Method for cooling on a reversing hot rolling mill

Abstract

The invention relates to a reversible hot rolling mill equipped with one or more cooling systems consisting of nozzle banks that spray an aluminum blank. It also relates to the hot rolling process associated with this reversible hot rolling mill in which the cooling system is used at least once which makes it possible to produce aluminum sheets advantageously. It also relates to the method for rolling an aluminum alloy of the AA6xxx series in which a blank is cooled during hot rolling and to a thin sheet obtained by this method. The invention makes it possible to improve the productivity of reversible rolling mills by improving the metallurgical quality and / or the productivity of the other processing steps. The invention is particularly useful for providing high-quality 6xxx alloy sheets for the automotive industry.

Description

Domaine de l'invention

[0001] The invention relates to the field of rolling flat aluminum alloy products. More specifically, the invention relates to a reversible hot rolling mill equipped with a particularly rapid, homogeneous and reproducible cooling system for flat aluminum alloy products.

[0002] The invention also relates to the method implemented by said reversible hot rolling mill equipped with a cooling system which allows better thermal control of flat aluminum alloy products during rolling. The invention also relates to a thin sheet whose method uses cooling during hot rolling which can be obtained by the invention. Etat de la technique

[0003] A hot rolling line for aluminum alloys always includes a reversible rolling mill (i.e. one that rolls back and forth) also called a roughing mill or rougher and, possibly, a multi-stand rolling mill also called a tandem rolling mill, at the exit of which the still hot metal is rolled. The number of passes and the pass take-up (thickness reduction per pass) depend on the hardness of the product (its flow stress) and of course, the power of the rolling mill, in terms of torque and force. Productivity requires that the greatest possible reductions be taken at each pass. However, we are then limited by the capacity of the rolling mill in terms of rolling force and / or rolling torque, as described for example in the article "Forming aluminum - Rolling - Patrick Deneuville, ©< Techniques de l'Ingénieur - 2010".During hot processing of aluminium such as hot rolling, the temperature of the metal is always at least typically 200°C.

[0004] We also know of hot lines in which two reversible rolling mills follow one another followed by a tandem rolling mill.

[0005] Reversible hot rolling mills are often production bottlenecks in factories and given the considerable investments they represent, increasing their productivity is a major challenge and obviously we have always thought about increasing the capacity of the rolling mill in terms of force and / or rolling torque.

[0006] In the technical state, it has often been considered to improve the productivity of tandem rolling mills rather than that of the reversible rolling mill. The following requests relate in particular to cooling methods or processes installed on hot finishing tandem rolling mills.

[0007] Patent application WO201558902 relates to a hot rolling mill for aluminum strips and a method for hot rolling an aluminum strip.

[0008] This application aims to propose, for a hot rolling mill for aluminium strips comprising a multi-stand tandem finishing mill having at least one decoiler mounted downstream in the rolling direction and at least one associated cooling section, a solution which makes it possible to better adjust the cooling curves and the temperature-time paths in the product to be rolled during the hot rolling of aluminium strips. For this purpose, the cooling section(s) are arranged in the exit zone of the hot rolling mill for aluminium strips, and at least one trimming shear installed downstream in the rolling direction is associated with the tandem finishing mill.

[0009] Patent EP2991783 relates to a method for manufacturing a metal strip. This patent relates to a method for manufacturing a metal strip in which the strip is rolled in a multi-stand rolling mill, is taken out behind the last stand of the rolling mill in the transport direction and cooled in a cooling device.In order to achieve a favourable grain structure and a high degree of flatness, according to the patent, the strip or sheet is subjected directly after passing through the working rolls of the last rolling stand to additional rapid cooling, the cooling of the strip or sheet still taking place at least partly within the extent of the last rolling stand in the conveying direction, the rapid cooling taking place by applying a coolant from above and below to the strip or sheet, the volume flow of coolant applied from below to the strip or sheet amounting to at least 120% of the volume flow of coolant applied from above to the strip or sheet.

[0010] Patent application WO200889827 relates to a device for cooling a metal strip. This application relates to a device for cooling a metal strip between two rolling mill stands, the strip being guided on an upper guide element of planar design. Below the upper guide element is arranged a spray element which conducts cooling fluid through at least one opening in the upper guide element to the underside of the strip. In order to achieve an improved spray pattern, according to this application, at least two openings juxtaposed in the direction transverse to the strip feed direction are made in the upper guide element and have an elongated shape. The longitudinal axis of the opening is oriented at an angle to the strip feed direction.

[0011] There are also processes and equipment for cooling the trays before they start feeding the hot rolling mill.

[0012] Patent application WO2016 / 012691 relates to a cooling method and equipment. This application relates to a method for cooling an aluminum alloy rolling plate, after the metallurgical homogenization heat treatment of said plate and before its hot rolling, characterized in that the cooling of a value of 30 to 150°C is carried out at a rate of 150 to 500°C / h, with a homogeneity of less than 40°C over the entire treated part of the plate. This application also relates to the installation allowing the implementation of said method as well as said implementation.

[0013] Patent application WO 2018 / 011245 relates to a method for manufacturing a thin sheet of 6xxx series aluminum alloy comprising the following steps: casting a 6xxx series aluminum alloy to form an ingot; homogenizing the ingot; cooling the homogenized ingot at a cooling rate of at least 150 °C / h directly to the starting temperature of hot rolling; hot rolling the ingot to a final thickness and coiling to the final thickness after hot rolling under conditions allowing a recrystallization rate of at least 50% to be obtained; cold rolling in order to obtain a cold-rolled thin sheet.The method of the invention is particularly useful for the manufacture of thin sheets for the automotive industry which combine high tensile strength and formability suitable for cold stamping operations, as well as excellent surface quality and high corrosion resistance with high productivity.

[0014] For 6000 series alloys other modifications are also considered to improve productivity and / or metallurgical properties.

[0015] Patent application EP1165851 relates to a process for converting an ingot of a 6000 series aluminum alloy into a self-annealing sheet. This process involves subjecting the ingot to a two-step homogenization treatment, first at a temperature of at least 560 °C, and then at a temperature between 450 °C and 480 °C. This process then involves hot rolling the homogenized ingot at a starting temperature between 450 °C and 480 °C, and then at an arrival temperature between 320 °C and 360 °C. This results in a hot-rolled sheet having an exceptionally low Cube recrystallization component.

[0016] Patent application US2016 / 0201158 relates to novel processes for increasing productivity on a continuous annealing and solution heat treatment line for heat-treatable aluminum sheet products for the automotive industry having high T4 and post-bake strengths and reduced straightness. By way of non-limiting example, the processes according to the invention can be used in the automotive industry. The heat-treatable alloys and processes according to the invention can also be applied in the maritime, aerospace and transportation industries.

[0017] Patent application EP1375691 relates to a 6000 type aluminum alloy rolled sheet containing Si and Mg as main components and having excellent formability sufficient to enable flat-flap machining, excellent dent resistance, and good hardenability during coating baking. The alloy sheet has a Lankford coefficient anisotropy greater than 0.4 or a coefficient of resistance for cube texture orientations greater than or equal to 20, and has a critical bending radius less than or equal to 0.5 mm at 180 °C, bending even when the yield strength exceeds 140 MPa by aging at room temperature.Also provided is a method for producing the aluminum alloy rolled sheet, which comprises subjecting an ingot to a homogenization treatment, cooling it to a temperature below 350°C at a cooling rate of 100°C / hour or more, optionally to room temperature, reheating it to a temperature of 300 to 500°C and subjecting it to hot rolling, cold rolling the hot rolled product, and subjecting the cold rolled sheet to a solution treatment at a temperature of 400°C or higher before quenching.

[0018] Application EP0786535 relates to homogenizing, at a temperature not lower than 500°C, an aluminum alloy ingot containing not less than 0.4% by weight and less than 1.7% by weight of Si, not less than 0.2% by weight and less than 1.2% by weight of Mg, and Al and unavoidable impurities as balance, and then cooling the resulting product from a temperature not lower than 500°C to a temperature in the range of 350 to 450°C, the starting point of which is suitable for hot rolling. After the hot rolling step is completed at a temperature in the range of 200 to 300°C, the resulting product is subjected to cold rolling at a reduction ratio not lower than 50%, immediately before its solution treatment.The cold-rolled product is then subjected to a solution treatment in which it is kept at a temperature in the range of 500 to 580°C at a temperature increase rate of not less than 2°C / s for not more than 10 minutes, and then the resulting product is subjected to hardening in which it is cooled to a temperature of not more than 100°C at a cooling rate of not less than 5°C / s. Thereby, a method for producing an aluminum alloy plate for casting, which has high strength and moldability, and an excellent exterior appearance on its post-casting surface, is provided, which is suitably used as a material for transportation equipment parts, such as exterior plates for automobiles.

[0019] Patent application JP2015067857 relates to providing an Al-Mg-Si based aluminum alloy sheet for automobile panel excellent in drawability, bendability capable of processing flat bending, shape stability property, coating seizing hardening and corrosion resistance, and to providing a manufacturing method therefor, with an Al-Mg-Si based aluminum alloy sheet for automobile panel contains Si: 0.4-1.5%, Mg: 0.2-1.2%, Cu: 0.001-1.0%, Zn: 0.5% or less, Ti: 0.1% or less, B: 50 ppm or less, one or more kinds of Mn: 0.30% or less, Cr: 0.20% or less and Zr: 0.15% or less, and the balance Al with unavoidable impurities.A density distribution of cube direction at a depth part of 1 / 4 of sheet thickness from a surface is in a range of 10 to 25, an average of rr value (r = (r + r + r × 2) / 4) is 0.50 or more, an absolute value of an in-plane anisotropy index of r value Δr (Δr = (r + rr × 2) / 2) is 0.30 or less and an average diameter of crystal particles is 50 µm or less.

[0020] For metallurgical or productivity reasons, it may be considered to harden the strip after hot rolling.

[0021] For example, we know of a reversible rolling mill followed by a "pool" into which the metal at the final hot thickness is immersed to be cooled ("Shaping of aluminum - Rolling - Patrick Deneuville, ©< Techniques de l'Ingénieur - 2010").

[0022] Patent application WO2019241514 relates to systems and methods for quenching a metal strip after rolling. This application relates to systems and methods for quenching a metal substrate, comprising cooling a top surface and a bottom surface of the metal substrate until a strip temperature is cooled to an intermediate temperature. Cooling of the top surface of the metal substrate is discontinued when the strip temperature reaches the intermediate temperature, and cooling of the bottom surface of the metal substrate continues until the metal substrate reaches a target temperature, the target temperature being lower than the intermediate temperature.

[0023] Patent application FR2378579 relates to a method for the rapid cooling of a continuous casting bar, round or slab, resting on a rolling track and subjected to water spraying. According to this application, this method is characterized in that said bar is moved in a back and forth movement during the total cooling period, the stroke of this movement being greater in the extraction direction than in the opposite direction.

[0024] US6309482 relates to the in-line combination of a reversing mill (Steckel mill) and its coil furnaces with a controlled accelerated cooling apparatus immediately downstream thereof and the associated method for sequentially rolling steel in a reversible manner to achieve an overall reduction of at least about 3:1.

[0025] Patent US9643224 relates to a device for cooling rolled products, preferably for cooling during cold rolling, comprising a nozzle for applying a cooling agent to the rolled products, a cooling chamber in fluid communication with the nozzle and extending substantially parallel to the plane of travel of the strip being provided for applying the cooling agent to the rolled products

[0026] Patent EP2979769 relates to a method and an installation for manufacturing a steel plate by which a high-quality steel plate having less quality variation can be ensured. It also relates to a method for manufacturing a steel sheet, comprising a hot rolling step, a shape correction step and an accelerated cooling step in that order. Problème posé

[0027] The problem that the present invention seeks to solve is to improve the productivity of reversible rolling mills without degrading the metallurgical quality of the products obtained, or even by improving the metallurgical quality and / or the productivity of the other processing steps. In particular, there is a demand in the automotive industry for methods with high productivity for providing high-quality 6xxx alloy sheets, particularly in terms of mechanical strength, formability and assembly, and surface appearance after painting. Objet de l'invention

[0028] A first object of the invention is a hot reversible rolling mill comprising two working rolls, an upper working roll (21) and a lower working roll (22), and at least one cooling system for cooling a blank (11), said blank (11) moving on rollers (23) and passing through the hot reversible rolling mill between the two working rolls (21) and (22), said cooling system consisting of two cooling devices: an upper blank cooling device (11) and a lower blank cooling device (11) characterized in that: the upper cooling device comprises at least one ramp (30) of nozzles (35) arranged substantially parallel to the axis of the upper working cylinder (21), the nozzles (35) spraying the upper face of the blank (11) with jets of cooling fluid (36), the lower cooling device comprises at least one ramp (40) of nozzles (45) arranged between the rollers (23) or between the lower working cylinder (22) and the nearest roller (23), substantially parallel to the axis of the lower working cylinder (22), the nozzles (45) spraying the lower face of the blank (11) with jets of cooling fluid (46), the axis of the jets of cooling fluid (46) being oriented substantially perpendicular to the lower surface of the blank (11).

[0029] Another object of the invention is a method for hot rolling aluminum alloys comprising the successive steps of a. supplying an aluminum alloy rolling plate with one or more aluminum alloys at a hot rolling inlet temperature, b. carrying out a plurality of hot rolling and / or cooling passes with the hot rolling mill according to the invention, the cooling system being used at least once, c. transferring the blank (11) or the finished product in the form of sheet or strip at a hot rolling outlet temperature for the further processing.

[0030] Yet another object of the invention is a method of rolling an aluminum alloy of the AA6xxx series comprising the successive steps of: a. casting a rolling slab of AA6xxx series alloy, b. homogenizing the rolling slab, optionally followed by reheating, c. first hot rolling to transform the rolling slab into a blank having a first output thickness from a first hot rolling start temperature, d. cooling the blank thus obtained with a typical average cooling rate from the average temperature of the blank of the order of V= C / e to a second hot rolling start temperature, where V is in °C / s, e is the thickness of the blank in mm, and C is a constant value which is between 400 and 1000°C / s*mm, preferably between 600 and 900°C / s*mm, more preferably between 700 and 800°C / s*mm, e.second hot rolling to transform the blank thus cooled into a strip at the final hot rolling thickness under deformation and temperature conditions such that the strip is recrystallized to at least 50%, f. cold rolling of the strip into a thin sheet.

[0031] Yet another subject of the invention is a thin sheet obtained according to the method of the invention, such that after solution treatment in a continuous heat treatment furnace operating in such a way that the holding time equivalent to 560°C, t eq 560 ° , is less than 20 s, the equivalent holding time being calculated using the equation t eq 560 ° = ∫ temps dans le four exp − Q R . 1 T ° C t + 273 − 1 560 + 273 . dt Q being an activation energy of 200 kJ / mol and R = 8.314 J / mol / K, it achieves a tensile strength of at least 90% and preferably at least 95% of the maximum tensile strength obtained after solution treatment with a holding time equivalent to 560°C, t eq 560 ° , from 98s. Description des figures

[0032] Figure 1 : perspective diagram of a blank passing through a rolling mill, the cooling system not being shown. Figure 2 : top view of a blank passing through a rolling mill according to the invention, the convex envelope of the surfaces sprayed directly by the jets of cooling fluid during their first impact on the blank being shown. Figure 3 : bottom view of a blank passing through a rolling mill according to the invention, the convex envelope of the surfaces sprayed directly by the jets of cooling fluid during their first impact on the blank being shown. Figure 4 : another top view of a blank passing through a rolling mill in a preferred embodiment of the orientation of the cooling fluid jets, the cooling fluid jets at their first impact on the blank being shown. Figure 5a : nozzle diagram with fast response valves. Figure 5b : nozzle diagram with fast response valves. Figure 6 : longitudinal sectional diagram of an embodiment of a rolling mill according to the invention. Figure 7 : longitudinal sectional diagram of another embodiment of a rolling mill according to the invention. Figure 8 : longitudinal sectional diagram of another embodiment of a rolling mill according to the invention. Figure 9 : longitudinal sectional diagram of another embodiment of a rolling mill according to the invention. Figure 10 : longitudinal sectional diagram of another embodiment of a rolling mill according to the invention. Figure 11a : cross-sectional diagram of an embodiment of a rolling mill according to the invention. Figure 11b : cross-sectional diagram of an embodiment of a rolling mill according to the invention. Figure 12 : longitudinal sectional diagram of another embodiment of a rolling mill according to the invention. Figure 13 : longitudinal sectional diagram of another embodiment of a rolling mill according to the invention. Figure 14 : longitudinal sectional diagram of another embodiment of a rolling mill according to the invention. Figure 15 : a longitudinal sectional diagram of another embodiment of a rolling mill according to the invention. Figure 16 : diagram of the cooling system control principle. Figure 17 : example of the temperature heterogeneity of the blank for a process according to the prior art. Figure 18 : example of the temperature heterogeneity of the roughing using the rolling mill according to the invention according to a preferred embodiment. Figure 19 : example of rapid cooling of a 114 mm AA6XXX aluminium sheet from 470°C to 420°C for 8s with hot rolling emulsion with a rolling mill according to the invention according to another preferred embodiment. Figure 20 : example of rapid cooling of a 140 mm AA6XXX aluminium sheet from 470°C to 420°C for 10s with hot rolling emulsion with a rolling mill according to the invention according to another preferred embodiment. Figure 21 : photo of the surface quality in roping without the invention as described in example A. Figure 22 : photo of the surface quality in roping without the invention as described in example B. Figure 23 : photo of the surface quality in roping with the invention as described in example D. Figure 24 : photo of the surface quality in roping with the invention as described in example E. Figure 25 : metallographs showing the rate of recrystallization under different conditions Figure 26 : graph showing the effect of solution time on a mechanical property Description de l'invention :

[0033] All aluminum alloys referred to hereinafter are designated, unless otherwise stated, according to the rules and designations defined by the Aluminum Association in the Registration Record Series which it publishes from time to time.

[0034] The metallurgical states in question are designated according to European standard EN-515.

[0035] The static mechanical characteristics in traction are determined by a tensile test according to standard NF EN ISO 6892-1.

[0036] Unless otherwise stated, the definitions of EN 12258 apply.

[0037] Here, a blank is an intermediate product made of aluminum alloy obtained by rolling a rolling plate such as an ingot or a foundry plate, optionally scalped, optionally plated with one or more aluminum alloys, intended for the manufacture of a finished product in the form of sheets, strips or foils made of aluminum alloy, optionally plated with one or more aluminum alloys. A blank is therefore a rolled product whose thickness is intermediate between the rolling plate and the finished product.

[0038] Unless otherwise indicated, the term "rolling mill" here refers to a "reversible rolling mill".

[0039] Unlike the prior art in which either the productivity of reversible rolling mills is increased by increasing the capacity of the rolling mill in terms of rolling force and / or torque, or the productivity of the earlier or later stages is improved, the present inventors have managed to improve the productivity of reversible rolling mills without resorting to these solutions.

[0040] The present inventors have notably noted that given their hardness, most aluminum alloys tend to heat up excessively with each pass. It is then necessary to slow down the rolling mill by making smaller passes, for example, or by leaving a waiting time between each rolling pass.

[0041] According to the invention, it has been found that cooling the blank during the hot rolling step makes it possible to improve the productivity of a hot rolling mill or to create new, more economical manufacturing processes by eliminating production steps, while maintaining the same or improved metallurgical quality of the products. Thus, cooling the blank during rolling on reversible rolling mills can also surprisingly make it possible to give the finished rolled product additional physical properties, such as mechanical properties, surface condition or corrosion resistance.

[0042] The hot reversible rolling mill according to the invention comprises two working rolls, an upper working roll (21) and a lower working roll (22), and at least one cooling system for cooling a blank (11), said blank (11) moving on rollers (23) and passing through the hot reversible rolling mill between the two working rolls (21) and (22), said cooling system consisting of two cooling devices: an upper blank cooling device (11) and a lower blank cooling device (11). The numerous other parts and systems of the hot rolling mill well known to those skilled in the art, for example, non-limiting support rolls, motors, columns, extensions, are not shown in the figures.

[0043] The upper cooling device comprises at least one ramp (30) of nozzles (35) arranged substantially parallel to the axis of the upper working cylinder (21), the nozzles (35) spraying the upper face of the blank (11) with jets of cooling fluid (36). The lower cooling device comprises at least one ramp (40) of nozzles (45) arranged between the rollers (23) or between the lower working cylinder (22) and the nearest roller (23), substantially parallel to the axis of the lower working cylinder (22), the nozzles (45) spraying the lower face of the blank (11) with jets of cooling fluid (46), the axis of the jets of cooling fluid (46) being oriented substantially perpendicular to the lower surface of the blank (11).

[0044] There figure 1 shows a blank (11) passing through a reversible hot rolling mill (the cooling system is not shown in this figure). The figure 1 shows the banks (111), the edges (1111) and the ends (112). The outline (11) is represented in a simplified way as a parallelepiped while the reality is more complex.

[0045] The ends (112) correspond to the part of the blank (11) which engages first or which disengages last from the grip of the cylinders (21) and (22). The ends (112) are shown on the Figure 1 in a simplified way as a parallelepiped. The person skilled in the art is familiar with the ends (112) because they will have to be removed to guarantee the manufacturing and quality of the final product. The ends (112) generally deform by rounding and opening in two under the effect of hot rolling, this phenomenon is called "crocodiling" by the person skilled in the art. The ends (112) also correspond to the areas of the blank where the rolling is not homogeneous in length. The ends (112) can also contain areas corresponding to the transient regimes of start or end of the casting during which the plate was manufactured. The length of the ends (112) depends on the alloys, the rolling and casting conditions and the final applications.This removal of the ends (112) can take place both on a shear installed on the hot train and later in the manufacturing process according to the specific constraints of the final product and its manufacturing process. The length of the ends (112) can typically take the maximum values ​​of 100mm, 200mm, 300mm, 400mm, 500mm or 600mm. The edges (1111) are the faces which connect the upper face of the blank (11) in contact with the upper cylinder (21) and the lower face of the blank (11) in contact with the lower cylinder (22) without being part of the ends (112). The edges (111) are the part of the blank (11) near the edges (1111) excluding the ends (112). The edges (111) are well known to those skilled in the art because they must be removed to ensure the manufacture and quality of the finished product.In industrial reality, the banks (111) and the edges (1111) have a much more complex shape than that schematized by the . figure 1 because cracks and folds often appear there, well known to those skilled in the art. These deformations must be removed. The edges (111) are not rolled homogeneously in width given the proximity of the edges (1111) and they must be removed in order to guarantee the properties of the final product. This removal of the edges (111) can take place both at the end of hot rolling and later in the manufacturing process depending on the specific constraints of the final product and its manufacturing process. The width of the edges (111) can typically take the maximum values ​​of 25mm, 50mm, 50mm, 75mm, 100mm, 125mm, 150mm, 175mm, 200mm or 250mm.

[0046] For each cooling system, an upper (52) or lower (62) convex envelope is defined as the convex envelope of the surfaces (51) or (61) sprayed directly by the cooling fluid jets (36) or (46) during their first impact on the blank (11). An example of a convex envelope (52, 62) of the sprayed surfaces (51, 61) is illustrated by the figures 2 And 3where the cooling system is not represented. Splashing and runoff are not taken into account in the convex hull. A set is convex if for any segment, whose endpoints are in this set, every point of the segment is entirely included in this set. The convex hull of a set is the smallest convex set containing it. The determination of convex hulls is carried out by separating the different cooling systems according to their function. Two cooling systems are separated if there are cylinders (21) and (22) between them. figure 7 illustrates a non-limiting example comprising a second cooling system. In this example, the convex hulls of each system are analyzed separately because one system cools the blank (11) before passing between the cylinders (21) and (22) and the other after passing between the cylinders (21) and (22). Two cooling systems are separate when there are at least two, or at least three, or at least four, or at least five rollers (23), between which there is no nozzle (45) for cooling the underside of the blank. The figure 15 shows an example with 3 cooling systems, two on either side of the hot reversible rolling mill and a third which is further away and which serves, in the case of this non-limiting example, for rapid cooling before transferring the blank (11) to a second hot rolling mill with its cylinders (25) and (26). It will be noted that in the figure 15 two sketches are represented at two positions although it is possible that these sketches cannot be simultaneously present.

[0047] As illustrated by the Figure 2 , for each cooling system, the maximum distance D55 to the cylinder (21) of the convex envelope (52) is the maximum of the distance of any point of the convex envelope (52) with the line C1 which is the projection of the axis of rotation of the cylinder (21) on the upper surface, of the blank (11), reduced by the radius R1 of the cylinder (21).

[0048] As illustrated by the Figure 2 , for each cooling system, the minimum distance D57 from the convex envelope (52) to the cylinder (21) is the minimum of the distance from any point of the convex envelope (52) with the line C1 which is the projection of the axis of rotation of the cylinder (21) on the upper surface, of the blank (11), reduced by the radius R1 of the cylinder (21).

[0049] As illustrated by the Figure 3 , for each cooling system, the maximum distance D65 to the cylinder (22) of the convex envelope (62) is the maximum of the distance of any point of the convex envelope (62) with the line C2 which is the projection of the axis of the cylinder (22) on the lower surface, of the blank (11), reduced by the radius R2 of the cylinder (22).

[0050] As illustrated by the Figure 3 , for each cooling system, the minimum distance D67 from the convex envelope (62) to the cylinder (22) is the minimum of the distance from any point of the convex envelope (62) with the line C2 which is the projection of the axis of the cylinder (22) on the lower surface, of the blank (11), reduced by the radius R2 of the cylinder (22).

[0051] For each cooling system, the area opposite the rolling mill (54) and the area next to the rolling mill (53) are surfaces which are part of a half-plane which contains the upper convex envelope (52) of the blank (11) considered as the simplified parallelepiped of the figure 1 and which is delimited by the line C1.

[0052] For each cooling system, as shown in the figure 2 , the area opposite the rolling mill (54) is a half-plane which does not contain the convex envelope (52) and which is delimited by a straight line E1 which is parallel to the straight line C1 and to the maximum distance D55 added to the radius R1 of cylinder (21) of the straight line C1.

[0053] For each cooling system, the area next to the rolling mill (53) is delimited by the line C1 and by the line D1 which is parallel to the line C1 and at the minimum distance D57 added to the radius R1 of the cylinder (21) of the line C1.

[0054] The direction S is that of the displacement of the blank (11).

[0055] According to the figure 2 , for each cooling system, the distance D56 along the direction S of the convex envelope (52) is the subtraction of the length D57 from the length D55.

[0056] According to the figure 3 , for each cooling system, the distance D66 along the direction S of the convex envelope (62) is the subtraction of the length D67 from the length D65.

[0057] In the embodiment illustrated non-limitingly by the figure 6 , the upper cooling device consists of a ramp (30) of nozzles (35) arranged substantially parallel to the axis of the upper working cylinder (21), the nozzles (35) spraying the upper face of the blank (11) with jets of cooling fluid (36). The lower cooling device illustrated by the Figure 6 consists of two ramps (40) of nozzles (45) arranged between the rollers (23), substantially parallel to the axis of the lower working cylinder (22), the nozzles (45) spraying the lower face of the blank (11) with jets of cooling fluid (46), the axis of the jets of cooling fluid (46) being oriented substantially perpendicular to the lower surface of the blank (11). In an embodiment illustrated by the figure 10 , the lower cooling device consists of a nozzle ramp (45) located between the lower working cylinder (22) and the nearest roller (23).

[0058] The embodiments illustrated non-limitingly for example by the figure 8 and the figure 12 show upper cooling devices consisting respectively of two and three ramps (30) of nozzles (35).

[0059] Preferably, the lower nozzles (45) produce jets of cooling fluid (46) which do not directly reach either the rollers (23) or the cylinder (22) in the presence of the blank (11) and which are preferably almost tangent to the rollers (23) and whose distance D67 is preferably greater than a radius of the lower cylinder (22), more preferably than the diameter of the lower cylinder (22) and / or the upper nozzles (35) produce jets of cooling fluid (36) which do not directly reach the upper working cylinder (21), preferably the distance D57 is greater than the radius of the upper cylinder (21), more preferably the distance D57 is greater than the diameter of the upper cylinder (21). In an embodiment illustrated by the figure 5b , the cooling fluid jets (46) do not directly reach the rollers (23) so that these jets only influence the temperature of the blank (11). In an embodiment illustrated by the figure 10 , in which the ramp (40) is arranged between the cylinder (22) and a roller (23), the jets of cooling fluid (46) do not directly reach the cylinder (22) so that these jets only influence the temperature of the blank and do not disturb the temperature field of the cylinder (22) which is an important factor for the quality of the hot rolling. It is advantageous for the distance D67 to be greater than the radius R1 of the lower cylinder (22), preferably than the diameter of the lower cylinder (22) to prevent splashes of the fluid jet (46) from reaching the cylinder (22) and disturbing the temperature field of the cylinder (22). It is also advantageous for the area of ​​the lower surface of the blank (11) sprayed by the lower jets of cooling fluid (46) to be maximized to improve the heat exchange.To maximize the surface area sprayed by the jets (46) without touching the rollers (23), it is advantageous for the jets (46) to pass flush with said rollers (23) without touching them as illustrated by the . figure 5b These lower jets (46) are therefore preferably almost tangent to the rollers (23). The invention thus makes it possible to maximize the sprayed surface to increase the surface area useful for heat exchange. The jets (36) advantageously do not touch the cylinders (22) so as not to disturb the temperature field of the cylinders (21) which is an important factor in the quality of hot rolling. It is advantageous for the distance D57 to be greater than the radius R1 of the upper cylinder (21), preferably for the distance D57 to be greater than the diameter of the upper cylinder (21) to prevent splashes from the fluid jet (36) from reaching the cylinder (21) and disturbing its temperature field.

[0060] Nozzles (24) illustrated on the Figure 6 and dedicated to the cylinders (21) and (22) can be installed in order to cool or lubricate these members according to their specific needs independently of the blank (11). In an embodiment not illustrated, specific nozzles can be installed to cool the rollers (23). The position of the nozzles (24) on the figure 6 is only a principle and is not limiting.

[0061] Preferably, the lower nozzles (45) are below the plane passing through the axes of rotation of the rollers (23) located near said nozzles (45) and / or the lower nozzles (45) are protected by a part (47) having openings to allow the jets of cooling fluid (46) to pass through and / or the upper nozzles (35) are protected by a part (37) having openings to allow the jets of cooling fluid (36) to pass through. Protecting the nozzles (35) and (45) is advantageous because hot rolling can cause an opening of the ends (112) of the blank (11) which the person skilled in the art calls "crocodiling" and which can strike the nozzles. The blanks (11) can also form bridges or boats during hot rolling, i.e. the blank (11) instead of being substantially flat can bend in the longitudinal direction when leaving the rolling mill, the ends of the blank (11) pointing upwards or downwards.Protecting the nozzles (35) and (45) from the blanks (11) is therefore advantageous to avoid damage to said nozzles. A non-limiting example of the parts (37) and (47) protecting the nozzles (35) and (45) is illustrated in the . figure 8 , there figure 9 and the figure 13 . There figure 7 is a non-limiting example where only the nozzles (35) are protected by a protective part (47). When the rollers (23) are very close to each other, installing the nozzles (45) below the plane of the axes of the rollers (23) makes it possible to protect them economically without installing the protective parts (47), as illustrated by the figures 6 et 7 .

[0062] Preferably, each nozzle (35) and (45) is supplied individually by a fast-response valve (49) whose response time is advantageously less than 1 s, preferably less than 0.5 s, and more preferably less than 0.2 s. figures 5a et 5b show non-limiting examples of fast-response valves (49) mounted between a ramp (30) respectively (40) and a nozzle (35) respectively (45). Supplying the nozzles individually with fast valves is advantageous because it allows each point of the upper surface and the lower surface of the blank (11) to be cooled specifically. These response times make it possible in particular to be able to spray with sufficient reliability the ends (112) of the blanks (11) to adjust their temperature so as to facilitate their engagement between the cylinders (21) and (22). It is then possible to adapt the temperature at the ends (112) of the blank (11) to facilitate its engagement in the reversible hot rolling mill. It is also possible to adapt the temperature on the edges (111) for example to limit cracking phenomena which reduce the useful width of the blank or which can lead to its rupture.It is therefore also possible to optimize the temperature of the other parts of the blank (11) according to the properties required for the finished product or according to the properties required for the subsequent stages of production. For example, this is advantageous for better controlling the properties of the final product such as the anisotropy in the width for AA3104 alloy products or the uniformity of the mechanical properties of AA6xxx alloy products. Finally, cooling each point of the blank (11) in a specific way also makes it possible to control the flatness of the blank (11) by controlling the effects of differential expansions.

[0063] In one embodiment, the nozzles (35) and (45) are capable of producing jets of cooling fluid (36) and (46) in a flat and / or conical and / or cylindrical form. If the shape of the jets is cylindrical, the section of the cylinder is preferably circular. In one embodiment, the nozzles (35) and (45) are capable of producing jets of cooling fluid (36) and (46) by spraying, preferably the nozzles (35) and (45) are capable of producing jets of cooling fluid (36) and (46) by spraying, in a full cone shape, called conical jets. The conical jets (46) and (36) are a better configuration than flat or cylindrical jets. Indeed, the conical jets allow a better distribution of the cooling fluid on the blank (11).This allows a more homogeneous heat exchange and it is thus possible to obtain a blank (11) with, for example, a temperature heterogeneity of less than 20°C, preferably less than 10°C.

[0064] Preferably, the conical jets of cooling fluid (46) have a cone angle of 90°. This angle can be limited, for example to 60°, by the presence of the rollers (23) so as not to spray them, in particular when the nozzles (45) are below the plane passing through the axes of rotation of the rollers (23). If the rollers (23) are very close, it may be preferable to place the nozzles (45) above the plane passing through the axes of the rollers (23) to spray a larger surface (61). On the figure 5b , the nozzle (451) is placed below the plane of the axes of rotation of the rollers 23 and produces a cooling jet (461). On the figure 5b , the nozzle (452) is placed above the plane of the axes of rotation of the rollers (23) and produces a cooling jet (462), the protective part (47) which must preferably be installed in this situation, is not shown. The jet (462) therefore waters a larger surface of the blank (11) not shown than the jet (461).

[0065] Preferably, for each cooling system, at least one device (38) for evacuating the cooling fluid from the upper surface of the blank (11) is installed above the blank. Non-limiting examples of this device (38) are given with the figure 8 , there figure 10 or the figure 12 . A device (38) can be installed above the area opposite the rolling mill (54) and / or above the area next to the rolling mill (53). Preferably, said device (38) is an air blower which pushes the cooling fluid towards one of the edges (111) of the blank (11) and preferably gives the cooling fluid sufficient speed so that it does not run off the edges (1111). The device (38) makes it possible to prevent the cooling fluid from running off over the entire upper face of the blank (11). This helps to ensure controlled cooling to have good repeatability and good reproducibility of the heterogeneity of the temperature of the blank (11). Preventing the cooling fluid from dripping onto the edge (1111) contributes to the thermal control of the edges of the blank (11), and in particular prevents the edges from being overcooled, which limits the appearance of cracks in the edges (111).When the upper cooling device is close to the cylinder (21), the device (38) for discharging the cooling fluid is advantageously supplemented or replaced by the cylinder (21) which acts as a barrier blocking the flow of the cooling fluid. This makes it possible in particular to reduce the energy consumption of the device (38). A non-limiting example of the configuration in which the device (38) for discharging the cooling fluid close to the cylinder (21) is replaced by the cylinder (21) is illustrated by the . figure 10 .

[0066] In one embodiment, the conical jets of the upper cooling device (36) have a cone angle α of at most 20°, preferably substantially 15° or less and the cones of said conical jets have a substantially vertical axis. This configuration makes it possible to limit the runoff of the cooling fluid onto the blank (11). Preferably, the cooling system having at least one such conical jet is framed by a device for discharging the cooling fluid (38) as illustrated non-limitingly by the figure 12 . The cone angle α is illustrated by the figure 5a , the cone angle α is the cone angle of the cooling fluid jet produced by the nozzles.

[0067] In another embodiment, the conical jets of the upper cooling device (36) are inclined relative to the vertical. The inclination angle β is illustrated by the figure 5a , this is the angle that the axis of the nozzles makes with the straight line V perpendicular to the upper face of the blank (11). Preferably, the difference β - α / 2 is greater than -20°, preferably substantially greater than -15°, more preferably positive or zero. Preferably, if the difference β - α / 2 is negative, a cooling fluid evacuation device (38) is preferably installed to prevent runoff onto the surface of the blank (11). If the cooling fluid jets of the upper cooling device (36) are close to the working cylinder (21), the axis of the cooling fluid jets (36) are advantageously oriented to bring the sprayed surfaces (51) closer to the working cylinder (21) to take advantage of the barrier effect of the cylinder (21). This configuration also allows for an increase in the sprayed surfaces (51) to increase the cooling capacity of the cooling system.If the coolant jets are located far from the working cylinder, it is advantageous to group the ramps of the upper cooling device (30) two by two and to orient the axes of the coolant jets (36) so as to bring their respective sprayed surfaces (51) closer together. This configuration is advantageous because it causes the coolant to concentrate in at least part of the overlap zone of the jets (36) and thus to reject the coolant on the edges with enough speed so as not to trickle on the edges (1111) of the blank (11), which makes it possible not to cool the edges (111) of the blank (11) too much.

[0068] There figure 8 is a non-limiting example of the preceding embodiments. The nozzles near the working cylinder (351) have their axis oriented towards the working cylinder (21) and the difference β - α / 2 is greater than -20°. The nozzle (352) is oriented vertically and the angle α of its conical jet (36) is less than 20°.

[0069] There figure 9 is another non-limiting example of the preceding embodiments. The nozzles near the working cylinder (351) are all inclined to bring the sprayed surfaces (51) closer to the working cylinder and the difference β - α / 2 of the conical jets is positive or zero to avoid runoff of the cooling fluid onto the blank (11).

[0070] There figure 12 is another non-limiting example of the preceding embodiments with vertical conical cooling jets (36) whose cone angle α is less than 20°.

[0071] There figure 13 is another non-limiting example of the preceding embodiments. The ramps (303) and (304) are paired, the nozzles (353) and (354) are oriented so that the sprayed surfaces (513) and (514), illustrated by the figure 4 , are approaching. The differences β - α / 2 are positive or zero.

[0072] Preferably, for each cooling system, the upper sprayed convex envelope (52) is opposite with a tolerance of two, preferably one, times the dimension of the diameter of the upper working cylinder (21) of the lower sprayed convex envelope (62), preferably said convex envelopes (52, 62) are substantially opposite. The determination of the convex envelopes is carried out by separating the different cooling systems of the invention. figure 7 illustrates a non-limiting example where there is a second cooling system. In this case, the convex hulls of each system are analyzed separately because one system cools before the passage between cylinders (21) and (22) and the other after the passage between cylinders (21) and (22). The figure 15 shows an example with 3 cooling systems, two on either side of the hot reversible rolling mill and a 3rd which is further away and which serves, in the case of this non-limiting example, for rapid cooling before joining a second hot rolling mill with its cylinders (25) and (26). This arrangement is advantageous because it contributes to the thermal homogeneity of the blank (11). Placing said upper and lower convex envelopes (52, 62) of each cooling system opposite each other is particularly advantageous because it allows homogeneous cooling in the thickness of the blank (11), which contributes to controlling the flatness of the blank (11), which is an important characteristic for blanks which are flat products.

[0073] Preferably, the set of nozzles (35) and (46) are capable of providing a surface flow rate per face of the blank (11) of cooling fluid of 1500 l / min / m 2< maximum, preferably 600 to 1200 l / min / m 2< . This fluid can be propelled by a propellant gas. The cooling fluid can be water, deionized water, a liquefied or non-liquefied gas, preferably an emulsion of water, preferably deionized, and oil and rolling additives, which is used for the lubrication of the cylinders (21) and (22) with the blank (11). Preferably, the deionized water has a resistivity greater than 105 kΩcm.

[0074] In one embodiment, the nozzles of the upper cooling device (35) are movable and maintained at a constant distance from the upper surface of the blank (11), preferably by being attached to the mechanism which holds the cylinder (21). This ensures better repeatability of the cooling of the blank (11). In another embodiment, the nozzles (35) are not movable. In this less expensive non-movable embodiment, it is necessary to control accordingly the nozzles (35) which water the banks (111) or near the banks (111) for example in the case where the nozzles (35) produce conical jets (36). Indeed, in the case of conical jets (36) projected by fixed nozzles (35), the distribution of cooling fluid on the banks (111) widens as the thickness of the blank decreases during the successive passes of the reversible hot rolling scheme. figures 11a And 11bare non-limiting examples of this situation. The blank (11) is shown at the start of hot rolling with the figure 11a and at the end of hot rolling with the figure 11b with each time the same number of upper nozzles (35) which produce jets of cooling fluid (36). Due to the conical shape of the jets (36) and the reduction in the thickness of the blank (11), the edges (111) are not sprayed at the start of rolling illustrated in 11a while they are partially sprayed at the end of rolling illustrated in 11b. Therefore in one embodiment, the intersection between the upper surfaces (51) sprayed directly by the jets of cooling fluids (36) with the upper face of the edge (111) is empty at the start of hot rolling, preferably throughout the duration of hot rolling. Therefore, in one embodiment, the intersection between the lower surfaces (61) sprayed directly by the jets of cooling fluids (46) with the lower face of the edge (111) is empty at the start of hot rolling, preferably throughout the duration of the hot rolling.

[0075] In a preferred embodiment, illustrated for example without limitation in figure 10 , the nozzles (351) in the vicinity of the upper working roll (21) produce jets of cooling fluid (36) all of whose displacement components, projected onto the direction S of displacement of the blank (11), are oriented towards the working rolls (21) and (22) of the rolling mill. Preferably, the jets of cooling fluid (36) of the upper cooling device are conical and the difference β - α / 2 is positive or zero. In a more preferred embodiment as illustrated by the figure 6 , there is only one upper ramp (30) and two lower ramps (40).

[0076] In a preferred embodiment illustrated by the non-limiting example of the figure 6 , the upper sprayed convex envelope (52) and the lower sprayed convex envelope (62), not shown in the figure 6 , are close to the rolling mill rolls; preferably the maximum distances D55 and D65 to the rolls (21) and (22) of the sprayed convex envelopes (52) and (62) are less than 3 times the largest of the diameters of the working rolls (21) and (22) and / or the lengths D56 and D66 of said convex envelopes (52, 62) are less than two diameters, preferably one diameter of the largest of the working rolls (21) or (22). This embodiment is advantageous because it allows the blank (11) to be cooled as soon as it leaves the grip of the rolls (21) and (22) and to prevent the blank from moving too far from the rolls before leaving in the other direction for the next hot rolling pass. This is particularly advantageous because it improves the productivity of the hot rolling mill.In fact, the speed of reversible hot rolling mills is often limited to avoid heating which leads to burns, cracks, crocodiling or even breaks of the blank (11).

[0077] In a preferred embodiment illustrated by a non-limiting example of the figure 7 , there is a second cooling system on the other side of said hot reversible rolling mill, the second cooling system preferably being symmetrical to the first with respect to a plane passing through the axes of the working rolls (21) and (22). This arrangement is advantageous because it makes it possible to cool the blank (11) until it enters the grip of the reversible rolling mill and as soon as it leaves the grip of the reversible rolling mill at each rolling pass and in an identical manner.

[0078] In another preferred embodiment illustrated by a non-limiting example in figures 4 And 13, the upper cooling device comprises at least one pair of ramps (303 and 304) of nozzles (353, 354), preferably 3 pairs of ramps (303 and 304), in each pair of ramps (303 and 304), the jets of cooling fluid (363, 364) being oriented in opposition, the difference β - α / 2 being positive or zero, preferably zero, α being the angle of the cone of the jet of cooling fluid produced by the nozzles and β being the angle of inclination that the axis of the nozzles (353, 354) makes with the straight line V perpendicular to the upper face of the blank (11), the sprayed surfaces (513, 514) of the blank (11) by the jets (363, 364) preferably overlapping by a factor between 1 / 3 and 2 / 3, preferably 1 / 2, and the lower cooling device comprises at least one ramp (40) of nozzles (45), preferably 8 ramps (40), the jets of cooling fluid (46) of which are conical and have an axis substantially normal to the blank (11).Preferably, the rough sketch (11) is substantially horizontal. The angles are shown diagrammatically in the general case on the . figure 5a with the nozzles (35), the ramps (30) and the jets of cooling fluids (36). The figure 4 illustrates the sprayed surfaces (51). This configuration is advantageous because it causes the cooling fluid to concentrate in at least part of the overlap zone of the jets (36) and thus to reject the cooling fluid on the edges with enough speed so as not to run off the edges (1111) of the blank (11), which makes it possible not to cool the edges (111) of the blank (11) too much. This makes it possible to reduce the energy consumption of the devices (38) for discharging the cooling fluid or even to be able to eliminate them.

[0079] In another preferred embodiment shown diagrammatically without limitation in figure 12 , the upper cooling device comprises at least one ramp (30), preferably 6 ramps (30), of nozzles (35) and the lower cooling device comprises at least one ramp (40), preferably 8 ramps (40), of nozzles (45), all producing conical jets of cooling fluid (36) and (46) whose axes are substantially perpendicular to the blank (11), and whose angle α of the cone of the jets (36) is less than 20°, preferably the angle α of the cone of the jets (36) is substantially 15°. This device has the advantage of being simpler to construct. The angle of the conical jets makes it possible to limit the horizontal component of the speed of the cooling fluid during its impact on the blank (11), and consequently to limit the spreading of the cooling fluid on the blank (11) to control its cooling.

[0080] In another preferred embodiment illustrated without limitation by the figure 14 and the figure 15 the reversible hot rolling mill according to the invention is part of a hot train in which the reversible hot rolling mill according to the invention is preferably followed by a second hot rolling mill, shown diagrammatically with its working rolls (25) and (26), which may be a reversible rolling mill or a tandem rolling mill. In the embodiment illustrated by the figure 14 , the cooling system of the reversible hot rolling mill according to the invention is placed between the reversible hot rolling mill according to the invention and the second hot rolling mill, preferably the distance between the cooling system and the second hot rolling mill being sufficient for the cooling system according to the invention and the second hot rolling mill to operate independently. This arrangement is advantageous because it allows the cooling operation to be carried out in the production flow and without loss of capacity during the transfer of the blank from the first to the second reversible hot rolling mill. The distance between the cooling system and the second hot rolling mill is also important because, if it is sufficient in relation to the length of the blank, it allows for example to choose different speeds for passing through the cooling system and for passing through the second hot rolling mill.The length of the blank is evaluated by EP*LP / e, where EP is the thickness of the plate, LP the length of the plate and e the thickness of the blank between the two rolling mills. In the embodiment illustrated by the . figure 15 , there are three cooling systems for the reversible hot rolling mill according to the invention, two systems positioned close to and on either side of the working rolls (21, 22) and one system placed between the reversible hot rolling mill according to the invention and the second hot rolling mill, preferably the distance between the cooling system and the second hot rolling mill being sufficient for the cooling system according to the invention and the second hot rolling mill to operate independently.

[0081] The invention also relates to a method for hot rolling aluminum alloys comprising the successive steps of a. supplying a rolling plate of optionally plated aluminum alloy at a hot rolling inlet temperature, b. carrying out a plurality of hot rolling and / or cooling passes with the reversible hot rolling mill according to the invention, the cooling system being used at least once, c. transferring the blank (11) or the finished product in the form of sheet or strip at a hot rolling outlet temperature for the continuation of the hot transformation process.

[0082] The minimum width of the blank (11) can typically take the values ​​of 100mm, 200mm, 300mm, 400mm, 500mm, 700mm, 800mm, 900mm and 1000mm. The maximum width of the blank (11) can typically take the values ​​of 1500mm, 2000mm, 2500mm, 3000mm, 3500mm, 4000mm, 4500mm and 5000mm.

[0083] The minimum thickness of the blank (11) can typically take the values ​​of 5mm, 6.35mm, 10mm, 12mm, 12.7mm, 15mm, 20mm, 30mm, 40mm, 50mm, 60mm, 70mm, 80mm, 90mm 100mm, 110mm 120mm, 130mm, 150mm, 200mm and 250mm. The maximum thickness of the blank (11), which is typically close to that of the cast plate, can typically take the values ​​of 300mm, 350mm, 400mm, 450mm, 500mm, 550mm, 600mm, 650mm, 700mm and 800mm.

[0084] The minimum length of the blank (11) can typically take the values ​​of 2m, 3m, 4m, 5m. The maximum length of the blank (11) can typically take the values ​​of 6m, 7m, 8m, 9m 10m, 15m, 20m, 30m, 40m, 50m, 75m, 100m, 150m, 200m, 300m, 400m. Two constraints act to limit the maximum length of the blank (11). The first is the quantity of metal in the rolling plate before the start of hot rolling. The order of magnitude of the maximum length in this case will be the length of the plate before the start of hot rolling divided by the thickness of the blank at the end of hot rolling multiplied by the thickness of the plate before the start of hot rolling. The second limitation of the length of the blank depends on the industrial plant in which the hot rolling mill is installed.For non-limiting example, if the industrial installation consists of a reversible hot rolling mill followed by a tandem hot rolling mill or a second reversible hot rolling mill, the maximum length is imposed by the distance between the reversible rolling mill according to the invention and the tandem rolling mill or the second reversible hot rolling mill. This implies that all the configurations of lengths, thicknesses, before and after hot rolling listed above may not all be feasible depending on the industrial installation.

[0085] The plate is supplied at hot rolling inlet temperature. It may have been reheated and / or homogenized.

[0086] The reversible hot rolling mill according to the invention performs a plurality of hot rolling and / or cooling passes with the hot rolling mill. There may therefore be cooling passes without rolling, therefore without reducing the thickness of the blank. This function is advantageous because it makes it possible to increase the cooling capacity of the cooling system if necessary. There may also be rolling passes without cooling, but the method according to the invention comprises at least one pass with cooling with the cooling system according to the invention. Since the plate is supplied at the hot rolling inlet temperature, there is preferably no cooling before the first rolling pass.Operations such as cutting ends, stranding, cutting the blank into several smaller blanks, holding the blank, rotating the blank to change the hot rolling orientation of the blank (11) or the plate are usual operations during hot rolling. The examples of the steps mentioned are not limiting. The presence of said usual operations is not an interruption of the hot rolling and does not limit the scope of the invention because they are part of the usual hot rolling operations.

[0087] The blank is then transferred to a hot rolling outlet temperature of the reversible rolling mill according to the invention. The hot rolling outlet temperature is preferably at least 200°C, preferably at least 220°C, more preferably at least 240°C and preferably at least 260°C. This hot rolling outlet temperature is a temperature compatible with carrying out a second hot rolling. The blank (11) can be transferred to any usual step on a hot train: hot tandem rolling mill, second hot reversible rolling mill, hot coiling or hot cutting.

[0088] Preferably, the blank comprises an aluminum alloy of the AA6xxx, AA5xxx, AA7xxx, AA3xxx, AA2xxx series. Preferably, the blank comprises an alloy chosen from AA3003, AA3004, AA3207, AA3104, AA4017, AA4025, AA5006, AA5052, AA5083, AA5086, AA5088, AA5154, AA5182, AA5251, AA5383, AA5754, AA5844, AA6005, AA6009, AA6013, AA6014, AA6016, AA6022, AA6056, AA6061, AA6111, AA6181, AA6216, AA6316, AA6451, AA6501, AA6502, AA6603, AA6605, AA6607, AA7072 AA7075, and an alloy of composition, in % by weight, Si<0.5, preferably <0.3, Fe<0.7, preferably <0.3, Mn <1.9, preferably 1-1.5, Cu<1.5, preferably 0.5-1, preferably 0.5-0.8, Ti<0.15, preferably <0.1, Mg <0.5, preferably <0.3, preferably <0.05, remainder in aluminum and the inevitable impurities 0.05 maximum each and 0.15 their totality.Optionally, the blank is plated on one or both sides with one or more aluminum alloys of the AA1xxx, AA4xxx or AA7xxxx series, and preferably AA4004, AA4104, AA4045, AA4343, AA7072.

[0089] Preferably, the heterogeneity of the surface temperature of the blank (11) after its release from the grip of the rolling mill and the cooling device is less than 20°C and preferably less than 10°C. This characteristic, obtained thanks to the cooling system according to the invention, is useful for improving the repeatability of the metallurgical properties of the products. The heterogeneity of the blank (11) is defined as the difference between the temperature of the hottest point of the blank (11) with the temperature of the coldest point of the blank (11) except on the edges (111) and / or except on the ends (112) and alternatively as the difference between the temperature of the hottest point of the blank (11) with the temperature of the coldest point of the blank (11).

[0090] With a hot rolling mill which is not equipped with the invention, the edges (111) are naturally colder than the rest of the blank (11) given the heat exchange surface of the edge (1111). The lower temperature of the edges (111) is a cause of cracks or fissures on the edges which reduce the useful width of the blank or which can cause it to break. The edges (111) of the blank (11) are therefore preferentially less cooled than the rest of the blank by spraying the edges less than the rest of the blank (11). Preferably, the nozzles (35) and (45) whose jets (36) and (46) could spray the edges (111) are closed so as not to spray said edges (111). figures 11a And 11b show a non-limiting example with a section along a plane perpendicular to the direction S passing through the upper (30) and lower (40) ramps. Certain upper (35) and lower (45) nozzles are closed so as not to water the banks (111).

[0091] With a hot rolling mill that is not equipped with the invention, the ends (112) are naturally cooler than the rest of the blank (11) given the additional heat exchange surface at the ends. The lower temperature of the ends (112) is a cause of refusal of engagement of the blank during hot rolling. With a rolling mill that is equipped with the invention, the ends (112) are therefore preferentially less cooled than the rest of the blank by spraying the ends (112) less than the rest of the blank (11). Preferably, the nozzles (35) and (45) whose jets (36) and (46) could spray the ends (112) are closed when these ends pass. This function is preferably achieved by individually supplying each nozzle (35) and (45) by a fast response valve (49) whose response time is advantageously less than 1 s, preferably less than 0.5s, and more preferably less than 0.2s. The fast response valves (49) are illustrated by the non-limiting example of . figures 5a et 5b . Therefore in one embodiment, the intersection between the upper surfaces (51) sprayed directly by the jets of cooling fluids (36) with the upper face of the ends (112) is preferably empty throughout the duration of the hot rolling. Therefore in one embodiment, the intersection between the lower surfaces (61) sprayed directly by the jets of cooling fluids (46) with the lower face of the ends (112) is preferably empty throughout the duration of the hot rolling.

[0092] The coolant is preferably in heating on the blank. Heating is a thin layer of vapor that appears between a fluid on a surface whose temperature is sufficiently high (Leidenfrost effect). This is advantageous because it ensures a homogeneous heat exchange compared to the situation where there are areas of the surface on which the fluid is not heating.

[0093] Preferably, a thermal model calculates the watering width and chooses the cooling mode at the ends (112), preferably the thermal model pre-regulates the hydraulic system which supplies the ramps (30) and (40), then at each pass the thermal model compares the desired temperature with the calculated or measured temperature of the blank (11), and the thermal model controls the valves (49) of the nozzles (35) and (45) according to the position of the blank (11), preferably the thermal model manages the upper nozzles (35) and lower nozzles (45) differently.

[0094] Preferably, the principle of the control of the cooling system is as shown diagrammatically in figure 16. A thermal model coded on a computer or an automaton calculates the watering width corresponding to the width of the blank. Preferably the watering width excludes the edges (111) to cool them as little as possible to reduce defects such as edge cracks. The thermal model chooses the cooling mode at the ends (112). Preferably, the ends (112) are not watered to cool them as little as possible to facilitate engagement in the hot rolling mill and reduce the crocodiling phenomenon. Preferably, the model defines a pre-setting of the hydraulic system which supplies the ramps (30) and (40) so that the jets of cooling fluid (36) and (46) are established quickly as soon as the valves (49) are opened.Then, at each pass, the thermal model compares the desired temperature with the calculated or measured temperature of the blank (11). The measured temperature can be obtained, for example, but not limited to, by a surface temperature measurement by non-contact infrared pyrometry or by a contact measurement on the surface of the blank (11). The calculated temperature can be either a surface temperature or an average temperature. The calculated temperature can be calculated with thermal simulation software, for example, but not limited to MSC Marc. With the comparison between the desired temperature and the temperature of the blank (11), the thermal model controls the valves (49) of the nozzles (35) and (45) using the position and dimensions of the blank (11). The position of the blank (11) can be calculated or measured.In the absence of a blank (11) between the upper and lower devices of the cooling system, the nozzles (35) and (45) are not supplied to avoid, for example but not limited to, the jets (46) of the lower nozzles (45) spraying the upper cylinder (21) or the jets (36) of the upper nozzles (36) spraying the lower cylinder (22). The maximum heterogeneity of the surface temperature of the blank (11), preferably of the blank (11) except on the edges (111) and / or on the ends (112), after its release from the grip of the rolling mill and the cooling device may be less than 20°C and preferably less than 10°C. Preferably, the thermal model manages the upper nozzles (35) and the lower nozzles (45) differently in order to avoid the formation of bridges or boats of the roughing (11).Preferably, the absolute value of the temperature difference between the upper face and the lower face of the blank (11) is less than 10°C, more preferably 7°C, more preferably 5°C, more preferably 2°C. More preferably, the temperature of the upper face of the blank (11) is substantially equal to the temperature of the lower face of the blank (11).

[0095] The maximum heterogeneity level of temperature of the blank (11) desired with or without the edges (111) and or the ends (112), the desired temperature are metallurgical choices which depend on the products to be produced. Preferably the control of the cooling system is integrated into the control system of the reversible hot rolling mill which controls the rolling parameters.

[0096] Preferably, the thermal device does not cool the surface of the blank (11) below the Leidenfrost temperature of the cooling fluid. The Leidenfrost temperature is the temperature above which the cooling fluid is heating. The Leidenfrost temperature of the cooling liquid sprayed onto the blank depends on the nature of the cooling liquid and its surface flow rate. The value of this temperature is typically and approximately about 300°C for the typical cooling fluid, an emulsion of oil and rolling additives, which is lower than the usual hot rolling temperatures on a reversible rolling mill. The cooling system can cause a high temperature heterogeneity between the surface and the core of the blank (11).By watering the blank (11) for too long or too intensely, the surface temperature of the blank (11) is likely to be momentarily lower than the Leidenfrost temperature, which would significantly increase the risk of loss of thermal control in average value and homogeneity of the blank (11) thus cooled. The thermal model therefore checks at each pass that the watering planned for the following pass does not risk generating a blank temperature lower than the Leidenfrost temperature.

[0097] Preferably, the typical average cooling rate V of the average temperature of the blank (11) during the passage of the blank (11) between the upper (52) and lower (62) convex envelopes is of the order of V= C / e, where V is in °C / s, e is the thickness of the blank in mm, and C is a constant value which is between 400 and 1000°C / s*mm, preferably between 600 and 900°C / s*mm, more preferably between 700 and 800°C / s*mm. The formula V=C / e is an approximation which requires in particular that the surface of the blank (11) remains above the Leidenfrost temperature. The decrease in the average temperature DT in degrees °C of the blank (11) after having passed through the upper (52) and lower (62) convex envelopes of the cooling system is typically of the order DT = C / e*d, d being the duration of passage of a point of the blank (11) between said convex envelopes, the speed of the blank (11) being constant.This formula is an approximation which requires in particular that the surface of the blank (11) remains above the Leidenfrost temperature. Preferably, the thickness range of the blank (11) for the application of said formulas has a minimum of 25mm, preferably 50, preferably 75mm, preferably 100mm, preferably 110mm and a maximum of 200mm, preferably 175mm, preferably 150mm, preferably 140mm, preferably 130mm, preferably 125mm, preferably 120mm.

[0098] In a preferred embodiment, the cycle time for hot rolling a blank (11) made of AA6xxx alloy, preferably of AA6016 alloy, is reduced by at least 30 seconds, preferably by at least 60 seconds, more preferably by at least 90 seconds with the method according to the invention, compared to rolling without the aid of said method. In a preferred embodiment, the cycle time for hot rolling a blank (11) made of AA5182 alloy is preferably reduced by at least 15 seconds, preferably by 20 seconds, more preferably by 45 seconds compared to rolling without the aid of said method. The cycle time is the duration between the start of the first pass and the end of the last pass of hot rolling with the reversible hot rolling mill of the invention.

[0099] In another preferred embodiment, the cooling system is preferably used only once so as to reduce the average temperature of the blank by at least 50°C to an average temperature above 400°C, in less than 10 seconds, preferably in less than 8 seconds for a blank (11) with a thickness of at most 114 mm.

[0100] In one embodiment, the cooling system allows the temperature of the blank (11) to be controlled over a predefined thermal path during hot rolling. The thermal path is the evolution of the temperature of the blank (11) during the duration of hot rolling. The thermal path is a metallurgical choice that depends on the alloy, the desired properties of the finished product and the capabilities of the hot rolling mill.

[0101] In a preferred embodiment, the cooling system allows the blank (11) to be controlled on an isothermal thermal path. A thermal path is isothermal if the temperature of the blank (11) during hot rolling does not vary by plus or minus 10°C relative to the temperature of the plate just before the start of hot rolling. Preferably, the temperature of the blank (11) remains substantially equal to the temperature of the plate before the start of hot rolling. Detailed description of certain embodiments

[0102] In a first embodiment illustrated by the Figure 6, for each cooling system, the upper sprayed convex envelope (52) and the lower sprayed convex envelope (62) are close to the rolling mill rolls; preferably the maximum distances D55 and D65 to the rolls (21) and (22) of the sprayed convex envelopes (52) and (62) along the direction S are less than 3 times the largest of the diameters of the working rolls (21) and (22) and / or the lengths D56 and D66 along the direction S of said convex envelopes (52, 62) are less than a diameter of the largest of the working rolls (21) or (22). Preferably, the convex envelopes (52, 62) are substantially opposite each other. This embodiment is advantageous because it allows the blank (11) to be cooled as soon as it leaves the grip of the cylinders (21) and (22).This is particularly advantageous because the speed of reversible hot rolling mills is often limited to avoid heating of the blank (11) which results in burning or even breaking of the blank (11). This is particularly advantageous because it improves the productivity of the hot rolling mill. Indeed, the speed of reversible hot rolling mills is often limited to avoid heating which results in burning or even breaking of the blank (11).

[0103] In this first embodiment, there is preferably a second cooling system on the other side of said hot reversible rolling mill, the Figure 7is a non-limiting example. The second cooling system is preferably symmetrical to the first with respect to a plane passing through the axes of the working rolls (21) and (22). This arrangement is advantageous because it allows the blank (11) to be cooled until it enters the grip and as soon as it leaves the grip of the reversible rolling mill at each rolling pass and in an identical manner.

[0104] This system is advantageous because it allows better control of the temperature of the blank during its reversible rolling and this at each pass, which is beneficial for the metallurgical quality of the product and for the productivity of said reversible rolling mill.

[0105] Other non-limiting examples of the first embodiment are given by the Figure 9 and the Figure 10 .

[0106] In the first preferred embodiment, the cycle time of the hot rolling of the blank (11) is preferably reduced by at least 30 seconds for the AA6xxx alloys, preferably for the AA6016 alloy, preferably by 60s, more preferably by 90s.

[0107] In the first preferred embodiment, the cycle time of the hot rolling of the blank (11) is preferably reduced by at least 15 seconds for the AA5182 alloy, preferably by 20 s, more preferably by 45 s.

[0108] A second embodiment is a cooling system for rapidly cooling a blank (11) during hot rolling.

[0109] This embodiment is designed to water each point of the blank (11) for 10 seconds, preferably 8 seconds. Those skilled in the art will know how to adapt the characteristics below to their particular rolling mill and to the speed of the blank (11).

[0110] In a preferred embodiment of the second preferred embodiment, illustrated in a non-limiting manner by the figure 13, the upper cooling device comprises at least one pair of ramps (303 and 304) of nozzles (353, 354), preferably 3 pairs of ramps (303 and 304), in each pair of ramps (303 and 304), the jets of cooling fluid (363, 364) being oriented in opposition, the difference β - α / 2 being positive or zero, preferably zero, the sprayed surfaces (513, 514) of the blank (11) by the jets (363, 364) preferably overlapping by a factor between 1 / 3 and 2 / 3, preferably 1 / 2, and the lower cooling device comprising at least 1 ramp (40) of nozzles (45), preferably 8 ramps (40), the jets of cooling fluid (46) of which are conical and with an axis substantially perpendicular to the blank (11). The angle β is the angle that the axis of the nozzles (353, 354) makes with the line V perpendicular to the upper face of the blank (11). The angle α is the angle of the cone of the jet of cooling fluid produced by said nozzles.These angles are shown diagrammatically on the . Figure 5a with the ramps (30), the nozzles (35) and the jets (36). This configuration is interesting because it causes the cooling fluid to concentrate in at least part of the overlap zone of the jets (36) and thus to reject the cooling fluid on the edges with enough speed so as not to trickle towards the ends of the blank (11), which makes it possible to cool uniformly the entire length of the blank. This system also makes it possible to reduce the energy consumption of the devices (38) for discharging the cooling fluid or even to be able to eliminate them.

[0111] In another preferred embodiment of the second preferred embodiment, illustrated in a non-limiting manner by the Figure 12 or the figure 14, the upper cooling device comprises at least 1 ramp (30) of nozzles (35), preferably 6 ramps, and the lower cooling device comprises at least 1 ramp of nozzles (45), preferably 8 ramps, all producing conical jets of cooling fluid (36) and (46) whose axes are substantially normal to the blank (11), and whose angle α of the cone of the jets (36) is less than 20°, preferably the angle of the cone of the jets (36) is substantially 15°. This device has the advantage of being simpler to construct. The angle α of the conical jets of less than 20°, preferably substantially 15°, makes it possible to limit the horizontal component of the speed of the cooling fluid during its impact on the blank (11), and consequently to limit the runoff of the cooling fluid on the blank (11) to control its cooling.

[0112] In the second preferred embodiment, the cooling system is preferably used only once so as to reduce the average temperature of the blank (11) by at least 50°C to an average temperature above 400°C, in less than 10 seconds, preferably in less than 8 seconds for a blank (11) with a thickness of at most 114 mm as shown in figure 19 .

[0113] In another embodiment, it is possible to cool the blank (11) further, for example by making two passes under the cooling system.

[0114] In another embodiment, it is possible to cool a thicker blank by 50°C by reducing the speed of passage of the blank (11) or by increasing the length of the sprayed surfaces (51) and (61). For non-limiting example, a 140mm blank (11) can be cooled by 50°C in at least 15 seconds, preferably at least 10 seconds as shown in figure 20.

[0115] In another embodiment, the typical average cooling rate V of the average temperature of the blank (11) during the passage of the blank (11) between the upper (52) and lower (62) convex envelopes is of the order of V= C / e, where V is in °C / s, e is the thickness of the blank in mm, and C is a constant value which is between 400 and 1000, preferably between 600 and 900, more preferably between 700 and 800. The formula V=C / e is an approximation which requires in particular that the surface of the blank (11) remains above the Leidenfrost temperature. The decrease in the average temperature DT in degrees °C of the blank (11) after having passed through the upper (52) and lower (62) convex envelopes of the cooling system is typically of the order DT = C / e*d, d being the duration of passage of a point of the blank (11) between said convex envelopes, the speed of the blank (11) being constant.This formula is an approximation which requires in particular that the surface of the blank (11) remains above the Leidenfrost temperature. Preferably, the thickness range of the blank (11) for the application of said formulas has a minimum of 25mm, preferably 50, preferably 75mm, preferably 100mm, preferably 110mm and a maximum of 200mm, preferably 175mm, preferably 150mm, preferably 140mm, preferably 130mm, preferably 125mm, preferably 120mm.

[0116] A third preferred embodiment is a method of rolling an AA6xxx series aluminum alloy comprising the steps: a. casting a rolling slab of AA6xxx series alloy, b. homogenizing the rolling slab, optionally followed by reheating, c. first hot rolling to transform the rolling slab into a blank having a first output thickness from a first hot rolling start temperature, d. cooling the blank thus obtained with a typical average cooling rate from the average temperature of the blank of the order of V= C / e to a second hot rolling start temperature, where V is in °C / s, e is the thickness of the blank in mm, and C is a constant value which is between 400 and 1000°C / s*mm, preferably between 600 and 900°C / s*mm, more preferably between 700 and 800°C / s*mm, e.second hot rolling to transform the blank thus cooled into a strip at the final hot rolling thickness under deformation and temperature conditions such that the strip is recrystallized to at least 50%, f. cold rolling of the strip into a thin sheet.

[0117] The first hot rolling and cooling are preferably carried out with a reversible hot rolling mill according to the invention. During the cooling of step d, the cooling system is preferably used only once so as to preferably reduce the average temperature with a typical average cooling rate from the average temperature of the blank of at least 50°C to an average temperature above 400°C. Preferably, the thickness range of the blank during this cooling has a minimum of 25mm, preferably 50mm, preferably 75mm, preferably 100mm, preferably 110mm and a maximum of 200mm, preferably 175mm, preferably 150mm, preferably 140mm, preferably 130mm, preferably 125mm, preferably 120mm.

[0118] In an embodiment of the third preferred embodiment, during the cooling of step d the cooling system is preferably used only once so as to reduce the average temperature of the blank by at least 50°C to an average temperature greater than 400°C, in less than 10 seconds, preferably in less than 8 seconds for a blank (11) with a thickness of at most 114 mm.

[0119] The inventors surprisingly found that this process makes it possible to improve productivity while maintaining mechanical properties, surface quality and corrosion resistance at least equal to those obtained without the process according to the invention. These products can be particularly useful in the automotive industry, in particular for producing exterior body parts.

[0120] In the third preferred embodiment, among the AA6xxx series alloys, the preferred alloys are AA6005, AA6009, AA6013, AA6014, AA6016, AA6022, AA6056, AA6061, AA6111, AA6181, AA6216, AA6316, AA6451, AA6501, AA6502, AA6603, AA6605, AA6607.

[0121] In an embodiment of the third preferred embodiment, the composition of the AA6xxx series alloy plate is an alloy comprising in % by weight: Si: 0.5 - 0.8; Mg: 0.3 - 0.8; Cu: maximum 0.3; Mn: maximum 0.3; Fe maximum 0.5; Ti: maximum 0.15, remainder in aluminum and the inevitable impurities 0.05 maximum each and 0.15 their totality, and preferably Si: 0.6 - 0.75; Mg: 0.5 - 0.6; Cu: maximum 0.1; Mn maximum 0.1; Fe 0.1- 0.25; Ti: maximum 0.05, remainder in aluminum and the inevitable impurities 0.05 maximum each and 0.15 their totality.

[0122] In another embodiment of the third preferred embodiment the composition of the AA6xxx series alloy plate is an alloy comprising in % by weight: Si 0.7 - 1.3; Mg: 0.1- 0.8; Cu: maximum 0.3; Mn: maximum 0.3; Fe maximum 0.5; Ti: maximum 0.15, remainder in aluminum and the inevitable impurities 0.05 maximum each and 0.15 their totality, and preferably Si: 0.8 - 1.1; Mg: 0.2 - 0.6; Cu: maximum 0.1; Mn maximum 0.2; Fe 0.1 - 0.4; Ti: maximum 0.1, remainder in aluminum and the inevitable impurities 0.05 maximum each and 0.15 their totality.

[0123] After casting, the plate is preferably homogenized at a temperature between 500 and 570°C, and preferably between 540 and 560°C, typically for a period of at least 4 hours, and preferably for at least 8 hours. In a preferred embodiment, the maximum homogenization temperature is at most 555°C. The homogenization can be in one step or in several steps with increasing temperatures to reduce the risk of burning.

[0124] In the third preferred embodiment, the plate is then rolled into a blank during a first hot rolling on a reversing mill. The starting rolling temperature of the first hot rolling is preferably above 470°C, more preferably above 490°C, and even more preferably above 500°C. Preferably, during this first hot rolling, the temperature is maintained above 450°C, preferably above 470°C and more preferably above 490°C. Preferably, the first output thickness is between 90mm and 140mm, preferably between 100 and 130mm, and more preferably between 110mm and 120mm.

[0125] This roughing thickness is particularly useful in factories whose hot rolling train consists of two successive reversible hot rolling mills and optionally a hot tandem rolling mill. In fact, this roughing thickness corresponds to the thickness of the roughing when it is transferred between the first reversible rolling mill and the second reversible rolling mill. Cooling can then be done without any loss of time.

[0126] The blank is then cooled at a cooling rate of at least 5°C / s from the average temperature of the blank to a second temperature at the start of the second hot rolling. Advantageously, the first hot rolling and the cooling are carried out with a reversible hot rolling mill according to the invention, as illustrated in particular by the figures 12 to 15 .

[0127] After cooling, the blank is rolled with a second hot rolling into a strip. The second hot rolling may be carried out successively on several hot rolling mills, for example a second reversing hot rolling mill followed by a tandem rolling mill or on the reversing hot rolling mill used for the first hot rolling followed by a tandem rolling mill. Preferably, the start temperature of the second hot rolling is between 380 and 450°C, more preferably between 400 and 440°C, and most preferably between 420 and 435°C. The strip is rolled to a final hot rolling thickness under conditions such that the strip after cooling is recrystallized to at least 50%, preferably at least 80%, and more preferably at least 90%, and particularly preferably at least 98%.A recrystallization of at least 50%, 80%, 90% and 98% respectively means that the recrystallization rate measured across the thickness and in at least 3 points across the width is at least 50%, 80%, 90% and 98% respectively. Typically, recrystallization varies across the thickness and may be complete at the surface and incomplete at mid-thickness. The preferred recrystallization rate depends on the strip alloy.

[0128] To obtain said recrystallization, it is advantageous for the exit temperature of the second hot rolling to be at least 345°C, preferably at least 350°C and more preferably at least 355°C. The reduction in thickness during the last pass of the second rolling is a parameter to ensure recrystallization. Said reduction in the last pass of the second hot rolling is at least 25%, preferably at least 30%, preferably 40%, and more preferably at least 45%. The typical thickness of the strip obtained with the second hot rolling is between 4 and 10mm.

[0129] The strip is then cold rolled into a thin sheet. With the method of the invention, it is not necessary to perform annealing and / or solution treatment between hot rolling and cold rolling or during cold rolling to obtain the mechanical, formability, surface condition or corrosion properties. Preferably, annealing and / or solution treatment is not performed between hot rolling and cold rolling or during cold rolling. The thin sheet has a thickness typically between 0.5 and 2 mm. In a preferred embodiment, the reduction by cold rolling is between 70% and 80%. In another preferred embodiment, the reduction rate between the strip and the thin sheet is at least 80% to obtain the most advantageous surface quality.

[0130] Preferably, after step f, an additional step g can be carried out: solution treatment and quenching of the thin sheet thus obtained in a continuous heat treatment furnace.

[0131] Said continuous heat treatment furnace preferably operates in such a way that the holding time equivalent to 560°C, t eq 560 ° is less than 30 s, preferably less than 25 s and more preferably less than 20 s, the equivalent holding time being calculated using the equation t eq 560 ° = ∫ temps dans le four exp − Q R . 1 T ° C t + 273 − 1 560 + 273 . dt Q being an activation energy of 200 kJ / mol and R = 8.314 J / mol / K

[0132] Preferably, after the solution treatment and quenching, pre-tempering is optionally carried out, and the mature thin sheet at room temperature, so as to reach the T4 metallurgical state, is cut and shaped until its final shape is obtained, is painted and hardened by baking.

[0133] The thin sheet, after solution treatment in a continuous heat treatment furnace operating in such a way that the holding time is equivalent to 560°C, t eq 560 ° , is less than 20 s, the equivalent holding time being calculated using the equation t eq 560 ° = ∫ temps dans le four exp − Q R . 1 T ° C t + 273 − 1 560 + 273 . dt

[0134] Q being an activation energy of 200 kJ / mol and R = 8.314 J / mol / K, achieves a tensile strength of at least 90% and preferably at least 95% of the maximum tensile strength obtained after solution treatment with a holding time equivalent to 560°C, t eq 560 ° , from 98s.

[0135] Thin sheet metal from cold rolling is particularly advantageous if only because it is easy to process by solution treatment. Conventional processes aimed at obtaining a good surface finish, compatible with a quality for exterior bodywork sheets, generally include an additional heat treatment during the processing process compared to the sheet metal obtained according to the invention. The presence of this additional heat treatment means that the person skilled in the art needs to use high temperatures and long equivalent holding times on solution treatment lines with continuous annealing in order to obtain sufficiently high mechanical strengths in the metallurgical states as supplied and with the paints after baking.On the contrary, the cold-rolled thin sheet of the invention may use solution treatment in a continuous annealing line operated in such a way that the holding time equivalent to 560°C, . t eq 560 ° , is short, typically less than 25s, the equivalent holding time being calculated using the equation t eq 560 ° = ∫ temps dans le four exp − Q R . 1 T ° C t + 273 − 1 560 + 273 . dt Q being an activation energy of 200 kJ / mol and R = 8.314 J / mol / K.

[0136] Generally, the continuous annealing line operates in such a way that the heating rate of the thin sheet is greater than or equal to 10°C / s for a metal temperature below 400°C, the time spent above 530°C is between 15s and 90s, and the quenching rate is greater than or equal to 10°C / s, preferably greater than or equal to 15°C / s for a thickness of 0.9 to 1.1mm. The solution treatment causes the metal to reach a temperature lower than but close to the solidus temperature, namely generally greater than 530°C and less than 570°C. The coiling temperature after the solution treatment is preferably between 50°C and 90°C, and preferably between 60°C and 80°C.

[0137] After solution treatment and quenching, the thin sheet can age to reach the T4 metallurgical state, before being cut and shaped to its final geometry, painted and hardened by baking.

[0138] The method of the invention is particularly useful for the manufacture of thin sheets intended for the automotive industry which combine a high tensile yield strength and formability suitable for cold stamping operations, as well as excellent surface quality on the part and high corrosion resistance with high productivity.

[0139] In a fourth preferred embodiment, the hot rolling mill combines the first preferred embodiment and the second embodiment.

[0140] A non-limiting example is given in Figure 15The hot rolling mill is surrounded by cooling systems that improve productivity. A third cooling system allows rapid cooling during transfer to the hot rolling process. This fourth embodiment combines the productivity gain on the reversible hot rolling mill, rapid cooling without impact on productivity during transfer to the rolling process, the whole making it possible to supply AA6xxx alloy sheets with good surface quality and improving the productivity of the solution treatment and quenching lines. Examples Example 1:

[0141] A reversible hot rolling mill according to the invention illustrated by the Figure 7comprises two cooling systems installed on either side of working rolls in a symmetrical manner. Each of these two cooling systems is composed of an upper cooling device and a lower cooling device. The upper cooling device comprises a ramp (30) of nozzles (35) oriented towards the roll (21). Each upper ramp of nozzles is protected by a protective piece (37). The lower cooling device comprises two ramps (40) of lower nozzles (45) installed below the plane of the axes of the rolls (23); a first ramp (40) between the first roll (23) from the roll (22) and the second roll (23), and the second ramp (40) of nozzles (45) between the second and third rolls (23). The rolls (23) are sufficiently close so as not to require the installation of a protective piece (47). The nozzles (35) and (45) produce full conical jets by spraying.The nozzles (45) produce conical jets which are almost tangent to the rollers (23). The nozzles (35) and (45) are supplied by fast response valves whose response time is 0.2s. The convex envelope of the upper sprayed surface is substantially opposite the convex envelope of the lower sprayed surface. Said convex envelopes are less than 3 diameters from the largest of the two working rolls of the hot reversible rolling mill. The average surface flow rate per surface is approximately 1200 l / min / m 2 < . The cooling fluid is the rolling mill emulsion which is used to lubricate the blank (11) during its hot rolling. The cooling fluid is heating on the surface of the blank (11).

[0142] A 500mm thick plate was hot rolled with cooling according to the invention at each hot rolling pass. Figure 18shows the thermal field on the upper surface of a 2000 mm wide, 50 mm thick and 5000 mm long AA6016 alloy blank, just after the last reversible hot rolling pass. The surface temperature heterogeneity of the blank, including the edges and ends, is 10°C both along the length and width.

[0143] An identical plate of the same alloy was also hot rolled but without the use of the cooling system of the invention. Figure 17 shows the thermal field on the upper surface of the blank obtained with the same dimensions as that presented in Figure 18 just after the last reversible hot rolling pass. The heterogeneity of the surface temperature of the blank is 25°C both in the length and in the width in the absence of the use of the cooling system of the invention.

[0144] In addition to the significant improvement in the thermal uniformity of the blank using the invention compared to practice without using the invention, cooling the blank during the rolling flow allows the reversible hot rolling cycle time to be reduced by 90 seconds.

[0145] Two AA5182 alloy plates, 1480mm wide and 510mm thick, were hot rolled with the invention, the first with the invention and the second without the invention. The hot rolling cycle time of the first plate was 64s shorter than the second. Example 2:

[0146] A hot rolling mill according to the invention comprising working rolls (21, 22) and a cooling system having six upper ramps (30) of nozzles (35) and eight lower ramps (40) of nozzles (45) is shown in the figure 14. It is part of a hot train comprising a second reversible rolling mill comprising working rolls (25, 26). These two reversible hot rolling mills are part of a hot train additionally comprising a hot tandem rolling mill. The nozzles of the upper ramps (35) are oriented perpendicular to the plane of the blank (11). The jets of the upper nozzles (36) are full conical with a cone angle of substantially 15°. The cooling fluid is the emulsion used for lubricating the working rolls during hot rolling. The nozzles (45) of the lower ramps (40) are oriented perpendicular to the underside of the blank (11). The jets of the lower nozzles are full conical with a cone angle of substantially 90°. The sprayed surfaces (52) and (62) are substantially opposite each other.

[0147] The system is capable of cooling a 114mm thick sheet from a temperature of 470°C to an average temperature of 420°C in 8 seconds as shown in the graph of the figure 19obtained by numerical simulation. 20 seconds after the start of cooling, the heterogeneity in the thickness of the blank is about 9°C, and 30s after the start of cooling, the heterogeneity in the thickness of the blank is about 2°C. In Table 1, examples D and E, which are 114 and 109mm blanks made of AA6xxx series alloy, were cooled with the system without any special adjustment to have hotter edges or ends. The temperatures mentioned in Table 1 are measurements taken on the surface of the blanks. Given the transfer time of more than 30 s between the first hot reversing mill and the cooling system and between the cooling system and the second hot reversing mill, the surface temperatures of blanks D and E are representative of the average temperature of said blanks as well as the core temperatures. Sheets D and E were therefore cooled to 57 and 75°C. Table 1 A B C D E Reference Example A Reference Example B Reference Example C Example D according to the invention- Example E according to the invention- Composition (% by weight) If 0.66 0.67 0.70 0.69 0.69 Fe 0.14 0.15 0.14 0.15 0.15 Cu 0.01 0.01 0.01 0.01 0.01 Mn 0.08 0.07 0.09 0.07 0.07 Mg 0.64 0.64 0.52 0.54 0.56 Cr 0.01 0.01 0.01 0.01 0.01 You 0.03 0.04 0.05 0.05 0.04 Heat treatment of the plate homogenization 6.5h 554°C 6.7h 554°C 30h 554°C 8 p.m. 554°C 4 p.m. 554°C cooling N / A N / A room temperature N / A N / A reheating N / A N / A at rolling temperature N / A N / A First hot rolling rolling start temperature (°C) 554 553 393 511 537 Final thickness (mm) 114 114 114 114 109 end of rolling temperature (°C) 524 523 360 481 507 cooling cooling rate N / A N / A N / A 5°C / s 5°C / s second hot rolling rolling start temperature (°C) 519 519 356 424 432 Final hot rolling thickness (mm) 3.05 3.05 6.35 5.08 5.08 reduction to the last hot pass 41% 39% 44% 47% 47% winding temperature (°C) 332 327 343 352 357 Cold rolling cold reduction (%) 73.7 73.8 85.0 81.3 81.3 final thickness (mm) 0.8 0.8 0.95 0.95 0.95

[0148] Five plates whose compositions are given in Table 1 in % by weight were cast. Table 1 also details the transformation process. Columns A and B describe a plate and its transformation steps into a blank then into a strip then into a thin sheet to produce internal bodywork elements which do not have any surface quality requirements. Column C describes a plate and its typical transformation steps into a blank then into a strip then into a thin sheet to produce external bodywork elements which have high surface quality requirements. These are reference examples in which no cooling is carried out during hot rolling. Columns D and E are examples of the invention.

[0149] The 5 plates A, BCD and E were homogenized with the conditions in Table 1. Plates A, B, D and E were transferred to the first reversing hot rolling mill. Plate C was cooled to room temperature and then reheated to the starting temperature of the first hot rolling and transferred to the first reversing hot rolling mill. The 5 plates were hot rolled by the first hot rolling mill into a 114mm thick blank except for plate E which was rolled into a 109mm thick blank. The 5 blanks were then transferred to the second reversing hot rolling mill by passing through the cooling system of the first hot rolling mill. Blanks A, B and C passed through the cooling system without being sprayed, and only underwent natural air cooling during their transfer to the second reversing hot rolling mill.Blanks D and E passed through the cooling system in operation and were thus cooled to the surface temperature indicated in Table 1. The 5 blanks were then rolled with the second reversing hot rolling mill and then with a tandem hot rolling mill into a strip. Upon exiting the hot tandem rolling mill, the strips were coiled according to the characteristics in Table 1. After cooling, the 5 coils were cold rolled into thin sheets.

[0150] Samples of strips C, D and E were taken after the last hot rolling pass and before coiling. These samples were cooled rapidly by immersing them in a water tank at room temperature. Then recrystallization kinetics were carried out in the laboratory by heating each sample to different temperatures, then the samples are cooled in a manner similar to the cooling of a coil after hot rolling. Metallographies were then carried out ( figure 25 ) and the estimated recrystallization rate (Table 2). Table 2 Heating temperature 310°C 321°C 332°C 343°C 355°C 365°C C Example ref. 0% 75% 98% 100% 100% 100% D invention 0% 15% 33% 44% 95% 100% E invention 0% 6% 43% 94% 99% 100%

[0151] The quality of the roping surface condition was characterized on thin sheets A, B, D and E. The roping is measured as follows. A sample measuring approximately 270 mm (transverse to the rolling direction) by 50 mm (in the rolling direction) is cut from the thin sheet. A tensile pre-strain of 15%, perpendicular to the rolling direction, i.e. in the length of the sample, is then applied. The sample is then subjected to the action of P800 type abrasive paper in order to reveal the roping

[0152] The thin sheets D and E, produced according to the invention, have a surface quality suitable for producing external bodywork elements as shown in figure 23 for thin sheet D and the figure 24 for thin sheet E. This is not the case for thin sheets A and B as shown in figure 21 for thin sheet A and the figure 22for thin sheet B. The cooling system demonstrates its usefulness in obtaining surface quality with a more economical process by eliminating reheating as for thin sheet C, not specifically characterized in surface quality, which is used to produce external bodywork elements.

[0153] To evaluate the solution kinetics of the 3 thin sheets C, D and E, the following characterizations were carried out. Samples were taken after cold rolling to the final thickness on the 3 thin sheets C, D and E. Various solution heat treatments were first carried out on the samples by varying the solution times of the samples in a fluidized bed furnace at 570 °C. A long immersion period of 90 s at 570 °C was used to completely solution the samples. The duration of 90 s at 570 °C is equivalent to a duration of 98 s at 560 °C using the formula t eq 560 ° = ∫ temps dans le four exp − Q R ⋅ 1 T ° C t + 273 − 1 560 + 273 . dt Q being an activation energy of 200 kJ / mol and R = 8.314 J / mol / K.

[0154] Shorter solution hardening times in the fluidized bed furnace at 570 °C were used to achieve incomplete solution hardening of the alloys. These solution hardening heat treatments were all followed by water quenching to 80 °C and an 8-hour pre-tempering treatment at 80 °C. After these various solution hardening, then quenching, and then pre-tempering heat treatments, the samples were tempered for 2 hours at 205 °C in an oil bath to achieve the T6 metallurgical temper.

[0155] Tensile tests were then carried out. The yield strength (Rp0.2) obtained after the final tempering treatment in the T6 metallurgical state is used as an indicator of the solution treatment quality of the samples. Indeed, depending on the precipitation state existing in the thin sheets, the solution treatment time at the solution treatment temperature (here 570 °C) necessary to dissolve these precipitates varies. For productivity reasons on the production machines performing solution treatment, it is advantageous to keep the solution treatment time as short as possible.

[0156] The results of the tensile tests of the 3 thin sheets C, D and E are shown in Table 3 and on the figure 26 . In this graph, each measured yield point (T6YS) is normalized with the yield point obtained for the same thin sheet after a solution time of 90 seconds in the fluidized bed at 570 °C (T6YSmax).

[0157] There figure 26 shows that the solution kinetics of the two thin sheets D and E according to the invention is much faster than that of comparative example C. Indeed, after immersion for 50s in the fluidized bed at 570°C, the yield strength in the T6 state of examples D and E according to the invention reached more than 99% of its maximum yield strength in the T6 state, whereas comparative example C is just above 98% of its maximum yield strength in the T6 state.

[0158] Similarly, after a 30s dissolution in the fluidized bed at 570°C, the yield strength in the T6 state of examples D and E according to the invention reached more than 98% of its maximum yield strength in the T6 state, while comparative example C is at 96% of its maximum yield strength in the T6 state. Therefore, the invention also makes it possible to accelerate the productivity of the dissolution. Table 3 immersion time in the fluidized bed (s) at 570°C elastic limit (T6YS - MPa) Elastic limit at state T6 divided by maximum elastic limit at state T6 (T6YS / T6YS max) D invention 1 10 143 0.52 D invention 1 20 264 0.96 D invention 1 30 271 0.98 D invention 1 50 275 1.00 D invention 1 90 276 1.00 E Invention 2 10 134 0.49 E Invention 2 20 262 0.96 E Invention 2 30 271 0.99 E Invention 2 50 274 1.00 E Invention 2 90 274 1.00 C ref example 3 30 264 0.96 C ref example 3 50 271 0.98 C ref example 3 90 275 1.00

Claims

1. Hot reversible rolling mill comprising two working rolls, an upper working roll (21) and a lower working roll (22), and at least one cooling system for cooling a blank (11), said blank (11) moving on rollers (23) and passing through the hot reversible rolling mill between the two working rolls (21) and (22), said cooling system consisting of two cooling devices: an upper blank cooling device (11) and a lower blank cooling device (11) characterized in that: • the upper cooling device comprises at least one ramp (30) of nozzles (35) arranged substantially parallel to the axis of the upper working cylinder (21), the nozzles (35) spraying the upper face of the blank (11) with jets of cooling fluid (36), • the lower cooling device comprises at least one ramp (40) of nozzles (45) arranged between the rollers (23) or between the lower working cylinder (22) and the nearest roller (23), substantially parallel to the axis of the lower working cylinder (22), the nozzles (45) spraying the lower face of the blank (11) with jets of cooling fluid (46), the axis of the jets of cooling fluid (46) being oriented substantially perpendicular to the lower surface of the blank,• each nozzle (35) and (45) is fed individually by a fast response valve (49) • the upper sprayed convex envelope (52) and the lower sprayed convex envelope (62), are close to the rolling mill cylinders; the maximum distances D55 and D65, D55 being the maximum of the distance of any point of the convex envelope (52) with the line C1 which is the projection of the axis of rotation of the cylinder (21) on the upper surface, of the blank (11), reduced by the radius R1 of the cylinder (21), D65 being the maximum of the distance of any point of the convex envelope (62) with the line C2 which is the projection of the axis of the cylinder (22) on the lower surface, of the blank (11), reduced by the radius R2 of the cylinder (22), are less than 3 times the largest of the diameters of the working cylinders (21) and (22) and / or the lengths D56 and D66, D56 being the subtraction of the length D57 from the length D55, D66 being the subtraction of the length D67 from the length D65,said convex envelopes (52, 62) are less than two diameters, preferably one diameter of the largest of the working cylinders (21) or (22)., 2. Hot reversible rolling mill according to claim 1 characterized in that the intersection between the upper surfaces (51) sprayed directly by the jets of cooling fluids (36) with the upper face of the edge (111) is empty at the start of hot rolling, preferably throughout the duration of the hot rolling, and / or the intersection between the lower surfaces (61) sprayed directly by the jets of cooling fluids (46) with the lower face of the edge (111) is empty at the start of hot rolling, preferably throughout the duration of the hot rolling.

3. Hot reversible rolling mill according to claim 1 or 2. characterized in thatthe intersection between the upper surfaces (51) sprayed directly by the jets of cooling fluids (36) with the upper face of the ends (112) is empty during the entire duration of the hot rolling and / or the intersection between the lower surfaces (61) sprayed directly by the jets of cooling fluids (46) with the lower face of the ends (112) is empty during the entire duration of the hot rolling.

4. Hot reversible rolling mill according to one of claims 1 to 3 characterized in thatthe lower nozzles (45) produce jets of cooling fluid (46) which do not directly reach either the rollers (23) or the cylinder (22) in the presence of the blank (11) and which are preferably almost tangent to the rollers (23) and whose distance D67, which is the minimum of the distance of any point of the convex envelope (62) with the straight line C2 which is the projection of the axis of the cylinder (22) on the lower surface of the blank (11), reduced by the radius R2 of the cylinder (22), is preferably greater than a radius of the lower cylinder (22), more preferably than the diameter of the lower cylinder (22) and / or the upper nozzles (35) produce jets of cooling fluid (36) which do not directly reach the upper working cylinder (21), preferably the distance D57,which is the minimum of the distance of any point of the convex envelope (52) with the line C1 which is the projection of the axis of rotation of the cylinder (21) on the upper surface, of the blank (11), reduced by the radius R1 of the cylinder (21), is greater than the radius of the upper cylinder (21), more preferably the distance D57 is greater than the diameter of the upper cylinder (21)., 5. Hot reversible rolling mill according to at least one of claims 1 to 4 characterized in that the lower nozzles (45) are below the plane passing through the axes of rotation of the rollers (23) located near said nozzles (45) and / or the lower nozzles (45) are protected by a part (47) having openings to allow the jets of cooling fluid (46) to pass and / or the upper nozzles (35) are protected by a part (37) having openings to allow the jets of cooling fluid (36) to pass.

6. Hot reversible rolling mill according to at least one of claims 1 to 5 characterized in that the nozzles (35) and (45) are capable of producing jets of cooling fluid (36) and (46) in a flat and / or conical and / or cylindrical shape, and / or the nozzles (35) and (45) are capable of producing jets of cooling fluid (36) and (46) by spraying, preferably the nozzles (35) and (45) are capable of producing jets of fluid by spraying in a full cone shape.

7. Hot reversible rolling mill according to at least one of claims 1 to 6. characterized in that, for each cooling system, at least one device (38) for evacuating the cooling fluid from the upper surface of the blank (11) is installed above the area opposite the rolling mill (54) and / or above the area next to the rolling mill (53), preferably said device (38) is an air blower which pushes the cooling fluid towards one of the edges (111) of the blank (11) and gives the cooling fluid sufficient speed so that it does not run off the edges (1111).

8. Hot reversible rolling mill according to at least one of claims 1 to 7 characterized in that , for each cooling system, the upper sprayed convex envelope (52) is opposite with a tolerance of two preferably one times the dimension of the diameter of the upper working cylinder (21) of the lower sprayed convex envelope (62), preferably said convex envelopes (52, 62) are substantially opposite.

9. Hot reversible rolling mill according to at least one of claims 1 to 8 characterized in that the set of nozzles (35) and (46) are capable of providing a surface flow rate per face of the blank (11) of cooling fluid of 1500 l / min / m 2 maximum, preferably 600 to 1200 l / min / m 2 .

10. Hot reversible rolling mill according to at least one of claims 1 to 9 characterized in that the nozzles (35, 351) near the upper working cylinder (21) produce jets of cooling fluid (36) all of whose displacement components, projected onto the direction S of displacement of the blank (11), are oriented towards the working cylinders (21) and (22) of the rolling mill.

11. Hot reversible rolling mill according to at least one of claims 1 to 10. characterized in thatit comprises a second cooling system on the other side of said hot reversible rolling mill, the second cooling system preferably being symmetrical to the first with respect to a plane passing through the axes of the working rolls (21) and (22).

12. A method of hot rolling aluminum alloys comprising the successive steps of a. supplying an optionally clad aluminum alloy rolling plate at a hot rolling inlet temperature, b. carrying out a plurality of hot rolling and / or cooling passes with the hot rolling mill according to any one of claims 1 to 11, the cooling system being used at least once, c. transferring the blank (11) or the finished product in the form of sheet or strip at a hot rolling outlet temperature for the continuation of the hot transformation process.

13. Method according to claim 12. characterized in thata thermal model calculates the watering width and chooses the cooling mode at the ends (112), preferably the thermal model pre-sets the hydraulic system which supplies the ramps (30) and (40), then at each pass the thermal model compares the desired temperature with the calculated or measured temperature of the roughing (11), and the thermal model controls the valves (49) of the nozzles (35) and (45) according to the position of the roughing (11), preferably the thermal model manages the upper nozzles (35) and lower nozzles (45) differently.

14. Method according to at least one of claims 12 to 13. characterized in thatthe heterogeneity of the surface temperature of the blank (11), preferably of the blank (11) except on the edges (111) and / or on the ends (112), after its release from the grip of the rolling mill and the cooling device is less than 20°C, preferably less than 10°C and / or the absolute value of the temperature difference between the upper face and the lower face of the blank (11) is less than 10°C, more preferably 7°C, more preferably 5°C, more preferably 2°C and more preferably, the temperature of the upper face of the blank (11) is substantially equal to the temperature of the lower face of the blank (11).

15. Method according to at least one of claims 12 to 14. characterized in thatthe average cooling rate of the average temperature of the blank (11) during the passage of the blank (11) between the upper (52) and lower (62) convex envelopes is V= C / e, where V is in °C / s, e is the thickness of the blank in mm, and C is a constant value which is between 400 and 1000 °C / s*mm, preferably between 600 and 900°C / s*mm, more preferably between 700 and 800°C / s*mm.

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