Steel A217 C12A N+T+PWHT
Heat-treated state
ASTM A217 C12A
N+T+PWHT = n+T plus post-weld heat treatment 750–770 °C
Condition of weld-repaired or field-welded castings; slightly lower strength and hardness than fresh N+T, with restored HAZ toughness.
Values for the N+T+PWHT condition
Other A217 C12A tempers and conditions
A217 C12A is listed in 4 conditions; see the grade overview at A217 C12A.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Pick only as an intermediate shop condition; castings must be re-normalized and tempered before service. | 380 | 600 | 24 | 11 HRC | 3 % IACS |
N+T+PWHTThis page N+T plus post-weld heat treatment 750–770 °C | Condition of weld-repaired or field-welded castings; slightly lower strength and hardness than fresh N+T, with restored HAZ toughness. | 465 | 650 | 22 | 15 HRC | 2.9 % IACS |
N+TDefault Normalized and tempered | Standard and effectively the only delivery condition for C12A castings — mandatory for ASME code service. | 490 | 680 | 22 | 18 HRC | — |
As fabricated | Untempered as-cast martensite — brittle and crack-prone; never supplied or used in service. | 930 | 1,230 | 5 | 41 HRC | 2.7 % IACS |
What is A217 C12A N+T+PWHT?
A217 C12A N+T+PWHT is A217 C12A heat treated to N+T+PWHT — condition of weld-repaired or field-welded castings; slightly lower strength and hardness than fresh N+T, with restored HAZ toughness. A217 C12A N+T+PWHT has a yield strength of 465 MPa (67.4 ksi) and a tensile strength of 650 MPa (94.3 ksi) — stronger than 56% of steel grades. Elongation at break is 22% and the elastic modulus is 218 GPa (31.6 Msi). A217 C12A N+T+PWHT 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). N+T is the default condition FabDigit quotes; N+T+PWHT is available on request or by drawing note.
Advantages
- High service temperature — 600°C (1,112 °F), better than 98% of steel grades
- Good corrosion resistance — 28/100, better than 94% of steel grades
- Tough — resists crack growth — 125 MPa·√m (113.8 ksi·√in), better than 85% 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
- Limited formability — 15/100, worse than 87% of steel grades
- Difficult to machine — 40/100, worse than 77% of steel grades
A217 C12A N+T+PWHT properties
Typical room-temperature values for A217 C12A N+T+PWHT; 23 are specific to this condition. Other listed values are A217 C12A reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
A217 C12A N+T+PWHT 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
A217 C12A N+T+PWHT has a yield strength of 465 MPa (67.4 ksi) and a tensile strength of 650 MPa (94.3 ksi) — stronger than 56% of steel grades. Elongation at break is 22% and the elastic modulus is 218 GPa (31.6 Msi).
Thermal6
A217 C12A N+T+PWHT is rated for continuous service to 600°C (1,112 °F). It conducts heat at 26 W/m·K (15 BTU/hr·ft·°F), worse than 87% of steel grades. Thermal expansion is 10.8 µm/m·K (6 µin/in·°F).
Electrical3
A217 C12A N+T+PWHT conducts electricity at 2.9 % IACS, worse than 93% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (28/100), better than 94% of steel grades.
Sustainability4
Producing a kilogram of A217 C12A N+T+PWHT takes about 32 MJ of energy and emits 2.4 kg of CO₂ — more than 70% of steel grades. Typical recycled content is 75%.
Manufacturability8
A217 C12A N+T+PWHT's machinability is fair (40/100, worse than 77% of steel grades); weldability fair (35/100); formability poor (15/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with A217 C12A N+T+PWHT
Is A217 C12A easy to machine?
Machine in the N+T condition at 190–250 HB with rigid setups, coated carbide and moderate speeds; work-hardening and abrasive carbides shorten tool life versus low-alloy cast steel.
Can A217 C12A be welded?
Use matching 9CrMoV-N filler (E9015-B9 / ER90S-B9), 200–250 °C preheat and interpass, no interruption below Ms, and mandatory 750–770 °C PWHT below Ac1; never exceed the tempering temperature.
Can A217 C12A be formed, bent or molded?
Sand-cast with generous risering and controlled Al/N chemistry to protect VN strengthening; hot-tearing-prone sections need progressive solidification and slow shakeout.
What surface finishes work on A217 C12A?
Not anodizable — protect with high-temperature aluminium/silicone paint, thermal-spray aluminizing or leave insulated; keep surfaces clean of chlorides to avoid corrosion under insulation.
A217 C12A 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 | 0.08 – 0.12 | 0.1 |
| Mn | 0.3 – 0.6 | 0.45 |
| Si | 0.2 – 0.5 | 0.35 |
| P | ≤ 0.02 | — |
| S | ≤ 0.01 | — |
| Cr | 8 – 9.5 | 8.7 |
| Mo | 0.85 – 1.05 | 0.95 |
| V | 0.18 – 0.25 | 0.21 |
| Nblisted as Cb (columbium) in ASTM A217 | 0.06 – 0.1 | 0.08 |
| N | 0.03 – 0.07 | 0.05 |
| Ni | ≤ 0.4 | 0.2 |
| Alkept low to preserve free nitrogen for VN strengthening | ≤ 0.02 | — |
| Ti | ≤ 0.01 | — |
| Zr | ≤ 0.01 | — |
| Fe | balance | — |
A217 C12A N+T+PWHT — frequently asked
What is A217 C12A N+T+PWHT used for?
A217 C12A N+T+PWHT is typically used for ultra-supercritical steam turbine casings, high-pressure valve bodies, boiler header castings and advanced fossil power plant components. In short: strongest A217 cast grade; cast P91 equivalent; hardest to weld.
What is the yield strength of A217 C12A N+T+PWHT?
A217 C12A N+T+PWHT has a typical yield strength of 465 MPa (67.4 ksi) and a tensile strength of 650 MPa (94.3 ksi) — stronger than 56% of steel grades. Strength varies by condition: see the 4 listed tempers.
Is A217 C12A N+T+PWHT easy to machine?
Not especially — machinability is rated fair (40/100, worse than 77% of steel grades). Machine in the N+T condition at 190–250 HB with rigid setups, coated carbide and moderate speeds; work-hardening and abrasive carbides shorten tool life versus low-alloy cast steel.
Can A217 C12A N+T+PWHT be welded?
With care — weldability is rated fair (35/100). Use matching 9CrMoV-N filler (E9015-B9 / ER90S-B9), 200–250 °C preheat and interpass, no interruption below Ms, and mandatory 750–770 °C PWHT below Ac1; never exceed the tempering temperature.
What surface finishes work on A217 C12A N+T+PWHT?
Not anodizable — protect with high-temperature aluminium/silicone paint, thermal-spray aluminizing or leave insulated; keep surfaces clean of chlorides to avoid corrosion under insulation.
Can A217 C12A N+T+PWHT be formed, bent or molded?
Sand-cast with generous risering and controlled Al/N chemistry to protect VN strengthening; hot-tearing-prone sections need progressive solidification and slow shakeout.
What is the maximum service temperature of A217 C12A N+T+PWHT?
A217 C12A N+T+PWHT is rated for continuous use to about 600°C (1,112 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between A217 C12A N+T and A217 C12A-F?
N+T is the default condition — standard and effectively the only delivery condition for C12A castings — mandatory for ASME code service. F: untempered as-cast martensite — brittle and crack-prone; never supplied or used in service. Yield strength is 490 MPa in N+T versus 930 MPa in F.
Sources
- ASTM A217/A217M — Steel Castings, Martensitic Stainless and Alloy, for Pressure-Containing Parts, Suitable for High-Temperature Service — ASTM International (2021)
- ASME BPVC Section II Part D — Properties (Metric), P91/C12A allowable stresses and physical properties — ASME (2023)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- Steel Castings Handbook, 6th ed. — Steel Founders' Society of America (1995)
- NIMS Creep Data Sheets — modified 9Cr-1Mo steel — National Institute for Materials Science (Japan) (2014)
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.