Rolling apparatus and rolling method

Abstract

To measure highly accurately the stress distribution of a roll bite in a wide rolling load range.SOLUTION: A rolling apparatus 10 includes a rolling mill 1 and an arithmetic device 30. A stress measuring roll 2 of the rolling mill 1 includes a pressure receiving member 15 which is arranged in a recess 12c so as to be sandwiched between an inner surface of a holder 14 and a pressure sensor 11, and has: a tip 15a in point-contact with the inner surface of the holder 14; and a base 15b in contact with the pressure sensor 11. An arithmetic part 33 of the arithmetic device 30 calculates a rolling stress distribution of a roll bite based on: a measured value of the pressure sensor 11 during rolling of a rolled material 100 in the rolling mill 1; and a transfer function stored in a storage part 31.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a rolling apparatus and a rolling method. [Background technology]

[0002] Non-Patent Documents 1 and 2 describe that pins for measuring stress in the roll bite are embedded in the rolling roll, and the rolling stress distribution in the roll bite (contact area between the roll and the rolled material) is measured, and an attempt is made to derive the friction coefficient distribution from the measured rolling stress distribution.

[0003] Non-Patent Document 3 describes an attempt to measure the rolling stress distribution in the roll bite by attaching a strain gauge inside a rolling roll to measure normal stress and shear stress, and to derive the friction coefficient distribution from the measured stress distribution. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Yuji Matsuura, Mitsugu Motomura, "Rolling Pressure Distribution of Roll Contact Arc in Cold Rolling", Light Metals, Japan Institute of Light Metals, April 1971, Vol. 21, No. 4, pp. 199-213 [Non-patent document 2] Yuji Matsuura, Mitsugu Motomura, "Rolling Pressure Distribution in the Contact Arc", Plasticity and Processing, Japan Society for Technology of Plasticity, March 1968, Vol. 9, No. 86, pp. 168-172 [Non-patent document 3] T.Luks et.al."Contact stress distribution and roll surface temperature in the roll gap analyzed with different sensors", La Metallurgia Italiana-n.1 / 2014 Summary of the Invention [Problem to be solved by the invention]

[0005] In the test methods of Non-Patent Documents 1 and 2, the presence of a pin in the roll bite changes the coefficient of friction, making it difficult to accurately measure the interface between the material and the roll. Also, in these test methods, the stress distribution changes depending on the length of the pin. Therefore, the measurement methods of Non-Patent Documents 1 and 2 have problems with measurement accuracy.

[0006] The test method in Non-Patent Document 3 requires the use of a special structure in the rolling rolls to attach shear strain gauges, and the rolling rolls cannot withstand high-load rolling. Therefore, with this measurement method, measurement of stress distribution is limited to low-load rolling.

[0007] An object of the present invention is to provide a rolling apparatus and a rolling method that can measure the stress distribution in the roll bite with high accuracy over a wide range of rolling loads. [Means for solving the problem]

[0008] A first aspect of the present invention is a rolling mill in which at least one of a pair of work rolls is a stress measurement roll; stressand a calculation device that performs calculations based on input from the measuring roll, wherein the stress measuring roll comprises a roll body having a recess formed in a barrel portion, the recess opening to the surface of the barrel portion, a pressure sensor accommodated in the recess, a holder that is attached to the barrel portion so as to close the opening and whose outer surface forms the same cylindrical surface as the surface of the barrel portion, and a pressure receiving member that is arranged in the recess so as to be sandwiched between the inner surface of the holder and the pressure sensor, and whose tip is in point contact with the inner surface of the holder and whose base end is in contact with the pressure sensor, and a calculation unit that calculates the rolling stress distribution in the roll bite based on the measured values ​​of the pressure sensor and the transfer function, wherein the measured values ​​of the pressure sensor and the transfer function are input and output, respectively, and the calculation unit calculates the rolling stress distribution in the roll bite based on the measured values ​​of the pressure sensor and the transfer function when the material to be rolled is being rolled in the rolling mill.

[0009] The stress acting on the stress measurement roll is transmitted to the pressure sensor not through a pin but through a holder whose outer periphery forms the same cylindrical surface as the barrel surface, allowing for accurate measurement of the stress state of the material and the stress measurement roll. Furthermore, the pressure-receiving member interposed between the holder and the pressure sensor is in point contact with the holder, providing high spatial resolution for stress measurement by the pressure sensor. Therefore, the rolling stress distribution in the roll bite can be calculated with high precision based on the pressure sensor measurements during rolling of the rolled material and the transfer function.

[0010] Since the stress acting on the stress measuring roll is transmitted to the pressure sensor housed in the barrel via the holder, there is no need to employ a special structure that is inferior in strength for attaching a strain gauge to the stress measuring roll. In this respect, it is possible to measure the rolling stress distribution in the roll bite over a wide range of rolling loads.

[0011] As described above, this rolling mill makes it possible to measure the rolling stress distribution in the roll bite with high accuracy over a wide range of rolling loads.

[0012] In addition, as described above, the stress acting on the stress measuring roll is transmitted to the pressure sensor not through the pin but through the holder whose outer surface forms the same cylindrical surface as the surface of the barrel, so that it is possible to measure the rolling stress distribution during lubricated rolling.

[0013] The storage unit may store a theoretical rolling formula, and the calculation unit may calculate a calculated stress distribution of the roll bite using the rolling stress distribution and the theoretical rolling formula.

[0014] The pressure-receiving member may be substantially conical in shape.

[0015] A second aspect of the present invention provides a rolling mill in which at least one of a pair of work rolls is a stress measurement roll, the stress measurement roll comprising: a roll body having a recess formed in a barrel portion and the recess opening into the surface of the barrel portion; a pressure sensor accommodated in the recess; a holder attached to the barrel portion so as to close the opening and having an outer surface that forms the same cylindrical surface as the surface of the barrel portion; and a pressure-receiving member disposed in the recess so as to be sandwiched between the inner surface of the holder and the pressure sensor, the tip of which is in point contact with the inner surface of the holder and the base end of which is in contact with the pressure sensor. The present invention provides a rolling method in which, as the stress measurement roll rotates, the orientation of the tip of the pressure-receiving member rotates around the axis of the stress measurement roll, kiss roll rolling is performed in the rolling mill, and a transfer function is calculated using measurements of a pressure sensor during kiss roll rolling, with the input being a stress acting on the roll body at a certain angle in a region including the roll bite and the output being a stress acting on the pressure sensor at a certain rotation angle around the axis, and a material to be rolled is rolled in the rolling mill, and the rolling stress distribution in the roll bite is calculated based on the measurements of the pressure sensor during rolling of the material to be rolled and the transfer function. [Effects of the Invention]

[0016] According to the rolling apparatus and rolling method of the present invention, the stress distribution in the roll bite can be measured with high accuracy over a wide range of rolling loads. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic diagram of a rolling mill according to an embodiment of the present invention; [Figure 2] FIG. [Figure 3] FIG. 2 is a cross-sectional view of the stress measuring roll in the axial direction. [Figure 4] FIG. 2 is a cross-sectional view of the stress measuring roll taken in a direction perpendicular to the axis. [Figure 5] FIG. [Figure 6A] 10 is a graph showing an example of a transfer function. [Figure 6B] FIG. 6B is a schematic cross-sectional view showing the stress distribution at point P1 in FIG. 6A. [Figure 6C] FIG. 6B is a schematic cross-sectional view showing the stress distribution at point P2 in FIG. 6A. [Figure 6D] FIG. 6B is a schematic cross-sectional view showing the stress distribution at point P3 in FIG. 6A. [Figure 7] FIG. 2 is a schematic cross-sectional view showing the stress distribution in and around the roll bite. [Figure 8] Schematic diagram for explaining stress distribution under Hertzian contact conditions. [Figure 9] Schematic diagram for explaining stress distribution under Hertzian contact conditions. [Figure 10] 10 is a graph showing an example of a measured stress and a transfer function relative to the rotation angle of a stress measuring roll. [Figure 11] 1 is a graph showing an example of calculated stress distribution when individual friction coefficients are set on the inlet and outlet sides using the roll bite stress versus the rotation angle of the stress measurement roll and a theoretical rolling formula. [Figure 12] Graph showing an example of calculated stress distribution when individual friction coefficients are set on the inlet and outlet sides using the roll bite stress versus contact length and the rolling theory formula. DETAILED DESCRIPTION OF THE INVENTION

[0018] Next, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0019] Referring to FIG. 1, a rolling mill 10 according to an embodiment of the present invention includes a rolling mill 1 and a computing device 30.

[0020] (Rolling mill) The rolling mill 1 in this embodiment is a four-high rolling mill, but the application of the present invention is not limited by the number of rolls in the rolling mill. The rolling mill 1 is equipped with a roll surface type stress measurement roll 2 that functions as an upper work roll, a lower work roll 3, an upper backup roll 4, and a lower backup roll 5, which are rotatably supported in a housing 6. Only the lower work roll may be the stress measurement roll 2. Both the upper and lower work rolls may be stress measurement rolls.

[0021] Although not shown, the compressor 1 is equipped with a drive mechanism including a prime mover for rotating the stress measurement roll 2 and the lower work roll 3, and a roll lifting mechanism for raising and lowering the two upper rolls, i.e., the stress measurement roll 2 and the upper backup roll 4, to adjust the gap (reduction amount) between the stress measurement roll 2 and the lower work roll 3.

[0022] 2 to 4, the stress measurement roll 2 has a built-in pressure sensor 11 for stress measurement. In this embodiment, the pressure sensor 11 is of a piezoelectric type (piezo type), but is not limited to this. A piezoelectric pressure sensor is preferable compared to a strain gauge type sensor because it requires less deformation to detect pressure, in other words, it has a higher elastic modulus.

[0023] The stress measuring roll 2 comprises a roll body 12 and other elements or members including the pressure sensor 11 described above. The roll body 12 comprises a body portion 12a whose surface is a cylindrical surface and a pair of shaft portions 12b extending from both ends of the body portion 12a. A recess 12c is provided in the body portion 12a. The recess 12c opens to the surface of the body portion 12a. In this embodiment, the recess 12c has a rectangular shape in a plan view, but the shape of the recess 12c is not particularly limited.

[0024] The pressure sensor 11, base 13, holder 14, and pressure-receiving member 15 are housed in a recess 12c formed in the trunk portion 12a of the roll body 12. The base 13 is a roughly flattened rectangular parallelepiped and is arranged to fill the bottom side of the recess 12c. The holder 14 is placed on the base 13. The base 13 and holder 14 are fixed to each other with bolts 16. As will be described in detail later, the pressure sensor 11 and pressure-receiving member 15 are housed between the base 13 and holder 14. The holder 14 is fixed to the trunk portion 12a with bolts 17. The outer surface 14a of the holder 14a forms the same cylindrical surface as the surface of the trunk portion 12a of the roll body 12.

[0025] 3 and 4, a bottomed hole 14c that is open on the inner surface 14b side and closed on the outer surface 14a side is formed in the holder 14. A storage chamber 18 is defined by the hole wall of the bottomed hole 14c and the upper surface 13a of the base 13, and the pressure sensor 11 and the pressure-receiving member 15 are stored in this storage chamber 18. The pressure sensor 11 is fixed to the base 13 with a nut 19.

[0026] The pressure-receiving member 15 is accommodated in the accommodation chamber 18 so as to be sandwiched between the inner surface 14b of the holder 14 and the pressure sensor 11. In this embodiment, the pressure-receiving member 15 is generally conical in shape, with its pointed tip 15a in point contact with the holder 14, more specifically, with the top of the wall of the bottomed hole 14c, and its large-diameter base end 15b in contact with the pressure sensor 11. A through-hole 14d provided in the holder 14 spatially communicates with a through-hole 12d formed in the body 12a. A cable 20 (shown only in FIG. 5) for extracting a measurement signal output by the pressure sensor 11 is routed to the outside of the stress measuring roll 2 via these through-holes 14d and 12d.

[0027] As the stress measuring roll 2 rotates around the axis line AX, the direction of the tip 15a of the pressure receiving member 15 rotates around the axis line AX.

[0028] (computing device) 1, the arithmetic device 30 of this embodiment includes a storage unit 31, an input unit 32, a calculation unit 33, an output unit 34, and a display unit 35. The arithmetic device 30 can be constructed by hardware including storage devices such as a CPU (Central Processing Unit), RAM (Random Access Memory), and ROM (Read Only Memory), and software implemented therein.

[0029] As will be described in detail later, the memory unit 31 stores a transfer function (used to calculate the stress distribution of the roll bite from the measurement signal of the pressure center 11) that takes as input the stress acting at a certain angle on the roll body 12 of the stress measurement roll 2 in an area including the roll bite, and outputs the stress acting on the pressure sensor 11 via the pressure-receiving member 15 at a certain rotation angle around the rotation axis AX of the stress measurement roll 2. The memory unit 31 also stores, as will be described in detail later, a theoretical rolling equation that is used to calculate the calculated stress distribution of the roll bite from the stress distribution of the roll bite.

[0030] The measurement signal of the pressure sensor 11 is input to the input unit 32 via a filter 36 and an A / D converter 37 .

[0031] The calculation unit 33 calculates the rolling stress distribution and the friction coefficient distribution of the roll bite.

[0032] The output unit 34 outputs the rolling stress distribution and friction coefficient distribution of the roll bite calculated by the calculation unit 33 to, for example, an external information device (not shown).

[0033] The display unit 35 includes a display that visually displays the rolling stress distribution and friction coefficient distribution of the roll bite calculated by the calculation unit 33.

[0034] (Overview of rolling mill operation) An outline of the operation of the rolling mill 10 of this embodiment will be described below.

[0035] 1, when the rolling mill 1 rolls the material 100 to be rolled, the pressure sensor 11 detects stress via the pressure-receiving member 15, whose tip 15a rotates about the axis AX as the stress measuring roll 2 rotates about the axis AX, as described above. Here, the pressure sensor 11 is not exposed on the surface of the body 12a of the stress measuring roll 2 (roll body 12), and therefore the stress detected by the pressure sensor 11 is not the stress on the surface of the body 12a, but rather the stress in the portion that is located inside the body 12a by the thickness of the holder 14.

[0036] The stress acting on the stress measuring roll 2 (roll body 12) during rolling is transmitted to the pressure sensor 11 not via a pin but via the holder 14, whose outer surface 14a forms the same cylindrical surface as the surface of the barrel 12a of the roll body 12, making it possible to measure the accurate stress state at the interface between the material and the stress measuring roll 2. In addition, the pressure-receiving member 15 interposed between the holder 14 and the pressure sensor 11 is in point contact with the holder 14, so the spatial resolution of stress measurement by the pressure sensor 11 is high.

[0037] In addition, since the stress acting on the stress measuring roll 2 is transmitted to the pressure sensor 11 housed in the barrel portion 12a of the roll body 12 via the holder 14, there is no need to employ a special structure that is inferior in strength for attaching a strain gauge to the stress measuring roll. In this respect, it is possible to measure the stress in the roll bite over a wide range of rolling loads (and more specifically, to measure the rolling stress distribution and friction coefficient distribution as will be described later).

[0038] As described above, the stress acting on the stress measuring roll 12 is transmitted to the pressure sensor 11 not through the pin but through the holder 14 whose outer surface 14a forms the same cylindrical surface as the surface of the barrel portion 12a, making it possible to measure the rolling stress distribution during lubricated rolling.

[0039] The measurement signal of the pressure sensor 11 during rolling is input to the calculation device 30, more specifically to the input unit 32. The calculation unit 33 calculates the rolling stress distribution of the roll bite based on the measurement values ​​of the pressure sensor 11 inputted moment by moment to the input unit 32 and the transfer function stored in the memory unit 31. The calculation unit 33 also calculates the friction coefficient distribution of the roll bite using the calculated rolling stress distribution and the theoretical rolling equation stored in the memory unit 31. The rolling stress distribution and friction coefficient distribution calculated by the calculation unit 33 are stored in the memory unit 31 and are output by the output unit 34 or displayed on the display unit 35 as necessary.

[0040] As described above, the rolling apparatus 10 of this embodiment can measure the rolling stress distribution and friction coefficient distribution of the roll bite with high accuracy over a wide range of rolling loads.

[0041] (Rolling equipment) The rolling method (including calculation of the transfer function) executed by the rolling mill 10 will be described in more detail below.

[0042] This rolling method includes the following steps (1) to (5), which will be described in order below. (1) Kiss Rolling (2) Calculation of the transfer function (3) Rolling of the material to be rolled (4) Calculation of stress distribution (5) Calculation of friction coefficient distribution

[0043] (Kiss roll rolling) First, the rolling mill 1 is operated under kiss-roll rolling conditions, i.e., under conditions where there is no material 100 to be rolled and there is no gap between the stress measuring roll 2 and the bottom work roll 3. During this kiss-roll rolling, the pressure sensor 11 outputs measured values ​​(measurement signals) from time to time. In this embodiment, the measured values ​​output by the pressure sensor 11 are input to the calculation device 30 and stored in the memory unit 31.

[0044] (Calculation of transfer function) In this embodiment, the calculation unit 33 calculates a transfer function from the measured values ​​of the pressure sensor 11 during kiss rolling stored in the storage unit 31.

[0045] As mentioned above, the stress detected by the pressure sensor 11 is not the stress on the surface of the body 12a of the stress measurement roll 2, but rather the stress in the area inside the body 12a by the thickness of the holder 14. In other words, the stress measured by the stress measurement roll 2 does not represent the actual stress distribution in the area where the stress measurement roll 2 and the rolled material 100 are in contact (the roll bite). Specifically, as is clear from FIGS. 6A to 6D (the higher the stress in FIGS. 6A to 6D, the higher the density of scattered points. This also applies to FIG. 7, which will be described later), due to the structure of the stress measurement roll 2 described above, the pressure sensor 11 measures not only the stress in the roll bite but also the stress in the surrounding area. In other words, the pressure sensor 11 cannot detect only the stress actually acting on the body 12a when the tip 15a of the pressure-receiving member 15 is in the roll bite. Therefore, a transfer function is calculated, where the stress acting at a certain angle to the stress measurement roll 2 (roll body 12) in the area including the roll bite is used as the input and the stress acting on the pressure sensor 11 at a certain rotational angle around the axis AX is used as the output. Using this transfer function, the stress detected by the pressure sensor 11 can be converted into the rolling stress of the roll bite. An example of the derivation of the transfer function will be described below.

[0046] Referring to FIG. 7, the relationship between the measurement value of the pressure sensor 11 (hereinafter sometimes referred to as "sensor-measured stress") and the stress actually acting on the stress measuring roll 2 in the roll bite can be expressed by the following equation (1).

[0047]

number

[0048] The rotation angles θ and ω are defined as positive clockwise and negative counterclockwise with respect to the line Lorg connecting the uppermost position in FIG. 7 where the tip 15a of the pressure-receiving member 15 can be located and the stress measuring roll 12.

[0049] Equation (1) contains two unknowns: the transfer function f(θ, ω) and the rolling stress distribution p(ω) of the roll bite. In deriving the transfer function f(θ, ω), the rolling stress distribution p(ω) of the roll bite is assumed to be in an ideal state for kiss roll rolling as described above. Specifically, the transfer function f(θ, ω) is found using the sensor-measured stress φ(θ) during kiss roll rolling, that is, the value measured by the pressure sensor 11 during kiss roll rolling, and the Hertzian contact stress distribution for two-cylinder contact shown in equation (2) below (also see Figures 8 and 9).

[0050]

number

[0051] The Hertzian maximum contact stress p in Eq. (2) max is expressed by the following equation (3).

[0052]

number

[0053] The symbol c (1 / 2 of the Hertzian contact width) in equation (2) is expressed by the following equation (4):

[0054]

number

[0055] By applying equation (1) to the rolling stress distribution p(ω) in the roll bite during kiss rolling, which was calculated based on the Hertzian contact stress distribution, and the stress φ(θ) measured by the sensor during kiss rolling, which is an actual measurement value, the transfer function f(θ,ω) can be obtained. Figure 10 shows an example of the transfer function f(θ,ω) derived in this way.

[0056] The calculation unit 33 stores the derived transfer function f(θ, ω) in the storage unit 31.

[0057] The transfer function may be derived by numerical analysis and stored in the storage unit 31.

[0058] (Rolling of the rolled material) Next, the material 100 to be rolled is rolled using the compressor 10. In this embodiment, rolling was performed under the rolling conditions shown in Table 1 below. During this rolling, measurement values ​​(measurement signals) are output from the pressure sensor 11 every moment. FIG. 10 shows the measurement values ​​relative to the rotation angle θ. In this embodiment, the measurement values ​​output by the pressure sensor 11 are input to the calculation device 30 and stored in the memory unit 31.

[0059] In this embodiment, the rolling conditions shown in the following Table 1 were adopted. Note that the above-mentioned kiss roll rolling also adopted the same conditions as the rolling conditions in Table 1 for rolls, lubrication, and speed.

[0060] [Table 1]

[0061] (Calculation of estimated stress distribution) In this embodiment, the calculation unit 33 calculates the rolling stress distribution in the roll bite using the measurement value of the pressure sensor 11 during rolling of the rolled material stored in the memory unit 31, i.e., the sensor-measured stress φ(θ), and the transfer function stored in the memory unit 31. Figures 11 and 12 show the calculated rolling stress distribution for a reduction ratio of 6%. Specifically, the solid line in Figure 11 shows the estimated stress versus the rotation angle θ, and the solid line in Figure 12 shows the estimated stress versus the position in the rolling direction (contact length).

[0062] (Calculation of stress distribution) In this embodiment, the calculation unit 33 calculates the calculated stress distribution of the roll bite using the rolling stress distribution stored in the storage unit 31 and a theoretical rolling formula stored in advance in the storage unit 31. The following formulas (5) and (6) are examples of the theoretical rolling formula. However, the theoretical rolling formula used to calculate the calculated stress distribution is not limited to formulas (5) and (6).

[0063]

number

[0064] Figures 11 and 12 show the calculated stress distribution when individual friction resistances are set on the inlet and outlet sides using the theoretical rolling formula. Specifically, the dashed line in Figure 11 shows the calculated stress distribution relative to the rotation angle θ derived from the theoretical rolling formula when the inlet friction resistance is set to μ and the outlet friction resistance is set to μ × 1.8, and the dashed line in Figure 12 shows the calculated stress distribution relative to the position in the rolling direction (contact length). [Explanation of symbols]

[0065] 1. Rolling mill 2 Stress measurement roll 3 Lower work roll 4 Upper backup roll 5 Lower backup roll 6. Housing 10. Rolling equipment 11 Pressure Sensor 12 Roll body 12a Torso 12b Shaft 12c Recess 12d through hole 13. Bass 13a Top side 14 Holder 14a Exterior 14b Inner surface 14c Bottomed hole 14d through hole 15 Pressure-receiving member 15a tip 15b Proximal end 16,17 Bolt (holder and body) 18 Containment Room 19 Nut 20 Cable 30 Arithmetic unit 31 Storage section 32 Input section 33 Arithmetic section 34 Output section 35 Display section 36 filters 37 A / D converter 100 Rolled material

Claims

1. a rolling mill in which at least one of a pair of work rolls is a stress measurement roll; a computing device that performs a calculation based on an input from the stress measuring roll; Equipped with The stress measuring roll is a roll body having a recess formed in a barrel portion, the recess opening to a surface of the barrel portion; a pressure sensor accommodated in the recess; a holder attached to the body portion so as to close the opening, the holder having an outer surface that forms the same cylindrical surface as the surface of the body portion; a pressure-receiving member that is disposed in the recess so as to be sandwiched between the inner surface of the holder and the pressure sensor, the tip of which is in point contact with the inner surface of the holder and the base of which is in contact with the pressure sensor; Equipped with With the rotation of the stress measuring roll, the orientation of the tip of the pressure-receiving member rotates around the axis of the stress measuring roll, The computing device an input unit to which a measurement value from the pressure sensor is input; a storage unit that stores a transfer function in which a stress acting at a certain angle on the roll body in an area including a roll bite is used as an input, and a stress acting on the pressure sensor at a certain rotation angle around the axis is used as an output; a calculation unit that calculates a rolling stress distribution of a roll bite based on the measurement values of the pressure sensors when the material to be rolled is being rolled in the rolling mill and the transfer function; A rolling device comprising:

2. the storage unit stores a theoretical rolling formula, 2. The rolling apparatus according to claim 1, wherein the calculation unit calculates the distribution of the friction coefficient of the roll bite using the rolling stress distribution and the rolling theoretical formula.

3. 3. The rolling mill according to claim 1, wherein the pressure-receiving member is substantially conical in shape.

4. A rolling mill is provided in which at least one of a pair of work rolls is a stress measurement roll, the stress measurement roll comprising: a roll body having a recess formed in a barrel portion and the recess opening into the surface of the barrel portion; a pressure sensor accommodated in the recess; a holder attached to the barrel portion so as to close the opening and having an outer surface that forms the same cylindrical surface as the surface of the barrel portion; and a pressure receiving member disposed in the recess so as to be sandwiched between the inner surface of the holder and the pressure sensor, the pressure receiving member having a tip that is in point contact with the inner surface of the holder and a base end that is in contact with the pressure sensor, wherein the orientation of the tip of the pressure receiving member rotates around the axis of the stress measurement roll as the stress measurement roll rotates, Kiss roll rolling is performed in the rolling mill; Using measurements of the pressure sensors during kiss rolling, a transfer function is calculated in which the stress acting at a certain angle on the roll body in a region including the roll bite is used as an input and the stress acting on the pressure sensor at a certain rotation angle around the axis is used as an output; The rolling mill rolls the material to be rolled, and calculating a rolling stress distribution in a roll bite based on measurements of the pressure sensor during rolling of the rolled material and the transfer function.

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