Steel P255QL +QT (Quenched and tempered)
Heat-treated state · default condition
EN P255QL
Standard supply condition for P255QL: use whenever guaranteed -50 °C Charpy toughness and Rp0.2 ≥ 255 MPa are required.
Values for the +QT condition
Other P255QL tempers and conditions
P255QL is listed in 3 conditions; see the grade overview at P255QL.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Normalized | Pick when the mill supplies the low-temperature C-Mn analysis in normalized form (plate, heavy wall) and slightly lower proof strength is acceptable. | 270 | 400 | 30 | 125 HB | 10 % IACS |
+QTDefaultThis page Quenched and tempered | Standard supply condition for P255QL: use whenever guaranteed -50 °C Charpy toughness and Rp0.2 ≥ 255 MPa are required. | 290 | 420 | 28 | 135 HB | — |
Cold drawn, then quenched and tempered | For precision low-temperature tubing where tight OD/ID tolerance and better surface finish are needed; final heat treatment restores full impact toughness. | 305 | 440 | 26 | 145 HB | 10 % IACS |
What is P255QL +QT?
P255QL +QT is P255QL heat treated to +QT — standard supply condition for P255QL: use whenever guaranteed -50 °C Charpy toughness and Rp0.2 ≥ 255 MPa are required. P255QL +QT has a yield strength of 290 MPa (42.1 ksi) and a tensile strength of 420 MPa (60.9 ksi) — weaker than 88% of steel grades. Elongation at break is 28% and the elastic modulus is 210 GPa (30.5 Msi). P255QL +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
- Easy to machine — 65/100, better than 93% of steel grades
- Readily welded — 90/100, better than 90% of steel grades
- Ductile — tolerates forming and impact — 28%, better than 89% of steel grades
- Forms and bends easily — 70/100, better than 86% of steel grades
- High electrical conductivity — 10 % IACS, better than 83% of steel grades
Limitations
- Low strength — 290 MPa (42.1 ksi), worse than 88% of steel grades
- Hard to polish — 45/100, worse than 84% of steel grades
- Limited service temperature — 300°C (572 °F), worse than 78% of steel grades
P255QL +QT properties
Typical room-temperature values for P255QL +QT; 12 are specific to this condition. Other listed values are P255QL reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
P255QL +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
P255QL +QT has a yield strength of 290 MPa (42.1 ksi) and a tensile strength of 420 MPa (60.9 ksi) — weaker than 88% of steel grades. Elongation at break is 28% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
P255QL +QT is rated for continuous service to 300°C (572 °F). It conducts heat at 48 W/m·K (27.7 BTU/hr·ft·°F), better than 79% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
P255QL +QT conducts electricity at 10 % IACS, better than 83% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of P255QL +QT takes about 25 MJ of energy and emits 2 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 25%.
Manufacturability7
P255QL +QT's machinability is good (65/100, better than 93% of steel grades); weldability excellent (90/100); formability very good (70/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with P255QL +QT
Is P255QL easy to machine?
Machines like a normalized C-Mn steel (~70 % of AISI 1212); use sharp positive-rake carbide, moderate speeds and good chip control to avoid built-up edge on the gummy low-carbon matrix.
Can P255QL be welded?
Excellent weldability with CEV typically ≤ 0.40; use low-hydrogen consumables matching low-temperature toughness, preheat 100–150 °C for heavy walls, and keep heat input moderate to protect the -50 °C Charpy requirement (PWHT per EN 13445/13480 where required).
Can P255QL be formed, bent or molded?
Good cold bendability for tube bending and plate rolling; hot forming above ~950 °C must be followed by re-quenching and tempering to restore the specified properties.
What surface finishes work on P255QL?
No self-protecting oxide — shot blast to Sa 2½ then zinc-rich primer, epoxy paint, hot-dip galvanizing or insulation cladding; passivation/anodizing not applicable.
P255QL 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 | ≤ 0.18 | 0.14 |
| Si | ≤ 0.35 | 0.25 |
| Mn | 0.5 – 1.4 | 1.1 |
| P | ≤ 0.03 | 0.02 |
| Slow S for toughness | ≤ 0.02 | 0.01 |
| Altotal Al, grain refinement | ≥ 0.02 | 0.03 |
| N | ≤ 0.01 | 0.01 |
| Crresidual | ≤ 0.3 | 0.1 |
| Curesidual | ≤ 0.3 | 0.1 |
| Niresidual | ≤ 0.3 | 0.1 |
| Moresidual | ≤ 0.08 | 0.02 |
| Nbmicro-alloying | ≤ 0.05 | 0.02 |
| Timicro-alloying | ≤ 0.04 | 0.01 |
| Vmicro-alloying | ≤ 0.05 | 0.01 |
| Fe | balance | — |
P255QL +QT — frequently asked
What is P255QL +QT used for?
P255QL +QT is typically used for pressure vessel heads, reactor shells, high-pressure storage tanks and structural vessel components. In short: quenched-and-tempered vessel plate; strength plus -50 °C toughness; weldable at CEV ≤ 0.40.
What is the yield strength of P255QL +QT?
P255QL +QT has a typical yield strength of 290 MPa (42.1 ksi) and a tensile strength of 420 MPa (60.9 ksi) — weaker than 88% of steel grades. Strength varies by condition: see the 3 listed tempers.
Is P255QL +QT easy to machine?
Reasonably — machinability is rated good (65/100, better than 93% of steel grades). Machines like a normalized C-Mn steel (~70 % of AISI 1212); use sharp positive-rake carbide, moderate speeds and good chip control to avoid built-up edge on the gummy low-carbon matrix.
Can P255QL +QT be welded?
Yes — weldability is rated excellent (90/100). Excellent weldability with CEV typically ≤ 0.40; use low-hydrogen consumables matching low-temperature toughness, preheat 100–150 °C for heavy walls, and keep heat input moderate to protect the -50 °C Charpy requirement (PWHT per EN 13445/13480 where required).
What surface finishes work on P255QL +QT?
No self-protecting oxide — shot blast to Sa 2½ then zinc-rich primer, epoxy paint, hot-dip galvanizing or insulation cladding; passivation/anodizing not applicable.
Can P255QL +QT be formed, bent or molded?
Good cold bendability for tube bending and plate rolling; hot forming above ~950 °C must be followed by re-quenching and tempering to restore the specified properties.
What is the maximum service temperature of P255QL +QT?
P255QL +QT is rated for continuous use to about 300°C (572 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- EN 10216-4 — Seamless steel tubes for pressure purposes, Part 4: Non-alloy and alloy steel tubes with specified low temperature properties — CEN (2013)
- EN 10027-2 — Designation systems for steels: numerical system (1.0452) — CEN (2015)
- EN 13480-3 / EN 13445-3 — Metallic industrial piping and unfired pressure vessels, design material data — CEN (2021)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASTM A370 hardness/strength conversion tables — ASTM (2022)
- worldsteel LCI data for steel products — World Steel Association (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.