Materials, Science and Metallurgy
Weldability of Cast Iron
What is cast iron? Cast iron is an alloy of iron that contains 2 to 4 percent carbon, along with different amounts of silicon, manganese, and traces of impurities such as sulfur and phosphorus. It is made by reducing iron ore in a blast furnace. The liquid iron is then cast, or poured and hardened, into crude ingots called pigs, and the pigs are then remelted along with scrap and alloy elements in a ‘cupola furnace’ and recast into molds for producing a variety of products. The Chinese first produced cast iron as early as the 6th century BC, and was produced off and on by the 14th century in Europe. In 1619, the first ironworks in America were established in Virginia, on the James River. During the 18th and 19th centuries, cast iron was a cheaper engineering material than wrought iron because it didn’t require a lot of refining and working with hammers, but it was more brittle and very low in tensile strength. Its load-bearing strength made it the first important structural metal, and it was used in some of the earliest skyscrapers, but in the 20th century, steel replaced cast iron in construction, yet cast iron continues to have its many uses. There are various types of cast iron: gray cast iron; containing carbon in the pearlite structure and has graphite flakes, white cast iron; has no graphite, all of its carbon is combined as cementite or as pearlite, alloy cast irons; numerous and have various properties, such as tensile strength mach inability, depth of hardening, wear, fatigue, and corrosion resistance, plus many others, nodular iron; sometimes referred to as “ductile iron”, produced by adding magnesium and\or cerium, chilled iron; has a chemical composition similar to gray cast iron but with a lower silicon content, and malleable iron; made by heating white cast iron for a long time below the critical temperature. Cast iron is a...
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