EP1687455A1 - Cooling process and device for a steel sheet - Google Patents

Cooling process and device for a steel sheet

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Publication number
EP1687455A1
EP1687455A1 EP04797129A EP04797129A EP1687455A1 EP 1687455 A1 EP1687455 A1 EP 1687455A1 EP 04797129 A EP04797129 A EP 04797129A EP 04797129 A EP04797129 A EP 04797129A EP 1687455 A1 EP1687455 A1 EP 1687455A1
Authority
EP
European Patent Office
Prior art keywords
tubes
strip
cooling
temperature
thickness
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP04797129A
Other languages
German (de)
French (fr)
Other versions
EP1687455B1 (en
Inventor
Stéphane Lecomte
André Fouarge
Denis Bouquegneau
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ArcelorMittal France SA
Original Assignee
USINOR SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by USINOR SA filed Critical USINOR SA
Priority to EP04797129A priority Critical patent/EP1687455B1/en
Priority to PL04797129T priority patent/PL1687455T3/en
Publication of EP1687455A1 publication Critical patent/EP1687455A1/en
Application granted granted Critical
Publication of EP1687455B1 publication Critical patent/EP1687455B1/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/54—Furnaces for treating strips or wire
    • C21D9/56—Continuous furnaces for strip or wire
    • C21D9/573—Continuous furnaces for strip or wire with cooling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/54—Furnaces for treating strips or wire
    • C21D9/56—Continuous furnaces for strip or wire
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/54—Furnaces for treating strips or wire
    • C21D9/56—Continuous furnaces for strip or wire
    • C21D9/573—Continuous furnaces for strip or wire with cooling
    • C21D9/5735—Details
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/62—Quenching devices
    • C21D1/63—Quenching devices for bath quenching
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/62—Quenching devices
    • C21D1/667—Quenching devices for spray quenching

Definitions

  • the present invention relates to a device for implementing the cooling of a steel strip, as part of a continuous annealing process.
  • this cooling is achieved by means of immersed water jets.
  • This cooling operation can be carried out consecutively to a first cooling operation in a boiling water bath.
  • Continuous annealing is a thermochemical treatment that is applied to steel strips after cold rolling.
  • the "strip" of steel is the steel product which, when cut, will produce sheets used in particular for the manufacture of automobile bodies, carcasses of household appliances, etc.
  • the continuous annealing process consists in scrolling the steel strip through an oven where it is exposed to controlled heating and cooling. In the continuous annealing furnace, the steel strip travels vertically along a series of successive strands, up and down, and thus scrolls sequentially through the various processing steps.
  • the treatment of the strip in the oven generally comprises the following successive thermal stages:
  • the strip reaches a temperature of 700 to 850 ° C in 2 to 3 minutes;
  • the cooling phase plays a particularly crucial role since it allows, in certain cases, to reduce the concentration of expensive alloying elements necessary for the realization of particular microscopic structures, such as for example of the type " dual phase ", multiphase," HLE “(High Limit Elastic), etc.
  • the cooling process therefore corresponds to a significant metallurgical and economic challenge.
  • the Applicant has developed a cooling method which consists in immersing the steel strip in a water bath close to its boiling point. Although this process is characterized by exceptional cooling homogeneity and a constant heat transfer coefficient regardless of the conditions of the line, it also has certain limitations. On the one hand, the cooling speeds that can be achieved are relatively low, namely about 50 ° C / s for a 1mm thick steel strip.
  • JP-A-60 009834 uses a set of cooling ramps, disposed on either side of the steel strip, and immersed in a tank of water whose temperature is between 60 and 75% of the boiling temperature. For a given configuration of the spray booms, a laminar flow is generated, which prevents the formation of a vapor film in the vicinity of the steel strip.
  • Another solution is still to circulate water between two flat plates parallel and against the current relative to the running direction of the strip (EP-A-210847, JP-A-63 145722, JP- A-62 238334).
  • Another document proposes to use the impact pressure of the jets in order to eliminate the deformations of the band during quenching (see JP-A-11 193418).
  • the present invention aims at carrying out a so-called quenching operation, typically at a speed greater than 1000 ° C./s, applicable to products flat metallurgical materials, preferably of steel, in the form of cold-rolled strips.
  • This quenching operation must be implemented by means of jets of cold water, whose temperature is preferably between 0 ° C and 50 ° C, said jets being immersed.
  • the invention aims to ensure cooling conditions at high power as homogeneous as possible over the entire width of the steel strip, by controlling the flow within the device.
  • the temperature of the strip at the inlet of the device must be between 750 ° C and 350 ° C and the temperature at the outlet should preferably be between 0 ° C and 150 ° C.
  • a first object of the present invention relates to a basic cooling device, for carrying out a quenching operation during the continuous annealing treatment of a flat product in the form of a metallurgical strip.
  • a basic cooling device for carrying out a quenching operation during the continuous annealing treatment of a flat product in the form of a metallurgical strip.
  • said device being located in a vertical strand ascending or descending, comprising a weir in which is completely immersed a plurality of tubes stacked substantially vertically and symmetrically on either side of the strip along the latter and ejecting each, in the form of turbulent jets substantially horizontally, a cooling fluid to the band through a slot or a plurality of holes.
  • the device is further provided in its lower part with sealing means.
  • any two successive tubes, arranged on the same side of the strip are separated by an identical interval for all the tubes in question. view of the evacuation of the cooling fluid. Said interval is then chosen, at a given value of the specific flow rate of the cooling fluid, expressed in cubic meters per hour and per square meter of one face of the strip, to minimize the pressure drop in the evacuation channels corresponding to said interval (the pressure drop for each interval and the total pressure drop are identical).
  • the wall of the weir located at the rear of the tubes, has a width at least equal to that of the tubes and the horizontal distance of the wall relative to the face rear of the tubes is chosen such that the pressure loss caused by the presence of the weir is less than 5% of the pressure loss caused by the intervals between two successive tubes, which is considered negligible.
  • the flow is then two-dimensional.
  • the invention advantageously avoids local boiling phenomena by choosing a specific flow rate of the cooling fluid on one side of the strip between 250 and 1000 m 3 per hour and per m 2 . In an exemplary device tested by the Applicant, the maximum specific flow per face was about 580 m 3 per hour per m 2 .
  • the loss of load caused by the intervals is less than 150 mm of water column.
  • the distance between the end of each tube and the band is identical for all the tubes and is between 50 mm and 200 mm.
  • the ejection speed (V JE ⁇ ) satisfies the following criterion, respectively: for holes, A y JET ⁇ ⁇ u- T for slots, ( ⁇ X, F TM ⁇ 0.25
  • A represents the distance between the tube and the band and d represents the diameter of a hole or the thickness of the slot.
  • a and d are expressed in the same units of length, in meters for example. Their quotient is dimensionless.
  • V JE ⁇ is expressed in m / s.
  • the device is located in substantially vertical strand amount (angular deviation from the vertical less than 30 °) while being directly preceded by a tank of water essentially brought to the boiling temperature.
  • the invention will advantageously be implemented on an installation where the metallurgical product to be treated has a running speed of between 0.25 m / s and 20 m / s, and a thickness of between 0.1 mm and 10 mm. mm.
  • An important feature of the invention lies in the fact that the cooling tubes are dimensioned such that the ejection speed of the cooling fluid is homogeneous over the entire bandwidth.
  • the tubes are dimensioned so that the speed distribution is such that there is a relative difference between the maximum speed (V max ) and the minimum speed (V m ⁇ n ) ejection along the width tube less than 5% or
  • the ratio between the passage section of a tube and the free section of this tube is greater than 1.
  • said tubes have a rectangular section.
  • the ratio of one side to an adjacent side of the rectangular section is 0.1 to 10 and the thickness of the tubes is 0.25 to 10 times the hole diameter or the thickness of the tube.
  • the slot in order to control the coherence of the jet, the ratio between the thickness of the tubes and the diameter of the holes being, if appropriate, still preferably equal to 2/3.
  • the aforementioned sealing means comprise a double pair of roll locks, allowing both the passage of the band and the creation of a pressure loss limiting to a value minimal spillway leaks down.
  • these sealing means also comprise injection means a fluid between the rollers, whose pressure and / or temperature can be controlled.
  • the upper tube is equipped with a dam whose height is at least equal to the sum of the thickness of the water slide at the spillway and the height of the water column corresponding to the loss of load between the tubes at maximum flow rate.
  • a second object of the present invention relates to a quenching process during the continuous annealing treatment of a flat product in the form of a metallurgical strip, preferably a steel strip, implementing the device described. under one of the embodiments above, to achieve a specific cooling power of between 1000 W / m 2 and 10000 kW / m 2 per metallurgical product face.
  • the temperature of the strip at the inlet of the device is between 350 ° C. and 750 ° C. and the temperature at the outlet is between 50 ° C. and 450 ° C., preferably between 50 ° C and 100 ° C or between 350 and 450 ° C.
  • FIG. 1 schematically represents a sectional view of the cooling device according to the present invention.
  • Figure 2 schematically shows an arrangement of the holes for the projection of water on the steel strip in the device of the present invention.
  • FIG. 3 graphically illustrates the thermal performance of the cooling device according to the invention.
  • Figure 4 illustrates the performance of said device in terms of flatness of the steel strip.
  • Figures 5 and 6 illustrate the impact of the uniformity of cooling on the homogeneity of the mechanical properties of the steel strip.
  • Figure 5 relates to a steel of the "dual phase" family, while Figure 6 relates to a steel of the family of multiphase steels.
  • FIG. 7 schematically gives the different positions of the specimens taken as a function of the width of the sheet, for carrying out the tests relating to FIGS. 5 and 6.
  • FIG. 8 indicates the parameters making it possible to calculate the index of flatness, these parameters characterizing the sinusoid to which is assimilated the longitudinal profile of the strip at the edge.
  • the cooling device consists of a set of tubes 1, called “ramps” or “cooling ramps”, arranged symmetrically. on both sides of the steel strip to be cooled. These ramps are submerged and fed laterally with cooling fluid. Their section is preferably rectangular. In the following description of the invention, the terms “tubes” and “ramps” will be used indistinctly.
  • the immersion of the ramps is achieved by means of a sealing system, located in the lower part of the device, which allows both the passage of the steel strip 2 and the creation of a loss of maximum load so as to minimize the flow of coolant leakage to the bottom of the box.
  • this sealing system consists of a double pair of rollers 3, applied against the steel strip and positioned symmetrically with respect to this. this.
  • a fluid is injected whose pressure and / or temperature can be controlled.
  • the cooling fluid is preferably water.
  • the cooling ramps are located at a distance A from the pass line of the strip 2.
  • the maximum distance between the belt and the cooling ramps is 200mm.
  • a space B is left between two successive ramps so that the water injected by the ramps can be evacuated therebetween. This ensures a flow as homogeneous as possible along the width of the steel strip.
  • the choice of the distance B results from a compromise between a maximum specific cooling power P, the specific power being defined as the cooling power per unit area and per band face to be cooled, and a minimum pressure drop across the evacuation channels, to ensure a sufficiently rapid renewal of the cooling fluid in the vicinity of the sheet, and thus prevent the formation of local boiling zones in the vicinity of the strip.
  • the distance B is chosen to be identical between two successive ramps for all the ramps, in order to ensure identical flow conditions in front of all the spray bars. This therefore makes it possible to obtain a vertical homogeneity of the flow. In this way, the cooling fluid injected by a given ramp is discharged by means of the channels directly adjacent to this ramp.
  • Each cooling ramp 1 is provided, on the face exposed to the strip, with at least one slot or a set of holes, as shown in FIG. 2, intended for the projection of the cooling fluid towards the bandaged.
  • the distance between two successive holes should be such that the flow in the near vicinity of the strip can be likened to that of a slot.
  • the ejection velocity of the fluid must be sufficient to avoid forming boiling zones in the vicinity of the strip.
  • This ejection speed V is chosen as a function of the distance A with respect to the band and is typically between 0 and 10 m / s.
  • the device or cooling box Downstream of the evacuation channels, the device or cooling box comprises a spillway 4, over the entire width of the box and whose height corresponds to the level of the jet of the last ramp, which ensures that in all conditions of operation, the last ramp is immersed in the same way as the others.
  • the upper cooling ramp is surmounted by a dam 5 whose height is at least equal to the sum of the thickness H of the water table. water at the spillway and the water column height ⁇ H corresponding to the pressure drop ⁇ P through the discharge channels, for the maximum flow rate Qmax;
  • FIG. 3 shows that the specific cooling power, expressed in k per square meter and per strip face, is a linear function of the specific flow rate, itself expressed in cubic meters per hour and per square meter for the two cumulative faces.
  • Figure 4 illustrates the performance of the device with respect to the flatness of the steel strip. They are the image of the homogeneity of the cooling and consequently of the control of the flows in the device. The characterization of flatness concerns here long banks.
  • Each point in the figure represents an operating point of the device - defined by the associated specific cooling power - at a given time during the industrial test campaign.
  • a flatness index expressed in "I" units, is associated.
  • a unit "I” corresponds to a relative elongation of 1mm per 100m of steel strip.
  • FIG. 4 shows two reference thresholds, 120 and 240 "I" units, which correspond to the acceptable flatness tolerances for two electrogalvanizing lines. The figure shows that the majority of operating points are below the threshold of the most demanding line.
  • Figures 5 and 6 illustrate the impact of uniformity of cooling on the homogeneity of mechanical properties.
  • Figure 5 relates to a steel of the "dual phase” family.
  • Figure 6 refers to a multi-phase steel (ferrite, martensite, bainite, perlite).
  • the mechanical properties are characterized by a tensile test.
  • the specimens are taken at different positions according to the width of the sheet, according to the diagram shown in Figure 7: 1) Extreme bank, 2) Bank, 3) Quarter, 4) Center, 5) Center, 6) Quarter, 7) Shore, 8) Extreme shore.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Strip Materials And Filament Materials (AREA)
  • Heat Treatments In General, Especially Conveying And Cooling (AREA)
  • Coating With Molten Metal (AREA)

Abstract

A cooling device for tempering during continuous annealing of a flat product or metal band, preferably a steel band where the device consists of a number of symmetrically arranged horizontal tubes (1) along the band (2) along which a coolant fluid is projected across a slot or a number of holes (cavities, sic). An independent claim is included for a method of tempering during continuous annealing of a flat product or metal band.

Description

PROCEDE ET DISPOSITIF DE REFROIDISSEMENT D'UNE BANDE D'ACIER METHOD AND DEVICE FOR COOLING A STEEL BAND
Objet de 1 ' invention [0001] La présente invention se rapporte à un dispositif destiné à la mise en œuvre du refroidissement d'une bande d'acier, dans le cadre d'un processus de recuit en continu. En particulier, ce refroidissement est réalisé au moyen de jets d'eau immergés. Cette opération de refroidissement peut être réalisée consécutivement à une première opération de refroidissement dans un bain d'eau bouillante .OBJECT OF THE INVENTION [0001] The present invention relates to a device for implementing the cooling of a steel strip, as part of a continuous annealing process. In particular, this cooling is achieved by means of immersed water jets. This cooling operation can be carried out consecutively to a first cooling operation in a boiling water bath.
Etat de la technique [0002] Le recuit continu est un traitement thermochimique que l'on applique aux bandes d'acier après le laminage à froid. La "bande" d'acier est le produit sidérurgique qui, découpé, donnera des tôles utilisées notamment pour la fabrication des carrosseries automobiles, des carcasses d'appareils électroménagers, etc. [0003] Le procédé de recuit continu consiste à faire défiler la bande d'acier dans un four où elle est exposée à un chauffage et à un refroidissement contrôlés. Dans le four de recuit continu, la bande d'acier circule verticalement, selon une série de brins successifs, montants et descendants, et défile ainsi séquentiellement au travers des diverses étapes du traitement . [0004] Le traitement de la bande dans le four comprend généralement les étapes thermiques successives suivantes :State of the art [0002] Continuous annealing is a thermochemical treatment that is applied to steel strips after cold rolling. The "strip" of steel is the steel product which, when cut, will produce sheets used in particular for the manufacture of automobile bodies, carcasses of household appliances, etc. [0003] The continuous annealing process consists in scrolling the steel strip through an oven where it is exposed to controlled heating and cooling. In the continuous annealing furnace, the steel strip travels vertically along a series of successive strands, up and down, and thus scrolls sequentially through the various processing steps. [0004] The treatment of the strip in the oven generally comprises the following successive thermal stages:
- préchauffage et chauffage : la bande atteint une température de 700 à 850°C en 2 à 3 minutes ;preheating and heating: the strip reaches a temperature of 700 to 850 ° C in 2 to 3 minutes;
- maintien à la température maximale durant 1 minute environ ; refroidissement lent, par exemple à l'eau bouillante ; refroidissement rapide (appelé "trempe") ,' par exemple par eau sous forme liquide projetée sur la bande à une température pouvant aller au maximum jusqu'à sa température d' ébullition. survieillissement ; refroidissement final . [0005] Ces différentes étapes sont nécessaires à la mise en œuvre du traitement métallurgique visé, à savoir la recristallisation, la précipitation des carbures, l'obtention des structures finales ou encore l'obtention d'un acier non vieillissant, etc. [0006] En particulier, ces dernières années, on a vu l'émergence d'une demande accrue, émanant notamment de l'industrie automobile, pour des tôles d'acier présentant simultanément des propriétés de résistance et de for abilité améliorées. [0007] Dans ce cadre, la phase de refroidissement joue un rôle particulièrement crucial puisqu'elle permet, dans certains cas, de réduire la concentration en éléments d'alliage coûteux nécessaires à la réalisation de structures microscopiques particulières, comme par exemple de type "dual phase", multiphase, "HLE" (Haute Limite Elastique), etc. Le procédé de refroidissement correspond donc à un enjeu métallurgique et économique non négligeable. [0008] Les principales technologies de refroidissement appliquées industriellement sont :- keeping at the maximum temperature for about 1 minute; slow cooling, for example boiling water; rapid cooling (called "tempering"), 'for example by water projected in liquid form onto the strip at a temperature of up to at most the boiling temperature. overaging; final cooling. These different steps are necessary for the implementation of the targeted metallurgical treatment, namely recrystallization, the precipitation of carbides, obtaining the final structures or obtaining a non-aging steel, and so on. In particular, in recent years, we have seen the emergence of increased demand, emanating in particular from the automotive industry, for steel sheets simultaneously having improved strength and strength properties. In this context, the cooling phase plays a particularly crucial role since it allows, in certain cases, to reduce the concentration of expensive alloying elements necessary for the realization of particular microscopic structures, such as for example of the type " dual phase ", multiphase," HLE "(High Limit Elastic), etc. The cooling process therefore corresponds to a significant metallurgical and economic challenge. [0008] The main cooling technologies applied industrially are:
- le refroidissement par jets de gaz ;- cooling by gas jets;
- l'immersion dans un bain d'eau, éventuellement "agitée" ; le refroidissement par passage sur des rouleaux refroidis ; le refroidissement par jets d'eau ; le refroidissement par un brouillard d'eau créé par pulvérisation au moyen d'un gaz supersonique, cette technologie étant appelée "misting jet". [0009] Par le passé, la Demanderesse a développé un procédé de refroidissement qui consiste à immerger la bande d'acier dans un bain d'eau proche de sa température d' ébullition. Bien que ce procédé soit caractérisé par une homogénéité de refroidissement exceptionnelle et par un coefficient de transfert thermique constant quelles que soient les conditions de la ligne, il possède également certaines limitations. [0010] D'une part, les vitesses de refroidissement qu'il est possible d'atteindre sont relativement faibles, à savoir environ 50°C/s pour une bande d'acier de 1mm d'épaisseur. Cette limitation provient du fait que lorsqu'une bande d'acier est immergée à haute température dans un bain d'eau bouillante, il se forme au voisinage de sa surface un film de vapeur stable, dans un régime dit de "caléfaction" , qui limite considérablement les échanges thermiques. On entend par caléfaction la présence d'un film de vapeur, engendré par ébullition importante, entre une paroi chaude et un fluide qui est soit un liquide, soit un mélange diphasique de liquide et de vapeur, cette présence ayant pour conséquence un mauvais transfert de chaleur entre la paroi et le fluide. [0011] D'autre part, la température de la bande d'acier à la sortie du bain d'eau bouillante doit rester supérieure à 300°C environ. Lorsque la température de la bande devient inférieure à cette température, le film de vapeur devient instable et on passe en régime d' ébullition dite nucléée. Dans ce dernier régime, des régions voisines de la bande sont soumises à des flux de chaleur différents, ce qui crée des différences de température importantes. Ces gradients de température induisent dans 1 ' acier des contraintes mécaniques, qui risquent de créer des déformations plastiques, donc permanentes et de mener à des défauts de planéité. [0012] Des solutions ont été proposées afin de pallier ces défauts. On peut par exemple immerger la bande d'acier dans un bain d'eau froide statique. Mais cette solution conduit également à l'apparition de défauts de planéité.- immersion in a water bath, possibly "agitated"; cooling by passage over cooled rollers; cooling by jets of water; cooling by a mist of water created by spraying with supersonic gas, this technology being called "misting jet". [0009] In the past, the Applicant has developed a cooling method which consists in immersing the steel strip in a water bath close to its boiling point. Although this process is characterized by exceptional cooling homogeneity and a constant heat transfer coefficient regardless of the conditions of the line, it also has certain limitations. On the one hand, the cooling speeds that can be achieved are relatively low, namely about 50 ° C / s for a 1mm thick steel strip. This limitation stems from the fact that when a steel strip is immersed at high temperature in a boiling water bath, a stable vapor film is formed in the vicinity of its surface, in a so-called "caulking" regime, which considerably limits heat exchange. The term "calefaction" is understood to mean the presence of a vapor film, generated by high boiling, between a hot wall and a fluid which is either a liquid or a two-phase mixture of liquid and vapor, this presence resulting in a poor transfer of heat between the wall and the fluid. On the other hand, the temperature of the steel strip at the outlet of the boiling water bath must remain above about 300 ° C. When the temperature of the strip becomes lower than this temperature, the vapor film becomes unstable and one goes into the so-called nucleate boiling regime. In the latter regime, regions adjacent to the band are subjected to different heat fluxes, which creates significant temperature differences. These temperature gradients induce in the steel mechanical stresses, which may create plastic deformations, therefore permanent and lead to flatness defects. Solutions have been proposed to overcome these defects. For example, the steel strip can be immersed in a static cold water bath. But this solution also leads to the appearance of flatness defects.
[0013] D'autres solutions ont été avancées, qui consistent à refroidir la bande d'acier au moyen de jets immergés, afin d'empêcher la formation locale de zones d' ébullition dans le voisinage de celle-ci. Ces systèmes de refroidissement peuvent être ou non précédés par un refroidissement plus lent, de type "gas jet cooling" ou immersion dans un bain d'eau statique. [0014] Ainsi, dans la demande de brevet JP-A-58 039210, la bande est d'abord refroidie dans un bain d'eau dont la température est supérieure à 60°C, jusqu'à une température comprise entre 200 à 500°C, gamme de températures dans laquelle se produit la transition entre 1' ébullition en film et l' ébullition nucléée. On préconise alors de refroidir la bande juste avant ou juste après la transition au moyen de jets d'eau immergés jusqu'à ce que la bande atteigne la température du bain. [0015] Une solution similaire (JP-A-60 009834) utilise un ensemble de rampes de refroidissement, disposées de part et d'autre de la bande d'acier, et immergées dans une cuve d'eau dont la température est comprise entre 60 et 75% de la température d' ébullition. Pour une configuration donnée des rampes d'aspersion, un écoulement laminaire est généré, ce qui permet d'éviter la formation d'un film de vapeur au voisinage de la bande d'acier. [0016] Une autre solution consiste encore à faire circuler de 1 ' eau entre deux plaques planes parallèlement et à contre-courant par rapport au sens de défilement de la bande (EP-A-210847, JP-A-63 145722, JP-A-62 238334) . [0017] Un autre document propose d'utiliser la pression d'impact des jets afin de supprimer les déformations de la bande lors de la trempe (voir JP-A-11 193418). Le déposant préconise d'appliquer de part et d'autre de la bande d'acier une pression d'au moins 500M/cm2. [0018] Enfin, il est également possible de contrôler le refroidissement au moyen d'additifs dans le bain de trempe, de manière à éviter l' ébullition et ainsi limiter le niveau des contraintes internes dans l'acier lors de la trempe (JP-A-57 085923) . [0019] Bien que de nombreuses solutions aient été avancées, l'obtention simultanée de performances thermiques élevées et d'une bonne planéité en sortie de refroidissement rapide par voie liquide reste à ce jour un défi majeur.Other solutions have been advanced, which consist in cooling the steel strip by means of submerged jets, in order to prevent the local formation of boiling zones in the vicinity of the latter. These cooling systems may or may not be preceded by slower cooling, such as "gas jet cooling" or immersion in a static water bath. Thus, in the patent application JP-A-58 039210, the strip is first cooled in a water bath whose temperature is greater than 60 ° C, up to a temperature between 200 to 500 ° C, range of temperatures in which the transition between film boiling and nucleate boiling occurs. It is then recommended to cool the strip just before or just after the transition by means of immersed water jets until the strip reaches the temperature of the bath. A similar solution (JP-A-60 009834) uses a set of cooling ramps, disposed on either side of the steel strip, and immersed in a tank of water whose temperature is between 60 and 75% of the boiling temperature. For a given configuration of the spray booms, a laminar flow is generated, which prevents the formation of a vapor film in the vicinity of the steel strip. Another solution is still to circulate water between two flat plates parallel and against the current relative to the running direction of the strip (EP-A-210847, JP-A-63 145722, JP- A-62 238334). Another document proposes to use the impact pressure of the jets in order to eliminate the deformations of the band during quenching (see JP-A-11 193418). The applicant recommends applying on both sides of the steel strip a pressure of at least 500M / cm 2 . Finally, it is also possible to control the cooling by means of additives in the quenching bath, so as to avoid boiling and thus limit the level of internal stresses in the steel during quenching (JP- A-57 085923). Although many solutions have been advanced, obtaining simultaneous high thermal performance and good flatness output fast cooling liquid is still a major challenge.
Buts de 1 ' inventionAims of the invention
[0020] La présente invention vise à réaliser une opération dite de trempe, typiquement à une vitesse supérieure à 1000°C/s, applicable à des produits métallurgiques plats, de préférence en acier, sous forme de bandes laminées à froid. [0021] Cette opération de trempe doit être mise en œuvre au moyen de jets d'eau froide, dont la température est de préférence comprise entre 0°C et 50°C, lesdits jets étant immergés . [0022] L'invention vise à assurer des conditions de refroidissement à des puissances élevées aussi homogènes que possible sur toute la largeur de la bande d'acier, par la maîtrise des écoulements au sein du dispositif. [0023] Ainsi, la température de la bande à l'entrée du dispositif doit être comprise entre 750°C et 350°C et la température à la sortie doit être comprise de préférence entre 0°C et 150°C.The present invention aims at carrying out a so-called quenching operation, typically at a speed greater than 1000 ° C./s, applicable to products flat metallurgical materials, preferably of steel, in the form of cold-rolled strips. This quenching operation must be implemented by means of jets of cold water, whose temperature is preferably between 0 ° C and 50 ° C, said jets being immersed. The invention aims to ensure cooling conditions at high power as homogeneous as possible over the entire width of the steel strip, by controlling the flow within the device. Thus, the temperature of the strip at the inlet of the device must be between 750 ° C and 350 ° C and the temperature at the outlet should preferably be between 0 ° C and 150 ° C.
Principaux éléments caractéristiques de l'invention [0024] Un premier objet de la présente invention concerne un dispositif de refroidissement de base, pour réaliser une opération de trempe lors du traitement de recuit en continu d'un produit plat sous forme d'une bande métallurgique, de préférence une bande d'acier, ledit dispositif étant localisé en brin essentiellement vertical montant ou descendant, comprenant un déversoir dans lequel est complètement immergée une pluralité de tubes empilés essentiellement verticalement et symétriquement de part et d'autre de la bande le long de celle-ci et qui éjectent chacun, sous forme de jets turbulents essentiellement horizontalement, un fluide de refroidissement vers la bande au travers d'une fente ou d'une pluralité de trous. Le dispositif est pourvu en outre dans sa partie inférieure de moyens d' étanchéité.Main characteristic elements of the invention [0024] A first object of the present invention relates to a basic cooling device, for carrying out a quenching operation during the continuous annealing treatment of a flat product in the form of a metallurgical strip. , preferably a steel strip, said device being located in a vertical strand ascending or descending, comprising a weir in which is completely immersed a plurality of tubes stacked substantially vertically and symmetrically on either side of the strip along the latter and ejecting each, in the form of turbulent jets substantially horizontally, a cooling fluid to the band through a slot or a plurality of holes. The device is further provided in its lower part with sealing means.
[0025] Selon l'invention, deux tubes successifs quelconques, disposés d'un même côté de la bande, sont séparés par un intervalle identique pour tous les tubes en vue de l'évacuation du fluide de refroidissement. Ledit intervalle est alors choisi, à une valeur donnée de débit spécifique du fluide de refroidissement, exprimé en mètres cubes par heure et par mètre carré d'une face de la bande, pour minimiser la perte de charge dans les canaux d'évacuation correspondants audit intervalle (la perte de charge pour chaque intervalle et la perte de charge totale sont identiques) . [0026] Selon un mode d'exécution préféré de l'invention, la paroi du déversoir, située à l'arrière des tubes, possède une largeur au moins égale à celle des tubes et la distance horizontale de cette paroi par rapport à la face arrière des tubes est choisie telle que la perte de charge occasionnée par la présence du déversoir soit inférieure à 5% de la perte de charge occasionnée par les intervalles entre deux tubes successifs, ce qui est considéré comme négligeable. L'écoulement est alors bidimensionnel . [0027] L'invention permet avantageusement d'éviter les phénomènes d' ébullition locale en choisissant un débit spécifique du fluide de refroidissement sur une face de la bande compris entre 250 et 1000 m3 par heure et par m2. Dans un exemple de dispositif testé par la Demanderesse, le débit spécifique maximum par face était d'environ 580 m3 par heure et par m2. [0028] De préférence, la perte de charge occasionnée par les intervalles est inférieure à 150 mm de colonne d' eau . [0029] Toujours avantageusement, la distance entre l'extrémité de chaque tube et la bande est identique pour tous les tubes et est comprise entre 50 mm et 200 mm. [0030] Toujours selon l'invention, la vitesse d'éjection ( VJEτ) satisfait le critère suivant, respectivement : pour des trous, A y JET ≥ <u- T pour des fentes, ( Λ X, F™ ≥ 0,25According to the invention, any two successive tubes, arranged on the same side of the strip, are separated by an identical interval for all the tubes in question. view of the evacuation of the cooling fluid. Said interval is then chosen, at a given value of the specific flow rate of the cooling fluid, expressed in cubic meters per hour and per square meter of one face of the strip, to minimize the pressure drop in the evacuation channels corresponding to said interval (the pressure drop for each interval and the total pressure drop are identical). According to a preferred embodiment of the invention, the wall of the weir, located at the rear of the tubes, has a width at least equal to that of the tubes and the horizontal distance of the wall relative to the face rear of the tubes is chosen such that the pressure loss caused by the presence of the weir is less than 5% of the pressure loss caused by the intervals between two successive tubes, which is considered negligible. The flow is then two-dimensional. The invention advantageously avoids local boiling phenomena by choosing a specific flow rate of the cooling fluid on one side of the strip between 250 and 1000 m 3 per hour and per m 2 . In an exemplary device tested by the Applicant, the maximum specific flow per face was about 580 m 3 per hour per m 2 . Preferably, the loss of load caused by the intervals is less than 150 mm of water column. Always advantageously, the distance between the end of each tube and the band is identical for all the tubes and is between 50 mm and 200 mm. Still according to the invention, the ejection speed (V JE τ) satisfies the following criterion, respectively: for holes, A y JET ≥ <u- T for slots, (Λ X, F ™ ≥ 0.25
où A représente la distance entre le tube et la bande et d représente le diamètre d'un trou ou l'épaisseur de la fente. A et d sont exprimés dans les mêmes unités de longueur, en mètres par exemple. Leur quotient est adimensionnel . VJEτ est exprimé en m/s. [0031] Ces deux critères, issus de la théorie des jets turbulents, donnent l'atténuation de la vitesse maximale d'un jet turbulent avec un environnement à vitesse nulle. Les critères sont calculés sur base d'une vitesse minimale de 2,5 m/s. La vitesse maximale du jet à A = 50 mm (position de la bande par rapport à l'orifice du jet) est de 0,65 m/s. La vitesse de 0,65 m/s est donc considérée comme la vitesse minimale du jet lorsque celui-ci atteint la bande, pour casser la couche de caléfaction. [0032] De préférence, le fluide de refroidissement est de l'eau liquide maintenue à une température inférieure à 50°C.where A represents the distance between the tube and the band and d represents the diameter of a hole or the thickness of the slot. A and d are expressed in the same units of length, in meters for example. Their quotient is dimensionless. V JE τ is expressed in m / s. These two criteria, derived from the theory of turbulent jets, give the attenuation of the maximum speed of a turbulent jet with a zero speed environment. The criteria are calculated based on a minimum speed of 2.5 m / s. The maximum speed of the jet at A = 50 mm (position of the strip with respect to the orifice of the jet) is 0.65 m / s. The speed of 0.65 m / s is therefore considered as the minimum speed of the jet when it reaches the band, to break the layer of calefaction. [0032] Preferably, the cooling fluid is liquid water maintained at a temperature below 50 ° C.
[0033] De préférence, le dispositif est localisé en brin essentiellement vertical montant (écart angulaire par rapport à la verticale inférieur à 30°) tout en étant directement précédé par une cuve d'eau essentiellement portée à la température d' ébullition.Preferably, the device is located in substantially vertical strand amount (angular deviation from the vertical less than 30 °) while being directly preceded by a tank of water essentially brought to the boiling temperature.
[0034] L'invention sera avantageusement mise en œuvre sur une installation où le produit métallurgique à traiter possède une vitesse de défilement comprise entre 0,25 m/s et 20 m/s, et une épaisseur comprise entre 0,1 mm et 10 mm. [0035] Une caractéristique importante de l'invention réside dans le fait que les tubes de refroidissement sont dimensionnés de telle manière que la vitesse d'éjection du fluide de refroidissement soit homogène sur toute la largeur de bande. [0036] De préférence, on dimensionne les tubes pour que la distribution des vitesses soit telle que l'on ait un écart relatif entre la vitesse maximale (Vmax) et la vitesse minimale (Vmιn) d'éjection suivant la largeur du tube inférieur à 5 % ou The invention will advantageously be implemented on an installation where the metallurgical product to be treated has a running speed of between 0.25 m / s and 20 m / s, and a thickness of between 0.1 mm and 10 mm. mm. An important feature of the invention lies in the fact that the cooling tubes are dimensioned such that the ejection speed of the cooling fluid is homogeneous over the entire bandwidth. Preferably, the tubes are dimensioned so that the speed distribution is such that there is a relative difference between the maximum speed (V max ) and the minimum speed (V m ι n ) ejection along the width tube less than 5% or
[0037] De préférence, le rapport entre la section de passage d'un tube et la section libre d'aspersion de ce tube, c'est-à-dire l'aire de la fente ou l'aire cumulée des trous, est supérieur à 1.Preferably, the ratio between the passage section of a tube and the free section of this tube, that is to say the area of the slot or the cumulative area of the holes, is greater than 1.
[0038] Selon une modalité préférée de l'invention, lesdits tubes ont une section rectangulaire. De préférence, le rapport d'un côté à un côté adjacent de la section rectangulaire est compris entre 0,1 et 10 et l'épaisseur des tubes est comprise entre 0,25 fois et 10 fois le diamètre des trous ou l'épaisseur de la fente, en vue de contrôler la cohérence du jet, le rapport entre l'épaisseur des tubes et le diamètre des trous étant le cas échéant encore de préférence égal à 2/3. [0039] Selon une autre caractéristique avantageuse de l'invention, les moyens d'étanchéité précités comprennent un sas à double paire de rouleaux, permettant à la fois le passage de la bande et la création d'une perte de charge limitant à une valeur minimale les fuites du déversoir vers le bas.According to a preferred embodiment of the invention, said tubes have a rectangular section. Preferably, the ratio of one side to an adjacent side of the rectangular section is 0.1 to 10 and the thickness of the tubes is 0.25 to 10 times the hole diameter or the thickness of the tube. the slot, in order to control the coherence of the jet, the ratio between the thickness of the tubes and the diameter of the holes being, if appropriate, still preferably equal to 2/3. According to another advantageous characteristic of the invention, the aforementioned sealing means comprise a double pair of roll locks, allowing both the passage of the band and the creation of a pressure loss limiting to a value minimal spillway leaks down.
[0040] Toujours selon l'invention, ces moyens d'étanchéité comprennent également des moyens d'injection d'un fluide entre les rouleaux, dont on peut contrôler la pression et/ou la température. [0041] Avantageusement, le tube supérieur est équipé d'un barrage dont la hauteur est au moins égale à la somme de l'épaisseur de la lame d'eau au déversoir et de la hauteur de colonne d'eau correspondant à la perte de charge entre les tubes à débit maximum. [0042] Un deuxième objet de la présente invention concerne un procédé de trempe lors du traitement de recuit en continu d'un produit plat sous la forme d'une bande métallurgique, de préférence une bande d'acier, mettant en œuvre le dispositif décrit sous l'une des modalités d'exécution ci-dessus, pour atteindre une puissance spécifique de refroidissement comprise entre 1000 W/m2 et 10000 kW/m2 par face de produit métallurgique. [0043] Selon le procédé de l'invention, la température de la bande à l'entrée du dispositif est comprise entre 350°C et 750°C et la température à la sortie est comprise entre 50°C et 450°C, de préférence entre 50°C et 100°C ou entre 350 et 450°C.[0040] Still according to the invention, these sealing means also comprise injection means a fluid between the rollers, whose pressure and / or temperature can be controlled. Advantageously, the upper tube is equipped with a dam whose height is at least equal to the sum of the thickness of the water slide at the spillway and the height of the water column corresponding to the loss of load between the tubes at maximum flow rate. A second object of the present invention relates to a quenching process during the continuous annealing treatment of a flat product in the form of a metallurgical strip, preferably a steel strip, implementing the device described. under one of the embodiments above, to achieve a specific cooling power of between 1000 W / m 2 and 10000 kW / m 2 per metallurgical product face. According to the process of the invention, the temperature of the strip at the inlet of the device is between 350 ° C. and 750 ° C. and the temperature at the outlet is between 50 ° C. and 450 ° C., preferably between 50 ° C and 100 ° C or between 350 and 450 ° C.
Brève description des figures [0044] La figure 1 représente schématiquement une vue en coupe du dispositif de refroidissement selon la présente invention.BRIEF DESCRIPTION OF THE FIGURES [0044] FIG. 1 schematically represents a sectional view of the cooling device according to the present invention.
[0045] La figure 2 représente schématiquement une disposition des trous destinés à la projection d'eau sur la bande d'acier dans le dispositif de la présente invention.[0045] Figure 2 schematically shows an arrangement of the holes for the projection of water on the steel strip in the device of the present invention.
[0046] La figure 3 illustre graphiquement les performances thermiques du dispositif de refroidissement selon l'invention.Figure 3 graphically illustrates the thermal performance of the cooling device according to the invention.
[0047] La figure 4 illustre les performances dudit dispositif en termes de planéité de la bande d'acier. [0048] Les figures 5 et 6 illustrent l'impact de l'uniformité du refroidissement sur l'homogénéité des propriétés mécaniques de la bande d'acier. La figure 5 se rapporte à un acier de la famille "dual phase", tandis que la figure 6 se rapporte à un acier de la famille des aciers multiphasés . [0049] La figure 7 donne schématiquement les différentes positions des éprouvettes prélevées en fonction de la largeur de la tôle, pour la réalisation des essais relatifs aux figures 5 et 6. [0050] La figure 8 indique les paramètres permettant de calculer l'indice de planéité, ces paramètres caractérisant la sinusoïde à laquelle est assimilé le profil longitudinal de la bande en rive.[0047] Figure 4 illustrates the performance of said device in terms of flatness of the steel strip. Figures 5 and 6 illustrate the impact of the uniformity of cooling on the homogeneity of the mechanical properties of the steel strip. Figure 5 relates to a steel of the "dual phase" family, while Figure 6 relates to a steel of the family of multiphase steels. FIG. 7 schematically gives the different positions of the specimens taken as a function of the width of the sheet, for carrying out the tests relating to FIGS. 5 and 6. FIG. 8 indicates the parameters making it possible to calculate the index of flatness, these parameters characterizing the sinusoid to which is assimilated the longitudinal profile of the strip at the edge.
Description d'une forme d'exécution préférée de l'invention [0051] Comme le montre la figure 1, le dispositif de refroidissement est constitué d'un ensemble de tubes 1, dits "rampes" ou "rampes de refroidissement", disposés symétriquement de part et d'autre de la bande d'acier à refroidir. Ces rampes sont immergées et alimentées latéralement en fluide de refroidissement. Leur section est de préférence rectangulaire . Dans la suite de 1 ' exposé de l'invention, les termes "tubes" et "rampes" seront indistinctement utilisés. [0052] L'immersion des rampes est réalisée au moyen d'un système d'étanchéité, situé dans la partie inférieure du dispositif, qui permet à la fois le passage de la bande d'acier 2 et la création d'une perte de charge maximum de manière à limiter au minimum le débit de fuite du fluide de refroidissement vers le bas du caisson. Dans l'application présentée, ce système d'étanchéité est constitué d'une double paire de rouleaux 3, appliqués contre la bande d'acier et positionnés symétriquement par rapport à celle- ci. Entre les rouleaux, on injecte un fluide dont on peut contrôler la pression et/ou la température. [0053] Le fluide de refroidissement est préférentiellement de l'eau. Les rampes de refroidissement sont situées à une distance A de la ligne de passe de la bande 2. Pour des raisons d'encombrement, d'une part, et afin de limiter le débit total dans le système, pour des performances équivalentes, d'autre part, la distance maximum entre la bande et les rampes de refroidissement est fixée à 200mm. [0054] Un espace B est laissé entre deux rampes successives afin que l'eau injectée par les rampes puisse être évacuée entre celles-ci. Ceci garantit un écoulement aussi homogène que possible suivant la largeur de la bande d'acier. Le choix de la distance B résulte d'un compromis entre une puissance de refroidissement spécifique P maximum, la puissance spécifique étant définie comme la puissance de refroidissement par unité de surface et par face de bande à refroidir, et une perte de charge minimale à travers les canaux d'évacuation, afin d'assurer un renouvellement suffisamment rapide du fluide de refroidissement au voisinage de la tôle, et ainsi éviter la formation de zones d' ébullition locales au voisinage de la bande. La distance B est choisie identique entre deux rampes successives pour toutes les rampes, afin d'assurer des conditions d'écoulement identiques en face de toutes les rampes d'aspersion. Ceci permet donc d'obtenir une homogénéité verticale de l'écoulement. De cette manière, le fluide de refroidissement injecté par une rampe donnée est évacué au moyen des canaux directement adjacents à cette rampe. On évite ainsi de créer des chemins préférentiels et on minimise le temps de passage du fluide de refroidissement au voisinage de la bande, toujours pour éviter la formation locale de zones d' ébullition. [0055] Chaque rampe de refroidissement 1 est pourvue, sur la face exposée à la bande, d'au moins une fente ou d'un ensemble de trous, comme représenté à la figure 2, destinés à la projection du fluide de refroidissement vers la bande. La distance entre deux trous successifs doit être telle que 1 ' écoulement dans le proche voisinage de la bande puisse être assimilé à celui d'une fente. La vitesse d'éjection du fluide doit être suffisante afin d'éviter de former des zones d' ébullition au voisinage de la bande. Cette vitesse d'éjection V est choisie en fonction de la distance A par rapport à la bande et est typiquement comprise entre 0 et lOm/s. [0056] En aval des canaux d'évacuation, le dispositif ou caisson de refroidissement comprend un déversoir 4, sur toute la largeur du caisson et dont la hauteur correspond au niveau du jet de la dernière rampe, ce qui garantit que dans toutes les conditions de fonctionnement, la dernière rampe soit immergée au même titre que les autres . [0057] Afin d'assurer des conditions d'écoulement identiques en face de chaque rampe : la rampe de refroidissement supérieure est surmontée d'un barrage 5 dont la hauteur est au moins égale à la somme de l'épaisseur H de la nappe d'eau au déversoir et de la hauteur de colonne d'eau ΔH correspondant à la perte de charge ΔP au travers des canaux d'évacuation, pour le débit maximum Qmax ;DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION As shown in FIG. 1, the cooling device consists of a set of tubes 1, called "ramps" or "cooling ramps", arranged symmetrically. on both sides of the steel strip to be cooled. These ramps are submerged and fed laterally with cooling fluid. Their section is preferably rectangular. In the following description of the invention, the terms "tubes" and "ramps" will be used indistinctly. The immersion of the ramps is achieved by means of a sealing system, located in the lower part of the device, which allows both the passage of the steel strip 2 and the creation of a loss of maximum load so as to minimize the flow of coolant leakage to the bottom of the box. In the application presented, this sealing system consists of a double pair of rollers 3, applied against the steel strip and positioned symmetrically with respect to this. this. Between the rollers, a fluid is injected whose pressure and / or temperature can be controlled. The cooling fluid is preferably water. The cooling ramps are located at a distance A from the pass line of the strip 2. For reasons of space, on the one hand, and in order to limit the total flow in the system, for equivalent performance, on the other hand, the maximum distance between the belt and the cooling ramps is 200mm. A space B is left between two successive ramps so that the water injected by the ramps can be evacuated therebetween. This ensures a flow as homogeneous as possible along the width of the steel strip. The choice of the distance B results from a compromise between a maximum specific cooling power P, the specific power being defined as the cooling power per unit area and per band face to be cooled, and a minimum pressure drop across the evacuation channels, to ensure a sufficiently rapid renewal of the cooling fluid in the vicinity of the sheet, and thus prevent the formation of local boiling zones in the vicinity of the strip. The distance B is chosen to be identical between two successive ramps for all the ramps, in order to ensure identical flow conditions in front of all the spray bars. This therefore makes it possible to obtain a vertical homogeneity of the flow. In this way, the cooling fluid injected by a given ramp is discharged by means of the channels directly adjacent to this ramp. This avoids creating preferential paths and minimizes the passage time of the cooling fluid in the vicinity of the band, always to avoid the local formation of boiling zones. Each cooling ramp 1 is provided, on the face exposed to the strip, with at least one slot or a set of holes, as shown in FIG. 2, intended for the projection of the cooling fluid towards the bandaged. The distance between two successive holes should be such that the flow in the near vicinity of the strip can be likened to that of a slot. The ejection velocity of the fluid must be sufficient to avoid forming boiling zones in the vicinity of the strip. This ejection speed V is chosen as a function of the distance A with respect to the band and is typically between 0 and 10 m / s. Downstream of the evacuation channels, the device or cooling box comprises a spillway 4, over the entire width of the box and whose height corresponds to the level of the jet of the last ramp, which ensures that in all conditions of operation, the last ramp is immersed in the same way as the others. In order to ensure identical flow conditions in front of each ramp: the upper cooling ramp is surmounted by a dam 5 whose height is at least equal to the sum of the thickness H of the water table. water at the spillway and the water column height ΔH corresponding to the pressure drop ΔP through the discharge channels, for the maximum flow rate Qmax;
- un canal d'évacuation est réalisé en dessous de la dernière rampe . [0058] Ainsi, lorsque le système fonctionne, une différence de niveau d'eau existe entre la face avant, ou côté bande, et la face arrière, ou côté déversoir, des rampes. Cette différence est égale à la hauteur de colonne d'eau correspondant à la perte de charge entre deux rampes, pour un débit donné. [0059] Les performances de refroidissement du dispositif, illustrées à la figure 3, ont été mesurées en conditions industrielles par bilan thermique sur base des grandeurs suivantes : températures de la bande d'acier à l'entrée et à la sortie du dispositif, longueur de la section de refroidissement et vitesse de défilement de la bande d'acier à travers le dispositif. La figure 3 montre que la puissance de refroidissement spécifique, exprimée en k par mètre carré et par face de bande, est une fonction linéaire du débit spécifique, lui-même exprimé en mètres cubes par heure et par mètre carré pour les deux faces cumulées. Dans les conditions envisagées ici, la puissance spécifique est comprise entre 4000 et 6000k /m2 et par face de produit . [0060] La figure 4 illustre les performances du dispositif pour ce qui concerne la planéité de la bande d'acier. Elles sont l'image de l'homogénéité du refroidissement et par conséquent de la maîtrise des écoulements dans le dispositif. La caractérisation de la planéité concerne ici des rives longues. Chaque point de la figure représente un point de fonctionnement du dispositif - défini par la puissance de refroidissement spécifique associée - à un instant donné durant la campagne d'essais industriels. A chaque point de fonctionnement, on associe un indice de planéité, exprimé en unités "I". Une unité "I" correspond à un allongement relatif de 1mm pour 100m de bande d'acier. [0061] Dans le cas d'un défaut de type "rive longue", le profil longitudinal de la bande en rive peut être assimilé à une sinusoïde, de longueur d'onde L et d'amplitude X. L'indice de planéité est calculé sur base des mesures de L et de X (voir figure 8) au moyen de la relation suivante : [0062] Sur la figure 4 ont été représentés deux seuils de référence, 120 et 240 unités "I", qui correspondent aux tolérances de planéité admissibles par deux lignes d' électrozingage. La figure montre que la majorité des points de fonctionnement se situent en deçà du seuil de la ligne la plus exigeante. [0063] Les figures 5 et 6 illustrent l'impact de l'uniformité du refroidissement sur l'homogénéité des propriétés mécaniques . La figure 5 se rapporte à un acier de la famille "dual phase" . La figure 6 se rapporte à un acier multiphasé (ferrite, martensite, bainite, perlite) . Dans les deux cas, les propriétés mécaniques sont caractérisées par un essai de traction. Les éprouvettes sont prélevées à différentes positions suivant la largeur de la tôle, selon le schéma représenté à la figure 7 : 1) Extrême rive, 2) Rive, 3) Quart, 4) Centre, 5) Centre, 6) Quart, 7) Rive, 8) Extrême rive.- An evacuation channel is made below the last ramp. Thus, when the system operates, a difference in water level exists between the front face, or side band, and the rear face, or side weir, ramps. This difference is equal to the column height of water corresponding to the pressure drop between two ramps, for a given flow rate. The cooling performance of the device, illustrated in Figure 3, were measured in industrial conditions by thermal balance on the basis of the following quantities: temperatures of the steel strip at the inlet and the outlet of the device, length of the cooling section and speed of travel of the steel strip through the device. FIG. 3 shows that the specific cooling power, expressed in k per square meter and per strip face, is a linear function of the specific flow rate, itself expressed in cubic meters per hour and per square meter for the two cumulative faces. Under the conditions envisaged here, the specific power is between 4000 and 6000k / m 2 and per product face. Figure 4 illustrates the performance of the device with respect to the flatness of the steel strip. They are the image of the homogeneity of the cooling and consequently of the control of the flows in the device. The characterization of flatness concerns here long banks. Each point in the figure represents an operating point of the device - defined by the associated specific cooling power - at a given time during the industrial test campaign. At each operating point, a flatness index, expressed in "I" units, is associated. A unit "I" corresponds to a relative elongation of 1mm per 100m of steel strip. In the case of a "long bank" type defect, the longitudinal profile of the strip at the edge can be likened to a sinusoid, of wavelength L and amplitude X. The index of flatness is calculated on base measurements of L and X (see Figure 8) using the following relation: FIG. 4 shows two reference thresholds, 120 and 240 "I" units, which correspond to the acceptable flatness tolerances for two electrogalvanizing lines. The figure shows that the majority of operating points are below the threshold of the most demanding line. Figures 5 and 6 illustrate the impact of uniformity of cooling on the homogeneity of mechanical properties. Figure 5 relates to a steel of the "dual phase" family. Figure 6 refers to a multi-phase steel (ferrite, martensite, bainite, perlite). In both cases, the mechanical properties are characterized by a tensile test. The specimens are taken at different positions according to the width of the sheet, according to the diagram shown in Figure 7: 1) Extreme bank, 2) Bank, 3) Quarter, 4) Center, 5) Center, 6) Quarter, 7) Shore, 8) Extreme shore.
[0064] Sur les figures 5 et 6, on a représenté respectivement la charge à rupture, la limite élastiqueIn Figures 5 and 6, there is shown respectively the breaking load, the elastic limit.
(uniquement Fig. 6) et l'allongement à 80% de la charge à rupture. On peut conclure de ces observations qu'il y a une bonne homogénéité des propriétés mécaniques suivant la largeur de la bande . (only Fig. 6) and the elongation at 80% of the breaking load. It can be concluded from these observations that there is a good homogeneity of the mechanical properties according to the width of the band.

Claims

REVENDICATIONS 1. Dispositif de refroidissement, pour réaliser une opération de trempe lors du traitement de recuit en continu d'un produit plat sous forme d'une bande métallurgique (2), de préférence une bande d'acier, ledit dispositif : étant localisé en brin essentiellement vertical montant ou descendant ; comprenant un déversoir (4) dans lequel est complètement immergée une pluralité de tubes (1) empilés essentiellement verticalement et symétriquement de part et d'autre de la bande (2) le long de celle-ci et qui éjectent chacun, sous forme de jets turbulents essentiellement horizontaux, un fluide de refroidissement vers la bande au travers d'une fente ou d'une pluralité de trous ; étant pourvu dans sa partie inférieure de moyens d'étanchéité (3) ; caractérisé en ce que deux tubes (1) successifs quelconques, disposés d'un même côté de la bande (2) , sont séparés par un intervalle (B) identique pour tous les tubes (1) en vue de l'évacuation du fluide de refroidissement, ledit intervalle (B) étant choisi, à une valeur donnée de débit spécifique du fluide de refroidissement, exprimé en mètres cubes par heure et par mètre carré d'une face de la bande, pour minimiser la perte de charge dans les canaux d'évacuation correspondants audit intervalle (B) .  1. Cooling device, for carrying out a quenching operation during the continuous annealing treatment of a flat product in the form of a metallurgical strip (2), preferably a steel strip, said device: essentially vertical strand ascending or descending; comprising a weir (4) in which is immersed completely a plurality of tubes (1) stacked substantially vertically and symmetrically on either side of the strip (2) along the latter and which eject each, in the form of jets substantially horizontal turbulent, cooling fluid to the web through a slot or a plurality of holes; being provided in its lower part with sealing means (3); characterized in that any two successive tubes (1), arranged on the same side of the strip (2), are separated by an identical gap (B) for all the tubes (1) in order to evacuate the cooling, said interval (B) being chosen, at a given value of specific flow rate of the cooling fluid, expressed in cubic meters per hour and per square meter of one side of the strip, to minimize the pressure drop in the d channels; corresponding evacuation to said interval (B).
2. Dispositif selon la revendication 1, caractérisé en ce que la paroi du déversoir (4) , située à l'arrière des tubes (1), possède une largeur au moins égale à celle des tubes (1) et la distance horizontale de cette paroi par rapport à la face arrière des tubes (1) est choisie telle que la perte de charge occasionnée par la présence du déversoir (4) soit inférieure à 5% de la perte de charge occasionnée par les intervalles (B) entre deux tubes (1) successifs. 2. Device according to claim 1, characterized in that the wall of the weir (4), located at the rear of the tubes (1), has a width at least equal to that of the tubes (1) and the horizontal distance of this wall relative to the rear face of the tubes (1) is chosen such that the pressure loss caused by the presence of the weir (4) is less than 5% of the pressure drop caused by the intervals (B) between two successive tubes (1).
3. Dispositif selon la revendication 1 ou 2, caractérisé en ce que le débit spécifique du fluide de refroidissement est compris entre 250 et 1000 m3 par heure, par m2 et par face de la bande. 3. Device according to claim 1 or 2, characterized in that the specific flow rate of the cooling fluid is between 250 and 1000 m 3 per hour, per m 2 and per side of the strip.
4. Dispositif selon la revendication 1, 2 ou 3, caractérisé en ce que la perte de charge occasionnée par les intervalles (B) est inférieure à 150 mm de colonne d' eau. 4. Device according to claim 1, 2 or 3, characterized in that the loss of load caused by the intervals (B) is less than 150 mm of water column.
5. Dispositif selon l'une quelconque des revendications précédentes, caractérisé en ce que la distance (A) entre l'extrémité de chacun des tubes (1) et la bande (2) est identique pour tous les tubes et comprise entre 20mm et 200mm. 5. Device according to any one of the preceding claims, characterized in that the distance (A) between the end of each of the tubes (1) and the strip (2) is identical for all tubes and between 20mm and 200mm .
6. Dispositif selon la revendication 5, caractérisé en ce que la vitesse d'éjection ( VJET) à chaque tube satisfait le critère suivant, respectivement : - pour des trous, JET ≥ o,ι— , d pour des fentes , où A représente la distance entre le tube et la bande et d représente le diamètre d'un trou ou l'épaisseur de la fente . 6. Device according to claim 5, characterized in that the ejection speed (V JET ) to each tube satisfies the following criterion, respectively: - for holes, JET ≥ o, ι-, d for slots, where A represents the distance between the tube and the band and d represents the diameter of a hole or the thickness of the slot.
7. Dispositif selon l'une quelconque des revendications précédentes, caractérisé en ce que le fluide de refroidissement est de l'eau liquide maintenue à une température inférieure à 50°C. 7. Device according to any one of the preceding claims, characterized in that the cooling fluid is liquid water maintained at a temperature below 50 ° C.
8. Dispositif selon l'une quelconque des revendications précédentes, caractérisé en ce que le dispositif est localisé en brin vertical montant et est directement précédé par une cuve d'eau essentiellement portée à la température d' ébullition. 8. Device according to any one of the preceding claims, characterized in that the device is located vertical rising strand and is directly preceded by a tank of water essentially brought to the boiling temperature.
9. Dispositif selon l'une quelconque des revendications précédentes, caractérisé en ce que le produit métallurgique plat à traiter a une épaisseur comprise entre 0,1 mm et 10 mm. 9. Device according to any one of the preceding claims, characterized in that the flat metallurgical product to be treated has a thickness of between 0.1 mm and 10 mm.
10. Dispositif selon l'une quelconque des revendications précédentes, caractérisé en ce que le produit métallurgique plat à traiter possède une vitesse de défilement comprise entre 0,25 m/s et 20 m/s. 10. Device according to any one of the preceding claims, characterized in that the flat metallurgical product to be treated has a running speed of between 0.25 m / s and 20 m / s.
11. Dispositif selon l'une quelconque des revendications précédentes, caractérisé en ce que les tubes de refroidissement (1) sont dimensionnés pour que la distribution des vitesses d'éjection soit telle que l'on ait un écart relatif (Vmax - V n/ Vmax) entre la vitesse maximale (Vmax) et la vitesse minimale (Vmm) d'éjection suivant la largeur du tube inférieur à 5 %. 11. Device according to any one of the preceding claims, characterized in that the cooling tubes (1) are sized so that the distribution of ejection speeds is such that one has a relative distance (V max - V n / V max ) between the maximum speed (V max ) and the minimum speed (V mm ) of ejection according to the width of the tube less than 5%.
12. Dispositif selon la revendication 11, caractérisé en ce que le rapport entre la section de passage d'un tube et la section libre d'aspersion de ce tube, c'est-à-dire l'aire de la fente ou l'aire cumulée des trous, est supérieur à 1. 12. Device according to claim 11, characterized in that the ratio between the passage section of a tube and the free section of this tube, that is to say the area of the slot or the cumulative area of the holes, is greater than 1.
13. Dispositif selon l'une quelconque des revendications précédentes, caractérisé en ce que lesdits tubes (1) ont une section rectangulaire. 13. Device according to any one of the preceding claims, characterized in that said tubes (1) have a rectangular section.
14. Dispositif selon la revendication 13, caractérisé en ce que le rapport d'un côté à un côté adjacent de la section rectangulaire est compris entre 0,1 et 10. 14. Device according to claim 13, characterized in that the ratio of one side to an adjacent side of the rectangular section is between 0.1 and 10.
15. Dispositif selon la revendication 13 ou 14, caractérisé en ce que l'épaisseur des tubes est comprise entre 0,25 fois et 10 fois le diamètre des trous ou l'épaisseur de la fente, le rapport entre l'épaisseur des tubes et le diamètre des trous étant le cas échéant de préférence égal à 2/3. 15. Device according to claim 13 or 14, characterized in that the thickness of the tubes is between 0.25 times and 10 times the diameter of the holes or the thickness of the slot, the ratio between the thickness of the tubes and the diameter of the holes being, if appropriate, preferably equal to 2/3.
16. Dispositif selon l'une quelconque des revendications précédentes, caractérisé en ce que lesdits moyens d'étanchéité (3) comprennent un sas à double paire de rouleaux, permettant à la fois le passage de la bande (2) et la création d'une perte de charge limitant à une valeur minimale les fuites du déversoir (4) vers le bas. 16. Device according to any one of the preceding claims, characterized in that said sealing means (3) comprise a dual pair of roll locks, allowing both the passage of the strip (2) and the creation of a pressure drop limiting at a minimum value the spillway leaks (4) downwards.
17. Dispositif selon la revendication 16, caractérisé en ce que lesdits moyens d'étanchéité (3) comprennent en outre des moyens d'injection d'un fluide entre les rouleaux, dont on peut contrôler la pression et/ou la température. 17. Device according to claim 16, characterized in that said sealing means (3) further comprises means for injecting a fluid between the rollers, the pressure and / or temperature of which can be controlled.
18. Dispositif selon l'une quelconque des revendications précédentes, caractérisé en ce que le tube (1) supérieur est équipé d'un barrage (5) dont la hauteur est au moins égale à la somme de l'épaisseur de la lame d'eau (H) au déversoir et de la hauteur de colonne d'eau (ΔH) correspondant à la perte de charge entre les tubes à débit maximum. 18. Device according to any one of the preceding claims, characterized in that the upper tube (1) is equipped with a dam (5) whose height is at least equal to the sum of the thickness of the blade. water (H) at the spillway and the water column height (ΔH) corresponding to the pressure drop between the maximum flow tubes.
19. Procédé de trempe lors du traitement de recuit en continu d'un produit plat sous la forme d'une bande métallurgique, de préférence une bande d'acier, mettant en œuvre un dispositif selon l'une quelconque des revendications précédentes, pour atteindre une puissance spécifique de refroidissement comprise entre 1000 kW/m2 et 10000 kW/m2 par face de produit métallurgique. 19. Quenching process during the continuous annealing treatment of a flat product in the form of a metallurgical strip, preferably a steel strip, implementing a device according to any preceding claim, to achieve a specific cooling power of between 1000 kW / m 2 and 10000 kW / m 2 per face of metallurgical product.
20. Procédé selon la revendication 19, caractérisé en ce que la température de la bande à 1 ' entrée du dispositif est comprise entre 350°C et 750°C et la température à la sortie est comprise entre 50°C et 450°C, de préférence entre 50°C et 100°C ou entre 350°C et 450°C. 20. The method of claim 19, characterized in that the temperature of the strip at the inlet of the device is between 350 ° C and 750 ° C and the The temperature at the outlet is between 50 ° C and 450 ° C, preferably between 50 ° C and 100 ° C or between 350 ° C and 450 ° C.
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CA2544269C (en) 2012-03-13
ES2282918T3 (en) 2007-10-16
BRPI0416333A (en) 2007-01-09
DE602004005362T2 (en) 2007-11-29
EP1687455B1 (en) 2007-03-14
US7645417B2 (en) 2010-01-12
PT1687455E (en) 2007-05-31
KR20060128880A (en) 2006-12-14
EP1538228A1 (en) 2005-06-08
DE602004005362D1 (en) 2007-04-26
CN100465303C (en) 2009-03-04
CA2544269A1 (en) 2005-06-16
AU2004294469A1 (en) 2005-06-16
ATE356891T1 (en) 2007-04-15
BRPI0416333B1 (en) 2017-05-16
CN1886524A (en) 2006-12-27
WO2005054524A1 (en) 2005-06-16
DK1687455T3 (en) 2007-05-29
KR101089082B1 (en) 2011-12-07
PL1687455T3 (en) 2007-08-31
US20060243357A1 (en) 2006-11-02
AU2004294469B2 (en) 2009-07-16
RU2356949C2 (en) 2009-05-27
RU2006124519A (en) 2008-01-27
JP2007512431A (en) 2007-05-17

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