JPH091240A - Method for preventing deviation in surface temperature of thick steel plate - Google Patents

Abstract

PURPOSE: To lessen the deviation in the surface temp. in the transverse direction of a thick steel plate which occurs at the time of accelerated cooling by controlling the rolling reduction of plural pieces of the straightening rolls disposed in a hot straightening machine by roll screw down devices on plural pieces of these straightening rolls by surface temp. distribution patterns at the time of straightening the thick steel plate with hot straightening and by regulating the surface roughness of the thick steel plate. CONSTITUTION: The roll screw down devices 6 which are insertable and removable in a direction perpendicular to the axial direction of the straightening rolls disposed above upper backup rolls 4 in accordance with the information from the measured quantity of the surface temp. of the steel plate are moved and inserted to the corresponding points from the progressing direction of the thick steel plate, by which upper work rolls 2 are pressed from above by the roll screw down devices 6 and the axial bend of the work rolls are utilized. As a result, the surface roughness of the thick steel plate of the required points is previously roughened and the cooling effect of the parts where the surface roughness is high is eventually intensified as a result of controlled cooling is executed in next stage and the cooling of these parts is intensified. The temp. of the high-temp. parts is lowered and the surface temp. over the entire part of the steel plate is thus made uniform.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing surface temperature deviation of a thick steel sheet, which reduces surface temperature deviation in the width direction of the thick steel sheet during accelerated cooling of the thick steel sheet.

[0002]

2. Description of the Related Art The surface temperature of a rolled thick steel sheet does not always maintain a uniform temperature distribution on the entire surface of the thick steel sheet depending on the operating conditions such as rolling and cooling during rolling. The thick steel plate that they have is manufactured.

For example, a temperature deviation of a thick steel plate is caused by a cooling rate difference, and when a typical example thereof is schematically shown in FIG. 5, a temperature distribution having a low temperature portion 11 is obtained in the thick steel plate. That is, the center cooling in which only the central portion of the thick steel plate has a lower temperature than the peripheral portion of the normal temperature 10 (Fig. 5a), and conversely, the edge cooling in which both ends of the thick steel plate have a lower temperature than the central portion (Fig. 5b) Is. The widthwise temperature distribution is roughly 2
1, 22 and the general shape of the temperature distribution in the length direction are as shown in 23 and 24.

The means for detecting the deviation of the temperature distribution on the surface of the thick steel plate is disclosed in Japanese Patent Application No. 6-200 filed previously by the present inventors.
The details can be known by 286.

The outline is that the surface temperature in the width direction of the thick steel sheet moving after rolling is repeatedly scanned and measured, and two-dimensional temperature distribution patterns in the width direction and the length direction of the thick steel sheet are obtained from the measured values, From the results of the two-dimensional temperature distribution pattern in the width direction and the length direction of the thick steel plate, the temperature distribution pattern in the width direction and the length direction of the thick steel plate obtained by the discrete Fourier transform processing based on the trigonometric function waveforms respectively determined, The thickness value in the width direction of the thick steel plate and the amplitude value in the length direction of the thick steel plate are obtained, and the amplitude value in the width direction of the thick steel plate and the amplitude value in the length direction of the thick steel plate are within any of the amplitude value ranges preset for each temperature distribution pattern. By determining that, the temperature distribution pattern of the thick steel plate is automatically determined.

However, even if the surface temperature distribution of the thick steel plate is grasped in this way, an appropriate action for the thick steel plate has not been taken based on the result.

[0007]

Whether or not the surface temperature distribution of the thick steel sheet is optimized has a great influence on the shape of the thick steel sheet after cooling at room temperature, and there are many demands for measures against the surface temperature deviation of the thick steel sheet. It was done. It is an object of the present invention to solve this problem by a very simple method based on a new concept in response to these demands, and to provide a means therefor.

[0008]

The gist of the present invention is to measure the surface temperature in the width direction of a thick steel sheet, recognize the temperature distribution pattern in the width direction of the thick steel sheet from the measured value, From the temperature distribution in the width direction of
Edge cold, divided into the other, according to the surface temperature distribution pattern at the time of straightening the thick steel plate by hot straightening, the straightening roll is rolled down by a roll rolling down device for a plurality of straightening rolls provided in the hot straightening machine. Also, the temperature distribution pattern in the width direction of the thick steel plate and its deviation amount are recognized, and the rolling amount of the straightening roll is controlled by the roll reduction device of the hot straightening machine according to the deviation amount to adjust the surface roughness of the thick steel plate. Especially.

[0009]

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a diagram schematically showing a thick steel plate hot straightening roll machine (hereinafter referred to as a hot straightening machine) when explaining the method of the present invention.
(Partly omitted) The upper part is sent to the hot straightening machine R.
However, several work rolls 2 and 3 are installed at the top and bottom of the hot straightening machine, and the backup roll 4 and
5 is also installed, and the backup roll supports the work roll from the rear side.

Thick steel plates are provided above and below such a hot straightener.
By passing between the work rolls 2 and 3, the shape defects of the thick steel plate, such as selvedges, medium waves, and warp, are corrected.
In the roll straightening method for a thick steel plate, when there is a temperature deviation on the surface of the thick steel plate as described above, the contact amount of the work rolls 2 and 3 that come into contact with a high temperature portion of the surface of the thick steel plate depending on the deviation condition is set. By increasing it, the roughness of the thick steel plate surface in that part is roughened, the heat transfer area of the steel plate surface is expanded, and as a result, the cooling effect in the post process is improved and the part is cooled more than other parts. The amount is strengthened, and the operation is performed so that a uniform temperature distribution is obtained on the entire surface of the thick steel plate.

In order to obtain such a situation, in the present invention, although not shown, based on the information from the measured amount of the steel plate surface temperature, a direction perpendicular to the straightening roll axial direction provided above the upper backup roll 4 is provided. A roll reduction device 6 that can be inserted and removed is moved and inserted into a corresponding position in the traveling direction of the thick steel plate, so that the upper work roll 2 is pressed from above by the roll reduction device 6 to prevent bending of the work roll in the axial direction. By using it, the surface roughness of the thick steel plate at the required location is made rough, and as a result of controlled cooling in the next step, the cooling effect of the part with rough surface roughness is strengthened, and the cooling of that part is enhanced. Then, the high temperature portion is cooled, and the surface temperature of the steel sheet as a whole becomes uniform.

[0012] Fig. 2 shows the normal condition for correcting thick steel plates (Fig. 2a).
And the condition of straightening thick steel plate when the edge is cold (Fig. 2b).
In normal straightening, the roll reduction device is inserted in equal amounts in both the central portion and both side portions, so both the backup roll and the straightening roll are kept flat (Fig. 2a). On the other hand, in the case of edge cooling, the center portion is higher in temperature than both side portions, so it is necessary to cool the center portion, and the roll reduction device 6b at the center portion is hot-corrected by the roll reduction devices (6a, 6c) at both sides. It can be seen that the diameter of the roll reduction device 6b is larger than the other 6a and 6b because it is inserted deeply inside the machine. As a result, the central portions of both the upper backup roll 4 and the upper work roll 2 are pushed in from both sides (FIG. 2b). Therefore, the contact area and contact pressure of the work roll 2 at the central portion of the thick steel plate are increased, the roughness of the surface of the thick steel plate is increased, and the cooling capacity is strengthened.
The temperature drop in the next step is performed smoothly.

In this case, the insertion / extraction amount of the roll reduction device is controlled according to the deviation amount of the surface temperature of the thick steel plate, and the operation is performed so that a uniform temperature distribution can be obtained on the entire surface of the thick steel plate. This temperature deviation amount determines the adjustment according to the thick steel plate surface temperature information measured before straightening by the hot straightening machine,
It is best to adopt the above-mentioned measurement method of the present inventors and adjust based on the result.

In the present invention, an example in which the number of roll reduction devices is three has been described, but the number is not limited to this, and the number of roll reduction devices in the hot straightening machine depends on the thick steel plate to be straightened. Although depending on the width, 3 to 5 pieces are suitable in view of the surface temperature deviation of the thick steel plate. That is, if it is less than 3, it is impossible to deal with both center cooling and edge cooling.
Whatever the condition of the center cooling and the edge cooling is, it can be dealt with by selecting the movable roll reduction device. Further, although not described above, local streak cooling often occurs in the form of streaks in the rolling direction of the thick steel plate. In such a case, it is also possible to prevent the temperature deviation due to the streaking by moving the roll pressure reducing device at another location corresponding to the streak portion.

Furthermore, it is preferable that the number of roll reduction devices is large because it can cope with various situations, but from the viewpoint of equipment, the equipment cost increases correspondingly, which is not practical.
The limit is about five. Further, the shape of the roll pressing device is not limited to the shape shown in FIG. 1, but it is preferable that the force is optimally applied to the backup roll, and the conical shape from the insertion / extraction surface from the outside. A shape of a body or a pyramid is suitable, and the pressing force can be transmitted arbitrarily to the straightening roll, which is preferable. Further, if the tip portion is a truncated cone or a pyramid, it is advantageous in manufacturing and operation.

Furthermore, a rectangular parallelepiped or a columnar shape may be provided outside the cone or the like. In this case, for example, a descending device such as a screw system for pushing down the rolling down device is provided on each rolling down device of the rectangular parallelepiped roll. It can be operated to roll down the straightening roll. An example of these shapes is schematically shown in FIG. 3, where (a) is a pyramid, (b) is a cone, (c) is a truncated pyramid, and (d) is a truncated cone. e)
Is a rectangular parallelepiped and (f) is a cylinder.

FIG. 4 shows the relationship between the roll reduction amount, which is the difference between the center roll reduction amount and the edge roll reduction amount of the hot straightening machine, and the widthwise temperature deviation after controlled cooling of the material of this method. It is the figure which showed. Points A, B, and C in the figure correspond to Table 1 of the embodiment described below. Even if the temperature deviation in the width direction immediately before the controlled cooling is almost the same, the temperature after cooling is changed by changing the roll reduction amount. It is possible to control the deviation.

Although various explanations have been given for the roll reduction device in the present invention, in the hot straightening machine, an existing roll bending device is installed for adjusting the thick steel plate crown when the plate width is changed. Therefore, when the roll bending device can be used as it is or after being modified, the roll bending device can be utilized.

[0019]

EXAMPLES Table 1 shows an example (A) in which the present invention was carried out and a comparative example (B, C) in which proper control was not carried out. In the example (A), the surface temperature of the thick steel plate before the hot straightening has a tendency that the edge temperature is 18 ° C. lower than the central part of the steel plate and there is a tendency for edge cooling, but the temperature deviation is In order to make the temperature uniform, the roll reduction device was operated, the roll reduction amount was controlled to 1.7 mm, hot straightening was performed, and control cooling was performed. As a result, the temperature of the end portion was 11 ° C. higher, and the center temperature tended to be slightly cold. In the comparative example (B), the surface temperature of the thick steel plate before hot working has a tendency that the edge temperature is 22 ° C. lower than the central part of the steel plate and there is a tendency for edge cooling, but the roll reduction amount for hot working is When it was set to 4.8 mm, straightening was performed, and control cooling was performed, the surface temperature of the thick steel plate was
The edges were 95 ° C. higher than the center cooling, and in Comparative Example (C), the surface temperature of the thick steel sheet was 18 ° C. lower than the center of the steel sheet before the hot straightening, and slightly edge cold. However, the roll reduction amount by the hot straightening machine is -1.0.
After setting to mm, straightening was carried out and control cooling was carried out. As a result, the surface temperature of the thick steel plate was 55 ° C. lower at the edges than at the center of the steel plate.

[0020]

[Table 1]

In the roll reduction device of this embodiment, since three rolls can be inserted / removed with respect to the work roll width, the roll reduction device 6b in the central portion and the side roll reduction devices 6a and 6c can be inserted. The thickened steel plate was straightened by increasing the insertion amount of 6b for the steel plate with edge cooling. The center cold-rolled steel sheet was subjected to the reverse operation. As described above, the temperature deviation of the surface temperature of the thick steel plate after controlled cooling was eliminated, and a uniform temperature distribution was obtained by the straightening effect of the hot straightening machine. Further, the flatness of the thick steel plate was naturally ensured, and a normal thick steel plate was obtained. On the other hand, in the comparative example, the roll bending by the hot straightening machine was performed without appropriate control corresponding to the example, but the deviation was not eliminated because the amount was not appropriate.

[0022]

According to the present invention, by controlling the roll reduction by the hot straightening machine, it is possible to eliminate the deviation of the surface temperature of the thick steel plate which has been conventionally desired to be solved with a simple device. It is an epoch-making invention that can be implemented easily from both the aspect of operation and the aspect of operation, and its effect is extremely excellent, and it is extremely important to contribute to industrial development.

[Brief description of the drawings]

FIG. 1 is an overall explanatory view of the present invention schematically shown for understanding the principle of the invention.

FIG. 2 is a diagram schematically showing a situation in which a straightening roll is pressed by a roll reduction device.

FIG. 3 is a diagram showing an example of a roll reduction device.

FIG. 4 is a diagram showing a roll reduction amount and a cooling temperature deviation of the hot straightening machine.

FIG. 5 is a diagram showing an outline of a deviation condition of a surface temperature of a thick steel plate.

[Explanation of symbols]

 S thick steel plate R thick steel plate hot straightening roll machine 1 transport roll 2 upper work roll 3 lower work roll 4 upper backup roll 5 lower backup roll 6 roll reduction device 10 normal temperature part 11 low temperature part 21 center cold, length direction temperature Distribution 22 Edge cooling, lengthwise temperature distribution 23 Center cooling, lengthwise temperature distribution 24 Edge cooling, lengthwise temperature distribution

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kiyoyuki Egusa 1 Nishinosu, Oita-shi, Oita Pref., Nippon Steel Co., Ltd. Oita Works (72) Inventor, Shinto 1st place Nishinosu, Oita-shi, Oita Pref. Oita Steel Works, Ltd.

Claims (9)

[Claims] 1. A surface temperature in the width direction of a thick steel sheet is measured, a temperature distribution pattern in the width direction of the thick steel sheet is recognized from the measured value, and the thick steel sheet is center-cooled from the temperature distribution in the width direction of the thick steel sheet. , Edge cooling, and the like, and according to the surface temperature distribution pattern at the time of straightening the thick steel plate by hot straightening, the straightening roll is rolled down by a roll rolling down device for a plurality of straightening rolls provided in the hot straightening machine. A method for preventing surface temperature deviation of a thick steel plate, which is characterized by the following. 2. A width direction surface temperature of a thick steel plate is measured, a temperature distribution pattern in the width direction of the thick steel plate and its deviation amount are recognized from the measured value, and the roll of a hot straightening machine is determined according to the deviation amount. The method for preventing surface temperature deviation of a thick steel sheet according to claim 1, wherein the reduction amount of the straightening roll is controlled by a reduction device. 3. The method for preventing surface temperature deviation of a thick steel plate according to claim 1, wherein the surface roughness of the thick steel plate is adjusted by pressing down a straightening roll of a hot straightening machine. 4. The surface temperature of the thick steel sheet according to claim 1, wherein the number of the plurality of roll reduction devices for the straightening rolls provided in the hot straightening machine for the thick steel sheet is 3 to 5. Deviation prevention method. 5. A position in which a plurality of roll reduction devices for a straightening roll provided in a hot straightening machine for thick steel plates have a high temperature based on the temperature distribution in the width direction of the thick steel plates previously recognized. 5. The method for preventing surface temperature deviation of a thick steel sheet according to claim 1, wherein the pressing force of the straightening roll is increased by movably inserting it into the straightening roll portion at a position corresponding to. 6. A device for rolling down a straightening roll, which is provided in a hot straightening machine for thick steel plates, has an axis perpendicular to the straightening roll axial direction and has a conical or pyramidal shape. The method for preventing surface temperature deviation of a thick steel plate according to claim 4. 7. The method for preventing surface temperature deviation of a thick steel plate according to claim 4, wherein the roll reduction device has a truncated cone shape or a truncated pyramidal shape. 8. A plurality of roll reduction devices for a straightening roll provided in a hot-rolling machine for thick steel plates, where the temperature is high based on the temperature distribution in the width direction of the thick steel plates previously recognized. The method for preventing surface temperature deviation of a thick steel plate according to claim 1 or 3, wherein the method is to descend to a portion of the straightening roll corresponding to the above to increase the rolling force of the straightening roll. 9. A plurality of roll reduction devices for a straightening roll, which are provided in a hot plate straightening machine for thick steel plates, have a rectangular parallelepiped or columnar shape having an axis perpendicular to the straightening roll axial direction. The method for preventing surface temperature deviation of a thick steel plate according to claim 4, which is characterized in that.