Materials
Materials questions here are rarely about metallurgy for its own sake; they ask whether the documentation and marking you reviewed actually support the design.
The reference set
Section II Part A - ferrous specifications; Part B - nonferrous; Part C - welding consumables; Part D - properties, including allowable stress tables and their notes. A specification is acceptable only if it appears in Section II; ASTM specifications are adopted with ASME additions. P-numbers group base metals for procedure qualification (P-1 carbon steel, P-8 stainless), F-numbers group filler metals, and A-numbers describe weld metal chemistry. Section IX qualifications are written in these numbers, not in trade names.
Verifying a material
- Match specification, grade, and product form on the Certified Material Test Report to the design and to the marking on the item: heat number, chemistry, tensile and yield strength, and required impact values.
- Where impact testing is required, Section VIII expects Charpy V-notch results meeting code minimums - typically 20 ft-lb average with lateral expansion of at least 15 mils on full-size specimens - at a test temperature at or below the minimum design metal temperature.
- Confirm the allowable stress used in design came from Part D for that product form; pipe and plate rarely share a value.
- Unknown or unmarked material in an existing item cannot be presumed to be the original specification; identity must be established by testing or acceptable documentation.
Worked example. A test report for SA-516 Gr. 70 plate lists heat 12345, tensile 78 ksi, yield 45 ksi, and no impact results; the design is 0.75 in. thick at an MDMT of −20 °F. That MDMT falls below the UCS-66 exemption curve for the thickness, so impact testing is mandatory and is missing. Finding: the material cannot be accepted until impact results are supplied.
Traps. Accepting a report with no heat number; substituting equivalent steel not listed in Section II; assuming P-1 identifies a specific grade; ignoring Part D notes that reduce allowable stress.