By H. Ries, Ph.D.t
T he la b o ra to ry in v e s tig a tio n o f m o u ld in g san d s is n o t a new id e a , fo r te s ts of one s o rt or a n o th e r h av e been tr ie d fo r a n u m b e r of y ears, th e fine
ness te s t b e in g p e rh a p s th e one m ost com m only a p p lie d . M any of th e s e te s ts h a v e been m ade, how ever, acco rd in g to th e in d iv id u a l ideas of th e e x p e rim e n te r, so t h a t th e y con fo rm ed to no com
mon s ta n d a rd , a n d we co n seq u en tly lacked a common basis f o r com parison, w hich is, of course, very u n fo r tu n a te .
I n re c e n t y e a rs th e r e h a s been a s tro n g m ove
m e n t n o t only in th e U n ite d S ta te s , b u t also in E u ro p e, looking b o th to w a rd s a re fin e m e n t of la b o ra to ry te s t m ethods, as well as th e i r s ta n d a r d i
sa tio n . T he a d v a n ta g e of th i s is alm o st self- e v id e n t, b u t th e re a so n s m ay be s ta te d h ere.
S ta n d a r d te s ts (1) e n a b le th e co n su m er to d e te r
m in e th e q u a litie s of new sands, a n d in te llig e n tly com pare th è m w ith o th e rs a lre a d y in u se ; (2) p e rm it th e p ro d u c e r to keep a check on th e u n ifo rm ity of h is p r o d u c t; (3) m ak e i t possible fo r th e consum er to check all sh ip m e n ts as received in o rd e r to d e te rm in e w h e th e r th e y con
form to his re q u ire m e n ts a n d sp ecificatio n s; an d (4) a re of v a lu e fo r d aily co n tro l in th e fo u n d ry . The la s t of th e se a d v a n ta g e s is by no m ean s th e le a st, an d its r a p id sp re a d in th e U n ite d S ta te s, accom panied b y re p o rts of th o se who a re u sin g it, te s tif y to its im p o rta n c e an d value.
W h ilst th e d iffe re n t te s ts, w hich w ill, i t is hoped, e v e n tu a lly become sta n d a rd is e d , m ay be la rg e in n u m b er, i t is n o t to be th o u g h t t h a t all of th e m will be used fo r fo u n d ry co n tro l. In d e e d , th e n u m b er em ployed fo r th e l a t t e r p u rp o se w ill p ro bably be lim ite d , b u t a d d itio n a l ones m ay serve
* T h is P a p e r w a s s u b m itte d o n b e h a lf o f t h e A m eric a n F ou m d rym en 's A s s o c ia tio n t o t h e G la sg o w C o n fe ren ce o f t h e I .B .F .
t D r. H ies is Chairm an o f th e S ub -C om m ittee o n T ests, J o in t C om m ittee on M oulding S and R esearch.
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fo r th e e x a m in atio n of new sands su b m itte d to th e consum er by th e p ro d u cer, a n d still others m ay be used m ain ly in research w ork on sands.
T he im p o rta n t p o in t, how ever, as is generally realise d , is th e necessity of g e ttin g th e various m ethods s ta n d a rd is e d . I n a d d itio n th e y should be as sim ple as possible, an d th o se w hich a re to be used d aily in th e fo u n d ry should n o t only he easily u n d ersto o d , hut, th e a p p a ra tu s em ployed should be as n e a rly foolproof as possible, an d of a d u ra b le n a tu r e .
I n th e p re s e n t c o n trib u tio n , th e w rite r in te n d s to d eal chiefly w ith w h a t h as been d o n e in th e U n ite d S ta te s, b u t th is is n o t to be ta k e n as an in d ic a tio n t h a t A m erican eyes have been closed to th e w ork of th e i r fellow in v e stig a to rs across th e sea. In d e e d , th e y h a v e followed th e se efforts in th e sam e lines w ith th e keenest in te re s t and a p p re c ia tio n . Some referen ces to an d com
p ariso n s w ith fo reig n te s ts w ill be m ade.
Joint Committee on Moulding Sand Research.
I n D ecem ber, 1921, th e r e w as o rg an ised a J o in t C om m ittee on M oulding S an d R esearch, a c tin g u n d e r th e auspices of th e Am e rican F o u n d ry - m e n ’s A ssociation an d th e E n g in e e rin g D ivision of th e N a tio n a l R esearch Council. T his com
m itte e in c lu d e d n o t only re p re se n ta tiv e s of th e fo u n d ry in d u s try , b u t also one fro m each of th e sev eral te c h n ic a l societies o r o th e r scientific o rg a n isa tio n s w hich m ig h t be in te re ste d in such a n in v e s tig a tio n .
An ex ecu tiv e com m ittee w as selected to exer
cise c o n tro l over th e e n tir e in v e s tig a tio n , except th e h a n d lin g of th e fu n d s re q u ire d . The la t te r a re k e p t an d disb u rsed by th e tr e a s u r e r of th e A m erican F o u n d ry m e n ’s A ssociation, w hich is th e fin an cial an d ch ief te c h n ic a l sponsor of th e jo in t research .
As th e w ork of th e in v e s tig a tio n was som ew hat diversified, i t was recognised a t once t h a t sub
co m m ittees w ould be re q u ire d to ta k e ch a rg e of a n d c a rr y on th e several phases of th e w ork.
As a re s u lt th e r e w ere o rg an ised sub-com m ittees on (1) co n serv atio n an d re c la m a tio n ; (2) geolo
g ical su rv e y s; (3) te s ts ; (4) finance; a n d (5) pu b licity . S ub-com m ittee n u m b er fo u r w as p a
r-c
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tio u la rly im p o rta n t, as such a b ro ad in v e s tig a tio n oould n o t be c a rr ie d on w ith o u t fu n d s. I t is a p le a su re to re m a rk t h a t c o n trib u tio n s to th e fu n d fo r re s e a rc h h a v e been ap p reciab le.
To re f e r m ore specifically to th e w o rk of th e S ub-C om m ittee on Tests, i t m ay be said t h a t th e d evelopm ent of s ta n d a r d te s ts by th is c o m m ittee h a d a tw o-fold im p o rta n c e , because th e y w ere n o t only to be used by th e fo u n d ry m e n th e m selves in th e i r own la b o ra to rie s, b u t w ere also to be used a t th e te s tin g s ta tio n s s u p p o rte d by th e A m erican F o u n d ry m e n ’s A ssociation, w h ere th e san d sam ples collected by th e d iffe re n t s t a te geologioal surveys—to d a te o v er 800 sam ples from 15 s ta te s — a re b ein g in v e s tig a te d .
A p o in t n o t to be overlooked is t h a t each te s t in g m eth o d recom m ended by th e sub-com m ittee on te s ts is te n ta tiv e ly a d a p te d for one y e a r ’s tr ia l, in o rd e r to d e te rm in e by use w h e th e r it m eets all d em an d s, needs rev isio n , o r should be rep laced by a b e tte r te s t d iscovered d u rin g its p ro b a tio n period.
The reco m m en d atio n s th u s f a r m ad e by th e S ub-C om m ittee on T ests h av e been p r in te d in a p a m p h le t w hich w as issued b y th e A m erican F o u n d ry m e n ’s A ssociation in J u n e , 1924.
Fineness Test.
T h is te s t, as a t p re s e n t recom m ended by th e A m erican F o u n d ry m e n ’s A ssociation, is e sse n tia lly a siev e te s t. F o r core san d s w ith n o clay th e sand is sieved d ry , b u t fo r those sands c o n ta in in g clay su b stan ce th e sand is first sh ak en in w a te r to w hich N aO H h a s been ad d ed , a n d th e so-called clay su b stan ce se p a ra te d from th e ‘ ‘ g ra in ’ 1 by sip h o n in g . F o r th e fineness te s t sieves Nos. 6, 12, 20, 40, 70, 100, 140, 200 an d 270* a re used.
T h a t m a te ria l w hich passes 270 is c a u g h t in th e p an. T he o p en in g s of th e No. 270 a re 0.053 mm.
a n d th e a v erag e d ia m e te r of th e m a te ria l re m a in in g in th e p a n is a b o u t 0.035 mm.
F o r p urposes of com jiarison, i t is n a tu r a lly im p e ra tiv e t h a t th e sam e sieve sizes should in all cases b e used, a lth o u g h even now in th e O.S.
th is is n o t alw ays done. I t is, fu rth e rm o re , im p o rta n t t h a t th e sieves should be c a lib ra te d
* T h ese n u m b ers r e fe r to t h e U .S . B u rea u o f S ta n d a r d s s ie v e s e r ie s .
before use, because even carefu lly woven ones may
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th o u g h t, th e exception r a t h e r th a n th e ru le in m ost sa n d s; (2) th e é lu tria tio n m ethod re q u ire s con
sid erab ly m ore tim e th a n th e A .F .A . -sieve te s t ; (3) th e é lu tr ia tio n m eth o d re q u ire s th e use of sieves fo r th e m edium a n d coarser sizes, b u t th e la r g e r sizes se p a ra te d by w a te r, come w ith in th e ra n g e o f th e finer sieve sizes of th e A .F .A . te s t ; (4) th e A .F .A . m ethod is in a c tu a l p ra c tic a l use in fo u n d rie s in th e U n ite d S ta te s , an d is g iv in g sa tisfa c to ry r e s u lts ; (5) th e A .F .A . sieve te s t se p a ra te s p a rtic le s down to 0.035 mm. d ia . ; an d (6) a lth o u g h th e a u th o r h a s seen th e re s u lts of m an y é lu tr ia tio n te s ts p lo tte d , he does n o t rem em b er h a v in g seen an y p ra c tic a l use m ade of th is e x tre m e s e p a ra tio n of th e sm aller p a rtic le s.
Expression of Results of Fineness Test.
H a v in g s e p a ra te d th e sa n d in to its d iffe re n t g ro u p s of g ra in sizes, n e x t m u s t be co nsidered th e b e s t m a n n e r of ex p ressin g th e re s u lts of th e
Fi g. 1 . — Si e v e Me s h e s Pl o t t e d w i t h o u t Re g a r d t o Si z e o e t h e Op e n i n g.
te s ts. O bviously, to re c o rd th e m in ta b le s is th e m ost co n v en ie n t way, h u t w here a la rg e n u m b e r of san d s a re so a rr a n g e d , a com parison of th e m is n o t alw ays a ra p id o p e ra tio n .
T his leads th e n to th e po ssib ility of ex p ressin g th e te x tu r e g ra p h ic a lly , as by curves, o r b y m eans of a n u m b er.
Fineness Graphs.
I f ourves a re used to re p re s e n t th e te x t u r e one is obliged to choose betw een sev eral m eth o d s any
one o f which m ay a t le a st be considered fa irly sa tisfa c to ry . These a re (1) th e use of re c ta n g u la r o o -o rd in ate p a p e r (T ig. 1), p lo ttin g th e p erc e n t
age of each sieve as o rd in a te s, a g a in st th e sieve 6izes • ra n g e d as abscissae. On such p a p e r, th e sieve sizes m ay be p lo tte d a t re g u la r in te rv a ls, an d th e abscissae re p re s e n tin g th em m ay be cor
re c tly spaced in p ro p o rtio n to th e re a l size of th e screen openings (F ig . 2). The first m ethod is used by m any, th e second by few, an d i t is open to th e o b je c tio n t h a t th e co arser sizes ta k e u p a ll th e room on th e c h a rt, crow ding th e sm aller ones to g e th e r a t o n e end.
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Fi g. 2 . — Si e v e Op e n i n g s a r e Co r r e c t l y Sp a c e d o n Re c t a n g u l a r Co-o r d i n a t e s.
(2) T he use of lo g arith m ic co-o rd in ates for th e screen sizes w hile r e ta in in g th e re c ta n g u la r co
o rd in a te s fo r v e rtic a l p lo ttin g of percen tag e re ta in e d by each sieve (F ig . 3). I f lo g arith m ic co-ordinates a re used i t seem s best to p lo t th e size of th e a c tu a l sieve openings. Two ty p es of curves a p p e a r to have been used, reg ard less of th e k in d of co-o rd in ates em ployed. O ne of th e se is th e c u m u lativ e cu rv e (F ig . 4), pro b ab ly m ore u sed in E u ro p e th a n A m erica. The o th e r gives th e a c tu a l p e rcen tag e re ta in e d on each sieve. I t m ay be a m a tte r of personal choice which one is used, b u t, to th e w rite r, th e la t te r o f th e tw o seems p re fe ra b le , because an y excess of c e rta in sizes is d etec ted a t a glance, alth o u g h it m ay be arg u e d t h a t th e c u m u la tiv e cu rv e would also show i t by a p ronounced local steep en in g of th e line.
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