Non-destructive evaluation of seams of laser welded tools using the CS-eddy current technique

Present testing methods for evaluating the integrity of a welding seam of laser welded tools, like bend or shock testing, may possibly introduce damage into the tool. Statistically performed destructive tests are expensive and not reliable as 100% NDT (nondestructive testing). Furthermore, usual destructive tests for laser welded tools, like shearing or tearing tests, do not describe the complexity of the loads in service and therefore cannot deliver clear indications about the reliability of the seam. This article describes the possibilities of the nondestructive controlled signals (CS) pulsed eddy current technique for evaluating the characteristics of laser welded seams. The presented results were achieved from measurements on laser welded seams of saw blades. The used handling-system was built up similar to the requirements of a testing system suitable for online process control and the achieved results therefore describe well the possibilities in practice. The online description of different seam characteristics (pores and cracks in the seam, differing geometry of the seam, etc.) enables an optimisation of the welding process and consequently leads to the economic production of high quality products and to higher security in operation.