Non-destructive testing of refractories, especially AZS materials, with ultrasound, microwaves and γ-radiation

Abstract

In principle four different methods (ultrasound, microwaves, γ-radiation and x-rays) are available for the non-destructive testing of refractories. Three of these methods, i. e. ultrasound, microwaves and γ-radiation, are in use by different producers of AZS materials to carry out the quaUty control of their products. This paper will compare the three methods on the basis of the physical properties, present the existing devices, and show the advantages as well as the hmits of the different methods. γ-radiography, the oldest method in use, has one main disadvantage, which is the requirement of protection against radioactive radiation. Furthermore, while cracks and cavities can be detected with this method, structural changes can not be monitored. Therefore, the ultrasonic method was developed that allows to detect variations of porosity and grain size as well as cracks and voids when the ultrasonic parameters are tuned as well as possible. As an alternative method testing with microwaves is also possible. This method, however, shows its best results when testing sintered refractory products with open porosity.