What is the different between Cast, Forged, Ductile, and Malleable?

Lineman,

If the harware parts are subjected to tension then Cast Iron is not recommended.Forged steel is most reliable as it will not have any moulding defects like blow holes etc. but it might be costlier than Malleable/Ductile iron.

Suresh Sharma.

You've actually asked two different questions.

A cast material's grain structure is coarse and dendritic (looks like a christmas tree kind of.) and the grain growth is generally perpendicular to the surface of the mold. The object cools from the outside in which means the base of the dendritic "tree" is at the surface. If there is any tendency of the alloy to segregate the different alloy components of the metal, the elements with the highest melting point/lowest solubility will tend to migrate to the middle of the part. This is called hot shortness. This grain structure and segregation has implications for the creep behavior, toughness and strength of the part. Cast parts also tend to have some level of porosity.

Forged parts on the other hand are hammered or shaped while hot but still solid. this breaks up the cast grains and tends to close up porosity. The resulting grains structure is laminar and paralell with the surface of the part. This usually results in a stronger, tougher part with much less porosity.

Some years back there was a real problem of counterfeit API oilfield flanges (which are supposed to be forged) that were coming out of China that were actually cast. They were so porous they leaked like seives.

Malleability and ductility are actually one in the same and are a measure of how easily the material can be formed without cracking.

thanx for ur valuable information .........