EP1486573B1 - Process and device for cooling a moving metallic strip - Google Patents

Abstract

A cooling of continuously defiling metal strip (2) consists of applying the strip on a principal cooling roller (10); maintaining the strip in contact with the principal cooling roller by means of a thrust roller (14); and evacuating the heat transmitted by the strip. The cooling of continuously defiling metal strip (2) consists of: (a) applying the strip on a principal cooling roller (10) in a manner such that the strip forms an arc of which the inner surface delimits with the external surface of the roller a contact zone adapted for an evacuation of a part of the heat of the strip towards the interior of the roller; (b) maintaining the strip in contact with the principal cooling roller by means of a thrust roller (14) on the outer surface of the strip, made of a material that is elastically deformable and thermo-capacitive; and (c) evacuating the heat transmitted by the strip to the thrust roller via a secondary cooling roller (16). An independent claim is also included for an installation for cooling continuously defiling metal strip by this method.

Description

The present invention relates to a method and a cooling installation of a metal strip in scrolling.

It applies in particular to vacuum treatments such a strip, in particular to hot coatings.

To carry out treatment operations thermal, such as annealing or coatings continuous, of a steel strip, it is usually necessary to successively heat and cool the band, with predetermined speeds. To cool a such strip in a controlled manner, the strip is tempered either by a jet of gas, either by a jet of liquid, or by minus a cooling roll on which the band comes in contact.

Known methods of cooling by roll consist of applying a tape that moves in a continuous movement on at least one roll of cooling inside which circulates a liquid refrigerant, especially cold water. The roll is mobile in rotation about its axis, being driven either by the friction of the moving strip or by a motorized set clean. The band thus applied on the roll forms an arc whose intrados delimits with the outer surface of the roller a contact zone adapted for evacuate towards the inside of the roll part of the heat of the band. JP-A-60 255 933 discloses a method and an installation cooling of a scrolling steel strip during the continuous annealing or galvanizing.

To improve the contact between the tape and the roll in the past, it has been proposed to maintain the arc of tape in contact with the roll by means of metal support rollers on the upper surface of the arc. For guarantee the maintenance of a plating effect of the band on the cooling roll, each of these rollers support is mounted for free rotation around its axis, the end of rigid arms, whose distance from to the cooling roll is predetermined in function of the thickness of the band.

Although such metal backup rolls generate the expected maintenance of the tape on the roll of cooling, they run the risk of a share of mark the upper surface of the band, this marking being very deep in case of lack of parallelism of the axes of the cooling roll and backup rollers, and on the other hand to disturb the cooling of the band in because of the rapid accumulation of heat in the support rollers.

The object of the present invention is to propose a process and a cooling installation of a band metallic scrolling, which allow to maintain firmly tape against a cooling roll, while controlling this cooling and without impair the surface condition of the strip.

• on déplace en continu la bande métallique à refroidir,
• on applique la bande sur un rouleau de refroidissement principal mobile autour de son axe de façon à ce que la bande forme un arc dont l'intrados délimite avec la face extérieure du rouleau de refroidissement principal une zone de contact adaptée pour évacuer vers l'intérieur de ce rouleau une partie de la chaleur de la bande, et
• on maintient la bande en contact avec le rouleau de refroidissement principal au moyen d'au moins un rouleau d'appui sur l'extrados de l'arc formé par la bande, le ou chaque rouleau d'appui étant disposé sensiblement parallèlement au rouleau de refroidissement principal et mobile en rotation autour de son axe,

caractérisé en ce que le ou chaque rouleau d'appui est constitué, au moins en périphérie, d'une matière élastiquement déformable et thermo-capacitive, et en ce qu'on évacue la chaleur transmise de la bande à le ou chaque rouleau d'appui par des moyens de refroidissement secondaire adaptés pour former avec une partie de la face externe du ou de chaque rouleau d'appui une zone de transfert de chaleur vers ces moyens de refroidissement secondaire.For this purpose, the subject of the invention is a method for cooling a moving metal strip, of the type in which:

• the metal strip to be cooled is continuously moved,
• the strip is applied to a main cooling roll movable about its axis so that the band forms an arc whose intrados delimits with the outer face of the main cooling roll a contact zone adapted to evacuate inwards from this roll some of the heat of the band, and
• the strip is held in contact with the main cooling roller by means of at least one support roller on the extrados of the arc formed by the strip, the or each support roller being arranged substantially parallel to the roller of main cooling and mobile in rotation about its axis,

characterized in that the or each backing roll is constituted, at least peripherally, by an elastically deformable material and thermo-capacitive, and in that the heat transmitted from the strip is removed to the or each roll of supported by secondary cooling means adapted to form with a portion of the outer face of the or each support roller a heat transfer zone to these secondary cooling means.

• le ou chaque rouleau d'appui s'étend sur au moins toute la largeur de la bande de façon à appliquer sur l'extrados de l'arc formé par la bande une pression sensiblement homogène sur toute cette largeur ;
• la température de la bande appliquée en entrée du rouleau de refroidissement principal est inférieure à la température de dégradation de la matière constituant le ou les rouleaux d'appui ; et
• la température de la bande appliquée en entrée est inférieure à environ 200°C.

According to other characteristics of this process, taken separately or in any technically possible combination:

• the or each support roller extends over at least the entire width of the strip so as to apply on the extrados of the arc formed by the band a substantially homogeneous pressure over the entire width;
• the temperature of the strip applied at the inlet of the main cooling roll is less than the degradation temperature of the material constituting the at least one supporting roll; and
• the temperature of the input band is less than about 200 ° C.

The subject of the invention is also a plant of cooling a scrolling metal strip, said strip to be cooled being moved continuously, of the type having a main cooling roll on which the band is applied to form an arc whose the intrados demarcates with the outside face of this roll a contact zone adapted to evacuate inwards of the main cooling roll part of the heat of the tape, and at least one backup roll on the extrados of the arc formed by the strip, adapted for keep the tape in contact on the roll of main cooling, the or each support roll being disposed substantially parallel to the roll of main and mobile cooling in rotation around its axis, characterized in that the or each roller of support is constituted, at least at the periphery, of a an elastically deformable and thermo-capacitive material, and in that the installation comprises means for secondary cooling adapted to form with a part of the outer face of the or each support roll a zone of heat transfer to these means of secondary cooling to remove heat transmitted from the tape to the or each backup roll.

• le ou chaque rouleau d'appui est réalisé, au moins en périphérie, en élastomère, notamment en silicone vulcanisé ;
• la matière dont est constitué au moins en périphérie le ou chaque rouleau d'appui, possède un coefficient de conductibilité thermique inférieur à 1 W/m.K ;
• le diamètre du ou de chaque rouleau d'appui est compris entre un quart et un dixième du diamètre du rouleau de refroidissement principal ;
• les moyens de refroidissement secondaire comportent au moins un rouleau de refroidissement secondaire mobile en rotation autour de son axe et disposé sensiblement parallèlement aux rouleaux d'appui ; et
• l'installation comporte des moyens d'alimentation avec un fluide caloporteur, communs au rouleau de refroidissement principal et aux moyens de refroidissement secondaire.

According to other characteristics of this installation, taken separately or in any technically possible combination:

• the or each backing roll is made, at least peripherally, of elastomer, in particular vulcanized silicone;
• the material which is formed at least peripherally the or each support roller, has a coefficient of thermal conductivity of less than 1 W / mK;
• the diameter of the or each backing roll is between a quarter and a tenth of the diameter of the main cooling roll;
• the secondary cooling means comprise at least one secondary cooling roller movable in rotation about its axis and disposed substantially parallel to the support rollers; and
• the installation comprises supply means with a heat transfer fluid, common to the main cooling roller and the secondary cooling means.

• la figure 1 est une vue schématique d'une installation de refroidissement selon l'invention ;
• les figures 2 et 3 sont des vues analogues à la figure 1, illustrant deux variantes de l'installation selon l'invention.

The invention will be better understood on reading the description which follows, given solely by way of example and with reference to the drawings in which:

• Figure 1 is a schematic view of a cooling system according to the invention;
• Figures 2 and 3 are views similar to Figure 1, illustrating two variants of the installation according to the invention.

The installation 1 shown in FIG. for cooling a steel strip 2, scrolling next the direction indicated by the arrows 4. This installation is for example used in coating treatments of the band, especially under vacuum.

• deux cylindres 8A et 8B de déflection de la bande 2, pourvus éventuellement d'un système motorisé d'entraínement non représenté ;
• un rouleau 10 de refroidissement principal, d'axe X-X et agencé vis-à-vis des cylindres déflecteurs 8A et 8B de façon à ce que ces derniers guident la bande 2 de manière adéquate, respectivement en entrée et en sortie du rouleau 10 ;
• un rouleau 14 d'appui de la bande sur le rouleau de refroidissement 10, d'axe Z-Z sensiblement parallèle à l'axe X-X du rouleau 10 et de préférence disposé sensiblement à l'aplomb de la zone d'enroulement de la bande autour du rouleau 10 ; et
• un rouleau 16 de refroidissement secondaire, d'axe X'-X' parallèle à l'axe Z-Z des rouleaux 14, disposé en contact avec ces rouleaux 14 du côté opposé à celui du rouleau 10, un même plan P formant des plans médians pour les rouleaux 10 et 16.

This installation comprises:

• two rollers 8A and 8B deflection of the band 2, optionally provided with a motorized drive system not shown;
• a main cooling roll 10, of axis XX and arranged vis-à-vis the deflector rollers 8A and 8B so that the latter guide the strip 2 adequately, respectively at the inlet and at the outlet of the roll 10;
• a roll 14 for supporting the strip on the cooling roll 10, ZZ axis substantially parallel to the axis XX of the roll 10 and preferably disposed substantially above the winding zone of the strip around the roll 10; and
• a secondary cooling roll 16, of axis X'-X 'parallel to the axis ZZ of the rollers 14, disposed in contact with these rollers 14 on the opposite side to that of the roll 10, the same plane P forming median planes for the rollers 10 and 16.

Specifically, the cooling roll main 10 and the secondary cooling roll 16 are able to evacuate calories from their face outside towards the inside of the rollers when a body hot is applied on them. For this purpose, the rollers 10 and 16 comprise, in known manner, a double envelope to circulate in the inner periphery of these rolls a refrigerant, such as cold water. Other types of contact cooling rollers, known to those skilled in the art, are conceivable.

The support roller 14 meanwhile formed of a piece cylindrical monoblock of axis Z-Z or a stack of coaxial cylinders of small thickness dependent or not. The roller 14 is made of an elastic material deformable, especially elastomer. For the present invention, the expression "elastically deformable material" should be considered as generally referring to a material whose modulus of elasticity (or Young's modulus) is significantly lower than that of the material forming the band 2, for reasons developed later. As example of a suitable elastomer, there may be mentioned a vulcanized silicone.

The material constituting the support roll 14 presents in addition conductivity and capacitance properties preferred thermals, namely that it should not be totally or almost totally resistant to heat conduction, as could be for example a ceramic material but does not need either necessarily ensure a significant conduction like a current metal alloy. It must also be able to store within it the thermal energy withdrawn at the bandaged. The elastomer of which the support roll is made 14 has for example a conductivity coefficient less than about 1 W / m.K (watt per meter and by Kelvin) and a high heat capacity, for example on the order of 1000 J / kg.K (joule per kilogram and per Kelvin).

The diameter of the roller 14 is preferably included between one fourth and one tenth of the diameter of the roll 10. From more, the length of this roller 14 is at least slightly greater than the width of the strip 2.

The operation of the installation 1, which illustrates the according to the invention is as follows:

Tape 2, coming upstream of the installation 1 of an adjoining production facility, a coil or of a heating installation not shown, arrives in entry of plant 1 at a temperature considered as hot, especially between the temperature ambient and a high temperature beyond which the material constituting the support roll 14 may be degraded, that is to say for example between the temperature ambient and about 200 ° C. His training may be at less partially provided by the cylinder 8A.

The strip 2 is, at the output of the cylinder 8A, applied on the main cooling roll 10, around which the band forms the largest possible arc, by example of about 240 °, whose intrados is in contact with the outer face of the cylinder 10. At its application on the roll 10, the arc formed by the strip 2 is preferably in its winding start zone, kept in pressed contact on this roll by the rollers support 14.

The relative position of the roller 14 with respect to the outer surface of the roll 10 is either pre-set, in particular depending on the thickness of the strip 2, controlled by elastically support means deformable so that the upper surface of strip 2 is subject to sufficient contact pressure to smooth out the band along its width and to favor the transfer heat of the cooling roll strip 10 into increasing the contact area between the lower surface of this band and the outer face of this roll.

The low rigidity of the material forming the rollers support limits the risk of marking the upper surface of the band, even in the case where there is a lack of parallelism between the Z-Z and X-X axes. In addition, band 2 presents then a good transverse flatness.

In addition, the material forming the support rollers 14 being thermo-capacitive, part of the heat of the tape is transferred from the tape to the backup roll, thus ensuring a complementary cooling of the bandaged.

Scrolling the strip 2 causes the roll 14 in rotation about its axis, this roller 14 driving the cooling roller itself 16. The contact area that the roller holds 14 with the roller 16 allows the transfer of heat from the peripheral portion of the roller 14 to the inside of the roll 16. Since the material forming the support rollers is highly thermo-capacitive, the heat transferred from the tape to the backup roll 14 is stored on the periphery of roll 14 before being in turn transferred to the cooling rollers 16.

The elasticity of the material forming the support roll 14 even if there is a lack of parallelism between the axes Z-Z and X '-X', the formation of a large area of contact between the roller 14 and the outer face of the roller 16, and therefore a good heat transfer.

At the exit of the roll 10, the band 2 wraps around of the deflector roll 8B and leaves the installation 1.

The method according to the invention thus makes it possible to cool in a controlled way the band 2, without damaging or marking its surfaces. The cooling obtained is at once homogeneous, thereby ensuring the homogeneity of the qualities of the cooled band, and fast, which reduces the duration of cooling and so the length of the area corresponding.

The use of elastomer to form the rollers 14 is inexpensive and the roll of secondary cooling 16 is a technology already existing. Moreover, the fluid circulation network refrigerant sent to the main cooling roll 10 can advantageously be used, for example by means of of taps, to feed the roll of secondary cooling 16. In other words, from of a pre-existing cooling installation, the investment cost to have an installation according to the invention is minimal.

FIG. 2 shows a variant of the installation 1 which differs from that of Figure 1 by, on the one hand, setting up, between the roll of main cooling 10 and the roll of secondary cooling 16, two support rollers 14 instead of one, and, secondly, replacing the cylinder 8B outlet baffle by a second cylinder of main cooling 12, for example analogous to roll 10. The operation of this installation is substantially similar to that of Figure 1.

Rayon des Rouleaux de refroidissement 10, 12 et 16 Rayon des rouleaux d'appui 14 Vitesse de défilement de la bande 2 Débit d'eau de refroidissement envoyée aux rouleaux 10, 12 et 16 Longueur de l'arc formé par la bande 2 autour du rouleau 10 300 mm 62,5 mm 20 m/min 10 l/min 240° Examples of implementations of methods according to the prior art and according to the invention with the installation 1 of FIG. 2 are detailed below. The following two tables summarize the operating parameters of this installation:

Radius of Cooling Rolls 10, 12 and 16 Radius of support rollers 14 Scroll speed of tape 2 Cooling water flow to rolls 10, 12 and 16 Length of the arc formed by the band 2 around the roll 10 300 mm 62.5 mm 20 m / min 10 l / min 240 °

In the table below are summarized test results:

Tests 1 and 2 are performed without any roll while tests 3 and 4 are carried out with the two support rollers 14 of elastomer as shown in Figure 2.

There is a cooling efficiency fifteen times more important on the first roll of main cooling 10 when the latter is associated to the two support rollers 14, but also a significant increase on the second roll of 12. These results reflect the fact that the support rollers 14 make a good flatness transverse to band 2, allowing cooling important and homogeneous over the width of the band. of the temperature measurements by infra-red thermography confirm that temperature cooling is homogeneous.

Moreover, concerning the temperature reached by the support rollers 14, it has been determined that, locally, the surface layer of material of the rollers 14 can reach for a fairly short time, of the order the duration of the contact, the temperature of the band 2 with which rollers are in contact. This is especially the case when the tape speed is low, for example of the order of 20 m / min for the example of setting detailed in Tables 1 and 2 above.

However, when the scroll speed of the band increases, the contact time of the elastomer on the band is not sufficient for the heat exchange to be complete, the temperature of the elastomer remaining then less than that of the band. So, for a speed of scrolling of the order of 150 m / min, which corresponds to a scroll speed for an industrial installation, and for an input temperature of the band of the order of 150 ° C, the elastomer locally reaches a maximum of one temperature of the order of 100 ° C, which corresponds to a current service temperature for most vulcanized elastomers.

Various arrangements and variants of the process and the installation described above are possible. In The number of support rollers and rollers secondary cooling, their dimensions, as well as their layout is limited only by the free space available around the main cooling roll considered. Any combination is possible, provided that each backing roll is cooled by at least one secondary roller. For example, Figure 3 represents a main cooling roll 10 associated with five support rollers 14 and four rollers of secondary cooling 16.

In addition, the support roller or rollers 14 can have a multilayer structure, only the one and / or the outer layers to have the characteristics of flexibility and thermal capacity detailed above to achieve the invention.

Moreover, the cooling roller 16 is replaceable by other means of cooling secondary, such as gas-jet quenching systems as long as these means form with part of the face external support rollers a sufficient area heat evacuation.

Claims (10)

1. Procedure for cooling a running metallic strip, of the type in which:

   the metallic strip (2) to be cooled runs continuously,

   the band (2) is applied to a principal cooling roller (10) that is mobile about its axis (X-X) so that the strip forms an arc the intrados of which combines with the outer face of the principal cooling strip to produce a zone of contact suitable for removing part of the heat from the strip to the interior of the roller,

   the strip (2) is also kept in contact with the principal cooling roller (10) by means of at least one support roller (14) on the extrados of the arc formed by the strip. The position of this support roller (or of each support roller) is clearly parallel to the principal cooling roller (10) and the roller(s) is/are mobile about its/their axis Z-Z,

   characterised in that the support roller or each support roller (14) consists, at least in its peripheral sections, of a thermo-capacitive material capable of elastic distortion, and in that the heat transmitted from the strip (2) is removed into the or each support roller (14) by secondary cooling means (16) adapted to produce a zone for transferring heat towards these secondary cooling means (16) by combining with the outer face of the or each support roller (14).
2. Procedure according to Claim 1, characterised in that the or each support roller (14) extends at least right across the width of the strip (2) so that sufficiently homogeneous pressure is applied right across that width to the extrados of the arc formed by the strip.
3. Procedure according to Claim 1 or 2, characterised in that the temperature of the strip (2) applied on entry to the principal cooling roller (10) is less than the temperature at which the material making up the support roller(s) (14) begins to suffer damage.
4. Procedure according to Claim 3, characterised in that the said temperature of the strip applied on entry is less than about 200°C.
5. Cooling installation for a running metallic strip, with the strip (2) to be cooled running continuously through a device containing a principal cooling roller (10) to which the strip (2) is applied so as to form an arc the intrados of which combines with the outer face of the roller (10) to produce a zone of contact suitable for removing part of the heat from the strip to the interior of the roller, and at least one support roller (14) on the extrados of the arc formed by the strip, adapted to keep the strip in contact with the principal cooling roller (10), the position of the or each support roller being clearly parallel to the principal cooling roller and mobile about its axis Z-Z, characterised in that the support roller (14) consists, at least in its peripheral sections, of a thermo-capacitive material capable of elastic distortion, and in that the installation (1) contains secondary cooling means (16) adapted to produce, together with the outer face of the or each support roller (14) a zone for transferring heat into these secondary cooling means, with the aim of removing the heat transmitted from the strip (2) to the support roller or each support roller.
6. Installation according to Claim 5, characterised in that the or each support roller (14) consists, at least in its peripheral sections, of an elastomer, most notably vulcanised silicon.
7. Installation according to Claim 5 or 6, characterised in that the material of which at least the peripheral sections of the or each support roller (14) consist, has a heat conductivity coefficient of less than 1 W/m.K.
8. Installation according to any of Claims 5-7, characterised in that the diameter of the or each support roller (14) is between one quarter and one tenth of the diameter of the principal cooling roller (10).
9. Installation according to any of Claims 5-8, characterised in that the secondary cooling means contain at least one secondary cooling roller (16) mobile about its axis X'-X' and clearly positioned parallel to the support roller(s) (14).
10. Installation according to any of Claims 5-9, characterised in that it contains means of providing a supply of heat-bearing fluid, these means being common to the principal cooling roller (10) and the secondary cooling means (16).

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