EP0168300B1 - Method to prevent symmetry defects on girders while being rolled on a multi-purpose rolling mill, and device for carrying out this method - Google Patents

Abstract

Process and apparatus for preventing defects in the symmetry of rolled H-beams or I-beams, i.e., a faulty position of their webs (4) in relation to their flanges (5), by correcting such defects in situ. The differential between the torques applied to the upper and lower rolls (1,2) of the rolling stand is determined and compared to a predetermined threshhold value ( delta ). Any excess of the measured value over the threshhold value is eliminated by correction of the elevation of the inlet table of the rolling stand so as to reduce the measured value to below the threshhold value.

Description

The present invention relates to the rolling on a universal cage of beams, in particular steel, profiled in "H" or "1". More specifically, the invention relates to the prevention of symmetry defects which may appear on these beams during the rolling process.

It is known that laminated beams of the type under consideration are liable to exhibit symmetry defects, the most serious of which result in a shift in the position of the core relative to the wings of the profile which can lead to derating. Document FR-A-2 253 576 shows that this problem has been taken into consideration for a long time, but, despite the needs of industry in this field, it seems that no satisfactory rational solution has been proposed so far. . Also, the usual practice is it limited to note the defect on a laminated beam and to try to avoid it reproducing on the next beam by a correction "a priori" of the relative positioning in height of the table d entry of the rolling stand before the blank engages.

The object of the present invention is to provide a preventive solution making it possible to intervene in correction during the very operation of rolling the beam.

• - on effectue une mesure des couples appliqués aux cylindres supérieur et inférieur de la cage;
• - on calcule, à partir de cette mesure, une valeur représentative de l'écart entre les deux couples exprimé par un critère de dissymétrie des poutrelles librement choisi à l'avance;
• - on compare ladite valeur à une valeur de référence prédéterminée définissant un seuil de tolérance d'écart à ne pas dépasser, représentatif de la valeur maximale admissible du critère de dissymétrie;
• - et si la valeur absolue de la valeur calculée est supérieure à la valeur de référence, on agit sur la position relative en hauteur de la table d'entrée par rapport aux cylindres de façon à ramener ladite valeur absolue calculée en-dessous de la valeur de référence.

To this end, the subject of the invention is a method for preventing defects in the symmetry of the beams during rolling on a universal stand, according to which the relative position in height of the entry table of the rolling stand is adjusted relative to working cylinders, process characterized in that:

• - A measurement is made of the torques applied to the upper and lower cylinders of the cage;
• - We calculate, from this measurement, a value representative of the difference between the two couples expressed by an asymmetry criterion of the beams freely chosen in advance;
• - Said value is compared with a predetermined reference value defining a deviation tolerance threshold not to be exceeded, representative of the maximum admissible value of the asymmetry criterion;
• - and if the absolute value of the calculated value is greater than the reference value, the relative height position of the input table relative to the cylinders is acted on so as to bring said calculated absolute value below the value reference.

In accordance with an implementation, the calculated value A representative of the difference between the two pairs of cylinders is determined in accordance with the relationship, expressed as a percentage A% = ²⁰⁰ ( ^{Cs -} Ci) where Cs and Ci are the values meCs + Ci surées couples of the upper and lower cylinders respectively.

• - une cage de laminage munie de deux cylindres horizontaux, dits cylindre supérieur et cylindre inférieur, et d'une table d'entrée dont la position relative en hauteur par rapport aux dits cylindres est réglable;
• - un moteur réversible commandant ladite position en hauteur;
• - des moyens de mesure en continu du couple des cylindres supérieur et inférieur et élaborant des signaux représentatifs de la mesure de chaque couple;
• - une unité de calcul recevant lesdits signaux et qui élabore un signal représentatif de la valeur de l'écart entre les deux couples;
• - un comparateur dont une entrée est reliée à la sortie de l'unité de calcul, l'autre entrée recevant un signal «δ» représentatif d'une valeur d'écart de référence à ne pas dépasser, et dont la sortie est reliée au dit moteur réversible.

The invention also relates to a device for implementing the method comprising:

• - a rolling stand provided with two horizontal cylinders, called upper cylinder and lower cylinder, and an input table whose relative position in height relative to said cylinders is adjustable;
• - a reversible motor controlling said height position;
• - means for continuously measuring the torque of the upper and lower cylinders and developing signals representative of the measurement of each torque;
• - a calculation unit receiving said signals and which produces a signal representative of the value of the difference between the two pairs;
• a comparator, one input of which is connected to the output of the calculation unit, the other input receiving a signal "« "representative of a reference deviation value not to be exceeded, and the output of which is connected to the says reversible motor.

As will be understood, the invention is based on the discovery made by the inventors, according to which it was perfectly possible to translate the asymmetry of the beams, caused by a defective disposition of the core, in terms of difference between the measurements torques applied to the two working cylinders.

Going further, the inventors were even able to show that there was a linear relationship between the asymmetry criterion of the beams usually used (namely the criterion "d" calculated according to b ¹ - ^b2 where _b1 and b2 represent the hau- (b1 + b2) 2 sizes of the two complementary half-wings) and a criterion for the deviation of the couples on the cylinders defined by a completely analogous relationship where the heights of the half-wings would be replaced by the values of the couples. This relation defining the criterion A of deviation of the couples is written A =

où Cs et Ci sont les valeurs mesurées des couples des cylindres supérieur et inférieur respectivement. En conséquence, la simple mesure des couples appliqués au cylindre supérieur et au cylindre inférieur, permet de calculer A et de corriger, en cas de nécessité, la position relative en hauteur de la table d'entrée. En outre, le réglage peut se faire en continu pendant le laminage.

where Cs and Ci are the measured values of the couples of the upper and lower cylinders respectively. Consequently, the simple measurement of the torques applied to the upper cylinder and to the lower cylinder makes it possible to calculate A and to correct, if necessary, the relative height position of the input table. In addition, the adjustment can be made continuously during rolling.

• - la figure 1 représente schématiquement le profil en coupe d'une poutrelle;
• - la figur 2 représente schématiquement en vue de côté le positionnement relatif des cylindres horizontaux de laminage et de la table d'entrée;
• - la figure 3 représente graphiquement la relation linéaire entre la dissymétrie d'une poutrelle et l'écart entre les couples des cylindres supérieur et inférieur;
• - la figure 4 représente schématiquement, en coupe longitudinale, un mode de mise en oeuvre de l'invention;
• - la figure 5 représente graphiquement les essais effectués et leurs résultats.

Other advantages and characteristics of the invention will appear on reading the description which follows, and with reference to the appended drawing, in which:

• - Figure 1 schematically shows the sectional profile of a beam;
• - Figure 2 shows schematically in side view the relative positioning of the horizontal rolling rolls and the input table;
• - Figure 3 graphically represents the linear relationship between the asymmetry of a beam and the difference between the pairs of upper and lower cylinders;
• - Figure 4 shows schematically, in longitudinal section, an embodiment of the invention;
• - Figure 5 graphically represents the tests carried out and their results.

Following the example of Figure 1, the beam 3 profiled in "H" is composed of a core 4 connecting in their middle two wings 5. As we have seen previously, b1 corresponds to the height of the half - upper wing and b2 corresponds to the height of the lower half-wing. This beam, which is not yet finished, is intended to be rolled according to the method according to the invention in a rolling installation as partially shown in Figure 2. This installation comprises two horizontal cylinders 1 and 2, upper and lower respectively, which ensure the rolling of the beam 3, which is brought by the input table with carrying rollers 7 into the opening 6 of width a1 formed between the cylinders 1 and 2.

The entry table is made movable in vertical translation by the action of usual means not shown. The control of this movement will be described in detail in the following description.

Taking into account the above and knowing that a0 represents the initial core thickness 4 of the beam (ie before the rolling operation) and that T denotes the coast of the lower end of the wings of the beam relative to at the base of opening a1, we deduce that a symmetrical engagement of the beam between cylinders 1 and 2 corresponds to a dimension T = TO with TO = b2 +

A simple deregulation of the table 7 modifies this dimension T. If T is greater than T0, the table is too low, and conversely, if T is less than T0, the table is too high. This naturally results in a defect in symmetry of the laminated beam, resulting in a position of the core 4 offset upwards or downwards respectively with respect to the half-height line of the wings 5.

et un critère d'écart «A» des couples des cylindres 1 et 2 exprimé selon:

The inventors have highlighted a linear relationship between the asymmetry criterion "d" of the beam usually considered: d% = 100

and a criterion of deviation "A" of the couples of cylinders 1 and 2 expressed according to:

These two variables, as we can see, are expressed as a percentage.

FIG. 3 represents this linearity relationship of the asymmetry "d" as a function of the torque difference "Δ".

Different types of profiles were used to establish this relationship: the sign "0" corresponds to the profiled beams whose wings are parallel, ie the profiled beams in "H" and in "I", and the sign "0" corresponds to the beams whose wings are inclined, ie those which are profiled in “> - <”: As it can be seen in FIG. 3, there is indeed a relationship of linearity between “d” and “Δ”. In addition, it is noted that the sensitivity of the torque difference A to the adjustment of the relative position of the table is higher than that of the asymmetry d. Indeed, in Figure 3, we see that an asymmetry of 2% can induce a difference of. torque from 5 to 15%.

We can easily understand the interest of these results. First of all, measuring the torque difference is simple. In addition, this measurement can be made at any time and "continuously" during the rolling operation, which makes it possible to immediately remedy the defects in the beams that could be caused by poor positioning in height of the table 7.

FIG. 4 represents an exemplary embodiment for implementing the method according to the invention. The rolling rolls 1 and 2 are conventionally driven in rotation by a reduction motor M using the transmission extensions 8.

A est exprimé en pourcentage. Le signal représentant la valeur calculée A est alors envoyé dans un comparateur 12 qui reçoit sur son autre entrée 14 un signal «S» représentatif d'une valeur d'écart de référence à ne pas dépasser. En cas de dépassement, le comparateur envoie un signal de commande au moteur 13 de manière à ramener la valeur endeçà du seuil de référence «8». L'expérience a montré que de très bons résultats sont obtenus lorsque la valeur seuil à ne pas dépasser n'excède pas 3% environ. En outre, en-deçà de 1,3%, l'influence sur la symétrie des poutrelles n'est plus sensible.According to an embodiment of the invention, each extension is provided with a strain gauge 9 connected to a calculating unit 10 which controls a reversible motor 13 for actuating the members (not shown) for adjusting the height position of the entrance table. The gauges 9 deliver to the unit 10 signals representative of the measurement values of the couples Cs and Ci applied to the cylinders 1 and 2. The unit 10 then produces in a computer 11 a signal corresponding to the difference A between the two couples calculated in

A is expressed as a percentage. The signal representing the calculated value A is then sent to a comparator 12 which receives on its other input 14 a signal "S" representative of a reference deviation value not to be exceeded. If exceeded, the comparator sends a control signal to the motor 13 so as to bring the value below the reference threshold "8". Experience has shown that very good results are obtained when the threshold value not to be exceeded does not exceed approximately 3%. In addition, below 1.3%, the influence on the symmetry of the beams is no longer significant.

Different methods can be adopted to ensure the displacement of the table in the direction of reduction of A below the reference threshold and which are part of the current knowledge of the skilled person.

We will limit ourselves to briefly mentioning only two depending on whether we opt for taking into account the absolute value of A (denoted lΔl) or its algebraic value.

In the first case, a variation test of lΔ l will be provided between two successive measurements A i and A i + 1. If the test result shows that lΔ i + 1 l is larger than Δ il, we deduce that the correct tion of the table position was made in the wrong direction and the motor 13 is then inverted.

The test device can simply be a comparator provided with a memory, placed before, or preferably after the comparator 12. Its memory is initially set to zero and the first ₁ A it greater than the reference threshold is memorized then replaced by _l A i + 1l after comparing lΔ i + 1 l to lΔ l.

In the second case, if the absolute value of A calculated is greater than the threshold "δ", the identity of the cylinder (higher or lower) is taken into account, the value of the torque of which is deduced from the other in the computer 11, and we consider the sign of A to determine whether the table should be raised or lowered.

Thus, for example, if the operation Cs - Ci is carried out and if the result A, assumed to be greater than the threshold, has a negative sign (that is to say if the torque applied to the upper cylinder 1 is lower than that applied to the lower cylinder 2), this means that the table 7 must be mounted. Conversely, if A is positive, the entry table must be lowered. Conversely, if one performs Ci - Cs, a negative sign for A will lead to a descent from the table and a positive sign will lead to an ascent.

If necessary, adjust the height of the output table to that of the input table so as not to hinder the action of the latter.

As can be seen in Figure 5, which represents the relationship between the table setting (T-TO) and the torque deviation A in percentage in the case of a plasticine simulator of a universal rolling stand , we note that an incorrect adjustment of the table of 1 mm can cause a torque difference of about 10%. The sensitivity is therefore high enough to allow precise adjustment of the relative height position of the input table 7.

Table 1, which brings together the results of numerous tests on the simulator, clearly highlights the sensitivity of the measurement of the torque difference A.

In addition, tests were carried out to show the evolution of the asymmetry of a beam after several passes. To do this, the strikethrough (referenced 8H in the first column of Table I) was used to undergo subsequent rolling treatments. As can be seen in Table I, for this bar (8H) a torque difference A of -30% (5th column) corresponds to an asymmetry of height of wings "d" of -10% (column 8) with “b1” equal to 43.5 mm (column 6) and “b2” equal to 48 mm (column 7).

The bar, of which the asymmetry of height of wings has just been observed, was subjected to two different rolling treatments.

First of all, it was subjected to a pass where the difference A of the torques applied to the cylinders is equal to 0. After this test, it is found that the asymmetry of the bar (8H) is preserved. Then, the bar (8H) was subjected to a pass with a torque difference A equal to + 43%, that is to say an adjustment of 8 mm opposite to that noted in the initial pass (column 2 of the table I). Following this test, it can be seen that the asymmetry has been practically eliminated. Indeed, the results give an asymmetry criterion equal to 2% with "b1" equal to 48 mm and "b2" equal to 47 mm.

From these tests, it follows that it will be possible to correct a defect in symmetry of a beam appearing during a pass, by carrying out the next pass with an asymmetrical adjustment opposite to that which generated the defect in symmetry.

As can be understood, the advantage of the invention lies in the fact that it allows continuous control of the value of the torque difference and that, by a simple automatic device, it is possible during rolling to immediately correct the symmetry defects of the beams.

It goes without saying that the invention is not limited to the example described but extends to multiple variants in equivalents insofar as the characteristics set out in the appended claims are respected.

In particular, the adjustment of the relative height position of the table is entirely possible by modifying the height position of the working rolls when such mobility is permitted by the installation. In this case, the cylinders 1 or 2 are mounted in vertically adjustable chocks and the movement of these chocks will be controlled by the reversible motor 13.

Likewise, the means for measuring the couples of the upper 1 and lower 2 cylinders may be magnetic rings surrounding the elongations 8 for driving the rotating cylinders. Of course, other measurement means may also be suitable.

In addition, the invention applies to the rolling of metal beams of different types, in particular those which are profiled in "H" and in "1".

Claims (8)

1. A method to prevent symmetry defects on girders (3) while being rolled on multi-purpose rolling mill, by which one adjusts the relative vertical position of the feed table (7) of the multi-purpose mill in relation to the upper (1) and lower (2) horizontal work cylinders, a method characterised in that:

- one measures the couples applied to the upper (1) and lower (2) cylinders of the mill;

- one calculates from this measurement, a value representing the difference between the two couples expressed by a criterion of dissy- metry of the girders chosen freely beforehand;

- one compares said value to a predetermined reference value «δ» defining the threshold of tolerance in the difference which is not to be exceeded, representing the maximum admissible value of the criterion of dissymmetry;

- and if the value calculated is greater in absolute terms than the reference value «δ», one adjusts the vertical position of the table (7) in relation to the cylinders (1,2) so as to restore the said value below the reference value.

2. A method according to claim 1 characterised in that the calculated value (1) representing the difference between the two couples of the cylinders is determined in accordance with the formula expressed as a percentage

where Cs and Ci are the measured values of the couples of the upper and lower cylinders respectively.

3. A method according to claims 1 and 2 characterised in that the threshold of tolerance is selected at between about 1.5 and 3.0%.

4. A device for carrying out the method according to claim 1 comprising a rolling mill equipped with horizontal work cylinders (1, 2) and a feed table (7) .whose relative vertical position in relation to said cylinders is adjustable, and a reversible motor (13) controlling said height, the device characterised in that it comprises:

- a continuous means (9) of measuring the couple of the upper (1) and lower (2) cylinders emitting two signals representing the measurement of each couple;

- a calculating unit (11) receiving said signals and emitting a signal representing the value of the difference between the two couples;

- a comparator (12) of which one input is connected to the output of the calculating unit, the other input (14) receiving a signal «δ» representing a reference difference value which is not to be exceeded, and of which the output is connected to said reversible motor (13).

5. A device according to claim 4 characterised in that the feed table (7) is mounted so as to be vertically movable and in that the reversible motor (13) controls the vertical position adjustment.

6. A device according to claim 4 characterised in that at least one cylinder (1, 2) is mounted on vertically adjustable trunnions and in that the reversible motor (13) controls the adjustment of the vertical position of these trunnions.

7. A device according to claim 4 characterised in that the means of measuring the couples of the upper (1) and lower (2) cylinders are strain guages (9) placed on the drive extensions (8) of the rotating cylinders.

8. A device according to claim 4 characterised in that the means of measuring the couples of the upper (1) and lower (2) cylinders are magnetic- rings surrounding the drive extensions (8) of the rotating cylinders.

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