SURFACE TEXTURING OF DEFORMING TOOLS

Abstract

A method of producing a deforming tool (2) having a structured embossing surface (4) which can be brought into contact with a surface of a substrate (1) for plastic deformation thereof (of the substrate), the method comprising: determining a target structure to be produced on the substrate (1); geometrically distorting the target structure, such that an “embossing image structure” is obtained; inverting the “embossing image structure”, such that the embossing structure for the embossed surface (4) is obtained; and producing the embossing surface (4) of the deforming tool (2) according to the embossing structure.

Claims

1. A method of producing a deforming tool (2) having a structured embossing surface (4) which can be brought into contact with a surface of a substrate (1) for plastic deformation thereof (of the substrate), the method comprising: determining a target structure to be produced on the substrate (1); geometrically distorting the target structure, such that an “embossing image structure” is obtained; inverting the “embossing image structure”, such that the embossing structure for the embossed surface (4) is obtained; and producing the embossing surface (4) of the deforming tool (2) according to the embossing structure.

2. The method according to claim 1; characterized in that the target structure is defined by a transfer function (OA) the parameters of which comprise the embossing structure and one or more process parameters.

3. The method according to claim 2; characterized in that one or more of the process parameters describe(s) the deformation behavior of the substrate (1) during the plastic deformation along one or more main directions.

4. The method according to claim 3; characterized in that the process parameters are comprised of one, a plurality of, or all of, the following parameters: the “flow tension” of the substrate (1), a geometric parameter of the embossing surface (4), the elongation of the substrate (1) in the deformation along a main direction, the embossing speed, the tension along one or more main directions during the deformation, and a coefficient of friction between the embossing surface (4) and the substrate (1).

5. The method according to claim 1; characterized in that the deforming tool (2) comprises a working roll (3), preferably a dressing roll.

6. The method according to claim 5; characterized in that the target structure is described by a transfer function the parameters of which are comprised of the embossing structure and one, a plurality of, or all of, the following parameters: the “flow tension” of the substrate (1), the diameter of the working roll (3), the elongation of the substrate (1) along the rolling direction, the rolling speed, the substrate tension at the entrance to the working roll (3), the substrate tension at the exit from the working roll (3), and the friction in the roll gap.

7. The method according to one claim 1; characterized in that the substrate (1) is a sheet or plate, preferably a sheet or plate of metal.

8. The method according to claim 1; characterized in that the embossing structure has an anisotropic characteristic, wherewith the corresponding characteristic in the target structure is isotropic.

9. The method according to claim 1; characterized in that the embossing surface (4) is produced by one, a plurality of, or all of, the following techniques: SBT, EDT, LT, EBT, and Pretex.

10. A deforming tool (2) having a structured embossing surface (4) which can be brought into contact with a surface of a substrate (1) for plastic deformation thereof wherein the deforming tool (2) is characterized in that the deforming tool (2) has a working roll (3) a surface of which bears the embossing surface (4), and in that a structure of the embossing surface (4) has a plurality of elliptically shaped patterns which have their main axes oriented transversely to a rolling direction.

11-13. (canceled)

Description

BRIEF DESCRIPTION OF THE FIGURE

[0022] FIG. 1 illustrates schematically the progress of a re-rolling process, wherein a metal strip or the like is plastically embossed with a structure by means of a structured embossing surface.

DETAILED DESCRIPTION OF PREFERRED EXEMPLARY EMBODIMENTS

[0023] In the following, advantageous exemplary embodiments of the invention are described in detail, with reference to the FIGURE. It should be noted that the herein-described exemplary embodiments are not intended to limit the scope of the invention, but rather they serve to aid in describing and clarifying the invention, in which connection the features represented, or combinations of these, in the exemplary embodiments, should not all be deemed essential for the invention.

[0024] FIG. 1 shows schematically a process of re-rolling of a metal strip (or plate) 1, which serves as an example of the general designation “substrate”. The reference numeral 1 refers not only to a metal strip but also the surface structure of the metal strip which may be present at the strip entrance portion of the rolling stand 2 prior to the re-rolling. At this location, the metal strip 1 has a surface structure OE, a value of strip thickness h, and a value of “flow stress” kf.

[0025] The rolling stand 2 brings about a suitable geometric structure and/or texture in a combined embossing and thickness reduction process, on one or both surfaces of the metal strip 1. In other words, not only is embossing effected on the surface structure of the metal strip, but also the strip experiences lengthening accompanied by thickness reduction. In addition to the texturing itself, there is deformation along a further skin direction, in the present case the longitudinal and transport direction of the strip 1. By combining these two process operations (lengthening and structuring) in one step, the productivity of the process can be increased. In addition, it is possible to achieve surface textures of a higher degree of deformation (higher degree of roughness), which would not be possible without such a combined deformation along one or more main directions, or would be possible only at great expense, e.g. would require a substantial increase in the roll diameter. In the present example, the working roll 3, namely the roll having an embossing surface with a particular surface structure, which structure it embosses on the substrate 1, has a diameter of only ca. 400 mm. Obviously, other diameters are possible. E.g., successful tests with a roll diameter of ca. 230 mm have been carried out. It is significant that embossing with rolls having relatively small diameters is possible, with an embossing quality which previously was only attainable with larger rolls. The diameter of the working roll is designated D. It should also be noted that it is possible to perform the embossing with a plurality of working rolls, e.g. if both sides of the strip are to be embossed, or if the pattern sought to be realized requires more than one embossing step.

[0026] The working roll 3 has an embossing surface 4 (see FIG. 1). The embossing surface 4 has a structure suited for embossing the substrate 1. The structure of the embossing surface 4 can be described with a function which will be designated “OW”.

[0027] The resulting surface structure is the structure which, with passage through the roll stand 2, will be applied to the substrate 1, and will be designated surface structure 5; it is not only a function of OW but also depends on other process parameters, e.g. the elongation E which occurs as a consequence of the thickness reduction by the rolls, the roll speed v, the tension FE on the strip as it is being fed, the tension FA on the strip as it exits, and the friction p, in the roll gap. One or more of these parameters will determine the lengthening of the strip along the transport direction of the strip. The deformation which occurs distorts the structure intended to be imparted by the embossing surface 4 of the working roll 3, in particular resulting in an unintended “anisotropy” of the structure of the strip at the strip exit point.

[0028] The surface structure 5 which is present following the rolling step, i.e. at the exit from the roll stand 2, is described by a function “OA”. OA has the following general form:

OA=f(OW,OE,D,h,kf,∈,v,FE,FA,μ)  (1)

[0029] In the present context, the terms “isotropy” and “anisotropy” refer to one or more geometric characteristics which can be identified and compared in the embossing surface 4 and the target structure 5. E.g., if the embossing surface 4 of the working roll 3 has circles which result in ellipses having main axes parallel to the direction of transport, on the strip surface 5 at the exit of the roll stand 2, this is an example of the structure OW being anisotropic ally distorted.

[0030] In order to reduce the degree of anisotropy (or generally stated the distortion) of the rolling, as already mentioned it is possible to increase the diameter of the working roll, or to seek to increase the roll gap friction. Both of these options entail technical and/or process economics drawbacks, such as increasing the size of the apparatus and increasing the energy consumption.

[0031] The technical solution described in the following applies elsewhere as well. In the terminology used in connection with the above-described roll stand 2, the desired surface structure OA of the aluminum strip 1 is produced regardless of the degree of deformation by the working roll 3, by selecting a “compressed” (converted), generally distorted, surface texture OW. The distorted, generally anisotropic surface texture 4 of the working roll 3 is chosen as the inverse of the transfer function OA and is applied to the desired target texture OW. The structure defining the transfer function OA is referred to herein as the “embossing image structure”.

[0032] The process is then a combined embossing and thickness reduction process carried out by the working roll 3, with a suitably geometrically distorted embossing structure, wherewith the desired target structure is achieved through the lengthening of the strip 1. The nature and the degree of the geometric distortion of the pattern on the embossing surface 4 are selected such that it corresponds to the inverse transfer function OA on the substrate 1:

OW=f.sup.1(OA;OE,D,h,kf,∈,v,FE,FA,p)  (2)

[0033] In order to achieve a (the) fine adjustment of the embossing characteristics of the embossing roll 3, or of the apparatus in general, as applied to the substrate 1, one can modify additional process parameters, e.g. the tension on the strip at entry (at the entrance) FE and at exit FA, the elongation E, the roll speed v, and/or the friction p, (e.g. the lubrication) in the roll gap.

Exemplary Embodiment of the Transfer Function for Simple Elongation (“Stretching”):

[0034] OA is represented by a height profile zA(x, y);
OW is represented by a height profile zW(x, y);
x is the rolling direction;
y is the transverse direction.

zA(x,y)=−zW(x/(1+C.sub.2*∈),y/C.sub.1

with the factors C1, C2>0, which factors may be dependent on other process conditions such as h and

[0035] The inverse is:

zW(x,y)=−C1*zA(x*(1+C2*∈),y)

[0036] A fine adjustment, e.g. by adjusting the elongation E and the strip tension at entrance

ΔOA=[∂f(OW;OE,D,h,kf,∈,v,FE,FA,μ)/∂∈]Δ∈+[∂f(OW;OE,D,h,kf,∈,v,FE,FA,μ)/∂FE]ΔFE

FE, is expressed as follows:

[0037] After the embossing structure is determined in this manner, the embossing surface can be produced. Various methods are available to accomplish this, e.g. shot blast texturing (SBT), electrical discharge texturing (EDT), laser texturing (LT), electron beam texturing (EBT), and Pretex texturing.

[0038] To the extent practicable, individual features described in the exemplary embodiments can be combined and or interchanged, without departing from the scope of the invention.

LIST OF REFERENCE NUMERALS

[0039] 1 Substrate at the entrance point of the strip. [0040] 2 Roll stand. [0041] 3 Working roll. [0042] 4 Embossing surface. [0043] 5. Substrate having the target structure, at the exit point of the strip.