JPH08192211A - Manufacture of thick treated steel plate - Google Patents

Abstract

PURPOSE: To manufacture a thick tapered steel plate with a high accuracy without delayed response and without being affected by variation of plastic property at the time of manufacturing the thick tapered steel plate whose thickness is varied along the longitudinal direction in one coil with a tandem type rolling mill. CONSTITUTION: At the time of manufacturing the thick tapered steel plate 10 whose thickness is varied along the longitudinal direction in one coil using the gagemeter formula with the tandem type rolling mill, draft correcting values are determined by calculating the taper bias values of respective stands 1-7 taking the variation of forward slip into consideration with an arithmetic unit 40 provided that the mass flow balance in each of the stands 1-7 is constant and continuously changing the gagemeter formula based on the rolling length of the steel plate calculated with the arithmetic unit 60 for the length of rolled steel plate. These values are imparted to screw down devices 20 and rolling at each stand is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a tandem rolling mill to manufacture a tapered thick steel plate whose plate thickness changes in one coil along the longitudinal direction from one end to the other at a constant gradient. Regarding the method.

[0002]

2. Description of the Related Art As a method of controlling the plate thickness of a rolled steel plate to a desired value by a rolling mill, a plate thickness control method called a so-called gauge meter system is often adopted. This uses a rolling mill as a kind of plate thickness measuring device, calculates the actual plate thickness from the measured rolling position (roll gap) and rolling load, and compares the actual plate thickness with the target plate thickness. The roll roll-down position (roll-down amount) is feedback-controlled so that the deviation is always zero.

According to this gauge meter control system, when rolling a tapered thick steel plate whose plate thickness changes from one end to the other end with a constant gradient along the longitudinal direction of the steel plate, the target plate thickness is preset to a constant pass. Either a taper shape is set in a schedule, or a target plate thickness is continuously changed by a taper amount corresponding to a change in a measured value such as a rolling speed during rolling.

As a first conventional example of this type of control method, there is a plate thickness control method disclosed in Japanese Patent Publication No. 51-35183. This is a method of changing the target plate thickness with a value obtained by multiplying the desired taper gradient by the actual rolling speed.

As a second conventional example, there is a plate thickness control method disclosed in Japanese Patent Publication No. 55-61311. This is a method of controlling the plate thickness in a single-stand rolling mill, and in the plate thickness control method of detecting the load deviation between the rolling load and the reference load given from the outside and controlling the absolute value of the outlet side plate thickness. In this method, the reference load is changed according to the transport distance of the material being rolled to change the plate thickness in the longitudinal direction of the rolled steel plate.

Furthermore, as a third conventional example, Japanese Patent Publication No. Sho 58-1961.
No. 12 and the fourth conventional example are the plate thickness control methods disclosed in JP-B-63-130205. All of these targets single-stand rolling mills.

Furthermore, as a fifth conventional example, Japanese Patent Publication No. 60
There is a plate thickness control method disclosed in Japanese Patent Publication No. 124. This is a method of pre-calculating the roll reduction position in consideration of the variation of the plastic characteristic due to the change of the inlet side plate thickness, and performing the reduction setting at a suitable timing according to the reduction speed to prevent the deterioration of the control accuracy due to the response delay. is there.

[0008]

However, in the plate thickness control method according to the first conventional example, because of the response delay of the rolling system, the part of the steel plate at the position where the rolling load and the like are actually measured and the calculated value based on the measured value are obtained. The part of the steel plate on which the reduction control is performed does not match, and good plate thickness accuracy may not be obtained.

The plate thickness control method according to the second conventional example is as follows.
It is intended for single-stand rolling mills such as four-stage reversible rolling mills, and not for rolling mills having a plurality of stands such as hot continuous finishing mills. Therefore, since the taper addition of the former stand and the mass flow balance are not taken into consideration, when it is applied to a tandem rolling mill, stripability and strip thickness accuracy are deteriorated. The same applies to the methods according to the third and fourth conventional examples.

Further, in the strip thickness control method according to the fifth conventional example, even if a highly accurate rolling prediction formula considering the plasticity coefficient from the strip thickness and strip temperature is used, the tandem rolling mill has a problem of response delay. Therefore, it is not possible to obtain high plate thickness accuracy.

The present invention has been made in consideration of such circumstances, and an object of the present invention is to provide a tandem rolling mill with a taper in which the plate thickness changes along the longitudinal direction within one coil. In manufacturing thick steel plates, it is to manufacture tapered thick steel plates with high accuracy without a response delay and without being affected by changes in plastic characteristics.

[0012]

In order to solve the above-mentioned problems, the method for manufacturing a tapered thick steel plate of the present invention is a tandem rolling mill in which the plate thickness changes along the longitudinal direction within one coil. When manufacturing a thick gauge steel plate using the gauge meter method, determine the distribution ratio of the taper amount of each stand in advance considering the change in the advanced rate under the condition that the mass flow balance of each stand is constant. Is characterized by.

The taper steel plate may be manufactured by continuously changing the determined distribution ratio based on the rolling length. Specifically, for example, the final stand exit side target taper amount in consideration of the advance rate change of each stand, the taper application amount of each stand calculated in advance based on each stand exit side plate thickness preset value and the advance rate preset value, You may continuously change and roll based on the steel plate conveyance distance (rolling length) obtained from the length measuring device. Alternatively, the plate thickness on the delivery side of the final stand may be measured, and the roll reduction position of each stand may be corrected based on the deviation between the measured plate thickness and the delivery-side target plate thickness.

[0014]

In the method for manufacturing the tapered thick steel plate of the present invention,
By determining the distribution ratio of the taper application amount of each stand in consideration of the change of the advanced rate under a constant mass flow balance condition, it is possible to manufacture an accurate tapered thick steel plate without a response delay.

By continuously changing the determined distribution ratio based on the rolling length, it is possible to manufacture a tapered thick steel plate with high accuracy without being affected by the change in plasticity characteristics.

The plate thickness accuracy can be further improved by measuring the plate thickness on the delivery side of the final stand and correcting the roll reduction position of each stand based on the deviation between the measured plate thickness and the delivery side target plate thickness. .

[0017]

EXAMPLE FIG. 1 is a conceptual view of a tandem type rolling mill for producing a tapered thick steel plate.

The rolling mill is composed of a total of seven stages, that is, a first stand 1, a second stand 2, ..., And a seventh stand 7, and gives a taper in the rolling process of the steel sheet 10. Each stand is equipped with a reduction device 20 including an automatic thickness control device (AGC) by adjusting the reduction opening according to a gauge meter type.
A plate thickness gauge 30 is installed on the exit side of the final seventh stand 7.

Further, at the time of applying the taper, there is provided a calculation device 40 for calculating the taper bias value of each stand according to the target taper amount given from the outside and giving a reduction correction command to the reduction device 20. Furthermore, in order to improve the thickness accuracy, based on the actual thickness obtained from the thickness gauge 30,
Monitor correction controller 50 that corrects the reduction of the rear stand
Is provided. Further, a rolling length calculation device 60 for detecting the rolling length (steel plate conveying distance) is also provided.
The rolling peripheral speed of the final stand (seventh stand) 7 is input to the rolling length calculation device 60.

The target taper amount is, as shown in FIG.
It is the total amount of the plate thickness deviation when the plate thickness changes primarily between the front end and the rear end of 40. Further, in this case, the plate thickness taper is not given for a certain length from the tip of the steel plate.
Further, the thickness of the rear end of the steel plate is also constant.

In such equipment, the taper application amount of each stand is calculated in advance in consideration of the change of the advanced rate, and the calculated taper application amount is continuously changed according to the rolling length to manufacture the tapered thick steel plate. .

First, the distribution ratio of the taper amount given to each stand is obtained under the condition that the mass flow balance of each stand is constant. Equation (1) is obtained from the condition that the mass flow balance is constant.

[0023]

[Formula 1] h _i (1 + f _i ) V _i = h _{i + 1} (1 + f _{i + 1} ) V _{i + 1} (1) where h _i : i stand output side plate thickness preset value f _i : i stand Advance rate preset value V _i : i Stand roll peripheral speed Here, the mass flow balance after taper is given by the equation (2) considering the change in the advance rate.

[0024]

(2) (h _i + Δh _i ) (1 + f _i + Δf _i ) V _i = (h _{i + 1} + Δh _{i + 1} ) (1 + f _{i + 1} + Δf _{i + 1} ) V _{i + 1} (2) where , Δh _i : i-stand plate thickness change amount Δf _i : i-stand advance rate change amount From the formula (1), the formula (3) is obtained with respect to V _i.
Substituting into equation (2), we obtain equation (4).

[0025]

(Equation 3)

In the equation (4), since the third terms on both sides are minute, if approximated to 0, the equation (5) can be obtained for Δh _i .

[0027]

(Equation 5)

Furthermore, since the relationship between the advance rate and the rolling reduction can be defined as in equations (6) and (7), equation (6) is
Substituting into equation (5), equations (8) and (9) are obtained.

[0029]

(Equation 6)

H _i : Preset value of plate thickness on entrance side of i stand Δr _i : Change amount of reduction rate of i stand

[0031]

(Equation 8)

[0032]

[Equation 9]

As described above, under the condition that the mass flow between the adjacent stands is kept constant, the taper amount given to each stand is the target taper amount at the exit side of the final stand and the preset thickness value at each stand exit side. Based on h _i and the advanced rate preset value f _i , they can be sequentially calculated by the above equation (8).

Next, in order to detect the position of the steel plate, the rolled steel plate length calculation device 60 calculates the material speed from the roll peripheral speed of the seventh stand 7 and the material advance rate to determine the steel plate length. The gauge meter AGC of all stands is locked on when the taper length reaches a certain length from the above-mentioned tip, which is obtained every moment. Then, the gauge meter type based on the taper application amount of each stand is continuously changed according to the rolling length.

Next, a method of changing the gauge meter type according to the rolling length calculated by the rolling length calculation device 60 will be described.
First, a method of giving the taper amount Δh _i to the plate thickness control will be described.
The gauge meter formula is given by the formula (10), but in the actual plate thickness control, the scale factor is introduced and the formula (11) is used.

[0036]

[Equation 10]

However, ΔS _i : deviation of rolling position after i-stand lock-on ΔP _i : load deviation after i-stand lock-on K _Ai : i-stand scale factor M _i : i-stand mill constant Q _i : i-stand plasticity coefficient Then, as shown in equation (11), the required taper amount (thickness deviation) in the thickness control with the scale factor introduced.
In order to obtain Δh _i , Δh is used as a change in the plate thickness control formula.
_The taper bias value Δh _Tp-i must be given instead of _i .

The relationship between Δh _Tp-i and Δh _i can be obtained as follows. First, since the load deviation ΔP _i is defined by the equation (12), it is substituted into the equations (10) and (11) to obtain the equations (13) and (14).

[0039]

(Equation 12)

[0040]

(Equation 13)

When ΔS _i is eliminated from the equations (13) and (14), the relation between Δh _Tp-i and Δh _i can be obtained by the equation (15).

[0042]

(Equation 15)

As is clear from the equation (15), if the scale factor is not introduced (K _A = 1), the taper bias value Δ
h _Tp-i matches the originally required taper value Δh _i .

As described above, the taper bias value Δh _Tp-i , which is the change in the plate thickness control formula for each stand, is calculated from the amount of taper imparted Δh _i to each stand, and formula (11) is used as the material rolling length. By changing it accordingly, it becomes possible to manufacture the tapered steel plate with high accuracy.

Further, the plate thickness on the delivery side of the final stand is measured, and based on the deviation between the target value of the delivery side plate thickness and the measured plate thickness,
The plate thickness accuracy can be further improved by adopting the monitor AGC that corrects the roll rolling position of each stand.

However, since a taper bias value is given to this monitor AGC with respect to the final stand outlet side plate thickness deviation, the final stand taper amount Δ as shown in FIG.
Add h ₇ .

Next, FIG. 3 shows a plate thickness control block at the time of manufacturing the above tapered thick steel plate. As shown in FIG. 3, the taper application amount Δh _i to each stand and the taper application amount Δh _i
The taper bias value Δh _Tp-i for each stand plate thickness control calculated based on
It is possible to manufacture the tapered steel plate with high accuracy by changing the value according to the material rolling length.

In the above embodiments, it is not guaranteed that the plate thickness finally reaches the target plate thickness taper amount. Therefore, the plate thickness gauge 30 installed on the exit side of the final stand 7 measures the plate thickness on the exit side of the final stage stand, and the roll reduction of each stand is performed based on the deviation between the target value of the exit side plate thickness and the measured plate thickness. The plate thickness accuracy can be further improved by correcting the position.

(Experimental Example) The tandem rolling mill shown in FIG. 1 was used to calculate the amount of taper applied to each stand and the taper bias value in consideration of the advance rate according to the formula (8), and used this for each rolling device 20. According to the rolling length during rolling (1
Rolling was performed by changing the gauge meter formula shown in formula (1). As a result, as shown in FIG. 4, it was possible to manufacture a tapered thick steel plate with an accurate target taper amount of 0.3 mm.

[0050]

As described above, in the method for manufacturing a tapered thick steel plate of the present invention, the distribution ratio of the taper application amount of each stand is taken into consideration in consideration of the change of the advanced rate under the condition that the mass flow balance is constant. By determining, it is possible to manufacture an accurate tapered thick steel plate with no response delay.

By continuously changing the determined distribution ratio based on the rolling length, it is possible to manufacture a tapered thick steel plate with high accuracy without being affected by the change in plastic characteristics. Further, the plate thickness accuracy can be further improved by actually measuring the plate thickness on the delivery side of the final stand and correcting the roll reduction position of each stand based on the deviation between the measured plate thickness and the delivery side target plate thickness.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a tandem rolling mill used for carrying out the method of the present invention.

FIG. 2 is a conceptual diagram of a tapered thick steel plate.

FIG. 3 is a block diagram of a plate thickness control at the time of manufacturing a tapered thick steel plate according to the present invention.

FIG. 4 is a manufacturing example of a tapered thick steel plate according to the present invention.

[Explanation of symbols]

1 to 7: stand, 10: steel plate, 20: rolling down device, 30:
Plate thickness gauge, 40: Calculation device, 50: Monitor correction control device, 60: Rolled steel plate length calculation device

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B21B 37/18 BBH 8315-4E B21B 37/12 111 B 37/14 BBH

Claims (2)

[Claims] 1. When a tandem rolling mill is used to manufacture a tapered thick steel plate whose plate thickness varies along the longitudinal direction in one coil using a gauge meter system, the mass flow balance of each stand is constant. A method for manufacturing a tapered thick steel plate, characterized in that, under a certain condition, a distribution ratio of a taper application amount of each stand is determined in advance in consideration of a change in an advanced rate. 2. Further, the plate thickness on the delivery side of the final stand is measured, and based on the deviation between the measured plate thickness and the delivery side target plate thickness,
The method for manufacturing a tapered thick steel plate according to claim 1, wherein the roll rolling position of each stand is corrected.