Steel P355QH-QT (Quenched and tempered)
Heat-treated state · default condition
EN P355QH
Standard as-delivered condition for plate, forged hollows and thick-wall tube up to 50 mm wall; full 355 MPa yield class.
Values for the QT condition
Other P355QH tempers and conditions
P355QH is listed in 4 conditions; see the grade overview at P355QH.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
QT | Maximum-thickness qualification with lowest guaranteed strength; used for very thick-walled vessels where hardenability limits through-thickness properties. | 355 | 510 | 24 | 162 HB | 7.5 % IACS |
QT | Same heat treatment but standard-derated strength for heavy walls; choose for thick shells and forged hollow bodies. | 375 | 530 | 25 | 168 HB | 7.5 % IACS |
quenched, tempered and stress relieved (PWHT simulated) | Order this when the vessel will see PWHT/simulated post-weld heat treatment; slight strength loss but lower residual stress and better HIC/SCC behaviour. | 385 | 530 | 26 | 168 HB | 7.5 % IACS |
QTDefaultThis page Quenched and tempered | Standard as-delivered condition for plate, forged hollows and thick-wall tube up to 50 mm wall; full 355 MPa yield class. | 400 | 550 | 25 | 175 HB | 7.5 % IACS |
What is P355QH-QT?
P355QH-QT is P355QH heat treated to QT — standard as-delivered condition for plate, forged hollows and thick-wall tube up to 50 mm wall; full 355 MPa yield class. P355QH-QT has a yield strength of 400 MPa (58 ksi) and a tensile strength of 550 MPa (79.8 ksi) — weaker than 60% of steel grades. Elongation at break is 25% and the elastic modulus is 210 GPa (30.5 Msi). P355QH-QT has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,465°C (2,669 °F).
Advantages
- Tough — resists crack growth — 120 MPa·√m (109.2 ksi·√in), better than 81% of steel grades
- Ductile — tolerates forming and impact — 25%, better than 77% of steel grades
- Readily welded — 72/100, better than 75% of steel grades
P355QH-QT properties
Typical room-temperature values for P355QH-QT; 22 are specific to this condition. Other listed values are P355QH reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
P355QH-QT has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,465°C (2,669 °F).
Mechanical16
P355QH-QT has a yield strength of 400 MPa (58 ksi) and a tensile strength of 550 MPa (79.8 ksi) — weaker than 60% of steel grades. Elongation at break is 25% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
P355QH-QT is rated for continuous service to 400°C (752 °F). It conducts heat at 42 W/m·K (24.3 BTU/hr·ft·°F), worse than 56% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
P355QH-QT conducts electricity at 7.5 % IACS, worse than 67% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of P355QH-QT takes about 26 MJ of energy and emits 2.1 kg of CO₂ — less than 64% of steel grades. Typical recycled content is 25%.
Manufacturability7
P355QH-QT's machinability is good (55/100, better than 62% of steel grades); weldability very good (72/100); formability good (55/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with P355QH-QT
Is P355QH easy to machine?
Machines like a 170–200 HB Q&T low-alloy steel: coated carbide, moderate speeds, rigid setup; avoid heavy grinding that can re-temper or crack the surface.
Can P355QH be welded?
Good weldability with controlled CEV — use low-hydrogen consumables matching 355 MPa class, preheat 100–150 °C for heavy walls, cap heat input and keep interpass temperature low to protect the tempered microstructure.
Can P355QH be formed, bent or molded?
Cold forming possible with generous bend radii (≈3t) and grain-direction control; hot forming above the tempering temperature destroys the Q&T properties and requires re-quench-and-temper.
What surface finishes work on P355QH?
No anodizing; blast and prime/epoxy-coat, metallize or clad for corrosion service, and control weld/HAZ hardness (<250 HV) for wet sour duty.
P355QH 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 | 0.15 |
| Si | ≤ 0.6 | 0.35 |
| Mn | 0.8 – 1.7 | 1.3 |
| P | ≤ 0.03 | 0.01 |
| S | ≤ 0.02 | 0.01 |
| Altotal Al, grain refinement | ≥ 0.02 | 0.04 |
| Cr | ≤ 0.5 | 0.25 |
| Mo | ≤ 0.5 | 0.25 |
| Ni | ≤ 1 | 0.4 |
| Cu | ≤ 0.3 | 0.1 |
| Nbmicroalloying | ≤ 0.05 | 0.02 |
| Ti | ≤ 0.05 | 0.02 |
| V | ≤ 0.08 | 0.03 |
| Bhardenability, thick sections | ≤ 0.01 | 0 |
| N | ≤ 0.02 | 0.01 |
| Zr | ≤ 0.05 | — |
| Fe | balance | — |
P355QH-QT — frequently asked
What is P355QH-QT used for?
P355QH-QT is typically used for thick-wall pressure vessels, boiler drums and heavy pipe sections. In short: heavy-wall Q&T vessel grade; rated to 400 °C service; section-qualified P355Q variant.
What is the yield strength of P355QH-QT?
P355QH-QT has a typical yield strength of 400 MPa (58 ksi) and a tensile strength of 550 MPa (79.8 ksi) — weaker than 60% of steel grades. Strength varies by condition: see the 4 listed tempers.
Is P355QH-QT easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Machines like a 170–200 HB Q&T low-alloy steel: coated carbide, moderate speeds, rigid setup; avoid heavy grinding that can re-temper or crack the surface.
Can P355QH-QT be welded?
Yes — weldability is rated very good (72/100). Good weldability with controlled CEV — use low-hydrogen consumables matching 355 MPa class, preheat 100–150 °C for heavy walls, cap heat input and keep interpass temperature low to protect the tempered microstructure.
What surface finishes work on P355QH-QT?
No anodizing; blast and prime/epoxy-coat, metallize or clad for corrosion service, and control weld/HAZ hardness (<250 HV) for wet sour duty.
Can P355QH-QT be formed, bent or molded?
Cold forming possible with generous bend radii (≈3t) and grain-direction control; hot forming above the tempering temperature destroys the Q&T properties and requires re-quench-and-temper.
What is the maximum service temperature of P355QH-QT?
P355QH-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 10222-4 / EN 10216-3 (related quenched-and-tempered pressure part grades) — CEN (2017)
- 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 (P355Q/QH/QL1) — European plate 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.