GB2101918A

GB2101918A - Control for roughing train

Info

Publication number: GB2101918A
Application number: GB08122621A
Authority: GB
Inventors: Peter William Loose
Original assignee: EUROP ELECTRONIC SYST Ltd; European Electronic Systems Ltd
Current assignee: EUROP ELECTRONIC SYST Ltd; European Electronic Systems Ltd
Priority date: 1981-07-22
Filing date: 1981-07-22
Publication date: 1983-01-26

Abstract

In a rolling mill, a roughing train is set up with a rolling schedule designed to feed a slab of predetermined dimensions to a finishing mill. By continuous monitoring of the dimensions of a slab, at least at the output end of the roughing train but preferably also between intermediate stands of the roughing train, the schedule can be varied continuously to adapt it to variations in the dimensions or physical properties of the slab being rolled. <IMAGE>

Description

SPECIFICATION Control for roughing train The present invention relates to a roughing train for rolling slabs in a rolling mill to present a bar of correct thickness and width to the finishing mill.

Under the present operating practice, an input slab width and thickness is assumed and from that a mill set up profile is calculated to increase/decrease the width to be on target at the output of the final rougher. In order to do this effectively, it is important to know the width and thickness of the input slab. It is also preferable to know the grade and temperature of the steel since both these items of information are available in the mill, and affect of the optimum profile.

From the known data, an internal process computer assigns an edge/horizontal roll plan taking account of the known preferred width reduction per stand and roll power available.

Hitertho, having established the calculated optimum profile no further check was made to establish whether the actual dimension at the output of the rougher train corresponded to the desired dimensions for introducing into the finishing mill.

In accordance with the present invention, there is provided a roughing train for rolling slabs prior to introduction into a finishing mill having at the output end of the roughing tain means for continuously measuring the width and thickness of the slab and control means for varying the set up profile in dependence on the difference between the actual and desired dimensions of the slab.

The present invention therefore proposes in its broadest aspect to control the success of the computer predictor roll plan by comparing the actual width and thickness of the slab at the output of the roughing train with the predicted values. A self adaptive algorithm in the process computer then updates its data bank or roll plans for the particular grade, temperature, width and thickness of the slab.

This bank of data is stored in non-volatile memory and is used in rolling subsequent slabs.

A disadvantage of using a single measuring means positioned at the output of the last roughing stand is that too many assumptions are made with regard to the input material. Furthermore, by the time that the actual dimensions of the slab are compared with the predicted dimensions it is too late to introduce any corrections. It is true that slow changes can be counteracted by resorting to a single measuring means but since no two slabs have the same input dimensions it is preferable to perform a prediction before termination of rolling by the roughing stands.

In accordance with a preferred feature of the invention, in a roughing train consisting of a plurality of stands, means are additionally provided for measuring the dimensions of the rolled slab at a point between consecutive stands and a correction is applied to the set up profile of the mill in dependence upon the difference between the actual and the predicted dimensions of the slab.

The invention will now be described further, by way of example, with reference to the accompanying drawing which shows a continuous roughing train.

The roughing train in Figure 1 consists of a vertical scale breaker 10 followed by a horizontal scale breaker 12 the latter reducing the thickness of the slab by approximately 38%.

The next stand comprises a rolls 14 without edgers. The third stand includes a rolls 16 and edgers 18 arranged to give a reduction of 32%. The next stand consists of rolls 20 and edgers 22 to provide a reduction of 23% and, the final stand formed of rolls 24 and edgers 26 provides a further reduction of 7%.

The drawing is schematic and shows essentially the construction of a conventional roughing train but the invention is equally applicable to alternative roughing trains with a different number of stands and a different reduction ratio at the various stands.

Hitherto, in carrying out a roughing operation, the dimensions of the incoming slabs were assumed to be known and the reduction ratios were preset at each stand to give the desired dimensions for feeding to the finishing mill. The assumption that the roughing stands are operating as predicted does not however hold true and variations of the actual output dimensions from the predicted ones can prove both substantial and expensive. In particular, when it is noted that a typical mill may roll twenty five thousand tons of steel per week with a mean width of one metre, trimming of only one millimetre results in a loss of 25 tons per week. Currently, the over width is around 3 to 5 millimeters resulting in a loss of yield of between 75 and 125 tons per week which is clearly not insignificant.

In order to improve the yield, the present invention proposes effective accurate and automatic monitoring of the operation of the roughing train. At all points where measurements is to take place, it is desirable to obtain measurements of the slab being rolled to an accuracy of better than one millimetre. If the width is being measured by means of an overhead camera, it is important to derive a mea so resent also of the thickness automatically to better than one millimetre. It may be possible to derive such a measurement directly from the screws of the horizontal scale breaker roll 12 whereupon a transducer may measure the separation of the rolls 12 and provide an electrical output converted by an analogue digital converter into a signal capable of being processed by the control computer.Alternatively, the thickness may also be measured by means of an electronic camera.

In the present invention, an electronic camera which may for example consist of a charge coupled device sensitive to visible or infrared radiation emitted by the slab is provided at the input to the vertical scale breaker 10. The thickness of the slab is derived, as previously mentioned, from the screws of the horizontal scale breaker 12 and fed to the input computer. It should be noted that because the measurement positions of staggered the data will be time skewed but it is possible for this offset to be accommodated in the computer.

From this data a roll plan is calculated by the computer, based upon tables stored within the computer which takes into account the grade of the steel, its temperature the resilience of the roll stands etc. Based upon this roll plan, the computer additionally predicts the width at the output of each roll stand.

A second width gauge is placed downstream, the second camera being schematically represented as positioned after the roll 16. The actual width is measured at this position and compared against the computed width. Depending upon the variation between the desired and actual width, the computer any now apply fine tuning adjustments to the following rolls so that the slab dimensions should be on target at the output of the finishing mill. The errors between the actual and predicted widths are adaptadly fed back to the basic roll plan to give a learned response.

Afurtherwidth gauge is provided at the output of the roughing stand after the work roll 24 to serve the dual function of providing feed back to the computer and driving an accurate width measurement prior to the steel entering the finishing mill.

Claims

1. A roughing train for rolling slabs prior to introduction into a finishing mill having at least at the output end of the roughing mill means for continuously measuring the width and thickness of the slab and control means for varying the set up profile in dependence upon the difference between the desired and actual dimensions of the slab at the output end.

2. A roughing stand as claimed in Claim 1, comprising means at the entry to the roughing train for measuring the width and thickness of the slab, and wherein the control means includes a computer for setting up a nominal profile in dependence upon the dimensions of the slab at the entry, the temperature and the grade of steel.

3. A roughing train as claimed in Claim 2, wherein the computer is operative to predict the dimensions of the slab at the output of an intemediate roll stand of the roughing train and means are provided for measuring the actual dimensions of the slab between intermediate stands and for comparing the actual and desired dimensions to derive an error signal for fine tuning the rolls in the stand arranged downstream of the measurement point.

4. A method of controlling a roughing train which comprises measuring the dimensions of the slab at the entry of the train deriving values of the temperature and values of the steel, establishing a nominal profile for the roughing train, comparing the actual dimensions of the slab with dimensions predicted on the basis of the derived data to provide an error signal and applying an adjustment to the stands arranged downstream of the measurement point to apply a correction prior to the rolling of the slab by the roughing train being terminated.

5. A roughing train constructed as substantially herein described with reference to and as illustrated in the accompanying drawings.