JP2697573B2 - Control method of continuous rolling mill - Google Patents

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 a continuous rolling mill such as a finishing rolling mill for hot-rolled sheets, and more particularly to a calculation for setting rolling conditions when applying a change in running strip thickness.

[0002]

2. Description of the Related Art In order to improve product yield, improve sheet passing property, etc., continuous rolling of products having different thicknesses is carried out in a continuous rolling mill by changing a running thickness. In general, the calculation of setting rolling conditions (hereinafter referred to as schedule calculation) in changing the running thickness is often performed independently for the preceding plate portion and the following plate portion. When applying this method to hot rolling mills,
Since there are many influential variables compared to cold rolling, accurate calculation requires a lot of time or a large-sized computer, and accurate control of the calculation time is essential, resulting in an increase in the size of the control device. There was a problem.

[0003] By using a set condition table that incorporates various rolling experiences, this schedule calculation can be easily performed. After passing through the leading end of a product by a method based on a condition table, the center is changed to optimum rolling conditions based on the rolling performance. As a result, the optimum value for obtaining the desired rolling result is generally considerably different from the initial setting condition of the tip. Therefore, if this method is applied to the change in the running thickness, the optimum conditions obtained in advance are not reflected in the portion after the changing of the running thickness, so that the portion until the rolling conditions of the changed portion become stable becomes longer and the walking distance becomes longer. There was a problem that retention was reduced.

When there is no looper between the stands of the continuous rolling mill, or when the loop amount is kept constant even if there is a looper between the stands, all the stands are removed except for an error of about 1% due to widening. The mass speed of the plate obtained by multiplying the plate thickness on the inlet side and the outlet side by the plate speed is constant, and a control means using this is known as a so-called mass flow gauge. An apparatus for calculating a schedule using this principle has been proposed, for example, in Japanese Patent Application Laid-Open No. 60-177908. The outline is as follows. In this Japanese Unexamined Patent Publication No. Sho 60-177908, the equation (1) is first assumed on the assumption that the mass flow of each stand is constant. _{h n · v n · (1} + f n) = h i · v i · (1 + f i) ... (1) n: the final stand number i: each stand number (i = 1,2,3, ··· n) h : Outer side plate thickness v: Roll peripheral speed f: Advance rate In addition, v · (1 + f) indicates the speed of the plate on the outlet side of each stand, and is hereinafter referred to as “strip speed”.

The change amount of the target plate thickness on the exit side of the final stand is expressed by equation (2). ^{_{h n -h n * = Δh n}} ... (2) h n: thickness change before the final stand delivery side thickness h _n ^*: final stand out side the target thickness change amount of the delivery side thickness of each stand after the thickness change Is set as equation (3). ^{_{h i -h i * = Δhi ...}} (3) h i: plate thickness before the change of the i stand out side the target thickness h _i ^*: change of i stand delivery-side target thickness strip speed after the thickness change is stand between the tension variation Therefore, the strip speed is set to a constant value for each stand before and after the thickness change. Since the constant mass flow should be satisfied even after the change of the running thickness, the relationship of the formula (1) after the changing of the thickness becomes the formula (4). _{(H n + Δh n) ·} v n · (1 + f n) = (h i + Δh i) · v i · (1 + f i) ... (4) taking the difference from these relationships with equation (4) (1) And equation (5), from which the exit side plate thickness of each stand is calculated. _{Δh i = {[v n ·} (1 + f n)] / [v i · (1 + f i)]} · Δh n ... (5)

FIG. 3 is a diagram showing a path schedule calculation procedure of the above-mentioned Japanese Patent Application Laid-Open No. 60-177908. The path schedule calculation procedure of the above publication will be described again with reference to FIG. Since the finished plate thickness is the outlet plate thickness of the final stand N, the stand (pipot stand) serving as a reference for the calculation needs to be the final stand N. The strip speed v _n · (1 + f _n ) of the final stand and the strip speed v _i · (1 + f _i ) of the ith stand are known. To change the finish thickness in the thick direction by Delta] h _n is increment Delta] h _i of delivery side thickness of the i stands is calculated by (5), a Delta] h _i> Delta] h _n from the ratio of the velocity. Therefore, the calculation procedure, all out stand before from Hashimaban strip rate of the final stand of the pre-change thickness _{v n · (1 + f n} ) finishing thickness h _n, and the target thickness of the changed amount Delta] h _n It can be said that the setting of the side plate thickness is performed by proportional calculation.

[0007]

[0006] However, in the pass schedule calculation procedure of the above JP 60-177908 discloses, there is a problem that the material thickness h ₀ is not incorporated in the schedule calculation. In the hot rolling, a large reduction ratio of 20 to 50 times smaller than that of the cold rolling in the entire plurality of finishing stands. In this case (5) of the _{{[v n · (1 +} f n)] / [v i · (1 + f i)]}
Becomes a large value close to 20 to 50 when viewed for the first stand (i = 1), for example, Delta] h ₁ when the finishing thickness of the increased 0.5mm is increased 10 to 25 mm, usually of _h 0 -h ₁
= 10 to 20 mm, which may be an unreasonable result that the first stand becomes an empty pass.

Further, this method has a problem that errors in mass flow calculation are not considered. It is difficult to directly measure the strip speed and the plate thickness in a mass flow gauge, and a method of estimating a part by a gauge meter formula or the like is generally used. In this case, the estimated values of the strip speed and the plate thickness include an error. Also,
Even if the strip speed and strip thickness can be measured accurately, there is widening or shrinkage at the time of rolling. Thus, the rolling conditions determined by correcting the various errors by taking into account the problem are not utilized in the portion after the change in the running thickness, and there is a problem that the time until stabilization becomes long.

SUMMARY OF THE INVENTION The present invention has been made to solve these problems. It is an object of the present invention to easily and accurately calculate a pass schedule and control a continuous rolling mill based on the changed rolling conditions. It is an object of the present invention to provide a control method of a continuous rolling mill which is enabled.

[0010]

According to the present invention, there is provided a method for controlling a continuous rolling mill, comprising the steps of: Based on the process of measuring or estimating the rolling speed and sheet thickness of each stand entry / exit side to calculate the difference of each stand entry / exit side mass flow, and the finishing target sheet thickness of the succeeding plate part among the actual condition values A step of calculating the rolling conditions of the trailing plate portion under conditions that minimize the change in the mass flow difference of each stand between the leading plate portion and the trailing plate portion. The continuous rolling mill is controlled based on the conditions to roll the succeeding plate portion.

[0011]

According to the present invention, not only the thickness after changing the running thickness but also the thickness of the first stand entrance side is calculated through the calculation of the mass flow difference as a condition for creating the schedule, so that the reduction ratio of each stand is always reasonable. Distribution. The major cause of the error in the mass flow type preset calculation is the systematic one of the mechanical properties of the rolling mill with parameters such as the dimensional conditions and temperature conditions of the rolled material. If you look at each stand before and after the thickness change, it is considered constant. Therefore, if the mass flow difference between the stands is the same before and after the change in the thickness between runs, the error is temporarily canceled, so that the schedule of the thickness change with a small speed change can be easily and quickly created.

[0012]

FIG. 1 is a diagram showing a pass schedule calculation procedure in a method for controlling a continuous rolling mill according to an embodiment of the present invention. A tandem mill having three to seven stages is generally used as a finish rolling mill for rolling a material roughly rolled by hot rolling to a target thickness. In order to explain the general applicability, an N-stage tandem mill will be described mainly using a calculation formula. Is the material thickness h ₀ seen by measurement of roughing mill final stand out was calculated plate thickness or finish mill entry side thickness gauge. Entry-side velocity v ₀ mils and entry side of the table velocity or special speedometer or the first stand speed from the reverse ratio finish is seen. Mass flow M ₀ of the material entering the mill first stand finishing by these products can be calculated by the following equation (6). In this equation, in the first approximation, the width direction is fixed and the width expansion is ignored. M ₀ = h ₀ · V ₀ (6)

[0013] The strip speed of the first stand delivery side is obtained from the roll peripheral speed v ₁ and advanced rate f ₁ of the first stand. The plate thickness on the exit side of the first stand is determined by the gauge meter type of the first stand. The mass flow on the exit side of the first stand is expressed by the following equation (7). M ₁ = h ₁ · v ₁ · (1 + f ₁ ) (7) The mass flow difference between the exit side of the rough mill (the entrance side of the finishing mill) and the exit side of the first stand of the finishing mill using these measured values is (8) It becomes an expression. ΔM ₁ = M ₀ −M ₁ (8) Similarly, the mass flow difference between the (i−1) th stand and the (i) th stand is expressed by equation (9). _{ΔM i = M i-1 -M} i = h i-1 · v i-1 · (1 + f i-1) -h i · v i · (1 + f i) ... (9) These values, Hashimaban Immediately before the thickness change, it is obtained based on the actual measurement value or the estimation value of the rolling condition. These mass flow differences are zero from the rolling theory that does not consider the width expansion, but as described above, direct measurement is often difficult, and mainly includes mechanical systematic errors. number%
Appears as a positive / negative difference of about 10%.

Next, the target finish sheet thickness after the change of the sheet thickness during running is represented by h.
_n ^* . In addition, the entrance thickness h ₀ ^* is of course a constant value before and after the change in the running thickness. As described above, it is not preferable to greatly change the strip speed of each stand at the timing of changing the running strip thickness. Therefore, the speed after the change of each stand is targeted at the same value before the change. _{v i · (1 + f i} ) = constant N strip speed is constant before and after the-fly thickness change in the stand of the continuous rolling mill, the thickness change based on the thickness measurement or estimate of the previous Hashimaban thickness change Find the optimum value of the thickness afterwards. Thickness to be calculated is the N-1 thickness optimal value shown in FIG. ^{_{1 (h 1 *, h i}} -1 * ,, h i * ,,
hn _-1 ^* ). The mass flow difference between stands after the change of the plate thickness is defined as equation (12). ^{ΔMi * = Mi-1 * -Mi} * ... (10) = h i-1 * · v i-1 · (1 + f i-1) -h i * · v i · (1 + f i)

[0015] (9) thickness value of the difference (10) and minimum ^{_{(h 1 * ,, h i-}} 1 *, hi * ,, h n-1 *) means for calculating a are various likely, Here, means by the least square method is shown as an example. (11)
Expression. _{J = Σw i · (ΔM i} * -ΔM i) 2 i = 1,2,3,, N ... (11) where _{w i} is a weighting coefficient, based on the easiness of the schedule change of each stand Decide. The N-1 thickness value to obtain the minimum value of ^{_{J (h 1 * ,, h i-}} 1 *, h
_i ^* ,, hn _-1 ^* ) may be obtained by solving the partial differential coefficient equations of the equation (13) and solving the N-1 order simultaneous equations that make them zero simultaneously. Strip speed V _si = V _i (1+
The calculation formula for f _i ) and 7 stands is shown below.

[0016]

(Equation 1)

[0017]

(Equation 2)

Equations (17), (18) and (19) can quickly find the solution to x by ordinary matrix calculations. According to this method, the schedule can be made with higher accuracy, considering the mass flow errors of the stands at the same time, with the thicknesses of the upstream side and the downstream side as conditions by weighting in consideration of the characteristics of each stand. The above shows the procedure to be performed at the time of one change of the thickness between runs. When changing the thickness of three or more portions from one material, the above procedure may be repeated for the preceding portion and the succeeding portion. However, the first part of the schedule calculation mainly involves setting the rolling load and the rolling speed. Therefore, it is necessary to perform a large-scale calculation or a condition table calculation by a conventional method.

FIG. 2 is a block diagram showing the configuration of an apparatus for implementing the control method of the continuous rolling mill according to the embodiment. This embodiment is an example in which the above-described schedule calculation that minimizes the mass flow fluctuation in the change in the running thickness is applied to a 7-stand continuous finishing rolling mill. Are mainly extracted and shown. In FIG. 2, 1 is a tracking device for a change point between running distances, 2 is a thickness / strip speed calculating device, 3 is a mass flow calculating device, 4 is a pass schedule rolling speed calculating device, 5 is a rolling position (gap) changing device, Reference numeral 6 denotes a rolling mill speed changing device.

The track change point tracking unit 1 tracks the change point of the strip thickness at every moment by the pulse generator 10 of the stand F1, and determines the timing for taking in the rolling state. The strip thickness / strip speed calculation device 2 takes in the rolling state and calculates the strip thickness by a gauge meter type and the strip speed by an advanced rate type. The mass flow calculation device 3
The mass flow difference between the preceding plate portion and the following plate portion is smaller than the mass flow difference between the mass flow difference and the following plate portion, and the target plate thickness. Calculate the thickness correction amount. The rolling position (gap) changing device 5 changes the rolling amount so as to realize the target thickness correction amount obtained by the pass schedule rolling speed calculating device 4 in BISRAAGC. The rolling mill speed changing device 6 is a speed changing device for realizing the speed obtained by the pass schedule rolling speed calculating device 4.

In the embodiment described above, the pulse generator 1
Although the running thickness change point is tracked by 0, other means may be used as long as the position of the running thickness change point can be grasped, such as detecting the rough bar speed. Further, in the plate thickness / strip speed calculating device 2, the plate thickness is calculated by the gauge meter type and the strip speed is calculated by the advanced rate type. However, the plate thickness and the strip speed may be calculated by an external model formula or by using a measured value by a measuring instrument. good. Also,
In the pass schedule rolling speed calculation device 4, the target thickness change amount Δhi can be expressed by equation (20). On the other hand, the target plate thickness correction amount can be expressed by equation (21). At this time, considering the AGC tuning rate as the coefficient, the value to be set for k is given by equation (22). ^{_{Δh i = h i * -h i}} ... (20) Δh ref = k · Δh i ... (21) k = {K + M (1-α)} / K ... (22) where, K: mill modulus, M: Plasticity coefficient, α: tuning rate, and the rolling position (gap) changing device 5
Although the target path schedule is to be realized by the ISRA AGC, there is also a method of realizing the target path schedule such as calculating the target reduction amount again by performing the setup calculation from the target path schedule and directly changing the reduction.

[0022]

As described above, according to the present invention, the rolling speed and the sheet thickness of each stand entrance / exit side are included in the actual rolling condition values of the preceding sheet portion immediately before the sheet thickness change point enters the rolling mill. The difference between the mass flow difference of each stand between the preceding plate portion and the following plate portion is calculated based on the finish target thickness of the following plate portion by measuring or estimating the difference between the entrance and exit side mass flow of each stand. The rolling conditions of the succeeding plate portion were calculated under the condition that the minimum was obtained, and the succeeding plate portion was rolled by controlling the continuous rolling mill based on the calculated rolling conditions. The effect has been obtained. (1) Since the speed of each stand is set to the same target value before and after the thickness change, a stable schedule in which the rolling speed does not suddenly change can be automatically calculated. (2) A rational schedule can be calculated because the entry-side plate thickness is taken in, and the plate thickness change amount of each stand is small and the change time can be shortened. (3) Even if there are some errors in the calculation of the thickness and the advance rate by the gauge meter type, the direct influence on the mass flow change is small. (4) Since the calculation is simple, the calculation can be performed in a short time.

[Brief description of the drawings]

FIG. 1 is a diagram showing a path schedule calculation procedure in one embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an apparatus for implementing a control method for a continuous rolling mill according to one embodiment of the present invention.

FIG. 3 is a diagram showing a conventional path schedule calculation procedure.

Claims (1)

(57) [Claims] In a running thickness change control in a continuous rolling mill, a rolling speed and a rolling speed of each stand entrance / exit side are included in actual rolling condition values of a preceding plate portion immediately before a thickness change point enters a rolling mill. A step of measuring or estimating the plate thickness to calculate the difference between the entrance and exit mass flow of each stand, and, based on the finish target plate thickness of the succeeding plate portion, based on the preceding plate portion and the following plate portion, A step of calculating the rolling conditions of the trailing plate portion under the condition that the change in the mass flow difference is minimized, and controlling the continuous rolling mill based on the set and calculated rolling conditions to control the trailing plate portion. Control method of continuous rolling mill for rolling.