JPH07241612A - Method for controlling width of steel sheet in hot rolling - Google Patents

Abstract

PURPOSE:To remarkably reduce the deviation between the product width and the target width of a steel sheet by acceleration rolling in a finish rolling stage. CONSTITUTION:By completing the finish rolling of the steel sheet 7 at a temp. higher than the transformation temp. Ar3 and adjusting tension to be imparted to the steel sheet 7 between a coiler 11 and a finishing mill 9, the rate of decrease in the width of the steel sheet 7 is adjusted. The adjustment of the tension to be imparted to the steel sheet 7 is executed by preliminarily determining a tension imparting pattern to the steel sheet 7 for every product size and for every kind of steel based on a width decreasing pattern in the longitudinal direction of the steel sheet 7 and relationship between the tension to be imparted to the steel sheet and the shrinkage amount of width, or executed by measuring the width of the steel sheet 7 just after finish rolling, determining the deviation between this measured value of width and the target thickness of the steel sheet 7 and based on the relationship between the tension to be imparted to the steel sheet 7 and the decrease amount of width of the steel sheet 7 which are predetermined for every product size and for every kind of steel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the sheet width of a steel sheet in hot rolling, and more particularly to a hot rolling method capable of significantly reducing the deviation between the product sheet width of the steel sheet and the target sheet width. The present invention relates to a method for controlling the plate width of a steel plate in.

[0002]

2. Description of the Related Art Hot-rolled steel sheets are manufactured according to a side view showing a manufacturing line in FIG. In FIG. 9, 1 is a heating furnace for heating a slab to a predetermined temperature, 2 is a rough rolling mill including a plurality of horizontal roll rolling mills 3 and vertical roll rolling mills 4, and 5 is a rough rolling mill 2. A finish rolling mill comprising a plurality of horizontal roll rolling mills provided subsequently, 6 is a cooling zone for cooling the steel plate 7 on the hot run table to a predetermined temperature, and 8 is for winding the steel plate 7. Is a coiler.

A slab heated to a predetermined temperature by a heating furnace 1 is roughly rolled by a rough rolling mill 2 and then rolled by a finish rolling mill 5 into a steel plate 7 having a predetermined thickness. Then, the steel plate 7 is cooled by the cooling zone 6 while moving on the hot run table.
It is cooled to a predetermined temperature by and is wound around the coiler 8.

Conventionally, the above-described strip width control of the steel sheet in the hot rolling is performed by the width rolling by the vertical roll rolling machine 4 of the rough rolling mill 2 and the looper provided between the horizontal roll rolling mills of the finish rolling mill 5 (see FIG. This is done by adjusting the tension on the steel sheet between the horizontal roll rolling mills (not shown).

[0005]

However, the above-mentioned conventional technique has the following problems. That is, since the strip width control of the steel sheet in the conventional hot rolling is performed at the rolling stage in the rough rolling mill 2 or the finish rolling mill 5, that is, in the semi-finished product stage of the steel sheet, the strip width is controlled in the finish rolling stage. It was difficult to bring the final product strip width closer to the target strip width due to the problem of strip width decrease due to the temperature rise of the steel sheet due to the accelerated rolling.

Therefore, an object of the present invention is to significantly reduce the deviation between the product sheet width and the target sheet width, regardless of the sheet width reduction accompanying the temperature rise of the steel sheet due to accelerated rolling in the finish rolling stage. Another object of the present invention is to provide a method for controlling the width of a steel sheet in hot rolling.

[0007]

According to the present invention, a heated slab is hot-rolled by a finishing mill into a steel plate having a predetermined plate thickness, and then the steel plate thus hot-rolled to a predetermined plate thickness is , Cooled to a predetermined temperature by a cooling zone following the finish rolling mill, and by winding the steel plate cooled to a predetermined temperature in this manner on a coiler, in producing a steel plate having a predetermined plate thickness and characteristics, In a plate width control method for a steel plate, which reduces a deviation between a product plate width and a target plate width caused by a decrease in the plate width of the steel plate with a temperature rise of the steel plate during finish rolling, at a temperature of Ar ₃ transformation point or higher. It is also characterized in that the finish rolling of the steel sheet is terminated and the tension applied to the steel sheet between the coiler and the finish rolling mill is adjusted to adjust the reduction ratio of the sheet width of the steel sheet. It is.

One of the methods for adjusting the tension applied to the steel sheet between the coiler and the finish rolling mill is as follows. That is,
A strip width reduction pattern in the longitudinal direction of the steel sheet that occurs during finish rolling of the steel sheet is determined in advance for each product size and steel type, and this strip width reduction pattern, and each product size and steel type determined in advance in the steel sheet. Based on the relationship between the tension to be applied and the amount of contraction of the plate width, the tension is applied to the steel plate while the rear end of the steel plate exits the finishing rolling machine after the front end of the steel plate is wound around the coiler. A pattern is obtained in advance for each product size and steel type, and tension is applied to the steel sheet according to the tension application pattern.

Another method of adjusting the tension applied to the steel sheet between the coiler and the finish rolling mill is as follows. That is, the plate width of the steel plate immediately after finish rolling is measured, the deviation between the measured value and the target plate thickness of the steel plate is determined, and the product size and the steel type are determined in advance and given to the steel plate. Based on the relationship between the tension and the amount of contraction of the plate width of the steel plate, tension is applied to the steel plate between the coiler and the finish rolling mill so that the deviation becomes smaller.

The tension applied to the steel sheet between the coiler and the finish rolling mill can be adjusted by controlling the rotation speed of the coiler.

[0011]

It is known that when a steel sheet is cooled with tension applied in its longitudinal direction, the steel sheet shrinks in width at a temperature near the Ar ₃ transformation point. The width shrinkage has a constant relationship with the tension applied to the steel sheet.
Therefore, if the finish rolling of the steel sheet is finished at a temperature of Ar ₃ transformation point or higher and the tension applied to the steel sheet between the coiler and the finish rolling mill is adjusted, the strip width of the steel sheet can be controlled after the finish rolling. It is possible to significantly reduce the plate width deviation from the target plate width due to the temperature increase due to accelerated rolling during finish rolling.

A strip width reduction pattern in the longitudinal direction of the steel sheet that occurs during finish rolling of the steel sheet is obtained in advance for each product size and steel type, and this strip width reduction pattern and each product size and steel type are obtained in advance. Based on the relationship between the tension applied to the steel plate and the amount of contraction of the plate width, the product plate width during which the rear end of the steel plate is taken out from the finish rolling mill after the front end of the steel plate is wound around the coiler. To reduce the deviation between the target plate width and the target plate width, a tension application pattern to the steel sheet is obtained in advance for each product size and steel type, and according to the tension application pattern, if tension is applied to the steel sheet, during finish rolling, The plate thickness deviation from the target plate width due to the temperature rise due to accelerated rolling can be significantly reduced.

The width of the steel sheet just after finish rolling was measured,
The deviation between the measured value and the target plate width of the steel plate is obtained,
Then, previously determined for each product size and steel type, based on the relationship between the tension applied to the steel sheet and the width reduction amount of the steel sheet, in the steel sheet between the coiler and the finish rolling mill, the deviation If tension is applied so that
It is possible to significantly reduce the plate width deviation from the target plate width due to the temperature increase due to accelerated rolling during finish rolling.

The tension applied to the steel sheet between the coiler and the finish rolling mill can be easily adjusted by adjusting the current supplied to the mandrel of the coiler and controlling the rotation speed of the mandrel.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for controlling the width of a steel sheet in hot rolling according to the present invention will be described below with reference to the drawings.

FIG. 1 is a side view showing an embodiment of a plate width control method for steel plates in hot rolling according to the present invention.

In FIG. 1, 9 is a finish rolling mill comprising a plurality of horizontal roll rolling mills, 10 is a cooling zone for cooling the steel sheet 7 on the hot run table to a predetermined temperature, and 11 is the steel sheet 7 A coiler for winding up the coil and a controller 12 for controlling the rotation speed of the coiler 11 to bring the plate width of the steel plate 7 closer to the target plate width, as described later.

The slab heated to a predetermined temperature by a heating furnace (not shown) is roughly rolled by a rough rolling mill (not shown), and then rolled by a finish rolling mill 9 into a steel plate 7 having a predetermined thickness. . Next, the steel plate 7 is cooled to a predetermined temperature by the cooling zone 10 while moving on the hot run table,
Then, it is wound around the coiler 11.

In the present invention, the steel sheet between the coiler 11 and the finish rolling mill 9 is provided after the front end of the steel sheet 7 is wound by the coiler 11 until the rear end of the steel sheet 7 exits the finish rolling mill 9. Tension is applied to 7. This tension is
As will be described later, the controller 12 controls the rotation speed of the mandrel of the coiler 11 so that the plate width of the steel plate 7 is adjusted to approach the target plate width.

When the finish rolling of the steel sheet 7 is completed at a temperature equal to or higher than the Ar ₃ transformation point, the Ar ₃ transformation temperature is changed on the hot run table as shown in FIG. In this temperature range, the steel sheet 7 contracts in width due to tension.
As shown in FIG. 3, the tension applied to the steel sheet 7 and the width shrinkage amount of the steel sheet 7 at this time have a relationship that the greater the tension (stress) applied to the steel sheet 7, the greater the width shrinkage amount of the steel sheet 7. .

On the other hand, the temperature change of the steel sheet 7 and the reduction amount of the width of the steel sheet 7 due to the accelerated rolling during the finish rolling by the finish rolling mill 9 are as shown in FIG. 7 has a relationship in which the reduction amount of the plate width increases.

Therefore, the deviation between the plate width of the steel plate 7 after finish rolling and the target plate width gradually decreases from the front end to the rear end of the steel plate, as shown in FIG. That is, the steel plate 7
The width of the plate gradually decreases from the front end to the rear end of the steel plate.

Such a strip width reduction pattern in the longitudinal direction of the steel sheet is obtained in advance for each product size and steel type of the steel sheet 7. Then, based on this plate width reduction pattern and the relationship between the tension applied to the steel plate 7 and the plate width shrinkage amount, which is obtained in advance for each product size and steel type, the tip of the steel plate 7 is the coiler 1.
The deviation between the product strip width and the target strip width during the trailing end of the steel strip 7 from the finish rolling mill 9 after being wound up on the sheet 1 is reduced, for example, tension to the steel strip 7 as shown in FIG. The application pattern is obtained in advance for each product size and steel type.
Then, if a tension is applied to the steel sheet 7 according to this tension application pattern, the steel sheet 7 obtained by accelerated rolling in the finish rolling stage will be described.
It is possible to reduce the deviation between the product strip width and the target strip width regardless of the reduction in strip width due to the temperature rise.

In order to apply the tension to the steel plate 7 according to the tension application pattern, the controller 12 is operated by the controller 12.
This is done by controlling the rotation speed of the mandrel of 1.

According to the above method, the tension applying pattern to the steel sheet 7 is determined based on the pattern of decreasing the sheet width in the longitudinal direction of the steel sheet 7 and the relationship between the tension applied to the steel sheet and the amount of contraction of the sheet width. Instead of this, the strip width of the steel sheet 7 immediately after finish rolling is, as shown in FIG. 1, provided on the exit side of the finish rolling mill 9 instead of this.
3, the deviation between the measured plate width and the target plate width of the steel plate 7 is calculated by the controller 12, and the tension applied to the steel plate 7 and the steel plate are calculated in advance for each product size and steel type. Based on the relationship between the strip width reduction amount of 7 and the steel plate 7 between the coiler 11 and the finish rolling mill 9, tension is applied by controlling the rotation speed of the coiler 11 according to a command from the controller 12, This makes it possible to reduce the deviation between the product plate width of the steel plate 7 and the target plate width.

That is, in the conventional method, the strip width deviation (x ₁ ) on the delivery side of the finishing rolling mill is 4 mm or more on average, and the strip width variation (x _1
2 ) is 2 mm or more on average, whereas according to the method of the present invention, the strip width deviation (x ₁ ) on the delivery side of the finishing rolling mill is
Can be reduced to an average value of 2 mm or less, and the plate width variation (x ₂ ) can be reduced to an average value of 1 mm or less. Strip width deviation (x
₁ ) and plate width variation (x ₂ ) will be described later.

Next, an embodiment of a strip width control method for a steel sheet in hot rolling according to the present invention will be described.

According to the method of the present invention, the pattern for applying tension to the steel sheet 7 is determined in advance for each product size and steel type, and the hot rolled steel sheet having a product sheet thickness of 1.6 mm, a product sheet width of 900 mm and a carbon equivalent of 0.01%. 10 were manufactured. At this time, the steel sheet temperature on the delivery side of the finish rolling was 850 ° C, and the steel sheet temperature before winding was 640 ° C. The plate width deviation (x ₁ ) and the plate width variation (x ₂ ) of the product coil manufactured in this manner were measured. The results are shown in Table 1 together with the results of the above-mentioned conventional technique. The strip width deviation (x ₁ ) is the length between the valley of the strip width variation curve and the target strip width, as shown in FIGS. 7 and 8, and the strip width variation (x ₂ ) is the strip width. It is the length between the peak and the valley of the fluctuation curve. 7. FIG. 7 is a graph showing the strip width deviation on the delivery side of the finish rolling mill.
It is a plate width deviation and a variation amount according to a conventional technique. And
FIG. 8 is a graph showing the plate width deviation after the plate width is controlled by the method of the present invention.

[0029]

As is clear from Table 1, according to the method of the present invention, the plate width deviation (x ₁ ) and the plate width fluctuation amount (x ₂ )
Is significantly smaller than the prior art method, and it has been found that the deviation between the product strip width and the target strip width can be greatly reduced.

The plate width of the steel plate 7 immediately after finish rolling is measured, the deviation between this measured value and the target plate thickness of the steel plate 7 is determined, and the steel plate 7 is determined in advance for each product size and steel type. According to another method of the present invention, tension is applied to the steel plate 7 between the coiler 11 and the finish rolling mill 9 based on the relationship between the tension applied to the steel plate 7 and the reduction amount of the steel plate width. Results similar to those in the example were obtained.

[0032]

As described above, according to the present invention, the finish rolling of the steel sheet is completed at the temperature of the Ar ₃ transformation point or higher, and the tension applied to the steel sheet between the coiler and the finish rolling mill is Adjust according to the tensioning pattern obtained in advance,
Alternatively, by adjusting the steel plate just after the finish rolling according to the measured plate width, the industrially useful effect that the plate width deviation from the target plate width can be significantly reduced is brought about.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of a plate width control method for steel plates in hot rolling according to the present invention.

FIG. 2 is a graph showing a temperature change of a steel sheet from a finish rolling mill to a coiler.

FIG. 3 is a graph showing the relationship between the tension applied to a steel plate and the width shrinkage amount of the steel plate.

FIG. 4 is a graph showing a relationship between a temperature change of a steel sheet immediately after finish rolling and a width reduction amount of the steel sheet.

FIG. 5 is a graph showing the relationship between the strip width on the delivery side of the finish rolling mill and the strip width deviation.

FIG. 6 is a graph showing a tension application pattern to a steel plate.

FIG. 7 is a graph showing variations in strip width on the delivery side of the finish rolling mill.

FIG. 8 is a graph showing plate width variation after plate width control according to the present invention.

FIG. 9 is a side view showing a conventional steel plate production line.

[Explanation of symbols]

 1: heating furnace, 2: rough rolling mill, 3: horizontal roll rolling mill, 4: vertical roll rolling mill, 5: finishing rolling mill, 6: cooling zone, 7: steel plate, 8: coiler, 9: finishing rolling mill, 10: cooling zone, 11: coiler, 12: controller, 13: plate width gauge.

Claims (4)

[Claims] 1. A heated slab is hot-rolled to a steel plate having a predetermined plate thickness by a finish rolling mill, and the steel plate thus hot-rolled to a predetermined plate thickness is subsequently cooled by the finish rolling mill. By cooling the steel plate to a predetermined temperature by a strip, and then winding the steel plate cooled to a predetermined temperature in a coiler, when manufacturing a steel plate having a predetermined plate thickness and characteristics, the temperature of the steel plate during finish rolling In a plate width control method for a steel plate, which reduces a deviation between a product plate width and a target plate width, which is caused by a decrease in the plate width of the steel plate with a rise, finish rolling of the steel plate at a temperature of Ar ₃ transformation point or higher. ,, by adjusting the tension applied to the steel sheet between the coiler and the finish rolling mill, to adjust the reduction ratio of the sheet width of the steel sheet, the strip width control of the steel sheet in hot rolling Method. 2. A strip width reduction pattern in the longitudinal direction of the steel sheet, which occurs during finish rolling of the steel sheet, is obtained in advance for each product size and steel type, and is obtained in advance for each product size and steel type. Also, based on the relationship between the tension applied to the steel plate and the amount of contraction of the plate width, while the rear end of the steel plate is taken out from the finisher after the front end of the steel plate is wound around the coiler, the product To reduce the deviation between the plate thickness and the target plate thickness, a tension application pattern to the steel sheet is previously obtained for each product size and steel type, and according to the tension application pattern, a tension is applied to the steel sheet. The method for controlling the strip width of a steel sheet in hot rolling according to claim 1. 3. The steel sheet, which is obtained by actually measuring a sheet width of the steel sheet immediately after finish rolling, obtaining a deviation between the actually measured value and a target sheet width of the steel sheet, and obtaining the deviation in advance for each product size and steel type. Based on the relationship between the tension applied to the steel plate and the amount of contraction of the width of the steel plate, the steel plate between the coiler and the finish rolling machine is applied with tension such that the deviation becomes small. The method for controlling the strip width of a steel sheet in hot rolling according to claim 1. 4. A tension is applied to the steel plate by controlling the rotation speed of the coiler.
The strip width control method for a steel sheet in hot rolling according to any one of claims 1 to 3.