JPH0242002B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a setup method in a rolling mill consisting of a plurality of stands having upper work rolls and lower work rolls, and more specifically relates to a method for setting up rolls in a rolling mill consisting of a plurality of stands having upper work rolls and lower work rolls. The present invention relates to a method for setting up a rolling mill that can satisfy both of the above requirements.

[Background of the invention]

The rolling elements of the rolling mill are adjusted so that the material to be rolled, such as plate material, is rolled to meet the planned thickness, width, etc.
This is called rolling mill setup. This rolling element usually includes the rolling position of the work rolls and the roll speed of the work rolls. and,
The basis for determining these rolling elements for each of a plurality of stands having upper work rolls and lower work rolls is the target plate thickness at the exit side of each stand (FIG. 1). Determining this for each stand is called determining the draft schedule.
Conventionally, there have been draft schedules called a power distribution method, a reduction distribution method, and the like. Among these, the power distribution method determines the rolling load of the work rolls in each stand, and determines the draft schedule based on this. In the reduction distribution method, the reduction position of the upper work roll in each stand is determined, and the draft schedule is determined based on this. In either method, the rolling load and rolling position of each stand are determined based on empirically determined criteria for distribution to each stand.

As mentioned above, the allocation standards established for each of the power distribution method and the reduction allocation method are empirical, and even if a draft schedule is performed based on one distribution standard, it will not satisfy the other distribution standard. Ta. however,
In recent years, it has become necessary to meet both of these allocation criteria. The reason for this is that in both hot rolling and cold rolling, demands on the shape of the rolled material have become stronger, and a method for determining a draft schedule that allows rolling mill setup to be clearly taken into consideration has become necessary. This is because I came here. In other words, the load ratio between the final stand and its front stand, which affects the shape of the material to be rolled, is such that, for example, when the material to be rolled is a plate, the plate crown is constant, or the elongation rate in the width direction of the plate is This is because it is determined to be constant between the stand and the rear stand.

Next, a setup method for determining a draft schedule using the conventional reduction allocation method will be explained with reference to FIGS. 1 to 3.

FIG. 1 is a schematic diagram showing a state in which a rolling operation is performed by a rolling mill consisting of a plurality of stands having upper work rolls and lower work rolls. In order to determine the target plate thickness _i (Fig. 2) at each exit side at each stand by determining the draft schedule, first, the rolling reduction rate r _i for determining the rolling position of each upper work roll is determined as shown in Fig. 3. determined. The rolling reduction ratio r _i at each stand in FIG. 3 is determined based on an empirically determined distribution standard and is called reduction distribution. Based on this rolling reduction ratio r _i , the target plate thickness _i on the exit side at each stand is defined by the following formula.

Here, H represents the base material plate thickness.

Next, the roll circumferential speed v _Ri of the work roll in each stand is determined based on the principle of constant mass flow.
That is, v _Ri (1+f _i ) _i = v _R5 (1+f ₅ ) ₅ = const (2) where i=1 to 5 v _R1 is assumed to be given the roll circumferential speed v _R5 of each stand.

Here, f _i is the advance rate, and the following formula of Bland & Ford is used.

However, r _i : Reduction ratio μ _i : Friction coefficient h _i : Output plate thickness R _i : Work roll radius t _fi : Front tension of plate (given) S _fi : Output side deformation resistance t _bi : Back tension of plate (given) ) S _bi : Inlet side deformation resistance t _fi and t _bi in the above formula are values given in advance, and the input and output side deformation resistance of S _fi and S _bi is the following deformation resistance formula k _si = k _si (Ω, r _i , r〓 _i (v _Ri )) ...(4) However, Ω is calculated using parameters depending on the steel type. Note that the above deformation resistance formula is a function of the roll circumferential speed v _Ri , so strictly speaking S _fi and S _bi are obtained by convergence calculation of formulas (2), (3), and (4); Normally, in order to simplify the calculation, in equation (4), the speed of the rolled material (in this conventional example, the plate material) at the exit side of the work roll is used instead of the roll circumferential speed v _Ri . Also, (4)
The formula r〓 _i (V _Ri ) is given as Sims' formula on page 11 of the publication "Theory and Practice of Plate Rolling (published by the Iron and Steel Institute of Japan)". Since it is defined as , this is used as a publicly known formula.

Next, the rolling load P _i is determined by the following formula.

However, P _i : Rolling load (i = 1 to 5, same below) b : Plate width R _i ′ : Flat roll radius R _i : Roll radius Q _pi : Friction coefficient correction term K _pi : Tension correction term C _H : Hitchikotsukoku Constant Using the rolling load P _i obtained from this constant, the rolling position setting value S _i , which is the actual position of the work roll, is determined by the following formula.

S _i =h _i −P _i /K _i +S _pi (6) where S _i : Reduction position setting value K _i : Spring constant S _pi : Reduction position zero point [Problems in background technology] As described above, the conventional reduction distribution In the setup based on the method, first the target outlet plate thickness ₅ and rolling reduction r _i (third
) is given, and the roll circumferential speed v _Ri (i=
1 to 5) and the set value S _i (i=
1 to 5) are simply being sought in the end. Therefore, in this conventional setup method, although it is possible to achieve the target rolling reduction ratio _ri for each stand, it is not possible to simultaneously satisfy the target rolling load.

That is, the conventional set-up method is a reduction distribution method (Fig. 3), and the actual rolling load P _i obtained as a result is different from each other which is ideally distributed in the other power distribution method (Fig. 4). As shown in FIG. 5, the stand did not match the target rolling load.

[Purpose of the invention]

The present invention is a method of rolling using a rolling mill consisting of a plurality of stands each having an upper work roll and a lower work roll, which simultaneously satisfies both the target rolling reduction ratio in each stand and the target rolling load in each stand. The purpose of this invention is to provide a method for setting up a rolling mill.

[Summary of the invention]

The rolling mill setup method of the present invention adds the different speed ratio of the upper work roll and lower work roll as a new rolling element to the conventional rolling elements such as the roll circumferential speed and the rolling position of the work roll. The purpose is to match the actually occurring rolling load with the target rolling load by determining the speed ratio to an appropriate value. In other words, the draft schedule is determined based on the rolling reduction ratio (in this respect, it can be said that it is based on the conventional reduction distribution method), the rolling load that actually occurs based on this rolling reduction ratio is calculated, and the rolling load that actually occurs is calculated. The difference load between the rolling load and the target rolling load is calculated, and the different speed ratio is determined so as to finely adjust the rolling load that actually occurs without changing the rolling reduction ratio and make the deviation load zero.

The different speed ratio may be determined directly from the curve (Fig. 6) representing the relationship between the different speed ratio and the rolling load, or the slope at the inflection point of this curve may be used to determine the different speed ratio. The approximation may be made using a linear equation, and the determination may be made using this approximation equation.

Furthermore, since the curve representing the different speed ratio and rolling load has subtle errors in an actual rolling mill and may not match the actual one, the slope of the linear equation above is The correction may be made sequentially based on the determined and adopted different speed ratio and the changed rolling load.

[Embodiments of the invention]

(First Example) FIG. 6 shows a curve representing the relationship between the different speed ratio and the rolling load used in the first example.

The curve in Figure 6 was created based on actual measurement data, and was calculated by increasing the different speed ratio under the condition that the relationship between the inlet side plate thickness and the outlet side plate thickness of each stand (that is, the rolling reduction ratio) was not changed. It shows how the required rolling load decreases as time progresses. Therefore, it is understood that by adjusting the different speed ratio, the rolling load can be adjusted regardless of the plate thickness.

Therefore, in this example, based on the characteristic curve shown in FIG. 6, the actual rolling load P _i in the draft schedule when the different speed ratio C _vi = 1.0 is used as a reference, and the target rolling load P _i is set to make the deviation load zero. The different speed ratio C _vi corresponding to ′ is calculated. below,
I will explain in detail. As described above, when determining the different speed ratio C _vi using the curve in FIG. 6, it is possible to directly determine the different speed ratio C vi using the curve as it is. However, if the curve is used as it is, the calculation will be complicated, so an example will be explained in which this curve is approximated by a linear equation (straight line) to simplify the calculation. Here, when approximating to a linear equation, various methods can be considered for determining the slope. In this embodiment, in view of the fact that the adjustment of the different speed ratio C _vi is sufficient in a relatively narrow range around 1.2, and the fact that according to actual measurement data, an inflection point appears at C _vi = 1.2, the inflection point is A first-order approximation is made using the slope of , which simplifies the calculation process. first,
In FIG. 6, the slope α _i of the inflection point (C _vi =1.2) of the curve at each stand is determined using the following formula.

α _i = ∂P _i / ∂C _vi ｜ _Cvi = 1.2 ...(7) However, C _vi = V _H /V _L (different speed ratio) V _H : Upper roll circumferential speed V _L : Lower roll circumferential speed Using this slope α _i , the curve in FIG. 6 is approximated by the following equation.

P′ _i /b=P _i /b+α _i (C _vi −1.0)……(8) Here, P _i ′ is (C _vi ) of the function P _i ′ of C _vi , as is clear from Figure 6. be. Moreover, P _i is the actual rolling load, and corresponds to P _i ′ at C _vi =1.0.

Therefore, the first term on the right side of equation (8) represents the tangent of the vertical axis of the linear approximation equation, and the second term represents the rolling load variation of the linear approximation with respect to the variation of the different speed ratio C _vi . There is.

Using equation (8) approximated in this way, the rolling load P _i = P _i ' of the draft schedule is used to make the deviation load Δ _i explained in FIG.
(1.0) to the desired target rolling load P _{i '} can be determined. That is, since Δ _i =P′i/b−Pi/b=α _i (C _vi −1.0) …(9) holds, ∴C _vi =Δ _i /α _i +1.0 …(10) Therefore, The different speed ratio C _vi is determined. If a rolling mill is set up using this C _vi , it is expected that the deviation load Δ _i as shown in FIG. 5 will become zero.
However, in an actual rolling mill, the influence of the different speed ratio C _vi is not necessarily the same as that shown in FIG. 6, and it is necessary to modify the value to be suitable for the rolling mill. As a method for this correction, the different speed ratio C _viA determined and adopted in the previous actual rolling, the slope α _iA and the changed load Δ _iA are used. Then, using the well-known exponential smoothing method, α′ _i = α _i + δ _i (α _iA − α _i ) …(12) where δ _i : Determine the new slope α′ _i as the smoothing gain and correct the slope α _i do.
Then, by replacing α _i with α′ _i and repeating this correction, a more suitable slope α′ _i can be obtained.

(Second Example) In the above example, the slope α _i was calculated directly from the curve in FIG. 6, but in other examples, the slope α i was calculated from the curve in FIG. It is also possible to determine _i . This normalization is calculated using the circumferential speed ratio C _vi
Target rolling load for No. 1 stand with the least influence of
This is done by dividing by P _i .

First, in this embodiment, the normalized rolling load ε _i is also used for the rolling load P _i of the performance data.

ε _i = P _i / b / P ₁ / b = P _i / P ₁ ... (13) Also, the normalized rolling load _{ε' i is} determined for the rolling load P i which is affected by the different speed ratio C _vi . .

ε′ _i =P′ _i /b/P ₁ /b=P′ _i /P ₁ ...(14) However, the target rolling load P _i ′ is a function P _i ′ (C _vi ) of C _vi , and P _i '(1.0) corresponds to the actual rolling load P _i .

A graph of the different speed rolling load ε′ _i normalized in this way is shown in FIG. Then, as in the first embodiment, the slope _i at the inflection point is determined.

_i = ∂ε′ _i / ∂C _vi |C _vi =1.2 (7) Using this _i , approximate ε′ _i =ε _i + _i (C _vi −1.0) (8). Using this equation (8), to make the load deviation Δ _i (Figure 8) 0, _i = ε′ _i −ε _i = _i (C _vi −1.0) (9) and C _vi = Δ _i /α Determine the different speed ratio C _vi as _i +1.0 (10). This modification of the different speed ratio C _vi is also carried out using C _viA , _iA and _iA in the previous actual rolling, as in the first embodiment. Then, as in the first embodiment, a well-known exponential smoothing method is used to obtain ′ _i = _i + δ _i ( _iA − _i ) (10) where δ _i is corrected to a new slope ′ _i by smoothing gain.

The setup procedure based on this second embodiment will be explained below using the setup skeleton float shown in FIG.

In block A, the use of rolling, such as the rolling reduction ratio _ri, is incorporated.

In block B, the pattern of target rolling load P _i (see Fig. 4) is taken in. Then, a normalized target rolling load ε _i is calculated by dividing this target rolling load P _i by the rolling load P ₁ of the No. 1 stand (formula (13)).

In block C, the roll circumferential speed of the lower work roll
V _L is calculated using the conventional formula (2).

In block D, the actual rolling load P _i is calculated based on the rolling reduction ratio r _i using equations (1) to (5). after that,
This actual rolling load P _i is the rolling load of No. 1 stand.
Actual rolling load ε _i normalized by dividing by P _i
is calculated using equation (13).

Target rolling load ε _i normalized by block E
and _the normalized actual rolling load ε _i (8th
Figure).

Load _deviation i taken in block F
In order to correct the difference speed ratio based on the slope _i in Fig.
Calculate C _vi using equation (10).

Roll peripheral speed of upper work roll in block G
Calculate V _H using the proviso to equation (7).

Using the different speed ratio C _vi and the slope _i in the block F, the normalized rolling load ε′ _i when the different speed ratio is applied is calculated by the formula (8) using block H, and further the rolling load P′ _i is calculated as ( 14) Calculate by formula.

In the block, the set value S _i of the rolling position of the upper work roll is calculated using equation (6) using the rolling load P' _i . This completes the setup.

Block J actually performs rolling, and block K judges whether the product after rolling satisfies other conditions, such as the thickness and width of the exit side of the final stand, and if it does, the product is rolled. Proceed to L.

In block L, the different speed ratio C _viA adopted based on the actual rolling results and the changed rolling load _iA are taken in.

In block M, the slope _iA of the corrected approximate expression is calculated using equations (11) and (12) using the imported C _viA and the actually changed load _iA .

In block N, instead of the slope α _i that was used last time, '_i' calculated from equations (11) and (12) from the previous rolling results is used to set up the rolling mill for the next time. That is, based on this corrected _i , the program proceeds to block F and repeats the setup.

〔Effect of the invention〕

According to the rolling mill setup method of the present invention, it is possible to simultaneously satisfy both the target rolling ratio in each stand, the target rolling ratio in each stand, and the target rolling load in each stand, which has been strongly demanded in recent years. It is possible to perform a setup draft schedule that takes into consideration the rolling shape of the rolled material that has become more popular.

[Brief explanation of the drawing]

Figure 1 is a side view showing an outline of the rolling operation, Figure 2 is a graph showing the target thickness _i at the exit side of each stand to be determined based on the draft schedule, and Figure 3 is a graph showing the draft schedule in Figure 2. Figure 4 is a graph representing the target rolling load; Figure 5 is a graph representing the deviation between the target rolling load and the actual rolling load; Graph showing the relationship between different speed ratio and rolling load, FIG. 7 is a normalized graph of FIG. 6, FIG. 8 is a normalized graph of FIG. 5, and FIG. 9 is a second embodiment of the present invention. This is a skeleton flowchart showing the rolling procedure.

Claims (1)

[Claims] 1. In a method of rolling using a rolling mill consisting of a plurality of stands having upper work rolls and lower work rolls, a draft schedule is determined based on a rolling reduction ratio, and the actual rolling Calculate the rolling load that occurs, calculate the deviation load between the actually occurring rolling load and the target rolling load, and finely adjust the actually occurring rolling load to make the deviation load 0 without changing the rolling reduction ratio. A method of setting up a rolling mill involves determining the different speed ratio between the upper work roll and the lower work roll and performing set-up. 2 In claim 1, the different speed ratio is determined by approximating a curve representing the relationship between the different speed ratio and the rolling load by a linear equation using the slope at the inflection point of the curve. A method of setting up a rolling mill using the primary method. 3. A method for setting up a rolling mill according to claim 2, in which the slope of the linear equation is successively corrected based on the different speed ratio determined in the previous actual rolling and the slightly changed rolling load.