ISO 13947:2011 specifies a metallographic method for determining the non-metallic inclusion level in metal powders using a powder-forged specimen. The test method covers repress powder-forged test specimens in which there has been minimal lateral flow (< 1 %). The core region of the powder-forged test specimen contains no porosity detectable at 100 ´ magnification.
This test method can also be used to determine the non-metallic inclusion content of powder-forged steel parts. However, in parts where there has been a significant amount of material flow, the near-neighbour separation distance needs to be changed, or the inclusion sizes agreed between the parties need to be adjusted.
This test method is not suitable for determining the non-metallic inclusion level of parts that have been forged such that the core region contains porosity. At the magnification used for this test method, residual porosity is hard to distinguish from inclusions. Too much residual porosity makes a meaningful assessment of the inclusion population impossible.
This test method can be applied to materials that contain manganese suifide (admixed or prealloyed), provided the near-neighbour separation distance is changed from 30 µm to 15 µm.