Method and apparatus for predicting deformation of the end of an electric resistance welded steel pipe, and method and apparatus for adjusting the position of a sizer roll for an electric resistance welded steel pipe.

Abstract

To provide a deformation prediction device of an end of an electroseamed steel pipe for predicting a degree of deformation of an outer diameter at the end of the electroseamed steel pipe after cutting.SOLUTION: A deformation prediction device 100 includes a plurality of probe coils 10 arranged in a circumferential direction of an electroseamed steel pipe P between a sizer roll 1 and a cutting machine 2, and signal processing means 20 for predicting a degree of deformation of an outer diameter at an end of an electroseamed steel pipe after cutting, on the basis of induced voltages measured by each of the probe coils. The plurality of probe coils measure a first induced voltage generated by a magnetic field acting in a circumferential direction of the electroseamed steel pipe, and a second induced voltage generated by a magnetic field acting in an axial direction, extract induced voltage components VC and VL caused by magnetic change due to residual stress of the electroseamed steel pipe from the first induced voltage and the second induced voltage, calculate standard deviation σCL of a product VCVL of the components, and predict a degree of deformation using a first correlation among the standard deviation σCL, previously stored standard deviation σCL and the degree of deformation.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for predicting deformation of the ends of electric resistance welded (ERW) steel pipes, which are transported axially and whose outer diameter is adjusted by a sizer roll, and then cut into predetermined lengths, and to a method and apparatus for adjusting the position of a sizer roll for ERW steel pipes, which adjusts the position of the sizer roll based on the predicted degree of deformation of the outer diameter at the ends of the ERW steel pipes after cutting. [Background technology]

[0002] Electric resistance welded (ERW) steel pipes (also known as electric resistance welded steel pipes or ERW steel pipes) are manufactured, as is well known, in a pipe manufacturing line by forming a tubular shape from a material (steel sheet) unwound from a coil using a roll, and then welding (electric resistance welding) the two edges of the tubular material together. This electric resistance welding method uses an induction coil to which high-frequency power is applied to generate eddy currents at both edges of the material, and the two edges of the material, which are heated (induction heated) by these eddy currents, are then pressed together with a die-cast roll. The electric resistance welded (ERW) steel pipes, welded as described above, are transported axially (longitudinally), adjusted to the desired outer diameter using multiple sizing rolls, and then cut to the desired predetermined lengths to produce ERW steel pipes as finished products.

[0003] The position of the sizer roll (position perpendicular to the rotation axis of the sizer roll) is known to be a factor in causing deformation of the outer diameter of electric resistance welded (ERW) steel pipes, and especially in the case of thin-walled ERW steel pipes, it is due to the non-uniformity of residual stress in the ERW steel pipe, which can cause deformation of the outer diameter at the end (axial end) of the ERW steel pipe after cutting (see, for example, paragraph 0003 of Patent Document 1). Therefore, adjusting the sizer roll to the appropriate position is an important quality control item when manufacturing electric resistance welded steel pipes in order to sufficiently suppress deformation of the outer diameter at the end of the pipe after cutting, thereby preventing a large number of defective products at the end.

[0004] For example, Patent Document 1 proposes a method for manufacturing electric resistance welded steel pipes with excellent roundness, characterized in that the final stage sizer roll in the sizer process is divided into four or more sections, the bottom diameter of each roll is three times or more the diameter of the steel pipe, the bottom diameters of each roll are the same, the sizer rolls are undriven, and a drawing ratio of 0.05 to 0.5% or less is used to make the circumferential distribution of residual stress in the longitudinal and circumferential directions of the steel pipe uniform.

[0005] The method described in Patent Document 1 does not involve actually measuring the residual stress of the electric resistance welded steel pipe, which can vary depending on various settings in the process preceding the sizing process (for example, the process of forming the material into a tubular shape) and the material properties, and adjusting the position of the sizing roll according to the measured value (it is a method of setting a fixed reduction ratio within the range of 0.05 to 0.5% regardless of the residual stress). Therefore, there is a risk that deformation of the outer diameter at the end of the electric resistance welded steel pipe after cutting, which occurs due to residual stress, may not be sufficiently suppressed.

[0006] Therefore, in order to sufficiently suppress the deformation of the outer diameter at the end of the electric resistance welded (ERW) steel pipe after cutting, it is advisable to actually measure the residual stress of the ERW steel pipe and adjust the position of the sizer roll according to the measured value.

[0007] For example, Patent Document 2 proposes a method for measuring residual stress in a material using ultrasound. The method described in Patent Document 2 involves emitting ultrasonic waves from an oscillator toward the interior of the material to be measured, receiving the reflected waves from the material with a receiver, gradually sliding the position of the ultrasonic wave emission, and measuring the direction in which the received reflected waves take their maximum value to calculate the residual stress of the material to be measured (e.g., Claim 1 of Patent Document 2). The method described in Patent Document 2 assumes that the material to be measured is stationary, and therefore is difficult to use to measure the residual stress of electric resistance welded steel pipes that are being transported in the axial direction.

[0008] Furthermore, Patent Document 3 proposes a method for electromagnetically measuring the residual stress on the shot-peened surface of shot-peened steel material using a coil. The method described in Patent Document 3 involves placing coils provided in an inspection circuit on the shot-peened surface of a sample made of the same material as the object to be inspected and whose residual stress generation state is known, on the shot-peened surface of the object to be inspected, and on the surface of a reference material made of the same material as the object to be inspected but which has not undergone shot-peening treatment. An AC signal is input to the inspection circuit while changing the frequency, and the frequency response characteristics of the phase angle change of voltage and current in the inspection circuit are measured and compared to calculate the residual stress on the shot-peened surface of the object to be inspected (e.g., claim 1 of Patent Document 3). The method described in Patent Document 3 is based on the premise that the object being inspected is stationary, and therefore it is difficult to use to measure the residual stress of electric resistance welded steel pipes that are being transported in the axial direction.

[0009] Furthermore, Patent Document 4 proposes an X-ray diffractometer capable of measuring residual stress in an object being measured. The apparatus described in Patent Document 4 performs the first to third measurements by changing the placement conditions of the apparatus relative to the object to be measured, and calculates the residual stress in three mutually orthogonal axes based on the measurement results of the shape of the diffraction ring measured in each measurement (paragraphs 0010 to 0013 of Patent Document 4). The apparatus described in Patent Document 4 is based on the premise that the object to be inspected is stationary, and therefore it is difficult to use to measure the residual stress of electric resistance welded steel pipes that are being transported in the axial direction.

[0010] As described above, in order to sufficiently suppress the deformation of the outer diameter at the end of the electric resistance welded (ERW) steel pipe after cutting, no conventional method has been proposed for actually measuring the residual stress of the ERW steel pipe and adjusting the sizer roll to an appropriate position according to the measured value. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Patent No. 2543283 [Patent Document 2] Patent No. 3396287 [Patent Document 3] Patent No. 5004519 [Patent Document 4] Patent No. 5728753 [Overview of the project] [Problems that the invention aims to solve]

[0012] The present invention was made to solve the problems of the prior art described above, and aims to provide a method and apparatus for predicting deformation of the end of an electric resistance welded steel pipe, which predicts the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe after cutting, and a method and apparatus for adjusting the position of a sizer roll for an electric resistance welded steel pipe, which adjusts the position of the sizer roll based on the predicted degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe after cutting. [Means for solving the problem]

[0013] To solve the aforementioned problems, the present inventors focused on detecting magnetic changes caused by residual stress in electric resistance welded (ERW) steel pipes by arranging multiple probe coils opposite to the outer surface of the ERW steel pipe along the circumferential direction of the ERW steel pipe, applying a magnetic field to the ERW steel pipe using these probe coils, and measuring the induced voltage generated by electromagnetic induction of this magnetic field. The inventors then diligently investigated the relationship between the direction of the magnetic field applied by the probe coil, the induced voltage measured by the probe coil, and the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe after cutting, and obtained the following findings. (1) Each probe coil applies a magnetic field in the circumferential and axial directions to the electric resistance welded steel pipe (applying a magnetic field that extends in the circumferential direction and a magnetic field that extends in the axial direction). (2) Each probe coil measures the first induced voltage generated by electromagnetic induction of the magnetic field acting circumferentially on the electric resistance welded steel pipe and the second induced voltage generated by electromagnetic induction of the magnetic field acting axially on the electric resistance welded steel pipe. (3) Of the first induced voltage, the induced voltage component V caused by the magnetic change due to residual stress in the electric resistance welded steel pipe Cand an induced voltage component V resulting from the magnetic change due to the residual stress of the electric resistance welded steel pipe among the second induced voltages L are extracted. (4) The induced voltage component V at the same measurement point (the same circumferential position of the electric resistance welded steel pipe) C and the induced voltage component V L The product V C V L The standard deviation σ CL is calculated. This standard deviation σ CL is considered to be an index representing the non-uniformity of the residual stress of the electric resistance welded steel pipe. (5) The above standard deviation σ CL has a high correlation with the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe after cutting. As the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe after cutting, for example, the change amount of the longitudinal ovality at the end of the electric resistance welded steel pipe after cutting (= the longitudinal ovality at the end of the electric resistance welded steel pipe after cutting - the longitudinal ovality at the central part (axial central part) of the electric resistance welded steel pipe after cutting) can be exemplified. (6) Therefore, if the above correlation is obtained in advance, it is possible to predict the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe after cutting by using the above standard deviation σ CL and the above correlation.

[0014] The present invention has been completed based on the above findings of the present inventors. In other words, to solve the above problem, the present invention includes a measurement step in which, after adjusting the outer diameter of an electric resistance welded (ERW) steel pipe being conveyed in the axial direction with a sizer roll, and before cutting it into predetermined lengths, a magnetic field is applied to the circumferential and axial directions of the ERW steel pipe using a plurality of probe coils arranged facing the outer surface of the ERW steel pipe along the circumferential direction of the ERW steel pipe, and the induced voltage generated by the electromagnetic induction of the magnetic field is measured; and a prediction step in which the degree of deformation of the outer diameter at the end of the ERW steel pipe after cutting is predicted based on the induced voltage measured in the measurement step, wherein in the measurement step, a first induced voltage generated by the electromagnetic induction of the magnetic field acting in the circumferential direction of the ERW steel pipe and a second induced voltage generated by the electromagnetic induction of the magnetic field acting in the axial direction of the ERW steel pipe are measured at a plurality of locations along the circumferential direction of the ERW steel pipe where the plurality of probe coils are arranged, and in the prediction step, the induced voltage component V of the first induced voltage caused by the magnetic change due to residual stress in the ERW steel pipe is measured. C And, of the second induced voltage, the induced voltage component V is caused by the magnetic change due to the residual stress of the electric resistance welded steel pipe. L Extract the induced voltage component V C and the induced voltage component V L The product V C V L Standard deviation σ CL The standard deviation σ is calculated and CL And the previously obtained standard deviation σ CL The present invention provides a method for predicting the deformation of the end of an electric resistance welded steel pipe, characterized by predicting the degree of deformation using a first correlation between the degree of deformation and the given value.

[0015] According to the deformation prediction method of the present invention, in the measurement step, at multiple locations along the circumferential direction of the electric resistance welded steel pipe where multiple probe coils are arranged, a first induced voltage generated by electromagnetic induction of a magnetic field acting in the circumferential direction of the electric resistance welded steel pipe and a second induced voltage generated by electromagnetic induction of a magnetic field acting in the axial direction of the electric resistance welded steel pipe are measured using each probe coil. Then, in the prediction step, the induced voltage component V of the first induced voltage is determined to be caused by the magnetic change due to residual stress in the electric resistance welded steel pipe. CAnd, of the second induced voltage, the induced voltage component V is caused by the magnetic change due to residual stress in the electric resistance welded steel pipe. L Extract and the induced voltage component V C and the induced voltage component V L The product V C V L Standard deviation σ CL The induced voltage component V is calculated at multiple locations along the circumferential direction of the electric resistance welded steel pipe. C and the induced voltage component V L To extract the product V of these, C V L The product of these multiple points, V, is calculated at multiple points along the circumferential direction of the electric resistance welded steel pipe. C V L Standard deviation σ CL It is possible to calculate this. As mentioned above, according to the inventors' findings, the standard deviation σ CL This has a high correlation with the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe after cutting, therefore this standard deviation σ CL If the first correlation between the degree of deformation and the standard deviation σ is obtained in advance, then in the prediction step, CL Using the first correlation, it is possible to predict the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe after cutting. Although the deformation prediction method according to the present invention is not a method for directly measuring the residual stress of the electric resistance welded steel pipe, the standard deviation σ is an indicator of the non-uniformity of the residual stress. CL By actually measuring (calculating) this and using it to predict the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe after cutting, it is possible to make a highly accurate prediction.

[0016] Here, the tensile strength T of the steel plate that is the material for electric resistance welded steel pipes. S This is a parameter that can change depending on the material of the steel plate. On the other hand, the residual stress of electric resistance welded steel pipes is also a parameter that can change depending on the material of the steel plate. Therefore, the residual stress of electric resistance welded steel pipes is equal to the tensile strength T of the steel plate. S It can be said that this is a parameter that can change depending on the circumstances. Therefore, when manufacturing electric resistance welded (ERW) steel pipes using steel plates of various materials in an electric resistance welded (ERW) steel pipe manufacturing line, the tensile strength T of the steel plate is considered. SBy considering this and predicting the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe after cutting, it is expected that even more accurate predictions will be possible. According to the inventors' findings, the standard deviation σ CL The tensile strength T of the steel plate that is the material for electric resistance welded steel pipes S It was found that the value obtained by multiplying by the power of N (where N is a natural number greater than or equal to 1) has a high correlation with the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe after cutting.

[0017] Therefore, in the deformation prediction method according to the present invention, preferably, in the prediction step, the standard deviation σ CL And the previously obtained standard deviation σ CL Instead of predicting the degree of deformation using the first correlation between and the degree of deformation, the standard deviation σ CL The tensile strength T of the steel plate that is the material for the electric resistance welded steel pipe S A value obtained by multiplying by the Nth power of (where N is a natural number greater than or equal to 1) is calculated as an index, and the degree of deformation is predicted using the index and a second correlation between the index and the degree of deformation that was obtained in advance.

[0018] According to the preferred method described above, it is possible to predict with greater accuracy the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe after cutting.

[0019] In the deformation prediction method according to the present invention, in the prediction step, for example, by performing a phase analysis on the first induced voltage, the first induced voltage is decomposed into an induced voltage component obtained by the change in the lift-off of the probe coil and an induced voltage component whose phase is orthogonal to the said induced voltage component, and the orthogonal induced voltage component is the induced voltage component V C The second induced voltage is extracted and phase-analyzed to decompose it into an induced voltage component obtained by the change in the lift-off of the probe coil and an induced voltage component whose phase is orthogonal to the said induced voltage component, and the orthogonal induced voltage component is the induced voltage component V L It is possible to extract it as such.

[0020] Furthermore, in order to solve the above problems, the present invention is also provided as a method for adjusting the position of a sizer roll for an electric resistance welded steel pipe, which adjusts the position of the sizer roll using a method for predicting the deformation of the end of the electric resistance welded steel pipe, and is characterized by having an adjustment step of adjusting the position of the sizer roll so that the degree of deformation at the end of the electric resistance welded steel pipe after cutting, as predicted by the deformation prediction method, falls within a predetermined reference range.

[0021] According to the position adjustment method of the present invention, in the adjustment step, the position of the sizer roll is adjusted so that the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe after cutting is within a predetermined reference range, thereby preventing the generation of a large number of defective products at the end.

[0022] Furthermore, in order to solve the above problems, the present invention provides a plurality of probe coils positioned between a sizer roll that adjusts the outer diameter of an electric resistance welded (ERW) steel pipe being conveyed in the axial direction and a cutting machine that cuts the ERW steel pipe into predetermined lengths, which are arranged facing the outer surface of the ERW steel pipe along the circumferential direction of the ERW steel pipe and apply a magnetic field to the ERW steel pipe in the circumferential and axial directions to measure the induced voltage generated by the electromagnetic induction of the magnetic field, and a signal processing means that predicts the degree of deformation of the outer diameter at the end of the ERW steel pipe after cutting by the cutting machine based on the induced voltage measured by the plurality of probe coils, wherein the plurality of probe coils measure a first induced voltage generated by the electromagnetic induction of a magnetic field acting in the circumferential direction of the ERW steel pipe and a second induced voltage generated by the electromagnetic induction of a magnetic field acting in the axial direction of the ERW steel pipe at a plurality of locations along the circumferential direction of the ERW steel pipe where the plurality of probe coils are arranged, and the signal processing means measures the induced voltage component V of the first induced voltage caused by the magnetic change due to residual stress in the ERW steel pipe. C And, of the second induced voltage, the induced voltage component V is caused by the magnetic change due to the residual stress of the electric resistance welded steel pipe. L Extract the induced voltage component V C and the induced voltage component V L The product V C V L Standard deviation σCL The standard deviation σ is calculated and CL And the pre-stored standard deviation σ CL The invention is also provided as a deformation prediction device for the end of an electric resistance welded steel pipe, characterized by predicting the degree of deformation using a first correlation between the degree of deformation and the given value.

[0023] Furthermore, in order to solve the above-mentioned problems, the present invention is also provided as a sizer roll position adjustment device for electric resistance welded steel pipes, characterized by comprising: a deformation prediction device for the end of the electric resistance welded steel pipe; and an adjustment means for adjusting the position of the sizer roll so that the degree of deformation at the end of the electric resistance welded steel pipe after cutting, as predicted by the deformation prediction device, falls within a predetermined reference range. [Effects of the Invention]

[0024] According to the present invention, it is possible to predict the degree of deformation of the outer diameter at the end of an electric resistance welded (ERW) steel pipe after cutting. Furthermore, by adjusting the position of the sizer roll based on the predicted degree of deformation of the outer diameter at the end of the ERW steel pipe after cutting, it is possible to prevent a large number of defective ERW steel pipes from being produced at the end after cutting. [Brief explanation of the drawing]

[0025] [Figure 1] This figure schematically shows the general configuration of a deformation prediction device for the end of an electric resistance welded steel pipe according to one embodiment of the present invention. [Figure 2] This is an explanatory diagram illustrating the calibration procedure for the circuit section 21 shown in Figure 1. [Figure 3] This figure shows the correlation between the standard deviation σOD and the change in vertical ellipticity, as investigated and calculated by the inventors. [Figure 4] This figure shows the results of the tests in which the inventors have gained knowledge. [Figure 5] This figure shows the first correlation and the correlation between the standard deviation σC / L and the change in vertical ellipticity. [Figure 6] This figure shows the second correlation calculated using the same data as the first correlation shown in Figure 5. [Figure 7] Figure 1 is an explanatory diagram illustrating a specific example of adjusting the position of the sizer roll 1 shown in Figure 1. [Modes for carrying out the invention]

[0026] Hereinafter, with due reference to the attached drawings, a deformation prediction device for the end of an electric resistance welded steel pipe according to one embodiment of the present invention, and a position adjustment device for a sizer roll for electric resistance welded steel pipe using this deformation prediction device will be described.

[0027] <Device for predicting deformation of the end of electric resistance welded steel pipes> First, I will describe the device for predicting the deformation of the end of electric resistance welded steel pipes. Figure 1 is a schematic diagram showing the general configuration of a deformation prediction device for the end of an electric resistance welded steel pipe (hereinafter, as appropriate, simply referred to as the "deformation prediction device") according to one embodiment of the present invention. Figure 1(a) is a schematic side view (viewed from a horizontal direction perpendicular to the axial direction of the electric resistance welded steel pipe) showing the general configuration of the entire deformation prediction device. Figure 1(b) is a schematic front view (viewed from the axial direction of the electric resistance welded steel pipe) showing the general configuration of the first probe coil among the probe coils provided in the deformation prediction device. Figure 1(c) is a schematic front view showing the general configuration of the second probe coil among the probe coils provided in the deformation prediction device. In Figure 1, the X direction is the axial direction (longitudinal direction) of the electric resistance welded steel pipe P, the Y direction is the horizontal direction perpendicular to the axial direction of the electric resistance welded steel pipe P, and the Z direction is the vertical direction. Note that the dimensions, scale, and shape of each component shown in Figure 1 may differ from those of the actual components. As shown in Figure 1(a), the deformation prediction device 100 according to this embodiment includes a sizer roll 1 that adjusts the outer diameter of the electric resistance welded steel pipe P being transported in the axial direction (X direction), and a cutting machine 2 that cuts the electric resistance welded steel pipe P after the outer diameter adjustment into predetermined lengths. The device comprises a plurality of probe coils 10 positioned opposite the outer surface of the electric resistance welded steel pipe P along the circumferential direction (direction around the X direction) of the electric resistance welded steel pipe P, which apply a magnetic field in the circumferential and axial directions of the electric resistance welded steel pipe P and measure the induced voltage generated by the electromagnetic induction of the magnetic field, and a signal processing means 20 that predicts the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe P after cutting by the cutting machine 2 based on the induced voltage measured by the plurality of probe coils 10. Furthermore, as a preferred configuration, the deformation prediction device 100 according to this embodiment includes an encoder 30 that contacts the outer surface of the electric resistance welded steel pipe P and outputs a pulse signal with a number of pulses corresponding to the transport distance of the electric resistance welded steel pipe P (in the example shown in Figure 1, the transport distance of the electric resistance welded steel pipe P after cutting). The probe coil 10 and signal processing means 20 will be described in detail below.

[0028] [Probe coil 10] The deformation prediction device 100 according to this embodiment includes a probe coil 10 consisting of a first probe coil 11 arranged along the circumferential direction of the electric resistance welded steel pipe P and a second probe coil 12 arranged along the circumferential direction of the electric resistance welded steel pipe P. As shown in Figures 1(b) and 1(c), in this embodiment, four first probe coils 11 (11a to 11d) and four second probe coils 12 (12a to 12d) are arranged at equal pitches of 90° at positions of 45°, 135°, 225°, and 315° counterclockwise, with the position of the weld PW at the top of the electric resistance welded steel pipe P being the 0° position (the angles formed by the lines connecting the center of the electric resistance welded steel pipe P and each position are 45°, 135°, 225°, and 315° counterclockwise with respect to the line connecting the center of the electric resistance welded steel pipe P and the weld PW). However, the present invention is not limited thereto, and two to three or five or more probe coils 10 (first probe coil 11 and second probe coil 12) may be arranged along the circumferential direction of the electric resistance welded steel pipe P, and the arrangement pitch does not necessarily have to be equal. The lift-off of each probe coil 10 (the gap between each probe coil 10 and the outer surface of the electric resistance welded steel pipe P) is kept constant (e.g., about 1 mm) by a known tracking mechanism (not shown). In the example shown in Figure 1(a), the first probe coil 11 is positioned on the upstream side in the transport direction of the electric resistance welded steel pipe P, and the second probe coil 12 is positioned on the downstream side in the transport direction of the electric resistance welded steel pipe P. However, the present invention is not limited to this, and it is also possible to adopt a configuration in which the second probe coil 12 is positioned on the upstream side in the transport direction of the electric resistance welded steel pipe P, and the first probe coil 11 is positioned on the downstream side in the transport direction of the electric resistance welded steel pipe P.

[0029] The first probe coil 11 is a probe coil that applies a magnetic field in the circumferential direction of the electric resistance welded steel pipe P and measures the first induced voltage generated by electromagnetic induction of the magnetic field acting in the circumferential direction of the electric resistance welded steel pipe P. The second probe coil 12 is a probe coil that applies a magnetic field in the axial direction of the electric resistance welded steel pipe P and measures the second induced voltage generated by electromagnetic induction of the magnetic field acting in the axial direction of the electric resistance welded steel pipe P. As shown in Figure 1(b), the first probe coil 11 comprises a U-shaped yoke 111 in front view, an excitation coil 112 wound around the yoke 111, and a detection coil 113 wound around the yoke 111. By passing an alternating current through the excitation coil 112, an alternating magnetic field is formed in the direction passing through both ends of the yoke 111 (i.e., in the circumferential direction of the electric resistance welded steel pipe P), and this magnetic field acts on the electric resistance welded steel pipe P. The induced voltage (first induced voltage) generated by the electromagnetic induction of this magnetic field is then detected by the detection coil 113. In this embodiment, the first induced voltage is measured by four first probe coils 11a to 11d, respectively. Similarly, as shown in Figure 1(c), the second probe coil 12 comprises a U-shaped yoke 121 in front view, an excitation coil (not shown in Figure 1(c)) wound around the yoke 121, and a detection coil 123 wound around the yoke 121. By passing an alternating current through the excitation coil of the second probe coil 12, an alternating magnetic field is formed in the direction passing through both ends of the yoke 121 (i.e., the X direction, which is the axial direction of the electric resistance welded steel pipe P), and this magnetic field acts on the electric resistance welded steel pipe P. The induced voltage (second induced voltage) generated by the electromagnetic induction of this magnetic field is then detected by the detection coil 123. In this embodiment, the second induced voltage is measured by four first probe coils 12a to 12d, respectively. In this embodiment, the first probe coil 11 and the second probe coil 12 are probe coils with the same configuration. The first probe coil 11 is used with both ends of the yoke 111 positioned along the circumferential direction of the electric resistance welded steel pipe P, and the second probe coil 12 is used with both ends of the yoke 121 positioned along the axial direction of the electric resistance welded steel pipe P. However, the present invention is not necessarily limited to this, and it is also possible to use probe coils with different configurations as the first probe coil 11 and the second probe coil 12.

[0030] [Signal processing means 20] The signal processing means 20 of this embodiment comprises a circuit unit 21 and an arithmetic unit 22. The circuit section 21 includes an oscillator 211, a bridge circuit 212, an amplifier 213, a synchronous detection circuit 214, a phase rotater 215, and an A / D converter 216. The oscillator 211 is connected to each of the excitation coils, which consist of a total of eight probe coils 10 (four first probe coils 11 and four second probe coils 12), and the oscillation signal (alternating current) output from the oscillator 211 is applied to each excitation coil. As a result, a magnetic field is formed in each probe coil 10, and this magnetic field acts on the electric resistance welded steel pipe P. Furthermore, the oscillator 211 is also connected to the excitation coils of eight balance-adjusting probe coils RC (not shown in Figure 1), which have the same configuration as the probe coil 10. The oscillation signal (AC current) output from the oscillator 211 is applied to the excitation coil of each probe coil RC, thereby forming a magnetic field in each probe coil RC. Note that the probe coils RC are connected not only when calibrating the circuit section 21 described later, but also when measuring the induced voltage of the electric resistance welded steel pipe P.

[0031] A bridge circuit 212 is provided for each probe coil 10 (i.e., eight are provided in this embodiment), and each probe coil 10 and each probe coil RC are connected to each bridge circuit 212. Specifically, the detection coil 113 of probe coil 11 and the detection coil of probe coil RC (or the detection coil 123 of probe coil 12 and the detection coil of probe coil RC) are connected in series to two adjacent sides of the bridge circuit 212. As will be described later, a magnetic field is formed and an induced voltage is detected when probe coil RC is in an air-core state (when the outer surface of the electric resistance welded steel pipe P is not facing the probe coil RC). Therefore, the bridge circuit 212 is calibrated so that when probe coil 10 is also in an air-core state (when the outer surface of the electric resistance welded steel pipe P is not facing the probe coil 10), the bridge circuit 212 is in a balanced state (i.e., the output from the bridge circuit 212 is 0). In other words, the bridge circuit 212 outputs an induced voltage that is calculated by canceling out the effect of the impedance of the probe coil 10 in the air-core state, based on the induced voltages (first induced voltage and second induced voltage) measured by the probe coil 10.

[0032] An amplifier 213 is provided for each probe coil 10 (i.e., eight are provided in this embodiment), and it amplifies the induced voltage output from the bridge circuit 212 (the first induced voltage and the second induced voltage after the effect of the air core state has been canceled out) and outputs it to the synchronous detection circuit 214.

[0033] The synchronous detection circuit 214 synchronously detects the input induced voltage (the amplified first induced voltage and the second induced voltage) based on the oscillation signal output from the oscillator 211 (the same oscillation signal applied to the excitation coil of the probe coil 10), decomposes it into two induced voltage components whose phases are orthogonal to each other, and outputs them to the phase rotator 215. Specifically, the synchronous detection circuit 214 decomposes the input first induced voltage into an induced voltage component obtained by the lift-off change of the first probe coil 11 and an induced voltage component V whose phase is orthogonal to the said induced voltage component and is caused by the magnetic change due to residual stress in the electric resistance welded steel pipe P. C The voltage is then decomposed and output to the phase rotator 215. The synchronous detection circuit 214 also analyzes the input second induced voltage as an induced voltage component obtained by the change in the lift-off of the second probe coil 12 and an induced voltage component V which is orthogonal in phase to the said induced voltage component and is caused by the magnetic change due to the residual stress of the electric resistance welded steel pipe P. L It is then decomposed and output to the phase rotator 215.

[0034] The phase rotator 215 rotates the phases of two mutually orthogonal induced voltage components that are input, and displays the induced voltage components on the XY2 axis plane such that one induced voltage component is displayed as a value on the X axis and the other induced voltage component is displayed as a value on the Y axis which is orthogonal to the X axis. Specifically, the phase rotator 215 of this embodiment, for the first induced voltage, the induced voltage component V C It is adjusted to display as the value on the X axis. Similarly, the phase rotator 215 of this embodiment is adjusted for the second induced voltage, and the induced voltage component V L It has been adjusted to display the value on the X axis. Note that the induced voltage component V C and induced voltage component V L A specific example of the calibration procedure for displaying the value on the X axis will be described later.

[0035] The A / D converter 216 converts the induced voltage components (values ​​of the X and Y axes in the XY2-axis plane) output from the phase rotator 215 into digital signals and then outputs them to the calculation unit 22. The calculation processing in the calculation unit 22 includes the induced voltage component V, which is the value of the X axis. C and induced voltage component VL Since only the X-axis value is used, either only the X-axis value is converted into a digital signal, or both the X-axis and Y-axis values ​​are converted into digital signals, but only the X-axis value is output to the calculation unit 22. The calculation unit 22 of this embodiment calculates the standard deviation σ, which will be described later. CL It consists of computers on which programs are installed to perform calculations such as calculating and predicting the degree of deformation. In this embodiment, since the lift-off fluctuation of the probe coil 10 during the measurement of the induced voltage of the electric resistance welded steel pipe P is small, only the X-axis value is used in the calculation processing by the calculation unit 22. However, if the lift-off fluctuation of the probe coil 10 is large, it is also possible to calculate the amount of lift-off fluctuation from the Y-axis value and correct the measurement error caused by the lift-off fluctuation.

[0036] The calculation unit 22 processes the induced voltage component V extracted from the first induced voltage output from the A / D converter 216. C and the induced voltage component V extracted from the second induced voltage L The product V C V L The induced voltage component V is calculated at four locations along the circumferential direction of the electric resistance welded steel pipe P. C and V L Since it is extracted, the product V is generated at four locations along the circumferential direction of the electric resistance welded steel pipe P. C V L This will be calculated. Here, the calculation unit 22 receives the pulse signal output from the encoder 30. Based on the pulse signal output from the encoder 30, the calculation unit 22 calculates the product V at a predetermined pitch in the transport direction of the electric resistance welded steel pipe P. C V L The calculation unit 22 calculates the product V every 1m. For example, when cutting machine 2 cuts electric resistance welded steel pipe P every 5.5m, the calculation unit 22 calculates the product V every 1m. C V L It is possible to calculate this. Furthermore, especially in the case of thin-walled electric resistance welded (ERW) steel pipes P, the deformation of the outer diameter at the end of the ERW steel pipe P after cutting becomes significant, so the product V C V LThe calculation pitch (and thus, the prediction pitch of the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe P after cutting) may be set to an appropriate value in consideration of the t / D (ratio of wall thickness to outer diameter) of the electric resistance welded steel pipe P and the conveyance speed of the electric resistance welded steel pipe P.

[0037] The arithmetic unit 22 of the present embodiment simply calculates the product V C of the induced voltage component V L extracted from the first induced voltage and the second induced voltage measured at the same timing, respectively. Therefore, the calculated product V C V L is not the product of the induced voltage component V C V L obtained for the same cross-section of the electric resistance welded steel pipe P and the induced voltage component V C and the induced voltage component V L . It is the product of the induced voltage component V C and the induced voltage component V L obtained for cross-sections separated by the separation distance (separation distance in the conveyance direction (X direction) of the electric resistance welded steel pipe P) between the first probe coil 11 that measures the first induced voltage and the second probe coil 12 that measures the second induced voltage. As shown in FIG. 1(a), in the present embodiment, since the separation distance between the first probe coil 11 and the second probe coil 12 is small, although the product V C V L calculated in the present embodiment is not the product of the induced voltage component V C obtained for the same cross-section of the electric resistance welded steel pipe P and the induced voltage component V L , it is considered that the variation in the axial direction of the residual stress of the electric resistance welded steel pipe P is small, and thus it is considered that it does not have a great influence on the prediction accuracy of the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe P after cutting. However, for example, when the separation distance between the first probe coil 11 and the second probe coil 12 has to be set large due to restrictions on the pipe manufacturing line, the pulse signal output from the encoder 30 is used to multiply the induced voltage component V C V L by the induced voltage component V L when calculating the product V CBy delaying this according to the distance between the first probe coil 11 and the second probe coil 12, the induced voltage component V obtained for the same cross-section can be calculated. C and the induced voltage component V L The product V C V L This can be calculated to improve the accuracy of predicting the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe P after cutting.

[0038] The calculation unit 22 calculates the product V at four locations along the circumferential direction of the electric resistance welded steel pipe P. C V L Standard deviation σ CL The calculation unit 22 then calculates the previously obtained standard deviation σ. CL The first correlation between the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe P after cutting is stored. The calculation unit 22 calculates the standard deviation σ CL Using the stored first correlation, the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe P after cutting is predicted. A specific example of the first correlation will be described later.

[0039] As an example of the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe P after cutting, the change in vertical ellipticity can be cited. The vertical elliptosis refers to the difference between the outer diameter of the electric resistance welded steel pipe P at the 0° position (i.e., the outer diameter in the Z direction) and the outer diameter of the electric resistance welded steel pipe P at the 90° position (i.e., the outer diameter in the Y direction) (= outer diameter at 0° - outer diameter at 90°). The change in vertical ellipticity represents the difference between the vertical ellipticity of the end of the electric resistance welded (ERW) pipe P and the vertical ellipticity of the central part of the ERW pipe P (= vertical ellipticity of the end of the ERW pipe P - vertical ellipticity of the central part of the ERW pipe P). As will be discussed later, if the length of the ERW pipe P after cutting is 2m, the central part of the ERW pipe P corresponds to a point about 1m away from the end face (cut surface) of the ERW pipe P. However, if the distance from the cut surface is about 1m, it is considered that the residual stress will not change significantly before and after cutting the ERW pipe P.

[0040] According to the deformation prediction device 100 having the above configuration, the standard deviation σ calculated by the calculation unit 22 CLHowever, since this has a high correlation with the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe P after cutting, by acquiring and storing this first correlation in advance, the calculation unit 22 calculates the standard deviation σ CL Using this and a pre-stored first correlation, it is possible to predict the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe P after cutting. If the predicted degree of deformation is outside the predetermined reference range, for example, the calculation unit 22 outputs an alarm (and furthermore, the calculated standard deviation σ CL By configuring the system to display the first correlation on the monitor, the operator who detects this alarm can take action such as adjusting the position of the sizer roll 1.

[0041] In this embodiment, the circuit section 21 rotates the phases of two mutually orthogonal induced voltage components using the phase rotator 215, and then converts the induced voltage components into digital signals using the A / D converter 216. In other words, the invention describes a case where analog processing is performed up to the phase rotator 215. However, the present invention is not limited to this. For example, it is also possible to amplify the induced voltage with the amplifier 213, and then convert the amplified induced voltage into a digital signal with the A / D converter 216, thereby replacing the analog processing performed by the aforementioned synchronous detection circuit 214 and phase rotator 215 with digital processing.

[0042] Furthermore, in this embodiment, the calculation unit 22 calculates the standard deviation σ CL And the first correlation (standard deviation σ) that is remembered CL The present invention has been described in which the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe P after cutting is predicted using the correlation between the coefficient of deformation and the degree of deformation, but the present invention is not limited thereto. The tensile strength T of the steel plate that is the material for electric resistance welded steel pipe P. S The calculation unit 22 inputs and stores the calculated standard deviation σ beforehand. CL Tensile strength T SThe system is configured to calculate an index by multiplying the index by the power of N (where N is a natural number greater than or equal to 1). The calculation unit 22 stores a second correlation relationship, which has been acquired in advance, between the index and the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe P after cutting. It is also possible for the calculation unit 22 to use the index and the stored second correlation relationship (the correlation relationship between the index and the degree of deformation) to predict the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe P after cutting. Specific examples of the above second correlation relationship will be described later. The residual stress in electric resistance welded steel pipe P is equal to the tensile strength T of the steel plate material. S It can be said that this is a parameter that can change depending on the situation. For this reason, when manufacturing electric resistance welded steel pipes P using steel plates of various materials in an electric resistance welded steel pipe manufacturing line, the tensile strength T of the steel plate is a parameter that can change depending on the situation. S By considering this factor and predicting the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe P after cutting, it is expected that even more accurate predictions will be possible.

[0043] <Adjusting device for the sizer roll of electric resistance welded steel pipes> Next, we will describe the position adjustment device for the sizer roll of electric resistance welded steel pipes. The position adjustment device for the sizer roll of electric resistance welded steel pipe according to this embodiment (hereinafter, as may be simply referred to as the "position adjustment device") comprises the deformation prediction device 100 described above, and an adjustment means (not shown in Figure 1) that adjusts the position of the sizer roll 1 so that the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe P after cutting, as predicted by the deformation prediction device 100, falls within a predetermined reference range. In other words, the position adjustment device automates the operator's actions described above.

[0044] In the example shown in Figure 1, four sizer rolls 1a to 1d are arranged as sizer roll 1. Each sizer roll 1a to 1b consists of a pair of perforated rolls (rolls with arc-shaped grooves (perforations) formed on their outer surface, having a curvature corresponding to the outer diameter of the electric resistance welded steel pipe P) positioned opposite each other on either side of the electric resistance welded steel pipe P. The sizer rolls 1a and 1c, positioned in odd-numbered rows, are perforated rolls (sometimes called V-rolls) that press the electric resistance welded steel pipe P in the vertical direction (Z direction) so that its outer diameter in the vertical direction (Z direction) becomes smaller. The sizer rolls 1b and 1d, positioned in even-numbered rows, are perforated rolls (sometimes called H-rolls) that press the electric resistance welded steel pipe P in the horizontal direction (Y direction) so that its outer diameter in the horizontal direction (Y direction) becomes smaller. The subsequent sizer rolls 1c and 1d are perforated rolls that determine the outer diameter of the electric resistance welded steel pipe P as a product, and therefore their positions cannot be adjusted as they are determined by the outer diameter specifications of the product. For this reason, in this embodiment, the positions of the preceding sizer rolls 1a and 1b are adjusted by an adjustment means. Specifically, the adjustment means adjusts the amount of reduction in the outer diameter of the electric resistance welded steel pipe P in the vertical direction (Z direction) by opening and closing the sizer roll 1a in the vertical direction (Z direction), and adjusts the amount of reduction in the outer diameter of the electric resistance welded steel pipe P in the horizontal direction (Y direction) by opening and closing the sizer roll 1b in the horizontal direction (Y direction). Specific examples of position adjustment of the sizer roll 1 by the adjustment means will be described later. While not limited to this, the adjustment method can include, for example, a configuration comprising a single-axis stage with a servo motor attached to the rotation axis of the sizer rolls 1a and 1b, respectively, and a control unit that controls the amount of movement of the single-axis stage by controlling the amount of rotation of the servo motor. The calculation unit 22 of the deformation prediction device 100 is electrically connected to this control unit, and the control unit can control the amount of rotation of the servo motor, and thus the amount of movement of the single-axis stage, according to the amount of change in vertical ellipticity predicted by the calculation unit 22.

[0045] With the position adjustment device having the above configuration, the adjustment means adjusts the position of the sizer roll 1 (especially the preceding sizer rolls 1a and 1b) so that the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe P after cutting, as predicted by the deformation prediction device 100, falls within a predetermined reference range, thereby preventing the generation of a large number of defective products at the end. Furthermore, the position adjustment of the sizer roll 1 by the adjustment means is not limited to immediately performing the adjustment if the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe P after cutting falls outside a predetermined reference range once. For example, the calculation unit 22 calculates the product V every 1m. C V L When calculating and predicting the degree of deformation every 1m, if the predicted degree of deformation is outside the standard range for five consecutive times (i.e., outside the standard range for 5m), the position of sizer roll 1 can be adjusted. Similarly, only when the degree of deformation is outside the standard range for multiple consecutive times (in other words, when there is a very high probability that the actual degree of deformation will be outside the standard range) can the position of sizer roll 1 be adjusted so that the degree of deformation falls within a predetermined standard range.

[0046] The following describes the deformation prediction device 100 and the position adjustment device in more detail.

[0047] <Calibration Procedure> The calibration procedure for the circuit section 21 of the signal processing means 20 will be described below. Figure 2 is an explanatory diagram schematically illustrating the calibration procedure of the circuit section 21. Figures 2(a) and 2(b) show the positional relationship between each probe coil and the electric resistance welded steel pipe P. Figure 2(c) shows the induced voltage components on the XY2 axis plane displayed by the phase rotator 215. In the following explanation, we will use the procedure for calibrating the circuit section 21 with respect to the induced voltage measured by the second probe coil 12d shown in Figure 2 as an example. However, the procedure is the same when calibrating the circuit section 21 with respect to the induced voltage measured by the other second probe coils 12a to 12c or the first probe coils 11a to 11d. As described above, the second probe coil 12d and probe coil RC are connected to the bridge circuit 212 of the circuit section 21. In the air-core state, probe coil RC forms a magnetic field and an induced voltage is detected.

[0048] When calibrating the circuit section 21, first, as shown in Figure 2(a), not only the probe coil RC but also the second probe coil 12d is made air-core. That is, the second probe coil 12d is positioned so that it faces a point ET0 in space, rather than facing the outer surface of the electric resistance welded steel pipe P. Then, the bridge circuit 212 is calibrated so that the bridge circuit 212 connected to both the second probe coil 12d and the probe coil RC is in a balanced state (i.e., the output from the bridge circuit 212 is 0). Then, as shown in Figure 2(c), the calculation unit 22 confirms that the induced voltage component obtained by the induced voltage measured by the second probe coil 12d in the state shown in Figure 2(a) is plotted at the origin (X=0[V], Y=0[V]) on the XY2 axis plane displayed by the phase rotator 215.

[0049] Next, as shown in Figure 2(b), the probe coil RC is kept in an air-core state without moving, while the second probe coil 12d is moved gradually towards the outer surface of the electric resistance welded steel pipe P, until the lift-off of the second probe coil 12d (lift-off relative to the outer surface of the electric resistance welded steel pipe P) is minimized at point ET on the outer surface of the electric resistance welded steel pipe P. S Move it to a position opposite to it. Point ET on the outer surface of the electric resistance welded steel pipe P. S For this purpose, select a point where the residual stress is 0 or extremely small. Point ET S The residual stress can be measured, for example, using an X-ray diffractometer such as the one described in Patent Document 4. As described above, point ET on the outer surface of the electric resistance welded steel pipe P SWhen moving the second probe coil 12d to a position opposite to the point ET, the phase rotator 215 is adjusted so that the plotted point of the induced voltage component gradually moves along the Y axis on the XY2 axis plane displayed by the phase rotator 215, as shown by the thick arrow in Figure 2(c), and the value of the Y axis gradually increases. Then, the second probe coil 12d is positioned at point ET on the outer surface of the electric resistance welded steel pipe P. S When the device reaches the position opposite the target, the gain of amplifier 213 is adjusted so that the value of the Y-axis becomes a predetermined constant value (5[V] in the example shown in Figure 2(c)).

[0050] By performing the calibration procedure for the circuit section 21 described above on the induced voltage measured by all probe coils 10, the induced voltage component obtained due to the lift-off change of the probe coils 10 is displayed as the Y-axis value on the XY2-axis plane displayed by the phase rotator 215, and the induced voltage component V due to the magnetic change caused by residual stress in the electric resistance welded steel pipe P is displayed. C , V L This will be displayed as the X-axis value on the XY2-axis plane shown by the phase rotator 215. In Figure 2(c), the data plotted with "○" represent the induced voltage component V measured at four locations along the circumferential direction of each electric resistance welded (ERW) steel pipe P, which was prepared using four different types of steel plates, four pipes for each material (16 pipes in total). (The position of the weld PW at the top of the ERW steel pipe P is set as 0°, and the four locations are 45°, 135°, 225°, and 315° counterclockwise.) L (Total of 64 induced voltage components V) L This is a plot of the combined values. For the 16 electric resistance welded steel pipes P, it was confirmed using an X-ray analyzer that each electric resistance welded steel pipe P has residual stress of a certain magnitude or greater. As shown in Figure 2(c), the induced voltage component V due to the magnetic change caused by residual stress in the electric resistance welded steel pipe P L It appears that this is correctly displayed as the value on the X axis.

[0051] <Correlation> A specific example of a correlation used by the calculation unit 22 of the signal processing means 20 to predict the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe P after cutting will be described. First, the calculation unit 22 uses the correlation (standard deviation σ) for prediction. CL The first correlation, or standard deviation σ, is the correlation between the degree of deformation and the degree of deformation. CL The tensile strength T of the steel plate that is the material for the electric resistance welded steel pipe P S Before explaining a specific example of the second correlation between the index, which is a value obtained by multiplying by the Nth power of the value, and the degree of deformation, we will explain the correlation between other parameters and the degree of deformation that the inventors have investigated, and the process by which the inventors came up with the configuration in which the calculation unit 22 predicts the degree of deformation using the first correlation.

[0052] [Correlation between the standard deviation of the outer diameter of electric resistance welded steel pipes and the degree of deformation] The inventors prepared 16 electric resistance welded steel pipes P, each 2m long after cutting, formed from four different types of steel plates. They measured the outer diameter at the center of each pipe, with the welded joint PW at position 0°, and at positions 0°, 45°, 90°, and 135°. They then measured the standard deviation σ of the outer diameter measured at each position. OD The following was calculated. Meanwhile, the outer diameter was measured at the ends of the electric resistance welded steel pipe P after cutting, at positions of 0°, 45°, 90°, and 135°, and the change in the vertical ellipticity, as described above, was calculated as the degree of deformation of the outer diameter at the ends of the electric resistance welded steel pipe P after cutting. The standard deviation σ was then calculated. OD The correlation between the change in vertical ellipticity and the standard deviation σ was calculated. Specifically, the change in vertical ellipticity was compared with the standard deviation σ. OD It was approximated by a linear equation. Note that the standard deviation σ OD As described above, this is calculated from the outer diameter measured at the center of the electric resistance welded steel pipe P after cutting. However, since the outer diameter at the center is not expected to change significantly before and after cutting the electric resistance welded steel pipe P, even if a known outer diameter meter is installed on the pipe manufacturing line to measure the outer diameter of the electric resistance welded steel pipe P before cutting, the above standard deviation σ OD It is expected that a standard deviation equivalent to this value will be calculated.

[0053] Figure 3 shows the standard deviation σ calculated as described above.OD This figure shows the correlation between the change in vertical ellipticity and the standard deviation σ. The dashed line in Figure 3 represents the standard deviation σ. OD This is an approximate straight line that can be represented by a linear equation. As shown in Figure 3, the square of the correlation coefficient R between the two is small at 0.348, indicating that the correlation between them is not very high. Therefore, even if the outer diameter of the electric resistance welded steel pipe P is measured before cutting in the pipe manufacturing line, this standard deviation σ OD It is difficult to accurately predict the change in the vertical ellipticity of the end of the electric resistance welded steel pipe P after cutting using this method.

[0054] [Correlation between parameters obtained using an X-ray diffractometer and the degree of deformation] Although details will be omitted, the inventors used an X-ray diffractometer as described in Patent Document 4 to measure residual stress and investigated the correlation between various parameters obtained from the measured values ​​and the change in the vertical ellipticity of the end of the electric resistance welded steel pipe P after cutting. As a result, it was found that there was no high correlation between any of the parameters and the change in vertical ellipticity. When using an X-ray diffractometer, the measurement area is generally a small circular region on the outer surface of the electric resistance welded steel pipe P with an outer diameter of several micrometers and a depth (thickness direction) of several tens of micrometers. In other words, when using an X-ray diffractometer, local residual stress is measured, and it is presumed that a good correlation cannot be obtained between this measurement and the degree of deformation of the outer diameter (change in vertical ellipticity) at the end of the electric resistance welded steel pipe P after cutting.

[0055] [How the inventors came up with the configuration to predict the degree of deformation using the first correlation] As mentioned above, it is difficult to use an X-ray diffractometer like the one described in Patent Document 4 to measure the residual stress of an electric resistance welded steel pipe P being transported in the axial direction. Furthermore, it was found that the correlation between the parameters obtained from the residual stress measurements by the X-ray diffractometer and the change in vertical ellipticity is not high. The inventors considered that if the reason for the low correlation is due to the small measurement area of ​​the X-ray diffractometer, then they should consider a method to widen the measurement area. They decided to investigate a method using a probe coil 10 to detect magnetic changes caused by the residual stress of the electric resistance welded steel pipe P. The measurement range of the probe coil 10 is, for example, 10 mm × 25 mm on the outer surface of the electric resistance welded steel pipe P, with a depth (thickness direction) of several mm, which is far wider than the measurement area of ​​the X-ray diffractometer. Furthermore, by examining the correlation between various parameters obtained from the induced voltage measured by the probe coil 10 and the change in longitudinal ellipticity, it was found that the aforementioned first correlation may have a high correlation. Specifically, the probe coil 10 measures the first induced voltage generated by electromagnetic induction of the magnetic field acting circumferentially on the electric resistance welded steel pipe P, and the second induced voltage generated by electromagnetic induction of the magnetic field acting axially on the electric resistance welded steel pipe P, and the induced voltage component V of the first induced voltage caused by the magnetic change due to residual stress in the electric resistance welded steel pipe P C And, of the second induced voltage, the induced voltage component V is caused by the magnetic change due to residual stress in the electric resistance welded steel pipe P. L Extract and the induced voltage component V C and the induced voltage component V L The product V C V L Standard deviation σ CL If you calculate this standard deviation σ CL It was found that this may have a high correlation with the change in vertical ellipticity.

[0056] The details of the tests in which the inventors obtained the above findings will be described below. In the above test, three electric resistance welded steel pipes P (TP1, TP2, TP3), each 2m long after cutting, were prepared from three different types of steel plates made of different materials. At the center of each pipe, with the welded joint PW positioned at 0°, the outer diameter was measured at 0°, 45°, 90°, and 135°, and the change in vertical ellipticity was calculated. Furthermore, for the same three electric resistance welded steel pipes P (TP1, TP2, TP3) as described above, the induced voltage was measured using the probe coil 10 at positions 45°, 135°, 225°, and 315°, with the position of the weld PW at the center of the pipe being 0°. The induced voltage component V caused by the magnetic change due to residual stress in the electric resistance welded steel pipe P was then measured. C , V L Extract the induced voltage component V C and the induced voltage component V L The product V C V L Standard deviation σ CL The result was calculated. And the standard deviation σ CL The correlation between the change in vertical ellipticity and the standard deviation σ was calculated. Specifically, the change in vertical ellipticity was compared with the standard deviation σ. CL It was approximated by a linear equation.

[0057] Figure 4 shows the results of the above test. Figure 4(a) shows the results of calculating the change in longitudinal ellipticity for each electric resistance welded steel pipe P. Figure 4(b) shows the standard deviation σ for each electric resistance welded steel pipe P. CL The results of the calculation are shown. Figure 4(c) shows the standard deviation σ CL The results of calculating the correlation between the change in vertical ellipticity and the standard deviation σ are shown. The dashed line in Figure 4(c) represents the standard deviation σ. CL This is an approximate straight line that can be represented by a linear equation. As shown in Figure 4(c), the standard deviation σ CL The square of the correlation coefficient R between the change in vertical ellipticity and the coefficient of correlation was 0.9804, indicating a very high correlation between the two.

[0058] [Specific examples of the first correlation] Based on the above findings, the inventors used 16 electric resistance welded steel pipes P, each 2m long after cutting, the same as when the correlation shown in Figure 3 was obtained. At the center of the pipe, with the welded joint PW at position 0°, the inventors measured the induced voltage at positions 45°, 135°, 225°, and 315° using a probe coil 10. The induced voltage component V was determined to be caused by the magnetic change due to residual stress in the electric resistance welded steel pipe P. C , V L Extract the induced voltage component V C and the induced voltage component V L The product V C V L Standard deviation σ CL Calculate the standard deviation σ CL The first correlation between the change in vertical ellipticity and the standard deviation σ was calculated. Specifically, the change in vertical ellipticity was compared with the standard deviation σ. CL The relationship was approximated by a linear equation. Furthermore, to compare with the first correlation, the induced voltage component V measured at each position was examined. C The induced voltage component V L The standard deviation σ of the value obtained by dividing by C / L The correlation between the change in vertical ellipticity and the change in vertical ellipticity was also calculated. Specifically, the change in vertical ellipticity was compared with the standard deviation σ C / L It was approximated by a linear equation.

[0059] Figure 5 shows the first correlation and standard deviation σ calculated as described above. C / L This figure shows the correlation between the change in vertical ellipticity and the standard deviation σ. Figure 5(a) shows the first correlation. Figure 5(b) shows the standard deviation σ C / L This shows the correlation between this and the change in vertical ellipticity. As shown in Figure 5(a), the square of the correlation coefficient R of the first correlation is 0.7408, indicating that a high correlation is maintained even as the number of data points increases. Therefore, by acquiring such a first correlation in advance and storing it in the calculation unit 22, the calculation unit 22 calculates the standard deviation σ for the electric resistance welded steel pipes P transported in the pipe manufacturing line. CL Using the first correlation shown in Figure 5(a), which is stored in advance, it is possible to predict the amount of change in the vertical ellipticity at the end of the electric resistance welded steel pipe P after cutting. On the other hand, as shown in Figure 5(b), the standard deviation σ C / LThe square of the correlation coefficient R between the change in vertical ellipticity and the value of the value is 0.0076, which is very small, indicating that there is no correlation between the two. Therefore, the standard deviation σ C / L It is difficult to use this to predict the change in vertical ellipticity. Note that the standard deviation σ CL As described above, the induced voltage component V was measured at the center of the electric resistance welded steel pipe P after it had been cut. C , V L Although calculated from the above, the residual stress in the central part is not expected to change significantly before and after cutting the electric resistance welded steel pipe P, so the deformation prediction device 100 installed on the pipe manufacturing line is used to predict the induced voltage component V of the electric resistance welded steel pipe P before cutting. C , V L Even when measuring, if the measurement position is 1m or more away from the end face (cut surface) of the electric resistance welded steel pipe P, the above standard deviation σ CL It is expected that a standard deviation equivalent to this value will be calculated.

[0060] [Specific examples of the second correlation] Figure 6 shows the second correlation calculated using the same data as the first correlation shown in Figure 5. Figure 6(a) shows the calculated standard deviation σ CL Tensile strength T S The second correlation is shown, calculated using the value obtained by multiplying by the first power of σ. Figure 6(b) shows the calculated standard deviation σ CL Tensile strength T S The second correlation is shown, calculated using the value obtained by multiplying by the square of σ as an indicator. Figure 6(c) shows the calculated standard deviation σ CL Tensile strength T S The second correlation is shown, calculated using the value obtained by multiplying by the cube of the given value. The dashed line shown in Figure 6 is the approximate straight line represented by a linear equation for each parameter shown on the horizontal axis. From the squared value of the correlation coefficient R shown in Figure 6, it can be seen that the second correlation is approximately equivalent to the first correlation shown in Figure 5 (in the case of Figure 6(a)), or has an even higher correlation than the first correlation (in the cases of Figures 6(b) and 6(c)). Therefore, in the electric resistance welded steel pipe P manufacturing line, steel plates of various materials (various tensile strengths T) SWhen manufacturing electric resistance welded (ERW) steel pipes P using steel plates (which have a specific material), it is expected that a second correlation can be calculated using the ERW steel pipes P formed from each material, and this second correlation can be used to predict the change in vertical ellipticity at the end of the ERW steel pipe P after cutting, thereby enabling more accurate predictions.

[0061] [Specific examples of adjusting the sizer roll position] Figure 7 is an explanatory diagram illustrating a specific example of adjusting the position of the sizer roll 1 (specifically, sizer rolls 1a and 1b). Here, we explain an example in which the change in longitudinal ellipticity at the end of the electric resistance welded steel pipe P after cutting is predicted using the first correlation shown in Figure 5(a), and the position of the sizer roll 1 is adjusted based on this predicted change in longitudinal ellipticity. When the outer diameter tolerance is set to ±0.2 mm of the nominal outer diameter, as can be seen from Figure 7, the standard deviation σ CL If the value is 0.005 or less, the absolute value of the predicted change in vertical ellipsoid is within 0.4 mm (nominal outer diameter ±0.2 mm). For a change in vertical ellipsoid of this magnitude, adjustment of the sizer roll 1 position is considered unnecessary. On the other hand, the standard deviation σ CL If the value exceeds 0.005, for example, if it exceeds 0.01, the absolute value of the predicted change in vertical ellipsoid will exceed 0.8 mm (nominal outer diameter ±0.4 mm). With a change in vertical ellipsoid of this magnitude, it is considered necessary to adjust the position of the sizer roll 1.

[0062] For example, the standard deviation σ calculated for electric resistance welded steel pipes P manufactured on a pipe manufacturing line. CLIf the value is 0.01 and the predicted change in vertical ellipsoid is -0.85 mm (i.e., the difference between the outer diameter in the vertical direction (Z direction) and the outer diameter in the horizontal direction (Y direction) at the end of the electric resistance welded steel pipe P is predicted to increase by 0.85 mm in the horizontal direction (Y direction) compared to the central part of the electric resistance welded steel pipe P), then the sizer roll 1b that presses the electric resistance welded steel pipe P in the horizontal direction (Y direction) should be adjusted to close so that the outer diameter of the electric resistance welded steel pipe P in the horizontal direction (Y direction) becomes smaller. At this time, the control unit of the adjustment means should monitor the change in vertical ellipsoid predicted sequentially (for example, at 1 m intervals) by the calculation unit 22, and the control unit should control the amount of movement of the uniaxial stage that adjusts the position of the sizer roll 1b so that the absolute value of the monitored change in vertical ellipsoid is within 0.4 mm (nominal outer diameter ±0.2 mm). In other words, one could pre-determine a reference range of 0.4 mm (nominal outer diameter ±0.2 mm) and adjust the position of the sizer roll 1b (or sizer roll 1a) so that the absolute value of the change in vertical ellipticity falls within this reference range. Furthermore, the first correlation is used to determine the standard deviation σ CL Since the correspondence with the predicted change in vertical elliptic is known in advance, for example, the standard deviation σ calculated sequentially by the calculation unit 22 CL The control unit of the adjustment means monitors the standard deviation σ that it is monitoring. CL The control unit may control the amount of movement of the uniaxial stage that adjusts the position of the sizer roll 1b so that the value is 0.005 or less. Even with this adjustment method, the same effect as when adjusting the position of the sizer roll 1b so that the change in vertical ellipticity is within ±0.4 mm can be obtained. [Explanation of symbols]

[0063] 1, 1a, 1b, 1c, 1d... Sizer roll 2...cutting machine 10. Probe coil 11, 11a, 11b, 11c, 11d... First probe coil 12, 12a, 12b, 12c, 12d... Second probe coil 20. Signal processing means 21...Circuit section 22... Arithmetic section 100...Deformation prediction device 111, 121... York 112...Excitation coil 113, 123... Detection coil P...ERW steel pipe PW... Welded section

Claims

1. After adjusting the outer diameter of the electric resistance welded (ERW) steel pipe being conveyed axially with a sizer roll, and before cutting it to predetermined lengths, a measurement step is performed in which a magnetic field is applied to the circumferential and axial directions of the ERW steel pipe using a plurality of probe coils positioned opposite the outer surface of the ERW steel pipe along the circumferential direction of the ERW steel pipe, and the induced voltage generated by the electromagnetic induction of the magnetic field is measured. The method includes a prediction step that predicts the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe after cutting, based on the induced voltage measured in the measurement step. In the measurement step, the first induced voltage generated by electromagnetic induction of a magnetic field acting in the circumferential direction of the electric resistance welded steel pipe and the second induced voltage generated by electromagnetic induction of a magnetic field acting in the axial direction of the electric resistance welded steel pipe are measured at multiple locations along the circumferential direction of the electric resistance welded steel pipe where the plurality of probe coils are arranged. In the prediction step, an induced voltage component V caused by a magnetic change due to the residual stress of the electric resistance welded steel pipe among the first induced voltages ＣＬ and an induced voltage component V caused by a magnetic change due to the residual stress of the electric resistance welded steel pipe among the second induced voltages Ｌ are extracted, and the product V of the induced voltage component V Ｃ and the induced voltage component V Ｌ is calculated, and the standard deviation σ Ｃ V Ｌ is calculated. Using the standard deviation σ ＣＬ and the first correlation relationship between the standard deviation σ ＣＬ acquired in advance and the degree of deformation, the degree of deformation is predicted.​​ A method for predicting the deformation of the end of an electric resistance welded steel pipe, characterized by the features described above.

2. In the prediction step, the standard deviation σ ＣＬ And the previously obtained standard deviation σ ＣＬ Instead of predicting the degree of deformation using the first correlation between and the degree of deformation, the standard deviation σ ＣＬ The tensile strength T of the steel plate that is the material for the electric resistance welded steel pipe Ｓ A value obtained by multiplying by the Nth power of (where N is a natural number greater than or equal to 1) is calculated as an index, and the degree of deformation is predicted using the index and a second correlation between the index and the degree of deformation that was obtained in advance. The method for predicting the deformation of the end of an electric resistance welded steel pipe according to feature 1.

3. In the aforementioned prediction step, By performing a phase analysis on the first induced voltage, the first induced voltage is decomposed into an induced voltage component obtained by the change in the lift-off of the probe coil and an induced voltage component whose phase is orthogonal to the said induced voltage component, and the orthogonal induced voltage component is the induced voltage component V Ｃ Extracted as follows: By performing a phase analysis on the second induced voltage, the second induced voltage is decomposed into an induced voltage component obtained by the change in the lift-off of the probe coil and an induced voltage component whose phase is orthogonal to the said induced voltage component, and the orthogonal induced voltage component is the induced voltage component V Ｌ Extract as follows: A method for predicting deformation of the end of an electric resistance welded steel pipe according to feature 1 or 2.

4. A method for adjusting the position of a sizer roll for an electric resistance welded steel pipe, which involves adjusting the position of the sizer roll using the deformation prediction method for the end of the electric resistance welded steel pipe described in claim 1 or 2, The method includes an adjustment step of adjusting the position of the sizer roll so that the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe after cutting, as predicted by the deformation prediction method, falls within a predetermined reference range. A method for adjusting the position of a sizer roll for electric resistance welded steel pipes, characterized by the features described herein.

5. Between a sizer roll that adjusts the outer diameter of an electric resistance welded (ERW) steel pipe being conveyed in the axial direction and a cutting machine that cuts the ERW steel pipe into predetermined lengths after the outer diameter adjustment, there are multiple probe coils positioned facing the outer surface of the ERW steel pipe along the circumferential direction of the ERW steel pipe, which apply a magnetic field to the ERW steel pipe in the circumferential and axial directions, and measure the induced voltage generated by the electromagnetic induction of the magnetic field, The system includes a signal processing means that predicts the degree of deformation of the outer diameter at the end of the electric resistance welded steel pipe after it has been cut by the cutting machine, based on the induced voltage measured by the plurality of probe coils. The plurality of probe coils measure, at multiple locations along the circumferential direction of the electric resistance welded steel pipe where the plurality of probe coils are arranged, a first induced voltage generated by electromagnetic induction of a magnetic field acting in the circumferential direction of the electric resistance welded steel pipe and a second induced voltage generated by electromagnetic induction of a magnetic field acting in the axial direction of the electric resistance welded steel pipe. The signal processing means processes the induced voltage component V of the first induced voltage that is caused by the magnetic change due to residual stress in the electric resistance welded steel pipe. Ｃ And, of the second induced voltage, the induced voltage component V is caused by the magnetic change due to the residual stress of the electric resistance welded steel pipe. Ｌ Extract the induced voltage component V Ｃ and the induced voltage component V Ｌ Product V Ｃ V Ｌ Standard deviation σ ＣＬ The standard deviation σ is calculated and ＣＬ And the pre-stored standard deviation σ ＣＬ Using the first correlation between the degree of deformation and the degree of deformation, the degree of deformation is predicted. A device for predicting the deformation of the end of an electric resistance welded steel pipe, characterized by the above.

6. A device for predicting the deformation of the end of an electric resistance welded steel pipe according to claim 5, The system includes an adjustment means for adjusting the position of the sizer roll so that the degree of deformation at the end of the electric resistance welded steel pipe after cutting falls within a predetermined reference range, based on the degree of deformation predicted by the deformation prediction device. A position adjustment device for electric resistance welded steel pipe sizer rolls, characterized by the following features.

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