S690QL
EN 10025-6 · 1.8928
S690QL is a structural steel (Q&T High Yield family) to EN 10025-6 (1.8928). It has a specified 0.2 % proof stress of 690 MPa and a typical tensile strength of about 770 MPa, with a uniform elongation of 14 %. Nominal carbon content is around 0.20 %. For nonlinear FEA, a bilinear model uses E = 210 GPa up to yield and a tangent modulus of 594 MPa above it. The quenched-and-tempered condition gives a high strength-to-weight ratio for demanding structural duty.
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 (~0.20%) 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 q&t high yield steel — use the mill certificate for the specific product.
Chemical composition (wt %)
Typical composition per EN 10025-6 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
The quenched-and-tempered high-yield structural steels brought fabricated-steel strength once reserved for armour and pressure work to cranes, mobile plant and heavy structures — a low-carbon boron/Cr/Ni/Mo steel quenched and tempered to very high yield while staying weldable. EN 10025-6 covers the S…Q family (and mirrors the proprietary Strenx/Weldox-type plates). The number, 690, is the minimum yield strength in MPa.
- 1960Q&T low-alloy plate (e.g. T-1 / A514) developed for high-strength welded structures
- 1990European Q&T structural plate standardised (EN 10137, later EN 10025-6)
- 2004EN 10025-6:2004 — the S…Q / QL / QL1 high-yield 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.