C / min and hold for 1.5 - 2 h. After the holding is completed, transfer the first gear to a quenching tank filled with polymer quenching liquid within 5 - 10 s; adjust the flow rate of the circulation pump of the quenching tank filled with polymer quenching liquid to 600 - 800 L / min, and adjust the flow rate of the polymer quenching liquid so that the cooling rate of the first gear is 80 - 100°C / s; until the temperature of the first gear drops to 495 - 550°C, transfer the first gear to a quenching tank filled with water-based coolant within 3 - 5 s; adjust the flow rate of the circulation pump of the quenching tank filled with water-based coolant to 300 - 500 L / min, and adjust the flow rate of the water-based coolant so that the cooling rate of the first gear is 30 - 50°C / s until the temperature of the first gear drops to 190 - 210°C to obtain the second gear.

7. The optimized method for the heat treatment process of the large gear of the rotary kiln according to claim 1, characterized in that The method for obtaining the fifth gear includes: Step 1: Demagnetize the fourth gear with a pulsed electromagnetic field having a frequency of 1 kHz and a magnetic field strength of 1.5 T for 5 min. Step 2: Impact the fillet of the tooth root of the fourth gear with high-frequency ultrasound having a frequency of 20 kHz and an amplitude of 80 μm for 10 min, and set the impact energy density to 15 J / cm²; synchronously apply an alternating circular magnetic field having a frequency of 50 Hz and a magnetic field strength of 0.8 T. Step 3: Impact the fourth gear with a Nd:YAG laser having a wavelength of 1064 nm and an energy density of 10 J / cm² for 5 min to obtain the fifth gear.

8. The optimization method for the heat treatment process of large gears of a rotary kiln according to claim 1, characterized in that, The method for obtaining a large gear of a rotary kiln includes: Use a laser scanning probe to measure the tooth profile of the fifth gear. The probe scans along the tooth profile of the fifth gear to obtain the tooth profile data of the fifth gear. Compare the tooth profile data of the fifth gear with the pre-designed tooth profile data, calculate to obtain the tooth profile error data, and perform finish machining on the fifth gear based on the plasma-assisted cutting method according to the tooth profile error data. During the finish machining process, at every preset time interval, scan and measure the tooth profile of the fifth gear being machined with a laser scanning probe, compare the measured tooth profile data of the fifth gear with the pre-designed tooth profile data, and calculate to obtain the tooth profile error compensation data.

9. The optimization method for the heat treatment process of large gears of rotary kilns according to claim 8, characterized in that The method for performing finish machining on the fifth gear based on the plasma-assisted cutting method according to the tooth profile error data includes: Mix Ar and H₂ in a ratio of 5:1 - 10:1 to obtain a mixed gas. Introduce the mixed gas into a plasma generator. The plasma generator ionizes the mixed gas to generate plasma. Adjust the plasma generator so that the temperature of the plasma is 110 - 130°C, and inject the plasma into the cutting area at an injection pressure of 0.12 MPa; control the cutting tool to perform cutting machining on the fifth gear according to the tooth profile error data at a preset cutting speed, preset feed rate, preset cutting depth, preset rake angle, preset clearance angle, and preset edge radius; The method for obtaining the tooth profile error compensation data includes: Taking the heat treatment process parameters and machining process parameters as the inputs of the deformation compensation model, obtaining the tooth profile error data, calculating the difference between the tooth profile error data and the actually measured tooth profile error data, taking the difference as the tooth profile error compensation data, and compensating and machining the tooth profile of the fifth gear according to the tooth profile error compensation data; the heat treatment process parameters include the heating rate, furnace temperature, and holding time during the gear heat treatment; the machining process parameters include the plasma mixing ratio, temperature, injection pressure, cutting speed, feed rate, cutting depth, as well as the rake angle, clearance angle, and edge radius of the cutting tool.

10. The optimization method for the heat treatment process of the large gear of the rotary kiln according to claim 1, characterized in that, The method for obtaining the preselected material with refined grains includes: Putting the preselected material into a heating furnace, raising the furnace temperature of the heating furnace to 890 °C at a heating rate of 5 - 10 °C / min and holding for 4 h, taking out the preselected material from the heating furnace, and naturally cooling it to room temperature in the air; then putting the preselected material into the heating furnace again, raising the furnace temperature of the heating furnace to 850 °C at a heating rate of 5 - 10 °C / min and holding for 3 h, taking out the preselected material from the heating furnace, and naturally cooling it to room temperature in the air to obtain the preselected material with refined grains.

11. The optimization method of the heat treatment process of the large gear of the rotary kiln according to claim 1, characterized in that, The method for obtaining the first gear includes: Putting the gear after natural cooling into a vacuum furnace with a pressure of 10 - 100 Pa, introducing nitrogen into the vacuum furnace until the pressure in the vacuum furnace reaches 500 - 1000 Pa, raising the furnace temperature of the heating furnace to 520 °C at a heating rate of 5 - 10 °C / min and holding for 8 h, after the holding is completed, waiting for the furnace temperature of the heating furnace to drop to room temperature, closing the introduced nitrogen, and taking out the gear in the heating furnace to obtain the first gear.

12. A heat treatment process optimization system for large gears of rotary kilns, which implements the heat treatment process optimization method for large gears of rotary kilns described in any one of claims 1-11, characterized in that, Including: Material pretreatment module: performing two normalizing forging operations on the preselected material to obtain the preselected material with refined grains, machining the preselected material with refined grains to obtain a gear, placing the gear in the air for natural cooling, and performing vacuum nitriding treatment on the gear after natural cooling to obtain the first gear; Heat treatment module: performing gradient quenching treatment on the first gear to obtain the second gear; Performing carburizing treatment and isothermal quenching treatment on the second gear to obtain the third gear; Detection and optimization module: presetting the scanning range, scanning step size, and scanning speed, collecting the X-ray diffraction pattern, neutron diffraction data, and eddy current signal on the surface of the third gear; performing feature extraction on the X-ray diffraction pattern, neutron diffraction data, and eddy current signal to obtain the X-ray diffraction feature, neutron diffraction feature, and eddy current feature; splicing the X-ray diffraction feature, neutron diffraction feature, and eddy current feature to obtain the feature vector; Taking the feature vector as the input of the parameter prediction model, obtaining the tempering temperature and tempering time, and performing isothermal tempering treatment on the third gear according to the obtained tempering temperature and tempering time to obtain the fourth gear; Post-treatment module: strengthening the fourth gear through a multi-field coupling stress elimination process to obtain the fifth gear; Finishing module: collecting the tooth profile data of the fifth gear, and performing finishing machining on the fifth gear through a deformation compensation cutting strategy to obtain the large rotary kiln gear.

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