Steel A439 Type D-2 D-3A
Grade
ASTM A439 Type D-2 · EN EN-GJSA-XNiCr20-2
D-3A = type D-3A
Lower-chromium D-3 for better ductility and machinability where carbide-forming Cr is not needed.
Values for the D-3A condition
Other A439 Type D-2 tempers and conditions
A439 Type D-2 is listed in 12 conditions; see the grade overview at A439 Type D-2.
Compare all 12 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Type D-2C | Most ductile and reliably non-magnetic A439 grade; used for pressure-tight housings, instrument and non-magnetic parts. | 215 | 430 | 28 | 145 HB | 13 W/m·K |
ASTM A571 Type D-2M Class 2 or 4 | Same cryogenic Ni-Mn iron at a slightly lower strength/ductility acceptance class, typically for heavier sections. | 215 | 440 | 30 | 150 HB | — |
Type D-2S | Higher-silicon version of D-2 for better scaling/growth resistance in hot exhaust and furnace hardware. | 220 | 420 | 12 | 170 HB | 13 W/m·K |
D-3AThis page Type D-3A | Lower-chromium D-3 for better ductility and machinability where carbide-forming Cr is not needed. | 220 | 400 | 14 | 160 HB | 13 W/m·K |
Type D-5 | Use where minimum thermal expansion and dimensional stability matter (machine tools, optical/scientific mounts, glass moulds). | 220 | 400 | 25 | 155 HB | 13 W/m·K |
Type D-5B | Chromium-bearing 35Ni grade for hot gas and furnace parts needing higher strength and oxidation resistance than D-5. | 225 | 410 | 8 | 165 HB | 13 W/m·K |
Type D-3 | Choose for lower thermal expansion than D-2 with good thermal-shock and dimensional stability in hot service. | 230 | 410 | 8 | 170 HB | 13 W/m·K |
ASTM A571 Type D-2M Class 1 or 3 | Pressure-containing LNG/cryogenic valve and pump castings requiring high ductility and impact energy down to −196 °C. | 230 | 470 | 35 | 145 HB | — |
Type D-5S | Best A439 grade for cyclic high-temperature exhaust/turbine hardware to ~870 °C with useful ductility. | 235 | 430 | 12 | 160 HB | 13 W/m·K |
D-2Default Type D-2 | General-purpose Ni-Resist ductile iron for seawater pumps, valves and turbocharger housings. | 250 | 450 | 12 | 170 HB | 13 W/m·K |
Type D-2B | Pick when extra oxidation, growth and erosion resistance at temperature is wanted and slightly lower ductility is acceptable. | 255 | 460 | 9 | 180 HB | 13 W/m·K |
Type D-4 | Hard, high-silicon/chromium grade for maximum scaling and growth resistance; accept near-zero ductility. | 280 | 430 | 2 | 235 HB | 13 W/m·K |
What is A439 Type D-2 D-3A?
A439 Type D-2 D-3A is A439 Type D-2 in the D-3A grade — lower-chromium D-3 for better ductility and machinability where carbide-forming Cr is not needed. A439 Type D-2 D-3A has a yield strength of 220 MPa (31.9 ksi) and a tensile strength of 400 MPa (58 ksi) — weaker than 98% of steel grades. Elongation at break is 14% and the elastic modulus is 122 GPa (17.7 Msi). A439 Type D-2 D-3A has a density of 7.45 g/cm³ (0.269 lb/in³), lighter than 98% of steel grades. It melts at 1,150°C (2,102 °F). D-2 is the default condition FabDigit quotes; D-3A is available on request or by drawing note.
Advantages
- High service temperature — 800°C (1,472 °F), better than 100% of steel grades
- Good corrosion resistance — 62/100, better than 100% of steel grades
Limitations
- Low electrical conductivity — 1.7 % IACS, worse than 100% of steel grades
- Low stiffness — 122 GPa (17.7 Msi), worse than 99% of steel grades
- Poor heat conductor — 13 W/m·K (7.51 BTU/hr·ft·°F), worse than 99% of steel grades
- Low strength — 220 MPa (31.9 ksi), worse than 98% of steel grades
- High embodied carbon — 3.5 kg CO₂/kg, worse than 93% of steel grades
A439 Type D-2 D-3A properties
Typical room-temperature values for A439 Type D-2 D-3A; 16 are specific to this condition. Other listed values are A439 Type D-2 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
A439 Type D-2 D-3A has a density of 7.45 g/cm³ (0.269 lb/in³), lighter than 98% of steel grades. It melts at 1,150°C (2,102 °F).
Mechanical13
A439 Type D-2 D-3A has a yield strength of 220 MPa (31.9 ksi) and a tensile strength of 400 MPa (58 ksi) — weaker than 98% of steel grades. Elongation at break is 14% and the elastic modulus is 122 GPa (17.7 Msi).
Thermal6
A439 Type D-2 D-3A is rated for continuous service to 800°C (1,472 °F). It conducts heat at 13 W/m·K (7.51 BTU/hr·ft·°F), worse than 99% of steel grades. Thermal expansion is 13.4 µm/m·K (7.44 µin/in·°F).
Electrical3
A439 Type D-2 D-3A conducts electricity at 1.7 % IACS, worse than 100% of steel grades.
Chemical & Environmental3
Corrosion resistance is good (62/100), better than 100% of steel grades.
Sustainability4
Producing a kilogram of A439 Type D-2 D-3A takes about 45 MJ of energy and emits 3.5 kg of CO₂ — more than 93% of steel grades. Typical recycled content is 60%.
Manufacturability6
A439 Type D-2 D-3A's machinability is fair (45/100, worse than 65% of steel grades); weldability fair (50/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with A439 Type D-2 D-3A
Is A439 Type D-2 easy to machine?
Machines like a tough ductile iron but the austenite work-hardens: use rigid setups, positive-rake carbide, moderate speed and heavy positive feed to stay under the hardened skin; high-Si D-4/D-5S are abrasive and need ceramic/CBN.
Can A439 Type D-2 be welded?
Weldable with Ni-Fe or pure-Ni electrodes (ENiFe-CI/ENi-CI), 300–350 °C preheat for high-Cr types, short stringer beads and peening; low-Cr D-2C and D-2M are the most weld-friendly.
Can A439 Type D-2 be formed, bent or molded?
Sand-cast only — good fluidity with 20–35 % Ni, but requires generous risering (shrinkage ~2 %), Mg treatment for nodularity and controlled section cooling to avoid carbides.
What surface finishes work on A439 Type D-2?
Takes paint, epoxy and Ni/Cr plating after abrasive blast; graphite nodules limit mirror polish, and no anodizing applies — surfaces are usually left bare in seawater duty.
A439 Type D-2 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 |
|---|---|---|
| Ctotal carbon, ASTM A439 Type D-2 | ≤ 3 | 2.8 |
| Si | 1.5 – 3 | 2.2 |
| Mn | 0.7 – 1.25 | 1 |
| Ni | 18 – 22 | 20 |
| Cr | 1.75 – 2.75 | 2.2 |
| P | ≤ 0.08 | — |
| Mgnodulizing residual, not specified in A439 but typical | 0.03 – 0.08 | 0.05 |
| Fe | balance | — |
A439 Type D-2 D-3A — frequently asked
What is A439 Type D-2 D-3A used for?
A439 Type D-2 D-3A is typically used for pump casings, valve bodies, turbine housings and seawater equipment. In short: ductile austenitic Ni-Resist; 12 % elongation at 760 °C rating; marine corrosion service.
What is the yield strength of A439 Type D-2 D-3A?
A439 Type D-2 D-3A has a typical yield strength of 220 MPa (31.9 ksi) and a tensile strength of 400 MPa (58 ksi) — weaker than 98% of steel grades. Strength varies by condition: see the 12 listed tempers.
Is A439 Type D-2 D-3A easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% of steel grades). Machines like a tough ductile iron but the austenite work-hardens: use rigid setups, positive-rake carbide, moderate speed and heavy positive feed to stay under the hardened skin; high-Si D-4/D-5S are abrasive and need ceramic/CBN.
Can A439 Type D-2 D-3A be welded?
With care — weldability is rated fair (50/100). Weldable with Ni-Fe or pure-Ni electrodes (ENiFe-CI/ENi-CI), 300–350 °C preheat for high-Cr types, short stringer beads and peening; low-Cr D-2C and D-2M are the most weld-friendly.
What surface finishes work on A439 Type D-2 D-3A?
Takes paint, epoxy and Ni/Cr plating after abrasive blast; graphite nodules limit mirror polish, and no anodizing applies — surfaces are usually left bare in seawater duty.
Can A439 Type D-2 D-3A be formed, bent or molded?
Sand-cast only — good fluidity with 20–35 % Ni, but requires generous risering (shrinkage ~2 %), Mg treatment for nodularity and controlled section cooling to avoid carbides.
What is the maximum service temperature of A439 Type D-2 D-3A?
A439 Type D-2 D-3A is rated for continuous use to about 800°C (1,472 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between A439 Type D-2 D-2 and A439 Type D-2 D-2C?
D-2 is the default condition — general-purpose Ni-Resist ductile iron for seawater pumps, valves and turbocharger housings. D-2C: most ductile and reliably non-magnetic A439 grade; used for pressure-tight housings, instrument and non-magnetic parts. Yield strength is 250 MPa in D-2 versus 215 MPa in D-2C.
Sources
- ASTM A439/A439M — Austenitic Ductile Iron Castings — ASTM International (2018)
- ASTM A571/A571M — Austenitic Ductile Iron Castings for Pressure-Containing Parts Suitable for Low-Temperature Service — ASTM International (2019)
- EN 13835 — Founding: Austenitic Cast Irons — CEN (2012)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- Engineering Properties and Applications of Ni-Resist and Ductile Ni-Resist Alloys — Nickel Institute (2020)
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.