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Full text of "Metallurgy Of Cast Iron"

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EFFECTS   OF   BLAST   TEMPERATURES.                   75
ture of the blast was soon raised by degrees until 1,500 to i,600 degrees were often utilized with benefit where a furnace had " chilled " or " got off "; but the general practice of high temperature of blast in the normal working of a furnace is not to exceed 1,300 degrees, being kept at 1,100 to 1,200 degrees with brick stoves and goo to 1,000 degrees with iron stoves. When a furnace is working well, any increase over 1,200 degrees in the temperature of the blast is claimed by many to be more injurious in its results on the stock than beneficial in assisting a furnace to produce a good yield of iron, or '' drive well.'' The reason that high degrees of heat in the blast will not cause the desirable and economical reduction of ore in the furnace, that high heat derived from the fuel will, is a phenomenon which all seem at a loss to understand. Experience has demonstrated that a temperature between 1,000 and 1,200 degrees is the most desirable to maintain. The temperature of the blast may be raised from 600 to 800 degrees with but little improvement, but let this 200 degrees in-                I
crease   be   added  to   1,000  degrees  and  the  benefit                \
derived is extraordinarily greater than any increase of                |
200 degrees on a lower temperature.    In the normal                I
working of a furnace the best  results  are  obtained                ^
with a temperature of blast ranging between r,ooo and                K
1,200 degrees F.                                                                    '      *,
By reason of utilizing the waste gases of a furnace                |j
to heat cold  blast, blast  furnace practice excels all                |j
other industries in obtaining  the  greatest efficiency                :|,
from fuel, as about 75 per cent of the heat generated from the solid fuel is utilized. This is attained where one ton of coke will produce one ton of iron; and Sir........................    2,720     "