JP3397904B2 - Pretreatment method of metal workpiece in laser processing - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent substance which absorbs a laser wavelength, such as an oxide, when a metal material to be processed is subjected to melting processing, heat treatment, surface modification and the like using a laser. The present invention relates to a pretreatment method for a metal material to be processed, which enables effective use of energy of laser light by forming the coating.

[0002]

2. Description of the Related Art Generally, metal materials such as aluminum, aluminum alloys, steel materials, and copper have a low absorptance with respect to laser light. The efficiency is very small. Further, although the YAG laser has a higher absorptivity than the carbon dioxide laser, most of the applied energy is also reflected. For this reason, in various types of thermal processing using a laser as a heat source, increasing the absorption ability of laser light leads to improvement in processing efficiency and energy efficiency, and has great technical significance.

As a method of increasing the absorptance of laser light, a method of coating an absorbent mainly containing graphite or phosphate has been generally used. However, these absorbents are black and deteriorate the working environment, and have difficulty in removing work after the end of processing. It has also been pointed out that phosphorus penetrates into the material from the laser irradiation portion and causes cracking.

As an alternative to graphite or phosphate, a method of adhering a mixture of graphite and an inorganic oxide to the surface of a metal material workpiece with an organic binder (for example, Japanese Patent Publication No. 62-54166), nitriding as a solid lubricant A method of applying boron or silicon carbide powder (for example, Japanese Patent Laid-Open No. 1-191738) or a method of spray coating boron nitride ( Japanese Patent Laid-Open No. 2-19420 ) has been developed. However, since these coatings are powder coatings even if they are colored or not colored, they need to be removed to some extent after processing, and there is a limit to the improvement of the laser absorption rate due to scattering and the like. There was a problem with the processing capacity.
Further, it has been proposed to improve the laser absorptance by coating with water glass (Japanese Patent Publication No. Sho 63-9004), but in this case, since the coating agent is an alkali, it becomes a problem depending on the metal material of the work material.

Further, the conventional laser beams intended to improve the absorption rate are all carbon dioxide lasers, and no treatment agent for improving the absorption rate of the YAG laser is found.

[0006]

According to the present invention, such a pretreatment agent in the conventional laser processing is colored, and a removal operation is required after the laser processing, or a powder is included, so that the laser absorption rate is limited. Therefore, it is not possible to process it sufficiently, and it is necessary to consider the problems that pretreatment cannot be performed depending on the metal material to be processed.
An object of the present invention is to provide a pretreatment method for a workpiece in laser processing for the purpose of improving the absorption rate of G laser.

[0007]

According to the present invention, before laser processing, the surface of a metal material to be processed ( metal material such as aluminum, aluminum alloy, steel, copper) is previously absorbed in the laser wavelength range. As shown, the visible light transmittance is high,
That is, the above-mentioned problems were solved all at once by forming a transparent film containing no powder.

That is, in the laser processing (melting processing, welding, heat treatment, surface modification ) of a workpiece made of a metal material , a transparent film which absorbs in the vicinity of the laser wavelength and has a large visible light transmittance is formed . metal in the laser processing, which comprises coating the surface of the pre-workpiece without machine polymer
This is a pretreatment method for a material workpiece. The transparent coating mentioned here is not only colorless, but also a coating layer that does not contain powder (particles) and is homogeneous in its entirety.

The substance forming the transparent film used in this method is mainly composed of an organometallic compound or an inorganic polymer which absorbs in the vicinity of the laser wavelength and has a large visible light transmitting ability. It should be noted that absorption in the vicinity of the laser wavelength means not only when the coating layer itself made of a material forming a transparent film has absorption in the laser wavelength range, but also oxides and nitrides produced by heating the coating layer. And the like have absorption in the laser wavelength range.

Transparent films obtained from various organometallic compounds and inorganic polymers show absorption in a specific wavelength region derived from a chemical structure in the infrared / ultraviolet region. From this, it is possible to judge the selection of a film suitable for the target laser beam from the results of infrared / ultraviolet spectroscopic analysis.

For example, as a material showing a large absorption in the vicinity of the wavelength (10.6 μm) of a carbon dioxide gas laser, an organometallic compound is Si (OCH ₃ ) ₄ , Si (OC ₂ H ₅ ) ₄ , Si (OC ₃ H ₇ ) ₄ , Si (O
C ₄ tetraalkoxysilane H _{9) 4,} etc., and the like phenylalanine triethoxysilane, polysilazane inorganic polymer (SiHaNb) ceramic precursor precursor polymer of n such (inorganic polymer be converted into a ceramic by firing), hexamethyldisilazane _{(NH (Si (CH 3)} 3) 2), vinyltriethoxysilane _{(CH 2 = CHSi (OC 2} H 5) 3) , and the like.

Although there are very few existing data of the spectroscopic analysis results in the YAG laser wavelength range (1.06 μm), as a result of earnest study in the present invention, as a result of ZrO ₂ , Zr (OCH ₃ ) ₄ and Zr (OC ₂ H ₅₎ )
It has been found that tetraalkoxyzirconium such as ₄ , Zr (OC ₃ H ₇ ) ₄ and Zr (OC ₄ H ₉ ) ₄ , SiO ₂ and TiO ₂ are effective. The metal surface is coated with such a compound or an organic metal compound or an inorganic polymer which becomes an oxide obtained by firing.

As a coating method of these materials for forming a transparent film, there is a coating by a sol-gel method which can coat a large area at a low cost. Further, vapor phase film forming methods such as ion plating, sputtering and CVD (chemical vapor deposition) can also be applied. Of course, coating or spray coating can be performed depending on the material of the coating material. The film thickness of the film changes depending on the absorption rate of the film for laser light. That is, a coating having a low absorptivity requires a thick film, but a material having a high absorptivity requires a small film thickness. Usually 1 nm to 100 μm, preferably 5 nm to 10 μm
m.

[0014]

When the pretreatment is carried out according to the present invention, since the treating agent does not contain powder, the laser light is efficiently absorbed in the vicinity of the wavelength of the laser light used, and the laser light on the metal surface having a large reflectance is obtained. Laser processing efficiency of melting processing, cutting, welding, heat treatment, surface modification, etc. is improved. Further, since the film has a large visible light transmittance, it has a large transparency and does not impair the appearance of the work piece, and also acts as a protective layer on the surface.

Since a general coating method can be used as the treatment method, a particularly large-scale device is not required,
The work is not so difficult. Even if the film is 1 μm or less and is extremely thin, it is effective.

[0016]

Example 1 An aluminum plate (A1100P, 2 mm thick) was taken as a metal material to be processed having a large laser reflectance, and its surface was coated with SiO ₂ by a sol-gel method. An aluminum plate was pulled up from the solution having the composition shown in Table 1 at a rate of 30 mm / min and baked in the atmosphere at 200 ° C for 2 hours. A transparent film of about 66 nm was formed by a single operation of dipping, pulling up, and firing. The thick film was formed by repeating a series of operations. As a result of infrared spectroscopic analysis of the formed film, formation of SiO ₂ was confirmed although organic matter remained.

[0017]

[Table 1]

[0018] SiO ₂ transparent coating treatment alms samples and untreated aluminum plate carbon dioxide laser (output 780 W (cw),
The result of irradiation with assist gas O ₂ and a feed rate of 600 mm / min) is shown in FIG. For untreated and up to 2 immersions,
No change was observed in the laser irradiation part and no trace was observed. However, in the sample that was immersed 4 times, there was evidence that the coating was changed in the laser-irradiated portion, and in the sample that was immersed 8 times, a clear melting of the aluminum plate was observed. Thus, it was confirmed that the absorption rate of the carbon dioxide laser can be clearly improved by coating the aluminum plate with a film of SiO ₂ of about 530 nm.

The formation of a transparent SiO ₂ film is not limited to the above conditions, but may be a solution based on a different liquid composition or another alkoxide, and it may be performed once by selecting a pulling rate, a firing temperature and the like. Film thickness obtained by dipping operation of
The film structure and the like can be changed. Further, instead of firing after immersion, it is also possible to directly change to an oxide by laser irradiation.

Example 2 As in Example 1, an aluminum plate (A1100P, 2 mm thick) was coated with ZrO ₂ by the sol-gel method. An aluminum plate was pulled up from the solution having the composition shown in Table 2 at a rate of 30 mm / min and baked in the atmosphere at 200 ° C for 2 hours. Immersion, pulling up once
A calcination operation formed a transparent film of about 8 nm. The thick film was formed by repeating a series of operations. As a result of infrared spectroscopic analysis of the formed transparent film, formation of ZrO ₂ was confirmed although organic substances remained.

[0021]

[Table 2]

FIG. 2 shows the results of irradiation of a YAG laser (output 500 W (cw), assist gas N ₂ , feed rate 600 mm / min) on the ZrO ₂ transparent coated sample and the untreated aluminum plate. Since the absorption rate of the YAG laser is higher than that of the carbon dioxide laser, melting occurs even in the untreated sample.
A clear increase in the melt zone is seen with increasing number of dips for coating.

As described above, it was confirmed that the absorptivity of the YAG laser can be clearly improved by forming the ZrO ₂ transparent film of about 8 nm or more on the aluminum plate.

The formation of a transparent ZrO ₂ film is not limited to the above conditions, but may be a solution based on a different liquid composition or another alkoxide. The film thickness, film structure, etc. obtained by the dipping operation can be changed. Further, instead of firing after immersion, it is also possible to directly change to an oxide by laser irradiation.

Example 3 On a aluminum alloy plate (1 mm thick), as a reference, high-frequency ion plating was used to form transparent SiO 2 having a thickness of 2.5 and 1.0 μm.
_Two films were coated, and carbon dioxide laser (output 300 W (cw), assist gas Air) was irradiated and cut. The results are shown in Table 3.

The maximum feed rate for stable cutting was 1000 mm / min for the untreated sample, but stable cutting was possible for the sample coated with the SiO ₂ transparent film even at a feed rate of 1200-1500 mm / min. Met. Thus, the coating of the SiO ₂ transparent film improved the cutting efficiency by about 1.5 times as compared with the untreated sample. Dynamic hardness measurement results (measurement method:
Shimadzu Corporation, using dynamic micro hardness tester, measuring load 1
In the case of gf, apex angle 115 ° triangular indenter), the untreated material was 97, whereas the sample coated with SiO ₂ showed an increase in surface hardness such as 347 and 202. Although detailed data are omitted, these are average values of 5-point measurement.

[0027]

[Table 3]

Example 4 The same aluminum alloy plate as in Example 3 was coated with a 0.7 μm-thick ZrO ₂ transparent film by high-frequency ion plating as a reference, and a YAG laser (pulse laser, average output 80) was used.
w, Assist gas Air) was irradiated and it cut. The results are shown in Table 4.

In the untreated sample, the maximum feed rate at which stable cutting was possible was 200 mm / min. However, in the sample coated with the ZrO ₂ film, stable cutting was possible even at a feed rate of 400 to 500 mm / min. Met. Thus, the coating with the ZrO ₂ film improved the cutting efficiency 2.5 times as compared with the untreated sample.

[0030]

[Table 4]

Example 5 Carbon steel (S55C: normalized, 6 mm thick) was used as a reference and subjected to high frequency ion plating to obtain Si having a thickness of 1.2 μm.
The O ₂ film was coated and irradiated with a carbon dioxide laser (output 890 W (cw), feed rate 1 m / min, assist gas O ₂ ). The irradiation position was set 30 mm above the focal position to increase the irradiation beam diameter, and surface hardening was tried. A structure photograph of the cross section of the sample after irradiation by an optical microscope is shown in FIG.

In the untreated material, no change in surface appearance was observed even by laser irradiation, and the cross-sectional structure remained the normalized structure. However, the coating material changed due to laser irradiation, and a clear quenched structure was observed in the cross-sectional structure. As described above, it was confirmed that the SiO ₂ coating can remarkably improve the laser absorption capacity during surface quenching.

Example 6 An aluminum plate (A1100P, 2 mm thick) was coated with polysilazane (Si
A coating material (polysilazane concentration: 20.3%) obtained by diluting HaNb) n with xylene was coated by a dipping method, and heated at 150 ° C. for 30 minutes for the purpose of scattering the solvent to obtain a coating material. The polysilazane-coated aluminum plates having different pulling rates were irradiated with a carbon dioxide gas laser (output 780 W (cw), feed rate 300 mm / min, assist gas O ₂ ). The resulting macro photograph is shown in FIG.

In the untreated material, no change such as melting was observed by laser irradiation. However, the polysilazane coating allows melting to be observed. Lifting speed 30
A partial trace is recognized in the sample of mm / min, and a continuous trace of irradiation is seen in the irradiation position in the sample of 60 mm / min. further,
In the samples of 150 mm / min and 600 mm / min, scattering of molten aluminum and molten grooves are clearly observed. As described above, a clear improvement in the laser light absorption ability was observed with an increase in the pulling rate (that is, an increase in the coating thickness).

The type of solvent used to dilute the polysilazane,
The concentration does not have to be limited to the concentration and type of this example, and ceramic powder or the like can be added if necessary. The coating method is not limited to the dipping method, and any means such as spin coating, coating and spray coating can be adopted. Also,
A heat treatment after coating is not always necessary.

The cause of the absorption of this agent in the wavelength region of the carbon dioxide gas laser is due to the Si--N bond in polysilazane. Instead of polysilazane, a silicon nitride (for example, Si ₃ N ₃₎ is formed by the PVD method or the CVD method. The same effect can be obtained by coating ₄ ).

Example 7 Carbon steel (S55C: normalized, 6 mm thick) was applied to Example 6
A polysilazane solution with the same composition as above
The coating was applied for 30 minutes at 150 ° C. for 30 minutes, and irradiated with a carbon dioxide laser (output 890 W (cw), feed rate 1 m / min, irradiation position 30 mm above focus position, assist gas O ₂ ). Results are shown in FIG.

In the untreated material, no change in surface appearance was observed even by laser irradiation, and the cross-sectional structure remained the normalized structure. However, the coating material changed due to laser irradiation, and a clear quenched structure was observed in the cross-sectional structure. As described above, it was confirmed that the coating of polysilazane can remarkably improve the laser absorption capacity during surface quenching. As in Example 6, the conditions regarding the solvent, the coating method, and the heat treatment are not limited to those in this example, and the same effect can be obtained by coating the ceramic with silicon nitride.

Example 8 On a mirror-finished SUS304 plate (2 mm thick), for reference, a SiO ₂ film (1.2 μm thick) by high frequency ion plating, a polysilazane film under the same conditions as in Example 7, and a commercially available silicon carbide-based film were used. Each of the laser processing coating agents was coated and irradiated with a carbon dioxide laser (pulse laser, average output 10 w, assist gas N ₂ ). Results are shown in FIG.

In all of the coating materials of SiO ₂ , polysilazane and the commercial coating agent, the melting traces due to laser irradiation are larger than those of the untreated material, and it is confirmed that the absorption capacity is increased by the coating. However, while the laser traces of the polysilazane of the coating treatment material according to the present invention are relatively uniform in shape, the laser traces of the treatment material with the commercially available coating agent used for comparison are not uniform. This indicates that polysilazane has excellent positional uniformity of the laser absorption effect.

[0041]

According to the present invention, the efficiency of laser processing such as melting, cutting, welding, heat treatment and surface modification of metallic materials is improved. Further, since the film is transparent, the appearance of the work piece is not impaired, and it is not necessary to remove the film even after laser processing. Furthermore, in the case of coating an inorganic material such as an oxide or a nitride or an organic material, a function as a protective film (corrosion resistance, abrasion resistance, etc.) of a material to be processed can be imparted. Therefore, it is useful as a surface pretreatment on a metal material for laser processing intended to be laser processed.

[Brief description of drawings]

FIG. 1 is a surface view showing a surface state of a work piece.

FIG. 2 is a surface view showing a surface state of a workpiece.

FIG. 3 is a tissue cross-sectional view of a cross section of a sample after irradiation by an optical microscope.

FIG. 4 is a macro surface view of a result obtained by irradiating a polysilazane-coated aluminum plate having a different pulling rate with a carbon dioxide gas laser.

FIG. 5 is a surface view showing the result of irradiating carbon steel with carbon dioxide laser after polysilazane treatment.

FIG. 6 is a surface view of a result obtained by coating a SUS304 plate with a SiO ₂ , polysilazane film, and a commercially available non-black coating agent for laser processing and irradiating a carbon dioxide laser.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Minoru Hiramatsu 4-3-18 Ifukucho, Okayama City, Okayama Prefecture Okayama Prefectural Industrial Technology Center (56) Reference JP-A-58-93811 (JP, A) 58-224796 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C21D 1/02-1/84 B23K 26/00-26/18 C23C 16/00-16/56 C23C 26/00-26/02

Claims (3)

(57) [Claims] 1. A melt processing of a workpiece made of a metal material, welding, heat treatment, when carbon dioxide gas laser processing to perform surface modification process, an absorption at the laser wavelength near and large transparent coating of permeability of visible light A pretreatment method for a metal material workpiece in laser processing, which comprises pretreating a surface of a workpiece with a ceramic precursor polymer to be formed in advance and coating the surface with ceramic . 2. A transparent film that absorbs in the vicinity of the laser wavelength and has a high visible light transmittance during carbon dioxide laser processing for melting, welding, heat treating and surface-modifying a workpiece made of a metal material. Tetraalkoxysilane
Pre-treat the surface of the work piece in advance with solution coating
A pretreatment method for a metal material workpiece in laser processing, which comprises coating with SiO ₂ . 3. A transparent film which absorbs in the vicinity of the laser wavelength and has a high visible light transmittance during YAG laser processing for melting, welding, heat treating, and surface-modifying a workpiece made of a metal material. preparing a surface of a previously workpiece a coating of tetraalkoxy zirconium solution
A method for pretreating a metal material to be processed in laser processing, which comprises performing ZrO ₂ coating. "