JPH01218713A - Method for controlling plate width of heat rolled steel plate - Google Patents

Abstract

PURPOSE:To stably manufacture a heat rolled plate excellent in plate width accuracy by correcting the roll opening of a width rolling mill according to the electric power of an edge heater in a hot rolling line. CONSTITUTION:The position right under the edge heater 1 of a rolled stock fed out of a group of rough rolling mills is measured by a measuring roll 6 and the result is sent to a rolling stock position storage device 7. The electric power value of the edge heater 1 at that position is sent to an electric power storage device 8 of the edge heater. A necessary rolling reduction of the width rolling mill 2 is computed by a width rolling reduction arithmetic unit 9 through the information of dimensions, material, finish rolling conditions, etc., of a rolled stock obtained from the above two signals and a host computer 10. A signal is sent from a rolling stock position storage device 7 to a roll opening controlling device 11 of the width rolling mill 2 so that a necessary width rolling reduction can be actualized considering a time lag between an edge heater 1 and a width rolling mill 2.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a strip width control method in a width rolling mill in a hot rolling line equipped with an edge heater.

<Prior art and its problems> A hot rolling line for steel sheets generally consists of a rough rolling mill group consisting of multiple width rolling mills and horizontal rolling mills, and a finishing rolling mill group consisting of multiple horizontal rolling mills. However, in the rough rolling mill group, a strip width control method has been put into practical use that uses a width gauge to correct the roll opening of the width rolling mill.

However, the requirements for plate width accuracy are becoming increasingly strict.
More and more hot rolling lines are installing a width rolling mill with a strip width control function on the entry side of the finishing mill group.

By the way, the temperature drop of hot-rolled steel strip is large at the width edges of the strip, which causes deterioration of the mechanical properties of the product.Furthermore, the deformation resistance of the strip width edges increases due to the temperature drop, which causes the roll to deteriorate. Problems such as scratches occurring at positions corresponding to the width edges of the board sometimes occurred. Therefore, recently there has been a tendency to install an edge heater on the entry side of a finishing rolling mill to heat the edge of the strip width by induction heating.

In this case, the width rolling mill is generally installed just before the finishing rolling mill, and the edge heater is usually installed on the entry side of the width rolling mill.

However, in hot rolling lines where such consideration has been taken, even if the strip width accuracy is good on the exit side of the roughing mill group, the accuracy tends to deteriorate on the exit side of the finishing rolling mill group. The problem has been pointed out.

For this reason, in actual work, hot rolling is carried out with the target width always set wider than the product width in consideration of the strip width deviation, which inevitably results in a significant yield loss.

Means for Solving the Problems> Therefore, the present inventors proposed a hot rolling sheet manufactured in a "hot rolling line in which an edge heater, a width rolling mill, and a horizontal rolling mill are arranged after a group of rough rolling mills". As a result of basic research into the causes of sheet width accuracy deterioration when edge heaters are installed, we were able to obtain the following knowledge.

(Al A width rolling mill is placed just before the finishing rolling mill group,
Furthermore, the reason why strip width accuracy deteriorates when rolling is performed on a hot rolling line that incorporates an edge heater on the entry side is that the reduction effect of width rolling changes depending on the heating conditions of the edge heater.

(bl) When the reduction amount condition for width rolling is constant, there is a specific relationship between the power used by the edge heater and the width accuracy of the edge heater. By investigating the relationship between □ and edge heater power, it will be possible to calculate the ``width reduction amount that will suitably maintain board width accuracy'' based on this relationship and the edge heater power.

That is, FIG. 1 is a graph showing the relationship between the edge heater power and the strip width deviation on the exit side of the finishing mill group.

Here, "the strip width deviation on the exit side of the finishing mill group" is defined as "the strip width on the finishing mill group exit side when an edge heater is used".
This is the value obtained by subtracting the width of the side plate of the finishing mill group when the edge heater is not used. A hot rolling line equipped with an edge heater 1° width rolling mill 2, a finishing rolling mill group 3 and a width gauge 4 was used, and the width reduction amount of the width rolling mill 2 was kept constant at 25 m, and the finishing rolling mill group 3
The heating conditions of the edge heater 1 were also set to the same rolling conditions, and the heating conditions of the edge heater 1 were varied.
0 m) was obtained by rolling test.゛It can be seen from Fig. 1 that there is a certain regular relationship between the edge heater power and the strip width deviation on the side of the finish rolling mill, and as the edge heater power increases, the strip width deviation increases accordingly. .

(C) This is because when the edge heater power increases, the temperature at the edges of the strip rises, and the temperature difference with the center of the strip, where there is almost no temperature rise, increases, which increases the relative temperature when width rolling is performed. The restraining force at the center of the strip width increases, increasing the bulge at the edges of the strip width, and this is pushed out in the next horizontal rolling, resulting in an increase in width. This is thought to be due to the appearance of

Figure 3 is a graph showing the relationship between the edge heater power and the temperature difference in the board width direction (the temperature difference between the 25 points from the edge of the board and the center). It is clear that there is a regular relationship between the temperature difference in the width direction of the strip, which is almost the same as the relationship between the edge heater power and the strip thickness deviation at the exit side of the finishing mill group, and the above speculation is correct. You can see that it is shooting. The results shown in FIG. 3 were obtained by further installing a width direction thermometer 5 between the edge heater 1 and the width rolling mill 2 of the equipment shown in FIG. 2. This was obtained through an experiment under the same conditions as above.

(dl) On the other hand, the edge heater power has a regular relationship with the temperature difference in the strip width direction, and it also has almost the same regular relationship with the strip width deviation on the exit side of the finishing mill group. As expected, there is also a regular relationship between the temperature difference in the width direction of the rolled material after being heated by the edge heater and the width deviation of the strip at the exit side of the finishing mill group, and there is a regular relationship between If you investigate the relationship between the temperature difference in the strip width direction and the strip width accuracy, you can calculate the "width reduction amount that maintains the strip width accuracy suitably" from the actual value of the temperature difference in the strip width direction and this relationship. Be possible.

This invention has been made based on the above findings, and includes: [In a hot rolling line in which an edge heater for heating the width end of a rolled material, a width rolling mill, and a horizontal rolling mill are arranged,
Adjust the roll opening degree of the width rolling mill according to the power of the edge heater, or measure the widthwise temperature of the rolled material by using a temperature measuring device in the width direction of the rolled material placed between the edge heater and the width rolling mill. It is characterized by the ability to stably produce hot-rolled sheets with good sheet width accuracy by adjusting the roll opening of the width rolling mill according to the measured value of the temperature difference with the edge. It is something that you have.

Next, the present invention will be explained in more detail based on examples.

<Example> In carrying out the present invention, a hot rolling line as shown in FIG. 4 (the rough rolling mill group is not shown) was constructed.

In the hot rolling line shown in FIG. 4, first, the position directly below the edge heater of the rolled material sent out from the rough rolling mill group (not shown) is measured by the measuring roll 6,
The result is sent to the rolled material position storage device 7. Also,
The power value of the edge heater 1 at that position is sent to the edge heater power storage device 8. Then, the width reduction calculation device 9 calculates the required reduction amount of the width rolling mill 2 based on the above two signals and information such as the dimensions of the rolled material, material quality, finish rolling conditions, etc. from the host computer 10. Here, in consideration of the time delay between the edge heater 1 and the width rolling mill 2, a signal is sent from the rolled material position storage device 7 to the roll opening control device 11 of the width rolling mill in order to realize the required width reduction amount. It looks like this.

Note that the control device may be configured to use "the temperature difference in the sheet width direction measured by the width direction thermometer" instead of the edge heater power value as data for calculating the necessary rolling amount of the width rolling mill.

Next, in this hot finishing rolling line, the plate sent out from the rough rolling mill group has a thickness of 25 to 60 fi and a plate width of near 50 to 1.
When rolling a 650fi ordinary steel material, the deviation between the average sheet width at the exit side of the finishing mill group and the target width was within ±4 points if the power of the edge heater was not taken into consideration. On the other hand, in the example of the present invention in which the opening degree of the width rolling mill is controlled in consideration of the edge heater power, the deviation is ±l+m.
It was confirmed that it was within

On the other hand, we also carried out a test in which rolling was performed using the "temperature difference in the width direction of the strip placed on the outlet side of the edge heater - width direction due to course change" instead of "edge heater power" as the opening control data for the width rolling mill. It was also confirmed that the deviation between the average strip width on the exit side of the finishing mill group and the target width could be suppressed to within ±1.

Summary of Effects> As explained above, according to the present invention, poor sheet width accuracy caused by edge heaters in hot rolling lines can be eliminated, a significant improvement in yield can be achieved, and high quality and high precision hot rolling can be achieved. Industrially, extremely useful effects are brought about, such as making it possible to manufacture steel plates stably at low cost.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the edge heater power in the hot rolling line and the strip width deviation on the exit side of the finishing mill group. FIG. 2 is an explanatory diagram of the hot rolling line used in the experiment. FIG. 3 is a graph showing the relationship between the edge heater power and the temperature difference in the sheet width direction in the hot rolling line. FIG. 4 is an explanatory diagram of the hot rolling line used in the example. In the drawings: 1...edge heater, 2...width rolling mill. 3... Finishing rolling mill group, 4... Width meter. 5...Width direction thermometer. 6...Measuring roll.

Claims (2)

[Claims] (1) In a hot rolling line equipped with an edge heater that heats the width end of the material to be rolled, a width rolling mill, and a horizontal rolling mill, the roll opening of the width rolling mill is corrected according to the power of the edge heater. A method for controlling the width of a hot-rolled steel plate, characterized in that: (2) In a hot rolling line equipped with an edge heater that heats the width end of the rolled material, a width rolling mill, and a horizontal rolling mill, the temperature in the width direction of the rolled material is maintained between the edge heater and the width rolling mill. 1. A hot-rolled steel wire, characterized in that the roll opening of a width rolling mill is adjusted in accordance with the measured value of the temperature difference between the center and end portions of the rolled material in the width direction. A method for controlling the width of a plate.