What Is A Malleable Iron?
Malleable iron is cast as white iron, the structure being a metastable carbide in a pearlitic matrix. Through an annealing heat treatment, the brittle structure as first cast is transformed into the malleable form. Carbon agglomerates into small roughly spherical aggregates of graphite leaving a matrix of ferrite or pearlite according to the exact heat treatment used. Three basic types of malleable iron are recognized within the casting industry: blackheart malleable iron, whiteheart malleable iron and pearlitic malleable iron.
Malleable iron is often used for small parts due to its excellent tensile strength. This includes electrical fittings, hand tools, pipe fittings, washers, brackets, fence fittings, power line hardware, farm equipment, and more. Companies around the world make fittings and other such equipment out of malleable iron, which is a testament to how well it still works 70+ years after the advent of ductile iron.