Austempered Ductile Iron (ADI), also known as ausferritic ductile iron, is the most recent addition to the ductile iron family. It is produced by giving conventional ductile iron a special heat treatment called “austempering”.

The austempering heat treatment transforms ductile iron to ADI, bringing about excellent strength, toughness, and fatigue characteristics.

EXPERIMENTAL PROCEDURE Two heats(H1andH2) of spheroidal graphite iron were produced in a

tea spout ladle method.

charges consist of 100kg pig iron, 400kg SG returns , 500kg steel scrap , 35kg coconut charcoal

1.3 kg of 75% foundry grade ferrosilicon

Melted in 1000kg capacity of coreless induction furnace 2 kg of cu was added in second heat during melting .

Tapping &pouring of metal to ensure the high level of nodule count .

The final chemistry of iron treated iron given In table 1

HEAT

C Si

M n S P Cr Ni Mo Cu Mg

H1 3.65

2.22

0.16 0.009

0.024

0.02 0.05 0.02 0.06 0.04

H2 3.64

2.19

0.17 0.010

0.023

0.02 0.05 0.02 0.45 0.046

Table1: Final chemistry of treated iron (wt %)

The treated iron was poured into dry sand mold bounded with furan resin catalyst to cast Y block as per ASTM 897

For each heat three molds were poured . After 48 hours pouring ,casting ,cut specimen by austempering process then sample heat 900c, for 1 hour muffle furnace ,austemperd in salt bath

maintaning 3 diff . Temp ,Time, Sample machined &polished as per standard for XRD analysis.

1. A-B: Heating up to austenizing temperature

2. B-C: Holding at austempering temperature

3. C-D: Quenching to the austempering temperature

4. E-F: Air cooling to the room temperature

FIG 1 : Austempering process

RESULTS AND DISCUSSIONSXRD analysis performed for both the sample of H1 &H2

FIG 2 : Control of Time and Temperature on the process

The attractive properties of ADI are due to the uniqueness in its microstructure which consist of

1)Ferrite (α)

2)High carbon austenite (γHC)

The product of austempering reaction in DI is refferd to as ausferrite rather than bainite.

The XRD pattern of austemperd ductile iron (H1) austemperd at different temp and different time shown in fig (3,4,5,6,and7)

Fig.3: Austempered at 2500C for one hour

Fig.4:Austempered at 2500C for one and half hour

Fig.5: Austempered at 2500C for two hours Fig.6: Austempered at 3000C for one hour

Fig.7 : Austempered at3500C for one hour

The bainitic transformation in austemperd ductile ductile iron has 2 stage phase trasformation

Stage 1: γα + γ HC

Stage 2: HC α + Carbide (steel brittle)

The XRD pattern of austempered ductile iron (H2) austempered at different temperatures and different times as shown in following figures (Fig 8, 9, 10, 11,and 12).

Fig.8: Austempered at 2500C for one hour

Fig.9: Austempered at 2500C for two hours

The best combination of mechanical properties in ADI can be obtained after the completion of the first stage reaction but before the onset of the second reaction. The time interval between the completion of the first reaction and the onset of the second reaction is termed as ‘‘process window’’.

Fig.10 : Austempered at 2500C for half an hour

Fig.11. Austempered at 3500C for one hour

Fig.12: Austempered at3000C for one hour

Stage 1Cu supresses carbide formation in lower bainite .Cu widen the austenite zone of phase diagram .

Stage 2 Due to Cu addition and results in prevention of properties

APPLICATION OF ADI