ADI

Foundry-Institut

Basics of ADI

(Heat treatment, structures, properties) Dr.-Ing. Claudia Dommaschk

TU Bergakademie Freiberg, Germany

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Introduction Definition according to ASTM A 644-92: „A ductile cast iron that has been produced by a controlled thermal process which consists of predominantly acicular ferrite and high carbon

austenite“

Matrix:  (Residual) Austenite  Ferrite  no carbides ADI and Bainite is not identic!!!

The properties of ADI depend on the matrix and the nodule count and nodule shape. 2

Definitions Bainite = mainly acicular structure of Austenite, Ferrite and e-Carbides

Ausferrite = mainly acicular ferrite and high-carbon austenite

5000:1

5000:1

Ausferrite

Bainite

α

γ

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Definitions Heat treatment between pearlite- and martensitic range Austenite

Ausferrite

Martensite

Temperature

Temperature

Pearlite

Bainite

Time TTT-diagram for isothermal treatment of unalloyed cast steel

Time

4

Heat treatment Aim: Transformation of the perlitic matrix into the austenitic-ferritic structur

Base: Time-Temperature-Transformation diagram Austenite

Temperature

Pearlite

Ausferrite

Bainite

Martensite Time

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Influence parameter: Chemical composition

Change of TTTdiagram caused by alloying with Cu and Ni

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Heat treatment Austenitizing

 Heating up to a temperature range from 840 to 950 °C, holding for some hours for dissolving of perlitic matrix and C-saturation of austenite Austenite

Attention! Holding time to low: Temperature

Pearlite

Residue pearlite degrades the material properties

Ausferrite

Bainite

Martensite Time

7

Heat treatment Cooling:  fast cooling to a temperature range from 230 to 450°C (in front of the pearlitic nose)  Austenitic structure Austenite

Attention! Cooling to low: Formation of Pearlite

Temperature

Pearlite

Cooling to deep  Formation of Martensite Ausferrite

Bainite

Martensite

Time

8

Heat treatment

Isothermal holding:

 Holding on constant temperature (230 ..... 450°C)  Precipitation of ferrite splits, C-enrichment of austenite  Stabilization of austenite Austenite

Attention! Holding to long: Formation of Bainite

Temperature

Pearlite

Holding to short: Residual austenite Ausferrite

Bainite

Martensite

Time

9

Heat treatment Cooling to room temperature:  Cooling to room temperature with optional cooling rate  Austenite is stable to room temperature Austenite

Temperature

Pearlite

Ausferrite

Bainite

Martensite

Time

10

Effect of alloying elements:

Example Molybdenum: Displacement of the

 Alloying up to 0.5 % Molybdenum offer a

Temperature

Pearlite- nose to the right

lower cooling rate before isothermic holding

Time

11

Stability of the structure:

The ausferritic structure is thermodynamic instable - that means, it can disintegrate !

 Thermal durability to appr. 300°C – above transformation into pearlite  Limitation of using temperature of components  Welding of components not possible  Mechanical stability – stress introduced transformation into martensite (SITRAM)  Attention during machining of castings 12

Structures

ADI GJS-1000-5 orange = Austenite

light = Austenite

blue = Ferrite

dark = Ferrite 13

Structures

Carbides

ADI GJS-800-8 Compound of austenite and ferrite 14

Properties of ADI Specific adjustment of properties

High-strength and ductile material Very high-strength and wear resistant material but low ductility

Temperature (°C)

 Using of a suitable heat treatment

Time (h)

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Comparison of ADI with GJL and GJS EN-GJL

ADI

EN-GJS

100 bis 350

800 bis 1400

320 bis 700*

98 bis 285

500 bis 1100

200 bis 400* (0,2%)

0,8 bis 0,3

8 bis 1

18 bis 1*

Young´s Modulus kN/mm2

78 bis 143

165 bis 170

169 bis 176

Damping capacity

very good

good

good

Thermal conductivity W/(m.K)

43 bis 50

21 bis 22

31 bis 36 (300°C)

N/mm2

Tensile strength min. Yield stress min.

N/mm2

(0,1%)

Elongation min.

%

(300°C)

Machinability

very good

difficult

good

Castability

very good

very good

very good

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Tensile strength (Mpa)

Properties of grey iron, ductile iron and ADI

Elongation A5 (%) 17

Properties of ADI Hardness and abrasion resistant ... are determined by the ausferritic matrix

 High brinell hardness  High tensile strength  high abrasion resistant

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Standardisation DIN EN 1564

Tensile Strength min. N/mm2

0.2 % yield stress min. N/mm2

Elongation %

EN-GJS-800-8

800

500

6 bis 15

EN-GJS-1000-5

900

600

5 bis 12

EN-GJS-1200-2

1200

950

2 bis 5

EN-GJS-1400-1

1500

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Fields of application High strength components for the automotive engineering 304.8 m

3 0 4 .8 m m (1 2 in )

Crankshaft of steel (34,0 kg)

Crankshaft for a sports car: ADI substitute steel 3 0 4 .8 m m (1 2 in )

Crankshaft of ADI (29,9 kg) 20

Fields of application 10-cylinderdiesel engine 1010

Carrier Plate, EN-GJS-800-8 21

Fields of application

Horse shoe of ADI (source: ADI Treatments)

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