20MnCr5 Steel
Mn-Cr case-hardening steel with higher hardenability
Typical values for the temper in the title
20MnCr5 is the "big sister" of 16MnCr5: slightly more carbon, manganese and chromium. The addition raises hardenability, so a stronger core results even in larger sections.
It is used for gears and shafts in vehicles and gearboxes, when the section is too large for 16MnCr5. The close American equivalent is SAE 5120, and in JIS SMnC420H.
Mechanical and physical properties
| Property | Value | Note |
|---|---|---|
| Tensile strength Rm | ≥960 MPa (core, typical) | |
| Yield strength Rp0.2 | ≥645 MPa (core, typical) | |
| Elongation A | ≥8% | |
| Hardness | ≤217 (annealed) | |
| Modulus of elasticity E | 210 GPa | |
| Density ρ | 7.85 g/cm³ | |
| Machinability | 62% | relative rating in the site database |
Chemical composition (wt %)
| Element | Range | Role |
|---|---|---|
| C carbon | 0.17–0.22 | stronger core |
| Mn manganese | 1.10–1.40 | hardenability |
| Cr chromium | 1.00–1.30 | hardenability and wear resistance |
| Si silicon | max 0.40 | |
| Fe iron | balance |
Ranges per EN 10084 (thyssenkrupp).
Conditions and heat treatment
Case-hardening steels are supplied annealed or normalized for machining, and get their final properties only after carburizing and hardening. Table values are for the core, and depend strongly on section size.
| Condition | Properties | When to choose it |
|---|---|---|
| Annealed (+A) / treated for machinability (+FP) | soft, easy to machine | machining before case hardening |
| Carburized, hardened and tempered | case HRC 58–62, tough core | the finished part |
Applications
- Automotive gears
- Gearbox shafts
- Medium-section gears
- Differential parts
- Loaded pins
Fabrication
Case hardening (carburizing)
Carburize at about 880–950 °C to the required case depth, quench and temper at about 150–200 °C. Case depth is set by the tooth load.
Machining
Most machining is done before case hardening. After it, precision surfaces are ground.
Distortion
Case hardening causes small distortion and dimensional change. Leave grinding allowance.
Compared with similar materials
| Material | Rm / Rp0.2 | Welding | When it is the better choice |
|---|---|---|---|
| 16MnCr5 | 800–1100 MPa (core, typical) / ≥590 MPa (core, typical) | Good — before case hardening | 16MnCr5: for smaller sections · material page |
| 18CrNiMo7-6 | 1080–1320 MPa (core, typical) / ≥785 MPa (core, typical) | Fair | 18CrNiMo7-6: tougher, for heavy sections · material page |
| 8620 | 530–620 / 385–415 MPa | Good | 8620: the common American counterpart · material page |
Common mistakes
Switching to 16MnCr5 in a large section
The core will be weaker.
Using it without case hardening
It is meant to be case hardened.
Not checking case depth
Insufficient depth causes contact fatigue failure.
Equivalents, standards and supply
| DIN | 1.7147 |
|---|---|
| SAE | 5120 (close) |
| JIS | SMnC420H |
| Standards | EN 10084 / ISO 683-3 |
| Forms | bar · forging · strip |
| Producers | Ovako · thyssenkrupp |
Learn more
Values are typical and for comparison only, and depend strongly on condition and diameter. For design, rely on the standard and on the mill certificate. Sources: SAE J403 and J404, ASTM A29, A322 and A519 (composition), producer data sheets, and the METAL HUB materials database.
Updated: October 31, 2026