A post-coiling expansion amount simulation method for defect regulation of 65Mn steel flat coil
By analyzing the CCT curve and cooling expansion curve of 65Mn steel, and selecting an appropriate cooling rate range, the problem of flat coil defects in 65Mn steel was solved, and the expansion amount was effectively controlled, reducing production costs and improving production efficiency.
Patent Information
- Application Number
- CN202410715617.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-06-04
- Publication Date
- 2025-11-07
- Estimated Expiration
- 2044-06-04
AI Technical Summary
During the hot rolling and coiling process of 65Mn steel, the occurrence of flat coil defects is mainly affected by the phase transformation and cooling rate. Existing technologies are unable to effectively control the changes in expansion, which makes it impossible for hot-rolled coils to proceed to subsequent processes.
By analyzing CCT curves and cooling expansion curves, the factors affecting the expansion variation within different cooling rate ranges were determined. A suitable cooling rate range was selected to control the flat coil defects of 65Mn steel. This included cooling simulation, microstructure observation, and Vickers hardness testing. CCT curves were plotted, and a cooling rate range that met the conditions was selected for controlling the flat coil defects.
Effective control of flat coil defects in 65Mn steel was achieved, the expansion variation law under different cooling rates was determined, a low-cost and effective improvement method was provided, and the probability of flat coil defects was reduced.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of plastic working of metal materials, in particular to a post-coiling expansion amount simulation method for defect regulation of 65Mn steel flat coil. BACKGROUND
[0002] 65Mn high-strength tool steel is widely used in various fields due to its excellent mechanical properties and low price. However, in actual production, quality defects of flat coil often occur after hot rolling and coiling, which leads to the failure of subsequent uncoiling of hot rolled coil and affects the cold rolling and annealing process. The occurrence of flat coil is related to many factors, mainly including uneven distribution of residual stress in the coil, improper tension adjustment during coiling, uneven phase change, insufficient stiffness, etc. To reduce the occurrence of flat coil defects, the strength of the strip steel can be improved, the coiling tension can be adjusted, and the post-coiling residence time can be controlled. These adjustment methods are mainly based on the root cause of the occurrence of flat coil, that is, the large volume expansion of the strip steel after coiling due to phase change leads to the sliding between layers and the occurrence of loose coil phenomenon.
[0003] In addition, due to the thermal expansion and contraction of steel during actual cooling, volume shrinkage will occur. When the volume shrinkage force cannot resist the phase change expansion force, the strip steel will appear flat coil defects under the action of its own gravity. Therefore, it is crucial to study the expansion amount of the strip steel under the combined action of phase change and cooling to regulate the phase change and post-coiling cooling rate, and thus to inhibit the occurrence of flat coil. The occurrence of flat coil is mainly affected by the expansion amount under the combined action of phase change and cooling rate. The former is the factor leading to the occurrence of flat coil, and the latter is the reason for inhibiting the occurrence of flat coil. During the cooling stage after coiling, due to the different specific volumes of each structure caused by phase change, as the cooling speed increases, a large volume expansion will occur. At the same time, due to the thermal expansion and contraction characteristics of steel, the faster the cooling speed, the greater the temperature change, and the greater the shrinkage amount in the same time. Finally, under the interaction of the two opposite forces, it determines whether the flat coil occurs.
[0004] Therefore, it is necessary to study the variation law of the expansion amount and shrinkage amount under different cooling speeds during the cooling process after coiling of the strip steel, and to determine the dominant position relationship of the interaction between the expansion amount caused by phase change and the shrinkage amount caused by cooling at different cooling stages. SUMMARY
[0005] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide a post-coiling expansion amount simulation method for defect regulation of 65Mn steel flat coil, which uses CCT curve and temperature drop expansion curve to analyze the main factors affecting the expansion amount change in different cooling speed ranges after coiling of 65Mn steel, and thus to realize the regulation of flat coil defects.
[0006] To achieve the above object, the application provides a post-coiling expansion amount simulation method for defect regulation of 65Mn steel flat coil, which comprises the following steps:
[0007] Cut the 65Mn test steel into a cylindrical sample with a diameter of 6 mm and a length of 100 mm, and perform cooling simulation on the cylindrical sample at different cooling speeds;
[0008] Perform microstructure observation and Vickers hardness detection on the cylindrical sample after cooling simulation, and obtain a CCT curve in combination with the expansion curve of the cylindrical sample;
[0009] Select a cooling speed range meeting the conditions according to the CCT curve, analyze the cooling expansion curve of the selected cooling speed range, and count the expansion amount change caused by phase transition alone and the expansion amount change caused by the comprehensive action of cooling speed in the phase transition process, so as to solve the problem of 65Mn steel flat coil.
[0010] Optionally, the mass percentage of the cylindrical sample is as follows: C: 0.66%, Si: 0.21%, Mn: 0.98%, P: 0.014%, S: 0.007%, Ni: 0.021%, Cr: 0.04%, Cu: 0.021%, and the remaining amount is Fe.
[0011] Optionally, the cooling simulation process of the cylindrical sample is as follows:
[0012] Use a Gleeble-3500 thermal simulation testing machine to heat the cylindrical sample to an austenitizing temperature at a heating rate of 10 ℃ / s, detect the heating expansion curve and determine the critical transformation points Ac1 and Ac3, heat the cylindrical sample to room temperature at cooling speeds of 0.5 ℃ / s, 2 ℃ / s, 5 ℃ / s, 10 ℃ / s, 15 ℃ / s, 20 ℃ / s, 30 ℃ / s and 50 ℃ / s respectively after 5 min of holding after heating, complete the cooling simulation process, and obtain the cooling expansion curve;
[0013] The austenitizing temperature is 950 ℃, and the Gleeble-3500 thermal simulation testing machine is connected with argon as a protective atmosphere during the experiment.
[0014] Optionally, the process of obtaining the CCT curve is as follows:
[0015] Cut the middle part of the cylindrical sample after cooling simulation to obtain a thermocouple welding section, measure the Vickers hardness of multiple positions on both sides of the cutting part of the thermocouple welding section and take the average value, then measure the critical transformation points and phase transformation points of the heating expansion curve and the cooling expansion curve respectively by using the tangent method, and draw the CCT curve in combination with the average value of the Vickers hardness, the critical transformation points and the phase transformation points;
[0016] The CCT curve abscissa time starts from the temperature drop after the cylindrical sample is kept for 5 minutes.
[0017] Optionally, the process for solving the 65Mn steel flat coil problem is as follows: selecting a cooling speed range that meets the conditions according to the CCT curve, analyzing the cooling expansion curve of the selected cooling speed range, and counting the expansion amount change caused by the phase change alone and the expansion amount change caused by the cooling speed comprehensive action.
[0018] According to the best structure of the 65Mn steel, a cooling speed that meets the conditions is selected on the CCT curve, and the measurement of the proeutectoid ferrite content of the best structure is performed; wherein the best structure includes proeutectoid ferrite and pearlite structure, and the selected cooling speed that meets the conditions includes 0.5℃ / s, 2℃ / s, 5℃ / s and 10℃ / s;
[0019] The expansion curves and the expansion amount change degree under the phase change alone and the cooling speed comprehensive action under the cooling speeds of 0.5℃ / s, 2℃ / s, 5℃ / s and 10℃ / s are determined, the main factors affecting the expansion amount in each cooling range are compared, and the main factors are used to solve the 65Mn steel flat coil problem; wherein each cooling range includes 0.5-2℃ / s, 2-5℃ / s and 5-10℃ / s.
[0020] The present application provides a post-coiling expansion amount simulation method for 65Mn steel flat coil defects, and the following technical effects are disclosed:
[0021] 1、The present application can determine the relationship between the phase type and the content difference of each proportion caused by different cooling speeds of 65Mn steel and the expansion amount change caused by the phase change alone.
[0022] 2、In the actual cooling process, the expansion amount caused by the phase change under different cooling speeds and the cooling comprehensive action is not the same, and the present application gives the expansion change rule caused by different cooling speeds and the main influencing factors in each cooling stage.
[0023] 3、The present application determines the corresponding cooling speed range according to the actual cooling speed when the phase change occurs and each cooling speed stage in the cooling process, and regulates the main factors causing the expansion amount in the range, thereby effectively controlling the occurrence of 65Mn steel flat coil.
[0024] 4、The test method of the present application is simple, low in cost, and provides a new idea for effectively improving the 65Mn steel flat coil defect.
[0025] The technical solutions of the present application will be further described in detail below with the aid of the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS
[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed in the embodiments will be briefly introduced as follows. Obviously, the accompanying drawings in the following description only represent some embodiments of the present application, and all other drawings obtained by those of ordinary skill in the art based on these drawings without creative effort should fall within the protection scope of the present application.
[0027] Figure 1 The method flowchart provided for the embodiments of the present application is provided.
[0028] Figure 2 The 65Mn steel CCT curve schematic diagram provided for the embodiments of the present application is provided.
[0029] Figure 3 The 65Mn steel CCT curve detailed schematic diagram provided for the embodiments of the present application is provided.
[0030] Figure 4 The percentage of proeutectoid ferrite content under the qualified cooling rate provided for the embodiments of the present application is provided.
[0031] Figure 5 The expansion amount change schematic diagram of the cooling expansion curve provided for the embodiments of the present application is provided.
[0032] Figure 6 The expansion curve schematic diagram under the phase change alone provided for the embodiments of the present application is provided.
[0033] Figure 7 The expansion amount change schematic diagram under the phase change alone provided for the embodiments of the present application is provided.
[0034] Figure 8 The expansion curve schematic diagram under the comprehensive action provided for the embodiments of the present application is provided.
[0035] Figure 9 The expansion amount change schematic diagram under the comprehensive action provided for the embodiments of the present application is provided. DETAILED DESCRIPTION
[0036] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments only represent some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the protection scope of the present application.
[0037] In order to make the above objectives, characteristics and advantages of the present application more apparent, the present application will be further described in detail with reference to the accompanying drawings and specific embodiments.
[0038] As Figures 1-9As shown, the present application provides a post-coiling expansion amount simulation method for defect regulation of 65Mn steel flat coil, which realizes effective regulation of defects of 65Mn steel flat coil, and comprises the following steps:
[0039] 1. Cutting 65Mn test steel into a cylindrical sample with a diameter of 6mm and a length of 100mm, and cooling the cylindrical sample at different cooling speeds. Specifically:
[0040] The mass percentage of the cylindrical sample is: C: 0.66, Si: 0.21, Mn: 0.98, P: 0.014, S: 0.007, Ni: 0.021, Cr: 0.04, Cu: 0.021, and the remaining amount is Fe (% by mass).
[0041] As shown, Figures 1-3 the cooling simulation process of the cylindrical sample is: using a Gleeble-3500 thermal simulation testing machine, heating the cylindrical sample to an austenitizing temperature at a heating rate of 10℃ / s, detecting the heating expansion curve and determining the critical transformation points Ac1 and Ac3, after heating, keeping the cylindrical sample at temperature for 5min to completely austenitize the cylindrical sample, and then cooling the completely austenitized cylindrical sample to room temperature at cooling speeds of 0.5℃ / s, 2℃ / s, 5℃ / s, 10℃ / s, 15℃ / s, 20℃ / s, 30℃ / s and 50℃ / s, respectively, to complete the cooling simulation process and obtain the cooling expansion curve.
[0042] Wherein, the austenitizing temperature is 950℃, and the Gleeble-3500 thermal simulation testing machine is connected with argon as a protective atmosphere during the experiment.
[0043] 2. Observing the microstructure of the cylindrical sample after cooling simulation and detecting the Vickers hardness, and combining the expansion curve of the cylindrical sample to obtain the CCT curve. Specifically:
[0044] As shown, Figures 1-3 cutting the middle part of the cylindrical sample after cooling simulation to obtain a thermocouple welding section, measuring the Vickers hardness at multiple positions on both sides of the cutting part of the thermocouple welding section and taking the average value, and then measuring the critical transformation points (Ac1, Ac3) and phase transition points (Ms) of the 10℃ / s heating expansion curve and the 50℃ / s cooling expansion curve respectively by using the tangent method, combining the average value of the Vickers hardness, the critical transformation points and the phase transition points to draw the CCT curve.
[0045] Wherein, the horizontal coordinate time of the CCT curve starts from the time when the cylindrical sample is kept at temperature for 5min and then cooled
[0046] 3. Select a cooling rate range meeting the condition according to the CCT curve, analyze the cooling expansion curve of the selected cooling rate range, and count the expansion amount change caused by the phase change alone and the expansion amount change caused by the comprehensive action of the cooling rate in the phase transition process, so as to solve the 65Mn steel flat coil problem. Specifically:
[0047] According to the best structure of the 65Mn steel, a cooling rate meeting the condition is selected on the CCT curve, the content of proeutectoid ferrite of the best structure is measured, and the percentage of the proeutectoid ferrite content is obtained (as shown in Figure 4 The best structure includes proeutectoid ferrite and pearlite structure, and the selected cooling rate meeting the condition includes 0.5 ℃ / s, 2 ℃ / s, 5 ℃ / s and 10 ℃ / s.
[0048] As shown in Figure 5 Because the expansion amount change is affected by the comprehensive action of the phase change and the cooling in the cooling process, the expansion amount change caused by the phase change alone and the expansion amount change caused by the comprehensive action of the two are determined for experimental analysis.
[0049] As shown in Figures 6-9 The present application determines the expansion curve and the expansion amount change degree under the cooling rate of 0.5 ℃ / s, 2 ℃ / s, 5 ℃ / s and 10 ℃ / s, compares the main factors affecting the expansion amount in each cooling range, and solves the 65Mn steel flat coil problem based on the main factors; wherein each cooling range and its influencing factors include: under the small cooling rate of 0.5-2 ℃ / s, the shrinkage amount caused by cooling is dominant; when the cooling rate is increased to the range of 2-5 ℃ / s, the expansion amount caused by the phase change plays a major role; when the cooling rate reaches 5-10 ℃ / s, the shrinkage amount caused by cooling is dominant again. Therefore, in order to effectively solve the flat coil problem, the dominant factor should be adjusted in different post-coiling cooling rate ranges.
[0050] Therefore, the present application provides a post-coiling expansion amount simulation method for 65Mn steel flat coil defects, uses the CCT curve and the cooling expansion curve, analyzes the main factors affecting the expansion amount change in different cooling rate ranges of the 65Mn steel after coiling, and realizes the regulation of the flat coil defects.
[0051] Each embodiment in the specification is described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same or similar parts of each embodiment can be referred to each other.
[0052] The principles and implementation manners of the present application are described by using specific examples in the present application, and the above examples are only used to help understand the method of the present application and its core idea; meanwhile, for the general technical personnel in the art, the specific implementation manners and application ranges will be changed according to the idea of the present application. In conclusion, the content of the present specification should not be understood as the limitation of the present application.
Claims
1. A post-coil expansion amount simulation method for defect regulation of 65Mn steel flat coil, characterized in that, The method comprises the following steps: cutting 65Mn test steel into a cylindrical sample with a diameter of 6mm and a length of 100mm, and performing cooling simulation on the cylindrical sample at different cooling speeds; performing microstructure observation and Vickers hardness detection on the cylindrical sample after the cooling simulation, and combining the expansion curve of the cylindrical sample to obtain a CCT curve; selecting a cooling speed range meeting the conditions according to the CCT curve, analyzing the cooling expansion curve in the selected cooling speed range, and counting the expansion amount change caused by the phase transition alone and the expansion amount change caused by the comprehensive action of the cooling speed in the phase transition process, so as to solve the problem of 65Mn steel flat coil; the process of obtaining the CCT curve is as follows: cutting the middle part of the cylindrical sample after the cooling simulation to obtain a thermocouple welding section, measuring the Vickers hardness of multiple positions on both sides of the cutting part of the thermocouple welding section and taking the average value, then measuring the critical transition point and phase transition point of the heating expansion curve and the cooling expansion curve respectively by using the tangent method, combining the average value of the Vickers hardness, the critical transition point and the phase transition point, and drawing the CCT curve; wherein the horizontal coordinate time of the CCT curve starts from the time when the cylindrical sample is cooled after being kept for 5min; the process of selecting a cooling speed range meeting the conditions according to the CCT curve, analyzing the cooling expansion curve in the selected cooling speed range, counting the expansion amount change caused by the phase transition alone and the expansion amount change caused by the comprehensive action of the cooling speed in the phase transition process, and solving the problem of 65Mn steel flat coil is as follows: according to the best organization of 65Mn steel, selecting a cooling speed meeting the conditions on the CCT curve, and measuring the proeutectoid ferrite content of the best organization; wherein the best organization includes proeutectoid ferrite and pearlite structure, and the selected cooling speed meeting the conditions includes 0.5℃ / s, 2℃ / s, 5℃ / s and 10℃ / s; determining the expansion curve and the expansion amount change degree under the phase transition alone and the comprehensive action of the cooling speed at the cooling speeds of 0.5℃ / s, 2℃ / s, 5℃ / s and 10℃ / s, comparing the main factors affecting the expansion amount in each cooling range, and solving the problem of 65Mn steel flat coil based on the main factors; wherein each cooling range includes 0.5~2℃ / s, 2~5℃ / s and 5~10℃ / s.
2. The post-coil expansion amount simulation method for defect regulation of 65Mn steel flat coil according to claim 1, characterized in that, The mass percentage of the cylindrical sample is: C: 0.66%, Si: 0.21%, Mn: 0.98%, P: 0.014%, S: 0.007%, Ni: 0.021%, Cr: 0.04%, Cu: 0.021%, and the remaining amount is Fe.
3. The post-coil expansion amount simulation method for defect regulation of 65Mn steel flat coil according to claim 2, characterized in that, The cooling simulation process of the cylindrical sample is as follows: The cylindrical sample is heated to an austenitizing temperature at a heating rate of 10 ℃ / s by using a Gleeble-3500 thermal simulation testing machine, a heating expansion curve is detected, and critical transformation points Ac1 and Ac3 are determined; after the heating is completed, the cylindrical sample is kept for 5 min to completely austenitize the cylindrical sample, and then the completely austenitized cylindrical sample is cooled to room temperature at cooling rates of 0.5 ℃ / s, 2 ℃ / s, 5 ℃ / s, 10 ℃ / s, 15 ℃ / s, 20 ℃ / s, 30 ℃ / s and 50 ℃ / s respectively, a cooling simulation process is completed, and a cooling expansion curve is obtained. In the formula, the austenitizing temperature is 950 ℃, and the Gleeble-3500 thermal simulation testing machine is connected with argon as a protective atmosphere during the experiment.