JPH0433522B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a rolling method for changing the running plate thickness in a hot finishing rolling mill, and is capable of stably and accurately changing a predetermined finishing plate thickness. The present invention relates to a method in which the finish rolling temperature can also be kept within a predetermined rolling temperature range.

[Prior art]

A rolling method that changes the thickness of the finished product while rolling a single rolled material makes it possible to reduce the number of non-customized products and eliminate threading and tailing work, which is especially useful in production lines for high-mix, low-volume production. A dramatic improvement in production efficiency can be expected.

Regarding this sheet thickness change rolling, all the technologies that have been published and implemented so far are for cold rolling mills, and mass flow control and inter-stand tension control are performed using feedback control based on tension detection values.

However, in hot rolling mills, tension control is usually performed using a looper, and no tension detector is particularly provided, so the responsiveness of tension control is not so fast at present. Moreover, in hot rolling, the amount of variation in tension value allowed is extremely small compared to cold rolling.

If the tension value changes by more than a certain amount, there is a risk of plate breakage, double folding, etc. In the case of tension control using louvers, this risk is reduced because the responsiveness is not sufficient. It's large.

Now, assume that the finished plate thickness of one rolled material is changed to be thicker in a 6-stand mill, and as the change point moves, the relationship between the rolling speeds of each stand calculated based on the constant mass flow law is calculated as follows. Shown in Figure 1.

_The figure shows the _stand rolling speed pattern at the timing when the plate thickness change point passes through each stand. This is the rolling speed of each stand at the time when the thickness change is completed. Below, the pattern of stand rolling speed is changed as the plate thickness change point progresses, and the rolling speed of each stand is curve C ₆ when the plate thickness change in stand No. 6 is completed.
The relative speed ratio is shown as .

[Problem that the invention seeks to solve]

In this way, conventionally, it was necessary to correct the stand rolling speed ratio at each point in time in synchronization with changes in plate thickness, and timing delays and excess or deficiency in the amount of change could result in plate breakage, loops, and doubles. This can cause serious problems such as

When absorbing such large changes in mass flow due to plate thickness changes by mass flow control using a looper, which is normally used in hot rolling, due to the limit of response speed, excessive mass flow may occur during transient periods. Unbalance and changes in tension values may occur, and the above-mentioned troubles may make it impossible to continue rolling. Good thickness change rolling cannot be expected due to occurrence of off-gauge, etc.

On the other hand, in hot rolling, the finish rolling temperature is
It is recognized as an important factor in determining product quality. When changing the thickness of a plate while it is being rolled, there are changes in the heat dissipation characteristics of the plate due to the change in plate thickness, changes in the heat dissipation time itself between stands, or changes in rolling heat generation due to changes in the rolling reduction rate at each stand. Due to the change, the finish rolling temperature greatly deviates from the normal range (in fact, when changing the plate thickness to a higher temperature,
Furthermore, when the thickness of the plate is reduced during rolling, the temperature becomes lower), which poses a major problem in maintaining quality.

Now, regarding the same base material dimensions and the same entrance plate temperature,
Figure 2 shows the results of calculating the rolling speed of each stand using a rolling model formula in which only the product plate thickness was changed and the same appropriate rolling temperature was specified.
As shown in the figure, in order to change the product plate thickness, the relative relationship between the rolling speeds of each stand (speed cone) must be changed, and the entire continuous rolling mill including the pivot stand must be changed in order to maintain the plate rolling temperature within the specified value range. It can be seen that it is necessary to change the rolling speed.

[Means for solving problems]

This invention provides a method for changing the thickness of a hot rolled sheet in which a sheet of material to be rolled is rolled to change the sheet thickness between runs, and each time the point of change in sheet thickness on the material to be rolled passes through each rolling stand, Change the rolling position of each stand according to the pre-calculated results,
By correcting the rolling speed at this stand and the upstream stand, changes in the forward and backward mass flow due to changes in plate thickness and rolling reduction at each stand are absorbed, and the relative speed between the stands is controlled.
In order to correct the rolling temperature change due to the plate thickness change each time the plate thickness change point passes through each rolling stand, the pivot stand and all other rolling stands are adjusted to correct the rolling speed absolute value of the entire continuous rolling mill. The rolling speed is changed.

[Effect]

With this configuration, in order to assist the response delay of mass flow control by the looper, in the present invention, when the rolling position of each stand is changed, the rolling speed of the stand concerned and its upstream stand is simultaneously changed. The speed is adjusted according to changes in rolling reduction rate. Here, the rolling reduction rate change can be calculated using the entry side plate thickness value, the rolling force change, and the rolling position change amount, and if the speed is corrected in this way, it can be calculated at an earlier point in time than the looper angle changes due to the mass flow change. Mass flow control becomes possible, and excessive tension value changes and looper angle fluctuations can be suppressed.

Furthermore, the rolling speed of the entire continuous rolling mill is changed at an appropriate timing when the plate thickness change starts, and the speed is set so that the rolling speed for the new product plate thickness is reached at the end of the plate thickness change at the final stand. The plate temperature maintenance function can be achieved by changing the machine output (MRH speed).

〔Example〕

An example of implementing the present invention will be explained with reference to FIGS. 3 and 4. FIG. FIG. 3 shows the configuration of the present invention in a 6-stand mill with the final stand as a pivot point,
FIG. 4 shows its operating state.

In FIG. 3, 1 is a rolled material, 21 to 26 are rolling rolls, 31 to 36 are motors that drive the rolling rolls, and the rolling speed of 40 stands is determined by a speed ratio device 41 provided for each stand. ~4
5 and the output of the main speed setting device 5, the motors are driven to the respective set speed values. The sixth stand serves as a pivot stand and verifies its rolling speed based on the output of the speed setting device 5.

The rolling position control devices 61 to 66 are the rolling rolls 21
The finishing rolling mill calculation control device 7 outputs rolling position commands and rolling speed commands for each rolling mill to the respective rolling position control devices and roll drive motors. It controls the accuracy of finished products and the stability of operations. 81-8
Reference numeral 5 indicates a looper device for keeping the strip tension value between stands constant, and the strip tension value is controlled by correcting the rolling speed of an adjacent rolling stand in accordance with a change in the operating angle of the looper. Successive speed ratio devices 91 to 94 correct the rolling speed of the upstream stand based on the product of the rolling speed change value made at each downstream stand and the set value of the successive speed ratio device. Therefore, each of the rolling roll drive motors 31 to 34 is controlled by the outputs of the speed ratio devices 41 to 44, the successive speed ratio devices 91 to 94, and the correction signal of the finishing rolling mill calculation control device 7, which will be described later.
The motor 35 is driven by the output of the speed ratio device 45 and the correction signal of the finishing mill calculation control device 7.

The finishing mill calculation control device 7 rolls the plate material 1 for a certain length using the finished product dimensions before changing the plate thickness, and then
When the plate thickness change point reaches the rolling stand where the rolling position is to be changed, the rolling position change command [△S] is sequentially issued to each stand rolling position control device, and the rolling position change command is issued based on the actual measurement value of the plate thickness change at each stand. ,
The amount of change in the forward rate and the amount of change in the backward rate are calculated, and a relative value correction {△Vr} of the stand rolling speed is commanded to each stand drive motor so as to correct the change in mass flow amount due to the change in plate thickness. That is, since changes in the advance rate and reverse rate are determined, changes in plate thickness are actually measured, and the circumferential speed of the roll is known in advance, changes in the mass flow amount of the stand can be determined. In order to correct this change in mass flow amount, speed correction is performed. Furthermore, in order to correct rolling temperature changes due to changes in plate heat dissipation characteristics due to plate thickness change rolling, a correction {△V _M } of the rolling speed absolute value of the entire continuous rolling mill is added to the output of the main speed setting device 5 described above. , and commands each stand drive motor to change the rolling speed of the pivot stand and other stands. That is, the finish rolling temperature after changing the plate thickness is determined using a well-known rolling temperature model, and the heat dissipation time between the stands, that is, the roll speed is corrected so that this temperature becomes a predetermined temperature.

Next, the means for determining ΔVr and ΔV _M will be explained based on well-known techniques.

First, the determination of △Vr as the advance rate changes will be explained using the first stand as an example. When the rolling position is corrected by △S ₁ on the first stand, the amount of change in thickness on the exit side △h ₁
is, △h ₁ = M ₁ /M ₁ +Q ₁・△S ₁ ...(1) However, M ₁ is Mill's constant.

Q ₁ is the material plasticity coefficient.

given as.

Then, as the exit side plate thickness changes △h ₁ , an advance rate change △f ₁ expressed by the following equation occurs.

△f ₁ = K ₁ △h ₁ /H ₁ ...(2) However, H ₁ is the entry side plate thickness.

K ₁ is a constant.

Here, the above equation (2) is based on the fact that the advance rate is given by the function f=KH-h/H of the plate thickness reduction rate.

Therefore, the change in the exit side plate speed V ₁ out of the first stand is derived as shown in Equation (4) by differentiating Equation (3) below with V _R1 and f ₁ .

V ₁ out=V _R1 (1+f ₁ )...(3) △V ₁ out=V _R1 (1+f ₁ )+V _R1・△f ₁ ...(4) In order to absorb this change in the outlet plate speed, the first It is sufficient to correct the roll speed of the stand by △V _R1 = K ₁ · △h ₁ / (1 + f ₁ ) · H ₁ · V _R1 ... (5).

Next, the determination of ΔVr in accordance with a change in the reverse speed ratio will be explained using the second stand as an example.

When the plate thickness change point reaches the second stand, the second
The lowering position of the stand is corrected and the exit plate thickness _h2 is changed.

At this time, the entrance speed V ₂ in of the second stand is: V ₂ in=h ₂ /H ₂・V ₂ out=h ₂ /H ₂・V _R2 (1+f ₂ )...(6) From the relationship, Differentiating equation (6) with △h ₂ and △H ₂ , △V ₂ in=[△h ₂ /H ₂ −h ₇ /H ₂ ²・△H ₂ ] ・V _R2 (1+f ₂ )... (7) The entrance plate speed change occurs.

This change in speed at the entrance of the second stand changes the roll speed of the first stand by △V _R1 = [△h ₂ /H ₂ −h ₂ /H ₂ ²・△H ₂ ] 1+f ₂ /1+f ₁・V _R2 ... (8) can be absorbed by speed correction.

Next, a speed correction V _M of the absolute value of the rolling speed of the entire continuous rolling mill will be described in order to correct a change in rolling temperature due to a change in the heat dissipation characteristics of the plate material due to a change in the plate thickness.

As a means of deriving the plate temperature of rolled material, for example, "Mitsubishi Heavy Industries Technical Report" Vol. 11, No. 1, (1974-1)
There are things mentioned on pages 53 to 59. This document clearly specifies all the factors that change to the plate temperature, such as inter-stand radiation heat Q _R , convection heat Q _C , and machining heat Q _M .In particular, Equation (2) in the left column on page 54 specifies the elapsed time t
It can be seen that the plate temperature is determined as a function of the plate thickness h. Simplifying equation (2), the plate temperature is determined as follows.

Ti＝K _H・hi ……(9) Ti＝K _V・1/Vi ……(10) However, Ti is the plate temperature, hi is the plate thickness, Vi is the rolling speed, and K _H and K _V are the coefficients.

From equations (9) and (10) above, as the plate thickness on the outlet side of each stand increases, the plate temperature change that occurs increases.

(B) It can be seen that the temperature drop between each stand is proportional to the traveling time between the stands and inversely proportional to the traveling speed.

Therefore, if the plate thickness changes by △h due to a change in plate thickness, if the rolling speed of the stand is changed by △V _M according to equations (9) and (10), the rolling temperature can be changed before and after changing the plate thickness. Can be maintained at the optimum value.

That is, using equations (9) and (10), the rolling speed of each stand may be corrected as follows: △V _M =K _V /K _H ·△hi (11).

In Fig. 4 a, b, and c, t ₁ on the time axis,
t ₂ ... t ₆ indicate the time at which the thickness change point on the plate reaches each rolling stand. In Figure 4a,
At the above times t ₁ , t ₂ ... t ₆ , the reduction position is changed to the reduction position control device of each stand △S ₁ , △S ₂
...△S ₆ is commanded, indicating that the finished product plate thickness value is to be changed. The amount of change in the rolling position can be calculated in advance according to the amount of change in plate thickness.

Figure 4b shows the relative value correction {△Vr} of the rolling speed of each stand in order to correct the speed change of the plate entering and exiting the stand that occurs in each stand due to the change in the rolling position described above. The amount (ΔVr ₁ to ΔVr ₅ ) is calculated based on the detected value of plate thickness change and rolling speed value at each stand. In other words, at t ₁ , the rolling position changes in the first stand, so the advance rate changes,
The plate speed at the exit side of the first stand changes. In order to keep it constant, the first stand rolling speed is corrected. At t ₂ , the second
The stand rolling speed is corrected, and the first stand rolling speed is corrected as the mass flow amount of the second stand increases. Similarly, corrections are made each time the plate thickness change point reaches each stand.

Figure 4c shows changes in the lowering position of each stand {△
S}, indicates the correction output {△V _M } of the absolute value of the rolling speed of the entire continuous rolling mill, which is performed simultaneously with the stand rolling speed correction {△Vr}. It can be calculated using a rolling temperature model formula that incorporates

[Effects of the Invention] As described above, by using the two speed corrections that are the characteristics of the present invention, it is possible to maintain the mass flow balance during sheet thickness change rolling, and also to keep the change in finish rolling temperature within a certain range. can be secured.

[Brief explanation of drawings]

Figure 1 is a curve diagram showing the rolling speed of each stand during sheet thickness change rolling, and Figure 2 is a curve diagram showing the finished product thickness before changing the sheet thickness.
[mm], and the finished product thickness after changing the plate thickness is 3 (mm). Figure 3 is a curve diagram showing the results of rolling speed calculations performed on the rolling model formula by specifying the same rolling temperature for each. FIG. 4 is a block diagram showing an example of a continuous rolling mill to which the method of the present invention is applied, and is an explanatory diagram for explaining the present invention. 1 is a rolled material, 21-26 are rolling rolls, 31-
36 is a roll drive motor, 41 to 45 are stand speed ratio devices, 5 is a main speed setting device that provides the speed during sheet passing, 61 to 66 are rolling position control devices, 7 is a finishing mill calculation control mechanism, and 81 to 85 are Looper angle controllers, 91-95 indicate successive speed ratios.

Claims (1)

[Claims] 1. In the hot rolling sheet thickness changing method in which a piece of material to be rolled is rolled to change its thickness between runs, each time the thickness change point on the material to be rolled passes through each rolling stand, By changing the rolling position according to the pre-calculated results and correcting the rolling speed at the stand concerned and the upstream stand, changes in mass flow forward and backward due to changes in plate thickness and rolling reduction at each stand can be avoided. In addition to controlling the relative speed between the stands, the absolute value of the rolling speed of the entire continuous rolling mill is A method for changing the thickness of a hot rolled plate, characterized in that the rolling speed of a pivot stand and all other rolling stands is changed to compensate.