Steel S690Q-QL1
Heat-treated state
EN S690Q · GB Q690Q
QL1 = s690QL1
Highest toughness class for cryogenic-service structures and heavy offshore sections down to −60 °C.
Values for the QL1 condition
Other S690Q tempers and conditions
S690Q is listed in 6 conditions; see the grade overview at S690Q.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Q&T, plate thickness 100–150 mm | Very heavy plate; lowest guaranteed properties of the grade and the practical thickness ceiling for S690. | 690 | 790 | 16 | 22 HRC | 7.5 % IACS |
Q&T, plate thickness 50–100 mm | Heavy plate condition — standard permits reduced guaranteed yield/tensile because of lower quench severity through thickness. | 710 | 830 | 16 | 24 HRC | 7.5 % IACS |
Stress relieved | Post-weld stress relief below the tempering temperature for dimensionally critical or thick welded assemblies; expect a small strength drop. | 720 | 810 | 17 | 24 HRC | 7.5 % IACS |
QDefault S690Q | Standard stocked quality for general high-strength welded structures operating down to about −20 °C. | 750 | 840 | 16 | 25 HRC | 7.5 % IACS |
S690QL | Choose when service or test temperature reaches −40 °C (cranes, arctic vehicles, offshore topsides); tighter P/S limits. | 755 | 845 | 16 | 25 HRC | 7.5 % IACS |
QL1This page S690QL1 | Highest toughness class for cryogenic-service structures and heavy offshore sections down to −60 °C. | 760 | 850 | 17 | 24 HRC | 7.5 % IACS |
What is S690Q-QL1?
S690Q-QL1 is S690Q heat treated to QL1 — highest toughness class for cryogenic-service structures and heavy offshore sections down to −60 °C. S690Q-QL1 has a yield strength of 760 MPa (110 ksi) and a tensile strength of 850 MPa (123 ksi) — stronger than 85% of steel grades. Elongation at break is 17% and the elastic modulus is 210 GPa (30.5 Msi). S690Q-QL1 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F). Q is the default condition FabDigit quotes; QL1 is available on request or by drawing note.
Advantages
- Tough — resists crack growth — 155 MPa·√m (141.1 ksi·√in), better than 97% of steel grades
- High strength — 760 MPa (110 ksi), better than 85% of steel grades
Limitations
- Difficult to machine — 38/100, worse than 80% of steel grades
S690Q-QL1 properties
Typical room-temperature values for S690Q-QL1; 23 are specific to this condition. Other listed values are S690Q reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
S690Q-QL1 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical16
S690Q-QL1 has a yield strength of 760 MPa (110 ksi) and a tensile strength of 850 MPa (123 ksi) — stronger than 85% of steel grades. Elongation at break is 17% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
S690Q-QL1 is rated for continuous service to 400°C (752 °F). It conducts heat at 40 W/m·K (23.1 BTU/hr·ft·°F), worse than 64% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
S690Q-QL1 conducts electricity at 7.5 % IACS, worse than 67% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (14/100), better than 70% of steel grades.
Sustainability4
Producing a kilogram of S690Q-QL1 takes about 29 MJ of energy and emits 2.3 kg of CO₂ — less than 53% of steel grades. Typical recycled content is 25%.
Manufacturability7
S690Q-QL1's machinability is fair (38/100, worse than 80% of steel grades); weldability good (66/100); formability fair (42/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with S690Q-QL1
Is S690Q easy to machine?
Machine with rigid setups and coated carbide at moderate speed (roughly 60–110 m/min) and generous feed; the tough tempered structure work-hardens edges and dulls HSS quickly.
Can S690Q be welded?
Fully weldable with low-hydrogen (H5) 690-class consumables; keep hydrogen out, preheat typically 100–175 °C by thickness/CEV, control interpass ≤ 200 °C and limit heat input to protect HAZ toughness and avoid softening.
Can S690Q be formed, bent or molded?
Cold bend transverse to rolling direction with punch radii of about 3–4 × t (larger for thick plate); hot forming above the tempering temperature destroys the Q&T properties and requires re-heat-treatment.
What surface finishes work on S690Q?
Grit-blast to Sa 2½ and paint or metallize for corrosion protection; grind weld toes to improve fatigue life and avoid acid pickling or uncontrolled electroplating because of hydrogen-embrittlement risk.
S690Q chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Cladle analysis, t ≤ 50 mm | ≤ 0.2 | 0.16 |
| Si | ≤ 0.8 | 0.3 |
| Mn | ≤ 1.7 | 1.3 |
| P0.020 max for QL, 0.020 max for QL1 | ≤ 0.03 | 0.01 |
| S0.010 max for QL and QL1 | ≤ 0.02 | 0 |
| Cr | ≤ 1.5 | 0.5 |
| Nihigher Ni for QL/QL1 toughness | ≤ 2 | 0.6 |
| Mo | ≤ 0.7 | 0.4 |
| Cu | ≤ 0.5 | 0.15 |
| V | ≤ 0.12 | 0.04 |
| Nb | ≤ 0.06 | 0.02 |
| Ti | ≤ 0.05 | 0.02 |
| Zr | ≤ 0.15 | — |
| Bboron-treated for hardenability | ≤ 0.01 | 0 |
| N | ≤ 0.02 | 0.01 |
| Fe | balance | — |
S690Q-QL1 — frequently asked
What is S690Q-QL1 used for?
S690Q-QL1 is typically used for cranes, mobile equipment chassis, structural fabrications and trailers. In short: baseline EN 690 MPa plate; widely stocked Q&T plate; weight-saving structural steel.
What is the yield strength of S690Q-QL1?
S690Q-QL1 has a typical yield strength of 760 MPa (110 ksi) and a tensile strength of 850 MPa (123 ksi) — stronger than 85% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is S690Q-QL1 easy to machine?
Not especially — machinability is rated fair (38/100, worse than 80% of steel grades). Machine with rigid setups and coated carbide at moderate speed (roughly 60–110 m/min) and generous feed; the tough tempered structure work-hardens edges and dulls HSS quickly.
Can S690Q-QL1 be welded?
Yes — weldability is rated good (66/100). Fully weldable with low-hydrogen (H5) 690-class consumables; keep hydrogen out, preheat typically 100–175 °C by thickness/CEV, control interpass ≤ 200 °C and limit heat input to protect HAZ toughness and avoid softening.
What surface finishes work on S690Q-QL1?
Grit-blast to Sa 2½ and paint or metallize for corrosion protection; grind weld toes to improve fatigue life and avoid acid pickling or uncontrolled electroplating because of hydrogen-embrittlement risk.
Can S690Q-QL1 be formed, bent or molded?
Cold bend transverse to rolling direction with punch radii of about 3–4 × t (larger for thick plate); hot forming above the tempering temperature destroys the Q&T properties and requires re-heat-treatment.
What is the maximum service temperature of S690Q-QL1?
S690Q-QL1 is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between S690Q-Q and S690Q-SR?
Q is the default condition — standard stocked quality for general high-strength welded structures operating down to about −20 °C. SR: post-weld stress relief below the tempering temperature for dimensionally critical or thick welded assemblies; expect a small strength drop. Yield strength is 750 MPa in Q versus 720 MPa in SR.
Sources
- EN 10025-6: Hot rolled products of structural steels — Technical delivery conditions for flat products of high yield strength structural steels in the quenched and tempered condition — CEN (2019)
- GB/T 16270 High strength structural steel plates in the quenched and tempered condition (Q690D/E/F) — SAC (2009)
- High-strength quenched and tempered structural plate datasheets (S690Q/QL/QL1) — SSAB / Dillinger / voestalpine (2023)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- EN 1993-1-12 — Design of steel structures: additional rules for steel grades up to S700 — CEN (2007)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.