GB2291988A

GB2291988A - Method of temperature control when rolling hot-rolled strip

Info

Publication number: GB2291988A
Application number: GB9515290A
Authority: GB
Inventors: Achim Schneider; Reimar Finck; Ludwig Niemeyer
Original assignee: Mannesmann AG
Current assignee: Vodafone GmbH
Priority date: 1994-08-01
Filing date: 1995-07-26
Publication date: 1996-02-07
Also published as: BR9503506A; GB9515290D0; FR2723012A1; CN1119969A

Abstract

A method for temperature control when rolling a hot-rolled strip (1) is described which is particularly suitable for use when rolling aluminium strip in a multiple-stand hot-rolled strip train (F1, F2, FN). The strip 1 is cooled at (3) before entering the train (F1, F2, FN) and the cooling intensity between the head and tail of the strip is controlled to keep the entry temperature constant. … <IMAGE> …

Description

2291988 Method for Temperature Control When Rolling Hot-Rolled Strip The

present invention relates to a method for temperature control for use when rolling hot-rolled strip, in particular when rolling aluminium strip in a multiplestand hot-rolled strip train.

When rolling metal special emphasis is placed on obtaining certain metallurgical properties and in particular the constancy thereof over the length of the strip. This is especially so in the case of hot-rolled strip trains for aluminium. The metallurgical properties of the rolled strip depend on the shaping conditions, especially decisive parameters being the degree of deformation, the deformation rate, and also, to a particular extent, the deformation temperature in the final stand or roll pass. Whereas the degree of deformation and the deformation rate can be kept virtually constant, temperature fluctuations on the entry side of the installation always cause problems.

ItemDerature wedaes11 So called are produced there, i.e. the temperature decreases between the head of the strip and the tail of the strip.

It is known to compensate for such "temperature wedges" by changing the deformation rate. This method is known as temperature speed-up. It is also known to combine variable deformation rates and controlled strip cooling, with the aim of achieving uniform deformation conditions in the rolling train, see for example, EP 0024 849. With the known methods, although the shaping temperature in the final stand can be kept approximately constant and the deformation forces in the rolling train can also be kept substantially uniform by controlled cooling of the strip, the deformation rate may vary to a considerable extent which in turn has a corresponding effect on the metallurgical properties. Also an increased drive power capacity is required for the speed-up and the speed changes which are necessary during rolling.

2 It is an object of the present invention to keep constant the temperature of a strip upon entry into a hotrolling train or into a hot-rolling stand, in order thereby to enable performance of the entire deformation process at constant speed, to produce a rolled strip with constant metallurgical properties.

A method for temperature control when rolling a hot-rolled strip is provided in which the strip is cooled before entering a single stand or a train of stands and the cooling intensity between the head of the strip and the tail of the strip during the passage of the strip through the stand(s) is controlled so as to keep the entry temperature constant.

If the entry temperature before the first stand is kept constant and if furthermore the entry thickness remains constant, then, if the speed remains the same, the entire deformation process is also constant. The degree of deformation, the deformation rate and the deformation temperature can adopt the same values from the head of the strip to the tail of the strip, so that the desired constancy of the metallurgical properties of the rolled strip is yielded. Additionally, a particular advantage of the proposed method is that a speed-up for temperature regulation can be dispensed with, so that the power requirement for the drive of the train is reduced. In addition to keeping the temperature constant, the overall level can likewise be influenced, which means that selective characteristics can become obtainable.

The cooling intensity is preferably reduced between the head of the strip and the tail of the strip, so that the head of the strip is cooled more and the end of the strip cooled less. This avoids the "temperature wedge" described above, so that the temperature speed-up can be dispensed with.

Preferably also the temperature of the strip is 3 measured before and after the cooling of the strip and also after leaving the train and is registered in a computer. If it deviates from a predetermined target temperature a signal is given to control the cooling intensity. Feedback of the temperature value measured on the exit side of the train as a signal to the control means for the cooling intensity only occurs if the exit temperature shows intolerable deviations from the target temperature.

The advantages of the present invention can be represented in summary as follows:

(a) constant entry conditions cause constant conditions over the entire length of strip in the entire train, which means that "constant" material properties are achieved.

(b) owing to temperature compensation on the entry side, it is no longer necessary to speed-up. This means that the drive power can be reduced.

The invention will be further described by way of example with reference to the sole Figure which shows a multiple-stand hot-rolled strip. As will be appreciated, however, the method can also be applied to single stands.

In the Figure, 1 designates the strip which is to be rolled out in the four-high rolling stands Fl, F2 and FN. The graph 2 indicates that the strip has a decreasing temperature T over the length L beginning from the head end, which temperature decreases in a wedge shape towards the tail end. This temperature wedge is prevented by subjecting the strip 1, before it enters the first stand Fl of the hot-rolled strip train, to strip cooling, by means indicated at 3. To this end, the entry temperature of the hot-rolled strip 1 is measured at Pl, the exit temperature is detected at P2 and the intensity of the strip cooling 3 is controlled with reference to a predetermined target temperature. The strip 1 leaving the strip cooling means 3 then has a temperature T which is 4 constant over the strip length L, as indicated at 4, at which temperature the strip 1 enters the stand F1 of the hot-rolled strip train and is rolled out therein. A further measurement of the strip temperature is effected at P3. As long as the exit temperature of the strip 1 shows only tolerable deviations from the target temperature, no feedback is effected, in order to ensure maximum constancy.

Claims

1. A method for temperature control when rolling a hot-rolled strip in which the strip is cooled before entering a single stand or a train of stands and the cooling intensity between the head of the strip and the tail of the strip during the passage of the strip through the stand(s) is controlled so as to keep the entry temperature constant.

2. A method as claimed in Claim 1, wherein the cooling intensity is reduced between the head of the strip and the tail of the strip.

3. A method as claimed in either Claim 1 or Claim 2 wherein the temperature of the strip is measured before and after cooling of the strip and after it exits the stand or train and is registered in a controller operable, on deviations of a measured temperature, from a predetermined target temperature, to control the cooling intensity.

4. A method substantially as hereinbefore described and illustrated in the accompanying drawings.