BASIC OPEN-HEARTH PRACTICE

I t was previously s ta te d t h a t th e sub-divisions of th e o p en -h earth in d u s try in to basic and acid are

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m ore a m a tte r of use of th e p ro d u c t th a n of th e location of th e p la n t as re g a rd s m e ltin g stock supply. P ro b a b ly th is needs som e e x p la n a tio n . J u s t as Sheffield h as grow n from very e a rly b eg in ­ n in g s to be th e sig n ific a n t p ro d u c e r of c u tle ry , an d sim ilarly as D e tro it h a s become th e c e n tre fo r a u to ­ m obile c o n stru c tio n , so h a s th e m id d le w est in A m erica developed as a p ro d u c in g section o f co n ­ siderable im p o rta n c e fo r m a k in g ste e l c a stin g s fo r g e n e ra l ra ilw a y use, p a rtic u la rly as a p p lie d to q u a n tity p ro d u c tio n an d specialised m a n u fa c tu re . As in d ic a te d in p reced in g p a ra g r a p h s , g ree n -sa n d m oulding was from th e b e g in n in g h ig h ly fa v o u re d fo r th is class o f w ork. I t is in d eed a d m ira b ly a d a p te d th e r e fo r. E q u a lly so is steel of th e com ­ po sitio n c h a ra c te ris in g t h a t m a d e fro m th e basic op en -h earth . T he low er su lp h u r c o n te n t of basic o p e n -h e a rth ste e l pro d u ced in th e fo u n d ry (generally u n d e r 0.035 p e r c e n t., a n d in some p la n ts ra re ly re a c h in g 0.030 p e r c e n t.) , gives a se c u rity a g a in s t red -sh o rtn ess t h a t m a te ria lly a id s th e p ro d u ctio n of m an y im p o r ta n t c a stin g s whose designs p lace th em in a susceptible class as to

“ s h rin k a g e crack s ” or “ checks.” F o r such c a s t­

in g s as d raw -b ars or couplers, b o lsters, sid e -fra m e s (all re q u ire d fo r A m erican ra ilw a y tr u c k a p p lic a ­ tio n ), it is n o t e ss e n tia l t h a t th e m e ta l h a s th e u tm o st freedom fro m m in u te blow -holes, which m ore o fte n ex ist in b asic o p e n -h e a rth steel th a n in acid o p e n -h e a rth m etal. T he fa c to r of s a fe ty in m any mem bers of th e sp ecialised c a stin g s m ade in la rg e q u a n titie s in m iddle w estern fo u n d rie s is la rg e r th a n t h a t re q u ire d sim ply by good e n g in e e r­

ing p ractice, because of th e c o m p a ra tiv e ly la rg e a re a re q u ire d in m an y m em bers to m a k e th e steel p ro p erly fill all th e cav ities in th e m ould.

I t m u st n o t be supposed from th e fo reg o in g t h a t A m erican basic o p e n -h e a rth steel p ro d u c e d fo r c astin g s is essen tially “ s p o n g y ” m e ta l. R e f e r ­ ence to blow-holes or gas c a v itie s h a s b een m ad e from a re la tiv e sta n d p o in t, a n d t h a t fa c to r h a s been properly considered by m a n u f a c tu r e rs , in connection w ith o th e rs t o be m e n tio n e d , in th e final selection of th e lin in g . T h e a d d itio n a l elem ents of a v a ila b ility an d c o st of m e ltin g stock are, of course, alw ays k e p t in m in d . L ocal in d u s­

tr ia l an d m a r k e t c o n d itio n s re g u la te th e fa c to rs

la s t m en tio n ed , an d h ave been im p o rta n t con­

sid eratio n s in th e selection of basic bottom s for m any fo u n d ries in m id d le W estern S ta te s.

I t would be a w aste of tim e fo r th e a u th o r of th is P a p e r to dwell u p o n those d etails of steel fu rn ace c o n stru c tio n o r o p e ra tio n t h a t a re c h a r­

a c te ris tic of p ra c tic e b o th a t home and abroad.

C e rta in fe a tu re s will p robably be o f in te re st, due to differing local c o n d itio n s. T he a u th o r, in his m ark ed ig n o ran ce of d e ta ils of fo reig n p ractice, hopes to to u ch u p o n those fe a tu re s which a re sig­

n ifican t in c o m p arativ e studies. In such a n effort he m u st depend larg ely on h is conception of th e m ajo r item s of in te re s t to B ritis h foundrym en.

In o p e ra tin g basic o p e n -h e a rth fo u n d ries in th e S ta te s, th e com position of th e p ro d u c t desired and th e n a tu r e o f ty p ic a l m etal ch arg es are generally such as to call fo r a p ro p o rtio n of lim estone re p r e ­ sen tin g fro m 1 2 p e r c en t, to 18 p e r cent, of th e m etal c h a rg e . T his lim estone fre q u e n tly exceeds 96 p e r c e n t, in calcium c a rb o n a te , an d often co n tain s no m ore th a n 1 p e r cent, of silica, alu m in a or m agnesia. T h ere is a n ab u n d an ce of su itab le lim estone widelv q u a rrie d .

Fuel Considerations.

I n th e selection o f fuel fo r th e basic open -h earth fu rn ace, th e re is n a tu r a lly m ore co n sid eratio n given to th e low er su lp h u r c o n te n t t h a t o b tain s in n a tu r a l g as an d in fuel o il as com pared w ith p ro ­ ducer gas. F o rtu n a te ly fo r th e o p en -h earth in d u stry , an d p a rtic u la rly for th e basic o p en -h earth founders, th e stead y decrease of n a tu r a l gas flow­

in g fro m A m erican wells in re c e n t y ears h as not been very seriously fe lt in fo u n d ry o p e ra tio n s, due to th e very g r e a t sim u ltan eo u s d ev elo p m en t of th e oil in d u stry , an d th e re s u ltin g a v a ila b ility of th e oil for m eltin g . Only in c e rta in r a th e r isolated p o rtio n s of th e S ta te s a re th e cru d e oils of objec­

tio n ab ly h ig h su lp h u r c o n te n t. T he o u tp u t of the A m erican oil wells w hen delivered fo r fuel p u r­

poses a fte r e x tr a c tio n of th e lig h te r an d m ore valuable oils, is gen erally less th a n 0.50 p e r cent, and freq u en tly u n d e r 0.33 p e r cent, in su lp h u r c ontent.

Oil fro m m an y of th e W estern S ta te s h as an a sp h alt base, w hile t h a t from e a s te rn wells generally h a s a p araffin base, m a k in g i t th e m ost

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c o n v en ie n t 'for use in cold w eath er. T he h e a v ie r oil w ith an a sp h a lt base re q u ire s a m o d e ra te te m ­ p e ra tu re to he s a tis fa c to rily p u m p ed . W h e re such oils a re used in w in te r tim e , s to ra g e ta n k s a re eq u ip p ed w ith steam coils, an d p ip in g system s a re a rr a n g e d fo r a rtific ia l h e a tin g . W h en th e se sa fe ­ g u a rd s a re p ro v id ed , use of th e w estern o il is sa tisfa c to ry .

W h e th e r th e fuel-oil be fre e fro m e a s te rn o r w estern sources, i t is u sually fo u n d to c o n ta in n o t less th a n 18,500 B.T.TT. p e r lb., an d fre q u e n tly h as even a h ig h e r h e a t v alu e. P re f e re n c e f o r ste a m o r com pressed a ir as an ato m isin g a g e n t fo r th e com bustion of th e fu el oil is a b o u t eq u ally d iv id ed , an d is p ro b ab ly due in m an y cases to th e a v a il­

ab ility o f th e re q u ire d volum e o f ste a m or a i r . T he a u th o r ’s p referen ce is fo r th e u se o f s te a m as th e m ore econom ical a to m is in g a g e n t,* as h e believes th e r e h a s n o t been d e m o n s tra te d u n d e r ru n n in g te s t c o n d itio n s any s u p e r io rity of e ith e r ato m isin g a g e n t, considered irre s p e c tiv e of delivered co st to th e b u rn e r.

I n m any A m erican b asic o p e n -h e a r th fo u n d rie s th e p erc e n ta g e of p ig -iro n used in th e c h a rg e will ru n fro m 35 p e r c e n t, to 50 p e r c e n t., th e b a la n c e of th e m etal ch arg e b ein g m ade u p of g a te s , rise rs an d o th e r w aste m a te ria l p ro d u c e d in th e fo u n d ry , an d p u rch ased scrap fro m m an y sources selected p rin c ip a lly because o f s u ita b le le n g th , w id th of piece an d th ick n ess of section. V ery t h i n scrap is, of course, objected to because of th e h ig h e r m eltin g loss re s u ltin g from its u se in th e open- h e a rth .

The c h a rg in g of th e basic o p e n -h e a rth fu rn a c e in m ost A m erican fo u n d rie s is p e rfo rm e d w ith th e aid of e lec tric pow er. T h ere a re sev eral ty p e s of elec trically -o p erated c h a rg in g m ach in es em ployed, no n e of which is in use in som e of t h e sm a lle r o p en -h earth fo u n d rie s. T hese m a ch in es a re fa m ilia r to B ritis h fo u n d ry m en .

Stationary and Tilting Furnaces.

T here are few im p o rta n t f e a tu r e s in c o n stru c ­ tio n of roofs, p o rts, checkers o r re g e n e r a tiv e cham bers, o r o th e r m a jo r d e ta ils in b asic o r acid

, , * “ T ransactions of th e Am erican F o u n d ry m en 's A ssociation ” Vol. X X IV ., pages 429 to 453.— R ep o rt for C om m ittee on Steel

Jovm dty S tan d ard s, h y th e a u th o r, *

open-hearth fu rn aces employed in A m erican foundries w hich ju s tify special m en tio n in th is P a p e r. In a m in o rity of in stan ces fu rn a c e doors a n d d oor fra m e s a re w ater-cooled. T he ‘fu rn a c e itself, as g e n e ra lly fo u n d , e ith e r of th e basic o r acid ty p e, is s ta tio n a ry , alth o u g h th e r e are some fu rn aces t h a t a re elec trically tilte d , and a lesser n um ber t h a t are hydraulica'lly tilte d . As m ig h t be supposed, roof-life is m uch g re a te r in th e case of s ta tio n a ry fu rn aces. I t is th is fa c to r which has had m ost influence in th e stro n g g en eral p re fe r­

ence fo r th e s ta tio n a ry ty p e of o p en -h earth fu rnace.

Som e A m erican in v e n to rs h av e devised roof designs, of course, ap p licab le to e ith e r basic or acid fu rn aces, w ith th e idea of p ro lo n g in g th e life of th is v ery im p o rta n t elem ent in o p en -h earth co n stru ctio n . One such device provides fo r a su p p lem en tary th ick n ess by m eans of special re fra c ­ to ry shapes. The roof-life of th e basic o p e n -h e a rth fu rn ace in m any A m erican fo u n d ries is close to 350 heats, w hereas t h a t of an acid fu rn a c e is o ften 1,000 h eats. T his is pro b ab ly re p re s e n ta tiv e of resu lts when th e o p e ra tio n s are con tin u o u s, except for b rief periods on .Sundays.

As a class th e basic o p en -h earth fo u n d ry in A m erica produces day in a n d d ay o u t b u t one grad e of steel, which th e fo u n d ry re g a rd s as m ost su itab le for its p ro d u ct, which, as previously in d ic a te d , is generally a specialised one. P ro b ab ly th e carbon c o n te n t of m ost of th is basic o p e n -h e a rth steel is aro u n d 0.24 p e r c e n t., w ith a m anganese c o n te n t of ab o u t 0.70 p e r c e n t., a n d a silicon c o n te n t close to 0.35 p er c e n t. T he av erag e p e rc e n ta g e s of phos­

phorus an d su lp h u r a re each gen erally u n d e r 0.03 p er c e n t., t h a t of th e phosphorus b ein g th e lower. In some p la n ts w here designs a re produced th a t are p ecu liarly susceptible to sh rin k ag e cracks o r red-shortness, co n siste n t efforts a re m a in ta in e d to m ake th e su lp h u r co n te n t av erag e ap p reciab ly u n d e r 0.03 p e r c e n t. T hus is re g u la te d th e p e r­

cen ta g e o f lim estone used in th e ch arg e.

The norm al tim e fo r m ak in g a basic o p en -h earth h e a t in th e A m erican steel fo u n d ry is a b o u t seven hours when th e ch arg e is in tro d u c e d m echanically, and ab o u t e ig h t an d one-half ho u rs when th e f u r ­ nace is h an d -ch arg ed . S ta c k -d ra fts an d

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cham ber p ro p o rtio n s have a g r e a t deal to do * 1

m elting speed, an d differences in th ese e x p lain some wide ra n g e s in d a ta re p o rte d .