Non-metallic inclusions such as sulfides and oxides form during deoxidation, or because some elements have limited solubility in solid steel. ASTM E45 rates them but sets no limits: where cleanliness matters, the specification or the order says how it is judged.
Grain size matters in both directions. Alloy socket screws to A574, F835 and F912 must be made from fine-grain steel, with E112 as the referee on finished screws. For creep strength at high temperature, coarse grain is wanted: A193 S9 and A194 S6 require No. 7 or coarser on non-H austenitic bolting used above 1000 °F (540 °C).
Read the full metallography page →
model dataSection along the bar, at least 160 mm² (0.25 in.²) polished, 100× fields 0.71 mm (0.028 in.) square, the four inclusion types with their thin and heavy widths, and Methods A and D from ASTM E45. Grain size methods from ASTM E112; grains per square inch at 100× from N = 2^(G−1). The cut-off saw, polisher and microscope are generic, and the microstructures are schematic.
© 2026 Innovation Fasteners. This interactive drawing, its 3D models and its code may not be copied, hosted elsewhere, scraped or used to train AI models. Terms of use.