Laghdaíonn insínteacht (arna thomhas ag fadú) de réir mar a ardaíonn an t -ábhar carbóin. Íseal - Cruach bhabhta carbóin (m.sh., SAE 1018, 0.18% C) Taispeánann 25 - 30% fadú, ag ligean lúbadh agus foirmiú. Meánach {- Titeann carbón (SAE 1045, 0.45% C) go dtí fadú 15-20%, atá oiriúnach le haghaidh foirmiú teoranta. Ardcharbón (SAE 1095, 0.95% C)<10% elongation, making it brittle but hard. This trend occurs because carbon forms iron carbides, which restrict dislocation movement-essential for plastic deformation. For applications requiring both strength and ductility (e.g., automotive parts), medium-carbon grades with heat treatment are preferred.