Method and device for rapidly cooling a metal strip and continuous production line for metal strips

Abstract

The invention relates to a device and method for rapidly cooling metal strips on a continuous production line, the invention being arranged so as to cool the strip as it travels by spraying a liquid, or a mixture of a gas and a liquid, thereon by means of nozzles (21) arranged on spraying units (3, 4), the invention being characterised in that the cooling device comprises spraying units (3) that are rotatable on a plane perpendicular to the strip (8) and perpendicular to the direction of travel of the strip, thereby making it possible to adjust a spraying angle of the spraying units that are movable relative to the strip.

Description

METHOD AND DEVICE FOR RAPID COOLING OF A METAL STRIP, CONTINUOUS LINE FOR PRODUCING METAL STRIPS Designation of the technical field concerned

[0001] The invention relates to metal strip processing lines equipped with a rapid cooling section by spraying liquid or a mixture of liquid and gas, for example nitrogen or a mixture of nitrogen and hydrogen.

[0002] It particularly concerns the production of steels with very high elastic limit, typically greater than 500 MPa, which require heat treatments with high cooling rates, typically greater than 200 °C / s, to establish complex structures with a variable distribution of different metallurgical phases including the austenitic, ferritic, pearlitic, bainitic and martensitic phases.

[0003] In particular, very high elastic limit AHSS and UHSS steels can be produced by controlling cooling rates, from a totally austenitic or mixed ferritic and austenitic metallurgical structure.

[0004] The heat treatment to be applied to the strip depends on the chemical composition of the steel, its initial state, in particular its metallurgical structure and mechanical properties, and the metallurgical characteristics and mechanical properties expected at the end of treatment. It includes, for example, a heating step up to a temperature between 750°C and 950°C, a holding time at this temperature followed by slow cooling, for example to 650°C, then ultra-rapid quenching to room temperature or an intermediate temperature, for example 300°C, with a specific cooling rate for each metallurgical grade.

[0005] For example, obtaining a given steel may require an annealing temperature higher than its austenitizing temperature, then a holding time at this temperature, followed by slow cooling for a partial transformation of the austenite into ferrite and finally rapid cooling for a transformation of the austenite into martensite. Technical problems addressed by the invention

[0006] The quality of the products at the end of treatment, which includes the metallurgical characteristics, the flatness and the homogeneity of the mechanical properties, depends on the thermal homogeneity of the products during the different operations of the heat treatment consisting of a succession of stages of heating, temperature maintenance and cooling.

[0007] In particular, the homogeneity of the metallurgical structure and mechanical properties at the end of processing depends on the similarity of the thermal histories for all points across the product width.

[0008] Flatness depends on the differences in expansion or contraction during heat treatment, observed in the length, width and thickness of the products, causing internal stresses in the strip.

[0009] The constraints depend on: The geometry of the product, i.e. the width, thickness and initial flatness defect, The temperature distribution in the product, in the direction of travel and in the width and also in the thickness of the product for thick strips, Variations in the thermo-physical properties of the product depending on the variation in temperature during heat treatment.

[0010] The defects are of variable types and amplitudes depending on the cooling process applied and the type of steel considered.

[0011] Common flatness defects encountered during heat treatment of metal strips of common low yield strength steels, for moderate cooling rates below 200 °C / s are typically transverse undulations in response to breaks in cooling slopes in the direction of travel of the product.

[0012] Common flatness defects encountered during heat treatment of metal strips of high elastic limit steels with complex metallurgical structure, for rapid cooling by liquid spraying, or by spraying a mixture of gas and liquid, and for cooling rates of the order of 200 °C / s to 1000 °C / s, are typically longitudinal undulations for example long edges or a long center in response to a thermal deviation between the center and edges of the products.

[0013] Dispersed blister-type defects can be observed for locally very heterogeneous cooling, for example during immersion or spray cooling with low pressures. Technical background

[0014] Depending on the state of the art, different technologies can be used to rapidly cool steel strips in a continuous line.

[0015] Cooling in contact with a liquid makes it possible to obtain slopes greater than 200 °C / s according to 3 types of technologies: cooling by spraying a mixture of gas and liquid using bi-fluid nozzles, cooling by spraying a liquid using mono-fluid nozzles, quenching by immersion in a liquid, possibly combined with liquid spraying.

[0016] According to the state of the art, rapid cooling technologies in contact with a liquid are the source of thermal heterogeneity which results from several physical phenomena and several technical constraints.

[0017] The first physical phenomenon to consider is the Leidenfrost phenomenon which consists of a sudden increase in the convection heat transfer coefficient during the transition between the vapor phase cooling regime and the liquid phase cooling regime.

[0018] When cooling a surface at high temperature by contact with a liquid, by immersion or by spraying, all points of the surface follow a non-linear thermal path, depending on the evolution of the heat exchange coefficient according to the four successive cooling regimes representative of cooling by contact with a liquid:For high temperatures of the cooled surface, typically above about 600 °C, we have a vapor film cooling. A vapor layer completely isolates the strip from contact with the liquid which leads to a stable and low heat exchange coefficient.For intermediate temperatures defining a transition domain, typically between about 600 °C and 200 °C, the cooling regime is unstable and a strong variation of the heat exchange coefficient is observed.For lower temperatures, i.e. typically between about 200 °C and 100 °C, we have cooling in the nucleate boiling regime, with a rapid decrease in the heat transfer coefficient as the surface temperature decreases. For low temperatures, typically below 100 °C, the cooling regime is a convection regime.

[0019] Local thermal instability in the transition zone between vapor-phase cooling and liquid-phase cooling, usually observed between 600 °C and 200 °C, can cause flatness defects in response to local thermal heterogeneity.

[0020] The second phenomenon to consider is the discontinuity of the physical and mechanical properties of the products observed during the transformations of metallurgical phases linked to rapid cooling processes, for example at 500°C for a typical bainitic transformation temperature and at 350°C for a typical martensitic transformation start temperature.

[0021] The thermal stresses resulting from differential expansions in the direction of travel of the product and across the width of the product are superimposed on the stresses of transformation of metallurgical phases, leading to a very heterogeneous distribution of internal stresses, with alternating tensile stresses and compressive stresses at different points of the product.

[0022] A first technical constraint is the control of the cooling rate and the final temperature for the realization of specific thermal cycles to obtain steels with complex structures such as TRIP or Q&P or CP steels.

[0023] Another technical constraint is the control of the difference in thermal efficiency across the product width, regardless of the fluid used, resulting from the preferred fluid flow paths between the center and edges of the product related to the nozzle arrangement, gas or liquid distribution heterogeneity related to the feed geometry, initial flatness defect or belt vibration.

[0024] Another technical constraint is the control of the discontinuity of cooling efficiency in the direction of movement of the products created by the cooling ancillary equipment such as the stabilization rollers, the water knives or the air knives placed between the different spraying sections to interrupt the water runoff which disturbs the transverse homogeneity of the products.

[0025] The constraints of controlling transverse thermal homogeneity, controlling cooling continuity in the direction of travel and controlling the precision of the final temperature cannot be effectively met with current immersion cooling processes according to the state of the art.

[0026] Spray cooling processes allow adjustment of the cooling in the direction of travel, for example by adjusting the longitudinal pitch between the rows of nozzles, adjusting the geometry of the nozzles, flat jets or conical jets and adjusting the characteristics of the coolant

[0027] FR2940978 of the applicant describes a method for controlling the homogeneity of cooling by projection of a liquid or a mixture of gas and liquid along the width and / or length of a metal strip, by determining the zone of disappearance of the vapor film and adapting the cooling parameters such as the temperature of the liquid, the speed, the flow rate or the size of the drops and the gas flow rate for cooling by projection of a mixture of gas and liquid in order to maintain the vapor phase at all points.

[0028] The invention does not allow the control of thermal homogeneity for carrying out thermal cycles with a final temperature lower than the Leidenfrost temperature (between 300°C and 500°C).

[0029] On the other hand, this process, which maintains spray cooling in the vapor film phase, which is not very efficient in terms of heat exchange, does not allow the cooling slopes required for the production of steels with very high elastic limits to be achieved.

[0030] FR 16 62421 of the applicant describes a cooling device with a variation of the geometry of the nozzles in the direction of movement of the products for an adjustment of the heat exchange coefficients and the maintenance of a constant cooling speed for all cooling regimes.

[0031] This invention allows the control of cooling continuity in the direction of movement of the products only.

[0032] FR 1911391 of the applicant describes a method for reducing flatness defects by adjusting the thermal path in the direction of travel of the product according to the evolution of the proportions of metallurgical phases, in particular for complex Dual Phase steels, TRIP steels or martensitic steels.

[0033] The improvement in flatness results from the reduction of internal stresses in the strip by a compensating effect of thermal stresses and microstructure change stresses.

[0034] The solutions described according to the state of the art generally propose an improvement in the flatness of the products by controlling the cooling efficiency only in the direction of movement of the product, and sometimes also in the direction of the width of the product.

[0035] According to the state of the art, a common solution for adjusting the cooling capacity across the width of the products is to divide the cooling device into a plurality of cooling units arranged transversely and independently controlled in terms of cooling fluid flow.

[0036] The number of independent units is limited by industrial operating constraints, typically five units equipped with fluid control valves, which leads to discontinuous cross-control.

[0037] On the other hand, these solutions do not allow precise adjustment of cooling efficiency to the varying width of the products.

[0038] They do not allow cooling adjustment for the application of a variable thermal profile, for example convex or concave or of a more complex wave shape, for example to compensate for the effects of runoff along a preferred path linked to an initial shape defect of the product.

[0039] They do not allow the correction of an initial non-uniform thermal profile across the width of the products.

[0040] The object of the invention is to propose a method for cooling a steel strip which improves the performance of the processes according to the state of the art, in particular by allowing a progressive and continuous adjustment of the cooling efficiency in the running direction and in the transverse direction of the products, adaptable according to the initial geometric and thermal state of the strip and the particularity of its thermomechanical behavior according to its composition and the evolution of the proportions of metallurgical phases.

[0041] The invention proposes an improvement in the control of the intensity of cooling of the products, according to their width and length, in the process of rapid cooling by spraying liquid, or gas and liquid, in order to improve the homogeneity of the metallurgical characteristics and mechanical properties and also to improve the flatness of the steel strips at the end of heat treatment.

[0042] According to a first aspect of the invention, there is provided a rapid cooling device in a continuous line for producing metal strips, arranged to cool the running strip by spraying a liquid, or a mixture of a gas and a liquid, onto it, by means of nozzles arranged on spraying units, characterized in that the cooling device comprises spraying units, movable in rotation on a plane perpendicular to the strip and perpendicular to the running direction of the strip, allowing individual and multidirectional adjustment of the projection angle of said spraying units, movable relative to the strip.

[0043] With liquid spray cooling, or gas-liquid mixture cooling, the cooling efficiency depends primarily on the surface flow rate of liquid over the surface to be cooled.

[0044] The principle of the invention is based on a combination, on the one hand, of the variation of the impact surface of the jet from a nozzle on the strip, which depends on the distance of the nozzle from the cooled surface, the angle of inclination of the jet and the distance of the nozzles from each other and, on the other hand, of the simultaneous variation of the lateral flow of the liquid on the surface of the product coming from the neighboring nozzles.

[0045] The invention is also based on controlling the location of the impact surface of the jets according to the direction of travel of the product.

[0046] The device according to the invention allows progressive and continuous control of the cooling efficiency by local adjustment of the total surface flow rate of liquid on each portion of the strip and control of the location of the impact surface of the jets on the strip.

[0047] The multidirectional adjustment of independent cooling units allows in particular a differentiated adjustment according to the thermal profile and the geometric profile of the strip at the inlet of the cooling section and during cooling.

[0048] At a point on the strip, the total surface flow rate corresponds to the sum of the flow rate projected at this point by a nozzle, or at least two nozzles in the case of overlapping jets at this point, and the runoff flow rate on the strip which results from other jets not impacting the strip at this point.

[0049] The runoff flow flows partly from top to bottom due to the Earth's attraction but also in other directions due to the speed of a jet in these directions.

[0050] The movement of a mobile projection unit in rotation on a plane perpendicular to the strip and perpendicular to the direction of travel of the strip makes it possible to easily adjust a projection angle of said mobile projection unit relative to the strip for all the nozzles that this projection unit comprises. This rotation makes it possible to modify the location of the impact surface of the jets as well as the size and shape of the impact surface of the jets produced by these nozzles.

[0051] According to an exemplary embodiment of the invention, the rotational movement of a mobile projection unit is obtained by a pivot element arranged on a first side of the mobile projection unit and a sliding element arranged on a second side of the mobile projection unit, opposite the first.

[0052] The pivot element is advantageously arranged on the side of the projection unit closest to the center of the strip. Thus, the effect on the cooling of the strip of the rotation of a projection unit is more marked towards the edge of the strip.

[0053] According to an exemplary embodiment of the invention, two projection units, movable in rotation, are arranged side by side, in a direction defined by the width of the strip, the two movable projection units covering the entire width of the strip, their pivot elements being arranged in the vicinity of the center of the strip.

[0054] The two mobile projection units can be of the same width, depending on the bandwidth, each covering half of the bandwidth. They can also be of different widths.

[0055] According to an exemplary embodiment of the invention, two projection units, movable in rotation, are arranged on either side of a central projection unit, in a direction defined by the width of the strip, the three projection units covering the entire width of the strip, the pivot elements of the movable projection units being proximal to the central projection unit.

[0056] The central projection unit arranged between the two side units may not be rotatable.

[0057] The transverse division into three units makes it possible to maintain constant cooling conditions on the central part while varying those on the edges of the strip by rotating the side units.

[0058] The length of the units, depending on the strip width, is determined in particular by the maximum strip width and by the size of the strip surface on the edges where cooling adjustment must be possible. Thus, the rotating side parts can be longer or shorter than the central part. The side parts can, for example, be twice as long as the central part.

[0059] The side spray units may be in one part or they may comprise at least two parts movable relative to each other.

[0060] For example, in the case where they comprise two parts which can rotate, the part furthest from the centre of the strip can be rotatable relative to the second part around an axis of rotation situated between the two parts.

[0061] In this configuration, a first rotation of the spray unit can allow the nozzles of both parts of the strip to be moved away from each other by the same angle and a second rotation limited to the part furthest from the center of the strip can allow the nozzles to be moved further away from this part. Conversely, it is possible to move the nozzles of both parts away from the strip by the same angle and then bring those of the part furthest from the center of the strip closer together.

[0062] Similarly, a first rotation of the spray unit can bring the nozzles of both parts of the strip closer together by the same angle and a second rotation limited to the part furthest from the center of the strip can bring the nozzles closer to this part. Conversely, it is possible to bring the nozzles of both parts closer to the strip by the same angle and then move those of the part furthest from the center of the strip further away.

[0063] According to another example, in the case where a spray unit comprises two rotatable parts, the part furthest from the center of the strip may be rotatable relative to the second part about an axis of rotation located in the vicinity of the end of the spray unit furthest from the center of the strip.

[0064] The rotational movement of a first part of a mobile projection unit relative to a second part of this mobile unit can be obtained by a pivot element arranged on a first side of the first part and a sliding element arranged on a second side of said first part, opposite the first.

[0065] A sliding element may comprise a roller rotating about its longitudinal axis.

[0066] The sliding element facilitates the rotation of the mobile unit, or part of it, by providing mechanical support reducing the weight to be supported by the pivot element.

[0067] According to the invention, the angle of rotation of a mobile projection unit is between -30° and +30° relative to a plane parallel to the strip passing the axis (61) of rotation of the mobile unit. The angle of rotation of a first part of a mobile projection unit relative to a second part of this mobile unit can also be between -30° and +30°.

[0068] These large angular openings allow a wide range of adjustment of the impact surface of the jets on the belt, in position, shape and extent, in particular over the width of the belt.

[0069] A mobile projection unit comprises at least one row of nozzles in a direction parallel to the strip width. Advantageously, it comprises several rows of nozzles, for example five or ten rows.

[0070] A row of nozzles of a mobile projection unit forms a longitudinal axis parallel to the direction defined by the strip width. According to an exemplary embodiment of the invention, a row of nozzles is rotatable about this longitudinal axis. Advantageously, at least two rows of nozzles of a mobile projection unit are rotatable about their respective longitudinal axes.

[0071] Advantageously, projection units which are not rotatable also have one or more rows of nozzles which are rotatable around their longitudinal axes.

[0072] The inclination of one or more rows of nozzles makes it possible to adjust the location of the impact surface of the jets from said nozzles according to the length of the strip. It also makes it possible to act on the shape and extent of the impact surface of the jets on the strip. Modifying the inclination of rows of nozzles thus allows control of the cooling profile of the strip according to the length of the cooling section.

[0073] The inclination of nozzles along their longitudinal axis is advantageously carried out at critical locations on the cooling profile of the strip, for example in the vicinity of the Leidenfrost point, where metallurgical transformations occur, or where there is equipment introducing a cooling discontinuity, such as stabilising rollers.

[0074] The angle of rotation of a row of nozzles of a mobile projection unit around its longitudinal axis is between -30° and +30° relative to a plane perpendicular to the strip and perpendicular to the direction of travel of the strip comprising this longitudinal axis. This large angular opening allows a large range of adjustment of the impact surface of the jets on the strip, in position, shape and extent, depending on the length of the strip.

[0075] According to an exemplary embodiment of the invention, the movable projection units are movable in translation on a plane perpendicular to the strip and perpendicular to the direction of travel of the strip in order to adjust the projection distance of said movable projection units relative to the strip.

[0076] Advantageously, any non-rotatable projection units arranged in the center of the strip are also translationally movable in the same direction as the rotating units.

[0077] All the spraying units arranged on the same belt width can be arranged on a common frame so that they are moved in translation simultaneously over the same length. Alternatively, each unit can be moved in translation independently of the others, allowing different distances to the belt depending on the spraying unit.

[0078] The translational movement of the projection units provides a complementary means of acting on the shape and extent of the impact surface of the jets, and therefore on the intensity of the cooling.

[0079] Advantageously, the translation of a mobile projection unit is possible over a distance from the belt of between 50 and 500 mm so as to have a large range of adjustment of the impact surface of the jets on the belt.

[0080] The translational movement of the mobile spraying units can be achieved by a sliding element in the plane perpendicular to the strip and perpendicular to the direction of travel. This sliding element makes it possible to limit the force required for moving the spraying units. The sliding element can comprise a slide or one or more rollers rotating about a longitudinal axis.

[0081] The two freedoms of movement of the mobile spray units resulting from the combination of a rotary and a translational movement allow a great freedom of adjustment and thus precise control of the intensity and distribution of the cooling of the strip. They can allow a large amplitude of simultaneous adjustment of the distance and the angle of spraying of the cooling fluid on the moving strip.

[0082] The rapid cooling device according to the invention comprises all or part of the following elements: nozzles for spraying a liquid, or a mixture of a gas and a liquid, arranged on either side of the strip relative to its running plane, means for adjusting the impact surface of the jets of liquid or of a mixture of gas and liquid on the product, means for adjusting the flow rate of the cooling fluids, means for measuring the temperature across the width of the products before cooling and after spray cooling, means for measuring the flatness of the strip before cooling and after spray cooling, means for calculating the metallurgical transformation temperatures of the strip as a function of its chemical composition and expected thermal cycles,means for calculating the Leidenfrost temperature as a function of the characteristics of the spray nozzles installed in the cooling device, the fluid flow rates applied to achieve the expected thermal cycles, means for calculating the optimal temperature distribution across the width and in the direction of travel of the strip in the cooling zone, means for controlling the cooling device, in particular adjusting the impact surface and the flow rate of the cooling fluid.,

[0083] According to the invention, the cooling intensity of the strip can be regulated by adjusting the surface flow rate according to the direction of travel and according to the transverse direction of the strip.

[0084] The surface flow rate adjustment can be achieved by adjusting the quantity of liquid, or gas and liquid mixture, projected onto the strip. Cooling zones limited by a transverse subdivision and a longitudinal subdivision can comprise elements for adjusting the quantity of liquid, or gas and liquid mixture, projected onto the strip. Thus, adjustment means can allow adjustment of the feed rate of the nozzles over the length and / or width of the strip.

[0085] Surface flow adjustment can be achieved by adjusting the angle of rotating spray units. It can also be achieved by translational movement of mobile spray units, without tilting the spray units or in addition to tilting the spray units.

[0086] The inclination of jets towards the edges of the strip leads to an increase in the impact surface of these jets and to an increase in the overlap rate of these jets adjacent to the edges of the strip.

[0087] The lateral flow of liquid along the surface towards the edges of the strip compensates for the decrease in surface flow rate that results from the increase in the impact surface with a constant feed rate for a jet.

[0088] The combination of redistribution of the impact surface coverage and liquid flow at the belt surface leads to an increase in the total flow rate received by the belt edges.

[0089] Similarly, tilting the jet towards the center of the band leads to a decrease in the jet impact surface and an increase in the overlap rate of contiguous jets at the center of the band.

[0090] The combination of redistribution of the impact surface coverage and the flow of liquid from the surface of the strip towards the center leads to an increase in the total flow rate received by the center of the strip.

[0091] According to one possibility offered by the invention, the liquid, or the mixture of a gas and a liquid, can be chosen to be non-oxidizing for the strip. The liquid is for example an aqueous solution comprising between 0.1% and 6% by mass of formic acid. The gas is for example nitrogen, or a mixture of nitrogen and hydrogen.

[0092] Advantageously, the spray nozzles are staggered in rows of nozzles. For example, the nozzles of a second row are offset from those of a first row, depending on the width of the strip, by half the distance between two nozzles. The nozzles arranged on either side of the strip are also staggered so that there are no nozzles facing each other on either side of the strip.

[0093] The cooling intensity can also be regulated by adjusting the temperature of the cooling fluid in the running direction and in the transverse direction of the strip.

[0094] According to an exemplary embodiment of the invention, the rapid cooling device comprises at least three projection units, movable in the direction of travel of the strip and three projection units, movable according to the strip width, each unit comprising at least two rows of nozzles movable in rotation around their longitudinal axes.

[0095] According to a second aspect of the invention, there is provided a continuous line for producing metal strips, characterized in that it comprises a cooling device according to the first aspect of the invention, the line further comprising a means for determining the geometric transverse profile of the strip and a means for determining the transverse temperature profile of the strip at the inlet of the cooling section.

[0096] The means of determining the geometric transverse profile of the strip is, for example, a laser or an optical camera.

[0097] The means of determining the transverse temperature profile of the strip is, for example, a pyrometer.

[0098] Knowledge of the geometric cross-sectional profile and the cross-sectional temperature profile of the strip at the inlet of the cooling section is used to adjust the cooling intensity across the width of the strip, depending on the nature of these profiles.

[0099] According to a third aspect of the invention, there is proposed a method for rapidly cooling a strip moving in a continuous line for producing metal strips, by spraying a liquid, or a mixture of a gas and a liquid, onto it, by means of a rapid cooling device according to the first aspect of the invention, characterized in that the intensity of the cooling is locally adjusted on a portion of the strip by modifying the quantity of surface flow rate of liquid on said portion by acting on the projection angle of a mobile projection unit arranged in the vicinity of said portion.

[0100] Advantageously, the adjustment of the cooling intensity of a mobile projection unit is refined by moving it closer to or further away from the strip by a translational movement of the latter in a direction parallel to the plane perpendicular to the strip and perpendicular to the direction of travel.

[0101] According to the invention, the intensity of the cooling of a mobile projection unit is adjusted by acting on its projection angle, and optionally on its distance from the strip, to minimize internal stresses which result from differences in strip temperatures in the direction of travel and in the transverse direction of the strip.

[0102] Advantageously according to the invention, the method comprises a step of determining the geometric transverse profile and the transverse temperature profile of the strip at the inlet of the cooling section and the intensity of the cooling is locally adjusted on a portion of the strip by modifying the quantity of surface flow rate of liquid on said portion according to said transverse profiles of the strip.

[0103] Changing the surface flow rate of liquid is advantageously achieved by adjusting the spray angle of the nozzles.

[0104] Advantageously, the adjustment of the spray angle, and optionally the spray distance, is determined for each spraying unit as a function of the target temperature distribution over the length and width of the strip along the cooling section and the initial shape of the strip at the entrance to the cooling section and its evolution during cooling.

[0105] Advantageously, the method according to the invention further comprises a step of determining the thermomechanical behavior of the strip as a function of its composition and the evolution of the proportions of metallurgical phases during its cooling and in that the intensity of the cooling is locally adjusted on a portion of the strip by modifying the quantity of surface flow rate of liquid on said portion according to said behavior.

[0106] The control parameters of the mobile projection units are adjusted to minimize internal stresses resulting from temperature differences in the direction of travel and in the transverse direction of the web.

[0107] The method for determining the control parameters of the rapid cooling device to improve the thermal homogeneity of the strip in the running direction and in the transverse direction can be described as comprising three stages.

[0108] The first step is to evaluate the characteristic parameters of the products to be cooled.

[0109] The first characteristic parameter is the temperature of the metallurgical transformations. These are accompanied by a strong variation in the mechanical and thermo-physical properties of the strip, in particular a strong variation in the coefficient of thermal expansion.

[0110] Indeed, the transformations from the austenitic phase to the ferritic, pearlitic, bainitic or martensitic phases are accompanied by a change in crystallographic structure and an increase in volume which results in a reduction in the coefficient of thermal expansion.

[0111] This rupture observed on the curve of evolution of the coefficient of thermal expansion during the cooling process generates internal stresses which result from the changes in volumes which accompany the changes in phases.

[0112] The combination of this metallurgical phenomenon with the thermal heterogeneity resulting from the state-of-the-art cooling process leads to a heterogeneous stress distribution, with alternating tensile stresses and compressive stresses at different points of the strip.

[0113] The metallurgical transformation temperatures and the evolution of the expansion coefficient depend mainly on the composition of the strip and the annealing thermal cycle which determines the percentage of austenite likely to transform during cooling and the cooling rate.

[0114] The metallurgical transformation temperatures and the thermophysical property evolution curves during rapid cooling can be precisely determined by the usual laws available according to the state of the art from operating data such as the chemical composition of the strip and the associated thermal cycles. Typical values ​​of the bainitic transformation temperature are between 600 °C and 400 °C. Typical values ​​of the martensitic transformation onset temperature are between 450 °C and 250 °C.

[0115] The second characteristic parameter is the minimum cooling rate required to obtain the desired metallurgical transformation(s).

[0116] In the case where only a transformation of austenite into martensite is sought, the minimum cooling rate is calculated which avoids a transformation into another phase, for example bainite.

[0117] The cooling rates required to achieve the required metallurgical microstructures depend on the steel composition, the annealing temperature, and the holding time at the annealing temperature.

[0118] The type of metallurgical transformation observed from a totally or partially austenitic structure obtained at the end of the holding zone depends on the cooling rate applied.

[0119] For slow cooling rates, below 1 °C / s, a transformation from the austenitic structure to the ferritic and pearlitic structures is observed. For medium cooling rates, below 25 °C / s, a transformation from the austenitic structure to the ferritic and bainitic structures is observed. For fast cooling rates, above 100 °C / s, a transformation from the austenitic structure to the martensitic structure is mainly observed when the end of cooling temperature is lower than that of the start of the martensitic transformation. The content of alloying elements, such as Manganese, Chromium or Molybdenum, impacts these cooling rate thresholds.

[0120] The second step is to determine the optimal temperature distribution along the length and width of the product using predictive models to achieve the expected product quality, namely homogeneity of metallurgical characteristics, homogeneity of mechanical properties and flatness.

[0121] These three characteristics, which determine the quality of the final product, depend on thermal homogeneity during the cooling stage.

[0122] The thermal predictive model is based on the evolution curve of the heat exchange coefficient between the strip and the fluid as a function of the cooling regimes.

[0123] For rapid cooling processes by liquid spraying, the Leidenfrost phenomenon generates a strong increase in the exchange coefficient in the transition zone between vapor phase and liquid phase, which implies a strong variation in internal stresses in the strip.

[0124] The Leidenfrost temperature depends on many parameters, in particular spray characteristics such as droplet velocity and diameter, nozzle mesh, nozzle distance from the band, temperature and nature of the fluid.

[0125] These parameters can be determined experimentally for different types of spray nozzles in order to create tables applicable to industrial production cases.

[0126] Typical Leidenfrost temperature values ​​range from 200°C for the lowest spray speeds to 1000°C for the highest speeds.

[0127] The thermal predictive model makes it possible to determine the temperature distribution in the direction of travel and in the width of the product by integrating the characteristic parameters of the product identified in step 1, i.e. the minimum cooling rate, the characteristic temperatures of the metallurgical transformations and the characteristic temperature of the evolution of the heat exchange coefficient, namely, the Leidenfrost temperature.

[0128] The thermomechanical predictive model allows the evaluation of internal stresses and flatness defects that result from the temperature distribution evaluated by the thermal predictive model.

[0129] The combination of the two predictive thermal and thermomechanical models makes it possible to determine the optimal temperature distribution to achieve the expected flatness and reduce local temperature variations and the overall temperature variation between the center and edges of the product to achieve the expected quality including homogeneity of metallurgical characteristics, homogeneity of mechanical properties and flatness.

[0130] The third step consists of determining the adjustment parameters to be applied to the cooling device according to the invention in order to obtain the temperature distribution calculated in step 2.

[0131] The line according to the invention may include means for measuring the temperature across the width of the products and means for measuring the flatness, before cooling and after spray cooling.

[0132] According to one aspect of the invention, the predictive models described in step 2 make it possible to complete a table of control parameters for the cooling device to obtain the optimal temperature distribution for each production case.

[0133] Advantageously, the line equipped with the cooling device according to the invention can comprise artificial intelligence means for linking the data collected by the temperature and flatness sensors to the temperature distribution objectives determined by the predictive models and finally to the control parameters of the cooling device according to the invention to achieve these objectives.

[0134] The line includes a control and command system capable of determining and applying the operating parameters of the cooling section according to the characteristics of the strip entering the cooling section and the evolution of these along the cooling section.

[0135] The control and command system includes calculation means for determining the operating parameters of the cooling section, in particular for implementing thermal and metallurgical models and artificial intelligence algorithms.

[0136] Advantageously, the line control and command system can determine and apply the operating parameters of the cooling section autonomously, without requiring operator intervention.

[0137] The invention consists, apart from the arrangements set out above, of a certain number of other arrangements which will be discussed more explicitly below with regard to exemplary embodiments described with reference to the appended drawings, but which are in no way limiting. Brief description of the figures

[0138] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which:

[0139] is a schematically and partially represented view, in longitudinal view, of a continuous vertical furnace treatment line comprising a rapid cooling section 1, equipped with units 2 for cooling by spraying a cooling fluid, according to an exemplary embodiment of the invention;

[0140] is a schematically and partially represented view, in front view of a cooling unit 2 of the rapid cooling section 1 of the comprising two lateral projection units 3, movable in rotation and a central projection unit 4, movable in translation;

[0141] is a schematically and partially represented view, in top view of a cooling unit 2 of the, in a position where the central spray unit 4 and the lateral spray units 3 are aligned in a direction parallel to the width of the strip, producing a jet perpendicular to the strip 8;

[0142] is a schematically and partially represented view, in top view of the cooling unit 2 of the, in a position where the side units 3 are inclined by 10° leading to an increase in the spraying distance;

[0143] is a schematically and partially represented view, in top view, of the cooling unit 2 of the, in a position where the side units 3 are inclined by -10° leading to a reduction in the spraying distance;

[0144] adds to the schematic view of the jet impact surface for this arrangement of the side units 3;

[0145] adds to the schematic view of the jet impact surface for this arrangement of the side units 3;

[0146] is a graph illustrating the evolution of the surface flow distribution of cooling fluid in the width of the strip along the median axis of the jet impact for the cases represented in Figures 6 and 7;

[0147] adds to the schematic view of the jet impact surface for this arrangement of the side units 3;

[0148] is a graph illustrating the evolution of the surface flow distribution of cooling fluid in the width of the strip along the median axis of the impact of the jets in the cases of Figures 6 and 9;

[0149] is a schematic view of the jet impact surface for the case of a jet perpendicular to the strip as shown in but with a decrease in flow rate at the edges of the strip;

[0150] is a graph illustrating the evolution of the surface flow rate distribution of cooling fluid in the width of the strip along the median axis of the jet impact in the case of Figure 13;

[0151] is a schematically and partially represented view, in top view of a cooling unit 2 of the, in a position where the central spray unit 4 and the lateral spray units 3 are aligned in a direction parallel to the width of the strip, the strip 8 having a geometric profile initially concave in the plane perpendicular to the plane of the strip and perpendicular to the direction of travel;

[0152] is a schematic view of the combination of the jet impact surfaces for the 2 faces of the strip for the arrangement of the lateral units 3 of the;

[0153] is a schematically and partially represented view, in top view of a cooling unit 2 of the, in a position where the lateral spraying units 3 are inclined, the strip 8 having an initially concave geometric profile in the plane perpendicular to the plane of the strip and perpendicular to the direction of travel;

[0154] is a schematic view of the combination of the jet impact surfaces for the 2 faces of the strip for the arrangement of the lateral units 3 of the;

[0155] is a schematically and partially represented view, in side view, of two spraying units 3 arranged opposite each other on either side of the strip, each unit comprising six spraying ramps 11 and 12 perpendicular to the plane of the strip 8, the ramps 11 of one face being offset from the ramps 12 of the other face in the plane perpendicular to the strip and parallel to the movement of the strip;

[0156] is a view similar to that of the, with the first row of nozzles inclined by 10° in the plane perpendicular to the plane of the strip 8 and parallel to the movement of the strip, in the direction opposite to the movement of the strip, the latter being from top to bottom;

[0157] is a view similar to that of the, with the first row of nozzles being inclined by 10° in the plane perpendicular to the plane of the strip 8 and parallel to the movement of the strip, in the direction of movement of the strip;

[0158] includes on its left part a schematically and partially represented view, in side view of two successive spraying units 3 according to the, and on its right part a curve 20 illustrating the evolution of the temperature of the strip and on which are visible discontinuities 15, 16, 17, 18 in the direction of travel of the strip obtained when the jets are perpendicular to the strip;

[0159] is a view similar to that of the with jets inclined according to the direction of travel of the strip to adjust the cooling efficiency when passing the discontinuity points observed in ;

[0160] is a graph illustrating the evolution of the thermal profile in the width of the strip obtained after cooling with and without inclination of the jets in the plane perpendicular to the strip and perpendicular to the direction of travel, from an initial concave transverse thermal profile. Detailed description of the invention

[0161] According to an exemplary embodiment of the invention, cooling units 2 according to the are integrated into a rapid cooling section 1 of a vertical treatment line according to the. They comprise a transverse division into three spraying units 3, 4, movable in translation in the horizontal plane perpendicular to the strip according to the. The lateral units 3 are also movable in rotation on a plane perpendicular to the strip and perpendicular to the direction of travel of the strip.

[0162] The spray units 3, which are rotatable, comprise a pivot element 6 arranged in the vicinity of their end 31 located towards the centre of the strip and a sliding element 5 arranged in the vicinity of their end 32 located towards an edge of the strip. A complementary sliding element 7 contributes to the translational movement of the spray units 3, 4. In this example illustrated in, the three units 3, 4 are mechanically linked. They move in translation in the same movement to move closer to or further away from the strip by the same distance.

[0163] In this embodiment, each unit 3, 4 of the transverse subdivision of a cooling unit comprises six rows of spray nozzles in the direction of travel of the strip. Each spray row is equipped with twenty spray nozzles 21, spaced 80 mm apart in the horizontal plane perpendicular to the plane of the strip. The rows of nozzles are spaced 150 mm apart in the direction of travel of the strip. The distance between the strip and the nozzles is, in this example, equal to 300 mm for all the nozzles when the units 3, 4 of the transverse subdivision are all parallel to the strip.

[0164] The rotation angle of the lateral spray units 3 allowing the inclination of the jets of cooling fluid is between -30° and +30° in the plane perpendicular to the strip and perpendicular to the running direction. This angle is zero when the nozzles are parallel to the strip, it is -30° when the nozzles are close to the strip and it is +30° when the nozzles are far from the strip.

[0165] The translation distance of the spraying units 3, 4 allowing the increase or decrease of the length of the sprayed jet is between 50 and 500 mm in the plane perpendicular to the strip and perpendicular to the direction of travel.

[0166] A rotation of a side unit away from the belt has the effect of increasing the distance of its nozzles from the belt. Conversely, a rotation of a side unit towards the belt has the effect of reducing the distance of its nozzles from the belt. This increase or decrease in distance resulting from the rotation of the side units depends on the position of the nozzle on the spray unit. The magnitude of this increase or decrease will be greater the further the nozzle is from the axis of rotation of the unit. Thus, nozzles positioned towards one edge of the belt move further away from or closer to the belt than nozzles located towards the centre of the belt when the axis of rotation of the spray unit is on the side of the unit closest to the centre of the belt.

[0167] Figures 6 to 12 illustrate the surface flow distribution across the width of an initially flat strip of a row of nozzles in the strip width direction, for different inclination configurations of the lateral orientable spray units 3.

[0168] Illustrates the surface flow distribution for the case of jets perpendicular to the strip. In this configuration, the surface 9 of impact of the jets on the strip is circular and the overlap of the jets is such that it leads to a substantially uniform distribution of the water flow along a median axis 10 of the impact of the jets of a row of nozzles.

[0169] Illustrates the surface flow distribution when the side spray units are inclined at an angle of +10°, away from the belt. This inclination leads to an increase in the spray distance in the plane perpendicular to the belt and perpendicular to the running direction. This increase in spray distance varies depending on the nozzles. It is greatest for the nozzles furthest from the center of the belt, for this example of realization where the axis of rotation of the spray unit is on the side of the unit closest to the center of the belt. The central spray unit 4 remains parallel to the belt. The distance of its nozzles from the belt is constant.

[0170] In this configuration, the impact surface 9 of the jets of the lateral units is elliptical with a main axis in the direction of the width of the strip.

[0171] On the surface of the strip affected by the lateral spray units 3, the combination of the increase in the impact surface, the resulting overlap of the jets and the effect of the evacuation of the water towards the edges of the strip leads to an increase in the surface flow rate received by the edge of the strip, along the median axis 10 of the impact of the jets. The central spray unit 4 remaining parallel to the strip, the central part of the strip receiving the jets from it is not impacted by the inclination of the lateral units 3. The distance to the strip and the overlap between the jets remain constant there.

[0172] Advantageously, the effect resulting from the inclination of the lateral spray units 3 makes it possible to compensate for an initial transverse thermal profile characterized by strip edges hotter than the middle of the strip.

[0173] Illustrates the evolution of the surface flow distribution of cooling fluid in the strip width along the median axis of the jet impact for the two configurations illustrated in Figures 3 and 4: in solid line, in the case of a jet perpendicular to the strip; in broken line, in the case of a jet inclined at an angle of +10° for the lateral units 3.

[0174] Illustrates the surface flow distribution for the case where the lateral spray units 3 are inclined at an angle of -10°, approaching the belt. This results in a reduction in the spray distance in the plane perpendicular to the belt and perpendicular to the running direction for these units.

[0175] In this configuration, the impact surface 9 of the jets is elliptical with a main axis in the direction of the width of the product. For the nozzles of the spray units 3, arranged towards the center of the strip, the inclination of the units has the effect of increasing the impact surface and the overlap of the jets. Conversely, for the nozzles arranged towards the edges of the strip, the inclination of the units has the effect of reducing the impact surface and the overlap of the jets. Combined with the effect of the evacuation of the water towards the center of the strip, this leads to a reduction in the surface flow rate received by the edge of the strip and an increase in the surface flow rate received by the center of the strip, along a median axis 10 of the impact of the jets.

[0176] Advantageously, this effect makes it possible to compensate for an initial transverse thermal profile characterized by edges of the strip colder than the middle of the strip.

[0177] Illustrates the evolution of the surface flow distribution of cooling fluid in the strip width along the median axis of the jet impact for the two configurations illustrated in Figures 6 and 9: In solid line, in the case of a jet perpendicular to the strip, In broken line, in the case of a jet inclined at an angle of -10° for the lateral units 3, with the reduction in the spraying distance in the plane perpendicular to the strip and perpendicular to the direction of travel which results from this inclination.

[0178] The simultaneous adjustment of the inclination of the side-mounted spray units and the resulting spray distance also allows precise adjustment of the cooling efficiency to the varying width of the products.

[0179] Illustrates the surface flow distribution for the case of a jet perpendicular to the strip, with a decrease in the coolant flow at the edges of the strip.

[0180] The impact surface 9 of the jets is circular and the overlap of the jets leads to a distribution of the water flow along the median axis 10 of the impact of the jets uniform in the central part of the strip and a progressive decrease in the surface flow rate towards the edges of the strip.

[0181] This adjustment leads to a discontinuous surface flow distribution profile, characterized by a uniform distribution in the central part of the strip and a linear decrease in surface flow at the edge of the strip.

[0182] The strip width influenced by the flow rate adjustment depends on the nozzle feed. These can be equipped with means for individually adjusting the flow rate of each nozzle. In another example, the adjustment is carried out collectively for a row of nozzles arranged vertically on the same strip width or on two or more vertical rows of nozzles. Other combinations are possible. The nozzle group feed can also be different along the length of the cooling section, in the direction of travel of the strip.

[0183] For example, for a feed subdivided into five cross sections, the bandwidth influenced by a flow adjustment is at least equal to the width of one section.

[0184] Illustrates the evolution of the surface flow distribution of cooling fluid in the strip width along the median axis of the jet impact for the two configurations illustrated in Figures 6 and 11: In solid line, in the case of a jet perpendicular to the strip, applied uniformly over the entire width of the strip, In broken line, in the case of a uniform distribution in the central part of the strip and a progressive decrease in the flow rate towards the edge of the strip.

[0185] The discontinuity of application of the cooling fluid flow leads to a discontinuity of the transverse thermal profile and an increase in internal stresses causing flatness defects.

[0186] Adjusting the inclination of the lateral orientable spray units and the resulting spray distance makes it possible to modify the surface flow distribution of cooling fluid on the surface of the strip to adjust the cooling efficiency in the transverse direction of the products and to compensate for the effects of runoff along a preferred path linked to an initial shape defect, or to correct an initial non-uniform thermal profile across the width of the products.

[0187] According to another exemplary embodiment of the invention, the strip is non-planar before cooling, for example characterized by an initial concave shape defect associated with a concave thermal profile resulting in edges of the strip being hotter than the center.

[0188] Illustrates the variation in spray distance and spray angle for spray bars aligned in the plane perpendicular to the plane of the strip and perpendicular to the running direction. This results in non-symmetrical spraying for both sides of the strip.

[0189] Illustrates the overlap of the jet impact surfaces for both sides of the strip. It can be seen that if the opposite impact surfaces are superimposed on both sides of the strip, a compensation effect is obtained, with an overall impact surface that is substantially constant across the width of the strip.

[0190] For this configuration, the compensating effect of the opposing effects on the two faces relative to the spraying distances and spraying angles does not allow to modify the initial thermal profile in particular to reduce the temperature difference between the center and edges of the product and to reduce the difference in cooling rate between the center and edges of the product.

[0191] The differentiated inclination of the cooling units on each side of the strip, as illustrated by the, makes it possible to accentuate the cooling in the center of the strip by combining the effect of concentrating the water runoff on the convex side of the strip and the effect of reducing the spray distance in the center of the concave side of the strip.

[0192] Illustrates the overlap of the jet impact surfaces for the two sides of the strip and the surface flow accentuation effect obtained by the superposition of the opposing surfaces.

[0193] Unlike the, it is found that if the opposite impact surfaces are superimposed on the two faces of the strip, a substantially different overall impact surface is obtained over the width of the strip. According to an exemplary embodiment of the invention, the cooling unit according to theintegrated into a vertical processing line according to thealso comprises means for adjusting the cooling efficiency in the direction of travel of the products.

[0194] For example, on the, each row 210 of nozzles of the cooling device forms a longitudinal axis 62 and comprises a device 13 for rotation around this longitudinal axis 62.

[0195] These means for adjusting the cooling efficiency in the direction of movement of the products complement all or part of the means for adjusting the cooling efficiency described in the previous embodiments, in particular by being combined with an offset of the jets in the plane perpendicular to the strip and parallel to the movement of the strip.

[0196] Illustrates the surface flow distribution for six spray bars 11, 12 aligned in the plane perpendicular to the plane of the strip 8 and parallel to the movement of the strip.

[0197] In this configuration, the impact surface of the jets is circular and the overlap of the surfaces leads to a uniform distribution of the water flow along a median axis of the impact of the jets.

[0198] Illustrates the surface flow distribution for the case where the first pair of ramps in the direction of travel of the strip produces an inclined jet in the plane perpendicular to the strip and parallel to the direction of travel of the strip, in the direction opposite to the travel of the strip.

[0199] In this configuration, modifying the overlap of the jet impact surfaces makes it possible to reduce the cooling intensity in the impact zone of the first two ramps for slower cooling at the start of the spray unit.

[0200] Illustrates the surface flow distribution for the case where the first pair of ramps produces an inclined jet in the plane perpendicular to the strip and parallel to the strip travel direction, in the strip travel direction.

[0201] In this configuration, modifying the overlap of the jet impact surfaces makes it possible to increase the cooling intensity in the impact zone of the first two ramps for faster cooling at the start of the spray unit.

[0202] According to another exemplary embodiment, the inclination of the sprayed jet in the plane perpendicular to the strip and parallel to the direction of travel of the product makes it possible to compensate for the discontinuity in cooling efficiency which results from the discontinuity in the heat transfer coefficient as a function of the successive cooling regimes in vapor film, transition boiling, nucleate boiling or forced convection observed during cooling by spraying or immersion in a liquid of a hot sheet.

[0203] It also makes it possible to compensate for the cooling discontinuity at the metallurgical transformation points.

[0204] It also makes it possible to compensate for the discontinuity of the heat transfer coefficient generated by ancillary equipment such as stabilization rollers, water knives or air knives.

[0205] Consider a carbon steel composed of 0.1% Carbon, 1% Manganese and 1% Silicon, annealed at a temperature above 850°C for complete austenitization, cooled from 850°C to 650°C in a slow cooling section and then from 650°C to 150°C in a rapid spray cooling section comprising two cooling units according to the invention, each composed of six pairs of ramps equipped with conical jet nozzles.

[0206] The average cooling gradient required in the rapid cooling section to achieve complete martensitic transformation can be determined from the metallurgical transformation curves established for the steel composition, i.e. 200 °C / s for the example considered.

[0207] For this example, four discontinuities in the cooling slope can be observed on the thermal profile 14 of the strip in the direction of travel of the product.

[0208] Illustrates, on its left part, the surface flow distribution on one side of the strip for the embodiment example comprising two cooling units and a total of twelve spray ramps perpendicular to the strip and, on the right part, the thermal profile 20 of the strip in the running direction corresponding to the associated uniform surface flow distribution.

[0209] A first discontinuity 15 is observed at the entrance to the rapid cooling section resulting from the increase in the cooling rate between the upstream slow cooling section and the rapid cooling section.

[0210] A second discontinuity 16 is observed when the strip temperature reaches the Leidenfrost temperature at 550 °C.

[0211] A third discontinuity 17 is observed at the transition between the two rapid cooling sections.

[0212] A fourth discontinuity 18 is observed when the strip temperature reaches the martensitic transformation temperature at 300 °C.

[0213] Illustrates the implementation of all the provisions described in the first examples of implementation allowing the cooling efficiency to be adjusted in the direction of travel of the product to reduce the internal stresses causing flatness defects.

[0214] For example, the inclination of the spray jet in the plane perpendicular to the strip and parallel to the direction of travel of the strip, in the opposite direction to the travel of the strip at the entrance to the rapid cooling section makes it possible to soften the break in slope at the transition between slow cooling and rapid cooling.

[0215] The inclination of the spray jet in the opposite direction to the running before the strip reaches the Leidenfrost temperature makes it possible to attenuate the effect of the sudden increase in the heat exchange coefficient during the transition between the vapor film cooling regime and the transition regime towards nucleate boiling.

[0216] The inclination of the spray jet in the direction of travel at the outlet of the first cooling device makes it possible to compensate for the discontinuity of the heat transfer coefficient generated by the ancillary equipment such as the stabilizing rollers, the water knives or the air knives.

[0217] The inclination of the spray jet in the direction of travel before the strip reaches the martensitic transformation temperature makes it possible to compensate for the internal stresses induced by the transformations from austenitic phase to martensitic phase.

[0218] The implementation of provisions of the invention described in the first exemplary embodiments makes it possible to adjust the cooling efficiency across the width of the product to compensate for an initial transverse thermal profile characterized by product edges that are colder than the middle of the product.

[0219] The inclination of the jets at an angle of -10° and the resulting reduction in the spraying distance in the plane perpendicular to the strip and perpendicular to the running direction makes it possible to increase the thermal efficiency in the center of the strip.

[0220] The graph illustrates this result for transverse thermal profiles: in solid line, before rapid cooling, in broken line, after rapid cooling in the case of a jet perpendicular to the strip applied uniformly over the entire width of the strip, in dotted line, after rapid cooling in the case of a jet inclined at -10° with the resulting reduction in the spraying distance in the plane perpendicular to the strip and perpendicular to the running direction.

[0221] According to another exemplary embodiment of the invention, the cooling device according to the integrated in a vertical processing line according to the and comprising means for adjusting the cooling efficiency in the width of the product and in the direction of travel of the product as described in the first exemplary embodiments, is equipped with flat jet spray nozzles or a combination of conical jet and flat jet nozzles.

Claims

Rapid cooling device in a continuous metal strip production line, arranged to cool the moving strip by spraying a liquid, or a mixture of a gas and a liquid, onto it, by means of nozzles (21) arranged on spraying units (3, 4), characterized in that the cooling device comprises spraying units (3), movable in rotation on a plane perpendicular to the strip (8) and perpendicular to the direction of travel of the strip, allowing individual and multidirectional adjustment of the projection angle of said spraying units, movable relative to the strip. Cooling device according to claim 1, characterized in that the rotational movement of a mobile projection unit (3) is obtained by a pivot element (6) arranged on a first side (31) of the mobile projection unit and a sliding element (5) arranged on a second side (32) of the mobile projection unit, opposite the first. Cooling device according to the preceding claim, characterized in that two projection units (3), movable in rotation, are arranged side by side, in a direction defined by the width of the strip, the two movable projection units covering the entire width of the strip, their pivot elements (6) being arranged in the vicinity of the center of the strip. Cooling device according to claim 2, characterized in that two rotationally movable projection units (3) are arranged on either side of a central projection unit (4), in a direction defined by the strip width, the three projection units (3, 4) covering the entire width of the strip, the pivot elements (6) of the movable projection units (3) being proximal to the central projection unit (4). Cooling device according to one of the preceding claims, characterized in that the angle of rotation of a rotating projection unit (3) is between -30° and +30° relative to a plane parallel to the strip passing through the axis (61) of rotation of the mobile unit. Cooling device according to claim 1, characterized in that a row (210) of nozzles (21) of a mobile projection unit (3) forms a longitudinal axis (62) parallel to the direction defined by the strip width and in that this row of nozzles is rotatable around this longitudinal axis. Cooling device according to the preceding claim, characterized in that the angle of rotation of a row of nozzles around its longitudinal axis is between -30° and +30° relative to a plane perpendicular to the strip and perpendicular to the direction of travel passing through the longitudinal axis (62). Cooling device according to claim 1, characterized in that the projection units (3, 4) are movable in translation in a direction parallel to the plane perpendicular to the strip and perpendicular to the running direction in order to adjust the projection distance of said projection units relative to the strip. Cooling device according to the preceding claim, characterized in that the translation of a mobile projection unit is possible over a distance from the belt of between 50 and 500 mm. Continuous line for the production of metal strips, characterized in that it comprises a cooling device according to one of claims 1 to 9, the line further comprising a means for determining the geometric transverse profile of the strip and a means for determining the temperature profile of the strip at the inlet of the cooling section. Method for rapid cooling of a strip moving in a continuous line for producing metal strips, by spraying a liquid, or a mixture of a gas and a liquid, onto it, using a rapid cooling device according to one of the preceding claims, characterized in that the intensity of the cooling is locally adjusted on a portion of the strip by modifying the quantity of surface flow of liquid on said portion by acting on the projection angle of a mobile projection unit (3) arranged in the vicinity of said portion. Method according to the preceding claim, characterized in that the local adjustment of the cooling intensity on the strip portion is refined by acting on the distance from the strip of the mobile projection unit (3) arranged in the vicinity of said portion by a translational movement of the latter in a direction parallel to the plane perpendicular to the strip and perpendicular to the direction of travel. Method according to one of claims 11 or 12, characterized in that it further comprises a step of determining the geometric transverse profile and the transverse temperature profile of the strip at the inlet of the cooling section and in that the intensity of the cooling is locally adjusted on a portion of the strip by modifying the quantity of surface flow rate of liquid on said portion according to said transverse profiles of the strip. Method according to one of claims 11 to 13, characterized in that it further comprises a step of determining the thermomechanical behavior of the strip as a function of its composition and the evolution of the proportions of metallurgical phases during its cooling and in that the intensity of the cooling is locally adjusted on a portion of the strip by modifying the quantity of surface flow of liquid on said portion according to said behavior.

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