FR2473915A1 - Automatic thickness control of rolled prods. esp. metal strip - Google Patents

Abstract

A material such as metal sheet travels through at least two rolling mill stands (15,1). In the second stand (1), a load cell (8) is employed to measure the actual rolling force (F), which is fed into an electrical appts. (13) supplied with the desired rolling force (Fref), so a signal(dF) is obtd. due to the difference between the two values (F,Fref). - Signal (dF) is then fed to a controller (14) employed to move a looping roller (16) vertically in the gap between the two stands (15,1). The movement of roller (16) alters the tension on the metal sheet travelling from the first stand (15) into the second stand (1). (4)

Description

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1 Method and device for regulating the thickness of a laminate.

 The present invention relates to a method for regulating the thickness of a rolled product at the outlet of a cage of a rolling mill comprising at least one other cage upstream of the cage considered, this method being of the type according to which one s 'endeavor to keep the thickness of the rolled product constant by an action in response to the measurement of a variation in the rolling force in the cage considered with respect to a set value.

 It also relates to a device for implementing a method of the aforementioned type.

 In previous processes and devices of this type, and in particular in the process well known under the name of "AUTOMATIC GAGE CONTROL", it has been observed, as will be better explained below, that the proposed regulation aggravates the variations in rolling force , which is of course detrimental to the flatness of the rolled products in strip form.

 The object of the invention is to remedy the drawbacks of the methods and devices of the prior art and to propose a new regulation method of the aforementioned type, which is both simple and reliable.

 This object is achieved by the method of the invention which is characterized in that, in response to a signal representative of an instantaneous variation in the rolling force, the interlacing traction is modified in the direction leading to cancellation of said signal and therefore of said variation in the rolling force, without acting on the empty height of the intercylinder space of the cage considered.

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modifier la traction intercage du laminé, ces moyens c agissant en réponse audit signal représentatif dans le sens conduisant à une annulation dudit signal. 1 The device of the invention is characterized in that it also comprises means for generating a signal representative of an instantaneous variation of the rolling force compared to a set value of this force and means for

modify the interlining traction of the laminate, these means c acting in response to said representative signal in the direction leading to cancellation of said signal.

 Advantageously, the means for modifying the intercage traction act on the drive torque - of a looper roller situated between the considered cage and the upstream cage, or alternatively, the means for modifying the intercage traction act on the speed relative of the cylinders of the cage considered and the upstream cage.

 Thanks to the process and to the device according to the invention, the rolling force is constant and so is also the bending of the rolls, which makes it possible to observe good flatness of the rolled product.

 Because, unlike the systems of the prior art, no assumption is made on the coding module, as will be explained in more detail below, the risks of divergence are averted.

 Finally, we can see, in some cases, an improvement in response time.

reillage sophistiqué tel que des jauges à rayons X, et, 0 d'autre part, n'assure pas nécessairement la constance de la force de laminage et donc la planéité du produit laminé, enfin limite les performances du fait du temps It should be noted immediately that other types of regulation have already been proposed which have an action on the tension of the laminate. This is the case, for example, in French patents 2,003,835,
2,072,388 or 2,403,839. However, in these patents, the modification of the intercage voltage comes in response to signals resulting from a measurement of the thickness of the laminated product, which on the one hand requires an appraisal.

sophisticated reillage such as X-ray gauges, and, on the other hand, does not necessarily ensure the constancy of the rolling force and therefore the flatness of the rolled product, finally limits the performance due to time

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 for transporting the product to the thickness gauge.

 The characteristics and advantages of the present invention will be better understood on reading the description which will be made with reference to the accompanying drawings in which: - Figures 1 and 2 respectively represent the principle and the device for regulating the prior art.

 - Figures 3 and 4 respectively represent the principle and the regulating device according to the invention.

 Figures 1 and 2 illustrate the conventional control process known as "Automatic Gage Control", according to which variations in thickness, hardness or temperature, due to the product, are corrected by an action on the tightening of the cylinders .

 The rolling mill stand 1 conventionally comprises between its columns 2 working rolls 3 placed between support rolls 4. The tightening of the rolls is controlled by a tightening mechanism 5, consisting for example either of electric motors driving clamping screws 6 (as shown here), or in hydraulic cylinders.

 The rolling force F exerted on the rolled product 7 is measured by the means 8, such as a cell. dump.

 In the conventional regulation method, the clamping mechanism 5 comprises means for measuring the clamping, which is a function of the intercylinder vacuum space S.

We know that HOOKE's law gives a relationship between the exit thickness H of the rolled product, the rolling force F, the vacuum intercylinder space S, and the ceding module K of the cage columns:

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Assuming K constant and known, the instantaneous variations of the aforementioned quantities are linked by the relation:

La régulation classique vise à obtenir

AH = 0 en commandant des variations d'entrefer AS s -L1F égales aux variations calculées de cédage 1 ('

A cette fin, le dispositif connu de ré-

AF gulation comporte des moyens 9 de calcul du cédage AF K-' et des moyens 10 de mesure de la variation d'entrefer AS, cette variation résultant d'une action sur le mécanisme de serrage 6 en réponse à un signal élaboré par un comparateur 11, via un dispositif de commande approprié 12.

The classic regulation aims to obtain

AH = 0 by controlling air gap variations AS s -L1F equal to the calculated variations in yielding 1 ('

To this end, the known device for

AF gulation comprises means 9 for calculating the ceding AF K- 'and means 10 for measuring the variation in air gap AS, this variation resulting from an action on the tightening mechanism 6 in response to a signal produced by a comparator 11, via an appropriate control device 12.

 On the classic diagram of FIG. 1, the curve H represents the force necessary to apply to the product as a function of the thickness of exit desired for the product, and obviously cuts the axis of the abscissae at a point of abscissa H corresponding to the inlet thickness of the product.

 Line E represents the force applied to the rollers as a function of the cage yielding (HOOKE relationship).

 The point of intersection M of the two curves H and E gives the rolling force and the exit thickness of the product considered for the setting considered.

Without regulation, the point M would become M 'under the effect of a variation of the thickness of entry
H, hardness, or temperature of the product.

 With conventional regulation, acting by modification AS of the vacuum air gap S, the operating point H "results from the intersection of the curves H ', corresponding to the modified input thickness, and E', corresponding to l modified modified air gap.

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 It can therefore be seen that conventional regulation aggravates the variations in rolling force, which is detrimental to the flatness of the products rolled in the form of strips.

 On the other hand, K is assumed to be known, but in certain configurations, the error on its value can lead to divergence in the regulation.

 The device according to the invention, illustrated in FIG. 4, is based on the following principle, which will be better understood by looking at FIG. 3.

The objective of the invention is to bring the point M '(due to a variation in the inlet thickness H, the hardness or the temperature of the product) to a point M "merged with M, and this , by prohibiting any movement of the clamping mechanism 5 of the cage, and by canceling the variations in the rolling force F by action on the traction of the product.

 To this end, the device according to the invention comprises means 8 for measuring the rolling force F, such as a load cell placed in the cage 1 considered.

 Downstream of the means 8 for measuring the rolling force, means 13 generate a signal representative of an instantaneous variation AF of the rolling force F, with respect to one. reference value of this force, corresponding, according to the diagram in FIG. 3, to a thickness at the output of reference H.

 This deviation signal is communicated, via appropriate control means 14, to the means for controlling the traction of the laminate between the cage considered 1 and the upstream cage 15.

 These control means can be, as symbolized in FIG. 6, a conventional looper roller 16 allowing, by acting on the torque of its motor, a modification of the interage traction.

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 The modification of the intercage traction acts in the direction of the correction necessary to reduce the difference LF to a zero value, and therefore so as to cancel the deviation signal.

 In this way, the rolling force is reduced to its value of. setpoint, without modifying the tightening of the cylinders, which corresponds in the diagram of FIG. 3, to the return from point M'to point M "merged with M.

 It is possible, independently or simultaneously to the previous action, and as is known per se, to modify the interage traction by action on the relative speeds of the cylinders of the cages 1 and 15, in response to the difference signal received by the means of command 14.

 The same device can be used on several successive cages or not, the rolling force of each cage being kept constant by action on the traction in the upstream interconnection.

Claims (6)

 sure of a variation (LF) of the rolling force (F) in the cage considered with respect to a set value, characterized in that, in response to a signal representative of an instantaneous variation (AF) of the force of rolling (F), the intercage traction is modified in the direction leading to a cancellation of said signal and therefore of said variation of the rolling force, without acting on the empty height of the intercylinder space of the cage considered (1) .

CLAIMS 1. Method for regulating the thickness of a rolled product at the outlet of a cage (1) of a rolling mill comprising at least one other cage (15) upstream of the cage considered (11), this method being of the type according to which an effort is made to keep the thickness of the laminated product (7) constant by an action in response to the me- 2. Method according to claim 1, characterized in that the intercage traction is modified by action on the torque of the motor controlling a looper roller (16) located between the cage considered (1) and the upstream cage (15). 3. Method according to one of claims 1 or 2, characterize that the interage traction is modified by action on the relative speeds of the cylinders of the cage considered (1) and the upstream cage (15). 4. Device for regulating the thickness of a rolled product (7) at the outlet of a cage (1) of a rolling mill comprising at least one other cage (15) upstream of the cage in question, this device being of the type comprising means (8) for measuring the rolling force (F), characterized in that it also comprises means (13) for generating a signal representative of an instantaneous variation (AF) of the rolling force with respect to a set value of this force (F) and the means (14,16) for modifying the inter-traction <Desc / Clms Page number 8>  laminate cage (7), these means (14,16) acting in response to said representative signal in the direction leading to cancellation of said signal. 5. Device according to claim 4, characterized in that the means for modifying the intercage traction act on the drive torque of a looper roller (16) located between the cage

 1 flabbergasted (1) and the upstream cage (15). 6. Device according to any one of claims 4 and 5, characterized in that the means for modifying the intercage traction act on the relative speed of the cylinders of the cage considered (1) and of the upstream cage (15).