METAL PRODUCTION

Crucible.

B efore th e in tro d u c tio n of th e e le c tric fu r n a c e q u ite a larg e q u a n tity of lig h t c a stin g s w as m ade from crucible steel. O ne of th e w orks w ith w hich th e a u th o r is associated b eg an its c a re e r m any y ears ago as a crucible steel fo u n d ry , a n d sam ples of its p ro d u ctio n a t th a t tim e h a v e c o m p a ra tiv e ly re cen tly been seen by th e a u th o r.

P lum bago p ots w ere used, an d Sw edish b a r iron was th e m a te ria l m elted , an d th e r e is no d o u b t th a t an adm irab le q u a lity of m e ta l was pro d u ced for lia h t castin g s. Such d ead so ft m a te ria l,

how-Fio. 1—ElectroMetalsFurnaces. Tira BraintreeSteelCastingsCompany.

isver, is ex trem ely difficult to m e l t; an d also th e p ro d u c t is liable to co n sid erab le v a ria tio n s in c a r­

bon c o n te n t. These tw o draw backs, coupled w ith high m elting-costs an d th e ad v an ce w hich has ta k e n place in th e efficiency an d know ledge of w o rk in g of o th e r ty p es of m e ltin g a p p a ra tu s , have c au sed th e alm ost com plete disuse of th e c r u c i b l e

fo r th is class of w ork. W h ere only a few castin g s a re w an ted , or in th e case of a firm re q u irin g odd iots of sm all c a stin g s fo r its own use, of a class difficult to o b ta in from th e p ro d u ctio n fo u n d rie s, i t m ay be w orth while to use th e crucible fu rn a c e

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Fi g. 2 .— Hbr o u lt Fu r n a c e. Th e Na t io n a l Steel Fo u n d r y (1 9 1 4 ), Li m i t e d, Le v e n, N .B .

for th e p u rp o s e ; b u t as a com m ercial p ro p o sitio n th e success of a fo u n d ry re ly in g on cru cib le-m elted steel would be, to say th e least, dubious.

Converter.

S ev eral ty p es of th is fu rn a c e e x ist, th e basic p rin cip le being th e sam e in all cases, an d w ith o u t d ou b t th is ty p e of fu rn a c e re p re s e n ts a m ost th o ro u g h ly -tested an d s a tisfa c to ry m ean s of p ro ­ ducing steel fo r lig h t an d m edium c a stin g s. T he p rin c ip le involved is th e a p p lic a tio n of a stream of a ir to m olten cupola-m etal, e ith e r im p in g in g

upon th e su rface, as in th e side-blown co n v erter, or blown d ire c tly th ro u g h th e m e ta l as in bottom - blown p ractice. T his re su lts in th e com bustion of th o carbon, silicon an d m an g an ese of th e m olten iron, and th e consequent p ro d u ctio n of a v ery high te m p e ra tu re . To th e blown m etal, which co n ta in s m ere tra c e s of carbon, silicon, an d m anganese, finishing alloys such as ferro-silicon, ferro -m an - ganese o r spiegeleisen, a re added in th e necessary q u a n tity to produce th e desired analysis, an d ,

pro-F i o . 3 — 'Sn y d e r Fu r n a c e. T h e Nation a l Steel Fo u n d r y (1 9 1 4 ), Li m i t e d, L e v e n ,

perly controlled, th e re su ltin g m etal is a steel of consistently high an d re g u la r q u a lity , sufficiently h o t to r u n th e th in n e s t sections usually dem anded.

In alm ost all cases converters in th is c o u n try are acid-lined, th a t is, lined w ith m a te ria l of a sili- cious n a tu r e , th e basic, o r dolom ite-lined con­

v e rte r seem ingly h a v in g never found much fav o u r.

I t follows, th e re fo re , th a t no red u ctio n of th e im ­ p u rities, su lp h u r an d phosphorus, ta k e s place, b q t

ra th e r an increase, in th e fo rm e r from th e coke used in th e cupola, an d in th e la t te r ow ing to h a th c o n c e n tra tio n . Obviously, th e re fo re , a p ig-iron h av in g a high degree of p u r ity in th e se elem ents is a n e ssen tial to re g u la r p ra c tic e .

T he Stock c o n v e rte r is designed fo r oil m eltin g in th e c o n v e rte r itse lf, an d th u s o b v ia te s th e use of a cupola w ith its in e v ita b le in crease in su lp h u r

c o n te n t. . , ,

The m olten iro n is a fte rw a rd s blow n a n d finished in th e u su a l way. F o r lig h t c astin g s a sm all con­

v e rte r of th is ty p e pro d u ces a v e ry s u ita b le steel, high te m p e ra tu re an d flu id ity b e in g m ark ed fe a tu re s.

Electric Furnaces.

A m a rk e d step fo rw a rd took place in th e effi­

ciency of th ese fu rn a c e s in th e tw o or th r e e y e a rs p rio r to an d d u rin g th e w ar.

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Fi g. 4 .— M a c h in e - M o u ld e d S t e e l C a s t i n g s . S h o rtag e of p ig -iro n ow ing to enorm ous w ar p ro ­ ductio n dem ands, th e p ro d u c tio n of v a s t q u a n ti­

tie s of scrap m a te ria l in th e fo rm of ste e l tu r n in g s , tu rn e d th e a tte n tio n of m a n u f a c tu r e rs to th e elec­

tric fu rn a c e as a quick, easily -co n tro lled , an d very a c c u ra te m eans of steel p ro d u c tio n , a n d m an y steel fo u n d ries in s ta lle d th em . S ev eral q u ite sa tisfa c to ry ty p es of th is fu rn a c e a re in c o n s ta n t use for th e p ro d u c tio n of steel fo r steel c a stin g s, and given a cheap su p p ly of e le c tric ity in th e necessary q u a n tity , th e r e is no d o u b t of th e i r suc­

cess fo r th e purpose.

B oth acid- and basic-lined fu rn a c e s a re in use, th e la t te r b ein g th e m ore p o p u la r ow ing to th e f a c t of th e ir a b ility to refiue m a te ria ls h ig h in

sul-pliur an d phosphorus. These d eleterio u s elem ents are rem oved to alm ost tra c e s w ith th e g re a te st ease. One of th e g re a te s t a d v a n ta g e s of th e basic- lined electric fu rn a c e is th e r e g u la r ity of com posi­

tio n of th e p ro d u c t, due a tte n tio n to slag condi­

tio n s producing com positions alm ost ex actly to calc u latio n , w ith w h at am o u n ts to clockwork re g u la rity .

The acid-lined fu rn a c e is, how ever, q u ite s a tis­

facto ry assum ing t h a t scrap of a know n d eg ree of p u r ity can be o b tain ed , th is fu rn a c e being u n ab le to be used for refining purposes.

Fluidity of Electric Steel.

The question of flu id ity is one of v ery g re a t im p o rtan ce to th e m a n u fa c tu re r of lig h t steel

cast-y3

Fi g. 5 .— Jolt- Rasi Pi n Lif t Mo u l d in g Ma c h in e.

ings, and d u rin g th e p a st y ear or so m uch discus­

sion h a s ta k e n place re g a rd in g th e re la tiv e flu id ity of electrically-produced, an d c o n v erter steels. I f c o n v erter steels a re com pared in te rm s of flu id ity w ith th e u ltra -d e a d electric steel, produced u n d e r a highly-basic strongly-reducing slag, th e a u th o r is definitely of th e opinion t h a t th e c o n v erter steel is th e m ore fluid. T his has been s ta te d to be due to v ario u s causes, th e m ost u su al one being th e assum ed presence of oxides.

I t h as been sta te d t h a t th e lo n g er “ l i f e ” of converter steel is due to incom plete re a c tio n s

betw een th e finishing alloys a n d dissolved oxides th ese re a c tio n s c o n tin u in g w ith th e p ro d u ctio n o t h e a t d u rin g th e c a s tin g o f th e m e ta l. T he a u t *10-T would only say t h a t he h a s n ev er been able to find differences of an aly sis a t th e b e g in n in g an d e n d in g of a c a st of c o n v e rte r steel, p ro p e rly m ade, of an a m p litu d e sufficient to su g g est t h a t an y a p p re ­ ciable a m o u n ts of silicon a n d m an g an e se w ere oxidised an d passed to th e slag d u rin g c a s tin g .

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Fi g. 6 . — Jo l t- Ra m Tu r n o v e e Mo u l d i n g Ma c h i n e.

This, in sp ite of th e fa c t t h a t , on sm all c a stin g s, i t m ay ta k e close upon th i r t y m in u te s to dispose of 30 cw ts. of m etal.

I n c o n tra d istin c tio n th e a u th o r believes t h a t D r.

W . H . H atfield has s ta te d in discussion t h a t in properly m ade steel no fre e o x id e can e x ist. I t is assum ed, th e re fo re , given c o n s ta n t co m p o sitio n in th e orthodox steel-m ak in g sense, t h a t flu id ity is m erely a fu n c tio n of te m p e r a tu r e . I n th e a u th o r ’s own ex p erien ce in th e p ro d u c tio n of so ft steels for lig h t c a stin g s a m a rk e d difference does n o t only ex ist betw een c o n y e rte r a n d e lec tric

Fig. 7.—The BeardsleyPiperSandSlinger—StationaryType. (BraintreeSteel CastingsCompany.)

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steels m ade u n d e r a stro n g ly re d u c in g slag, b u t also betw een w h a t is know n as single-slag and double-slag electric fu rn a c e charges. As is well- know n, single slag ch arg es a re n ev er su b jected to such a h ig h ly re d u c in g slag actio n as are those in which th e first slag is rem oved, an d a new one m ade fo r finishing p urposes w here refin in g is re q u isite . The a u th o r h as seen m any ch arg es w hich have been su b jected to re fin in g slags fo r a longei p eriod th a n n o rm al, w hich h a v e been so h o t t h a t th e fu rn a c e h a s been badly dam aged, a n d th e sto p p er in th e ladle q u ite u n a b le to w ith s ta n d th e te m p e ra tu re , w hich, when h a n d sh an k ed , h a v e n o t

“ lived ” by an y m eans so long as a sin g le slagged ch arg e m ade in a p erfectly n o rm al m a n n e r a n d of a v erag e a p p a re n t te m p e ra tu re . I n h is o p in io n , only a reliab le m eans of re g u la rly a s c e r ta in in g m olten-steel te m p e ra tu re s, n o t on a single c h a rg e , b u t over a prolonged p erio d , to g e th e r w ith th e evolution o'f a really reliab le m ethod of e s tim a tin g oxygen, or r a th e r th e oxides, in steel, can th ro w an y tr u e lig h t 011 th e problem . I n its p re s e n t s ta te th e m a tte r stops a t assu m p tio n based on observed phenom ena.

Composition of Metal.

The m ost common physical specifications fo r c a r ­ bon steel c a stin g s a re as follows : — (1) 26 to 35 to n s ten sile p e r sq. in ., 15 to 20 p e r cen t, e lo n g a tio n . (2) 35 to 40 to n s te n sile p e r sq. in ., 10 to 14 p e r cen t, elo n g atio n .

These a re easily m e t by steels of th e follow ing com positions, given n o rm al h e a t tr e a tm e n t.

(1) (2)

C .C ... 0.18 to 0.23 0.30 to 0.35 S i ... 0.25 to 0.30 0.20 to 0.25 Mn ... 0.70 to 0.90 0.70 to 0.90 S. & P u n d e r 0.06 u n d e r 0.06 Sulphur and Phosphorus in Steel Castings.

The influence of su lp h u r an d p h o sp h o ru s h a s, in th e a u th o r 's o p in io n , been som ew hat e x a g g e ra te d from th e s ta n d p o in t of th e i r effect in cau sin g defects in steel castin g s, m an y cases h a v in g come to his notice w here th ese im p u ritie s h a v e been blam ed fo r crack s in castin g s, w hich on considera­

tio n could be definitely assig n ed to n e g le c t d u rin g m oulding to p ro v id e m ean s of easy c o n tra c tio n of

V •

th e c a stin g w hilst cooling. T h e re is no d o u b t th a t an excess of su lp h u r is liable to m ake m ild steels cast in to sand m oulds less able to re s is t th e stresses to which castin g s a re su b jected d u rin g solidification an d a f te r cooling.

I n th e a u th o r’s exp erien ce, how ever, larg e n um bers of in tric a te castin g s m ade from steel con­

ta in in g 0.06 to 0.08 p e r c e n t, su lp h u r, h av e given n o t th e slig h te st difficulty in th is d ire c tio n , assum ­ ing design to be reasonable, and th e necessary care ta k e n d u rin g m oulding and eorem aking.

The effect of phosphorus in excessive q u a n titie s is m ore liable to be shown w hilst th e c a stin g is in

Fi g. 8 . — A Gr o u p o f El e c t r i c St e e l Ca s t i n g s.

service, its tendency being to reduce th e resistan ce of a c a stin g to re p e a te d shocks.

This ap p ears to be th e case reg ard less of th e fa c t t h a t such steels, say, c o n ta in in g 0.10 p er cen t, or m ore of phosphorus, show no signs of in fe rio rity u n d er th e o rd in a ry te s ts to which castin g s are sub­

jected, th e tensile an d elongation ca p a b ilitie s of the m etal being alm ost, if n o t q u ite, as good as in th e case of steels c o n ta in in g m ere tra c e s of phos­

phorus. G iven an u p p er lim it of 0.06 p er c e n t., however, no tro u b le need be a n tic ip a te d .

T h e ir freedom from su lp h u r and phosphorus has o ften been given as th e reason fo r elec tric steels g iving a h ig h er s ta n d a rd of p erfo rm an ce u n d e r te s t, th a n th e av erag e c o n v erter steel of sim ilar com position. I t is th e a u th o r ’s opinion, how ever, th a t m ore probably th e reason is th e freedom of th e electric steel from non-m etallic inclusions, and its susceptibility to h e a t tr e a tm e n t.

E

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T he “ as-cast ” s tr u c tu r e of an e le c tric steel h as alw ays ap p e a re d to th e a u th o r to be m o re easily rem oved by h e a t tr e a tm e n t th a n t h a t of c o n v e rte r steel of sim ila r analysis.

Influence of Aluminium.

T he use of a lu m in iu m in reaso n ab le q u a n titie s is beneficial, a n d in d eed e ss e n tia l to th e p ro d u c ­ tio n of steel c a stin g s. A ny la rg e excess, how ever, is v ery d eleterio u s. I n a n e x p e rim e n t c a rr ie d o u t by th e a u th o r , com parisons of re s u lts o b ta in e d on te s t b a rs a tta c h e d to steel c a stin g s dosed w ith v a ry in g q u a n titie s of a lu m in iu m , show ed t h a t e x ­ cessive a m o u n ts low ered m ax im u m stre ss, y ield p o in t an d elo n g atio n , an d decidedly red u ced th e c a p a c ity of th e m a te ria l to r e s is t shock.

C arb o n -free f e r ro -tita n u m h a s b een used as a final deoxidiser, th e re s u lt b e in g a sm all b u t re g u la r in crease in th e te n s ile s tre n g th .

W ith elec trically -p ro d u ced steels, how ever, th is m a te ria l is n o t a necessity.

Mould Production.

T he v a s t m a jo rity of steel c a s tin g s o f th e ty p e h e re in d e a lt w ith , is p ro d u c e d by m achines. I rider th e p re s e n t c o n d itio n s of low p rices, a n d severe co m p etitio n fo r ev ery o rd e r a v a ila b le , i t is no longer possible to p ro d u ce such m oulds econom ic­

ally by h a n d , ex cep t in c e rta in h ig h ly specialised cases. W h ere of special in tric a c y o r in cases w here diffiulties of design o r a m u ltip lic ity of loose pieces m ake m achine m oulding in ad v isab le, i t is th e p ra c ­ tic e in th e a u th o r ’s w orks to u se oddsides.

T he m a te ria l of w hich th e od d sid e is m ad e n a tu r a lly depends upon th e n u m b e r o f m oulds to be produced from it, an d in th e se w orks p la s te r o r wood is g en e ra lly used. F o r m an y sm all p a r ts , p a rtic u la rly th e sm aller ty p e s o f chassis c a stin g s, in which design, fro m th e p o in t of view o f r a p id p ro d u ctio n , is n o t alw ays all i t m ig h t be, th i s h a s been found to be q u ite an econom ical m ethod.

W henever possible, how ever, p a tt e r n s a re m ounted on m e ta l p la te s or b o a rd s fo r p ro d u c tio n on some ty p e of m o u ld in g m achine. T he squeezer, jo lt-ram p in - lift, jo lt-ra m tu r n o v e r ty p e s of m achines a re in c o n s ta n t u se fo r such w ork, b u t th e a u th o r’s p re fe re n c e fo r sm all w ork is fo r th e jo lt-ra m p in -lift ty p e.

F o r a la rg e r class of castin g , probably involving m ore in tric a c y , an d a g r e a te r d ep th of draw , th e

Fi g. 9 .— De n is o n Te n s il e Te s t in g Ma c h in e. Br a in t r e e Steel Ca st­ in g s Co m p a n y.

best resu lts h a v e been o b ta in e d from jo lt-ra m t u r n ­ over m achines w ith p a tt e r n d raw in g a tta c h m e n ts.

v 2

U nskilled la b o u r can be v ery q u ick ly tr a in e d to h a n d le th ese m achines, an d w hen p ro p e rly e q uipped w ith good boxes an d w ell-m ade p a tte r n s , p re fe ra b ly of m etal, th e o u tp u t of m oulds is very larg e.

A t th e sam e tim e th e c a s tin g p ro d u ced is alm o st alw ays o f b e tte r finish, an d m ore tr u e to p a tt e r n , th a n is th e case w hen h a n d m oulded.

T h e m ain p o in t to be co nsidered in m a c h in e m oulding is th e a d e q u a te su p p ly o f s a tis f a c to r y ta c k le . F irs t-c la s s boxes m ach in ed o n th e jo in t, an d bu sh ed w ith h a rd bushes, c a se -h a rd e n e d lo catin g -p in s o n th e p a tte r n - p la te , a n d case- h a rd e n e d closing p in s h a v e been fo u n d , a lo n g w ith well finished m etal p a tte r n s , to be essentials, if th e full benefits of m ach in e p ro d u c tio n a re to be a tta in e d .

A co m p a ra tiv e ly re c e n t in n o v a tio n in m ach in e m oulding is th e B eard sley P ip e r sa n d slin g e r. T he a u th o r h as re c e n tly h a d th e o p p o r tu n ity o f observ­

in g th is m ach in e over a f a i r p e rio d , in w hich i t was used fo r sev eral k in d s of w ork. I n th i s m achine, p re p a re d sand is fe d in to a n im p eller h ead by a conveyor b elt, an d p ro je c te d a t t h e p a t­

te r n by m eans of ra p id ly re v o lv in g b lad es. T he m achine is cap ab le of ra m m in g sa n d a t t h e r a t e of a b o u t 10 cw ts. p e r m in u te , a n d u n d o u b te d ly re p re se n ts a m a rk e d step fo rw a rd in th e e v o lu tio n of m achine m oulding. T h e q u estio n o f fa c in g sa n d re p re se n ts some litt le difficulty, as obviously only one ty p e of san d can be h a n d le d by th e m a ch in e, b u t i t is claim ed t h a t th e o r d in a r y b a c k in g sa n d c a n be k e p t in such c o n d itio n as to be p e rfe c tly sa tisfa c to ry on th e face of th e m ould. T h e a u th o r feels, how ever, t h a t i t is to o e a rly to m a k e an y very definite s ta te m e n t re g a r d in g th i s m a c h in e , b u t should its claim s be fu lly s u b s ta n tia te d , th e r e is no d o u b t t h a t as a m ean s of p ro d u c in g m oulds fo r castin g s of a m edium w eig h t i t w ill o ccu p y a v ery p ro m in e n t position in th e f u tu r e .

T he use of m achines, of any ty p e , m a k e s a v e ry heavy dem an d on th e core shop, an d in o rd e r to cope w ith it, m achines to m ak e cores will h a v e to keep ste p w ith th e advances in m o u ld in g m a c h in e p ra c tic e . B o th jo lt-ra m an d squeezer m ach in es a re in use fo r th is purpose, b u t th e a u th o r co n ­ siders t h a t th e a tte n tio n p a id to th e m achine p ro ­

100

duction of cores is still well behind t h a t p aid to m achine m ould p ro d u ctio n .

Moulding Sands.

T he basis of all san d m ix tu re s used for th e ty p e of c astin g s h ere d e a lt w ith , is a sh arp silica san d , to which v ario u s m a te ria ls are added to give th e

m ix tu re th e necessary p la s tic ity an d bonding power to re ta in its sh ap e in th e m ould. The o u ts ta n d in g qualifications such a sa n d -m ix tu re m u st possess a r e : —R e fra c to rin e ss sufficiently h ig h to re sist fusion by th e stre a m of extrem ely h o t m etal to which i t is subjected, th e c a p a b ility of being ram m ed sufficiently firm to re sist th e erosive action

of th e m etal, and sufficient p la s tic ity to allow it to be easily w orked. I n a d d itio n i t m u st possess th e m axim um degree of p e rm e a b ility , to allow of th e escape, a t th e m ax im u m possible speed, of gases evolved d u rin g c a stin g . T he m a jo rity of th e c a s t­

ings d e a lt w ith in th i s P a p e r a re c a s t in gTeen j san d m oulds, t h a t is, m oulds w hich a re n o t d rie d before c a stin g , an d ow ing to th e u n av o id ab le P r ®"

sence of considerable a m o u n ts o f m o istu re , th e q u estio n of p e rm e a b ility o f th e sa n d is o f first g ra d e im p o rtan ce.

M ix tu re s of san d s for g reen w ork v a ry in d iffe re n t fo u n d ries, b u t in th e w orks w ith w hich th e a u th o r is associated, th e b e st re s u lts h a v e been o b ta in e d from a coarse g ra d e of silica san d , th o ro u g h ly m illed w ith a sufficient q u a n tity of sa n d y loam to give th e n ecessary p la s tic ity . T he m in im u m

M ix tu re s of san d s for g reen w ork v a ry in d iffe re n t fo u n d ries, b u t in th e w orks w ith w hich th e a u th o r is associated, th e b e st re s u lts h a v e been o b ta in e d from a coarse g ra d e of silica san d , th o ro u g h ly m illed w ith a sufficient q u a n tity of sa n d y loam to give th e n ecessary p la s tic ity . T he m in im u m