A control method for preventing deformation of strip specimens

Abstract

This invention relates to a control method for preventing deformation of strip specimens, comprising the following steps: 1) Selecting a group of strip specimens in the same state, and conducting a strip annealing process simulation experiment on one of them, keeping the clamps holding both ends of the strip specimen in a fixed position, and recording the force on the strip specimen; 2) Straightening the strip specimen after the experiment and measuring its total length to obtain the elongation of the strip specimen; 3) Plotting the recorded force on the strip specimen as a loading curve of the loading force value over time; 4) Calculating the instantaneous displacement of one end of the clamps holding the strip specimen relative to the other end over time using the loading curve; 5) Selecting another strip specimen and conducting a strip annealing process simulation experiment, so that one end of the clamps holding the strip specimen is automatically controlled to move, and the distance of movement is controlled according to step 4); This effectively avoids deformation of the strip specimen, obtains a strip specimen with good shape, and improves experimental accuracy and success rate.

Description

Technical Field

[0001] This invention relates to the field of hot working technology for steel materials, and in particular to a control method for preventing deformation of strip samples. Background Technology

[0002] The sheet and strip annealing process can recrystallize the sheet and strip material, eliminate work hardening, and is a heat treatment process that restores plasticity to obtain the desired physical and physicochemical properties.

[0003] To develop high-performance cold-rolled products more quickly and efficiently, continuous annealing simulation testing machines are commonly used to study the relationship between the microstructure and properties of cold-rolled products and the annealing process. Patent CN200510023266.9, entitled "A Continuous Annealing Process Simulation Device for Strip Steel," can continuously simulate the heating, homogenization, slow cooling, rapid cooling, and over-aging processes of strip steel samples in a continuous annealing furnace. However, because strip samples have low strength at high temperatures, the expansion of the samples during heating and homogenization can cause bending deformation. This invention does not explicitly propose effective measures to prevent strip sample deformation.

[0004] Thermodynamic simulation testing machines manufactured by Dynamic Systems, Inc. in the United States can be equipped with different components or units to complete specific physical simulation experiments. The strip annealing system is one such example. When using this system to simulate the strip annealing process, a constant tensile force is applied to both ends of the strip sample using clamps holding the sample to keep it straight. However, due to the system's structural characteristics, when the strip is under vacuum, the main shaft of the clamps holding the sample is subjected to atmospheric pressure, generating compressive stress on the sample. This necessitates setting specific parameters for the stress applied to the strip... The force on the sample must be large enough to counteract the effect of atmospheric pressure. During the annealing process, the strip sample needs to be cooled by spraying cooling medium, which will disrupt the vacuum state of the strip sample and weaken the effect of atmospheric pressure on the main shaft of the clamp holding the strip sample. This will increase the resultant force on the strip sample, and since the strip is in a tensile state, it is easy for the strip sample to undergo tensile deformation. If the tension applied to both ends of the strip sample is too small, the strip sample may bend due to thermal expansion, which will ultimately affect the experimental accuracy and reduce the experimental efficiency.

[0005] To overcome the shortcomings of the above methods, it is necessary to develop more effective control methods to prevent deformation of strip specimens, so as to obtain well-shaped strip specimens and improve the accuracy and efficiency of experiments. Summary of the Invention

[0006] This invention provides a control method to prevent deformation of strip samples, so as to obtain strip samples with good shape after continuous annealing process simulation experiment, thereby improving the accuracy and efficiency of the experiment.

[0007] To achieve the above objectives, the present invention employs the following technical solution:

[0008] A method for controlling deformation of a strip sample includes the following steps:

[0009] 1) Select a group of strip samples in the same state, take one of them to conduct a strip annealing process simulation experiment, keep the clamps holding the two ends of the strip sample in a fixed position, heat, heat and cool the sample, and record the force on the strip sample.

[0010] 2) Straighten the strip sample after the experiment and measure its total length to obtain the elongation of the strip sample:

[0011] ΔL=L1-L0 (1)

[0012] Where L1 is the total length of the strip sample measured after the test, and L0 is the original length of the strip sample before the test.

[0013] 3) Plot the forces on the strip specimen recorded in the simulation experiment as a loading curve of the loading force value over time;

[0014] 4) Calculate the displacement that one end of the clamps at both ends of the specimen needs to travel relative to the other end over time using the loading curve. The formula is as follows:

[0015]

[0016] Among them, L x ΔL is the elongation of the strip specimen within the time interval 0 to t, which is the displacement that one end of the clamps holding the strip specimen needs to travel relative to the other end over time. ΔL is the displacement that one end of the clamps holding the strip specimen needs to travel relative to the other end over the time interval 0 to t0. E is the cumulative value of the strip force on the strip specimen over time over the time interval 0 to t, and E0 is the cumulative value of the strip force on the strip specimen over time over the time interval 0 to t0.

[0017] 5) Select another strip sample and install it between the two clamps holding the strip sample. Conduct a strip annealing process simulation experiment. Automatically control one end of the two clamps holding the strip sample to move, and the moving distance is according to formula (2) L x To take control.

[0018] Furthermore, based on its shape characteristics, the loading curve is represented by a function as follows:

[0019] F = f(t) (3)

[0020] Where F is the applied force, and f(t) is a polynomial divided into different intervals according to time t;

[0021] By fitting the loading curve with a polynomial, the relationship between the loading force and time in formula (3) is obtained. Integrating formula (3) corresponding to the loading curve, we get:

[0022]

[0023] Furthermore, the cumulative amount of the loading force F during the simulated annealing process of the strip sample from 0 to t0 is...

[0024]

[0025] Where t0 is the total time used in the annealing process simulation experiment.

[0026] Furthermore, the movement control accuracy of the clamps at both ends of the clamping plate with the sample is 0.008 to 0.012 mm.

[0027] Furthermore, the sample is heated at a rate of 10–15 °C / s to a temperature of 800–1000 °C.

[0028] Furthermore, the sample is subjected to heat preservation and cooling, with a heat preservation time of 3 to 5 minutes and a cooling rate of 10 to 15 °C / s.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] By determining the total elongation of the strip sample due to thermal expansion during the experiment in the strip annealing apparatus, and reflecting the stress characteristics of the strip sample during this process, the elongation of the strip sample at different time periods can be obtained. This can be used to control the displacement of the clamp holding one end of the strip sample at different time periods, which can effectively prevent the strip sample from deforming and obtain a strip sample with good shape. This can improve both experimental accuracy and success rate. Detailed Implementation

[0031] The specific embodiments of the present invention will be further described below:

[0032] This invention discloses a method for controlling deformation of strip samples, which specifically includes the following steps:

[0033] 1) Select a group of strip samples in the same state, and take one of them to conduct a strip annealing process simulation experiment. When the strip sample is installed on the testing machine, keep the clamps holding the two ends of the strip sample in a fixed position. Heat, hold and cool the sample. The heating rate is 10-15℃ / s, the heating temperature is 800-1000℃, the holding time is 3-5min, and the cooling rate is 10-15℃ / s. Record the force on the strip sample during this process.

[0034] 2) Take out the strip sample that has been heated, kept warm and cooled in step 1), straighten it, and measure its total length as L1. The original length of the strip sample before the experiment is L0. The elongation of the strip sample is ΔL=L1-L0.

[0035] 3) Based on the force values ​​recorded in step 1 during the experiment, plot the loading curve of the loading force value over time.

[0036] 4) The loading curve in step 3 is represented by the following function:

[0037] F = f(t) (6)

[0038] Where F is the loading force, and according to the shape characteristics of the loading curve, f(t) is a polynomial, or a polynomial divided into different intervals according to time t. By fitting the polynomial of the loading curve, the relationship between the loading force and time in formula (6) can be obtained. Integrating formula (6) corresponding to the loading curve, we get:

[0039]

[0040] Where E is the cumulative force on the strip sample over time 0 to t. Assuming the strip sample undergoes heating, heat preservation, and cooling, and the total time for this process is t0, then:

[0041]

[0042] Where t0 is the total time used in the annealing process simulation experiment, and E0 is the cumulative amount of the strip sample bearing force over time from 0 to t0.

[0043] The elongation or shortening of the strip is closely related to the force it experiences. If the cumulative force on the strip sample during the entire heating, holding, and cooling process is distributed according to the force acting on the strip sample, then:

[0044]

[0045] The cumulative force on the strip specimen and the strip elongation can be expressed by the following formula:

[0046]

[0047] Wherein, ΔL is the total elongation of the strip sample during the time interval 0-t0;

[0048] L can be obtained from formula (10) x L x It can be expressed by the following formula:

[0049]

[0050] Among them, L x This refers to the amount of displacement that one end of the clamps holding the strip sample needs to travel relative to the other end over time, in order to prevent the strip sample from bending and deforming.

[0051] 5) Select another strip sample and install it between the two clamps holding the strip sample to conduct a strip annealing process simulation experiment. At this time, one end of the two clamps holding the strip sample can be automatically controlled to move, and the distance of movement is controlled according to formula (11), that is, the displacement of one end of the clamps holding the strip sample relative to the other end over time is L. x This can effectively prevent deformation of the strip sample.

[0052] The following embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments. Unless otherwise specified, the methods used in the following embodiments are conventional methods.

[0053]

Example 1

[0054] 1) Select a group of strip samples in the same state. The sample material is a low-carbon low-alloy steel and the size of the strip sample is 50×180×1mm. Take one of them to conduct a strip annealing process simulation experiment. When the strip sample is installed on the testing machine, keep the clamps holding the strip sample at both ends from moving. On the thermodynamic simulation testing machine, heat the strip sample to 900℃ at a heating rate of 10℃ / s, hold it at this temperature for 3min, and then cool it to room temperature at a cooling rate of 10℃ / s. Record the force on the strip sample during this process.

[0055] 2) Take out the strip sample that has been heated, kept warm and cooled in step 1), straighten it, and measure its total length as 182.8 mm. The original length of the strip is 180 mm, and the length of the strip sample is 2.8 mm.

[0056] 3) Based on the force values ​​of the strip specimen recorded in step 1) during the experiment, plot the loading curve of the loading force value over time.

[0057] 4) The function corresponding to the loading curve in step 3) can be fitted with a fifth-order polynomial. The result obtained by fitting with a fifth-order polynomial is:

[0058] F = -45.8 - 5.25t + 0.05t 2 -5×10 -4 t 3 +1.27×10 -6 t 4 -1.17×10 -9 t 5 (12)

[0059] Where F is the loading force, and integrating the formula (12) corresponding to the loading curve yields:

[0060] E = -45.8t - 2.62t 2 +0.017t 3 -1.25×10 -4 t 4 +2.54×10 -7 t 5 -1.9×10 -10 t 6 (13)

[0061] The strip sample underwent heating, heat preservation, and cooling, with a total time of 338 seconds. Substituting this into formula (13), we get E0 = 2.13 × 10⁻⁶. 4 ;

[0062] The elongation or shortening of the strip is closely related to the force applied to it. Therefore, by combining equations (9), (10), (11), and (13), we can obtain:

[0063]

[0064] Among them, L x This refers to the amount of displacement that one end of the clamps holding the sample on the plate needs to travel relative to the other end over time.

[0065] 5) Select another strip sample and install it between the two clamps holding the strip sample to conduct a strip annealing process simulation experiment. At this time, one end of the two clamps holding the strip sample can be automatically controlled to move. The distance of movement is controlled according to formula (14), that is, the displacement of one end of the clamps holding the strip sample relative to the other end is L over time. x This can effectively prevent deformation of the strip sample.

[0066]

Example 2

[0067] 1) Select a set of strip specimens in the same state. The specimen material is a low-carbon low-alloy steel, and the specimen size is 50×180×1mm. Take one of them for a strip annealing process simulation experiment. When mounting the strip specimen on the testing machine, keep the clamps holding the strip specimen at both ends in a fixed position. On the thermodynamic simulation testing machine, heat the strip specimen to 900℃ at a heating rate of 10℃ / s, hold it at this temperature for 3 minutes, and then cool it to room temperature at a cooling rate of 10℃ / s. Record the forces acting on the strip specimen during this process.

[0068] 2) Take out the strip sample that has been heated, kept warm and cooled in step 1), straighten it, and measure its total length as 182.8 mm. The original length of the strip is 180 mm, and the length of the strip sample is 2.8 mm.

[0069] 3) Based on the force values ​​of the strip specimen recorded in step 1) during the experiment, plot the loading curve of the loading force value over time.

[0070] 4) The function corresponding to the loading curve in step 3) is divided into two segments: one from 0 to 52 seconds and the other from 52 to 338 seconds. The first segment can be fitted with a quadratic function, and the second segment can be fitted with a third-order polynomial. The fitting results are as follows:

[0071] F = -79.29 - 1.51t + 0.004t 2 (0 <t<52) (15)

[0072] F = -347.7 + 3.88t - 0.016t 2 +2.19×10 -5 t 3 (52 <t<388) (16)

[0073] Where F is the loading force, and by integrating the formulas (15) and (16) corresponding to the loading curve respectively, we get:

[0074] E = -79.29t - 0.71t 2 +0.0013t 3 (0 <t<52) (17)

[0075] E = -347.7t + 1.94t 2 -0.005t 3 +5.5×10 -6 t 4 (52 <t<388) (18)

[0076] Substituting the times of 52 seconds and 388 seconds into formulas (17) and (18) respectively, we get E. 01 =5.71×103 E is the value calculated according to formula (17). 02 =1.56×10 4 The value is calculated according to formula (18);

[0077] The elongation or shortening of the strip is closely related to the force it is subjected to. Therefore, by combining equations (9), (10), and (11) with equations (17) and (18) respectively, we can obtain:

[0078] L x = -9.67 × 10 -3 t-8.66×10 -5 t 2 +1.59×10 -7 t 3 (0 <t<52) (19)

[0079] L x =0.7 - 4.69 × 10 -2 t+2.62×10 -4 t 2 -6.75×10 -7 t 3 +7.43×10 -10 t 3 (52 <t<388)(20)

[0080] Among them, L x This refers to the displacement of one end of the clamps holding the sample at both ends relative to the other end.

[0081] 5) Select another strip sample and install it between the two clamps holding the strip sample to conduct a strip annealing process simulation experiment. At this time, one end of the two clamps holding the strip sample can be automatically controlled to move. The distance of movement is controlled according to formulas (14) and (15), that is, the displacement of one end of the clamps holding the strip sample relative to the other end is L over time. x This can effectively prevent deformation of the strip sample.

Claims

1. A method for controlling deformation of a strip sample, characterized in that, Includes the following steps: 1) Select a group of strip samples in the same state, take one of them to conduct a strip annealing process simulation experiment, keep the clamps holding the two ends of the strip sample in a fixed position, heat, heat and cool the sample, and record the force on the strip sample. 2) Straighten the strip sample after the experiment and measure its total length to obtain the elongation of the strip sample: ΔL=L1-L0 (1) Where L1 is the total length of the strip sample measured after the test, and L0 is the original length of the strip sample before the test. 3) Plot the forces on the strip specimen recorded in the simulation experiment as a loading curve of the loading force value over time; 4) Calculate the displacement that one end of the clamps at both ends of the specimen needs to travel relative to the other end over time using the loading curve. The formula is as follows: Among them, L x ΔL is the elongation of the strip specimen within the time interval 0 to t, which is the displacement that one end of the clamps holding the strip specimen needs to travel relative to the other end over time. ΔL is the displacement that one end of the clamps holding the strip specimen needs to travel relative to the other end over the time interval 0 to t0. E is the cumulative value of the strip force on the strip specimen over time over the time interval 0 to t, and E0 is the cumulative value of the strip force on the strip specimen over time over the time interval 0 to t0. 5) Select another strip sample and install it between the two clamps holding the strip sample. Conduct a strip annealing process simulation experiment. Automatically control one end of the two clamps holding the strip sample to move, and the moving distance is according to formula (2) L x To take control.

2. The method for controlling deformation of a strip sample according to claim 1, characterized in that, Based on its shape characteristics, the loading curve is represented by a function as follows: F=f(t) (3) Where F is the applied force, and f(t) is a polynomial divided into different intervals according to time t; By fitting the loading curve with a polynomial, the relationship between the loading force and time in formula (3) is obtained. Integrating formula (3) corresponding to the loading curve, we get: .

3. The method for controlling deformation of a strip sample according to claim 2, characterized in that, The loading force F is the cumulative value of the force borne by the strip during the simulation experiment of the strip sample annealing process from 0 to t0. Where t0 is the total time used in the annealing process simulation experiment.

4. The method for controlling deformation of a strip sample according to claim 1, characterized in that, The movement control accuracy of the clamps at both ends of the clamping plate with the sample is 0.008 to 0.012 mm.

5. The method for controlling deformation of a strip sample according to claim 1, characterized in that, The sample is heated at a rate of 10-15°C / s to a temperature of 800-1000°C.

6. The method for controlling deformation of a strip sample according to claim 1, characterized in that, The sample is subjected to heat preservation and cooling, with a heat preservation time of 3 to 5 minutes and a cooling rate of 10 to 15 °C / s.

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