A method for improving the efficiency of laser blackening

Abstract

The present application relates to a kind of methods for improving laser blackening efficiency, comprising the following steps: cleaning, auxiliary gas purging, carrying out first stage double laser beam processing, carrying out second stage laser blackening processing.The present application uses two stages of laser blackening treatment to cooperate auxiliary gas, a large number of nanometer scale oxides are generated on microstructure surface, and micro-nano scale convex composite structure is generated on surface, which significantly reduces optical reflectivity, and improves blackening efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of surface treatment, in particular to a method for improving the laser blackening efficiency of high-reflectivity metal surfaces. BACKGROUND

[0002] Metal laser blackening treatment refers to using a pulsed laser beam to process the surface of a metal multiple times, thereby significantly improving the absorption rate of the surface to light of different wavelengths, and having wide application requirements in new energy, military and other fields.

[0003] However, for high-reflectivity metal materials such as copper, aluminum and titanium, the material itself has a high reflectivity to laser, and only a small part of the laser energy is absorbed at the initial stage of laser blackening processing. During laser blackening, the surface blackening degree increases, the absorption rate of laser increases, and the material removal efficiency can be significantly improved during further blackening processing. Compared with picosecond and femtosecond ultrafast lasers, the cost advantage of nanosecond laser processing is significant. However, due to the low single-pulse energy of nanosecond laser, the problem of low processing efficiency caused by low absorption of the material to the laser at the initial stage of laser blackening processing needs to be solved. Further improving the efficiency of nanosecond laser blackening processing is of great significance to promote the widespread use of this technology.

[0004] Therefore, a method for improving the efficiency of nanosecond laser blackening of high-reflectivity metal is needed. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a method for improving the efficiency of laser blackening of high-reflectivity metal.

[0006] The technical solution adopted by the present application to solve the above technical problem is:

[0007] A method for improving the efficiency of laser blackening, comprising the following steps:

[0008] a. Take a high-reflectivity metal component to be blackened, and clean the area to be blackened;

[0009] b. Place the high-reflectivity metal component on the processing plane of a dual-light-source laser system, the dual-light-source laser system comprising a quasi-continuous laser light source and a nanosecond laser light source;

[0010] c. Blow auxiliary gas to the area to be processed, the auxiliary gas being industrial pure oxygen or a mixed gas containing oxygen with a content of 35% or more;

[0011] d. Perform first-stage laser blackening processing: use the combined beam processing of quasi-continuous laser and nanosecond laser, set the corresponding processing parameters, and process n times, the value of n being in the range of 2-10;

[0012] e. performing the second stage laser blackening processing: using nanosecond laser to process alone, setting corresponding processing parameters, and the processing times is m, and the value range of m is 4-40.

[0013] Further preferably, the processing times of the steps d and e satisfy the following formula: n

[0014] Preferably, the high-reflective metal component is aluminum, copper, titanium or other metal materials.

[0015] Preferably, the cleaning of the step a uses organic solvents such as alcohol.

[0016] Preferably, the two light sources of the double light source laser system of the step b use the same galvanometer system, so as to realize the beam combination or separate processing of the two light sources.

[0017] Preferably, the mixed gas of the step c further comprises at least one gas selected from nitrogen, carbon dioxide, argon and the like in addition to oxygen.

[0018] Preferably, the oxygen content of the mixed gas of the step c is ≥55%; further preferably, the oxygen content of the mixed gas is ≥60%; further preferably, the oxygen content of the mixed gas is ≥75%.

[0019] Preferably, the flow rate of the auxiliary gas of the step c is in the range of 2-50 L / min, so as to ensure that the processing area can be fully swept by the auxiliary gas. Further preferably, the flow rate of the auxiliary gas of the step c is in the range of 5-30 L / min.

[0020] Preferably, the processing parameters of the quasi-continuous laser of the step d are as follows: the laser power is 200-3000 W, the minimum pulse width is 10-1000 ms, and the duty cycle is 5%-100%; the nanosecond laser parameters are as follows: the laser power is 20-1200 W, the repetition frequency is 1-70 kHz, and the pulse width is 1-200 ns; and the processing parameters of the beam combination processing are as follows: the spot diameter is 20-100 μm, the filling line spacing is 10-120 μm, and the scanning speed is 10-500 mm / s.

[0021] Further preferably, the processing parameters of the quasi-continuous laser of the step d are as follows: the laser power is 500-2000 W, the minimum pulse width is 20-500 ms, and the duty cycle is 40-80%; the nanosecond laser parameters are as follows: the laser power is 50-200 W, the repetition frequency is 30-60 kHz, and the pulse width is 10-30 ns; and the processing parameters of the beam combination processing are as follows: the spot diameter is 25-50 μm, the filling line spacing is 30-60 μm, and the scanning speed is 50-200 mm / s.

[0022] Preferably, the nanosecond laser processing parameters of step e are: nanosecond laser average power 50-1000W; laser pulse repetition frequency 10-70kHz; laser pulse width 5-50ns; spot diameter 25-60μm; fill line spacing 20-80μm; scanning speed 50-500mm / s.

[0023] Further preferably, the laser blackening process parameters of step e are: nanosecond laser average power 50-300W; laser pulse repetition frequency 30-60kHz; laser pulse width 10-30ns; spot diameter 25-50μm; fill line spacing 30-60μm; scanning speed 100-300mm / s.

[0024] Compared with the prior art, the advantages of the present application are:

[0025] 1. The laser blackening process is divided into two stages, the first stage of laser blackening uses nanosecond laser and quasi-continuous laser beam processing, enhances the thermal effect of laser blackening, promotes the removal of materials and surface oxidation, and quickly realizes preliminary blackening; when the laser absorption rate of the high-reflective metal is improved, the second stage of laser blackening is carried out using only nanosecond laser processing, which realizes rapid material removal while avoiding heat accumulation causing damage to the material surface;

[0026] 2. The present application realizes rapid blackening treatment of high-reflective metal by using a quasi-continuous laser + nanosecond pulse laser dual light source laser processing system instead of ultrafast laser, which reduces the processing cost of laser blackening treatment of high-reflective metal;

[0027] 3. By the action of the auxiliary gas rich in oxygen, the laser blackening process occurs simultaneously with oxidation reaction, which promotes the laser removal of materials and significantly improves the nanosecond laser blackening processing efficiency.

[0028] 4. The present application uses two-stage laser blackening treatment with auxiliary gas, laser and material interaction to realize rapid material removal, and at the same time, due to the addition of auxiliary gas, a large number of nanoscale oxides are produced on the microstructure surface. After laser processing, a micro-nano scale convex composite structure is produced on the surface, which significantly reduces the optical reflectivity and improves the blackening efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The surface macroscopic morphology of the laser beam combined laser blackening of red copper of embodiment 1 of the present application;

[0030] Figure 2 The surface macroscopic morphology of the laser beam combined + nanosecond laser blackening of red copper of embodiment 1 of the present application;

[0031] Figure 3 The surface microscopic morphology of the laser beam combined + nanosecond laser blackening of red copper of embodiment 1 of the present application;

[0032] Figure 4 Optical reflectance test chart of red copper after laser beam combination laser blackening of Example 1 of the present application;

[0033] Figure 5 Optical reflectance test chart of red copper after laser beam combination + nanosecond laser blackening of Example 1 of the present application;

[0034] Figure 6 Surface macroscopic morphology of red copper after nanosecond laser blackening of Comparative Example 1 of the present application;

[0035] Figure 7 Optical reflectance test chart of red copper after nanosecond laser blackening of Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0036] The specific embodiments of the present application are described in further detail below in conjunction with the accompanying drawings and examples. The specific conditions are not specified in the examples, and are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not specified by the manufacturer, and are all conventional products that can be purchased on the market.

[0037] Example 1

[0038] The process method for improving laser blackening efficiency comprises the following steps:

[0039] (1) Select red copper products as the sample to be laser blackened, and clean the surface contaminants such as oil stains with alcohol before blackening treatment;

[0040] (2) Place the surface of the metal member to be blackened in the processing plane of the dual light source laser system, wherein the quasi-continuous laser is a 1500W fiber laser, and the nanosecond laser is a 70W fiber laser;

[0041] (3) Turn on the oxygen auxiliary system and blow oxygen to the processing area at a gas flow rate of 15L / min;

[0042] (4) Set the pre-laser blackening area to a square area of 10mm x 10mm, and place the red copper surface to be blackened at the focal point position of the laser beam. The power of the quasi-continuous laser is 450W, the pulse width is 200ms, and the duty cycle is 50%; the nanosecond laser power is set to 50W, the pulse width is 24ns, and the repetition frequency is 55kHz. The filling mode of the two laser beam combination processing is grid filling, the spot diameter is 30μm, the filling line spacing is 20μm, the scanning speed is 200mm / s, and the scanning number is 5 times.

[0043] (5) Turn off the continuous laser processing system and only carry out the nanosecond laser processing system, the nanosecond laser processing parameters are the same as step (4), and the scanning number of the second stage nanosecond laser is 10 times.

[0044] (6) Figure 1 and Figure 2 are the macroscopic morphology of the red copper surface after the first stage of beam combining processing and after the beam combining + nanosecond pulse laser separate processing, respectively. During the beam combining processing, due to the strong thermal effect, a strong oxidation reaction occurs in the processing area, and microstriations are generated on the surface due to material melting; after further nanosecond processing, the surface blackening effect is obvious. As shown in Figure 3 , the laser blackened surface after two-stage processing produces a micro-nano composite structure in the form of micro-cones. On the one hand, the light beam acting on the surface will produce a "light trapping" effect, and on the other hand, the oxidation and other chemical reaction products on the surface have a higher optical absorption rate than the base copper. The optical reflectivity of the processing area after beam combining processing and after beam combining + nanosecond laser processing is tested and analyzed using a spectrophotometer. As shown in Figure 4 , the optical reflectivity of the red copper after beam combining processing is reduced to about 60%, but the ideal blackening effect has not been achieved. As shown in Figure 5 , after two-stage processing, the optical reflectivity of the laser blackened surface under different wavelengths is less than 25%, achieving the ideal laser blackening effect.

[0045] Comparative Example 1

[0046] The laser blackening method includes the following steps:

[0047] (1) Select red copper products as the laser blackening sample, and clean the surface contaminants such as oil stains with alcohol before blackening treatment;

[0048] (2) Place the metal component surface to be blackened on the double light source laser processing system processing plane, including the quasi-continuous laser and nanosecond pulse laser processing system;

[0049] (3) Set the pre-laser blackening area to a square area of 10 mm x 10 mm, only turn on the nanosecond laser processing system, place the blackened red copper surface near the laser beam focal point, set the laser power to 50 W, the spot diameter to 30 μm, the pulse width to 24 ns, the repetition frequency to 55 kHz, the filling mode to grid filling, the filling line spacing to 20 μm, the scanning speed to 200 mm / s, and the scanning number to 15 times.

[0050] (4) Figure 6 is the surface macroscopic morphology after nanosecond pulse laser separate processing, and the optical reflectivity of the blackened processing area is tested and analyzed using a spectrophotometer. The optical reflectivity under different wavelengths is tested Figure 7 . The results show that although the number of nanosecond laser separate processing is the same as the total scanning number in Example 1, the red copper surface is light black, and the optical reflectivity under different wavelengths is still large, exceeding 70%.

[0051] Example 2

[0052] The process for improving laser blackening efficiency comprises the following steps:

[0053] (1) 6061 aluminum alloy products were selected as samples to be laser blackened, and alcohol was used to clean the surface oil and other pollutants before blackening treatment;

[0054] (2) The surface of the metal component to be blackened is placed on the processing plane of a dual-light source laser system, where the quasi-continuous laser is a 1500W fiber laser and the nanosecond laser is a 70W fiber laser;

[0055] (3) Turn on the oxygen assist system to purge oxygen into the processing area at a gas flow rate of 15 L / min;

[0056] (4) The pre-laser blackening area was set to a 10 mm × 10 mm square area, and the aluminum alloy surface to be blackened was placed at the focal point of the laser beam. The power of the quasi-continuous laser was 350 W, the pulse width was 200 ms, and the duty cycle was 30%. The power of the nanosecond laser was set to 56 W, the pulse width was 24 ns, and the repetition frequency was 55 kHz. The filling method of the two laser beam combination processing was grid filling, with a spot diameter of 30 μm, a filling line spacing of 20 μm, a scanning rate of 200 mm / s, and a number of scans of 3 times.

[0057] (5) Turn off the continuous laser processing system and only carry out the nanosecond laser processing system. The nanosecond laser processing parameters are the same as those in step (4). The number of scans of the nanosecond laser in the second stage is 8 times.

[0058] (6) After the above-mentioned blackening treatment, the processed area of ​​the aluminum plate of this embodiment is black, and the reflectivity of the material to light in the wavelength range of 200-1400nm is less than 30%, achieving an excellent blackening effect.

[0059] Example 3

[0060] The process for improving laser blackening efficiency comprises the following steps:

[0061] (1) TC4 titanium alloy products were selected as samples to be laser blackened, and alcohol was used to clean the surface oil and other pollutants before blackening treatment;

[0062] (2) The surface of the metal component to be blackened is placed on the processing plane of a dual-light source laser system, where the quasi-continuous laser is a 1500W fiber laser and the nanosecond laser is a 70W fiber laser;

[0063] (3) Turn on the oxygen assist system to purge oxygen into the processing area at a gas flow rate of 15 L / min;

[0064] (4) Set the pre-laser blackening area to a square area of 10mm*10mm, and place the aluminum alloy surface to be blackened at the focal point of the laser beam. The power of the quasi-continuous laser is 500W, the pulse width is 200ms, and the duty cycle is 50%; the power of the nanosecond laser is 65W, the pulse width is 24ns, and the repetition frequency is 30kHz. The filling mode of the two lasers is grid filling, the spot diameter is 40μm, the filling line spacing is 50μm, the scanning speed is 300mm / s, and the scanning number is 4.

[0065] (5) Turn off the continuous laser processing system and only carry out the nanosecond laser processing system. The nanosecond laser processing parameters are the same as step (4). The scanning number of the second stage nanosecond laser is 12.

[0066] (6) After the above blackening treatment, the processing area of the aluminum plate of the embodiment is black, the reflectivity of the material to light in the wavelength range of 200-1400nm is less than 20%, and excellent blackening effect is achieved.

[0067] The technical means disclosed in the present application scheme is not limited to the technical means disclosed in the above embodiments, but also includes technical solutions composed of any combination of the above technical features. It should be noted that for ordinary skilled persons in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, which are also considered within the scope of protection of the present application.

Claims

1. A method for improving the efficiency of laser blackening, characterized in that The method comprises the following steps: a. cleaning the high-reflectivity metal component to be blackened; b. placing the high-reflectivity metal component to be blackened on a processing plane of a dual-light-source laser system, wherein the dual-light-source laser system comprises a quasi-continuous laser light source and a nanosecond laser light source; c. blowing an auxiliary gas to the processing area, wherein the auxiliary gas is industrial pure oxygen or a mixed gas containing oxygen in an amount of ≥ 35%; d. performing first-stage laser blackening processing: using the combined processing of the quasi-continuous laser and the nanosecond laser, setting corresponding processing parameters, and processing n times, wherein n is in the range of 2-10; the processing parameters of the quasi-continuous laser in step d are: laser power of 350-500 W, minimum pulse width of 20-500 ms, and duty cycle of 30-80%; the processing parameters of the nanosecond laser are: laser power of 20-65 W, repetition frequency of 30-60 kHz, and pulse width of 10-200 ns; the processing parameters of the combined processing are: spot diameter of 25-50 µm, fill line spacing of 20-60 µm, and scanning speed of 50-300 mm / s, e. performing second-stage laser blackening processing: using the nanosecond laser alone, setting corresponding processing parameters, and processing m times, wherein m is in the range of 4-40; the processing parameters of the laser blackening in step e are: average power of the nanosecond laser of 50-65 W, laser pulse repetition frequency of 30-60 kHz, laser pulse width of 10-30 ns, spot diameter of 25-50 µm, fill line spacing of 20-60 µm, and scanning speed of 100-300 mm / s; the processing times of steps d and e satisfy the following formula: n < m, and m + n ≤ 30.

2. The method for improving the efficiency of laser blackening according to claim 1, characterized in that: The mixed gas in step c further comprises at least one of nitrogen, carbon dioxide, and argon in addition to oxygen.

3. The method for improving the efficiency of laser blackening according to claim 2, characterized in that: The oxygen content of the mixed gas in step c is ≥ 55%.

4. The method for improving the efficiency of laser blackening according to claim 1, wherein: The flow rate of the auxiliary gas in step c is in the range of 2-50 L / min.

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