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Full text of "Metallurgy Of Cast Iron"

THE   MANUFACTURE   AND   PROPERTIES   OF   COKE.         23
requires chemical analysis to detect the former, while                 $
the eye may at times detect the latter.                                             j
The best brand or grade of coke to use in smelting                 j •
or melting iron is often regulated by its cost.    Certain                  jv
localities  in  the  Connellsville   region   are  generally conceded to give the best grades of coke to be found
in this country, but the great distance of many con-                 j sumers from this point makes the cost so great that
they use other brands.    However, almost every locality                 '!
can furnish different grades, and it is often surprising                 j'
how much less of the best grade is required than of                 \ poorer ones in doing the same work in melting.    It is                  ; *,
rare that there is any economy in using poor grades
of coke if the difference in price is at all reasonable.                     !• '
In the first use of coke in cupolas it was bought and                 ; charged by the bushel,   instead of by weight  as at
present.    Coke weighs from thirty to seventy pounds                 P  /
per bushel, the more dense and hard, the heavier it is.                 y ;
In using coke in cupolas it is very important to note                  > \^f
its hardness and be governed by the same, as with the                  * /j1
same weight of coke in good soft and hard grades one                 ; J
can readily conceive that the bed and charges of coke                  f?',t
would vary in height and could often cause trouble, as                  f |f;
for example the same weight in a soft coke that would'                ,j£j
bring it up to eighteen inches or so above the top of                 jjp
the  tuyeres,  could, in hard  coke, bring  it  only to  a                 •! |'< level of the tuyeres or a little above, which all experi-            •     |{f ,<
enced founders know would soon bung up or prevent                 ;l||j
a cupola from melting.    Where one is called upon to               ' ?}4! use a soft coke — and which will not permit Qupolas                   jp,<
to run as clean or as long as hard coke, although soft                 |$,'
coke may give good hot iron—he should, as a rule, use                ||M
less weight of the soft coke than of the hard in the bed                )*fy