The present invention relates to the field of stainless steels formed into rolled flat products, including strips, plates and metal plates,

or cut and / or shaped from such strips, plates and sheets.

Stainless steels are used in many areas to form objects to remain visible and present a clean and attractive surface appearance to the eye with its brilliance. This is in particular the case when they are used to make furniture, appliances, cutlery, building facades coverings ...

However, they have the disadvantage of making highly visible fingerprints left by users of the objects, so that the surfaces of these objects must be cleaned regularly so that we take full advantage of the aesthetic properties of stainless steel.

various technical solutions have already been devised to alleviate this problem. Thus, there are varnish that by coating is deposited on the surface of stainless steel, and which make fingerprints visible only if the object is observed by particular angles. This solution however is not ideal because it does not completely solve the problem because fingerprints are visible under certain viewing conditions. Also this varnish should be introduced in a manufacturing operation especially dedicated, which inevitably increases significantly the cost of manufacture of the object, and degrades the productivity of the manufacturing line items, or that of semi-finished products precursors (strips, plates, sheets or the like) from which they originate. For the finger antimark fact remains, we also need the varnish layer is not significantly deteriorated during the use of the object, which is not guaranteed when the object is likely being subjected to friction during use (if, for example, knives, kitchen worktops ...). Finally, the coating is susceptible to deterioration if, after application, the treated object must undergo a shaping by stamping, bending or the like. And applying the coating only after this formatting is not always possible or easy.

The object of the invention is to provide stainless steel manufacturers or items stainless steel rolled products that are not sensitive to fingerprints, and certainly in a sustainable manner, without this significantly affects too the duration and cost of manufacturing objects or semifinished products from which they come.

To this end, the invention relates to a laminated object of stainless steel, characterized in that its surface has a relief pattern and having a hollow Random juxtaposition of at least two kinds of polygons, each of said polygons having at least three sides, having a surface area of between 1 and 9 mm 2 , a difference between its smallest and largest dimension of between 0.5 and 3 mm, each polygon being constituted by substantially parallel rectilinear grooves, each deviating ± 15 ° with respect to the average orientation of the striations, from 5 to 30 μηι depth separated by ridge lines and the axes of which are spaced 0.1 to 0.3 mm, and having a spectral transform analysis Fourier performed on a square at least 100 mm 2 , shows that it has an isotropy of at least 40% between the rolling direction and the transverse direction and whose top three angular orientations préférenti them, two adjacent preferential angular orientations are separated by at least 20 ° and at most 60 °.

Preferably, the reference plane of each polygon is inclined with respect to the reference planes of its adjoining polygons, 1 to 10 °.

Preferably, the spectral analysis of its surface has between three and eight preferential angular orientations.

Preferably, the flanks of said grooves have curved surfaces and / or having asperities.

It may be a sheet, a plate or a band.

The object may have been made by cutting and / or shaping of a metal sheet, plate or tape of the above type, constituting a precursor of said object

The invention also relates to a method of manufacturing an object of the above type, characterized in that said surface having said pattern is obtained during the rolling of the object, or a precursor of said object, by the pressure a rolling roller on the surface of the object or its precursor, said cylinder itself having on its surface a pattern for obtaining said pattern on the surface of the object.

As will have been understood, the invention is to print, at a lamination on the surface of the object, or the surface of a semi-finished product which is a precursor, a pattern engraved in relief and hollow of a particular type well defined. This pattern is based on a random juxtaposition of at least two species of polygons, not necessarily regular, having at least three sides. The planes of neighboring polygons surfaces are preferably slightly inclined from each other. Polygons themselves delimit each an area where are present of substantially parallel ridges depths and widths defined. They each have an area of between 1 and 9 mm 2 , a difference between their smallest and their largest dimension

between 0.5 and 3 mm, and the reference plane of each polygon is inclined 1 to 10 ° relative to that of its immediate neighbors polygons.

Each polygon is made up of substantially parallel ridges, that is to say away from each of ± 15 ° with respect to the average orientation of striae. They have 5 to 30 μηι depth and are separated by ridge lines. Their axes are spaced from 0.1 to 0.3 mm. Spectral analysis by Fourier transform of the surface of the object, performed on a square area of 100 mm 2 at least, shows that it has an isotropy of at least 40% between the rolling direction and cross direction and among the three main preferential angular orientations determined by spectral analysis, two neighboring directions are spaced at 20 to 60 °.

Preferably, the design printed on the surface of the object comprises between three and eight preferential angular orientations. Beyond eight such preferred orientations, it is not assured that the angular distance between two neighboring preferential orientations would always be sufficient for the intended attenuation effect fingerprints is properly obtained.

The depth of the grooves of 5 to 30 μηι is justified by the fact that below 5 μηι, printing would be too difficult and its outcome would anyway more efficient enough. Above 30 μηι, the finger anti-trace effect obtained is not significantly improved, and we risk ending up with a roughness of the metal that may be excessive for some applications. The engraving of the cylinders of the rolling mill with such a high roughness would also be problematic.

The inventors also tested other types of etching the surface of stainless steel sheets. An example of such other type of engraving will be described later. But it turned out that the type of engraving of the invention was the fittest, among those tested, to provide the surface the characteristics of isotropy and multidirectional thinking that can best solve the problem of visibility fingerprints.

This printing is effected by the rolling mill of the work roll which comes into contact with the surface to be treated. The cylinder itself has on its surface an etched pattern that is at least approximately, the "negative" of the pattern you want to burn to the surface of the object. Must be rolled without polishing, the depressions of the surface of the object are printed by corresponding reliefs provided on the cylinder, and the reliefs of the surface of the object are printed by corresponding recesses provided on the cylinder. The degree of identity between the cylinder units of the dimensions and the pattern to be printed, in particular on the dimensions of reliefs / hollow of the cylinder, are to be determined by experience and may vary depending on the respective hardnesses of the cylinder surfaces and

of the surface to be treated and according to the pressure intensity applied to the surface by the cylinder.

If only one surface of the laminated object to be treated, it is of course necessary to use only one working cylinder having on its negative etching surface of the pattern to be printed. If both surfaces of the laminated object to be processed, the two rolling mill working rolls must have this engraving in negative. The rolling mill may be of any known type, conventional in a pair of work rolls and one or more pairs of supporting rollers, or, for example, Sendzimir type, or a planetary type rolling mill.

The cylinders are themselves etched by an industrial process such as laser etching, electrical discharge ...

The invention will now be described more specifically with reference to the following appended figures:

Figure 1 and Figure 2 which show the surface of a stainless steel sheet unetched prior art, and its spectral analysis diagram, taking as reference direction the direction of rolling (for Figure 1 ) and the cross direction (in Figure 2);

Figures 3 and 4, which show the surface of a stainless steel sheet engraved with a manner inconsistent with the invention, and its spectral analysis diagram, taking as reference direction the direction of rolling;

Figures 5 to 7 which show examples of isolated polygons belonging to etching performed on a stainless steel sheet according to the invention, with their respective spectral analysis charts;

Figure 8 shows perspective view of an exemplary portion of a sheet of stainless steel surface engraved according to the invention;

Figures 9 to 12 which show, seen from above, examples of stainless steel sheet surface portions etched according to the invention, with their respective spectral analysis charts;

Figure 13 shows the surface of a stainless steel sheet refers to the unetched surface on which a finger trace is visible;

Figure 14 shows at the same magnification as Figure 13, the surface of a stainless steel sheet refers to the surface engraved according to Figs 3 and 4, on which a finger trace is visible;

Figure 15 shows at the same magnification as Figure 13, the surface of a stainless steel plate engraved according to the invention and on which a finger trace is hardly visible.

By way of reference, Figures 1 and 2 show samples of surfaces of a sheet 1 laminated with stainless steel substantially smooth work rolls as is usually the case, and which therefore had no particular etching . The sheets of sample surfaces are themselves relatively smooth: it sees only shallow grooves (about 1 to 1, 5 μηι) and very narrow frankly oriented in the rolling direction, and their analytical diagrams spectral Fourier transform, achieved by a conventional method (see, for example, the document "Technical Engineer, the Fourier transform and its applications", 2007, vol. AFM3, AF1440-1443) are presented. In the example of Figure 1, the analysis is carried out taking as a reference direction (90 °) the rolling direction, and in the example of Figure 2, the analysis is carried out taking as reference orientation cross direction, that is to say the direction perpendicular to the rolling direction.

The rate of isotropy between rolling direction and the transverse direction is, logically because it is of the same sheet, the same for both images, and it is 11, 6%. It is a low rate, which is normal since no special measures have been taken so that the effect of laminating the sheet on the structure of the surface is reduced, this rolling being carried out according to a well-defined direction. This very low isotropic surface is a disadvantage for the visibility of fingerprints because it promotes the reflection of light according to defined directions in which the fingerprints is particularly visible.

Observed in the rolling direction (Figure 1), the striations have preferred directions of 90.0 °, 95.5 ° and 84.3 ° with respect to the transverse direction (the angles 0 ° and 180 ° corresponding to the two directions the transverse direction) which are identical to or very close to, the direction of rolling.

Observed in the transverse direction (Figure 2), the striations have preferred directions of 0.289 °, 5.48 ° and 174 ° with respect to the one direction of the cross direction, and are therefore very substantially perpendicular to the direction through and therefore correspond to the rolling direction. The consistency of the results of measurements of 1 and 2 is reasonably assured, the usual inaccuracies of the measurements.

Figures 3 and 4 show a sheet surface engraved according to a pattern not in accordance with the invention. It includes reliefs in two regular networks nested.

A first network, oriented according to the rolling direction, comprises reliefs 2 of height 45 μηι, and substantially elliptical cross-section which, at the base, the major axis measurement 1, 25 mm and the minor axis 0.85 mm. They are staggered, according to section lines 1, 13 mm. The section of each raised gradually decreases the lelong

height of the relief, and the vertices of two adjacent projections 2 situated on the same line are spaced 2 mm.

A second network, oriented along the transverse direction, comprises reliefs 3, intercalated regularly between the projections 2 of the first network. The reliefs 3 have a height of 30 μηι and a substantially elliptical cross section which, at the base, the major axis extent 0.88 mm and 0.57 mm minor axis. They are staggered, according to section lines 1 mm. The section of each raised gradually decreases according to the height of the relief, and the peaks of two adjacent reliefs 3 situated on the same row are spaced 2.26 mm.

The spectral analysis chart shows that this surface isotropy is 40.9%, which is relatively high and could be favorable from the perspective of the lack of visibility of fingerprints. However, this diagram shows only three preferred directions, 16 °, 89.9 ° and 160 ° with respect to the transverse direction. These differences are very important, higher than the maximum of 60 ° required by the invention, and we'll see that in fact fingerprints remain highly visible on a stainless steel surface with this print.

Figures 5 to 7 show the individual polygon surfaces 4 making part of a printed pattern on the surface of the object, made according to the invention. As seen, these polygons are 4, in the represented case, irregular hexagons, within which are formed of straight lines 5, which are themselves separated by ridge lines 6. The axes of each rib 5 are separated from 0.2 mm in the illustrated example, and according to the invention this distance may vary between 0.1 and 0.3 mm. The depth of the grooves 5 with respect to the tops of the ridges 6 is, in the example shown, about 20 μηι. According to the invention, it could be 5 to 30 μηι. Figures 5-7 also show the diagrams of spectral analysis by Fourier transform of the isolated polygon corresponding 4

5 shows a polygon 4 whose axis striae 5 is oriented almost parallel to the rolling direction. The rate of isotropy between the rolling direction and the transverse direction is 8.36%, and is therefore very low, indicating a very marked orientation of the grooves as a whole. The main preferred direction is actually in the direction of 99.1 ° with respect to the transverse direction, a second preferred direction is in the direction 90 °, a third preferred direction is in the direction of 84.3 °.

6 shows a polygon 4 identical to that of Figure 3, whose axis is oblique striations (about 45 °) relative to the rolling direction. The isotropic rate is 4.92%. The main preferred direction is in the direction of 130 ° with respect to the transverse direction, a second preferred direction is in the direction 136 °, a third preferred direction is in the direction 123 °.

7 shows another polygon 4 identical to that of Figure 3, the axis of the lines 5 is substantially perpendicular to the rolling direction. The isotropic rate is 7.08%. The main preferred direction is in the direction of 0.0729 ° with respect to the transverse direction, a second preferred direction is in the direction 171 °, a third preferred direction is in the direction 166 °.

Figure 8 shows in perspective a portion of the surface of a sheet 1 according to the invention, whose surface has a random dither polygons 4 as defined above. It shows that the contours and orientations streaks of 4 different polygons are varied, so we should expect that the isotropic rate of the surface taken as a whole is relatively high, as confirmed the measures that will be seen later. We also see that, according to a preferred variant of the invention, the polygons 4 are not all located in the same plane, and that the reference planes of two contiguous polygons are inclined 1 to 10 ° with respect to the other.

9 shows a top view of a portion of 400 mm 2 of the surface of a sheet 1 according to the invention, with its spectral analysis chart by Fourier transform. Measurements of isotropy rate between rolling direction and the transverse direction and angular orientations are preferred, as in Figures 1, 2 and 3, carried out on all of the represented surface and not, as in Figures 5 7, on isolated polygons. The isotropy is significantly more pronounced since the Preferred directions streaks of various polygons are very diverse: 40.3%. Rays preferred orientations of the surface taken as a whole form a sheaf of rays of six groups, these groups with different main directions frankly. It is therefore no longer find an almost single preferred orientation in the rolling direction as in the reference examples of FIGS 1 and 2. The three preferred directions are 97.0 °, 75.5 ° and 119 °, and are thus frankly distinct from each other since between two adjacent preferred directions there is a gap of, respectively, 21, 5 ° and 22 °. But the difference between these three preferred directions is significantly lower than in the case of the reference engraving, not according to the invention, figures 3 and 4.

10 shows another example of a surface of a sheet 1 according to the invention. Isotropy is 53.3% therefore even better than for example in Figure 7. It is seen in the spectrum seven preferred orientations, the top three are separated by 21, 8 ° and 22.2 ° with respect to their (s) close (s), as is clear from the chart data.

11 shows another example of a surface of a sheet 1 according to the invention. Isotropy is 50.2%. It is seen in the spectrum preferred orientations in September, the three main are spaced 22.8 ° and 30 ° relative to their (s) close (s), as shown by the chart data.

12 shows another example of a surface of a sheet 1 according to the invention. It has, in particular, many polygons having four sides. Isotropy is 60.5% therefore even better than those of the other examples shown in Figures 7 to 9. It is seen in the spectrum seven preferred orientations, the top three are separated by 54 ° and 30 ° relative to their ( s) close (s), as is clear from the chart data.

Figure 13 shows the smooth surface 7 of reference of a sheet of a stainless steel type AISI 304 having undergone bright annealing, that a user left a clearly visible fingerprint.

14 shows, with the same magnification as Figure 13, the surface 8 of a sheet stainless steel type AISI 304 having undergone bright annealing, on which a user also left a visible fingerprint, although 8 shows the surface etching in accordance with that shown in figures 3 and 4. It is clear that any type of etching the surface of the stainless steel sheet is not suitable to solve the problem of mitigation visibility traces satisfactorily finger.

15 shows, with the same magnification as Figure 13, the surface 9 of a stainless steel sheet of the same type as that of Figure 13 and viewed in the same lighting conditions, the surface is etched in accordance with the present invention (it is the type of etching Figure 12) and on which a user put his finger also. Here, the fingerprints not visible as such, and only manifested by the presence of a slightly darker area, indicating a reflection of slightly less light than the rest of the surface of the sheet. The aesthetic appearance of the surface 9, including its brilliance, is not significantly altered for an observer who looks at a normal distance.

It is preferable that the sides of the ridges 5 are not straight, but have a curved surface and / or better asperities. In this way, the distribution of the outgoing light streaks 5 is more random, and this enhances the effect of attenuation of the visibility of fingerprints.

The invention is applicable to all types of stainless steels, regardless of their microstructure. It is particularly interesting to use for steels undergoing bright annealing, and on which fingerprints are the most visible. But steels treated with conventional annealing, for which a surface gloss is also obtained, can also advantageously benefit from the invention.

CLAIMS

1. - Laminated Object stainless steel, characterized in that its surface has a relief pattern and having a hollow Random juxtaposition of at least two polygons species (4), each of said polygons (4) having at least three sides having an area of between 1 and 9 mm 2 , a difference between its smallest and largest dimension of between 0.5 and 3 mm, each polygon (4) consists of grooves (5) substantially parallel rectilinear, s' spreading each of ± 15 ° with respect to the average orientation of the striations, from 5 to 30 μηι depth separated by ridge lines (6) and the axes of which are spaced 0.1 to 0.3 mm, and whose spectral analysis by Fourier transform performed on a square of at least 100 mm 2, Shows that it has an isotropy of at least 40% between the rolling direction and the transverse direction and whose top three preferred angular orientations, two adjacent preferential angular orientations are separated by at least 20 ° and at most 60 °.

2. - An article according to Claim 1, characterized in that the reference plane of each polygon (4) is inclined with respect to the reference planes of its polygons (4) contiguous from 1 to 10 °.

3. - The article of claim 1 or 2, characterized in that the spectral analysis of its surface has between three and eight preferential angular orientations.

4. - Object according to one of claims 1 to 3, characterized in that the flanks of said ridges (5) have curved surfaces and / or having asperities.

5. - Object according to one of claims 1 to 4, characterized in that it is a sheet, a plate or a band.

6. Article according to one of claims 1 to 4, characterized in that it was created by cutting and / or shaping of a metal sheet, plate or strip as claimed in claim 5, constituting a precursor of said object

7. A method of manufacturing an object according to one of claims 1 to 6, characterized in that said surface having said pattern is obtained during the rolling of the object, or a precursor of said object by the pressure a rolling roller on the surface of the object or its precursor, said cylinder itself having on its surface a pattern for obtaining said pattern on the surface of the object.