CN106702411B - A Method of Using Pulsed Laser to Clean Carbon on Metal Surface - Google Patents

Abstract

The invention relates to a method for cleaning carbon on the surface of a metal by using a pulsed laser. In this method, a water-alcohol mixed liquid film with a thickness of 10-20 μm is sprayed on the surface of the carbon deposit, and then the pulse laser generated by the laser is focused on the metal surface of the carbon deposit, and the parameters of the pulse laser are selected so that the pulse laser cleaning threshold range is 6.0× Between 10 ⁵ ～8.1×10 ⁷ W/cm ² , the scanning path is S-shaped, the scanning speed is 5.0cm‑30cm/s, the scanning width is 5～15cm, and the scanning overlap rate is 1%～5%, realizing the detection of metal materials Surface carbon cleaning. The method has a cleaning rate of 40cm ² /s-120cm ² /s, a cleanliness of over 95%, a surface quality of Sa3, no damage to the surface of the laser cleaning, and no influence on the mechanical properties of the cleaned material. The method has the remarkable characteristics of high efficiency, high quality, greenness, simple process, low cost, continuous large-scale operation and the like.

Description

A Method of Using Pulsed Laser to Clean Carbon on Metal Surface

technical field

The invention relates to a method for cleaning carbon on a metal surface by using a pulsed laser, and belongs to the technical field of laser application and the technical field of metal surface pretreatment.

Background technique

The carbon on the surface of some key important parts is formed in the harsh service environment of high temperature, high pressure, and high oil fume. Rust is more difficult to remove than paint. If the carbon deposits are not removed in time, it will often lead to increased fuel consumption and shortened service life of key important parts such as engines, and even seriously affect the safety of key important parts.

At present, traditional single cleaning methods such as ultrasonic cleaning, chemical solvent method, water jet cleaning method, etc. are difficult to clean the surface of key important parts with carbon deposits. Instead, a mixed cleaning method such as chemical solvent ultrasonic cleaning method and water jet abrasive cleaning method is used. , but the above two mixed cleaning methods also have the following deficiencies:

One is that the chemical solvent ultrasonic cleaning method often introduces toxic chemical substances during the cleaning process, which is likely to cause secondary pollution to the environment.

The second is that the water jet abrasive cleaning method is likely to cause surface damage to key important parts during the cleaning process, and at the same time cause a large amount of waste of water resources.

The 3rd, above-mentioned two kinds of hybrid cleaning methods have deficiencies such as complex process, low cleaning efficiency and poor cleaning quality when cleaning surface area carbon.

Laser cleaning technology has the advantages of green, high quality, simple process, low operating cost, and can clean the surface of parts with complex structures. It is expected to solve the problem of green cleaning of surface pollutants. For example, the patented short-pulse laser cleaning method for metal surfaces (200810134880.6) uses laser cleaning technology to clean the surface pollutants of titanium alloys and aluminum alloys before welding in a vacuum environment or a protective atmosphere such as argon; Surface dirt laser cleaning system and method (CN103817113 A) provides methods and examples of laser cleaning rust, oil stains and paint layers. However, none of the above-mentioned patents deals with the problem that it is difficult to effectively clean carbon deposits by conventional cleaning techniques. At present, the laser cleaning technology mainly has the problems of difficult control of surface burns and low cleaning efficiency in practical applications. The present invention mainly solves the problems of surface burn control of laser cleaning surface carbon, and improvement of cleaning quality and efficiency.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for cleaning carbon on the surface of a metal with a pulsed laser.

The technical problem to be solved by the present invention is to provide a method for liquid film laser cleaning of carbon on the metal surface, and the laser cleaning threshold and cleaning process involved in the method. The method has the remarkable characteristics of high efficiency, high quality, greenness, simple process, low cost, continuous large-scale operation and the like.

Focus the pulse laser generated by the solid-state laser on the carbon-deposited metal surface, and use the liquid film laser cleaning method to continuously scan the carbon-deposited metal surface with a certain scanning path and scanning speed within the laser cleaning threshold range to obtain clean metal. surface. Specifically, the method of the present invention is embodied in:

In order to use the above technology to obtain excellent results, the present invention provides a method for scanning the carbon-deposited metal surface with pulsed laser radiation to obtain a clean metal surface. The method includes the following steps: spraying an alcohol-water mixed film on the carbon-deposited metal surface, and then The pulsed laser generated by the solid-state laser is focused on the carbon-deposited metal surface, the laser cleaning parameters are selected within the cleaning threshold range, and the carbon-deposited metal surface is continuously scanned with a certain scanning path and scanning speed to obtain a clean metal surface.

Preferably, the thickness of the liquid film in the liquid film laser cleaning method is between 10 and 20 μm, and the composition is a mixture of water and alcohol. Preferably, the alcohol is isopropanol or n-butanol, and the mass percentage is 5% to 15%. between.

The laser cleaning threshold is represented by the peak power density of the pulsed laser, peak power density=P/fS, where f is the repetition rate, S is the spot area, P is the laser average power under the repetition rate, and ι is the pulse width, The selection of laser parameters needs to meet the laser cleaning threshold between 6.0×10 ⁵ and 8.1×10 ⁷ W/cm ² .

The scanning path of the pulsed laser is S-shaped.

The scanning speed is 5.0cm-30cm/s, the scanning width is 5-15cm, and the scanning overlapping rate is 1%-5%.

The wavelength of the pulsed laser used in the laser scanning is 1064nm, and the spot shape of the pulsed laser is square or circular.

The metals are titanium alloys, aluminum alloys, iron-based alloys, copper alloys and magnesium alloys.

The cleanliness of the metal surface obtained by cleaning carbon deposits by the method of the present invention is above 95%, the cleaning rate is 40cm ² /s-120cm ² /s, the laser cleaning surface has no damage, and has no influence on the mechanical properties of the cleaned material.

The core of the invention is the pulse laser cleaning threshold range and the liquid film laser cleaning method. The threshold range of pulsed laser cleaning is the key technical parameter to control the burn of the cleaning surface. Below the threshold range of laser cleaning, the carbon on the metal surface cannot be completely removed; above the threshold range of laser cleaning, it will cause burns on the metal surface while removing carbon deposits. The liquid film laser cleaning method can effectively improve the cleaning efficiency and quality of carbon deposits, and prevent damage to the laser cleaning surface. The key is the composition of the liquid film. The key technology of the pulse laser cleaning carbon deposit of the present invention: the liquid film is composed of a mixture of water and alcohol, wherein the alcohol is isopropanol or n-butanol, and the mass percentage is 5-15 wt%. The cleaning threshold of pulse laser cleaning carbon deposits ranges from 6.0×10 ⁵ to 8.1×10 ⁷ W/cm ² , the scanning path is S-shaped, and the cleaning rate is 40cm ² /s to 120cm ² /s.

The present invention has following remarkable effects:

(1) The pulse laser radiation cleaning carbon deposition process is simple and practical, the cleaning quality is high, up to Sa3 level; the cleaning speed is fast, the cleaning rate is 40cm ² /s ~ 120cm ² /s; the cleaning surface has no microscopic damage, and has no effect on the mechanical properties of the material. influences.

(2) Using a mixture of water and alcohol as the liquid film composition, compared with dry laser cleaning under the same conditions, the cleaning efficiency is more than doubled.

(3) No chemical reagents are used in the process of cleaning carbon deposits by pulsed laser radiation, and no waste water and waste liquid are generated, which belongs to green cleaning.

The invention provides a new method for cleaning large-scale, high-quality, precise and controllable carbon deposition and obtaining a clean metal surface.

Description of drawings

Figure 1A is the SEM image of the titanium alloy surface after laser cleaning carbon deposits, and Figure 1B is the elemental energy spectrum of the titanium alloy surface after laser cleaning carbon deposits.

Figure 2A is the SEM image of the surface of the aluminum alloy after laser cleaning the carbon deposit, and Figure 2B is the energy spectrum of the elements on the surface of the aluminum alloy after the laser cleaning of the carbon deposit.

Detailed ways

The examples of the present invention will further illustrate the specific implementation of the method for cleaning the metal surface by pulsed laser to remove carbon deposits on the metal surface, but the present invention is not limited to the following examples.

Unless otherwise specified, the chemical reagents used in the examples are conventional commercially available reagents, and the technical means used in the examples are conventional means well known to those skilled in the art.

Example 1

Step 1: spray n-butanol water film on the surface of the carbon-deposited titanium alloy, the mass percentage of n-butanol is 3wt%, and the thickness of the liquid film is 15±2 μm.

Step 2: Select the pulse laser parameters and calculate the laser cleaning threshold: the pulse laser wavelength is 1064nm, the repetition frequency is 18kHz, the laser pulse width is 80ns, the output power is 500W, the square spot size is 4mm×4mm, and the laser cleaning threshold is 2.17× 10 ⁷ W/cm ² .

Step 3: Select the pulse laser scanning parameters: the scanning path is S-shaped, the scanning speed is 10cm/s, the scanning width is 6cm, and the scanning overlap rate is 2%.

Step 4: Clean carbon deposits with pulsed laser: focus the pulsed laser on the surface of carbon deposits, and scan once in S-shape reciprocatingly to obtain a clean titanium alloy surface.

Fig. 1 A is the SEM picture of the surface of the titanium alloy cleaned in this embodiment, the surface of the titanium alloy cleaned by laser is smooth, and there is no particle adsorption on the surface; There is only Ti element on the surface of the alloy and no C element, which shows that the surface of the ferroalloy is very clean after cleaning carbon deposits in the above embodiment, the cleanliness is 100%, and the cleaning speed is 60cm ² /s. The quality of the cleaned surface reaches Sa3 level, which is one level higher than the surface quality of carbon deposits cleaned by water jets at present.

Example 2

Step 1: Spray an isopropanol water film on the surface of the carbon-deposited aluminum alloy, the mass percentage of isopropanol is 5wt%, and the thickness of the liquid film is 15±2 μm.

Step 2: Select the pulse laser parameters and calculate the laser cleaning threshold: the wavelength of the pulse laser is 1064nm, the repetition frequency is 8kHz, the laser pulse width is 150ns, the output power is 300W, the diameter of the circular spot is 3mm, and the laser cleaning threshold is 3.53× 10 ⁶ W/cm ² .

Step 3: Select the pulsed laser scanning parameters: the scanning speed is 10cm/s, the scanning width is 10cm, and the scanning overlap rate is 4%.

Step 4: Pulse laser cleaning of carbon deposits: Focus the pulse laser on the surface of carbon-deposited aluminum alloy, and scan it back and forth in an S-shaped path to obtain a clean aluminum alloy surface.

Fig. 2A is the SEM image of the aluminum alloy surface cleaned in the above embodiment, it can be seen that the aluminum alloy surface after cleaning is very smooth, and there is no particle adsorption on the surface; Fig. 2B is the element energy spectrum diagram of the aluminum alloy surface cleaned in the above embodiment, cleaning The finished aluminum alloy surface contains Al, C, O elements, wherein the mass percent of C element on the aluminum alloy surface is 0.55Wt%, as shown in Table 1, illustrates that the cleanliness of the aluminum alloy surface after the above-mentioned embodiment cleans the carbon deposit is 99.45% , the cleaning speed is 100cm ² /s, and the surface quality level reaches Sa3 level. Table 2 shows the changes in mechanical properties of aluminum alloys before and after laser cleaning of carbon deposits. It can be seen that there is no significant change in the mechanical properties of aluminum alloys before and after laser cleaning.

Example 3

No liquid film was sprayed on the aluminum alloy surface, and other laser cleaning parameters and cleaning steps were as in Example 2.

The cleanliness of the aluminum alloy surface after cleaning the carbon deposit in the above embodiment is 96.3%, and the surface quality grade reaches Sa2.5 grade. In comparison with Example 2, if no liquid film is sprayed on the surface of the aluminum alloy, the cleanliness and surface quality level of the surface cleaned by laser under the same laser cleaning parameters are both reduced.

Table 1

Table 2

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, some improvements and modifications can also be made. These improvements and modifications It should also be regarded as the protection scope of the present invention.

Claims (6)

1. A method of utilizing pulsed laser to clean metal surface area carbon is characterized in that: pulsed laser is focused on the carbon-deposited metal surface, and liquid film laser cleaning method is adopted to scan the carbon-deposited metal surface within the laser cleaning threshold range to obtain clean metal surface; Wherein, the liquid film laser cleaning method is to spray a water-alcohol mixed liquid film with a thickness of 10-20 μm on the carbon-deposited metal surface, and then focus the pulse laser on the carbon-deposited metal surface; Wherein, the water-alcohol mixed liquid film is a mixture of water and alcohol; wherein the mass percentage of alcohol in the water-alcoholic mixed liquid is 5% to 15% by weight; Among them, the cleaning threshold is represented by the peak power density of the pulsed laser, and its range is between 6.0×10 ⁵ and 8.1×10 ⁷ W/cm ² ; Wherein, the metal is titanium alloy, aluminum alloy, copper alloy or magnesium alloy. 2. The method according to claim 1, characterized in that, the alcohol is Virahol or n-butanol. 3. The method according to claim 1, characterized in that: the scanning path of the pulsed laser is S-shaped, the scanning speed is 5.0cm-30cm/s, the scanning width is 5-15cm, and the scanning overlap rate is 1%-5 %. 4. The method according to claim 1, characterized in that the pulsed laser has a wavelength of 1064nm, and the spot shape is square or circular. 5. The method according to claim 4, characterized in that the size of the square light spot is 3mm×3mm˜6mm×6mm. 6. The method according to claim 4, characterized in that the diameter of the circular light spot is 2mm-8mm.