Illustration:  Pig  iron  blown  in  a  basic-lined  converter  con-
tained 1.22  per  cent,  silicon,  2.18  phosphorus,  1.03  manganese
and  3.21  carbon.  It  is  blown  until  all  of  these  and  2.00  per
cent,  of  iron  are  oxidized,  and  burnt  lime  is  added  to  form
slag  during  the  blow.  Composition  of  the  burnt  lime:  MgO,
1.00  per  cent.;  SiO2,  2.00  per  cent.;  CaO,  97  per  cent.  How
much  lime  should  be  added  per  10  metric  tons  of  pig  iron  charged?

The  slag-forming  ingredients  from  the  oxidation  of  the  bath,
and  the  addition  of  X  kilos,  of  lime,  are

SiO2  10,000X0. 0122 X  60/28  =  261.4  kg.
P2O5  .    10,000X0.0218X142/62  =  499.3    "

MnO  10,000X0. 0103 X  71/55=133.0    "

FeO  10,000X0. 0200 X  72/56=257.1    "

fCaO  XX 0.9700  =    0.97  X

\  MgO  XX 0.0100  =    0.01  X

[SiO2  XX 0.0200  =    0.02  X


Weight  for  slag  =  X  + 1150.8  kg.
Corrosion  of  the  lining  will  undoubtedly  increase  this  weight,
so  some  allowance  should  be  made,  say  to  increase  it  5  per


348  METALLURGICAL  CALCULATIONS.
cent.,  probably  an  outside  figure.  Of  this  5  per  cent.,  half  can
be  considered  lime  and  half  magnesia.  The  total  weight  of
slag  will  then  be  1.05  X-f  1208.3,  and  of  the  ingredients  prin-
cipally in  question:

SiO2  =  261.  kg. +  0.02  X
MgO  =  28.7  "  +0.035  X
CaO  =  28.7  "  +  0.995  X

To  make  our  slag  50  per  cent.  CaO  will  require  the  addition
of  enough  to  make

28. 7  +  0. 995  X  =  0.50  (1.05  X  +  1208.3)
X  =  1224  kg.
To  make  a  slag  with  at  most  15  per  cent,  of  SiO2  requires

261.4  +  0.02  X  =  0.15  (1.05  X  +  1208.3)
X  =    583  kg.
