Pig iron - Sen-tetsu (English spelling)

High-carbon iron made in a blast furnace. The process of steel smelting, which is widely used today, begins by charging iron ore, limestone as a slag-making agent, and coke as a fuel and reducing agent into a blast furnace, then blowing in hot air to heat and reduce the iron ore, resulting in molten iron containing around 4% carbon. This is called pig iron. This pig iron is then transferred to a converter, where oxygen is blown into it to oxidize and remove the carbon and other impurities, and it is then solidified and rolled or otherwise processed into steel plates or bars. There are two types of pig iron: pig iron for steelmaking, which is used as a raw material for steel, and pig iron for casting, which is used to adjust the composition to make cast iron castings without oxidation smelting. Because graphite crystals must form during solidification in cast iron castings, pig iron for casting contains more silicon and less manganese than pig iron for steelmaking, and other trace impurities are also kept to a minimum by carefully selecting the iron ore. Various types of special pig iron are produced, such as blast furnace pig iron, pig iron made in an electric furnace, electric pig iron, made using charcoal as a reducing agent and fuel, Bessemer pig iron, which is pig iron for steelmaking in an acid converter, and other special pig irons, such as low-phosphorus pig iron, which has a particularly low phosphorus content, silvery pig iron, which has a high silicon content, and banchit pig iron, which contains vanadium and titanium.

[Katsuya Igawa]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

溶鉱炉によってつくられた高炭素の鉄。現在広く行われている鉄鋼製錬の工程は、まず鉄鉱石と造滓(ぞうさい)剤である石灰石と燃料および還元剤としてのコークスを溶鉱炉に装入し熱風を吹き込んで鉄鉱石を加熱、還元し、炭素を4％前後含む溶融状態の鉄とする。これを銑鉄という。この銑鉄を転炉に移し、酸素を吹き付けて炭素やその他の不純物を酸化して除去し、これを凝固させて圧延その他の塑性加工により鋼の板や棒をつくる。銑鉄にはこのように鋼の原料に用いる製鋼用銑鉄と、酸化製錬をせずに成分を調整して鋳鉄鋳物にするための鋳物用銑鉄とがある。鋳鉄鋳物には凝固時に黒鉛結晶を形成させる必要があるので、鋳物用銑鉄は製鋼用銑鉄に比べてケイ素が多くマンガンが少なく、またその他の微量不純物も鉄鉱石を吟味して少なくしている。溶鉱炉でつくった銑鉄を高炉銑、電気炉でつくったものを電気銑、木炭を還元剤および燃料としてつくったものを木炭銑、酸性転炉用の製鋼用銑をベッセマー銑、その他とくにリンの少ない低リン銑やケイ素の多いシルバリー銑、バナジウムとチタンとを含むバンチット銑など種々の特殊銑鉄がつくられている。

［井川克也］

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