25CrMo4
4130 · EN 10083-3 · 1.7218
25CrMo4 (4130) is an engineering steel (Chromium-Molybdenum family) to EN 10083-3 (1.7218). It has a specified 0.2 % proof stress of 635 MPa and a typical tensile strength of about 790 MPa, with a uniform elongation of 14 %. Nominal carbon content is around 0.22 %. For nonlinear FEA, a bilinear model uses E = 210 GPa up to yield and a tangent modulus of 1148 MPa above it. The Cr–Mo alloying provides good hardenability and creep/temper resistance.
Bilinear material model — nonlinear FEA
Uniform elongation εu = 14.0% · conservative analysis limit ½εu = 7.0%
Bilinear (BISO) approximation. Elastic modulus E up to the 0.2% proof stress R_p0.2, then a single tangent slope Eₜ to the ultimate tensile strength: Eₜ = (Rₘ − R_p0.2) / (εu − R_p0.2/E − 0.002), where εu is the uniform elongation and Rₘ is a typical (nominal) UTS within the specified band. The half-εu figure is a conservative strain limit for the analysis. Treat these as guidance for first-pass models; for critical work use a measured true stress–strain curve for the actual product and condition.
Ratings — engineering judgement
Weldabilitygood
Low carbon (~0.22%) gives good weldability by all common processes; preheat rarely needed in thin sections.
Machinabilitymoderate
Soft and gummy at low carbon — sharp tooling helps surface finish.
Corrosion resistancepoor
No inherent corrosion resistance — protect by paint, galvanising or plating in exposed use.
Hardenabilitygood
Responds well to quench-and-temper (and, for the case-hardening/nitriding grades, to surface treatment).
Toughnessmoderate
Adequate toughness for general use at ambient temperature.
Indicative ratings derived from composition and family — engineering guidance, not specification values.
Physical properties
| Density | 7850 | kg/m³ |
| Elastic modulus | 210 | GPa |
| Shear modulus | 80.8 | GPa |
| Poisson's ratio | 0.30 | |
| Thermal expansion | 12.0 | ×10⁻⁶/°C |
| Thermal conductivity | 48 | W/(m·K) |
| Specific heat | 470 | J/(kg·K) |
| Magnetic | Yes |
Typical values for chromium-molybdenum steel — use the mill certificate for the specific product.
Chemical composition (wt %)
Nominal composition per EN 10083-3 for 25CrMo4 — confirm exact limits against the standard.
Available forms
Common applications
- Shafts, axles and spindles
- Gears, pinions and couplings
- Connecting rods and levers
- General machined components and fasteners
History
The alloy engineering steels add chromium, nickel and molybdenum for deep hardenability and a high strength-to-toughness balance — the shafts-gears-and-bolts steels. They grew from early-1900s automotive and aircraft demand and were unified across Europe by EN 10083.
- 1910Ni–Cr and Cr–Mo alloy steels adopted for automotive and aircraft parts
- 1942BS 970 defines the EN-series alloy steels (EN19, EN24, EN36…)
- 1991EN 10083-3 harmonises the alloy quench-and-temper grades
This profile is generated from the grade's core data and family. Composition is decoded from the designation where its naming system defines it; physical properties are family-typical and ratings are indicative. Confirm critical values against the governing standard or the mill certificate. Equivalents, historical designations and hand-written expert notes are added per grade over time.