JP2008255400A - Metal surface working method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal surface working method having relatively simple processes, by which stable color which does not change depending on the viewing direction or angle can be developed without utilizing the interference of light. <P>SOLUTION: A method for irradiating a metal surface with laser is changed. Concretely, a process for irradiating the metal surface with a laser beam having a wavelength in an infrared region and a high frequency of repetition, preferably a wavelength of about 1 μm and a frequency of repetition of 30 kHz under such condition that the energy density in atmosphere is ≥100 mj/cm<SP>2</SP>, preferably ≥400 mj/cm<SP>2</SP>is repeated several times so that scanning spots are overlapped. Preferably, a color is formed by repeating the process at least three times with this energy density. Then, after forming an oxide film having a thickness of at least ≥50 nm, preferably ≥100 nm on the metal surface, the metal surface is irradiated several times with a weak laser beam having an energy density of <400 mj/cm<SP>2</SP>. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a metal surface processing method, for example, a processing method for coloring a surface of a metal by applying heat to the surface.

  In general, it is known that when a metal is heated in an electric furnace or the like, the metal surface is oxidized and colored in rainbow, gold, black, or the like. It is also known that there are a gas torch, plasma, laser, electron beam, etc. used for bonding cutting as a heating method.

  Among them, the laser is easy to control the energy and can easily color the metal surface because local heating is possible in the air. Several proposals have been made for the method and mechanism. For example, a method (for example, Patent Document 1) in which fine grooves are carved on a metal surface and an interference color by reflection of light at the top and bottom of the groove is obtained to make it appear as if wrinkles are colored, or an oxide film on the metal surface There is known a method (for example, Patent Documents 2 and 3) in which various colors are formed by interference of light between the oxide film and the surface of the metal base material under the oxide film.

  In particular, Patent Document 1 relates to a technique for forming fine irregularities on a metal surface with a laser, and effectively uses surface ablation by laser or deformation by heat. Patent Document 1 also mentions the formation of a film by reaction with a reactive gas on the fine irregularities and the rainbow color development by interference of reflected light from the surface of the film and the metal base material.

  Further, Patent Document 2 discloses that various colors (specifically, blue and orange colors) can be expressed by changing laser irradiation conditions with regard to laser coloring and patterning methods. . Also in this coloring method, it is specified that the color is developed by the interference of light between the metal base material and the oxide film formed thereon.

  Further, Patent Document 3 also proposes a pattern coloring (color marking) method for forming an oxide film by laser irradiation on a metal surface. According to this method, the colored color can be changed by a reducing action by reheating. Patent Document 3 also clearly states that the color development principle is due to the interference of light between the surface of the metal base material and the oxide film. Examples of the metal material include stainless steel, Ni—Cr alloy, and titanium, and examples of the film formed on the surface include an oxide film or a nitride film having a thickness of 100 to 200 Å. As a method for enhancing the coloring effect, it is shown that the laser irradiation surface is heated by an electric furnace. In addition, the wavelength range of the laser used is in the infrared to visible range.

JP-A-6-212451 JP-A-7-61198 Japanese Patent Laid-Open No. 2004-250786

  However, in any metal surface processing method according to any patent document, rainbow color is developed by using interference of light, or the appearance of color is varied depending on how the light strikes. Further, the thickness of the oxide film realized by these is very thin, and there is a drawback that the film is easily damaged (physical damage or change with time in the thickness of the oxide film). Therefore, for example, when it is desired to color an object as an identification mark, the above-described processing method is inappropriate.

  Also, in Patent Document 3, since various gases must be used for the purpose of color control and reheating or reprocessing in a reducing atmosphere must be performed in an electric furnace, the number of extra steps is increased and the process is complicated. Gas management is required. Further, it is impossible to color the surface of a product (electric product or the like) that is vulnerable to heating.

  The present invention has been made in view of such circumstances, and realizes a stable color development that does not vary in color depending on the viewing direction and angle, regardless of light interference, and has a relatively simple process. Is to provide.

In order to solve the above problems, the present invention changes the laser irradiation method on the metal surface. Specifically, the laser beam is an infrared light having a high repetition rate, preferably a light with a wavelength of about 1 μm and a repetition rate of 30 kHz, and an energy density of 100 mJ / cm ² or more, preferably 400 mJ / cm ² or more. In this case, the irradiation is performed several times so that the scanning spots overlap each other, preferably three times or more at this energy density to form a color.

Then, after forming an oxide film on the metal surface at least 50 nm or more, preferably 100 nm or more, a weak laser beam having an energy density of less than 400 mJ / cm ^{2 is} further irradiated several times.

  Further, in order to accelerate the formation of an oxide film on the metal surface, laser irradiation may be performed while oxygen gas is blown onto the metal test piece. Oxygen gas may be drifted by making an enclosure in the vicinity of the metal surface with a container or a cylinder. Note that an oxide layer can be formed earlier when the oxygen concentration is higher than the oxygen concentration in the atmosphere.

That is, the metal surface processing method according to the present invention is a metal surface processing method for irradiating a metal surface with a laser beam and coloring at least a part of the metal surface, and applying a laser beam with an energy density of 400 mJ / cm ^2. The method includes irradiating the metal surface with at least three overlapping times.

  The metal surface processing method further includes a step of setting laser irradiation conditions including the number of times of laser beam irradiation on the metal surface and the energy density according to the type of metal to be colored and the type of coloring. Furthermore, you may provide the process of mirror-polishing the said metal surface before laser irradiation. Further, a pulse laser having a wavelength of 1 μm may be used as the laser light.

Moreover, in this invention, irradiation of a laser beam is performed under air | atmosphere with respect to a metal surface.
Further, the metal surface is treated so that a predetermined element is dispersed, and a portion where the predetermined element exists and a portion where the predetermined element does not exist are colored with different colors by laser light irradiation.

  Further features of the present invention will become apparent from the best mode for carrying out the present invention and the accompanying drawings.

  According to the present invention, it is possible to realize stable color development that does not vary in color depending on the viewing direction and angle, irrespective of light interference, and to realize metal surface processing with a relatively simple process.

  Hereinafter, embodiments and examples of the present invention will be described with reference to the accompanying drawings. However, it should be noted that this embodiment is merely an example for realizing the present invention and does not limit the present invention. In each drawing, the same reference numerals are assigned to common components.

<Configuration of metal surface processing equipment>
FIG. 1 is a diagram showing a schematic configuration of a metal surface processing apparatus 100 according to an embodiment of the present invention. As shown in FIG. 1, the metal surface processing apparatus 100 is an apparatus that performs color processing on the surface of the metal plate 6, and includes a laser oscillation apparatus 1 that emits laser light 7, a laser output, an irradiation range, and a number of times. A laser oscillation output control device 2 for controlling, a galvano scanner 3 for scanning laser irradiation on the metal surface in accordance with the set irradiation range, and a collector for condensing the laser on the surface of the metal plate It has an optical lens 4, a lens protective cover 5 for preventing laser light reflection on the lens 4 and protecting the surface of the lens 4, an oxygen gas cylinder 81 and an oxygen gas nozzle 82, and blowing an oxygen gas 83 onto the metal plate 6. And an oxidation promoting device 8 for promoting oxidation of the metal surface.

  In the metal surface processing apparatus 100, for example, data indicating a coloring range and a color type such as drawing data is input to the laser oscillation output control apparatus 2 on the surface of the metal plate 6. Based on the data, the scanning range of the galvanometer mirror 3 and where and how many times the surface of the metal plate 6 is irradiated with the laser beam 6 are determined.

The laser oscillation device 1 is preferably configured to selectively emit laser light having an energy density of 400 mJ / cm ² or more and light having an energy density lower than 400 mJ / cm ² depending on the type of processing. That is, depending on the type of coloring process, the number of laser light irradiations of 400 mJ / cm ² and the number of laser light irradiations less than that are controlled to give the desired color to the metal surface. As the laser light, light having a wavelength from the infrared region to the ultraviolet region can be used, but it is preferable to use pulsed laser light of 10 kHz (more preferably 30 kHz) or more with light in the infrared region of about 1 μm. Since the light in the infrared region of about 1 μm can be realized by an existing laser device for marking on a metal surface, the present invention can realize a suitable coloring process using the existing device. .

<Coloring process>
FIG. 2 is a process diagram for explaining the procedure of coloring processing on the surface of the metal plate 6 using the metal surface processing apparatus 100 shown in FIG. First, a metal plate (metal piece) 6 to be colored is prepared (process P1). As the metal plate 6 to be colored, for example, an iron-based metal such as stainless steel, copper, a chromium alloy, a nickel alloy, or the like can be used. Also, use an alloy prepared by mixing a metal material with a predetermined element (indium, tin, zinc, titanium, etc.), or disperse a predetermined element on the metal surface (for example, by PVD, CVD, ion implantation, etc.) Alternatively, a metal may be used. If such an alloy or a metal with elements dispersed on the surface is used, it is possible to color the surface of aluminum or the like, which is usually difficult to produce an oxide film.

  Subsequently, the processed surface of the metal plate 6 prepared in Process 1 is mirror-polished (Process 2). The mirror finish can make the energy absorbed by the metal surface uniform, and can be finished finely. However, this process 2 is not essential and can be colored without a mirror finish. Further, the prepared metal plate is washed to remove dust, oil, polishing debris, etc. adhering to the metal plate (process 3).

  Moreover, an oxygen gas flow is prepared as needed, and oxygen gas is injected with respect to the metal plate 6 (process 4). Since the oxygen gas is injected to promote the generation of the oxide film, the process 4 is not an essential process. Then, the pulse laser is started up and the optical system is adjusted according to the thickness of the metal plate 6 (the distance from the lens 4 to the surface of the metal plate 6 is adjusted to a predetermined distance). In addition, the laser irradiation conditions such as how many times the energy density is irradiated with the laser are determined (process 5). Since the color varies depending on the progress of oxidation, the energy density and the number of irradiations of the laser beam vary depending on the desired color.

Laser irradiation is performed on the surface of the metal plate 6 under the laser irradiation conditions determined in the process 5 (process 6). If the energy density is too low, an oxide such as a non-conductive film is formed on the metal surface, and oxidation on the metal surface will not proceed even if laser irradiation is performed further. In such a case, the conventional iridescent coloring by light interference is possible, but stable coloring in which the color does not vary depending on the viewing angle cannot be realized. Therefore, it is preferable to perform laser irradiation at an energy density of 400 mJ / cm ² or more for the first several times (preferably 3 to 4 times depending on the color to be colored).

  By the processing as described above, an oxide film (oxide layer) having a thickness of 50 nm or more can be formed in a specified region / part of the surface of the metal plate 6. If the oxide film has such a thickness, the possibility of breakage is very low.

[Example 1]
Using the metal surface processing apparatus 100 of FIG. 1, the mirror-polished SUS304 was irradiated with YVO4 laser pulse light in the atmosphere to develop colors such as brown, purple, orange, amber and green. The energy density of the laser irradiated at this time was 400 mJ / cm ² or more, and the laser was scanned with a mirror (galvano scanner 3) while oscillating at a repetition rate of 30 kHz. By repeating this 3 to 4 times, the surface was colored.

  The results of this coloring process are shown in (1) and (2) of Table 1. Results (1) and (2) show processing examples for coloring brown and blue, respectively.

[Example 2]
Using the metal surface processing apparatus 100 shown in FIG. 1, a mirror polished SUS304 is scanned with a mirror (galvano scanner 3) while oscillating light with an energy density of 400 mJ / cm ² or more at a repetition rate of 30 kHz in the atmosphere. After repeating 3 to 4 times, by irradiating energy less than 400 mJ / cm ² (must be noted in the table, attention is required) in the same way, vividly brown, purple, orange, amber, green, etc. The color of was developed. Note that the thickness of the oxide film is not sufficient in the two times of repeated irradiation, and a desired color cannot be obtained. Therefore, it is desirable to irradiate three or more times.

  The results of this coloring process are shown in Tables (3) to (6). Results (3) to (6) show examples of processing for coloring orange, purple, blue-green, and young grass color, respectively.

[Example 3]
1 is used. In addition to SUS304, SUS316, SUS310, SUS430, SUS416, SUS403, SS400, and the above-mentioned laser light is applied to the Cr plating material in the atmosphere at an energy density of about 400 mJ / cm ^2. By irradiating twice, colored regions based on red (iron oxide), yellow (chromium oxide), green (chromium oxide, nickel oxide) and the like were formed on the metal surface. As described above, when the metal surface processing method of the present invention is used, even if the same processing method is used, the color development is different if the metal component is different.

[Example 4]
Using the metal surface processing apparatus 100 of FIG. 1, after irradiating light with an energy density of about 400 mJ / cm ^{2 at} a repetition rate of 30 kHz while blowing oxygen gas to the mirror-polished SUS304 in the atmosphere (0.1 Mpa), By irradiating laser light with a weaker energy density, colors such as brown, purple, orange, amber, and green were developed with an energy lower than that described above.

  The results of this coloring process are shown in (7) and (8) of Table 1. Results (7) and (8) show processing examples for coloring purple and green. In particular, in the case of coloring green, the number of times of irradiation with a laser of 1400 mW was reduced by half, and the color could be produced (total time of 1/2 to 2/3).

<Summary>
As described above, the present invention is a technique for forming a colored layer that is difficult to peel off unlike the application method, although the color does not change depending on the viewing direction of the colored portion or the direction of light. Yes, it is extremely useful to be used as a display / plate used at the work site.

  The present invention can be applied to decorative crafts (for example, plates) and machine parts (for example, parts of automobiles and motorcycles). Especially, by applying to a part of machine parts, Differentiation becomes possible. In addition, it can be applied to individual identification such as various plates, and it has been difficult to distinguish with conventional single-color patterning, or a long mark for simplification can be simplified. Can be reduced. Furthermore, by forming a functional oxide, it is possible to perform different colors with a plurality of lights, and it is possible to provide a new identification tool that changes to a barcode or the like.

  In the present invention, laser light is irradiated on a metal surface, particularly a surface of an iron-based metal, a chromium alloy, a nickel alloy, or the like, and irradiation is performed with a light energy density that forms an oxide layer with a sufficient thickness on the surface. The oxide layer is further irradiated with energy by laser light. Thereby, the coloring process which forms the colored oxide layer irrespective of how to hit light and the kind of light is realizable. Here, the sufficient oxide layer preferably has an oxide film thickness of about 50 nm or more, and this is performed at an energy density that can be formed by three to four laser beam scans. It is characterized by. After that, it is preferable to perform laser beam irradiation, but in this case, it is desirable to lower the energy density as compared to that. Furthermore, according to the present invention, irradiation with a high energy density is not required for forming an oxide layer, so that formation of fine cracks due to surface thermal strain is suppressed, and a highly durable oxidized colored layer is formed. Is possible.

The wavelength of the laser beam used for the metal surface coloring process can be from the infrared region to the ultraviolet region. Preferably, the laser beam oscillates 1000 times (10 kHz) or more per second with infrared light of about 1 micrometer ( Laser light capable of being preferably 30 kHz or higher is preferable. The energy density of the irradiated light is 400 mJ / cm ² or more, and it is desirable to repeat the irradiation action several times (preferably three times or more) so that the scanning spots overlap. Thereby, an oxide film having a sufficient strength can be formed in a short time, and a coloring process in which the color does not vary depending on the viewing direction can be realized. In addition, it is possible to form a colored layer with less oxygen defects in the oxide and less deterioration than in the case of irradiation in air.

  Coloring characterized in that it is performed in the atmosphere when irradiating a metal surface with laser light, and processing is performed at the same temperature as room temperature without performing heating using a heat source other than laser or cooling using a refrigerator, etc. In order to make the laser oscillation state the same during processing, it is desirable to arrange the environment so that the room temperature conditions are always the same. According to the present invention, since an electric furnace for performing the heating step is not required, the coloring process can be simplified. In addition, it is possible to easily color the metal part of a product (electric product or the like) that is vulnerable to heating.

  In addition, by controlling the energy density and the total energy amount of the laser light to be irradiated, the kind of oxide formed on the metal surface is changed, and different colors are developed depending on the combination of the oxides. Preferably, at the time of laser irradiation, the oxygen concentration in the vicinity of the metal surface is set higher than in the atmosphere so that oxide formation and different oxides are easily generated. Thereby, a coloring process can be performed stably and in a short time.

  Furthermore, the plurality of oxides to be generated are not only oxides having different valences with the same metal oxide and oxides having oxygen defects, but also oxides of different metals and oxides having oxygen defects. . For this reason, different colors can be emitted, and it is possible to draw pictures, characters and other patterns by utilizing the fact that different oxides are formed depending on the amount of energy applied.

  In addition, in order to simultaneously generate conductive and photocatalytic metal oxides, a plurality of metals such as indium, tin, zinc, and titanium are present on the metal surface as films or particles, or as metal compounds (predetermined elements are added). Or may be irradiated with pulsed laser light. By using a pulse laser, heat on the metal surface can be actively released during a period of a pulse that does not oscillate. In addition, by applying a treatment to disperse a predetermined element on a metal, various colors can be applied to the metal surface, and it is possible to color a metal that is difficult to color by itself, such as aluminum. become able to.

It is a figure which shows schematic structure of the metal surface processing apparatus by embodiment of this invention. It is a figure for demonstrating the process procedure of the metal surface processing method by embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser oscillation apparatus 2 Laser oscillation output control apparatus 3 Galvano scanner 4 Condensing lens 5 Lens protective cover 6 Metal plate 7 Laser beam 81 Oxygen gas cylinder 82 Oxygen gas nozzle 83 Oxygen gas 11 Electrical wiring

Claims (8)

A metal surface processing method for irradiating a metal surface with laser light and performing a coloring process on at least a part of the metal surface,
A metal surface processing method comprising a step of irradiating the metal surface with laser light having an energy density of 400 mJ / cm ² or more at least three times.   The method further comprises a step of setting a laser irradiation condition including an energy density and the number of times the laser light is applied to the metal surface in accordance with the type of metal to be colored and the type of coloring. 2. The metal surface processing method according to 1. The metal surface processing method according to claim 1, further comprising a step of irradiating the metal surface with a laser beam having an energy density of less than 400 mJ / cm ² at a plurality of overlapping times.   The metal surface processing method according to any one of claims 1 to 3, further comprising a step of mirror polishing the metal surface before the laser light irradiation.   The metal surface processing method according to claim 1, wherein the laser beam is a pulse laser having a wavelength of 1 μm.   6. The metal surface processing method according to claim 1, wherein the laser light irradiation is performed in the atmosphere on the metal surface. Furthermore, a process of spraying oxygen gas on the metal surface to be processed is provided,
The metal surface processing method according to claim 1, wherein the laser light irradiation is performed in a state where the oxygen gas is sprayed. A predetermined element is dispersed on the metal surface,
The metal surface processing method according to any one of claims 1 to 7, wherein the portion where the predetermined element exists and the portion where the predetermined element does not exist are colored differently by the laser light irradiation.

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