V.S. Heat Treatment
Heat treatment & metal finishing experts
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V.S. Heat Treatment
Heat treatment & metal finishing experts
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A practical decision page for design, purchasing and QC, with realistic service ranges and section-size limits.
S45C vs SCM440
Both grades can reach similar surface hardness after quenching. SCM440 contains chromium and molybdenum, so its hardenability is higher and it holds hardness more uniformly through thicker sections. S45C is often the economical choice for small, general-purpose parts.
| Decision factor | S45C | SCM440 |
|---|---|---|
| Steel family | Medium-carbon steel | Cr–Mo alloy steel |
| Closest equivalents | AISI 1045 / C45 | AISI 4140 / 42CrMo4 |
| Typical carbon | 0.42–0.48% | 0.38–0.43% |
| Primary route | Quench & temper | Quench & temper |
| Typical as-hardened surface | About 50–58 HRC | About 50–58 HRC |
| Typical tempered service range | About 40–55 HRC | About 28–48 HRC |
| Hardenability | Moderate; section-size sensitive | Higher; more uniform in thicker sections |
| Typical use | Pins, small shafts, general bolts | High-strength bolts, shafts, pins, loaded parts |
Choose S45C for modest section sizes, general loads and cost-sensitive parts where extreme strength and core hardenability are unnecessary.
Choose SCM440 for thicker sections, more uniform core hardness, cyclic or impact loading, and tighter strength/toughness control after tempering.