On-line measurement of hardening depth during induction hardening using ultrasonic backscattering

The ultrasonic backscattering technique is a powerful tool for the nondestructive dtermination of hardening depth of the heat affected zone which in many cases directly correponds to the hardening depth as measured destructively. For industrial application, we have developed an automated system which enables on-line measurements of the hardening depth immediately after the hardening process. The evaluation of the ultrasonic signals as well as the presentation of the results is performed in realtime by measn of a PC. the system can easily be adapted to individual customer requirements. In the article, the principles of the technique and the set-up of the system are described. Examples of application are given.