Guided by YB Metal — Austempered Ductile Iron process, simulation-led gating/risers, in-house machining, and traceable QA.
Austempered ductile iron (ADI) combines castability with steel-like strength and wear. This guide shows the process window (austenitize & austemper), grade options (ASTM A897 / EN 1564 style), section size limits, and where ADI outperforms steel—plus design/machining rules and test plans you can drop into your RFQ.
Table of contents
- What is ADI and why it’s different
- Process window: austenitize → quench → austemper
- Grades & properties (indicative tables)
- Section size & alloying (Ni/Cu/Mo)
- Design & machining rules for ADI
- Where ADI beats steel (and where it doesn’t)
- Quality & testing plan (what to specify)
- FAQs
What is ADI and why it different
ADI is ductile iron that’s austenitized then isothermally transformed to an ausferritic matrix (acicular ferrite + high-carbon austenite). You get high strength/toughness with cast geometry freedom, damping, and good wear—often at lower cost per finished part than alloy steels that need machining from forgings.
Process window: austenitize → quench → austemper
Values below are practical ranges; confirm with your heat-treater for your section size and chemistry.
Table A — Typical ADI heat-treat window (indicative)
| Step | Parameter | Practical range (°C / °F) | Typical time |
|---|---|---|---|
| Austenitize | Furnace setpoint | 840–900°C / 1545–1650°F | 0.5–2 h (by section) |
| Quench to salt | Transfer time | ≤ 10–30 s | — |
| Austemper | Bainitic salt setpoint | 230–400°C / 446–752°F | 0.5–3 h (by grade) |
| Rinse/temper | Stabilize | Water/oil/air as spec | — |
- Lower austemper temps (230–300°C / 446–572°F) → higher strength, lower elongation, higher hardness.
- Higher austemper temps (330–400°C / 626–752°F) → higher ductility & impact, lower hardness.
Grades & properties（indicative, for selection）
Use these as spec starting points; for purchase specs, cite ASTM A897 or EN 1564 grade callouts.
Table B — ADI property tiers vs austemper temperature (indicative)
| Austemper setpoint | UTS (MPa / ksi) | YS (MPa / ksi) | Elong (%) | Hardness (HBW) | Use case |
|---|---|---|---|---|---|
| 230–270°C (446–518°F) | 1400–1600 / 203–232 | 1000–1200 / 145–174 | 1–3 | 430–500 | High wear & strength (gears, sprockets) |
| 300–340°C (572–644°F) | 1050–1200 / 152–174 | 750–900 / 109–131 | 4–7 | 320–400 | Balanced strength/ductility (axles, knuckles) |
| 360–400°C (680–752°F) | 800–900 / 116–131 | 600–700 / 87–102 | 8–12 | 269–330 | Impact & fatigue (suspension, brackets) |
Table C — Common grade labels you’ll see
| Standard | Examples (callout style) | Notes |
|---|---|---|
| EN 1564 | EN-GJS-800-10, 900-8, 1050-6, 1200-3, 1400-1 | First number ≈ UTS (MPa), second ≈ elongation (%) |
| ASTM A897 | ADI 800-10, 900-8, 1050-7, 1200-4, 1400-1 (naming varies by revision) | Order sheet should list min tensile/elongation + hardness window |
Section size & alloying（hardenability matters）
Table D — Practical section size guidance（indicative）
| Chemistry set | Max effective section for high-strength ADI* | Notes |
|---|---|---|
| Base ductile iron (low alloy) | ≤ 25–35 mm (1.0–1.4 in) | For 230–300°C grades; slower cooling risks pearlite/banite mix |
| Ni-Cu alloyed DI | ≤ 40–50 mm (1.6–2.0 in) | Ni/Cu boost hardenability; best for balanced grades |
| Ni-Cu-Mo alloyed DI | ≤ 50–65 mm (2.0–2.6 in) | Small Mo additions help thick sections—control to avoid carbides |
*Effective section = the thinnest path for heat extraction in the casting region of interest.
Pro Tip by YB Metal: Ask your foundry for a critical thickness map from simulation and a chemistry window (C, Si, Ni, Cu, Mo) tied to your target grade.
Design & machining rules for ADI
- Cast for uniform sections; use ribs + R ≥ 3–5 mm (0.12–0.20 in) to avoid hot spots and microshrinkage.
- Core simplification lifts yield and reduces tool wear.
- ISO 8062-3 CT grades: green sand CT9–CT10, no-bake CT8–CT9, shell CT6–CT7.
- Machine before austempering whenever possible; after austempering, use rigid fixturing and coated carbides.
- Surface finish targets: as-cast Ra 6.3–12.5 μm (250–500 μin); machined Ra 1.6–3.2 μm (63–125 μin).
- Fasteners: design for cored holes sized to standard taps; avoid post-austemper drilling in high-HBW grades when you can.
Where ADI beats steel (and where it doesn’t)
Table E — ADI vs common steels（part-level perspective）
| Aspect | ADI (by grade) | Typical alloy steel (e.g., 1045N / 4140 Q&T) | So what? |
|---|---|---|---|
| Net-shape potential | High (cast) | Low (machined from bar/forging) | Lower machining, complex geometry okay |
| Strength/weight | 800–1600 MPa UTS options | 600–1100 MPa typical | Pick grade to light-weight brackets/hubs |
| Wear + damping | Good wear (low-temp ADI) + high damping | Wear via Q&T; low damping | Less noise/vibration; longer life in abrasive duty |
| Cost per finished part | Often lower at volume | Higher (material + machining) | ADI wins when machining minutes dominate |
| Through-section hardenability | Limited by section | Better in very thick parts | For >65 mm thick, steel may win |
| Field welding/repair | Not preferred | Easier | Design for bolt-on or bimetal wear faces |
Rule of thumb: If your part is ≤ 50 mm effective section, has complex geometry and wear/strength goals, ADI is a strong steel alternative.
Quality & testing plan
Table F — Acceptance tests & documents
| Topic | Spec / Method | Notes |
|---|---|---|
| Material certs | Chemistry (OES), HBW hardness map | Map hardness across critical zones |
| Tensile | Per ASTM A897 / EN 1564 grade callout | Record UTS/YS/Elong; list test location |
| Microstructure | Ausferrite verification | Nital/LePera etch; % ausferrite target (qualitative) |
| Dimensional | ISO 8062-3 per drawing | CMM on datums; mismatch control |
| NDT (as needed) | RT/UT on hot spots; DPI/MPI for cracks | Define zones & levels |
| Surface | Ra check on machined faces | 1.6–3.2 μm (63–125 μin) typical |
| Process | Heat-treat logs | Austenitize & austemper temps/times; transfer time |
Why YB Metal for ADI
- One roof: green sand / no-bake / shell + machining + austempering partners
- Simulation-led risers/chills; critical thickness mapping
- Hardness mapping & serialized traceability for heat-treat lots
- PPAP/FAI package with CMM, material, and NDT, where required
FAQs
CTA — get ADI with proof, not promises
YB Metal delivers ADI castings with simulation, controlled heat-treat windows, and documented QA so engineering and SQE can sign off fast.