
228 Engineering Materials Technology
machining takes place. Such a treatment involves heating to about 550°C, i.e.
below the A\ temperature.
Malleable cast irons
Malleable cast irons are produced by the heat treatment of white cast irons.
Three forms of malleable iron occur: whiteheart, blackheart and pearlitic.
Malleable irons have better ductility than grey cast irons and this combined
with their high tensile strength makes them useful materials.
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Composition
Figure 11.20 Production of blackheart malleable iron
In the blackheart process, white iron castings are heated in a non-oxidizing
atmosphere to 900°C and soake ...