EP0141762A2 - Method and device for the manufacture of reinforced metallic strips - Google Patents

Abstract

Metal sheets of aluminum are provided with raised reinforcing portions of substantial height by rolling. The rolls have recesses or channels (6) whose side faces are in a counter-taper configuration with respect to a plane perpendicular to the axis of the cylinder, with an angle of inclination ( alpha ) of up to 5 DEG . The resulting product may advantageously be used for producing perforated metal sheets with high modulus of inertia.

Description

The object of the present invention is a method for obtaining by rolling metal strips provided with reinforcing reliefs of considerable height, as well as the device for implementing the method, that is to say the cylinders of corresponding appropriate form.

For the economic realization of decking and cladding, it has long been known to use sheets whose moment of inertia is reinforced by ribs. To this end, aluminum panel elements in the shape of a veil are commonly manufactured by spinning, reinforced on one side by longitudinal ribs. By spinning, elements are even made in the form of a box with a closed section in the direction of spinning. However, spinning remains an expensive process.

By rolling between cylinders having patterns or grooves engraved in the hollow, aluminum strips are commonly manufactured comprising corresponding patterns in relief, which can then be cut into sheets of desired format. However, these patterns such as those of teardrop sheets are thin, of the order of a millimeter. They have a decorative or non-slip effect, but have practically no influence on the bending strength of the sheets.

To facilitate the rise of the rolled metal in the cavities of the cylinder, avoid incipient fractures at the base of the relief patterns of the sheet, the cavities of the cylinder are connected without a sharp angle with the surface of the cylinder, most often by a surface rounded or at least chamfered. In general, in the prior art, the lateral faces of the cavities of the cylinder are inclined surfaces converging towards the bottom of the cavities and not perpendicular to the surface of the cylinder.

The calculation shows, moreover, that, in order to obtain patterns of significant thickness on the strip, it is desirable to have a significant coefficient of friction between metal and cylinder, also a sharp reduction in thickness of the metal on both sides. other of the motif. These are difficult and expensive rolling conditions. However, it appeared that, if it was not desirable to have sharp edges at the connection between the surface of the cylinder and the surface of the cavities but, in accordance with the prior art, rather rounded or at least chamfered connections, it was, however, undesirable , contrary to popular belief, to continue these inclined surfaces converging to the bottom of the cavities (normal draft). The metal coming to fill the cavities of the cylinder is, in fact, braked in its lateral displacement by friction on the inclined surfaces of the cavities. It has been found that much better results are obtained by producing cavities on the rolling cylinders, the lateral surfaces of which, with the exception of the mouth, are perpendicular to the axis of the cylinder, or even inclined "against". skin ", that is to say cavities with a dovetail profile which widens towards the bottom. The metal, by penetrating into such cavities, is no longer braked by friction against these side walls. However, the widening of the cavities towards their bottom can only be small. The inclination (a) "undercut" of the side walls with respect to the perpendiculars to the axis of the cylinder must be limited to an angle of the order of 5 °, this in order to limit the possible development of the metal pushed back into the cavities and allow without too much difficulty, in the subsequent step, the exit from the cavities of the cylinder of the patterns formed in relief on the strip. This shape, slightly flared towards the bottom of the cavities of the rolling rolls, has proved particularly advantageous for the production of sheets ribbed longitudinally in the rolling direction, the cavities then having the form of circular grooves.

Obviously, the high ribs with parallel lateral faces adhere strongly in the cavities or grooves of the cylinder. This phenomenon is further accentuated when the cavities or grooves of the cylinder have "undercut" side faces which generate in the strip ribs with a dovetail cross section, in the axial plane of the cylinders.

It is necessary, at the exit of the cylinder, to exert a significant traction on the strip to detach it from the cylinder and avoid its winding on the latter. The head of the ribs, or at least their middle part, if the metal has not filled all the volume of the grooves, is in some so rolled laterally as they exit through the reduced outlet opening of the grooves. Contrary to what one might have thought, there is no tearing of a rib, nor even the beginning of a rupture at the root of the ribs, this obviously on the condition that the inclination to undercut the lateral faces of the grooves of the cylinder remains weak, that is to say of the order of 5 ° with respect to planes perpendicular to the axis of the cylinder. The traction to be exerted on the laminated strip to detach it from the grooved cylinder, if it is expressed with respect to the cross section of the strip, may be greater than 40 N / mm2. For aluminum and its alloys, it is generally around 40 to 50 N / mm2.

However, in view of the powers available on current cold rolling mills, high reliefs can only be obtained on relatively soft metals and alloys that are cold enough ductile; aluminum alloys in the annealed or neighboring states, for which the elastic limit is less than or equal to 200 MPa, are particularly well suited to the process according to the invention. Furthermore, the filling of the cavities requires certain geometrical conditions, the depth (p) of these being generally greater than their width (1), and they must be separated by a distance (d) of between 0.5 1 and 3 1. Below 0.5 1, the mechanical resistance of the cord separating two splines becomes insufficient; beyond 3 1, "the filling of the grooves with the metal is insufficient.

, S étant la section transversale initiale et s étant la section transversale finale du produit, soit élevé, en général supérieur à 60.It is preferable that the overall wrinkling imposed on the strip, measured by

, S being the initial cross section and s being the final cross section of the product, ie high, generally greater than 60.

The method according to the invention therefore consists in machining at least in one of the cylinders cavities or grooves conforming to the description above and in setting them up, in introducing a strip the thickness of which is such that the overall working is greater than 60% with a slight tightening (P) of the rollers, to fix the strip on the winder and to exert a certain traction (F), to gradually and simultaneously increase the speed, the tightening (P) and the traction (F), so that obtain the desired canvas thickness (e).

It was thus possible to produce sheets with high ribs, that is to say sheets provided with longitudinal ribs whose height (h) is more than twice the thickness (e) of the metallic veil joining them to the base. . This height (h) can easily be five times the thickness (e) of the web joining the ribs.

For example, with ribs whose height (h) is equal to their spacing (d), that is to say whose pitch is of the order of twice their height, we obtain, with inertia module equal in the longitudinal direction, a weight gain of the order of half compared to a solid sheet of the same kind and of the same total thickness.

This rolling method also applies to composite strips where the metal core is coated with at least one surface metal layer (such as brazing, cathodic protection or the like) or even to metal-plastic composites.

The junction of two ribbed strips or sheets thus obtained by any known means (brazing, bonding, etc.) makes it possible to obtain structures resistant to biaxial forces when the ribs are crossed (not parallel).

• La figure 1 représente, en vue cavalière, une installation de laminage réalisée conformément à l'invention.
• La figure 2 représente, à plus grande échelle, en coupe, une portion de la surface cannelée du cylindre de laminage.
• La figure 3 représente, à la même échelle, une portion de bande d'aluminium réalisée selon l'invention, le plan de coupe étant perpendiculaire aux nervures de la bande.
• La figure 4 représente une vue en coupe selon l'axe _AA' (figure 5) d'une tôle à nervures hautes dont le voile a été perforé selon des fentes équidistantes des nervures.
• La figure 5 représente la même tôle (figure 4) vue en plan.
• La figure 6 représente une vue en coupe selon l'axe BB' (figure 7) de la tôle des figures 4 et 5 dont les fentes ont été élargies par traction latérale de la tôle.
• La figure 7 représente la vue en plan de la même tôle.

The invention will be better understood from the description below of a particular embodiment and by examining the corresponding figures.

• FIG. 1 represents, in a side view, a rolling installation produced in accordance with the invention.
• FIG. 2 represents, on a larger scale, in section, a portion of the grooved surface of the rolling cylinder.
• FIG. 3 represents, on the same scale, a portion of aluminum strip produced according to the invention, the cutting plane being perpendicular to the ribs of the strip.
• 4 shows a sectional view along the axis _AA '(Figure 5) of a sheet with high ribs, the web has been perforated according to equidistant slots of the ribs.
• Figure 5 shows the same sheet (Figure 4) in plan view.
• 6 shows a sectional view along the axis BB '(Figure 7) of the sheet of Figures 4 and 5 whose slots have been widened by lateral traction of the sheet.
• Figure 7 shows the plan view of the same sheet.

In FIG. 1, we see a flat strip (1) 12 mm thick and 950 mm wide, made of annealed quality aluminum 3003, which is laminated between two cylinders (2, 3) to give a strip (4) whose cross section is shown in Figure 3. At the exit of the cylinders, this strip (4) is wound on a winder (5) which exerts a tensile force (F) of the order of 200,000 N. The clamping force (P) between the two cylinders (2, 3) is of the order of 7,000,000 N, that is to say relative to the width of the sheet (1) of the order of 7,000 N / mm.

The cylinder (2) comprises a series of parallel peripheral grooves (6) the cross section of which is shown in FIG. 2, while the cylinder (3) comprises, according to the prior art, a series of hollow patterns (7) of shallow depth , regularly arranged on its surface.

In FIG. 2, it can be seen that, if the grooves (6) of the cylinder are connected laterally by chamfered surfaces (8) with the cylindrical surface (9) of the cylinder (2), these grooves (6) have lateral faces ( 10) divergent with "undercut", which gives the grooves (6) a greater width at the bottom than at the periphery of the cylinder (2). The flaring of these grooves (6) towards the bottom is very low. The angle (a) of the generatrices of the lateral faces (10) with the perpendiculars to the axis of the cylinder (or the axial plane of the groove) is only 5 °. These grooves have a depth (d) of 7 mm and a width (1 ₁ ) of 4 mm at their narrowest part, at the periphery of the cylinder (2). They are 4 mm apart (d).

In Figure 3, we see that the ribbed strip (4) has on one side ribs (11) of height (h) substantially equal to the depth (p) of the grooves (6) of width (1 ₁ ) substantially equal to the width (1) of the grooves (6), in their narrowest part and of pitch (p) equal to the pitch of said grooves (6). On the other side, the strip (4) has asperities (12) of small thickness, here 0.2 mm corresponding to the patterns (7) of the cylinder (3). These asperities correspond to the prior art.

Finally, in its thinnest part, constituting the web (13) connecting between the ribs (11), the strip (4) has a thickness (e) of only 1.8 mm.

During rolling, the metal of the strip (1) pushed back by the peripheral surface of the cylinder (2) penetrates substantially to the bottom of the grooves (6) of the cylinder (2) to form ribs (11). The metal flourished in these grooves (6) wider at the bottom than at the inlet, however without filling them completely, as shown by the width (1 ₂₎ of the ribs (11) at their upper end. This width (1 ₂ ) is slightly less than the width (1 ₁ ) of said grooves (6) at their entry. In this particular case, 1 ₁ = 3.8 mm. It is only at the base of the ribs (11) that these have their greatest width 1 _. and are limited by parallel faces (14). During rolling, the metal of the strip (1) was forced back by the pressure exerted by the external surface (9) of the cylinder, in the grooves (6). It flourished in these grooves following their divergent lateral faces (10), this up to substantially mid-height of the grooves (6), before being "stretched" at the outlet of the groove.

At the outlet of the cylinders (2, 3), the divergent base of the ribs (11), trapped in the grooves (6) against the undercut, retains the strip (4) pressed against the cylinder (2). The strip (4) would be wound on the cylinder (2) if it was not pulled by the winder (5) with a force (F) of the order of 200,000 N. We thus notice in FIG. 1, that at the exit of the cylinders (2, 3), the strip (4) forms a slight fold (15) against the cylinder (2). The force (F) allowing the extraction of the sheet (4), causes a sort of lateral rolling of the base of the ribs (11). Provided not to be exaggerated, and to bring breaking points at the base of the ribs (11), the lateral rolling of these ribs makes it possible to obtain the desired great heights and proves to be beneficial by compressing the metal.

In the case of aluminum or its alloys with cylinders (2) to deeper grooves, a pressure (P) between cylinders (2, 3) greater than 7000 N / mm in sheet metal width and a tensile force greater than 40 N / mm2 in sheet metal section, we can easily make ribs higher, for example ribs of height h of the order of 10 mm for a thickness of web (e) of the order of 2 mm.

One can use the laminated sheets with high ribs described above to make perforated and ribbed sheets in the form of thick grids having an appearance quite similar to grids made of "expanded metal". But these grids have a much better mechanical resistance thanks to their reinforcement by their high ribs. The high ribs of the initial sheet are, in fact, preserved and only deformed in a zig-zag. They constitute a very resistant framework.

For the production of such perforated sheets in the form of ribbed grids, one begins by making known perforations in the thin parts of the sheet (4), that is to say the web (13). As shown in Figures 4 and 5, these perforations (16) are made in the form of equidistant parallel slots of the ribs (11) in each of the intervals between ribs (11). As can be seen in Figure 5, these slots are staggered in a horizontal plane. The middle of each slot (16) is at the height of an unperforated part of the web between two neighboring ribs (11).

A lateral traction is then carried out on the sheet. The slots (16) widen in the form of substantially hexagonal holes (17), as shown in Figures 6 and 7. Simultaneously, the ribs (11) deform in a zig-zag (18). The high and relatively wide ribs give good rigidity to the perforated sheet which has a honeycomb appearance.

In the example described, the slots all have the same length, but one could also obtain perforated and ribbed sheets with slots of different lengths. It is important, however, by good execution, that they are regularly staggered in a horizontal plane.

In the example described, the cylinder (3) has small hollow patterns (7) which give rise to roughness (12). The cylinder (3) could just as easily be smooth or, on the contrary, include deep grooves similar to the grooves (6) of the cylinder (2). With a grooved cylinder (3), we would obtain a sheet (4) with ribs (11) on its two faces.

Claims (10)

1 ° / Cold rolling mill cylinder for producing strips (or sheets) with very high reliefs comprising cavities (6) whose depth is at least equal to the width (1) and whose distance (d) is between 0.5 and 3 1, characterized in that these cavities have a transverse dovetail profile whose side walls (10) diverge slightly towards the bottom. 2 ° / rolling mill cylinder according to claim 1, characterized in that the cavities (6) have the form of circumferential grooves. 3 ° / cylinder according to claim 1 or 2, characterized in that the angle (a) of inclination of the lateral faces (10) of the grooves or cavities, with perpendiculars to the axis of the cylinder, is between 0 and 5 ° (limits included). 4 ° / rolling mill cylinder, according to one of claims 1 to 3, characterized in that the grooves or cavities (6) having a dovetail profile, are connected with the envelope surface (9) of the cylinder by rounded or at least chamfered edges (8). 5 ° / Cold rolling process of aluminum metal strips (or its alloys), characterized in that: a) at least one of the working rollers according to one of claims 1 to 4 is machined and it is installed, b) a strip (1) whose thickness is such that the overall working is introduced

more than 60%, with a slight tightening (P) of the cylinders (2, 3), c) the strip (4) is fixed to the winder (5) and a certain traction (F) is exerted, d) the speed and pressure of the working rollers (P) are gradually increased while increasing the traction (F) on the ribbed strip, so as to obtain the desired canvas thickness (e). 6 ° / A method according to claim 5, characterized in that the traction (F) is greater than 40 _{N /} mm2 of cross section (s) of the final strip (4). 7 ° / strip (or sheet) with long longitudinal ribs obtained by the method according to claim 5 or 6, the distance of the ribs (d) is between 0.5 and 3 times their thickness at the base (1 ₁ ), characterized in that their height (h) is greater than twice the thickness (e) of the web joining them. 8 ° / strip or ribbed sheet according to claim 7, characterized in that the height (h) is of the order of 5 times the thickness of the fabric (e). 9 ° / Use of a sheet according to claims 7 or 8, for the production of a perforated and ribbed sheet, characterized in that the sheet is first of all perforated by equidistant slots of the ribs and staggered in a plane horizontal then said sheet undergoes lateral traction. 10 ° / perforated sheet in the form of a honeycomb obtained according to claim 9.

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