Establishment method of strip steel buckling phenomenon prediction model in continuous annealing process

Abstract

The invention discloses a method for establishing a strip steel buckling phenomenon prediction model in a continuous annealing process, which relates to the technical field of ferrous metallurgy and comprises the following steps: acquiring parameters of a strip steel heating section and a soaking section in the continuous annealing process; the parameters comprise equipment parameters and process parameters; constructing a strip steel transverse temperature distribution model; constructing a strip steel yield stress model; constructing a strip steel tensile stress distribution model; constructing a strip steel transverse pressure stress distribution model; constructing a strip steel buckling wrinkle criterion; correcting a model coefficient based on field measured data; according to the method, the strip steel operation process of the heating section and the soaking section is divided into different research units and strip steel bar elements, the whole-process strip steel buckling phenomenon prediction in the continuous annealing process can be achieved, and the real condition of strip steel buckling under the thermal-mechanical coupling effect in the continuous annealing process can be reflected more accurately and more reliably.

Description

Technical Field

[0001] The present invention relates to the field of iron and steel metallurgy, and particularly to a method for establishing a prediction model for strip buckling during continuous annealing. Background Art

[0002] The continuous annealing unit is an important part of the modern cold-rolled strip production line and has become the main unit for the production of products such as automotive sheets and household appliance sheets. With the continuous increase in market demand and the continuous improvement of quality requirements, achieving the continuous and stable operation of the continuous annealing unit on the premise of the finished strip quality is the key task of on-site production.

[0003] During the continuous annealing process of the strip, multiple influencing factors such as process tension, furnace temperature, and furnace roll profile are coupled with each other, resulting in a complex stress distribution inside the strip. After certain conditions are met, the internal stress balance of the strip is broken, leading to macroscopic defects such as buckling and wrinkling. During the operation of the strip in the continuous annealing furnace, the generation process of the transverse compressive stress can be described as follows: when the strip enters from one process section to another, if the local tension of the strip decreases or the annealing temperature increases, the strip expands in the width direction in this area. However, due to the transverse friction between the furnace roll and the strip and the centripetal force generated by the rotation of the furnace roll, the strip will be laterally restricted to a certain extent, and the transverse friction will prevent the lateral deformation of the strip, thereby generating transverse compressive stress inside the strip; if the local tension of the strip increases or the annealing temperature decreases, the strip contracts in the width direction in this area. At this time, the force of the strip contracting in the width direction constitutes the transverse compressive stress in this stress state. When this transverse compressive stress exceeds the critical value, the strip at this part will be unstable and piled up, resulting in hot buckling defects. Therefore, on the premise of clarifying the process tension of the strip and the temperature distribution in the furnace area, accurately calculating the transverse compressive stress distribution of the strip and the critical instability threshold under the corresponding working conditions, that is, the buckling critical stress, and comparing the two values can accurately judge whether the strip buckles under this working condition and the possible position where buckling may occur.

[0004] The existing models calculate inaccurately the transverse compressive stress distribution of the strip and the critical instability threshold under the corresponding working conditions, that is, the buckling critical stress, resulting in the inability to accurately predict the strip buckling and wrinkling phenomenon. For the critical instability threshold, that is, the buckling critical stress, the existing models do not consider the evolution of the dislocation density of the material under the action of recovery and recrystallization during the continuous annealing process, and the influence of the dislocation density evolution on the yield stress of the strip, resulting in the inability to accurately obtain the buckling critical stress. On the other hand, the existing models ignore the mutual influence between the furnace rolls in the furnace area, resulting in the inability to accurately calculate the transverse compressive stress distribution of the strip. Summary of the Invention

[0005] In view of the above technical problems, the present invention provides a method for establishing a prediction model for strip buckling during continuous annealing, including: S1. Obtain the parameters of the strip heating section and soaking section during continuous annealing; the parameters include equipment parameters and process parameters; S2. Construct a strip transverse temperature distribution model; S3. Construct a strip yield stress model; S4. Construct a strip tensile stress distribution model; S5. Construct a strip transverse compressive stress distribution model; S6. Construct a strip buckling and wrinkling criterion; S7. Modify the model coefficients based on on-site measured data.

[0006] Further, when obtaining the parameters in S1, the following steps are included: S11. For the continuous annealing production line where buckling phenomenon needs to be predicted, obtain the equipment parameters of the heating section and soaking section. The equipment parameters include: furnace roll profile, roll body length, straight section length, furnace roll neck, and furnace roll position distribution; S12. For the continuous annealing production line where buckling phenomenon needs to be predicted, obtain the process parameters of the heating section and soaking section during production. The process parameters include: strip thickness, strip width, passing speed, heating section tension, soaking section tension; S13. For the continuous annealing production line where buckling phenomenon needs to be predicted, measure the strip center temperature at different furnace rolls in the heating section and soaking section during production.

[0007] Further, when constructing the strip temperature distribution evolution model in S2, the following steps are included: S21. Construct a strip middle temperature calculation model: ; ; Among them, is the strip center temperature at time t, is the inlet temperature of the heating section, k is the strip middle temperature rising rate, t is the strip running time, are all model coefficients; S22. Construct a strip transverse temperature distribution calculation model: ; Among them, is the temperature at position x from the strip center at time t.

[0008] Further, when constructing the strip yield stress model in S3, the following steps are included: S31. Construct a static recrystallization kinetics model: ;

[0009] Among them, , are the static recrystallization rate and the degree of static recrystallization respectively, is the normalized dislocation density, is the nucleation rate, and are both model coefficients; S32. Construct a dislocation density evolution model: ;

[0010] wherein, is the evolution rate of the normalized dislocation density, , , and are both model coefficients; S33. Construct a yield stress calculation model: ;

[0011] wherein, is the yield stress, , are the strain rate and the deformation temperature respectively, R is the gas constant, , h and are both model coefficients.

[0012] Furthermore, when constructing the strip tensile stress distribution model, S4 includes the following steps: S41. Divide the entire furnace area from the inlet to the outlet into I research units according to the number of furnace rolls. Each research unit includes an upper furnace roll and a lower furnace roll; Divide the strip between the upper and lower furnace rolls of the research unit into 2 J +1 strip elements, and calculate the tensile stress of each strip element; S42. Simultaneously solve the tensile stress of each strip element of the research unit by the following formula : ; wherein, is the coordinate value of the th strip element of the th research unit, is the number of this strip element, is the strip element width, is the strip width, is the deformation difference caused by the transverse non-uniform distribution of the strip element temperature, is the thermal expansion coefficient, is the th strip element of the The average temperature of each strip element, is the average temperature of the middle strip element of the th research unit, is the distance between the center lines of the upper and lower furnace rolls, is the furnace roll radius of the th research unit, is the difference in strip element deformation between the th strip element and the middle strip element of the th research unit caused by the difference in incoming strip shape, is the incoming strip shape of the th research unit represented by a sixth-degree curve, is the incoming strip shape coefficient of the 、 are respectively the actual roll profile distributions of the upper and lower furnace rolls of the th research unit, 、 are respectively the original roll profile distributions of the upper and lower furnace rolls of the th research unit, 、 are respectively the hot roll profile distributions of the upper and lower furnace rolls of the th research unit, 、 The th research unit's upper and lower furnace roll wear distributions, is the difference in deformation between the th strip element and the middle strip element within the th research unit caused by the furnace roll profile, is the difference in strip element deformation caused by the installation errors of the horizontal and vertical degrees of the furnace rolls in the th research unit, 、 are respectively the maximum verticality error values above the horizontal line on the operating sides of the upper and lower furnace rolls of the th research unit; 、 are respectively the maximum horizontality error values on the operating sides of the upper and lower furnace rolls of the th research unit pointing to the operating side, is the difference in deformation between the th strip element and the middle strip element within the th research unit caused by uneven tension, is the deformation amount of the th strip element caused by tension within the th research unit, is the The deformation amount caused by tension of the th strip element within a research unit, is the elastic modulus of the strip steel, is the Poisson's ratio, is the th research unit, and the tension value of the th strip element; is the total tension of the strip steel in the

[0013] th research unit. S51. The division of the research unit and the strip elements is the same as S41; S52. The calculation formula for the Poisson stress inside the strip steel is as follows: ;

[0014] where is the Poisson stress caused by the difference in the tensile stress distribution between the front and rear research units of the th strip element of the strip steel, is the tensile stress of the th strip element in the th research unit of the strip steel, S53. The calculation formula for the thermal stress caused by the temperature difference in the width direction of the strip steel is as follows: ; where is the thermal stress caused by the temperature difference in the width direction of the th strip element of the strip steel; S54. The calculation formula for the sliding friction force when the strip element of the strip steel moves laterally is as follows: ; where is the sliding friction force when the th strip element of the strip steel moves laterally, is the friction coefficient, is the total tensile stress in the th strip element of the strip steel, is the maximum serial number of the strip elements covered by the straight section of the furnace roll, is the length of the straight section of the furnace roll; S55. The calculation formula for the centripetal force received by the strip element of the strip steel is as follows: ; where is the centripetal force received by the th strip element of the strip steel, is thei The strip passing speed of each research unit, is the speed influence coefficient, is the i taper of the furnace roll of the is the critical taper angle, q is the maximum number of strip elements; S56. The calculation formula for the transverse compressive stress on the strip element is as follows: ; Among them, is the transverse compressive stress received by the

[0015] Furthermore, when constructing the strip buckling and wrinkling criterion, the S6 includes the following steps: S61. The calculation formula for the critical buckling stress of the strip is as follows: ; Among them, is the strip thickness.

[0016] Furthermore, when the S7 corrects the model coefficients based on on-site measured data, it includes the following steps: S71. Based on the equipment and process parameters measured in S1 and the corresponding strip buckling conditions, correct the above model coefficients.

[0017] The present invention has the following beneficial effects compared with the prior art: (1) The prediction model constructed by the present invention takes into account the influence of recovery and recrystallization phenomena during the continuous annealing process on the yield stress of the strip, conforms to the actual processing situation, and has high reliability and feasibility; (2) The prediction model constructed by the present invention has a wide application range and requires less data volume, and is suitable for industrial applications.

[0018] (3) The prediction model constructed by the present invention divides the strip running process in the heating section and soaking section into different research units and strip elements, can realize the prediction of the strip buckling phenomenon during the whole process of continuous annealing, and can more accurately and reliably reflect the true situation of strip buckling under the thermo-mechanical coupling effect during the continuous annealing process. Brief Description of the Drawings

[0019] Figure 1 is a flowchart of a method for establishing a prediction model for strip buckling phenomenon during continuous annealing according to the present invention.

[0020] Figure 2 is a flowchart of the strip tensile stress transverse distribution model according to the present invention.

[0021] Figure 3This is the flow chart of the prediction model for the strip camber phenomenon of the present invention.

[0022] Figure 4 This is the comparison between the prediction result of the prediction model for the strip camber phenomenon of the present invention and the actual measurement situation of the production line. Specific implementation mode

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0024] The present invention will be further described below in conjunction with specific embodiments. The illustrative embodiments and descriptions here are used to explain the present invention, but not to limit the present invention.

[0025] Embodiment: As Figures 1 - 4 shown, a method for establishing a prediction model for the strip camber phenomenon in a continuous annealing process includes the following steps: S1. Obtain the parameters of the strip heating section and soaking section during the continuous annealing process; the parameters include equipment parameters and process parameters; S2. Construct a strip transverse temperature distribution model; S3. Construct a strip yield stress model; S4. Construct a strip tensile stress distribution model; S5. Construct a strip transverse compressive stress distribution model; S6. Construct a strip camber fold criterion; S7. Modify the model coefficients based on the on-site measured data.

[0026] When obtaining the parameters in S1, it includes the following steps: S11. For the continuous annealing production line where the camber phenomenon needs to be predicted, obtain the equipment parameters of the heating section and soaking section. The equipment parameters include: furnace roll profile, roll body length, straight section length, furnace roll neck, and furnace roll position distribution; S12. For the continuous annealing production line where the camber phenomenon needs to be predicted, obtain the process parameters during the production process of the heating section and soaking section. The process parameters include: strip thickness, strip width, passing speed, heating section tension, soaking section tension; S13. For the continuous annealing production line where the camber phenomenon needs to be predicted, measure the strip center temperature at different furnace rolls during the production process of the heating section and soaking section.

[0027] When constructing the strip temperature distribution evolution model in S2, it includes the following steps: S21. Construct a strip middle temperature calculation model: ; ; Among them, is the strip center temperature at time t, is the inlet temperature of the heating section, k is the heating rate in the middle of the strip, t is the strip running time, are all model coefficients; S22. Construct a calculation model for the transverse temperature distribution of the strip: ; Among them, is the temperature at position x from the strip center at time t.

[0028] S3 When constructing the strip yield stress model, the following steps are included: S31. Construct a static recrystallization kinetics model: ; Among them, , are the static recrystallization rate and the static recrystallization degree respectively, is the normalized dislocation density, is the nucleation rate, and are all model coefficients; S32. Construct a dislocation density evolution model: ; Among them, is the evolution rate of the normalized dislocation density, , , and are all model coefficients; S33. Construct a yield stress calculation model: ; Among them, is the yield stress, , are the strain rate and the deformation temperature respectively, R is the gas constant, , h and are all model coefficients.

[0029] S4 When constructing the strip tensile stress distribution model, the following steps are included: S41. Divide the entire furnace area from the inlet to the outlet into I research units according to the number of furnace rolls. Each research unit includes an upper furnace roll and a lower furnace roll; Divide the strip between the upper and lower furnace rolls of the research unit into 2J +1 strip element, calculate the tensile stress of each strip element ; S42. Simultaneously solve the tensile stress of each strip element of the research unit using the following formula : ; Among them, is the coordinate value of the th strip element of the th research unit, is the number of this strip element, strip element width, is the strip width, is the deformation difference caused by the non-uniform transverse temperature distribution of the strip elements, is the coefficient of thermal expansion, is the average temperature of the th strip element of the th research unit, is the average temperature of the middle strip element of the th research unit, is the distance between the center lines of the upper and lower furnace rolls, is the radius of the furnace roll of the th research unit, is the deformation difference between the th strip element and the middle strip element of the th research unit due to the shape difference of the incoming material, is the shape of the incoming material of the th research unit represented by a sixth-degree curve, is the shape coefficient of the incoming material of the th research unit, 、 are respectively the actual roll profile distributions of the upper and lower furnace rolls of the th research unit, 、 are respectively the original roll profile distributions of the upper and lower furnace rolls of the th research unit, 、 are respectively the thermal roll profile distributions of the upper and lower furnace rolls of the th research unit, 、 The wear distributions of the upper and lower furnace rolls of the th research unit, is the deformation difference between the th strip element and the middle strip element within the th research unit caused by the roll profile of the furnace roll, is the The deformation difference of strip elements caused by the installation errors of the horizontal and vertical degrees of the furnace rolls in a research unit 、 are respectively the maximum verticality error values above the horizontal line on the operating sides of the upper and lower furnace rolls of the th research unit; 、 are respectively the maximum horizontality error values on the operating sides of the upper and lower furnace rolls of the th research unit, pointing to the operating side, is the deformation difference caused by uneven tension between the th strip element and the middle strip element within the th research unit, is the deformation amount caused by tension of the th strip element within the th research unit, is the deformation amount caused by tension of the th strip element within the th research unit, is the elastic modulus of the strip steel, is the Poisson's ratio, is the tension value of the th strip element in the th research unit, is the total tension of the strip steel in the th research unit.

[0030] When constructing the transverse compressive stress distribution model of the strip steel, the following steps are included: S51. The division of the research unit and the strip elements of the strip steel is the same as that in S41; S52. The calculation formula for the Poisson stress inside the strip steel is as follows: ; Among them, is the Poisson stress caused by the difference in the tensile stress distribution of the front and rear research units for the th strip element of the strip steel, is the tensile stress of the th strip element in the th research unit of the strip steel; S53. The calculation formula for the thermal stress caused by the temperature difference in the width direction of the strip steel is as follows: ; Among them, is the thermal stress caused by the temperature difference in the width direction for the th strip element of the strip steel; S54. The calculation formula for the sliding friction force when the strip element of the strip steel moves laterally is as follows: ; Among them, is the sliding friction force when the th strip element of the strip steel moves horizontally, is the friction coefficient, is the total tensile stress within the th strip element of the strip steel, is the maximum serial number of the strip elements covered by the straight section of the furnace roll, is the length of the straight section of the furnace roll; S55. The calculation formula for the centripetal force received by the strip steel strip element is as follows: ; Among them, is the centripetal force received by the th strip element of the strip steel, is the strip steel passing speed of the i th research unit, is the speed influence coefficient, is the furnace roll taper of the i th research unit, is the critical taper angle, q is the maximum serial number of the strip steel strip element; S56. The calculation formula for the transverse compressive stress received by the strip steel strip element is as follows: ; Among them, is the transverse compressive stress received by the th strip element of the strip steel.

[0031] S6. When constructing the strip steel buckling and wrinkling criterion, the following steps are included: S61. The calculation formula for the critical buckling stress of the strip steel is as follows: ; Among them, is the thickness of the strip steel.

[0032] S7. When correcting the model coefficients based on on-site measured data, the following steps are included: S71. Based on the equipment, process parameters measured in S1 and the corresponding strip steel buckling conditions, correct the above-mentioned model coefficients.

[0033] Among them, the data of predicting the strip steel buckling phenomenon in the heating section and soaking section by applying the model to the continuous annealing production line are as Figure 4 shown. The model accurately predicts the buckling conditions of strip steels of different specifications; the model constructed in this embodiment can accurately predict the strip steel buckling conditions during the continuous annealing process, and has high reliability and feasibility.

[0034] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for establishing a prediction model of strip buckling phenomenon during continuous annealing process, characterized in that It includes the following steps: S1. Obtain the parameters of the strip heating section and soaking section during continuous annealing; the parameters include equipment parameters and process parameters; S2. Construct a strip transverse temperature distribution model; S3. Construct a strip yield stress model; S4. Construct a strip tensile stress distribution model; S5. Construct a strip transverse compressive stress distribution model; S6. Construct a strip buckling and wrinkling criterion; S7. Modify the model coefficients based on on-site measured data.

2. The method for establishing a prediction model for the phenomenon of strip buckling during continuous annealing according to claim 1, characterized in that, When obtaining the parameters in S1, it includes the following steps: S11. For the continuous annealing production line where buckling phenomenon needs to be predicted, obtain the equipment parameters of the heating section and soaking section. The equipment parameters include: furnace roll profile, roll body length, straight section length, furnace roll neck, and furnace roll position distribution; S12. For the continuous annealing production line where buckling phenomenon needs to be predicted, obtain the process parameters during production in the heating section and soaking section. The process parameters include: strip thickness, strip width, threading speed, heating section tension, soaking section tension; S13. For the continuous annealing production line where buckling phenomenon needs to be predicted, measure the strip center temperature at different furnace rolls during production in the heating section and soaking section.

3. The method for establishing a prediction model for strip buckling phenomenon during continuous annealing according to claim 2, characterized in that, When constructing the strip temperature distribution evolution model in S2, it includes the following steps: S21. Construct a strip middle temperature calculation model: ； ； Among them, is the strip center temperature at time t, is the inlet temperature of the heating section, k is the heating rate in the middle of the strip, t is the strip running time, are all model coefficients; S22. Construct a strip transverse temperature distribution calculation model: ； Among them, is the temperature at position x from the center of the strip at time t.

4. The method for establishing a prediction model for strip buckling phenomenon during continuous annealing according to claim 3, characterized in that, When constructing the strip yield stress model in S3, it includes the following steps: S31. Construct a static recrystallization kinetics model: ； Among them, , are the static recrystallization rate and the static recrystallization degree respectively, is the normalized dislocation density, is the nucleation rate, and are both model coefficients; S32. Construct a dislocation density evolution model: ； Among them, is the normalized dislocation density evolution rate, , , and are all model coefficients; S33. Construct a yield stress calculation model: ； Among them, is the yield stress, , are the strain rate and the deformation temperature respectively, R is the gas constant, , h and are both model coefficients.

5. The method for establishing a prediction model for strip buckling phenomenon during continuous annealing according to claim 4, characterized in that, When constructing the strip tensile stress distribution model in S4, it includes the following steps: S41. Divide the entire furnace area from the entrance to the exit into I research units according to the number of furnace rolls. Each research unit includes an upper furnace roll and a lower furnace roll; divide the strip steel between the upper and lower furnace rolls of the research unit into 2 J +1 strip elements, and calculate the tensile stress of each strip element ; S42. Combine the following formulas to solve the tensile stress of each element in the research unit : ； Among them, is the coordinate value of the th strip element of the th research unit, is the serial number of this strip element, is the strip element width, is the strip width, is the deformation difference caused by the non-uniform transverse temperature distribution of the strip element, is the coefficient of thermal expansion, is the th research unit, is the average temperature of the th strip element of the th research unit, is the distance between the centerlines of the upper and lower furnace rolls, is the th research unit, is the th research unit, is the strip element deformation difference between the th strip element and the middle strip element caused by the incoming strip shape difference, is the incoming strip shape of the th research unit represented by a sixth-degree curve, is the incoming strip shape coefficient of the 、 are respectively the th research unit, 、 are respectively the th research unit, 、 are respectively the th research unit, 、 The th research unit, is the th research unit, is the strip element deformation difference between the th strip element and the middle strip element caused by the furnace roll profile, is the strip element deformation difference caused by the installation errors of the horizontal and vertical degrees of the furnace roll in the 、 are respectively the th research unit, The maximum verticality error value above the horizontal line on the operating side of the upper and lower furnace rolls; 、 They are respectively the maximum levelness error values on the operation side of the upper and lower furnace rolls of the th research unit, pointing to the operation side, is the deformation difference caused by uneven tension between the th strip element and the middle strip element within the th research unit, is the deformation amount caused by tension of the th strip element within the th research unit, is the deformation amount caused by tension of the th strip element within the th research unit, is the elastic modulus of the strip steel, is the Poisson's ratio, is the tension value of the th strip element of the th research unit, is the total tension of the strip steel of the th research unit.

6. The method for establishing a prediction model for strip buckling phenomenon during continuous annealing according to claim 5, characterized in that, When constructing the strip transverse compressive stress distribution model in S5, it includes the following steps: S51. The division of the research unit and strip element is the same as S41; S52. The formula for Poisson stress inside the strip is as follows: ； Among them, is the Poisson stress caused by the difference in the tensile stress distribution of the front and rear research units for the th strip element of the strip steel, is the tensile stress of the jth strip element in the ith research unit of the strip steel, is the tensile stress of the th strip element in the (i + 1)th research unit of the strip steel; S53. The formula for thermal stress caused by temperature difference in the strip width direction is as follows: ； Among them, is the thermal stress caused by the temperature difference in the width direction of the th strip element of the strip steel; S54. The formula for sliding friction force when the strip element moves laterally is as follows: ； Among them, is the sliding friction force when the th strip element of the strip steel moves horizontally, is the friction coefficient, is the total tensile stress within the th strip element of the strip steel, is the maximum serial number of the strip elements covered by the straight section of the furnace roll, is the length of the straight section of the furnace roll; S55. The formula for centripetal force received by the strip element is as follows: ； Among them, is the centripetal force received by the th strip element of the strip steel, is the i th strip steel passing speed of the research unit, is the speed influence coefficient, is the i th furnace roll taper of the research unit, is the critical taper angle, q is the maximum number of strip steel elements; S56. The formula for transverse compressive stress received by the strip element is as follows: ； Among them, is the transverse compressive stress received by the th strip element of the strip steel.

7. The method for establishing a prediction model for strip buckling phenomenon during continuous annealing according to claim 6, wherein When constructing the strip buckling and wrinkling criterion in S6, it includes the following steps: S61. The formula for critical buckling stress of the strip is as follows: ； Among them, is the strip thickness.

8. The method for establishing a prediction model for the phenomenon of strip buckling during continuous annealing according to claim 7, characterized in that When modifying the model coefficients based on on-site measured data in S7, it includes the following steps: S71. Modify the model coefficients based on the equipment, process parameters measured in S1 and the corresponding strip buckling conditions.

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