JPH0899110A - Method for controlling thickness with rolling mill - Google Patents

Abstract

PURPOSE: To control thickness with a high accuracy from the time when a material to be rolled is bitten into a rolling mill in the case that the same material is rolled changing the direction every pass. CONSTITUTION: In a thickness control method with the rolling mill 4 at the time of rolling the material (steel sheet) to be rolled which is extracted from a heating furnace 1 changing the direction every pass, every alternate rolling of the material to be rolled in the forward direction 5 and in reverse direction 6, the temp. the predicting calculation of the bitten end part of the material to be rolled is executed before the end part is bitten into the rolling mill, the rolling load at the time of biting the material into the rolling mill is calculated based on the predicted temp., the opening degree of roll is determined from the rolling load and the opening degree of roll is set to the rolling mill.

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 plate thickness by a rolling mill, and in particular, highly accurately estimates the tip temperature of a material to be rolled that is caught in the rolling mill when rolling in different rolling directions. The present invention relates to a strip thickness control method by a rolling mill capable of performing highly accurate roll opening setting by using it for rolling load calculation.

[0002]

2. Description of the Related Art Accurately predicting a rolling temperature when rolling a material to be rolled, for example, a thick steel plate, is the most basic requirement for manufacturing a steel plate with good dimensional accuracy by controlling the thickness and flatness. It is one of the important and important elemental technologies. That is, if the temperature estimation of the steel sheet is inaccurate, the estimation of the rolling load will be erroneous, which will lead to a reduction in sheet thickness accuracy and a defective shape. Particularly, since the plate thickness accuracy of the steel plate tip portion (hereinafter, also referred to as a biting end portion) that is first bit into the rolling mill cannot be controlled by the automatic plate thickness control device, the plate thickness accuracy of the tip portion is improved. For that purpose, it is necessary to accurately predict the load when the steel plate is bitten into the rolling mill, but for that purpose it is essential to accurately predict and evaluate the temperature of the biting end of the steel plate. Is.

Conventionally, as a technique for predicting the steel plate tip temperature during the rolling of a thick steel plate, for example, JP-A-62-409 is used.
As disclosed in Japanese Unexamined Patent Publication No. 27-27, the average temperature of the tip of the steel sheet is calculated from the temperature distribution in the longitudinal direction of the steel sheet when present in the heating furnace and the air-cooling time and the water-cooling time until the steel sheet is caught in the rolling mill. There was a method of estimating the difference between the average temperature of the steel plate central part and the average temperature of the steel plate tip part when the rolling mill is engaged.

[0004]

However, in rolling in which the rolling direction for the same material to be rolled is changed for each pass, for example, in the odd-numbered and even-numbered passes, the direction is alternately changed in the longitudinal direction of the steel sheet. When rolling is performed, as shown in FIG. 7, the temperature changes at the front end and the rear end of the steel sheet are shown along with the change in the sheet thickness with respect to the time from the extraction of the heating furnace to the end of rolling. (Front end) and tail end (rear end)
Since the temperature is different in and, even if it is possible to predict the temperature of the front end of the steel plate longitudinal direction at the time of extracting the heating furnace, even if it is possible to determine the roll opening for an appropriate plate thickness in the odd numbered passes from the predicted temperature, In the next even-numbered pass, the bite end changes to the tail end, so if the same predicted temperature is used, the roll opening cannot be obtained, so high-precision thickness control cannot be performed. was there.

This problem arises not only when a rectangular steel plate is rolled in the longitudinal direction (longitudinal direction) but also when it is rolled in the lateral direction (width direction) orthogonal to that direction, at normal temperature at both ends in the width direction. Exists because they are different.

The present invention has been made to solve the above-mentioned conventional problems, and when the same material to be rolled is rolled by changing the direction for each pass, the plate is caught from the time of being caught in the rolling mill. An object of the present invention is to provide a strip thickness control method by a rolling mill capable of controlling the thickness with high accuracy.

[0007]

DISCLOSURE OF THE INVENTION The present invention relates to a method for controlling a plate thickness by a rolling mill when rolling a material to be rolled while changing the direction for each pass, and Predictive calculation is made before the end bites into the rolling mill, the rolling load at the time of rolling mill biting is calculated based on the predicted temperature, the roll opening is determined from the rolling load, and the roll opening is rolled. The problem is solved by setting the machine.

In the present invention, in the above plate thickness control method, the material to be rolled may be rolled alternately in the forward direction and the reverse direction.

In the present invention, in the above plate thickness control method, the material to be rolled may be rolled not only in the longitudinal direction but also in the lateral direction.

[0010]

In the present invention, with respect to the biting end of the material to be rolled which changes for each pass, the temperature of the biting end before the biting of the rolling mill is accurately predicted and calculated each time. Also, since the roll opening can be set to an appropriate value according to the predicted temperature, it is possible to control the plate thickness with high accuracy even after the rolling mill is engaged.

In the present invention, when the material to be rolled is rolled alternately in the forward and reverse directions, a rectangular material to be rolled is alternately rolled in the longitudinal direction in the forward and reverse directions. When rolling with a rolling mill, whether it is an odd number of passes rolling from the front end or an even number of passes rolling from the tail end, always use the predicted temperature of the biting tip before biting the steel plate Since the rolling load is predicted at the time of insertion, the prediction accuracy of the rolling load is improved, so that it is possible to control the plate thickness with high accuracy even after the biting into the rolling mill.

In the present invention, when the material to be rolled is rolled not only in the longitudinal direction but also in the transverse direction, the order of the longitudinal direction in the case of claim 2 is set by a thick plate rolling line in which a reversing rolling machine is combined with a turning table. In addition to the rolling in the direction and the reverse direction, also when performing the rolling in the forward direction and the reverse direction in the width direction, it is possible to similarly control the plate thickness with high accuracy.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing the outline of a rolling line applied to the plate thickness control method of the first embodiment according to the present invention.

In the rolling line, a steel plate (not shown) is heated in the heating furnace 1 to a predetermined temperature, then extracted from the heating furnace 1, conveyed on the conveying table 2 and passed through the descaling device 3. And reaches the rolling mill 4 with the scale removed. This rolling mill 4 is a reversible rolling mill and has a forward pass (forward rolling) for rolling in the direction of arrow 5,
Reverse passes for rolling in the direction of arrow 6 (reverse rolling) are alternately performed.

In the present embodiment, when the rolling mill 4 performs reversible rolling, it is possible to constantly change the rolling direction of the steel sheet by the method described below in response to the change in the biting direction of the steel sheet by the rolling mill for each pass. The temperature of the bite end is predicted, the rolling load is predicted from the predicted temperature, the roll opening is calculated based on the value, and the sheet thickness accuracy is improved by setting the opening value.

That is, in the present embodiment, the end temperature calculation positions of the steel sheet are given at two points in the front and rear in the longitudinal direction as shown in FIG. 2, and the front end of the steel sheet in the longitudinal direction during extraction of the heating furnace (hereinafter referred to as the front end). ), The temperature of the longitudinal tail end (hereinafter referred to as the rear end) is estimated. From this predicted temperature at both ends, the steel plate temperature used as the basis for the load prediction calculation by selecting the temperature of the steel plate end on the side that is caught in the rolling mill in accordance with the rolling direction during reversible rolling of the steel plate. Prediction accuracy is improved, and the roll opening is calculated from the obtained predicted load.
By making settings, highly accurate thickness control is realized.

As shown in FIG. 7, the normal temperature is different between the leading end and the trailing end due to the initial temperature difference generated during heating by the heating furnace 1 and the like, so that it is finally used for calculating the roll opening. The acquisition position of the temperature of the biting end is selected for each pass according to the rolling direction. That is, when reversibly rolling the steel sheet extracted from the heating furnace 1, the first pass (rolling start pass:
In the forward pass (forward pass) rolling, the front end shown in FIG. 2 is the rolling-mesh end, so the predicted temperature of the front end is obtained and used for calculation of the rolling load at the cutting-end.

When the steel sheet moves to the rear of the rolling mill 4 (right side in the figure) after the rolling in the forward direction is completed, the steel sheet is rolled in the reverse direction as the second pass (reverse pass).
At the pass, the trailing end is the rolling mill bit end. Therefore, before reverse rolling, the predicted temperature of the trailing end, which is the biting end of the second pass, is calculated, the rolling load is calculated using this temperature, and the roll opening is set from the calculated rolling load. , Roll in the opposite direction.

When the rolling of the second pass is completed, the steel sheet returns to the front of the rolling mill 4 (left side in the drawing) again. Therefore, since the next third pass is a positive pass, the predicted temperature of the front end is used for the rolling load calculation as in the first pass. in this way,
In the present embodiment, the steel sheet front end temperature is used in the odd-numbered passes of the reversible rolling, and the rear end temperature is used in the even-numbered passes as the temperature of the bite end for the rolling load calculation.

Next, the method of predicting the temperature of the steel plate end portion in this embodiment will be described in detail. This temperature predictive calculation can be calculated using an analytical solution model of the heat conduction equation or a difference model. As an example, a case of using a temperature prediction model using an analytical solution will be described here.

When the heat conduction inside the steel material is expressed using a quadratic heat conduction equation, the following equation (1) is obtained.

∂T / ∂t = a (∂ ² T / ∂x ² + ∂ ² T / ∂y ² ) ... (1) t: time [hr] x: plate thickness direction position [m] y: longitudinal direction Position [m] a: Temperature transfer rate [m ² / hr] T: Temperature [° C]

By applying the above equation (1) to the steel sheet shown in FIG. 2 and solving it under appropriate boundary conditions, the following (2)
The thermal conductivity analysis solution shown in the equation is obtained, and this equation is used as the rolling temperature prediction model.

[0025]

[Equation 1]

However, μ _m and ν _n are obtained from the solutions of the expressions (3) and (4), respectively, and λ _mn has the relationship of the following expression (5).

CotX _m = {k / (α _s d)} _× X _m , μ _m = X _m / d (d: 1/2 plate thickness (mm)) (3) cotY _n = {k / (α _e l)} · Y _n , ν _n = Y _n / l (l: calculated length in longitudinal direction (mm)) (4) λ _mn ² = μ _m ² + ν _n ² (5) where A _mn : analysis Solution coefficient k: Thermal conductivity (kcal / mhr ℃) α _s : Surface heat transfer coefficient (kcal / m ² hr ℃) α _e : Edge side heat transfer coefficient (kcal / m ² hr ℃) T _s : Surface temperature (° C) T _e : End side temperature (° C) T ∞: Refrigerant temperature (° C)

The rolling temperature prediction model constructed as described above is used to predict the temperature at the end of the steel sheet, and the rolling load at the bite end is calculated based on the predicted temperature at the end.

The rolling load F is expressed by the following equation (6) as a function of deformation resistance k (T), strip width w, roll radius R, strip thickness h and the like.

F = f (k (T), w, R, h) (6)

Since the deformation resistance k (T) greatly depends on the temperature, it is possible to expect the accuracy of the rolling load prediction to be improved by accurately predicting the temperature. From the predicted rolling load calculated by the above equation (6), the roll opening is determined using the following equation (7), and the rolling mill is set.

S ₀ = h ₂ −F / M (7) S ₀ : Set roll opening [mm] h ₂ : Delivery side plate thickness [mm] F: Predicted rolling load [ton] M: Predicted mill constant [ton] / Mm]

That is, with the delivery side plate thickness h ₂ as the target plate thickness, the mill extension amount is calculated from the predicted load F and the predicted mill constant M, and the correction is added to obtain the set roll opening.

Further, this predicted rolling load is used as a set load of the automatic plate thickness control device, and the difference ΔF from the actually measured load during rolling is used.
Is converted into a sheet thickness variation amount Δh by the following equation (8), and the sheet thickness control is performed by changing the roll opening so as to cancel the sheet thickness variation.

Δh = ΔF / M (8) ΔF: load fluctuation [ton] Δh: plate thickness fluctuation [mm] M: predicted mill constant [ton / mm]

As an example, FIG. 3 shows a method of controlling the plate thickness when there is a change in the plastic constant. In FIG. 3, the rolling load F fluctuates by ΔF due to the plastic constant fluctuation as shown by the plasticity curve, and when the plate thickness fluctuation Δh occurs due to the load fluctuation ΔF, the roll is set to cancel this Δh. Open S
A control method for changing from ₀ to S is shown.

According to the plate thickness control method by the rolling mill of the present embodiment described in detail above, the calculation of the rolling load when the steel plate is bitten by the rolling mill is calculated for each pass by using the temperature prediction value at the biting end. Since it is performed with high accuracy by setting the roll opening degree using this, it is possible to improve the plate thickness accuracy.

In practice, the method of this embodiment is applied to the slab thickness 215.
mm, rolled rolled steel plate 9 having a rolled thickness of 6 mm to 40 mm
As a result of comparing the plate thickness accuracy evaluated by applying it to 0 pieces with the plate thickness accuracy by the conventional method, the tip plate thickness accuracy could be improved by 9.7%.

FIG. 4 is a schematic diagram showing the outline of a rolling line applied to the plate thickness control method of the second embodiment according to the present invention.

In the rolling line, a front turning table 7 and a rear turning table 8 are installed in front of and behind the rolling mill 4, respectively, and the direction can be changed by turning a steel plate. It is substantially the same as the rolling line of FIG. 1 applied to the first embodiment.

In this embodiment, the steel sheet heated in the heating furnace 1 is conveyed to the rolling mill 4 and is rolled in both forward and reverse directions by the rolling machine 4, and the steel sheet is turned 90 ° by the turning table 7 or 8. Then, the rolling in the longitudinal direction can be changed to the rolling in the width direction, and conversely, the rolling in the width direction can be changed to the rolling in the longitudinal direction.

The main purpose of turning the steel plate is to obtain the target plate width for the whole. That is, the direction in which the steel sheet is stretched by rolling is mainly in the rolling line direction perpendicular to the rolling rolls, so in tenter rolling, the steel sheet is turned 90 ° so that the width direction of the sheet coincides with the rolling direction. . Therefore, at the time of tenter rolling, the rolling table 7 on the front side of the rolling mill or the rolling table 8 on the rear side of the rolling mill turns 90 ° from right to left.

The steel sheet extracted from the heating furnace 1 has a temperature difference between the front end and the rear end in the longitudinal direction as described above, but the temperature difference also exists at both ends in the width direction. Therefore, when performing reversible rolling in the width direction as in the present embodiment, it is necessary to consider the temperature difference.

Therefore, in the present embodiment, as shown in FIG. 5, the temperature calculation positions of the end portions of the steel sheet are given at four points, and the steel sheet at the time of extracting the heating furnace has a longitudinal tip portion A, a longitudinal tail portion B, The temperatures at the widthwise ends C and D are estimated. By selecting the temperature at the time of rolling mill biting in correspondence with the rolling direction at the time of rolling the steel plate from these four predicted temperatures, the steel plate predicted temperature accuracy used for load prediction is improved, and the roll is calculated from the predicted load. By determining the opening and setting the opening, highly accurate plate thickness control can be realized.

In the present embodiment, the plate thickness control can be performed according to the flow chart shown in FIG.

That is, as in the case of the first embodiment, when the turning operation by the turning table 7 or 8 is not performed (No in step 110), the steel sheet extracted from the heating furnace 1 is not rolled. In the first pass (normal pass), the end portion A shown in FIG. 5 becomes the biting end portion, so the predicted temperature of the end portion A is used for the rolling load calculation of the tip end portion and the second pass (reverse pass). )
In this case, the end portion B becomes the biting end portion of the rolling mill, so the predicted temperature of the end portion B is used for the rolling load calculation of the tip portion (step 11).
2, 114, 116). By repeating steps 110 to 116 in the same way from the third pass onward, the predicted temperature of the end portion in the appropriate direction can be used for the rolling load calculation.

On the other hand, when the rolling table 7 or 8 is used for rolling (yes in step 110), the longitudinal direction of the steel sheet before rolling is perpendicular to the rolling direction after rolling, and the width direction of the steel sheet before rolling is the rolling direction. Since it changes, the plate width direction end C or D of the steel plate in FIG. 5 becomes the rolling mill bit end.
Therefore, in step 118, it is determined whether the turning is to the right or to the left in accordance with the change in the biting end portion with respect to the rolling mill.
In the case of s), the temperature of the widthwise end D is the temperature of the end A, the temperature of the end C is the temperature of the end B, the temperature of the end A is the temperature of the end C, and the temperature of the end B is By changing the temperature to the temperature of the end portion D (step 120), the temperature of the rolling-mesh-engaging end portion of the steel sheet in rolling is changed to the first embodiment even when the rolling table 7 or 8 is accompanied by the rolling operation. It becomes possible to make an accurate prediction in the same manner as.

On the contrary, in the case of the left turn (step 118, n
o) indicates that the temperature of the end C is the temperature of the end A, the temperature of the end D is the temperature of the end B, the temperature of the end B is the temperature of the end C, and the temperature of the end A is the end. By changing to the temperature of the portion D (step 122), it is possible to similarly predict the temperature of the meshed end portion of the steel sheet.

After converting the predicted position as described above,
If it is a positive pass in step 112, the above step 114
The predicted temperature of the end portion A is used for calculating the rolling load of the biting tip portion of the rolling mill in step 116 in the case of a reverse pass. The above operation is executed until the rolling is completed (step 124).

The temperature calculation method will be described. In addition to the equations (1) to (8) used in the case of the first embodiment,
In order to predict the temperatures of the widthwise end portions C and D shown in FIG. 5, the following equation (9) using a quadratic heat conduction equation is used for the heat conduction inside the steel sheet, and the first embodiment is used. The temperature of each of the ends A to D can be predicted in the same manner as in the above case.

[0051] ^{∂T / ∂t = a (∂ 2} T / ∂x 2 + ∂ 2 T / ∂z 2) ... (9) t: Time [hr] x: thickness-direction position [m] z: width Position [m] a: Temperature transfer rate [m ² / hr] T: Temperature [° C]

The above equation (9) has substantially the same form as the above equation (1), and is solved in exactly the same manner as the above equation (2) to analyze the heat conduction in the plate thickness and width direction. You can get a solution.

According to the plate thickness control method of the present embodiment described in detail above, the calculation of the rolling load when the steel plate is bitten into the rolling mill is calculated for each pass even when the reversible rolling involving the rolling of the steel plate is performed. Since the temperature prediction value of the biting end portion is used to perform the processing with high accuracy, it is possible to improve the sheet thickness accuracy by setting the roll opening degree using the rolling load.

Actually, the method of this embodiment is applied to a slab having a thickness of 215 m.
m, rolled thick steel plate 90 having a rolling end thickness of 6 mm to 400 mm
As a result of comparing the plate thickness accuracy evaluated by applying to the book with the plate thickness accuracy by the conventional method, the plate thickness deviation at the end of the steel plate was reduced by 11.3%.

Although the present invention has been specifically described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.

For example, the equation used for predictive calculation of the temperature of the steel sheet edge is not limited to the one shown in the above embodiment.

[0057]

As described above, according to the present invention,
When the same material to be rolled is rolled by changing the direction for each pass, the plate thickness can be controlled with high accuracy even after the rolling mill is engaged.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a rolling line applied to a first embodiment according to the present invention.

FIG. 2 is an oblique view showing a temperature calculation range of a rolled steel sheet that is a control target of the first embodiment.

FIG. 3 is a diagram qualitatively showing a roll opening correction method.

FIG. 4 is a schematic configuration diagram showing a rolling line applied to a second embodiment according to the present invention.

FIG. 5 is an oblique view showing a temperature calculation range of a rolled steel sheet that is a control target of the second embodiment.

FIG. 6 is a flowchart showing a temperature calculation procedure according to the second embodiment.

FIG. 7 is a diagram for explaining that the temperature differs between the front end and the rear end of the steel plate.

[Explanation of symbols]

 1 ... Heating furnace 2 ... Conveying table 3 ... Descaling device 4 ... Rolling machine 5 ... Forward path 6 ... Reverse path 7 ... Forward turning table 8 ... Backward turning table

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B21B 39/20 A 8315-4E B21B 37/12 111 F (72) Inventor Kazuhiro Yahiro Kurashiki City, Okayama Prefecture Mizushima Kawasaki Dori 1-chome (without street number) Kawasaki Steel Co., Ltd. Mizushima Steel Works (72) Inventor Isamu Okamura Mizushima Kawasaki Dori 1-chome (without street number) Kawasaki Steel Co., Ltd. Mizushima Steel Mfg.

Claims (3)

[Claims] 1. A method for controlling a plate thickness by a rolling mill when rolling a material to be rolled by changing the direction for each pass, wherein the temperature of the biting end of the material to be rolled is determined by determining the temperature at the biting end of the material to be rolled into the rolling mill. The calculation is performed before the rolling temperature is calculated, the rolling load when the rolling mill is bitten based on the predicted temperature is calculated, the roll opening is determined from the rolling load, and the rolling opening is set in the rolling mill. Method for controlling plate thickness by rolling mill. 2. The plate thickness control method according to claim 1, wherein the material to be rolled is alternately rolled in a forward direction and a reverse direction. 3. The plate thickness control method according to claim 1, wherein the material to be rolled is rolled not only vertically but also laterally.