ADI

Report
Foundry-Institut
Basics of ADI
(Heat treatment, structures, properties)
Dr.-Ing. Claudia Dommaschk
TU Bergakademie Freiberg, Germany
1
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
3
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
5
Influence
parameter:
Chemical
composition
Change of TTTdiagram caused by
alloying with Cu
and Ni
6
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)
15
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
16
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
18
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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19
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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