JPS6240081B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling plate shape in plate rolling.

When rolling metal plates such as iron, aluminum, copper, etc.
It is important that not only the thickness of the material be uniform in the rolling direction, but also that the elongation distribution in the width direction, that is, the plate shape, be uniform.

A lot of research and development has been carried out on the former, based on the rolling theory of Karman and Orowan, and supported by advances in thyristors, ICs, control computers, and the advent of high-performance thickness gauges. It has reached the stage of completion as a thickness control (AGC).

On the other hand, regarding the latter, it has been an extremely difficult problem to detect the elongation distribution of the plate, but in recent years several detection methods have been developed and are being put into practical use as plate shape detectors.

However, for the former, the rolling theory that clarifies the relationship between rolling parameters and rolled plate thickness has been established, and has played a major role in investigating control methods, but for the latter, the elongation distribution in the width direction, especially An effective theory that clarifies the relationship between rolling parameters or control parameters at important plate edges has not yet been established.

Therefore, the above-mentioned plate shape detector is used as a television monitor that allows the rolling mill operator to visually check the plate shape, and the roll can be detected by simple proportional control based on the deviation amount at each point in the width direction of the plate from the reference flat surface. It is used for relatively simple individual control, such as changing the bending force, or detecting local minute irregularities on a plate and controlling the flow rate of the coolant nozzle in that area to change the thermal crown of the work roll. Currently, the data from the plate shape detector cannot be used effectively, and therefore the overall plate shape cannot be automatically controlled with high precision.

The present invention attempts to automatically control the plate shape by effectively utilizing data from a plate shape detector.

The present invention includes a plate shape detector that detects the spatial distribution of the elongation rate of a rolled plate material in the width direction, calculates and extracts several parameters for evaluating the plate shape from the plate shape detector, and calculates the parameters. This is carried out in a rolling mill that controls roll bending force and controls the coolant flow rate distribution of a group of roll coolant injection nozzles divided in the width direction of the sheet so as to correspond to the parameters of the best sheet shape set in advance. The control method includes regressing only the output signal near the plate end of the shape detector using a shape function representing a preset plate shape, and negatively feeding back the obtained regression coefficient to the roll bending force.
The absolute value of the above regression coefficient is used as a control command for the slope of the thermal crown on the surface of the work roll at the plate edge, and the coolant flow rate or coolant flow rate and temperature distribution of the roll coolant injection nozzle group near the plate edge is controlled by the slope of the thermal crown. It is characterized by being controlled so that it increases.

The present invention was created based on the recognition that the effectiveness of mechanical strain control in work rolls by roll bending forces is significantly influenced by the slope of the thermal crown at the plate ends. This will be explained below with reference to the attached drawings.

In FIG. 1, 1 is a pair of work rolls, 2 is a back-up roll, and 3 is a rolling plate.

Generally, when a rolling load is applied to the back-up roll 2, the center line O of the work roll ₁ is deflected in the direction of the curve O1, but the deformation of the work roll surface at the contact area with the plate caused by this deflection is offset. For this purpose, an initial crown is provided on the surface of the work roll in advance. However, this initial crown is fixed, and a thermal crown is formed on the work roll surface by the heat flow generated during rolling, so the shape of the unevenness on the work roll surface changes variously depending on the rolling conditions.

Therefore, coolant control and roll bending control are generally performed in order to obtain a good work roll surface unevenness under various rolling conditions.

As is well known, roll bending is divided into two types: separate bending, in which a load _F1 is applied between the bearings of a pair of work rolls 1, and the center line O of the work rolls ₁ is bent in the direction of a curve O2; There are two types of reverse bending, in which a load _F2 is applied between the bearings of the uproll 2 and the center line O of the work roll 1 is bent in the direction of the curve _O1 .

Therefore, the uneven shape of the work roll surface is
It is determined as a combination of the above-mentioned initial crown, thermal crown, rolling load, separate bending, reverse bending, etc.

By the way, the following heat flow exists in the work roll, and a thermal crown as shown by the curve S ₀ shown in Fig. 1 is formed (the amount of protrusion of the thermal crown in the roll radial direction is usually on the order of several tens of microns. (This is shown enlarged.)

At the contact portion between the plate and the work roll, about half of the frictional heat determined from the rolling load, the relative speed difference between the circumferential speed of the work roll and the plate rolling speed distribution, the coefficient of friction between the work roll and the plate, etc. flows into the work roll.

The contact between the work roll and the plate causes an inflow and outflow of heat determined by the temperature difference between the two and the contact heat transfer coefficient. Contact heat transfer coefficient is affected by rolling speed and rolling load.

The work roll is cooled with coolant by a group of roll coolant injection nozzles that are divided and arranged in the width direction of the work roll. The heat transfer coefficient resulting from this is approximately proportional to the coolant injection flow rate.

Outside the board, under typical natural cooling (including sub-irradiation) conditions, there is a heat flow proportional to the temperature gradient from the center to the periphery.

At the point of contact with the back-up roll, heat flows out and is determined by the temperature difference between the two and the contact heat transfer coefficient.
There is an influx.

The thermal crown S protrudes substantially flat in a portion corresponding to the plate width, and the amount of protrusion decreases in portions corresponding to both sides of the plate width, forming a slope K ₂ .

The inventor has determined that this slope of the thermal crown K ₂
As a result of conducting numerical analysis experiments on the relationship between the slope K ₂ and the plate shape, we found an interesting fact that the steeper the slope K ₂ , the flatter the plate shape, especially the edge shape of the plate. I came to find out. this gradient
If K ₂ is small, even if the roll bending force is changed, the uneven shape at the edge of the plate will not become flat as a whole even if its position and shape change.

At first glance, the gradient _K2 of the thermal crown appears to be maximum as the difference between the temperature at the center (corresponding approximately to the width of the plate) and the temperature outside the width of the plate determined by the rolling conditions and coolant cooling conditions is large. , in reality, reaches its maximum when the temperature difference is an appropriate value that is not too large. If the heat generation of the work roll is large and the temperature of the work roll is still rising even after maximizing the coolant cooling, increase the coolant temperature and inject the coolant to a part of the outside of the work roll. By doing so, the temperature gradient K ₂ can be controlled to an appropriate value.

The present invention performs control as shown in the flowchart of FIG. ₂ based on the recognition of the above relationship between the slope K2 of the thermal crown and the plate shape.

First, the distance from the center of the board in the board width direction is x, and the board shape is expressed as a function; f _(x) = a + bx + c | , c are determined by regression analysis. b quantitatively indicates the left-right imbalance of the plate shape, and c quantitatively indicates the overall distortion of the plate shape.

Next, the plate shape parameter b determined above,
The function value is obtained by substituting c into the regression function, and the difference δ _(x) between each x point and the shape detection signal is obtained. This δ _(x) quantitatively indicates the local distortion of the plate shape.

The left-right imbalance of the plate shape evaluated by the shape parameter b is corrected by the system indicated by circles in the figure. That is, this is done by adjusting the left-right balance of the rolling load. On the other hand, the overall distortion of the plate shape evaluated by the above-mentioned shape parameter c is corrected by the system indicated by ◯ in the figure. That is,
This is done by correcting the rolling load. Furthermore, the error δ _(x) for evaluating the local minute strain at each part in the width direction of the plate is corrected by the system indicated by ○ in the figure. That is, this is done by partially correcting the coolant flow rate in the coolant valve flow rate distribution control system [].

As explained above, the left and right imbalance of the plate shape,
Although the correction of the overall distortion and the partial minute distortion are the same as in the conventional method, the present invention, as described above,
Since the slope K ₂ at the plate edge of the thermal crown has a significant influence on the plate shape, and the strain profile at the plate edge and the overall strain profile show separate responses,
Instead of regressing the entire shape detection signal with one function as in the past, for the plate edge, we use a function that makes it easier to extract the plate edge shape (for example, increasing the value of γ in equation (1) above). Only the nearby shape detection signals are further regressed. Then, coolant flow rate distribution control and coolant temperature control near the plate ends are additionally performed. The plate ends are on the same side as the drive motor of the work roll (drive side plate edge) and the opposite side (work side plate edge).
There is a distinction between the two, and their shapes are slightly different, so both are controlled independently.

That is, as mentioned above, the gradient K ₂ of the thermal crown of the work roll at the point where the shape near the sheet edge corresponds to the sheet edge and the roll bending force (separate bending force and reverse bending force)
Considering that it is determined by the synergistic effect of
Negative feedback is applied to the separate bending force and reverse bending force in the roll bending control system, and the absolute value of the above regression coefficient is used as a control command for the gradient K ₂ of the thermal crown on the work roll surface near the plate edge. The flow rate and temperature distribution of the coolant injection nozzle group are controlled so that the above gradient K ₂ increases.
The reason why the absolute value of the regression coefficient is used as the control command is because the distortion at the plate edge occurs when the gradient K ₂ of the thermal crown is small, regardless of whether the regression coefficient is positive or negative. Because it does.

As mentioned above, by controlling the coolant valve flow rate and coolant temperature near each plate end on the drive side and working side, the heat flow of the work roll changes, and the slope of the thermal crown of the work roll near the plate end changes. K ₂ is formed to the maximum, and the plate is rolled by the rolling load controlled by the control system paths ○A and ○B in the figure, and the separate bending force and reverse bending force controlled by the bending control system [ ]. Shape distortions at the ends (both drive side and work side) are corrected.

In FIG. 2, the automatic plate thickness control system [ ] controls the rolling speed and plate rolling tension to ensure a desired exit plate thickness.

Figure 3 shows the thermal crown of the work roll. The curve A in the figure shows the control method of the present invention.
The flow rate and temperature of the coolant in the vicinity of the plate edge are optimally determined according to the rolling conditions, and the thermal crown slope K ₂ becomes steep. The temperature difference between the roll temperature on the roll surface and the work roll surface corresponding to the outside of the sheet width was too large, so the heat flow became large and the slope of the thermal crown at the sheet end became gentle.

The present inventor conducted rolling using the thermal crowns of the above two curves A and B, and the work roll surface shape was as shown in FIG. 4 for the former and as shown in FIG. 4 for the latter.

As shown in Figure 4, according to the thermal crown of curve A, when reverse bending force is applied, the work roll surface shape is slightly curved at the part corresponding to the sheet edge, but the overall width of the work roll is the same as that of the sheet. It is clear that the sections are flattened and that well-shaped plates can be rolled. On the other hand, as shown in Fig. 4, according to the thermal crown of curve B, the work roll surface near the plate edge is flattened when either reverse bending force or separate bending force is applied. Therefore, it can be seen that the plate shape cannot be rolled well. In this case, end extension generally occurs in the plate material,
Also, if separate bending is used too much, quarterbuckling will occur.

As is clear from the above experimental results, the slope of the thermal crown formed on the work roll surface at the plate end is an important factor in controlling the plate shape, and the steeper the slope of this thermal crown, the more difficult the plate shape is. Become good.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing bending control of a work roll, FIG. 2 is a flowchart of a control method according to an embodiment of the present invention, FIG. 3 is a graph showing the shape of a thermal crown, and FIG. A in the diagram
It is a graph showing the shape of the work roll surface when rolling with a curved thermal crown or a B curved thermal crown. 1... Work roll, 2... Backup roll,
3...Rolled plate material.

Claims (1)

[Scope of Claims] 1. A plate shape detector that detects the elongation rate in the width direction of a rolled plate material is provided, several parameters for evaluating the plate shape are calculated and extracted from the plate shape detector, and these parameters are In a rolling mill that performs roll bending force control and coolant flow rate distribution control of a group of roll coolant injection nozzles dividedly arranged in the width direction of the strip so as to correspond to the parameters of the best strip shape set in advance, Only the output signal near the plate edge of the shape detector is regressed using a shape function representing the plate shape set in advance, and the obtained regression coefficient is negatively fed back to the roll bending force, and the absolute value of the regression coefficient is control command for the slope of the thermal crown on the surface of the work roll at the end of the work roll, and the coolant flow rate or the coolant flow rate and temperature distribution of the roll coolant injection nozzle group near the plate end are controlled so that the slope of the thermal crown increases. A method for controlling plate shape in plate rolling.