JP2953334B2 - Manufacturing method of tapered thick steel plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art As a method for controlling the thickness of a steel sheet to be rolled to a desired value in a rolling mill, a so-called gauge meter method for controlling the thickness is often employed. In this method, a rolling mill is used as a type of thickness measuring device. The actual thickness is calculated from the measured rolling position (roll gap) and rolling load, and the actual thickness is compared with a target thickness. In this method, the roll reduction position (roll reduction amount) is feedback-controlled so that the deviation always becomes zero.

According to this gauge meter control method, when rolling a tapered thick steel sheet whose thickness changes at a constant gradient from one end to the other end along the longitudinal direction of the steel sheet, the target sheet thickness is previously set to a predetermined pass. A method in which a taper shape is determined in a schedule or a method in which a target thickness is continuously changed by a taper amount corresponding to a change in an actually measured value such as a rolling speed during rolling is adopted.

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 by a value obtained by multiplying a desired taper inclination by an actual rolling speed.

As a second conventional example, there is a thickness control method disclosed in Japanese Patent Publication No. 55-61311. This is a method of controlling the sheet thickness in a single-stand rolling mill, and in a sheet thickness control method of detecting a load deviation between a rolling load and an externally applied reference load and controlling an absolute value of an exit side sheet thickness. In this method, the reference load is changed in accordance with the transport distance of the material being rolled, and the thickness of the rolled steel sheet in the longitudinal direction is changed.

Further, as a third conventional example, Japanese Patent Publication No. 58-1961
As a fourth conventional example, there is a thickness control method disclosed in Japanese Patent Publication No. 63-130205. These are all intended for single stand rolling mills.

Further, as a fifth conventional example, Japanese Patent Publication No.
No. 124 discloses a thickness control method. This is a method of calculating the roll reduction position in advance in consideration of the change in the plastic property due to the change in the thickness of the entry side, setting the reduction at a good timing according to the reduction speed, and preventing a decrease in control accuracy due to a response delay. is there.

[0008]

However, in the sheet thickness control method according to the first conventional example, due to a delay in response of the rolling system, a part of the steel sheet at a position where the rolling load or the like is actually measured and the actual measured value are used to obtain the calculated value. There is a case where the portion of the steel plate to which the reduced control is performed does not match, and good thickness accuracy cannot be obtained.

[0009] The thickness control method according to the second conventional example is as follows.
It is intended for a single-stand rolling mill such as a four-stage reversible rolling mill, and is not intended for a rolling mill composed of a plurality of stands such as a hot continuous finishing rolling mill. Therefore, since the application of the taper of the former stand and the mass flow balance are not taken into account, when the present invention is applied to a tandem type rolling mill, the sheet passing property and the sheet thickness accuracy are deteriorated. The same applies to the methods according to the third and fourth conventional examples.

Further, in the sheet thickness control method according to the fifth conventional example, even if a high-precision rolling prediction formula is used in consideration of the plastic coefficient from the inlet and outlet sheet thickness, the sheet temperature, and the like, the problem of response delay in a tandem rolling mill. Cannot obtain high plate thickness accuracy.

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

[0012]

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

The tapered steel plate may be manufactured by continuously changing the determined distribution ratio based on the pressure elongation. Specifically, for example, the final stand exit side target taper amount in consideration of the advance ratio change of each stand, the taper addition amount of each stand calculated in advance based on each stand exit side plate thickness preset value and the advance ratio preset value, Rolling may be continuously changed based on the steel sheet transport distance (pressure extension) obtained from the length measuring device. Alternatively, the roll thickness of each stand may be corrected based on the deviation between the actually measured plate thickness and the target plate thickness on the discharge side by actually measuring the plate thickness on the exit side of the final stand.

[0014]

In the method for producing a tapered steel plate according to the present invention,
By determining the distribution ratio of the amount of taper applied to each stand under the condition of a constant mass flow balance in consideration of the change in the advance rate, a tapered thick steel plate with no response delay and high accuracy can be manufactured.

By continuously changing the determined distribution ratio based on the elongation of the pressure, it is possible to manufacture a tapered thick steel plate with high accuracy without being further affected by fluctuations in plastic characteristics.

Further, the sheet thickness accuracy can be further improved by actually measuring the sheet thickness at the exit side of the final stand, and correcting the roll reduction position of each stand based on the deviation between the actually measured sheet thickness and the exit side target sheet thickness. .

[0017]

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

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

Further, an arithmetic unit 40 is provided for calculating the taper bias value of each stand according to a target taper amount given from the outside at the time of applying the taper, and for giving a draft reduction command to the drafting unit 20. Furthermore, in order to improve the thickness accuracy, based on the thickness results obtained from the thickness gauge 30,
Monitor compensation controller 50 to correct the rear stand pressure reduction
Is provided. Further, a pressure extension calculating device 60 for detecting the pressure extension (steel plate transport distance) is also provided.
The roll peripheral speed of the final stand (seventh stand) 7 is input to the pressure extension length calculating device 60.

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

In such a facility, the taper application amount of each stand is calculated in advance in consideration of the change in the advance rate, and the calculated taper application amount is continuously changed by the elongation of the pressure to produce a tapered thick steel plate. .

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

[0023]

[Number 1] _{h i (1 + f i)} V i = h i + 1 (1 + f i + 1) V i + 1 ··· (1) However, h _{i: i} stand delivery side thickness preset value f _{i: i} stand forward slip preset value V _i: i stand roll peripheral speed, where the mass flow balance after taper grant is given by considering the change in the forward slip (2).

[0024]

## EQU2 ## (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) , Delta] h _i: i stand thickness variation Delta] f _i: the i stand forward slip change (1), with respect to V _i (3) is obtained, the (3)
By substituting into equation (2), equation (4) is obtained.

[0025]

(Equation 3)

[0026] In equation (4), the third term of both sides if approximated to 0 because it is very small, with respect to Delta] h _i is (5) is obtained.

[0027]

(Equation 5)

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

[0029]

(Equation 6)

H _i : Preset value of plate thickness on entry side of i-stand Δr _i : Change in reduction rate of i-stand

[0031]

(Equation 8)

[0032]

(Equation 9)

As described above, under the condition that the mass flow between 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 value of the plate thickness at each exit side of the stand. Based on h _i and the advanced rate preset value f _i , it can be sequentially calculated by the above equation (8).

Next, in order to detect the position of the steel sheet, the rolled steel sheet length calculating device 60 calculates the material speed from the roll peripheral speed of the seventh stand 7 and the material advance rate, and calculates the steel sheet length. The gauge meters AGC of all the stands are locked on when the taper length becomes constant from the above-mentioned tip. Thereafter, the gauge meter type based on the taper application amount of each stand is continuously changed according to the pressure extension.

Next, a method of changing the gauge meter type based on the pressure extension calculated by the pressure extension calculating device 60 will be described.
First, a method for imparting a taper amount Delta] h _i of plate thickness control.
The gauge meter equation is given by equation (10), but in actual sheet thickness control, equation (11) is used by introducing a scale factor.

[0036]

(Equation 10)

Where ΔS _i : rolling position deviation 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 Therefore, as shown in equation (11), the required taper amount (thickness deviation) in thickness control with scale factor introduced
In order to obtain Δh _i , Δh is used as a change in the thickness control formula.
_A 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 equation (12), substituting this into equations (10) and (11) yields equations (13) and (14).

[0039]

(Equation 12)

[0040]

(Equation 13)

When ΔS _i is eliminated from the expressions (13) and (14), the relationship between Δh _Tp-i and Δh _i is obtained by the expression (15).

[0042]

(Equation 15)

As is apparent 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 .

[0044] As mentioned above, the taper providing amount Delta] h _i for each stand, and calculate a tapered bias value Delta] h _Tp-i is a thickness-controlled change-from each stand, (11) to the material rolling length By changing the thickness in accordance with it, it becomes possible to manufacture a tapered steel plate with high accuracy.

Further, the sheet thickness at the exit side of the final stand is actually measured, and based on the deviation between the target sheet thickness at the exit side and the actually measured sheet thickness,
By adopting the monitor AGC which corrects the roll reduction position of each stand, the thickness accuracy can be further improved.

However, since a taper bias value is applied to the monitor AGC for the deviation of the sheet thickness on the exit side of the final stand, as shown in FIG.
the h ₇ to grant.

Next, FIG. 3 shows a 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
And the taper bias value Δh _Tp-i for each stand plate thickness control calculated based on
Is changed in accordance with the elongation of the material pressure, thereby making it possible to accurately manufacture a tapered steel plate.

In the above embodiment, it is not guaranteed that the plate thickness finally reaches the target plate thickness taper amount. Therefore, the thickness of the sheet on the exit side of the final stand is actually measured by the thickness gauge 30 installed on the exit side of the final stand 7, and based on the deviation between the target sheet thickness on the exit side and the actually measured sheet thickness, the roll pressure of each stand is reduced. By correcting the position, the thickness accuracy can be further improved.

(Experimental example) The amount of taper applied to each stand and the taper bias value were calculated by the tandem rolling mill shown in FIG. (1) depending on the elongation during rolling.
Rolling was performed by changing the gauge meter formula shown in formula 1). As a result, as shown in FIG. 4, a tapered thick steel plate with high accuracy with respect to the target taper amount of 0.3 mm could be manufactured.

[0050]

As described above, in the method of manufacturing a tapered thick steel plate according to the present invention, the distribution ratio of the taper application amount of each stand is determined under the condition of a constant mass flow balance, taking into account the change in the advance rate. By determining, it is possible to manufacture a tapered steel plate with high accuracy without response delay.

Incidentally, by continuously changing the determined distribution ratio based on the elongation of the pressure, it is possible to manufacture a tapered thick steel plate with high accuracy without being further affected by the change in the plastic characteristic. Further, the thickness of the sheet at the exit side of the final stand is measured, and the roll reduction position of each stand is corrected based on the deviation between the actually measured thickness and the target thickness of the exit side, so that the thickness accuracy can be further improved.

[Brief description of the 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 thickness control block diagram when a tapered thick steel plate is manufactured according to the present invention.

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

[Explanation of symbols]

1-7: Stand, 10: Steel plate, 20: Roll-down device, 30:
Thickness gauge, 40: Calculation device, 50: Monitor correction control device, 60: Rolled steel plate length calculation device

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-16813 (JP, A) JP-A-51-97565 (JP, A) JP-B-61-14890 (JP, B2) (58) Field (Int.Cl. ⁶ , DB name) B21B 37/24

Claims (2)

(57) [Claims] 1. In a tandem rolling mill, when a taper thick steel plate whose thickness changes along a longitudinal direction in one coil is manufactured by a gauge meter type, a mass flow balance of each stand is constant. A method of manufacturing a tapered thick steel plate, wherein a distribution ratio of a taper application amount of each stand is determined in advance under a certain condition in consideration of a change in an advanced rate. Further, the sheet thickness at the exit side of the final stand is actually measured, and based on a deviation between the actually measured sheet thickness and the target sheet thickness at the exit side,
2. The method for manufacturing a tapered thick steel plate according to claim 1, wherein the roll reduction position of each stand is corrected.