Patent Application
20220266617
A method for marking workpieces is specified. In addition, a workpiece with a marking is specified.
International Patent Application Publication No. WO 2011/101001 A1 describes a method in which metallic components are provided with a fluorescent marking.
US Patent Application Publication No. 2016/0339495 A1 relates to a method in which workpieces with a marking are hot-formed.
Embodiments provide a workpiece with a marking that survives a surface treatment in a readable manner.
According to at least one embodiment, the method includes the step of providing a workpiece. The workpiece is, for example, a metallic material, in particular a metal sheet. The workpiece can be an iron sheet or a steel sheet or else an aluminum sheet. A thickness of the workpiece is, for example, at least 0.1 mm or 0.3 mm or 0.5 mm and/or at most 8 mm or 5 mm or 3 mm.
According to at least one embodiment, the method comprises the step of attaching the marking to the workpiece, so that the marking is bonded to the workpiece in a positive substance joining manner. The attachment is, for example, pressing components of the marking into the workpiece surface.
According to at least one embodiment, the method comprises the step of applying one or more raw materials for one or more markings to the workpiece. The at least one raw material, and thus the at least one marking, is preferably applied to the workpiece only in places and not over the entire surface. The at least one raw material, and thus the at least one marking, is applied, for example, in the form of a lettering or a number. The at least one raw material, and thus the at least one marking, is preferably a machine-readable coding, in particular in the form of a bar code or a two-dimensional code. Via the finished marking, it is possible, for example, to give the workpiece a unique component number.
According to at least one embodiment, the method comprises the step of heating the workpiece with the at least one raw material. As a result of the heating, the marking is formed from the raw material. In this case, the marking is connected to the workpiece in a materially bonded manner. This takes place, for example, in that a part of the raw material reacts chemically with the workpiece or fuses to the workpiece. As a result, the marking adheres firmly to the workpiece.
According to at least one embodiment, the method comprises the step of performing a surface treatment of the workpiece. The surface treatment is carried out at least in one region with the marking. The surface treatment can extend on an entire main side of the workpiece or also on two main sides of the workpiece.
According to at least one embodiment, the surface treatment is a shot peening, a sand blasting, a sliding grinding, and alternatively or additionally a material-removing treatment. Examples of a material-removing treatment are etching or removal by means of electromagnetic radiation.
According to at least one embodiment, the marking remains readable at least until after the surface treatment, preferably machine-readable, on the workpiece. In particular, the marking can be read, specifically machine-read, both after the heating step and immediately before the surface treatment and after the surface treatment. This means that the marking is not destroyed by the surface treatment.
According to at least one embodiment, the marking has, at least in a part of the near ultraviolet, the visible and/or the near-infrared spectral range with respect to the workpiece after the surface treatment, preferably also with respect to the workpiece before the surface treatment, a degree of reflection difference and/or a degree of reflectance difference and/or an albedo difference, in particular under optimized lighting conditions and detection conditions, of at least 10 percentage points or 20 percentage points or 30 percentage points.
In other words, due to its optical properties, the marking can be clearly distinguished both from a surface of the workpiece and preferably also before the surface treatment, for example, by a camera or by the human eye. In other words, the marking on a surface of the workpiece has a high contrast, at least under suitable illumination conditions which are used for reading out the marking.
The near ultraviolet spectral range is understood to mean, in particular, the range from 300 nm to 420 nm, the visible spectral range denotes in particular wavelengths from 420 nm to 760 nm and the near-infrared spectral range wavelengths from 760 nm to 1500 nm. It is possible that optical filters are used for reading out the marking, which filters, for example, block an excitation wavelength of a phosphor, so that only the radiation generated by the phosphor of the marking due to the excitation is detected. Preferably, the marking with respect to the contrast and/or a difference in brightness satisfies the standard ISO IEC TR 29158 (2011) (previously standard AIN DPM-1-2006), which is required for directly marked components.
In at least one embodiment, the method comprises the following steps, preferably in the stated sequence:
This method enables an individual identification of metal components which are subjected to the process of shot peening, sand blasting, sliding grinding or another surface process, such as chemical etching. The identification is preferably applied before the process and is still readable, in particular machine-readable, after the process.
The shot peening is used, for example, to adjust the surface hardness or to clean metal components. Typical conventional identifications, above all laser engraving and printing with conventional, in particular organic inks, frequently fail in this context. The reason for this is the change or even the removal of the surface, which leads to washing of the contrast, for example, of a laser marking, or to removal of an ink. This is particularly critical when a high-temperature process, such as press hardening, is directly connected upstream of the shot peening. In the case of a conventional marking, such a high-temperature process can already impair its adhesion to the workpiece or the contrast thereof to the workpiece.
Similarly, sand blasting is used to remove scale from, for example, stainless steel sheets which have previously passed through a high temperature process.
In the method described here, on the other hand, a raw material for a marking, for example, a data matrix code, DMC for short, is applied to the workpiece, for example, printed. The ink used here preferably contains ceramic pigments which are bonded to a workpiece surface, which is in particular a metal surface, in a materially bonded manner and thus highly resistant. This connection is carried out in a temperature step, for example, the temperature treatment, which occurs anyway in a processing process of the workpiece. Alternatively, an additional temperature step, for example, by inductive heating or by a direct flame, can be used.
Furthermore, with the method described here, it is possible that pigments of the marking are pressed into the workpiece surface by the shot peening, whereby a temperature step can be dispensed with. Alternatively or additionally, the step of heating and the shot peening and/or sand blasting and/or sliding grinding follow one another.
The marked workpieces can thus be individually identified. This enables component tracking and monitoring of a component current over the production process. Process optimizations can be carried out on the basis of this monitoring. This applies in particular in metal processing, for example, in the production of automotive components, such as car body components.
According to at least one embodiment, the marking comprises at least one temperature-resistant, coloring material or consists of one or more such materials. Such a material is formed in particular by pigments, for example, from temperature-resistant ceramic pigments and/or metal oxide pigments with a color different from the workpiece. For example, the ceramic pigments are white, colored or black. A plurality of subregions of the marking can be present which have different colors in order to ensure an increased contrast within the marking.
According to at least one embodiment, the marking includes one or more kinds of metal oxide pigments. For example, the pigments of the marking are composed of titanium dioxide.
According to at least one embodiment, the marking contains one or more phosphors. The at least one phosphor effects a difference in reflectance between the marking and the blank and the workpiece. Phosphors can have a reflectance of more than 100% in spectral subregions in which the phosphor emits via photoluminescence. A degree of reflection exceeding 100% is caused by the secondary light generated by the phosphor.
The phosphor or the phosphor mixture preferably contains at least one of the following phosphors or consists thereof: Eu2+-doped nitrides like (Ca,Sr)AlSiN3:Eu2+, Sr(Ca,Sr)Si2Al2N6:Eu2+, (Sr,Ca)AlSiN3*Si2N2O:Eu2+, (Ca,Ba,Sr)2Si5N8:Eu2+, (Sr,Ca)[LiAl3N4]:Eu2+; garnets from the general system (Gd,Lu,Tb,Y)3(Al,Ga,D)5(O,X)12:RE with X=halide, N or divalent element, D=three- or four-valent element and RE=rare earth metal like Lu3(All-xGax)5Ol2:Ce3+, Y3O1-xGax)5O12:Ce3+; Eu2+-doped sulfides like (Ca,Sr,Ba)S:Eu2+; Eu2+-doped SiONs like (Ba,Sr,Ca)Si2O2N2:Eu2+; SiAlONs, for example, from the system LixMyLnzSi12-(m+n)Al(m+n)OnN16-n; beta-SiAlONs from the system Si6-xAlzOyN8-y:REz; nitrido-orthosilikates like AE2-x-aRExEuaSiO4-xNx, AE2-x-aRExEuaSi1-yO4-x-2yNx with RE=rare earth metal and AE=alkaline earth metal; orthosilikates like (Ba,Sr,Ca,Mg)2SiO4:Eu2+; chlorosilikates like Ca8Mg(SiO4)4Cl2:Eu2+; chlorophosphates like (Sr,Ba,Ca,Mg)10(PO4)6Cl2:Eu2+; BAM phosphors from the BaO—MgO—Al2O3 system like BaMgAl10O17:Eu2+; halophosphates like M5(PO4)3(Cl,F):(Eu2+,Sb3+, Mn2+); SCAP phosphors like (Sr,Ba,Ca)5(PO4)3Cl:Eu2+; KSF phosphors based on potassium, silicon and fluorine such as K2SiF6:Mn4+. Furthermore, the phosphor can have a quantum well structure and can be grown epitaxially.
The phosphor can be configured to shorten the wavelength of an excitation radiation, also referred to as upconversion, and, for example, to convert infrared light into visible light. Alternatively, the phosphor can convert short-wave light into long-wave light. Excitation of the phosphor takes place in the near ultraviolet, in the visible and/or near-infrared spectral range. The phosphor is preferably read out in the visible or near ultraviolet spectral range.
According to at least one embodiment, the coloring material, that is, the ceramic or metal oxide pigments or the phosphor, is present as particles. An average diameter of the particles, in particular a D50 diameter, is preferably at least 50 nm or 500 nm and/or at most 20 μm or 5 μm. Particles having an average diameter of 50 nm to 500 nm are used in particular in order to keep mechanical damage to the particles low during the surface treatment, especially during shot peening. In order to obtain a high thermal resistance of the particles, the average diameter is preferably between 0.5 μm and 5 μm inclusive.
According to at least one embodiment, the particles are only partially pressed into the workpiece during the surface treatment. A penetration depth of the particles into the workpiece is in particular at least 20% and less than 100%. This applies, for example, to at least 50% or 80% of the particles.
According to at least one embodiment, the surface treatment comprises etching as the material-removing treatment or the surface treatment is etching. The etching is in particular a wet chemical etching. Preferably, the marking is resistant to the etching. This means that removal of material from the workpiece preferably remains limited to regions adjacent to the marking. In other words, the marking can serve as a type of etching mask. This does not rule out that the marking can be undercut by the etching, so that a material of the workpiece is partially removed from a region covered by the marking.
According to at least one embodiment, the raw material is applied directly to a base material of the workpiece. The base material is, for example, a metal such as a copper sheet, an aluminum sheet, an iron sheet or a steel sheet. The marking is thus preferably produced directly on the base material.
According to at least one embodiment, the workpiece comprises a coating. The raw material is applied to the coating. In this case, the coating covers the base material of the workpiece in places or completely. This means that the marking is produced directly on the coating. Optionally, the marking remains spaced from the base material. Alternatively, the marking is pressed through the coating and contacts the base material in places.
According to at least one embodiment, when the marking and/or the raw material is heated in regions next to the marking, an additional layer, for example, a scaling layer, is produced. This applies in particular to iron-containing workpieces. Preferably, the additional layer, that is, specifically the scaling layer, is partially or completely removed during the surface treatment.
According to at least one embodiment, the step of heating the raw material comprises hot forming the workpiece or is a hot forming of the workpiece. This means that the marking is then formed from the raw material during the hot forming.
According to at least one embodiment, the hot forming takes place at a deformation temperature. For example, the deformation temperature is at least 350° C. or 550° C. or 700° C. or 800° C. or 880° C. Alternatively or additionally, the deformation temperature is at most 1100° C. or 1000° C. or 950° C. In particular, the deformation temperature is about 930° C. The hot forming is then, for example, deep drawing or pressing.
At the deformation temperature, the phosphor and/or the ceramic of the marking are preferably thermally stable. It is possible for the phosphor to be changed in its luminescence properties, in particular by the temperatures during the hot forming. As a result, it is also possible to obtain a quality control as to whether the hot forming takes place with correct process parameters.
According to at least one embodiment, the raw material is attached to the workpiece in a wiping-proof manner after the step of applying, but still before the step of heating. That is to say, the marking does not adhere very firmly to the workpiece immediately after application, but at least so strongly that running of the marking or removal of the marking remains under a slight contact.
According to at least one embodiment, the marking remains permanently on the workpiece. In other words, the marking adheres to the workpiece in such a way that, in the intended use of the finished workpiece, no detachment or significant detachment of the marking from the workpiece takes place.
According to at least one embodiment, the raw material and/or the marking comprises a matrix material. The matrix material is, for example, a translucent, inorganic material, in particular a glass based on silicon dioxide. The matrix material acts as an adhesion promoter and as an adhesive between the workpiece and a coloring material of the marking. This means that the at least one phosphor or the ceramic pigments adhere to the workpiece due to the matrix material, that is to say on the basis of the adhesion promoter.
According to at least one embodiment, the raw material has an intermediate matrix. The intermediate matrix comprises in particular a binder and/or a solvent and/or a dispersant and/or a plasticizer. The intermediate matrix can be made of organic materials, for example, based on acrylate. The raw material, in particular the coloring component of the marking, such as the phosphor, is temporarily fastened to the workpiece via this intermediate matrix. In the finished marking, the intermediate matrix is preferably no longer present or only decomposition residues of the intermediate matrix are present.
According to at least one embodiment, the raw material comprises the inorganic adhesion promoter and the inorganic pigment particles or consists thereof. The adhesion promoter is a glass, a ceramic or a glass ceramic. The pigment particles are the phosphor and/or the ceramic pigments.
In particular, a phosphorus paste composition is used for the raw material, as described in document DE 602 18 966 T2. The disclosure content of this document with regard to the phosphorus paste composition is incorporated by reference.
According to at least one embodiment, the marking remains partially or completely embossed over the workpiece. This means that the marking is not pressed into the workpiece surface in particular during the surface treatment. As a result, a hardness of the workpiece at the workpiece surface can be increased by means of the shot peening. This effect can otherwise be reduced by significantly pressing the marking into the workpiece.
According to at least one embodiment, the marking comprises a plurality of point-like islands as seen in plan view. The islands are separated from one another and are not connected to one another by a material of the marking. An average diameter of the islands is, for example, at least 0.5 μm or 1 μm and/or at most 50 μm or 20 μm or 10 μm. In this case, at least one marking field of the marking, viewed in plan view, is preferably composed of the individual islands which can be present in a density modulation. An overall mean extent of the at least one marking field is preferably at least 20 times or 50 times the average diameter of the islands.
According to at least one embodiment, a coherent marking field is present. A continuous material connection of a material of the marking is preferably present within the marking field. The marking field can be a closed region which is continuous and uninterrupted in plan view.
According to at least one embodiment, the average roughness of the workpiece surface deviates from an average roughness of the marking by at least a factor of 2 or 5 or 10. As a result, the optical properties, in particular with regard to scattering, of the marking and of the workpiece can differ greatly, which can increase the contrast for reading out the marking.
According to at least one embodiment, in a further step, after the surface treatment, one or more lacquers are applied to the workpiece. The at least one lacquer preferably completely covers the marking. It is possible for the marking to be no longer recognizable through the lacquer for an observer or for a reading device. In this way, it can be that the marking is only visible and readable by removing the lacquer. A structure or form of the marking is preferably not or not significantly impaired by the lacquer.
In addition, a workpiece is specified. The workpiece is particularly preferably produced by a method as indicated in connection with one or more of the above-mentioned embodiments. Features of the method are therefore also disclosed for the workpiece and vice versa.
In at least one embodiment, the workpiece comprises a marking which is attached in places to a workpiece surface of the workpiece. The marking rests in a materially bonded manner on the workpiece surface. The workpiece surface was subjected to a shot peening, so that the workpiece surface shows a plurality of impressions of balls of the shot peening. The impressions extend over the marking.
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 identical elements in the individual figures. However, no true-to-scale references are shown; rather, individual elements may be exaggerated for a better understanding.
An exemplary embodiment of a method for marking a workpiece 1 is illustrated in
In the step of
As shown in
In the step of
The shot peening and/or the sand blasting is preferably carried out in accordance with DIN 8200. Preferably, blasting agents 6 with the following properties are used:
If, as an alternative or in addition to the shot peening and/or for sand blasting, a sliding grinding is used as surface treatment, the sliding grinding is preferably carried out in accordance with DIN 8589. A size of abrasive bodies is preferably between 0.5 mm and 50 mm. A sliding grinding is used, for example, for post-treatment of press-hardened metal sheets.
This structure with the impressions 7 is preferably also present below the marking 3 in the workpiece surface 10. The marking 3 preferably forms this structure. This means that the structure of the workpiece surface 10 is preferably recognizable on a marking side facing away from the workpiece surface 10.
Deviating from the illustration in
A further method is shown schematically in
Deviating from the illustration in
In the subsequent step, see
Otherwise, the explanations regarding
A further method is illustrated in connection with
The marking 3 is applied to the coating 12, for example, as described in connection with
According to
In the variant of
The coating 12 is, for example, a scaling protection layer, for example, of an aluminum-silicon alloy. A thickness of the scaling protective layer is, for example, at least 100 nm or 250 nm or 1 μm and/or at most 30 μm or 10 μm or 2 μm. A preferred composition of the scaling layer is: 87% Al, 10% Si and 3% Fe. The preferred thickness of the scaling layer is 1.5 μm. These properties preferably also apply to coatings 12 in other exemplary embodiments.
The marking 3 is preferably thicker than the coating 12. This is preferably also true in all other exemplary embodiments.
In the method of
Optionally, a coating on the base material 11 is also present in the method of
The composition of the raw material 2 and of the marking 3 is described in more detail in
According to
The raw material 2 is preferably composed of an adhesion promoter 31, for example, a low-melting glass, of pigment particles 32, preferably phosphor particles or alternatively ceramic pigments, and of a binder and/or solvent 33.
The raw material 2 is preferably an ink-jet-capable ink, in particular having a viscosity in the range of from 1 mPas to 20 mPas and/or with a surface tension in the range from 20 mN/m to 60 mN/m, especially at the temperature at which the raw material 2 is printed.
The ink-jet-capable raw material 2 is preferably composed as follows:
If the raw material 2 is a screen printing paste, the raw material 2 preferably has a viscosity between 1 dPas and 200 dPas at the application temperature and is composed, in particular, as follows:
Unlike in
In the method step of
To simplify the illustration, the impressions 7 in
The fragmentation of the marking 3 during the shot peening illustrated in
In
In this case, the marking 3 can be formed by the coherent marking fields 39 present as closed layers; see
The invention described here is not limited by the description on the basis of the exemplary embodiments. Rather, the invention encompasses any novel feature and any combination of features, which in particular includes any combination of features in the claims, even if this feature or this combination itself is not explicitly specified in the claims or exemplary embodiments.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2019 121 447.5 | Aug 2019 | DE | national |
This patent application is a national phase filing under section 371 of PCT/EP2020/071888, filed Aug. 4, 2020, which claims the priority of German patent application 102019121447.5, filed Aug. 8, 2019, each of which is incorporated herein by reference in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/071888 | 8/4/2020 | WO |
