S690QL Steel
A quenched and tempered high-strength structural steel (QL)
Typical values for the temper in the title
S690QL is a high-strength structural steel per EN 10025-6: a minimum yield of 690 MPa (for thickness up to 50 mm), 770–940 MPa tensile, and impact toughness of 30 J at -40 °C. Q indicates quenching and tempering, and L low-temperature impact testing.
Thanks to its strength, structures can be much lighter than with S355. It is used in crane booms, earthmoving and mining equipment, trucks and bridges.
Mechanical and physical properties
| Property | Value | Note |
|---|---|---|
| Tensile strength Rm | 770–940 MPa | up to 50 mm, per EN 10025-6 |
| Yield strength Rp0.2 | 690 MPa | up to 50 mm |
| Elongation A | 14% | |
| Hardness | 270-320 HB | |
| Modulus of elasticity E | 210 GPa | |
| Density ρ | 7.85 g/cm³ | |
| Machinability | 40% | relative rating in the site database |
Chemical composition (wt %)
| Element | Range | Role |
|---|---|---|
| C carbon | max 0.20 | |
| Mn manganese | max 1.70 | |
| Si silicon | max 0.80 | |
| Cr chromium | max 1.50 | hardenability |
| Mo molybdenum | max 0.70 | hardenability |
| Ni nickel | max 2.0 | toughness |
| B boron | max 0.005 | hardenability |
| P / S | max 0.020 / 0.010 | |
| Fe iron | balance |
Maximum limits per EN 10025-6 (Tata Steel and Macsteel data). Per Tata, CEV max 0.65 for thickness up to 50 mm.
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 |
|---|---|---|
| Up to 50 mm | yield 690, Rm 770–940 MPa | 30 J at -40 °C (longitudinal) |
| 50–100 mm | yield 650, Rm 760–930 MPa | |
| 100–150 mm | yield 630, Rm 710–900 MPa |
Applications
- Crane booms and lifting equipment
- Earthmoving and mining equipment
- Truck and trailer chassis
- Bridges and lightweight structures
- Offshore structures
Fabrication
Welding
Possible, with preheat by thickness and CEV, heat-input control, and filler of suitable strength.
Heating
Per Macsteel, do not heat above about 560 °C: it damages the original temper and properties.
Forming
Cold bending is possible, but needs much more force and a larger bend radius than ordinary structural steel.
Compared with similar materials
| Material | Rm / Rp0.2 | Welding | When it is the better choice |
|---|---|---|---|
| A514 | 760-895 / 690 MPa | Medium | the American equivalent · material page |
| S355 | 470–630 / 355 MPa | Good | an ordinary structural steel, much weaker · material page |
| Hardox 400 | 1250 / 1000 MPa | Medium | for abrasion resistance, not load bearing · material page |
Common mistakes
Heating above 560 °C for straightening
The quench-and-temper properties are destroyed.
Welding without a procedure
Risk of hydrogen cracking and a weak weld zone.
Using the 50 mm yield for a thick plate
In thick sections yield drops to 650 and 630 MPa.
Equivalents, standards and supply
| EN | S690QL (1.8928) |
|---|---|
| DIN | TStE 690 V (old) |
| ASTM | A514 (close) |
| BS | Weldox 700 |
| Standards | EN 10025-6 |
| Forms | plate only (mostly) |
| Producers | SSAB Weldox · Dillinger Dillimax · ArcelorMittal Amstrong |
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