鑄鐵

鐵的合金,含碳2~4%,還含有數量不等的矽、錳、硫、磷。鑄鐵是在高爐內還原鐵礦石生產的,放出鐵水澆注冷卻成錠,稱為生鐵。鑄鐵與熟鐵不同,不能鍛造,只能鑄造成型,性脆、抗拉強度低,但產品價廉。鑄鐵有較高的抗壓強度,以致成為首要的結構金屬。18~19世紀時,鑄鐵是比熟鐵較為便宜的工程材料。20世紀建筑業以鋼取代鑄鐵,但在工業中仍有許多用途,如汽車發動機缸體、農業機械和機器零件、管道、凹形器皿、火爐、熔爐等。按照斷面顏色,鑄鐵有灰口或白口之分;铱阼F含矽較高,硬度較低,比白口鐵加工性能好。白口鐵和灰口鐵均較脆。18世紀,在法國發展了白口鑄鐵經長時間加熱處理生產可鍛鑄鐵。1948年在美國和英國發明了在鑄造狀態下就有延伸性的鑄鐵。這類韌性鑄鐵,現已形成重要的金屬體系,廣泛用於齒輪、模具、汽車曲軸和許多其他機械零件。

cast iron

Alloy of iron that contains 2-4% carbon, along with silicon, manganese, and impurities. It is made by reducing iron ore in a blast furnace (cast iron is chemically the same as blast-furnace iron) and casting the liquid iron into ingots called pigs. Pig iron is remelted, along with scrap and alloying elements, in cupola furnaces and recast into molds for a variety of products. In the 18th-19th century, cast iron was a cheaper engineering material than wrought iron (not requiring intensive refining and hammering). It is more brittle and lacks tensile strength. Its compressive (load-bearing) strength made it the first important structural metal. In the 20th century, steel replaced it as a construction material, but cast iron still has industrial applications in automobile engine blocks, agricultural and machine parts, pipes, hollowware, stoves, and furnaces. Most cast iron is either so-called gray iron or white iron, the colors shown by fracture; gray iron contains more silicon and is less hard and more machinable than white iron. Both are brittle, but malleable cast iron (produced by prolonged heat treating), first made in 18th-century France, was developed into an industrial product in the U.S. (see Seth Boyden). Cast iron that is ductile as cast was invented in 1948. The latter now constitutes a major family of metals, widely used for gears, dies, automobile crankshafts, and many other machine parts.

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