The casting process has demonstrated radiographic similarities between internal discontinuities for ductile cast iron and cast steel to the extent that the reference radiographs for steel castings are applicable. The exact application and usage of discontinuity classifications contained within steel casting reference radiographs must, however, give consideration to the differences in material properties between cast steel and ductile cast iron. In some applications, reference radiographs for steel castings may not be entirely applicable to ductile cast iron material dependent upon design or other usage criteria.

When employing steel casting reference radiographs to evaluate ductile iron castings, the applicable E446, E186, or E280 steel casting written standard shall also be used for specific guidance and evaluation procedures.

These reference radiographs are intended as a basis from which manufacturers and purchasers may, by mutual agreement, select particular discontinuity classes to serve as standards representing minimum levels of acceptability. Reference radiographs represented by these steel casting standards may be used, as agreed upon in a purchaser supplier agreement, for radiation energy levels, thicknesses or both outside the range of these standards when determined applicable for the casting service application