B efore re p ly in g to th e p o in ts ra ise d in th e dis
cussion on th is P a p e r, M r. W ilson p o in te d o u t t h a t he h a d tr ie d to m ak e i t as p ra c tic a l as possible, fo r th e reaso n t h a t q u ite a n u m b e r of fo u n d ry m en who w ere k een on b rin g in g th e i r p la n t u p to a h ig h s t a t e of efficiency, desired to h av e re s u lts based on a c tu a l p ra c tic e r a t h e r th a n to o m u ch th e o ry . T he a v erag e m a n ask ed for so m eth in g w hich w ould help h im to p ro d u c e b e tte r an d c h e a p e r c a stin g s.
R e p ly in g to M r. Shaw , M r. W ilson s ta te d , w ith re g a rd to th e t e s t m e n tio n e d a t th e b o tto m of p a g e 4 of th e P a p e r, t h a t th e p re s su re s w ere ta k e n d ire c tly a f t e r th e cupola w as blow n in . Special a rra n g e m e n ts w ere m ad e to allow fo r th e tu b es to descend w ith th e c h a rg e , b u t i t was only possible to c o n tin u e th is te s t for a p eriod of fifteen m in u te s, due to th e flexible co nnecting tu b es b u rn in g a f t e r t h a t tim e .
R e fe rr in g to th e te s ts in w hich v a ry in g volumes w ere used, several te s ts n o t p u b lish ed in th e P a p e r h a d been m a d e fo r a lo n g p eriod w ith d ifferen t volum es, b u t th e o b ject of ta k in g th is p a rtic u la r te s t on one d ay was to en su re t h a t th e conditions re m a in e d th e sam e. T he cupola w as n o t blown dow n a t each c h an g e o f volum e. The volum es w ere changed a t in te rv a ls of o n e h o u r.
H e h a d a lre a d y e x p la in e d in th e P a p e r th e p eriods a t which th e v ario u s sam ples w ere ta k e n , a n d p a r t ic u l a r c a re was ta k e n to keep th e condi
tio n of th e cupola an d th e h e ig h t o f th e bed, e tc ., as n e a r c o n s ta n t as possible.
W ith referen ce to th e e x p an sio n p o in ts, as shown in th e d ia g ra m , on b a rs o b ta in e d fro m iron c a st in chills m elted a t v a ry in g volum es, th e chilled m ould in w hich th e se b a rs w ere c a s t was
w a te r cooled, w ith a n a rra n g e m e n t for m a in ta in in g a c o n s ta n t te m p e ra tu re a t th e tim e of castin g . R e p ly in g to M r. Cook, he expressed th e view t h a t , a lth o u g h i t was well know n t h a t th e p e r
c e n ta g e of oxygen in th e a ir v a rie d u n d e r d iffe re n t clim atic conditions, th e m easu rem en t of a ir by w e ig h t in s te a d of volum e would he a co m p licated a rra n g e m e n t. T he m easu rem en t of a ir by w e ig h t w as a n ex cellen t m ethod, h u t he was a fr a id t h a t u n d e r o rd in a ry fo u n d ry condi
tio n s th is was im p racticab le.
Wilson Blast Meter is Standardised.
T he in s tru m e n t re fe rre d to in th e P a p e r is specially d esigned to w ith s ta n d th e conditions u su a lly fo u n d ro u n d an d a b o u t a cupola. In o th e r w ords, i t is n o t affected by d u st an d g rit c o n ta in e d in th e a ir. As to th e accuracy of th e in s tru m e n t, h e said t h a t each in s tru m e n t was
c a lib ra te d w ith a P i t o t tu b e u n d e r s ta n d a rd co n d itio n s.
H e ag reed w ith M r. C am pion t h a t th e q u an t i t y of a ir should be re fe rre d to in term s of
“ Coke C onsum ed,” an d n o t “ P e r to n of Iron M e lte d .” I t is obvious t h a t th is is m ore correct, as th e coke r a t i o v aries considerably, an d for th is reason th e formulae re fe rre d to in th e P ap er a re based on, n o t only th e a m o u n t of coke, b u t also th e i r carb o n c o n te n t.
R e p ly in g to M r. G resty ’s re m a rk s as to th e te m p e ra tu re o f gases a t v a ry in g h eig h ts, as shown in P ig . 2, h e said th e te m p e ra tu re was ta k e n a t th e tu y e r e level a t a p o in t a few inches inside tb e cupola. H e believed t h a t th e m axim um te m p e ra tu re was n o t o b tain ed a t th is p o in t. I t would n a tu r a lly be g re a te r a t th e m e ltin g zone, b u t it w ould be v ery difficult t o o b ta in th e te m p e ra tu re a t t h a t p o in t, so t h a t u n d o u b ted ly th e curve as shown in F ig . 2 w ould h a v e a k in k in i t a t some p o in t above th e tu y e r e level.
T he o b je c t o f th is te s t was n o t to o b ta in th e m ax im u m te m p e ra tu re a t th e m e ltin g zone, b u t to show th e v a ria tio n in te m p e ra tu re due to th e h e ig h t o f th e cupola. I n o th e r w ords, to prove t h a t in th e case of cupolas w ith a c h arg in g door to o low, th e loss in sensible h e a t was m ore exces
sive th a n in th e case of h ig h e r cupolas.
W ith re g a rd to th e in creased exp an sio n o b ta in e d on bars c a st fro m iro n m elted w ith a h ig h b la s t, a larg e n u m b e r of e x p e rim e n ts m ade in co u rse of in v e s tig a tio n s in co nnection w ith c a stin g in p e r m a n e n t m oulds prove t h a t a h ig h e r ex p an sio n is o b ta in e d w ith o x id ised iro n . R e fe rr in g to F ig . 14, th e re g u la r ity of th e p ressu re an d volum e c u rv e proved t h a t th e cu p o la w as w orking effi
cien tly , th e tu y e re s re m a in in g clean th r o u g h o u t th e m elt.
Tuyere D etails.
R ep ly in g to M r. H u d so n , i t is fo u n d t h a t w ith a n open slag hole a n d c o n tin u o u s slag g in g , th e re is s lig h t re d u c tio n in te m p e ra tu re , an d also a h ig h e r p e rc e n ta g e of iro n sh o t in th e slag.
R ep ly in g to a n o th e r m em ber w ith re g a rd to th e sh ap e an d n u m b e r of tu y e re s used in th e cupola, he said t h a t in th e p a r tic u la r cupola re fe rre d to in th e P a p e r th e n u m b e r of tu y e re s used was e ig h t. T hese w ere oval in sh ap e, an d th e tu y e re a re a w as 18 p e r c en t, of th e cross sectio n al a re a a t th e m e ltin g zone. T he h e ig h t o f th e coke bed above th e u p p er tu y e r e w as 18 in.
H e agreed w ith M r. F le tc h e r t h a t w ith iron h a v in g a h ig h p hosphorus c o n te n t one could w ork w ith a low er coke co n su m p tio n , b u t w ith a cupola p ro p e rly c o n stru c te d , w ith m ean s of re g u la tin g th e b la s t su p p lies, th is could efficiently d eal w ith th e p ro d u c tio n of high-class iro n s w ith o u t an y difficulty. I n th e la t te r case i t is m ore im p o rta n t to h a v e som e m eth o d of b la s t control th a n w hen u sin g comm on irons.
W ith re g a rd to d e trim e n ta l gases, m entioned by M r. L o g an , i t is well know n t h a t m olten m etal can c o n ta in in v a ry in g degrees— oxygen, h y d ro gen, n itro g e n , carb o n m onoxide an d carbon d ioxide. An excess o f an y of th e s e gases produces u n so u n d c a stin g s an d affects th e physical s tre n g th of th e m etal. C astin g s pro d u ced from h o t m e ta l a re less liab le to be affected by absorbed gases th a n a re c astin g s p ro d u ced from cold sluggish m etal.
Factors Governing Melting Rates.
R e p ly in g to M r. H ir d ’s q u estio n w ith re g a rd to in c re a sin g th e o u tp u t of th e cupola by in c re a sin g
th e coke r a tio , he sa id t h a t w h a t he m e a n t to convey was t h a t th e low er th e p e rc e n ta g e of coke, or th e h ig h e r th e r a t io of iro n to coke, th e g re a te r th e m e ltin g r a te .
W ith r e g a r d to M r. Y oung’s w ritte n com m uni
c a tio n s t a ti n g t h a t a P i t o t tu b e was all t h a t was necessary, M r. W ilson p o in ted o u t t h a t , ta k in g in to co n sid e ra tio n th e collection of d u st u n d e r o rd in a ry w o rk in g co n d itio n s, th is m u st affect th e re a d in g of th e P i t o t tu b e , an d unless these tubes w ere k e p t clean th e re s u lts m u s t he u n reliab le.
W ith r e g a r d to th e ex p an sio n of th e iron re f e rre d to , th e o b je c t of q u o tin g th ese figures was to show t h a t th is co n d itio n can arise w here iron is h ig h ly oxidised, p ro d u cin g a g r e a t expansion.
The p a r tic u la r case m en tio n ed by him was n o t o b ta in e d w ith in reaso n ab le lim its, h u t was only given to show th e possible re s u lts u n d e r very a b n o rm al co n d itio n s. The figures given were n o t o b ta in e d in th is c o u n try , b u t in a cupola
a b ro a d w here v ery h ig h b la s t was used.