Mar 03, 2020
At present, the large number of laser welding applications in the automotive industry shows that laser welding technology is matured. However, laser welding technology is more complicated than the traditional welding technology, and the quality control link is different from the traditional welding quality control. Therefore, strengthening quality control is of great significance to the development of laser welding.
The most basic characteristics of lasers are monochromaticity, directionality, and correlation. These unique properties coupled with the resulting high brightness and ultra-short pulses make it very suitable for welding. The application of laser welding technology in the manufacturing field from pulse to continuous, from low power to high power, from thin plates to thick parts, from simple single welds to complex shapes, has gradually become a mature modern processing technology.
In the quality defects and influencing factors of automobile laser welding, it is mentioned that most of the quality defects are caused by equipment failures, so daily equipment maintenance and repairs are particularly important. The following summarizes several requirements for laser equipment maintenance:
Dimensional accuracy requirements for welding workpieces:
Laser welding also requires very high assembly accuracy of welding parts. For example, the workpiece assembly accuracy or beam positioning accuracy cannot meet the requirements, which can easily cause welding defects. Therefore, good and accurate clamping technology is the guarantee of laser welding. The gap between the parts to be welded in ordinary welding is about 2mm, and the ideal situation for laser welding is that the smaller the gap, the better. 威廉希尔官方下载ually, in the body-in-white production, the gap between the parts to be welded is controlled by 0.2mm.
Quality control of body functional dimensions:
Based on on-site body-in-white laser welding quality control experience, it is necessary to set up a size group to monitor key dimensions that affect laser welding quality. The size group consists of the measurement part, production part, quality assurance part, and model part. The team members hold regular dimensional meetings to discuss and resolve any dimensional deviations. The measurement part needs to measure the key dimensions every day and provide corresponding reports. The production part needs timely feedback information, the quality assurance part judges the quality problems generated and assists the same board part to develop solutions.
Laser welding quality inspection and rework standards:
The quality of laser welds is generally divided into non-destructive inspection and destructive inspection.
1) Non-destructive inspection: Non-destructive inspection of laser welds is mainly visual inspection. The inspector uses some suitable tools such as magnifying glass, camera, or other measuring inspection tools to check the existence, number, length, appearance, and location of the welds in accordance with the requirements of the drawings. Among the above-mentioned defects in laser welding quality, such issues as pores, welding spatter, welding penetration interrupted welds, and edge welding can all be visually checked. In the production of car body-in-white, a visual inspection of each weld is required to judge its quality.
2) Destructive inspection: The destructive inspection of laser welds is divided into metallographic test and gouge test.
The metallographic test is a test method to judge the cross-section abrasive disc of laser weld through a microscope. Common defects are no connection, edge notches, root protrusions, etc. The frequency of inspection depends on the reliability of the process. In actual production, the production part and the quality assurance part of each supervisor negotiate and confirm, at least once a month. After adjusting laser parameters due to equipment failure or quality defects, metallographic tests must be performed on the weld.
The gouge test is to use a chisel to force the laser weld seam until it breaks, and then measure the fracture surface (the length and width of the weld seam). The gouge test can reflect the functional reliability of the laser welding equipment, so the gouge test is generally carried out very close to the production line. When the welding seam is found to be different, it can notify the corresponding process and maintenance staff. In the production of car body-in-white, all-laser welds are inspected at a frequency of 2 times/month.
3) Rework method: For laser welds found to have defects through various inspection methods described above, rework is required. The general rework method of laser welding for car body-in-white is as follows
In the 21st century, the automobile industry is stepping into a method that can carry out flexible modular production according to user requirements. Traditional processing techniques can no longer meet the needs of new production methods. With the continuous application of laser welding technology and other laser processing technologies in the automotive field, it will become one of the important processing methods in the automotive industry.