Sas4 Radius Crack |link|

Grinding or turning marks left at the radius act as micro-notch initiators. An SAS4 radius crack often begins at a deep tool mark.

Yes. SAS4 grades are often heat-treated to high hardness (40–50 HRC), which makes them more sensitive to radius-induced fatigue than lower-strength steels like 4140 or mild steel. sas4 radius crack