Carbon.
H ig h -carb o n c o n te n t is p re ju d ic ia l to th e a n n e a l
in g of w h ite -h e a rt, as i t fa v o u rs g r a p h itis a tio n an d co n seq u en tly decreases th e e x te n t of d é c a r
b u risa tio n . W h ilst low -carbons m ig h t be a d v a n
l ü l
tag eo u s, th e p ro d u c tio n of such iron in th e cupola is difficult. E x p erie n ce shows t h a t carbon fro m 2.8 to 3.1 p e r cen t, gives th e best results.
Silicon.
W ith silicon-contents below 0.40 p er cent, i t is alm ost im possible to a n n eal th e hard, iron
satis-Fi g. 1 6b.— 2 ^ -i n. d i a m. Wh i t e- He a r t Bl o c k. An n e a l e d. | -i n. f r o m e d g e. Et c h e d x 5 0 .
f a c to r ily. Silicon a ro u n d 1.0 p er c en t, increases th e e x te n t of g ra p h itis a tio n on an n ealin g , an d is opposed to th e rem oval of carb o n o n account of th is. As w ith b la c k -h e a rt, th e c o n te n t has to be v a rie d inversely w ith th e carb o n in ord er to p roduce a g ra p h ite -fre e castin g . W ith th e d esir
able c arb o n c o n te n ts in d ic a te d above silicon from 0.50 to 0.80 p e r cent, w ill be found su itab le fo r m ost purposes.
Sulphur.
T h is e le m e n t is no d o u b t th e co n tro llin g facto r in th e p ro d u c tio n of w h ite -h e a rt. I t s effect on
g ra p h itis a tio n is so well know n as to need 110
ex p la n a tio n . I t is th e one e le m e n t w hich m ak es th e esse n tia l difference betw een th e tw o ty p e s of m alleable.. I f th e s u lp h u r-c o n te n t is below 0.10 p e r cen t, g ra p h itis a tio n will ta k e place in pre-' feren ce to d é c a rb u ris a tio n an d th e r e s u lt is a
Fi g. 1 6c.— 2 J -i n. d i a m. Wh i t e- He a r t Bl o c k. An n e a l e d. | -i n. p r o m e d g e. Et c h e d x 5 0 .
w eak iro n , li tt le b e tte r th a n g rey iro n , a n d is in f a c t very sim ila r to th e r e s u lt of a high-silicon c o n te n t.
S u lp h u r above 0.45 p e r c e n t, p re v e n ts p ra c tic a b le a n n e a lin g . R easo n ab le s u lp h u r c o n te n ts to p ro d u ce good a n n e a le d c astin g s a re fro m 0 . 2 0
to 0.30 p e r c en t.
Manganese.
F ro m th e foregoing re m a rk s 011 s u lp h u r c o n te n t, i t w ill be realise d t h a t th e m an g an e se m u s t be low enough to allow th e su lp h u r to e x e r t its r e s tr a in in g influence on g ra p h itis a tio n . Y e t i t
103
m u st n o t be so low as to p e rm it the sulp h u r to p re v e n t th e dissociation of th e carbide and so p ro h ib it th e rem oval of carb o n by o x id atio n from the ore. I t h a s been fo u n d by ex p erience t h a t th e
Pi g. 1 6d.— 2 1 -i n. d i a m. Wh i t e- He a r t Bl o c k. An n e a l e d. Ce n t r e. Et c h e d x 5 0 .
a to m ic ra tio of 1.72 tim es th e su lp h u r gives th e b est conditions.
Phosphorus.
The effect of th is elem ent is as previously given in referen ce to b lack -h eart.
Chromium.
H ig h e r chrom ium is perm issible in w h ite -h e a rt th a n in b la c k -h e a rt, as its stab ilisin g effect upon th e c a rb id e is n o t so d e trim e n ta l an d up to a c e rta in p o in t is beneficial. Q u a n titie s above
0 . 2 0 p e r c en t, how ever a p p e a r to reduce th e ra te of d é c a rb u risa tio n seriously.
Ta b l e X .-—Physical Properties of Black-Iiearl Malleable
f
105
Hoursafter CoiyrrrencetycnrofF~'ring Fio. 17.—Temperature-TimeChartofBlack-HeartAnnealingCycle.
is shown by m alleab le th a n by o th e r fe rro u s m a te ria ls of sim ila r shock a n d s tra in - re s is tin g q u a litie s. T his is pro b ab ly due to th e s u rfa c e of a m alleable c a s tin g b ein g p ra c tic a lly c arb o n free.
M achinability of Black-heart.
T he fr e e -c u ttin g p ro p e rtie s a n d speeds of m a c h in in g a tta in e d on b la c k -h e a rt m alleab le a re exem plified by th e follow ing figures. T hese w ere o b ta in e d fro m a w ell-know n firm of m a c h in is ts who com pletely finish some 20 to 30 to n s of m o to r e a r d e ta ils p e r week.
T u rn in g an d fa c in g fla n g e 10 in . dia. on a large casting.
R o u g h in g speed ... 108 f t. p e r m in . F in is h in g speed ... 182 f t. p e r m in . T u rn in g a n d fa c in g cylin d rica l piece 6J in . dia.
R o u g h in g speed ... 140 f t . p e r m in . F in is h in g speed ... 400 f t. p e r m in.
T u rn in g a n d screw -cu ttin g a lig h t sleeve casting R ou g h tu r n in g ... ... 100 f t. p e r m in . F in is h tu r n in g ... ... 235 f t. p e r m in . Screw c u ttin g w ith
single p o in t tool ... 170 f t . p e r m in . T his job is one of g r e a t accu racy , th e w o rk in g lim it allowed b ein g p lus or m in u s 0.0005 in . P r e cision in th e d ia m e te r of th e th r e a d is secured by w o rk in g to a d ia l in d ic a to r, an d h u n d re d s of th e piece a re so pro d u ced w ith o u t re g r in d in g th e tool.
As re g a rd s u n ifo rm m a c h in a b ility a n d absence of h a r d spots th e re c o rd of m a c h in in g 39,207 r a d ia to r fe rru le s 1| in . d ia . screw ed rig h t- an d le ft-h a n d th re a d s , w ith o u t re g r in d in g th e dies is sufficient evidence.
Picture Fram e Material.
I t will be seen from th e fo reg o in g re m a rk s on m a c h in a b ility t h a t th i s m a te ria l w ill n o t be s u i t
able fo r all classes of c a stin g s, especially th o se w hich h ave to w ith s ta n d a b ra s io n a n d w ear. S u ch re q u ire m e n ts can be m e t by th e p ro d u c tio n of c a st
ings w ith w h a t is com m only called “ p ic tu re fra m e ” f r a c tu re . F ig . 19 shows th is f e a tu re . I t will be seen fro m th is p h o to g ra p h an d fro m th e m icro g ra p h s F ig s. 20 an d 21, t h a t th e core of th e m a te ria l is of u su a l b la c k -h e a rt q u a lity a n d s tru c
*
I vi) V}
Fig. 18. ShowingProgressiveIncreaseopDuctility, withTenacityopBlack-Heart Malleable.
1
shape an d size. T he ch ief item s of in creased cost m ay be briefly su m m arised as follow s: —
(1) H ig h e r cost of p ig -iro n , ow ing to n ecessity of e n s u rin g th e a c c u ra te an aly sis o f ch arg e, a n d th e sp ecial q u a litie s of h e m a tite re q u ire d .
(2) F o r b la c k -h e a rt, h ig h o p e ra tio n cost of m e lt
in g in a ir fu rn a c e , caused by a m o u n t of fu e l re q u ire d a n d h e av y expense of m a in ta in in g b ric k w ork. F o r w h ite -h e a rt a d d itio n a l cost of e x tr a fuel fo r cupola.
Fi g. 1 9 .— Fr a c t u r e o f “ Pi c t u r e Fr a m e ” Ma t e r i a l.
(3) H ig h e r m elting-losses.
(4) A d d itio n a l w e ig h t of m o lten m e ta l re q u ire d to r u n th e c a stin g s ow ing to th e n ecessity of feed ers, etc.
(5) A n n e a lin g expense co v erin g p la n t, m a in te n ance o f b rickw ork, a n d fuel.
(6) E x tr a cost of c lea n in g c a stin g s r u n a t hio-her te m p e ra tu re , n e c e ss ita tin g s a n d -b la stin g in m an y cases also f u r th e r c le a n in g a n d b a rr e llin g a f t e r a n n e a lin g .
(7) H ig h e r g rin d in g an d f e ttlin g costs ow ing to excess m e ta l a ris in g fro m fe e d e r head s an d c h ip p in g aw ay of tie s n o t rem ovable before a n n e a lin g -
a n d 67
(8) A c c u ra te s e ttin g u n d e r press o r d rop ham m er to e n ab le th e c a stin g s to be lo cated in in t r i c a te jig s fo r m ass m a ch in in g .
I l l
W hen rev iew in g th e foregoing item s, i t is of in t e r e s t to n o te t h a t re g a rd in g item 4, th e re is a v ery g r e a t v a ria tio n in th e w eig h t of feeders fo r d iffe re n t castin g s, w hich is caused by th e v a rie ty of designs. T h is re s u lts in a difference of betw een 30 an d 70 p e r c e n t, on good castin g s p e r to n of m e ta l m elted . I t is e v id e n t from th is t h a t th e re m u s t be a w ide v a ria tio n in th e cost of
produc-Fi g. 2 0 . — Ri m o f “ Pi c t u b e Fb a m e ” Me t a l. An n e a l e d. Et c h e d x 5 0 .
tio n , a n d t h a t an y fla t r a te covering a ra n g e of c a stin g s could n o t be sa tisfa c to ry , e ith e r to th e fo u n d e r o r th e b u y er, an d is th e re fo re economic
ally u n so u n d .
W ith re g a r d to th e q u estio n of a n n e a lin g ex
pense, th is v ita l p o rtio n of th e process is an ex p en sive o p e ra tio n to c a rry o u t sa tisfa c to rily , an d th e a n n e a lin g cycle c a n n o t be sh o rten ed if re g u la r a n d re lia b le re s u lts a re to be o b tain ed . Some firm s ta lk a b o u t a n n e a lin g periods which a re very
m u ch s h o r te r th a n th o se g iv en in th is P a p e r, h u t t h e a u th o rs u p to d a te have n o t been ab le to achieve a n y of th e s e w o n d erfu l re su lts.
I t o fte n h a p p e n s t h a t th e m alleab le ir o n fo u n d e r o b ta in s w ork from th e e n g in e e r because a grey - iro n c a s tin g has fa ile d in service, a n d th e e n g in e e r ex p ects to re p la c e i t by m alleab le iro n a t a p p ro x i
m a te ly th e sam e price. N eedless to say, th is is
F i g . 2 1 . — C e n t r e of “ P i c t u r e F r a m e ” M e t a l . A n n e a l e d . E t c h e d x 5 0 .
im possible, a lth o u g h w ith th e re d u c tio n w hich can be b ro u g h t a b o u t in w eig h t by u sin g m alleab le iro n , h is u ltim a te cost is n o t v ery m u ch g r e a te r, a lth o u g h i t m ay a p p e a r so w hen view ing th e prices o n th e cw t. basis. F irs t-c la s s m alleab le c a stin g s in e ith e r b la c k -h e a rt o r w h ite - h e a rt c a n n o t be p ro du ced e x c e p t by u sin g th e b est m eth o d s o f p ro d u c tio n , a n d n e ith e r m a te r ia l is eq u ally s u ita b le fo r all classes of w ork.
E x tre m e sections, b o th v e ry heavy a n d v ery lig h t, a re to be avoided in b o th m a te ria ls as m uch
as possible. Some desig n ers o fte n tr y to reduce
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h e a r t could be s a tis f a c to r ily m ad e from m e ta l o f v ery v a ria b le com position, a n d t h a t m uch con
sid e ra tio n need n o t be given to low su lp h u r a n d c arb o n c o n te n ts. T a k in g th e fo u r ex am p les of w hich M r. M u r ra y g av e th e an aly sis, N o. 1 w as a v ery in f e rio r b la c k -h e a rt, an d d id n o t e q u a l th e B .E .S .A . specification fo r elo n g a tio n , a n d i t w as v ery d o u b tfu l if i t w ould g iv e 90 p e r c e n t, bend
Fi g. 22.— Mi c r o N o. 1.
on th e s ta n d a r d b a r. T he com bined carb o n con
t e n t of 0.37 p e r cen t, was responsible fo r h ig h te n sile s tr e n g th a n d m o d e ra te d u c tib ility . T h a t com
b in e d c arb o n w as d u e to th e b a d su lp h u r an d m an g an e se balan c e. A m a n g an e se of a b o u t 0.37 p e r c e n t, w ould be necessary w ith t h a t su lp h u r c o n te n t to p ro d u ce a n iro n w hich w ould give n o rm al b la c k -h e a rt p h y sical p ro p e rtie s.
E x am p les No. 2 a n d N o. 3 w ere n o t t r u e black- h e a r t m alleable, an d w ere a p p a re n tly a tte m p ts
to m ake b la c k -h e a rt from th e cupola by ra isin g th e m a n g a n e se c o n te n t. Such com positions tr e a te d as b la c k -h e a rt in th e a n n ealin g process w ould give v ery poor resu lts.
N o. 4 w as a tr u e b la c k -h e a rt, an d ag reed fa irly well in com position w ith th e re q u ire m e n ts sta te d in th e P a p e r. The physical te s ts w ere s a tis fa c to ry , a lth o u g h th e ten sile s tre n g th would be
117
Fi g. 23.— Mi c r o No. 2.
ex p ected to be h ig h e r, considering th e composition.
I t w as, how ever, p robable t h a t th e iro n h ad been a n n e a le d a t a h ig h te m p e ra tu re , an d t h a t free c arb o n w as p re s e n t in la rg e nodules, which would acco u n t fo r a s tre n g th of no m ore th a n 2 0 tons.
T h e s ta te m e n t t h a t th e essen tial difference be
tw een th e tw o m alléables w as in th e one case th e rem oval of c arb o n an d in th e o th e r th e deposition of fre e carbon was s u b s ta n tia lly co rre c t; b u t th e s ta te m e n t t h a t t h a t depended on a n n e a lin g only
w a s d e f in it e ly w r o n g . G r a p h it is a t io n h a d b e e n
119
like th e a u th o rs to e n la rg e u pon t h a t p o rtio n of th e i r P a p e r.
M anganese-Sulphur Ratios.
M r . J . G. Pe a r c e th o u g h t all those who had r e a d th e P a p e r ca re fu lly w ould agree t h a t i t re p re se n te d th e best P a p e r ever given in E n g lan d on b la c k -h e a rt m alleable, a n d th e y should con
g r a tu la t e th e a u th o rs accordingly. I n all p ro b a b ility , }t w ould become th e s ta n d a rd P a p e r for th e f u tu r e . On p ag e 102 th e a u th o rs suggested th a t low s u lp h u r w h ite -h e a rt g ra p h itis e d r a th e r th a n de- e a rb u rise d , an d g ave a r e s u lt n o t m uch b e tte r th a n th e w eak g re y iro n . P e rh a p s th e a u th o rs could e x p la in a r e s u lt of th e k in d which re c e n tly h a d been o b ta in e d in some te s ts by th e R esearch A ssociation, w hich w as as follows : — I r o n of 3.0 p e r cen t, to ta l c a rb o n ; 0.6 p er cen t, silicon, w ith only 0.015 p er c e n t su lp h u r—m ade to B .E .S .A . specification—b u t w hich gave 10 p er c e n t, e lo n g a tio n an d 1 2 0 degrees bend on th e s ta n d a rd b a r. I t d ecarb u rised an d th é degree of carb o n rem o v al w as 70 p e r c en t, on 120 h o u rs’
a n n e a lin g , which th e y w ould re g a rd as norm al fo r a m a te r ia l of t h a t th ick n ess. H e d id n o t call t h a t w eak m alleable.
R e fe rr in g to m anganese, th e a u th o rs said th a t i t h a d been fo u n d by ex p erien ce t h a t th e atom ic ra tio of 1.72 tim e s of su lp h u r (m anaganese sul
p h u r ra tio ) gave th e best w orking conditions. H e w ould be g lad if th e a u th o rs could am plify t h a t , because in P a p e rs p u b lish ed in 1925 an d 1927.
M r E . R . T ay lo r showed th a t th e m anganese s u lp h u r r a tio should be 1.71. I n p o in t of fa c t th e se P a p e rs , w ith some a d d itio n a l w ork, were su m m arised a t th e Sheffield C onvention la s t y ear.
J u d g in g fro m th e w ork w hich h a d been done since th e n , h e believed t h a t t h a t r a tio re q u ire d m odi
fication. I t w ould be p a rtic u la rly h elp fu l if th e a u th o r s could pick o u t fro m th e ir experience say a dozen b a rs of v a ry in g m an g an ese su lp h u r ra tio , a n d so confirm th e o r ig in a l view t h a t 1.71 m an gan ese s u lp h u r r a tio w as based on physical te s ts.
T h a t w as r a t h e r a n im p o r ta n t p o in t a t t h a t m om ent.
Improved Grey Iron Available.
Mit. F . lv. Ne a t h sa id t h a t 011 p ag e 99
Initial Composition.
123
w h ite -h e a rt m alleable, an d th e w ork of M r.
H u rre n , w hich s ta te d t h a t t h a t w as th e figure w hich he w orked to , an d also th e research work of M r. E . R . T ay lo r. H e was n o t in to u ch w ith all th e su b se q u e n t w ork w hich th e C ast-Iro n R esearch A ssociation h a d done. W ith re g a rd to M r. S h aw ’s q u estio n ask in g w h a t was th e effect of m an g an e se in so fte n in g th e w h ite-iro n of low s u lp h u r w h ite -h e a rt, he could only say he really d id n o t know . W hen M r. Shaw g o t up and asked a q u estio n , one could be p r e tty sure t h a t th e re w as n o pu b lish ed answ er to it. B u t, very d efinitely, one o b ta in e d a n in crease of te m p e ra tu r e w hen one ad d ed m an g an ese to low -sulphur iro n in th e lad le, an d th e r e was a considerable ev o lu tio n of g as w hich m ig h t h av e som ething to do w ith th e so fte n in g effect w hich undoubtedly w as very m ark ed . As to M r. Cook’s referen ce to th e silicon to su lp h u r ra tio , he m u st say th a t he h a d n o t co n sid ered t h a t a t all, an d could n o t say t h a t h e h a d n o ticed an y d efin ite ra tio w hich gave good re s u lts in b la c k -h e a rt. I n answ er to M r.
N e a th ’s su g g estio n w h eth er an y cerium h a d been used in place of m anganese to overcome th e h a rm fu l effects of su lp h u r, he h e a rd some y ears ago t h a t a n u m b e r o f o th e r elem ents were being tr ie d o u t in b la c k -h e a rt m alleable in th e S ta te s, b u t th e nam es a t t h a t tim e w ere n o t divulged, an d since th e n he h a d n o t h a d any com m unication on the su b ject.