Inclusions in Steel

Inclusion Content in Steel – Qualifying Material Lots

Metallographic Microscopy The specimen shown in this optical metallographic microscope image was similar to the one shown above in the epoxy potting compound. Each specimen was prepared and evaluated according to the requirements of ASTM Standard E 45, “Standard Test Methods for Determining the Inclusion Content of Steel,” Method A (Worst Fields). In this evaluation a specimen is ground and polished according to selected procedures outlined in ASTM Standard E 3. A visual survey over 160 mm2 (0.25 in.2) of the surface is then performed at 100x in fields that have an area of 0.50 mm2 each. The entire sample is rated by its worst field for a number of different potential inclusions, such as the “Type D Globular Oxide” heavy inclusion indicated by the circle. By comparing the worst fields to preset acceptance criteria, this type of evaluation can be used to qualify bulk material lots before introducing them into manufacturing processes.