Lustrous Carbon
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The heating of the coal dust by the liquid iron causes the formation of a type of carbon called lustrous carbon which is not wetted by the liquid iron, so the cast surface is improved.
The formation of ‘lustrous carbon’ from the thermal degradation of the volatiles given off during casting improves casting surface finish and strip.
The casting of iron components was initially very difficult due to the formation of lustrous carbon defects on the surface and subsurface carbonaceous inclusions, which were only revealed on machining.
