Steel ER90S-B9 N+T
Heat-treated state
UNS S50482
N+T = normalized and tempered
Used when the whole fabrication is re-austenitized (e.g. forged/cast components with weld build-up), restoring uniform fine martensite and best creep response.
Values for the N+T condition
Other ER90S-B9 tempers and conditions
ER90S-B9 is listed in 4 conditions; see the grade overview at ER90S-B9.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
extended temper 760 °C / 4–8 h (heavy-wall, hardness-controlled) | Choose for thick-wall headers or repeated PWHT cycles where hardness must be driven below ~250 HV; softer and tougher, slightly lower strength. | 540 | 670 | 22 | 15 HRC | 2.9 % IACS |
N+TThis page Normalized and tempered | Used when the whole fabrication is re-austenitized (e.g. forged/cast components with weld build-up), restoring uniform fine martensite and best creep response. | 570 | 700 | 22 | 19 HRC | 2.9 % IACS |
PWHTDefault Post-weld heat treated | Standard delivered/qualified condition for P91 joints: temper at 745–775 °C after cooling below ~100 °C, giving tempered martensite with balanced strength and toughness. | 590 | 720 | 20 | 21 HRC | — |
As-welded deposit | Condition immediately after welding — very hard and brittle; only an interim state, never acceptable for service on P91 pressure parts. | 850 | 1,100 | 11 | 43 HRC | — |
What is ER90S-B9 N+T?
ER90S-B9 N+T is ER90S-B9 heat treated to N+T — used when the whole fabrication is re-austenitized (e.g. forged/cast components with weld build-up), restoring uniform fine martensite and best creep response. ER90S-B9 N+T has a yield strength of 570 MPa (82.7 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 74% of steel grades. Elongation at break is 22% and the elastic modulus is 218 GPa (31.6 Msi). ER90S-B9 N+T has a density of 7.77 g/cm³ (0.281 lb/in³), lighter than 92% of steel grades. It melts at 1,420°C (2,588 °F). PWHT is the default condition FabDigit quotes; N+T is available on request or by drawing note.
Advantages
- High service temperature — 620°C (1,148 °F), better than 99% of steel grades
- Good corrosion resistance — 30/100, better than 95% of steel grades
- Tough — resists crack growth — 140 MPa·√m (127.4 ksi·√in), better than 94% of steel grades
Limitations
- Low electrical conductivity — 2.9 % IACS, worse than 93% of steel grades
- Poor heat conductor — 26 W/m·K (15 BTU/hr·ft·°F), worse than 87% of steel grades
- High embodied carbon — 2.6 kg CO₂/kg, worse than 87% of steel grades
- Difficult to machine — 38/100, worse than 80% of steel grades
ER90S-B9 N+T properties
Typical room-temperature values for ER90S-B9 N+T; 23 are specific to this condition. Other listed values are ER90S-B9 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
ER90S-B9 N+T has a density of 7.77 g/cm³ (0.281 lb/in³), lighter than 92% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
ER90S-B9 N+T has a yield strength of 570 MPa (82.7 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 74% of steel grades. Elongation at break is 22% and the elastic modulus is 218 GPa (31.6 Msi).
Thermal6
ER90S-B9 N+T is rated for continuous service to 620°C (1,148 °F). It conducts heat at 26 W/m·K (15 BTU/hr·ft·°F), worse than 87% of steel grades. Thermal expansion is 10.6 µm/m·K (5.89 µin/in·°F).
Electrical3
ER90S-B9 N+T conducts electricity at 2.9 % IACS, worse than 93% of steel grades.
Chemical & Environmental2
Corrosion resistance is poor (30/100), better than 95% of steel grades.
Sustainability4
Producing a kilogram of ER90S-B9 N+T takes about 34 MJ of energy and emits 2.6 kg of CO₂ — more than 82% of steel grades. Typical recycled content is 20%.
Manufacturability7
ER90S-B9 N+T's machinability is fair (38/100, worse than 80% of steel grades); weldability fair (45/100); formability poor (32/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with ER90S-B9 N+T
Is ER90S-B9 easy to machine?
Weld metal machines like a Q&T low-alloy steel after PWHT (~40 % of AISI 1212); in the as-welded 400+ HV state use carbide/CBN or machine only after tempering.
Can ER90S-B9 be welded?
GTAW/GMAW with Ar (or Ar+2–5 % CO₂ for GMAW); preheat and interpass 200–300 °C, cool to 80–100 °C to transform martensite, then PWHT 745–775 °C, 2 h min — never leave a P91 joint untempered.
Can ER90S-B9 be formed, bent or molded?
Supplied as drawn and copper-free (bright) wire on spools or cut rods; no forming of the deposit, but keep wire dry and clean to protect the tight N and Al balance.
What surface finishes work on ER90S-B9?
Grind flush and PT/UT inspect; verify hardness ≤ ~265 HV after PWHT, then paint or insulate — the 9Cr deposit rusts in humid air like a low-alloy steel.
ER90S-B9 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 |
|---|---|---|
| C | 0.07 – 0.13 | 0.1 |
| MnMn + Ni ≤ 1.40 % (AC1 control) | ≤ 1.2 | 0.6 |
| Si | 0.15 – 0.3 | 0.25 |
| P | ≤ 0.01 | 0.01 |
| S | ≤ 0.01 | 0.01 |
| Cr | 8 – 9.5 | 8.8 |
| Mo | 0.85 – 1.05 | 0.95 |
| V | 0.15 – 0.25 | 0.2 |
| Nbreported as Cb in AWS | 0.02 – 0.1 | 0.05 |
| NAl/N ratio must be kept low for creep strength | 0.03 – 0.07 | 0.05 |
| NiMn + Ni ≤ 1.40 % | ≤ 0.8 | 0.4 |
| Cu | ≤ 0.2 | 0.05 |
| Al | ≤ 0.04 | 0.01 |
| Ti | ≤ 0.01 | — |
| Zr | ≤ 0.01 | — |
| Fe | balance | — |
ER90S-B9 N+T — frequently asked
What is ER90S-B9 N+T used for?
ER90S-B9 N+T is typically used for P91/T91 boiler piping welding, supercritical power plant construction and high-temperature steam header welds. In short: matched P91/T91 filler; 600 °C creep-rated deposit; PWHT mandatory after welding.
What is the yield strength of ER90S-B9 N+T?
ER90S-B9 N+T has a typical yield strength of 570 MPa (82.7 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 74% of steel grades. Strength varies by condition: see the 4 listed tempers.
Is ER90S-B9 N+T easy to machine?
Not especially — machinability is rated fair (38/100, worse than 80% of steel grades). Weld metal machines like a Q&T low-alloy steel after PWHT (~40 % of AISI 1212); in the as-welded 400+ HV state use carbide/CBN or machine only after tempering.
Can ER90S-B9 N+T be welded?
With care — weldability is rated fair (45/100). GTAW/GMAW with Ar (or Ar+2–5 % CO₂ for GMAW); preheat and interpass 200–300 °C, cool to 80–100 °C to transform martensite, then PWHT 745–775 °C, 2 h min — never leave a P91 joint untempered.
What surface finishes work on ER90S-B9 N+T?
Grind flush and PT/UT inspect; verify hardness ≤ ~265 HV after PWHT, then paint or insulate — the 9Cr deposit rusts in humid air like a low-alloy steel.
Can ER90S-B9 N+T be formed, bent or molded?
Supplied as drawn and copper-free (bright) wire on spools or cut rods; no forming of the deposit, but keep wire dry and clean to protect the tight N and Al balance.
What is the maximum service temperature of ER90S-B9 N+T?
ER90S-B9 N+T is rated for continuous use to about 620°C (1,148 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between ER90S-B9 PWHT and ER90S-B9-AW?
PWHT is the default condition — standard delivered/qualified condition for P91 joints: temper at 745–775 °C after cooling below ~100 °C, giving tempered martensite with balanced strength and toughness. AW: condition immediately after welding — very hard and brittle; only an interim state, never acceptable for service on P91 pressure parts. Yield strength is 590 MPa in PWHT versus 850 MPa in AW.
Sources
- AWS A5.28/A5.28M — Low-Alloy Steel Electrodes and Rods for Gas Shielded Arc Welding (ER90S-B9) — AWS (2020)
- ASME BPVC Section II Part C, SFA-5.28 — ASME (2023)
- ASME BPVC Section II Part D — Physical properties of Grade 91 (9Cr-1Mo-V) — ASME (2023)
- EN ISO 21952-A — Wire electrodes for gas shielded arc welding of creep-resisting steels (W CrMo91) — ISO (2012)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels — ASM International (1990)
- Thermanit MTS 3 / Böhler C 9 MV-IG all-weld-metal data — voestalpine Böhler Welding (2022)
- Metrode 9CrMoV-N TIG/MIG wire datasheet — Lincoln Electric (Metrode) (2021)
- EPRI Grade 91 Steel Handbook — welding and PWHT guidance — EPRI (2015)
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.