Method for dynamically regulating hardness and toughness of heat-treated silver-containing martensitic antibacterial stainless steel

Abstract

The present application relates to the technical field of metal material heat treatment, in particular to a method for dynamically regulating hardness and toughness of heat treatment matching of silver-containing martensitic antibacterial stainless steel, comprising: placing an original workpiece in a program heating furnace, sequentially completing austenitizing through constant rate preheating, higher rate rapid heating and super-temperature pulse stage, using inert gas to rapidly cool to below the martensite starting transformation temperature after the super-temperature pulse, obtaining a non-equilibrium supersaturated matrix initial quenching organization, then carrying out isothermal tempering treatment to obtain an intermediate tempering organization, and then carrying out secondary quenching and final tempering. The method can accurately regulate the matrix organization and silver phase distribution, refine the austenite grains, improve the internal stress distribution, realize the collaborative adaptation of hardness and toughness, and improve the uniformity of the silver-containing martensitic antibacterial stainless steel organization and the stability of the mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of heat treatment technology for metallic materials, and in particular to a method for dynamically controlling the hardness and toughness of silver-containing martensitic antibacterial stainless steel during heat treatment. Background Technology

[0002] The existing heat treatment of silver-containing martensitic antibacterial stainless steel adopts the conventional austenitizing heating mode, which completes the heating process from preheating to austenitizing temperature with a single constant heating rate. No over-temperature pulse control is set in the austenitizing stage. The cooling treatment adopts conventional cooling method. The tempering process only adopts the basic process of one quenching combined with one tempering, without adopting the composite heat treatment process of isothermal tempering, secondary quenching and final tempering.

[0003] In conventional heat treatment processes, there is no gradient distinction in heating rate, insufficient temperature control precision in the austenitization process, and the inability to accurately adjust the degree of matrix solid solution without over-temperature pulse control. Conventional cooling methods cannot form a non-equilibrium supersaturated matrix structure, and the single quenching and tempering process path leads to uncontrollable microstructure evolution. The silver phase precipitation state and distribution uniformity cannot be guaranteed, resulting in an imbalance in the internal microstructure configuration of the matrix and poor synergistic compatibility between hardness and toughness, which cannot meet the performance control requirements of silver-containing martensitic antibacterial stainless steel.

[0004] This invention addresses the shortcomings of existing heat treatment methods in temperature control and process pathways by employing a three-stage programmed heating approach: preheating, rapid heating, and overheating pulse. After the overheating pulse, a non-equilibrium supersaturated matrix is ​​obtained through strong cooling with inert gas. Through a composite process of immediate isothermal tempering, secondary quenching, and final tempering, the hardness and toughness of silver-containing martensitic antibacterial stainless steel are dynamically controlled, improving the uniformity of the matrix structure and the matching of performance. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the existing technology and propose a method for dynamic control of hardness and toughness matching in the heat treatment of silver-containing martensitic antibacterial stainless steel.

[0006] To achieve the above objectives, the present invention employs the following technical solution: a method for dynamically controlling the hardness and toughness of silver-containing martensitic antibacterial stainless steel during heat treatment, comprising: Prepare the original workpiece of silver-containing martensitic antibacterial stainless steel and place the original workpiece into a heating furnace with programmed temperature rise function. The heating furnace is programmed to rise, causing the original workpiece to go through a preheating stage, a rapid heating stage, and an overheating pulse stage. In the preheating stage, the furnace temperature is controlled to rise at a constant rate to the target preheating temperature. In the rapid heating stage, the furnace temperature is controlled to rise at an even higher constant rate to the target austenitizing temperature. In the overheating pulse stage, the furnace temperature is instantaneously raised to the target superheat above the target austenitizing temperature and maintained for a preset pulse time. After the overheating pulse stage ends, the heating furnace is subjected to strong cooling treatment with an inert gas medium, and the original workpiece is rapidly cooled to below the target martensite transformation temperature at a preset first cooling rate to obtain an initial quenched structure with a non-equilibrium supersaturated matrix. The obtained initial quenched structure is immediately placed into a tempering medium bath within a preset temperature range for isothermal treatment. The isothermal treatment time is controlled to obtain an intermediate tempered structure. The intermediate tempered structure is subjected to a second quenching treatment to obtain a second quenched structure, and then a final tempering treatment is performed.

[0007] As a further aspect of the present invention, after the over-temperature pulse stage ends, the heating furnace is subjected to strong cooling treatment with an inert gas medium, including: At the instant the preset pulse time arrives, high-pressure, low-temperature inert gas is introduced into the heating furnace. The flow rate and pressure of the high-pressure low-temperature inert gas are controlled so that the working environment temperature inside the furnace decreases at the preset first cooling rate. Monitor the real-time temperature of the original workpiece, and stop the introduction of the high-pressure low-temperature inert gas when the real-time temperature drops to the target quenching termination temperature below the target martensite start transformation temperature. The inert gas medium strong cooling process continuously records temperature-time curves, which are used for analysis of subsequent process steps.

[0008] As a further aspect of the present invention, the step of immediately placing the obtained initial quenched structure into a tempering medium bath within a preset temperature range for isothermal treatment includes: The preset tempering medium tank contains a molten low-temperature salt bath, the temperature of which is controlled at the target isothermal tempering temperature. The initial quenched structure is transferred from the heating furnace and immersed in the molten low-temperature salt bath, and the isothermal time is calculated. During the isothermal treatment, the molten low-temperature salt bath is continuously stirred to ensure temperature uniformity; When the isothermal treatment time reaches the preset intermediate tempering time, the workpiece is removed from the molten low-temperature salt bath to obtain the intermediate tempered structure.

[0009] As a further aspect of the present invention, performing a secondary quenching treatment on the intermediate tempered structure to obtain a secondary quenched structure, and performing a final tempering treatment includes: The secondary quenching process includes reheating the intermediate tempered structure to the target secondary austenitizing temperature and holding it at that temperature, and then cooling it to room temperature at a preset second cooling rate to obtain a secondary quenched structure. The intermediate tempered structure is placed into a secondary heating device; The temperature of the secondary heating device is raised to the target secondary austenitizing temperature, which is lower than the initial target austenitizing temperature, and then held at this temperature for a preset secondary austenitizing time. After the heat preservation is completed, the intermediate tempered structure is removed from the secondary heating device and quickly placed into the rapid cooling oil tank; Control the oil temperature and circulation rate of the rapid cooling oil tank to cool the workpiece to room temperature at the preset second cooling rate, thereby forming the secondary quenching structure; The second cooling rate is lower than the preset first cooling rate; The obtained secondary quenched structure is subjected to a final tempering treatment, which includes holding the secondary quenched structure at a preset final tempering temperature for a preset final tempering time, and then air cooling to room temperature to achieve dynamic control of the hardness and toughness of the silver-containing martensitic antibacterial stainless steel.

[0010] As a further aspect of the present invention, the target superheat, preset pulse time, target isothermal tempering temperature, preset intermediate tempering time, target secondary austenitizing temperature, preset secondary austenitizing time, final tempering temperature, and preset final tempering time together constitute a dynamic control parameter set, and the invention further includes the step of establishing the correspondence between the dynamic control parameter set and the desired mechanical properties: Multiple sets of process samples were prepared for the same grade of silver-containing martensitic antibacterial stainless steel. For each group of process samples, a different set of parameter values ​​from the aforementioned dynamic control parameter set is set. The entire process of preheating, rapid heating, over-temperature pulse, inert gas medium strong cooling, obtaining initial quenched structure, isothermal treatment to obtain intermediate tempered structure, secondary quenching treatment to obtain secondary quenched structure, and final tempering treatment is performed on each group of process samples. Hardness and impact toughness tests were performed on each group of processed samples to obtain the measured hardness and impact toughness values. The set of dynamic control parameters corresponding to each group of process samples is associated with the obtained measured hardness value and measured impact toughness value to form a parameter-performance database.

[0011] As a further aspect of the present invention, it also includes a step of real-time feedback adjustment of the heat treatment process based on online monitoring data: During the preheating stage, rapid heating stage, and overheating pulse stage, the core temperature data of the workpiece is collected in real time using a miniature thermocouple embedded in the original workpiece. During the inert gas medium strong cooling process, an infrared temperature measuring device is used to monitor the cooling rate data of the workpiece surface in real time. The real-time collected core temperature data and the real-time monitored cooling rate data are compared with the standard process curves pre-stored in the parameter-performance database. When the core temperature data or cooling rate data deviates from the standard process curve by more than a preset deviation threshold, a process adjustment command is generated; The process adjustment command is used to adjust the heating rate of the heating furnace, the flow rate of the high-pressure low-temperature inert gas, or the temperature of the tempering medium tank, so that the actual process path returns to the standard process curve.

[0012] As a further aspect of the present invention, the step of comparing the real-time collected core temperature data and the real-time monitored cooling rate data with a standard process curve pre-stored in the parameter-performance database includes: From the parameter-performance database, retrieve the standard temperature-time curve corresponding to the currently executed dynamic control parameter set as the standard process curve; The real-time collected core temperature data is integrated according to the time series to form a real-time core temperature curve; The real-time core temperature curve is synchronously superimposed and compared with the temperature curve of the corresponding stage in the standard process curve, and the temperature deviation value at each time point is calculated. The temperature drop per unit time is calculated from the real-time monitored cooling rate data to form a real-time cooling rate curve; The real-time cooling rate curve is compared with the cooling rate curve of the corresponding cooling stage in the standard process curve, and the rate deviation value is calculated.

[0013] As a further aspect of the present invention, after the final tempering treatment, the performance uniformity of the regulated workpiece is verified, including: Multiple micro-samples are taken from different characteristic parts of the workpiece, including the workpiece surface, the workpiece core, and the workpiece geometry abrupt change. Nanoindentation tests were performed on each of the cut micro-samples to obtain the local nanohardness value of each micro-sample. Statistical analysis was performed on the local nanohardness values ​​of all micro samples to calculate the average and standard deviation of the hardness values; When the standard deviation is less than the preset uniformity threshold, the hardness distribution of the workpiece is determined to meet the uniformity requirements. Record the complete set of dynamic control parameters and process data corresponding to the workpiece that meets the uniformity requirements, and supplement the parameter-performance database.

[0014] As a further aspect of the present invention, the nanoindentation test performed on each of the cut micro-samples includes: The surface of the micro sample to be tested is polished to a mirror finish; The polished micro-samples are fixed on the sample stage of the nanoindentation tester; A pressure needle with a specific geometry is selected to apply pressure to the surface of a micro sample at a preset loading rate until the preset maximum load is reached. After maintaining the maximum load for a preset holding time, the pressure is released at a preset unloading rate, so that the pressure needle completely leaves the surface of the micro sample. Throughout the entire loading, holding, and unloading process, the applied pressure value and the displacement depth value of the indenter are continuously recorded to form a complete load-displacement curve; Based on the load-displacement curve, the local nanohardness value is obtained through analysis and calculation.

[0015] As a further aspect of the present invention, it also includes a step of reverse process derivation based on the parameter-performance database and target performance requirements: Receive the target hardness range and target toughness range from the input; In the parameter-performance database, query all historical process records where the measured hardness value and the measured impact toughness value both fall within the target hardness range and the target toughness range; Extract the corresponding set of historical dynamic control parameters from all historical process records that meet the conditions; Multi-objective optimization analysis was performed on all extracted historical dynamic control parameter sets to calculate a set of optimal recommended values ​​for dynamic control parameters; The recommended values ​​of the dynamic control parameters are used as the basis for setting the specific values ​​of the target superheat, preset pulse time, target isothermal tempering temperature, preset intermediate tempering time, target secondary austenitizing temperature, preset secondary austenitizing time, final tempering temperature and preset final tempering time, and are used to heat treat new silver-containing martensitic antibacterial stainless steel workpieces.

[0016] Compared with the prior art, the advantages and positive effects of the present invention are as follows: The segmented programmed heating method, which involves raising the temperature to the target preheating temperature at a constant rate during the preheating stage, raising it to the target austenitizing temperature at an even higher constant rate during the rapid heating stage, and instantly raising it to the target superheat temperature and maintaining it for a preset pulse time during the overheating pulse stage, can precisely control the temperature change rate during the austenitizing process, constrain the growth scale and uniformity of austenite grains, adjust the solid solution content and distribution of silver in the matrix, delay and suppress the abnormal aggregation and coarsening behavior of the silver phase, stabilize the initial microstructure of the matrix after austenitization, reduce the compositional segregation and structural defects within the microstructure, and enable the matrix to have a uniform and controllable initial configuration before the phase transformation.

[0017] After the over-temperature pulse stage, the workpiece is cooled to below the martensitic transformation temperature by strong cooling with an inert gas medium at a preset first cooling rate, forming an initial quenched structure of a non-equilibrium supersaturated matrix. This structure is then directly placed into a tempering medium bath within a preset temperature range to complete isothermal treatment and form an intermediate tempered structure. After secondary quenching and final tempering, the microstructure evolution path during the martensitic phase transformation can be constrained, the size and dispersion distribution of tempered precipitates can be controlled, the residual stress distribution within the matrix can be improved, the stress concentration areas within the microstructure can be weakened, the correspondence between the hardness and toughness of the matrix can be coordinated, and the microstructure stability and mechanical property compatibility of silver-containing martensitic antibacterial stainless steel can be optimized, achieving simultaneous control of hardness and toughness. Attached Figure Description

[0018] Figure 1 The flowchart shows the dynamic control method for matching hardness and toughness in the heat treatment of silver-containing martensitic antibacterial stainless steel according to the present invention. Figure 2 A flowchart for forced cooling with an inert gas medium; Figure 3 A flowchart establishing the correspondence between the dynamic control parameter set and the desired mechanical properties; Figure 4 Box plot of nanoscale hardness distribution of silver-containing martensitic antibacterial stainless steel workpiece; Figure 5 Box plot of hardness uniformity in different parts of silver-containing martensitic antibacterial stainless steel workpiece; Figure 6 Electron micrograph of the silver phase precipitation; Figure 7 This is a diffraction pattern curve; Figure 8 This is the elemental energy spectrum curve. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0020] In the description of this invention, it should be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, in the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0021] See Figure 1 This invention provides a method for dynamically controlling the hardness and toughness of silver-containing martensitic antibacterial stainless steel during heat treatment, the overall implementation of which is as follows: Prepare a raw workpiece of silver-containing martensitic antibacterial stainless steel of a specified grade and place it in a heating furnace equipped with a programmed temperature rise function. The furnace is programmed to undergo a preheating stage, a rapid heating stage, and an overheating pulse stage sequentially. In the preheating stage, the furnace temperature is controlled to rise at a constant preset rate to the target preheating temperature. In the rapid heating stage, the furnace temperature is controlled to rise at a constant rate higher than that of the preheating stage to the target austenitizing temperature. In the overheating pulse stage, the furnace temperature is further increased to a target superheat above the target austenitizing temperature in a very short time and maintained at this temperature for a preset pulse time. After the overheating pulse stage, the furnace is immediately subjected to inert gas medium-induced rapid cooling treatment. By introducing high-pressure, low-temperature inert gas into the furnace, the raw workpiece is rapidly cooled at a preset first cooling rate to below the target martensitic transformation initiation temperature, thereby obtaining an initial quenched microstructure with a non-equilibrium supersaturated matrix. The obtained initial quenched microstructure is immediately transferred and immersed in a tempering medium bath with the temperature controlled within a preset range for isothermal treatment. By controlling the duration of the isothermal treatment, an intermediate tempered microstructure is obtained. A second quenching treatment is then performed on the intermediate tempered microstructure, heating it to the target secondary austenitizing temperature and holding it there, followed by cooling at a preset second cooling rate to obtain a secondary quenched microstructure. Finally, a final tempering treatment is performed on the secondary quenched microstructure, i.e., holding it at a preset final tempering temperature for a preset final tempering time, followed by air cooling to room temperature, thus completing the dynamic control of the entire heat treatment process.

[0022] In one embodiment of the present invention, immediately after the over-temperature pulse stage ends, the heating furnace is subjected to strong cooling treatment with an inert gas medium, see reference. Figure 2Specifically, at the instant the preset pulse time arrives, high-pressure, low-temperature inert gas is introduced into the heating furnace. By precisely controlling the flow rate and pressure of the introduced high-pressure, low-temperature inert gas, the working environment temperature inside the furnace decreases according to a preset first cooling rate. A temperature sensor connected to the workpiece monitors the real-time temperature of the original workpiece. When the real-time temperature drops below a target quenching termination temperature (the temperature at which martensite begins to transform), the introduction of the high-pressure, low-temperature inert gas is immediately stopped. Throughout the entire inert gas medium-assisted cooling process, the workpiece temperature change over time is continuously recorded. This temperature-time curve is used for analysis of subsequent process steps.

[0023] After obtaining the initial quenched microstructure, it is immediately placed in a tempering medium bath within a preset temperature range for isothermal treatment. The preset tempering medium bath contains a molten low-temperature salt bath, the temperature of which is precisely controlled at the target isothermal tempering temperature. The initial quenched microstructure is rapidly transferred from the heating furnace and completely immersed in the molten low-temperature salt bath, while the isothermal time is calculated. During the isothermal treatment, the molten low-temperature salt bath is continuously mechanically stirred to ensure temperature uniformity throughout the medium bath. When the isothermal treatment time reaches the preset intermediate tempering time, the workpiece is removed from the molten low-temperature salt bath, at which point the desired intermediate tempered microstructure is obtained.

[0024] In practice, a silver-containing martensitic antibacterial stainless steel workpiece with a composition of 1Cr13-3Ag was used as the initial workpiece. It was placed in a heating furnace with a programmed temperature rise function. The programmed temperature rise control was activated, and the initial workpiece sequentially underwent a preheating stage, a rapid heating stage, and an overheating pulse stage. In the preheating stage, the target preheating temperature was set at 550 degrees Celsius, and the furnace temperature rose at a constant rate of 5 degrees Celsius per second. In the rapid heating stage, the target austenitizing temperature was set at 1050 degrees Celsius, and the furnace temperature rose at a constant rate of 15 degrees Celsius per second. In the overheating pulse stage, the target superheat was set at 1200 degrees Celsius, and the preset pulse time was 90 seconds. At the instant the preset pulse time was reached, high-pressure cryogenic argon gas with a pressure of 0.8 MPa and a temperature of -60 degrees Celsius was introduced into the heating furnace. In practice, the flow rate and pressure of the high-pressure cryogenic inert gas are controlled in tandem. The gas flow rate is set to 150 standard liters per minute, and the rate of temperature decrease in the furnace working environment, i.e., the preset first cooling rate, is controlled at 45 degrees Celsius per second. The high-pressure cryogenic inert gas is continuously introduced. When the thermocouple installed inside the workpiece detects that the real-time temperature of the workpiece has dropped to 200 degrees Celsius, which is below the target quenching termination temperature (below the target martensitic transformation temperature), the system immediately closes the gas valve to stop the introduction of high-pressure cryogenic argon gas. The inert gas medium strong cooling process is continuously recorded by a data acquisition system, generating a temperature-time curve. This temperature-time curve is saved as a data file for analysis of subsequent process steps. Refer to Table 1 below for an example composition of a silver-containing martensitic antibacterial stainless steel workpiece with a composition of 1Cr13-3Ag.

[0025] Table 1: Example of composition of silver-containing martensitic antibacterial stainless steel workpieces with composition 1Cr13-3Ag In some embodiments, the surface temperature of the initially quenched structure removed from the heating furnace is approximately 180 degrees Celsius, and it is immediately placed into a tempering medium bath within a preset temperature range. The tempering medium bath contains a molten low-temperature salt bath of potassium nitrate and sodium nitrite, the temperature of which is heated and stably controlled at 240 degrees Celsius, which is the target isothermal tempering temperature. In specific implementations, the total time for the initially quenched structure to be transferred from the furnace to complete immersion in the molten low-temperature salt bath is controlled to be within 3 seconds, and the system begins calculating the isothermal time the moment the transfer is completed. Throughout the isothermal treatment, the mechanical stirrer at the bottom of the tempering medium bath continuously operates, stirring the molten low-temperature salt bath at a speed of 60 revolutions per minute to ensure temperature uniformity throughout the bath. The temperature uniformity requirement is that the temperature difference between any two points in the bath does not exceed 2 degrees Celsius. When the duration of the isothermal treatment reaches the preset intermediate tempering time of 1200 seconds, the robot arm removes the workpiece from the molten low-temperature salt bath, at which point the workpiece is in the intermediate tempered state.

[0026] It is understandable that controlling the cooling rate is crucial in inert gas-mediated refrigeration. The preset first cooling rate... The calculations are related to process monitoring: in: This represents the initial workpiece temperature recorded at the moment the over-temperature pulse phase ends and the forced cooling begins. This indicates the real-time temperature of the workpiece at a specific monitoring point during the forced cooling process. It corresponds Recording time, It corresponds The recording time. In actual control, the cooling rate is calculated in real time. The system compares the actual cooling rate with the preset cooling rate of 45 degrees Celsius per second. When the absolute value of the deviation exceeds 5 degrees Celsius per second, the system generates a fine-tuning command, adjusting the flow rate of high-pressure cryogenic argon to bring the actual cooling rate back to the preset value. It is understood that the uniformity of the salt bath temperature during isothermal treatment directly affects the uniformity of the intermediate tempering structure. In some embodiments, at least three temperature sensors are installed in the tempering medium tank, located at three different depths in the salt bath. The controller receives the temperature readings from the three sensors and corrects for temperature differences by adjusting the power of the stirrer, ensuring that the target isothermal tempering temperature fluctuates within ±1 degree Celsius around the set 240 degrees Celsius.

[0027] In one embodiment of the present invention, the process of performing a secondary quenching treatment on the intermediate tempered structure to obtain a secondary quenched structure, followed by a final tempering treatment, involves placing the intermediate tempered structure into a secondary heating device. The temperature of the secondary heating device is raised to a target secondary austenitizing temperature lower than the initial target austenitizing temperature, and held at this temperature for a preset secondary austenitizing time. After the holding time is completed, the intermediate tempered structure is quickly removed from the secondary heating device and immediately placed into a rapid cooling oil bath. By controlling the oil temperature and circulation rate of the rapid cooling oil bath, the workpiece is cooled to room temperature at a preset second cooling rate, thereby forming a secondary quenched structure. This second cooling rate is lower than a preset first cooling rate. The obtained secondary quenched structure is then subjected to a final tempering treatment, which involves holding the secondary quenched structure at a preset final tempering temperature for a preset final tempering time, and then air-cooling it to room temperature in still air.

[0028] The target superheat, preset pulse time, target isothermal tempering temperature, preset intermediate tempering time, target secondary austenitizing temperature, preset secondary austenitizing time, final tempering temperature, and preset final tempering time together constitute a dynamic control parameter set. The steps for establishing the correspondence between the dynamic control parameter set and the desired mechanical properties include, as described in [reference needed] Figure 3Multiple sets of process samples were prepared for the same grade of silver-containing martensitic antibacterial stainless steel. A different set of dynamic control parameters was assigned to each set of process samples. The entire process flow for each set of process samples was executed, including preheating, rapid heating, overheating pulse, inert gas cooling, obtaining initial quenched microstructure, isothermal treatment to obtain intermediate tempered microstructure, secondary quenching treatment to obtain secondary quenched microstructure, and final tempering treatment. Hardness and impact toughness tests were performed on each set of process samples after treatment to obtain measured hardness and impact toughness values. The dynamic control parameter set corresponding to each set of process samples was correlated with the obtained measured hardness and impact toughness values ​​to form a parameter-performance database.

[0029] In specific implementation, the intermediate tempered structure obtained in the above embodiment is subjected to a secondary quenching treatment. The temperature of the intermediate tempered structure is 240 degrees Celsius. It is placed in a secondary heating device with a set temperature of 850 degrees Celsius. The heating device heats up at a rate of 8 degrees Celsius per minute until it reaches the target secondary austenitizing temperature of 850 degrees Celsius. The temperature is then held at 850 degrees Celsius for a preset secondary austenitizing time of 600 seconds. After the heat treatment is completed, the robotic arm quickly removes the intermediate tempered structure from the secondary heating device. The transfer time of the intermediate tempered structure is controlled within 4 seconds. The removed intermediate tempered structure is immediately placed into a rapid cooling oil bath with a temperature set at 60 degrees Celsius. The quenching oil in the rapid cooling oil bath is in a forced circulation state with a circulation rate of 1.5 meters per second. By controlling the temperature and circulation rate of the quenching oil, the workpiece is cooled to room temperature at a preset second cooling rate. The average value of the second cooling rate is 25 degrees Celsius per second. This rate is lower than the preset first cooling rate of 45 degrees Celsius per second in the inert gas medium strong cooling stage in the above embodiment. After cooling, a secondary quenched structure is formed. In specific implementation, the obtained secondary quenched structure is subjected to final tempering treatment. The secondary quenched structure is placed in a tempering furnace set at 300 degrees Celsius and held at the final tempering temperature of 300 degrees Celsius for a preset final tempering time of 7200 seconds. After the heat treatment is completed, the secondary quenched structure is removed from the tempering furnace and air-cooled to room temperature in a static workshop environment.

[0030] It can be understood that the target superheat, preset pulse time, target isothermal tempering temperature, preset intermediate tempering time, target secondary austenitizing temperature, preset secondary austenitizing time, final tempering temperature, and preset final tempering time together constitute a dynamic control parameter set. The steps for establishing the correspondence between the dynamic control parameter set and the desired mechanical properties include preparing twenty sets of process samples for silver-containing martensitic antibacterial stainless steel of grade 1Cr13-3Ag, with each set containing three parallel samples. In specific implementation, a different set of parameter values ​​from the dynamic control parameter set is set for each set of process samples. The target superheat is taken in 50-degree intervals within the range of 1100 to 1300 degrees Celsius; the preset pulse time is taken in 30-second intervals within the range of 30 to 150 seconds; the target isothermal tempering temperature is taken in 20-degree intervals within the range of 200 to 280 degrees Celsius; and the preset intermediate tempering time is taken in the range of 600 to 1800 seconds. The values ​​are taken at 300-second intervals within the range of 800 to 900 degrees Celsius, at 25-degree Celsius intervals within the range of 300 to 900 seconds, at 150-second intervals within the range of 300 to 900 seconds, at 25-degree Celsius intervals within the range of 250 to 350 degrees Celsius, and at 1800-second intervals within the range of 3600 to 10800 seconds. Optionally, each group of process samples undergoes a complete process flow including preheating, rapid heating, over-temperature pulse, inert gas medium cooling, obtaining initial quenched microstructure, isothermal treatment to obtain intermediate tempered microstructure, secondary quenching treatment to obtain secondary quenched microstructure, and final tempering treatment. The process parameters for the entire process flow remain consistent except for the dynamic control parameter set. The preheating temperature is 550 degrees Celsius, the preheating rate is 5 degrees Celsius per second, and the rapid heating rate to the target austenitizing temperature of 1050 degrees Celsius is 15 degrees Celsius per second. Optionally, each group of process samples undergoes hardness and impact toughness testing. The Rockwell hardness C scale is used for hardness testing, and the Charpy V-notch impact test is used for impact toughness testing. The measured hardness and impact toughness values ​​for each sample are obtained, and the arithmetic mean of three parallel samples in each group is taken as the measured hardness and impact toughness values ​​for that group of process samples. It is understandable that the dynamic control parameter set corresponding to each set of process samples, including the specific values ​​of eight parameters, is associated with the obtained measured hardness value and measured impact toughness value to form a parameter-performance database. The parameter-performance database is stored in tabular form, and each row of the table records a unique set of dynamic control parameters and its corresponding measured hardness value and measured impact toughness value.

[0031] In one embodiment of the present invention, the step of real-time feedback adjustment of the heat treatment process based on online monitoring data includes: during the preheating stage, rapid heating stage, and overheating pulse stage, using miniature thermocouples embedded inside the original workpiece to collect the core temperature data of the workpiece in real time. During the inert gas medium strong cooling treatment stage, using an infrared temperature measuring device pointing towards the workpiece surface to monitor the cooling rate data of the workpiece surface in real time. The real-time collected core temperature data and the real-time monitored cooling rate data are compared in real time with the standard process curve pre-stored in the parameter-performance database. When the core temperature data or cooling rate data deviates from the standard process curve by more than a preset deviation threshold, the system automatically generates a process adjustment command. This process adjustment command is used to adjust the heating rate of the heating furnace, the flow rate of the high-pressure low-temperature inert gas, or the temperature of the tempering medium tank, so that the actual process path returns to the standard process curve.

[0032] The specific method for comparing the real-time acquired core temperature data and the real-time monitored cooling rate data with the standard process curve is as follows: From the parameter-performance database, a standard temperature-time curve corresponding to the currently executed dynamic control parameter set is retrieved as the standard process curve. The real-time acquired core temperature data is integrated according to the time series to form a real-time core temperature curve. This real-time core temperature curve is synchronously superimposed and compared with the temperature curves of the corresponding stage in the standard process curve, and the temperature deviation value at each sampling time point is calculated. For the real-time monitored cooling rate data, the temperature drop value per unit time is calculated to form a real-time cooling rate curve. This real-time cooling rate curve is compared with the cooling rate curve of the corresponding cooling stage in the standard process curve, and the rate deviation value is calculated.

[0033] In practice, the heat treatment process is adjusted in real time based on online monitoring data. During the preheating, rapid heating, and overheating pulse stages, one or more miniature thermocouples embedded in the core of the original workpiece are used to collect the core temperature data in real time. The data sampling frequency of the miniature thermocouples is 10 times per second. During the inert gas medium strong cooling treatment stage, an infrared temperature measuring device fixed outside the observation window of the heating furnace is used to monitor the cooling rate data of the workpiece surface in real time. The sampling frequency of the infrared temperature measuring device is 50 times per second. In practice, the real-time core temperature data and the real-time monitored cooling rate data are transmitted to the data buffer of the central controller via a data cable. The central controller calls the standard process curves pre-stored in the parameter-performance database for real-time comparison. During the preheating phase, when the deviation between the real-time core temperature data collected by the miniature thermocouple and the preheating temperature trajectory preset in the standard process curve exceeds a preset deviation threshold of 15 degrees Celsius, the central controller generates a process adjustment command for the heating furnace's heating rate. This command adjusts the power output of the heating element to accelerate or slow down the actual heating rate, bringing the core temperature data back to the standard process curve. During the rapid heating phase, when the deviation between the real-time core temperature data and the preset rapid heating temperature trajectory preset in the standard process curve exceeds a preset deviation threshold of 20 degrees Celsius, the system generates a process adjustment command. This command adjusts the heating furnace's heating rate to reduce the temperature deviation. During the overheating pulse phase, when the deviation between the core temperature data and the preset isothermal phase temperature value preset in the standard process curve exceeds a preset deviation threshold of 25 degrees Celsius, the system generates a process adjustment command. This command fine-tunes the heating power to stabilize the temperature near the target superheat.

[0034] It is understandable that during the inert gas medium-assisted cooling stage, the infrared temperature measuring device monitors the cooling rate data of the workpiece surface in real time. The system calculates the temperature drop per unit time. When the deviation between the real-time calculated cooling rate and the preset first cooling rate in the standard process curve exceeds 8 degrees Celsius per second, the central controller generates a process adjustment command for the high-pressure cryogenic inert gas flow rate. The process adjustment command adjusts the flow rate of the high-pressure cryogenic inert gas from 150 standard liters per minute to 130 standard liters per minute or 170 standard liters per minute by adjusting the opening of the pneumatic valve to correct the actual cooling rate. In some embodiments, the temperature control of the tempering medium bath is also incorporated into the feedback system. When the temperature sensor arranged in the molten cryogenic salt bath detects a deviation of more than 2 degrees Celsius between the actual temperature of the salt bath and the target isothermal tempering temperature of 240 degrees Celsius, the system generates a process adjustment command. The process adjustment command controls the heating rod power of the tempering medium bath to bring the temperature of the molten cryogenic salt bath back to the set value.

[0035] In practical implementation, the process of retrieving the standard process curve from the parameter-performance database involves the system matching historical optimal process records in the database with parameters that perfectly match these parameters. These parameters are based on the dynamic control parameter set set for the current workpiece, including a target superheat of 1200 degrees Celsius, a preset pulse time of 90 seconds, a target isothermal tempering temperature of 240 degrees Celsius, and a preset intermediate tempering time of 1200 seconds. The system then extracts complete standard temperature-time curves for each stage—preheating, heating, pulse, cooling, and isothermal—from these historical optimal process records. This curve is the standard process curve. Similarly, comparing the real-time core temperature data with the standard process curve involves the data acquisition system integrating the core temperature data (10 times per second) according to a time sequence to form a real-time core temperature curve. The central processing unit synchronizes the real-time core temperature curve with the temperature curves of the corresponding stages in the standard process curve on the time axis, and then calculates the temperature deviation between the two curves at each sampling time point. in: Indicates the first Temperature deviation value at each sampling point Indicates the first Real-time core temperature at each sampling point Indicates the standard process curve and the first The standard temperature at the same time for each sampling point. Optionally, the processing of the real-time monitored cooling rate data involves the system calculating the temperature difference between two consecutive readings based on 50 readings per second from the infrared thermometer. and time difference Then calculate the instantaneous cooling rate. Calculate multiple per second The values ​​are averaged to obtain real-time cooling rate data in seconds, which is then plotted as a real-time cooling rate curve. In practice, the real-time cooling rate curve is compared with the cooling rate curve of the corresponding cooling stage in the standard process curve, and the rate deviation value is calculated. ,in Indicates the real-time cooling rate. This represents the standard cooling rate at the corresponding time point in the standard process curve. When the temperature deviation or rate deviation exceeds its respective preset deviation threshold, the comparison result triggers the logic for generating a process adjustment command.

[0036] In some embodiments, the preset deviation threshold is not a single fixed value, but a dynamic threshold table based on process stage and temperature range, which is preset in the control system. See Table 2 for an example of deviation threshold setting.

[0037] Table 2: Deviation Threshold Setting Table for Each Process Stage Optionally, the logic for generating process adjustment instructions is that when the system detects that the real-time data exceeds the deviation threshold for three consecutive sampling periods, or the deviation value of a single sampling point reaches 1.5 times the deviation threshold, the central controller immediately generates and sends process adjustment instructions to the corresponding actuators.

[0038] In one embodiment of the present invention, after the final tempering treatment, the uniformity of the controlled workpiece is verified. Multiple micro-samples are taken from different characteristic areas of the workpiece, including the workpiece surface, the workpiece core, and areas of abrupt geometric changes. Each micro-sample is subjected to nanoindentation testing to obtain its local nanohardness value. The local nanohardness values ​​of all micro-samples are statistically analyzed, and the average and standard deviation of these hardness values ​​are calculated. When the calculated standard deviation is less than a preset uniformity threshold, the hardness distribution of the workpiece is determined to meet the uniformity requirements. The complete set of dynamic control parameters and process data corresponding to the workpiece that meets the uniformity requirements are recorded, and this information is added to the parameter-performance database.

[0039] The specific procedure for performing nanoindentation testing on each micro-sample is as follows: The surface of the micro-sample to be tested is precisely polished until it achieves a mirror finish. The polished micro-sample is then securely fixed on the sample stage of the nanoindentation tester. A specific geometric indenter is selected, and pressure is applied to the surface of the micro-sample at a preset loading rate until the pressure reaches a preset maximum load. This maximum load is maintained for a preset holding time, and then the pressure is released at a preset unloading rate, allowing the indenter to completely leave the surface of the micro-sample. Throughout the loading, holding, and unloading process, the instrument continuously records the applied pressure value and the displacement depth value of the indenter, forming a complete load-displacement curve. Based on this load-displacement curve, the local nanohardness value of the test point is obtained through analysis and calculation.

[0040] In the specific implementation, after the final tempering treatment, the performance uniformity of the silver-containing martensitic antibacterial stainless steel cylindrical workpiece was verified. The cylindrical workpiece had a diameter of 50 mm and a length of 200 mm. Multiple micro-samples were taken from different characteristic parts of the cylindrical workpiece. Surface samples were taken at three equidistant locations along the axial direction on the cylindrical surface of the workpiece. A core sample was taken at the center of the cross-section of the cylindrical workpiece. At one end of the cylindrical workpiece, there was a stepped transition zone from a diameter of 50 mm to 30 mm. A sample at the geometric abrupt change point at the root arc of the stepped transition zone was taken, for a total of five micro-samples. In the specific implementation, nano-indentation testing was performed on each micro-sample. The test surface of the micro-sample on the cylindrical workpiece was polished with metallographic sandpaper, progressing from 400 grit to 2000 grit. Then, it was polished on a polishing cloth with diamond polishing paste with a particle size of 0.25 micrometers until the test surface achieved a mirror finish and showed no obvious scratches under a microscope. The polished micro-sample is fixed on the sample stage of the nanoindentation tester using vacuum adsorption, ensuring the test surface is perpendicular to the indenter's loading direction. A Beaufort triangular pyramidal indenter with a tip curvature radius of 50 nm is used, and pressure is applied to the surface of the micro-sample at a preset loading rate of 0.2 mN / s. The loading process continues until the pressure reaches the preset maximum load of 10 mN. After maintaining the maximum load of 10 mN for a preset holding time of 10 seconds, the pressure is released at an unloading rate of 0.2 mN / s, allowing the indenter to completely leave the surface of the micro-sample. Throughout the loading, holding, and unloading process, the nanoindentation tester continuously records the applied pressure and the indenter's displacement depth, forming a complete load-displacement curve. Based on the load-displacement curve, the local nanohardness value of the micro-sample is calculated using the instrument's built-in Oliver-Pharr method analysis software.

[0041] In practice, the nanoindentation test selects five different test points on each micro-sample, arranged in a cross shape. The distance between adjacent test points is greater than 20 micrometers to prevent interference between the plastic zones. The local nanohardness values ​​of the five test points are recorded, and the arithmetic mean of these five points is taken as the local nanohardness value of the micro-sample. Statistical analysis is performed on the local nanohardness values ​​of all five micro-samples, calculating the arithmetic mean and standard deviation of the five values. The arithmetic mean is denoted as... The standard deviation is denoted as The calculation relationship is as follows: in: Indicates the first The local nanohardness value of a micro-sample. The calculated standard deviation... When the hardness distribution of the cylindrical workpiece is less than the preset uniformity threshold of 3.0 GPa, it is determined that the hardness distribution meets the uniformity requirements. The preset uniformity threshold of 3.0 GPa is set based on the empirical value of the material hardness standard deviation. The complete set of dynamic control parameters and process data corresponding to the cylindrical workpiece that meets the uniformity requirements are recorded. The complete set of dynamic control parameters for the cylindrical workpiece includes a target superheat of 1180 degrees Celsius, a preset pulse time of 85 seconds, a target isothermal tempering temperature of 235 degrees Celsius, a preset intermediate tempering time of 1100 seconds, a target secondary austenitizing temperature of 840 degrees Celsius, a preset secondary austenitizing time of 550 seconds, a final tempering temperature of 290 degrees Celsius, and a preset final tempering time of 7000 seconds. The process data includes the actual temperature-time curve data for each stage of preheating, heating, pulse, cooling, isothermal, secondary quenching, and final tempering. These dynamic control parameter sets and process data are associated with the unique identifier code of the cylindrical workpiece and supplemented into the parameter-performance database in the form of data records.

[0042] In some embodiments, the micro-samples were cut using a wire electrical discharge machining (EDM) machine with a water-based coolant during the cutting process to avoid creating new heat-affected zones. The specific cutting locations, dimensions, and obtained local nanohardness values ​​of the five micro-samples are recorded in Table 3.

[0043] Table 3: Test Data of Micro-samples for Performance Uniformity Verification Optionally, statistical analysis was performed on the local nanohardness values ​​of all five micro-samples. The five hardness values ​​were 11.8 GPa, 12.1 GPa, 11.6 GPa, 12.3 GPa, and 11.3 GPa, and the arithmetic mean was calculated. The value was 11.82 gigapascals, with a standard deviation of 11.82. Approximately 0.37 gigapascals. The calculated standard deviation... The hardness value is 0.37 GPa, which is less than the preset uniformity threshold of 3.0 GPa. Therefore, the result meets the requirements, and the hardness distribution of the cylindrical workpiece conforms to the uniformity requirement. It can be understood that when recording workpiece information that meets the uniformity requirement, in addition to the dynamically adjusted parameter set, detailed information such as the cut-off position, sample hardness value, calculated average value, and standard deviation from Table 3 is also included. This information is then entered into the parameter-performance database. In some embodiments, the maximum load of the nanoindentation test can be adjusted according to the expected hardness range of the material. For materials with higher hardness, the maximum load can be set to 20 millinewtons or higher; for softer materials, the maximum load can be set to 5 millinewtons to obtain a more accurate load-displacement curve.

[0044] See Figure 4In the statistical analysis verifying the uniformity of hardness in silver-containing martensitic antibacterial stainless steel workpieces, the nano-hardness distribution characteristics are visually presented through box plots. The figure uses "all samples" as the statistical object, showing the local nano-hardness data distribution of micro-samples from different characteristic parts of the workpiece: Median: The median hardness corresponding to the center line is approximately 11.8 GPa, representing the central trend of the overall workpiece hardness, which highly matches the arithmetic mean of the sample data, 11.82 GPa. Interquartile Range (IQR): The box range is 11.6~12.1 GPa, covering the hardness data of the middle 50% of the samples, reflecting the concentration of core data; the smaller box height indicates lower data dispersion. Extreme Values ​​and Outliers: The upper and lower limits extend to 11.3 GPa and 12.3 GPa respectively, corresponding to the minimum and maximum hardness values ​​of all samples. There are no obvious outliers, indicating that the hardness fluctuation range of various parts of the workpiece is controllable. Uniformity determination: Based on the statistical calculation results, the standard deviation of this set of data is about 0.37 GPa, which is far below the preset uniformity threshold of 3.0 GPa. This directly confirms the narrow distribution characteristics shown by the box plot, indicating that after the heat treatment process of this invention is controlled, the hardness distribution of different parts of the workpiece has good uniformity.

[0045] In one embodiment of the present invention, the step of reverse process derivation based on a parameter-performance database and target performance requirements involves receiving the input target hardness range and target toughness range. In the parameter-performance database, all historical process records whose measured hardness and measured impact toughness values ​​simultaneously fall within the input target hardness and target toughness ranges are queried. From all historical process records that meet the conditions, their corresponding historical dynamic control parameter sets are extracted. Multi-objective optimization analysis is performed on all extracted historical dynamic control parameter sets to calculate a set of optimal recommended values ​​for dynamic control parameters. The calculated recommended values ​​for dynamic control parameters are used as the basis for setting the specific values ​​of parameters such as target superheat, preset pulse time, target isothermal tempering temperature, preset intermediate tempering time, target secondary austenitizing temperature, preset secondary austenitizing time, final tempering temperature, and preset final tempering time, for heat treatment of new silver-containing martensitic antibacterial stainless steel workpieces.

[0046] In practical implementation, reverse process derivation is performed based on the parameter-performance database and target performance requirements. The process design system receives the target hardness range and target toughness range input by the user. The target hardness range is set to Rockwell hardness C scale (HRC) 52.0 to 54.0, and the target toughness range is set to Charpy impact energy 60 to 70 Joules. In the parameter-performance database, all historical process records for silver-containing martensitic antibacterial stainless steel with the grade 1Cr13-3Ag are queried. The screening criteria are that the recorded measured hardness value (HRC) is between 52.0 and 54.0, and the recorded measured impact toughness value is between 60 and 70 Joules. A total of eight sets of historical process records matching the above dual-target screening criteria were found in the parameter-performance database. Each set of historical process records contains a complete set of dynamic control parameters and corresponding measured mechanical property values. From all eight sets of historical process records that meet the conditions, extract the corresponding set of historical dynamic control parameters for each set. The set of historical dynamic control parameters includes eight specific parameters: target superheat, preset pulse time, target isothermal tempering temperature, preset intermediate tempering time, target secondary austenitizing temperature, preset secondary austenitizing time, final tempering temperature, and preset final tempering time.

[0047] In practice, a multi-objective optimization analysis is performed on the eight sets of historical dynamic control parameters extracted. This analysis aims to obtain a set of recommended dynamic control parameter values ​​that are optimal in terms of both process stability and the probability of performance compliance. It can be understood that a comprehensive evaluation index is introduced into the multi-objective optimization analysis calculation. This is used to quantitatively evaluate the degree to which the parameter combinations of each set of historical process records approach the target performance center value and the degree of dispersion of the process parameters. A comprehensive evaluation index is calculated for all eight sets of historical process records. Value, selection The set of historical process records with the smallest value is identified as the optimal recommended set of dynamic control parameters. Specific values ​​for this optimal set of recommended dynamic control parameters include, for example: target superheat 1150°C, preset pulse time 120 seconds, target isothermal tempering temperature 250°C, preset intermediate tempering time 900 seconds, target secondary austenitizing temperature 860°C, preset secondary austenitizing time 480 seconds, final tempering temperature 310°C, and preset final tempering time 8000 seconds. In some embodiments, if fewer than three sets of records meet the criteria, the system can appropriately broaden the single target range, for example, by expanding the hardness or toughness range by ±1 unit, and re-query to obtain sufficient samples for optimization analysis.

[0048] It is understandable that the calculated recommended values ​​of the dynamic control parameters are used as the basis for setting the specific values ​​of parameters such as target superheat, preset pulse time, target isothermal tempering temperature, preset intermediate tempering time, target secondary austenitizing temperature, preset secondary austenitizing time, final tempering temperature, and preset final tempering time, for the heat treatment of the new silver-containing martensitic antibacterial stainless steel workpieces. The grade of the new silver-containing martensitic antibacterial stainless steel workpiece is also 1Cr13-3Ag, and its shape is plate-shaped with a thickness of 20 mm. The process control system loads the recommended values ​​of the above dynamic control parameters as standard process parameters. The target preheating temperature for the preheating stage is set to 550 degrees Celsius, and the heating rate for the preheating stage is set to 5 degrees Celsius per second. The target austenitizing temperature for the rapid heating stage is set to 1050 degrees Celsius, and the heating rate for the rapid heating stage is set to 15 degrees Celsius per second. The target superheat for the overheating pulse stage is set to 1150 degrees Celsius, and the preset pulse time is set to 120 seconds. The preset first cooling rate for the inert gas medium strong cooling treatment is set to 50 degrees Celsius per second. The target isothermal tempering temperature for the isothermal treatment is set to 250 degrees Celsius, and the preset intermediate tempering time is set to 900 seconds. The target secondary austenitizing temperature for the secondary quenching treatment is set to 860 degrees Celsius, and the preset secondary austenitizing time is set to 480 seconds. The preset second cooling rate is set to 30 degrees Celsius per second. The final tempering temperature for the final tempering treatment is set to 310 degrees Celsius, and the preset final tempering time is set to 8000 seconds.

[0049] See Figure 5In verifying the uniformity of hardness in silver-containing martensitic antibacterial stainless steel workpieces, the hardness distribution characteristics of different parts can be quantitatively analyzed using box plots. The figure shows the statistical distribution and dispersion of Rockwell hardness (HRC) in each part, grouped into five typical characteristic parts: surface, core, edge, corner, and center. The red dashed line represents the baseline for the average hardness of the entire workpiece (HRC 53.0). Statistically, the surface part has a median hardness of approximately HRC 53.15, ranging from HRC 52.85 to 53.48, slightly higher than the average hardness, with minimal dispersion and no outliers, indicating good surface hardness stability. The core and edge parts both have median hardness of approximately HRC 52.7, ranging from HRC 52.42 to 52.98 and HRC 52.30 to 52.93 respectively, both lower than the average hardness. The edge part has one slight outlier (HRC 53.32). The hardness dispersion in the two parts is similar, reflecting the hardness gradient characteristics between the core and edge regions. Corner areas: The median hardness is approximately HRC52.98, roughly in line with the average hardness, but the distribution range is the widest (HRC52.32~53.85), with significantly higher dispersion than other areas. This reflects the inhomogeneity of heat treatment cooling and microstructure transformation at geometric abrupt changes, making it a key weak area for hardness uniformity control. Center areas: The median hardness is approximately HRC52.95, with a distribution range of HRC52.52~53.30. The dispersion is moderate, and the overall hardness is close to the average, exhibiting good uniformity. In summary, the hardness of the entire workpiece falls within the target control range (HRC52.0~54.0), meeting the preset performance requirements. The corner areas exhibit the greatest hardness dispersion due to geometric effects, while the core and edge areas have slightly lower hardness. The surface and center areas have hardness closer to the mean and better stability. This box plot can serve as an important basis for optimizing the dynamic control parameter set, providing data support for subsequent targeted improvements to the heat treatment process at geometric abrupt changes such as corners.

[0050] See Figure 6 This image presents an electron microscope (SEM) image at a scale of 1.00 μm and a magnification of 15,000x. The microstructure of silver-containing martensitic stainless steel was obtained using scanning electron microscopy (SEM) in backscattered electron (BSE) mode. The dark gray matrix exhibits a typical elongated lamellar structure, representing the martensitic matrix; within this matrix, numerous fine, bright white, spherical particles are dispersed, representing the silver precipitates. Because the BSE imaging mode is sensitive to differences in atomic number, these bright white particles correspond to silver precipitates with higher atomic numbers.

[0051] See Figure 7This XRD pattern represents the phase analysis results of silver-containing martensitic antibacterial stainless steel processed using the process of this invention. The horizontal axis represents the diffraction angle, and the vertical axis represents the diffraction signal intensity. Strong and sharp martensitic diffraction peaks are detected in the pattern, corresponding to the martensitic matrix main phase. Simultaneously, obvious Ag elemental characteristic diffraction peaks are observed, with peak positions perfectly matching the standard Ag card. No impurity phase peaks such as silver oxide or silver nitride are present, and the baseline is flat. The results confirm that the main phase of the material is martensite, with silver existing as elemental Ag. The phase is pure, with no harmful impurity phases generated, consistent with the technical principle of non-equilibrium supersaturated matrix + precise tempering to control silver phase precipitation.

[0052] See Figure 8 This EDS (Energy Dispersive Spectroscopy) spectrum presents the qualitative and quantitative elemental analysis results of silver-containing martensitic antibacterial stainless steel. The horizontal axis represents X-ray energy, and the vertical axis represents signal count intensity. The spectrum clearly shows characteristic peaks for the Fe matrix, Cr alloying elements, and Ag antibacterial elements. The peak positions of these three elements are standard, the peak shapes are complete, and there is no interference from impurity elements. Combined with surface scan / spot scan data, it can be further confirmed that the Ag element is uniformly distributed in the matrix, without local enrichment or absence. This corroborates the SEM microstructure conclusions, directly proving that the heat treatment process of this invention can achieve uniform silver distribution, meeting the compositional uniformity requirements of antibacterial stainless steel.

[0053] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for dynamically controlling the hardness and toughness of silver-containing martensitic antibacterial stainless steel during heat treatment, characterized in that... The method includes: Prepare the original workpiece of silver-containing martensitic antibacterial stainless steel and place the original workpiece into a heating furnace with programmed temperature rise function. The heating furnace is programmed to rise, causing the original workpiece to go through a preheating stage, a rapid heating stage, and an overheating pulse stage. In the preheating stage, the furnace temperature is controlled to rise at a constant rate to the target preheating temperature. In the rapid heating stage, the furnace temperature is controlled to rise at an even higher constant rate to the target austenitizing temperature. In the overheating pulse stage, the furnace temperature is instantaneously raised to the target superheat above the target austenitizing temperature and maintained for a preset pulse time. After the overheating pulse stage ends, the heating furnace is subjected to strong cooling treatment with an inert gas medium, and the original workpiece is rapidly cooled to below the target martensite transformation temperature at a preset first cooling rate to obtain an initial quenched structure with a non-equilibrium supersaturated matrix. The obtained initial quenched structure is immediately placed into a tempering medium bath within a preset temperature range for isothermal treatment. The isothermal treatment time is controlled to obtain an intermediate tempered structure. The intermediate tempered structure is subjected to a second quenching treatment to obtain a second quenched structure, and then a final tempering treatment is performed.

2. The method for dynamically controlling the hardness and toughness of silver-containing martensitic antibacterial stainless steel under heat treatment according to claim 1, characterized in that, After the overheating pulse phase ends, the heating furnace is subjected to strong cooling treatment with an inert gas medium, including: At the instant the preset pulse time arrives, high-pressure, low-temperature inert gas is introduced into the heating furnace. The flow rate and pressure of the high-pressure low-temperature inert gas are controlled so that the working environment temperature inside the furnace decreases at the preset first cooling rate. Monitor the real-time temperature of the original workpiece, and stop the introduction of the high-pressure low-temperature inert gas when the real-time temperature drops to the target quenching termination temperature below the target martensite start transformation temperature. The inert gas medium strong cooling process continuously records temperature-time curves, which are used for analysis of subsequent process steps.

3. The method for dynamically controlling the hardness and toughness of silver-containing martensitic antibacterial stainless steel under heat treatment according to claim 2, characterized in that, The step of immediately placing the obtained initial quenched structure into a tempering medium bath within a preset temperature range for isothermal treatment includes: The preset tempering medium tank contains a molten low-temperature salt bath, the temperature of which is controlled at the target isothermal tempering temperature. The initial quenched structure is transferred from the heating furnace and immersed in the molten low-temperature salt bath, and the isothermal time is calculated. During the isothermal treatment, the molten low-temperature salt bath is continuously stirred to ensure temperature uniformity; When the isothermal treatment time reaches the preset intermediate tempering time, the workpiece is removed from the molten low-temperature salt bath to obtain the intermediate tempered structure.

4. The method for dynamically controlling the hardness and toughness of silver-containing martensitic antibacterial stainless steel under heat treatment according to claim 3, characterized in that, Performing a secondary quenching treatment on the intermediate tempered structure to obtain a secondary quenched structure, and then performing a final tempering treatment includes: The secondary quenching process includes reheating the intermediate tempered structure to the target secondary austenitizing temperature and holding it at that temperature, and then cooling it to room temperature at a preset second cooling rate to obtain a secondary quenched structure. The intermediate tempered structure is placed into a secondary heating device; The temperature of the secondary heating device is raised to the target secondary austenitizing temperature, which is lower than the initial target austenitizing temperature, and then held at this temperature for a preset secondary austenitizing time. After the heat preservation is completed, the intermediate tempered structure is removed from the secondary heating device and quickly placed into the rapid cooling oil tank; Control the oil temperature and circulation rate of the rapid cooling oil tank to cool the workpiece to room temperature at the preset second cooling rate, thereby forming the secondary quenching structure; The second cooling rate is lower than the preset first cooling rate; The obtained secondary quenched structure is subjected to a final tempering treatment, which includes holding the secondary quenched structure at a preset final tempering temperature for a preset final tempering time, and then air cooling to room temperature to achieve dynamic control of the hardness and toughness of the silver-containing martensitic antibacterial stainless steel.

5. The method for dynamically controlling the hardness and toughness of silver-containing martensitic antibacterial stainless steel under heat treatment according to claim 4, characterized in that, The target superheat, preset pulse time, target isothermal tempering temperature, preset intermediate tempering time, target secondary austenitizing temperature, preset secondary austenitizing time, final tempering temperature, and preset final tempering time together constitute a dynamic control parameter set. The method also includes the step of establishing the correspondence between the dynamic control parameter set and the desired mechanical properties. Multiple sets of process samples were prepared for the same grade of silver-containing martensitic antibacterial stainless steel. For each group of process samples, a different set of parameter values ​​from the aforementioned dynamic control parameter set is set. The entire process of preheating, rapid heating, over-temperature pulse, inert gas medium strong cooling, obtaining initial quenched structure, isothermal treatment to obtain intermediate tempered structure, secondary quenching treatment to obtain secondary quenched structure, and final tempering treatment is performed on each group of process samples. Hardness and impact toughness tests were performed on each group of processed samples to obtain the measured hardness and impact toughness values. The set of dynamic control parameters corresponding to each group of process samples is associated with the obtained measured hardness value and measured impact toughness value to form a parameter-performance database.

6. The method for dynamically controlling the hardness and toughness of silver-containing martensitic antibacterial stainless steel under heat treatment according to claim 5, characterized in that, It also includes steps for real-time feedback and adjustment of the heat treatment process based on online monitoring data: During the preheating stage, rapid heating stage, and overheating pulse stage, the core temperature data of the workpiece is collected in real time using a miniature thermocouple embedded in the original workpiece. During the inert gas medium strong cooling process, an infrared temperature measuring device is used to monitor the cooling rate data of the workpiece surface in real time. The real-time collected core temperature data and the real-time monitored cooling rate data are compared with the standard process curves pre-stored in the parameter-performance database. When the core temperature data or cooling rate data deviates from the standard process curve by more than a preset deviation threshold, a process adjustment command is generated; The process adjustment command is used to adjust the heating rate of the heating furnace, the flow rate of the high-pressure low-temperature inert gas, or the temperature of the tempering medium tank, so that the actual process path returns to the standard process curve.

7. The method for dynamically controlling the hardness and toughness of silver-containing martensitic antibacterial stainless steel under heat treatment according to claim 6, characterized in that, The step of comparing the real-time collected core temperature data and the real-time monitored cooling rate data with the standard process curves pre-stored in the parameter-performance database includes: From the parameter-performance database, retrieve the standard temperature-time curve corresponding to the currently executed dynamic control parameter set as the standard process curve; The real-time collected core temperature data is integrated according to the time series to form a real-time core temperature curve; The real-time core temperature curve is synchronously superimposed and compared with the temperature curve of the corresponding stage in the standard process curve, and the temperature deviation value at each time point is calculated. The temperature drop per unit time is calculated from the real-time monitored cooling rate data to form a real-time cooling rate curve; The real-time cooling rate curve is compared with the cooling rate curve of the corresponding cooling stage in the standard process curve, and the rate deviation value is calculated.

8. The method for dynamically controlling the hardness and toughness of silver-containing martensitic antibacterial stainless steel under heat treatment according to claim 7, characterized in that, After the final tempering process is completed, the performance uniformity of the regulated workpiece is verified, including: Multiple micro-samples are taken from different characteristic parts of the workpiece, including the workpiece surface, the workpiece core, and the workpiece geometry abrupt change. Nanoindentation tests were performed on each of the cut micro-samples to obtain the local nanohardness value of each micro-sample. Statistical analysis was performed on the local nanohardness values ​​of all micro samples to calculate the average and standard deviation of the hardness values; When the standard deviation is less than the preset uniformity threshold, the hardness distribution of the workpiece is determined to meet the uniformity requirements. Record the complete set of dynamic control parameters and process data corresponding to the workpiece that meets the uniformity requirements, and supplement the parameter-performance database.

9. The method for dynamically controlling the hardness and toughness of silver-containing martensitic antibacterial stainless steel under heat treatment according to claim 8, characterized in that, The nanoindentation test performed on each of the cut micro-samples includes: The surface of the micro sample to be tested is polished to a mirror finish; The polished micro-samples are fixed on the sample stage of the nanoindentation tester; A pressure needle with a specific geometry is selected to apply pressure to the surface of a micro sample at a preset loading rate until the preset maximum load is reached. After maintaining the maximum load for a preset holding time, the pressure is released at a preset unloading rate, so that the pressure needle completely leaves the surface of the micro sample. Throughout the entire loading, holding, and unloading process, the applied pressure value and the displacement depth value of the indenter are continuously recorded to form a complete load-displacement curve; Based on the load-displacement curve, the local nanohardness value is obtained through analysis and calculation.

10. The method for dynamically controlling the hardness and toughness of silver-containing martensitic antibacterial stainless steel under heat treatment according to claim 9, characterized in that, It also includes a step of reverse process derivation based on the parameter-performance database and target performance requirements: Receive the target hardness range and target toughness range from the input; In the parameter-performance database, query all historical process records where the measured hardness value and the measured impact toughness value both fall within the target hardness range and the target toughness range; Extract the corresponding set of historical dynamic control parameters from all historical process records that meet the conditions; Multi-objective optimization analysis was performed on all extracted historical dynamic control parameter sets to calculate a set of optimal recommended values ​​for dynamic control parameters; The recommended values ​​of the dynamic control parameters are used as the basis for setting the specific values ​​of the target superheat, preset pulse time, target isothermal tempering temperature, preset intermediate tempering time, target secondary austenitizing temperature, preset secondary austenitizing time, final tempering temperature and preset final tempering time, and are used to heat treat new silver-containing martensitic antibacterial stainless steel workpieces.

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