JP2005211960A - Method for manufacturing hot rolled steel strip and winding device for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a hot rolled steel strip which can prevent the edges of the steel strip across width from waving when the steel strip comes down to room temperature after being hot rolled and wound, and can improve the flatness of the steel strip, and to provide a winding device for the steel strip. <P>SOLUTION: In the process of coiling the hot rolled steel strip, the amount of the expansion or contraction of a mandrel diameter during winding is measured, and the steel strip is wound, while the position of the mandrel diameter is controlled to make the initial winding diameter constant, on the basis of the measured amount so that the mandrel diameter does not contract after the steel strip is tightly coiled during winding. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a hot-rolled steel sheet and a winding device for the same, and in particular, unwinding at the foremost front part (length direction tip: coil inner peripheral part) when the hot-rolled steel sheet is wound in a coil shape. The present invention relates to a method for manufacturing a hot-rolled steel sheet and a winding device for the same that can prevent the problem that the flatness of the steel sheet deteriorates due to the generation of ear waves and the like.

Conventionally, in the production of hot-rolled steel sheet, the steel sheet is wound into a coil shape through hot rolling and cooling, but the steel sheet wave (ear wave) when rewinding after further cooling to a temperature at which the next process can be performed. It might be a problem. For such ear waves, a steel plate wave is overcompensated by generating a slight steel plate wave (medium wave) in the center in the width direction with a hot rolling mill or a hot straightening machine after hot rolling. And how to prevent it was known. However, if the steel plate wave control is not sufficient even with this method, it is necessary to perform correction processing separately in a refining process.
For this reason, various methods for preventing the steel plate wave have been proposed so far.

For example, in Patent Document 1, as a method for controlling the flatness shape of a metal strip, in a method of correcting the flatness by installing a tension leveler after winding the metal strip before winding the metal strip, just before the final roll of the tension leveler. The shape of the metal strip is a shape detection roll that can measure the distribution of tension in the width direction of the metal strip, and the flatness of the metal strip is changed by changing the push amount setting of the shape detection roll based on the flatness information of the metal strip from the shape detection roll. An invention for controlling the shape is disclosed.
Moreover, in patent document 2, it extends from the flatness information by the flatness meter installed in the exit side of a hot finishing rolling mill, and the flatness information before winding measured by the flatness meter installed in front of the winding machine. An invention is disclosed in which the flatness shape of a metal strip is controlled by obtaining the rate difference and feeding it back to the vendor control of the finishing mill. Further, in Patent Document 2, an invention is disclosed in which an ear wave shape is prevented by measuring a temperature distribution after a hot rolling mill and performing temperature equalization using a heating device such as an edge heater.
JP 05-269527 A JP-A-10-263658

However, in the flatness shape control method of the metal strip described in Patent Document 1 or Patent Document 2 described above, the reference information for flatness shape control is the flatness or elongation strain difference, and the temperature distribution information over the plate width direction. It is not based on. Normally, most materials are wound up at a high temperature to make the material, and for this reason, the temperature distribution in the plate width direction has a temperature deviation in which the plate end is lower than the center. Occur. Therefore, even if the elongation strain difference is eliminated by such a conventional method at the time of winding, the temperature deviation at the time of winding causes a difference in the amount of thermal shrinkage until it reaches room temperature, and remains as thermal stress. Therefore, the flatness cannot be improved.
In addition, the flatness control method described in Patent Document 2 is not a measure against a factor that causes a wave shape to deteriorate after a winder described later, and thus is not sufficient as a measure against flatness.

  Therefore, the present invention advantageously solves the above-mentioned problems of the prior art, and prevents the ear waves generated at the edge in the width direction of the steel sheet after cooling with respect to the rolling front part of the hot-rolled steel sheet. An object of the present invention is to provide a method of manufacturing a hot-rolled steel sheet and a winding device thereof that can improve flatness.

The present invention has been made to solve the above-described problems, and the gist thereof is as follows.
(1) When winding a hot-rolled steel sheet into a coil shape with a mandrel, the expansion / contraction state of the mandrel diameter during winding is measured. A method for producing a hot-rolled steel sheet, characterized in that the winding is continued in such a manner that the mandrel diameter after the tightening force is balanced maintains a constant diameter that does not further decrease.
(2) The method for producing a hot-rolled steel sheet according to (1) above, wherein a gap between the wedge shaft and the segment of the mandrel that is waiting for winding is set to 0 to 0.5 mm.
(3) The steel sheet width edge is heated either at the finish rolling mill entry side of the hot rolled steel sheet, between the rolling mill stands, or at the exit side, or in addition to this edge heating, the steel sheet at the finish rolling mill entry side. The method for producing a hot-rolled steel sheet according to (1) or (2) above, wherein the temperature deviation between the steel sheet edge part and the center part is reduced.
(4) A hot-rolled steel sheet winding device, wherein a check valve circuit and / or a relief valve is installed on the expansion side of the cylinder in the hydraulic circuit of the mandrel expansion / contraction cylinder.
(5) Winding of hot-rolled steel sheet according to (4) above, characterized in that the gap between the segment and the wedge shaft is eliminated by integrally manufacturing the wedge shaft and the segment of the mandrel or fastening with a bolt. apparatus.

According to the present invention described above, the following effects can be expected.
(a) According to the winding method of the present invention described in claim 1, it is possible to prevent the deterioration of the shape caused by the ear wave caused by the reduction of the mandrel diameter during winding in the coiler, and to keep the mandrel diameter constant. Therefore, stable operation of the steel plate shape is possible.
(b) In the present invention described in claim 2, when the segment and the wedge shaft are configured separately, the shape deterioration caused by the gap is prevented by appropriately managing the gap between the wedge shaft and the segment of the mandrel. Can be prevented.
(c) In the present invention according to claim 3, in addition to the deterioration of the shape caused by the mandrel reduction, the thermal distortion caused by the temperature deviation can be made uniform, so that the deterioration of the shape can be further prevented.
(d) According to the present invention as set forth in claim 4, it is possible to improve the mandrel expansion force by simply modifying an existing coiler or by providing a check valve and / or a relief valve in the hydraulic circuit. Can contribute to stable operation.
(e) According to the present invention described in claim 5, the mandrel cylinder expanded by centrifugal force is integrally manufactured or fastened with a bolt, thereby further preventing diameter reduction due to a gap between the segment and the wedge. It becomes possible to prevent shape deterioration. Furthermore, the replacement cycle defined by the wear of the segment jaws is integrated, so that the lifetime can be extended by 10 times or more.

The present inventors conducted an actual machine experiment as a preliminary study in order to grasp the mechanism of deterioration of flatness of a steel sheet in the manufacturing process of the hot-rolled steel sheet.
FIG. 1 is a schematic diagram of manufacturing equipment after a finish rolling mill in a manufacturing process of a hot-rolled steel sheet that has been subjected to preliminary examination. The hot-rolled steel sheet 1 passes through a finish rolling mill 2 and is rolled to a predetermined production size. The temperature distribution in the width direction is measured with a thermometer 3 and is passed through a run-out table (ROT) 4 to make a predetermined material. For this purpose, it is cooled to a predetermined plate temperature by the ROT cooling device 5 and wound by a coiler (winding machine) 6 in a coil shape.

  An edge heater 7 for selectively heating the edge portion of the steel plate 1 is installed on the entry side of the finish rolling mill 2. A tunnel furnace 8 can be installed separately from the edge heater 7 on the rolling mill entrance side. The tunnel furnace 8 is, for example, a tunnel-shaped furnace along a plate pass line, and is an apparatus that can heat a steel plate by heating means (such as a burner) disposed inside.

Since the edge heater 7 is for compensating for the temperature drop of the steel sheet edge after winding the steel sheet, the edge heater 7 is not limited to the entrance side of the rolling mill, but the position inside the rolling mill row (between the stands) or the exit side of the rolling mill. The bar heater device may be installed in place of the tunnel furnace.
The tunnel furnace or bar heater device was also considered for the purpose of uniformly heating the steel plate to reduce the temperature deviation between the edge portion and the center portion.

  Next, the state of starting the winding operation in the coiler will be described with reference to FIG. The coiler 6 bends the steel plate 1 with a pinch roll 9 and passes through the chute 10. There, the wrapper roll 12 is closed (contact with the mandrel) before the tip of the steel plate 1 reaches the mandrel 11, and is waiting while rotating at a speed several percent higher than the steel plate speed. When the steel plate 1 reaches the mandrel 11 and the wrapper roll 12, the steel plate 1 is wound while being sandwiched. As will be described later, the diameter of the mandrel 11 can be enlarged or reduced by a hydraulic cylinder. When the coil is wound by a predetermined number of turns, the mandrel 11 starts to expand, and the diameter increases when the expansion force and the coil tightening force are balanced. And the wrapper roll 12 is opened and moves away from the coil.

The structure of the mandrel used in the preliminary study as a representative example of the structure of the mandrel will be described with reference to FIG. The mandrel is basically composed of a mandrel segment 13, a wedge 14, a slide rod 15, and a wedge shaft 16 in order to expand and contract the diameter during the winding operation, and slides between the wedge shaft 16 and the slide rod 15. The cylinder part 17 is comprised. By sliding the wedge 14 with this sliding hydraulic cylinder, the mandrel segment 13 slides in the radial direction in the expansion / contraction direction along the gradient applied to the wedge shaft 16.
Further, as shown in FIG. 4, this mandrel has a gap at the gap A portion between the segment flange portion 18 and the wedge jaw portion 19, and when it rotates, the mandrel has a mechanism in which the gap at the A portion disappears due to centrifugal force. Reference numeral 20 denotes a set of segments and wedges, and these four sets constitute a mandrel.

The temperature of the plate to be wound varies depending on the material, but is in the range of about 100 to 800 ° C. The flatness, which is a problem in the present invention, can be heard at the edge when unwinding when the coil temperature is lowered to room temperature. The flatness in the case of causing a wave-like out-of-plane deformation called a wave. The flatness deterioration that occurs in many hot-rolled steel sheets is ear waves, and the present invention is intended to improve the ear waves. In other cases, if the coiler shaft or pinch roll has a convex crown shape and the winding tension is abnormally large, a medium wave may be generated at the center instead of the edge in the width direction. This is outside the scope of the present invention.
FIG. 5 shows the definition of the steepness indicating the degree of ear waves. Divide the wave height H of the steel plate edge portion by the wave pitch L, multiply by 100, and express it in percentage.

The corrugated shape of the plate can be interpreted as a buckling strength against compressive stress acting perpendicularly to the cross section of the plate C (cross section perpendicular to the rolling direction) and a large deflection problem after buckling.
In this preliminary study, residual stress occurs due to temperature unevenness on the exit side of the rolling mill, and the shape deteriorates particularly when compressive stress is generated due to large thermal distortion due to the temperature deviation of the steel sheet width edge and the center. I found out. The result is shown in FIG. Therefore, as a measure for equalizing the temperature, the present inventors performed heating by the edge heater 7 installed on the entrance side of the rolling mill as shown in FIG. .

However, the middle part of the hot-rolled steel sheet, which was tensioned by winding, was improved by eliminating the temperature deviation, but the front part (coil inner periphery) where tension was not applied was improved even if there was almost no temperature deviation. It turned out that it might not disappear completely. The present inventors have found that the following mechanism exists as a cause of deterioration of the shape of the inner peripheral portion of the coil other than the temperature deviation, while studying the cause.
(1) When the coil is wound with a constant tension by a winder, the tension at the inner periphery of the coil near the mandrel is in a compressive stress state.
(2) Furthermore, since the steel plate generally has a plate crown having a convex central portion in the width direction, a greater compressive stress is generated in the width center portion of the coil inner peripheral portion than in the edge portion.
(3) In actual operation, the mandrel is waiting for the steel plate to come in the standby diameter, and if the steel plate is wound by the predetermined number of turns, it will be further expanded (over-expanded), but the mandrel will be expanded. When the pressing force of the cylinder and the surface pressure from the coil balance, the expansion stops, and the mandrel diameter remains constant. However, in reality, the tightening force becomes excessive due to the influence of the tension during winding, the plate thickness, the frictional force between the steel plates, etc. Gradually shrink. Due to such a reduction in the diameter of the mandrel, the steel plate on the inner periphery of the coil has to handle the compression tightening force that the mandrel should originally receive.
(4) If the above phenomenon overlaps, compressive stress will increase at the inner circumference of the coil, especially in the center of the width, and it will be operated in a hot state, so compression plastic deformation and creep deformation will occur at the center of the width. Will occur. As a result, the central portion of the width apparently shrinks, and an ear wave is generated.

  FIG. 7 shows a situation where the mandrel reduction phenomenon is captured. The horizontal axis in FIG. 7 is the time from the start of coil winding. The vertical axis indicates the mandrel diameter (radial distance on the outer surface of the segment) converted from the stroke amount of the cylinder installed in the expansion / reduction cylinder. First, the mandrel starts winding, and after several turns, overexpansion is performed, and once the winding tightening force and the mandrel expanding force are balanced, the expansion is stopped. Thereafter, it can be seen that the diameter becomes smaller than the point a as the number of turns of the coil increases with time and the tightening force of the inner periphery of the coil increases. It has been found that the tightening amount during winding (mandrel diameter reduction amount) is not constant but varies from coil to coil.

  As described above, in addition to the temperature deviation after rolling as a factor for promoting the deterioration of the shape, it has been shown that there is a mandrel reduction phenomenon. FIG. 8 shows the relationship between the mandrel diameter reduction amount (MD reduction amount) due to the tightening of the mandrel investigated by the present inventors and the steepness of the ear wave. As a result, this is due to the lack of expansion of the original mandrel, but in addition, it can also occur mechanically. The contents are shown below.

  In the rotation before the steel plate bites into the mandrel, it is expanded by the gap between the segment flange portion and the A portion of the wedge jaw portion by centrifugal force. Then, after several turns, the mandrel began to expand, the back of the segment and the top of the wedge contacted, and when the tightening force and the expansion force were balanced, the cylinder stroke installed on the expansion / contraction cylinder stopped, Judgment is made and the control shifts to constant diameter control. In reality, however, there are four combinations of segments and wedges. Not all mandrel segments are necessarily enlarged in diameter and contact the back of the segment and the top of the wedge. Then, it will wind up in the state where the gap is generated. Then, if the coil continues to overlap, the tightening force increases, and the mandrel segment shrinks until the back surface and the top of the wedge come into contact. Even though the apparent mandrel diameter is reduced, this variation is not directly linked to the cylinder stroke, and can be uncontrollable and worsen in shape.

Based on the analysis result of the mechanism of such shape deterioration, in the present invention, in order to improve the shape of the hot-rolled steel sheet, when the hot-rolled steel sheet is wound into a coil shape by a coiler, the coil is wound during winding. After tightening, the winding is continued at a constant diameter so that the mandrel diameter does not further decrease.
In the present invention, the mandrel diameter is measured in order to prevent the mandrel from deteriorating due to the tightening phenomenon during winding of the coil in the coiler winding process, and the mandrel is measured based on the measured value. By sequentially grasping the enlargement / reduction state and controlling it to have a constant diameter, an excessive compressive stress is not reliably generated in the inner peripheral portion of the coil.

  Normally, the enlargement / reduction mechanism of the coiler mandrel is configured by a hydraulic circuit, and the enlargement / reduction operation is performed by a hydraulic cylinder. As shown in FIG. 3, the wedge is slid by the hydraulic cylinder and the mandrel is operated. Move the segment in the radial direction to expand or contract the mandrel. If there is a problem that coil winding tightening occurs in the current apparatus, it can be dealt with by changing the coiler based on the present invention. That is, when the current coiler does not have enough mandrel pressing force, it is desirable to increase the expansion force by expanding the rod area of the cylinder. In addition, even if the wedge angle of the mandrel is changed (for example, the angle is reduced), the same effect can be obtained, which is a desirable mode. In addition, the coil winding phenomenon can be similarly solved by installing a check valve circuit and a relief valve on the enlarged side of the cylinder immediately after winding. These operations may be performed alone or in combination of two or three operations.

Next, in the present invention, the influence of the reduction in mandrel diameter, which cannot be detected by the cylinder stroke due to the gap between the wedge shaft and the segment, can be minimized by managing the gap in the range of 0 to 0.5 mm. The reason for maintaining the gap in the range of 0 to 0.5 mm is that in FIG. 8, it is necessary to reduce the mandrel reduction amount to 0.5 mm or less in order to reduce the steepness to 1% or less. is there.
Further, in the present invention, after winding the coil during winding, winding is performed with a constant diameter so that the mandrel diameter is not further reduced, and the temperature deviation between the steel plate edge portion and the center portion is reduced, thereby further flattening. In order to improve the degree, it is desirable to heat the steel sheet width edge portion at the entry side, between the stands, and the exit side of the hot rolling steel sheet finish rolling mill. In addition to this, it is desirable to install a tunnel furnace or bar heater device on the entrance side of the finish rolling mill to uniformly heat the steel sheet, in order to promote elimination of temperature deviation.

Examples of the present invention will be described below. The edge heater 7 installed on the entry side of the finishing mill 2 in FIG. 1 uses the width direction thermometer 3 on the exit side of the rolling mill so that the temperature at the 20 mm width edge is the center temperature. The temperature was controlled to be within ± 5 ° C. (in some examples, a condition for installing the tunnel furnace 8 on the entrance side of the rolling mill was also added).
In order to improve the coil tightening force, the original pressure of the operating hydraulic circuit of the mandrel is changed from 15 MPa to 17 MPa, the rod area of the expansion / contraction cylinder is doubled, and the wedge angle of the wedge shaft is further reduced by 1 deg. Thus, the frictional force in the reduction direction of the cylinder due to the tightening was improved, and the control was made to keep constant while measuring the change of the mandrel diameter so that the tightening force was balanced and the mandrel diameter was not reduced. In addition, since the installation of the check valve has a function of forcibly preventing the diameter reduction due to the tightening of the coil, an embodiment in which the check valve is replaced with the check valve instead of the constant mandrel diameter control is also added. In addition, the mandrel with an integrated segment was also manufactured and operated.

As a result, in the examples based on the present invention, the incidence of ear waves with a steepness of 1.0% or more was 0 out of 1000 coils. On the other hand, as a comparative example, when the same temperature control as described above was performed and reduction during mandrel winding was allowed, the incidence of ear waves with a steepness of 1.0% or more was 30 out of 1000 coils. It was. When the mandrel was allowed to be retracted without temperature control, the incidence of ear waves with a steepness of 1.0% or more was 300 out of 1000 coils.
From the above, it can be seen that the application of the present invention prevents the generation of ear waves in the steel sheet, and makes it possible to obtain a steel sheet with good flatness.

It is a figure which shows typically the manufacturing process of the hot-rolled steel plate used in the preliminary examination before making this invention, and the Example of this invention. It is a figure which illustrates the structure of a coiler typically. It is a figure explaining the outline of the structure of a mandrel with an axial sectional view. It is a figure explaining the clearance gap produced by the structure of a mandrel with sectional drawing perpendicular | vertical to an axis | shaft. It is a figure for demonstrating the definition of the steepness degree showing the grade of an ear wave. It is a figure which shows the relationship between the width direction deviation of the finishing mill delivery side temperature obtained by the preliminary examination until this invention is made, and steepness. It is a figure which shows an example which measured the diameter reduction phenomenon during mandrel winding. It is the figure which showed the relationship between the amount of diameter reduction of a mandrel and the steepness in the actual operation obtained in the Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steel plate 2 Finish rolling mill 3 Thermometer 4 Hot run table (ROT)
5 ROT cooling device 6 Coiler (winding machine)
7 Edge heater 8 Tunnel furnace or bar heater device 9 Pinch roll 10 Chute 11 Mandrel 12 Wrap roll 13 Segment 14 Wedge 15 Slide rod 16 Wedge shaft 17 Slide cylinder part 18 Segment flange part 19 Wedge jaw part 20 One set of segment and wedge A gap

Claims (5)

  When winding a hot-rolled steel sheet in a coil shape with a mandrel, measure the expansion / reduction state of the mandrel diameter during winding, and based on the measured value, the force for expanding the mandrel and the force for winding the coil at the beginning of winding A method for producing a hot-rolled steel sheet, characterized in that winding is continued so as to maintain a constant diameter at which the mandrel diameter after balancing is not further reduced.   The method for producing a hot-rolled steel sheet according to claim 1, wherein the gap between the wedge shaft and the segment of the mandrel that is waiting for winding is set to 0 to 0.5 mm.   Heat the steel sheet width edge part at the entrance side of the finish rolling mill, between the rolling mill stands, and the exit side of the hot rolled steel sheet, or in addition to this edge heating, make the steel sheet uniform on the entrance side of the finish rolling mill The method for producing a hot-rolled steel sheet according to claim 1 or 2, wherein heating is performed to reduce a temperature deviation between the steel sheet edge part and the center part.   A hot-rolled steel sheet take-up device, wherein a check valve circuit and / or a relief valve is installed on the expansion side of a cylinder in a hydraulic circuit of a mandrel expansion / contraction cylinder.   5. The hot-rolled steel sheet take-up device according to claim 4, wherein a gap between the segment and the wedge shaft is eliminated by integrally manufacturing the wedge shaft and the segment of the mandrel or fastening them with bolts.

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