S420M
EN 10025-4 · 1.8825
S420M is a structural steel (Fine Grain TMCP family) to EN 10025-4 (1.8825). It has a specified 0.2 % proof stress of 420 MPa and a typical tensile strength of about 500 MPa, with a uniform elongation of 19 %. Nominal carbon content is around 0.14 %. For nonlinear FEA, a bilinear model uses E = 210 GPa up to yield and a tangent modulus of 430 MPa above it. Thermomechanical rolling gives high strength with a low carbon equivalent, so weldability stays good despite the elevated yield.
Bilinear material model — nonlinear FEA
Uniform elongation εu = 19.0% · conservative analysis limit ½εu = 9.5%
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 (~0.14%) 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.
Hardenabilitylow
Limited hardenability at low carbon — surface hardening is possible but through-hardening is not.
Toughnessgood
Fine-grain / alloy processing gives good low-temperature toughness for its strength.
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 fine grain tmcp steel — use the mill certificate for the specific product.
Chemical composition (wt %)
Typical composition per EN 10025-4 for this grade — confirm exact limits (thickness-dependent) against the standard.
Available forms
Common applications
- Building and bridge steelwork
- Platforms, frames and support structures
- Crane and lifting structures
- General heavy fabrication
History
Thermomechanically rolled (TMCP) steels get their strength from tightly controlled rolling and cooling rather than added carbon or alloy, giving a very low carbon equivalent — so they weld and bend far better than a Q&T steel of the same strength. EN 10025-4 defines the family. The number, 420, is the minimum yield strength in MPa.
- 1980Thermomechanical controlled processing (TMCP) matures for plate and pipe
- 1993EN 10113-3 / EN 10025-4 standardise the S…M / ML grades
- 2004EN 10025-4:2004 — current form
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.