EP1357205A2 - Process and apparatus for treating strips - Google Patents

Abstract

Variation in strip velocity in a treatment section (2) of, e.g., a pickling installation is compensated by variation in strip length between the treatment section (2) outlet end and a downstream tensioner, so that constant strip length is maintained between the outlet end and an upstream tensioner (61) without perceptible variation in tractive force applied to the strip (4) between tensioners. A metallic strip (4) moves in a longitudinal direction through an installation comprising at least three successive sections, namely a feed section (1), a section (2) for treatment in at least one extended tank containing processing fluid and having an inlet (23) and an outlet located at an upper level and between which the moving band forms a curve (40) whose lower part (43) is located at a lower level that depends on the length of the strip between the inlet (23) and outlet, and a discharge section. The treatment section (2) is connected to an upstream tensioner (61) and a downstream tensioner located before the inlet end (20) and behind the outlet end of the treatment section (2), respectively. Any variation in strip velocity in the treatment section (2) is compensated immediately, at least during strip acceleration or deceleration, by a corresponding variation in the length of the strip between the outlet end of the treatment section (2) and the downstream tensioner, so as to maintain a substantially constant length of the strip between the outlet end of the treatment section (2) and the upstream tensioner (61) without any perceptible variation in the tractive force applied to the strip (4) between the two tensioners. An Independent claim is given for an installation for implementation of the invented process.

Description

The subject of the invention is a method and an installation for treatment of a product in a strip and applies especially to pickling of a metal strip.

We know that, in general, the manufacture of a metal product requires a so-called "hot" preparation of a raw product obtained by casting in a mold or continuous casting and undergoing a hot transformation by forging and / or hot rolling. The product thus produced is then subjected to a cold transformation comprising various stages which depend on the nature of the metal and the quality of the product to manufacture.

In the case of the manufacture of metal strips, in steel, it forms during cooling more or less important layer composed of oxides, which must be eliminated by appropriate treatment. It is advantageous, in particular, to carry out a chemical pickling by leaving stay the strip, for a determined time, in a fluid treatment such as an acid capable of dissolving oxides by transforming them into an acid salt.

Generally, this stripping is carried out by scrolling the strip, successively, in one or more trays, filled acid. We can thus vary the processing time which depends on the submerged length and the scrolling speed.

In an old process called "push-pull", the pickling tank is placed between two winders, respectively unwinding of a reel and rewinding thereof after scrolling in the bin.

However, to increase productivity, it is possible perform continuous processing of multiple coils successive. In this case, at the end of the unwinding of a reel, its tail, i.e. its downstream end in the direction is fixed on the head of a new reel which is thus dragged to the processing section. In the same way, the evacuation section comprises shearing means of the strip to allow the evacuation of the reel at the end winding and engagement on the head winder of the next reel. This produces a continuous strip of large length that scrolls at a certain speed between an unwinder provided with means for replacing a coil with a next, and a winder associated with evacuation means coils wound.

Such a continuous online installation therefore includes, in the direction of scrolling, at least three successive sections, respectively, a feed section, a feed section treatment comprising one or more successive tanks and a evacuation section.

It is, however, necessary to stop scrolling in the supply section for joining two coils successive, as well as in the evacuation section to evacuate the wound coil and engage the next strip on the reel. However, the effectiveness of pickling obviously depends on the strip residence time in the tanks. To get a homogeneous pickling, so as much as possible continue scrolling of the tape in the bins, during the downtime in the supply section or in the discharge section.

Continuous stripping lines must therefore be equipped with means of accumulation of variable length from tape, allowing to store in advance, upstream of the processing section, sufficient strip length to supply the treatment section during the downtime necessary, in the supply section, for the junction of the tail of a reel with the next reel head.

Similarly, at the end of the winding of a coil, the strip must be sheared to allow the evacuation of the wound coil and the tape head thus formed must be engaged on the winder for winding the reel next. During the downtime necessary for these operations, the scrolling of the strip continues in the pickling tanks and the length of tape thus produced is stored in a accumulator placed upstream of the discharge section.

Previously, accumulators consisted of wells deep in which we let unfold, under its own weight, a strip descending into the well and towed at the outlet of it, for example by pinch rollers.

The speed difference between entering and leaving the well allows you to vary the length of the loop and therefore the accumulated tape length.

In some cases, we even let the tape build up, in superimposed folds, at the bottom of the well, but this results in significant friction and a risk of deterioration which can only be mitigated by filling the well with water. For avoid it, it is preferable that the strip forms inside the well, a single loop between two support rollers. The length of accumulated band then depends on the depth of the well but can be increased by using several successive wells called "loop pits".

Such an arrangement only requires relatively basic pull-ups, but cannot be used only in low or medium capacity installations and for products that do not require a level of quality Student.

On the other hand, it is necessary, in an installation in continuous line, to use batteries of another type, can have a very large capacity.

Indeed, treatment facilities, in particular of pickling, operating in continuous line, were not planned, so far, only for very large productions, which can exceed 1 million tonnes per year, for example.

Since the coils have a limited weight of the order about twenty tonnes, these must succeed each other fairly quickly, which requires frequent scrolling stops to allow, upstream, the welding of the next coil and, downstream, the evacuation of the wound coil.

In addition, to allow high production, the speed scrolling must be large enough and, to get a time sufficient stay, we have to increase the length of the treatment section which includes several successive tanks.

It is therefore necessary to place accumulators of very large capacity upstream and downstream of the treatment section.

For example, for a scrolling speed of 250 m / min, 1.5 minutes downtime to replace a coil requires an accumulation capacity of approximately 400 m.

Such accumulators are well known and include, in general, a set of fixed deflection rollers and a set of movable rollers mounted on a carriage looping so as to form several superimposed strands running in opposite directions. Horizontal movement of the carriage one way or the other allows, then, to increase or decrease the length of strip passing over the rollers. However, to avoid contact between two overlapping strands, respectively outward and return, it is necessary to interpose between these a series of separating arms which are distributed along the path of the looping carriage and must therefore move away to allow the passage of it (FR-A-2778350).

The operation of such an accumulator requires a precise control of the tensile force applied to the so that the different strands of it stay tight during the movement of the looping carriage. Each accumulator must therefore be associated with two tensioners placed respectively upstream and downstream and constituted, usually S rollers

Furthermore, the processing section can be constituted relatively deep tanks filled with pickling fluid in which the strip plunges by forming a loop more or less long. A difference between the frame rates at the entry and exit of the bin causes, in fact, a variation corresponding to the length of the submerged strip.

However, a deep container requires a large amount of treatment liquid and for some time now we have proposed to use relatively flat tanks for pickling in which the strip has a slight deflection, this which reduces the amount of liquid needed in the tank. For further reduce the capacity of a bin, it can, moreover, be provided with a curved bottom so as to substantially follow the shape in the chain of the loop.

We know, in fact, that a band stretched between two supports under the effect of its own weight, forms a curve called "Chain", the lower part of which is placed below the level of the supports, at a certain height called "arrow", which depends on the length of the stretched loop between the two support.

However, the tensile force to be applied at the level of each support in a chain-shaped curve depends on the orientation of the end of the loop and becomes very important when the strip must follow a relatively tight curve. The arrow of the chain is therefore very sensitive to a variation in tensile forces applied to the entry and exit of the tank. Gold, in case of contact with the bottom of the tank, the strip, which scrolls high speed, risk of deterioration. To avoid faults, it is therefore necessary to precisely control the effort of traction applied to both ends of the strip so that the length of the chain and the level of its lower part remain substantially constant.

For this, the strip must be kept stretched by two tensioning devices, respectively an upstream tensioner placed in front, in the direction of travel, of the end in the processing section and a downstream tensioner placed behind the exit end of the section of treatment.

In this case, the downstream tensioner determines the speed of scrolling of the strip which is retained by the upstream tensioner. Adjustment of the torques applied on the two tensioners allows precise control of the belt tension in order to keep its length constant and, therefore, the arrow in each bin.

However, the levels of traction to be ensured in the tanks are not the same as in accumulators and the two tensioners placed upstream and downstream of the section of treatment are therefore added to those associated with Accumulators.

US-A-4,886,199 describes an arrangement simplified in which the upstream accumulator and the accumulator downstream use the same loop cart or two cars united on the move.

It is thus possible to maintain a constant speed in the treatment section, the upstream accumulator draining while the downstream accumulator is filling and vice versa.

Such an arrangement makes it possible to reduce the number of tensioners and remove the control means of the displacement of the looping carriage since we use for this effect the traction exerted by the band. Because of this, however, it it is not possible to precisely control this effort of traction.

The disposition of document US-A-4,886,199 can therefore be used, for example, for continuous rolling, but does not not allow, in the case of a pickling line using relatively flat bins, to maintain the tractive effort at a level constant enough to avoid a risk of contact of the strip with the bottom of the tank.

On the other hand, such an installation still requires the use two large capacity accumulators which are very bulky and expensive devices.

Such equipment, whose immobilization is very costly, are therefore only profitable for large lines production or coupled lines on tandem rolling mills. It is why, until now, continuous line stripping has been expected that for large annual tonnages of bands pickled, for example between 1 and 2 million tonnes per year, the classic technique called "push-pull" being used usually in lower capacity installations.

Developments in the steel market show that the qualities required of materials, in particular steels laminates, are more and more precise and you have to be able to respond very flexibly to customer needs.

It therefore appeared that it would be interesting to carry out installations having substantially the same advantages as a large capacity continuous line, especially for quality of the product obtained and remaining, however, profitable, even for low or medium production ranging, for example, between 500,000 and 750,000 tonnes per year.

The invention therefore aims to solve this problem thanks to a new tape drive process in continuous online installation, allowing the use of much simpler and more economical equipment than in conventional large capacity installations.

In addition, the arrangements according to the invention allow the use of modern technologies such as low height pickling with rapid acid recirculation without risk of deterioration of the strip.

The invention therefore applies to an installation comprising, in general, at least three successive sections respectively a power section, a section of treatment by passing the strip through at least one tank elongated containing a processing fluid and a section evacuation, said treatment section being associated with a upstream tensioner and a downstream tensioner placed respectively in front of the entry end and behind the exit end of the section.

According to the invention, any variation in the speed of scrolling in the processing section is compensated immediately, at least during an acceleration phase or deceleration, by a corresponding variation in length of tape between the outlet end of the section of treatment and the downstream tensioner, so as to maintain permanently a substantially constant strip length between said outlet end of the processing section, and the upstream tensioner, without appreciable variation in the tensile force applied to the strip between the two tensioners.

Particularly advantageously, to allow stopping the tape running during an evacuation cycle of a reel, at the end of the winding, the running speed in the processing section is reduced to a minimum value compatible with tape quality and tape length scrolling, at said minimum speed, during this downtime, is stored in a capacity accumulator corresponding to this minimum speed, which is interposed between the outlet end of the processing section and the tensioner downstream.

Similarly, to allow the tape to stop running during a replacement cycle with a new reel, of a reel at the end of the unwinding, the running speed in the processing section is reduced to a minimum value compatible with the quality of the tape and the length of the running tape, at said minimum speed, during this downtime, is put in reserve in a capacity accumulator corresponding to this minimum speed, which is interposed between the output of the supply section and the upstream tensioner.
In all cases, thanks to the invention, the dynamic effect of a variation in the running speed in the processing section is immediately compensated for by a corresponding variation in the length of strip comprised between the output of the processing section and the downstream tensioner, without modification of the tensile force and, consequently, of the deflection of the chains formed in the tanks.

To replace or remove a coil, this reserved length may be limited due to the reduction of the speed in the tanks to a minimum value and we can therefore use a simpler accumulator and economical than in conventional continuous lines.

The invention also covers an installation for placing implementing the method, comprising two tensioners placed respectively upstream and downstream of a processing section. According to the invention, the installation comprises means for control of a variation in the length of the strip passing between the outlet end of the processing section and the tensioner downstream, for maintaining, at all times, a length of substantially constant band between said outlet end and the upstream tensioner, without appreciable variation in the force of traction applied to the strip between the two tensioners, respectively upstream and downstream.

According to another particularly characteristic advantageous of the invention, the interposed accumulation device between the outlet end of the treatment section and the downstream tensioner can constitute, on the one hand, a means of maintaining, at all times, a strip length and a substantially constant tensile force between the ends of each bin and, on the other hand, a means of setting aside a sufficient length of strip for the maintenance of a minimum tape running speed in the processing section during a scrolling stop time in the evacuation section.

In a preferred embodiment, such accumulator has a maximum accumulation capacity corresponding to the length of the strip running for the duration a coil discharge cycle, for a reduced speed of scroll through the processing section. For example, the accumulation capacity can be at most a few tens of meters. Preferably, the duration of an evacuation cycle is the order of 1 to 2 minutes and the scrolling speed, during this cycle, is reduced to about 10 m / min, the capacity of the accumulator can be 15 to 20 m.

Particularly advantageously, such a tape accumulator has a deflection roller on which pass two strands of the strip, respectively back and forth, said deflection roller being movable, preferably horizontally, between two accumulation positions, respectively a retracted minimum accumulation position and a position for maximum accumulation.

In this case, the first accumulator placed between the outlet of the supply section and the upstream tensioner, is advantageously of the loop pit type.

The invention thus makes it possible to carry out an installation of particularly simple and economical stripping, run online profitably for a production in the range of 500,000 to 750,000 tonnes per year.

But the invention also covers other characteristics advantageous which will appear in the following description of a particular embodiment given by way of example and shown in the accompanying drawings.

Figure 1 shows schematically a first part of an installation according to the invention comprising a section feed and the start of a treatment section.

Figure 2 shows schematically the second part of such an installation comprising the outlet of the section of treatment and an evacuation section.

In Figures 1 and 2, there is therefore shown schematically the whole of a pickling installation chemical of a metal strip comprising three sections, respectively, a feed section 1, a feed section treatment 2 and a discharge section 3 placed successively along a longitudinal direction of scrolling of a metal strip 4.

The supply section 1 comprises, in a conventional manner, an unwinder 10 receiving a reel to be treated 41, rollers nippers 11 ensuring the unwinding of the coil 41, and a block 12-scraper remover for straightening the strip coming out of the coil and making a coarse leveling to avoid that the strip may catch fixed parts, in particular when scrolling through the pickling tanks.

A trimming shears 13 makes it possible to cut the head and the tail of each reel, in order to eliminate them.

Processing section 2 consists of several tanks stripping 21, generally three or four trays, which are followed by a rinsing device 22.

As shown schematically in the drawings, flat type tanks are used with a shallow depth by relative to their length, each bin being provided at its entrance and at its outlet, deflector rollers 23 between which the strip follows a chain-shaped curve with the lowest part 43 passes a short distance from the bottom 24 of the tank, which can, possibly be provided with a series of spaced supports for avoid direct contact.

Such flat trays, allowing the quantity to be reduced necessary treatment liquid, have been known since have been the subject of various refinements.

For example, to further limit the volume of the tank, it is possible to give the bottom 24 thereof a curved shape parallel to the chain-shaped curve followed by the strip between the two ends of the tank.

In addition, it is possible to directly inject the liquid processing on the tape being scrolled by means of a series of nozzles arranged to follow the shape of the curve formed by the strip in the tank, according to a described arrangement in document FR-A-2 784 998, by the same applicant. The amount of liquid used is thus greatly reduced. In addition, the pressure spraying of the acid increases the efficiency of the treatment.

In general, the number of bins and their lengths are determined based on the maximum frame rate planned, taking into account the type of strip to be treated, in particular its format and the nature of the material and type of acid used. Of more, the treatment section 2 is equipped with circulation and flow control of the pickling fluid in each tank, ensuring regeneration of the acid in order to maintain optimal chemical treatment conditions. Of such means are well known and are therefore not shown on the diagram.

To allow the use of fairly low flat tubs capacity it is necessary to control the tensile state of the strip running. Indeed, so that the arrow f of the curve in the form of a chain followed by the band in each tray remains small compared to the distance between the deflection rollers 23, 23 'placed respectively at the entrance and at the exit of the tank, the strip should be subjected to fairly high traction and a even a fairly small decrease in tractive effort results in an extension of the strip length between the two rollers deflectors 23, 23 'and an increase in deflection f.

The strip can then come into contact with the bottom 24 of the tank and it this results in a risk of deterioration and marking of the strip by friction. In addition, the tensile force applied to the strip must also be checked to avoid premature wear and the deterioration of the support and guidance devices of the strip inside the trays such as pinch rollers, thresholds bins or other.

To control the tensile forces and, therefore, the arrows taken by the chains inside each bin, the processing section 2 is therefore associated with two tensioning 6, 6 ′ placed respectively upstream and downstream, in the direction of travel, the input ends 20 and outlet 20 'from processing section 2.

The upstream tensioning device 6 thus comprises a upstream tensioner 61 of the "S-block" type comprising at least two rollers with parallel axes on which the strip follows a path in S and followed by a guiding device 62 which makes it possible to keep the strip well centered at entry 20 in the first bin treatment 5a.

Similarly, the downstream tensioning device 6 ′ comprises a guide block 62 ′ allowing the centering of the strip at the outlet 20 'of the rinsing section 22 and a block tensioner 62 '.

The upstream tensioner 61 thus allows, on the one hand to drive the tape in the feed section 1 and, on the other part, to retain the strip which is driven by the downstream tensioner 61 '. The torques applied by the two tensioners 61, 61 'are adjusted one according to the other so as to control the effort of traction applied to the strip.

It is generally planned to shear the edges of the strip which may have defects and a 63 edge shears is therefore placed at the exit of the treatment section. This shears edge 63 which can be of the towed type is placed advantageously between the tensioner 61 'which makes it possible to pull the band and the guide block 62 'which allows the band to be centered in the shears so as to minimize falling from the shore.

The discharge section 3 placed downstream of the tensioning machine 61 'conventionally comprises a winder 30 associated, on the one hand with a shears 31 making it possible to cut the strip at the end of the winding of a coil 41 'and, on the other hand, to means for removing the completed coil and to means for engaging the head of the strip for winding a new coil. Such means are well known and do not are therefore not shown in the diagram.

The installation being provided to allow scrolling in continuous strip to be treated, it is necessary, as we have seen, to connect the tail of a strip at the end of the scroll to the head of the next reel.

For that, it is necessary successively to trim the tail of strip in the shears 13, put in place a new coil on the unwinder 10, engage the new strip in the unwinding devices 11 and 12, trimming the head off and connect it to the tail of the previous reel using a joining device 14.

During all the time necessary for this cycle of replacement, the tape running must be stopped in the feed section 1 but must continue, however treatment section 2 because a stop in the acid tanks would be detrimental to the quality of the tape and would result in loss of metal.

It is therefore necessary to plan, at the exit of the section supply 1, an accumulation device 15 in which a sufficient tape length is set aside at the start of unwinding of a reel. To allow effective control of the tensile force on the strip in the treatment section 2, this accumulator 15 must be placed upstream of the tensioner 61 which retains the strip driven by the downstream tensioner 61 '.

Likewise, a second accumulation device must be provided upstream of the winder 30 to reserve the length of strip leaving treatment section 2 during stopping the winding for the evacuation of a completed coil.

As mentioned above, in an installation of large production, the tape runs at a very high speed, by example 250 m / min and this speed must also be maintained as constant as possible so as not to disturb the operation of the installation. As a result, one must use very large capacity accumulators which are each associated with two tensioners and that only a high production allows to make such an expensive installation profitable.

In the case, on the contrary, of a weak installation or medium capacity having to adapt to changes in manufacturing program it's less important to maintain the productivity and for the installation to be profitable you have to essentially reduce investment costs and operation. This is why, until now, we used commonly called "push-pull" installations operating from reel to reel.

In such an installation, each coil must have re-engage the band between all the rollers and this results in a risk of tape marking. In addition, productivity is obviously quite low, due to the periodic shutdown of installation.

The invention is based on the idea that by admitting a certain loss of productivity compared to processing facilities continuous line carried out so far for large capabilities we could use simpler layouts and less expensive allowing, however, to keep the essential advantages of continuous treatment and that it would be possible to sufficiently reduce investment costs and for such an installation to be profitable for an average production, for example from 500,000 to 750,000 tonnes / year.

In particular, whereas until now, we used very large accumulators to maintain substantially constant the scrolling speed in the bins, it appears that a reduction in the scrolling speed up to a minimum speed of 10 m / min for example allows the use of a very simple and inexpensive accumulator, of low capacity.

We know, in fact, that the downtime required for a coil replacement or drain cycle is about 1.5 minutes. If we can reduce the speed of scrolling to a minimum value, for example 10 m / min, the capacity of the accumulator must be, simply, 15 to 20 m.

However, even in large capacity installations, it is already possible, for example in case of damage, to reduce the speed scrolling to a very low value, especially if you performs a hydrochloric pickling. In the invention, instead to be exceptional, such a speed reduction will be periodically at the end of each reel. As a result, obviously a loss of productivity but this is entirely acceptable for a low or medium installation capacity and, in any case, the production capacity remains higher than that of a "push pull" installation.

So we will use low capacity accumulators, both upstream and downstream of treatment section 2.

Preferably, as shown in FIG. 1, the accumulator 15 placed upstream of the input tensioner 61 of the treatment section 2 can be of the "loop pit" type.

We know, in fact, that such an accumulator is particularly economical because it is made up simply one or two pits 16 in which the strip forms a loop that hangs freely under the effect of its own weight. The length of tape thus accumulated in each pit is controlled by pinch rollers 17 which can be adjusted speeds as a function, on the one hand of the scrolling speed at the exit from the unwinder 10 and, on the other hand, the speed of scrolling maintained in processing section 2 by the tensioner 61. Thus, at the start of the unwinding of a reel, it is possible to adjust the speed given by the rollers pinchers 17 slightly above the frame rate in the trays to form loops 42 in the two pits 16 which are equipped with tape detection devices in order to check the accumulated lengths.

As indicated, in the case of a large arrow with respect to the distance between supports, the tension of the strip has no need to be checked with great precision. Level general traction is therefore determined simply by adjusting the relative speeds of the tensioner 61 placed upstream of the section feed and pinch rollers 11 and 17.

Of course, other known means could be employees in the power section who don't need to be described in detail. However, since the installation according to the invention is intended for lines of small or medium capacity, it is worth saving investment using less expensive equipment than in a large production facility and allowing, however, to achieve the desired quality. In this regard, it is interesting to use a stapler 14 for the connection of successive bands but, if necessary, we could use another means of junction such as, for example, a welder.

Likewise, a low capacity accumulator must be placed downstream of treatment section 2. However, according to another essential characteristic of the invention, this accumulator 5 is integrated in the downstream setting device voltage 6 'and is therefore placed between the outlet end of the processing section 2 and the downstream tensioner 61 '. So then that before, we placed a large capacity accumulator downstream of the output tensioner of the treatment section, in the invention, this accumulator 5 is placed upstream of this tensioner 61 'because it can have a fairly low capacity and can be arranged so as to maintain tension in the section of treatment 2 at a constant level.

Such an accumulator 5 therefore makes it possible not only absorb the length of tape produced during a cycle evacuation, but also to maintain constant, at each instant, the strip length between the two tensioners 61, 61 ' and therefore the lengths and arrows in each bin 21.

As noted above, the normal duration of a evacuation cycle after complete winding, of a coil 41 ' is approximately 1.5 minutes. If we reduce the scrolling speed to 10 m / min, the capacity of accumulator 5 must therefore be in the range of 15 to 20 m and, in any case not more than a few tens of meters.

Therefore, as shown schematically in the figure, the accumulator 5 can be of the roller type dancer comprising a single deflection roller 51 associated with two fixed rollers 52, 52 'and movable over a length of one ten meters.

Preferably, the deflection roller 51 moves horizontally below the rinsing section 22, one of the fixed rollers 52 being fixed at the exit of the section feed 2 and the other fixed roller 52 'which can be part of the centering device 62 'placed in front of the downstream tensioner 61'.

Thanks to this arrangement, the tension applied to the strip 4 in the pickling tanks 21, which determines the level of the lower part 43 of the curve formed, in each tank, by the band, depends only on the couples applied respectively on the downstream tensioner 61 'which determines the force drive and on the upstream tensioner 61 which exerts a retaining force and is not separated from the 20 'inlet of the first tank by any device other than a deflection roller, which allows to precisely control the tensile force on the strip.

The dancer roller 51 of the downstream accumulator 5 is, from preferably operated by one or more cylinders not shown associated with a hydraulic control system which allows respond immediately to a variation in tractive effort applied between the two tensioners 61, 61 ', for example, in due to the dynamic effect of a change in speed, in acceleration or deceleration phases.

The accumulator 5 therefore constitutes a regulating device traction to keep the length of strip between the two tensioners 61, 61 ′ and, consequently, the arrow f of the chain-shaped curve followed by the strip in each bin.

The installation which has just been described therefore operates from the as follows:

After placing a reel 41 on the unwinder 10, we controls the unwinding of strip 4 and its passage through successive sections of the installation until the commitment of the head of the strip on the rewinder 30. The installation can then operate continuously at a normal speed of scrolling in the bins, for example 200 m / min. The torques applied respectively by the two tensioners 61, 61 'are adjusted so as to apply to the strip, at the ends 23, 23 'of each bin 21, compatible tensile forces with the level of stresses admissible by the material constituting the strip, maintaining a minimum distance between the bottom 24 of the tray 21 and the lower part 43 of the strip.

At the start of the unwinding of the coil 41, the pinch roller speeds 17 so as to form, in each pit 16, a loop 42. On the other hand, the roller dancer 51 of the downstream accumulator 5 is placed in his position minimum accumulation reentry with, however, some possibility of horizontal displacement in order to compensate, in case as needed, slight variations in the tensile force applied on the tape.

At the end of the unwinding of the coil 41, it must be replaced by a new coil. During the cycle of replacement the tape scrolling is stopped at the shears 13 in order to eliminate the tail of the strip, and the speed scrolling in the bins 21 is reduced to a speed minimum of the order of 10 m / min for which the lengths of loops 42 previously accumulated in pits 16 are sufficient to continue treatment.

In conventional installations, a speed variation at the entry or exit of the line is compensated by a accumulator associated with its own tensioners and capacity sufficient to keep the frame rate constant in the processing section whose tensioners therefore do not have to change speed.

On the contrary, in the simplified installation according to the invention, we only use two tensioners 61, 61 'which we can change speeds simultaneously to go down to speed minimum scrolling or to return to normal speed, all keeping constant the tensile force applied to the strip.

However, this adaptation is not immediate, taking into account the inertia of the drive devices.

This results in a risk of voltage variation and, by therefore, increased chain deflection in each bin. This risk is avoided, according to the invention, thanks to the hydraulic control of the downstream accumulator 5 which performs a real regulation. Any variation in the tensile force can, indeed, be detected immediately and compensated by a corresponding movement of the dancer roller 51 in order to keep the length of the strip between input 20 and the outlet 20 ′ from the supply section 2 as well as the effort of traction applied to the strip. So when the speed of scrolling in the bins 21 is reduced to allow a stop in the supply section 1, the deceleration is absorbed by a slight movement of the dancer roller 51 which allows keep the length and the arrow f of the chain constant formed by the strip 4 in each tray 21 and, thus avoiding a deterioration of the strip by friction with the bottom 24 of the tank, even if you observe a minimum safety distance.

After welding the tail of the strip during pickling on the head of the new coil, the speed of scrolling is increased but the dynamic effect of this acceleration is still absorbed by the dancer roller 51 whose the displacement makes it possible to keep the efforts of tension and the length of strip between the two ends 23, 23 ' of each tray 21.

When the coil 41 'formed on the reel 30 arrives at its maximum diameter, the scrolling speed in the bins 21 is reduced again to a minimum speed, for example 10 m / min, and the scrolling is stopped at the level of the downstream shears 31 which cuts the strip to allow the evacuation of the reel finished 41 'then the engagement of the next part of the band on the rewinder 30 to form a new coil.

As before, the accumulator 5 allowed to absorb this deceleration so as to keep constant the length of each chain, despite the inertia of the devices drive. Then, the deflection roller 51 has little move in order to absorb the length of tape processed in the section 2 at this reduced speed, this length possibly being, as we have seen, from 15 to 20 m for a stopping time of 1.5 min.

Thus, the downstream accumulator 5 placed between the outlet 20 'of the processing section and the downstream tensioner 61 'fills both functions, respectively of maintaining, at each instant, a substantially constant length of strip between the two ends of each bin and set aside a length constant band running through processing section 2 to a minimum speed during the coil discharge cycle completed.

When the frame rate has returned to its level normal, the tape unrolls continuously between the unwinder 10 and rewinder 30 and deflection roller 51 of the accumulator 5 is returned to its accumulation position minimal without modification of the tensile force applied to the strip by the tensioner 61 '.

Of course, the invention is not limited to the details of the embodiment which has just been described by way of simple example, other devices that can be used for setting implementing the process without departing from the protective framework defined by the claims.

For example, it is advantageous and particularly economical to use loop pits to build the upstream accumulator 15 but other arrangements could be used to perform the same function, for example a dancer roll.

In addition, if a movable dancer roller horizontally reduces clutter it would obviously possible to use a movable roller vertically.

Likewise, the guiding devices 62, 62 ′ can be at two or three rollers and the tensioners 61, 61 'with two or four rolls. The fractionation shears 13, 31 can also be of any type adapted to the capacity of the line, desired frame speeds and the nature of the materials to be treat. The same is true of the pickling system used, by example shallow flat tank or tank with injection acid, as well as means for reducing the scrolling speed to a level compatible with a accumulation capacity reduced to a few tens of meters. We know, in particular, that it is advantageous, for this purpose, to perform a hydrochloric pickling and that can also be use inhibitors to reduce the effect of the acid to prevent do not over-attack the metal at low speed.

Furthermore, the invention is intended especially for the production of continuous pickling lines average, for example of the order of 500,000 to 750,000 tonnes per year. However, the invention would also have advantages for higher capacity lines because the regulation of traction provided by the dancer roller would allow the use of low height bins with a very tight band, without risk deterioration thereof.

Claims (16)

Method for driving a product in a moving strip, in a longitudinal direction, in an installation comprising at least three successive sections, respectively a feed section (1), a section (2) for processing by passing the strip ( 4) in at least one elongated tank (21) containing a treatment fluid and having an inlet (23) and an outlet (23 ') placed at a higher level, between which the strip which runs forms a curve (40) having a lower part (43) placed at a lower level which depends on the length of strip between the inlet and the outlet of the tank (21), and a discharge section (3), said treatment section (2) being associated an upstream tensioner (61) and a downstream tensioner (61 ') placed respectively in front of an inlet end (20) and behind an outlet end (20') of the section treatment (2),
characterized in that any variation in the running speed in the processing section (2) is immediately compensated for, at least during an acceleration or deceleration phase, by a corresponding variation in the length of strip (44) between the outlet end (20 ') of the treatment section (2) and the downstream tensioner (61'), so as to permanently maintain a substantially constant length of strip between said outlet end (20 ') of the section treatment (2) and the upstream tensioner (61), without appreciable variation in the tensile force applied to the strip (4) between the two tensioners (61, 61 '). Method according to claim 1, characterized in that a possible variation in the tensile force applied to the strip between the two tensioners, respectively upstream (61) and downstream (61 '), due to the dynamic effect of a variation in the running speed, is detected and immediately absorbed by a device (5) for accumulating a variable length of strip, interposed between the outlet (20 ') of the processing section (2) and the downstream tensioner ( 61 '). Method according to claim 2, for driving a strip (4) in an installation in which the discharge section (3) comprises a winder (30) for winding up the strip (4) after treatment, unrolling of the strip (4) being stopped at the end of the winding of a reel during an evacuation cycle of the wound reel (41 '), characterized in that , during the duration of an evacuation cycle , the running speed in the treatment section (2) is reduced to a minimum value and the length of strip running at said minimum speed during the duration of the evacuation cycle is put in reserve, with maintenance of the traction force , in an accumulator (5) of corresponding capacity, interposed between the outlet end (20 ') of the treatment section (2) and the downstream tensioner (61'). Method according to one of the preceding claims, for driving a strip in an installation in which the supply section (1) comprises means (10, 11) for unwinding a reel (41) to be treated, the scrolling of the strip (4) being stopped at the end of the unwinding of the reel (41) for the replacement of the latter with a new reel,
characterized in that , during the duration of a replacement cycle, the running speed in the treatment section (2) is reduced to a minimum value and the length of strip running at said minimum speed during the duration of the cleaning cycle replacement is placed in reserve in an accumulator (15) of capacity corresponding to this minimum speed, interposed between the outlet (20 ') of the supply section (1) and the upstream tensioner (61). Method according to either of Claims 3 and 4, characterized in that , during the duration of a coil replacement or discharge cycle, the speed of travel in the treatment section (2) is reduced to one minimum value corresponding to an accumulation capacity of at most a few tens of meters. Installation for processing a strip product comprising: means (11, 61, 61 ', 30) for controlling the movement of a strip (4), along a longitudinal axis, in at least three successive sections, respectively: a section (1) for feeding the strip at an adjustable speed between a zero speed and a processing speed; a treatment section (2) having an inlet end (20) and an outlet end (20 ') and comprising at least one elongated tank (21) having an inlet (23) and an outlet (23') and containing a treatment fluid; a strip discharge section (3) at an adjustable speed between a normal speed and a zero speed; two tensioner assemblies, respectively an upstream tensioner (61) placed in front, in the direction of travel, of an inlet end (20) of the treatment section (2) and a downstream tensioner (61 ') placed behind an outlet end (20 '), for maintaining said strip (4) under a substantially constant tensile force between the inlet (23) and the outlet (23') of each tank, characterized by the fact that it comprises means (5) for controlling a variation in the length of the strip (44) running between the outlet end (20 ') of the treatment section (2) and the downstream tensioner (61 '), for maintaining, at all times, a length of strip (40) substantially constant between said outlet end (20') and the upstream tensioner (61), without appreciable variation in the tensile force applied to the strip (4) between the two tensioners, respectively upstream (61) and downstream (61 '). Installation according to claim 6, characterized in that at least one accumulator (15) of the loop pit type is placed in the path of the strip (4), at the outlet of the supply section (1) and in front of the upstream tensioner (61). Installation according to claim 6, characterized in that the accumulation device (5) placed between the outlet (20 ') of the treatment section (2) and the downstream tensioner (61') constitutes, on the one hand a means for regulating the traction on the strip for maintaining, at all times, a substantially constant length of strip between the inlet (23) and outlet (23 ′) ends of each tank (21) and, d on the other hand, a means of reserving a sufficient length of strip for maintaining the running of the strip (4) in the processing section (2) during a time for stopping the running in the discharge section (3) of the installation. Installation according to claim 8, in which the discharge section (3) comprises a winder (30) associated with means for discharging a wound coil (41 '), characterized in that the accumulator (5) has a maximum accumulation capacity corresponding to a length of strip running for the duration of a cycle for discharging a reel (41 '), for a reduced running speed in the processing section (2). Installation according to claim 9, characterized in that the accumulator (5) has a maximum accumulation capacity of at most a few tens of meters. Installation according to one of claims 4 to 10, characterized in that the accumulator (5) is hydraulically controlled for adjusting the length of the accumulated strip. Installation according to one of claims 4 to 11, characterized in that the strip accumulator (5) comprises a deflection roller (51) movable between two accumulation positions, respectively maximum and minimum. Installation according to claim 12, characterized in that the movement of the deflection roller (51) is controlled by at least one hydraulic cylinder associated with a supply circuit comprising means for detecting a variation in the tensile force applied to the strip (4) passing over the roller (51). Installation according to one of claims 12 and 13, characterized in that the deflection roller (51) moves horizontally between a retracted position for minimum accumulation and an extended position for maximum accumulation. Installation according to one of claims 12 and 13, characterized in that the deflection roller (51) moves vertically between a retracted position for minimum accumulation and an extended position for maximum accumulation. Installation according to one of claims 6 to 15, characterized in that it comprises means (62, 62 ') for guiding the strip (4) placed respectively between each end (20, 20') of the section of treatment (2) and the corresponding tensioning assembly (61, 61 ').

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