EP0763391A1 - Method of compensating forces resulting from horizontal movements of the rolls in a rolling stand - Google Patents

Abstract

Compensation method is one in which the pressure in two adjustment cylinders for the determination of the rolling forces on one side of the roller gap, and the indicated forces of the force measuring devices to determine the rolling forces on the opposite side of the roller gap are co-ordinated. By including the working roller axial forces determinable by the pressure in the displacement cylinders of the working rollers, the total axial forces (T) in the plant can be determined by calculation during the operation of the rollers.

Description

The invention relates to a method for compensating forces or force components, resulting from horizontal movements of the rolls in roll stands for the hot and cold rolling of flat products, equipped with work rolls and with one or more backup rolls, with hydraulic adjustments and with force measuring devices on the opposite side of the Roll gap and with hydraulic devices for horizontal displacement of the work rolls.

The problem with the rolling of flat products in hot and cold rolling plants is that all the rollers involved run axially in the stand in different directions during the rolling process and generate axial forces by pressing on the respective locks. From these axial forces, the associated reaction force creates free pairs of forces at a distance from the center of the roll to contact with the neighboring roll. Each of these pairs of forces causes reaction forces in the roller bearings and thus in the two uprights of the stand.

Figure 1 describes the basic problem by way of example on the upper support roller 1 of a four-high stand. The horizontally acting forces T are line-volatile vectors, ie they can be shifted along their line of action. As a result, it is irrelevant on which side of the stand the roller is locked. In principle, such pairs of forces always arise from the axial force in the contact area with the neighboring roller. The individual forces overlap and are expressed in different axial forces on everyone involved Rolls with correspondingly difficult to overlook reaction forces in the roll stands.

In the case of reversing stands in particular, the reaction forces in the roll stands have extremely adverse effects. When the direction of rotation is reversed, the screwing direction of all the rollers involved also changes. The rollers run to the opposite side, which results in a reversal of the axial forces. The reaction forces in the roll stands change accordingly, with the result that the force measuring devices arranged in the stands report changes which are not related to the actual rolling process. The result is incorrect reactions of all control loops, which depend on the forces measured in the roll stands, such as flatness control, automatic calibration for parallel adjustment of the roll gap, roll alignment control to compensate for the effects of an eccentric position of the rolled product and other control loops, depending on Type of mill stand and rolled product.

It is already state of the art to record the vertical forces arising in the stand, such as, for example, forces from their own weights, the roller balancing and the roller bending, by calculation or measurement technology and to take them into account when measuring the forces in the two roller stands. However, such compensations were not carried out for the reaction forces from the described axial forces of the rolls.

It is therefore the task of determining the reaction forces in the roll stands with sufficient certainty without having to set up additional measuring points in the roll stand.

The object is achieved with a method for compensating forces or force components, resulting from horizontal movements of the rolls in roll stands according to the type mentioned at the beginning with the features of claim 1.

The invention opens up the possibility of continuously determining all the straying forces occurring in a roll stand from horizontal movements of the rolls and of compensating the force components resulting therefrom in the measured roll forces. Further embodiments of the invention are the subject of claims 2 to 7.

The invention is described in more detail with reference to FIGS. 2 to 5.

Modern roll stands for cold and hot rolled flat products are now almost exclusively equipped with hydraulic adjustment 2 as an actuator for the thickness control. The adjusting cylinders of the hydraulic adjustment are located above the upper support roll chocks 3 or below the lower support roll chocks 4. In a preferred embodiment, force measuring devices 5 are also located on the opposite side of the stand from the roll gap in the two roll stands, with which the forces occurring in the rolling process measured continuously in the two roll stands.

The two hydraulic cylinders of the hydraulic adjustment preferably supply additional measured values for the forces in the two roll stands via the hydraulic pressure, so that a total of measured values for the forces in the two roll stands above the upper support roll chocks and below the lower support roll chocks are available without additional effort.

Another feature of modern roll stands for the hot and cold rolling of flat products are displaceable work rolls 6, for example for influencing the roll gap profile or to even out the roll wear. In a preferred embodiment, the work rolls 6 are shifted with the aid of hydraulic cylinders 7. Regardless of whether the two work rolls are shifted during an operating phase or in a particular one Position, 7 pressures arise in the hydraulic cylinders depending on the axial forces emanating from the work rolls 6. The axial forces of the work rolls can therefore be determined in a preferred manner without additional effort by measuring the pressure in the displacement cylinders. This provides a total of six measured values for vertical and horizontal forces in the roll stand.

Figure 2 shows an analysis of the forces in a roll stand. Only the forces F from the rolling process and the axial forces T of the rolls were recorded. The representation of balancing forces, bending forces and weight forces has been omitted because the compensation of these forces is known.

The equilibrium conditions for horizontal forces T, vertical forces F and moments M at the upper and lower roller set lead to a total of six equations. These six following equations GL represent the balance of forces as follows:

Scaffolding above:

$$\begin{array}{c}\begin{array}{c}\begin{array}{}\text{(1)}{\text{vertical forces F: F}}_{\text{w}}{\text{- F}}_{\text{1}}{\text{- F}}_{\text{2nd}}\text{= 0 GL}\end{array}\\ \begin{array}{}\text{(2)}{\text{horizontal forces T: T}}_{\text{w}}{\text{- T}}_{\text{1}}{\text{- T}}_{\text{2nd}}\text{= 0 GL}\end{array}\\ \begin{array}{}\text{(3)}{\text{Moments M: F}}_{\text{w}}{\text{· X - F}}_{\text{1}}\text{·}\frac{\text{a}}{\text{2nd}}{\text{+ F}}_{\text{2nd}}\text{·}\frac{\text{a}}{\text{2nd}}{\text{- T}}_{\text{2nd}}{\text{(r}}_{\text{A}}{\text{+ r}}_{\text{S}}{\text{) + T}}_{\text{w}}{\text{(2r}}_{\text{A}}{\text{+ r}}_{\text{S}}\text{) = 0 GL}\end{array}\end{array}\end{array}$$

Scaffold below:

$$\begin{array}{c}\begin{array}{c}\begin{array}{}\text{(4)}{\text{vertical forces F: F}}_{\text{w}}{\text{- F}}_{\text{3rd}}{\text{- F}}_{\text{4th}}\text{= 0 GL}\end{array}\\ \begin{array}{}\text{(5)}{\text{horizontal forces T: T}}_{\text{w}}{\text{+ T}}_{\text{3rd}}{\text{+ T}}_{\text{4th}}\text{= 0 GL}\end{array}\\ \begin{array}{}\text{(6)}{\text{Moments M: F}}_{\text{w}}{\text{· X - F}}_{\text{3rd}}\text{·}\frac{\text{a}}{\text{2nd}}{\text{+ F}}_{\text{4th}}\text{·}\frac{\text{a}}{\text{2nd}}{\text{- T}}_{\text{3rd}}{\text{(r}}_{\text{A}}{\text{+ r}}_{\text{S}}{\text{) - T}}_{\text{w}}{\text{(2r}}_{\text{A}}{\text{+ r}}_{\text{S}}\text{) = 0 GL}\end{array}\end{array}\end{array}$$

From these six equations, the equations for the forces T ₁ and T ₄ originating from the support rolls and the tangential force T _w occurring in the roll gap can be determined with mathematical transformations. This means that all horizontally acting forces occurring in the scaffolding are known.

Figure 3 shows the composition of the equation set.

Of particular interest is the derivation of a center deviation X for the position of the resulting rolling force in the roll gap (cf. FIG. 2). This quantity can also be derived continuously from the six measured values in the rolling operation. The equation for the center deviation X is given in FIG. 3. The size X can be used for automatic calibration, i.e. for the automatic parallel positioning of the two work rolls, by prestressing the stand without rolling stock with rotating rolls after a roll change and calculating the eccentricity X calculated from the six measured values. By swiveling with the hydraulic adjustment, the value X is regulated to zero, with the result that the upper and lower rollers are perfectly parallel.

A further use of the center deviation X is the monitoring of the rolling process, in particular in the case of reversing stands, in which the strip or the sheet can run from the center of the stand. The center deviation X can be used to report such events and to make a corresponding correction.

Of course, the automatic calibration and monitoring of the rolling process can also take place in that instead of introducing a center deviation, the measured forces F ₁ to F _{4 are} corrected (compensated) with the aid of the calculable reaction forces from the axial forces. The required equations for the sum of the reaction forces all the rolls involved are indicated by R ₁ to R ₄ in FIG. 4. After such compensation, the measured values F ₁ to F _{4 can be used} in a manner known per se by forming the difference F ₁ minus F ₂ or F ₃ minus F ₄ for the roll calibration and for monitoring the rolling process.

In the equations for determining the roller axial forces and the eccentricity, it is particularly advantageous that the measured values for the axial forces in the upper or lower stand area are always included in the evaluation as difference values. The result of this is that the frictional forces contained in the measured values, particularly in the case of the measured values from the pitch cylinders, are not included in the evaluation, provided that the frictional forces on both sides of the frame are the same. This applies to a recording of the measured values during double-sided approach movements or double-sided opening movements of the hydraulic adjustments. In the case of a pivoting movement, the frictional forces on both sides of the scaffold would add up. The recording of measured values during a swivel movement must therefore be suppressed in the operational sequence.

It has also proven to be advantageous to use the measured and calculated axial forces T ₁ to T ₄ and T _w for monitoring the state of maintenance and the perfect roller grinding. A high degree of wear and defects in the roller grinding increase the entanglement of the rollers with each other and lead to increased axial forces. The display of these forces is therefore an excellent means of continuously monitoring the rolling mill.

FIG. 4 shows the set of equations for the reaction forces from the axial forces and for the reaction forces from the eccentricity of the rolling force.

FIG. 5 contains a calculation example with assumed roll stand data and roll data and the roll axial forces and reaction forces calculated therefrom with the aid of the equations given above.

Claims (9)

Process for the compensation of forces or force components, resulting from horizontal movements of the rolls in roll stands for the hot and cold rolling of flat products, equipped with work rolls and with one or more backup rolls, with hydraulic adjustments and with force measuring devices on the opposite side of the roll gap and with hydraulic ones Devices for the horizontal displacement of the work rolls,
characterized,
that the pressures in the two adjusting cylinders for determining the rolling forces on one side of the roll gap and the indicated forces of the force measuring devices for determining the rolling forces on the opposite side of the roll gap are used, and that including the work rolls which can be determined via the pressures in the shift cylinders of the work rolls -Axial forces all axial forces in the stand during the rolling operation can be determined mathematically. Method according to claim 1,
characterized,
that correction values for the rolling force displays in the two roll stands are derived from the measured and calculated axial forces of the rollers in order to compensate for the reaction forces of the axial forces. Method according to claim 1,
characterized,
that the current eccentricity of the rolling force is calculated from the four measured rolling forces and the two measured axial forces. A method according to claim 1 and claim 3,
characterized,
that the calculated eccentricity of the rolling force is adjusted to zero when the rolling stand is calibrated to parallelize the rolls. Method according to claims 1 to 4,
characterized,
that the reaction forces resulting from the axial forces in the expansions assigned to the two roll stands are determined by calculation and are compensated for by corresponding infeed of the hydraulic adjustments. Method according to claim 4,
characterized,
that when the automatic calibration is carried out, the six measured values for rolling forces and axial forces are recorded only during a rectified adjustment movement carried out on both sides of the stand. Method according to claim 1,
characterized,
that the measured and calculated axial forces T ₁ to T ₄ and T _w are continuously displayed for monitoring the state of preservation. Method according to claims 1 and 2,
characterized,
that after compensation of the rolling force displays with the reaction forces calculated from the axial forces, the remaining difference between the rolling force displays in the upper or lower part of the stand for parallel positioning of the rolls is regulated to zero. Method according to claims 1 and 2,
characterized,
that after compensation of the rolling force displays with the reaction forces calculated from the axial forces, the remaining difference between the rolling force displays in the upper and lower part of the stand is used for the continuous monitoring of the rolling process.

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