Steel P355Q-QT (Quenched and tempered)
Heat-treated state · default condition
EN 1.8866, 10028-6
Standard stocked condition for pressure-vessel plate up to 50 mm; full 355 MPa yield class.
Values for the QT condition
Other P355Q tempers and conditions
P355Q is listed in 7 conditions; see the grade overview at P355Q.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
QT | Thick-section vessel shells and forged-plate substitutes; lowest strength class of the grade. | 355 | 520 | 24 | 160 HB | 8.2 % IACS |
QT | Heavy plate condition; mandatory strength de-rating due to lower quench severity in section. | 380 | 540 | 25 | 168 HB | 8.2 % IACS |
quenched, tempered and post-weld stress relieved (simulated PWHT) | Specify when vessel fabrication requires PWHT; plate is delivered tested in the simulated PWHT condition with slightly softened properties. | 385 | 540 | 27 | 168 HB | 8.2 % IACS |
QTDefaultThis page Quenched and tempered | Standard stocked condition for pressure-vessel plate up to 50 mm; full 355 MPa yield class. | 400 | 560 | 26 | 175 HB | — |
Q&T, elevated-temperature properties guaranteed | Choose when the code case needs guaranteed proof stress at elevated temperature plus −20 °C impact values. | 400 | 560 | 26 | 175 HB | 8.2 % IACS |
Q&T, low-temperature grade, impact at −40 °C | Pick for cold-climate or refrigerated service down to about −40 °C. | 400 | 560 | 26 | 175 HB | 8.2 % IACS |
Q&T, low-temperature grade, impact at −60 °C | Cleanest chemistry of the family (low P/S) for LPG/ammonia and Arctic vessels down to −60 °C. | 405 | 560 | 27 | 175 HB | 8.2 % IACS |
What is P355Q-QT?
P355Q-QT is P355Q heat treated to QT — standard stocked condition for pressure-vessel plate up to 50 mm; full 355 MPa yield class. P355Q-QT has a yield strength of 400 MPa (58 ksi) and a tensile strength of 560 MPa (81.2 ksi) — weaker than 60% of steel grades. Elongation at break is 26% and the elastic modulus is 210 GPa (30.5 Msi). P355Q-QT 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).
Advantages
- Tough — resists crack growth — 130 MPa·√m (118.3 ksi·√in), better than 89% of steel grades
- Ductile — tolerates forming and impact — 26%, better than 82% of steel grades
- Readily welded — 82/100, better than 81% of steel grades
Limitations
- Hard to polish — 45/100, worse than 84% of steel grades
P355Q-QT properties
Typical room-temperature values for P355Q-QT; 10 are specific to this condition. Other listed values are P355Q reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
P355Q-QT 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
P355Q-QT has a yield strength of 400 MPa (58 ksi) and a tensile strength of 560 MPa (81.2 ksi) — weaker than 60% of steel grades. Elongation at break is 26% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
P355Q-QT is rated for continuous service to 400°C (752 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
P355Q-QT conducts electricity at 8.2 % IACS, better than 61% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of P355Q-QT takes about 26 MJ of energy and emits 2 kg of CO₂ — less than 64% of steel grades. Typical recycled content is 25%.
Manufacturability8
P355Q-QT's machinability is good (58/100, better than 75% of steel grades); weldability very good (82/100); formability good (60/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with P355Q-QT
Is P355Q easy to machine?
Machines like a 175 HB Q&T low-alloy steel — carbide inserts, 120–180 m/min, rigid setups; avoid overheating that would locally temper the plate.
Can P355Q be welded?
Good weldability at CEV ≤ 0.45: use low-hydrogen consumables (matching ~ 460–550 MPa yield), preheat 100–150 °C for thick sections, control interpass ≤ 250 °C and limit heat input to preserve HAZ toughness.
Can P355Q be formed, bent or molded?
Cold form with bend radius ≥ 2–3 t across the rolling direction; hot forming above about 580 °C degrades the Q&T condition and requires re-quench-and-temper.
What surface finishes work on P355Q?
No anodizing; shot-blast then epoxy/zinc-rich primer, metallize or weld-overlay clad for corrosive duty — bare surfaces rust rapidly.
P355Q 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 | ≤ 0.16 | 0.14 |
| Si | ≤ 0.4 | 0.3 |
| Mn | 0.8 – 1.7 | 1.35 |
| P≤0.020 for QL1, ≤0.020 for QL2 | ≤ 0.03 | 0.01 |
| S≤0.010 / ≤0.005 for QL grades | ≤ 0.02 | 0 |
| Altotal Al, grain refining | ≥ 0.02 | 0.04 |
| Cr | ≤ 0.5 | 0.25 |
| Mo | ≤ 0.5 | 0.2 |
| Ni | ≤ 0.5 | 0.25 |
| Cu | ≤ 0.3 | 0.1 |
| Nb | ≤ 0.05 | 0.02 |
| Ti | ≤ 0.05 | 0.02 |
| V | ≤ 0.08 | 0.03 |
| Zr | ≤ 0.05 | — |
| N | ≤ 0.02 | 0.01 |
| B | ≤ 5×10⁻⁴ | — |
| Fe | balance | — |
P355Q-QT — frequently asked
What is P355Q-QT used for?
P355Q-QT is typically used for pressure vessels, boilers and storage tanks. In short: base Q&T vessel grade; 355 MPa class, easily welded; wide condition and variant range.
What is the yield strength of P355Q-QT?
P355Q-QT has a typical yield strength of 400 MPa (58 ksi) and a tensile strength of 560 MPa (81.2 ksi) — weaker than 60% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is P355Q-QT easy to machine?
Reasonably — machinability is rated good (58/100, better than 75% of steel grades). Machines like a 175 HB Q&T low-alloy steel — carbide inserts, 120–180 m/min, rigid setups; avoid overheating that would locally temper the plate.
Can P355Q-QT be welded?
Yes — weldability is rated very good (82/100). Good weldability at CEV ≤ 0.45: use low-hydrogen consumables (matching ~ 460–550 MPa yield), preheat 100–150 °C for thick sections, control interpass ≤ 250 °C and limit heat input to preserve HAZ toughness.
What surface finishes work on P355Q-QT?
No anodizing; shot-blast then epoxy/zinc-rich primer, metallize or weld-overlay clad for corrosive duty — bare surfaces rust rapidly.
Can P355Q-QT be formed, bent or molded?
Cold form with bend radius ≥ 2–3 t across the rolling direction; hot forming above about 580 °C degrades the Q&T condition and requires re-quench-and-temper.
What is the maximum service temperature of P355Q-QT?
P355Q-QT 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 P355Q-QT and P355QL2?
QT is the default condition — standard stocked condition for pressure-vessel plate up to 50 mm; full 355 MPa yield class. P355QL2: cleanest chemistry of the family (low P/S) for LPG/ammonia and Arctic vessels down to −60 °C. Yield strength is 400 MPa in QT versus 405 MPa in P355QL2.
Sources
- EN 10028-6: Flat products made of steels for pressure purposes — Part 6: Weldable fine grain steels, quenched and tempered — CEN (2017)
- EN 10027-2 Steel numbers (1.8866 P355Q) — CEN (2015)
- EN 13445-3 Unfired pressure vessels — Design (physical property data) — CEN (2021)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.19 — Fatigue and Fracture — ASM International (1996)
- Quenched and tempered pressure vessel plate datasheets (Dillinger, voestalpine, SSAB) — Producers (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.