gives a ty p ical exam ple of th e h a rd n e ss figures o b ta in e d in n o rm al an d n ick el-iro n c a stin g s, an d illu s tra te s well th e e q u a lisin g effects m en tio n ed . R ecords show t h a t in some cases a h ard n ess difference of a b o u t 200 B rin e ll betw een th e i- in . an d 1-in. section of a c a stin g m ay be red u ced to a b o u t 20 p o in ts in a c a stin g s u ita b ly alloyed w ith nickel, an d a t th e sam e tim e th e iro n is very a p p re c ia b ly h a rd e n e d an d stre n g th e n e d in th e h eav ie r sections.
Uniformity of Product.
o b ta in e d by th e re g u la r in c o rp o ra tio n of a sm all
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ca stin g . By th e re d u c tio n of silicon, th is castin g was re n d e re d sound, b u t chill spots on th e bottom of th e s k ir t sp o ilt th e m a c h in a b ility . By th e a d d itio n of nickel th is tro u b le has been en tire ly overcom e, since nickel resto res th e m ach in ab ility of th e c a stin g w ith o u t g iv in g an y tendency to openness in th e heavy sections. I n T able I th e analyses of these tw o pisto n s a re given, and also c o m p arativ e B rin ell h ard n ess figures for th e boss and th e s k irt.
Fx g. 2 . Two P i s t o n s , o f w h i c h t h a t o n t h e l e f t i s m a d e f r o m Ni c k e l Ir o n.
Such c a stin g s as couplings, an d g e a r blanks re q u irin g easy m a c h in ab ility on th e flanges, often show porosity in th e c e n tre boss. As in th e case of pistons, nickel has provided a solu
tio n of th is tro u b le fo r m an y fo undrym en. In such a p p lic a tio n s several firms have found t h a t th e a d d itio n of nickel resu lts definitely in re ductio n of scrap a n d w aste castin g s, th u s m a in ta in in g th e p ro d u ctio n r a t e of th e fo u n d ry and giving a m ore reliable p ro d u ct. E ach foundry- m an will no d o u b t find sim ila r a p p lic a tio n s in his own w ork.
Soundness of Heavy Sections.
As a m ore p ra c tic a l ap p lic a tio n of th is fe a
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w earing su rfaces have been o b ta in e d in th e n o n c a stin g . A sim ila r a p p lic a tio n is illu s tra te d in F ig . 4, a c a st-iro n p la te w hich form s p a r t of a m odern ty p e -s e ttin g m ach in e. I h e form of c a stin g , w hich is ro u g h ly a b o u t 9 in . sq u a re an d 2 in. th ic k , is clearly seen, a n d th e m ach in ed p la te in th e b a c k g ro u n d illu s tra te s th e sev erity of th e service re q u ire m e n ts of th e c a s tin g in t h a t p n e u m a tic p ressu re is a p p lie d to th e v ario u s bored-holes an d th e r e m u s t be no leak a g e
be-Fi g. 3 . — S e c t i o n A c r o s s t h e C e n t r e o e L a r g e C y l i n d r i c a l B l o c k i n N i c k e l I r o n .
tw een one hole to th e n e x t. The tw o sections in th e fo re g ro u n d w ere ta k e n fro m c a stin g s m ade u n d e r ex actly sim ila r co n d itio n s e x c e p t t h a t fo r th e u p p e r section, silicon h a d been r e duced in th e iro n an d nickel w as ad d ed . The an aly sis of th e tw o iro n s a re g iv en in T able I I I . The un so u n d n ess of th e o rd in a ry iro n is clearly s e e n ; an d th ese c a stin g s o fte n re q u ire d to have th e holes d rilled th r o u g h th em , subsequently bushed w ith c ast-iro n bushes in o rd e r to m ake
th em p ressu re tig h t. T he nickel-iron in th is case gave a sound c astin g w hich has given e n tire ly s a tisfa c to ry service. These exam ples a re ty p ic a l of th e soundness w hich can be ob
ta in e d in heavy sections by th e use of nickel in cast iro n .
M any o th e r ap p licatio n s in th e fo u n d ry will occur in castin g s w hich give tro u b le due to
Fi g. 4 . — Se c t i o n o f Pl a t e Pr e s s u r e Ca s t i n g s i n No r m a l a n d Ni c k e l Ir o n.
openness and p o rosity. In th is connection active in te re s t is being ta k e n in th e use of nickel in locomotive c y lin d er castin g s, w hich notoriously give tro u b le w ith porosity a t th e ju n c tio n of th e sections w here th e piston-valve-cham ber and steam -ports jo in th e cy lin d er p ro p er. In c e rta in of these castin g s, cau lk in g has been considered inevitable, b u t i t is believed t h a t , alth o u g h th is
188
m ay n o t be e n tire ly e lim in a te d , i t m ay v ery easily be red u ced by th e use of nickel in an iro n of su ita b le com position, an d e x p e rim e n ts a re now proceeding on th ese lines.
C y lin d er covers of all form s a re also n o to rio u s fo r g iv in g tro u b le , w ith p o ro sity a t ch an g e of section or a t th e ju n c tio n of v a ry in g sections, an d h e re a g a in nickel is b ein g a p p lied success
fu lly to th e p ro d u c tio n of sound c a stin g s. In th e case of one jo b b in g fo u n d ry , one o u t of every tw o castin g s of a w a te r-ja c k e te d cover off a diffi
c u lt p a tte r n w ere s c r a p p e d ; th e silicon c o n te n t of th e iro n w as red u ced from 1.8 to 1.5 p e r c en t, an d 1 p er c en t, nick el was ad d ed . S ince th e n th e scrap loss has been red u ced , so t h a t a t le a st th re e o u t of fo u r c a stin g s a re now e n tire ly sa
tis-Ta b l e I I I .— Plates subject to Pressure Test.
Normal iron. Nickel iron.
T.C... 3.4 3.4
Si 1 . 8 1.54
Mn 0.8 0.94
S 0.14 0.07
P 0.25 0 . 1 2
Ni — 0.91
Plate Unsound Sound.
fa c to ry , an d i t is hoped t h a t w ith f u r th e r m odi
fication of th e com position th is figure m ay be im proved upon f u r th e r .
I n t e r e s t in th e use of n ick el in th e p ro d u c tio n of sound an d close c a stin g s is also re a c h in g to th e p ro d u c tio n of m any sm all pum p p a r ts foi- valve c astin g s an d g e n e ra l h y d ra u lic c a stin g s an d fo r v ario u s gas-en g in e c a stin g s such as breach-ends.
T he th o r e tic a l e x p la n a tio n of th is benefit, which can be o b ta in e d by th e use of nickel, lies u n d o u b ted ly , as m en tio n ed b efore, in th e e q u al
ising actio n of th e alloy a d d itio n . I n irons w hich te n d to show coarse, open s tr u c tu r e s in h eavy sections, im p ro v em en t is o b ta in a b le by th e re d u c tio n of silicon. T he su b seq u en t
th e m a c h in a b ility of th e c a stin g w ith o u t te n d in g to open u p th e s tr u c tu r e in th ic k sections. The ph o tom icrographs, F ig s. 5 an d 6, show th e effect of th e alloy on th e p e a rlitic s tru c tu r e of th e iron, in d ic a tin g a very m ark ed refin in g influence which
F i g . 5 .— C y l i n d e r I r o n ,
cast
2 .2dia . x 500.
is associated w ith th e im proved hard n ess and d ensity of th e s tru c tu r e . As a g en e ra l ru le also, a finer form of g ra p h ite is associated w ith th e alloyed iron.
Function of Chromium.
In some of th e analyses an d exam ples of ap p li
catio n s of nickel, given in th is P a p e r, chrom ium is found associated w ith th e nickel. The action