Steel P355QL1-QT (Quenched and tempered)
Heat-treated state · default condition
EN 1.8868
Standard supply condition for plate up to 50 mm — full 355 MPa yield class with -40 °C impact guarantee.
Values for the QT condition
Other P355QL1 tempers and conditions
P355QL1 is listed in 4 conditions; see the grade overview at P355QL1.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
QT | Thickest standard class for very heavy vessel shells and forged-plate nozzles; lowest guaranteed strength. | 360 | 520 | 24 | 165 HB | 7.8 % IACS |
QT | Heavy plate class — strength de-rated for section size, same -40 °C toughness requirement. | 380 | 540 | 25 | 170 HB | 7.8 % IACS |
quenched, tempered and stress-relieved (simulated PWHT) | Choose when the vessel will see post-weld heat treatment; properties are certified after a simulated PWHT cycle (typically 530–580 °C). | 385 | 545 | 27 | 168 HB | 7.8 % IACS |
QTDefaultThis page Quenched and tempered | Standard supply condition for plate up to 50 mm — full 355 MPa yield class with -40 °C impact guarantee. | 400 | 560 | 26 | 175 HB | 7.8 % IACS |
What is P355QL1-QT?
P355QL1-QT is P355QL1 heat treated to QT — standard supply condition for plate up to 50 mm — full 355 MPa yield class with -40 °C impact guarantee. P355QL1-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). P355QL1-QT has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,460°C (2,660 °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 — 80/100, better than 79% of steel grades
Limitations
- Hard to polish — 45/100, worse than 84% of steel grades
P355QL1-QT properties
Typical room-temperature values for P355QL1-QT; 23 are specific to this condition. Other listed values are P355QL1 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
P355QL1-QT has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,460°C (2,660 °F).
Mechanical16
P355QL1-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
P355QL1-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
P355QL1-QT conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of P355QL1-QT takes about 26 MJ of energy and emits 2 kg of CO₂ — less than 64% of steel grades. Typical recycled content is 25%.
Manufacturability7
P355QL1-QT's machinability is good (55/100, better than 62% of steel grades); weldability very good (80/100); 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 P355QL1-QT
Is P355QL1 easy to machine?
Machines like a 400 MPa-yield low-alloy steel — rigid setups, coated carbide at ~120–180 m/min, avoid heavy work hardening on drilled nozzle bores.
Can P355QL1 be welded?
Excellent weldability at low CEV; use low-hydrogen consumables matching 355 MPa class, control preheat (typically 100–150 °C for t > 40 mm) and keep heat input moderate to protect HAZ toughness at -40 °C.
Can P355QL1 be formed, bent or molded?
Cold-form shells and heads with generous bend radii (≥3t); hot forming above the tempering temperature requires re-quenching and tempering to restore certified properties.
What surface finishes work on P355QL1?
No anodizing — blast to Sa 2½ and apply epoxy/zinc-rich paint, metallizing or internal cladding for corrosive service.
P355QL1 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, EN 10028-6 | ≤ 0.16 | 0.13 |
| Si | ≤ 0.5 | 0.3 |
| Mn | 1 – 1.7 | 1.35 |
| P | ≤ 0.02 | 0.01 |
| S | ≤ 0.01 | 0 |
| Altotal Al, grain refinement | ≥ 0.02 | 0.04 |
| Cr | ≤ 0.3 | 0.15 |
| Cu | ≤ 0.3 | 0.1 |
| Mo | ≤ 0.25 | 0.1 |
| Ni | ≤ 0.5 | 0.25 |
| Nb | ≤ 0.05 | 0.02 |
| Ti | ≤ 0.03 | 0.01 |
| V | ≤ 0.05 | 0.02 |
| Zr | ≤ 0.05 | — |
| N | ≤ 0.02 | 0.01 |
| B | ≤ 5×10⁻⁴ | — |
| Fe | balance | — |
P355QL1-QT — frequently asked
What is P355QL1-QT used for?
P355QL1-QT is typically used for pressure vessels, boilers, low-temperature storage tanks and piping systems. In short: weldable -40 °C vessel plate; fine-grain quenched and tempered; low carbon equivalent.
What is the yield strength of P355QL1-QT?
P355QL1-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 4 listed tempers.
Is P355QL1-QT easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Machines like a 400 MPa-yield low-alloy steel — rigid setups, coated carbide at ~120–180 m/min, avoid heavy work hardening on drilled nozzle bores.
Can P355QL1-QT be welded?
Yes — weldability is rated very good (80/100). Excellent weldability at low CEV; use low-hydrogen consumables matching 355 MPa class, control preheat (typically 100–150 °C for t > 40 mm) and keep heat input moderate to protect HAZ toughness at -40 °C.
What surface finishes work on P355QL1-QT?
No anodizing — blast to Sa 2½ and apply epoxy/zinc-rich paint, metallizing or internal cladding for corrosive service.
Can P355QL1-QT be formed, bent or molded?
Cold-form shells and heads with generous bend radii (≥3t); hot forming above the tempering temperature requires re-quenching and tempering to restore certified properties.
What is the maximum service temperature of P355QL1-QT?
P355QL1-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.
Sources
- EN 10028-6: Flat products made of steels for pressure purposes — Weldable fine grain steels, quenched and tempered — CEN (2017)
- EN 10027-2 Steel numbering (1.8868) — CEN (2015)
- EN 13445-3 Unfired pressure vessels — Design (material physical data) — CEN (2021)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- Quenched and tempered pressure vessel plate datasheets (Dillinger / Industeel / voestalpine) — various mills (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.