METHOD FOR PRODUCING A SHEET METAL PRODUCT AND SHEET METAL PRODUCT

Abstract

A method for producing a sheet metal product (1) from a sheet metal preliminary product (2) is proposed, wherein at least one surface (7) of the sheet metal preliminary product (2) is coated with a coating, wherein the sheet metal preliminary product (2) is rolled, wherein depressions (6) are rolled into the surface (7) during the rolling operation, wherein after the coating and rolling operations lubricant (8.1) is introduced into the depressions (6), wherein after the introduction of lubricant (8.1) the sheet metal preliminary product (2) is mechanically formed by a forming tool (5), characterized in that the surface (7) is coated in such a way that, in the forming tool (5) during the forming process, in particular under relative movement between sheet metal surface and tool surface, the coating is elastically deformable under loads of 0.5 MPa to 20 MPa and plastically deformable under loads of above 20 MPa.

Claims

1. A method for producing a sheet metal product (1) from a sheet metal preliminary product (2), wherein at least one surface (7) of the sheet metal preliminary product (2) is coated with a coating, wherein the sheet metal preliminary product (2) is rolled, wherein depressions (6) are rolled into the surface (7) during the rolling operation, wherein after the coating and rolling operations lubricant (8.1) is introduced into the depressions (6), wherein after the introduction of lubricant (8.1) the sheet metal preliminary product (2) is mechanically formed by a forming tool (5), characterized in that the surface (7) is coated in such a way that, in the forming tool (5) during the forming process, the coating is elastically deformable under loads of 0.5 MPa to 20 MPa and plastically deformable under loads of above 20 MPa.

2. The method as claimed in claim 1, wherein the surface (7) is coated in such a way that, in the forming tool (5) during the forming process, the coating is elastically deformable under loads of 0.5 MPa to 15 MPa and plastically deformable under loads of above 25 MPa.

3. The method as claimed in either of the preceding claims, wherein the depressions (6) are rolled in as closed depressions (6) with respect to a main plane of extent of the sheet metal preliminary product (2).

4. The method as claimed in claim 3, wherein the depressions (6) are rolled in in the shape of an I, rectangle or square with respect to the main plane of extent of the sheet metal preliminary product (2).

5. The method as claimed in one of the preceding claims, wherein the depressions (6) are rolled in with a depth of 2 μm to 15 μm, preferably 2 μm to 10 μm, and particularly preferably 2 μm to 5 μm.

6. The method as claimed in one of claims 3 to 5, wherein the depressions (6) are rolled with a ratio of depth to volume of the depression (6) of 1:3 to 1:15, and preferably 1:5 to 1:10.

7. The method as claimed in one of the preceding claims, wherein depressions (6) are rolled in on at least 30% of the area of the surface (7) of the sheet metal preliminary product (2).

8. The method as claimed in one of the claims, wherein the depressions (6) are rolled such that a base (6.1) of the depression (6) has a smaller area than the projection of the depression (6) onto the main plane of extent of the surface (7).

9. The method as claimed in claim 8, wherein the depressions (6) are rolled in such that walls (6.2) of the depressions (6) form an angle (α) of 105° to 140°, and preferably 110° to 120°, with the main plane of extent of the surface (7).

10. The method as claimed in one of the preceding claims, wherein zinc is used as the coating.

11. The method as claimed in one of the preceding claims, wherein the sheet metal preliminary product (2) is coated by hot-dip galvanizing, wherein the sheet metal preliminary product (2) is coated before the rolling operation.

12. The method as claimed in one of claims 1 to 10, wherein the sheet metal preliminary product (2) is coated by electrolytic means, wherein the sheet metal preliminary product (2) is coated after the rolling operation.

13. A sheet metal product (1) produced by a method as claimed in one of the preceding claims.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1 schematically shows the method according to an exemplary embodiment of the present invention.

[0027] FIG. 2 schematically shows a detail of a sheet metal preliminary product according to an exemplary embodiment of the present invention.

[0028] FIG. 3 schematically shows a detail of the surface of a sheet metal preliminary product according to an exemplary embodiment of the present invention.

EMBODIMENTS OF THE INVENTION

[0029] In the various figures, the same parts are always provided with the same reference signs and will therefore generally also be specified or mentioned only once in each case.

[0030] FIG. 1 schematically illustrates the method according to an exemplary embodiment of the present invention. The sheet metal preliminary product 2 is provided in the form of a strip (coil material) or blank and rolled with skin pass rollers 3. In this context, the skin pass rollers 3 roll trough-shaped depressions (see FIG. 2) into the surface of the sheet metal preliminary product 2. The depressions are several micrometers deep, several micrometers long and wide, have a regular arrangement and are rolled in on approx. 40% of the surface. For this purpose, the skin pass rollers 3 have previously been processed, preferably by a laser texturing process, such that they have a corresponding negative on their surface for rolling in the depressions. It should be noted here that the negative has an elevation for each depression, the elevation being higher than the depth of the depression rolled in by the elevation. The reason for this is because, among other things, during the rolling operation the skin pass rollers 3 are not in contact with the surface of the sheet metal preliminary product 2 over the entire surface area, this possibly having negative effects on the rolling/skin passing operation. In order to avoid this, a skin passing liquid is preferably introduced between sheet metal preliminary product 2 and skin pass roller 3, for example.

[0031] Following the rolling/skin passing operation, the surfaces are zinc-coated by electrolytic means to a thickness of approx. 7 μm in the coating installation 4. After the coating by electrolytic means, the zinc layer follows the surface geometry of the underlying surface, in particular the rolled-in depressions. As an alternative, it is conceivable that the zinc-coating is performed by means of hot-dip galvanization. In this case, however, the coating would have to be carried out before the rolling/skin passing operation, because a coating applied by hot-dip galvanizing follows the surface geometry of the underlying surface, in particular the rolled-in depressions, less well than coating by electrolytic means. The rolling in of the depressions downstream of the hot-dip galvanization would, however, compensate for this disadvantage again.

[0032] In the oiling installation 8, the lubricant 8.1 is now introduced into the depressions on the coated surface. In order to avoid unnecessary costs and to have a positive environmental impact, it should be ensured that essentially only as much lubricant 8 as the depressions can accommodate is introduced.

[0033] The rolled and coated sheet metal preliminary product 2 is cut to length from the strip to form a blank and then subjected to forming in a forming tool 5. Deep drawing is illustrated by way of example here as one possible form of the forming operation. The sheet metal preliminary product 2, which is still in the form of a blank, is inserted into the forming tool 5. Outer edges of the sheet metal preliminary product 2 are retained by hold-down devices 5.3 of the forming tool 5 on supports 5.4 of the forming tool 5, while the punch 5.1 presses the inner region of the sheet metal preliminary product 2 into the die 5.2. This produces loads that act on the sheet metal preliminary product 2, including on the hold-down devices 5.3, on the supports 5.4 and on the punch 5.1. These loads are in the single-figure MPa range. Loads likewise act on the sheet metal preliminary product 2 at the drawing edges 5.5. However, the loads here are significantly higher and are situated in a region in which the coating is plastically deformed, the depressions are leveled and the lubricant 8.1 in the depressions is released for the purpose of lubrication. The flow of the sheet from the supports 5.4 in the direction of the drawing edges 5.5 during the deep drawing operation repeatedly transports new depressions to the drawing edges 5.5, which new depressions are likewise leveled there by plastic deformation and release the lubricant 8.1 present therein. This enables continuous and very precisely selective local lubrication. One skilled in the art will understand that the method according to the invention can likewise be used in other forming processes. Bending, twisting, pressing and stretching are mentioned only as further examples, the examples mentioned not being a complete list of the possible forming methods.

[0034] FIG. 2 schematically illustrates a detail of a sheet metal preliminary product 2 according to an exemplary embodiment of the present invention. A section orthogonal to the main plane of extent of the surface 7 of the sheet metal preliminary product 2 can be seen. The regularly arranged depressions 6 are several micrometers deep and comprise the base 6.1 and the walls 6.2. The walls 6.2 form an angle α from 110° to 120° with the main plane of extent of the surface 7.

[0035] FIG. 3 schematically shows a detail of the surface 7 of a sheet metal preliminary product 2 according to an exemplary embodiment of the present invention. What can be seen are depressions 6, the projections of which onto the main plane of extent of the surface 7 are I-shaped. The surface 7 has the depressions 6 on more than 30% of its area.

LIST OF REFERENCE SIGNS

[0036] 1 Sheet metal product [0037] 2 Sheet metal preliminary product [0038] 3 Roller [0039] 4 Coating installation [0040] 5 Forming tool [0041] 5.1 Punch [0042] 5.2 Die [0043] 5.3 Hold-down device [0044] 5.4 Support [0045] 5.5 Drawing edge [0046] 6 Depression [0047] 6.1 Base [0048] 6.2 Wall [0049] 7 Surface [0050] 8 Oiling installation [0051] 8.1 Lubricant [0052] α Angle