Steel P420NH-N (Normalized)
Heat-treated state · default condition
EN P420NH
Standard mill delivery condition for pressure-vessel plate; use unless the fabricator specifies PWHT or through-thickness testing.
Values for the N condition
Other P420NH tempers and conditions
P420NH is listed in 4 conditions; see the grade overview at P420NH.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
N, heavy gauge | Same normalized condition but ordered in heavy plate, where EN 10028-3 lowers the guaranteed yield and tensile bands. | 380 | 580 | 25 | 175 HB | 8 % IACS |
Normalized then stress-relieved / PWHT | Condition of the finished vessel after code-required post-weld heat treatment; expect a small loss of proof strength. | 440 | 595 | 26 | 175 HB | 8 % IACS |
Normalized and tempered | Optional mill tempering after normalizing for tighter hardness scatter and slightly better toughness uniformity in heavy sections. | 455 | 600 | 25 | 180 HB | 8 % IACS |
NDefaultThis page Normalized | Standard mill delivery condition for pressure-vessel plate; use unless the fabricator specifies PWHT or through-thickness testing. | 460 | 620 | 24 | 185 HB | 8 % IACS |
What is P420NH-N?
P420NH-N is P420NH heat treated to N — standard mill delivery condition for pressure-vessel plate; use unless the fabricator specifies PWHT or through-thickness testing. P420NH-N has a yield strength of 460 MPa (66.7 ksi) and a tensile strength of 620 MPa (89.9 ksi) — stronger than 55% of steel grades. Elongation at break is 24% and the elastic modulus is 210 GPa (30.5 Msi). P420NH-N 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
- Readily welded — 80/100, better than 79% of steel grades
P420NH-N properties
Typical room-temperature values for P420NH-N; 22 are specific to this condition. Other listed values are P420NH reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
P420NH-N 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
P420NH-N has a yield strength of 460 MPa (66.7 ksi) and a tensile strength of 620 MPa (89.9 ksi) — stronger than 55% of steel grades. Elongation at break is 24% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
P420NH-N 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
P420NH-N conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (13/100), better than 66% of steel grades.
Sustainability4
Producing a kilogram of P420NH-N takes about 25 MJ of energy and emits 2.1 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability7
P420NH-N's machinability is good (55/100, better than 62% of steel grades); weldability very good (80/100); formability good (58/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with P420NH-N
Is P420NH easy to machine?
Machines like a normalized 500–600 MPa low-alloy steel — carbide tooling, moderate speeds, good chip control; slightly gummier than free-machining grades due to low sulphur.
Can P420NH be welded?
Readily weldable by SAW/SMAW/GMAW with matching low-hydrogen consumables; CEV ≈ 0.43 so preheat 100–150 °C for t > 30 mm, control heat input to protect HAZ toughness, PWHT per vessel code.
Can P420NH be formed, bent or molded?
Cold-forms and rolls into shells at generous bend radii (≥ 2.5–3 t); hot forming 850–950 °C must be followed by re-normalizing to restore the fine-grain properties.
What surface finishes work on P420NH?
No inherent corrosion resistance — shot-blast to Sa 2½ then zinc-rich primer, epoxy paint, hot-dip galvanizing or weld-overlay/clad for wet and chloride service.
P420NH 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 | ≤ 0.2 | 0.16 |
| Si | ≤ 0.5 | 0.35 |
| Mn | 1 – 1.7 | 1.45 |
| PNH grade limit | ≤ 0.03 | 0.02 |
| S | ≤ 0.02 | 0.01 |
| Altotal Al, grain refining | ≥ 0.02 | 0.04 |
| N | ≤ 0.02 | 0.01 |
| Cr | ≤ 0.3 | 0.1 |
| Cu | ≤ 0.7 | 0.2 |
| Mo | ≤ 0.1 | 0.04 |
| Nilow nickel alloying for toughness | ≤ 0.8 | 0.45 |
| Nb | 0.02 – 0.05 | 0.03 |
| Ti | ≤ 0.03 | 0.01 |
| VNb+Ti+V ≤ 0.22 combined | 0.1 – 0.2 | 0.14 |
| Fe | balance | — |
P420NH-N — frequently asked
What is P420NH-N used for?
P420NH-N is typically used for boiler and pressure vessel plate, petrochemical reactors and high-temperature piping. In short: elevated-temperature vessel plate; low CEV, easy welding; below P460NH in strength.
What is the yield strength of P420NH-N?
P420NH-N has a typical yield strength of 460 MPa (66.7 ksi) and a tensile strength of 620 MPa (89.9 ksi) — stronger than 55% of steel grades. Strength varies by condition: see the 4 listed tempers.
Is P420NH-N easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Machines like a normalized 500–600 MPa low-alloy steel — carbide tooling, moderate speeds, good chip control; slightly gummier than free-machining grades due to low sulphur.
Can P420NH-N be welded?
Yes — weldability is rated very good (80/100). Readily weldable by SAW/SMAW/GMAW with matching low-hydrogen consumables; CEV ≈ 0.43 so preheat 100–150 °C for t > 30 mm, control heat input to protect HAZ toughness, PWHT per vessel code.
What surface finishes work on P420NH-N?
No inherent corrosion resistance — shot-blast to Sa 2½ then zinc-rich primer, epoxy paint, hot-dip galvanizing or weld-overlay/clad for wet and chloride service.
Can P420NH-N be formed, bent or molded?
Cold-forms and rolls into shells at generous bend radii (≥ 2.5–3 t); hot forming 850–950 °C must be followed by re-normalizing to restore the fine-grain properties.
What is the maximum service temperature of P420NH-N?
P420NH-N 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 P420NH-N and P420NH N-thick?
N is the default condition — standard mill delivery condition for pressure-vessel plate; use unless the fabricator specifies PWHT or through-thickness testing. N-thick: same normalized condition but ordered in heavy plate, where EN 10028-3 lowers the guaranteed yield and tensile bands. Yield strength is 460 MPa in N versus 380 MPa in N-thick.
Sources
- EN 10028-3 — Flat products of steels for pressure purposes: Weldable fine grain steels, normalized — CEN (2017)
- EN 10164 — Steel products with improved deformation properties perpendicular to the surface — CEN (2018)
- EN 13445-3 — Unfired pressure vessels: Design — CEN (2021)
- EN 1011-2 — Welding recommendations for ferritic steels — CEN (2001)
- 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)
- Fine-grain pressure vessel plate EN 10028-3 data sheets — European plate mills (Dillinger / Voestalpine / Industeel) (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.