Name : Patel Ishan P. Sub. : MSM Enr No. : 130940119083 Branch : Mechanical -B Guided By , Umang Patel ..

CAST IRON

Cast Iron Ferrous Steels Cast iron Grey White Nodular Malleable

What is cast iron?

Iron accounts for more than 95 wt% of the alloy material, while the main alloying elements are carbon (between 2.1- 4.5 wt%) and silicon (normally 1-3 wt%). From the iron-iron carbide phase diagram, cast iron has a eutectic point at 1153 °C and 4.2 wt% carbon. Since cast iron has roughly this composition, its melting temperature of 1150 to 1200 °C is about 300 °C lower than the melting point of pure iron. The most common cast iron types are: grey, white, nodular, malleable and compacted graphite.

Grey Cast Iron

graphite flakes surrounded by a- ferrite or pearlite matrix Grey cast iron is named after its grey fractured surface that occurs when the graphitic flakes deflect a passing crack and initiate many new cracks as the material breaks. graphite flakes surrounded by a- ferrite or pearlite matrix weak & brittle in tension (the graphite flake tips are sharp; act as stress raisers) stronger in compression excellent vibrational dampening wear resistant grey grey

Grey Cast Iron Carbon content: 3.0 – 4.0 wt% Silicon content: 1.0 – 3.0 wt % Modifying silicon content and cooling rate affects microstructure. Casting shrinkage is low

Microstructure of Grey Cast Iron (200X, Nital etch.)

White Cast Iron

White cast iron is named after its white surface when fractured due to its carbide impurities that allow cracks to pass straight through; the crystalline fractures are shiny compared to the dull gray fractures of graphite irons. < 1 wt% Si, rapid cooling rates pearlite + most of the carbon forms cementite, not graphite. very hard and brittle;

White Cast Iron thickness may result in non-uniform microstructure from variable cooling; white iron develops from faster cooling; slower cooling rate yields grey iron. limited applications; used as intermediate to produce malleable cast iron.

Nodular Cast Iron (Ductile)

graphite forms nodules not flakes Normally a pearlite matrix. Nodular Cast Iron in Adding Mg and/or Cerium to grey iron before casting produces a distinctly different microstructure and mechanical properties. graphite forms nodules not flakes Normally a pearlite matrix. grey nodular nodular (Nodular Cast Iron)

Nodular Cast Iron Photo (nodular) shows ferrite matrix that was heat treated for several hours at 700˚C. Castings are stronger and much more ductile than grey iron.

Malleable Cast Iron

reasonably strong and ductile (malleable) white iron nodular Malleable cast iron formed by heat treating white iron at 800- 900ºC for a prolonged period causes decomposition of cementite into graphite. graphite forms clusters or rosettes that are surrounded by a ferrite or pearlite matrix. reasonably strong and ductile (malleable) Carbon content: 2.3 – 2.7 wt% Silicon content: 1.0 – 1.75 wt % malleable malleable

Application & Properties of Cast Iron Wide range of applications (including pipes, machine and car parts, such as cylinder heads, blocks and gearbox cases) due to: low melting point, good fluidity, relatively easy to cast, excellent machinability, resistance to deformation wear resistance Cast iron tends to be brittle, except for malleable cast irons, so shaping these by deformation is very difficult. Cast iron coated with durable porcelain enamel distributes heat slowly and evenly.

Variety of Cast Iron Microstructures Gf , graphite flake Gr , graphite rosettes Gn, graphite nodules P, pearlite = a + cementite a, ferrite

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