Elongation calculation method and rolling operation method

Abstract

To accurately calculate elongation percentage of a rolled material with respect to rolling load even when rolling is performed by using a roll having prescribed surface roughness.SOLUTION: An elongation percentage calculation method calculates an elongation percentage of a rolled material rolled by using a roll having prescribed surface roughness and has: a data acquisition step for acquiring data showing relations between rolling load when the rolled material is rolled by using the roll and an elongation percentage of the rolled material; a regression expression calculation step which, on the basis of the data, calculates a regression expression showing relations between the rolling load when the rolled material is rolled with the roll and the elongation percentage of the rolled material; and an elongation percentage calculation step which calculates the elongation percentage when the rolled material is rolled with the roll by using an elongation percentage calculation formula with an expression obtained by multiplying the regression expression by m-th power (m being a prescribed positive number) of an inverse number of surface roughness as the elongation percentage calculation formula.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to a method for calculating the elongation of a material to be rolled, which calculates the elongation of a material to be rolled using rolls having a predetermined surface roughness in cold rolling, and a rolling operation method. [Background technology]

[0002] In rolling a material to be rolled, the necessary rolling load is estimated in order to obtain a desired elongation of the material to be rolled. Various methods have been proposed for estimating the rolling load.

[0003] For example, Patent Document 1 discloses a learning control method for rolling load, which learns deformation resistance based on rolling records of a material to be rolled to calculate a deformation resistance model correction coefficient, learns friction coefficient based on rolling records of friction phenomena to calculate a friction coefficient model correction coefficient, and corrects each set value of deformation resistance and friction coefficient with each correction coefficient. As a result, each correction coefficient of deformation resistance and friction coefficient to be substituted into the rolling load model is accurately calculated, and the set value of the rolling load for the material to be rolled is predicted with high accuracy using the rolling load model.

[0004] Patent Document 2 discloses a method for estimating the rolling load in temper rolling of a steel strip, in which the operational factor setting conditions, actual elongation rates, and actual rolling loads in temper rolling of a steel strip are accumulated as a database, and the rolling load is predicted based on the operational factor setting conditions and target elongation rate of the next coil to be predicted, and actual data with a high degree of similarity due to weighting. This allows the rolling load to be estimated accurately in a short calculation time.

[0005] Patent Document 3 discloses a method for cold rolling a metal strip, in which a rolling load is predicted by combining a rolling load formula using a two-dimensional wedge array planar indentation model and a Bland & Ford rolling load formula based on the maximum thickness reduction amount during indentation, the target elongation rate of the rolled material, and the thickness of the rolled material at the entry side of the rolling mill, and the rolling mill is controlled based on the predicted rolling load. As a result, when the reduction rate is low, such as in a temper rolling mill, the rolling load value can be accurately predicted and rolling can be performed as targeted. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-226596 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-123726 [Patent Document 3] Japanese Patent Application Publication No. 09-253727 [Non-patent literature]

[0007] [Non-Patent Document 1] W.L.Roberts, “An approximate theory of Temper Rolling”, Iron and Steel Engineering Year Book, 1972, pp.530-542. [Non-patent document 2] Toru Akashi and four others, "Elucidation of Dull Work Roll Temper Rolling Phenomenon - Numerical Analysis of Temper Rolling Phenomenon of Ultra-Thin Steel Plates -", ​​2015, Nippon Steel & Sumitomo Metal Technical Report No. 402, pp. 35-49 Summary of the Invention [Problem to be solved by the invention]

[0008] The Roberts' formula, which is a theoretical formula for temper rolling, is known as a formula used to estimate the rolling load (for example, Non-Patent Document 1). The Roberts' formula includes influential factors such as the material quality (YP, TS), elongation, tension, friction coefficient, thickness, rolling speed, and roll diameter, and by using these factors with precision, it becomes possible to estimate the rolling load with high precision.

[0009] However, when thin materials are rolled using rolls with a specified surface roughness (dull rolls), the Roberts formula, which does not include surface roughness as an influencing factor, cannot be applied directly to calculate the elongation rate. In particular, when new materials are rolled using dull rolls or when the target elongation rate is changed, it is not possible to set the rolling conditions appropriately, which can result in parts within a single coil not achieving the desired elongation rate, resulting in problems such as a drop in yield.

[0010] Therefore, the present invention has been made in consideration of the above problems, and an object of the present invention is to provide an elongation calculation method and a rolling operation method that can accurately calculate the elongation of a rolled material relative to a rolling load, even when rolling is performed using rolls with a predetermined surface roughness. [Means for solving the problem]

[0011] In order to solve the above problem, according to one aspect of the present invention, there is provided an elongation calculation method for calculating the elongation of a rolled material rolled using rolls having a predetermined surface roughness, the method comprising: a data acquisition step for acquiring data showing the relationship between the rolling load and the elongation of the rolled material when the rolled material is rolled using the rolls; a regression equation calculation step for calculating, based on the data, a regression equation showing the relationship between the rolling load and the elongation of the rolled material when the rolled material is rolled using the rolls; and an elongation calculation step for multiplying the regression equation by the mth power of the reciprocal of the surface roughness (m is a predetermined positive number) to obtain an elongation calculation equation, and using the elongation calculation equation to calculate the elongation of the rolled material when it is rolled using the rolls.

[0012] Furthermore, the elongation calculation method may include a finite element data acquisition step of acquiring data showing the relationship between the rolling load and the elongation of the rolled material when the rolled material is rolled with the roll, using finite element analysis with a model in which the surface roughness of the roll is represented by protrusions on the roll surface, and a modified elongation calculation step of modifying the elongation calculation formula using an approximation coefficient obtained by approximating the data acquired in the finite element data acquisition step and the data acquired in the data acquisition step, and calculating the elongation when the rolled material is rolled with the roll using the modified elongation calculation formula.

[0013] In addition, in order to solve the above-mentioned problems, according to another aspect of the present invention, there is provided a rolling operation method for performing rolling using rolls having a predetermined surface roughness, comprising: an operational data acquisition step for acquiring data showing the relationship between the rolling load during rolling operation using the rolls and the elongation of the material to be rolled; a surface roughness calculation step for calculating the surface roughness of the roll from the data acquired in the operational data acquisition step using an elongation calculation formula obtained by the above-mentioned elongation calculation method; a rolling load calculation step for calculating a rolling load for realizing a desired elongation in the rolling operation from the surface roughness calculated in the surface roughness calculation step using the elongation calculation formula; and a rolling step for performing rolling using the rolling load calculated in the rolling load calculation step.

[0014] Furthermore, in order to solve the above-mentioned problems, according to another aspect of the present invention, there is provided a rolling operation method for performing rolling using rolls having a predetermined surface roughness, comprising: an operation data acquisition step for acquiring data showing the relationship between the rolling load during rolling operation using the rolls and the elongation of the material being rolled; a surface roughness calculation step for calculating the surface roughness of the roll from the data acquired in the operation data acquisition step using an elongation calculation formula obtained by the above-mentioned elongation calculation method; and a roll replacement step for replacing the rolls if the surface roughness of the roll calculated in the surface roughness calculation step is less than a reference value. [Effects of the Invention]

[0015] As described above, according to the present invention, when a rolled material is rolled using a roll having a predetermined surface roughness, the elongation of the rolled material relative to the rolling load can be accurately calculated by using an elongation calculation formula that reflects the influence of the surface roughness of the roll. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a graph showing an example of the relationship between the elongation rate of a steel sheet and the rolling load, showing estimated values ​​according to Roberts' formula and actual values ​​in actual operation. [Figure 2] FIG. 2 is a schematic diagram showing the contact state between a work roll and a steel plate during rolling, obtained by finite element analysis. [Figure 3] 1 is a graph showing an example of the relationship between the rolling load on the work roll surface and the elongation of the steel plate when the surface roughness of the work roll is changed. [Figure 4] This graph shows the relationship between the reciprocal of the surface roughness of the work roll and the elongation of the steel plate for each rolling load, as shown in FIG. 3 . [Figure 5] 4 is a graph showing an example of a regression equation representing the relationship between the rolling load and the elongation of the steel plate, obtained from the relationship between the rolling load on the work roll surface and the elongation of the steel plate shown in FIG. 3. [Figure 6] 4 is a graph showing another example of a regression equation representing the relationship between the rolling load and the elongation of the steel plate, obtained from the relationship between the rolling load on the work roll surface and the elongation of the steel plate shown in FIG. 3. [Figure 7] 1 is a graph illustrating the change in the formula for calculating the elongation rate of the rolled material when the reciprocal m of the surface roughness of the work roll is changed. [Figure 8] 1 is a graph showing the relationship between the output value of the elongation rate of the steel plate and the estimated value of the elongation rate of the steel plate obtained by finite element analysis. [Figure 9] 10 is a graph showing the relationship between the output value of the elongation rate of the steel plate after correction and the estimated value of the elongation rate of the steel plate obtained by finite element analysis. [Figure 10] 1 is a flowchart showing an example of a method for calculating an elongation rate of a rolled material according to an embodiment of the present invention. [Figure 11] 4 is a flowchart showing an example of processing when setting up rolling conditions according to the embodiment. [Figure 12] 10 is a flowchart illustrating an example of a role reconfiguration determination process according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant explanations will be omitted.

[0018] [1. Calculation of the elongation rate of the rolled material against the rolling load, taking into account the surface roughness of the roll] In the elongation calculation method of the present invention for calculating the elongation of a rolled material, a regression equation expressing the relationship between the rolling load and the elongation of the rolled material is calculated based on data on multiple levels of rolling load and the elongation of the rolled material when rolling is performed using rolls with a predetermined surface roughness, and the regression equation is made to reflect the influence of the surface roughness of the work rolls that roll the rolled material, thereby forming the elongation calculation equation for the rolled material.

[0019] When rolling thin materials using rolls with a specified surface roughness, the elongation of the rolled material estimated using the Roberts equation, which is a theoretical formula for temper rolling (which does not include surface roughness as an influencing factor), may differ from the elongation of the rolled material in actual operation using rolls with surface roughness.

[0020] For example, Figure 1 shows an example of the relationship between the elongation of a steel sheet and the rolling load for two types of steel sheets (E150 and E500) with a thickness of 0.4 mm and a width of 920 mm. The rolling load is expressed as a linear load. Figure 1 also shows the estimated values ​​of the rolling load and the elongation of the rolled material using Roberts' formula, as well as the actual values ​​of the rolling load and the elongation of the rolled material in actual operation using rolls with surface roughness. While the estimated values ​​using Roberts' formula and the actual values ​​using rolls with surface roughness are sometimes close to each other, the actual values ​​using rolls with surface roughness tend to be larger than the estimated values ​​using Roberts' formula. Furthermore, when a thinner steel sheet with a thickness of 0.3 mm and a width of 950 mm is rolled using rolls with surface roughness, the actual value of the elongation of the rolled material relative to the rolling load is approximately twice the value estimated using Roberts' formula, showing a further deviation.

[0021] In investigating the causes of this phenomenon, the present inventors focused on the fact that the surface roughness of the rolls used to roll the rolled material affects the elongation of the rolled material relative to the rolling load (see Non-Patent Document 2). Temper rolling is performed by imparting a slight reduction strain to annealed steel sheets to obtain desired mechanical properties, flatness, and the like. In this process, dull rolls with a predetermined surface roughness, which have been dulled, are generally used as work rolls for rolling the steel sheets. While the asperities on the work roll surface actually have complex three-dimensional shapes, in practice they are represented by a two-dimensional model, and the surface roughness is often expressed as the arithmetic mean roughness Ra. While Non-Patent Document 2 simulates the asperities on the work roll surface with a sinusoidal wave, in the present invention, a rolling simulation of a steel sheet was performed using a finite element model in which the asperities on the work roll surface are simulated with a triangular wave and the effective value obtained by absolute value processing of the height of the triangular wave is assumed to be the arithmetic mean roughness Ra.

[0022] Figure 2 shows a schematic diagram of the contact state between the work roll and steel plate during rolling, obtained through finite element analysis. Because temper rolling is performed under light reduction, the work roll contacts the steel plate in an elastically deformed state. Figure 2 shows that the work roll itself is flattened and deformed in an almost front-to-back symmetrical shape, and that plastic deformation occurs starting from the protrusions on the work roll surface, with plastic deformation progressing mainly in the surface layer of the steel plate. The enlarged view of Figure 2 also shows that the work roll and steel plate contact each other in such a way that the protrusions on the work roll surface bite into the steel plate, with the steel plate filling the depressions between the protrusions.

[0023] FIG. 3 shows an example of the relationship between the rolling load on the work roll surface and the elongation of the steel sheet when the surface roughness of the work roll is changed. ave This shows the results of changing the surface roughness (arithmetic mean roughness Ra) of the work roll by changing the asperity height d ave It can be seen that the larger the σ, that is, the larger the surface roughness, the smaller the elongation rate of the steel plate relative to the rolling load.

[0024] If the graph in Figure 3 is expressed as the relationship between the reciprocal of the work roll surface roughness (arithmetic mean roughness Ra) and the elongation of the steel plate for each rolling load, the graph shown in Figure 4 is obtained. From the results in Figure 4, it can be seen that there is a positive correlation between the reciprocal of the work roll surface roughness and the elongation of the steel plate, and that there is a proportional relationship.

[0025] From the above results, the inventors of the present application considered that the surface roughness of the dull rolls used as work rolls influences the discrepancy between the elongation of the rolled material relative to the rolling load estimated using Roberts' formula and the actual value in actual operation using rolls with surface roughness. Therefore, they investigated a method for calculating the elongation of the rolled material relative to the rolling load taking into account the surface roughness of the rolls, calculated a regression equation expressing the relationship between the rolling load and the elongation of the rolled material by approximation based on data on multiple levels of rolling load and the elongation of the rolled material, and came up with the idea of ​​using an elongation calculation formula for calculating the elongation of the rolled material by reflecting the influence of the surface roughness of the work rolls that roll the rolled material into the regression equation.

[0026] As shown in Figure 3, from the relationships between the rolling load and the elongation of the steel sheet at multiple levels of the work roll surface obtained, a formula for calculating the elongation of the rolled material will be obtained, focusing on the case where the work roll surface roughness is 0.48 μm, for example. In Figure 3, four levels of rolling load and elongation of the steel sheet are obtained for each level of work roll surface roughness.

[0027] First, assume the structure of a regression equation that shows the relationship between the rolling load and the elongation of the steel plate being rolled. Various functions can be assumed for the structure of the regression equation, such as an nth-order function or an irrational function for the rolling load. An nth-order function is a linear function (n=1), a quadratic function (n=2), a cubic function (n=3), etc., where n in an nth-order function is a natural number. An irrational function is a function that includes a radical, and the radical roots of an irrational function are natural numbers.

[0028] For example, the structure of the regression equation may be assumed to be a quadratic function, which is an example of a multi-order function, as shown in the following formula (1): where p represents the rolling load (line load).

[0029]

number

[0030] Next, using the data for the four levels shown in Figure 3, for example, equation (1) is approximated using the least squares method or the like to find the regression coefficients (a1, a2, a3) of equation (1). The regression coefficients thus obtained are applied to the assumed regression curve to find the regression equation g(p) that shows the relationship between the rolling load and the elongation of the steel plate.

[0031] Figure 5 is a graph showing an example of a regression equation representing the relationship between the rolling load and the elongation of a steel sheet, obtained from the relationship between the rolling load on the work roll surface and the elongation of the steel sheet shown in Figure 3. The curve shown in Figure 5 is a regression curve based on a regression equation obtained from data on the rolling load and elongation when the surface roughness is 0.48 μm, and the values ​​of the regression coefficients (a1 = -0.1988, a2 = 3.2185, a3 = -1.2993) are shown as an equation at the top of Figure 5.

[0032] Furthermore, for example, the structure of the regression equation may be assumed to be a linear irrational function, as shown in the following equation (2).

[0033]

number

[0034] Here, the radical root n is a natural number. The radical root n can be set in the range of n = 2 to 5. For example, using the four levels of data shown in Figure 3, the least squares method or the like is used to approximate Equation (2) and determine the regression coefficients (a, b) of Equation (1). The regression coefficients thus obtained are applied to a hypothetical regression curve to determine the regression equation g(p) that expresses the relationship between the rolling load and the elongation of the steel plate. For example, in the quadratic function shown in Figure 5, when the rolling load increases beyond a certain value, the elongation decreases, resulting in a large deviation from the actual value. In such cases, by configuring the regression equation as a linear irrational function, as in Equation (2), it is possible to calculate an elongation close to the actual value even when the rolling load increases.

[0035] Figure 6 is a graph showing another example of a regression equation representing the relationship between rolling load and elongation of a steel sheet, obtained from the relationship between the rolling load on the work roll surface and the elongation of the steel sheet shown in Figure 3. Figure 6 shows the results of organizing the relationship between the rolling load and elongation of the steel sheet at the four levels shown in Figure 3, using the power root n=2 of equation (2) above. The dashed straight line shown in Figure 6 is a linear function based on the regression equation obtained from data on the rolling load and elongation when the surface roughness is 0.48 μm, and the values ​​of the regression coefficients (a=6.1934, b=−4.1886) are shown as an equation at the top of Figure 6.

[0036] As mentioned above, it is believed that there is a positive correlation between the reciprocal of the surface roughness of the work roll and the elongation of the steel plate, so by multiplying the obtained regression equation by the mth power of the reciprocal of the surface roughness of the work roll (m is a predetermined positive number and may be a decimal or fraction), it is possible to obtain an elongation calculation formula F(p, Ra), which is a formula for calculating the elongation of the rolled material when it is rolled with rolls having surface roughness. The elongation calculation formula F(p, Ra) is expressed by the following formula (3).

[0037]

number

[0038] That is, for example, when the surface roughness of the work roll shown in Figure 5 is 0.48 μm, the elongation calculation formula F(p, Ra) of the rolled material obtained from the regression formula g(p) based on the above formula (1) is expressed by the following formula (3-1): Note that the reciprocal of the surface roughness of the work roll in the following formula (3-1) is m=1.

[0039]

number

[0040] Furthermore, for example, the elongation calculation formula F(p, Ra) of the rolled material obtained from the regression formula g(p) based on the above formula (2) is expressed by the following formula (3-2): As a specific example, when the surface roughness of the work roll shown in Figure 6 is 0.48 μm, the elongation calculation formula F(p, Ra) of the rolled material obtained from the regression formula g(p) based on the above formula (2) is expressed by the following formula (3-3):

[0041]

number

[0042] Figure 7 shows the change in the elongation calculation formula F(p, Ra) for the rolled material when the reciprocal of the surface roughness of the work roll in equation (3-2) above is set to m = 1.0 and when m = 1.2. The plot in Figure 7 is the same as the plot in Figure 6, and the curve in Figure 7 shows the elongation value of the steel plate obtained by finite element analysis.

[0043] As shown in Figure 7, even when m = 1.0, the calculated value using the elongation calculation formula F(p, Ra) for the rolled material is close to the elongation value of the steel plate obtained by finite element analysis, but as the surface roughness increases, a deviation occurs. On the other hand, when m = 1.2, even when the surface roughness is large, the calculated value using the elongation calculation formula F(p, Ra) for the rolled material is closer to the elongation value of the steel plate obtained by finite element analysis than when m = 1.0. In this way, by adjusting the reciprocal m of the work roll's surface roughness, the accuracy of the elongation calculation formula F(p, Ra) for the rolled material can be further improved.

[0044] Therefore, in formula (3), the reciprocal m of the work roll surface roughness may be appropriately set so as to coincide with the value of the elongation percentage of the steel plate obtained by finite element analysis. For example, the reciprocal m of the work roll surface roughness may be set in the range of m = 1.0 to 2.0, and may be an integer, decimal, or fractional number as long as it is a positive number.

[0045] Furthermore, Figure 8 shows the relationship between the output value of the elongation of the steel plate obtained from the regression equation g(p) shown in Figure 5 and the estimated value of the elongation of the steel plate obtained by known finite element analysis when the surface roughness of the work roll is 0.48 µm. Figure 8 shows that there is a high correlation between the calculated value of the elongation of the steel plate obtained from the regression equation g(p) and the estimated value of the elongation of the steel plate obtained by finite element analysis.

[0046] In Figure 8, when the output value of the elongation of the steel plate obtained from the regression equation g(p) is x and the estimated value of the elongation of the steel plate obtained by finite element analysis is y, a linear function was approximated using the least squares method, and a relationship was found to be expressed by the approximate equation (y = 0.4728x - 0.1246). Therefore, in order to improve the accuracy of the elongation calculation formula F(p, Ra) for the rolled material, the elongation calculation formula F(p, Ra) may be modified so that the elongation value obtained from the elongation calculation formula F(p, Ra) shown in the above equation (3) more accurately matches the elongation value obtained from the rolling load and the elongation of the steel plate obtained by finite element analysis. The above approximate equation can be calculated by performing finite element analysis using a model in which the surface roughness of the roll is represented by continuous triangular protrusions on the roll surface, obtaining multiple levels of rolling load and elongation of the rolled material, and approximating the value obtained from the above equation (3).

[0047] For example, when the above formula (3) is modified, it is expressed as the modified elongation calculation formula F'(p, Ra) as shown in the following formula (4). As a specific example, when the above formula (3-1) is modified, it becomes the modified elongation calculation formula F'(p, Ra) as shown in the following formula (4-1).

[0048]

number

[0049] Figure 9 shows the relationship between the calculated value of the elongation percentage of the steel plate after correction calculated by formula (4-1) and the calculated value of the elongation percentage of the steel plate obtained by finite element analysis. As can be seen from Figure 9, the calculated value of the elongation percentage of the steel plate after correction is almost the same as the calculated value of the elongation percentage of the steel plate obtained by finite element analysis.

[0050] In this way, by calculating the elongation of the rolled material relative to the rolling load while taking into account the surface roughness of the rolls, it becomes possible to more accurately calculate the elongation of the rolled material before the start of operation. As a result, it becomes possible to appropriately set the rolling conditions, and a rolled material with the desired elongation can be obtained, thereby reducing yield loss.

[0051] [2. Calculation method for elongation rate] The method for calculating the elongation rate of a rolled material according to this embodiment will be described with reference to Fig. 10. Fig. 10 is a flowchart showing an example of the method for calculating the elongation rate of a rolled material according to this embodiment.

[0052] In the method for calculating the elongation of a rolled material according to this embodiment, first, the rolled material is rolled using a roll (dull roll) having a predetermined surface roughness, and multiple levels of rolling load and elongation of the rolled material are obtained (S100). At least two levels of rolling load and elongation of the rolled material are sufficient, but the more levels there are, the more accurate the elongation calculation formula can be.

[0053] Next, a regression equation expressing the relationship between the rolling load and the elongation of the rolled material is calculated based on the multiple levels of rolling load and the elongation of the rolled material obtained in step S100 (S110). The structure of the regression equation may be a quadratic function or may be expressed by other functions.

[0054] Then, the regression equation calculated in step S110 is multiplied by the reciprocal of the surface roughness of the dull roll to calculate the elongation calculation formula (S120). This is based on the finding that, as mentioned above, there is a positive correlation between the reciprocal of the surface roughness of the dull roll and the elongation. This allows the elongation calculation formula to reflect the characteristic that the greater the surface roughness, the smaller the elongation of the rolled material relative to the rolling load.

[0055] The elongation calculation formula calculated in step S120 may be used as is in setting up the rolling conditions, etc., but may also be corrected so that the calculated value of elongation comes closer to the actual value and coincides with the calculated value of elongation obtained by finite element analysis. In this case, whether or not to correct the elongation calculation formula calculated in step S120 may be determined (S130) depending on whether or not the error between the elongation calculated by the elongation calculation formula and the elongation obtained by finite element analysis is equal to or greater than an allowable value.

[0056] The error between the elongation calculated using the elongation calculation formula and the elongation obtained by finite element analysis may be expressed, for example, as the ratio of the elongation calculated using the elongation calculation formula in step S120 to the elongation obtained by finite element analysis for a given rolling load. In this case, if the ratio of the elongations is not within a predetermined allowable range, it is determined that the elongation calculated using the elongation calculation formula in step S120 deviates significantly from the elongation obtained by finite element analysis, and the elongation calculation formula may be modified so that the elongation calculated and the elongation obtained by finite element analysis match (S140). If the ratio of the elongations is within the predetermined allowable range, the elongation calculation formula in step S120 does not need to be modified.

[0057] Then, the elongation rate when the rolled material is rolled by the rolls is calculated using the elongation rate calculation formula calculated in step S120 or the elongation rate calculation formula corrected in step S140 (S150). Once the calculation of the elongation rate is completed, the processing of FIG. 10 ends.

[0058] The method for calculating the elongation of a rolled material according to this embodiment has been described above.

[0059] [3. Rolling operation method] The elongation calculation formula calculated based on the method for calculating the elongation of a rolled material in Figure 10 shows the relationship between the rolling load, the elongation of the rolled material, and the surface roughness of the roll. This elongation calculation formula can be used to set up rolling conditions, determine roll changes, etc.

[0060] [3-1. Setup of rolling conditions] First, application to the setup of rolling conditions will be described with reference to Fig. 11. Fig. 11 is a flowchart showing an example of processing when setting up rolling conditions.

[0061] As shown in FIG. 11, first, before rolling operation, the surface roughness of the rolls that will roll the material to be rolled is determined. The surface roughness of the rolls can be measured using a roughness meter. Then, an elongation calculation formula to be used in the rolling operation is calculated (S200). In step S200, for example, a regression formula is calculated that expresses the relationship between the rolling load and the elongation of the material to be rolled, calculated based on multiple levels of rolling load and the elongation of the material to be rolled obtained in past rolling operations. The calculation of the regression formula can be performed in the same manner as in step S110 of FIG. 10. Then, by multiplying the regression formula by the reciprocal of the surface roughness of the roll, an elongation calculation formula for calculating the elongation of the material to be rolled with respect to the rolling load can be calculated.

[0062] Next, when the rolling operation is started (S210), the processing of steps S220 to S260 is carried out at any timing during the operation.

[0063] First, the actual rolling load value and the actual elongation value of the rolled material are obtained (S220). Then, from the obtained actual rolling load value and actual elongation value of the rolled material, the surface roughness of the roll at that time is calculated using an elongation calculation formula (S230). The actual rolling load value is the load applied by the reduction device of the rolling mill. The actual elongation value of the rolled material can be calculated by measuring the threading speed of the rolled material. The elongation rate e (%) is defined by the following formula (5-1) using the entry side threading speed V1 and the exit side threading speed V2. Alternatively, the elongation rate e (%) can also be defined by the following formula (5-2) using the entry side thickness H1 and the exit side thickness H2 measured by entry and exit side thickness gauges installed before and after the rolling mill.

[0064] e=(V2-V1) / V2×100 (5-1) e=(H1-H2) / H1×100 (5-2)

[0065] The entry-side strip threading speed V1 and the exit-side strip threading speed V2 can be measured using speedometers installed on the entry and exit sides of the rolling mill. Examples of speedometers include a laser Doppler type that calculates the speed based on the frequency of scattered light from a laser irradiated onto the rolled material during rolling, and a roller encoder type that calculates the speed by bringing a roller into contact with the rolled material and measuring its rotational speed with an encoder.

[0066] Once the actual rolling load value and the actual elongation rate value of the rolled material are obtained, the actual rolling load value and the actual elongation rate value of the rolled material are substituted into the elongation rate calculation formula calculated in step S200 to calculate the surface roughness of the roll.

[0067] Next, the roll surface roughness calculated in step S230 is used in an elongation calculation formula to calculate the rolling load for bringing the rolled material to the target elongation (S240). That is, by substituting the target elongation into the elongation calculation formula, the rolling load for bringing the rolled material to the target elongation is calculated.

[0068] Thereafter, the material to be rolled is rolled with the rolling load calculated in step S240 (S250). During the rolling operation (S260: NO), the process returns to step S230, and the processes of steps S230 to S260 are repeatedly performed. When the rolling operation is completed (S260: YES), the process of FIG. 11 ends.

[0069] In this way, by using the elongation calculation formula, the rolling load can be appropriately changed so that the rolled material achieves the desired elongation, taking into account the surface roughness of the roll, which changes over time during rolling operations.

[0070] [3-2. Role reassignment decision] Next, application to role reconciliation determination will be described with reference to Fig. 12. Fig. 12 is a flowchart showing an example of role reconciliation determination processing. In the following description, detailed description of processing similar to that in Fig. 9 will be omitted.

[0071] As shown in Fig. 12, first, before the rolling operation, the surface roughness of the rolls that will roll the material to be rolled is determined. Then, an equation for calculating the elongation percentage to be used in the rolling operation is calculated (S300). The processing of step S300 may be performed in the same manner as the processing of step S200 in Fig. 11.

[0072] Next, when the rolling operation is started (S310), the processes of steps S320 to S350 are carried out at predetermined timing.

[0073] First, the actual rolling force value and the actual elongation value of the rolled material are acquired (S320). Then, from the acquired actual rolling force value and actual elongation value of the rolled material, the surface roughness of the roll at that time is calculated using an elongation calculation formula (S330). The processing of step S330 may be performed similarly to the processing of step S230 in FIG. 11. Then, the surface roughness of the roll calculated in step S330 is compared with a preset reference value of surface roughness (S340). The reference value is a surface roughness that serves as a reference for determining whether or not roll replacement is necessary, and is set in advance based on past operational records, etc.

[0074] If the calculated value of the roll surface roughness is equal to or greater than the reference value (S340: NO), it can be determined that the required roll surface roughness is being maintained. In this case, the process returns to step S320, and steps S320 and S330 are repeated. On the other hand, if the calculated value of the roll surface roughness is less than the reference value (S340: YES), it is determined that the roll surface roughness has decreased, and a new roll needs to be used, and roll replacement is performed (S350).

[0075] In this way, by using the elongation calculation formula, it is possible to calculate the surface roughness of the rolls, which changes over time during rolling operation, and to carry out roll replacement at an appropriate timing.

[0076] The above has described the method for calculating the elongation of a rolled material and the rolling operation method according to this embodiment. According to this embodiment, a regression equation expressing the relationship between the rolling load and the elongation of the rolled material is calculated based on actual data on multiple levels of rolling load and the elongation of the rolled material, and an equation for calculating the elongation of the rolled material is created by reflecting the influence of the surface roughness of the work rolls that roll the rolled material into the regression equation. This makes it possible to accurately calculate the elongation of the rolled material relative to the rolling load.

[0077] Furthermore, by applying the elongation calculation formula to rolling operations, it is possible to appropriately change the rolling load and to perform roll reassembly at appropriate times in accordance with the surface roughness of the rolls, which changes over time during rolling operations. [Example]

[0078] In order to confirm the effectiveness of the method for estimating the elongation of a rolled material according to this embodiment, a low-carbon steel plate with a thickness of 0.4 mm was rolled to a target elongation of 0.9%. In the example, an elongation calculation formula was obtained based on the method for calculating the elongation of a rolled material shown in Fig. 10, and the rolling load for achieving the target elongation of 0.9% was calculated using the elongation calculation formula. In the comparative example, the rolling load for achieving the target elongation of 0.9% was calculated using Roberts' formula.

[0079] In the comparative example, the rolling load calculated using Roberts' formula was 400 tf. When the steel plate was rolled under rolling conditions that would result in 400 tf based on past operational results, the actual elongation was 1.3%. Furthermore, because the roll gap was adjusted while checking the elongation meter in order to set the rolling load to the target elongation, a 100m section occurred where the elongation was outside the allowable elongation, resulting in a drop in yield.

[0080] On the other hand, in the example, the rolling load at which the elongation of the steel plate was 0.9% could be accurately calculated from the elongation calculation formula, so roll gap adjustment was not necessary and rolling was possible without any drop in yield.

[0081] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications and alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

Claims

1. A method for calculating an elongation rate of a rolled material rolled using a roll having a predetermined arithmetic mean roughness (unit: μm), a data acquisition step of acquiring data showing the relationship between the rolling load and the elongation of the rolled material when the rolled material is rolled using the rolls; a regression equation calculation step of calculating a regression equation showing the relationship between the rolling load and the elongation of the rolled material when the rolled material is rolled with the rolls based on the data; an elongation calculation step of using an equation obtained by multiplying the regression equation by the mth power of the reciprocal of the arithmetic mean roughness as an elongation calculation equation (where m is a predetermined positive number that is adjusted so that the elongation value obtained by the elongation calculation equation for the rolled material and the elongation value obtained by finite element analysis are close to each other), and using the elongation calculation equation to calculate the elongation when the rolled material is rolled with the rolls; A method for calculating elongation rate, including:

2. a finite element data acquisition step of acquiring data showing the relationship between the rolling load and the elongation of the rolled material when the rolled material is rolled with the rolls, using a finite element analysis using a model in which the arithmetic mean roughness of the roll is represented by protrusions on the roll surface; a corrected elongation calculation step of correcting the elongation calculation formula using an approximation coefficient obtained by approximating the data acquired in the finite element data acquisition step and the data acquired in the data acquisition step to a linear function using the least squares method, and calculating an elongation when the rolled material is rolled with the rolls using the corrected elongation calculation formula; The method for calculating elongation according to claim 1 , comprising:

3. A rolling operation method for performing rolling using rolls having a predetermined arithmetic mean roughness, comprising: an operational data acquisition step of acquiring data showing the relationship between the rolling load during rolling operation using the rolls and the elongation of the rolled material; an arithmetic mean roughness calculation step of calculating an arithmetic mean roughness of the roll from the data acquired in the operation data acquisition step by using an elongation calculation formula obtained by the elongation calculation method according to claim 1 or 2; a rolling load calculation step of calculating a rolling load for realizing a desired elongation in a rolling operation from the arithmetic mean roughness calculated in the arithmetic mean roughness calculation step using the elongation calculation formula; a rolling step of performing rolling using the rolling load calculated in the rolling load calculation step; A rolling operation method comprising:

4. A rolling operation method for performing rolling using rolls having a predetermined arithmetic mean roughness, comprising: an operational data acquisition step of acquiring data showing the relationship between the rolling load during rolling operation using the rolls and the elongation of the rolled material; an arithmetic mean roughness calculation step of calculating an arithmetic mean roughness of the roll from the data acquired in the operation data acquisition step by using an elongation calculation formula obtained by the elongation calculation method according to claim 1 or 2; a roll rearrangement step of rearranging the rolls when the arithmetic mean roughness of the rolls calculated in the arithmetic mean roughness calculation step is less than a reference value; A rolling operation method comprising:

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