The higher IS 2062 quality grades (notably C and D) carry Charpy V-notch impact requirements at specified test temperatures. Notch toughness is the property that prevents sudden, catastrophic brittle fracture of welded, thick-section or low-temperature structures — strength and tensile ductility do NOT guarantee it, and steel has a ductile-to-brittle transition with temperature, so the impact grade must suit the service condition.
Key Requirements
•Quality C/D grades: minimum Charpy V-notch absorbed energy at the specified temperature (IS 1757)
•Specify the impact (quality) grade for welded, thick, or low-temperature/impact/fatigue structures
•Test Charpy at the SERVICE (lowest) temperature where it governs — steel has a ductile-brittle transition
•Strength/tensile ductility do not imply notch toughness — it is a separate, necessary acceptance
•Combine tough steel with notch-free detailing & sound welds (IS 816) — both prevent brittle fracture
Practical Notes
✓Brittle fracture is sudden, low-energy and near-warningless, propagating from notches/weld defects — the impact grade exists precisely to prevent the dramatic welded-structure failures it causes.
✓Specify the quality grade by the service condition (welded/thick/cold), not by strength — the E-number says nothing about toughness.
Common Mistakes
⚠Assuming tensile ductility implies impact toughness (it does not).
⚠Using a non-impact (basic) quality where welded/thick/cold service needs C/D.
⚠Testing Charpy only at room temperature when service is colder.