01.10.2014 Views

Introduction to Basic Manufacturing Processes and ... - always yours

Introduction to Basic Manufacturing Processes and ... - always yours

Introduction to Basic Manufacturing Processes and ... - always yours

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

134 <strong>Introduction</strong> <strong>to</strong> <strong>Basic</strong> <strong>Manufacturing</strong> <strong>Processes</strong> <strong>and</strong> Workshop Technology<br />

δ iron<br />

Temperature°C<br />

δ Fe + liquid<br />

1600<br />

A t 1<br />

1500<br />

B<br />

H J<br />

t 2<br />

1400 δ-Iron<br />

+<br />

Austenite<br />

1300<br />

1200<br />

1100<br />

1000<br />

G<br />

900<br />

800<br />

723<br />

700<br />

α-Iron<br />

Fe 600<br />

500<br />

Solidus<br />

Austenite<br />

γ-iron<br />

Fe+Austenite<br />

( α+ γ)<br />

A 3<br />

P S<br />

0.025%<br />

Carbon<br />

Eutec<strong>to</strong>id<br />

Liquid<br />

γ S olid Solution<br />

crystals<br />

t 3 Liquidus<br />

(Austenite)<br />

t 4<br />

E<br />

1130°<br />

Solidus<br />

Austenite<br />

+<br />

Acm Ledeburite<br />

Austenite<br />

+<br />

Cementite<br />

A 1<br />

C<br />

Eutectic<br />

Liquid<br />

+<br />

Cementite<br />

Cementite<br />

+<br />

Ledeburite<br />

D<br />

F<br />

K<br />

400<br />

300<br />

200<br />

Fe +<br />

Pearlite<br />

Pearlite<br />

+<br />

Cementite<br />

Cementite<br />

+<br />

Pearlite<br />

+<br />

Ledeburite<br />

Cementite<br />

+<br />

Ledeburite<br />

100<br />

Q 0.8<br />

0<br />

1<br />

H ypoeutec<strong>to</strong>ieutec<strong>to</strong>id<br />

H yper-<br />

2 3 4 4.3 5 6 6.7<br />

Steel<br />

Cast Iron<br />

Carbon Percentage<br />

Fig. 8.6 Fe-C equilibrium diagram<br />

8.6.1.1 Austenite<br />

Austenite is a solid solution of free carbon (ferrite) <strong>and</strong> iron in gamma iron. On heating<br />

the steel, after upper critical temperature, the formation of structure completes in<strong>to</strong> austenite<br />

which is hard, ductile <strong>and</strong> non-magnetic. It is able <strong>to</strong> dissolve large amount of carbon. It is<br />

in between the critical or transfer ranges during heating <strong>and</strong> cooling of steel. It is formed<br />

when steel contains carbon up <strong>to</strong> 1.8% at 1130°C. On cooling below 723°C, it starts transforming<br />

in<strong>to</strong> pearlite <strong>and</strong> ferrite. Austenitic steels cannot be hardened by usual heat treatment methods<br />

<strong>and</strong> are non-magnetic.

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!