Steel P690Q-QL1
Heat-treated state
EN 1.8879
QL1 = p690QL1
Pick for cold-climate or refrigerated pressure service down to about −40 °C.
Values for the QL1 condition
Other P690Q tempers and conditions
P690Q is listed in 7 conditions; see the grade overview at P690Q.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Q+T, 100 < t ≤ 150 mm | Thickest standard section; lowest guaranteed strength due to reduced quench severity. | 690 | 790 | 17 | 23 HRC | 7.2 % IACS |
Q+T, 50 < t ≤ 100 mm | Heavy plate condition; strength de-rated for section size per EN 10028-6. | 710 | 820 | 17 | 24 HRC | 7.2 % IACS |
Q+T + stress relieved | Choose when the fabricated vessel must be PWHT'd; expect a modest drop in yield and hardness. | 720 | 810 | 18 | 24 HRC | 7.2 % IACS |
QT-T50Default Q+T, t ≤ 50 mm | Standard stocked delivery condition for P690Q plate up to 50 mm; full 690 MPa minimum yield. | 750 | 830 | 17 | 25 HRC | — |
P690QH | Use for pressure equipment operating above ambient where proof strength at temperature must be guaranteed. | 750 | 830 | 17 | 25 HRC | 7.2 % IACS |
QL1This page P690QL1 | Pick for cold-climate or refrigerated pressure service down to about −40 °C. | 750 | 830 | 17 | 25 HRC | 7.2 % IACS |
P690QL2 | Highest toughness variant for arctic/cryogenic-adjacent pressure vessels down to about −60 °C. | 750 | 830 | 17 | 25 HRC | 7.2 % IACS |
What is P690Q-QL1?
P690Q-QL1 is P690Q heat treated to QL1 — pick for cold-climate or refrigerated pressure service down to about −40 °C. P690Q-QL1 has a yield strength of 750 MPa (109 ksi) and a tensile strength of 830 MPa (120 ksi) — stronger than 84% of steel grades. Elongation at break is 17% and the elastic modulus is 210 GPa (30.5 Msi). P690Q-QL1 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F). QT-T50 is the default condition FabDigit quotes; QL1 is available on request or by drawing note.
Advantages
- Tough — resists crack growth — 140 MPa·√m (127.4 ksi·√in), better than 94% of steel grades
- High strength — 750 MPa (109 ksi), better than 84% of steel grades
Limitations
- Difficult to machine — 35/100, worse than 84% of steel grades
P690Q-QL1 properties
Typical room-temperature values for P690Q-QL1; 23 are specific to this condition. Other listed values are P690Q reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
P690Q-QL1 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
P690Q-QL1 has a yield strength of 750 MPa (109 ksi) and a tensile strength of 830 MPa (120 ksi) — stronger than 84% of steel grades. Elongation at break is 17% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
P690Q-QL1 is rated for continuous service to 400°C (752 °F). It conducts heat at 38 W/m·K (22 BTU/hr·ft·°F), worse than 69% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
P690Q-QL1 conducts electricity at 7.2 % IACS, worse than 71% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (13/100), better than 66% of steel grades.
Sustainability4
Producing a kilogram of P690Q-QL1 takes about 30 MJ of energy and emits 2.3 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 30%.
Manufacturability7
P690Q-QL1's machinability is fair (35/100, worse than 84% of steel grades); weldability good (58/100); formability fair (35/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with P690Q-QL1
Is P690Q easy to machine?
Machine as a 250–290 HB Q&T alloy steel — rigid setups, coated carbide, moderate speeds (~40 % of 1212), and avoid burning the tempered surface layer.
Can P690Q be welded?
Weldable with low-hydrogen processes and matching 690 MPa consumables; preheat typically 100–150 °C (higher for thick/high-CEV heats), interpass ≤200 °C and controlled heat input to protect HAZ toughness.
Can P690Q be formed, bent or molded?
Cold-bend only with generous radii (≈3–4×t transverse) and de-burred, crack-free edges; hot forming above the tempering temperature destroys the Q&T properties and requires re-quench and temper.
What surface finishes work on P690Q?
No natural corrosion resistance — shot-blast to Sa 2.5 and apply zinc-rich primer, metallizing or paint; avoid electroplating that risks hydrogen embrittlement at this strength level.
P690Q 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 max | ≤ 0.2 | 0.16 |
| Si | ≤ 0.8 | 0.3 |
| Mn | 0.4 – 1.7 | 1.2 |
| P | ≤ 0.03 | 0.01 |
| S | ≤ 0.02 | 0 |
| N | ≤ 0.02 | 0.01 |
| Altotal Al; other grain-refining elements permitted | ≥ 0.02 | 0.04 |
| Cr | ≤ 1.5 | 0.5 |
| Cu | ≤ 0.5 | 0.2 |
| Mo | ≤ 0.7 | 0.5 |
| Ni | ≤ 2.5 | 1.5 |
| Nb | ≤ 0.06 | 0.03 |
| Ti | ≤ 0.05 | 0.02 |
| V | ≤ 0.12 | 0.05 |
| Zr | ≤ 0.05 | — |
| B | ≤ 0.01 | 0 |
| Fe | balance | — |
P690Q-QL1 — frequently asked
What is P690Q-QL1 used for?
P690Q-QL1 is typically used for mobile crane structures, heavy earthmoving equipment, high-strength pressure vessels and structural steel for bridges. In short: 690 MPa yield class; weight-saving structural plate; higher strength than P500Q.
What is the yield strength of P690Q-QL1?
P690Q-QL1 has a typical yield strength of 750 MPa (109 ksi) and a tensile strength of 830 MPa (120 ksi) — stronger than 84% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is P690Q-QL1 easy to machine?
Not especially — machinability is rated fair (35/100, worse than 84% of steel grades). Machine as a 250–290 HB Q&T alloy steel — rigid setups, coated carbide, moderate speeds (~40 % of 1212), and avoid burning the tempered surface layer.
Can P690Q-QL1 be welded?
Yes — weldability is rated good (58/100). Weldable with low-hydrogen processes and matching 690 MPa consumables; preheat typically 100–150 °C (higher for thick/high-CEV heats), interpass ≤200 °C and controlled heat input to protect HAZ toughness.
What surface finishes work on P690Q-QL1?
No natural corrosion resistance — shot-blast to Sa 2.5 and apply zinc-rich primer, metallizing or paint; avoid electroplating that risks hydrogen embrittlement at this strength level.
Can P690Q-QL1 be formed, bent or molded?
Cold-bend only with generous radii (≈3–4×t transverse) and de-burred, crack-free edges; hot forming above the tempering temperature destroys the Q&T properties and requires re-quench and temper.
What is the maximum service temperature of P690Q-QL1?
P690Q-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 P690Q QT-T50 and P690Q-QH?
QT-T50 is the default condition — standard stocked delivery condition for P690Q plate up to 50 mm; full 690 MPa minimum yield. QH: use for pressure equipment operating above ambient where proof strength at temperature must be guaranteed. Yield strength is 750 MPa in QT-T50 versus 750 MPa in QH.
Sources
- EN 10028-6 Flat products made of steels for pressure purposes — Part 6: Weldable fine grain steels, quenched and tempered — CEN (2020)
- EN 10025-6 Hot rolled products of structural steels — Part 6: Flat products of high yield strength structural steels in the quenched and tempered condition (comparison grade S690Q) — CEN (2019)
- EN 1011-2 Welding — Recommendations for welding of metallic materials, Part 2: Arc welding of ferritic steels — CEN (2001)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- Quenched and tempered high-strength plate datasheets (690 MPa class) — SSAB / Dillinger / Thyssenkrupp (2023)
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.