Lecture 10 Cast Iron

Dong-A University

Lecture 10. Cast iron

Dong-A University Page 2

Casting

Melting point

Shape forming

Property


How to reduce M.P.

Microstructure

+ Fe3C ?

Dong-A University

Cementite vs. Graphite

Page 4

Super-saturated

+ Fe3C + C(graphite)

By carbon diffusion By MORE carbon diffusion

Meta-stable state Stable state

Formation condition

of cementite and graphite(pure carbon)

C content

Diffusion time

Dong-A University

Microstructures of cast iron

Page 5

(White cast iron) Cementite + pearlite

(gray cast iron) Ferrite + pearlite + flake carbon

(malleable cast iron) Ferrite + temper carbon

(Nodular/ductile cast iron) Ferrite/pearlite + nodular carbon

Chilled cast iron

Compacted/vermicular cast iron (C/V)

Austempered cast iron (ADI)

Alloyed cast iron

, , ,

Ausferrite acicular ferrite+carbon = stabilized austenite

Strongest cast iron

Si : , Al : Ni : Cr : ,


Form Description of t

he form

Main spatial

characteristics Occurrence

I Lamellar (flake)

graphite

Interconnected particles

within eutectic cells;

lamellar (flake) graphite

with sharp ends

Principal form in grey cast iron

Austenitic cast iron with

lamellar/flake graphite

Can occur in the rim zone of other ca

st-iron materials

II Crab graphite Aggregate of graphite

flakes

Can occur in rapidly cooled

hypereutectic grey cast irons

Can also occur in segregation areas

of thick-walled spheroidal-graphite

cast-iron castings

III

Compacted (ve

rmicular)

Graphite

Usually interconnected par

ticles within eutectic

cells; worm-like

appearance with

rounded ends

Principal form in compacted-graphite

cast irons

Can occur in spheroidal graphite

cast irons

IV

Temper carbon

Irregular sphero

idal graphite*

Isolated particles Principal form in malleable cast irons

Can occur on spheroidal-graphite

cast iron

V

Slightly irregula

r spheroidal

Graphite

Isolated particles

Principal form in thick-walled casting

s made of spheroidal graphite cast ir

ons

Occurs to a specified extent in comp

acted-graphite cast irons

Can occur in malleable cast irons

VI Spheroidal gra

phite* Isolated particles

Principal form in castings made of

spheroidal-graphite cast irons

Occurs to a specified extent in

compacted-graphite cast irons

Table1: Graphite forms

Dong-A University

Si effect on Fe-C phase diagram

Page 10

+ Fe3C + L

Graphite(or Fe3C)

stabilizing

Dong-A University

Solidification sequence

Page 11

Dong-A University

Eutectic cell and nodule counts

Page 12

Dong-A University

Graphite in gray cast iron ASTM A247-10

Page 13

Fast cooling Low C.E.

Slow cooling

A+D Hyper-eutectic

Dong-A University

Graphite microstructure ASTM A247-10

Page 14

Type A

Type B

Type C

Type D

Type E

Dong-A University

Inoculation

Page 15


Phases during austempering treatment

Lecture 10 Cast Iron

Documents

Transcript of Lecture 10 Cast Iron