JP2013180335A - Method of straightening steel sheet with roller leveler and roller leveler straightener - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of straightening a steel sheet with a roller leveler, by which working state in a steel sheet width direction is recognized accurately and an appropriate correction can be performed on straightening rollers.SOLUTION: There is provided a method of straightening a steel sheet with a roller leveler, using a roller leveler straightener including a plurality of straightening rollers 1U, 1D which are provided zigzag up and down along the pass line of the steel sheet 10 and a plurality of roll deflection corrector for correcting the deflection of the straightening rollers. In the method, width-direction temperature distribution of the steel sheet 10 after passing through one or more straightening rollers 1U, 1D is measured and correction by means of the roller deflection corrector is performed in accordance with the measured temperature distribution using the roller deflection corrector.

Description

  The present invention relates to a steel sheet roller leveler straightening method and a roller leveler straightening machine, and in particular, a steel sheet roller leveler straightening method capable of accurately grasping the processing state in the width direction of the steel sheet and appropriately correcting the straightening roll, and the straightening method. The present invention relates to a roller leveler straightening machine used in the manufacturing process.

A hot-rolled steel plate such as a thick steel plate is re-heated in a heating furnace with a steel slab such as a slab, and then hot-rolled with a rolling mill to obtain a desired plate thickness, plate width, and length. Thereafter, accelerated cooling is performed as necessary, and after further cooling in a cooling bed, the product is cut into predetermined dimensions to obtain a product. A steel sheet manufactured in such a process may have a defective shape due to the presence of the temperature distribution of the steel sheet during rolling or due to non-uniform elongation and deformation during rolling.
Causes of temperature distribution include slab heating unevenness in the heating furnace, non-uniformity of high-pressure water injection in descaling, influence of roll cooling water in hot rolling and cooling for controlled rolling, and after rolling Non-uniform cooling in accelerated cooling of Moreover, even if the steel plate is apparently flat, residual stress may be generated in the steel plate after cooling. In particular, when there is a temperature distribution of the steel sheet during rolling, the amount of thermal shrinkage becomes non-uniform during the cooling process, which greatly affects the generation of residual stress.

When a flatness defect occurs in the steel sheet, cold roller leveler or press correction is performed to correct this. In general, roller leveler correction is often used from the standpoint of efficiency and cost. In addition to improving flatness, cold leveler correction is effective for reducing residual stress remaining in the steel sheet. It is known. In the correction by the roller leveler, the correction is performed by repeatedly bending the steel sheet using correction rolls provided up and down along the pass line of the steel sheet.
It is desirable to reduce the residual stress of the steel sheet as much as possible because it changes the shape of the steel sheet after cutting when cutting the steel sheet during use and causes the cutting dimensions to deteriorate. By doing so, the residual stress can be effectively reduced, and the upper and lower roller gaps are set so that the bending curvature gradually decreases, and repeated bending is performed to correct the steel sheet.

  In recent years, the need for high-strength steel sheets has increased, and therefore, the production of steel sheets with large thickness and high strength has increased. When such a high-strength thick steel plate is corrected with a roller leveler, a load applied to the roller (hereinafter also referred to as a correction load) increases. For this reason, when the steel plate passes over the roll, there is a problem that the correction roll is bent in the width direction of the steel plate (roll deflection), and a uniform bending curvature cannot be secured in the width direction.

In order to reduce the influence of such roll deflection, the roller leveler straightening machine includes a plurality of roll deflection correction means for correcting the roll deflection. And several techniques are proposed as a correction method of the steel plate by this roll deflection correction means.
For example, in Patent Document 1, the amount of bending at a plurality of positions in the body length direction of the correction roll is determined based on the reference setting position of the correction roll, the dimension of the material to be corrected, the mechanical property value of the material to be corrected, and the like. Disclosed is a method for determining the amount of fluctuation of the push amount at each position in the body length direction of the correction roll from the amount, and setting the position of the correction roll before correction so that the obtained amount of fluctuation of the push amount is equal to or less than an allowable value. Yes.

  Moreover, in patent document 2, it sets based on the plastic deformation rate of the correction | amendment by which the entry side reduction amount in the roller leveler correction of a steel plate is made into a target, and the curvature after the correction | amendment of a steel plate according to the entry side reduction amount is below an allowable value. A method is disclosed in which the output side reduction amount is set within the range to be set, and the roll deflection correction amount is set so that the output side reduction amount in the plate width direction is within a predetermined range.

  Furthermore, in Patent Document 3, the straightening load and straightening power during roller correction are measured, and based on these measured values, the material constant of the straightened material and the amount of bending deformation given to the straightened material during roller straightening are calculated. presume. Then, using the estimated material constant of the material to be corrected, when the amount of bending deformation to be applied to the material to be corrected is optimal for flattening the warp and wave shape of the material to be corrected A method is disclosed in which predicted values of the straightening load and straightening power are calculated, and the roller leveler is operated by correcting each roll position of the roller leveler so that these measured values coincide with the predicted values.

JP 2002-292427 A JP 2005-103589 A JP 2010-172925 A

However, the straightening load applied to the straightening roll in a roller leveler straightener greatly depends on the mechanical properties such as the yield strength of the material, and the mechanical properties of the material to be straightened are affected by the material temperature during rolling and the subsequent accelerated cooling conditions. However, these operating conditions usually vary, and the mechanical properties of the material to be corrected also vary.
The technique of Patent Document 1 is a method of setting the position of the correction roll before correction, and it is difficult to accurately grasp the mechanical characteristics of the material to be corrected in advance. Is large, the error of the correction correction of the correction roll set based on it becomes large. For this reason, the bending state in the width direction of the material to be straightened becomes non-uniform, and the residual stress of the steel sheet after straightening also becomes non-uniform in the width direction, resulting in local warping and shape defects, and warping after cutting. There was a problem that shape defects occurred.

  In addition, the technique of Patent Document 2 is also calculated by a relational expression from mechanical characteristics such as the yield stress of the steel sheet in calculating the correction load for correcting the roll deflection. In addition, it is inevitable that a deflection correction error due to variations in the mechanical characteristics of the material to be corrected occurs. Therefore, similarly to the technique of Patent Document 1, as a result of the residual stress of the steel sheet after correction becoming non-uniform in the width direction, there is a problem that local warpage or shape failure occurs, or warpage or shape failure occurs after cutting. there were.

  Furthermore, the technique of Patent Document 3 measures the correction load and correction power during roller correction, and corrects each roll position of the roller leveler based on the measurement, but does not consider the correction of the correction roll deflection. However, the problem of non-uniformity of residual stress in the width direction of the material to be corrected due to roll deflection correction error has not been solved.

  The present invention has been proposed in order to solve the above-described problems. By accurately grasping the processing state in the width direction of the steel sheet and appropriately correcting the straightening roll, the residual stress due to roll deflection is reduced. It aims at suppressing generation | occurrence | production to a steel plate and preventing generation | occurrence | production of the curvature and bending at the time of the cutting process of the steel plate in a post process.

As a result of intensive studies to achieve the above object, the present inventors have obtained the knowledge that the processing state of the metal material can be grasped by measuring the temperature distribution after the processing of the metal material. That is, not only in bending, but when plastic processing is performed on a metal material, the temperature of the material rises due to plastic heat generation (also referred to as processing heat generation). Therefore, for example, if the bending state of the material to be corrected on the correction roll is not uniform, it appears as a temperature change due to a difference in plastic heat generation.
And in the correction of the steel sheet using the roller leveler straightening machine, by measuring the temperature distribution in the width direction of the steel sheet after passing one or more straightening rolls, the processing defect due to the roll deflection actually generated in the steel sheet is increased. As a result of being able to grasp the accuracy and making appropriate corrections compared to the prior art, it is possible to suppress the occurrence of residual stress in the steel sheet and to prevent the occurrence of warpage and bending during the cutting process in the subsequent process. I found it.

That is, the gist configuration of the present invention is as follows.
(1) A roller leveler straightening machine provided with a plurality of straightening rolls provided in a staggered pattern along the pass line of the steel sheet and a plurality of roll deflection correcting means for correcting the deflection of the straightening roll was used. In the method for correcting the roller leveler of steel plates,
A method for correcting a roller leveler of a steel sheet, comprising: measuring a temperature distribution in a width direction of the steel sheet after passing through one or more straightening rolls, and performing correction by the roll deflection correcting means according to the measured temperature distribution.

(2) The method for correcting a roller leveler of a steel sheet according to (1), wherein the temperature distribution in the width direction of the steel sheet is measured by infrared thermography.

(3) Prior to the correction of the steel sheet, the correction reaction force of the steel sheet is predicted, and correction is performed based on the obtained predicted value. The steel sheet according to (1) or (2), Roller leveler correction method.

(4) A roller leveler straightening machine comprising a plurality of straightening rolls provided in a staggered manner along the pass line of the steel sheet, and a plurality of roll deflection correcting means for correcting the deflection of the straightening rolls. ,
It further comprises temperature distribution measuring means for measuring the temperature distribution in the width direction of the steel sheet after passing one or more of the straightening rolls, and performing correction by the roll deflection correcting means according to the measured temperature distribution. Characteristic roller leveler straightening machine.

  According to the present invention, it is possible to accurately grasp the processing state in the width direction of the steel sheet and perform appropriate correction of the correction roll, thereby suppressing the occurrence of residual stress in the steel sheet due to roll bending, and the steel sheet in the subsequent process. It is possible to prevent warping and bending during cutting.

In the correction of the steel plate using the roller leveler straightening machine by this invention, it is the side view which expanded and showed the state of the steel plate and the correction roll typically. It is the side view which showed the roller leveler correction machine by this invention. It is the front view which showed the roller leveler correction machine by this invention. It is the graph which showed the relationship between surface distortion and plastic heat_generation | fever about a structural steel plate. It is the graph which showed the width direction distribution of the surface temperature change about the structural steel plate of an Example. It is the graph which showed the width direction distribution of the bending curvature about the structural steel plate of an Example. It is the graph which showed the width direction distribution of the bending curvature after correction | amendment by the correction | amendment means about the structural steel plate of an Example.

Hereinafter, the present invention will be specifically described with reference to the drawings.
FIG. 1 schematically shows an enlarged view of a steel plate and a straightening roll viewed from the side when the steel plate is straightened. FIG. 2 is a view of the roller leveler straightening machine according to the present invention as seen from the side, and FIG. 3 is a view of the roller leveler straightener according to the present invention as seen from the front.

(Steel plate roller leveler correction method)
As shown in FIG. 2, the steel plate roller leveler correction method according to the present invention includes a plurality of correction rolls 1U and 1D provided in a zigzag pattern along the pass line of the steel plate 10, and the correction rolls 1U and 1D. A roller leveler straightening machine 9 including a plurality of roll deflection correcting means 5 for correcting the deflection in the width direction of the steel plate is used.

  As shown in FIG. 1, by repeatedly bending a plurality of straightening rolls 1U and 1D arranged in a zigzag pattern along the path line through which the steel plate 10 passes, warping or undulation of the steel plate 10 is performed. Shape defects can be corrected. Usually, the upper and lower straightening rolls 1U and 1D are supported by backup rolls 2U and 2D, respectively, and the backup rolls 2U and 2D are supported by integral upper and lower frames 3U and 3D.

  When the steel plate 10 is straightened, the upper straightening roll 1U or the lower straightening roll 1D is tilted together with the frame, and the distance between the upper straightening roll 1U and the lower straightening roll 1D is equal to that of the outgoing upper straightening roll 1U and the lower straightening roll 1D. It can set so that it may become smaller than the space | interval with the correction | amendment roll 1D. The amount of reduction on the entry side and the exit side can be individually set by the entry side and exit side reduction means 4 attached to the upper part of the straightening machine.

In addition, a plurality of roll deflection correction means 5 are provided on the upper frame 3U in the width direction of the correction rolls 1U and 1D. The roll deflection correction means 5 is not particularly limited as long as it can correct the deflection generated in the correction rolls 1U and 1D by the correction reaction force.
For example, as shown in FIGS. 2 and 3, there is roll deflection correcting means 5 that can independently adjust the amount of reduction in the correction roll width direction by moving the upper and lower wedge-shaped pedestals in the front-rear direction.
Here, the first upper correction roll 1U from the entry side is the reference roll for the entry side reduction amount, and the first upper correction roll 1U from the exit side is the reference roll for the exit side reduction amount, and the entry side reduction amount and the exit side reduction are set. The amount is the amount of reduction in each of these two rolls.

  And this invention measures the width direction temperature distribution of the steel plate 10 after passing 1 or more of the said correction | amendment rolls 1U and 1D, and performs the correction | amendment by the said roll deflection correction means 5 according to the measured temperature distribution. It is characterized by. By measuring the temperature distribution in the width direction of the steel sheet 10 after passing one or more of the straightening rolls 1U and 1D, that is, after being subjected to bending processing, processing defects due to roll bending actually occurring in the steel sheet can be accurately detected. As a result, it is possible to correct the roll deflection with high accuracy. Thereby, it can suppress that the residual stress resulting from roll bending generate | occur | produces in a steel plate, and can prevent generation | occurrence | production of the curvature at the time of the cutting process in a post process, and bending.

  Further, the measurement of the temperature distribution in the width direction of the steel sheet 10 is preferably performed by infrared thermography as shown in FIG. Thermography is a method that detects infrared radiation energy emitted from an object, converts it to an apparent temperature, and displays the temperature distribution as an image. In recent years, image sensors have developed rapidly, enabling precise measurement. It has become. If the bending state of the material to be straightened on the straightening roll is not uniform, it appears as a temperature change due to a difference in plastic heat generation. The unevenness of the bending process is caused by roll bending, so the difference in temperature change due to the difference in plastic heat generation is very subtle.However, the infrared thermography method makes this subtle difference in temperature characteristic. Therefore, it is possible to grasp the bending state of the steel sheet.

  The apparatus for acquiring the infrared thermography is not particularly limited. For example, as shown in FIG. 1, the infrared thermographic imaging camera 6 and infrared radiant energy detected by the camera are converted into an apparent temperature, There is an apparatus 8 composed of an apparatus 7 that displays an image of the temperature distribution.

Here, the surface strain ε is used as an index of the bending state. The surface strain ε has the following relationship with the bending curvature κ and the thickness t of the material to be corrected.
ε = (t / 2) × κ (1)

As the surface strain ε increases, the plastic heat generation ΔT of the material to be corrected also increases, and the relationship can be obtained experimentally in advance. FIG. 4 shows a graph obtained by experimentally calculating the relationship between the surface strain ε and the plastic heat generation ΔT for SM570 (JIS G3106), which is a structural high-tensile thick steel plate.
The relationship between the surface strain ε and the plastic heat generation ΔT can be arranged in a linear relationship as shown in Equation (2), and the proportional multiplier α may be calculated in advance for each material. In the example of SM570 (JIS G3106), α = 162.5.
ΔT = α × ε (2)
From the above formulas (1) and (2), the bending curvature κ can be calculated by measuring the plastic heat generation ΔT.
κ = ΔT / {(t / 2) × α} (3)

  From the above formula (3), it can be seen that the bending curvature κ in the width direction can be calculated from the temperature distribution in the width direction of the steel sheet 10 measured by infrared thermography. Then, the roll deflection correcting means 5 is adjusted so that the bending curvature κ in the width direction becomes uniform. This makes it possible to ensure uniform correction in the width direction of the material to be corrected.

Moreover, in the roller leveler correction method of the steel plate according to the present invention, it is preferable to predict the correction reaction force of the steel plate 10 and correct based on the obtained predicted value prior to the correction of the steel plate 10. This is because the roll deflection can be corrected more precisely.
Specifically, after setting the correction of roll deflection in accordance with the predicted correction load predicted in advance, at the time of correcting the actual steel sheet 10, by referring to the correction load obtained from the temperature distribution in the width direction, The error with the predicted correction load can be corrected in the deflection correction.

Ｌ：ロール間隔（mm）
Ｍｉ：ｉ番目のロールでの曲げモーメント
Ｐｉ：ｉ番目のロールでの矯正反力 The method for predicting the straightening reaction force of the steel sheet 10 may be a known method, and is not particularly limited.
For example, the calculation formula described in the Japan Society for Technology of Plasticity, “Correcting” (published first edition in 1992), Corona, P81 can be used. This document describes means for calculating the correction reaction force Pi of the i-th roll by the following equation.

L: Roll interval (mm)
Mi: Bending moment at the i-th roll Pi: Correction reaction force at the i-th roll

(Roller leveler straightening machine)
As shown in FIG. 2, the roller leveler straightening machine according to the present invention includes a plurality of straightening rolls 1U and 1D provided in a zigzag pattern along the pass line of the steel sheet, and the steel sheet 10 formed by the straightening rolls 1U and 1D. And a plurality of roll deflection correcting means 5 for correcting the deflection in the width direction.

  The roller leveler straightening machine according to the present invention further includes temperature distribution measuring means 8 for measuring the temperature distribution in the width direction of the steel sheet 10 after passing one or more straightening rolls 10 as shown in FIG. The roll deflection correction means 5 performs correction according to the measured temperature distribution. By measuring the temperature distribution in the width direction of the steel plate 10 after being subjected to bending, it becomes possible to accurately grasp the processing failure due to roll bending actually occurring in the steel plate, so the roll can be made with high accuracy. The deflection can be corrected. As a result, it is possible to suppress the residual stress caused by the roll deflection from being generated in the steel sheet, and to prevent the occurrence of warpage or bending during the cutting process in the subsequent process.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

(Example of the present invention)
The steel plate 10 was corrected using the roller leveler straightening machine 9 having the configuration shown in FIGS. 2 and 3. The roller leveler straightening machine 9 has nine straightening rolls 1U and 1D (four upper straightening rolls 1U and five lower straightening rolls 1D), a diameter of 280 mm, and a roll body length of 5500 mm. In addition, the roller leveler straightening machine 9 includes a hydraulic reduction mechanism in the main reduction device, and has a function of dynamically compensating for fluctuations in the chock position due to the correction reaction force in the plate. As the roll deflection correction means 5, a wedge-shaped adjusting device is provided that can control the width-direction reduction amount of the upper roll 1 </ b> U. In addition, as shown in FIG. 1, the roller leveler straightening machine 9 has an infrared thermography device 8 installed immediately below the first upper roll 1U from the entry side, and measures the surface temperature of the steel plate 10 on the roll. Then, the bending curvature is calculated in the width direction.
For the steel plate 10 to be straightened, SM570 (JIS G3106) having a thickness of 15 mm, a width of 3000 mm, and a length of 10000 mm was used. Several steel plates with the same dimensions and standards were prepared, and the tests were carried out with different correction conditions.

As the reduction conditions for correcting the steel sheet S, the entrance side reduction amount was set to 2.9 mm and the exit side reduction amount was set to 0 mm according to a reduction setting method that has been conventionally performed.
The predicted value of the correction reaction force was 654 tons, and the measured correction load was 710 tons. The predicted value of the straightening reaction force was calculated from the formula described in P81 of “Correcting” published by Corona, edited by the Japan Society for Technology of Plasticity.

In the example of the present invention, the amount of reduction, which is the amount of deflection correction by the roll deflection correction means 5, is first set so that the entry side and exit side reduction amounts at the roll end portion are 2.9 mm and 0 mm, respectively. The deflection distribution of the roll corresponding to the straightening load at 654, that is, 654 tons was calculated, and the adjustment amount of the wedge-shaped reduction device (roll deflection correction means 5) in the width direction was determined. Then, along with the start of correction of the steel sheet 10, the surface temperature change of the steel sheet S is measured by infrared thermography, and the bending curvature is calculated from the temperature according to the equation (3). In the equation (3), t = 15 and α = 162.5.
κ = ΔT / {(t / 2) × α} (3)
FIG. 5 shows the width direction distribution of the surface temperature change of the steel sheet 10 measured by infrared thermography, and FIG. 6 shows the width direction distribution of the bending curvature of the steel sheet 10 calculated from the above equation (3).

Thereafter, the bending correction amount of the roll bending correction means 5 was changed according to the bending curvature distribution calculated based on the measurement result by thermography so that the bending curvature distribution became uniform in the width direction.
FIG. 7 shows the bending curvature distribution of the steel sheet 10 after the roll deflection correction by the roll deflection correction means 5. Note that the bending curvature distribution in FIG. 7 is also calculated based on the width direction distribution of the surface temperature change of the steel sheet 10 measured by thermography.

From the results of FIG. 7, it can be seen that the bending curvature distribution of the steel sheet 10 after roll deflection correction is uniform in the width direction, and the bending process is performed in the width direction by the straightening roll.
Note that the bending curvature before roll deflection correction was larger at both ends in the width direction because the corrective load was larger than originally assumed, so the roll deflection increased, and the straight roll pressure was reduced at the center in the width direction. It is estimated that the amount is relatively small compared to the end.

(Comparative example)
Prediction value of the correction reaction force calculated from the formula described in P81 of “Correction” published by the Japan Society for Technology of Plasticity and Corona Co., Ltd., using a roller leveler straightening machine 9 that does not include the infrared thermography device 8 of the present invention example. Based on the above, the steel sheet was corrected under the same conditions as in the example of the present invention except that the correction by the roll deflection correction means 5 was performed.

As a result, the width direction distribution of the bending curvature of the steel sheet 10 was shown in the form as shown in FIG. That is, in the comparative example, the temperature distribution in the width direction of the steel sheet 10 is measured by the thermography of the example of the present invention, and the state is the same as before the correction based on the temperature distribution is performed.
Therefore, it was found that the roller leveler correction method for the steel sheet of the present invention example can eliminate the non-uniformity of bending due to roll deflection and suppress the residual stress of the steel sheet, as compared with the conventional method. .

  According to the present invention, it is possible to accurately grasp the processing state in the width direction of the steel sheet and perform appropriate correction of the correction roll, thereby suppressing the occurrence of residual stress in the steel sheet due to roll bending, and the steel sheet in the subsequent process. It is possible to provide a roller leveler straightening method for a steel sheet that can prevent the occurrence of warping and bending at the time of cutting, and a roller leveler straightening machine used in the straightening method.

1U, 1D straightening roll 2U, 2D backup roll 3U, 3D frame 4 rolling-down means 5 roll deflection correcting means 6 imaging camera 7 image display device 8 temperature distribution measuring means, infrared thermography device 9 roller leveler straightening machine 10 steel plate

Claims (4)

A steel plate using a roller leveler straightening machine comprising a plurality of straightening rolls arranged in a staggered manner along the pass line of the steel plate, and a plurality of roll deflection correcting means for correcting the deflection of the straightening roll. In the roller leveler correction method,
A method for correcting a roller leveler of a steel sheet, comprising: measuring a temperature distribution in a width direction of the steel sheet after passing through one or more straightening rolls, and performing correction by the roll deflection correcting means according to the measured temperature distribution.   The method for correcting a roller leveler of a steel sheet according to claim 1, wherein the temperature distribution in the width direction of the steel sheet is measured by infrared thermography.   Prior to the correction of the steel sheet, the correction reaction force of the steel sheet is predicted, and correction is performed based on the obtained predicted value. The roller leveler correction method for a steel sheet according to claim 1 or 2. A roller leveler straightening machine comprising a plurality of correction rolls provided in a zigzag pattern along the pass line of the steel sheet, and a plurality of roll deflection correction means for correcting the deflection of the correction rolls,
It further comprises temperature distribution measuring means for measuring the temperature distribution in the width direction of the steel sheet after passing one or more of the straightening rolls, and performing correction by the roll deflection correcting means according to the measured temperature distribution. Characteristic roller leveler straightening machine.

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