NONDESTRUCTIVE TESTING OF CERAMICALLY BONDED REFRACTORIES - APPLICATION OF ULTRASOUND AND MICROWAVES

Quality control on refractory bricks is either mostly destructive or m ethods are used which require samples with a certain geometry. In a jo int project between the University of Erlangen and industry the applic ability of non-destructive testing methods for sintered refractory bri cks was tested. Various materials with artificial flaws were measured in transmission with ultrasound (500 kc/s) as well as with microwaves (24 to 40 Gc/s) and the results were compared. Despite of good results , the testing with ultrasound proved to be unsuitable for the measurem ents of greater lots, because the open-pore blocks have to be coupled in water. An excellent alternative is the transmission measurement wit h microwaves. With both methods structural inhomogeneities as well as density differences or inclusions can be detected.