Austempered ductile iron grades
Who this helps: Design Engineers / Buyers evaluating austempered ductile iron (ADI) for gears, sprockets, arms and housings where high strength–fatigue and reasonable weight matter.
What you’ll get: a plain-English guide to austempered ductile iron grades, ASTM⇆EN cross-references, a strength–ductility cheat sheet, section-size (t-band) rules, acceptance notes you can copy-paste to drawings, and where ADI 1050 is the sweet spot.
Prepared by YB Metal Solution. Share your drawing via /rfq—YB Metal will return a part-specific ADI grade choice + cycle window, section review and a pilot test plan.
Author: YB Metal Solution Engineering Team (hereafter YB Metal)
Table of contents
- What “ADI grade” actually means
- Grade map: ASTM A897 ⇆ EN 1564 (with properties)
- Why ADI 1050 is the workhorse
- Pick the right grade: a quick decision path
- Section size, transfer time and chemistry notes
- Design & QA: what to put on the drawing
- Applications: where each grade shines
- What YB Metal delivers
- FAQs
What “ADI grade” actually means
An ADI grade specifies minimum tensile / yield / elongation delivered by a ductile iron that has been austempered (austenitize → rapid transfer above Ms → isothermal hold). The hold temperature sets the ausferrite balance and thus the strength–ductility trade-off.
- Deeper background: Open ADI Guide
- Process flow: ADI Casting Process
Grade map: ASTM A897 ⇆ EN 1564 (with properties)
Typical values at room temperature. Acceptances must be stated on the drawing/PO. Hardness is informational unless used for acceptance. EN properties depend on section thickness (t-band, usually t ≤ 30 mm / 1.18 in).
| ASTM A897 Grade | Nearest EN 1564 Grade (t ≤ 30 mm) | UTS Rm (MPa) | YS Rp0.2 (MPa) | Elong. A (%) | Hardness (HBW) | Usual hold band (°C/°F) | Use cues |
|---|---|---|---|---|---|---|---|
| 750-500-11 | EN-GJS-800-10 | 750 | 500 | 11 | 241–302 | ~330–380 / 625–715 | Brackets, arms with impact |
| 900-650-09 | EN-GJS-900-8 | 900 | 650 | 9 | 269–341 | ~320–360 / 610–680 | General structural parts |
| 1050-750-07 | EN-GJS-1050-6 | 1050 | 750 | 7 | 302–375 | ~300–340 / 572–644 | Workhorse housings, sprockets |
| 1200-850-04 | EN-GJS-1200-3 | 1200 | 850 | 4 | 341–444 | ~280–320 / 536–608 | Gears, chain wheels |
| 1400-1100-02 | EN-GJS-1400-1 | 1400 | 1100 | 2 | 388–477 | ~260–300 / 500–572 | Thin, highly loaded links |
| 1600-1300-01 (ASTM only) | — | 1600 | 1300 | 1 | 402–512 | ~260–290 / 500–554 | Steel-replacement niches |
- Cross-standard explainer: ADI Standards: ASTM A897 vs EN 1564
Grade trends & selection visuals: ADI Grade Selection Map - ASTM A897 – Austempered Ductile Iron Castings
- ISO 17804:2020 – Ausferritic spheroidal graphite cast irons — Classification
Inserts, edge prep & geometry
Grade/Coating:
- Gray iron: CVD-coated carbide handles abrasion; ceramic/PCBN for high-speed finishing (stable workholding only).
- Ductile iron: tougher PVD/CVD with honed edge (K-land) to resist chipping.
- Geometry: light-to-medium negative rake, strong edge hone for DI (e.g., hone 0.02–0.06 mm / .0008–.002 in); sharper edge for GI finishing.
- Hard spots: spot-use PCBN / ceramic where chill is proven; don’t blanket the process.
When to step up from 1050: thin, high-load teeth/links → 1200/1400.
When to step down from 1050: impact-critical brackets → 900/750 bands.
Pick the right grade: a quick decision path
What’s limiting—strength or fatigue?
- Gears, sprockets, linkages → start 1200; if life is over-achieving, relax to 1050.
- Housings/arms needing high strength but some impact → 1050.
- Impact-biased brackets → 900/750.
Section map (t-band) & transfer time
- Thin & uniform → high grades feasible.
- Heavy sections / long transfer → cap at 1050 or 900 unless you add Ni/Cu/Mo and lock a very short transfer.
Machining & fixturing
- Very hard grades (1200/1400) raise tooling load. If total cost matters, check 1050 first.
Section size, transfer time and chemistry notes
- Section (t-band) rules: EN 1564 lists properties by thickness. As thickness rises, maximum achievable grade drops unless chemistry and transfer time compensate.
- Transfer time: keep fast between austenitize and isothermal hold (above Ms). Delays cause pearlite—a property killer.
- Chemistry nudges: Ni/Cu/Mo help heavy sections but add cost—use them on purpose.
- Base casting must be sound: directional solidification, risers/chills at T/Y/X junctions to avoid shrinkage before heat treat. See Fix Shrinkage Porosity
- Minimum walls (for DI base): Minimum Wall for Ductile Iron
Design & QA: what to put on the drawing
Material & grade (example for 1050 workhorse):
Material: ASTM A897 Grade 1050-750-07 (or EN 1564 EN-GJS-1050-6, t ≤ 30 mm).
Austempering: Isothermal hold 300–340 °C (572–644 °F) above Ms to full ausferrite; no free pearlite.
Coupons: [separately cast / attached / from casting] — state in PO.
Hardness: 302–375 HBW (informational unless used for acceptance).
Casting & dimensional:
Casting tolerances per ISO 8062 (CT grade by size band). Maintain machining stock per control plan.
Supplier shall engineer directional solidification (risers/chills) at heavy junctions; provide layout.
QA acceptance (pilot & series):
Provide tensile (Rm/Rp0.2/A%) per grade, hardness (HBW), metallography (nodularity %, ausferrite present, no pearlite), and CMM FAI on datum stack.
Record austenitize temperature, hold setpoint and transfer time per lot.
Helpful references if you’re setting CT/GD&T:
Applications: where each grade shines
| Grade band | Typical parts | Why it fits |
|---|---|---|
| 750/900 | Shock-loaded brackets, arms, wheel hubs | Ductility/impact margin; machining friendlier |
| 1050 | Pump/comp housings, sprockets, drivetrain brackets | High strength with useful ductility; best economics |
| 1200/1400 | Gears, chain wheels, thin high-load links | Peak strength & fatigue; check tooling and cost |
| 1600 (niche) | Special links, compact high-load parts | Extreme strength; tight windows & high tooling load |
If NVH (damping) dominates over strength, consider gray iron housings instead: Why Gray Iron Wins NVH
What YB Metal delivers
YB Metal Solution quotes with an ADI grade plan attached:
- Grade recommendation with A897 ⇆ EN 1564 mapping tied to your section map.
- Cycle window: austenitize temperature, hold band, transfer-time limit, bath medium.
- Chemistry option (Ni/Cu/Mo) for heavy sections with cost/lead-time impact.
- Pilot evidence pack: tensile/hardness tables, metallography (ausferrite photos + nodularity %), and CMM FAI on critical features.
Need a part-specific plan? Upload your drawing—we’ll return recommendations and a quote.
FAQs
CTA — specify with proof, not guesses
Cut cycle time without burning inserts. Upload your drawing to /rfq—YB Metal will send cutting data, tool list, and a coolant/filtration plan tailored to your part.