On-line quality control system for laser brazing

Abstract

The laser brazing of steel (e.g. galvanized DC04) with copper solder (usually CuSi3) is already established in automotive manufacturing. Reasons for this are process advantages like a low working temperature and thus, a low thermal distortion. In addition, the quality of the joint with respect to surface appearance, joint strength and impermeability is fully ensured. The major challenge for a wide industrial spreading of laser brazing is the high sensitivity of the process. Slight disturbances of process variables such as an inaccurate wire feeder or misalignment of laser beam to seam cause imperfections such as pores, holes or one-side or even improper wetting. However, today it is still hardly possible to observe in-situ those failures reliably during laser brazing. Hence, the goal is the development and qualification of a new online quality control system for laser brazing. Therefore, in the first step the mechanisms of different joint imperfections are analyzed and evaluated. In the second step the joint failures that occurred during the process are captured and analyzed by using two cameras simultaneously. One camera uses human visible light wavelengths and the second captures the near-infrared spectral region. For the spatial-resolved in-situ-detection of different process and quality characteristics both camera modules are integrated coaxially into the laser beam path.The laser brazing of steel (e.g. galvanized DC04) with copper solder (usually CuSi3) is already established in automotive manufacturing. Reasons for this are process advantages like a low working temperature and thus, a low thermal distortion. In addition, the quality of the joint with respect to surface appearance, joint strength and impermeability is fully ensured. The major challenge for a wide industrial spreading of laser brazing is the high sensitivity of the process. Slight disturbances of process variables such as an inaccurate wire feeder or misalignment of laser beam to seam cause imperfections such as pores, holes or one-side or even improper wetting. However, today it is still hardly possible to observe in-situ those failures reliably during laser brazing. Hence, the goal is the development and qualification of a new online quality control system for laser brazing. Therefore, in the first step the mechanisms of different joint imperfections are analyzed and evaluated. In the second step the jo...