PROFILED METAL PLATE WITH GOOD PERFORMANCE UNDER ICY CONDITIONS

Description

technical field

[0001] The invention relates to a metal sheet having on one of its faces a plurality of periodically arranged raised patterns, each pattern itself consisting of one or more protruding parts, which we will call "reliefs." This sheet is intended for the construction of flooring, particularly for industrial vehicles. The present invention relates more specifically to flooring sheets for refrigerated vehicles. Metal sheets make it possible to create floors that are less slippery and more resistant to wear than floors made from plastic. Previous art

[0002] Many models of sheet metal with repetitive, embossed patterns are already available on the market. These patterns are described, for example, in the NF-EN-1386 standard and are often referred to evocatively (checkerboard, barleycorn, almond, diamond, rice grain, checkerboard 2, checkerboard 5, etc.). The "checkerboard 5" pattern, also called "quintet," frequently used for industrial flooring, features a group of five elongated, semi-ovoid, parallel bumps surrounded by four identical groups, each rotated 90° from the first group. Sheets with this "quintet" pattern are highly wear-resistant but have only average anti-slip properties.The "rice grain" pattern, described in patent FR 2 747 948, is also used for the production of aluminum alloy sheets for industrial floors, which have satisfactory performance properties, in particular because they have good wear resistance and offer friction contact conditions which allow pedestrians to walk without risk of slipping and trolleys to roll without skidding.

[0003] In addition to wear resistance properties and favorable conditions for friction contact, it is also desirable to reduce the noise generated by rolling stock, such as trolleys, which have to travel on floors fitted with such sheets, especially the floors of refrigerated trucks.

[0004] In practice, the sheet metal disclosed by FR 2 747 948, which features a set of embossed patterns in the shape of a grain of rice, proves to be less noisy than some competing sheets also used for the production of floors of refrigerated trucks, in particular the "quintet" sheets mentioned above, which prove to be very noisy.

[0005] However, the sheet metal with the "rice grain" pattern of FR 2 747 948 does not yet seem entirely satisfactory insofar as the noise level reached is a little too high due to the requirements, other solutions have been proposed.

[0006] Application EP 2 316 590 A1 describes an engraved sheet metal plate with a repeating pattern having a plurality of pattern units. Each pattern unit comprises one or more raised elongated reliefs, an elongated relief having a length along a major axis and a width less than its length along a minor axis perpendicular to the major axis. The pattern units comprise first pattern units (PU1) having first elongated reliefs (R1) with their major axis parallel to a first direction (D1), and second pattern units (PU2) having second elongated reliefs (R2) with their major axis parallel to a second direction (D2) oriented transversely to the first direction, wherein a first pattern unit is surrounded by an even number of identical second pattern units. An angle between the first direction (D1) and the second direction (D2) is between 50° and 75°.

[0007] EP 2 552 612 B1, on which the preamble of claim 1 is based, relates to a sheet metal for the construction of flooring, particularly for industrial vehicles on which trucks are to travel, featuring a plurality of patterns, the maximum height of said patterns being between 0.2 and 1.5 mm, said patterns having a friction surface with an average width of at least 1 mm, wherein said patterns are arranged in several aligned groups, all of the same shape and orientation, and with their centers of gravity substantially aligned in the same given direction (D), the minimum distance, measured in said direction (D), between two adjacent patterns of the same aligned group being less than 6 mm. Figure 3B and paragraph

[0034] illustrate the difficulty of achieving a pattern that closely matches the negative of the pattern engraved in the cylinder.

[0008] Utility model DE9409026 U1 relates to a stainless steel sheet in particular for vehicle flooring and cold storage rooms provided with a surface structure composed of distinct studs whose height is substantially between 0.5 and 2 mm obtained by stamping a sheet 0.8 mm thick.

[0009] Patent EP0438031 B1 relates to a surface machining process consisting of creating indentations in the surface by means of one or more knurled rollers, the surfaces prior to knurling having been roughened by grinding or brushing.

[0010] Patent application JPH01275036 relates to improving the adhesion of resins on thin aluminum sheets by obtaining a roughness Rmax of 8 to 18 µm.

[0011] US patent 11198163 relates to a process comprising very shallow embossing on a micrometer scale combined with shallow rolling, which involves a slight reduction in thickness, the process being applicable to plates a few millimeters thick and to aluminum sheets less than 0.3 mm thick, supplied, in both cases, in independent plates or in coils.

[0012] Patent application AT512773A4 relates to a method for producing an aluminum sheet with integrated safety features. An aluminum sheet is rolled to a thickness of less than 150 µm in several cold rolling passes, with a texture extending in the direction of rolling being induced simultaneously on both sides of the sheet. During a final cold rolling pass, the sheet is conveyed to a pair of working rollers, in which, on at least one roller surface, the raised surface texture generated in the direction of rolling by grinding is reduced based on contrast and pattern in a region of 10 to 50% relative to the average surface roughness to form a pattern for a safety feature, which is transferred to the side of the sheet surface facing the roller surface.The generated aluminum sheet has a glossy appearance on both sides so that the safety sign stands out clearly due to its dull appearance.

[0013] Slip resistance is particularly critical for refrigerated trucks because when the doors are opened, the moisture contained in the warmer outside air condenses on the cold floor surface, which can become covered with a thin layer of frost.

[0014] The present inventors sought to improve slip resistance, i.e. to increase friction effort, under the specific conditions of refrigerated trucks, while maintaining the requirements of slip resistance at ambient temperature, wear resistance and low noise level. Description of the invention

[0015] A first object of the invention is a metal sheet made of aluminum alloy for the production of floors, in particular of industrial vehicles, on which trolleys are to circulate, said sheet having on one face a plurality of patterns, each pattern comprising one or more protruding parts, called "reliefs", said patterns being arranged in a periodic, discrete and ordered manner, the maximum height (Hmax) of said reliefs being between 0.2 and 1.5 mm, said reliefs having a surface, called "friction surface", which is defined by the intersection of a relief with a plane (P) parallel to a face of the sheet and located midway from the top of said relief and which has, whatever the direction in which it is measured, an average width of at least 0.2 mm, the sheet comprising at least 18000 reliefs per square meter, said reliefs being arranged in a plurality of aligned groupings,that is to say a plurality of relief groupings in which the reliefs of each of said aligned groupings have the same shape, the same orientation and have their centers of gravity substantially aligned along the same given direction (D), characterized in that the minimum distance measured along said given direction (D) between two neighboring reliefs of the same aligned grouping is always less than 10 mm, said aligned groupings being arranged in such a way that the minimum distance along the direction perpendicular to said given direction (D) between two neighboring reliefs of two different aligned groupings is less than 15 mm, and in which the walls of the reliefs make an angle with the face (11) of the sheet greater than 45°.

[0016] Another object of the invention is a method for manufacturing a sheet of metal according to the invention comprising, successively, the preparation of a bath of liquid metal, the casting of said alloy typically in the form of a rolling plate, optionally the homogenization of the product thus cast, the deformation by hot rolling and optionally cold rolling of the product thus obtained in order to obtain a sheet, the creation on one face of the sheet of a plurality of patterns, each pattern comprising one or more protruding parts, called "reliefs", by chemical machining or by electrochemical machining or by mechanical machining or by rolling with an engraved cylinder.

[0017] Yet another object of the invention is the use of a sheet metal according to the invention to make a floor for a refrigerated vehicle. Figures

[0018] There figure 1a It shows a cross-section of a relief and illustrates the rubbing surface. figure 1b illustrates the principle of calculating an average width measured in a given direction (D1). figure 1cillustrates two adjacent landforms aligned with the same shape and orientation, whose centers of gravity are aligned along the direction D1. figure 2 shows the cold friction measurement device. figure 3 It shows a cross-section of a relief and illustrates the base surface. figure 4 It illustrates one of the rice grain type motifs according to earlier art. figure 5 illustrates one of the motifs according to earlier art. The figure 6 illustrates motifs according to the invention described in Example 1. The figure 7 illustrates motifs according to the invention described in Example 3. The figure 8 illustrates motifs according to the invention described in Example 3. The figure 9 shows an engraved cylinder used for making the sheet metal in example 3. Figure 10 shows an engraved cylinder used for making the sheets in example 3. Detailed description of the invention

[0019] The designation of alloys is carried out in accordance with the regulations of The Aluminium Association, which are familiar to those skilled in the art. The definitions of the metallurgical states are given in the European standard EN 515 - 2017. Unless otherwise specified, the definitions of the standard NF EN 1386 - 2007 entitled "Embossed Sheets" apply.

[0020] The static tensile mechanical properties, namely the tensile strength Rm, the conventional yield strength at 0.2% elongation Rp0.2, and the elongation at break A%, are determined by a tensile test according to standard NF EN ISO 6892-1, with the sampling and direction of the test defined by standard EN 485-1. Hot tensile tests are carried out according to standard NF EN 10002-5. Vickers hardness is measured according to standard ISO 6507-1. Unless otherwise specified, the definitions of standard EN 12258 apply.

[0021] The sheet metal according to the invention is a textured metal sheet intended for use on the floor of a vehicle. According to the definition in standard EN12258, a sheet metal sheet is a rolled product with a generally rectangular cross-section, an average thickness of at least 0.20 mm, and a width not exceeding 1 / 10th of its width. The term "textured metal sheet metal" used here covers both so-called "engraved" sheets and "textured sheets" as defined in standard EN12258. The term "engraved sheet metal" is a general term where the designs can be printed in relief or intaglio on one or both sides. This encompasses printing, engraving, embossing, or even machining such designs on a sheet metal sheet with a perfectly rectangular cross-section, as well as rolling with a final pass on an engraved cylinder, a process associated with the term "textured sheet metal," which refers to a sheet metal "printed with a raised design on one side by rolling."

[0022] The sheet metal according to the invention has patterns on one of its faces comprising one or more raised features which, like the unit cell of a crystal lattice, repeat periodically and in an ordered manner. The face bearing the raised features is intended to be the upper face during use, i.e., the face in contact with shoes or trolleys. A pattern is therefore a piece of sheet metal that repeats indefinitely by translation along two directions of the plane of the sheet metal. This piece of sheet metal may comprise only one raised feature, but it may also comprise several raised features which may have different shapes or orientations. It does not appear advantageous to have raised features of different heights, but this is not excluded a priori. To achieve acceptable wear resistance under practical conditions of use, the maximum height Hmax of these raised features is between 0.2 and 1.5 mm.Advantageously, especially with regard to embossed aluminum alloy sheets, it is between 0.2 and 1.0 mm, preferably between 0.3 and 0.8 mm, and even more preferably between 0.4 and 0.6 mm.

[0023] These patterns are also repeated discreetly, as this configuration enhances the floor's anti-slip properties. The raised areas act like indenters on the surface of the tire's sole or tread: under the weight of the pedestrian or cart, the surface deforms and "sinks" around the raised area to a certain depth, typically one, two, or three tenths of a millimeter. A discontinuous pattern encourages the formation of a ridge around the top edge of the sole or tread, which improves the grip of the sole, tread, or tire on the floor. Furthermore, the discreetly repeating patterns facilitate floor cleaning, as they allow for easier drainage and removal of liquids.The sheet metal according to the invention must not be entirely made up of continuous reliefs and preferably the sheet metal according to the invention does not have continuous reliefs.

[0024] Since it is difficult to define the actual contact area between these raised surfaces and the soles of pedestrians and / or the treads or tracks of cart wheels traveling on these floors, we will conventionally define a surface correlated to the anti-slip properties of the sheet metal's raised surface, which we will call the "friction surface." This surface results from the intersection of the raised surface with a plane parallel to the face of the sheet metal, located at mid-height, that is, halfway from the top of the raised surface. This definition is linked to the phenomenon described above: the raised surface behaves like an indenter acting on the surface of the sole or the tread of the wheel. figure 1aillustrates how said friction surface is obtained: the face (11) of the sheet (10) has a protruding relief (20) whose apex surface (22) is not necessarily flat and parallel to the face (11) of the sheet. The friction surface (30) is defined as the intersection of the relief (20) with a plane (P) parallel to the face (11) of the sheet and at a distance of Hmax / 2 from the apex (21) of the relief (20), the maximum height Hmax being the distance between said apex and the face (11) of the sheet. The walls (23) of the relief are shown on the figure 1a .

[0025] On the figure 1aThe friction surface extends over a width ℓ. The applicant noted that this width ℓ needed to reach a sufficient average value for the contact to result in effective friction: if ℓ is too small, the sole or tread material moves to one side or the other of the relief without being particularly retained. Therefore, the applicant defined a criterion according to which, regardless of the sweep direction, the average width of the relief must be at least 0.2 mm. figure 1bThis illustrates the principle of calculating an average width measured in a given direction (D1): along the direction (D2) perpendicular to the direction (D1), the endpoints E1 and E2 of the relief are defined, whose coordinates are respectively 0 and X on the axis (D2), and a straight line Mi (i=1 to n) parallel to the direction (D1) is drawn n times between these endpoints, intersecting the frictional surface over a length li. The average width of the relief, relative to the direction (D1), is given by: l ¯ = lim n → ∞ ∑ 0 n l i n It can obviously be approximated by an average calculated over N measurements ( ∑ 0 N l i N ), where N is an integer, more or less large depending on the complexity of the shape of the friction surface. Preferably, to improve the anti-slip property of the sheet metal, the average width of the friction surface in direction (D) is at least 0.5 mm, or even at least 0.7 mm, but preferably at most 5 mm and preferably at most 3 mm. In one embodiment of the invention, the average width of the friction surface is at most 1.5 mm in direction (D). The maximum width of the friction surface is also defined as the greatest width of the friction surface regardless of the direction in which it is measured.

[0026] The sheets according to the invention have raised features arranged in a plurality of aligned groups, that is, in a plurality of groups of features within which each feature has the same shape, the same orientation, and a center of gravity that lies substantially on a straight line parallel to a given direction (D), the minimum distance measured along said direction (D) between two adjacent features of the same aligned group always being less than 10 mm, preferably less than 6 mm, and most preferably less than 4 mm. To characterize the shape, orientation, and center of gravity of a feature, as well as the minimum distance between two features, one can again refer to the friction surface as defined previously and illustrated in figure 1a . There figure 1cThis illustrates two adjacent, aligned landforms of the same shape and orientation, whose centers of gravity are aligned along direction D1. It illustrates the principle of calculating a minimum distance measured in a given direction (D1): along direction (D2), perpendicular to direction (D1), projections E1 and E2 of the ends of the landforms are defined, with coordinates respectively 0 and X on axis (D2). A straight line Mi (i=1, n) parallel to direction (D1) is drawn n times between these ends. The line Mi intersects the friction surfaces of the landforms, creating intervals of length di between two friction surfaces. The minimum distance between adjacent landforms is given by: lim n → ∞ Min d i , i = 1 , n

[0027] Of course, this value can be approximated by a calculation performed on N measurements ( Min ( dii=1, N), N being an integer, more or less large, depending on the complexity of the shape of the rubbing surface of the relief relative to the aligned grouping. This minimum distance is always less than 10 mm, in the sense that the reliefs of the same aligned grouping may be non-uniformly distributed and that the minimum distance along direction (D) between two neighboring reliefs, while it may vary depending on the reliefs chosen, never exceeds 10 mm. The motifs are preferably aligned on the same line of direction (D). Obviously, the notion of aligned grouping also encompasses configurations of reliefs of the same shape, the same orientation, and whose centers of gravity are substantially aligned, that is to say, very close to the same line of direction (D), typically separated by no more than 1 mm from such a line.Advantageously, the given direction (D) of alignment of the raised features of the aligned groups is substantially parallel to the overall direction (Dc) of trolley movement over said sheets. Preferably, the rolling direction and the overall direction (Dc) of trolley movement coincide. The applicant has indeed observed that the quietest sheets are those with groups aligned in a direction close to the overall direction of trolley movement, with raised features of the same shape, orientation, and proximity, with a minimum distance measured along the overall direction of trolley movement of less than 10 mm, preferably less than 6 mm.Preferably, the sheet metal according to the invention has only one relief shape and one relief orientation per aligned grouping, with two adjacent reliefs not being too far apart. The typical maximum distance is given by the minimum distance along (D) between the rubbing apex surfaces of two adjacent aligned reliefs, which must be less than 10 mm, preferably 6 mm. This does not preclude the possibility of placing two aligned groups of reliefs of different shapes and / or orientations side by side, provided, however, that the lines joining their respective centers of gravity are not too close to each other, that is, are typically at least one millimeter apart.

[0028] The sheets have aligned groups arranged such that the minimum distance, along the direction perpendicular to the given direction (D), between two adjacent protrusions of two different aligned groups is less than 15 mm, preferably less than 8 mm, and most preferably less than 6 mm. In one embodiment of the invention, the minimum distance, along the direction perpendicular to the given direction (D), between two protrusions is at least 0.8 mm, preferably at least 1 mm. In another embodiment of the invention, the minimum distance, along the direction perpendicular to the given direction (D), between two protrusions is at least 2 mm, preferably at least 3 mm.

[0029] The inventors have found that, surprisingly, it is possible to significantly increase friction at low temperatures while maintaining the known requirements for slip resistance at room temperature, wear resistance, and low noise level, using the pattern density of embossed sheet metal. A key criterion for improving friction resistance at low temperatures is the density of the embossed pattern.

[0030] Thus the sheet metal according to the invention has at least 18,000 reliefs per square meter, preferably at least 20,000 reliefs per square meter, preferably at least 25,000 reliefs per square meter, preferably at least 30,000 reliefs per square meter and preferably at least 35,000 reliefs per square meter.

[0031] The present inventors have observed that when the number of reliefs per square meter is less than 18000, the cold friction effort is significantly reduced, which can lead to excessive slippage on sheet metal in refrigerated truck conditions.

[0032] The inventors present also noted that it is advantageous for the numerous raised areas to be small and pointed, like a fakir's rug. As illustrated by the figure 3 , the walls (23) of the reliefs are very steep, making an angle with the face (11) of the sheet greater than 45°, preferably greater than 60° and preferably greater than 70°.

[0033] Advantageously, the maximum width of the rubbing surface of the reliefs is less than 10 mm and preferably less than 8 mm, regardless of the direction in which it is measured. Similarly, advantageously, the average width of the rubbing surface of the reliefs is at most 5 mm, preferably at most 4 mm, and preferably at most 3 mm, regardless of the direction in which it is measured. Preferably, the sheet metal according to the invention has a surface (31), referred to as the "base surface", illustrated by the Figure 3, which is defined by the intersection of a relief with a plane (P') parallel to a face of the sheet metal and located at 10% of the height of the apex (21), whose area is between the area of ​​the friction surface and the area of ​​the friction surface plus 10%, and preferably between the area of ​​the friction surface and the area of ​​the friction surface plus 5%. Thus, with the base surface being close to the friction surface, the reliefs are highly salient. In an advantageous embodiment, the area of ​​the friction surface of a relief is less than 20 mm² and preferably less than 15 mm². The Figure 3 It also illustrates the angle α between the walls (23) of the reliefs and the face (11): it is determined at the intersection of the relief with the plane (P') parallel to the face (11) of the sheet and located at 10% of the height of the top (21).

[0034] The reliefs can be of various shapes such as circular, ellipsoidal, oval, semi-ovoid, parallelogram (including rhombus or square, possibly with rounded corners), trapezoidal, triangular, star, or combinations of these shapes such as a rectangle with rounded shorter sides. In an advantageous embodiment, the reliefs are in the form of parallelograms with sharp corners; typically, the corners of the reliefs are not rounded and correspond to the intersection of straight line segments. Preferably, the reliefs are in the form of squares. These shapes can be obtained, in particular, using a process according to the invention in which a plurality of motifs are produced by two successive rolling passes with grooved, engraved cylinders.

[0035] Preferably, the sheet according to the invention is made of an alloy belonging to the group comprising aluminum alloys of the 3xxx, 5xxx, and 6xxx series according to the Aluminum Association designation, as well as alloys of the 7xxx series, containing less than 0.4% Cu. An example of a usable 3xxx alloy is alloy 3104. An example of a usable 5xxx alloy is alloy 5086. An example of a usable 6xxx alloy is alloy 6061. An example of a usable 7xxx alloy is alloy 7020. The invention is advantageously particularly suited to aluminum alloy sheets with high hardness, such as sheets with a Vickers hardness of at least 60 HV, preferably at least 70 HV, preferably at least 80 HV, more preferably at least 90 HV, and even more preferably at least 100 HV.

[0036] In one embodiment of the invention, the second face of the sheet metal (12), that is to say the face which does not have any patterns, illustrated on the Figure 2 The surface has a roughened surface with a maximum roughness (Rmax) between 10 µm and 250 µm. This embodiment is particularly advantageous when this face is intended to be bonded to a substrate. The maximum roughness (Rmax) of said roughened surface is preferably between 50 µm and 150 µm, and preferably between 100 µm and 140 µm. The roughness of the roughened surface is typically obtained by electrochemical milling, mechanical milling, brushing, or by deformation, typically sandblasting, shot blasting, rolling, embossing, or debossing, preferably by rolling. The roughness of the second face can be obtained by a periodically repeating and ordered texture, preferably produced by rolling.

[0037] The sheets according to the invention are prepared by a process comprising, successively, the preparation of a bath of liquid metal, the casting of said alloy typically in the form of a rolling plate, optionally the homogenization of the product thus cast, the deformation by hot rolling and optionally cold rolling of the product thus obtained so as to obtain a sheet, the creation on one face of the sheet of a plurality of patterns, each pattern comprising one or more protruding parts (20), called "reliefs", by chemical machining or by electrochemical machining or by mechanical machining or by rolling with at least one engraved cylinder.

[0038] The pattern creation stage must, in particular, allow for obtaining advantageous density and geometric characteristics. Machining processes make it possible to create reliefs with the precise geometry desired. However, these processes are costly for producing large surfaces, and it is advantageous to create multiple patterns by rolling using engraved cylinders. Creating the patterns according to the invention can, however, prove difficult with an engraved cylinder. Indeed, the patterns are numerous and fine, and advantageously their walls are oriented vertically relative to the sheet metal surface at a high angle, which can make engraving the cylinder difficult because the fraction of the surface engraved in relief on the cylinder is small and the relief is fine. Furthermore, the rolling force required is very high in this case.The inventors have found that advantageously the production of a plurality of patterns according to the invention can be carried out by at least two successive rolling passes with identical or different grooved engraved cylinders.

[0039] The grooved and engraved cylinders used are cylinders with only continuous lines obtained by milling. These cylinders are more economical to produce than cylinders with multiple small cavities. An example of a cylinder that can be used is a fluted cylinder with grooves that create notches parallel to the rolling direction. This type of cylinder is illustrated by the Figure 9Another example of a cylinder that can be used is a chevron cylinder with chevron grooves that create slots at an angle to the rolling direction, between 30° and 60°, preferably between 40° and 50°, with 45° typically being advantageous. This type of cylinder is illustrated by the Figure 10Various types of chevrons can be used, typically with "V" or "W" patterns, repeating at varying frequencies across the width of the cylinder. Another example of a suitable cylinder is one with inclined grooves. These grooves create slots at the same angle to the rolling direction across the entire width, between 30° and 60°, preferably between 40° and 50°, with 45° typically being advantageous. However, this latter type of cylinder is more delicate to use due to the asymmetry of forces during rolling. By using successive rolling passes with grooved cylinders, the patterns are created in several stages to separate the longitudinal and transverse markings. This is achieved by rolling successively with cylinders grooved in different ways. Advantageously, two successive passes are performed.

[0040] Several combinations are possible depending on the order in which the cylinders are used, in order to obtain different patterns. Some preferred methods are described below.

[0041] In one embodiment, the sheet metal is rolled first with the fluted roll and then with the chevron roll. In another embodiment, the sheet metal is rolled first with the chevron roll and then with the fluted roll. In yet another embodiment, the sheet metal is rolled first with the chevron roll and then again with the chevron roll after rotating the sheet 180°. In this case, the end of the first pass with the chevron roll coincides with the beginning of the second pass with the chevron roll. In yet another embodiment, the sheet metal is rolled first with the chevron roll and then again with a chevron roll that is symmetrical to the first with respect to a vertical plane. In one embodiment, the two passes are carried out successively on a rolling mill with only one stand, of the duo or quarto type, preferably of the duo type.In another embodiment, the successive passes are carried out on a tandem rolling mill, i.e. comprising at least two rolling mill stands, the stands being equipped with cylinders having a different groove in order to create the desired roughness.

[0042] Another object of the invention relates to the use of a sheet metal according to the invention for making floors, advantageously floors for refrigerated vehicles. Advantageously, the sheet metal according to the invention is placed on the vehicle floor such that the rolling direction coincides with the length of the vehicle. Indeed, it is along the length of the vehicle that the trolleys travel most frequently and can reach the highest speed.

[0043] These aspects, as well as others of the invention, are explained in more detail with the help of the following illustrative and non-limiting examples. Examples COLD FRICTION MEASUREMENT DEVICE

[0044] There figure 2The diagram schematically illustrates, in cross-section, the measuring device for cold friction measurement. The sample (10) on which the measurements are performed is a piece of embossed sheet metal measuring 200 x 400 mm. The longer dimension corresponds to the direction of travel (Dc). The sample holder (50) comprises a flat support on which the sample is placed, presenting its embossed side to the passage of a safety shoe weighted with a 40 kg weight. A recess (51) is provided in the sample holder to insert a cooling medium, typically dry ice (52), under the embossed sheet metal. After supplying the recess with dry ice, a sheet of sheet metal from a freezer, at a temperature of -20 °C, is positioned on the sample holder. A defined quantity of water is sprayed onto the surface of the sheet metal using a misting nozzle, forming a controlled layer of frost.When the sheet metal reaches a temperature between -2°C and -10°C, the friction measurement test is performed. A force measurement cell (60) is connected to the shoe via a pulley (61). The force obtained is measured in Newtons (N). MEASURING NOISE LEVELS

[0045] The noise level was measured on a test bench similar to that described in application WO2011 / 121191. Rather than a sound evaluation, a vibration signal was measured in the vertical direction using three accelerometers. Indeed, noise and vibration studies have established a strong vibration / acoustic power correlation, allowing the vibration signal of different sheet metal types to be measured to assess their sound performance. The root mean square (RMS) value of the vibration signal in the vertical direction, hereafter designated by RMS-Z, is the value used and is expressed in g (9.80665 ms⁻²). ABRASION RESISTANCE

[0046] Abrasion resistance was measured by Taber abrasion tests according to the NF EN ISO5470 standard, with a mass of 500g on each wheel.

[0047] To assess the loss of adhesion due to wear, cold friction measurements were taken after one or two passes with a circular wire brush mounted on a pillar drill or milling machine. The wire brush was brought into contact with the sheet metal to be tested while it was not rotating, and then rotated. Example 1

[0048] In this example, several sheets of AA5086 alloy were prepared by machining in a as-rolled state and with a hardness of 110 HV, comprising only a plurality of aligned groups (26) according to the Figure 6The walls of the reliefs were steeply inclined, with the angle to the sheet metal close to 90°. Thus, the characteristics of the reliefs are practically identical regardless of the height considered. Table 1 summarizes the geometric characteristics a, b, c, and d of the reliefs. c corresponds approximately to the average width in the direction perpendicular to the rolling direction Dc. b corresponds to the minimum distance measured along the given direction Dc between two neighboring reliefs in the same aligned group. The friction resistance on frozen sheet metal was measured according to the method described.

[0049] All the sheets showed an acceptable result, with the best results being obtained for sheets B and E. [Table 1] Sheet metal B C D E F I J a (mm) 2 2 4 2 2 4 7 b (mm) 2 9 2 2 0,8 4 2 c (mm) 0,8 0,8 2 0,8 0,8 0,8 2 d (mm) 3 9 3 3 3 9 3 Maximum height (H max) 0,5 0,5 0,5 0,5 0,5 0,8 0,8 Angle of the principal dimension of the relief with the direction Dc 0 0 0 + / - 30° 0 0 0 Friction resistance on frozen sheet metal (N) 280 265 258 280 240 250 258 Number of reliefs / m² < in thousands 100 27, 8 50 100 132 19,2 28,6 Surface area of ​​a relief (mm2) 2,4 7,2 6 2,4 2,4 7,2 6 Example 2

[0050] In this example, prior art 5086 alloy sheets were characterized. The noise level of a sheet with a "rice grain" pattern according to patent FR2747948 was characterized, and the resulting RMS-Z vibration intensity was 0.79 g, significantly higher than that of the sheets according to the invention. Its friction resistance on frozen sheets, expressed in Newtons, was 229 N. Similarly, a sheet according to patent application EP2316590 was characterized. The resulting RMS-Z vibration intensity was 0.62 g, significantly higher than that of the sheets according to the invention. A sheet according to the figure 5The "Gripster" pattern, representative of patent EP2552612, was characterized. The resulting RMS-Z vibration intensity was 0.29 g, but its friction resistance on frozen sheet metal, expressed in Newtons, was 164 N, significantly lower than that of the sheets according to the invention. This sheet metal has approximately 7900 reliefs / m², each with an individual surface area of ​​71 mm².

[0051] The thickness losses obtained with the Taber abrasion tests are given in Table 2. [Table 2] Thickness loss (mm) 400 cycles 800 cycles 1200 cycles 1500 cycles Grain of rice 0,08 0,14 0,22 0,25 Gripster 0,04 0,06 0,07 0,08 Example 3

[0052] In this example, sheets according to the invention were prepared by rolling sheets of AA5086 alloy with a hardness of 110 HV. Engraved, grooved cylinders were prepared. A first cylinder had a fluted relief such as on the Figure 9 A second cylinder featured a chevron relief such as that on the Figure 10Two rolling passes were carried out with these engraved cylinders to obtain the patterns described in the figure 7 , sheet K, and to the figure 8 , sheet metal L. To obtain the pattern of the figure 7 The chevron-patterned cylinder was used twice, with the sheet metal reversed between passes. To obtain the pattern of the figure 8 First, a pass was made with the fluted relief cylinder, then a pass with the chevron relief cylinder. Thanks to these successive rollings, the walls of the reliefs obtained on the sheets were steeply inclined, with the angle with the sheet being close to 90°.

[0053] The geometric characteristics and the results of friction resistance on frozen sheets, vibration intensity and abrasion resistance, measured as in examples 1 and 2, are presented in Table 3. Pattern K enabled a particularly high friction resistance on frozen sheets. [Table 3] Sheet metal K L a (mm) 3,7 5,9 b (mm) 2,8 2,5 c (mm) 4,6 2,6 d (mm) 4,6 4,9 Maximum height (H max) 0,6 0,6 resistance to friction on frozen sheet metal (N) 324 300 Vibration intensity 0.40 0,36 RMS-Z (g) Thickness loss due to abrasion (mm) 400 Cycles 0,04 0,08 800 cycles 0,08 0,14 1200 cycles 0,14 0,21 1500 cycles 0,15 0,25 Number of reliefs / m² < in thousands 36,3 22,9 Surface area of ​​a relief (mm2) 10,6 12,7 Example 4

[0054] In this example, we measured the friction resistance on frozen sheet metal after one or two passes of a wire brush as described previously, for the Grain de Riz and Gripster sheets of example 2 and for the K and L sheets of example 3.

[0055] The results are given in Table 4. [Table 4] resistance to friction on frozen sheet metal (N) Initial After a back-and-forth pass with a wire brush After two passes with a wire brush Gripster 164 161 Grain of Rice 229 189 181 K 324 255 202 L 300 208

[0056] Even after abrasion, the K and L sheets according to the invention retain a high resistance to friction on frozen sheet.

Claims

1. Metal sheet (10) made of aluminium alloy for the production of floors, in particular of industrial vehicles, on which carriages are to circulate, said sheet having a plurality of patterns on one face, each pattern comprising one or more protruding parts (20), called "reliefs", said patterns being disposed in a periodic, discrete, and ordered manner, the maximum height (Hmax) of said reliefs being between 0.2 and 1.5mm, said reliefs having a "friction" surface (30) which is defined by the intersection of a relief with a plane (P) parallel to the surface of the sheet and located halfway to the top (21) of said relief and which has, regardless of the direction in which it is measured, an average width at least equal 0.2mm, the sheet comprising at least 18000 reliefs per square meter, said reliefs being disposed in a plurality of aligned groups (26, 28, 32), that is to say a plurality of groups of reliefs in which the reliefs of each of said aligned groups have the same shape, the same orientation and have their centers of gravity substantially aligned according to the same given direction (D), the minimum distance measured along said given direction (D) between two neighbouring reliefs of the same aligned group always being less than 10mm, said aligned groups being disposed so that the minimum distance in the direction perpendicular to said given direction (D) between two neighbouring reliefs of two different aligned groups is less than 15mm, characterised in that the walls (23) of the reliefs form an angle with the face (11) of the sheet greater than 45°.

2. Sheet according to claim 1, characterised in that the maximum width of the friction surface of said reliefs is less than 10mm and preferably less than 8mm regardless of the direction in which it is measured.

3. Sheet according to claim 1 or claim 2, characterised in that the area of the surface (31), called "of the base", which is defined by the intersection of a relief with a plane (P') parallel to the surface of the sheet and located at 10% of the height of the top (21), is between the area of the friction surface and the area of the friction surface plus 10% and preferably between the area of the friction surface and the area of the friction surface plus 5%.

4. Sheet according to any one of claims 1 to 3, wherein the area of the friction surface of the reliefs is less than 20mm2 and preferably less than 15mm2.

5. Sheet according to any one of claims 1 to 4, wherein the average width of the "friction" surface of the reliefs is at most 5mm, preferably at most 4mm and preferably at most 3mm regardless of the direction in which it is measured.

6. Sheet according to any one of claims 1 to 5, wherein the walls (23) of the reliefs form an angle with the face (11) of the sheet greater than 60° and preferably greater than 70°.

7. Sheet according to any one of claims 1 to 6, characterised in that said sheet is made of an alloy belonging to the group encompassing the aluminium alloys of the series 3xxx, 5xxx and 6xxx according to the designation of the Aluminum Association as well as the alloys of the series 7xxx, comprising less than 0.4% Cu.

8. Sheet according to any one of claims 1 to 7, the second face of the sheet (12) of which has a rough surface, the roughness Rmax of which is between 10µm and 250um.

9. Sheet according to any one of claims 1 to 8, the reliefs of which are in the shape of parallelograms, the angles of which are non-rounded.

10. Sheet according to any one of claims 1 to 9, the reliefs of which are in the shape of squares.

11. Sheet according to any one of claims 1 to 10, the Vickers hardness of which is at least 60HV.

12. Method for manufacturing a sheet according to one of claims 1 to 11, successively comprising - creating a liquid metal bath, - casting said alloy typically in the shape of a rolling ingot, - optionally homogenising the product thus cast, - deforming the product thus obtained by hot and optionally cold rolling so as to obtain a sheet, - creating a plurality of patterns on one face of the sheet, each pattern comprising one or more protruding parts (20), called "reliefs", by chemical machining or by electrochemical machining or by mechanical machining or by rolling with at least one embossed roll.

13. Method according to claim 12, wherein the creation of a plurality of patterns is carried out by two successive rolling passes with identical or different grooved, embossed rolls.

14. Use of a sheet according to any one of claims 1 to 11 to create a floor of a refrigerated vehicle.