Quality Analysis of AISI 321 Welds of Bellow Compensators Used in Shipbuilding

Abstract

The production of compensators (expansion joints), and especially of bellows as their most demanding elements, requires the usage of stainless materials. These stainless materials exhibit certain particularities at welding (and quality control) since they are very thin, i.e., their thickness ranges usually from 0.12 to 3.00 mm. This paper starts with the elaboration of compensators and their application, and further presents characteristics of the material selected for experimental testing. In the second part, the paper continues with a description of the experiment referring to longitudinal welding of samples without filler material. The experiment focused on the determination of accurate characteristics of radiographic recordings and their assessment based on comparison with the tensile testing (mechanical properties), FEM numerical simulation and dimensional control. The paper also presents the analysis of obtained results and conclusions made thereof. The research hypothesis was to determine in what way the welding parameters affect the mechanical properties, the geometric shape of the welds, and the exploitation possibilities of the compensator. According to the performed experimental part and the performed testing of mechanical properties, all welded joints are acceptable for use. Nevertheless, according to the standard that prescribes the acceptability criteria of defects that occur in welded joints, some of tested samples were not suitable for operating conditions. Such kinds of welded sheets must be repaired or eliminated from further processing.