SOME INTER-RELATIONSHIPS IN GREY-IRON METALLURGY

T5he^bnerian Sundri/m en’s ^Vssocution,

SOME INTER-RELATIONSHIPS IN GREY-IRON METALLURGY

By J. W. Bolton, M.Sc. (American Exchange Paper).

D iscussing relatio n sh ip between s tre n g th and com position, J . G. P e a rc e 1 s a i d : “ I f these (researches) can be shown to co rrelate (tests, w orking p ro p ertie s, an d o p e ra tin g conditions) even fo r a single set of m eltin g conditions, a g r e a t step fo rw ard in fo u n d ry control becomes possible.” The p re s e n t s ta te of knowledge of grey c a s t iro n as a n e n g in ee rin g m aterial gen erally is recognised as chaotic. A g re a t deal of v alu ab le q u a n tita tiv e research has been c a r

ried o u t. I n th e absence of intensive effort to w ard e x a c tin g co rrelatio n of th is m a te ria l, m ost of th e p resen t-d ay conclusions are h u t q u a lita tiv e . T his condition is understood by all grey iro n m e ta llu rg ists. Technical societies in A m erica are d ev o tin g m uch tim e to stu d y of the problem s involved. T his w ork undoubtedly will b rin g a b o u t m a jo r changes in specifications and m ethods of te s tin g . W ith m ore acc u ra te know

ledge of th e e n g in ee rin g p ro p e rtie s of various g rad es of iro n , th e c h a ra c te r an d q u a lity of p ro d u c t will become m ore n early stan d ard ised . The en g in ee r will m ake g re a te r use of grey iron c a stin g s to th e degree t h a t he is inform ed of its desirab le p ro p ertie s. Scientific foundrym en hold no b rie f fo r th is or t h a t en g in eerin g m ate

ria l. The b est m a te ria l is t h a t which fully satis

fies en g in e e rin g req u irem en ts in th e m ost eco

nomic m an n er. F o r th is purpose i t m ay be bronze, fo r t h a t steel, an d fo r th e other, grey iron. H ow ever, fo undrym en m u st seek accurate

1 Proceedings of The Iron and Steel In stitu te. 1928.

know ledge, t h a t th e y m ay select w ith o u t p re

based on th e sum m ation of silicon and carbon co n te n ts of g r e a t v alu e? (3) Is th e control of th e m a trix of m ore im p o rtan ce th a n th e control of th e g ra p h ite fo rm a tio n ? (4) Is th e condition

* s ! I I I I *

_y ¿//

Fi g. 1 . — Co o l i n g Ve l o c i t y, Co o l i n g Cu r v e s. Si I

! I t

of th e g ra p h ite d ep en d en t on th e n a tu re of the carbides re s u ltin g from com position or therm al h isto ry ? (5) C an th e recently discovered critical m anganese p e rcen tag e be definitely sta te d on

2 0 W l*< W 1-3 hJ & O (Ł| Ü W Hj |_i ¡2 O Ph

Log. mod. rupture. 2.56425 1.77577 1.83514 1.48504 1.66116 1.55630 I 1.42362 1 1.19496 1.31931 1.25527 ! 0.95424

Relative mod. rup. 366.640 59.672 68.414 03 < CO © © IQ CO 03 © © _ _ 1 iO00©©©°0'^><^

OiO©© >0000 0) CO ^ CO 03 f-H 03

Volume Surface area. 0.1200 0 1234 0.1951 0.2139 0.2308 0.2423 0.2444 0.2455 0.2924 0.2997 0.3156 0.3253 0.3253

Volume cub. in. 4.12 7.55 12.6 co io o co ^ t© © © 1 rHiJ^COOOh*^^ HHC3 0ÎHC3 10 10

Surface area sq. in. _t* t> o CO OO 00 CO CO lO

t^ OprH HOO©CO©© r-H i-H

Cross section area. 0.196 0.503 0.601 LO LOI C0Q0©COO3O3©© 1 t-t-©HC3COO©

O O H H H H 0 3 M

Length between sup ports. CO Cd CO 1 03 00 ^ 00 03 0 0 ^ ^ 1 H H N H H H 03C 3

Length cast.

HlOH03 r—l 03 I IO H ['--- IO H t>-1 r-'0303C3—i030303

Sizeofbar. 03 03

X rd ro ^ X ^ ^ ^ "d N O O IO N O O v O iO o T ? ^ -H O O L-r-iO O X 03 03 CO XX X to QC.CO x ^ ^ - . • • 03 r—<

—'03C0rtil0©t>00a5O'-H03C0

.30d. 21181.32788.427.90.315620.860

1.40d. 1.60d. 1.50d. 1.5x1.5 1x12x12 2.00d. 2.00d. 2X2 2.20d. 2.50d. 2.5x2.5 3.00d. 3.00d. 3x3 2x24x24 4.00d. 3 X 24X 24 6.00d. 4x24x24 8.00d.

^ ‘û œ ^ Q O Â O H N rt^ io c o t'û o o iO - H N fç

higb-silicon d ev elo p m en t be re la te d to one of th e e x is tin g th e o rie s? (7) C an th e s u p e r-h e a tin g th e o ry be definitely s u b s ta n tia te d ? (8) Is th e gas c o n te n t of c a s t iro n to be ta k e n as a serious

teoo

eooo

-/eoo

> /662°5

S600

' /400

Spec/me/? S / ze - g “Pu,r6 "/ < o rp '

Pour//?/ 7em/?erature, 2 2 0 0

T o ta / C a rp o s? , 3. P S °P>

S/Z/coe.?, 2 .0 Û K

Zo/u m e, A /3 eu. /s?.

S u r fa c e P r e a , 3 .8 2 se/, /s?

Zo/um e

S u r fa c e f r e o- Û./2Û2 I 1

H/çPest temperature reaches/

fn m o/c/, /" aPo i/e ca s///? # . /7 5 °F 45 m/putes a fte r pour/n/.

-/257 F.

1 /200

! 000

eoo

400

%

Therm o coup/e P o u r/n /

Ça/e-,

a = » < 3

T o p o f ¿S ro ys

5 /a s /r - /S 'Jf/B ‘SAS '

SO S5 20 25 30 35 40 45 50 55

A f / / / S f / / 77€ Sa? S rc O A A A te J

A S ( S /s femperoft/Aie rs? c/ep. 5 / Fi g. 2a.

fa c to r? (9) I s in g o tism of p a ra m o u n t im p o rt

an ce? (10) A re in te r n a l stresses receiv in g th e ir q u o ta of c o n sid e ra tio n in discu ssin g some phe

n o m en a? (11) C an fre e g r a p h ite e x is t in norm al cupola-m elted iro n ? I t is obvious t h a t f u r th e r P a p e rs are needed w hich will c la rify o u r id e a s .”

Four Factors influence Mechanical and Physical

T he iron-carbon-silicon series of alloys known as g rey iro n c o n tain p e a rlite , fe r rite , and as cast

d e m o n s tra te w h eth er or n o t th e so-called in

Relationship of Volume to Surface Area a Significant Factor.

I t is a p p a r e n t t h a t w ith carefu lly -reg u lated fo u n d ry p ra c tic e m any of these facto rs are n early co n sta n t, or a t le a s t susceptible to a

reason-ZZOO

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reoo

/ BOO

11400

/ZOO

t? /ooo

BOO

e o o

400

Spec/men S/ze - / 'fid X 6 * I ong Pour/ng Tempera fare, 27/3“P To fa / Car Aon, 3.5/ %

/959°F. ^S/Z/co/?, ^{2.02 %}

Vo/c/me, 2.49 cu /r?.

S urface Area. /5./Q sg /n Vo/ume

Surface Area ■■ 0/640

H/ghesf tempera/ure reached

■ /n mo/d, / “afore casf/ng, 247° f.

55 m/nvfes a f/er pour/ng

-/344°P

T herm om e/er^j^lTfjermocoup/Ve

' - •• f-l__—

- >

F/t 75* /5X/2X6

0 5 /O /5 20 25 30 35 40 45 SO 55

A X / / /s //me /r? seconds I

A O (6 /s fcm p e ra X u re /n ofeg. f J Fi g. 2b.

able degree of co n tro l. The m ost significant fa c to r is th e re la tio n sh ip of volum e to surface a re a —ex p ressin g th e well-known fo u n d ry fa c t t h a t cooling r a te is p ro p o rtio n a l to section size.

In T able I I is shown a lis t of v ario u s simple

shapes a rr a n g e d in th e o rd e r of th e i r v o lu m e/

su rfa c e a re a re la tio n sh ip .

I n F ig . 3 th e r e is e x p e rim e n ta l p roof of th e v a lid ity of th is r a tio fo r b a rs c a s t u n d e r c a re fu lly co n tro lled an d re p ro d u cib le c o n d itio n s. In

Spec/rver? S/ze- / "PcfX 5 0 Poar/spcf Te/rprra/are, 2700 °r ~

■2044 5 To/o/Cor/>or?t 3.39%

S/V/'cor?, Vo/u/ne,

/.98%

4.72 cu/n Surface Area, 20.42 s</. //?.

= a?3//

Surface Area

W/ffesf fe/rperafere reacOef /r? /no/o', /'oAoee casf/cx?, 3 //°f 32 /7?/r?ufes offer pour//pgr

/344‘f

77?er/7?oajefer

. r --- ^

•• "\ / .

F/os/r /5 f / 2 X5 *

/O /S 20 25 30 35 40 4 5 SO 5 5 Of / / as t/fee /r? secooc/s j

( & /is femperofc/re /r? obpr. f j Fi g. 2 o .

th is we h av e used th e a v e ra g e r a t e of cooling fro m th e solid ificatio n a r r e s t (a b o u t 1,121 deg.

C.) to th e p e a rlitic in v ersio n (a b o u t 732 deg. C.).

(T h a t th e r e is some g r a p h itis a tio n below 732 deg.

C. is well kno w n .) I t is in te r e s tin g to con

te m p la te th e n e t effect to tim e - te m p e ra tu r e (or

cooling curves) versus te m p e ra tu re -g ra p h itis a tio n ra te s on th e n e t r a te of g ra p h itis a tio n u n d e r c a stin g conditions.

The fa c to rs involved a n d th e ir co n tro llab ility fo llo w :— (1) I n i tia l te m p e ra tu re depends to some

etoo

Spec/men Ssee- 2"fid X 6*¿org Pouring Temperature, 2669*P.

To fa/ Cardon, 3.20%

,_

Sf/fcan,

I

^fo/utne, /.97%f&43 cu. in

> _

S u rface Area, 43.98 sg in _j/oJuntf

m —

^=Q^{4 / 7 3}

Surface Area ,

H ighest tem perature reached in aro/af, / 'ahoue castin g , 402*Vf 62 m in u tes a fte r pcur/ng.

~/344*F

Therm om eter

, ,

cThermocoup/e

~

f/crsk / rx ^ X S '

/o rs 20 2j j o s j jo 4 j j o j j A f /> / i //me /s? sec o m f s I 4 0 (9 /s fem pererfe/r# P? efep. C

./

Fi g. 2d.

degree on th e process em ployed an d on th e m ethod of o p e ra tio n of th e p ro cess; (2) pouring te m p e ra tu re is c o n tro lla b le ; (3) final te m p e ra tu re m ay be assum ed as c o n s t a n t; (4) specific h eats of v ario u s ty p e s of iro n do n o t v ary m u c h ; (5) m a g n itu d e of cooling g ra d ie n ts w ith in th e m etal

itse lf a re as y e t li tt le u n d ersto o d . T h a t th ey a re very im p o r ta n t is e v id e n t from th e v a r ia tio n s in g r a in size, e tc ., fo u n d on e x a m in a tio n of th e cross section of som e c a stin g s— n o tab ly

tt o o

i000

Vofa/ne Surface Area

Spec/w en S/'ze - 3*fid X 6 “Long Pour/ng Temperafure, 2633°P ~ To f a / CarAoo. 3.34 % .

5/ / / c o p , / 3 3 % — \—

do/u/Pe, 42.4/ cu. /n S u rfa c e Prea, 63.6/74 sg. /n '

■ 0.6666

~/3709P

TAer/po/ne/er ^

^

¿TAer/pocoap/e

rre

——■ ■ . . V i •

i(i\

i »-v--/■

I I I I . ^,

H/gAesf te/nperofvra reocAed //? __

mo/d, / " a/tore casAAg. 600“ P ecf/mofed TAer/Porrefer __

re ac/ted 7009P 3 S m/outes o ffe r poor/Ag

0 S /0 /S 20 2 d 30 3 S 40 4 S SO S f

/a f//v* //? s a cords ) 's fe/pperafcAre at? deg. £ /

Fi g. 2e.

heavy sections w ith h ig h -carb o n irons. This effect is m a n ife s t in m ech a n ical p ro p e rtie s ;*

(6) c o n d u c tiv ity of m ould m a te ria l, of course, v a rie s som ew hat. (See F ig . 3.) T h is is con

tro lla b le fo r re se a rc h p u rp o s e s ; (7) speed of

4 See A rthur S m ith — “ F ou n d ry Trade J ou rn al,” F eb . 2, 1928, p. 79, F ig. 2 ; also J . W . B olton — Trans. A .F .A ., 1928, V ol. 36,

p. 499, F ig . 8. I

p o u rin g d epends on g a tin g a n d w orkm anship—

b o th re la tiv e ly controllable, b u t ra re ly defined in e x p e rim e n ta l w o rk ; (8) m echanical facto rs o fte n a re overlooked, as, fo r exam ple, w ere th e

Fi g. 3 . — Re l a t i o n o f — t o Ac t u a l Co o l i n g

Ra t e.

b a rs san d -cast, w ere th e y tu m b led , w h at sort of rise rs w ere used, etc. ?

I n an y w ork of classifying irons according to m echanical te s t, th e m ethod of te s tin g should

be defined clearly an d com pletely. I n m uch re search w ork n e ith e r an aly sis n o r size of sections is m en tio n ed .

(stu d y of th e in flu en ce of m a n u f a c tu r in g p ra c tic e on given g ra d e s of c a s t iro n ) as follow s: —

(A) A rra n g e a classification of iro n s acco rd in g to com position : a n d (B) m ak e a n in te n siv e stu d y

Influence of Manufacturing Practice.

I t , th e n , is possible to solve th e firs t problem

0.30

Ratio

-0.40 0.50 Vo/t/ove

Sort&ce Are<7

Fi g. 4 . — St u d y o f Gr a d e o f Ir o n.

of each g ra d e . I n th is stu d y i t is necessary to give co n sid eratio n to th e influence of th e four fa c to rs in d ic a te d in a previous p a ra g ra p h . A lthough th e re are v a s t gaps in th e d a ta neces

sary , m ethods of s ta tis tic a l research can be a p p lied to very good a d v a n ta g e on e x is te n t d a ta . A lis t of several in te re s tin g com pilations of d a ta is a tta c h e d (Table I I I ) . A p a rtia l stu d y of one g ra d e of iron is shown in F ig . 4 a n d notes. The w rite r has com

piled d a ta covering m an y of th e groups, a n d re g re ts t h a t space is n o t available fo r

inclu-sion of th is volum inous, y e t in te re stin g , sub

s ta n tia tio n of th e p ra c tic a b ility of th e scheme of stu d y . These in d ic a te t h a t M r. P e a rc e ’s hope is q u ite possible of p ra c tic a l re a lisa tio n . W hile th e v ery com plexity of th e problem denies exact m a th e m a tic a l p re d ic tio n of each an d every p ro p e rty , i t is u n q u estio n ab le t h a t m ost of these will some d ay be c h a rte d to a degree of accuracy com patible w ith u su al e n g in ee rin g practice. An e x a c t analo g y can be d raw n to th e a r t and science of th e m a n u fa c tu re an d te s tin g of steel, w herein reaso n ab ly a c c u ra te e n g in ee rin g d a ta can be fo u n d in m any handbooks.

Relationship of Test Results.

T ensile T2 is slig h tly h ig h e r th a n T l, th e la t t e r b ein g in th e h eav ie r p o rtio n of th e rib.

S h ears IB an d 2B are close to T l, th e ir average 43,263 lbs. p e r sq. in . tr a n s fe r re d to ten sile in sh ear-ten sile c h a r t.3

62 Shear-44652

/ b p e r 5 4 m

8 f S h e a

r-4! 875 /A per 34

Fi g. 5c.

The av erag e of sh e a r s tre n g th s 1, 2 an d 3C, 46,005 lbs. p e r sq. in ., corresponds to a tensile of ab o u t 38,000 lbs. p er sq. in. (F ig . 6). This is com parable to 39,265 lbs. p er sq. in. of T2.

5 J. V f . B o l t o n —Trans. A .F .A ., 1928, p. 495, F ig. 4.

Teos/Ze SZmogrZ/?/Z? T/ro^sa/refsofZf./&<?/' sc?./,

ta k in g T1 an d T2 a v e ra g e v alu e (37,368 lbs. per sq. in .) as r e p r e s e n ta tiv e of th e c a s tin g , whose re la tiv e co o lin g -ra te a p p ro x im a te s t h a t of a 2.4-in. b a r, we ta k e th e v a lu e 37,800 p e r sq. in.

from th e w r it e r ’s d a ta . T his is a good check

+

o o

. y

o ...T

o 0

o c* o

n

o w r o f? s W /ft A /h ~ k e /

o o - /r o r ? s w /? /7 0 i/f A //e k e /

A / / G r a y / r e s t s o f L o w spZ?cir e ts

2 0 2 5 3 0 3 5 4 0 4 5 50

S f o o r 5 Ore/?o'//? //? T f o o s o / y a ’s o f /¿a / o e r sq . /p.

F i g . 6 . — S h e a r - T e n s i l e R e l a t i o n s h i p s .

w hen one considers t h a t th e ten siles T1 a n d T2 w ere ta k e n fro m a sectio n s u b je c t to some sh rin k a g e . The B rin e ll n u m b ers (195-203) w hen com pared show t h a t th ese com p are w ith th e te n sile w ith in th e lim ita tio n s of th e B rin e ll cor

re la tio n .

F i g. 7a.

û -

5e/7»-Stee/s

^{' y}

o - AZ/eÆ e/ S e * 7 7 '-S t* ł/s -T

• - Ato 5 fe e /

~td jr? Té ?£ ^ FF

% Grrt>os> * 0 3 (% S/Z/conJ E u 'e c f 'c

Fi g. 7b.

T a b le I I I . — Com pilath

Referenceserial. Total carbon. Silicon. Combined carbon. Manganese. Sulphur. Phosphorus. Dia. cast. Transverse load. Deflection. Span.

1 3.52 2.17 0.73 0.60 0.08 0.32 0.50 199 0.73 18

2 3.59 2.14 — “ Cra ne P at tern ” i in. dia. — ^— —

3 — Max. tests £-in. bars — __ 203 — —

4 3.52 2.17 — 0.60 0.08 0.32 0.75 566 0.49 18

5 — Max. tests f-in. bars — — 600 ^— ^—

6 3.52 2.17 — 0.60 0.08 0.32 1 . 0 0 1,191 0.275 18

7 — Max. test 1 .0-in. bar — — 1,275 ^—

_

8 3.52 2.10 — 0.60 0.10 0.34 1.06 1,917 — 12

10 3.54 2.20 0.56 0.64 0.07 0.27 1.20 1,922 0.276 18

11 3.52 2.14 0.48 0.49 0.12 0.63 1.20

_ _

₁₈

_

96 6 5 7.181

—

32,500 0.500 —

— --

6 1

_

—

33,760 0.375

— — -- —

_ _

1>,830 30,243 0.505 38,800 0.505 180 90 6 6 7.112

30,534 0.505

— — — —

— —

1,290 22,205 0.505 32,850 0.505 162 88 6 4 7.116

—

22,725 0.505

— — — — — — _

¿,900 21,250 0.875 — — — — O 3 —

.',900 22,125 0.686

_ _

₁₅₄ ₈₅ ₆ ₁₂ _7.094

:,500 ' 22,450 ?

— — — — —

1,075 13,485 0.800 24,325 0.505 112 — 6 3 7.087

i 1,090 15,330 0.875 — — — — 0 3 —

,700 square — — — — — 0 3 —

1,650 square — — — — — 0 3 —

1,950 15,130 0.875 — — — — 0 3 —

.,840 11,561 0.800 20,500 0.505 94 — 6 3 6.972

1,100 14,270 0.875

_

— — — 0 3

—

1,600 square — — — — — 0 3 —

—1i t . Talbot—-17. W, JLotber anti V. ila zu rie— Trans. A .F.A ., 1926—8, 14 ,1 5 , 19-22, 24, 25.

W.», 18,23.

F ollow ing th is sam e m ethod of checking the a c tu a l s tre n g th s of c a stin g s w ith c a l c u l a t e d

stre n g th s , we c ite helow six ty p ic a l e x a m p le s : — E x a m p le 1 (above).— A c tu a l te n s ile stre n g th , 37,368; c a lc u la te d te n s ile , 37,800.

Fi g. 7c.

E x a m p le 2.— 125-lb. c a s tin g of u n ifo rm sec

tio n . A c tu a l sh e a r, 31,345 lbs. p e r sq. in .;

av erag e, c a lc u la te d , 31,525.

E x a m p le 3.— 730-lb. c a s tin g , com plicated shape, u n ifo rm sectio n . A c tu a l te n s ile stre n g th , 28,433 lbs. p e r sq. i n . ; a v e ra g e , c a lc u la te d tensile, 22,500. (N o te .— V ery sm all c h o k e-g ate was used, sam ples c u t from f a r side.)

E x a m p le 4. — 700-lb. c a s tin g , sections 1 to Itj i n .; a c tu a l te n s ile , 28,843 lbs. p e r. sq. in., av e ra g e , c a lc u la te d te n s ile , 25,030.

E x a m p le 5.— 325-lb. c a s tin g . A c tu a l tensile, 27,055 lbs. p e r sq. i n .; a v e ra g e , c a lc u la te d te n sile, 26,000.

E x a m p le 6.— 300-lb. c a s tin g . A c tu a l tensile, 22,250 lbs. p e r sq. in.,; c a lc u la te d te n s ile , 21,250.

All th ese exam ples w ere m ade on commercial o astings, of reasonable com plicated design, all b u t E x am p le No. 1 w ere cored castin g s, and v a ria tio n s in section w ere those en co u n tered in sound e n g in e e rin g p ractice. A lthough th e

re-% CarAon + Ct3(fK S/V/co/y

Fi g. 7d.

suits above o b ta in e d re p re se n t d ire c t tests we have m ade, i t is conceivable t h a t g re a te r v a ria tions m ay be fo u n d in p ractice. H owever, i t is believed t h a t g re a te r v a ria tio n s usually will be explicable on com parison of th e facto rs in

fluencing th e b ars an d castin g s u n d e r considera

tion.

C alculated d a ta w ere o b tain ed from te s t bars which, e x c ep tin g E xam ple No. 1, w ere n o t cast on th e sam e day as th e castin g s, b u t were from the sam e cupola an d q u ite close to th e same analysis. As in E x am p le No. 1, te s ts using stre ss-stra in d iag ram s, B rin ell an d sh ear were m ade. Some of th e calc u lated d a ta w ere in te r

polated from curves. F ro m con sid eratio n of all these te s ts, th e follow ing opinions are ju s ti

fied.

R easonable c o rre la tio n of te s ts to th e pro

p e rtie s of th e c astin g s them selves m u s t be estab

lished or c a st-iro n re se a rc h is fu tile . I t is the c a stin g t h a t th e e n g in e e r designs, th e m an u fa c tu r e r sells a n d th e c u sto m er b uys. These m en care little a b o u t th e “ q u a lity of th e iron

tit *

---30

Kes

« >3

\

3 '/»I- . . . ___ _____

S i s 4.0 a „ 4 S 0 3 S 3 6 3 6J Ç- %

Cor&a? 1

Ss/tcon

in th e la d le .” T hey a re concerned only w ith w h a t th e y g e t, nam ely, th e c a s tin g . However, i t is possible to te ll a g r e a t d eal ab o u t the q u a lity of th e m e ta l in th e c a s tin g , as is evident fro m th e follow ing c o n s id e ra tio n s : —

(a) M any w o rk in g p ro p e rtie s of steel and o th e r m e ta ls a re p re d ic te d re g u la rly from tests.

G ra n tin g th e lim ita tio n s of th e te s ts an d th e difficulty of th e i r e x a c t in te r p r e ta tio n , which, by th e w ay, ap p lies to all m a te ria ls , no one w ould den y t h a t g r e a t p ro g ress h a s been made by use of te s ts . I n a g e n e ra l w ay te s ts are used every day to d e te rm in e p ro p e rtie s of comm ercial m etals.

(b) I f in tw o o r m ore cases e x a c tly th e same g rad o of m a te ria l is accorded th e same or

still be th e sam e, one to a n o th e r.

(c) T est-b ars a re castin g s of c e rta in specified shape a n d dim ensions. I f castin g s an d test-b ars all of th e sam e analysis an d cooling r a te are poured a t th e sam e tim e from th e sam e m a te ria l, one w ould ex p ect to find sim ilar m etal in each.

The problem s en co u n te red a r e : — (1) to m ake

D ef/ectio n /n /n c /ie s

F io . 8 .— C o m p a r i s o n o f S t r e s s - S x r a i n C u r v e s o f V a r i o u s I r o n s .

te s t-b a rs whose cooling ra te s are like those of th e castin g s, an d (2) to use common sense in m ak in g allow ance fo r p e c u lia ritie s in design and fo u n d ry p ra c tic e — p a rtic u la rly those which may prom ote sh rin k a g e or o th e r defects an d those which call fo r slow or f a s t p o u rin g of castings.

(d) These p o in ts a re borne o u t because th e fo u n d ry m an of w ide experience can ta k e an analysis an d a re s u lt on one of th e so-called a r b itr a tio n te s t-b a rs an d m any tim es p red ict q u ite closely w h a t th e iron in th e c a stin g will be like.

I t th e n is possible to solve th e second problem

—re la tio n sh ip of te s t resu lts to th e pro p erties of th e c astin g . W h a t is needed is co-operation in accu m u latio n an d in te r p r e ta tio n of sufficient

d a ta . C a re fu l s tu d y m u s t be m ade of test m ethods. I n th e c o rre la tio n show n in the exam ples above, th e g e n e ra l a g re e m e n t becomes m ore re m a rk a b le w hen i t is co n sid ered t h a t (a) th e m e ta l flow in th e c a stin g s m ay be slower th a n in th e b a r ; (b) t h a t th e m ach in ed tensile

C a s t S r e e c 0 .5 0 5 “ & a r T e s te P t//f/m e r f e S f n tp tf f f i 7 6 9 2 5 '/¿ t p e r m .

— % £/<y?07//a/7 20-5/r? 2“

% fier/t/cf/ao of Area 30

£r/r?e// ¿45

/ Cas r //row

/ /.(J ’B or C osr - 0.555‘Bor Teste?

V /r /m /te S /r r /T g /O 4 5 6 0 0 / ¿ .p e r s q . tr?.

C /o r /g a S /o r ? /V e g /z g / f / e S r / r e / / 2 3 0

Ca s t B #o* Z £

3/r/mare BrrergrO 39260/B per so- m_

% f/org/ar/ar 29 /'r? 2*

6r/r?e// (500Ag.) 65

/V o T e fx r e n s o m e r e r r e m a r e P B e fo r e O rea A .

0 a 0 0 / 0 .0 0 2 0 0 0 3 0 .0 0 4 0 .0 0 5 0 .0 0 6 0 0 0 7 S f r a /r ? /r ? 2 - /r ? ( J a g /e L e r ? g /f ? //? Z r r c f e s

Fi g. 9 . — St r e s s- St r a i n Di a g r a m s o f Va r i o u s Me t a l s.

b a r is in case of th e c a stin g s closer to th e cooling su rfaces th a n in th e te n s ile b a rs—th u s neglecting th e w ell-know n a n d d e m o n s tra te d differences due to cooling g ra d ie n ts of u n lik e sections of sim ilar v o lu m e /s u rfa c e a re a re la tio n s h ip . T his is most a p p a r e n t in la r g e r sections.

The u su a l com m ercial im p ra c tic a b ility of th e

The p re s e n t tr e n d of th o u g h t seem s to be th a t c o n tro l of a m o u n t a n d form of g r a p h ite is more im p o rta n t th a n c o n tro l of m a tr ix alone. A 2.70 p e r c en t, c arb o n iro n of 0.60 p e r c e n t, com

b in ed c arb o n possesses d iffe re n t p ro p e rtie s from a 3.70 p e r cen t, c arb o n iro n w ith 0.60 p e r cent, com bined c arb o n . H ow ever, n e ith e r fa c to r can

5tro//7, /ncfies /n £-w, Gaye ¿enpffi

F i g . 10.—T e n s i l e S t r e s s S t r a i n o f V a r i o u s G r a d e s o f C a s t I r o n .

—i---1---1---1---1---T e s fee/ on 0.50S " t ie r ta ke n /ro o t /2 " b a r a s cas/.

be ign o red . T he c o n d itio n of th e g ra p h ite u n d o u b ted ly is d e p e n d e n t on th e n a tu r e of the c a rb id e re s u ltin g fro m influences of b o th com

p o sitio n an d th e r m a l h is to ry .

T he w ork of th e U n ite d S ta te s B u re a u of S ta n d a r d s sheds a g r e a t d eal of lig h t on the lack of seriousness of th e gas p ro b le m .‘ The im p o rta n c e of th is fa c to r seem s to h av e been

6 Jordan, Eckm an & J om in y— The O xygen C ontent of Coke and Charcoal Cast Iron. Trans. A .F .A . V ol. 33, pp. 431-441, 1925.

e x a g g e ra te d u n d u ly in fo rm er y e a rs .7 W e re fe r

I n p re s e n ta tio n of th is P a p e r, th e w rite r has

Drop Test—

DISCUSSION.

age as we now know it. H e could n o t em phasise

co nnection w ith th e a m o u n t a n d form of

W ith re g a rd to gas, he was glad th a t th e

could be overcom e by c e rta in h e a t tr e a tm e n t.

the resu lts.

in 1918,* an d K eep used i t as f a r b ack as 1895.t

iron as influenced by cooling r a te an d composi

composi-Ah

tions, an d m any still believed th a t full know

re s u lt of a b a r of th e sam e com position a s th e

THE INFLUENCE OF GRAPHITISATION OF

W dokumencie Proceedings of the Institution of British Foundrymen, Vol. 21 (1928-1929) (Stron 70-114)