Steel A356 Grade 8 N+T+PWHT
Heat-treated state
ASTM A356 Grade 8 · UNS J11697
Condition of weld-repaired or fabricated castings after a 700–750 °C stress-relief cycle; slightly lower strength, best toughness and dimensional stability.
Values for the N+T+PWHT condition
Other A356 Grade 8 tempers and conditions
A356 Grade 8 is listed in 4 conditions; see the grade overview at A356 Grade 8.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Pick when maximum machinability or softest condition for heavy welding/repair is needed before final heat treatment. | 365 | 585 | 24 | 160 HB | 3.9 % IACS |
N+T+PWHTThis page normalized, tempered and post-weld heat treated / stress relieved | Condition of weld-repaired or fabricated castings after a 700–750 °C stress-relief cycle; slightly lower strength, best toughness and dimensional stability. | 430 | 620 | 22 | 12 HRC | 3.8 % IACS |
N+TDefault Normalized and tempered | Standard delivery condition for A356 Gr.8 turbine and valve castings: balanced strength, creep resistance and toughness. | 450 | 655 | 20 | 15 HRC | 3.8 % IACS |
Quenched and tempered | Used for thinner-section castings needing higher strength and uniform properties; tempering above 620 °C keeps it stable for hot service. | 550 | 725 | 18 | 21 HRC | — |
What is A356 Grade 8 N+T+PWHT?
A356 Grade 8 N+T+PWHT is A356 Grade 8 heat treated to N+T+PWHT — condition of weld-repaired or fabricated castings after a 700–750 °C stress-relief cycle; slightly lower strength, best toughness and dimensional stability. A356 Grade 8 N+T+PWHT has a yield strength of 430 MPa (62.4 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 51% of steel grades. Elongation at break is 22% and the elastic modulus is 207 GPa (30 Msi). A356 Grade 8 N+T+PWHT has a density of 7.78 g/cm³ (0.281 lb/in³), lighter than 91% of steel grades. It melts at 1,425°C (2,597 °F). N+T is the default condition FabDigit quotes; N+T+PWHT 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
Limitations
- Limited formability — 12/100, worse than 92% of steel grades
- Low electrical conductivity — 3.8 % IACS, worse than 84% of steel grades
- Poor heat conductor — 35 W/m·K (20.2 BTU/hr·ft·°F), worse than 75% of steel grades
A356 Grade 8 N+T+PWHT properties
Typical room-temperature values for A356 Grade 8 N+T+PWHT; 23 are specific to this condition. Other listed values are A356 Grade 8 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
A356 Grade 8 N+T+PWHT has a density of 7.78 g/cm³ (0.281 lb/in³), lighter than 91% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical17
A356 Grade 8 N+T+PWHT has a yield strength of 430 MPa (62.4 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 51% of steel grades. Elongation at break is 22% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
A356 Grade 8 N+T+PWHT is rated for continuous service to 620°C (1,148 °F). It conducts heat at 35 W/m·K (20.2 BTU/hr·ft·°F), worse than 75% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
A356 Grade 8 N+T+PWHT conducts electricity at 3.8 % IACS, worse than 84% of steel grades.
Chemical & Environmental2
Corrosion resistance is poor (30/100), better than 95% of steel grades.
Sustainability4
Producing a kilogram of A356 Grade 8 N+T+PWHT takes about 30 MJ of energy and emits 2.3 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 80%.
Manufacturability8
A356 Grade 8 N+T+PWHT's machinability is fair (48/100, worse than 57% of steel grades); weldability fair (50/100); formability not recommended (12/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with A356 Grade 8 N+T+PWHT
Is A356 Grade 8 easy to machine?
Machine in the N+T or annealed condition with rigid setups, carbide tooling and moderate speeds (~60–90 m/min); chromium carbides are abrasive and cast skin should be removed first.
Can A356 Grade 8 be welded?
Weldable with matching 5Cr-0.5Mo (E/ER 502) consumables using 200–300 °C preheat, controlled interpass temperature and a mandatory 700–760 °C post-weld temper to avoid hard martensitic HAZ and hydrogen cracking.
Can A356 Grade 8 be formed, bent or molded?
Supplied as sand castings — design generous fillets and directional solidification for heavy walls; the alloy air-hardens, so slow, controlled cooling from casting temperature is required.
What surface finishes work on A356 Grade 8?
Not anodizable; protect with high-temperature aluminium/silicone paint, aluminizing or thermal-spray coatings for outdoor and cyclic-service parts.
A356 Grade 8 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 |
|---|---|---|
| Ccarbon kept low for weldability of heavy sections | ≤ 0.2 | 0.15 |
| Mn | 0.4 – 0.7 | 0.55 |
| Si | ≤ 0.75 | 0.45 |
| Pheavy-walled turbine castings often ordered to tighter P/S | ≤ 0.03 | 0.02 |
| S | ≤ 0.03 | 0.01 |
| Crprovides steam-oxidation and sulfidation resistance | 4 – 6.5 | 5 |
| Mocreep strength | 0.45 – 0.65 | 0.55 |
| Niresidual | ≤ 0.5 | 0.2 |
| Fe | balance | — |
A356 Grade 8 N+T+PWHT — frequently asked
What is A356 Grade 8 N+T+PWHT used for?
A356 Grade 8 N+T+PWHT is typically used for petrochemical process equipment, high-temperature valve bodies and furnace components. In short: 5Cr-0.5Mo oxidation resistance; air-hardening cast steel; service to 620 °C.
What is the yield strength of A356 Grade 8 N+T+PWHT?
A356 Grade 8 N+T+PWHT has a typical yield strength of 430 MPa (62.4 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 51% of steel grades. Strength varies by condition: see the 4 listed tempers.
Is A356 Grade 8 N+T+PWHT easy to machine?
Reasonably — machinability is rated fair (48/100, worse than 57% of steel grades). Machine in the N+T or annealed condition with rigid setups, carbide tooling and moderate speeds (~60–90 m/min); chromium carbides are abrasive and cast skin should be removed first.
Can A356 Grade 8 N+T+PWHT be welded?
With care — weldability is rated fair (50/100). Weldable with matching 5Cr-0.5Mo (E/ER 502) consumables using 200–300 °C preheat, controlled interpass temperature and a mandatory 700–760 °C post-weld temper to avoid hard martensitic HAZ and hydrogen cracking.
What surface finishes work on A356 Grade 8 N+T+PWHT?
Not anodizable; protect with high-temperature aluminium/silicone paint, aluminizing or thermal-spray coatings for outdoor and cyclic-service parts.
Can A356 Grade 8 N+T+PWHT be formed, bent or molded?
Supplied as sand castings — design generous fillets and directional solidification for heavy walls; the alloy air-hardens, so slow, controlled cooling from casting temperature is required.
What is the maximum service temperature of A356 Grade 8 N+T+PWHT?
A356 Grade 8 N+T+PWHT 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 A356 Grade 8 N+T and A356 Grade 8-A?
N+T is the default condition — standard delivery condition for A356 Gr.8 turbine and valve castings: balanced strength, creep resistance and toughness. A: pick when maximum machinability or softest condition for heavy welding/repair is needed before final heat treatment. Yield strength is 450 MPa in N+T versus 365 MPa in A.
Sources
- ASTM A356/A356M — Steel Castings, Carbon, Low Alloy, and Stainless Steel, Heavy-Walled for Steam Turbines — ASTM International (2021)
- ASTM A217/A217M — Steel Castings, Martensitic Stainless and Alloy, for Pressure-Containing Parts, High-Temperature Service — ASTM International (2021)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASME BPVC Section II Part D — Material Properties (5Cr-1/2Mo) — ASME (2023)
- Steel Castings Handbook — Steel Founders' Society of America / ASM (1995)
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.