Method for marking workpieces, and workpiece

Abstract

A method for marking a wordpieces and workpiece are disclosed. In an embodiment the method includes applying an identification to a blank in places and after applying the identification to the blank, deforming the blank to form a metal body, wherein deforming the blank comprises rolling so that a thickness of the blank changes more strongly than a width of the blank when the metal body is formed, wherein the identification remains on the metal body at least until after deforming the blank and is not destroyed by deforming the blank, and wherein the identification, both to the blank and to the metal body, has at least one of a difference in reflection or a difference in remission and an albedo difference of at least 15 percentage points in at least part of at least one of a near ultraviolet spectral region, a visible spectral region or a near-infrared spectral region.

Claims

1. A method for marking workpieces, the method comprising: providing a blank; applying an identification comprising a phosphor to the blank in places; and after applying the identification to the blank, deforming the blank to form a metal body, wherein deforming the blank comprises rolling so that a relative change in thickness of the blank is larger than a relative change in width of the blank when the metal body is formed, wherein the identification remains on the metal body at least until after deforming the blank and is not destroyed by deforming the blank, and wherein the identification, both to the blank and to the metal body, has at least one of a difference in reflection, a difference in remission or an albedo difference of at least 15 percentage points in at least part of at least one of a near ultraviolet spectral region, a visible spectral region or a near-infrared spectral region.

2. The method according to claim 1, further comprising, after deforming the blank, tempering or annealing the metal body so that the metal body comprising the identification is heated to a temperature of at least 350° C. for a time period of at least one hour, wherein, while deforming the blank, the identification is completely pressed into the blank, and wherein the identification differs both from the blank and from the metal body before deforming the blank and after tempering or annealing in a machine-readable manner at least in the near ultraviolet spectral region, the visible spectral region or the near-infrared spectral region.

3. The method according to claim 1, wherein applying the identification comprises applying the identification at least at both ends of the blank and on two opposite sides of the blank, and wherein the identification differs both from the blank and from the metal body, before deforming the blank and after tempering or annealing, in a machine-readable manner in the visible spectral region.

4. The method according to claim 1, wherein the thickness is changed by at least a factor of 1.5 and the width is changed by at most a factor of 1.001 while deforming the blank, and wherein, after deforming the blank, the metal body has a length of at least 250 m.

5. The method according to claim 1, wherein applying the identification comprises applying the identification periodically over an entire length of the blank.

6. The method according to claim 1, wherein the identification is formed by at least one contiguous identification region, and wherein the at least one identification region has an average extent of at least 20 times a mean diameter of pigments of the identification.

7. A method for marking workpieces, the method comprising: providing a blank; applying an identification to the blank in places; and after applying the identification to the blank, deforming the blank to form a metal body, wherein deforming the blank comprises rolling so that a relative change in thickness of the blank is larger than a relative change in width of the blank when the metal body is formed, wherein the identification remains on the metal body at least until after deforming the blank and is not destroyed by deforming the blank, wherein the identification, both to the blank and to the metal body, has at least one of a difference in reflection, a difference in remission or an albedo difference of at least 15 percentage points in at least part of at least one of a near ultraviolet spectral region, a visible spectral region or a near-infrared spectral region, wherein the identification comprises at least one phosphor causing the difference in reflection, the difference in remission or the albedo difference, wherein the identification comprises a light-permeable, inorganic matrix material which seals the phosphor at least after deforming the blank, and wherein the identification is fastened to the blank and to the metal body by the matrix material.

8. The method according to claim 7, wherein, while deforming the blank, the identification is completely pressed into the blank.

9. The method according to claim 7, further comprising, after deforming the blank, tempering or annealing the metal body so that the metal body comprising the identification is heated to a temperature of at least 350° C. for a time period of at least one hour.

10. The method according to claim 7, wherein applying the identification comprises applying the identification at least at both ends of the blank and on two opposite sides of the blank, and wherein the identification differs both from the blank and from the metal body, before deforming the blank and after tempering or annealing, in a machine-readable manner in the visible spectral region.

11. The method according to claim 7, wherein the thickness is changed by at least a factor of 1.5 and the width is changed by at most a factor of 1.001 while deforming the blank, and wherein, after deforming the blank, the metal body has a length of at least 250 m.

12. The method according to claim 7, wherein applying the identification comprises applying the identification periodically over an entire length of the blank.

13. A method for marking workpieces, the method comprising: providing a blank; applying an identification to the blank in places; and after applying the identification to the blank, deforming the blank to form a metal body, wherein deforming the blank comprises rolling so that a relative change in thickness of the blank is larger than a relative change in width of the blank when the metal body is formed, wherein the identification remains on the metal body at least until after deforming the blank and is not destroyed by deforming the blank, wherein the identification, both to the blank and to the metal body, has at least one of a difference in reflection, a difference in remission or an albedo difference of at least 15 percentage points in at least part of at least one of a near ultraviolet spectral region, a visible spectral region or a near-infrared spectral region, wherein the identification, viewed in plan view, is formed by a plurality of punctiform, island-shaped subregions having an average diameter of at most 50 μm, wherein the identification, seen in plan view and all subregions taken together, has a mean extension of at least 20 times the average diameter, and wherein a mean roughness of a surface of the workpiece at the identification deviates from a mean roughness of remaining regions of the surface of the workpiece by at most a factor of 2.

14. The method according to claim 13, wherein the identification comprises at least one phosphor causing at least one of the difference in reflection, the difference in remission or the albedo difference, wherein the identification comprises a light-permeable, inorganic matrix material which seals the phosphor at least after deforming the blank, and wherein the identification is fastened to the blank and to the metal body by the matrix material.

15. The method according to claim 14, wherein the matrix material partially breaks while deforming the blank and is subsequently melted again in order to seal the phosphor, and wherein the phosphor has a greater hardness than the blank, the metal body and a rolling tool.

16. The method according to claim 13, wherein, while deforming the blank, the identification is completely pressed into the blank.

17. The method according to claim 13, further comprising, after deforming the blank, tempering or annealing the metal body so that the metal body comprising the identification is heated to a temperature of at least 350° C. for a time period of at least one hour.

18. The method according to claim 13, wherein applying the identification comprises applying the identification at least at both ends of the blank and on two opposite sides of the blank, and wherein the identification differs both from the blank and from the metal body, before deforming the blank and after tempering or annealing in a machine-readable manner in the visible spectral region.

19. The method according to claim 13, wherein the thickness is changed by at least a factor of 1.5 and the width is changed by at most a factor of 1.001 while deforming the blank, and wherein, after deforming the blank, the metal body has a length of at least 250 m.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) A method described here and a workpiece described here are explained in more detail below with reference to the drawing on the basis of exemplary embodiments. Identical reference signs indicate the same elements in the individual figures. However, no relationships to scale are shown; rather, individual elements can be represented with an exaggerated size in order to afford a better understanding.

(2) In the figures:

(3) FIGS. 1A to 1H and FIGS. 3A to 3D show exemplary embodiments of method steps of methods for producing workpieces in schematic sectional illustrations and perspective representations;

(4) FIGS. 2A to 2B show schematic perspective representations of exemplary embodiments of workpieces; and

(5) FIGS. 4A to 4B show schematic plan views of exemplary embodiments of workpieces.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

(6) FIG. 1 illustrates an exemplary embodiment of a method described herein. According to FIG. 1A, a slab is provided as a blank 2. The slab has, for example, approximate dimensions of 1 m×5 m×0.2 m. The slab is made of an iron alloy, for example.

(7) As an alternative to this, according to FIG. 1B a roll is provided as a blank 2. This roll is produced, for example, by hot rolling from a slab, for example, according to FIG. 1A. Measurements of the rolled-up blank 2 lie, for example, in the order of magnitude of 1 m×3 mm×5 km.

(8) According to FIG. 1C, an identification 3 is applied to the blank 2 in places. The identification 3 is printed or sprayed on, for example, as a paste/ink. The paste/ink contains pigment particles and optionally a solvent and/or a binder. The solvent is configured to evaporate without residue in subsequent method steps. The optional binder is preferably designed to fasten the pigment particles to one another or to the blank 2. The pigment particles are, for example, ceramic particles or phosphor particles, wherein different types of pigment particles can be applied as a mixture.

(9) Furthermore, FIG. 1C illustrates that the identification 3 is applied in a distorted manner, so that the individual regions of the identification 3 have a significantly smaller extent along a length L of the blank 2 than along a width B. The blank 2 of FIG. 1C is in particular the slab of FIG. 1A or the roll of FIG. 1B.

(10) In the method step of FIG. 1D, the blank 2 is rolled to form a metal body 11. This is carried out with the aid of at least one rolling tool 4, schematically shown as only one single roll. A thickness T of the blank 2 towards the metal body 11 is significantly reduced by the rolling, the width B remains unchanged or virtually unchanged. Furthermore, a significant change in the length L takes place by the rolling. The length L of the finished rolled metal body 11 is preferably several 100 m.

(11) Furthermore, the pigment particles, in particular a phosphor 33, are completely pressed into the metal body 11 by the rolling. The pigment particles have a greater hardness than the blank 2 and the metal body 11. The step of FIG. 1D is a hot rolling or a cold rolling.

(12) The change in the metal body 11 is illustrated in plan view in FIG. 1E. The rolling, symbolized by an arrow, changes the length L and thus also a distance between individual regions of the identification 3 along the length L. In the direction parallel to the width B, on the other hand, there is no or no significant change in the workpiece 11 and the identification 3. The thickness change cannot be seen from FIG. 1E.

(13) FIG. 1F shows the finished workpiece 1 with the metal body 11 and the identification 3. In this case, the workpiece 1 is rolled up in the form of a roll. One of the identifications 3 is located at both ends of the metal body 11 and on both main sides of the metal body 11. This allows the role to be identified in a simple manner.

(14) Furthermore, a temperature treatment, in particular a recrystallization annealing, takes place in the step of FIG. 1F. The temperature treatment is carried out, for example, at a temperature of approximately 710° C. and over a duration of one to two weeks. The identification is not destroyed by the temperature treatment.

(15) The temperature treatment, in particular the annealing, of whatever kind, can be carried out in a process gas such as, for example, in air, in an N.sub.2 atmosphere or an H.sub.2 atmosphere. In this case, it is advantageous if the identification contains pigments which do not react with the process gas, in particular do not oxidize or reduce, and thus a change in contrast occurs. In this way, alloy formations are also excluded. For example, TiO.sub.2 as common pigment would be reduced a to Ti in an H.sub.2 atmosphere; thus, the TiO.sub.2 would become grey, and an intermetallic phase would optionally be formed with the metal body. Such a reaction should be avoided by the selection of the pigments and of the process gas.

(16) In the representation of FIG. 1G, it can be seen that the identification 3 itself has also been stretched by the rolling in FIG. 1D, and not only the workpiece 11, see FIG. 1C. The identification can thus be easily read after the rolling.

(17) In particular in the case of temperature treatment after rolling, many different rolls are stored in a furnace over a comparatively long time. The identification of the roles is also possible after the temperature treatment by means of the identification 3, in contrast to this in the case of applied signs, which are destroyed by the rolling, or by means of inks on an organic basis, which are destroyed by the high temperatures.

(18) Optionally, see FIG. 1H, the identification can be removed before being delivered, so that a workpiece 1′ without identification results. The identification is removed without traces and without residue, for example, by punching, wherein the section of the workpiece bearing the identification is separated.

(19) Thus, in particular for the purpose of traceability using the method described herein, a unique identification of raw materials, semi-finished products and products is possible even across temperature treatments. For some objects, this marking is otherwise difficult, since extreme process conditions are run through which lead to failure of other marking methods. Without such an identification, confusion or the loss of marking, for example, in steel works and in rolling mills, occur quite often. The method of marking described here allows the identification 3 to be permanently attached to the workpiece 1. Confusion or loss of the identification 3 does therefore no longer occur.

(20) A main idea of the method described here is thus to apply an identification 3 which is in the form of an ink, paste or the like and which is applied directly to the material surface, in particular by printing on a code. The paste or the ink preferably contains hard, exclusively inorganic pigments, particularly preferably ceramic pigments and inorganic coloring substances and luminescent substances, which are permanently pressed on and/or into a metal surface by the rolling process. Adhesion of the pigments to or in the material surface is better than that to the rolling die.

(21) The coding by the identification 3 takes place, for example, in 1D form of a barcode, so that a stretching of the coding in the rolling direction does not impair the readability. The coding is preferably selected to be in 2D form, in such a way that a stretching of the coding in the rolling direction leads to a coding in the correct aspect ratio, since the identification 3 is initially applied to the unrolled blank 2 in a compressed form. The contrast between the workpiece surface and the pigments is high, even at low pigment concentration, relative to an area proportion, especially as a result of that the pigments can be a ceramic phosphor, so that stretching of the workpiece and the associated reduction of the pigment surface concentration during rolling do not lead to an unreadability of the coding. Thus, right from the start, a low concentration of the pigments can be applied and printed, which is preferably not visible to the naked eye. Due to the low concentration of the pigments on the surface, other functional-relevant properties of the workpiece are not changed or only insignificantly changed and follow-up processes, such as, in particular, painting, and the planned component use are not disturbed. Since such ceramic pigments are temperature-stable, long temperature treatments are also possible.

(22) According to FIG. 2, marking is carried out continuously by the identification 3 on the metal body 11, preferably as a recurring pattern, for example, in the form of a barcode or simply only in the form of points at a defined distance of, for example, 1 m. As a result, a proof of authenticity is possible over the entire roll, in particular during the rolling of the metal body 11 from the roll, for example, in that the pigments are a customer-specific mixture of phosphor pigments.

(23) In this case, see FIG. 2A, the individual regions for the identification 3 can be applied centrally along a longitudinal axis to a main side of the metal body ii. Likewise, see FIG. 2B, the individual regions of the identification 3 can be located on an edge of the metal body 11 so that the metal body 11 can also be identified in the rolled-up state.

(24) In the method of FIG. 3A, the pigment particles, in particular the phosphor 33, are applied to the blank 2. Subsequently, a matrix material 35, for example, a low-melting glass, is applied and optionally melted. As a result, the pigment particles 33 can be embedded in the matrix material 35.

(25) Prior to the representation in FIG. 3B, the rolling is carried out. As a result, the particles 33 are pressed into the metal body 11. In this case, the matrix material 35 was partially destroyed and broken during rolling. However, the matrix material 35 still surrounds the particles 33.

(26) In a subsequent step, see FIG. 3C, the matrix material 35 is melted again, resulting in a tight sealing of the particles 33. Optionally, the remaining regions of the surface of the metal body 11, on which no particles 33 are located, can be freed from the matrix material 35.

(27) Alternatively, see FIG. 3D, it is possible for core-shell particles to be used, which already have a seal 35 around the ceramic core or around the phosphor core 33 in the step of applying them. This core-shell structure is preferably not destroyed during rolling.

(28) Furthermore, it is possible for the pigment particles themselves to be thermally stable so that a matrix material or a seal can be omitted.

(29) The individual pigment particles of the identification 3 form island-shaped subregions 38 which are grouped, see FIG. 4A. The grouped subregions 38 combine the identification 3, for example, to form a bar code or to form a written text. The individual pigment particles in the partial regions are not interconnected by a material of the identification 3.

(30) FIG. 4B shows that the identification 3 is formed by a plurality of contiguous identification regions 39. A thickness of the identification regions is, for example, at least 0.5 μm or 2 μm and/or at most 10 μm or 25 μm; a degree of coverage of the metal body 11 with the pigment particles in the region of the identification is alternatively or additionally at least 5% or 10% and/or at most 50% or 30%, as can also be the case in all other exemplary embodiments.

(31) In the identification regions 39 of FIG. 4B, the pigment particles 33 can be densely or approximately densely packed next to one another, wherein the matrix material 35 can form a continuous layer.

(32) The invention described herein is not restricted by the description on the basis of the exemplary embodiments. Rather, the invention encompasses any new feature and also any combination of features, which includes in particular any combination of features in the patent claims, even if this feature or this combination itself is not explicitly specified in the patent claims or exemplary embodiments.