Two steels dominate crane gear manufacturing: 20MnCr5 (case-hardening, carburized) and 42CrMo4 (quenched and tempered, often nitrided or induction-hardened). Both can make a gear that runs for decades — but they fail differently, machine differently and cost differently. Here is how we help customers decide.
20MnCr5 — the case-hardening route
Carburize, quench, temper. Result: a hard surface (typically 58–62 HRC) over a tough, low-carbon core.
- Best for: hoisting gears, slewing pinions, anywhere with high contact stress and shock loads
- Strengths: highest surface hardness and rolling-contact fatigue life; excellent for ground gears to ISO 1328 / DIN 3962 quality
- Watch-outs: heat-treatment distortion — blanks must be machined with grinding allowance, and thin teeth can warp
42CrMo4 — the quenched & tempered route
Quench and temper to core strength (commonly 28–34 HRC for gears), then nitride or induction-harden the surface if wear demands it.
- Best for: travel-drive gears, larger modules where grinding every surface is impractical, gears finished after heat treatment
- Strengths: minimal distortion — teeth can be cut after heat treatment and still hold quality; simpler, shorter process chain
- Watch-outs: surface hardness tops out well below carburized 20MnCr5, so pure contact-stress capacity is lower
The practical decision matrix
| Factor | 20MnCr5 (carburized) | 42CrMo4 (Q&T / nitrided) |
|---|---|---|
| Surface hardness | 58–62 HRC | 28–34 HRC core; up to ~50 HRC nitrided case |
| Shock / overload tolerance | Excellent — tough core | Good |
| Distortion after HT | Higher — grinding required | Low — can finish-cut after HT |
| Typical use on cranes | Hoisting & slewing gear trains | Travel drives, wheels, large-modulus gears |
How we control the result
Whichever steel your drawing specifies, the certificate is what proves it. Every HCGR gear order ships with EN 10204 3.1 material certificates tied to heat numbers, plus CHD (effective case depth) and core-hardness verification records where carburizing is involved, and 100% dimensional inspection with FAI reports for new parts.
Unsure which steel suits your drive? Send the drawing and the duty cycle — torque, speed, hours per day. We will recommend the steel, heat treatment and quality grade in the quotation, within 24 hours.
Need these parts made to your drawing? Send your specification — clear quotation within 24 hours, EN 10204 3.1 certificates as standard.
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