Steel P690Q-QH (P690QH)
Grade
EN 1.8879
Use for pressure equipment operating above ambient where proof strength at temperature must be guaranteed.
Values for the QH 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 | — |
QHThis page P690QH | Use for pressure equipment operating above ambient where proof strength at temperature must be guaranteed. | 750 | 830 | 17 | 25 HRC | 7.2 % IACS |
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-QH?
P690Q-QH is P690Q in the QH grade — use for pressure equipment operating above ambient where proof strength at temperature must be guaranteed. P690Q-QH 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-QH 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; QH is available on request or by drawing note.
Advantages
- Tough — resists crack growth — 130 MPa·√m (118.3 ksi·√in), better than 89% 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-QH properties
Typical room-temperature values for P690Q-QH; 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-QH 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-QH 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-QH 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-QH 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-QH 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-QH'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-QH
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-QH — frequently asked
What is P690Q-QH used for?
P690Q-QH 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-QH?
P690Q-QH 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-QH 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-QH 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-QH?
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-QH 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-QH?
P690Q-QH 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.