A heat treatment method and device for improving the hardness of ADI castings

Abstract

The application relates to the technical field of casting heat treatment, in particular to a heat treatment method and device for improving the hardness of ADI castings, which comprises the following steps: acquiring temperature data of each position on the surface of an ADI casting in a quenching process of heat treatment of the ADI casting; acquiring a significant value of a rate difference and a non-smooth degree of temperature change of each position in an initial period of quenching, calculating an abnormal significant value of temperature change of the surface of the casting in each time window of each position, and a difference coefficient of a quenching temperature change state of each time window of each position, and then acquiring a stable consistency coefficient of a temperature state in each time window of each position, which is used for calculating a lag influence coefficient of temperature control of each time window, so as to optimize a temperature error in a quenching temperature control process of a PID controller, and then performing tempering treatment, thereby completing the heat treatment of the ADI casting. The application can improve the heat treatment effect of the ADI casting.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of casting heat treatment, in particular to a heat treatment method and device for improving the hardness of ADI castings. BACKGROUND

[0002] The isothermal quenching treatment of spheroidal graphite cast iron is a key step for preparing isothermal quenching spheroidal graphite cast iron (ADI) material. Specifically, the spheroidal graphite cast iron is heated to an austenitizing temperature and is kept for a certain time, and then is rapidly quenched into a salt bath furnace. In the salt bath furnace, the spheroidal graphite cast iron is first cooled to a bainite transformation temperature interval in a cooling stage before isothermal quenching, and then is kept for a certain time in a holding stage of isothermal quenching. Finally, tempering treatment is performed, so as to obtain ADI material with excellent performance.

[0003] The spheroidal graphite cast iron is rapidly cooled and kept for a long time in the salt bath furnace, and the temperature drop cooling process and the holding process of isothermal quenching have a great influence on the hardness performance. In the existing method, a stirring device is usually used to rapidly cool the salt bath furnace and maintain the stability of the temperature in the holding process. However, in the actual quenching process, the quenching medium is prone to aging and fouling in the salt bath furnace, which reduces the heat transfer performance and causes the temperature fluctuation of the salt bath furnace, so that it is difficult to ensure the stability and consistency of the quenching quality of the spheroidal graphite cast iron in each part. The existing heat treatment method does not fully consider the influence of the change of the heat transfer performance and the uneven stirring on the temperature fluctuation, and is not stable enough in the temperature control during quenching, which is prone to cause the problem of insufficient hardness of the castings after heat treatment. The application optimizes and adjusts the temperature in the holding process in the quenching stage, so as to improve the hardness performance of the ADI castings.

[0004] Among them, the publication number CN103088251B discloses a spheroidal graphite cast iron and a heat treatment method thereof, which adopts an isothermal quenching method for heat treatment, and is kept for 2-3 hours in a salt bath furnace with mixed molten salt, so as to improve the hardness of the spheroidal graphite cast iron. However, the holding process does not fully consider the temperature fluctuation caused by the aging and fouling of the quenching medium, and there may be the defect of insufficient hardness of the castings after heat treatment. SUMMARY

[0005] In order to solve the above technical problems, the purpose of the application is to provide a heat treatment method and device for improving the hardness of ADI castings, and the technical scheme adopted is as follows:

[0006] The embodiment of the application provides a heat treatment method for improving the hardness of ADI castings, which comprises the following steps:

[0007] Obtaining the temperature data of each position on the surface of the ADI casting in the isothermal quenching process of the heat treatment of the ADI casting;

[0008] The rate difference and non-smoothness of temperature change of each position in the initial quenching period are obtained by using the difference in temperature data change of each position and other positions in the initial quenching period and the smoothness of temperature change in the initial quenching period.

[0009] The abnormality significant value of temperature change of the casting at each position in each time window is extracted by using the deviation of the abnormal value from the average level of temperature data in the time window and the random fluctuation degree of the abnormal value and the dispersion degree of the time interval between adjacent abnormal values.

[0010] The difference coefficient of quenching temperature change state of each position in each time window is obtained according to the difference degree of temperature change trend of each position and other positions in the same time window, and the stable consistency coefficient of temperature state of each position in each time window is obtained in combination with the abnormality significant value of temperature change of the casting.

[0011] The lag influence coefficient of temperature control of each time window is obtained in combination with the rate difference and non-smoothness significant value of temperature change of each position in the initial quenching period and the stable consistency coefficient of temperature state of each position in each time window, so as to optimize the temperature error in the quenching temperature control process of the PID controller, and then the heat treatment of the ADI casting is completed through tempering.

[0012] Preferably, the determination method of the initial quenching period is that the time period from the start of quenching to the time when the temperature of the casting material surface near all positions reaches the preset isothermal quenching temperature for the first time is taken as the initial quenching period.

[0013] Preferably, the method for obtaining the rate difference and non-smoothness significant value of temperature change of each position in the initial quenching period is that

[0014] , wherein, is the rate difference and non-smoothness significant value of temperature change of the i th position in the initial quenching period, is the difference coefficient of the initial quenching temperature drop rate of the i th position, is the determination coefficient corresponding to the fitting curve of the temperature data of the i th position in the initial quenching period.

[0015] Preferably, the first-order difference sequence of the temperature data of each position in the initial quenching period is counted, and the average value of the DTW distance of the first-order difference sequence corresponding to the initial quenching period of each position and all other positions is calculated as the difference coefficient of the initial quenching temperature drop rate of each position.

[0016] Preferably, the method for obtaining the abnormal significant value of the casting surface temperature change in each time window at each position is as follows:

[0017] wherein, is the abnormal significant value of the casting surface temperature change in the jth time window at the ith position, is the randomness of the casting surface temperature change in the jth time window at the ith position, is the abnormal coefficient of the casting surface temperature change amplitude in the jth time window at the ith position.

[0018] Preferably, after the initial quenching period, a preset time length is taken as each time window, the abnormal values of the temperature data in the jth time window at the ith position are counted, the cumulative sum of the absolute values of the difference between each abnormal value and the average temperature in the time window is taken as the abnormal coefficient of the casting surface temperature change amplitude in the jth time window, and the product of the coefficient of variation of all abnormal values in the jth time window and the variance of the time interval of all adjacent abnormal values is taken as the randomness of the casting surface temperature change in the jth time window.

[0019] Preferably, the method for obtaining the difference coefficient of the quenching temperature change state in each time window at each position is as follows:

[0020] For the jth time window at each position, the test statistics of each position in the jth time window are extracted, the average of the difference between the test statistics of each position and other positions corresponding to the jth time window is calculated, the average of the difference between the average temperatures of each position and other positions in the jth time window is calculated, and the product of the two averages is taken as the difference coefficient of the quenching temperature change state of the jth time window at each position.

[0021] Preferably, the method for obtaining the stable consistency coefficient of the temperature state in each time window at each position is as follows:

[0022] wherein, is the stable consistency coefficient of the temperature state in the jth time window at the ith position, is the abnormal significant value of the casting surface temperature change in the jth time window at the ith position, is the difference coefficient of the quenching temperature change state of the jth time window at the ith position.

[0023] Preferably, the method for obtaining the lag influence coefficient of the temperature control in each time window to optimize the temperature error in the quenching temperature control process of the PID controller comprises:

[0024] The rate difference of temperature change of each position at the initial quenching period and the significant value of non-smooth degree are arranged in time sequence with the stable consistency coefficient of temperature state of each position in the jth time window to obtain the temperature state feature sequence of each position up to the jth time window, and the mean value of DTW distance between the temperature state feature sequences of any two positions up to the jth time window is calculated as the lag influence coefficient of temperature control of the jth time window;

[0025] The temperature error optimization value of the next time window The calculation formula is as follows: Wherein, is the temperature error of the current time window, is the lag influence coefficient of temperature control of the current time window.

[0026] The embodiment of the application further provides a heat treatment device for improving the hardness of ADI castings, which comprises a memory, a processor and a computer program stored in the memory and running on the processor, and the processor implements the steps of the heat treatment method for improving the hardness of ADI castings.

[0027] As can be seen from the above, the heat treatment method and device for improving the hardness of ADI castings provided by the application have at least the following beneficial effects:

[0028] The application optimizes the temperature fluctuation interference that may exist in the isothermal quenching stage, calculates the lag influence coefficient by deeply analyzing the temperature drop abnormal characteristics of the initial quenching period, the stability and uniformity of the surface temperature of the casting in the relatively stable state and the delay correlation characteristics of the temperature change state of each position, and optimizes the overall parameters of the PID controller based on the lag influence coefficient. The advantage is that it can reduce the influence of the change of salt bath heat transfer performance and uneven stirring, improve the response strength to temperature change, and further ensure the stability and consistency of the temperature in the isothermal quenching process, which helps to improve the hardness of ADI castings. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions and advantages of the embodiments of the application or the prior art, the drawings needed in the embodiment or the prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0030] Figure 1 The step flow chart of the heat treatment method for improving the hardness of ADI castings provided by the application. DETAILED DESCRIPTION

[0031] In order to further clarify the technical means and effects taken by the present application to achieve the predetermined object of the application, the following describes in detail the specific implementation, structure, features and effects of the heat treatment method and device for improving the hardness of ADI castings according to the present application, in combination with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0032] Unless otherwise defined, the terms such as "comprise", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that the circuit structure, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed or inherent to such article or device. Without more limitations, the element defined by the phrase "comprising a" does not exclude the presence of additional identical elements in the article or device comprising the element. In addition, the term "and / or" used herein includes any and all combinations of one or more related listed items. All technical and scientific terms used herein have the same meaning as understood by those skilled in the art to which the present application belongs.

[0033] The specific scheme of the heat treatment method and device for improving the hardness of ADI castings provided by the present application is described in detail below in combination with the accompanying drawings.

[0034] Please refer to Figure 1 which shows the step flow chart of the heat treatment method for improving the hardness of ADI castings provided by one embodiment of the present application, which includes the following steps:

[0035] Step one: Obtain the temperature data of each position on the surface of the ADI castings during the isothermal quenching process of the heat treatment of the ADI castings.

[0036] In this embodiment, the heat treatment process of the ADI castings generally includes austenitizing, isothermal quenching and tempering. Austenitizing is the process of heating the alloy to the austenite phase region to convert the ferrite and cementite in the alloy into austenite. In this embodiment, the castings are heated to - In the embodiment, the casting material is heated to 900°C. It should be noted that the specific temperature is adjusted according to the chemical composition and the organizational state of the casting, for example, when the silicon and phosphorus content in the casting is high, a higher austenitizing temperature should be selected; and when the casting contains copper, nickel, and molybdenum alloy elements, the austenitizing temperature can be appropriately reduced. After the austenite is formed, it needs to be kept at the austenitizing temperature for a certain period of time to homogenize the composition and organization of the austenite. After heating to the austenitizing temperature, the casting is kept for 2-4 hours to ensure complete internal austenitization. Preferably, the casting is kept for 3 hours in the embodiment.

[0037] After the austenitization is completed, the casting material is quickly transferred to a salt bath furnace for isothermal quenching treatment. Since the nitrate salt bath has good thermal stability and heat transfer performance, it can improve the temperature uniformity of the casting during isothermal quenching. The quenching medium used in the embodiment is a mixed salt of 50% KNO3 + 50% NaNO2. The isothermal quenching temperature is generally between - Different isothermal quenching temperatures will result in different organizations and properties. Within the above temperature range, the lower the isothermal quenching temperature, the less the residual austenite content in the organization, and the elongation and toughness of the ADI casting decrease significantly as the temperature increases, while the hardness gradually increases. Therefore, the isothermal quenching temperature in the embodiment is set to , and the quenching time is set to 2 hours.

[0038] The hardness of the ADI casting is easily affected by the isothermal quenching temperature, and it is crucial to ensure the stability and balance of the surface temperature of the ADI casting during the long isothermal quenching process. However, in the actual quenching process, the quenching medium may be aged and scaled, which can cause a decrease in heat transfer performance, and improper stirring can easily cause temperature differences in the salt bath, making it difficult to achieve accurate temperature control. Therefore, in the embodiment, thermocouple temperature sensors are placed at multiple positions near the surface of the ADI casting at equal intervals to monitor the temperature changes on the surface of the casting in real time, and the time interval for temperature data collection is set to 1 second. By analyzing the temperature state and change characteristics under the influence of the decline in salt bath heat transfer performance and uneven stirring, the stability of the isothermal quenching temperature is improved, and the hardness of the ADI casting is increased.

[0039] Step two: set the initial quenching period in the quenching process of the casting, and use the temperature data change difference of each position with other positions within the initial quenching period and the smoothness of the temperature change in the initial quenching period to obtain the significant value of the rate difference and non-smoothness of the temperature change of each position in the initial quenching period.

[0040] The heat transfer performance of the quenching medium will be affected after aging, and the heat transfer performance of the quenching medium may cause heat transfer during stirring, resulting in short-term rapid random changes in the surface temperature of the ADI casting, and further causing differences in quenching temperature and insufficient stability. After the ADI casting is transferred to the salt bath furnace, the temperature gradually decreases from the austenitizing temperature to the quenching temperature. If the surface temperature of the casting decreases too fast or too slow, it will affect the mechanical properties, and the different heat transfer performances may cause differences in cooling speed at different positions of the casting. Therefore, the greater the difference in temperature drop rate at different positions during quenching, the greater the influence on the hardness of the casting.

[0041] First, the time when the temperature of all positions near the surface of the casting material reaches the preset isothermal quenching temperature for the first time is obtained, and the time period from the start of quenching to this time is taken as the initial quenching period. Taking the temperature data collected at the i-th position as an example, the first-order difference sequence of the temperature data of this position in the initial quenching period is obtained, and each value in the first-order difference sequence reflects the temperature change amplitude between adjacent time points, that is, each element in the first-order difference sequence can be used to represent the temperature change rate at each time point.

[0042] Then, the DTW distance of the first-order difference sequence corresponding to the initial quenching period of each position and each other position is calculated, and the average of all the DTW distances is taken as the difference coefficient of the temperature drop rate of each position in the initial quenching period. The difference coefficient of the temperature drop rate of the i-th position in the initial quenching period is denoted as D, which is used to reflect the difference degree of the temperature drop rate between the i-th position and other positions in the initial quenching period.

[0043] In addition, due to the influence of the change of the heat transfer effect of the quenching medium or the stirring state, the temperature drop process may not be smooth due to random changes, affecting the mechanical properties of the ADI casting. Therefore, a quadratic polynomial fitting technique is used to obtain a fitting curve of the temperature data in the initial quenching period, and a determination coefficient of the obtained fitting curve is calculated. The determination coefficient corresponding to the fitting curve of the temperature data of the i-th position in the initial quenching period is denoted as R, and the higher the fitting degree, the smoother the temperature change. This value reflects the smoothness of the temperature change of the corresponding position in the initial quenching period.

[0044] Further, in this embodiment, the significant value of the rate difference and non-smoothness of the temperature change of each position in the initial quenching period is obtained, and the formula is: , in which is the significant value of the rate difference and non-smoothness of the temperature change of the i-th position in the initial quenching period, is the difference coefficient of the temperature drop rate of the i-th position in the initial quenching period, is the determination coefficient corresponding to the fitting curve of the temperature data of the i-th position in the initial quenching period.

[0045] The greater the obtained A is, the greater the difference in temperature change rate between the i-th position and other positions at the quenching initial period is, and the less smooth the temperature change at the quenching initial period is.

[0046] Step three: extract the outliers of the temperature data in each time window of each position of the casting, and obtain the abnormal significant value of the casting surface temperature change in each time window of each position by using the deviation of the outliers from the average level of the temperature data in the time window, the random fluctuation degree of the outliers, and the discrete degree of the time interval between adjacent outliers.

[0047] Further, considering that the surface temperature of the ADI casting fluctuates around the set isothermal quenching temperature after reaching a relatively stable state, as described above, the decline in the heat transfer performance of the quenching medium or uneven stirring will affect the stability and consistency of the surface temperature, so that the fluctuation has the characteristics of rapidness and randomness. To obtain the short-term change characteristics after the end of the quenching initial period, preferably, in the embodiment, a time window with a length of 2 minutes is set after the end of the quenching initial period. Taking the j-th time window of the i-th position as an example, the outliers of the temperature data in the j-th time window are obtained by using the SOS (Stochastic Outlier Selection) detection algorithm, and the fluctuation amplitude of the obtained outliers and the occurrence frequency of the outlier points reflect the fluctuation degree and random characteristics of the temperature change. Thus, the difference between each outlier and the average of all temperatures in the time window is calculated, and the cumulative sum of the absolute values of all the differences is taken as the abnormal coefficient of the temperature change amplitude of the casting surface in the j-th time window of the i-th position, denoted as The greater the obtained A is, the greater the difference in temperature change rate between the i-th position and other positions at the quenching initial period is, and the less smooth the temperature change at the quenching initial period is.

[0048] Further, to obtain the random characteristics of the abnormal fluctuation, the coefficient of variation of all the outliers is calculated. The greater the obtained coefficient of variation is, the stronger the randomness of the abnormal value change amplitude of the quenching temperature is. Then, the time intervals of all adjacent outliers in the time window are obtained, the variance of all the time intervals is calculated, and the greater the variance is, the greater the discrete degree of the time interval between adjacent outliers is, and thus the randomness of the position distribution of the outliers in the time window is reflected. The product of the obtained coefficient of variation and the variance is taken as the randomness of the casting surface temperature change, denoted as The greater the obtained A is, the greater the difference in temperature change rate between the i-th position and other positions at the quenching initial period is, and the less smooth the temperature change at the quenching initial period is. The greater the obtained A is, the greater the difference in temperature change rate between the i-th position and other positions at the quenching initial period is, and the less smooth the temperature change at the quenching initial period is.

[0049] , in the formula, is the abnormal significant value of the casting surface temperature change in the j-th time window of the i-th position, ​Let be the anomaly coefficient and the randomness of the surface temperature change of the casting within the j-th time window at the i-th position, respectively. Wherein, the obtained... The larger the value, the greater the instantaneous abnormal fluctuation of temperature change within that time window, and the stronger the randomness of the outlier distribution.

[0050] Step 4: Based on the degree of difference in temperature change trends between different locations of the casting and other locations within the same time window, obtain the difference coefficient of quenching temperature change state of each location within each time window. Combined with the abnormally significant value of the surface temperature change of the casting, obtain the stability and consistency coefficient of the temperature state of each location within each time window.

[0051] Furthermore, after the quenching temperature reaches a stable state, the heat transfer performance and uneven stirring of the quenching medium can cause differences in quenching temperatures in different parts of the ADI casting, thus affecting the overall hardness of the casting material. The salt bath furnace has a large thermal inertia, resulting in a delayed response of the casting surface temperature to changes in the salt bath temperature, leading to different overall temperature change trends. Therefore, the consistency of temperature states in different parts can be reflected by whether the temperature change trends at different locations are similar, and compared to simply comparing temperature data differences at different locations, this approach can reduce the interference from random outliers to some extent.

[0052] Therefore, taking the i-th position as an example, the Menkendall algorithm is used to obtain the trend characteristics of the temperature data corresponding to the i-th position within the j-th time window. The test statistic for the i-th position within the j-th time window is output. The mean of the differences between the i-th position and the test statistics of other positions within the j-th time window is calculated, and the mean of the differences between the i-th position and the average temperature of other positions within the j-th time window is also calculated. The product of these two means is taken as the difference coefficient of the quenching temperature change state of the i-th position within the j-th time window, denoted as... The result The larger the value, the worse the consistency of the surface temperature state between that location and other locations.

[0053] Among them, the abnormally significant values ​​of the surface temperature change of the casting reflect the stability characteristics of the temperature state at each location, while the difference coefficient of the quenching temperature change reflects the consistency characteristics of the temperature at each location with other locations. In a good heat treatment process, the surface temperature of the ADI casting needs to have both good stability and consistency. Therefore, the stability consistency coefficient of the temperature state at the i-th location within the j-th time window is calculated using the following formula: In the formula, Let be the stability and consistency coefficient of the temperature state within the j-th time window at the i-th position. The value representing the abnormally significant change in the surface temperature of the casting within the j-th time window at the i-th position is... The difference coefficient of the quenching temperature variation state of the i-th position in the j-th time window is obtained The stability and consistency of the temperature variation of the position are reflected.

[0054] Step five: combining the significant values of the rate difference and non-smoothness of the temperature variation of each position in the initial quenching period with the stability and consistency coefficient of the temperature state of each position in each time window, obtaining the lag influence coefficient of the temperature control of each time window to optimize the temperature error in the quenching temperature control process of the PID controller, and then completing the heat treatment of the ADI casting after tempering.

[0055] In the isothermal quenching salt bath furnace, there is a lag between the temperature state of the ADI casting and the adjustment of the stirring unit, which causes a certain delay correlation feature between the temperature states of different positions. If the variation state features of the surface temperatures of different positions are closer, it means that the stirring unit is more timely and effective in adjusting the temperature in the salt bath furnace. In view of this, taking the i-th position as an example, the significant values of the rate difference and non-smoothness of the temperature variation of each position in the initial quenching period are arranged in time sequence with the stability and consistency coefficient of the temperature state of each position in the j-th time window, obtaining the temperature state feature sequence of each position up to the j-th time window, calculating the average of the DTW distance between the temperature state feature sequences of all arbitrary two positions up to the j-th time window as the lag influence coefficient of the temperature control of the j-th time window. The larger the lag influence coefficient is, the greater the lag influence of the stirring unit on the ADI casting temperature in the process from isothermal quenching to the j-th time window.

[0056] To reduce the influence of salt bath furnace temperature fluctuation on the hardness of ADI casting, the PID controller is used to adjust the stirring unit in real time in this embodiment, and the response rate of the PID controller is optimized based on the obtained lag influence coefficient. The PID controller of this embodiment has a self-tuning function and can automatically adjust the PID parameters to achieve better control effect. The tuning of the proportional term parameter in the PID controller is calculated based on the error between the measured temperature and the preset target temperature, i.e. the isothermal quenching temperature. The larger the error is, the faster the response speed of the controller to the system. There is a delay between the real-time measured temperature data and the real temperature state of the ADI casting surface, which makes the error obtained in the tuning process not accurate enough and difficult to reflect the real temperature difference in time. If the obtained lag influence coefficient is larger, it means that the lag influence of the stirring unit is larger, and at this time, the response speed of the controller to the system needs to be increased, and a larger error is set in the tuning process of the proportional term parameter to improve the response speed of the system. Otherwise, a smaller error is set to avoid overshoot or oscillation in the adjustment.

[0057] Specifically, the hysteresis influence coefficient of temperature control for each time window is normalized by using a sigmoid function on the hysteresis influence coefficient of temperature control for the current time window, and the result is denoted as In the quenching temperature adjustment process, the specific formula of the temperature error optimization is: , wherein is the temperature error optimization value of the next time window, is the hysteresis influence coefficient of temperature control for the current time window, is the temperature error of the current time window, which is obtained by the difference between the actual temperature and the preset target temperature in the current time window. Further, in this embodiment, the proportional term parameter of the next time window can be obtained based on the optimized temperature error, and the quenching temperature is adjusted by using the PID controller according to the proportional term parameter of the next time window, so as to ensure the stability of the salt bath furnace temperature, and further improve the hardness of the ADI casting. It should be noted that the specific control process of the PID controller and the calculation process of the proportional term parameter are known to those skilled in the art, and will not be described in detail in this embodiment.

[0058] In order to further adjust the stability of residual austenite, improve the mechanical properties and reduce internal stress, in this embodiment, after the ADI casting completes isothermal quenching, it is transferred to the tempering furnace for tempering treatment. The castings in the tempering furnace are uniformly placed to avoid mutual contact to ensure uniform heating. The tempering temperature is set in the range of - In this embodiment, the tempering temperature is 350℃. When the casting reaches the set tempering temperature, the holding time is started, and the holding time is in the range of 1-4 hours, and in this embodiment, the holding time is 2 hours. It should be noted that in actual application scenarios, the implementer can set the specific tempering temperature and holding time according to the actual situation.

[0059] At this point, according to the above process of this embodiment, the heat treatment of the ADI casting can be completed.

[0060] Based on the same inventive concept as the above method, the embodiments of the present application also provide a heat treatment device for improving the hardness of ADI casting, which comprises a memory, a processor and a computer program stored in the memory and running on the processor. When the processor executes the computer program, the steps of the heat treatment method for improving the hardness of ADI casting described in any one of the above embodiments are implemented.

[0061] It can be understood that: the above-mentioned sequence of the embodiments of the present application is only for description, and does not represent the advantages and disadvantages of the embodiments. Moreover, the processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multi-task processing and parallel processing are also possible or can be advantageous.

[0062] The various embodiments in the specification are described in progressive manner, and the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the difference from other embodiments.

[0063] The above is only the implementation of the present application, and is not used to limit the scope of the present application. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings, or directly or indirectly applied in other related technical fields, is also included in the protection scope of the present application.

Claims

1. A heat treatment method for increasing the hardness of an ADI casting, characterized in that, The method comprises the following steps: obtaining temperature data of each position on the surface of the ADI casting during the isothermal quenching process of the ADI casting heat treatment; setting a quenching initial period in the quenching process of the casting, and obtaining a significant value of a rate difference and a non-smooth degree of temperature change of each position in the quenching initial period by using a temperature data change difference condition of each position and other positions in the quenching initial period and a temperature change smoothness degree of the quenching initial period; extracting an abnormal value of temperature data in each time window of each position of the casting, and obtaining an abnormal significant value of temperature change of the casting surface in each time window of each position by using a deviation condition of the abnormal value and an average level of temperature data in the time window, a random fluctuation degree of the abnormal value, and a discrete degree of a time interval between adjacent abnormal values; obtaining a difference coefficient of a quenching temperature change state of each time window of each position according to a difference degree of a temperature change trend of each position and other positions in the same time window, and obtaining a stable consistency coefficient of a temperature state of each time window of each position in combination with the abnormal significant value of the temperature change of the casting surface; obtaining a lag influence coefficient of temperature control of each time window in combination with the significant value of the rate difference and the non-smooth degree of temperature change of each position in the quenching initial period and the stable consistency coefficient of the temperature state of each position in each time window, so as to optimize a temperature error in a quenching temperature control process of a PID controller, and then performing tempering treatment to complete the heat treatment of the ADI casting; the method for obtaining the abnormal significant value of the temperature change of the casting surface in each time window of each position is as follows: wherein, is the abnormal significant value of the casting surface temperature change in the jth time window at the ith position, is the randomness of the casting surface temperature change in the jth time window at the ith position, is the abnormal coefficient of the casting surface temperature change amplitude in the jth time window at the ith position.

2. The heat treatment method for improving the hardness of an ADI casting according to claim 1, characterized in that, the determination method of the quenching initial period is as follows: time periods between a quenching start time and a time when temperature of each position on the surface of the casting material reaches a preset isothermal quenching temperature for the first time are obtained as the quenching initial period.

3. The heat treatment method for improving the hardness of an ADI casting according to claim 1, characterized in that, the method for obtaining the significant value of the rate difference and the non-smooth degree of temperature change of each position in the quenching initial period is as follows: wherein, is the significance of the difference in the rate of change of temperature during the initial period of quenching and the degree of non-smoothness at the i-th location, is the coefficient of difference in the rate of temperature drop at the initial period of quenching at the i-th location, is the coefficient of determination corresponding to the fitted curve of the temperature data at the initial period of quenching at the i-th location.

4. The heat treatment method for improving the hardness of an ADI casting according to claim 3, characterized in that, a first-order difference sequence of temperature data of each position in the quenching initial period is counted, and a mean value of a DTW distance of the first-order difference sequence of each position and all other positions in the quenching initial period is calculated as a difference coefficient of a temperature drop rate of each position in the quenching initial period.

5. The heat treatment method for improving the hardness of ADI castings as described in claim 1, characterized in that, a preset time length is taken as each time window after the end of the quenching initial period, an abnormal value of temperature data in the jth time window of the ith position is counted, a cumulative sum of absolute values of a difference value of each abnormal value and a mean value of temperature in the time window is calculated as an abnormal coefficient of a temperature change amplitude of the casting surface in the jth time window, and a product result of a variation coefficient of all abnormal values in the jth time window and a variance of a time interval between adjacent abnormal values is taken as a randomness degree of temperature change of the casting surface in the jth time window.

6. The heat treatment method for improving the hardness of ADI castings as described in claim 1, characterized in that, the method for obtaining the difference coefficient of the quenching temperature change state of each time window of each position is as follows: For the jth time window of each position, the test statistic of each position in the jth time window is extracted, the mean of the difference between the test statistic of each position and the test statistic of other positions corresponding to the jth time window is calculated, and the mean of the difference between the average temperature in the jth time window of each position and the average temperature in the jth time window of other positions is calculated. The product of the two means is taken as the difference coefficient of the quenching temperature change state of each position in the jth time window.

7. The heat treatment method for improving the hardness of ADI castings as described in claim 1, characterized in that, The method for obtaining the stable consistency coefficient of the temperature state of each position in each time window is: wherein, is the stability consistency coefficient of temperature state in the jth time window at the ith position, is the abnormal significant value of the casting surface temperature change in the jth time window at the ith position, is the difference coefficient of the quenching temperature change state in the jth time window at the ith position.

8. The method of heat treating an ADI casting to increase hardness of claim 1, wherein, The method for obtaining the lag influence coefficient of the temperature control of each time window to optimize the temperature error in the quenching temperature control process of the PID controller comprises: The significant value of the rate difference and the non-smoothness of the temperature change of each position in the initial period of quenching is arranged in time sequence with the stable consistency coefficient of the temperature state of each position in the jth time window to obtain the temperature state feature sequence of each position up to the jth time window. The mean of the DTW distance between the temperature state feature sequences of all arbitrary two positions up to the jth time window is calculated as the lag influence coefficient of the temperature control of the jth time window. Temperature error optimization value of next time window The calculation formula is: Wherein, Temperature error of current time window, Hysteresis influence coefficient of temperature control of current time window.

9. A heat treatment apparatus for increasing the hardness of an ADI casting, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that, The processor executes the computer program to realize the steps of the heat treatment method for improving the hardness of ADI castings according to any one of claims 1-8.

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