Key Relationships Between Composition and Mechanical Properties
The performance of S45C is directly determined by its chemical composition, with two core relationships:
Carbon vs. Strength/Hardenability: The 0.42–0.50% C content is the "sweet spot"-it enables significant strength gains after quenching (TS increases from 530 MPa to 750 MPa) while avoiding excessive brittleness. If C exceeds 0.50%, the steel becomes too hard to machine and prone to quenching cracks; if C is below 0.42%, hardenability drops, and the Q&T strength gain is minimal.
Manganese vs. Toughness: The 0.60–0.90% Mn content refines the grain structure of S45C, preventing the "brittleness trap" of medium-carbon steel. Without sufficient Mn, S45C would have lower impact toughness (＜20 J in Q&T state) and be unsuitable for dynamic load applications.