ADI Casting Process: From Heat Treatment to Performance

Table of contents

What the ADI casting process covers

ADI = ductile iron casting + austempering heat treatment.
The casting route (green/resin/shell) sets soundness, CT grade and machining stock. The austempering cycle converts a nodular-iron matrix into ausferrite (acicular ferrite + high-carbon austenite), enabling high strength–fatigue with useful toughness.

Quick primer: Open ADI Guide

Step-by-step flow: from melt to austemper

Melt → treat → inoculate (make a sound DI base)

• Stable Mg treatment and inoculation to achieve nodularity & nodule count appropriate for the section map.
• Pick the molding process by geometry/throughput:
• Green Sand Casting
• Resin vs Green Sand
• Shell Molding for Thin-Wall

Austenitize

Typical 840–920 °C (1545–1690 °F) with soak long enough to homogenize carbon and dissolve pearlite/carbides.

Quench/transfer above Ms

Rapid transfer into the isothermal bath (salt/alkaline) above Ms; minimize delay to avoid pearlite formation—especially on heavy sections.

Isothermal hold (austemper)

• Hold ≈260–380 °C (500–715 °F) until transformation to ausferrite completes.
• Lower hold → higher strength, lower ductility.
• Higher hold → lower strength, higher ductility.

Rinse, stabilize (if specified), inspect

Clean; optional stabilization/temper per control plan. Maintain heat-treat lot traceability to the casting heat.

Process window & controls: Austempering Cycle—Quality Gates

ASTM A897 – Austempered Ductile Iron Castings (official)

EN 1564 – Ausferritic spheroidal graphite cast irons (BSI official catalogue)

Grades vs hold temperature (how properties are set)

Choose the grade by load case & section size; confirm acceptance on the drawing/PO.

Cross-standard notes: ADI Standards: ASTM A897 vs EN 1564

Selection map: ADI Grade Selection (Strength–Ductility)

Section size, transfer time & chemistry nudges

Section (t-band) governs achievable grade; heavier sections require short transfer time and often Ni/Cu/Mo additions.

Respect minimum walls for the ductile-iron base: Minimum Wall for Ductile Iron

Engineer directional solidification (risers/chills) at T/Y/X junctions to eliminate shrinkage before heat treatment: Fix Shrinkage Porosity

Confirm coupon strategy (separately cast/attached / from casting) early; it affects reported properties.

Corrosion choices: Coatings vs Material

Quality gates & acceptance (PPAP-ready)

Metallurgy

• Nodularity % per spec; ausferrite present, no free pearlite (unless allowed).
• Hardness band per grade (informational unless used as acceptance).

Mechanical:

• Tensile (Rm/Rp0.2/A%) per A897/EN 1564 grade; impact if required.

Dimensional:

• CT per ISO 8062; keep machining stock for critical faces.
• ISO 8062 CT Grades
• Open GD&T Guide

Documentation：

• PPAP/FAI: tensile/hardness tables, metallography photos (ausferrite micrographs), CMM FAI on datum stack.
  • PPAP Levels & Docs
  • Foundry Quality KPIs

Cycle guidance & QA: ADI Process Window

Machining, distortion & coating notes

• Machinability: ADI cuts tougher than DI—use robust carbide, edge prep, and coolant strategy; see Machinability: Gray vs Ductile Iron — /machinability-gray-vs-ductile-iron-tool-life-coolant
• Distortion: fixture during heat treatment and machining; for big housings reference Heat-Treatment Distortion Control
• Corrosion: ADI ≈ DI—pick stacks per environment: Corrosion—Coatings vs Material Choices

What to put on the drawing

Material & heat treatment

Material: ASTM A897 Grade 1050-750-07 (or EN 1564 EN-GJS-1050-6, t ≤ 30 mm).
Coupons: [separately cast / attached / from casting] — state in PO.
Austempering: Hold 300–330 °C (572–626 °F) above Ms to full ausferrite; no pearlite allowed.
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.
Provide riser/chill plan for heavy junctions; avoid isolated pads.

QA (pilot & series):

Provide tensile (Rm/Rp0.2/A%), HBW, metallography (nodularity %, ausferrite check), and CMM FAI on datums. Record transfer time and bath setpoint per lot.

• Machining: carbide inserts, control heat; ADI is tougher than DI—optimize speeds/feeds and tool edge prep. Reference: Machinability: Gray vs Ductile Iron
• Distortion: fixture for stability; for large housings, see Heat-Treatment Distortion Control
• Coating: ADI ≈ DI for corrosion; pick stack & DFT by environment: Coatings vs Material
• Welding: generally not recommended; if allowed, qualify and consider re-austempering.

What YB Metal delivers

YB Metal Solution quotes with an ADI casting process plan attached:

• Grade decision matched to your section map & load case (A897 ⇆ EN 1564).
• Cycle window: austenitize temperature, hold band, transfer-time limit, bath medium.
• Chemistry nudges (Ni/Cu/Mo) for heavy sections with cost/lead-time impact.
• Pilot evidence pack: tensile/hardness tables, metallography (ausferrite photos), optional impact, and CMM FAI on critical features.

Need a plan for your part? Upload your drawing at /rfq—we’ll return recommendations and a quote.