GB1599223A - Rolling of hot strip in a continuous rolling train - Google Patents

Description

(54) ROL1 ING OF HOT STRIP IN A CONTINUOUS ROLLING TRAIN (71) We SCHLOEMANN SIEMAG AKTlENGESELLSCHAFT of Steinstrasse 13, 4(1(10 Düsseldorf 1. Federal Republic of Germany a joint stock company organised under the laws of the Federal Republic of Germany do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed. to be particularly described in and by the following statement: The present invention relates to the rolling of hot strip material in a continuous rolling train.

In the rolling of hot strip material in a continuous rolling train, entry and exit speeds as well as entry and exit crosssections of the material being rolled are interlinked by the law of volume constancy (AE VE = AA V). i.e. with a predetermined entry cross-section AE and a predetermined entry speed VE Of the material at a roll stand. either the exit speed VA is dependent on the cross-sectional reduction R of the material R = (AE - AA), or, in the converse. the extent of the cross-sectional reduction R between the entry cross-section AE and the exit section AA iS due to difference of entry speed VE and exit speed VA.

In the rolling process, the material throughflow speed coincides with the peripheral speed of the rolls only at the no-slip point, while the speed of the entering material deviates by rearward slippage and the speed of the issuing material by forward slippage from the peripheral speed of the rolls. It is therefore clear that there must be constant rotational speed regulation at least at those roll stands of the continuous rolling train which are upstream or downstream of the roll stand governing the flow speed.

In continuous rolling trains for the rolling of hot strip material. "loop" lifters or ''ioop" measuring apparatus are used for this purpose. They respond to the increase or decrease in size of the loop of rolled material which arises between successive roll stands and which results from erroneous setting of the rotational speeds of the stands. The loop lifters or loop measuring apparatus generate respective corrective values for the rotational speed regulation so as to provide a virtually tension-free material guidance between the stands.

However, the loop lifters or the loop measuring apparatus do not ensure that the exit cross-section AA Of the material issuing from the respective roll stand is always within the given tolerance. For the maintenance of the strip thickness tolerance, thickness meters, for example, gauge-meters, are associated with each roll stand and regulate the setting devices of the respective roll stand. Since, however, the roll gap corrections effected by the thickness meters can be only accomplished with a delay, undesirable transition regions of steadily increasing or reducing thickness - so-called skid marks which impair the strip quality frequently occur on the hot strip material. It is particularly disadvantageous that the corrections, initiated by the thickness meters, of the roll gap cannot for practical reasons be precisely followed by the setting devices.This results in the so-called skid marks frequently growing back during the rolling process.

All these difficulties are a consequence of the fact that the mass flow of the material through the roll gap is only controlled indirectly and, in consequence, can only be corrected with a delay in the sense of maintenance of the desired exit crosssection AA.

According to one aspect of the present invention, there is provided a rolling train for the continuous rolling of hot strip material with substantially constant mass flow of the material through the train, comprising a succession of roll stands, a material thickness regulator associated with and only with the first roll stand of the train to measure the thickness of rolled material issuing therefrom and to effect adjustment of and only of the first roll stand to at least partly compensate for any deviation of the measured thickness from a desired thickness, and a plurality of material tension regulators each associated with a respective one of the roll stands and individually operable to so vary the roll speed of the respective roll stands in response to both forward and backward slippage of the material thereat as to maintain a predetermined minimum tension of the material between the roll stands.

According to another aspect of the present invention there is provided a method of continuously rolling hot strip material with constant mass flow by a rolling train having a succession of roll stands, the method comprising the steps of measuring the thickness of rolled material issuing from and only from the first roll stand of the train, effecting adjustment of and only of the first roll stand to at least partly compensate for any deviation of the measured thickness from a desired thickness, and so varying the roll speed of the individual roll stands in response to both forward and backward slippage of the material thereat as to maintain a predetermined minimum tension of the material between the roll stands.

Since the tension regulators respond to longitudinal stresses (compression and tension) in the rolled strip material between successive roll stands which result either from rearward . slippage of the material entering a stand of from forward slippage of the material issuing from a stand, a constant mass flow is exactly maintained by rotational speed regulation at the individual roll stands, i.e. by influencing the peripheral speed of the rolls. The tension regulators are so designed that only tension stresses of 0.2 to 0.5 kilograms per square millimetre (2 to 5 Newtons per square millimetre) can arise in the rolled stock between each pair of successive roll stands. These stresses prevent rearward slippage of the material before the roll gap of each roll stand and also keep forward slippage of the material issuing from the roll stand within the limits of the constant mass flow.

By regulating material thickness only at the first stand of the rolling train, it is ensured that any arising setting error is within the desired tolerance limits and is proportionally maintained up to the last roll stand, thus leading to a substantially improved strip thickness tolerance. The occurrence of skid marks, the growing back of such skid marks and temperature wedges in the end product and thereby avoided.

An embodiment of the present invention will now be more particularly described by way of example and with reference to the accompanying drawing, which is a schematic view of a hot strip material rolling train.

A hot strip rolling train 10 has six roll stands 1 to 6 and is equipped with minimum tension regulation means 20. The minimum tension regulation means 20 comprises six minimum tension regulators 21 to 26 respectively associated with the six roll stands 1 to 6. Each regulator is so designed that between successive roll stands 1, 2: 2, 3; 3, 4; 4, 5; and 5, 6. tension stresses of between 0.2 to 0.5 kilograms per square millimetre (2 to 5 Newtons per square millimetre) are maintained in the rolled material.

For the rolling operation, the roll gaps in the individual roll stands 1 to 6 are so adjusted, with consideration of the resilience inherent in the stands and the play to be compensated for in the setting devices thereof, that the desired cross-sectional reduction - subject to the prerequisite of constant mass flow - is effected at each stand. Associated with the first roll stand 1 of the train 10 is a thickness meter 31, which monitors the thickness of the exit crosssection AA of the rolled strip material and corrects any deviation from the desired thickness by adjustment of the setting devices of the first roll stand 1.Since all succeeding roll stands 2, 3, 4, 5 and 6 of the train 10 are regulated individually by the respective tension regulators 21 to 26 in their operating speed, i.e. the peripheral speeds of their rolls, so as to maintain tension stresses of approximately 0.2 to 0.5 kilograms per square millimetre, only thickness tolerances in proportion to the correction effected by the thickness meter 31 at the first roll stand 1 are present in the finished rolled hot strip material, having regard to the principle of constant mass flow. If, for example, a cross-sectional reduction of 17% takes place in each roll stand 1 to 6 and the thickness of the entry cross-section AE at the first stand 1 is 25 millimetres, then the thickness of the exit cross-section AA at the last roll stand 6 is 8.2 millimetre. When the error to be corrected in the thickness at the exit cross-section AA at the first stand 1 is + 1 millimetre. then the error at the last stand is a third of this amount, and skid marks do not arise in the hot strip material.

WHAT WE CLAIM IS: 1. A rolling train for the continuous rolling of hot strip material with subtantially constant mass flow of the material through the train, comprising a succession of roll stands, a material thickness regulator associated with and only with the first roll stand of the train to measure the thickness of rolled material issuing therefrom and to effect adjustment of and only of the first roll stand

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. material thickness regulator associated with and only with the first roll stand of the train to measure the thickness of rolled material issuing therefrom and to effect adjustment of and only of the first roll stand to at least partly compensate for any deviation of the measured thickness from a desired thickness, and a plurality of material tension regulators each associated with a respective one of the roll stands and individually operable to so vary the roll speed of the respective roll stands in response to both forward and backward slippage of the material thereat as to maintain a predetermined minimum tension of the material between the roll stands. According to another aspect of the present invention there is provided a method of continuously rolling hot strip material with constant mass flow by a rolling train having a succession of roll stands, the method comprising the steps of measuring the thickness of rolled material issuing from and only from the first roll stand of the train, effecting adjustment of and only of the first roll stand to at least partly compensate for any deviation of the measured thickness from a desired thickness, and so varying the roll speed of the individual roll stands in response to both forward and backward slippage of the material thereat as to maintain a predetermined minimum tension of the material between the roll stands. Since the tension regulators respond to longitudinal stresses (compression and tension) in the rolled strip material between successive roll stands which result either from rearward . slippage of the material entering a stand of from forward slippage of the material issuing from a stand, a constant mass flow is exactly maintained by rotational speed regulation at the individual roll stands, i.e. by influencing the peripheral speed of the rolls. The tension regulators are so designed that only tension stresses of 0.2 to 0.5 kilograms per square millimetre (2 to 5 Newtons per square millimetre) can arise in the rolled stock between each pair of successive roll stands. These stresses prevent rearward slippage of the material before the roll gap of each roll stand and also keep forward slippage of the material issuing from the roll stand within the limits of the constant mass flow. By regulating material thickness only at the first stand of the rolling train, it is ensured that any arising setting error is within the desired tolerance limits and is proportionally maintained up to the last roll stand, thus leading to a substantially improved strip thickness tolerance. The occurrence of skid marks, the growing back of such skid marks and temperature wedges in the end product and thereby avoided. An embodiment of the present invention will now be more particularly described by way of example and with reference to the accompanying drawing, which is a schematic view of a hot strip material rolling train. A hot strip rolling train 10 has six roll stands 1 to 6 and is equipped with minimum tension regulation means 20. The minimum tension regulation means 20 comprises six minimum tension regulators 21 to 26 respectively associated with the six roll stands 1 to 6. Each regulator is so designed that between successive roll stands 1, 2: 2, 3; 3, 4; 4, 5; and 5, 6. tension stresses of between 0.2 to 0.5 kilograms per square millimetre (2 to 5 Newtons per square millimetre) are maintained in the rolled material. For the rolling operation, the roll gaps in the individual roll stands 1 to 6 are so adjusted, with consideration of the resilience inherent in the stands and the play to be compensated for in the setting devices thereof, that the desired cross-sectional reduction - subject to the prerequisite of constant mass flow - is effected at each stand. Associated with the first roll stand 1 of the train 10 is a thickness meter 31, which monitors the thickness of the exit crosssection AA of the rolled strip material and corrects any deviation from the desired thickness by adjustment of the setting devices of the first roll stand 1.Since all succeeding roll stands 2, 3, 4, 5 and 6 of the train 10 are regulated individually by the respective tension regulators 21 to 26 in their operating speed, i.e. the peripheral speeds of their rolls, so as to maintain tension stresses of approximately 0.2 to 0.5 kilograms per square millimetre, only thickness tolerances in proportion to the correction effected by the thickness meter 31 at the first roll stand 1 are present in the finished rolled hot strip material, having regard to the principle of constant mass flow. If, for example, a cross-sectional reduction of 17% takes place in each roll stand 1 to 6 and the thickness of the entry cross-section AE at the first stand 1 is 25 millimetres, then the thickness of the exit cross-section AA at the last roll stand 6 is 8.2 millimetre.When the error to be corrected in the thickness at the exit cross-section AA at the first stand 1 is + 1 millimetre. then the error at the last stand is a third of this amount, and skid marks do not arise in the hot strip material. WHAT WE CLAIM IS:

1. A rolling train for the continuous rolling of hot strip material with subtantially constant mass flow of the material through the train, comprising a succession of roll stands, a material thickness regulator associated with and only with the first roll stand of the train to measure the thickness of rolled material issuing therefrom and to effect adjustment of and only of the first roll stand

to at least partly compensate for any deviation of the measured thickness from a desired thickness, and a plurality of material tension regulators each associated with a respective one of the roll stands and individually operable to so vary the roll speed of the respective roll stands in response to both forward and backward slippage of the material thereat as to maintain a predetermined minimum tension of the material between the roll stands.

2. A method of continuously rolling hot strip material with constant mass flow by a rolling train having a succession of roll stands, the method comprising the step of measuring the thickness of rolled material issuing from and only from the first roll stand of the train, effecting adjustment of and only of the first roll stand to at least partly compensate for any deviation of the measured thickness from a desired thickness, and so varying the roll speed of the individual roll stands in response to both forward and backward slippage of the material thereat as to maintain a predetermined minimum tension of the material between the roll stands.

3. A rolling train substantially as hereinbefore described with reference to the accompanying drawing.

4. A method of rolling substantially as hereinbefore described with reference to the accompanying drawing.