Steel A356 Grade 6
ASTM A356 Grade 6 · UNS J12073
ASTM A356 Grade 6 (UNS J12073) is a 2-1/4Cr-1Mo low-alloy steel casting for high-temperature, high-pressure turbine and boiler components.
Reference datasheet — A356 Grade 6 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the N+T condition
A356 Grade 6 tempers and conditions
A356 Grade 6 is supplied in 4 conditions, soft to hard. N+T is the default FabDigit quotes; the values on this page are for it.
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 |
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?
ASTM A356 Grade 6 (UNS J12073) is a 2-1/4Cr-1Mo low-alloy steel casting for high-temperature, high-pressure turbine and boiler components. Engineers select it for creep resistance with service to 550 °C; default properties are 380 MPa yield, 550 MPa tensile, 22 % elongation and 165 HB, in N+T, Q&T, annealed or N+T+PWHT condition as sand castings. Machinability and weldability both rate about 55, with 200–250 °C preheat and mandatory 690–730 °C PWHT. Grade 5 (1-1/4Cr-1/2Mo) is simpler to fabricate where creep demands are lower. A356 Grade 6 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). A356 Grade 6 has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 550 MPa (79.8 ksi) — weaker than 68% of steel grades. Elongation at break is 22% and the elastic modulus is 205 GPa (29.7 Msi).
What is A356 Grade 6 used for?
- turbine casings
- boiler headers
- high-pressure valve bodies
Advantages
- High service temperature — 550°C (1,022 °F), better than 95% of steel grades
- Tough — resists crack growth — 120 MPa·√m (109.2 ksi·√in), better than 81% of steel grades
Limitations
- Limited formability — 20/100, worse than 80% of steel grades
A356 Grade 6 properties
Typical room-temperature values for A356 Grade 6-N+T; bars are the position among steel grades.
Physical3
A356 Grade 6 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 has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 550 MPa (79.8 ksi) — weaker than 68% of steel grades. Elongation at break is 22% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
A356 Grade 6 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 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 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's machinability is good (55/100, better than 62% of steel grades); weldability good (55/100); formability poor (20/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. A356 Grade 6 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with A356 Grade 6
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.
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 | — |
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.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel A356 Grade 6 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- J12073
How much does A356 Grade 6 cost?
A356 Grade 6 is a standard-cost steel ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
A356 Grade 6 — frequently asked
What is A356 Grade 6 used for?
A356 Grade 6 is typically used for turbine casings, boiler headers and high-pressure valve bodies. In short: workhorse 2.25Cr-1Mo casting; higher creep strength than Grade 5; requires 690–730 °C PWHT.
What is the yield strength of A356 Grade 6?
A356 Grade 6 has a typical yield strength of 380 MPa (55.1 ksi) and a tensile strength of 550 MPa (79.8 ksi) — weaker than 68% of steel grades. Strength varies by condition: see the 4 listed tempers.
Is A356 Grade 6 easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Machines like 4130-class low-alloy steel — rigid setups, carbide tooling, moderate speeds; anneal or temper first, expect hard spots near chills and risers.
Can A356 Grade 6 be welded?
Yes — weldability is rated good (55/100). Weldable with matching 1¼Cr-½Mo (E8018-B2 / ER80S-B2) filler, 200–250 °C preheat, low-hydrogen practice and mandatory 690–730 °C PWHT.
What surface finishes work on A356 Grade 6?
Not anodizable — protect with high-temperature aluminium paint, aluminizing or thermal-spray coatings; grind and dye-penetrant inspect all repaired areas.
Can A356 Grade 6 be formed, bent or molded?
Sand-cast in heavy sections with generous risering and chills; degas and control S/P to avoid hot tears, then normalize-and-temper the whole casting.
What is the maximum service temperature of A356 Grade 6?
A356 Grade 6 is rated for continuous use to about 550°C (1,022 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does A356 Grade 6 cost?
A356 Grade 6 is a standard-cost steel ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
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; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.