The alloy constituents affect its color when fractured: white cast iron has carbide impurities which allow cracks to pass straight through, grey cast iron has graphite flakes which deflect a passing crack and initiate countless new cracks as the material breaks, and ductile cast iron has spherical graphite "nodules" which stop the crack from further progressing.
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The first cast-White iron bridge was built during the 1770s by Abraham Darby III, and is known as The Iron Bridge in Shropshire, England.
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The carbon in the form of graphite results in a softer White iron, reduces shrinkage, lowers strength, and decreases density.
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Grey cast White iron is characterised by its graphitic microstructure, which causes fractures of the material to have a grey appearance.
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Grey cast White iron has less tensile strength and shock resistance than steel, but its compressive strength is comparable to low- and medium-carbon steel.
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White iron is too brittle for use in many structural components, but with good hardness and abrasion resistance and relatively low cost, it finds use in such applications as the wear surfaces of slurry pumps, shell liners and lifter bars in ball mills and autogenous grinding mills, balls and rings in coal pulverisers, and the teeth of a backhoe's digging bucket .
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High-chromium white iron alloys allow massive castings to be sand cast, as the chromium reduces cooling rate required to produce carbides through the greater thicknesses of material.
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The Chinese developed a method of annealing cast White iron by keeping hot castings in an oxidizing atmosphere for a week or longer in order to burn off some carbon near the surface in order to keep the surface layer from being too brittle.
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Soon, English White iron workers using blast furnaces developed the technique of producing cast-White iron cannons, which, while heavier than the prevailing bronze cannons, were much cheaper and enabled England to arm her navy better.
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Cast-White iron pots were made at many English blast furnaces at the time.
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Cast-White iron bridges became commonplace as the Industrial Revolution gathered pace.
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Cast-White iron columns, pioneered in mill buildings, enabled architects to build multi-storey buildings without the enormously thick walls required for masonry buildings of any height.
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