JP6385847B2 - Thickness control method of rolling mill - Google Patents

Description

  The present invention relates to a sheet thickness control method for a rolling mill, and more particularly to a roll gap setting method.

Conventionally, when rolling a rolled material such as a thick steel plate using a rolling device, adjusting a gap between a pair of work rolls of a rolling mill provided in the rolling device (hereinafter referred to as a roll gap amount), Thickness control is performed so that the exit side thickness of the rolled material matches the target value.
The rolling mill has a plate thickness control unit for controlling the plate thickness, and the plate thickness control unit calculates a roll gap amount for obtaining a target plate thickness. That is, in the plate thickness control unit, after calculating the rolling load P by the rolling model, the roll gap amount is calculated by using a gauge meter equation (the following equation) representing the relationship between the roll gap, the rolling load, and the target plate thickness. Yes.

H = S + P / M
Here, M is a mill constant, and (1 / M) is an opening amount of the roll gap at a position where the rolled material passes in the rolling mill when a unit load is applied. This gauge meter type always includes an error ΔS, although there is a difference in degree. That is, in order to obtain the target plate thickness H, the true roll gap needs to be set not to S but to a roll gap of S + ΔS. Note that the prediction error of the rolling load P is not considered.

The value of the error ΔS can be found by using the following result using the rolling result after the rolling is completed.
ΔH = ΔS + ΔP / M
ΔH ＝ H ^act −H ^ref
ΔP ＝ P ^act −P ^cal
Here, H ^act is a measured plate thickness, H ^ref is a target plate thickness, P ^act is a measured rolling load, and P ^cal is a rolling load calculated from H ^ref .

By the way, in the control of the plate thickness using the gauge meter type, as a factor that the above error ΔS (gauge meter error ΔS) occurs,
Factor (1): Roll diameter change due to roll wear and thermal expansion Factor (2): Roll gap change due to roll deflection Factor (3): Estimated error of mill constant M is considered.

Therefore, after the rolling of a predetermined pass (for example, the n-th pass) is finished, the gauge meter error ΔS is obtained by the gauge meter type, and the gauge meter error ΔS is corrected in the rolling of the next (n + 1) pass. A method for determining the roll gap _{Sn + 1} using a gauge meter type (following formula) has been conventionally employed.
H _{n + 1} = S _{n + 1} + ΔS + P _{n + 1} ^cal / M
Further, the gauge meter error ΔS does not use the value calculated from the rolling result of the nth pass, but also considers the influence of the previous pass, for example, the gauge meter error ΔS _{− at the} (n−1) th pass. _In many cases, ΔS ′ calculated by the following equation is used using ₁ .

ΔS ′ = αΔS + (1-α) ΔS ₋₁
In this way, the roll that realizes the plate thickness closer to the target plate thickness by learning the gauge meter error ΔS as the cause of the gauge meter error generation factors (1) to (3) described above. A gap can be set.
As described above, a number of techniques have been developed to improve the accuracy of the thickness control of the rolled material by the gauge meter method by reflecting the rolling result of the previous pass on the current pass. Applicable.

  In other words, the sheet thickness control method of the rolling mill disclosed in Patent Document 1 uses the gauge meter formula including the roll gap offset amount and the mill constant to control the sheet thickness of the rolled material. The offset amount and the mill constant are estimated based on the actual measurement data measured during the rolling, and the estimated roll gap offset amount and the mill constant at the previous rolling are corrected in consideration of the previous and next rolling conditions, This is a technique characterized by applying the corrected roll gap offset amount and the mill constant to sheet thickness control at the next rolling.

JP-A-8-155515

The above-described method calculates the gauge meter error ΔS based on the gauge meter equation, and corrects the roll gap S of the next pass rolling based on the calculated gauge meter error ΔS. However, this technique is based on the premise that ΔS in the rolling of the next pass can be completely predicted by ΔS estimated in the previous pass.
However, the gauge meter error ΔS is not constant over the entire path and is not completely predictable. This is because the gauge meter error due to the above factors (1) to (3) changes depending on the rolling amount, rolling load, sheet width, and the like. Thus, in the method of setting the roll gap by predicting ΔS from the rolling result before that, it is unavoidable that a plate thickness error occurs due to the deviation of prediction of ΔS.

The technique of the above-mentioned patent document 1 cannot cope with such a problem.
Therefore, in view of the above problems, the present invention improves the gauge meter error learning method in the thickness control method using the gauge meter type, and calculates the roll gap for obtaining the target thickness with higher accuracy. An object of the present invention is to provide a sheet thickness control method.

In order to achieve the above-described object, the present invention takes the following technical means.
The sheet thickness control method of the present invention is a sheet thickness control method for controlling the roll gap of a rolling mill that performs rolling in a plurality of passes with the same roll, and the measured value of the exit side sheet thickness in a plurality of passes prior to the current pass. From the set value of the roll gap, the mill elongation during rolling is obtained, and the relational expression (P = f _n (δ)) between the obtained mill elongation and the measured value of the rolling load is obtained. In setting the gap, obtain the rolling load from the plate thickness before the next pass and the target plate thickness after the next pass, and determine the mill elongation in the next pass using the relational expression (P = f _n (δ)), The roll gap amount in the next pass is calculated and set by subtracting the mill elongation obtained from the target plate thickness of the next pass.

Preferably, in the first pass rolling, a relational expression (P = f _n (δ)) between the mill elongation amount and the measured value of the rolling load is initialized, and the mill elongation amount and rolling load are calculated from the rolling data after the second pass. coefficient of measured values of the equation _{(P = f n (δ)} ) the coefficients in determining, the third pass after sequentially with increasing number of passes, within the relational expression _{(P = f n (δ)} ) It is good to correct.

  According to the present invention, it is possible to improve the gauge meter error learning method and calculate the roll gap for obtaining the target plate thickness with higher accuracy in the plate thickness control method using the gauge meter type. .

It is the flowchart which showed the roll gap setting method by the conventional method. 3 is a flowchart illustrating a roll gap setting method according to the present invention. It is the figure which showed the pass schedule at the time of performing rolling by this invention. It is the figure which showed the rolling load at the time of performing rolling by this invention. It is the figure which showed the gauge meter error at the time of rolling by the conventional method. It is the figure which showed the gauge meter error at the time of performing rolling by this invention. It is the figure which showed the outline of the rolling mill. It is the figure which showed the example of measurement of mill elongation and rolling load.

Hereinafter, a sheet thickness control method for a rolling mill according to the present invention will be described with reference to the drawings.
As shown in FIG. 7, a rolling apparatus 1 for rolling a rolled material W such as a thick steel plate has a heating furnace 2 that heats the rolled material W on the upstream side thereof, and a rolling material W on the downstream side of the heating furnace 2. The rough rolling machine 3 which performs rough rolling of this is provided. On the downstream side of the rough rolling mill 3, a finish rolling mill 4 for performing finish rolling is provided. The slab R heated in the heating furnace 2 is rolled a plurality of times (a plurality of passes) by the rough rolling mill 3 and the finish rolling mill 4 to become a rolled material W (thick steel plate) of the product.

A roughing mill 3 and a finish rolling mill 4 (hereinafter referred to as a rolling mill) provided in the rolling device 1 include a pair of work rolls 5 and 5 for rolling the rolled material W and a pair of backup rolls 6 for backing it up. 6.
Further, the rolling mill is provided with a hydraulically driven reduction device that adjusts the gap length between the work rolls 5 and 5 (hereinafter referred to as roll gap amount). The rolling mill is provided with a load cell for measuring the rolling load. On the exit side of the rolling mill, a thickness gauge for measuring the exit side plate thickness of the rolled material W is provided. As the thickness gauge, a γ-ray thickness gauge or the like can be employed. In addition, when the in-line plate | board thickness measuring means is not comprised, an operator may measure the delivery side plate | board thickness of the rolling material W manually using measuring tools, such as a micrometer.

The rolling mill receives the rolling load measured by the load cell and the exit side thickness measured by the thickness gauge, and controls the roll gap amount so that the exit side thickness of the rolled material W becomes a predetermined value. A control unit is provided. The plate thickness control unit is composed of a process control or a PLC, and an AGC control system, a vendor control system, and the like are incorporated in the form of a program.
The plate thickness control unit in the present embodiment basically executes AGC (for example, BISRA-AGC) using a gauge meter type to control the roll gap amount. The AGC using the gauge meter type is to determine the exit side thickness of the rolling mill in consideration of the elasticity of the rolling mill and the deformation resistance of the rolled material W. For example, the AGC is based on the rolling load measured by the load cell. The exit side plate thickness is estimated in consideration of the mill constant and the like, and the roll gap is changed based on the value to control the rolling mill.

Furthermore, the plate thickness control unit of the present embodiment includes a process for improving the learning method of the gauge meter error ΔS in the AGC using the gauge meter formula and calculating the roll gap for obtaining the target plate thickness with higher accuracy. ing. This process is specific to the plate thickness control method of the present invention.
Before describing the plate thickness control method of the present invention, first, a method for setting a roll gap by a conventional method will be described with reference to FIG.

First, as shown in STEP 101 of FIG. 1, a set value S ₁ of the roll gap of the first pass is calculated based on a gauge meter formula (following formula). Thereafter, the rolling on the basis of the set values S ₁ of the roll gap.
S ₁ = H ₁ ^ref -P ₁ ^cal / M
In STEP 102, the rolling result (H ₁ ^act , P ₁ ^act ) of the first pass is acquired.

In STEP 103, a gauge meter error value based on the rolling performance of the first pass is calculated by the following equation.
ΔS ₁ = ΔH ₁ -ΔP ₁ / M
ΔH ₁ = H ₁ ^act −H ₁ ^ref
ΔP ₁ = P ₁ ^act −P ₁ ^cal
Then, in STEP104, the second pass of the roll gap amounts S _2, set by the following equation, is rolling on the basis of the set value S ₂ of the roll gap.

S ₂ = H ₂ ^ref -P ₂ ^cal / M-ΔS ₁
In STEP 105, the rolling result (H ₂ ^act , P ₂ ^act ) of the second pass is acquired.
In STEP 106, a gauge meter error value based on the rolling performance in the second pass is calculated by the following equation.
ΔS ₂ = ΔH ₂ -ΔP ₂ / M
ΔH ₂ = H ₂ ^act −H ₂ ^ref
ΔP ₂ = P ₂ ^act −P ₂ ^cal
Based on the obtained ΔS ₂ , in STEP 107, the roll gap amount S ₃ of the third pass is set by the following equation, and rolling is performed based on the set value S ₃ of the roll gap.

S ₃ = H ₃ ^ref -P ₃ ^cal / M-ΔS ₂
In STEP 108, the rolling result (H ₃ ^act , P ₃ ^act ) of the third pass is acquired.
In STEP 109, a gauge meter error value based on the rolling performance in the third pass is calculated by the following equation.
ΔS ₃ = ΔH ₃ -ΔP ₃ / M
ΔH ₃ = H ₃ ^act −H ₃ ^ref
ΔP ₃ = P ₃ ^act −P ₃ ^cal
Hereinafter, the same calculation at STEP110～STEP112, set the roll gap amount S ₄ to S _n from the fourth pass to the n th pass.

The above is a method for setting a roll gap by a conventional method, and is a technique based on the premise that ΔS in rolling of the next pass can be completely predicted by ΔS estimated in the previous pass.
However, in actual rolling, the gauge meter error ΔS is not constant over the entire path and is not completely predictable. Therefore, in the method of setting the roll gap by predicting ΔS from the previous rolling result (conventional plate thickness control technology), it is unavoidable that a plate thickness error will occur due to the deviation of prediction of ΔS.

The plate thickness control method of the present invention is a technique that overcomes this difficulty.
Hereinafter, the plate thickness control method of the present invention will be described in detail with reference to FIG.
First, in the plate thickness control method of the present invention, the same calculation method as the conventional method is adopted up to the second pass. That is, as shown in STEP 1 of FIG. 2, the roll pass set value S ₁ for the first pass is calculated based on the gauge meter formula (following formula), and rolling is performed based on the roll gap set value S ₁ .

S ₁ = H ₁ ^ref -P ₁ ^cal / M
In STEP 2, the rolling result (H ₁ ^act , P ₁ ^act ) of the first pass is acquired.
In STEP 3, a gauge meter error value based on the rolling performance of the first pass is calculated by the following equation.
ΔS ₁ = ΔH ₁ -ΔP ₁ / M
ΔH ₁ = H ₁ ^act −H ₁ ^ref
ΔP ₁ = P ₁ ^act −P ₁ ^cal
Thereafter, in STEP 4, the calculation of the measured value δ ₁ of the mill elongation amount in the first pass is performed by the following equation.

δ ₁ ＝ H ₁ ^act −S ₁
In STEP5, the roll gap amount S _2, is set by the following equation.
S ₂ = H ₂ ^ref -P ₂ ^cal / M-ΔS ₁
Similarly, the rolling results (H ₂ ^act , P ₂ ^act ) of the second pass are acquired at STEP 6 and the measured value δ ₂ of the mill elongation at the second pass is calculated at STEP 7 using the following equation. .

δ ₂ ＝ H ₂ ^act −S ₂
Thereafter, in STEP 8, a mill elongation formula P = f ₂ (δ) up to the second pass is created. Here, f ₂ () is a function that satisfies P ₁ = f ₂ (δ ₁ ) and P ₂ = f ₂ (δ ₂ ). As f ₂ (δ), it is advisable to adopt a simple mathematical expression, for example, the following quadratic expression expressed as the relationship between the mill elongation δ and the measured values (P ₁ , P ₂ ) of the rolling load. .

P = a ₀ + a ₁ * δ ₁ + a ₂ * δ ₂ ²
Subsequently, in STEP 9, using the mill elongation formula P = f ₂ (δ) created in STEP 8, prediction calculation of δ ₃ of the mill elongation of the third pass is performed, and based on the result, in STEP 10 ,
Based on the following formula, the roll gap amount of the third pass is calculated.
S ₃ = H ₃ ^ref −δ ₃ ^cal
Thereafter, the rolling results (H ₃ ^act , P ₃ ^act ) of the third pass are acquired at STEP 11, and the measured value δ ₃ of the mill elongation at the third pass is calculated by STEP 12 at STEP 12.

δ ₃ ＝ H ₃ ^act −S ₃
In STEP 13, a mill elongation formula P = f ₃ (δ) up to the third pass is created. Here, f ₃ () is a function satisfying P _i = f ₃ (δ _i ) (i = 1, 2, 3).
Thereafter, STEPs 14 to 18 are performed in the same manner to predict calculation of δ ₄ of the fourth pass mill elongation amount, calculation of the fourth pass rolling, calculation of measured value δ ₄ of the fourth pass mill elongation amount, fourth pass Mill elongation formula P = f ₄ (δ) is created.

After that, rolling will proceed, but the sheet thickness control method at that time proceeds in accordance with STEPs 19 to 23. That is, the prediction calculation of δ _n of the mill elongation amount of the _n- th pass, the rolling of the n-pass, the calculation of the measured value δ _n of the mill elongation amount of the n-pass, the mill elongation formula P = f _n ( δ) is created.
Here, as f _n (δ), the relationship between the mill elongation δ and the measured value of rolling load (P _n-1 , P _n-2 , P _n-3 ,..., P _n ) is a simple mathematical expression. For example, what is expressed in the form of an n-order equation shown below may be adopted.

P = a ₀ + a ₁ * δ ₁ + a ₂ * δ ₂ ² + ... + a _n * δ _n ⁿ
As described above, in the thickness control method using the gauge meter type, the roll gap for obtaining the target thickness can be calculated with higher accuracy by improving the learning method of the gauge meter error ΔS. It becomes. In particular, it is possible to make the plate thickness at the tip of the rolled material W corresponding to the start of rolling coincide with the target value.

In the above-described sheet thickness control method of the present invention, in STEP 4, in accordance with the idea of STEP 8, for example, an average mill elongation formula based on past rolling results.
P = f _std (δ)
Create
δ ₁ = f ^-1 _std (P ₁ ^cal )
The roll elongation S ₁ for obtaining the target plate thickness H ₁ for the first pass may be calculated by predicting the mill elongation amount for the first pass.

Also, the mill elongation type up to the nth pass
P = f _n (δ)
In the production of, the rolling results (P ₁ , P ₂ ,…, P _n , δ ₁ , δ ₂ ,…, δ _n ) of all the first to n-th passes are not satisfied, but are approximately satisfied The function f _n () may be adopted. At that time, it is desirable to create an approximate expression with a greater weight based on the latest rolling performance. When the sheet width and strength class of the rolled material W change, it is desirable to newly rebuild the mill elongation formula.

When creating an approximate expression of mill elongation, when there are many rolling achievements close to a certain rolling achievement i (rolling load _Pi , mill elongation amount δ _i ) (rolling achievement j, rolling achievement j + 1, rolling achievement j + 2 ,..., The weight of the rolling record i is reduced, and conversely, if there is no rolling record close to the rolling record k (rolling load P _k , mill elongation δ _k ), the weight of the rolling record k is increased. It is preferable to do this.
The results of rolling experiments using the plate thickness control method according to the present invention described above are shown in FIGS.

3 and 4 show the pass schedule and the transition of rolling load when the plate thickness control method according to the present invention is applied.
On the other hand, FIG. 5 shows the gauge meter error when the setup calculation is performed by the conventional method, and FIG. 6 shows the gauge meter error when the setup calculation is performed by the present invention. As is clear from comparing FIG. 5 and FIG. 6, by applying the plate thickness control method of the present invention, various errors included in the gauge meter equation are accurately identified and the gauge meter equation is corrected. Thus, it can be seen that high thickness accuracy can be obtained during rolling.

  FIG. 8 shows an example in which the relational expression between the mill elongation amount δ and the rolling load P is constructed by applying the technique of the present invention when the same material is rolled by the same rolling mill. As is apparent from this figure, even when the same material (variety and size) is rolled by the same rolling mill, the mill elongation amount and the rolling load P at rolling chance 1 and then rolling chance 2 by rearranging the rolling rolls. The relational expression of is different. However, in any chance, if within the same chance, δ and P are plotted with good reproducibility on the same curve expressed by a quadratic expression, for example. Thus, by sequentially constructing the relational expression of δ and P, it is possible to predict the mill elongation from the rolling load prediction result and set an appropriate roll gap.

  It should be thought that embodiment disclosed this time is an illustration and restrictive at no points. In particular, in the embodiment disclosed this time, matters that are not explicitly disclosed, for example, operating conditions and operating conditions, various parameters, dimensions, weights, volumes, and the like of a component deviate from a range that a person skilled in the art normally performs. Instead, values that can be easily assumed by those skilled in the art are employed.

DESCRIPTION OF SYMBOLS 1 Rolling apparatus 2 Heating furnace 3 Rough rolling mill 4 Finish rolling mill 5 Work roll 6 Backup roll W Rolled material

Claims (2)

A gauge control method for controlling the roll gap of the rolling mill is rolling in multiple passes in the same roll,
From the measured value of the exit side plate thickness in multiple passes before the current pass and the set value of the roll gap, the mill elongation during rolling is obtained, and the relational expression between the obtained mill elongation and the measured value of the rolling load (P = f _n (δ))
In setting the roll gap of the next pass, the rolling load is obtained from the plate thickness before the next pass and the target plate thickness after the next pass, and the mill elongation in the next pass is calculated using the relational expression (P = f _n (δ)). A roll thickness control method for a rolling mill, characterized in that a roll gap amount in the next pass is calculated and set by subtracting the mill elongation obtained from the target plate thickness of the next pass. In the first pass rolling, the relational expression (P = f _n (δ)) between the mill elongation and the measured value of the rolling load is initialized,
From the rolling data after the second pass, determine the coefficient in the relational expression (P = f _n (δ)) between the mill elongation and the measured value of the rolling load,
The sheet thickness control method for a rolling mill according to claim 1, wherein the coefficient in the relational expression (P = f _n (δ)) is corrected sequentially with the increase in the number of passes after the third pass.