The wheelset is the part of the locomotive that is in contact with the rail, and is composed of the left and right wheels firmly pressed on the same axle. The role of the wheel pair is to ensure the running and steering of the rolling stock on the rail, to withstand all static and dynamic loads from the rolling stock, to transfer it to the rail, and to transfer the load generated by the uneven line to the parts of the rolling stock.
For high-speed trains, the wheels and axles are made of carbon steel without alloying elements, which tends to be the cause of cracks and brittle fractures. Therefore, high-speed rails need to be repaired after a period of operation. Before the inspection, the coating on the axle and the spokes needs to be completely peeled off. The traditional method is to use a wire brush to polish. Although this method can peel off the coating, the efficiency is very low, and the labor intensity of the operator is large. Damage to the wheel surface is affected, so as to affect the next flaw detection.
Laser cleaning technology can effectively remove the surface paint layer of the wheel, but the efficiency is low, the cleaning speed is slow under the condition of thick coating, and the limitation is very large. In view of the shortcomings of the currently used cleaning methods, and in order to expand the application range of laser cleaning, improve the cleaning quality, efficiency and avoid the limitations of pure pulse laser cleaning, a new cleaning process has been developed. The advantage of laser composite cleaning technology is not only the superposition of two kinds of lasers, but the emphasis is on the utilization of energy is much larger than the simple addition of two heat sources.
Laser composite cleaning technology is another new development direction of laser cleaning. It is an enhanced adaptive cleaning method formed by the interaction of pulsed laser and direct diode laser. In the process of treating the attachments on the surface of the substrate (dirt, scale, rust, organic coating, etc.), the direct diode laser irradiates the surface of the deposit with a large amount of laser energy that is equally distributed on the surface to generate thermal energy, forming a thermal expansion pressure between the metal material and the attachment to reduce the bonding force. When the pulsed laser outputs a high-energy laser beam, the generated vibration shock wave directly causes the adhesion of the bonding force to be detached from the metal surface, thereby achieving rapid laser cleaning.
Compared with other lasers, the direct diode laser has a uniform spot energy distribution, which can achieve a slow gradient of laser energy, and the direct diode laser acts as a heat conduction output during the cleaning process. By adjusting the laser power and radiation time, the metal material attachment is melted and heated. The thermal expansion pressure is formed between the metal material and the attachment, and the bonding force is reduced, and the attachment is more easily separated from the metal surface to achieve laser cleaning.
In order to reflect the advantages of laser composite cleaning technology compared to traditional laser cleaning technology, we carried out the wheel-to-coat coating paint cleaning test, while using Raycus 500W pulsed fiber laser cleaning and 300W pulsed fiber laser with 1500W direct diode laser for cleaning test, equipment and experimental sample information are as follows:
request for cleaning is:
Oxidation fringes cannot occur during cleaning；
The time for cleaning a wheel-to-shaft is controlled within 10 minutes;
Before the laser composite cleaning test, it is necessary to measure the thickness of the two-component epoxy resin on the surface of the wheel-to-shaft, respectively test the thickness of the four regions of the shaft, and then calculate the average thickness, as shown in the following table:\
For epoxy coating materials with a thickness of 150-250μm, we have done the following two tests:
When the 500W pulsed fiber laser cleaning epoxy coating material, the field lens with a focal length of 160mm is used, the scanning speed is 6m/s, the repetition frequency is 20KHz, the scanning width is 80mm, 210r/min, and the rotation speed per minute is 210rpm.
After cleaning, the temperatures of the front and back sides of the wheel pair were measured, 40 ° C and 30 ° C, respectively, and the cleaning efficiency was 1.5 m ² / h. The cleaning effect picture is as follows:
300W pulsed fiber laser cleaning with 1500W direct diode laser cleaning epoxy coating material, the scanning speed is 8m / s, the scanning width is 80mm, the duty ratio is 20%, the modulation frequency is 2000Hz, the interval between the semiconductor laser beam and the pulsed laser beam is set to 3mm.
After cleaning, the temperatures of the front and back sides of the wheel pair were measured, respectively 39 ° C and 30 ° C, and the cleaning efficiency was 8.5 m 2 / h. The cleaning effect picture is as follows:
Based on the test results and data analysis, we draw the following conclusions:
300W pulsed fiber laser cleaning with 1500W direct diode laser composite cleaning can meet the requirements in efficiency and effect;
The laser composite cleaning technology can be used to clean thick coating materials, improve the cleaning quality quickly and effectively, and the substrate is not easy to cause damage.
【Rayclass | 锐课堂】TIPS
In the composite cleaning, it is recommended to use the modulation mode to clean the coating. If the continuous mode input heat is too large, the workpiece will be thermally deformed. This test uses the modulation mode for cleaning. The surface temperature of the workpiece is lower than 45 °C. This temperature does not affect the axis.
In the composite cleaning process, it is recommended to use a pulsed laser to be separated from the semiconductor laser beam by 3 to 5 mm to reduce heat accumulation and improve cleaning efficiency.