Steel S420N-NL
Heat-treated state
EN S420N · GB Q420C
NL = normalized, low-temperature impact quality
Choose when guaranteed 27 J Charpy at -50 °C and tighter P/S limits are required (offshore, cryogenic-adjacent, Arctic structures).
Values for the NL condition
Other S420N tempers and conditions
S420N is listed in 7 conditions; see the grade overview at S420N.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
N | Very heavy plate; strength band drops to 500–650 MPa Rm and 340/330 MPa minimum yield. | 370 | 540 | 21 | 158 HB | 8.6 % IACS |
N | Thick plate for heavy welded structures; yield 370–360 MPa minimum, preheat recommended for welding. | 395 | 550 | 21 | 162 HB | 8.6 % IACS |
N | Heavy plate: 390 MPa minimum yield; check through-thickness toughness for welded joints. | 415 | 555 | 22 | 165 HB | 8.6 % IACS |
N + stress-relief annealed | For welded fabrications requiring PWHT at 530–580 °C; slight loss of yield strength, improved dimensional stability. | 420 | 550 | 24 | 163 HB | 8.6 % IACS |
N | Medium plate thickness: yield derated to 400 MPa minimum per EN 10025-3. | 425 | 560 | 22 | 168 HB | 8.6 % IACS |
NDefault Normalized | Standard delivery condition for plate, section and bar up to 16 mm; full 420 MPa yield with 40 J at -20 °C. | 440 | 570 | 23 | 170 HB | 8.6 % IACS |
NLThis page Normalized, low-temperature impact quality | Choose when guaranteed 27 J Charpy at -50 °C and tighter P/S limits are required (offshore, cryogenic-adjacent, Arctic structures). | 445 | 575 | 24 | 170 HB | 8.6 % IACS |
What is S420N-NL?
S420N-NL is S420N heat treated to NL — choose when guaranteed 27 J Charpy at -50 °C and tighter P/S limits are required (offshore, cryogenic-adjacent, Arctic structures). S420N-NL has a yield strength of 445 MPa (64.5 ksi) and a tensile strength of 575 MPa (83.4 ksi) — stronger than 51% of steel grades. Elongation at break is 24% and the elastic modulus is 210 GPa (30.5 Msi). S420N-NL 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). N is the default condition FabDigit quotes; NL is available on request or by drawing note.
Advantages
- Tough — resists crack growth — 150 MPa·√m (136.5 ksi·√in), better than 96% of steel grades
- Readily welded — 80/100, better than 79% of steel grades
- Forms and bends easily — 62/100, better than 78% of steel grades
Limitations
- Hard to polish — 45/100, worse than 84% of steel grades
S420N-NL properties
Typical room-temperature values for S420N-NL; 23 are specific to this condition. Other listed values are S420N reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
S420N-NL 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
S420N-NL has a yield strength of 445 MPa (64.5 ksi) and a tensile strength of 575 MPa (83.4 ksi) — stronger than 51% of steel grades. Elongation at break is 24% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
S420N-NL is rated for continuous service to 350°C (662 °F). It conducts heat at 45 W/m·K (26 BTU/hr·ft·°F), better than 66% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
S420N-NL conducts electricity at 8.6 % IACS, better than 66% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (11/100), worse than 73% of steel grades.
Sustainability4
Producing a kilogram of S420N-NL takes about 25 MJ of energy and emits 2.1 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 25%.
Manufacturability8
S420N-NL's machinability is good (55/100, better than 62% of steel grades); weldability very good (80/100); formability good (62/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with S420N-NL
Is S420N easy to machine?
Machines like a normalized C-Mn steel at ~55–60 % of 1212; use rigid setups, coated carbide and moderate feeds — sticky chips and mild work-hardening at low feed rates.
Can S420N be welded?
Good weldability with CEV ≤ 0.50; use low-hydrogen consumables, control heat input to 1.0–2.5 kJ/mm and preheat 100–150 °C above ~30 mm to protect HAZ toughness.
Can S420N be formed, bent or molded?
Cold formable with generous radii (≈2t transverse, 1.5t longitudinal for thin plate); hot forming above 900 °C requires re-normalizing to restore the fine-grain properties.
What surface finishes work on S420N?
No inherent corrosion resistance — blast to Sa 2½ then paint, metallize or hot-dip galvanize; keep Si low if bright galvanized appearance is required.
S420N 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 |
|---|---|---|
| Cmax for t ≤ 63 mm | ≤ 0.2 | 0.16 |
| Si | ≤ 0.6 | 0.35 |
| Mn | 1 – 1.7 | 1.45 |
| P0.025 max for S420NL | ≤ 0.03 | 0.02 |
| S0.020 max for S420NL | ≤ 0.03 | 0.01 |
| N0.020 for NL; limit may be exceeded if sufficient N-binding elements present | ≤ 0.03 | 0.01 |
| Altotal Al; alternative N-binding elements permitted | ≥ 0.02 | 0.04 |
| NbNb+Ti+V total ≤ 0.22 | ≤ 0.05 | 0.03 |
| V | ≤ 0.2 | 0.08 |
| Ti | ≤ 0.05 | 0.02 |
| Cr | ≤ 0.3 | 0.08 |
| Ni | ≤ 0.8 | 0.15 |
| Mo | ≤ 0.1 | 0.03 |
| Cu | ≤ 0.7 | 0.15 |
| Zr | ≤ 0.15 | — |
| FeCEV ≤ 0.50 for t ≤ 63 mm per EN 10025-3 | balance | — |
S420N-NL — frequently asked
What is S420N-NL used for?
S420N-NL is typically used for structural steelwork, pressure equipment, cranes and mobile equipment frames. In short: between S355 and S460; normalized, no QT needed; good weldability at 420 MPa.
What is the yield strength of S420N-NL?
S420N-NL has a typical yield strength of 445 MPa (64.5 ksi) and a tensile strength of 575 MPa (83.4 ksi) — stronger than 51% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is S420N-NL easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Machines like a normalized C-Mn steel at ~55–60 % of 1212; use rigid setups, coated carbide and moderate feeds — sticky chips and mild work-hardening at low feed rates.
Can S420N-NL be welded?
Yes — weldability is rated very good (80/100). Good weldability with CEV ≤ 0.50; use low-hydrogen consumables, control heat input to 1.0–2.5 kJ/mm and preheat 100–150 °C above ~30 mm to protect HAZ toughness.
What surface finishes work on S420N-NL?
No inherent corrosion resistance — blast to Sa 2½ then paint, metallize or hot-dip galvanize; keep Si low if bright galvanized appearance is required.
Can S420N-NL be formed, bent or molded?
Cold formable with generous radii (≈2t transverse, 1.5t longitudinal for thin plate); hot forming above 900 °C requires re-normalizing to restore the fine-grain properties.
What is the maximum service temperature of S420N-NL?
S420N-NL is rated for continuous use to about 350°C (662 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between S420N-N and S420N-NL?
N is the default condition — standard delivery condition for plate, section and bar up to 16 mm; full 420 MPa yield with 40 J at -20 °C. NL: choose when guaranteed 27 J Charpy at -50 °C and tighter P/S limits are required (offshore, cryogenic-adjacent, Arctic structures). Yield strength is 440 MPa in N versus 445 MPa in NL.
Sources
- EN 10025-3 Hot rolled products of structural steels — Part 3: Normalized/normalized rolled weldable fine grain structural steels — CEN (2019)
- GB/T 1591 High strength low alloy structural steels (Q420C/D) — SAC (2018)
- EN 1011-2 Welding — Recommendations for welding of metallic materials: arc welding of 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 structural steel plate datasheets (S420N/S420NL) — 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.