When duplex stainless steel (DSS) is applied to welded components, ferrite measurement with manual point count according to ASTM(1) E562 is often used during welding procedure qualification as heat affected zone (HAZ) of the weld tends to have high ferrite content. For this measurement method, there are several testing variables and it seems that standard testing variables are not used for ferrite measurements performed by various fabricators. In this paper, the effects of three major variables described in ASTM E562, which were the grid size i.e. number of testing points in a grid, number of fields and measurement locations, on the measured ferrite contents were studied. Also, ferrite measurement with automatic image analysis according to ASTM E1245 was performed across the fusion line of the weld to compare the ferrite content measured by manual point count according to ASTM E562. In addition to the ferrite measurement, pitting corrosion test according to ASTM G48, Method A was performed on the same sample as the one used for ferrite measurement in order to see where in the weld pitting corrosion occurs. The results have suggested a necessity of establishment of standardized testing variables to be used for ferrite measurement with manual point count according to ASTM E562.
Key words: Duplex Stainless Steel, Welding, Ferrite Content, Point Count, ASTM E562, Image Analysis