Steel A356 Grade 6 N+T+PWHT
Heat-treated state
ASTM A356 Grade 6 · UNS J12073
Final condition of fabricated or weld-repaired castings; slightly softer than as-tempered but lowest residual stress.
Values for the N+T+PWHT condition
Other A356 Grade 6 tempers and conditions
A356 Grade 6 is listed in 4 conditions; see the grade overview at A356 Grade 6.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
full anneal (soft, for machining or weld repair) | Use for maximum machinability and weld repair of raw castings before final normalize-and-temper. | 290 | 490 | 27 | 143 HB | 8 % IACS |
N+T+PWHTThis page normalized, tempered and post-weld heat treated / stress relieved | Final condition of fabricated or weld-repaired castings; slightly softer than as-tempered but lowest residual stress. | 360 | 530 | 24 | 156 HB | 7.8 % IACS |
N+TDefault Normalized and tempered | Standard supply condition for heavy-walled turbine casings — balanced creep strength, toughness and dimensional stability. | 380 | 550 | 22 | 165 HB | — |
Quenched and tempered | Chosen when higher room-temperature strength and uniform through-thickness properties are needed in thick sections. | 450 | 620 | 20 | 190 HB | — |
What is A356 Grade 6 N+T+PWHT?
A356 Grade 6 N+T+PWHT is A356 Grade 6 heat treated to N+T+PWHT — final condition of fabricated or weld-repaired castings; slightly softer than as-tempered but lowest residual stress. A356 Grade 6 N+T+PWHT has a yield strength of 360 MPa (52.2 ksi) and a tensile strength of 530 MPa (76.9 ksi) — weaker than 72% of steel grades. Elongation at break is 24% and the elastic modulus is 205 GPa (29.7 Msi). A356 Grade 6 N+T+PWHT has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,450°C (2,642 °F). N+T is the default condition FabDigit quotes; N+T+PWHT is available on request or by drawing note.
Advantages
- High service temperature — 550°C (1,022 °F), better than 95% of steel grades
- Tough — resists crack growth — 130 MPa·√m (118.3 ksi·√in), better than 89% of steel grades
Limitations
- Limited formability — 22/100, worse than 76% of steel grades
A356 Grade 6 N+T+PWHT properties
Typical room-temperature values for A356 Grade 6 N+T+PWHT; 22 are specific to this condition. Other listed values are A356 Grade 6 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
A356 Grade 6 N+T+PWHT has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,450°C (2,642 °F).
Mechanical16
A356 Grade 6 N+T+PWHT has a yield strength of 360 MPa (52.2 ksi) and a tensile strength of 530 MPa (76.9 ksi) — weaker than 72% of steel grades. Elongation at break is 24% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
A356 Grade 6 N+T+PWHT is rated for continuous service to 550°C (1,022 °F). It conducts heat at 38 W/m·K (22 BTU/hr·ft·°F), worse than 69% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical2
A356 Grade 6 N+T+PWHT has an electrical resistivity of 2.2×10⁻⁷ Ω·m.
Chemical & Environmental3
Corrosion resistance is poor (18/100), better than 83% of steel grades.
Sustainability4
Producing a kilogram of A356 Grade 6 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
A356 Grade 6 N+T+PWHT's machinability is good (58/100, better than 75% of steel grades); weldability good (58/100); formability poor (22/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with A356 Grade 6 N+T+PWHT
Is A356 Grade 6 easy to machine?
Machines like 4130-class low-alloy steel — rigid setups, carbide tooling, moderate speeds; anneal or temper first, expect hard spots near chills and risers.
Can A356 Grade 6 be welded?
Weldable with matching 1¼Cr-½Mo (E8018-B2 / ER80S-B2) filler, 200–250 °C preheat, low-hydrogen practice and mandatory 690–730 °C PWHT.
Can A356 Grade 6 be formed, bent or molded?
Sand-cast in heavy sections with generous risering and chills; degas and control S/P to avoid hot tears, then normalize-and-temper the whole casting.
What surface finishes work on A356 Grade 6?
Not anodizable — protect with high-temperature aluminium paint, aluminizing or thermal-spray coatings; grind and dye-penetrant inspect all repaired areas.
A356 Grade 6 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 walls | ≤ 0.2 | 0.15 |
| Mn | 0.5 – 0.8 | 0.65 |
| Si | ≤ 0.6 | 0.4 |
| P | ≤ 0.03 | 0.02 |
| S | ≤ 0.03 | 0.01 |
| Cr1¼Cr class (WC6-type) | 1 – 1.5 | 1.25 |
| Mocreep strength | 0.45 – 0.65 | 0.55 |
| Niresidual | ≤ 0.5 | 0.2 |
| Curesidual | ≤ 0.35 | 0.1 |
| Fe | balance | — |
A356 Grade 6 N+T+PWHT — frequently asked
What is A356 Grade 6 N+T+PWHT used for?
A356 Grade 6 N+T+PWHT is typically used for turbine casings, boiler headers and high-pressure valve bodies. In short: workhorse 2.25Cr-1Mo casting; higher creep strength than Grade 5; requires 690–730 °C PWHT.
What is the yield strength of A356 Grade 6 N+T+PWHT?
A356 Grade 6 N+T+PWHT has a typical yield strength of 360 MPa (52.2 ksi) and a tensile strength of 530 MPa (76.9 ksi) — weaker than 72% of steel grades. Strength varies by condition: see the 4 listed tempers.
Is A356 Grade 6 N+T+PWHT easy to machine?
Reasonably — machinability is rated good (58/100, better than 75% of steel grades). Machines like 4130-class low-alloy steel — rigid setups, carbide tooling, moderate speeds; anneal or temper first, expect hard spots near chills and risers.
Can A356 Grade 6 N+T+PWHT be welded?
Yes — weldability is rated good (58/100). Weldable with matching 1¼Cr-½Mo (E8018-B2 / ER80S-B2) filler, 200–250 °C preheat, low-hydrogen practice and mandatory 690–730 °C PWHT.
What surface finishes work on A356 Grade 6 N+T+PWHT?
Not anodizable — protect with high-temperature aluminium paint, aluminizing or thermal-spray coatings; grind and dye-penetrant inspect all repaired areas.
Can A356 Grade 6 N+T+PWHT be formed, bent or molded?
Sand-cast in heavy sections with generous risering and chills; degas and control S/P to avoid hot tears, then normalize-and-temper the whole casting.
What is the maximum service temperature of A356 Grade 6 N+T+PWHT?
A356 Grade 6 N+T+PWHT is rated for continuous use to about 550°C (1,022 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- ASTM A356/A356M — Steel Castings, Carbon, Low Alloy, and Stainless Steel, Heavy-Walled for Steam Turbines — ASTM International (2021)
- ASTM A217/A217M — Martensitic Stainless and Alloy Steel Castings for Pressure-Containing Parts (WC6 comparison) — ASTM International (2021)
- ASME BPVC Section II Part D — Material Properties (Cr-Mo allowable stresses, E, CTE, k) — ASME (2023)
- ASM Handbook Vol.1 / Vol.1A — Cast Steels and Cr-Mo Alloy Steels — ASM International (1990)
- Steel Castings Handbook, 6th ed. — Steel Founders' Society of America / ASM (1995)
- GB/T 16253 / ZG15Cr1Mo (2019)
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.