Investigation of the Graphite Nodule, with Special Reference to Its Relation to the Nodulizer

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INVESTIGATION 0 ? THE GRAPHITE NODULE, WITH SPECIAL REFERENCE TO I T S RELATION TO THE NODULIZER !■137? ART COLORADO c-DUOOl. OF GO juD fc.N. COLORADO

By B h a g w a n M. Ma.nl a r

ProQuest Number: 10781422

All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is d e p e n d e n t upon the quality of the copy subm itted. In the unlikely e v e n t that the a u thor did not send a c o m p le te m anuscript and there are missing pages, these will be noted. Also, if m aterial had to be rem oved, a n o te will ind ica te the deletion.

uest ProQuest 10781422 Published by ProQuest LLC(2018). C opyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States C o d e M icroform Edition © ProQuest LLC. ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 4 8 1 0 6 - 1346

A th ee ls

s u b m itte d to t h e F a c u l t y and t h e Board o f

T r u s t e e s o f t h e C o lo ra d o S c h o o l o f Mlnee I n p a r t i a l f u l ­ f i l l m e n t o f th e re q u ire m e n ts f o r th e d e g re e of M aster o f S cien ce.

S ig n e d

j

lu‘Bhagwwr-M r M aniar

A p p roved *

G o ld e n 9 C o lo r a d o . D ate

jJr. 1 9 5 0 .

ACKNOWLEDGMENT I w i s h t o e x p r e s s my i n d e b t e d n e s s t o P r o f e s s o r *

C l a r k B. C a r p e n t e r ,

He ad o f t h e D e p a r t m e n t o f M e t a l ­

lu rg y , a t th e C olorado School o f M ines, G olden, C o lo rad o , f o r su g g e stin g th e problem , f o r th e gen ero u s use o f h i s p e rs o n a l l i b r a r y , and f o r h i s g u id a n c e . I am a l s o g r a t e f u l t o D r . R. T. P h e l p s ,

o f t h e De ­

p a r t m e n t o f M e t a l l u r g y , who h a s g i v e n much o f h i s v a l u a b l e tim e to w a rd s th e In v estig a tio n ,

s u p e r v i s i o n o f X -ray and s p e e tr o c h e m ic a l

a n d f o r t h e w i d e us© o f h i s l a b o r a t o r y .

My t h a n k s a r e d u e t o P r o f e s s o r M. C. S m i t h , o f t h e D epartm ent o f M e ta llu rg y , a v ailab le

f o r h i s c o n s t a n t h e l p and m aking

t o me t h e f a c i l i t i e s

of h is lab o rato ry .

I am a l s o v e r y m uch o b l i g a t e d t o D r . L. B. G u l b r a n s e n , o f th e D epartm ent o f M e ta llu r g y ,

f o r h i s w i l l i n g h e lp and

g u id a n c e i n t h e X -ra y and s p e c tr o c h e m ic a l work.

TABLE OF CONTENTS

FAGS HISTORY AND INTRODUCTION................. ................................................

1

T r e n d s i n M e t a l l u r g y o f C a s t I r o n ............................

1

S ubject of the T h e s is

............ ...........................

4

PRODUCTION AND THEORIES OF NODULAR CAST IRON.............

6

P ro d u c tio n .

..........................................................................

6

................................................................

7

M orro g h* s T h e o r y . .

De S y ’ s T h e o r y ..................

12

o f De S y ’ s T h e o r y ..................

17

D is c u s s io n of th e T h e o rie s and th e A u th o r’ s P o i n t o f View ................................................................

19

D o u b l e T r e a t m e n t P r o c e s s .........................

20

R a d i a l S t r u c t u r e ........................................................................

21

FLAKE AND NODULAR GRAPHITE IN CAST IRON..........................

22

M orrogh’ s C r i t i c i s m

S tru ctu re

o f t h e G r a p h i t e F l a k e . ..............................

22

A dvantages o f N odular G ra p h ite o v er Flake G r a p h i t e . .................................

23

S tru ctu re

24

o f t h e G r a p h i t e N o d u l e ...............................

EXPERIMENTAL WORK............................

26

M ic ro sc o p ic E x a m in a tio n o f t h e N odules u n d e r O r d i n a r y a n d P o l a r i z e d L i g h t .........................................

27

E x p e r i m e n t a l w o r k .....................................................

27

C o n clu sio n s.

...........................................................

29

E x t r a c t i o n o f N odules and O th e r Shapes o f G r a p h i t e ............................................................................................

30

E x p e r i m e n t a l w o r k ..............................................................

30

C o n c l u s i o n s .....................................................................

31

S p e c t r o g r a p h ! c W o r k ................................................................

36

TABLE OF CONTENTS

(C ontinued) PAGE E xperim ental

w o r k ............................................

C o n c l u s i o n s ..................................................................... X - r a y P a t t e r n s ............................................................... E xperim ental

w o r k ....................................

C o n c l u s i o n s ...................................... S uggestions fo r

F u rth e r E xperim ental W o rk ....

SUMMARY...........................................................................................

36 37 46 46 48 52 53

%

CONCLUSION...................................

55

BIBLIOGRAPHY...............................................................................................

53

L IS T

OF FIGUKE3

1.

G rap hite

l a t t i c e . .................... .............. , .................................

24

2.

S chem atic r e p r e s e n t a t i o n of th e o r i e n t a t i o n o f g r a p h i t e c r y s t a l l i t e s ' i n c a r b o n n o d u l e s ................

24

3.

G r a p h i t e n o d u l e i n o r d i n a r y l i g h t ..............................

27

4.

Same n o d u l e , a s F i g . 3» b e t w e e n c r o s s e d n i c o l s .

27

5.

G r a p h i t e n o d u le show ing s l i g h t p o l a r i z a t i o n i n o r d i n a r y l i g h t . . . . .....................................................................

27

Same n o d u l e s h o w i n g r a d i a l s t r u c t u r e i n p l a n e p o l a r i z e d l i g h t ...............................................................

27

Same n o d u l e s h o w i n g d i s t i n c t r a d i a l b e t w e e n c r o s s e d n i c o l s ....................

27

6.

7. 8.

stru c tu re

G r a p h i t e n o d u l e s b e tw e e n c r o s s e d n i c o l s show ing d u p l e x s t r u c t u r e ..........................................................................

28

G r a p h i t e n o d u l e s b e t w e e n c r o s s e d n i c o l s ...............

28

10.

G raphite

f l a k e s a t 7 1 0 X .......................................................

33

11.

G r a p h i t e f l a k e s a t 1 5 0 X ........................................................

33

9.

12.

M eehanite g r a p h i t e

f l a k e s a t 3 9 0 X ................

33

13.

M eehanite g r a p h i t e

f l a k e s a t 1 5 0 X .............. .

33

14.

U nsuccessful nodular g ra p h ite

f l a k e s a t 150X ..

34

15.

M odular g r a n h l t e w i t h q u a s i f l a k e s

at

39O X .. . .

34

16.

N odular g r a p h i t e w ith q u a s i f l a k e s

at

390X .. . .

34

3 9 0 X .........................

35

17.

C om pletely n o d u la r g r a p h i t e a t

18.

C om pletely n o d u la r g r a p h i t e

a t 7 1 0 X .........................

35

19.

C o m p l e t e l y n o d u l a r g r a p h i t e a t 7 1 0 X .........................

35

20.

S p ectro g rap h ic p la te

No. 1 ...........................

39

21.

S p ectro g rap h ic p la te

No.

2 . . . ........................................

40

22.

S p ectro g rap h ic p la te

No.

3 ................................................

41

23.

C om parator p i c t u r e

of carbon b la n k s ,P la te

3...

4-2

L IS T

OF FIGURES

( C ontinued) fag ;

24.

C om parator p i c t u r e

25*

C om parator p i c t u r e o f n o d u la r g r a p h i t e 13, Plafce 3 ...........* ..............* * * ........................ * .................. *

42

C om parator p i c t u r e o f n o d u la r g r a p h i t e 13, P l a t e 2 .................................................................................................

42

C om parator p i c t u r e o f n o d u la r g r a p h i t e 16, P l a t e 3 .................................................................................................

42

C om parator p i c t u r e o f n o d u la r g r a p h i t e 16, P l a t e 2 ................................ ................................................................

42

26. 27* 28. 29* 30. 31.

o f carbon b la n k s ,

P late

2 ..

42

C om parator p i c t u r e o f u n s u c c e s s f u l n o d u l a r g r a p h i t e 1 7 , P l a t e 3 .......................................................

43

C om parator p i c t u r e o f u n s u c c e s s f u l n o d u la r g r a p h i t e 1 7 , P l a t e 2 .......................................................

43

C om parator p i c t u r e o f M eehanite a l l o y g r a p h i t e , P l a t e 3 .................................................................................................

43

C om parator p i c t u r e o f M eehanite a l l o y g r a p h i t e , P l a t e 2 ................................................................................................

43

C om parator p i c t u r e o f M eehanite p l a i n g r a p h i t e , P l a t e 3 ......................................................................................

43

34.

C om parator p i c t u r e

o f g r e y i r o n g r a p h i t e , P l a t e 3*

;-4

35*

C om parator p i c t u r e

o f g rey i r o n g r a p h i t e , P l a t e 2.

44

36.

C om parator p i c t u r e o f n o d u la r g r a p h i t e 13, P l a t e 3 ...............................................................................

44

C om parator p i c t u r e P l a t e 2 ______

44

32. 33.

37.

o f n o d u la r srraohite

13,

38.

C om parator p i c t u r e . o f c a rb o n b l a n k s ,

P late

3.*

44

39*

C om parator p i c t u r e

P late

2 ..

44

1 3 .........................

49

of carbon b la n k s,

40(a)X -ray p a tte rn

of nodularg ra p h ite

40(b)X -ray p a tte r n

o fco m p letely n o d u lar g r a p h ite

16.

49

40(c)X -ray p a tte r n

ofcom pletely n o d u lar g r a p h ite

16*

49

LIST OF FIGURES (C ontinued) pag:

4 0 (d)X -ray p a tte r n

of u n su c ce ssfu l nodular g ra p h ite .

49

40{e)X -ray p a tte r n

o f M eehanite a l l o y g r a p h i t e . . . . .

49

40(f)X -ray p a tte rn

of grey iro n g

r

a

p

h

i

t

e

,

49

LIS T OP TAPIRS

I ,

X

C om parison o f Coat and Prooe Ferrous A llo y s . ..............

II ,

T a b le o f C r y s t a l S y s t e m s .

J - I

T a b le o f Md w V a l u e s o f L i n e s

vf

X. HISTORY AND INTRODUCTION T rends In M etallurg y o f C ast Iro n The m e t a l l u r g y o f c a s t i r o n h a s a d v a n c e d g r e a t l y d u r i n g th e

last fifty

years,,

At t h e end o f th e n i n e t e e n t h o e n t u r y ,

the

m ainim p o rta n c e o f c a s t i r o n l a y i n i t s e x c e l l e n t f l u i d i t y

--its

s t r e n g t h was n o t a f a c t o r o f g r e a t v a l u e .

ever,

c a s t iro n w ith i t s

tility ,

in creased

has begun to re p la c e

ten sile

steel

T o d a y , how­

s t r e n g t h and d u c ­

I n some p h a s e s o f i n ­

d u s t r y . 1*7 T his hig h f l u i d i t y

o f c a s t i r o n i s due t o

its

high c a r ­

bo n c o n t e n t , w h ic h i s one o f t h e f a c t o r s t h a t d i f f e r e n t i a t e c a s t i r o n s from s t e e l s . above th e

so lu b ility

The h i g h c a r b o n c o n t e n t ,

lim i t of carbon in

so lid iro n ,

c a st iro n s th e ir c h a r a c te r is tic m icro stru ctu re embedded i n a s t e e l - l i k e

m atrix .

w hich i s

T his fr e e

g iv es to

of free

carbon

carbon o r g ra p h ite

in t u r n g iv e s to c a s t ir o n s t h e i r o th e r Im po rtant p r o p e r t i e s o f s u p e r i o r m a c h i n a b i l l t y , good w ear r e s i s t a n c e , o a p a c l t y , a n d so o n . tio n , its

As t h e r e a r e

h i g h dam ping

tw o s i d e s t o e v e r y q u e s ­

c a s t i r o n d e r i v e s from c a rb o n , b o th i t s b e n e f i c i a l and

in ju rio u s p ro p erties.

be b r i t t l e

G rap hite

and o f low t e n s i l e

D uring th e f i r s t

causes the c a s t iro n s to

stren g th .

h a lf of these

fifty

years,

progress in

t h e t e c h n o l o g y o f c a s t i r o n s was d i r e c t e d t o w a r d s 1 ) i m p r o v e ­ ment i n t h e

s t e e l m a t r i x a n d 2} r e d u c t i o n o f t h e a m o u n t o f

t o t a l c a r b o n and t h e r e b y o f th e amount o f g r a p h i t e .

Then i n

t h e m i d - t w e n t i e s , m a l l e a b l e c a s t i r o n wa s i n t r o d u c e d i n t h e m ark et.

M alleable c a s t I r o n i s a tr a n s fo r m a tio n p ro d u ct o f

w hite o a s t i r o n , the l a t t e r .

and i s

o b t a i n e d by t h e h e a t t r e a t m e n t o f

M a l l e a b l e i r o n a t once became a f a v o r i t e

consum er w orld due to i t s free

carbon in t h i s

nodule o r th e

in the

su p erio r p h y sical p ro p e rtie s .

iro n e x is ts

i n t h e form o f n o d u l e s .

s p h e r u l i t e w a s shown t o b e t h e

sh a p e s i n w hich th e g r a p h i t e

The The

l e a s t harm ful o f

could e x i s t i n c a s t i r o n s .

It

i s e v id e n t t h a t th e t r e n d s o f th o u g h t i n im proving th e q u a l i ­ tie s

o f c a s t i r o n w e r e now b e i n g d i r e c t e d

flu en ce of the

size,

p a r t i c l e s on t h e

tow ards th e I n ­

sh a p e , and d i s t r i b u t i o n

p ro p erties of cast

iro n .

of the g ra p h ite

T h i s m ethod o f e n ­

h a n c i n g t h e p h y s i c a l p r o p e r t i e s o f c a s t i r o n g a i n e d a n imme­ d iate

f a v o r w ith foundrym en, a s i t

I n v o l v e d no s a c r i f i c e

of

the flow ing p r o p e r tie s . Many w o r k e r s h a d o b s e r v e d n o d u l e s o f g r a p h i t e irons in

"as c a s t ” c o n d itio n .

in cast

Hanem ann a n d S c h r a d e r '

have

I l l u s t r a t e d a c a s e i n t h e i r w o r k , w h i c h was p u b l i s h e d i n 1 9 3 6 . Q N i p p e r 0 h a s sh ow n a s i m i l a r c a s e i n h i s w o r k , w h i c h w a s p u b ­ lish ed

i n 1933*

G-roe ber a n d Hanem ann^ h a v e a l s o r e p o r t e d t h e

p r e s e n c e o f s u c h n o d u l e s i n 1937® Morrogh and h i s a s s o c i a t e s ,

W illia m s and G ra n t,

B r i t i s h Oast I r o n R e se a rc h I n s t i t u t e ,

o f the

B i r m i n g h a m , E n g l a n d , who

h a v e c o n t r i b u t e d much t o t h e k n o w l e d g e r e g a r d i n g t h e g r a p h i t e stru c tu re s in c ast iro n s, on t h e p o s s i b i l i t y

began to

sp ecu late

of o b tain in g g rap h ite

c ast iro n s in "as c a s t” co n d itio n . on u n d e r c o o le d g r a p h i t e

stru c tu re s

a few y e a r s a g o

i n n o d u l a r form i n

T h e s e m en, w h i l e w o r k i n g in the b in a ry a llo y s of

c a rb o n and e a c h o f th e t r a n s i t i o n a l e le m e n ts i r o n , co b alt,

had n o d u la r g r a p h i t e

i n m ind.

n ick e l,

and

T hey e n c o u n t e r e d n o d u l e s

of g rao h lte

I n some o f t h e s e a l l o y s

T hey r e c o g n i z e d

heat trea tm e n t.

In the

f o r r. o f n o c i u l e s w i t h o u t t h e a i d o f

The p r e s e n t d a y n o d u l a r c&Bt i h o n i s

the

t h e w e l l o r g a n i z e d and e x t r e m e l y i n t e l l i g e n t

v e stig a tio n Oust

m anner.

t h e c o m m e r c i a l an d e n g i n e e r i n . x i m p o r t a n c e o f

o b ta in in g graphI te

outcom e o f

In a sy stem atic

of th is

p r o b l e m by t h e s e

sc ien tists

in ­

of the B r i ti s h

Iron r e s e a r c h I n s t i t u t e . M orrogh p u t a m i l e s t o n e

in the h i s t o r y

of cast

iro n ,

when he a n n o u n c e d i n M arch o f 1 9 4 3 , a p r o c e s s f o r t r e a t i n g cost

i r o n s to produce n o d u la r g r a p h ite

d itio n . to

Morrogh a c c o m p l i s h e d t h i s

m elts of h y o s r e u te c tic

a ttrac ted S tates In th is

iron3.

universal a tte n tio n .

i n the

Ma s c a s t ” c o n ­

by t h e a d d i t i o n o f c e r i u m Since

0.

then the

su b je c t has

K. D on o h o ^ 9 i n

the U n ited

n ro d u c e d n o d u l a r g r a p h i t e by th e a d d i t i o n o f p ro cess, the carbo : c o n te n t of th e c a s t

a n y more a l i m i t i n g

facto r.

su b ject.

o f M e t a l P r o g r e s s , he r e p o r t s by t h e a d d i t i o n o f l i t h i u m ,

i r o n was n o t

De 3y o f t h e U n i v e r s i t y

i n B elgium h a s c o n t r i b u t e d b o t h to c a l d e v e lo p lent o f t h e

m a g n e s iu m .

o f Ghent

the t h e o r e t i c a l and t e c h n i ­

In the

S e p t e m b e r 1S5C i s s u e

the p r o d u c tio n o f n o d u la r g r a p h i t e

calcium ,

barium ,

stro n tiu m ,

and

sodium . N odular c a s t in en ce and th e

iro n

in In d u stry . n ex t,

i s r a p i d l y o c c u p y in g a p l a c e o f prom­

The s t a t i s t i c s

are th e re

i n o r d e r to

a p p e a r i n g on t h i s ju stify

the

page

trem endous

e x p e n d i t u r e s , b o t h o f money a n d o f w o r t , t h a t a r e b e i n g made to

fu rth er

im prove th e p r o p e r t i e s and t h e t e c h n o l o g y o f n o d u l a r

cast iro n . A. P . G a g n e b i n ^ ,

research m etallu rg ist

fo r the

In ter-

4. n a t i o n a l N i c k e l Company o f C a n a d a I n c . , work i n t h e

field

L t d * , New Y o r k , w h o s e

o f n o d u l a r i r o n i s w e l l k n o w n , mad© a v e r y

i n t e r e s t i n g rem ark i n th e

Septem ber 25,

1950,

issu e of S te e l.

He s t a t e s t h a t t h e p r o d u c t i o n o f n o d u l a r c a s t i r o n d u r i n g t h e c u r r e n t y e a r o f 1 9 5 0 i s e x p e c t e d t o be b e t w e e n 1 5 * 0 0 0 a n d 20,000 t o n s o f c a s t i n g ,

and t h i s to n n a g e i s t o i n c l u d e p r o d u c t s

w e i g h i n g f r o m 5 o u n c e s t o 50 t o n s .

He f u r t h e r p r e d i c t s t h a t

someday i n t h e f u t u r e , t h e n o d u l a r i r o n i n d u s t r y w i l l c a s t f r o m tw o t o f i v e m i l l i o n t o n s o f t h i s m e t a l p e r y e a r . S u b je ct o f th e T h esis R e a l i z i n g t h e i m p o r t a n c e o f k n o w i n g how t h e s e g r a p h i t e n odules a re

form ed, th e p r e s e n t i n v e s t i g a t o r d e c id e d t o

th e f o llo w in g problem i n d e t a i l . was a 15$ magnesium a l l o y . p arts:

1) t o

is d irec tly

f in d o u t w hether th e a d d i t i o n a g e n t

resp o n sib ility

some p a r t i c l e

to

tw o

(m agnesium)

connected w ith the g ra p h ite n o d u les o r n o t, to fin d

nodule s .

The n o d u l i z e r i n t h i s c a s e

The p r o b l e m i s d i v i d e d i n t o

t h i s be t h e c a s e ,

study

2) i f

some e v i d e n c e w h e r e b y we c a n a s s i g n f o r th e grow th o f th e g r a p h ite

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6. PRODUCTION AND THEORIES 0 7 NODULAR CAST IRO& P ro d u ctio n The p r o d u c t i o n o f n o d u l a r i r o n i s a c c o m p l i s h e d i n two stag es.

The f i r s t

stag e c o n s i s t s i n adding the n o d u liz in g

a g e n t , w hich I s a c a r b id e Iron stru c tu re

s t a b i l i z e r a n d p r o m o t e s a whit©

i n an i r o n , w hich o r d i n a r i l y

The s e c o n d s t a g e o p p o s e s t h e

first

s o lid if ie s grey.

and c o n s i s t s o f a d d in g a

f e r r o s i l i c o n ty p e o f g r a p h i t i z i n g a g e n t , w hich p r e c i p i t a t e s grap h ite

i n n o d u la r form .

T h eories

4

The tw o t h e o r i e s r e g a r d i n g t h e n o & u l a r i z a t i o n o f g r a p h i t e i n c a s t i r o n t h a t a r e b e i n g g i v e n t h e most s e r i o u s c o n s i d e r a ­ tio n s are

first,

t h e one a d v a n c e d by D r. M orrogh o f t h e

B r i t i s h Cast Iro n R e se arch I n s t i t u t e ,

and s e c o n d , t h e one p r o ­

p o s e d b y P r o f e s s o r D© Sy o f t h e U n i v e r s i t y o f G h e n t , B e l g i u m . There i s e v id e n c e f o r and a g a i n s t e a c h t h e o r y . T h e s e tw o t h e o r i e s w i l l b e d i s c u s s e d v e r y b r i e f l y a t first,

w i t h m e n t i o n made o n l y o f t h e h i g h p o i n t s o f t h e s e

th eo ries;

th e n th e y w i l l be t a k e n up I n d e t a i l .

The b a c k b o n e o f M o r r o g h 1s t h e o r y i s t h e v i t a l p a r t p l a y e d by th e c r i t i c a l r a p i d c o o li n g i n th e p r o d u c t io n o f n o d u la r g rap h ite.

A c co rd in g t o him , t h e

tio n agent is

im portant r o le of th e a d d i­

in b rin g in g about the e f f e c t of c r i t i c a l ra p id

co o lin g . G en erally

s p e a k i n g , De Sy a g r e e s w i t h M o r r o g h o n t h e i m ­

portan ce of co o lin g r a t e s , n u cleatin g p a rtic le

but f u r th e r proposes t h a t

governs th e type of g ra p h ite

the

form ed.

7. M orro g h * s T h e o r y The b e h a v i o r o f t h e a l l o y s o f n i c k e l - c a r b o n a n d o f c o ­ b a l t - c a r b o n i s a n a lo g o u s to th e a l l o y s o f ir o n - c a r b o n and th e cast iro n s.

T h is an alog ous b e h a v io r i s not s u r p r i s i n g ,

if a

c l o s e e x a m i n a t i o n i s made o f t h e p o s i t i o n s o f t h e s e t h r e e t r a n s i t i o n a l elem en ts in th e p e rio d ic t a b l e .

I t was f u r t h e r

found t h a t th e a n a lo g ie s e x i s t i n g betw een n i c k e l- c a r b o n a l l o y s o n o n e h a n d a n d o a s t i r o n s o n t h e o t h e r w e r e much c l o s e r . W ith t h e s e

f a c t s i n m in d a n d f r o m a k n o w l e d g e o f t h e c o n d i t i o n s

u n d e r w h ioh s p h e r u l i t e s o f c a r b o n were o b t a i n e d i n n i c k e l carbon a llo y s ^ , tio n s,

M orrogh and W i l l i a m s 2 d e r i v e d a s e t o f c o n d i ­

w hich i n t h e i r o p i n i o n ,

la r grap h ite

if

sa tisfie d ,

in c ast Iro n s in "as c a s t” co n d itio n .

The a d d i t i o n a g e n t u s e d t o p r o d u c e ite

would g i v e n o d u ­

s p h e ru lite s of graph­

i n n i c k e l - c a r b o n a l l o y s was a c a lc lu m - m a g n e s iu m a l l o y .

T h is a l l o y , h o w ev er, would n o t d i s s o l v e

i n c a s t i r o n s and

t h e r e f o r e was n o t c a p a b l e o f g i v i n g n o d u l a r g r a p h i t e . many t r i a l s , of g rap h ite

a n e l e m e n t was fo u n d t h a t would g i v e in a llo y s of n ick el-carb o n ,

iro n -carb o n a llo y s ,

and f i n a l l y

A fter

sp h e ru lites

iro n -n ick el-carb o n ,

in cast iro n s.

T his elem en t

was c e r i u m . A l t h o u g h now,

s e v e r a l m o re s u b s t a n c e s h a v e b e e n f o u n d

t h a t a re cap ab le o f g iv in g n o d u les of g ra p h ite f i c i e n t way, t h e p o i n t s o f M o rro g h * s t h e o r y a r e

i n a m o re e f ­ still

ac­

cepted . It it

is

m igh t b e m e n tio n e d a g a i n t h a t Morrogh f i r m l y b e l i e v e s

th e c r i t i c a l ra p id

co o lin g t h a t i s resp o n sib le

p ro d u c tio n of n odular g r a p h ite .

fo r the

A c c o rd in g t o him , a l l t h a t

the a d d itio n agent does i s coo lin g r a t e . the

He s t a t e s ,

i r o n i s low ,

to give

the e f f e c t o f p ro p er

“p ro v id e d th e

sp h e ru lltic

sulphur c o n te n t of

n o d u le s can be produced i n c a s t

i r o n s m e r e l y b y a c r i t i c a l r a p i d c o o l i n g . * 1^

T his h a s been

shown t o h a p p e n b y M o r r o g h a n d W i l l i a m s i n n i c k e l - c a r b o n a l ­ l o y s.'^

F u rth e r ev id en ce to

s u p p o rt th e above

statem en t w ill

b e show n l a t e r . The r e q u i r e m e n t s f o r a n a d d i t i o n a g e n t a r e : 1)

The a d d i t i o n a g e n t h a s t o b e a n a c t i v e d e s u l p h u r ! z e r .

I f th e

s u l p h u r c o n t e n t o f t h e m e l t i s much a b o v e 0 . 0 2 $ ,

a part

of the a d d itio n agent w ill r e a c t in d e s u lp h u riz a tio n u n t i l the

su lp h u r c o n te n t has dropped to 0 .0 2 $ ,

2)

The a d d i t i o n a g e n t m u s t b e s o l u b l e i n t h e m e l t .

th e above d e s u l p h u r iz a t i o n i s

com plete,

A fter

th e rem ain d er o f th e

a d d itio n agent a llo y s i t s e l f w ith the m elt. 3) is,

The a d d i t i o n a g e n t h a s t o b e a c a r b i d e

sta b ilize r;

th at

it

te n d s to s o l i d i f y th e ir o n w hite r a t h e r th a n g rey . \ I t m ight be m en tio n ed t h a t th e c a r b i d e s t a b i l i z i n g e f f e c t i s

o n ly d e r i v e d from th e a d d i t i o n a g e n t t h a t h a 3 a l l o y e d I t s e l f w i t h t h e m e lt and n o t from t h e n o d u l i z e r com bined w i t h t h e su lp h u r. When c e r i u m i s a d d e d i n e x c e s s o f 0 . 0 2 ,$ a n d l e s s t h a n t h e amount n e c e s s a r y t o g iv e w h ite d e p o sits h y p ereu tectic

g rap h ite

m etal p ro p e r b e g in s to

so lid ify .

w hite,

so I m m e d i a t e l y a f t e r

iro n ,

t h e m e l t on c o o l i n g

i n form o f n o d u le s b e f o r e th e The m e t a l p r o p e r s o l i d i f i e s

s o li d if i c a tio n th e re e x is t hyper­

e u t e c t i c n o d u les i n a m a trix of w hite i r o n . so lid ific a tio n ,

the c e m e n tite o f th e w hite

S hortly a f t e r iro n b eg in s to de-

9. o o m p o s e , p r o d u c i n g more g r a p h i t e .

T his g r a p h ite

n o d u lar b u t roughly resem b les fla k e g ra p h ite c lo s e r exam in atio n ,

how ever, th e s e

from f l a k e g r a p h i t e and a r e to n o d u lar g ra p h ite

"quasi fla k e s."

Each h y p e r e u te c tic

fore,

i n shape*

fla k e s are

from o p t i c a l a n i s o t r o p i c

these

around i t ,

not q u ite On

found to d i f f e r

found t o be o f s i m i l a r o r i e n t a t i o n

To d i f f e r e n t i a t e

sphere of in f lu e n c e ,

is

from th e f l a k e s ,

because th ere

p o in t o f view .

Morrogh o a l l s

nodule

seems t o h a v e a

i s a c le a r r in g of m atrix

w hich d o e s n o t c o n t a i n any q u a s i f l a k e s .

n e ar the h y p e re u te c tic

them

nodules,

T here­

g r a p h i t e a r i s i n g from

th e w h ite i r o n d e c o m p o s i ti o n , d e p o s i t s I t s e l f on t h e s e n o d u l e s . Beyond t h e i n f l u e n c e i s d ep o sited

of th ese

as quasi fla k e s .

of h y p e re u tec tic g rap h ite flak es

should d e c r e a s e .

in p ra c tic e .

is

spheres, Thus,

the

secondary g ra p h ite

i f t h e number o f n o d u l e s

increased,

t h e amount o f q u a s i

T h is a ssu m p tio n i s proved to be t r u e

2

The f o r m o f t h e q u a s i f l a k e may v a r y c o n s i d e r a b l y a c ­ c o r d i n g t o th e amount o f n o d u l i z e r p r e s e n t , amount i n c r e a s e s ,

because as the

t h e q u a s i f l a k e t e n d s t o become n o d u l a r .

rea so n fo r t h i s behav ior i s

not c le a r.

Th©

Perhaps the In c re a se d

amount o f c e r iu m p r o v i d e s a n i n c r e a s e d number o f n u c l e i , e i t h e r by a n i n c r e a s e d num ber o f h y p e r e u t e c t i c p ro v id in g d ir e c t n u c le i.

It

n o d u l e s o r by

may a l s o b e t h a t t h i s i n c r e a s e d

a d d i t i o n a g e n t may c a u s e a g r e a t e r d e g r e e o f c a r b i d e

sta b ili­

z atio n ,

so t h a t t h e c e m e n t i t e d e c o m p o s e s a t a l o w e r t e m p e r a p t u r e , w h e re u p o n t h e g r a p h i t e w i l l t e n d t o become n o d u l a r . M orrogh and W il l ia m s have b a s e d a f a i r p r o p o r t i o n o f th eir

t h e o r e t i c a l know ledge on c o o l i n g c u r v e s ,

ta k e n on cerium

10 . treated

nodular lro n s^ ;

it

i s n o t n e c e s s a ry to m ention t h a t

s e v e r a l p r e c a u t i o n s had to he ta k e n to m a i n ta in th e cerium co n ten t.

C o o l in g c u r v e s o b t a i n e d ware v e r y

r e s t s were o b t a i n e d i n e a c h c a s e . 1150° and 1160°C. th an the

first

tem p eratu re,

The f i r s t

o ne w a s b e t w e e n

longer.

On s l o w c o o l i n g t o room

s a m p l e s sh o w ed m i c r o s t r u c t u r e h a v i n g w e l l

developed h y p e re u te c tic n o d u les w ith g ra p h ite

flak es

When q u e n c h e d f r o m t h e t e m p e r a t u r e

the

showed m i c r o s t r u c t u r e

o f 103?°C,

s im ila r to t h a t of the

ones.

When t h e q u e n c h i n g w a s c a r r i e d

of the

second a r r e s t ,

out a t

(quasi)*

sam ples

slow ly co o le d the te r m in a tio n

w hich c o rr e s p o n d s to th e

of th e w hite i r o n e u t e c t i c , p rac tic ally

tw o a r ­

The s e c o n d o n e f e l l a b o u t 3 ° t o 10°C l o w e r

and l a s t e d

the

sim ila r;

the m ic ro stru c tu re

so lid ific atio n o f s a m p le s was

w h ite w i t h s m a ll and l a r g e n o d u l e s o f g r a p h i t e .

The l a r g e n o d u l e s w e r e o f d u p l e x s t r u c t u r e a n d w e r e a l w a y s su rro u n d e d by a c a r b id e I r o n shows a c i c u l a r

free

zone.

stru ctu re.

The c a r b i d e o f t h e w h i t e

From t h e s e o b s e r v a t i o n s , we

i n f e r t h a t t h e s e h y p e r e u t e c t i c g r a p h i t e n o d u le s a r e form ed a t a very e a r ly due to th e

stage in the

s o lid if ic a tio n process.

sphere of in flu e n c e

of th ese n o dules,

F u rth er, g rap h itiz a -

t i o n p r o c e e d s v e r y r a p i d l y by d e p o s i t i o n on t h e h y p e r e u t e o t i c cen ters.

Sam ples q u en ch ed from t h e f i r s t a r r e s t and b e tw e e n

t h e two a r r e s t s , ite

a l l had m i c r o s t r u c t u r e s c o n s i s t i n g o f g ra p h ­

s p h e r u l i t e s in a m a trix of a c i c u l a r w hite ir o n . W hether t h e f i r s t

a r r e s t co rresp o n d s to the fo rm atio n

of the h y p e re u te c tic g ra p h ite or n o t,

is a d ebatable

q u estio n .

T h is g r a p h i t e

h a s b e e n sh o w n t o e x i s t much a b o v e t h e t e m p e r a ­

ture

arrest;

of f i r s t

a t the

same t i m e ,

these in v e s tig a to r s

IX. have n e v e r o b ta in e d an a r r e s t o f t h i s k in d i n u n t r e a t e d h y p e r­ e u tectic

i r o n s on d e p o s i t i o n o f th e

The p r i m a r y n o d u l a r g r a p h i t e to p o f the in g o ts .

In th ese

prim ary g r a p h i t e .

is

known t o

se g re g a tio n s the

seg reg ate to the s p h e ru lite s are

o f i m p e r f e c t s h a p e , and M orrogh and W illia m s s p e c u l a t e t h a t t h e s e may h a v e b e e n f o r m e d b y a p r o c e s s o t h e r t h a n t h a t o f uniform c o n c e n tric c r y s t a l l i z a t i o n . 2 M orrogh and W illia m s have e x p l a i n e d t h e

"double t r e a t ­

m ent" p r o c e s s by s a y i n g t h a t t h e number o f h y p e r e u t e c t i c sp h e ru lites is

Increased to

such an e x te n t t h a t t h e i r

o f in flu en ce o v erlap ,

and th u s e n t i r e l y

produced.

stren g th en t h i s

To f u r t h e r

spheres

n odular g ra p h ite i s

th e o r y , Eash h a s sug­

g e s te d t h a t th e norm al i n o c u l a t i n g e f f e c t o f f e r r o s i l l c o n I s due to l o c a l i z e d c o n c e n tr a ti o n o f s i l i c o n , so lu b ility

of grap h ite

in iro n

(becom es l o o a l l y h y p e r e u t e o t i c )

and th u s p r e c i p i t a t e s th e g r a p h i t e the m elt.

w hich r e d u c e s th e

p articles,

However, M orrogh and W illia m s

th e re are o b je c tio n s to Eash*s th eo ry .

w hich n u c le a t e

g iv e a w arning t h a t The f a c t t h a t t h e

f e r r o s i l l c o n t y p e o f g r a p h l t l z e r h a s t o b© a d d e d a f t e r , sim u ltan eo u sly w ith , th e n o d u llz e r,

or

h a s made t h i s t h e o r y m o re

com plex. L a t e r i n t h i s w ork, th e a u t h o r h a s v e n tu r e d to g iv e h i s own v i e w a n d e x p l a n a t i o n o f t h e

"double tre a tm e n t" p r o c e s s .

12.

De S y ^ T h e o r y De Sy a g r e e s w i t h M o r r o g h I n t h e i m p o r t a n c e o f t h e c r i t i ­ c a l r a p i d c o o l i n g i n t h e p r o d u c t i o n o f n o d u l a r g r a p h i t e i n "^Ts c a s t ” c o n d itio n , b u t th en f u r th e r proposes th a t th e n u c le a tin g p a r t i c l e s govern th e ty p e o f g r a p h ite

form ed.

C r y s t a l l i z a t i o n i s t h e a rra n g e m e n t o f th e atom s i n a n o rd erly

f a s h i o n around a c e n t e r o f c r y s t a l l i z a t i o n .

c r y s t a l l i z a t i o n c e n t e r may b e , a n d u s u a l l y i s , i n th e m olten m a t e r i a l .

a so lid p a rtic le

The i d e a l c e n t e r o f c r y s t a l l i z a t i o n

i s t h e on© b e l o n g i n g t o t h e

same c r y s t a l

s ta n c e w hich i s to be c r y s t a l l i z e d . of c ry stalliz a tio n ,

The

system a s t h e

sub­

Thus w i t h t h e id e a l c e n t e r

t h e atom s o f t h e c r y s t a l l i z i n g m a t e r i a l

have o n ly to a rra n g e th e m se lv e s i n an o r d e r a lr e a d y e x i s t i n g . I t w ould t h e r e f o r e

fo llo w ,

s t i t u e n t s A a n d B, a n d i f p articles

is

th at i f

a m e l t c o n s i s t s o f two c o n ­

the c r y s ta l

system o f th e

c l o s e r t o t h a t o f A, t h a n o f B i t

suspended

would n u c l e a t e

A r a t h e r t h a n B. De Sy t o c l a r i f y m a t t e r s h a s system s i n h i s a r t i c l e

of c ry s ta l

p u b l i s h e d i n the* J a n u a r y 1 9 5 0 i s s u e o f

Arner1 c a n F o u n d r y m e n . la t e s the o ry s ta l

g iven a ta b le

This ta b le ,

w hich i s g iv e n b elow , t a b u ­

system s o f a u s t e n l t e ,

oem en tit© , g r a p h i t e ,

" a n d some c o m p o u n d s w h i c h a r e g e n e r a l l y p r e s e n t i n a s o l i d state

a t the tem p era tu re

o f c a s t i r o n e u t e c t i c and w hich can

a l s o be p r e s e n t i n s u s p e n s io n o f c a s t i r o n e i t h e r a s a c o n s e ­ quence o f m e ltin g ,

itse lf,

o r as a r e s u l t of m an ip u latio n or

a d d itio n s of d eo x id izin g or in o c u la tin g m a te ria ls .

x

The l a s t

p a r t o f De S y * s s t a t e m e n t e x p l a i n s how t h e n u c l e a t i n g p a r t i c l e s may h a v e b e e n p r o d u c e d .

13 TABLE I I CRYSTAL SYSTEM 10 T etragonal

Cubic A u sten ite

* Hexag­ onal

drthorhom blc

Rhombohedral

G-raohitQ

C em entite

i

CaO

CaS

T1 0 2

(FeOjpSlOg

S i Og

A I 2 O3

Mgo

MgS

CaC 2

(Mn0) 2 S i 0 2

Fe S

CaSI2

SrO

SrS

0rC2

(F©0,M n0)S102

SiC

BaO

BaS

CeCg

MnO

MnS

LiC 2

FeO

l i 2s

ZrSiOj^

Ce 0 2

TIC

l i 2o

ZrC

TIN ZrN * M onocllnlo and t r i e l i n i c c r y s t a l sy ste m s, n o t b e in g p e r t i n e n t to th e d i s c u s s i o n , have b e e n o m itte d . \

Oxygen I n c a s t i r o n s i s FeQ d i s s o l v e d i n i r o n . the

su p p o sed t o e x i s t i n t h e form o f

W hile p o u r i n g , due t o t h e e x p o s u r e o f

ir o n to th e atm o sp h ere, th e q u a n tity o f th e

However,

FeO i s

s i l i c o n w hich i s a ls o p r e s e n t and i s a s t r o n g

Increased. deoxi­

d izer a cts as: 2 FeO -+ S i W ith c o o l i n g , g ives r is e

SiO g + 2F© +

66Kcal

t h e r e a c t i o n moves from

l e f t to r i g h t and

to h ex ag o n a l p a r t i c l e s o f S i0 2 , w hich n a t u r a l l y

fa v o rs the c r y s t a l l i z a t i o n of hexagonal g ra p h ite r a t h e r th a n o f cu b ic a u e t e n i t e .

It

i s &most a u n i v e r s a l l y a c c e p t e d f a c t

th a t undercooled g ra p h ite

i s a r e s u l t o f c a rb id e deco m p o sitio n .

14 . b u t w hether fla k e g r a p h ite

i s f o r m e d i n s. s i m i l a r m a n n e r o r

d i r e c t 1y f r o m t h e m e l t i s a c o n t r o v e r s i a l q u e s t i o n . b e Sy, up t o a c e r t a i n p o i n t ,

ag rees w ith the th eo ry put

f o r w a r d by M o r r o g h a n d h i s a s s o c i a t e s . f e r e n c e w i l l be n o t e d . g rap h ite

De 3y i s

The p o i n t s o f d i f ­

of the o p in io n t h a t a l l

i s a r e s u l t o f c a rb id e deco m p o sitio n ,

a h y p ereu tectic

iro n is rap id ly

co o led ,

i t b eg in s to

by t h e c r y s t a l l i z a t i o n o f p r i m a r y c e m e n t i t e . there

a n d t h a t when so lid ify

At t h i s p o i n t

i s a s l i g h t c o n f l i c t o f o p i n i o n b e tw e e n t h e two s i d e s .

W h i l e De Sy c o n s i d e r s t h e h y p e r e u t e c t i c

g rap h ite

to be d e r i v e d

from c e m e n t i t e d e c o m p o s i t i o n , M orrogh^ s a y s i n h i s a r t i c l e

in

March 1948 i s s u e o f t h e J o u r n a l o f I r o n and S t e e l I n s t i t u t e , p.

316,

th at i t

i s n o t c e r t a i n a s t o how i t

c a r b i d e d e c o m p o s itio n o r from th e m e l t . d irec tly p o rtan t.

fo rm s, w h e th e r from

T his p o in t i s n o t

c o n n e c te d w ith t h i s d i s c u s s i o n and i t

i s n o t v e r y im ­

M o r r o g h h a d ' p r e v i o u s l y made t h e a s s u m p t i o n t h a t a l l

n o d u l a r g r a p h i t e was a r e s u l t o f c a r b i d e d e c o m p o s i t i o n . t o c o n t i n u e w i t h De 8 y * s t h e o r y , g in to decom pose, b u t i t th e

so lid ific a tio n is

is

t h e p r i m a r y c e m e n t i t e may b e ­

o n ly c o m p le te ly decom posed a f t e r

com plete.

The e u t e c t i c

c e l l grows a ro u n d

t h e a l r e a d y decom posing n u c le u s and g i v e s a r a d i a t i n g of e u te ctic

g rap h ite.

De Sy1 0 f u r t h e r

c a tio n of the h y p e re u te c tic n o t form ;

Now

Iron is

says,

" I f th e

not ra p id ,

stru ctu re so lid ifi­

t h e n o d u l e s do

in t h i s c a se th e c e m e n tite decom poses i n th e l i q u i d

p h a se and g i v e s r i s e p o in t of d iffe re n c e .

to lam ellar g ra p h ite ."

T h is a g a in i s a

M orrogh and h i s a s s o c i a t e s b e l i e v e t h a t

t h e s e h y p e r e u t e c t i c n o d u l e s a r e f o r m e d a n d e x i s t when t h e b a t h is

still

m o lten .

They2 c i t e

the case o f se g re g a tio n o f hy p er-

15 . eu te ctic

n o d u le s i n i n g o ts to th e to p and a ls o i n c e n t r i f u g a l

c a s tin g to the in n e r sid e . th e liq u id m e lt, to p of a m e lt."

"It

seems c e r t a i n t h e y e x i s t i n

o r t h e y w ould n o t t e n d t o f l o a t t o t h e ( R e f e r e n c e No. 2 , p a g e 3 1 6 . )

From t h e d i s c u s s i o n o n c r y s t a l l i z a t i o n a n d c r y s t a l l i z a ­ t i o n c e n t e r s m entioned p r e v i o u s l y ,

i t would be l o g i c a l t o

state

t h a t p a r t i c l e s b e l o n g i n g t o t h e h e x a g o n a l sy stem would prom ote th e

fo rm atio n of hexagonal o r fla k y g r a p h ite .

tio n e d p rev io u sly th a t th e hexagonal s i l i c a are

I t h a s b e e n m en­

p articles,

w hich

p r o d u c t s o f d e o x i d a t i o n o f i r o n by s i l i c o n a r e r e s p o n s i b l e

fo r the

flak y n atu re

of grap h ite

De Sy, f r o m t h i s d e d u c t i o n ,

in grey c a s t iro n s . f u r th e r proposes t h a t ,

i f we

a d d some a g e n t w h i c h h a s a h i g h e r a f f i n i t y

f o r oxygen, w hich

d o e s n o t form compounds ( o x i d e s ,

n itrid es),

w hich c r y s t a l l i z e

carb id es,

in the hexagonal

system ,

and i f t h i s a g e n t

is

present in

s o l i d c o n d i t i o n above th e e u t e c t i c

it

would f a v o r t h e f o r m a t i o n o f n o d u l a r g r a p h i t e . From t h e t a b l e g i v e n a b o v e ,

are

it

tem perature,

c a n be s e e n t h a t t h e r e

s e v e r a l e l e m e n t s whose o x i d e s an d i n

and n i t r i d e s c r y s t a l l i z e

and

some c a s e s c a r b i d e s

i n cu b io and t e t r a g o n a l form s.

a c t as n u c le i w ith fav o r p rim a rily

tow ards a u s t e n i te

These

and

s e c o n d a rily tow ards c e m e n tite . T h i s t a b l e w a s p u b l i s h e d i n F e b r u a r y o f 194-9* liste d

in th is tab le

some e l e m e n t s ,

£© Sy ha®

t h e compounds o f w hich

b e lo n g to th e cu b ic and to th e t e t r a g o n a l

sy stem s.

Now a f t e r

a b o u t o n e a n d o n e - h a l f y e a r s , De Sy h a s r e p o r t e d t h e p r o ­ d u c tio n of n odular g ra p h ite o f sodium ,

calcium ,

lith iu m ,

i n c a s t i r o n s by t h e a d d i t i o n b a riu m , and s t r o n t iu m .

T his

16

a.f*Or*TT'2. C .'I G n

PlT* a

■ ■ ’'■ V

tab le

ft S F ,

2, a a S 'XT’$'■ i f '

A. i 1

acove.

t hit'

^ f* 1*, Vi w> rs &. a

c -e O t e T lh e v‘ ct

' o •jr'i ^ 3

V> *5 V £

1 ' ) '*'
§ ri

\

c; B JO 4. ^ 3

re t a l

v f*

f.tStfi

i

n the

*

M o r r o g h * s C r l t i c l s m o f De 3.7*8 T h e o r y

c

The d i f f e r e n c e s i n o p i n i o n b e t w e e n M o r r o g h a n d De Sy have a lr e a d y b een m e n tio n ed .

M orrogh i s a f i r m b e l i e v e r i n

the f a c t th a t th e n o d u la r iz a tio n i s rap id

c o o l i n g and t o

support h is

the r e s u l t o f p ro p e r

statem en t has c ite d

the case

where n o d u le s o f g r a p h i t e

h a v e b e e n p ro d u c e d by p r o p e r c o o l i n g p w i t h o u t t h e a i d o f any a d d i t i o n a g e n t . ~ Morrogh s a y s t h a t t h e r e e x isten ce

i s no d i r e c t e v i d e n c e f o r t h e

o f n u c l e i , w hich a r e

supposed to n u c le a te th e g rap h ­

ite . M orrogh a d m its t h a t t h e r a d i a l nodule i s tio n

He s a y s t h a t i t

i s easy to m istake th e w hite

seen i n n o d u le s a s th e n u c le u s .

presence of t h i s of th e g ra p h ite

sp h e ru llte . sectio n is

s e c tio n w ill out the

th e ir cen ters;

c u ttin g the

taken, g e n erally

later), it

speak­

s p h e r e s e i t h e r above o r below

spheres e x a c tly through t h e i r

c e n t e r s i s m ore o f a n e x c e p t i o n a l c a s e . of th e g rap h ite

He e x p l a i n s t h e

" a p p a r e n t n u c l e u s " by c o n s i d e r i n g t h e g e o m e tr y

When a m e t a l l o g r a p h i c in g , t h is

of th e g ra p h ite

s u g g e s t i v e o f g r o w t h f r o m a* c e n t e r o f c r y s t a l l i z a ­

or nu cleu s.

spot o fte n

stru ctu re

sn h e ru lites

(the

can be seen t h a t th e

Prom t h e

stru c tu re

stru c tu re d iscu ssed in d e ta il su rface of th e p o lish ed

seo tio n

w i l l be p a r a l l e l o r v e ry n e a r p a r a l l e l to th e b a s a l s e c t io n o f g rap h ite.

If th is basal

incom ing l i g h t , g en erally , th e

it

sectio n i s

p e r f e c t l y norm al t o th e

w i l l e x h i b i t no o p t i c a l a n i s o t r o p y ;

th ese b a sa l

s e c tio n s w i l l be a t a s l i g h t an g le to

s u r f a c e and t h e r e f o r ©

M o r r o g h sh o w s t h a t t h i s

but

w ill

show o p t i c a l a n i s o t r o p y .

" a p p a r e n t n u c le u s " need o n ly be

Thus

18 . g rap h ite.

M orrogh e n d s h i s l e t t e r

to the E d ito r o f th e

F o u n d r y T r a d e J o u r n a l p u b l i s h e d i n t h e M a r c h 23$ 1 9 5 0 issu e

o f t h e m ag azin e by s a y i n g ,

concerned, in d icate

it

is tru e

to

"A s f a r a s o a s t i r o n i s

s a y t h a t we h a v e no e v i d e n c e t o

t h a t th e m elt c o n ta in s s o l i d o x id e s o r s i l i c a t e s

w hich f u n c t i o n t o i n f lu e n c e th e g r a p h i t e some v e r y i n d i r e c t e v i d e n c e t h a t r e s i d u e s o f g r a p h i t e may e x i s t , n o th in g ."

p a ttern .

We h a v e

subm icroscopic l a t t i c e b u t b e y o n d t h i s we know

19 . D i s c u s s i o n o f t h e T h e o r i e s a n d t h e A u t h o r * a P o i n t o f View Though t h e r e th eo ries,

i s e v id e n ce f o r and a g a i n s t b o th th e

n e ith e r of th e s e th e o r ie s can e x p la in a l l th e phe­

n om ena o b s e r v e d . T h e r e i s no d o u b t t h a t t h e e v i d e n c e , b o t h t h e o r e t i c a l and e x p e r im e n ta l, i n the

support of h is b e lie f

im portance o f r a p id c o o lin g i n th e p ro d u c tio n o f n o d u la r

g raphite, i s

sound.

th e fo rm atio n , ite

o f f e r e d by M orrogh i n

However,

on t h i s b a s i s one c a n n o t e x p l a i n

s e g r e g a t i o n , and m a in te n a n c e o f n o d u la r g r a p h ­

in the liq u id phase. The s u c c e s s a t t a i n e d b y De Sy i n o b t a i n i n g n o d u l a r g r a p h ­

ite

i n c a s t i r o n s by t h e u s e o f d i f f e r e n t a d d i t i o n a g e n t s ,

r e f e r e n c e t o w h ic h h a s a l r e a d y b e e n made, l e a d s u s t o b e l i e v e t h a t t h e r e a s o n i n g f o l l o w e d b y De Sy m u s t a l s o b e s o u n d ; b u t one d o e s n o t f i n d any e x p l a n a t i o n i n h i s t h e o r y f o r t h e p h e ­ n o m en o n o f n o d u l a r g r a p h i t e does not in th e

seem t o b e l i e v e

liq u id

p h a s e . 10

J u s t m entioned.

In f a c t,

De Sy

t h a t n o d u la r g r a p h i t e c an be form ed T h i s b e l i e f o f De S y ’ s s e e m s t o t h e

a u th o r a d is r e g a r d o f f a i r l y d e f i n i t e evidence f o r th e ex o ls te n c e of no d u lar g ra p h ite in liq u id c a s t ir o n . The p o i n t o f c o n f u s i o n i s t h i s : th e no d u lar g ra p h ite

What i s

it

sta y n odular i n th e liq u id

th e m etal i s not s o l id ,

it

i s p erm issib le to

t h a t makes phase?

Since

say t h a t th e

c o o l i n g r a t © h a s n o t h a d much I n f l u e n c e o n t h e g r a p h i t e preserve so lid ,

it

i n n o d u la r form .

th ere

i s very l i t t l e

of th e g ra p h ite .

T herefore,

to

A lso,

since th e ir o n i s

not

o u tsid e

fo rc e to keep th e

shape

the au th o r

t h a t the fo rc e th a t h o ld s the g ra p h ite

is

led to b eliev e

i n n o d u l a r form m ust

20 . com© f r o m w i t h i n i t s e l f .

T herefore,

we m i g h t s a y t h a t t h e

c o n stitu tin g c ry s ta llite s

o f t h e n o d u le must be h e l d i n p l a c e

b y t h e way t h e y a r e a r r a n g e d a r o u n d t h e n u c l e u s . I f t h i s ded u ctio n Is

co rrect,

t h e n t h i s w ould s u p p o r t

De S y 18 p r o p o s a l t h a t t h e n u c l e a t i n g p a r t i c l e s g o v e r n t h e type o f g r a p h ite

form ed.

D ouble T re a tm e n t P r o c e s s V/e w i l l a s s u m e t h a t E a s h f s t h e o r y ,

reg a rd in g the graph-

l t i z a t l o n due to th e a d d i t i o n s o f f e r r o s l l i e o n type o f g ra p h itlz e rs,

is

co rrect.

The p o i n t o f c o n f u s i o n h e r © i s ,

Why d o e s t h e g r a p h i t e o f

t h e c a s t I r o n n o d u l a r i z e o n l y when t h e a d d i t i o n a g e n t i s a d d e d w ith or b e fo re the a d d itio n o f th e g r a p h itiz e r ? The a u t h o r v e n t u r e s t o e x p l a i n t h i s c o m b i n a t i o n o f t h e tw o t h e o r i e s .

c o n f u s i o n by t h e

We s h a l l a c c e p t t h e v a l i d i t y

o f th e e x is te n c e o f n o d u lar g ra p h ite in the liq u id phase.

We

s h a l l a l s o a c c e p t De S y f s p r o p o s a l t h a t n u c l e a t i n g p a r t i c l e s govern th e type of g r a p h ite

form ed.

When we a d d t h e n o d u l i z e r t o t h e m e l t , m elt,

o r p ro d u c e s by r e a c t i n g w ith th e m e l t,

th e fo rm atio n of no d u lar g ra p h ite . added to th e m e lt, h y p ereu tectic

it

it

g iv es to the

n u c le i w hich f a v o r

Now w hen t h e g r a p h i t i z e r i s

p r e c i p i t a t e s t h e g r a p h i t e by m aking l o c a l

sp o ts i n th e m elt

(Sa% h).

Now, t h e n u c l e i made

by th e n o d u l i z e r a r e a l r e a d y p r e s e n t , t h e p r e c i p i t a t i n g g r a p h ­ ite

fin d s these

p a r t i c l e s and s t a r t s

These n u c l e a t i n g p a r t i c l e s , give r i s e

to

c r y s t a l l i z i n g a ro u n d them .

b e in g o f c u b ic o r t e t r a g o n a l system ,

sp h erical g rap h ite.

The same e x p l a n a t i o n h o l d s

good i n t h e c a s e where t h e n o d u l i z e r and t h e g r a p h i t i z e r a r e

21 . added s im u lta n e o u s ly .

It

s h o u l d h e "borne I n m in d t h a t t h e r e ­

a c t i o n s o f n o d u l a r ! z a t i o n and g r a p h l t i z a t i o n a re e x tre m e ly fast.

I f now t h e g r a p h i t i z e r i s a d d e d b e f o r e t h e n o d u l i z e r ,

grap h ite w ill

s t a r t c o m i n g d own f r o m t h e m e l t t o f i n d no t

p articles g rap h ite

to c r y s t a l l i z e

on and t h e r e f o r e w i l l c r y s t a l l i z e

on

i t s e l f to give fla k e g r a p h ite .

R ad ial S tru o tu re M orro g h * s e x p l a n a t i o n o f t h e

Ma p p a r e n t n u c l e u s 11 i n t h e

g rap h ite

nodule i s v e ry

sound.

p article

is

may "be s u b m i c r o s c o p i c .

p resen t,

shown t h a t t h i s

it

A lso,

if

any o t h e r n u c l e a t i n g M orrogh h a s

" a p p a r e n t n u c le u s " c o u ld be g r a p h i t i c ;

same t i m e a s h e s a y s , not p re s e n t.. . . " .

"it

is

a t th e

not suggested t h a t n u c le i a re

FLAKS AND NODULAR GRAPHITE IN CAST IRONS Structure

o f th e

Free

O raphite

carbon in

grey

Flake cast

iro n s

g ra p h ite

embedded i n a m a t r i x o f

g ra p h ite

Is

a llo y s

un iqu e

(w ith rare

has a c r y s ta l the

oth er

th at

for

tio n ed

in

the

cast

g ra p h ite.

one above

another

of th is

g ra o h ite

c o v a le n t bonds e x i s t

m or e c l o s e l y

packed

so& cing betw een th e for

the

the

of

to

the

surface

to

p o lish

of

easy

of

gra p h ite of

the

the

slip

is

slig h t.

fla k e

due

Is

giv en

to

as

In t h i s the

fig u re la te r .

compared t o

G en erally

case,

constant

p o lish ed

fla k e.

basal it

The p r o b a ­

sectio n is

the

p a ra llel

not p o ssib le

slip p in g

ex p la in in g

the

m entioned a b o v e ,

m eets th e the

w h ile

Garbon a to m s a r e

p la n es.

its

no m e t a l ­

p la n es,

two f a c t o r s

dim en sion o f

the

new g r a p h i t e .

layer

p la n es.

sectio n

m i g h t be men­

So f a r , th is

the

betw een th e

a p p ea rin g w ith

A diagram m atic fla k es

These

It

l i e , atom

R iley d is c u s s e s

to

p lan es

has a

ca-st i r o n s h a s b e e n

w ork." ^

w ith in

th e

p la n es.

lo n g est

fla k e

in

sim ila r

la y ers

1 I"?

betw een th e se

w ith in

structure

Scherrer. h is

hexagonal b asal

alon g th e

b ility

ture

th e

from t h o s e

o th er .’ ’

has been attach ed

o n l y weak b on d s e x i s t

p la n es.

the

in

Pow erful

surface

w id ely

a ltern a te

form o f g r a p h i t e

im oortan ce

sp eak in g,

that

N atural g ra p h ite

s t r u c t u r e , where

lu rg ica l

account

of

and n o n - f e r r o u s

sense

has a c r y s ta l

r e p o r t e d b y D eb y e and

stru ctu re

th e

fla k es

T h is o c cu rr e n c e

ferrous

w hich d i f f e r s

iro n s

natural

norm ally

th at

recen tly

of

e x c e p t io n s ) , in

hexagonal

atom ,

phase

steel.

as

phases p r e se n t.

of

la y ered

the

structure

G -raphlte to

in

e x ists

o f the

crystal

basal

stru c­

G en erally the ready e x i s t i n g

secondary g r a p h ite

prim ary g r a p h it e

c r y s t a l l i z e s on t h e a l ­

i n a s m o o th band a ro u n d i t .

T h is sm ooth band u n d e r a h i g h m a g n i f i c a t i o n a p p e a r s f l u f f y . T his secondary g r a p h ite m ain g r a p h i t e

c ry stal,

is

u su a lly

but i t

is

90 d e g r e e s t o t h e m a i n c r y s t a l ;

sim ila rly

o r ie n te d to the

som etim es a l s o o r i e n t e d a t th is

is

speaking o p t i c a l l y .

F la k es of g r a p h ite e x h i b i t pronounced o p t i c a l a n is o tr o p y and r e f l e x p l e o c h r o i s m . g rap h ite

In se c tio n s p a r a lle l to b a sa l p lan es,

i s m e ta llic w ith high r e f l e c t i v i t y

a n d d o e s n o t show

any form o f o p t i c a l a n i s o t r o p y . A dvantages o f N odular G ra p h ite o v e r Flake G ra p h ite As g r a p h i t e h a s v e r y l o w t e n s i l e

stren g th ,

a r e •c o m p a r a b l e t o m i c r o s c o p i c c r a c k s i n t h e crack,

g eo m etrically

speaking, has a la rg e

ratio ,

n o d u le o r a s p h e ro id on th e

s u r f a c e t o volume r a t i o .

The f l a k e h a s , the ends.

in g en eral,

flak es

s te e l m atrix .

A

s u r f a c e t o volume

o t h e r h a n d h a s t h e minimum

Under t h i s c o n d i t i o n ,

g ra p h ite a c tin g as vo id s in the

th ese

the e f f e c t o f

s t e e l m a tr ix w i l l be m inim ized an e lo n g a te d body, p o in te d a t

Heavy s t r e s s c o n c e n t r a t i o n w i l l b e s e t u p a t t h e s e

\

p o in ts in the

s te e l m atrix .

In o th e r w ords,

c arb o n have h ig h n o tc h e f f e c t . sphere h as uniform

It

the f la k e s of

i s w e l l known t h a t t h e

s tr e s s d is tr ib u tio n over i t s

surface;

th ere

f o r e a s r e g a r d s d i s c o n t i n u i t y , th e nodule e n s u r e s m ost r e g u l a r d i s t r i b u t i o n of s tr e s s e s in th e

s te e l m atrix .

Summing u p t h e m a i n a d v a n t a g e s , we may s a y t h a t t h e m a i n advantages of the no d u lar g ra p h ite 1)

the e f f e c t of g ra p h ite

m a tr ix i s m inim ized .

in c ast Irons a r e :

a c tin g as v o id s in the

steel

24. 2)

the notch e f f e c t of the g ra p h ite

S tru ctu re

i a m inim ized.

o f t h e G r a p h i t e Nodule X



F ig.

Fig 2

1

The g r a p h i t e l a t t i c e . Grow th o f a g r a p h ite o c c u rs p r e f e r e n t i a l l y i n the p l a n e OZ, OY. ( P i c t u r e from R e f e r e n c e 1)

Schem atic r e p r e s e n t a t i o n o f th e o r i e n t a t i o n o f g ra p h ite c r y s t a l l i t e s in carbon n o dules. ( P i c t u r e f r o m R e f e r e n c e 1}

Since th e n o d u le s o c c u r r i n g i n n o d u la r c a s t i r o n s a re o f the

a p h eru litic v a rie ty ,

to th is v a rie ty

of nodules.

o u r d i s c u s s i o n w i l l be r e s t r i c t e d L ike a t r u e

sp h e ru litic

stru c tu re ,

t h e n o d u l e s o f g r a p h i t e a r e made u p o f a l a r g e n u m b e r o f a c i c u l a r c r y s t a l s r a d i a t i n g i n a s p h e r o i d a l f a s h i o n from a c e n te r or nucleu s.

Each c r y s t a l l i t e

is

so o r i e n t e d t h a t i t s

25 * b a s a l p lan e s are a t r i g h t an g les to

the r a d i i .

T his s t r u o tu r e

o f th e nodule c o rre s p o n d s to th e o r i e n t a t i o n r u l e l l t e s g i v e n by J a n s e n ^

for

sphenu­

who sh o w ed t h a t i n s p h e r u l i t e s t h e

m ost w id e ly spaced p la n e s te n d t o be o r i e n t e d a t r i g h t a n g le s to th e r a d i i o f the T his s t r u c t u r e lig h t.

sp h e ru lites. c a n be s e e n v e r y e a s i l y

Some p h o t o g r a p h s w e r e t a k e n w i t h p l a n e p o l a r i z e d

l i g h t and b e tw e e n c r o s s e d n i c o l s ,

and th e s e a re g iv e n l a t e r .

T h i s w ould be t h e r i g h t p l a c e tu re

in p o larized

of flak e

graD hite i s d i f f e r e n t

One o f t h e d i f f e r e n c e s b e t w e e n t h e

to m ention t h a t th e

stru c­

from t h a t o f q u a s i f l a k e s . two i s

i n the f a c t th a t

t h e s e have d i f f e r e n t o p t i c a l a n i s o t r o p i c p r o p e r t i e s .

The

b a s a l p la n e s i n the q u asi f la k e s a re o rie n te d a t r i g h t a n g le s to th e

long dim en sio n , w hereas i n th e o rd in a ry g r a p h ite th ey

a re p a r a l l e l to th e lon g dim ension. As i n t h e

fla k e g r a p h ite s , duplex s tr u c tu r e a ls o e x i s t s

in the no d u lar g ra p h ite , t im e s th e o u t e r band i s and som etim es i t

a n d e v e n m o re so i n t h i s c a s e . sim ila rly o rien ted

Some­

to th e m ain body,

i s n o t.

I n some c a s e s ,

p artial

a t th e top of th e m elt,

s p h e r u l i t e s have been e n c o u n te re d

where t h e y have f l o a t e d ;

t h e s e may

h a v e grown by a o r o c e s s o t h e r t h a n u n if o r m c o n c e n t r i c c r y s t a l ­ liz a tio n

(ju st d escrib ed ).

W illiam s.^

T his i s

t h e o p i n i o n o f M orrogh and

26 . EXPERIMENTAL WORK The o b j e c t o f t h e e x p e r i m e n t a l w o r k , a s m e n t i o n e d b e ­ f o r e , was: 1) t o

f in d o u t w hether th e a d d i t i o n a g e n t i s d i r e c t l y

con­

n ected w ith the g ra p h ite nodules or n o t, 2) i f

t h i s be t h e

case,

to fin d

can a s s ig n the r e s p o n s i b i li t y of the g ra p h ite

to

some e v i d e n c e w h e r e b y we

some p a r t i c l e

f o r th e grow th

n odule.

The e x p e r i m e n t a l w o r k i s d i v i d e d i n t o

four p a rts :

a) m icro sco pic e x am in a tio n w ith the a id of p o la r iz e d l i g h t , 0 i’T

.

b) e x t r a c t i o n of th e g ra p h ite

p reserv in g th e ir o rig in a l

s h a p e s from d i f f e r e n t c a s t i r o n s ,

and t h e i r m i c r o s c o p ic

exam in atio n . c)

s p e c t r o s c o p i c work on t h e s e n o d u l e s .

d ) X - r a y work on t h e s e n o d u l e s . The s a m p l e s o f t h e n o d u l a r c a s t i r o n s w e r e t a k e n f r o m t h e i n g o t s c a s t by V. A. A l t e k a r ^

fo r h is m aster’s th e s is ,

t h e a d d i t i o n a g e n t u s e d by him was 15$ m agnesium a l l o y w i t h ferro silico n .

MICROSCOPIC EXAMINATION OF THE NODULES UNDER ORDINARY AND POLARIZED LIG-HT E x p e r i m e n t a l Work E xam ination o f th e n o d u le s of g r a p h ite under th e m ic ro ­ scope w ith th e a id o f p o l a r i z e d l i g h t of th e m a jo rity , ch aracteristic

and t o

rad ial

show s t h a t t h e

some e x t e n t a l l

stru ctu re

of the nodules,

have a

stru ctu re.

The f o l l o w i n g p h o t o m i c r o g r a p h s t a k e n i n t h e l a b o r a t o r y s u p p ly th e n e c e s s a r y e v id e n c e f o r th e above

statem en t.

f

Same N o d u l e F ig . 3. Mag. 840X Exposure 6 s e c s . O rdinary L ight

F ig. 4 Mag. 840X E x p o su re 9 m in. Betw een c r o s s e d n i c o l s

Shows t h e R a d i a l S t r u c t u r e

Same N o d u l e F ig. 5 F ig. 6 O rdinary L ig h t P lane P o la r iz e d Shows s l i g h t r a d i a l L i g h t , stru c tu re . R ad ial s tr u c tu r e Mag. 540X Mag. 840X Exposure 6 s e c s . E x p o s u r e 14 s e c s .

Fig. 7 B etw een C ro s s e d N ico ls. R ad ial s tru c tu re Mag. 840X E x p o su re 7 m in.

28.

Photom icrograph, ta k e n w i t h specim en b etw een c r o s s e d c o ls. c e n t r a l n o d u le shows , th e d u p lex s t r u c t u r e , outer frin g e is ab ly o f e u t e c t ic graph!t

F ig. 9 A nother p h o to m icro g ra p h , betw een c r o ssed n i c o l s , shows t h a t a l l g r a p h it e p a r t i c l e s h a v e some k i n d o f ra d ia l stru ctu re.

Mag. f o r b o t h SI4.OX E xposure 6 m in .

29 • C o n c l u s i o n from t h e M i c r o s c o p i c

S tudy o f t h e M odules Under

P o la r iz e d L ig h t As a l r e a d y m e n t i o n e d , rad ia l

stru c tu re .

It

is

t h e n o d u l e s showed c h a r a c t e r i s t i c

g en erally

thought t h i s

o f c r y s t a l l i s a t i o n around a n u c le u s . o b se rv e d betw een c r o s s e d n i c o l s n o d u les In a co m p letely tra tio n

The r a d i a l

stru ctu re

sh o w s t h e g r o w t h o f t h e s e

spheroidal

fro n t.

Here i s

the I l l u s ­

o f w h a t wa s s a i d u n d e r t h e d i s c u s s i o n o f g r a p h i t e

stru ctu re.

I t m ig h t be m en tio n ed t h a t a l l n o d u le s d i d n o t

show t h i s r a d i a l sh ow ed t h i s

stru c tu re ,

stru c tu re

m ight be a l s o

b u t i n v a r i a b l e e a c h nodule t h a t

sh o w ed a w h i t e

stated th a t

t h i s w hite

spot a t spot

showed o p t i c a l a n i s o t r o p y .

o f n u c le i In nodules,

it

cen ter.

It

"apparent nu­ v

S i n c e we a r e h u n t i n g f o r some p a r t i c l e th e grow th o f th e n o d u le , and sin c e

its

( w h i c h De Sy b e ­

l i e v e s t o be a n u c l e u s an d Morrogh c a l l s t h e cleu s")

Is a re su lt

on w h ic h t o blam e

th ere e x is ts a su sp icio n

was d e c i d e d t o e x t r a c t t h e s e n o d u l e s

c h e m i c a l l y and exam ine them m i c r o s c o p i c a l l y , and w it h th e a i d o f X -ra y s .

sp ectro sc o p ica lly ,

30 . EXTRACTION OF THE NODULES AND OTHER SHAPES OF GRAPHITE E x p e r i m e n t a l Work Prom t h e w o r k c a r r i e d lig h t,

it

selv es.

out w ith the a id of p o la riz e d

was d e c i d e d t o e x a m i n e t h e g r a p h i t e

s h a p e s by th em ­

T h i s 18 p e r m i s s i b l e b e c a u s e o u r i n t e r e s t l i e s

In the g ra p h ite

only

stru c tu re .

Five d i f f e r e n t

sa m p le s o f c a s t i r o n s were t a k e n ,

so t h a t

we w o u l d h a v e t h e c o m p a r i s o n b e t w e e n t h e d i f f e r e n t k i n d s o f g r a p h i t e o b t a i n e d from d i f f e r e n t c a s t i r o n s . 1) A sam ple o f n o d u l a r c a s t i r o n , flak es.

w hich c o n ta in e d q u a s i

( H e a t No. 1 3 )

2) A sam ple fro m c o m p l e t e l y n o d u l a r i r o n . 3) U n s u c c e s s fu l n o d u la r i r o n .

( H e a t No. 1 6 )

( H e a t No. 1 7 )

4) A llo y e d M eehanite C ast I r o n . 3) Orey C a s t I r o n . These sa m p le s were t h e n d i s s o l v e d i n d i l u t e (sp.

gr.

1 .2 );

n itric

acid

t h e n t h e r e s i d u e was w a s h e d w i t h h y d r o f l u o r i c

a c i d t o remove t h e

silic a .

The s a m p l e s o f i r o n w e r e n o t

pow dered b e f o r e d i s s o l v i n g , b u t w hole p i e c e s were d i s s o l v e d to m aintain the

shape o f th e g r a p h i t e .

V isual in s p e c tio n of th e g ra p h ite s th u s o b tain ed co n sid era b le v a r ia tio n .

sh ow ed

The n o d u l a r g r a p h i t e was o f d u l l

c o l o r a nd seemed t o b e v e r y f i n e g r a i n e d , w h i l e t h e o t h e r t h r e e were s h in y and c o a r s e g r a i n e d . The p i c t u r e s o f a l l low .

the g ra p h ite o b tain ed are g iv en b e ­

A l l p i c t u r e s w e r e t a k e n w i t h B a u s c h a n d Lomb m i c r o s c o p e

a tta c h e d t o th e cam era. p ic tu re s in th is

sectio n .

G re e n f i l t e r was u s e d f o r a l l

the

Grey I r o n G ra p h ite* F lak es

are

seen In

o r I& eehanite irreg u la r clea r ly

cast

shape

F ig .

iro n , hut

seem t o

seem s

They are l i k e th o se

he sm a ller*

T hese are

The r o u g h s u r f a c e

of

is

th e uneven r e f l e c t i o n .

I r o n G raphite*

T h is

10 and 11*

and r o u g h s u r f a c e .

sh o r n due t o

M eeh an ite

10 a n d 11

F ig .

sim ila r

F ig , to

12 and 13

grey ir o n ,

hut

seem s t o he

sm a ller. U nsuccessful ^ h ls

N od u lar I r o n Graph! t e ,

is

sim ila r

com pact th a n

n o d u les

Q uasi F la k e s .

shows b o th n o d u le s

is

sm a lle r than th a t

n od u lar ir o n . ^ eeh a n ite

b u tseem s

N odu les

F ig .

o f the

lf> a n d l 6

n od u les

a r e much s m a l l e r

sm a ller.

of

The s i z e

of

co m p letely

th a n g r e y and

iro n fla k e s .

T h is

shows o n ly n o d u le s

o f th e

above.

These

.

F ig.

The s i z e

of

d im en sio n o f C o n clu sion

the

n od u les

16*

is

and 19

are b ig g e r than

are b ig g e r because

h a s b e e n p r o b a b ly added on t o these

17*

The n o d u l e s

g ra p h ite

the

eu tectic

th e p rim ary n o d u le s .

much s m a l l e r t h a n t h e

lo n g

fla k es*

and I n f e r e n c e

The s m a l l s i z e effect

t o be more

and q u a s i f l a k e s .

C o m p l e t e l y N o d u l a r I r o n ur a p h i t e «

th ose

llj-

g r e y i r o n , and p r o b a b ly a l i t t l e

N od u lar G rap h ite w ith T h is

to grey iro n ,

F ig .

com bin e

to

o f t h e n o d u l e s and t h e i r v e r y low n o t c h

give nodul

cast

Irons b e tte r p h y sic a l

p ro p erties. ^he n o d u le s u n d e r th e m ic r o s c o p e sh in in g

on them from an a n g l e ,

lo o k

and w it h th e

lik e

chunks o f

lig h t so lid

co a l.

32 . We may I n f e r t h a t : 1)

s i n c e t h e g r a p h i t e was fo rm ed a t a h i g h t e m p e r a t u r e

and t h e n was e x p o s e d t o t h e h i g h p r e s s u r e s o f t h e m etal,

it

is p o ssib le

so lid ify in g

t h a t the g r a p h ite , e s p e c ia lly th e

n o d u le s , b e ca u se o f th e u n ifo rm p r e s s u r e on a l l

sid es, be­

came v e r y c o m p a c t . 2) i f

th is

i s th e c a se ,

a d d itio n ag en t,

t h e n u c l e a t i n g compound o f t h e

or th e ad41t lo n i t s e l f ,

i f e v e r p r e s e n t , may

s t i l l be a t th e c e n t e r s o f th e s e n o d u le s e v en a f t e r a l l th e acid trea tm e n t. It

i s ad m itted th a t

some o f t h e n u c l e a t i n g a g e n t may

have d i s s o l v e d and a l s o t h a t t h i s a d d i t i o n a g e n t w i l l be p r e s e n t i n m inute q u a n t i t i e s .

PHOTOMICHOGRAPHIC COMPARISON OP GRAPHITE SHAPES IN DIFFERENT CAST IRONS Grey I r o n s

G raphite

F i g . 10 M a g n i f i c a t i o n 710X E xposure 12 m in . S ize o f f l a k e s 0 .0 0 3 ” Average s i z e o f M eeh an ite

Iron s

C h em ically E x tr a cted

F i g . 11 M a g n i f i c a t i o n 150X E xposure 12 m in . S ize o f f la k e s fla k e s 0.00k"

0 . 0 0 5 11

G raphite C h em ically E x tr a c te d

.

if ,

F ig . 12 Magni f I c a t i on 3 9 OX E xposure 12 m in . S i z e o f f l a k e s ----- 0 . 0 0 2 " Average s i z e o f

F i g . 13 M a g n i f i c a t i o n Ip OX Exposure 12 m in . S ize o f f la k e s — - 0 .0 0 3 5 ” f l a k e s ----- 0 . 0 0 2 8 "

U n s u c c e s s f u l N o d u la r C a s t I r o n ---- G r a p h i t e C h e m ic a lly E xtracted .

F ig. 14 M a g n if l o a t i o n 150X E x p o s u r e 12 min. S i z e o f f l a k e s ----- 0 . 0 0 4 w S im ila r to grey ir o n graph I t e , but tendency to lo s e fla k y nature.

N odular

C ast

Iron

----- G r a p h i t e

F i g . 15 M a g n i f i c a t i o n 390X E xposure 12 m in. S iz e o f n o d u le s 0 .0 0 0 5 " E vid en ce o f q u a si f l a k e s Average s i z e o f

C h em ically E x tr a c te d .

F i g . 16 M a g n i f i c a t i o n 390X E x p o s u r e 12 m in. S iz e o f n o d u les 0 .0 0 0 5 " E vid en ce o f q u a si f l a k e s n o d u l e s 0 . 0005 "

35 . N odu lar

C ast

I r o n -----

G raphite

F ig.

C hem ically E x tr a c te d .

17

M a g n i f i c a t i o n 390X E x p o s u r e 12 m in. S iz e o f n o d u les - 0 .0 0 0 9 * C o m p l e t e l y n o d u l a r , no q u a s i

P ig.

18

F i g . 19 M a g n i f i c a t i o n 710X E x p o s u r e 17 m in . No q u a s i f l a k e s Size o f n o d u le s 0 .0 0 1 "

fla k es

36. S P S G T R O G r R A P H IC

WORK

E x p e r i m e n t a l Work On t h e the

b a sis

n o d u les,

a lrea d y

it

o f th e

was d e c i d e d

ob tain ed the

exposure

v a r y i n g from 5

spectrograph.

to

more w as o b t a i n e d C ontact

on ly

p la te the

in v estig a tio n

four

have b een g iv e n . fir st

range

p la te

the

M eehan ite

p la in

in

T he p r e s e n c e (a llo y ed ) lin es are

iro n

on th e

on th e

is

M eehan ite

tim e

cast

p la tes 120

co n ta in s

iro n . The

On t h i s

T h is p la t e

ranges.

of

one

have been g iv e n .

were r u n .

d ifferen t

a d d itio n

by

Three d i f ­

o b ta in ed ,

copper e le c t r o d e .

p la te shows t h e

The e x p o s u r e

tim es

have b een run i n s e c o n d s and 125

th e

spectrum

the

seconds.

lin es

of

g ra p h ite.

o f m agnesium i n n o d u la r o u tsta n d in g .

com parator a re

le ft,

g ra p h ites

p la tes

T he t w o o t h e r

The t h i r d

g ra p h ites

were ru n w i t h tim e

125 % econds.

u n a llo y ed

g ra p h ites

w ith exposure

p la tes

of

in v estig a ted .

o f three

o f th ree

d ifferen t

sem i-q u a n tita tiv ely

to

the d i f f e r e n t

w a s made w i t h

made f r o m o b s e r v a t i o n the

and

seconds

from p l a i n ,

p rin ts

fir st

test

Several

s p e c t r a l r a n g e s were

In a d d itio n

fir st

to

q u a lita tiv ely

means o f

feren t

co n clu sio n s

p ictu res

i r o n s and M eeh a n ite

The p i c t u r e s

attach ed .

from P l a t e

o f m agnesium

P ictu res 2 are

from P l a t e

on th e

rig h t

3

hand

sid e . R esu lts N odu lar g r a p h it e w it h q u a s i ( H e a t No. 1 3 ) C o m p letely n od u larg r a p h it e ( H e a t No. 1 6 )

fla k es

------------ d e f i n i t e a m o u n t s o f m a g n e s i u m , a l s o some i r o n and s i l i c o n . ---------- m o r e m a g n e s i u m t h a n No. 13 ( a b o v e ) , a l s o some i r o n a n d s i l i c o n .

37 U n s u c c e s s fu l n od u lar

A lloyed

P la in

gra p h ite

c o n t a i n s d e f i n i t e amount o f m agnesium , b u t l e s s t h a n h o . 13 and No. 1 6 .

M eehan ite

c o n t a i n s d e f i n i t e am ounts o f m a g n e s iu m , a l i t t l e more th an u n s u c c e s s f u l nod u lar g r a p h i t e . A l s o i r o n and s i l i c o n , more t h a n a b o v e .

M eehan ite

c o n t a i n s v e r y l i t t l e mag­ nesium , a lm o st a s l i t t l e as carbon b la n k s. Iron a n d s i l i c o n , m or e t h a n Mo 13 a n d . N o . 1 6 .

G-rey I r o n

c o n t a i n s v e r y l i t t l e m ag ­ n e s i u m , a l i t t l e m or e t h a n carbon b la n k s. C ontains some i r o n a n d s i l i c o n .

C o n clu sio n Fr om t h i s

ev id en ce,

c o n t a i n s m agn esium . th ree th e

are

the

g ra p h ite

It

we c a n s a y a lso

co n stitu en ts

that

co n ta in s

o f the

th e

fir st

we may s a y t h a t

th e

n o d u lizin g e f f e c t

as th e It

silico n

is

two c a s e s

known t o

m ust be rem embered

shown by t h e

th at

h ig h r e a c t i v i t y

i r o n and

is

g iv e the

s p e c t r o g r a p h may a l s o

compound o f m a g n e siu m and t h i s

g rap h ite

n o d u lizin g

in

sium ,

the

in

silico n .

agent.

th e

presence me an t h e

Is. a lm o s t

These

S in ce

form o f n o d u l e s ,

com es from t h e fla k e

nod ule

magne­

g ra p h ite. o f m agnesium presence

c erta in ,

of

some

due t o

o f m a g n e s i u m * T h u s m a g n e s i u m may .mean t o

the be

a compound o f m a g n esiu m . A g o o d amount o f m agnesium i s M eeh an ite.

T h is m agnesium i s

p rob ab ly

scrap added a s a l l o y i n g

elem en ts.

m a teria l

g ra o h ite

o u tsid e

th erefore present

in

th is the

o f the

m agnesium i n g ra p h ite

a lso

the

itse lf.

p resen t in

the

p i c k e d up from t h e

We h a v e d i s s o l v e d by th e

a llo y ed

a cid

t r e a t m e n t and

M eehan ite g r a o h it e T herefore,

a ll

m ust be

we d r a w a n o t h e r

36

e on c l u a l c n , Q VS

such o t h e r

i 'o arr . I t , Cl V ^*h oe

rea

that

any n a g n e s i u n l e f t

over a f t e r v o l a t i l i z a t i o n

o r o c e s o , h a s a t« n d o n c y t o col l o o t t h e

T h i s rnagne3i ur . d o e s n o t h a v e a n y e f f e c t

c f the .graohite u n t i l a c e r t a i n

a.raphi. t e on t h e

concentration. h as been

39.

•• cva ttOo a P

■ H -cC ©

c ^ t> t> t>

&a

• to

54 P o ;.:•■ -PP >0> id O pj

o

o to -p > c]> to . h td ,£} co to

lH

MD

jzJ P4 !H £4 £4 *h *h o *. (H -p

a

cp CM m. chi -p * O " - - O to cm

ts.o

vr\ £4

.h

p a>

to a> p

& ■ * fH -P P r— ! o o OP m 525S3 to H >

50. TABLE OP "a" VALUES OP LINES Average E x p e r i m e n t a l V a lu e s

M a" V alues

In ten sity

Com ments

3 .2 2

v.w

p resen t in a l l

3.16

v.w .

p resen t in a l l ex­ cep t grey iro n

3.01

v.w .

p resen t in a l l

2 .9^

MS2Q3 ' d «’ V alues

In ten sity

j**.24

0 .8 0

3 .05

0 .2 4

v.w.

p resen t in a l l

2.78

v.w .

n o t p r e s e n t i n g rey and 2 .77 M eehanite, o th erw ise a ll

0 .2 4

2.65

v.w .

w eaker th a n above l i n e s , n o t i n g re y o r M eehanite

2 .46

weak

s tro n g e r th an above, v.w , i n g rey

2.45

1.00

2 .3 7

ex trem ely weak

2 .28

v.w .

not in nodular g ra p h ite No 16 a n d u n s u c c e s s f u l

2.22

v.w .

p r e s e n t i n n o d u la r/ffra p h - 2 .21 i t e , o n ly s t r o n g e r %han 3.22

2 .08

v.w .

p re se n t in g rey ,n o d u la r g r a p h i t e 16 a n d u n s u c ­ cessful

1.96

v.w .

w eaker th a n 3 .2 2

1.92

* v.w .

p resen t in a l l

1 .87

* v.w .

p r e s e n t i n n o d u la r g ra p h - 1 .8 7 i t e and u n s u c c e s s f u l , w eaker th a n 1 .9 2

1 .85

v.w .

p resen t in a l l except unsucce s s f u l

1 .8 1 5

v.w .

weaker th a n 1.85

1 .8 0

0.16

1 .75

v.w .

only in n o d u lar g rap h ites

1 .75

0.16

n o t i n M eehanite and in unsuccessful

1 .9 9

0 .4 0

0 .1 6

0.32

A verage E x p e rim e n ta l V a lu es

MggC^

"a"

*aM

V alues

In ten sity

1 .6 3

v.w .

present in a ll

1 .5 6

v.w .

only i n n o d u la r g rap h ites

1 .58

0 .2 4

1 .53

v.w .

present in a ll

1 .51

0 .3 2

1.49

v.',^.

present in a ll

1.42

v.w .

not present in M eehanite

1 .3 9

v.w .

Comments

present in a ll

1 .3 6

v.w .

only in n o d u la r g rap h ites

1 .33

v.w .

only in n o d u lar g rap h ites

1 .2 4

v .w .

p r e s e n t only i n nodular g ra p h ite

1 .2 1

v .w .

n o t i n M eehanite

1 .1 9

v .w .

p resent in a l l

1 .174

v.w .

not in unsuccessful

1 .0 7 8

v.w .

p resen t in a l l

1 .0 3 0

v.w .

present

in a l l

1.000

v.w .

present

in a l l

* in te n sity

not in order.

V alues

v

In ten sity

52. S u g g e s t i o n f o r F u r t h e r E x p e r i m e n t a l Work The r e s u l t s o b t a i n e d f r o m t h e e x p e r i m e n t a l w o r k c a r r i e d o u t so f a r a r e

in te restin g ,

a p relim in ary n a tu re .

b ut th ey

sh o u ld be term ed o f only

F u rth er in v e s tig a tio n

should be d iv id e d

i n t o two p a r t s : 1)

Im provem ent i n t h e t e c h n i q u e o f s e p a r a t i n g th e n o d u le s

from t h e c a s t i r o n s and t h e n th e nodules to

sp ectrographic

su b je ctio n of these

and X -ray work.

2) S e p a r a t i o n o f t h e n o d u l a r g r a p h i t e

from o t h e r n o d u l a r

c a s t i r o n s p r o d u c e d by o t h e r a d d i t i o n a g e n t s a s , dium ,

lith iu m , barium ,

stro n tiu m ,

v e s tig a tio n of th ese g ra p h itic C o n sid erin g the e le ctro ly sis;

first,

cerium ,

and c a l c i u m ; a n d t h e

so­

in ­

nodules.

the

i r o n m ig h t be d i s s o l v e d by

by c o n t r o l l i n g t h e c u r r e n t d e n s i t y ,

d i s t a n c e b e t w e e n t h e two e l e c t r o d e s , tio n to c o n tro l th e r a te

separated

e tc .,

v o ltag e,

we a r e i n a p o s i ­

o f d i s s o lu tio n o f the

iro n m atrix .

A n o th e r m ethod o f re m o v in g t h e i r o n i s by d i s s o l v i n g t h e i r o n in a n e u tral

s o lu tio n of copper su lp h ate.

th e n be s e p a r a t e d from th e

p rec ip ita te d

The g r a p h i t e c a n

c o p p e r by m e a n s o f

some g r a v i m e t r i c m e t h o d o r c e n t r i f u g a l m e t h o d . way w o u l d b e t o

s t i r t h i s m ix tu re i n a b u c k e t o f w a te r and

t h e n d e c a n t t h e w a t e r when t h e c o p p e r i s w hile th e g ra p h ite

is

C o n sid erin g th e the g ra p h ite

The s i m p l e s t

still

Just

s e t t l i n g down,

f l o a t i n g around In th e w a te r.

second p r o p o s i t i o n ,

in v estig atio n of

form ed by d i f f e r e n t a d d i t i o n a g e n t s m ig h t t e l l

u s a s to what a re th e o t h e r p a r t i c l e s t h a t n u c le a te g ra p h ite nod ules. com pared.

Then t h e i r

cry stal

stru ctu re

the

c o u l d be

53. SUMMARY The p r o b l e m o f t h e t h e s i s was t w o f o l d , p a r t d e p e n d e d on t h e f i r s t .

The f i r s t

though the

p a r t was t o

second

fin d out

w h e t h e r t h e a d d i t i o n a g e n t h a s any d i r e c t c o n n e c t i o n w i t h th e nodules of g ra p h ite .

Then se c o n d ,

d i d h a v e some d i r e c t c o n n e c t i o n ,

The f i r s t on t h i s b a s i s ,

some

o f th e grow th o f th e

some d e f i n i t e

p article.

s t e p i n s o l v i n g a problem i s to u n d e rs ta n d i t ; in v e s tig a tio n of th e o rie s of n o d u larizatio n

was c a r r i e d o u t . by D r.

th is a d d itio n agent

t h e o b j e c t was t o f i n d

e v id e n c e whereby th e r e s p o n s i b i l i t y n o d u le s c o u ld be a s s ig n e d t o

if

T h e r e a r e tw o m a i n t h e o r i e s ;

one p u t f o r w a r d

Morrogh o f t h e B r i t i s h C a st I r o n R e s e a r c h I n s t i t u t e ,

a n d t h e o t h e r p u t f o r w a r d b y P r o f e s s o r De Sy o f t h e U n i v e r s i t y o f G hent,

B elgium .

ra p id co o lin g i s g rap h ite. on th e cry stal

M orrogh sa y s t h a t t h e p r o p e r c r i t i c a l

t h e m ain f a c t o r i n t h e p r o d u c t i o n o f n o d u l a r

De S y , w h i l e m o re o r l e s s a g r e e i n g w i t h M o r r o g h

im portance o f c o o lin g r a t e , stru ctu re

type o f g ra p h ite

of th e n u c le a tin g p a r t i c l e s d eterm in es the form ed.

N e i t h e r o f them seem s t o e x p l a i n

how t h e n o d u l e s o f g r a p h i t e liq u id

phase.

f u r th e r proposes th a t the

preserve

th eir

The o t h e r p o i n t o f d o u b t i s ,

shape i n th e Why d o e s t h e

g r a p h i t i z i n g a g e n t have t o be added i n th e d o u b le t r e a t m e n t p ro c e s s , w ith o r a f t e r th e a d d itio n of n o d u liz e r to cause n o d u la riz a tio n o f th e g ra p h ite ? The g r a p h i t e

i n th e n o d u la r i r o n h a s b e e n found to be

o r i e n t e d a t 90 d e g r e e s fro m t h e f l a k e g r a p h i t e o f view o f o p t i c a l a n i s o t r o p y .

The b a s a l p l a n e

from t h e in flak e

po in t

54, g r a p h i t e m eets th e p o lis h e d dim ension of th e plane the

flak e.

p a r a l l e l to th e lo n g e s t

In then o d u le,

i s a t r ig h t an g les

to the

long d im ension of th e In the la b o ra to ry ,

surface

how ever,

the b a s a l

r a d i i or a t r ig h t a n g le s to

c ry stallite.

th e nod u les in the

o f c a s t i r o n were exam ined u n d e r p o l a r i z e d

p o lish ed lig h t.

sectio n s Most o f

/

t h e m sh ow ed some e v i d e n c e o f r a d i a l stru c tu re

suggests c r y s t a l l i z a t i o n

was t h e r e f o r e d e c i d e d t o p reserv in g th e ir

around a n u c le u s ,

The s e p a r a t e d n o d u l e s u n d e r t h e m i c r o ­

s o lid appearance o f th e nodule,

th at i f

and I t

s t e e l m a t r i x and t o exam ine

scope re s e m b le d round p i e c e s o f s o l i d a n t h r a c i t e th is

The r a d i a l

se p a ra te th e nodules of g r a p h ite ,

shape from th e

them f o r n u c l e i ! .

stru ctu re.

th e s e nodules a re

so s o l i d ,

co al;

from

I t was f u r t h e r a r g u e d , t h e n t h e n u c l e a t i n g com-

%

pounds o f th e a d d it i o n a g e n t, cen ters,

i f a t any tim e p r e s e n t a t th e

may s t i l l b e p r e s e n t e v e n a f t e r t h e a c i d t r e a t m e n t .

On t h i s b a s i s ,

i t w a s d e c i d e d t o d o some s p e c t r o s c o p i c w o r k .

The r e s u l t s p f t h i s w o r k a p p e a r e d t o b e e n c o u r a g i n g ----- - e v i d e n c e f o r m agnesium i n t h e g r a p h i t e n o d u l e was u n c o v e r e d . T h i s l e d t o t h e work w i t h X - r a y s ,

and th e c o n c lu s io n t h a t

t h i s m agnesium e x i s t e d a s m agnesium c a r b i d e .

55 * CONCLUSION In co n clu sio n ,

th e a u th o r v e n tu re s to

sa y t h a t by

m odify in g th e e x i s t i n g t h e o r i e s to a r e a s o n a b le e x t e n t , would be p o s s i b l e t o e x p l a i n f a c t o r y m anner.

it

some p h e n o m e n a i n a m ore s a t i s ­

For ex am p le,

i f Dr.

M orrogh would a c c e p t

th e p r o p o s a l t h a t th e n u c l e a t i n g p a r t i c l e s have an i n f lu e n c e on th e

shape o f g r a p h i t e

a cc ep t the

f o r m e d and, i f P r o f e s s o r De Sy w o u l d

fo rm a tio n o f th e n o d u les In th e

liq u id

sta te ,

It

w o u l d b e p o s s i b l e t o e x p l a i n how t h e n o d u l e s o f g r a p h i t e m ain tain t h e i r

shape i n th e l i q u i d

sta te .

It

i s known t h a t

some o f t h e n o d u l e s a r e d e f o r m e d i n f l o a t i n g t o the m elt,

the to p o f

and t h e r e have b e e n s u g g e s t i o n s t h a t t h e s e

nodules

may b e f o r m e d b y a p r o c e s s o t h e r t h a n u n i f o r m c o n c e n t r i c c ry stalliz atio n , to th e

su b ject,

but th is

I s only a su g g e s tio n .

we may s a y t h a t t h e r e

th e l i q u i d phase to keep th e g r a p h ite h o ld in g i t

is

no o u t s i d e

n o dular,

t o g e t h e r m u s t come f r o m w i t h i n .

come f r o m t h e way t h e g r a p h i t e

Coming b a c k

c ry stallites

force

and th e

in

force

T h i s f o r c e w ould are arranged

around th e c e n t e r . S im ilarly ,

a n e x p l a n a t i o n may b e g i v e n why i n t h e

"double

t r e a t m e n t p r o c e s s ” t h e g r a p h i t i z e r h a s t o be added w i t h o r a f t e r th e n o d u liz e r. after tatin g to

When t h e g r a p h i t i z e r i s a d d e d w i t h o r

the a d d i t i o n o f th e n o d u liz e r , from th e m e lt f i n d s

form, n o d u l e s .

ad d itio n .

su itab le

These n u c l e i a re

the g ra p h ite p r e c i p i ­ n u clei to

a resu lt

I t m u s t b e b o r n e i n m in d t h a t t h e

c ry sta lliz e

on

of the n o d u liz e r fo rm atio n of

t h e n u c l e i from t h e a d d i t i o n o f t h e n o d u l i z e r i s a n e x t r e m e l y

56. r a p id o r alm o st an in s ta n ta n e o u s p ro c e s s .

At t h e

same t i m e ,

th e p ro cess of g r a p h itiz a tio n i s

a l s o v e r y f a s t and i f t h e i; g r a p h i t e d o e s n o t f i n d any n u c l e i , i t w i l l r e ­

p rec ip ita tin g v e r t to i t s

hexagonal or flak y n a tu re .

The c o n c l u s i o n s d e r i v e d f r o m t h e e x p e r i m e n t a l w o r k a r e now g i v e n . What H w e Wo L e a r n e d f r o m t h e E x p e r i m e n t a l Work? 1)

^agnesium i s

found t o he p r e s e n t i n t h e n o d u le s o f

g rap h ite. 2)

Magnesium i s p r e s e n t i n a l l o y M e e h a n i te g r a p h i t e and very l i t t l e

3)

in grey Iro n .

Magnesium i s

found i n th e g r a p h ite

nodular g ra p h ite ,

of unsuccessful

though in l e s s e r q u a n tity th an i n

nodular g ra p h ite . 4)

The p r e s e n c e

is also

shown o f i r o n a n d

s ilic o n in

success­

f u l and u n s u c c e s s f u l n o d u la r g r a p h i t e . 3)

The p r e s e n c e o f s i l i c o n a n d i r o n i s

also

shown i n g r e y

i r o n and M eeh an ite. 6)

T h i s magnesium e x i s t s a s m agnesium c a r b i d e i n q u a n t i t i e s d ire c tly th is

p r o p o r t i o n a l t o t h e am ount o f m agnesium p r e s e n t ;

can be

seen from t h e i n t e n s i t y

and number o f m agnes­

iu m l i n e s . C o n clu sio n s The m a g n e s i u m i n t h e m e l t c o m e s f r o m s e v e r a l I t may j u s t come f r o m t h e scrap

sp e cifica lly

q u ite

lik e ly .

to

the m elt.

scrap.

I t may a l s o

added f o r i t e

a llo y v alu e,

Or i t

com© f r o m t h e and t h i s

may j u s t b e t h e r e b e c a u s e i t

A part of i t

may v o l a t i l i z e

sources.

is

was a d d e d

o r may b e l o s t

57. som ehow. h an ite

The s m a l l q u a n t i t y

from i t s

m elt i s

o f m a g n e s i u m p i c k e d u p b y Mee­

still

r e t a i n e d by t h e g r a p h i t e .

The

a m o u n t o f m a g n e s i u m i n M e e h a n i t e , a s sh ow n b y s p e c t r o g r a m , is

a little

le s s th an the

nodular g ra p h ite .

From t h i s we

co n clu de: 1)

a f t e r a c e r t a i n low l i m i t o f c o n c e n t r a t i o n o f

magnesium i s r e a c h e d ,

t h e magnesium l o s e s i t s

e sc a p e and re m a in s i n th e m e lt.

tendency to

T h is sta te m e n t i s

supported

*>y t h e o b s e r v a t i o n , t h a t t h e l o w e r t h e m a g n e s i u m c o n t e n t o f the n o d u liz e r,

the b e t t e r

is

its

reco v ery in the no d u lar

cast iro n . 2)

a p a r t o f t h e magnesium r e m a i n i n g i n t h e m e l t ,

more l i k e l y

a ll

of i t ,

or

t h e n r e a c t s w i t h some f o r m o f c a r b o n

i n t h e m e lt t o g i v e magnesium c a r b i d e . 3)

t h i s m agnesium c a r b i d e h a s t h e t e n d e n c y t o a c t a s

a n u cleu s fo r the g r a p h ite ; in flu e n ce

b u t t h e m a g n e s i u m c a r b i d e h a s no

on t h e 's h a p e o f t h e g r a p h i t e u n t i l a c e r t a i n l i m i t

o f c o n c e n t r a t i o n o f magnesium c a r b i d e c o n d itio n s fo r n o d u la riz a tio n are said

i s re a c h e d and o th e r

sa tisfie d .

I t may a l s o b e

from t h e o b s e r v a t i o n s t h a t t h e p r e s e n c e o f s i l i c o n i n

reaso n ab le

q u a n t i t i e s h a s no e f f e c t

nesium c a r b i d e .

o n t h e f u n c t i o n o f mag­

58. BIBLIOGRAPHY 1.

H. M o r r o g h a n d W. J . W i l l i a m s : " G r a p h i t e i n C a s t I r o n s and i n N ic k e l- C a r b o n and C o b a lt- C a r b o n A l l o y s . ” J o u r n a l o f t h e I r o n and S t e e l I n s t i t u t e , 1 9 4 7 , v o l u m e 155» p p . 3 2 1 - 3 7 1 .

2.

H. M o r r o g h a n d W. J . W i l l i a m s ; ” P r o d u c t i o n o f N o d u l a r G rap h ite S tr u c tu r e s in Cast I r o n s . ” Jo u rn a l of the I r o n a n d S t e e l I n s t i t u t e , 194-8, v o l u m e 1 5 8 , p p . 3 0 6 -

322.

3.

H. M o r r o g h ; " T h e P o l i s h i n g o f C a s t I r o n M i c r o s p e c i m e n s and th e M e tallo g ra p h y o f G ra p h ite F l a k e s . ” J o u r n a l o f t h e I r o n a n d S t e e l I n s t i t u t e , 194-1, v o l u m e C X L I I I (No. 1 ) , p p . 1 9 5 P - 2 0 5 P .

4.

H. M o r r o g h a n d J . W. G r a n t : "N o^ujar O ast I r o n s , t h e i r P r o d u c t i o n a n d P r o p e r t i e s . ” '''Foundry T r a d e J o u r n a l , 194-8, v o l u m e 8 5 , p p . 2 7 - 3 4 , 5 1 - 5 8 , 8 1 - 8 6 , 1 0 5 - 1 1 0 , 199-200, and 224.

5.

G. V e n n e r h o l m , H. B o g a r t , a n d R . M e l m o t h : ”N o d u lar O ast I r o n . ” F o u n d ry T ra d e J o u r n a l , March 1 9 5 0 , volum e 8 8 , pp. 247-256.

6.

H. M o r r o g h : C o r r e s p o n d e n c e , F o u n d ry T ra d e J o u r n a l , March 1950, pp. 321.

7.

H. Hanem ann a n d S c h r & d e r : A t l a s M e t a l l o g r a p h i c u s , v o l u m e 2 , s e c t i o n 5 , s h e e t 37? B e r l i n 1 9 3 6 , G e b r u d e r B o r n tra e g e r.

8.

H. N i p p e r :

G iesserel,

1 935# v o l .

22, pp.

280-287.

9.

H. G r o e b e r a n d H, H a n e m a n n : A rch lv f u r d a s S is e n h u tte n w e se n , 1 9 3 7 , volum e 11, p p . 1 9 9 -2 0 2 .

10.

A l b e r t De S y : " B e lg ia n R e s e a rc h Advances N odular G raph­ i t e T h e o r y . ” A m erican Foundrym an, J a n u a r y 1949, volum e 1 5 , 1 6 , p p . 5 5 - 6 2 .

11.

A l b e r t De S y : " N o d u l a r C a s t I r o n P r o d u c e d w i t h L i , Ca, B a, S r , N a . ” M e t a l P r o g r e s s , S e p te m b e r 1 9 5 0 , volume 5 8 (N o. 3 ) , P . 3 5 7 .

12.

A l t e k a r , V. A; " I n v e s t i g a t i o n o f P ro d u c tio n and P ro p e r­ t i e s o f N odular o a s t I r o n . " T h e s is , C olorado School o f M ines, G olden, C o lo rad o .

13.

H.

L. R i l e y : " s t r u c t u r e o f G r a p h i t e .” F uel i n Science a n d F i ' a c t l c e , v o l u m e 2 4 , 1 9 4 5 , PP* 8 - 2 4 .

14.

W.

Jansen: Z e i t s o h r i f t f u r K r l s t a l l o g r a p h l e , 1933, volum e 8 5 , p p . 2 3 9 -2 7 0 .

59. 15.

A. P . G a g n e b i n :

S teel,

Septem ber 25,

16.

C. K. D o n o h o , D. J . R e e s e , R. G-. Me E l w e e , a n d G o s t Vennerholm : " S y m p o s iu m o n N o d u l a r G r a p h i t e O a s t I r o n . ” A m e ric a n F o undrym an, 1949 > volum e 1 5 - 1 6 , pp. 32-41.

17.

G. K. D o n o h o : 21.

18.

G. V e n n e r h o l m , II. B o g a r t , R. M e l m o t h , F o r d M o t o r C o m p a n y : wN o d u l a r C a s t I r o n ” , P a p e r p r e s e n t e d a t t h e A n n u a l m e e tin g , S o c i e t y o f A utom otive E n g in e e r s , J a n u a r y 13, 1950.

19.

G. K. D o n o h o : " P r o d u c i n g N o d u la r G r a p h i t e W ith M ag n esiu m .” A m e r i c a n F o u n d r y m a n , v o l u m e 1 5 - 1 6 , F e b r u a r y 1 9 4 9 , PP* 30-37 *

20.

M. N a c k e n , E . P i w o w a r s k y : "On t h e S t r u c t u r e o f S p h e r u l l t l c G r a p h i t e . ” B r u t c h e r T r a n s l a t i o n No. 2 5 0 8 . T r a n s l a t e d f r o m D i e Neue G i e s s e r e i , T e c h n l s c h - W i s s e n s e h a f t l i c h e B e i h e f t e , F e b r u a r y 1 9 5 0 , No. 2 , p p . 7 5 - 7 6 .

2 1.

F. M o r r a l : " N o d u l a r --I r o n ----- A B i b l i o g r a p h y . ” F o u n d r y m a n , J u l y 1 9 5 0 , v o l u m e 18 ( No. l ) .

Product E n g in eerin g ,

1950.

A p r i l 1 9 5 0 , volume

A m erican