Alloy Structural Steel
Alloy structural steels add chromium, manganese, molybdenum, vanadium and titanium to carbon steel so that after quench-and-temper the strength reaches deeper into the section. Gears, transmission shafts, high-strength bolts and aerospace fittings — anywhere strength and toughness must coexist — start their material search here.
| Grade | Alloy system | Delivery condition | Typical parts |
|---|---|---|---|
| 20CrMnTi | Cr-Mn-Ti case-hardening | normalized / carburise then Q+low T | automotive gears, crosses |
| 20CrMn | Cr-Mn case-hardening | Q+T sample | gears, worms |
| 30CrMnSiA | Cr-Mn-Si high strength | Q+T | aerospace & defence fittings |
| 40Cr | Cr workhorse | Q+T | shafts, con-rods, bolts |
| 35CrMo | Cr-Mo elevated temp | Q+T | large shafts, high-temp bolts |
| 42CrMo | Cr-Mo deep hardening | Q+T | heavy gears, large shafts |
Typical applications
Ordering notes
Delivery condition is the decisive clause here: the same 42CrMo ordered hot-rolled, normalized or Q+T serves entirely different purposes and prices. Gear blanks in 20CrMnTi arrive normalized for machinability; fitted load-bearing parts come Q+T with hardness and tensile results on the certificate.
Carburised 20CrMnTi reaches HRC 58+ at the surface with a tough core — the classic gearbox gear steel; 30CrMnSiA has a mature record in defence and aerospace, where batch re-inspection requirements are common. We stock 20CrMnTi, 42CrMo and 30CrMnSiA and cut pre-hardened blanks to drawing.
常见问答
What is 20CrMnTi for?
The classic carburising gear steel: carburise and quench for a hard, wear-resistant case over a tough core. Gearbox and axle gears, crosses. Standard composition: C 0.17–0.23%, Cr 1.00–1.30%, Ti 0.04–0.10%.
Q+T or normalized delivery?
Follow the machining route: heavy roughing prefers normalized blanks (softer, easier to cut) with Q+T done later by the user; directly used blanks can be ordered Q+T to skip the user's heat treatment, at a longer lead and higher price.
42CrMo or 40Cr?
40Cr is the economical default for general shafts and bolts; 42CrMo adds molybdenum for hardenability and temper resistance — choose it for large sections, heavy loads and fatigue-critical parts where 40Cr stops hardening deeply enough.
Further reading
A few related pieces worth a look: