Possibilities of predicting the behaviour of ferrite-austenite welded joints in pressure equipment during exploitation

Abstract

Exploitation safety of pressure equipment depends, among other factors, on the possibility of predicting the behaviour of each of its components during exploitation. If the safety of analysis is oriented towards materials which are used for manufacturing of individual parts of pressure equipment, such as mantle, lids and flanges, predicting their behaviour is relatively simple since the properties of these materials are generally similar in all directions. However, predicting the behaviour of welded joints is significantly harder and less reliable, due to a number of reasons, including chemical and structural non-homogeneity, changes in wall geometry at the welded joint site, as well as residual stresses and weld forming defects. Occasionaly, different pressure equipment parts are made of different types of steel, due to optimisation, which results in heterogeneous welded joints. Because of the difference in physical and mechanical properties of these steels, their joints have their own specificities, which make predicting their behaviour during exploitation much more complicated.

Keywords

• cracks
• heterogeneous welded joint
• pressure equipment
• stresses
• structural non-homogeneity