Transcript ADI
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
---
---
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)
22
23
24