Building Materials, Third Edition

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much of the impurities in wrought iron are affiliated with the slag rather than iron. However,
a very high sulphur content (0.3–0.5%) is likely to cause the wrought iron to crumble or exhibit
red shortness, in forging or welding. Sections rolled from red short wrought iron are likely to
have rough edges. A phosphorus content of 0.4–0.5% causes the wrought iron to be cold short
(iron becomes brittle at low temperatures). Such wrought iron cannot be refined by heat
treatment. Spilly places, the defect due to burning of portions of the iron in puddling, are often
found as spongy spots in wrought iron sheets and plates. Blisters are also found on plates and
sheets of inferior wrought iron due to the oxidation of carbon in the iron by the oxide of iron
in the slag.

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Steel is the most suitable building material among metallic materials. This is due to a wide
range and combination of physical and mechanical properties that steels can have. By suitably
controlling the carbon content, alloying elements and heat treatment, a desired combination of
hardness, ductility and strength can be obtained in steel. On the basis of carbon content steel
may be calssified as under:

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The prominent steel-making processes are:

1. Bessemer process


2. Cementation process


3. Crucible process


4. Open Hearth process


5. Electric Smelting process


6. Duplex process


7. Lintz and Donawitz (L.D.) process
   The most prominent present-day steel-making
   process is the Bessemer process was introduced in


8. The pig iron is first melted in Cupola furnace
   and sent to Bessemer converter (Fig. 13.4) Blast of
   hot air is given to oxidize the carbon. Depending
   upon the requirement, some carbon and manganese
   is added to the converter and hot air is blasted once
   again. Then the molten material is poured into
   moulds to form ingots. L.D. process is modification
   of the Bessemer process in which there in no control
   over temperature. By this method steel can be made

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