JPS5938842B2 - Hot strip high spot prevention rolling method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hot strip rolling method for preventing high spots.

In tandem finish rolling of hot strip, as the rolling amount increases, the thickness profile of the rolled plate product in the width direction becomes locally protruding as shown in Figures 1 and 2. There is a tendency to arise.

Hereinafter, in this specification, among such local protrusions, abnormal protrusions exceeding the allowable limit value determined from the viewpoint of product quality will be referred to as high spots, to distinguish them from mere local protrusions below the allowable limit value.

The main cause of these high spots is local wear on the work rolls of the rolling stand.The causes of this local wear on the work rolls are: (1) when there is a temperature difference in the width direction of the hot strip; (2) If the oil concentration during hydraulic rolling is uneven in the strip width direction, (3) If the roll material or roll cooling conditions are uneven in the strip width direction, etc., but in either case, In order to prevent local wear of work rolls, it is considered important to strengthen maintenance management of rolling equipment, and various efforts have been made for this purpose.

However, if a high spot actually occurs,
Since it takes time and effort to confirm the cause, it is difficult to take preventive measures, and the current situation is that even an investigation takes several days.

For this reason, conventionally, the work rolls of all rolling stands had to be rearranged all at once, leading to a decrease in rolling efficiency and roll consumption.

In particular, when manufacturing hot coils for use with steel plates such as tinplate blanks and electromagnetic steel strips, which have strict requirements for shape quality after cold rolling, in order to meet these requirements, work roll wear is particularly low during hot finish rolling. I needed the above-mentioned rearrangement.

The inventors have developed an effective preventive measure against high spots in hot strips, and even if high spots occur, they can quickly determine which rolling stand's work rolls are caused by local wear, and can easily deal with the problem. Experiments and discussions were conducted regarding possible rolling control.

By the way, buy spots tend to occur at certain positions in the width direction of the hot strip, and do not grow rapidly.

In an experiment, a bi-spot was generated in the hot strip, and when the work roll of the rolling stand was moved in the roll axis direction, it was observed that the bi-spot disappeared at that position.

Furthermore, it has been found that this method can be used to detect whether local wear that can lead to bi-spots is occurring on the work rolls of a rolling stand during actual operation.

As mentioned earlier, vice spots tend to occur at certain positions in the width direction of the hot strip, and in this case, the thermal history of the rolled sheet, the rolling conditions at each rolling stand, and the cooling conditions of each work roll are almost constant throughout the rolling pass. Therefore, if the main cause of bispots is abnormal wear of the work rolls, it is thought that the abnormal wear is occurring in the same location on each work roll.

Therefore, if rolling is continued under the same conditions, as the amount of rolling increases, the degree of wear of the work rolls will increase and the amount of vice spots will also increase.

In this point, before local wear of the work roll occurs, or when bispots are found in the rolled plate product as a result,
It is thought that by moving the work roll in the roll axis direction before starting the next rolling, it is possible to effectively reduce the amount of vice spots that occur at certain positions.

Therefore, the inventors have made extensive studies on this point and have obtained the knowledge described below.

In other words, even if local abnormal wear occurs on the work rolls, if the work roll pair is moved in the roll axis direction before the local protrusions on the strip caused by the abnormal wear exceed the allowable limit value, such abnormal wear can be avoided. At the position where abnormal wear has occurred, that is, the position where absolute abnormal wear has occurred, the roll surface will be renewed to a smooth surface without wear, so the degree of wear at that position will be significantly reduced, and the growth of local protrusions will be suppressed. Moreover, regarding the worn parts of the work roll,
As the roll pair moves, it moves away from the position where absolute abnormal wear occurs, so after the roll pair moves, the degree of wear does not progress any further, but rather, the amount of wear on the roll is reduced by normal wear due to the passing of the strip. They discovered that it was getting smaller.

This invention is based on the above findings.

That is, the present invention provides a rolling mill 1 in which a pair of work rolls of each finish rolling stand is selectively moved in the roll axis direction every time one or several hot strips are passed during tandem finish rolling of a hot strip. This is a method of rolling strips to prevent vice spots.

In addition, this invention determines the permissible boundary value of the bispot during tandem finish rolling of hot strip, and compares the actual thickness profile in the width direction with the above permissible limit as measured by a profile meter installed on the exit side of the final rolling stand. To prevent bi-spots on pot strips, the necessity of bis-spot control is determined by calculation, and the work roll pair of each finishing rolling stand is selectively moved in the roll axis direction according to the result of this judgment to perform bis-spot control. This is a rolling method.

In normal rolling, the passing position of the rolled plate is set so that the pass line passes through the center of the width of the gap between the pair of work rolls, as shown in FIG.

In FIG. 3, 1 is a hot strip, Wi and W'i are upper and lower work rolls, B i and B'i are upper and lower reinforcing rolls, and in normal rolling, the upper and lower work rolls Wi.

W'i is installed at the position shown by the chain line.

In this invention, the pair of work rolls Wi and W'i are configured to be movable, so that, for example, when a vice spot is found on the hot strip 1, the pair of work rolls WiW'i is moved in the roll axis direction by a distance a shown in FIG. move it.

At this time, since the local wear of the work rolls does not progress rapidly, the movement of the work rolls Wi and W'i is limited from the end of rolling of the coil in which the sign of bispot has been detected until the next coil is subjected to rolling. It can be done in between.

Furthermore, the movable distance a of the pair of work rolls should be determined by considering the protrusion width of the generated bispot and the characteristics of the rolling stand. Due to the large number of targets, it is 30 to 50 m over a distance of about 100 mvt to the left and right of the roll setting position.
It is sufficient to move stepwise at intervals of m.

FIG. 4 shows an example of stand arrangement for a hot finishing rolling mill.

The number 1 is a Horatos l-IJ tube, and the number 2 is a profile meter installed on the exit side of the final finishing rolling mill, and the plate thickness profile of the hot strip 1 is measured by this profile making 2.

Preferred embodiments of this invention will be described below.

The arrangement of the work roll pairs of each rolling stand at the start of rolling remains as usual.

And after rolling one or several hot strips,
One stand or several pairs of work rolls are moved in the roll axis direction.

After rolling one or several hot-stuck IJ tubes again in this state, the pair of work rolls on each stand is selectively moved in the roll axis direction.

By repeating the above operations and performing hot finish rolling, the occurrence of bi-spots can be advantageously prevented.

It is preferable to move the work roll pairs in an order that has a stronger influence on the bispot, and generally the rear stand has a stronger influence than the front stand, so for example, the fifth stand (abbreviated as F't).

It is more effective if the order is as follows)→F6→F4→F7→F3→F2→F1.

Further, as a countermeasure when local wear actually occurs on the work roll and signs of bi-spots appear, the embodiment described below is advantageously suitable.

First, the target plate crown is determined along with its bispot tolerance limits.

A profile meter 2 measures the thickness profile of the hot strip 1 after rolling, and the data is transmitted to a process computer 3.

Here, a comparison calculation is made between the actual plate thickness profile and the above-mentioned allowable limit to determine whether bispot control is necessary.

If bispot control is required based on this judgment result,
Work roll moving device S1 attached to each rolling stand
A command is issued to S7 to sequentially move the work roll pairs in the roll axis direction according to the order described above.

Next, a detailed explanation will be given according to the flow sheet of bispot control shown in FIG.

In this example, a 7-stand Kundem rolling mill is used, and the work roll movement order is F5 → F6 → F4 → F7 → F3 → F2.
→F.

In addition, the value of the bispot is expressed by its protrusion height h, and is the control target value at which bacteriostatic control should be performed before the bispot reaches the permissible limit.

It was expressed as

As mentioned above, the process computer performs a comparison calculation between the actual plate thickness profile and the allowable limit of the bispot to determine whether bispot control is necessary, but the control target value is determined.

Rolling continues as long as no bispot exceeding 200 mm is detected.

If the bispot measurement value exceeds the management target value,
First stand F1 according to the predetermined order.
, in this example, the F5 work roll pair is an
move by a distance of

However, b≦a<a − where a: Distance that the work roll can move in the roll axis direction b: Protrusion width of the high spot If the measurement value of the bispot does not decrease even if the work roll pair of F5 above is moved The work roll pairs of each stand are sequentially moved by a distance, and this is continued until the measured value becomes h≦ho.

If h≦ho results from the movement of the work roll pair of the stand Fi, this means that the effect of this movement has been recognized.

At this time, check whether the vise bot, which can be detected even if h≦ho, has moved by a distance as the work roll moves, and if the vise bot is newly detected at a position a distance away, the stand This means that localized abnormal wear occurs on the Fi work roll.

Therefore, the rolling equipment should be inspected for any abnormalities and the work rolls should be reassembled and other measures taken.

Even if local wear occurs on the work rolls of stand Fi, rolling may be continued as long as h≦ho.

When the amount of rolling increases and the vice spot becomes h>ho, the work roll of this stand is further moved to the position an+1.

It is checked whether this position is a position where a bispot has occurred before, and if it is a position where a bispot has occurred before, it is further moved to the position an+2.

No matter which position the stand is moved to, if h>ho, the work roll of this stand is replaced.

By repeating the above operations, even if bispots occur during rolling, it is possible to detect at an early stage which rolling mill's work roll is experiencing local wear, and to ensure that the amount of bispots generated is always within the allowable range. can be controlled.

When the prevention of bispot according to this invention is not carried out,
The rolling tonnage before roll change is usually 800 to 100.
Previously, the rolling tonnage was controlled at about 0 tons, but the above-mentioned inventions have made it possible to increase the rolling tonnage to 1,500 to 1,800 tons.

In particular, in the second invention, even if a bi-spot occurs during rolling, it is possible to identify which stand's work roll is caused by local abrasion, so there is no need to rearrange the rolls of all stands at the same time as in the past. You can rearrange the roles only for the stands you need.

According to each of the inventions described above, bispots can be advantageously prevented during hot rolling, and roll consumption and rolling efficiency can be significantly improved.

[Brief explanation of the drawing]

Figure 1 is a diagram showing an example of the thickness profile of hot strip in the width direction, Figure 2 is a partially enlarged view of part A in Figure 1, showing the vise spot, and Figure 3 is a rolling stand. Figure 4 is a diagram showing an example of the stand arrangement of a hot finishing rolling mill.
The figure is an explanatory diagram of the bispot control procedure. 1...Hot strip, 2...Profilter 1-ta, 3...Process computer, F1 to F7...Each stand of hot finishing rolling mill , S1 to S7... A moving device for each of the work rolls F1 to F7.

Claims (1)

[Claims] During tandem finish rolling of one hot strip, the work roll pair of each finish rolling stand is selectively moved in the roll axis direction every time one or several hot strips are passed. Hot strip high spot prevention rolling method. 2 During tandem finish rolling of hot strip,
The permissible limit value of the high spot is determined, and the necessity of high spot control is determined by comparing the actual plate thickness profile in the width direction measured with the above permissible limit using a profile meter set on the exit side of the final rolling stand. A hot strip high spot prevention rolling method characterized in that high spot control is performed by selectively moving the work roll pair of each finishing rolling stand in the roll axis direction according to the determination result.