ASME Section VIII Division 1 UG-84 prescribes Charpy V-notch impact testing methodology for pressure vessel base metal, weld metal, and HAZ. 5 specification areas (specimen geometry / orientation / quantity / temperature / acceptance) + 4 notch locations (base + weld center + HAZ 1mm + HAZ 5mm) + 5-criterion acceptance + bath medium selection by MDMT + 5 pitfalls + 5 welding process implications.