Steel 20MnNb6 +NT (Normalized and tempered)
Heat-treated state
EN 20MnNb6
Chosen for heavy forgings where a tempering step stabilizes properties and lowers residual stress after normalizing.
Values for the +NT condition
Other 20MnNb6 tempers and conditions
20MnNb6 is listed in 6 conditions; see the grade overview at 20MnNb6.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Use when maximum machinability or deep cold forming is needed before a final normalizing treatment. | 300 | 470 | 30 | 135 HB | 10 % IACS |
Normalized then stress relieved / simulated PWHT | Ordered when the vessel will see post-weld heat treatment; properties are certified after simulated PWHT soak. | 360 | 515 | 26 | 148 HB | 10 % IACS |
Hot rolled | Lowest-cost bar stock for non-critical or subsequently heat-treated parts; toughness scatter is higher than normalized. | 365 | 550 | 23 | 160 HB | 10 % IACS |
+NTThis page Normalized and tempered | Chosen for heavy forgings where a tempering step stabilizes properties and lowers residual stress after normalizing. | 370 | 520 | 26 | 150 HB | 10 % IACS |
+NDefault Normalized | Standard delivery condition for pressure-vessel plate, forgings and bars; best balance of 355 MPa yield, toughness and weldability. | 385 | 540 | 25 | 155 HB | — |
Quenched and tempered | Pick for thick-section forgings or bolting-type parts needing higher yield and uniform through-thickness toughness. | 460 | 590 | 22 | 180 HB | — |
What is 20MnNb6 +NT?
20MnNb6 +NT is 20MnNb6 heat treated to +NT — chosen for heavy forgings where a tempering step stabilizes properties and lowers residual stress after normalizing. 20MnNb6 +NT has a yield strength of 370 MPa (53.7 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 70% of steel grades. Elongation at break is 26% and the elastic modulus is 210 GPa (30.5 Msi). 20MnNb6 +NT has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,490°C (2,714 °F). +N is the default condition FabDigit quotes; +NT is available on request or by drawing note.
Advantages
- Tough — resists crack growth — 140 MPa·√m (127.4 ksi·√in), better than 94% of steel grades
- Forms and bends easily — 72/100, better than 88% of steel grades
- Readily welded — 88/100, better than 87% of steel grades
- High electrical conductivity — 10 % IACS, better than 83% of steel grades
- Ductile — tolerates forming and impact — 26%, better than 82% of steel grades
Limitations
- Hard to polish — 45/100, worse than 84% of steel grades
20MnNb6 +NT properties
Typical room-temperature values for 20MnNb6 +NT; 22 are specific to this condition. Other listed values are 20MnNb6 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
20MnNb6 +NT has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,490°C (2,714 °F).
Mechanical16
20MnNb6 +NT has a yield strength of 370 MPa (53.7 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 70% of steel grades. Elongation at break is 26% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
20MnNb6 +NT is rated for continuous service to 400°C (752 °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
20MnNb6 +NT conducts electricity at 10 % IACS, better than 83% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (11/100), worse than 73% of steel grades.
Sustainability4
Producing a kilogram of 20MnNb6 +NT 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
20MnNb6 +NT's machinability is good (61/100, better than 87% of steel grades); weldability excellent (88/100); formability very good (72/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 20MnNb6 +NT
Is 20MnNb6 easy to machine?
Machines like a 1020/1524-class C-Mn steel at ~65 % of AISI 1212; use positive-rake carbide, moderate speeds and good chip control since the low-sulphur pressure-vessel chemistry gives stringy chips.
Can 20MnNb6 be welded?
Excellent weldability with low CEV — SAW/SMAW/GMAW with low-hydrogen consumables; preheat 100–150 °C for thick sections, PWHT 550–620 °C where code requires, keep heat input moderate to protect the Nb-refined HAZ toughness.
Can 20MnNb6 be formed, bent or molded?
Cold rolls and presses well in the normalized condition (min bend radius ≈ 1.5–2 t); hot form at 900–1150 °C followed by re-normalizing at 880–920 °C to restore fine grain.
What surface finishes work on 20MnNb6?
No anodizing — protect by shot-blast plus epoxy paint, metallizing, hot-dip galvanizing or weld-overlay/cladding for wet and chloride service.
20MnNb6 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 | ≤ 0.22 | 0.19 |
| Si | 0.1 – 0.5 | 0.3 |
| Mn | 1 – 1.6 | 1.35 |
| P | ≤ 0.03 | 0.02 |
| Slower S for through-thickness quality | ≤ 0.02 | 0.01 |
| Nbgrain-refining microalloy | 0.02 – 0.05 | 0.03 |
| Altotal Al, fully killed | ≥ 0.02 | 0.04 |
| Crresidual | ≤ 0.3 | 0.1 |
| Niresidual | ≤ 0.3 | 0.1 |
| Curesidual | ≤ 0.3 | 0.1 |
| Moresidual | ≤ 0.08 | 0.02 |
| Vresidual | ≤ 0.02 | 0.01 |
| Ti | ≤ 0.03 | 0.01 |
| N | ≤ 0.01 | 0.01 |
| Fe | balance | — |
20MnNb6 +NT — frequently asked
What is 20MnNb6 +NT used for?
20MnNb6 +NT is typically used for pressure vessel plate, boiler components, reactor vessels and chemical process equipment. In short: highest strength in family; nb-refined fine grain; low carbon equivalent plate.
What is the yield strength of 20MnNb6 +NT?
20MnNb6 +NT has a typical yield strength of 370 MPa (53.7 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 70% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is 20MnNb6 +NT easy to machine?
Reasonably — machinability is rated good (61/100, better than 87% of steel grades). Machines like a 1020/1524-class C-Mn steel at ~65 % of AISI 1212; use positive-rake carbide, moderate speeds and good chip control since the low-sulphur pressure-vessel chemistry gives stringy chips.
Can 20MnNb6 +NT be welded?
Yes — weldability is rated excellent (88/100). Excellent weldability with low CEV — SAW/SMAW/GMAW with low-hydrogen consumables; preheat 100–150 °C for thick sections, PWHT 550–620 °C where code requires, keep heat input moderate to protect the Nb-refined HAZ toughness.
What surface finishes work on 20MnNb6 +NT?
No anodizing — protect by shot-blast plus epoxy paint, metallizing, hot-dip galvanizing or weld-overlay/cladding for wet and chloride service.
Can 20MnNb6 +NT be formed, bent or molded?
Cold rolls and presses well in the normalized condition (min bend radius ≈ 1.5–2 t); hot form at 900–1150 °C followed by re-normalizing at 880–920 °C to restore fine grain.
What is the maximum service temperature of 20MnNb6 +NT?
20MnNb6 +NT 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 10222-2 — Steel forgings for pressure purposes: ferritic and martensitic steels with specified elevated temperature properties — CEN (2021)
- EN 10273 — Hot rolled weldable steel bars for pressure purposes with specified elevated temperature properties — CEN (2016)
- EN 10028-2/-3 — Flat products made of steels for pressure purposes — CEN (2017)
- EN 10027-2 / CR 10260 material number 1.0471 — CEN (2015)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- Machinery's Handbook, 31st ed. (machinability ratings) — Industrial Press (2020)
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.