S420 / S460 Steel
Fine-grain thermomechanically rolled structural steels (M)
Typical values for the temper in the title
S420 and S460 per EN 10025-4 are structural steels that get their strength from "thermomechanical" rolling: rolling at controlled temperatures that produces a very fine grain. This reaches 420 or 460 MPa yield with low carbon, low CEV and good weldability.
The letter M indicates thermomechanical rolling, and L indicates low-temperature impact testing (for S460ML: 27 J at -50 °C). They are used in weight-sensitive structures, bridges and offshore structures.
Mechanical and physical properties
| Property | Value | Note |
|---|---|---|
| Tensile strength Rm | 520-680 MPa | S420M (database value) |
| Yield strength Rp0.2 | 420 MPa | S420 (S460: 460) |
| Elongation A | 19% | |
| Hardness | 185-210 HB | |
| Modulus of elasticity E | 210 GPa | |
| Density ρ | 7.85 g/cm³ | |
| Machinability | 55% | relative rating in the site database |
Chemical composition (wt %)
| Element | Range | Role |
|---|---|---|
| C carbon | low (per standard and thickness) | weldability |
| Mn manganese | limited per the standard | |
| Nb / V / Ti | microalloying | fine grain |
| Fe iron | balance |
Descriptive composition. Exact limits are in EN 10025-4 and depend on grade and thickness.
Conditions and heat treatment
Structural, pressure and pipeline steels are selected by minimum yield strength and impact toughness at a given temperature, not by a heat treatment the user performs. The delivery condition is defined by the standard.
| Condition | Properties | When to choose it |
|---|---|---|
| M (thermomechanically rolled) | yield min 420 / 460 MPa | impact tested at -20 °C |
| ML | as M | impact tested at -50 °C (S460ML: 27 J) |
Applications
- Lightweight high-strength structures
- Bridges
- Offshore structures
- Cranes and lifting equipment
- Weight-sensitive structures
Fabrication
Welding
Weld well thanks to the low CEV, but with heat-input control.
Hot forming
Do not heat to high temperature for forming or straightening: it destroys the thermomechanical structure and lowers strength.
Machining
Reasonable.
Compared with similar materials
| Material | Rm / Rp0.2 | Welding | When it is the better choice |
|---|---|---|---|
| S355 | 470–630 / 355 MPa | Good | weaker, cheaper · material page |
| S690QL | 760-940 / 690 MPa | Difficult — Preheat mandatory | quenched and tempered, much stronger · material page |
| A572 Gr.50 | 450 / 345 MPa | Excellent | American, 345 MPa yield · material page |
Common mistakes
Heating for straightening or forming
Heat removes the strength gained by thermomechanical rolling.
Ordering M when extreme cold toughness is needed
For extreme cold, ML.
Substituting S355 without calculation
Yield is much lower.
Equivalents, standards and supply
| EN | S420ML / S460ML |
|---|---|
| ASTM | A572 Gr.65 (close to S460) |
| Standards | EN 10025-4 |
| Forms | plate · profile · wire |
| Producers | SSAB · ArcelorMittal · Dillinger |
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