JPS5923882B2 - Hot rolling mill strip width control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the strip width of a hot rolling mill comprising an edger roll and a horizontal roll roll.

For example, in a hot strip mill, a steel billet is rolled to a desired width and thickness using a rough rolling mill group that includes a plurality of rolling mills each consisting of an edger roll and a horizontal roll.
Subsequently, the finished product is rolled using a group of finishing mills to obtain finished products of various dimensions.

In this hot strip rolling, the strip width hardly changes in the finishing rolling process, so it can be said that the width of the finished product is almost determined in the rough rolling process.Therefore, the strip width in the rough rolling process must be precisely controlled. This is required.

Conventionally, as a strip width control method for rough rolling, the sum of the width expansion due to horizontal roll reduction of each rolling mill and the sum of the difference between the billet width and the target strip width on the rough rolling mill gun side side are calculated, and each rolling mill The amount of width loss for each edger is determined by distributing the load to the edger, and the width recovery amount (this is calculated as the amount of width recovery by the horizontal roll reduction of the dogbone part (bulging part of the edge part) that occurs during edge rolling). )
A method was used to determine the opening degree of the edger roll by taking into account the following.

However, the conventional sheet width control method described above has the following drawbacks.

In other words, the amount of dog bone recovery and the amount of width expansion are greatly affected by the temperature at the edge of the rolled material, but conventionally, the temperature in the width direction of the rolled material is not considered, so the amount of dog bone recovery and width expansion is The drawback was poor prediction.

In recent hot strip mills, walking beam type heating furnaces are often used as heating furnaces for steel billets, and since this type of heating furnace heats steel billets by charging them at regular intervals, Generally, the temperature of the edge of a steel slab is higher than that of the center, and the temperature often differs between the two edges.

The degree of bulge in the dog bone during edge rolling and the amount of dog bone recovery per width due to horizontal roll rolling are greatly affected by the temperature of the edge.
With the conventional method of using the temperature measured at the center of the rolled material as the representative temperature of the rolled material, it was not possible to accurately predict the amount of dog bone recovery and width expansion due to horizontal roll rolling.

In order to eliminate the drawbacks of the conventional method, the present invention measures the temperature in the width direction of the rolled material during rolling, especially the temperature of the portion corresponding to the dogbone portion produced by edge rolling, and uses this temperature measurement value. The amount of dog bone recovery and width expansion can be predicted with high accuracy.

That is, the gist of the present invention is to measure the temperature at both edges of the rolled material on the entry side of the rolling mill during hot rolling in a rolling mill consisting of an edger roll and a horizontal roll, and to compare the measured temperature value with the temperature of the rolled material. Calculation of dog bone recovery rate with horizontal roll including width and thickness (however, dog bone recovery rate = ----:--width recovery amount □ when leveling and rolling down Etshad bone part) Calculation of roll reduction amount formula and width Calculation of the expansion coefficient (width expansion coefficient - width expansion amount □ during thickness reduction with horizontal rolls) Calculate the dog bone recovery rate and width expansion coefficient during horizontal roll reduction of the rolled material using the horizontal roll reduction formula. The method is characterized in that the opening degree of the edger roll is predictively calculated, the opening degree of the edger roll is predictively controlled based on the calculated value, and the opening degree of the edger roll is calculated to obtain the target of the rolled material on the exit side of the rolling mill using the calculated value. This is a method for controlling strip width in a hot rolling mill.

The present invention will be explained in detail below based on the drawings.

FIG. 1 is a plan view for explaining the change in the width of the rolled material in a rolling mill consisting of an edger roll and a horizontal roll. In the figure, RE indicates the edger roll, RH indicates the horizontal roll, and P indicates the rolled material. It is.

As shown in the figure, the width at the entrance of the rolling mill is WI, and the width at the exit side is WO.
, if the exit width of the edger roll RE is WE, then the width reduction amount ΔW due to rolling is ΔW==WI −WO...
The amount of etching ΔE by the edger roll RE is expressed as ΔE = Wi −WE ・・・・・・
It is expressed as (2).

Shape (cross-sectional shape) of rolled material on exit side of Edger Roll RE
As shown in Figure 2, the material that was flat on the entry side as shown in Figure A becomes a dogbone shape as shown in Figure 2 through etching, and is then rolled with horizontal rolls RH as shown in Figure C. so that it becomes flat again.

During rolling by the horizontal rolls RH, the dogbone portion is first leveled and the width of the cut is expanded (as mentioned above, the amount of width expansion at this time is referred to as the dogbone recovery amount), and then the width is further expanded by the subsequent overall reduction in the thickness direction ( This is called the amount of width expansion), and the final width becomes Wo.

In the conventional width control method described above, in order to obtain the dogbone recovery amount, the dogbone recovery rate (
Ratio of recovery amount to etching amount (number smaller than 1)
is predetermined for each dimension (width, thickness) range of the rolled material, the amount of dogbone recovery is estimated from this, and the width expansion coefficient (reduction in the thickness direction) is similarly calculated empirically for the amount of width expansion. The ratio of the amount of width expansion to the amount of width expansion) is determined in advance for each range of dimensions (width, thickness) of the rolled material, and the amount of width expansion is estimated from this.

Then, the opening degree of the edger roll is determined using the amount of dog bone recovery and the amount of width expansion estimated in this way. Regarding the temperature of the rolled material, the temperature of the center of the rolled material is continuously measured, and the skid mark ( This method corrected the opening degree of the edger roll in response to temperature fluctuations caused by factors such as the area in contact with the skid in the heating furnace (where the temperature was lower than other areas).

Therefore, in the conventional method, the temperature of the edge portion, which greatly affects the amount of recovery and width expansion of the dogbone, is not taken into account, and the accuracy of these estimations is low.

Normally, the temperature distribution in the width direction of a rolled material during rough rolling in a hot strip mill is as shown in Figure 4, where the temperature is highest at a point approximately 100 mm inside from the side edge of the rolled material. The difference in temperature from the center or side edges is about 50°C.

The temperature at the edge that includes the peak point of this temperature distribution has a significant influence on the amount of recovery and width expansion of the dogbone, and the position corresponding to the peak point of this temperature distribution is
This almost coincides with the peak point of the bulge in the dogbone caused by rolling.

FIG. 5 is a diagram showing an example of the results of an experimental investigation by the present inventors regarding the relationship between edge temperature, dogbone recovery rate, and width expansion coefficient, and the horizontal axis is the peak of both edge portions. The average value of the point temperature, the vertical axis is the dogbone recovery rate or the width expansion coefficient, and the line A in the figure indicates the dogbone recovery rate, and the serpentine lines indicate the width expansion coefficient.

Based on this research data, the edge temperature can be determined to be, for example, 50
It was confirmed that when the temperature changed, the dogbone recovery rate changed by about o, i, and the width expansion coefficient changed by about 0.013.

In the present invention, as described below, the width and thickness of the rolled material arriving at the controlled rolling mill are actually measured or calculated based on other detected values, and the temperature of both edge portions of the rolled material is actually measured. From these values, the dogbone recovery rate and width expansion coefficient in the rolling mill are predicted and calculated over the length direction of the rolled material, and the calculated values are used to predict and control the opening degree of the edger roll.

In other words, the dogbone recovery rate is ΔWD=ft(WItHt+DEtTw+Td, Kp)
”-(3) ΔWD: Dog bone recovery rate WI: Width at the entrance of the rolling mill HI: Thickness at the entrance of the rolling mill DE: Diameter of the edger roll Tw: Temperature of the edge portion on the work side side of the rolled material Td: Rolling Temperature Kp of the drive side edge of the material: As a constant determined by the material of the rolled material, a calculation formula is determined in advance based on past actual values, and the width expansion coefficient is α=f2 (WI, HI, DH9Tw, Td , Kp)...
(4) α: Width expansion coefficient DH: A calculation formula is determined in advance as the diameter of the horizontal roll based on past actual values.

Then, the opening degree of the edger roll required to obtain the outlet width WO and the outlet thickness by rolling the rolled material having the inlet width WI and the inlet thickness HI is determined as follows.

WO=W, -ΔE+ΔE-ΔWD+(HI-HO)・α
WO=W, -ΔE(1-ΔWD)+(Hi-Ho)
・aHere, from equation (2), ΔE=WI-WE, so wo =WI-W, -(1-ΔWD)+WE-(1
-ΔWD )+(HI-HO)・α Wo-WI・ΔVv[y-1-WE・(1-, #l))
+(HI-HO)・α Therefore, edger outlet width WE
(approximately equal to the edge opening) In other words, the inlet width Wl and inlet thickness HI of the rolling mill are actually measured or calculated, the temperatures Tw and Td of both edge parts are actually measured, and equations (3) and (4) are obtained. ) Calculate the dog bone recovery rate ΔWD and the width expansion coefficient α, and use the formula (5) to determine the opening degree of the edger roll that will result in the edger roll exit width WE at a fixed period or for each fixed length section of the rolled material. This enables accurate width control over the entire length of the rolled material by predictively controlling the opening degree of the edger roll.

Next, an example will be described.

FIG. 3 is a block diagram showing a control system in an embodiment of the present invention, and is a block diagram showing two rolling mills, a first-stage rolling mill and a second-stage rolling mill (these are referred to as control rolling mills). This is an indication.

In the figure, 1 is a setting device, 2 to 7 are computing units, 8 is an edger roll opening control device, and 10 is a rolling mill consisting of an edger roll 11 and a horizontal roll 12 (this is the first stand). , 20 is a rolling mill consisting of an edger roll 21 and a horizontal roll 22 (this is the second stand), 13 is a roll opening detector for the edger roll, 14 is a rolling force detector for the edger roll, and 15 is a rolling force detector for the edger roll. A roll opening degree detector for the horizontal roll, 16 a rolling force detector for the horizontal roll, 31 a thermometer, 32 a plate width gauge, and P a rolled material.

In this example, the entrance width W1 and entrance thickness Hl of the rolled material P arriving at the second stand, which is a controlled rolling mill, are calculated from the roll opening degree, rolling force, etc. during rolling in the first stand in the preceding stage. In this case, the temperature of the rolled material P was actually measured using a thermometer 31 provided on the exit side of the first stand.

Here, the type of thermometer 31 is not particularly limited as long as it can measure the temperature in the width direction of the rolled material P (e.g., a radiation thermometer or a type that mechanically scans a photoelectric conversion element, A type that electronically scans the photoelectric conversion surface can be used, but in practice it is recommended to scan the photoelectric conversion surface at two specific points in the width direction (points corresponding to the peak points of the temperature distribution described above, 10
A thermometer that can measure 2 points inside the thermometer is sufficient.

In this example, the temperature at a point 1001 m inside from both ends is defined as the position corresponding to the temperature at the peak point of the temperature distribution (
This is referred to as TwtTd).

A method of implementing the present invention using such an apparatus will be explained.

First, the thickness and width of the rolled material P rolled by the first stand 10 are calculated as follows.

The thickness Hl of the exit side of the first stand is calculated from the following known gauge meter formula.

I H1=Sl+-+Δkl ・・・・・・・・・
... (6) 1 where 81: Opening degree Fl of the first stand horizontal roll: Rolling force Ml of the first stand horizontal roll: Rigidity ratio Δ of the first stand horizontal roll mill 1: Offset of the first stand horizontal roll The amount and the first stand exit width W1 are calculated from the following equation.

Wl-E1+ΔE1 ・・・・・・・・・
(7) Here, El: Opening degree of the first stand edger roll ΔE1: Width variation amount ΔEt calculated by the following formula = f3 (FEI, +Tw, Td, Kp) FEI
: Edger roll rolling force The calculation of equation (6) is performed by the calculation unit 2, the calculation of equation (7) is performed by the calculation unit 3, and the obtained Hl and Wl are respectively input to the calculation unit 4.

The calculator 4 calculates the width expansion amount ΔW of the second stand under horizontal roll pressure using the following equation.

ΔWH2= (Hl, H2)・α2...
(8) Here, H2 is the target thickness on the exit side of the second stand, and α2 is the width expansion coefficient under the horizontal roll reduction of the second stand, which corresponds to the equation (4) above. It can be obtained from the formula below.

α2=f4(Wl tHl , DHztTw+Td, K
p) ++++++++ (9) DH2: Diameter of the horizontal roll of the second stand Also, the calculator 5 calculates the dogbone recovery rate ΔWD2 under the pressure of the horizontal roll of the second stand using the above (
3) Calculate from the following formula corresponding to formula.

ΔWD22f5(Wl, Hl, DE2.Tw, Td, K
p)...(10) DE2: Etsuya of the 2nd stand
The diameter of the roll ΔwH2 and ΔWD2 determined above are input to the computing unit 6, and the computing unit 6 calculates the second
The opening degree wE2 of the edger roll of the stand is calculated.

W2: The opening degree wE2 of the edger roll of the second stand obtained by the target width calculator 6 on the exit side of the second stand is set in the edger roll opening degree control device 8.

The above operation is repeated at a certain period or every certain length of the rolled material.

Further, in this embodiment, a board width meter 32 is provided on the exit side of the second stand to measure the width of the exit side of the second stand, and based on this measured value W2', the calculator 7 calculates equations (9) and (10). This allows the coefficients among them to be dynamically modified (a detailed explanation of this will be omitted).

In addition, in the above-mentioned embodiment, the width and thickness of the rolled material arriving at the second stand are calculated from the detected values of the roll opening degree, rolling force, etc. during rolling in the first stand. The width and thickness may be measured using a width gauge or thickness gauge, and if the first stand is also a controlled rolling mill, the width and thickness of the rolled material (steel billet) at the entrance of the first stand can be measured using a width gauge or thickness gauge.
width.

The same operation as for the second stand described above may be performed using the same thickness.

Furthermore, if the opening degree of the edger roll is to be controlled for the subsequent stands (third stand and thereafter), the same operation as for the second stand described above may be performed for the subsequent stands.

Also, in Fig. 3, computing units 2 to 7 (M surrounded by dotted lines in the figure)
) may be replaced with a calculator.

Furthermore, the present invention is applicable not only to rough rolling mills such as hot strip mills, but also to reversible rolling mills such as plate mills as long as the rolling mill comprises edger rolls and horizontal rolls.

[Brief explanation of drawings]

Figure 1 is a plan view to explain the change in width due to rolling.
Fig. 2 is a diagram showing changes in the cross-sectional shape of a rolled material during rolling, Fig. 3 is a block diagram showing a control system in an embodiment of the present invention, and Fig. 4 is a diagram showing an example of the temperature distribution in the width direction of the rolled material. ,
FIG. 5 is a diagram showing an example of the relationship between edge temperature, dogbone recovery rate, and width expansion coefficient. 1: Setting device, 2 to 7: Arithmetic unit, 8: Edger roll opening control device, 10, 20: Rolling stand, 11.21:
Edger roll, 12, 22: Horizontal roll, 13.1
5: Roll opening degree detector, 14° 16: Rolling force detector, 3
1: Thermometer, 32: Plate width meter, P: Rolled material.

Claims (1)

[Claims] 1. During hot rolling in a rolling mill consisting of an edger roll and a horizontal roll, the temperature at both edges of the rolled material on the entry side of the rolling mill is measured, and the measured temperature value and the width and thickness of the rolled material are measured. Using the formula for calculating the dog bone recovery rate and the formula for calculating the width expansion coefficient, the dog bone recovery rate and width expansion coefficient are predicted and calculated when the rolled material is rolled by horizontal rolls, and the calculated values are used to calculate the width expansion coefficient of the rolled material on the exit side of the rolling machine. 1. A strip width control method for a hot rolling mill, comprising: calculating an edger roll opening to obtain a target width; and predictively controlling the edger roll opening based on the calculated value.