Ultrasonic characterization of Cr-Mo steels

摘要

Materials of pressure vessels are exposed to service conditions of temperatures above 400°C and high pressure of hydrogen. Such conditions result in changes to the structure of these materials and in turn to their properties. Different methods have been proposed which can be used to monitor changes in the microstructure and properties of materials exposed to these service conditions. Among the proposed methods, ultrasonic techniques are of special interest. In industrial practice, measurements of the two following ultrasonic parameters are carried out: (a) coefficient of attenuation, K, (b) the velocity ratio of transverse to longitudinal waves, R. These two parameters have been measured for a large number of chromium-molybdenum and carbon steels used in pressure vessels and piping systems in Poland's largest oil refinery. This paper presents an analysis of the results in terms of the evaluation of structural degradation of materials subjected to these service conditions.