Method for determining strain-induced precipitation kinetics of carbide based on thermal simulation experiment

Abstract

The invention discloses a method for measuring carbide strain-induced precipitation kinetics based on a thermal simulation experiment, and relates to the technical field of alloy steel hot working, and the method comprises the following steps: obtaining stress and time changes of alloy steel in a heat preservation process after deformation at different rolling temperatures in an austenitizing temperature interval; generating a stress and time curve at each rolling temperature according to the stress and time change after rolling; the starting time and the ending time of strain-induced precipitation of the carbide in the heat preservation process of the alloy steel are measured; a carbide precipitation kinetics curve is generated based on the start time, the end time, and the rolling temperature. Therefore, the carbide precipitation starting and ending time can be extracted only by continuously collecting stress and time in the single heat preservation process corresponding to each rolling temperature, heat preservation interruption and sample replacement are not needed, operation is easy, the workload is small, a traceable and comparable time curve can be conveniently formed, and the method is suitable for large-scale popularization and application. Meanwhile, the whole strain-induced precipitation process and the interaction relationship between precipitation and static recrystallization are intuitively reflected.

Description

Technical Field

[0001] This invention relates to the field of hot working technology for alloy steel, and more specifically, to a method for determining the strain-induced precipitation kinetics of carbides based on thermal simulation experiments. Background Technology

[0002] During the controlled rolling process of alloy steel, rolling deformation increases the deformation energy storage and defect quantity in the austenite, raising the precipitation chemical free energy in the austenite and leading to strain-induced precipitation of carbides. Excessive strain-induced carbide precipitation, if not properly controlled, will inevitably consume the limited alloying elements dissolved in the matrix, reducing the precipitation of nanoscale carbides on the matrix during subsequent phase transformations, thus diminishing the carbide precipitation strengthening effect and hindering the improvement of the overall properties of the alloy steel. Therefore, measuring and controlling the strain-induced precipitation of carbides has a significant impact on the final microstructure and properties of alloy steel.

[0003] When studying the precipitation characteristics and kinetics of strain-induced carbides in alloy steel, it is necessary to set appropriate rolling processes to fully utilize the beneficial effects of strain-induced carbides and improve the overall performance of the steel. Since the strain-induced precipitation kinetics of carbides are mainly characterized by precipitation-temperature-time (PTT) curves, measuring the strain-induced precipitation kinetics curves of carbides in alloy steel can provide data guidance for setting controlled rolling process parameters, thereby optimizing the microstructure and properties of the steel.

[0004] Currently, the commonly used methods for studying the strain-induced precipitation kinetics of alloy steel include resistivity measurement, two-pass hot compression, and electrolytic dissolution. However, these methods all obtain experimental data through a large number of independent individual experiments. The experimental operations are complex and the experimental volume is large, making it difficult to intuitively reflect the entire strain-induced precipitation process and the interaction between precipitation and static recrystallization. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a method for determining the strain-induced precipitation kinetics of carbides based on thermal simulation experiments. This method only requires analyzing the stress and corresponding time data continuously collected during a single isothermal holding process at each rolling temperature of the alloy steel sample. The start and end times of strain-induced precipitation of carbides can be directly extracted. The entire measurement process does not require interruption of the holding process or replacement of the sample. The experimental operation is simple and the experimental quantity is small. This allows for the formation of traceable, comparable, and modelable time curves based on the start and end times of precipitation. At the same time, it intuitively reflects the entire strain-induced precipitation process and the interaction between precipitation and static recrystallization.

[0006] To achieve the above objectives, in a first aspect, embodiments of the present invention provide a method for determining carbide precipitation kinetics based on thermal simulation experiments. The method includes: obtaining stress and time during the holding process after deformation of an alloy steel sample at different rolling temperatures, wherein the rolling temperature is lower than a preset solution temperature, and the preset solution temperature characterizes the critical temperature for carbide solid solution in the alloy steel; generating stress-time curves of the alloy steel sample during the holding period after deformation at different rolling temperatures based on the stress and time; determining the start and end times of carbide strain-induced precipitation of the alloy steel sample at different rolling temperatures based on the stress-time curves; and generating a carbide precipitation kinetics curve based on the start time, the end time, and the rolling temperature.

[0007] In this embodiment, by acquiring the stress and time of the alloy steel sample during the holding process after deformation at different rolling temperatures, stress-time curves of the alloy steel sample at different rolling temperatures are generated. This facilitates the determination of the start and end times of carbide precipitation during the holding process based on the stress-time curves. It also helps to directly generate a kinetic curve for carbide precipitation based on the start and end times and different rolling temperatures. The kinetic characteristics of carbide precipitation can be obtained by utilizing identifiable plateau segments or inflection points on the kinetic curves. Thus, only the stress and time data continuously collected during a single isothermal holding process corresponding to each rolling temperature need to be analyzed to directly extract the start and end times of strain-induced carbide precipitation. This eliminates the need to interrupt the holding process, replace the sample, or conduct additional microstructure observation or phase analysis experiments. The experimental operation is simple and requires minimal experimental quantity. Moreover, the kinetic curve is no longer a snapshot of discrete time points but a traceable, comparable, and modelable continuous time curve, thus intuitively reflecting the entire strain-induced precipitation process and its interaction with the static recrystallization of the alloy steel after rolling deformation.

[0008] In some embodiments, obtaining the stress and time of the alloy steel sample after rolling deformation during the heat preservation process includes: welding thermocouple wires to the sidewall of the alloy steel sample, and attaching tantalum sheets and graphite sheets to both ends in sequence to obtain the alloy steel sample; in an environment with inert gas, heat preservation is carried out on the alloy steel sample after deformation at different rolling temperatures to obtain the stress and time of the alloy steel sample during the heat preservation process after deformation at different rolling temperatures.

[0009] This setup ensures that the temperature feedback is closely attached to the center of the alloy steel by welding the thermocouple wire sidewalls, avoiding errors in center temperature measurement. The combination of tantalum / graphite sheets provides high-temperature lubrication to eliminate end-face friction interference and reduces temperature gradient, thereby ensuring that the measured stress truly reflects the intrinsic rheological response of the material. In the inert gas environment, high-temperature oxidation is effectively suppressed, avoiding the introduction of false stress fluctuation interference by the surface oxide layer.

[0010] In some embodiments, the step of holding the alloy steel sample deformed at different rolling temperatures in an inert gas environment to obtain the stress and time of the alloy steel sample during the holding process after different rolling temperatures includes: heating the alloy steel sample to a first preset temperature at a first preset speed in the inert gas environment and holding it for a first duration to obtain an initial shape of the alloy steel sample; cooling the initial shape to a second preset temperature at a second preset speed and holding it for a second duration, then rolling it at the second preset temperature to obtain a first deformed body; cooling the first deformed body to a third preset temperature at a third preset speed and holding it for a third duration, then rolling it at the third preset temperature to obtain a second deformed body; obtaining the stress and time of the alloy steel sample at the current third preset temperature during the process of holding the second deformed body at the third preset temperature for a fourth duration; changing the third preset temperature value and repeating the above process to obtain the stress and time of the alloy steel sample during the holding process after rolling at different third preset temperatures.

[0011] This setup simulates the two-stage rolling path from roughing to finishing in industrial controlled rolling. The first stage (second preset temperature) simulates the roughing path, providing sufficient driving force for strain-induced precipitation. The second stage involves deformation and immediate isothermal treatment at the third preset temperature (i.e., the finishing path). By using rapid cooling followed by short-term heat preservation, the uniformity of temperature and consistency of initial microstructure of each alloy steel sample are ensured, making the stress relaxation behavior at different temperatures strictly repeatable.

[0012] In some embodiments, the step of holding the alloy steel sample deformed at different rolling temperatures in an inert gas environment to obtain the stress and time of the alloy steel sample during the holding process after deformation at different rolling temperatures includes: heating the alloy steel sample to a first preset temperature at a first preset speed in an inert gas environment and holding it for a first duration to obtain an initial shape of the alloy steel sample; cooling the initial shape to a second preset temperature at a second preset speed and holding it for a second duration to obtain a first deformed body; cooling the first deformed body to a third preset temperature at the second preset speed and holding it for a third duration and then rolling it at a third preset temperature to obtain a second deformed body; obtaining the stress and time of the alloy steel sample during the holding process after rolling at a third preset temperature while holding the second deformed body at the third preset temperature for a fourth duration; changing the third preset temperature value and repeating the above process to obtain the stress and time of the alloy steel sample during the holding process after rolling at different third preset temperatures.

[0013] This setting eliminates the rolling process at the second preset temperature and the rough rolling process, allowing for rapid cooling directly from the first preset temperature to the finishing rolling temperature range. This can suppress premature precipitation of carbides, causing precipitation to occur at a lower rolling temperature range, thereby leveraging the advantage of grain refinement.

[0014] In some embodiments, the holding time of the alloy steel sample at different rolling temperatures is obtained by the following steps: taking the time from the start of heating of the alloy steel sample to the end of rolling as a first time; taking the time from the start of heating of the alloy steel sample to the end of rolling and holding it at a preset holding time as a second time; and subtracting the first time from the second time to obtain the time.

[0015] This setup avoids time disturbances during the deformation process itself, allowing the time axis of the entire heat preservation stage to focus entirely on the competitive evolution of precipitation and recrystallization; it is highly consistent with the nature of physical metallurgy, ensuring that the start and end times of carbide precipitation extracted at different temperatures have a unified time reference.

[0016] In some embodiments, generating stress-time curves corresponding to the holding at different rolling temperatures based on the stress and the time includes: generating initial stress-time curves corresponding to the different rolling temperatures based on the stress and the time; and performing a logarithmic transformation on the initial stress-time curves to obtain the stress-time curves corresponding to the holding at different rolling temperatures.

[0017] This setup, through logarithmic transformation, compresses the time scale of the long-term heat preservation period, amplifies the minute stress changes in the early precipitation response, and clearly separates the inflection points of the platform start and end, which were originally difficult to distinguish under conventional time coordinates. It linearizes the nonlinear stress relaxation process and highlights the dynamic inflection point characteristics.

[0018] In some embodiments, obtaining the start and end times of carbide precipitation in the alloy steel sample at different rolling temperatures based on the stress-time curve includes: acquiring a first inflection point and a second inflection point on the stress-time curve, wherein the first inflection point is the first inflection point to appear on the stress-time curve, and the second inflection point is the last inflection point to appear on the stress-time curve; taking the time corresponding to the first inflection point as the start time of carbide precipitation; and taking the time corresponding to the second inflection point as the end time of carbide precipitation.

[0019] With this setup, the first inflection point corresponds to the beginning of the precipitated phase pinning dislocations / grain boundaries, which inhibits recrystallization softening and hinders the stress reduction trend; the second inflection point corresponds to the coarsening and instability of the precipitated phase, the pinning force decays, and recrystallization restarts, causing the stress to decrease again; the time window between the two inflection points is the effective precipitation period (from the start time to the end time of carbide precipitation), and the C-shaped relationship (nose tip effect) between the width of the time window between the two inflection points and the temperature directly reflects the dynamic balance among precipitation nucleation rate, growth rate and coarsening rate.

[0020] Secondly, embodiments of the present invention provide a system for determining the kinetics of carbide strain-induced precipitation based on thermal simulation experiments. The system includes: an acquisition module for acquiring the stress and time of an alloy steel sample during the holding process after deformation at different rolling temperatures, wherein the rolling temperature is lower than a preset solution temperature, and the preset solution temperature characterizes the critical temperature for carbide solid solution in the alloy steel; and a processing module for generating stress-time curves of the alloy steel sample during the holding period after deformation at different rolling temperatures based on the stress and time; determining the start and end times of carbide strain-induced precipitation of the alloy steel sample at different rolling temperatures based on the stress-time curves; and generating a carbide precipitation kinetics curve based on the start time, the end time, and the rolling temperature.

[0021] Thirdly, embodiments of the present invention provide an experimental machine, including a controller, a clamp, and a thermocouple wire. The clamp is used to hold an alloy steel sample and apply pressure, the thermocouple wire is used to monitor the temperature of the alloy steel sample, and the controller is used to execute the computer program to realize the method for determining the strain-induced precipitation kinetics of carbides based on thermal simulation experiments as described in the first aspect.

[0022] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 A flowchart of a method for determining the strain-induced precipitation kinetics of carbides based on thermal simulation experiments, provided in an embodiment of the present invention; Figure 2 A process curve diagram of the entire rolling process of alloy steel samples provided in the embodiments of the present invention; Figure 3The stress-time curves of alloy steel held at different rolling temperatures are provided for embodiments of the present invention. Figure 4 The strain-induced precipitation temperature-time curve provided in the embodiments of the present invention; Figure 5 These are characteristic images of strain-induced carbide precipitation at different isothermal times at 900°C according to embodiments of this disclosure; Figure 6 This is a curve showing the temperature-time of strain-induced precipitation of carbides during a single rolling process, provided in an embodiment of the present invention. Figure 7 This is a schematic diagram of the functional modules of the carbide precipitation kinetics measurement system provided in an embodiment of the present invention.

[0025] Icons: 1000 - Carbide precipitation kinetics measurement system; 1100 - Acquisition module; 1200 - Processing module. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0027] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0028] It should be noted that relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0029] The following is a brief description of some of the technologies involved in the embodiments of the present invention.

[0030] In the controlled rolling process of alloy steel, rolling deformation increases the deformation energy storage and defect quantity of austenite, raising the precipitation chemical free energy in austenite and leading to strain-induced carbide precipitation. Correspondingly, strain-induced carbide precipitation can effectively pin grain boundary movement, refine grains, and simultaneously inhibit or even completely prevent the recrystallization process of deformed austenite, causing deformation strain accumulation and retaining deformation defects. The accumulated strain and retained deformation defects can promote the γ→α phase transformation of alloy steel and increase the nucleation sites for the phase transformation, further refining the grains and improving the performance of the alloy steel. However, the austenite strain-induced carbide precipitation generated during high-temperature rolling is prone to coarsening, weakening the pinning effect. Furthermore, excessive strain-induced carbide precipitation will inevitably consume the limited alloying elements dissolved in the matrix, reducing the precipitation of nanoscale carbides on the matrix in subsequent phase transformations, decreasing the carbide precipitation strengthening effect, and hindering the improvement of the overall performance of the alloy steel. Therefore, it is necessary to study the precipitation characteristics and kinetics of strain-induced carbide precipitation in alloy steel, and then set up a suitable rolling process to fully utilize the beneficial effects of strain-induced carbide precipitation in alloy steel and improve the comprehensive performance of the steel.

[0031] However, as mentioned in the background section, the commonly used methods for studying the strain-induced precipitation kinetics of alloy steel include resistivity measurement, two-pass hot compression, and electrolytic dissolution. But these methods all obtain experimental data through a large number of independent individual experiments. The experimental operation is complicated, the experimental quantity is large, and it is difficult to intuitively reflect the entire strain-induced precipitation process and the interaction between precipitation and static recrystallization.

[0032] Therefore, this invention provides a method for determining the strain-induced precipitation kinetics of carbides based on thermal simulation experiments. This method only requires analyzing stress and corresponding time data continuously collected during a single isothermal holding process at each rolling temperature to directly extract the start and end times of strain-induced precipitation. The entire measurement process does not require interruption of the holding period or replacement of the sample. The experimental operation is simple and requires minimal experimental quantity, facilitating the formation of traceable, comparable, and modelable time curves based on the start and end times of precipitation. This provides a direct reflection of the entire strain-induced precipitation process and the interaction between precipitation and static recrystallization. (See also...) Figure 1 , Figure 1 This is a flowchart of a method for determining the strain-induced precipitation kinetics of carbides based on thermal simulation experiments, provided in an embodiment of the present invention. The method includes steps S100 to S400: S100. Obtain the stress and time changes of alloy steel samples during the heat preservation process after deformation at different rolling temperatures.

[0033] In this embodiment, the rolling temperature is lower than the preset solution temperature, which characterizes the critical temperature for carbide solid solution in alloy steel. The preset solution temperature is denoted as T1, and is the highest temperature at which carbides completely dissolve in the austenite matrix under equilibrium conditions, calculated based on the chemical composition of the alloy steel and combined with thermodynamic formulas. The value of T1 varies with the type and content of alloying elements. For example, T1 is 1107℃ for Ti-containing microalloyed steel or 1135℃ for Ti-containing microalloyed steel. During the experiment, the rolling temperature of the last pass is strictly controlled to be below T1, specifically between 860℃ and 960℃, to ensure that the austenite is in a supersaturated state after rolling deformation, providing thermodynamic driving force for subsequent strain-induced precipitation. Stress and time are collected in real time by the force module of the thermal simulation test machine, where time is defined as the time period from the end of the last rolling pass to the holding period, corresponding to the entire process of the sample completing plastic deformation at the set deformation rate.

[0034] It should be noted that, for reference Figure 2 , Figure 2 The process curve of the entire rolling process of the alloy steel sample provided in this embodiment of the invention can be understood as follows: the alloy steel sample is heated to gradually austenitize, and then successively undergoes cooling and rolling. After the final rolling pass, it is held at a certain temperature, which is the stress relaxation stage in the curve. The kinetic measurement of carbide precipitation in this embodiment of the invention is specifically for the stress relaxation stage. During this stage, different rolling temperatures are used for holding to obtain the stress and time of the alloy steel sample during the holding process.

[0035] S200. Stress-time curves of alloy steel samples during the holding period after different rolling temperatures are generated based on stress and time.

[0036] In this embodiment, the stress-time curve specifically refers to the relationship between the true stress recorded immediately after rolling and the holding period, and the holding time. That is, with the rolling termination time as the zero point, the true stress values ​​borne by the sample during the holding process are continuously collected to form a dynamic response curve reflecting stress relaxation behavior. Figure 2 The curve describes the stress relaxation stage during rolling; it does not depict instantaneous stress changes during the rolling process, but rather focuses on the microstructure evolution stage dominated by the release of deformation energy, such as... Figure 3 As shown, Figure 3 The stress-time curve of alloy steel under different rolling temperatures provided in this embodiment of the invention is shown. The horizontal axis represents the holding time t, and the vertical axis represents the true stress σ measured at the corresponding time. All data are from temperature, time, and force signals synchronously collected by the Gleeble-3800 thermal simulation test machine under an argon protective atmosphere and imported into Origin software for visualization processing.

[0037] S300. Determine the start and end times of carbide strain-induced precipitation in alloy steel samples at different rolling temperatures based on the stress-time curve.

[0038] In this embodiment, during the heat treatment stage after rolling, the alloy steel sample will first undergo static recovery and static recrystallization, resulting in a decrease in dislocation density and a continuous decrease in stress. Once strain-induced precipitation begins, the newly formed carbide particles pin dislocations and grain boundaries, inhibiting the softening mechanism, which significantly slows down the stress decline trend and may even result in a brief plateau or a slight rebound, manifested as an inflection point in the stress-time curve. Subsequently, as the precipitated phase coarsens and becomes unstable, the pinning ability weakens, and the stress decreases again, forming a second inflection point. Therefore, the time corresponding to the first inflection point is the start time Ps of carbide strain-induced precipitation, and the time corresponding to the last inflection point is the end time Pf when the precipitation process is basically completed. Both are accurately determined by the tangent method from the logarithmically transformed stress-lg(t) curve.

[0039] S400, based on start time, end time and rolling temperature, generates carbide precipitation kinetic curves.

[0040] In this embodiment, the kinetic curve is the strain-induced precipitation temperature-time curve (PTT curve), such as... Figure 4 As shown, Figure 4 The strain-induced precipitation temperature-time curve provided in this embodiment of the invention is constructed by plotting the rolling temperature on the horizontal axis and the logarithmic time on the vertical axis. The Ps and Pf values ​​determined at each temperature point are plotted and connected to form two envelope lines, which together enclose a typical C-shaped region. The maximum bending position corresponds to the temperature range with the shortest precipitation incubation period, for example, about 900°C, at which point Ps is about 60 seconds and Pf is about 680 seconds. This curve does not rely on discrete measurements of multiple independent samples, but is obtained by analyzing the stress response of a single sample during a continuous holding process under a series of temperature conditions, thus possessing inherent consistency and physical interpretability.

[0041] In some embodiments, for step S100, one possible implementation of the present invention is that step S100 includes sub-steps S110~S120: S110. Thermocouple wires are welded to the sidewalls of the alloy steel sample, and tantalum sheets and graphite sheets are attached to both ends in sequence to obtain the alloy steel sample.

[0042] In this embodiment, K-type or R-type thermocouple wires are selected. One end of the wire is welded to the center of the cylindrical sample using a thermocouple welding machine at a voltage of 30–40V. The distance between the two thermocouple wires is controlled at approximately 1mm to ensure temperature measurement accuracy. Tantalum sheets and graphite sheets are sequentially attached to both ends of the sample using a high-temperature lubricant to reduce the interference of end-face friction on deformation uniformity during compression and to prevent the sample from sticking to the clamp under high temperature and pressure. Then, the axial displacement of the spindle of the thermal simulation test machine is adjusted so that the clamp just presses against the alloy steel sample. The sample is cylindrical in shape, with dimensions satisfying a length greater than 10mm and less than 20mm, an aspect ratio between 1 and 2, and a surface roughness controlled to ≤Ra0.4μm to balance thermal conductivity stability and mechanical contact reliability.

[0043] S120. In an environment with an inert gas, the alloy steel samples deformed at different rolling temperatures are kept at a constant temperature to obtain the stress and time of the alloy steel samples during the holding process after deformation at different rolling temperatures.

[0044] In this embodiment, the other end of the thermocouple wire is connected to the T1 temperature channel of the thermal simulation experimental machine. Then, the experimental chamber door is closed and a vacuum is drawn. After the required vacuum level is reached in the experimental chamber, the vacuuming is stopped, and then an inert gas is introduced into the experimental chamber. Specifically, the inert gas is high-purity argon, and the experimental chamber is evacuated to below 1.5 × 10⁻⁶ before introduction. - ¹Pa is used to eliminate the interference of oxygen and moisture on high-temperature oxidation and phase transformation behavior; the rolling operation is completed on the Gleeble-3800 thermal simulation test machine. The entire process is programmed and controlled by Quizsim software according to the experimental process flow data, and the thermal simulation test machine runs according to the given process, including multiple stages such as heating, cooling, heat preservation, deformation and isothermal operation; different rolling temperatures refer to the isothermal platform temperature at the last deformation pass. The temperature setting range is 860–960℃, and a complete set of experiments is carried out independently at each target temperature. The stress and time corresponding to the temperature point are collected for each set of experiments.

[0045] In some embodiments, for step S120, one possible implementation of the present invention is that step S120 includes sub-steps S121 to S124: S121. In an environment with an inert gas, the alloy steel sample is heated to a first preset temperature at a first preset speed and held for a first duration to obtain the initial shape of the alloy steel sample.

[0046] In this embodiment, the first preset speed is 1–50℃ / s, the first preset temperature is 1100–1300℃, and the first duration is 1–10 minutes, in order to achieve austenitization, so that the second phase other than nitrogen-containing compounds is fully dissolved, and a single-phase austenitic structure with uniform composition and appropriate grain size is obtained; heating and holding are both completed in an argon protective atmosphere to avoid surface decarburization and oxidation. After the holding is completed, the sample is in a fully austenitized state, providing a consistent initial microstructure basis for subsequent controllable deformation.

[0047] S122. The initial shape is cooled to a second preset temperature at a second preset speed, and held at that temperature for a second duration before being rolled at the second preset temperature to obtain a first deformed body.

[0048] In this embodiment, the second preset speed is 1–100℃ / s, the second preset temperature is 1000–1200℃, and the second duration is 5–20 seconds. This stage belongs to the rough rolling simulation process, and its main purpose is to introduce preliminary deformation energy storage and control the recrystallization state of austenite. After cooling, the temperature is held to make the temperature field tend to be uniform, and then a reduction of 10–50% is applied to complete the rolling, with a deformation rate of 0.5–20s. - ¹.

[0049] S123. The first deformed body is cooled to the third preset temperature at the third preset speed, and held at the temperature for the third time before being rolled at the third preset temperature to obtain the second deformed body.

[0050] In this embodiment, the third preset temperature is the final finishing rolling temperature, with a value range of 880–960℃, covering the typical controlled rolling process window; the holding time is 5–20 seconds to ensure temperature uniformity and microstructure stability; multiple sets of experiments are carried out within this temperature range, each set corresponding to a specific third preset temperature, to complete 10–40% reduction deformation, thereby obtaining a series of third deformed bodies with the same initial state but different final rolling temperatures, providing a variable control basis for subsequent systematic comparison of isothermal precipitation behavior.

[0051] S124. During the process of holding the second deformed body at the third preset temperature for the fourth time, the stress and time of the alloy steel sample at the current rolling temperature of the third preset temperature are obtained; the third preset temperature value is changed, and the above process is repeated to obtain the stress and time of the alloy steel sample after holding at different third preset temperatures.

[0052] In this embodiment, the third duration is 600–5400 seconds, corresponding to the duration of the heat preservation stage. During this stage, no macroscopic plastic deformation occurs; only constant temperature is maintained while waiting for the microstructure to evolve. The stress here is actually the true stress value recorded at the beginning of the heat preservation, that is, the stress peak at the moment the last rolling pass ends. This value is directly output by the force sensor of the thermal simulation test machine. The time refers to the actual time taken from the start of loading to the end of unloading for this pass, which is accurately captured by the built-in timing system of the equipment. All data are bound to the corresponding third preset temperature, forming the basic input parameters for the subsequent construction of the PTT curve.

[0053] In summary, the first preset speed range is 1-50℃ / s, preferably 5℃ / s. The first preset temperature range is 1100-1300℃, preferably 1200℃. The first duration range is 1-10min, preferably 5min. The second preset speed range is 1-100℃ / s, preferably 20℃ / s. The second preset temperature range is 1000-1200℃, preferably 1050℃. The second and third durations range are 5-20s, preferably 15s. It should be noted that the second and third durations do not necessarily have to be equal; generally, 15s is used.

[0054] In some embodiments, for step S120, one possible implementation of the present invention is that step S120 includes sub-steps S125 to S128: S125. In an environment with an inert gas, the alloy steel sample is heated to a first preset temperature at a first preset speed and held at that temperature for a first duration to obtain the initial shape of the alloy steel sample.

[0055] In this embodiment, it is completely consistent with S121, both being austenitizing treatments. The technical parameters and physical objectives have not been changed in any way. That is, the temperature is increased to 1100–1300℃ at 1–50℃ / s and held for 1–10 minutes. Under argon protection, the second phase is dissolved and the structure is homogenized, ensuring a high degree of repeatability and comparability of the starting conditions for each experiment.

[0056] S126. The initial shape is cooled to a second preset temperature at a second preset speed and kept at that temperature for a second duration to obtain the first deformable body.

[0057] In this embodiment, the rolling step in S122 is omitted, and only the holding and cooling process is performed, that is, the temperature is rapidly cooled from the first preset temperature to the second preset temperature and held for a second duration without any deformation. The first deformed body obtained at this time is essentially an undeformed austenitic sample, and its microstructure depends on the cooling path and the termination temperature. This process is used to analyze the effect of high-temperature non-deformation control on the strain-induced precipitation kinetics of carbides.

[0058] S127. The first deformed body is cooled to the third preset temperature at the third preset speed, and held at the temperature for the third time before being rolled at the third preset temperature to obtain the second deformed body.

[0059] In this embodiment, the different rolling temperatures are multiple different third preset temperatures. The first deformed body here comes from the undeformed cooled state described in S126; subsequently, it is held at each of the third preset temperatures and rolled. Although the degree of deformation of the obtained third deformed body is the same as that in S123, due to the lack of pre-deformation of the microstructure and accumulation of deformation energy brought about by the preceding rough rolling, the dynamic characteristics of strain-induced precipitation in its subsequent isothermal process will be delayed. This difference is used to reveal the cumulative promoting effect of rough rolling deformation on precipitation behavior.

[0060] S128. During the process of holding the second deformed body at a third preset temperature for a fourth duration, the stress and time of the alloy steel sample after rolling at the third preset temperature are obtained; the third preset temperature value is changed, and the above process is repeated to obtain the stress and time of the alloy steel sample after rolling at different third preset temperatures.

[0061] In this embodiment, this step is exactly the same as the operation process of S124. Both involve long-term isothermal heat preservation at the third preset temperature and synchronous acquisition of stress response. The only difference is the different microstructure origin of the third deformed body. The obtained stress is still taken from the instantaneous value at the end of the last rolling pass, and the time is still the duration of its deformation. The two together constitute the key experimental parameters at this temperature point, which are used to support the subsequent plotting of stress-time curves and identification of inflection points.

[0062] In some embodiments, for the time of alloy steel samples at different rolling temperatures, the present invention provides a possible implementation method in which the time is obtained through the following steps S130~S150: S130. The time from the start of heating the alloy steel sample to the end of rolling is taken as the first time.

[0063] In this embodiment, the first time specifically refers to the end time of the last rolling process, rather than the cumulative time of the entire rolling process; this time period is automatically recorded by the thermal simulation test machine, with the starting point being the time when the thermal simulation test machine begins to execute the experimental program, and the ending point being the end time of the last rolling process; its value is affected by the deformation amount, deformation rate, and deformation temperature.

[0064] S140. The time from the start of heating of the alloy steel sample to the end of rolling and the holding time to the preset holding time is taken as the second time.

[0065] In this embodiment, the second time is the time during which the entire experimental process is executed.

[0066] S150, Subtract the first time from the second time to obtain the holding time of the alloy steel sample at different rolling temperatures.

[0067] In this embodiment, the calculation is not used to obtain new physical quantities, but rather to unify the zero point of time so that the subsequently plotted stress-time curve can accurately reflect the evolution behavior during the heat preservation stage. Since the timestamp recorded by the thermal simulation experimental machine usually takes the start of the experiment as the global zero point, it needs to be offset and corrected using the time parameters defined in S130 and S140, i.e., t = t2. The original time series is converted into a local holding time t with the end of rolling as the zero point, where t2 (second time) is the absolute time of the current acquisition time relative to the start of the experiment, and t1 is the first time. This yields a standard holding time variable that can be used for plotting and analysis.

[0068] In some embodiments, for step S200, one possible implementation of the present invention is that step S200 includes sub-steps S201~S202: S201. Generate initial stress-time curves corresponding to different rolling temperatures based on stress and time.

[0069] In this embodiment, the initial stress-time curve is the original response curve plotted with the holding time as the horizontal axis and the measured true stress of the thermal simulation test machine as the vertical axis. Its shape exhibits typical three-stage characteristics: the initial rapid decline segment corresponds to stress relaxation dominated by static recovery; the intermediate plateau segment reflects the pinning effect of strain-induced precipitation on dislocations and grain boundaries; and the later slow decline segment indicates that static recrystallization restarts after pinning failure caused by coarsening of the precipitated phase. This curve has not undergone mathematical transformation and retains all the original data details, which is the prerequisite for subsequent logarithmic processing and inflection point identification.

[0070] S202. Perform a logarithmic transformation on the initial stress-time curve to obtain the stress-time curves corresponding to different rolling temperature holding times.

[0071] In this embodiment, the object of the logarithmic transformation is the heat preservation time t on the horizontal axis. That is, t in the original curve is replaced with lg(t), thereby changing the time scale from linear to logarithmic. This allows the precipitation events that originally occurred densely within a short time scale to be effectively displayed on the graph. This transformation significantly enhances the visibility and recognizability of inflection points, and is especially beneficial for capturing the subtle turning points corresponding to Ps and Pf. It is a necessary technical step for quantitative determination using the tangent method. The transformed curve is denoted as the σ–lg(t) curve, with the horizontal axis in log seconds and the vertical axis still in MPa. All data points maintain a one-to-one correspondence, and no interpolation or fitting operations are introduced.

[0072] In some embodiments, for step S300, one possible implementation of the present invention is that step S300 includes sub-steps S301 to S303: S301. Obtain the first and second inflection points on the stress-time curve. The first inflection point is the first inflection point that appears on the stress-time curve, and the second inflection point is the last inflection point that appears on the stress-time curve.

[0073] In this embodiment, the inflection point is determined by the tangent method, that is, the position with the most significant change in slope on the σ–lg(t) curve is selected, and tangents are drawn on the left and right sides respectively. The intersection point is projected onto the horizontal axis to obtain the inflection point time. The first inflection point appears at the beginning of the plateau segment, corresponding to the critical moment when nucleation occurs and the pinning effect begins to take effect. The second inflection point appears at the end of the plateau segment, corresponding to the turning point when the precipitated phase grows to the critical size, the pinning force decays, and the softening mechanism becomes active again. The two inflection points must be located on the same σ–lg(t) curve under the same temperature conditions, and their reproducibility must be verified by at least three repeated experiments before they can be included as valid data in the PTT curve construction.

[0074] S302. The time corresponding to the first inflection point is taken as the start time of carbide precipitation.

[0075] In this embodiment, the time is the starting moment Ps in the sense of strain-induced precipitation kinetics. Its physical meaning is the time node when the first stable carbide particles in the austenite formed by the alloy steel sample complete nucleation and reach a critical size sufficient to hinder dislocation movement. This moment is not the time when the precipitated phase is first observed under optical or electron microscopy, but a marker point of microstructure evolution inferred from macroscopic mechanical response. For example, Ps at 900℃ is about 60 seconds, which is highly consistent with the result observed by transmission electron microscopy that 10.2nm-sized spherical particles appear on the dislocation line at 100 seconds, confirming the reliability of this determination method.

[0076] S303. The time corresponding to the second inflection point is taken as the end time of carbide precipitation.

[0077] In this embodiment, the end time of carbide precipitation is the termination time Pf in the sense of strain-induced precipitation kinetics. It is the dividing point where the precipitation process transitions from rapid growth to coarsening-dominated stage. After this, the number of precipitated phases tends to saturate, the average size continues to increase, but the pinning efficiency per unit volume decreases, indicating that strain-induced precipitation is basically completed as an independent microstructure evolution event. Subsequent microstructure evolution is mainly dominated by the competition between coarsening and recrystallization. For example, Pf at 900°C is about 680 seconds, which is consistent with the phenomenon observed by electron microscopy that the number of precipitated particles increases significantly and the average size reaches 14.8 nm at 600 seconds, indicating that this time point has covered most of the effective precipitation behavior.

[0078] In some embodiments, alloy steel is specifically used as an example. The selected material is a Ti-containing microalloyed steel with the following chemical composition and content: C 0.053 wt%, Si 0.23 wt%, Mn 1.60 wt%, Ti 0.12 wt%, N 0.0048 wt%, P 0.011 wt%, S 0.0036 wt%, with the remainder being Fe and unavoidable impurities. Then, based on thermodynamic formulas, the solid solution temperature T1 = 1107℃ of the carbides in the alloy steel under thermal equilibrium conditions was calculated. Experiments were conducted on a Gleeble-3800 thermal simulation testing machine to determine the stress during the holding process after the alloy steel was rolled and deformed (the final rolling temperature < T1). Curve showing the change over isothermal time.

[0079] Specifically, the alloy steel sample was machined into a cylindrical specimen with a surface roughness Ra ≤ 0.4 μm and dimensions of φ10 × 15 mm. The thermocouple welding machine voltage was adjusted to 36 V, and one end of a K-type thermocouple wire was welded to the center of the cylindrical specimen, with the distance between the two thermocouple wires controlled to approximately 1 mm. Then, tantalum and graphite sheets were sequentially attached to both ends of the cylindrical specimen using a high-temperature lubricant. The cylindrical specimen with the attached tantalum and graphite sheets was then installed on both ends of the clamps in the experimental chamber. The axial displacement of the main shaft of the simulation experimental machine was finely adjusted so that the clamps just pressed against the cylindrical specimen. The other end of the K-type thermocouple wire was connected to the T1 temperature channel in the Gleeble-3800 experimental chamber, and then the chamber door was closed and a vacuum was created. The vacuum level inside the experimental chamber was below 1.5 × 10⁻⁶. -1 When the pressure reaches Pa, stop evacuating; then introduce argon gas into the experimental chamber until the pressure gauge pointer points to 0, then stop introducing argon gas.

[0080] Furthermore, the experimental process flow was programmed and set using the Quizsim software included with the Gleeble-3800 thermal simulation testing machine. For example, a cylindrical sample was heated to 1200℃ at 5℃ / s and held for 5 minutes on the thermal simulation testing machine to fully dissolve the second phase (excluding nitrogen-containing compounds) in the alloy steel. It was then cooled to 1050℃ at 20℃ / s and held for 15 seconds, resulting in a 20% deformation. Subsequently, it was cooled at 20℃ / s to different rolling temperatures of 880, 900, 920, 940, and 960℃, and isothermally held for 15 seconds, resulting in another 20% deformation. The deformation rate was 1.0 s. -1 After deformation, the material was held at a temperature for 1800 seconds, followed by water quenching.

[0081] Further, argon gas was introduced into the experimental chamber until the pressure gauge pointer pointed to "0", then the argon gas introduction was stopped. The "RUN" button on the Gleeble-3800 thermal simulation testing machine's control panel was then activated, followed by clicking "Run" in the Quizsim software to start the machine and run the set sample protocol for the experiment. After one experimental process was completed, the experimental process parameters were changed, and the above steps were repeated for the next experiment until all experiments were completed. After the experiments, the temperature, time, and true stress data collected by the thermal simulation testing machine under different process conditions were imported into the Origin software provided with the testing machine to obtain the stress during isothermal processes at different rolling temperatures. The curve of change with isothermal time is as follows: Figure 3 As shown, all curves generally exhibit a downward trend, showing three stages with increasing isothermal time: (i) the decreasing stage, where stress decreases with increasing isothermal time. This decrease in stress is caused by recovery and static recrystallization; (ii) the hysteresis plateau stage, where the trend of stress reduction is delayed and temporarily halted, even slightly increasing at relatively low temperatures, indicating that static recrystallization of austenite is almost completely prevented; and (iii) the re-decreasing stage, where continued increase in isothermal time leads to a further decrease in stress, indicating that austenite softens again. Furthermore, before the hysteresis stage, the slopes of the stress relaxation curves at different isothermal temperatures are not the same, indicating different softening mechanisms of austenite after deformation in alloy steel. It can be seen that at isotherms of 940°C and above, the stress relaxation curve first decreases slowly, then decreases rapidly due to static recrystallization. When the temperature is below 940°C, the stress relaxation curve decreases slowly until a plateau appears, corresponding to the corresponding recovery softening mechanism.

[0082] Furthermore, through stress The curves showing the change in temperature with isothermal time are used to determine the start (Ps) and end (Pf) times of carbide strain-induced precipitation at different rolling temperatures. For example, the time from the start of the experiment to the end of rolling for the alloy steel is recorded as t1; the time at a certain point in the experiment is recorded as t2; and the stress is plotted with the holding time after rolling of the alloy steel as 0 s. The curve showing the change in stress with respect to the holding time t, where t = t2 - t1. A logarithmic transformation is performed on the isothermal time t, and the curve showing the change in stress with respect to lg(t) is plotted. -1g(t) curve. Determined using the tangent method. The time of the inflection point on the -1g(t) curve. Wherein, The time of the first inflection point on the -1g(t) curve is the start time of carbide strain-induced precipitation (Ps), and the time of the last inflection point is the end time of carbide strain-induced precipitation (Pf).

[0083] Furthermore, by measuring the start time (Ps) and end time (Pf) of carbide strain-induced precipitation at different rolling temperatures, strain-induced precipitation-time-temperature (PTT) curves of carbides in alloy steel were plotted, as shown below. Figure 3 As shown, the value determined by the tangent point method Figure 3 The start and end times of the hysteresis phase of the curve are generally considered to be the start time (Ps) and end time (Pf) of austenite strain-induced precipitation. According to... Figure 3 The curves obtained the start and end times of strain-induced precipitation, and the strain-induced precipitation-temperature-time (PTT) curves of carbides in alloy steel during the isothermal process after deformation were plotted. Figure 3 In this embodiment, the PPT curve of the alloy steel is a typical C-shaped curve. The temperature at which the curve has the greatest curvature is around 900°C, corresponding to the shortest strain-induced precipitation start and end times, which are approximately 60 s and 680 s, respectively. The isothermal temperatures at which the longest precipitation start and end times occur are 860°C, at 180 s and 1050 s, respectively. Furthermore, based on the pinning effect of strain-induced precipitation on austenite grain boundaries and the PTT curve, the strain-induced precipitation process can be divided into three stages: nucleation stage, growth stage, and coarsening stage.

[0084] Furthermore, such as Figure 5 As shown, Figure 5 This image shows the characteristic features of strain-induced carbide precipitation at different isothermal times at 900°C according to embodiments of this disclosure. During the isothermal period of 100 s (the initial stage of strain-induced carbide precipitation), a small number of spherical particles with an average size of 10.2 ± 2.1 nm are unevenly distributed on dislocations, as indicated by the arrows. As the isothermal time increases to 600 s (the near-end stage of strain-induced carbide precipitation), the number of precipitated particles increases, and the average particle size increases to 14.8 ± 2.5 nm. When the isothermal time increases to 1800 s (the coarsening stage of strain-induced carbide), a large number of precipitated particles appear in the austenite. Magnified images clearly show that these precipitated particles are tightly aggregated and adhered together, with particles larger than 15 nm accounting for 85%, indicating that strain-induced precipitation has entered the coarsening stage. With increasing isothermal time, both the number and size of the precipitated phases continuously increase, leading to a trend where the pinning force of the particles on dislocations or grain boundaries first increases and then decreases. This change is consistent with… Figure 3 The three stages observed in the medium stress relaxation curve are consistent. This indicates that... Figure 3 The obtained stress-time logarithm curve is reasonable and can be used as a PTT curve to characterize the strain-induced carbide precipitation process.

[0085] In some embodiments, alloy steel is also used as a specific example, but the difference from the previous alloy steel example is that the experimental process flow can be programmed and set in the Quizsim software that comes with the Gleeble-3800 thermal simulation testing machine as follows: A cylindrical sample is heated to 1200°C at 5°C / s and held for 5 minutes on the thermal simulation testing machine to fully dissolve the second phase (excluding nitrogen-containing compounds) in the alloy steel. Then, it is cooled to 1050°C at 20°C / s and held for 15 seconds, resulting in 0% deformation. Next, it is cooled isothermally to 860-960°C at 20°C / s for 15 seconds, followed by rolling deformation of 20% at a deformation rate of 1.0 s. -1 The material was held at that temperature for 2400 seconds after deformation was complete, followed by water quenching. Figure 6 As shown, Figure 6 This is a strain-induced precipitation temperature-time curve for carbides under a single rolling process, provided in an embodiment of the invention. The nose temperature for carbide strain-induced precipitation is 920°C, and the shortest incubation time is 80 s (precipitation start time). Compared to the previous example of alloy steel, in this embodiment, no 20% rolling deformation was performed at 1050°C. The nose temperature of the PTT curve increased from 900°C in Example 1 to 920°C, and the corresponding fastest strain-induced precipitation start time increased from 65 s to 80 s. In other words, the introduction of the rough rolling process accelerated the strain-induced precipitation of carbides in the alloy steel.

[0086] Based on the above method, embodiments of the present invention also provide a system corresponding to the above method, such as... Figure 7 As shown, Figure 7 This is a schematic diagram of the functional modules of a system for determining the strain-induced precipitation kinetics of carbides based on thermal simulation experiments, provided in an embodiment of the present invention. It should be noted that the system 1000 for determining the strain-induced precipitation kinetics of carbides based on thermal simulation experiments provided in this embodiment has the same basic principle and technical effects as the method embodiment described above. For the sake of brevity, parts not mentioned in this embodiment can be referred to the corresponding content in the method embodiment.

[0087] In this embodiment, the system 1000 for determining the strain-induced precipitation kinetics of carbides based on thermal simulation experiments includes an acquisition module 1100 and a processing module 1200. The acquisition module 1100 is used to acquire the stress and time of the alloy steel sample during the holding process after deformation at different rolling temperatures. The rolling temperature is lower than a preset solution temperature, which characterizes the critical temperature for the melting of carbides in the alloy steel. It can be understood that the acquisition module 1100 is used to perform the above step S100.

[0088] The processing module 1200 is used to generate stress-time curves of alloy steel samples during the holding period after different rolling temperatures based on stress and time; to determine the start and end times of carbide strain-induced precipitation of alloy steel samples at different rolling temperatures based on the stress-time curves; and to generate carbide precipitation kinetic curves based on the start and end times and rolling temperature. It can be understood that the processing module 1200 is used to perform the above steps S200~S400.

[0089] In some embodiments, the acquisition module 1100 is used to weld thermocouple wires to the sidewalls of an alloy steel sample and sequentially attach tantalum sheets and graphite sheets to both ends to obtain an alloy steel sample; in an inert gas environment, the alloy steel samples deformed at different rolling temperatures are kept at a constant temperature to obtain the stress and time of the alloy steel sample during the holding process after deformation at different rolling temperatures. It can be understood that the acquisition module 1100 is used to perform the above steps S110~S120.

[0090] In some embodiments, the processing module 1200 is used to heat an alloy steel sample to a first preset temperature at a first preset speed in an inert gas environment, and hold it at that temperature for a first duration to obtain an initial shape of the alloy steel sample; to cool the initial shape to a second preset temperature at a second preset speed, and hold it at that temperature for a second duration, and then roll it at the second preset temperature to obtain a first deformed body; to cool the first deformed body to a third preset temperature at a third preset speed, and hold it at that temperature for a third duration, and then roll it at the third preset temperature to obtain a second deformed body; during the process of holding the second deformed body at the third preset temperature for a fourth duration, the stress and time of the alloy steel sample at the current third preset temperature rolling temperature are obtained; the third preset temperature value is changed, and the above process is repeated to obtain the stress and time of the alloy steel sample during the holding process after rolling at different third preset temperatures. It can be understood that the processing module 1200 is used to perform the above steps S121~S124.

[0091] In some embodiments, the processing module 1200 is used to heat an alloy steel sample to a first preset temperature at a first preset speed in an inert gas environment, and hold it at that temperature for a first duration to obtain an initial shape of the alloy steel sample; to cool the initial shape to a second preset temperature at a second preset speed, and hold it at that temperature for a second duration to obtain a first deformed body; to cool the first deformed body to a third preset temperature at a third preset speed, and hold it at that temperature for a third duration, and then roll it at the third preset temperature to obtain a second deformed body; during the process of holding the second deformed body at the third preset temperature for a fourth duration, the stress and time of the alloy steel sample during the holding process after rolling at the third preset temperature are obtained; the third preset temperature value is changed, and the above process is repeated to obtain the stress and time of the alloy steel sample during the holding process after rolling at different third preset temperatures. It can be understood that the processing module 1200 is used to perform the above steps S125~S128.

[0092] In some embodiments, the acquisition module 1100 is further configured to take the time from the start of heating of the alloy steel sample to the end of rolling as a first time; take the time from the start of heating of the alloy steel sample to the end of rolling and the time of holding it at a preset holding time as a second time; and subtract the first time from the second time to obtain the holding time of the alloy steel sample at different rolling temperatures. It can be understood that the acquisition module 1100 is used to perform the above steps S130~S150.

[0093] In some embodiments, the processing module 1200 is used to generate initial stress-time curves corresponding to different rolling temperatures based on stress and time; and to perform a logarithmic transformation on the initial stress-time curves to obtain stress-time curves corresponding to different rolling temperatures. It can be understood that the processing module 1200 is used to perform the above steps S201~S202.

[0094] In some embodiments, the processing module 1200 is used to obtain a first inflection point and a second inflection point appearing on the stress-time curve, wherein the first inflection point is the first inflection point appearing on the stress-time curve, and the second inflection point is the last inflection point appearing on the stress-time curve; the time corresponding to the first inflection point is taken as the start time of carbide precipitation; and the time corresponding to the second inflection point is taken as the end time of carbide precipitation. It can be understood that the processing module 1200 is used to execute the above steps S301~S303.

[0095] Based on the same inventive concept disclosed above, the present invention also provides a block diagram of a thermal simulation experimental machine for performing the above method, including a controller, a fixture and a thermocouple wire. The controller is used to execute a computer program to realize the above method for determining the strain-induced precipitation kinetics of carbides based on thermal simulation experiments.

[0096] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for determining the strain-induced precipitation kinetics of carbides based on thermal simulation experiments, characterized in that, The method includes: The stress and time of alloy steel samples after deformation and heat preservation at different rolling temperatures are obtained. The rolling temperature is less than the preset solution temperature, which characterizes the critical temperature for carbide solid solution in the alloy steel. Stress-time curves of the alloy steel sample during heat holding at different rolling temperatures are generated based on the stress and time. The start and end times of carbide strain-induced precipitation in the alloy steel sample at different rolling temperatures were determined based on the stress-time curve. The carbide precipitation kinetics curve is generated based on the start time, the end time, and the rolling temperature.

2. The method according to claim 1, characterized in that, The stress and time obtained during the heat preservation process after rolling deformation of the alloy steel sample include: Thermocouple wires were welded to the sidewalls of the alloy steel sample, and tantalum sheets and graphite sheets were attached to both ends in sequence to obtain the alloy steel sample. In an inert gas environment, the alloy steel samples deformed at different rolling temperatures were kept at a constant temperature to obtain the stress and time of the alloy steel samples during the holding process after deformation at different rolling temperatures.

3. The method according to claim 2, characterized in that, The process of holding alloy steel samples deformed at different rolling temperatures in an inert gas environment to obtain the stress and time of the holding process after deformation at different rolling temperatures includes: The alloy steel sample is heated to a first preset temperature at a first preset rate in an inert gas environment and held at that temperature for a first duration to obtain the initial shape of the alloy steel sample. The initial shape is cooled to a second preset temperature at a second preset speed, and held at that temperature for a second duration before being rolled at the second preset temperature to obtain a first deformed body. The first deformed body is cooled to a third preset temperature at a third preset speed, held at that temperature for a third duration, and then rolled at the third preset temperature to obtain the second deformed body. During the process of holding the second deformed body at the third preset temperature for a fourth duration, the stress and time of the alloy steel sample at the current rolling temperature of the third preset temperature are obtained; by changing the third preset temperature value and repeating the above process, the stress and time of the alloy steel sample after holding at different third preset temperatures are obtained.

4. The method according to claim 2, characterized in that, The process of holding alloy steel samples deformed at different rolling temperatures in an inert gas environment to obtain the stress and time of the alloy steel samples during the holding process after deformation at different rolling temperatures includes: The alloy steel sample is heated to a first preset temperature at a first preset rate in an inert gas environment and held at that temperature for a first duration to obtain the initial shape of the alloy steel sample. The initial shape is cooled to a second preset temperature at a second preset speed and held at that temperature for a second duration to obtain a first deformable body; The first deformed body is cooled to a third preset temperature at the third preset speed, held at the temperature for a third duration, and then rolled at the third preset temperature to obtain the second deformed body. During the process of holding the second deformed body at the third preset temperature for a fourth duration, the stress and time of the alloy steel sample after rolling at the third preset temperature are obtained; by changing the third preset temperature value and repeating the above process, the stress and time of the alloy steel sample after rolling at different third preset temperatures are obtained.

5. The method according to any one of claims 1-4, characterized in that, The holding time of the alloy steel sample at different rolling temperatures was obtained through the following steps: The time from the start of heating the alloy steel sample to the end of rolling is taken as the first time. The time from the start of heating the alloy steel sample to the end of rolling and the holding time to the preset holding time is taken as the second time. The time is obtained by subtracting the first time from the second time.

6. The method according to claim 1, characterized in that, The step of generating stress-time curves corresponding to the holding times at different rolling temperatures based on the stress and the time includes: The initial stress-time curves corresponding to the different rolling temperatures are generated based on the stress and the time. Logarithmic transformation is performed on the initial stress-time curve to obtain the stress-time curves corresponding to the holding times at different rolling temperatures.

7. The method according to claim 1, characterized in that, The process of obtaining the start and end times of carbide precipitation in the alloy steel sample at different rolling temperatures based on the stress-time curve includes: Obtain the first inflection point and the second inflection point that appear on the stress-time curve. The first inflection point is the first inflection point that appears on the stress-time curve, and the second inflection point is the last inflection point that appears on the stress-time curve. The time corresponding to the first inflection point is taken as the start time of carbide precipitation; The time corresponding to the second inflection point is taken as the end time of carbide precipitation.

8. A system for determining the strain-induced precipitation kinetics of carbides based on thermal simulation experiments, characterized in that, The system includes: The acquisition module is used to acquire the stress and time of the heat preservation process after deformation of alloy steel samples at different rolling temperatures. The rolling temperature is lower than the preset solid solution temperature, which characterizes the critical temperature for solid solution of carbides in the alloy steel. The processing module is used to generate stress-time curves of the alloy steel sample during the holding period after different rolling temperatures based on the stress and the time; determine the start and end times of carbide strain-induced precipitation of the alloy steel sample at different rolling temperatures based on the stress-time curves; and generate carbide precipitation kinetic curves based on the start time, the end time, and the rolling temperature.

9. An experimental machine, characterized in that, The device includes a controller, a clamp, and a thermocouple wire. The clamp is used to hold the alloy steel sample and apply pressure. The thermocouple wire is used to monitor the temperature of the alloy steel sample. The controller is used to execute the method for determining the strain-induced precipitation kinetics of carbides based on thermal simulation experiments as described in any one of claims 1-7.

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