Steel Ductile Iron Stress Relieved
Heat-treated state
also Nodular Iron, Nodular Cast Iron
Pick for dimensionally critical machined castings (hydraulic bodies, machine bases) where residual casting stress must be removed without changing strength class.
Values for the Stress Relieved condition
Other Ductile Iron tempers and conditions
Ductile Iron is listed in 6 conditions; see the grade overview at Ductile Iron.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
fully ferritic (ASTM A536 60-40-18 / EN GJS-400-18) | Pick when maximum ductility, impact energy and low-temperature toughness matter — pressure pipe, fittings, wind-turbine and safety-critical castings. | 300 | 440 | 20 | 160 HB | 36 W/m·K |
Stress RelievedThis page sub-critical stress relief (≈540–650 °C), matrix essentially as-cast | Pick for dimensionally critical machined castings (hydraulic bodies, machine bases) where residual casting stress must be removed without changing strength class. | 320 | 460 | 15 | 180 HB | 3.1 % IACS |
As CastDefault ferritic/pearlitic matrix, no heat treatment (ASTM A536 65-45-12 / EN GJS-450-10) | Default stocked condition: best cost/strength balance for general machinery castings, housings and brackets. | 340 | 480 | 14 | 187 HB | 33 W/m·K |
Normalized and tempered | Pick for higher strength and wear resistance with moderate ductility — gears, crankshafts, sprockets, heavy-duty linkages. | 510 | 730 | 5 | 25 HRC | 30 W/m·K |
Quenched and tempered | Pick for maximum strength and wear life in ductile iron where low elongation is acceptable — dies, rolls, high-load gears and pins. | 700 | 900 | 3 | 34 HRC | 26 W/m·K |
Austempered ductile iron, ausferrite matrix | Pick when you want steel-level strength and fatigue life plus useful ductility and wear resistance at casting cost — suspension arms, track links, gears, ground-engaging tools. | 750 | 1,050 | 7 | 35 HRC | 24 W/m·K |
What is Ductile Iron Stress Relieved?
Ductile Iron Stress Relieved is Ductile Iron heat treated to Stress Relieved — pick for dimensionally critical machined castings (hydraulic bodies, machine bases) where residual casting stress must be removed without changing strength class. Ductile Iron Stress Relieved has a yield strength of 320 MPa (46.4 ksi) and a tensile strength of 460 MPa (66.7 ksi) — weaker than 81% of steel grades. Elongation at break is 15% and the elastic modulus is 169 GPa (24.5 Msi). Ductile Iron Stress Relieved has a density of 7.1 g/cm³ (0.257 lb/in³), lighter than 99% of steel grades. It melts at 1,150°C (2,102 °F). As Cast is the default condition FabDigit quotes; Stress Relieved is available on request or by drawing note.
Advantages
- Easy to machine — 70/100, better than 96% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
Limitations
- Low stiffness — 169 GPa (24.5 Msi), worse than 97% of steel grades
- Limited formability — 8/100, worse than 97% of steel grades
- Low fracture toughness — 43 MPa·√m (39.1 ksi·√in), worse than 92% of steel grades
- Low electrical conductivity — 3.1 % IACS, worse than 89% of steel grades
- Low strength — 320 MPa (46.4 ksi), worse than 81% of steel grades
Ductile Iron Stress Relieved properties
Typical room-temperature values for Ductile Iron Stress Relieved; 23 are specific to this condition. Other listed values are Ductile Iron reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
Ductile Iron Stress Relieved has a density of 7.1 g/cm³ (0.257 lb/in³), lighter than 99% of steel grades. It melts at 1,150°C (2,102 °F).
Mechanical15
Ductile Iron Stress Relieved has a yield strength of 320 MPa (46.4 ksi) and a tensile strength of 460 MPa (66.7 ksi) — weaker than 81% of steel grades. Elongation at break is 15% and the elastic modulus is 169 GPa (24.5 Msi).
Thermal6
Ductile Iron Stress Relieved is rated for continuous service to 400°C (752 °F). It conducts heat at 33 W/m·K (19.1 BTU/hr·ft·°F), worse than 80% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
Ductile Iron Stress Relieved conducts electricity at 3.1 % IACS, worse than 89% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (16/100), better than 79% of steel grades.
Sustainability4
Producing a kilogram of Ductile Iron Stress Relieved takes about 21 MJ of energy and emits 1.9 kg of CO₂ — less than 99% of steel grades. Typical recycled content is 85%.
Manufacturability8
Ductile Iron Stress Relieved's machinability is very good (70/100, better than 96% of steel grades); weldability fair (38/100); formability not recommended (8/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Ductile Iron Stress Relieved
Is Ductile Iron easy to machine?
Machines better than steel of equal hardness — carbide at 150–300 m/min for ferritic/pearlitic grades, dry or with light coolant; watch for hard carbides in thin chilled sections and use CBN on Q&T/ADI.
Can Ductile Iron be welded?
Poor as-welded: use Ni or Ni-Fe electrodes (ENiFe-CI), 200–350 °C preheat, short low-heat beads with peening, then ferritize/stress-relieve to avoid carbides and martensite in the HAZ.
Can Ductile Iron be formed, bent or molded?
A casting alloy — green sand, shell, no-bake or permanent mold with Mg treatment plus late inoculation; feed for shrinkage and keep section modulus consistent since nodule count and matrix are section-sensitive, and it is not cold formed.
What surface finishes work on Ductile Iron?
No anodizing; shot blast then paint, powder coat, zinc/phosphate or electroless nickel; cement-mortar or fusion-bonded epoxy lining for water pipe; can be flame/induction hardened or nitrided for wear surfaces.
Ductile Iron 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; CE typically 4.3–4.6 | 3.2 – 3.9 | 3.6 |
| Sihigher Si strengthens ferrite, lowers toughness | 1.8 – 2.9 | 2.4 |
| Mnkept low for ferritic grades | 0.1 – 0.6 | 0.3 |
| Mgresidual Mg for nodularization | 0.03 – 0.06 | 0.04 |
| P | ≤ 0.05 | 0.03 |
| S | ≤ 0.02 | 0.01 |
| Cuoptional pearlite stabilizer (higher-strength grades) | 0 – 0.8 | 0.2 |
| Nioptional, hardenability/toughness | 0 – 1 | — |
| Mooptional, for ADI/Q&T sections | 0 – 0.4 | — |
| Fe | balance | — |
Ductile Iron Stress Relieved — frequently asked
What is Ductile Iron Stress Relieved used for?
Ductile Iron Stress Relieved is typically used for water and sewer pressure pipe and fittings, valve and pump housings, engine blocks and crankshafts, gearbox housings and gears, wheel hubs and steering knuckles and machine tool bases and heavy brackets. In short: stronger than gray iron.
What is the yield strength of Ductile Iron Stress Relieved?
Ductile Iron Stress Relieved has a typical yield strength of 320 MPa (46.4 ksi) and a tensile strength of 460 MPa (66.7 ksi) — weaker than 81% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is Ductile Iron Stress Relieved easy to machine?
Yes — machinability is rated very good (70/100, better than 96% of steel grades). Machines better than steel of equal hardness — carbide at 150–300 m/min for ferritic/pearlitic grades, dry or with light coolant; watch for hard carbides in thin chilled sections and use CBN on Q&T/ADI.
Can Ductile Iron Stress Relieved be welded?
With care — weldability is rated fair (38/100). Poor as-welded: use Ni or Ni-Fe electrodes (ENiFe-CI), 200–350 °C preheat, short low-heat beads with peening, then ferritize/stress-relieve to avoid carbides and martensite in the HAZ.
What surface finishes work on Ductile Iron Stress Relieved?
No anodizing; shot blast then paint, powder coat, zinc/phosphate or electroless nickel; cement-mortar or fusion-bonded epoxy lining for water pipe; can be flame/induction hardened or nitrided for wear surfaces.
Can Ductile Iron Stress Relieved be formed, bent or molded?
A casting alloy — green sand, shell, no-bake or permanent mold with Mg treatment plus late inoculation; feed for shrinkage and keep section modulus consistent since nodule count and matrix are section-sensitive, and it is not cold formed.
What is the maximum service temperature of Ductile Iron Stress Relieved?
Ductile Iron Stress Relieved is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Ductile Iron As Cast and Ductile Iron-ADI?
As Cast is the default condition — default stocked condition: best cost/strength balance for general machinery castings, housings and brackets. ADI: pick when you want steel-level strength and fatigue life plus useful ductility and wear resistance at casting cost — suspension arms, track links, gears, ground-engaging tools. Yield strength is 340 MPa in As Cast versus 750 MPa in ADI.
Can FabDigit make parts in Ductile Iron Stress Relieved?
Yes — Ductile Iron Stress Relieved is available for CNC machining and casting & forging; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM A536 — Standard Specification for Ductile Iron Castings — ASTM International (2019)
- ASTM A897/A897M — Austempered Ductile Iron Castings — ASTM International (2022)
- EN 1563 — Founding: Spheroidal graphite cast irons — CEN (2018)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- Ductile Iron Data for Design Engineers — Ductile Iron Society / Rio Tinto Iron & Titanium (2013)
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.