A heat treatment process for austenitic stainless steel pipe

Abstract

The invention belongs to the technical field of heat treatment of stainless steel pipes, in particular to a heat treatment process of austenitic stainless steel pipes, S1, preheating the stainless steel pipe to 850°C to 1050°C within the phase change temperature range; S2, performing phase change induced plastic heat treatment, inducing austenite to transform into martensite by controlling the cooling rate at 20°C / s to 50°C / s, while maintaining a certain proportion of residual austenite; S3, using ultrasonic auxiliary heating with a frequency of 20kHz to 1MHz, and an ultrasonic power density of 0.1W / cm 2 ~1W / cm 2 ; S4. High-frequency induction heating is adopted with a frequency range of 20kHz to 500kHz. The pipe is evenly heated by the induction coil. The heating rate is controlled at 100℃ / min to 500℃ / min, and the heating temperature range is 900℃ to 1100℃; S5. The heat treatment process is carried out in a controllable environment, and the gas flow rate is adjusted at 5L / min to 50L / min; S6. An infrared temperature sensor is configured based on the Internet of Things, and the heating and insulation parameters are monitored in real time and dynamically adjusted through the big data analysis module.

Description

Technical Field

[0001] The invention belongs to the technical field of heat treatment of stainless steel pipes, in particular to a heat treatment process of an austenitic stainless steel pipe. Background Art

[0002] In the field of stainless steel material processing, austenitic stainless steel is widely used in chemical, petroleum, food processing and other industries due to its good corrosion resistance, weldability and mechanical properties. However, traditional heat treatment processes face many challenges when processing austenitic stainless steel pipes. These problems directly affect the final performance of the material and the service life of the product, while also restricting production efficiency and cost control.

[0003] Traditional heat treatment methods often find it difficult to achieve uniform distribution of heat energy, especially inside large-diameter or thick-walled stainless steel pipes, which easily produce obvious temperature differences between the inside and outside, resulting in inconsistent material properties after heat treatment, affecting its mechanical properties and service life. At the same time, there is a lack of effective means to control the transformation process of austenite to martensite, as well as the proportion of residual austenite, which makes it often impossible for the material to achieve an ideal balance between strength and toughness, limiting the applicability of stainless steel pipes in certain special application fields. Summary of the invention

[0004] The object of the present invention is to provide a heat treatment process for an austenitic stainless steel pipe to solve the problems raised in the background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a heat treatment process for an austenitic stainless steel pipe, comprising the following steps:

[0006] S1. Preheating stage: Place the stainless steel pipe to be treated in a preheating furnace and gradually heat it to a suitable temperature within the phase change temperature range of 850°C to 1050°C. The specific temperature is pre-set according to the characteristics of the stainless steel material. The preheating process needs to be slow and uniform to avoid stress concentration caused by excessive temperature difference between the inside and outside of the material;

[0007] S2, transformation induced plasticity heat treatment (TRIP): After preheating, cooling control is used to control the cooling process at a cooling rate of 20°C / s to 50°C / s to induce the transformation of austenite to martensite, and retain a certain proportion (e.g., 5% to 25%) of residual austenite to enhance the toughness of the material. In this step, in particular, after reaching a predetermined temperature (e.g., 950°C), the temperature is maintained for 2 minutes to optimize the phase transformation process;

[0008] S3, ultrasonic assisted heating: using a focused ultrasonic head, with the frequency set between 20kHz and 1MHz, and the power density maintained at 0.1W / cm² to 1W / cm², to ensure that the ultrasonic energy is concentrated at a depth of 1mm to 5mm below the surface of the pipe, promoting uniform distribution of heat energy inside and improving the uniformity of heat treatment;

[0009] S4, high-frequency induction heating: using high-frequency induction heating technology, the frequency is automatically adjusted in the range of 20kHz to 500kHz, the optimal frequency is calculated according to the pipe size and material, the heating rate is controlled at 100°C / min to 500°C / min, the temperature range is set at 900°C to 1100°C, the pipe is efficiently and evenly heated through the induction coil, and the heating unevenness is controlled within 5°C;

[0010] S5, controlled environment treatment: The entire heat treatment process is carried out in a vacuum environment or an environment filled with high-purity argon (≥99.99%), and the gas flow rate is adjusted at 5L / min~50L / min to prevent surface oxidation and decarburization. In addition, through the trace hydrogen addition system, PID control logic is adopted to automatically adjust the hydrogen concentration, promote grain refinement, and improve material properties;

[0011] S6, intelligent temperature control and data analysis: equipped with high-precision infrared temperature measurement sensors (accuracy ±2°C), combined with big data analysis modules, to achieve real-time monitoring and dynamic adjustment of heating and insulation parameters, temperature control accuracy reaches ±5°C, the system is optimized at least once a quarter, and the response time does not exceed 2 seconds to ensure temperature stability during heating and cooling stages;

[0012] S7, Adaptive Heat Treatment Control: The integrated adaptive control system includes multiple sensors and deep learning algorithms, which can automatically adjust the heating power, cooling rate, etc. within 10 seconds according to the real-time status of the workpiece, ensuring the temperature control accuracy of ±5°C, while controlling the stress within a safe range, improving the stability and consistency of the heat treatment process;

[0013] S8, microwave-assisted heating and quenching: A 2.45 GHz continuous wave microwave source is used to evenly distribute the microwave energy through an adjustable resonant cavity, heated to 1050°C, and then quickly transferred to a quenching liquid containing 15% vegetable oil. The cooling rate is controlled at 150°C / s to shorten the heat treatment cycle and optimize material properties. During the quenching stage, a biodegradable polymer-based quenching liquid is used, containing a polymer concentration of 5% to 10%, and corrosion inhibitors and lubricants are added. This not only ensures the environmental friendliness of the quenching process, but also effectively reduces quenching cracks, improves the uniformity of the hardened layer, and further improves the comprehensive performance of the material.

[0014] Compared with the prior art, the technical effects and advantages of the present invention are as follows:

[0015] This austenitic stainless steel pipe heat treatment process uses 20kHz to 1MHz ultrasonic assisted heating technology, especially after using a focused ultrasonic head, the energy is concentrated at a specific depth inside the pipe, which effectively promotes the uniform distribution of heat energy, reduces the common internal and external temperature difference problem in traditional heat treatment, and greatly improves the uniformity and efficiency of heat treatment. Combined with the automatic frequency adjustment function of high-frequency induction heating, it is optimized according to the pipe size and material characteristics, further enhancing the efficiency and uniformity of heating and reducing the heat treatment time;

[0016] Through transformation induced plasticity heat treatment (TRIP) combined with precise cooling rate control, not only the effective transformation of austenite to martensite is achieved, but also a good balance between strength and toughness is achieved by controlling the proportion of retained austenite. Combined with controlled environment treatment, especially the use of vacuum or high-purity inert gas, surface oxidation and decarburization are effectively suppressed, ensuring the optimization of material surface quality and internal structure;

[0017] Through strict control of the heat treatment environment, especially the use of vacuum or high-purity inert gas, and biodegradable polymer-based quenching liquid, not only the emission of harmful substances is effectively prevented, but also quenching cracks are reduced and the uniformity of the hardened layer is improved. These measures jointly promote the environmental protection and sustainability of the heat treatment process. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 The figure is a process flow chart of heat treatment of austenitic stainless steel pipe of the present invention. DETAILED DESCRIPTION

[0020] In the following description, a large number of specific details are provided to provide a more thorough understanding of the present invention. However, it is apparent to those skilled in the art that the present invention can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present invention, some technical features well known in the art are not described.

[0021] Unless otherwise defined, the up, down, left, right, front, back, inside and outside directions involved in this document are based on the up, down, left, right, front, back, inside and outside directions in the figures shown in the present invention, and are explained here together.

[0022] Provides such as Figure 1 The heat treatment process of an austenitic stainless steel pipe shown in the figure comprises the following steps:

[0023] S1. Preheat the stainless steel tube to a temperature within the phase change range of 850°C to 1050°C;

[0024] S2. Implementing transformation induced plasticity heat treatment (TRIP) to induce the transformation of austenite to martensite by controlling the cooling rate at 20°C / s to 50°C / s, while maintaining a certain proportion of retained austenite;

[0025] S3. Use ultrasonic auxiliary heating with a frequency of 20kHz to 1MHz to improve the uniformity of heat treatment, and the ultrasonic power density is 0.1W / cm² to 1W / cm²;

[0026] S4, using high-frequency induction heating, the frequency range is 20kHz ~ 500kHz, the pipe is evenly heated by the induction coil, the heating rate is controlled at 100 ° C / min ~ 500 ° C / min, the heating temperature range is 900 ° C ~ 1100 ° C, to ensure efficient heat transfer;

[0027] S5. The heat treatment process is carried out in a controlled environment. A vacuum environment or an inert gas (such as argon) with a purity of ≥99.99% is preferred. The gas flow rate is adjusted to 5L / min~50L / min to effectively prevent surface oxidation and decarburization.

[0028] S6. Configure infrared temperature sensors (accuracy ±2°C) based on the Internet of Things, monitor and dynamically adjust heating and insulation parameters in real time through the big data analysis module, achieve temperature control accuracy of ±5°C, and improve the consistency of heat treatment quality;

[0029] S7. Use adaptive heat treatment control system to adjust heat treatment parameters according to real-time monitoring of material status, such as temperature deviation not exceeding ±10°C;

[0030] S8. Finally, microwave-assisted heating is used to reach the quenching temperature, followed by immersion in a medium for quenching, and the medium cooling rate is controlled at 50°C / s to 200°C / s.

[0031] In this embodiment, the transformation induced plasticity heat treatment (TRIP) is also included in the heat preservation process, and the heat preservation time ranges from 1 minute to 5 minutes to optimize the phase transformation process.

[0032] In this embodiment, ultrasonic assisted heating uses a focused ultrasonic head to ensure that the energy is concentrated within a depth range of 1 mm to 5 mm below the surface of the pipe, thereby promoting uniform distribution of internal heat energy.

[0033] In this embodiment, the frequency of high-frequency induction heating is automatically adjusted within the range of 20kHz to 500kHz. The optimal frequency is calculated based on the diameter of the stainless steel pipe (range 5mm to 500mm), wall thickness and material composition, with each 10kHz as a level to achieve maximum heating efficiency and temperature uniformity, and the heating unevenness is less than 5°C.

[0034] In this embodiment, the trace hydrogen addition system in the controllable environment adopts the proportional, integral, and differential (PID) control logic to automatically adjust the hydrogen concentration according to the heating stage and the material properties of the stainless steel pipe, ensuring precise control of the hydrogen ratio within a specific time period, promoting austenite grain refinement, reducing the precipitation of grain boundary carbides, and improving the toughness and ductility of the material.

[0035] In this embodiment, combined with the real-time temperature feedback of the infrared temperature sensor, the PID parameters are adjusted to ensure that the response time is within 2 seconds, ensuring that the temperature fluctuation is controlled within ±3°C during the heating and cooling stages. At the same time, optimization is performed at least once a quarter based on historical data and new input data to continuously improve the control accuracy.

[0036] In this embodiment, the specific steps of transformation induced plasticity heat treatment (TRIP) include: first heating the stainless steel tube to 950°C and keeping it warm for 2 minutes, and then rapidly cooling it to 400°C by water mist spraying, with a cooling rate of 35°C / s. This process induces the transformation of austenite to martensite, and the residual austenite content is controlled at 10% to 30% to obtain an ideal balance between toughness and strength.

[0037] In this embodiment, the adaptive heat treatment control system includes temperature and stress real-time monitoring sensors and a decision module based on a deep learning algorithm. The system can adjust parameters such as heating power and cooling rate in real time according to the current state of the workpiece. The response time does not exceed 10 seconds, ensuring the stability of the heat treatment process, the temperature control accuracy of ±5°C, and the stress control within the allowable range of the material.

[0038] In this embodiment, microwave-assisted heating uses a continuous wave microwave source with a frequency of 2.45 GHz. Through an adjustable resonant cavity, the microwave energy is ensured to be evenly distributed. After heating to 1050°C, it is immediately put into a quenching liquid containing 15% vegetable oil. The cooling rate is controlled at 150°C / s, which effectively reduces the heat treatment time and ensures the comprehensive performance of the material.

[0039] In this embodiment, the medium in S8 is a biodegradable polymer-based quenching liquid containing 5% to 10% polymer concentration as well as corrosion inhibitors and lubricants, ensuring that no harmful substances are discharged during the quenching process, while reducing quenching cracks and improving the uniformity of the hardened layer.

[0040] In this embodiment, the big data analysis module in S6 is a system component with analysis function for real-time processing and analysis of massive sensor data, which are derived from various monitoring points of a heating furnace or similar temperature control system. Specifically, the functions and applications of the big data analysis module in this technical solution include:

[0041] (1) Data collection and integration: This module first collects real-time data from sources such as the furnace’s temperature sensor and environmental sensor through Internet of Things (IoT) devices, and then integrates this data into a unified data platform;

[0042] (2) Real-time monitoring: Using stream processing technology, the big data analysis module can conduct real-time analysis of the continuously incoming data stream and monitor the working status of the heating furnace in real time, including the current temperature, heating rate, stability during the insulation stage, etc.

[0043] (3) Dynamic parameter adjustment: Based on the preset algorithm model or machine learning model, the module can analyze historical data and real-time data to identify key factors and patterns that affect temperature control. Based on these analysis results, the system can automatically adjust parameters such as heating power and insulation time to ensure that the temperature is controlled within a precise range of ±5°C, which helps improve production efficiency, reduce energy consumption and ensure product quality;

[0044] (4) Predictive maintenance: In addition to direct temperature control, big data analytics can also predict equipment failures by analyzing trends and anomalies in sensor data, schedule maintenance in advance, and reduce losses caused by unexpected downtime;

[0045] (5) Optimization strategy formulation: In the long run, the data and analysis results collected by the module can help optimize the control strategy of the entire heating process. Through continuous learning and adaptation, the control algorithm can be made more accurate and efficient.

[0046] (6) Visual display: The big data analysis module can also intuitively display the analysis results to operators in the form of charts, dashboards, etc., enabling them to quickly understand the current system status and make decisions.

[0047] Therefore, the big data analysis module in this technical solution is not only a tool to achieve precise temperature control, but also a key driving force for optimizing production processes and improving the system's intelligence level and response speed.

[0048] In this embodiment, in the adaptive heat treatment control system, the decision module based on the deep learning algorithm mainly analyzes the real-time monitoring data and autonomously adjusts the key parameters in the heat treatment process to achieve efficient and precise control of the heat treatment process. Specifically, the functions of this module include the following:

[0049] (1) Data reception and preprocessing: This module first receives a large amount of data from temperature and stress real-time monitoring sensors. These data reflect the real-time status of the heat treatment process. The data is preprocessed, such as cleaning, standardization, and normalization, to facilitate the processing of the deep learning model.

[0050] (2) Feature extraction and learning: Deep learning algorithms use a multi-layer neural network structure to automatically extract useful features from preprocessed data. These features may include temperature change trends, stress distribution patterns, etc., which are the basis for decision making. Through extensive training, the model learns to identify the complex relationship between different features and heat treatment results.

[0051] (3) Real-time decision-making and parameter adjustment: Based on the extracted features, the deep learning model can predict potential problems in the heat treatment process (such as temperature overshoot and stress concentration) in real time and respond to them. It dynamically adjusts parameters such as heating power, cooling rate, and holding time to ensure that the heat treatment process proceeds as expected and achieves the best material performance and processing efficiency.

[0052] (4) Self-learning and optimization: During the heat treatment process, the decision-making module will continue to learn and self-optimize. This means that as more batches of materials are processed, the model will continuously adjust and improve its decision-making strategy based on new data, making the control strategy more and more in line with the actual working conditions, thereby improving control accuracy and efficiency.

[0053] (5) Anomaly detection and response: Deep learning algorithms can also monitor abnormal conditions during the heat treatment process in real time, such as sensor failure, atypical temperature curves, etc., and issue alarms or take emergency measures in a timely manner to reduce the risk of defective products and equipment damage. Example

[0054] A heat treatment process for an austenitic stainless steel pipe comprises the following steps:

[0055] S1. Preheating preparation: A 304 stainless steel pipe with a diameter of 100 mm and a wall thickness of 5 mm is selected as the treatment object. First, the stainless steel pipe is placed in a preheating furnace and preheated to 925°C by gradually increasing the temperature. This temperature is within the phase transition temperature range of 850°C to 1050°C, which is suitable for the heat treatment requirements of 304 stainless steel.

[0056] S2, phase transformation induced plasticity heat treatment (TRIP): after preheating, cooling begins at a cooling rate of 30°C / s through a precise temperature control system. At this time, it is observed that the austenite structure begins to transform into martensite, while retaining about 20% of residual austenite to maintain the toughness of the material. According to claim 2, the holding time is 3 minutes to optimize the phase transformation process;

[0057] S3, ultrasonic assisted heating: Then, use a focused ultrasonic head with a frequency of 40kHz and a power density of 0.5W / cm² to assist heating of the surface of the stainless steel tube, ensuring that the energy is concentrated within a depth of 3mm below the surface of the tube to improve the uniformity of internal heat energy distribution;

[0058] S4, high frequency induction heating: select induction heating equipment with a frequency of 150kHz, which is the most suitable frequency according to the pipe size. The heating rate is controlled at 300°C / min, and the heating is heated to 1000°C to ensure that the heat energy is efficiently and evenly transferred to the inside of the pipe, and the heating unevenness is controlled within 3°C;

[0059] S5, Controlled environment treatment: The entire treatment process is carried out in a vacuum environment (vacuum degree reaches 10-4 Pa) to eliminate the risk of oxidation. At the same time, argon gas with a purity of 99.99% is introduced, and the flow rate is set to 20L / min to further optimize the treatment environment;

[0060] S6, Intelligent temperature control and data analysis: The configured infrared temperature sensor has an accuracy of ±1°C. Combined with big data analysis, it monitors the heating and insulation stages in real time. Through PID adjustment, it ensures that the temperature fluctuation is within ±3°C and the response time is less than 1 second. The control algorithm is optimized every quarter based on the accumulated data;

[0061] S7, Adaptive heat treatment control: The integrated control system includes multi-dimensional sensors and deep learning algorithms to monitor temperature and stress in real time, with a response time of no more than 5 seconds, and automatically adjust the heating power and cooling rate to ensure that the temperature is controlled at ±5°C and the stress is maintained at a safe level;

[0062] S8. Microwave-assisted heating and quenching: Using a 2.45 GHz continuous wave microwave source, the stainless steel tube is heated to 1050°C through a precisely tuned resonant cavity, and then immersed in a 15% vegetable oil-based biodegradable polymer quenching liquid, which contains 5% polymer concentration, corrosion inhibitors and lubricants. The cooling rate is controlled at 180°C / s to reduce the heat treatment time and optimize the overall performance of the material. Example

[0063] A heat treatment process for an austenitic stainless steel pipe comprises the following steps:

[0064] S1. Preheating preparation: Place a 316L stainless steel pipe with a diameter of 200 mm and a wall thickness of 10 mm into a preheating furnace and slowly heat it to 975°C at a heating rate of 50°C per minute. This temperature is suitable for the phase change treatment of 316L stainless steel, ensuring uniform preheating of the material and reducing internal stress.

[0065] S2, Transformation Induced Plasticity Heat Treatment (TRIP): Maintain at 975°C for 4 minutes, followed by cooling at a cooling rate of 40°C / s using a rapid cooling system. The cooling rate is precisely controlled to induce the transformation of austenite to martensite while retaining about 25% of retained austenite to achieve a good balance of toughness and strength.

[0066] S3, Ultrasonic assisted heating: Using a focused ultrasonic head with a frequency of 80kHz and a power density of 0.8W / cm², it ensures that the energy is accurately focused at a depth of 2 to 4mm below the surface of the pipe, and utilizes the mechanical and thermal effects of ultrasound to further promote the uniformity of heat treatment;

[0067] S4, high-frequency induction heating: according to the characteristics of 316L stainless steel, the induction heating frequency is automatically adjusted to 300kHz, the heating rate is set at 200°C / min, and the pipe is heated to 1050°C. During this process, the heating unevenness is strictly controlled to ≤3°C, ensuring efficient and uniform heat treatment;

[0068] S5. Controlled environment treatment: Heat treatment is carried out in a vacuum chamber (vacuum degree reaches 10-5 Pa), and argon gas with a purity of ≥99.999% is used for filling. The gas flow rate is 30L / min. The gas ratio is automatically adjusted through the PID control system to ensure accurate control of hydrogen concentration, so as to refine the grains and reduce carbide precipitation;

[0069] S6, Intelligent temperature control and data analysis: The infrared temperature sensor has a high accuracy of ±1°C. Combined with the advanced data analysis module, the temperature data is updated once a second. Through rapid PID parameter adjustment, the temperature fluctuation in the heating and insulation stages is controlled within ±2°C, ensuring the high stability of the processing process.

[0070] S7, Adaptive Heat Treatment Control: Using an integrated multi-sensor network and a machine learning-based decision algorithm, the system can monitor the material status in real time and automatically adjust the heat treatment parameters, including heating power and cooling rate, within 5 seconds, ensuring temperature control accuracy of ±3°C while effectively managing the internal stress of the material to prevent heat treatment defects;

[0071] S8. Microwave-assisted heating and quenching: Use a 2.45 GHz microwave source to heat to 1050°C, and then immediately transfer to a quenching liquid containing special additives. The quenching liquid is a biodegradable polymer-based liquid with a 7% polymer concentration and a customized corrosion inhibitor and lubricant formulation. The quenching is performed at a cooling rate of 120°C / s, which significantly reduces the risk of quenching cracks and improves the uniformity and depth of the hardened layer. Example

[0072] A heat treatment process for an austenitic stainless steel pipe comprises the following steps:

[0073] S1. Preheating preparation: put a duplex stainless steel pipe (such as 2205 stainless steel) with a diameter of 150mm and a wall thickness of 8mm into a preheating furnace, and use a gradient heating technology to gradually increase the temperature from room temperature to 900°C. This temperature ensures a good heat treatment prelude for duplex stainless steel and reduces the accumulation of thermal stress. Use a temperature sensor to monitor the entire process to ensure uniform preheating;

[0074] S2, Transformation Induced Plasticity Heat Treatment (TRIP): After preheating at 900°C, the holding time is 2 minutes, which is slightly shorter than the normal time. It aims to quickly pass through the sensitive phase transformation range and reduce the internal defects that may be generated during the phase transformation process. Then, the material is rapidly cooled at a cooling rate of 35°C / s to control the proportion of retained austenite at around 15% to balance the strength and toughness of the material.

[0075] S3, Ultrasonic assisted heating: Using an ultrasonic head with a frequency of 60kHz and a power density of 0.6W / cm², the optimal ultrasonic path is determined through computer simulation to ensure that the energy is focused on the center area of ​​the pipe with a depth of about 3mm to promote the balance of internal heat flow and reduce the temperature difference between the outer wall and the inner wall;

[0076] S4, high-frequency induction heating: According to the characteristics of 2205 stainless steel, the induction heating frequency is automatically adjusted to 450kHz. The built-in algorithm adjusts the heating rate according to the real-time temperature feedback of the pipe and maintains it at 250°C / min. The heating temperature is controlled at 1000°C, achieving efficient and uniform heating effect, and the heating unevenness does not exceed 4°C;

[0077] S5. Controlled environment treatment: Heat treatment is performed in a high vacuum environment (vacuum degree reaches 10-6 Pa), and helium with a purity of ≥99.999% is supplemented when necessary. The gas flow rate is controlled at 10L / min to 30L / min. Through more sophisticated PID control logic, the purity and stability of the gas environment are ensured, further reducing the risk of oxidation and decarburization;

[0078] S6, Intelligent temperature control and data analysis: Using the latest Internet of Things technology, the accuracy of the infrared temperature sensor is improved to ±0.5°C, real-time data is uploaded to the cloud every second, and the control strategy is updated every second for analysis. The response time is shortened to within 1 second, and the temperature fluctuation is controlled within ±1°C, achieving unprecedented temperature control accuracy;

[0079] S7, adaptive heat treatment control: In this embodiment, in addition to monitoring temperature and stress, the adaptive control system also incorporates a deformation prediction model, which can adjust the heating strategy in advance to prevent possible deformation problems. The response time does not exceed 3 seconds, ensuring that the heat treatment process is carried out under strictly controlled conditions. At the same time, the temperature control accuracy is maintained at ±3°C, and the stress level is always within the material safety range;

[0080] S8. Microwave-assisted heating and quenching: In the final heating stage, a 2.45 GHz microwave source is used to rapidly heat the steel to 1050°C, followed by rapid quenching into an eco-friendly quenching medium based on plant extracts containing 10% natural polymers, biodegradable corrosion inhibitors, and bio-lubricants. The cooling rate is controlled at 160°C / s, which not only improves the quenching efficiency but also ensures environmental sustainability.

[0081] This austenitic stainless steel pipe heat treatment process is aimed at 304 series stainless steel pipes. Three different heat treatment implementation schemes are designed to optimize the comprehensive performance of the material by adjusting key parameters such as heating temperature, holding time and cooling rate. The following is a comparison of the functional test results of Examples 1 to 3:

[0082] Example 1 adopts a classic solution treatment process, heating the material to 1050°C and keeping it warm for 2 hours, followed by rapid water quenching. The results show that this process effectively promotes the dissolution of carbides and enhances the corrosion resistance of the material, but the mechanical strength is limited and there is a certain amount of internal stress;

[0083] Example 2 adds a stabilization treatment step based on Example 1, that is, after the solution treatment, a low-temperature tempering treatment is performed at 850°C for 4 hours. This change significantly reduces the precipitation of chromium carbide in the material, further improves the corrosion resistance, reduces the internal stress, and improves the machining performance. However, the cost increases slightly due to the additional treatment steps;

[0084] Example 3 introduces an innovative graded quenching technology, that is, after solution treatment, it is first naturally cooled in air to a certain degree and then water quenched. This process not only effectively controls the deformation during the heat treatment process, but also achieves a better balance between mechanical properties and corrosion resistance by finely controlling the cooling rate. Compared with Examples 1 and 2, the stainless steel pipe of Example 3 exhibits higher toughness and strength, while maintaining good corrosion resistance, and reduces energy consumption to a certain extent.

[0085] In summary, by comparing Examples 1 to 3, it can be seen that by adjusting the specific parameters of the heat treatment process, the final performance of the stainless steel material can be significantly affected. Example 3 shows the most balanced performance improvement, which not only ensures efficiency increase (enhanced material performance), but also achieves reduction (reducing the negative effects of heat treatment such as deformation and energy consumption), reflecting the important value of stainless steel heat treatment process optimization. In addition, these examples also emphasize the key role of process innovation in meeting specific application requirements, improving the comprehensive performance of materials and promoting sustainable development.

[0086] It should be noted that, in this article, relational terms such as one and two are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions. The sentence "includes an element defined by ... does not exclude the existence of other identical elements in the process, method, article or device including the element".

[0087] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A heat treatment process for an austenitic stainless steel pipe, characterized in that: The following steps are involved: S1. Preheat the stainless steel tube to a temperature within the phase change range of 850°C to 1050°C; S2, performing phase transformation induced plasticity heat treatment, inducing austenite to transform into martensite by controlling the cooling rate at 20°C / s to 50°C / s, while maintaining a certain proportion of retained austenite; S3, use ultrasonic auxiliary heating with a frequency of 20kHz to 1MHz and an ultrasonic power density of 0.1W / cm² to 1W / cm²; S4, using high frequency induction heating, the frequency range is 20kHz ~ 500kHz, the pipe is evenly heated by the induction coil, the heating rate is controlled at 100 ° C / min ~ 500 ° C / min, and the heating temperature range is 900 ° C ~ 1100 ° C; S5. The heat treatment process is carried out under a controlled environment, and the gas flow rate is adjusted to 5L / min to 50L / min; S6. Configure infrared temperature sensors based on the Internet of Things, monitor and dynamically adjust heating and insulation parameters in real time through the big data analysis module, and achieve temperature control accuracy of ±5°C; S7. Use adaptive heat treatment control system to adjust heat treatment parameters according to real-time monitoring of material status, and the temperature deviation shall not exceed ±10°C; S8. Finally, microwave-assisted heating is used to reach the quenching temperature, followed by immersion in a medium for quenching, and the medium cooling rate is controlled at 50°C / s to 200°C / s.

2. The austenitic stainless steel pipe heat treatment process according to claim 1, characterized in that: The phase change induced plastic heat treatment also includes a heat preservation process, and the heat preservation time ranges from 1 minute to 5 minutes.

3. The heat treatment process for an austenitic stainless steel pipe according to claim 1, characterized in that: The ultrasonic assisted heating adopts a focused ultrasonic head to ensure that the energy is concentrated within a depth range of 1mm to 5mm below the surface of the pipe, thereby promoting uniform distribution of internal heat energy.

4. The austenitic stainless steel pipe heat treatment process according to claim 1, characterized in that: The frequency of the high-frequency induction heating is automatically adjusted within the range of 20kHz to 500kHz, and the frequency is calculated according to the diameter, wall thickness and material composition of the stainless steel pipe.

5. The heat treatment process for an austenitic stainless steel pipe according to claim 1, characterized in that: The trace hydrogen addition system in the controllable environment adopts proportional, integral, and differential (PID) control logic to automatically adjust the hydrogen concentration according to the heating stage and the material characteristics of the stainless steel pipe to ensure the control of the hydrogen ratio and promote the refinement of austenite grains.

6. The austenitic stainless steel pipe heat treatment process according to claim 1, characterized in that: Combined with the real-time temperature feedback of the infrared temperature sensor, by adjusting the PID parameters, the response time is within 2 seconds, ensuring that the temperature fluctuation is controlled within ±3°C during the heating and cooling stages.

7. The austenitic stainless steel pipe heat treatment process according to claim 1, characterized in that: The specific steps of the phase change induced plastic heat treatment include: first heating the stainless steel pipe to 950°C and keeping it warm for 2 minutes, then rapidly cooling it to 400°C by water mist spraying, with a cooling rate of 35°C / s. This process induces the transformation of austenite to martensite, and the residual austenite content is controlled at 10% to 30%.

8. The austenitic stainless steel pipe heat treatment process according to claim 1, characterized in that: The adaptive heat treatment control system includes real-time monitoring sensors for temperature and stress and a decision-making module based on a deep learning algorithm. The system can adjust parameters such as heating power and cooling rate in real time according to the current state of the workpiece. The response time does not exceed 10 seconds, ensuring the stability of the heat treatment process, the temperature control accuracy of ±5°C, and the stress control within the allowable range of the material.

9. The austenitic stainless steel pipe heat treatment process according to claim 1, characterized in that: The microwave-assisted heating adopts a continuous wave microwave source with a frequency of 2.45 GHz. The microwave energy is evenly distributed through an adjustable resonant cavity. After heating to 1050°C, it is immediately put into a quenching liquid containing 15% vegetable oil, and the cooling rate is controlled at 150°C / s.

10. The austenitic stainless steel pipe heat treatment process according to claim 9, characterized in that: In S8, the medium is a biodegradable polymer-based quenching liquid containing 5% to 10% polymer concentration as well as a corrosion inhibitor and a lubricant.

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