CAST IRON:
Cast iron is an important alloy of Fe and C are mostly employed within industry for its convenience to casting in intricate and superior mechanical properties. Steels could also be cast but process is frequently costlier. Figure of Iron-Carbon Phase Diagram, clearly shows the region of cast iron in equilibrium diagram. The demonstration presents that there is a eutectoid at 4.3% as point C such has solidification temperature of 1135oC. Alloys inside carbon range of 2.3% to 4.2% are occasionally submitted to as hypo-eutectic irons, because their carbon content is underneath the eutectic composition. Even though, the melting points of cast irons are higher than various non-ferrous alloys, still they are inside the reach of easy melting furnaces, some of which are commercially accessible. It is one cause as to why cast irons are as popular as structural material.
To know different phases that are represent in a cast iron one may refers as cooling of a typical Fe - C mixture from melt, say one having y % C as in figure of Iron-Carbon Phase Diagram. The first material to solidify is austenite that is an explanation of carbon into fcc iron. The line PG will give the amount of C in solution in austenite during solidification. This amount is all time less than the average percentage in the melt that means carbon is refused out of austenite whilst the liquid phase is enriched in carbon. The last liquid to solidify has the eutectic composition that is 4.3%. The eutectic has the austenite and carbon.
If the liquid is cooled gradually keeping near equilibrium situation, the carbon solidified like flakes of graphite in a soft ferrite matrix, in pearlite or in a mixture of pearlite and ferrite. If liquid is cooled quickly then ferrite is suppressed and cementite and pearlite precipitate.
Casting is a process whether molten is poured in a mould and on solidifying the casting of the shape of mould is acquired. Cast iron, as previously stated, in a superior material for casting. Universal properties of cast iron are as:
a) Cheap material.
b) Lower melting point as 1200oC as compared to steel as 1380-1500oC.
c) Good casting properties foe instant: high fluidity, sound casting, low shrinkage, ease of production in huge number.
d) Good in compression but CI along with ductility are available also.
e) CI is machinable is main cases.
f) Abrasion resistance is remarkably high.
g) Very significant property of CI is its damping characteristics that isolates vibration and makes it excellent material for foundation and housing.
h) Alloy CI might be good against corrosion.