Micromechanical model of quenching deformation

1
(No Transcript)
2
Objective
3
Approach
4
Austempering
5
ADI
6
ADI
7
Advantage of ADI
8
Application
9
Application
10
Cast Iron
11
Three important
Three important points to consider when selecting
the chemical composition of ADI

• The iron should be sufficiently to avoid
  transformation to pearlite, but not over-alloyed
  to avoid the retardation of the bainite
  transformation.
• The microstructure should be free from
  intercellular carbides and phosphides.
• The tendency for chemical segregation should be
  minimized for the sake of uniformity in the cast
  component.

12
Ductile Iron
13
Si-Mo
14
Austenitic Ductile Iron
15
ADI Process
16
Austenitizing Tp
17
Quenching Time
18
Austempering Tp
19
Austempering Time
20
Case Study 1
21
(No Transcript)
22
Case Study 2
23
(No Transcript)
24
Salt Bath
Current technology for ADI
Salt bath furnace

• Salt bath is the method of heating steel using a
  bath of molten salts.
• Advantages rapid heating, superior temperature
  uniform and control, and protection from air to
  eliminate oxidation.
• Salt bath may create pollution problem because
  the toxicity of utilized salts.

25
Current technology for ADI
Air quenching

• The part should be placed on a suitable rack so
  the air can reach all section.
• The air must be free of moisture cracking of the
  metal.

Water quenching

• Water absorbs with atmospheric gases, and when
  the hot piece of metal is quenched, the gases
  have a tendency to form bubbles on the surface.

26
Gas Quenching
Alternative technology for ADI
1. Gas quenching

• High pressure vacuum furnaces combine heating and
  high pressure gas quenching at pressure up to 20
  bar.
• Advantages more uniform, minimizing residual
  stresses and distortion, clean and dry
  components, and so on.
• Disadvantages the cooling rate which achieved in
  gas is lower than obtained in oil.

27
Oil Quenching
Alternative technology for ADI
2. Oil quenching

• Oil is used to quench high speed and oil hardened
  steels and is preferred for all other steels.
• Oil quenching is undesirable because residual
  stresses, cracking, distortion and the problem in
  ecological, toxicological and safety.

28
Work Plan
Work Plan

• Find an industrial partner for experimentation in
  vacuum furnace.
• Design experiments
• - Materials
• - Part
• - Instrumentation
• - Data analysis
• 3. Analysis of microstructure - Bainite