Basic oxygen steelmaking
Bessemer's idea perfected with pure oxygen: blow nearly pure oxygen down onto a bath of molten pig iron through a water-cooled lance, and its impurities burn out in minutes, refining hundreds of tonnes of iron into steel with no external fuel — the process that makes most of the world's steel today.
深層のアーカイブは当面英語で書かれています——検証済みの翻訳はロードマップに含まれています。このページではブラウザの翻訳機能がよく機能します。
✦ え、本当に？
A basic oxygen converter turns roughly 300 tonnes of molten iron into steel in about twenty minutes, burning no fuel at all — the impurities are the fuel. It is Henry Bessemer's 1856 dream come true, and the one thing that made it work was cheap oxygen: Bessemer's air blast poisoned steel with nitrogen, and only tonnage oxygen from air liquefaction removed that flaw.
これは何か
Basic oxygen steelmaking is Bessemer's converter reborn with pure oxygen. Like Bessemer, it refines molten pig iron by blowing an oxidising gas through it, letting the iron's own impurities — carbon, silicon, manganese, phosphorus — burn out and, by burning, supply all the heat the process needs. The two changes are decisive. Bessemer blew ordinary air up through holes in the base; basic oxygen steelmaking blows nearly pure oxygen down onto the surface through a water-cooled lance. Air is four-fifths nitrogen, which stole heat and dissolved into the steel to embrittle it; pure oxygen carries no nitrogen, so the blow is hotter, faster, and cleaner. A "basic" lime slag on top pulls out phosphorus, which the old acid-lined Bessemer never could.
なぜ重要だったのか
The open hearth made good, controllable steel but slowly — hours per heat. Bessemer was fast but crude, limited by phosphorus and nitrogen. Basic oxygen steelmaking captured the speed of the one and the quality of the other: a single converter refines several hundred tonnes of iron in about twenty minutes, with no fuel bill, into clean low-nitrogen steel fit for demanding use. The catch was oxygen. Robert Durrer proved the principle with small experiments in 1948, but blowing a converter needs oxygen by the tonne, and that only became affordable after air liquefaction turned the atmosphere into a cheap oxygen source. The Austrian works at Linz and Donawitz commercialised it in 1952–53, giving the process its name. Within a few decades it had displaced both Bessemer and the open hearth and become the way most of the world's steel is made.
何を解き放ったのか
Basic oxygen steelmaking is the source of the steel of the modern world — the beams, plate, pipe, rebar, sheet, and rail behind contemporary construction, shipping, cars, and appliances flow overwhelmingly from oxygen converters, usually paired with continuous casting downstream. It completed the long arc that began at the bloomery: from a spongy lump wrestled out by hand, to liquid cast iron by the ton, to Bessemer's twenty-minute blow, to a fuel-free furnace that makes clean steel by the hundreds of tonnes in the time it takes to boil down a pot — fed, at the last, by oxygen distilled from the air.
実用最小限の形
A basic-refractory-lined, tilting, pear-shaped converter charged with molten pig iron and cold scrap. A water-cooled lance descends and blows oxygen of over 99% purity onto the surface at high speed; carbon, silicon, manganese, and phosphorus burn out in a fierce fifteen-to-twenty-minute blow, and the heat of their own combustion keeps the bath molten. Then the converter is tilted and the steel tapped.
再建のレシピ
必要なもの
- · Molten pig iron from a blast furnace (~4% carbon), about 70–80% of the charge
- · Cold steel scrap, ~20–30% of the charge — it absorbs the excess heat the reactions release
- · Oxygen of greater than 99.5% purity (from air liquefaction), fed through a water-cooled lance
- · Burnt lime, to form a basic slag that captures phosphorus and sulfur
- · A tilting converter lined with basic (magnesia/dolomite) refractory
手順
- 01Tilt the converter and charge cold scrap, then pour in the molten pig iron; add lime.
- 02Right the vessel and lower the water-cooled lance to just above the bath.
- 03Blow oxygen down onto the surface at supersonic speed. Silicon and manganese burn first, then carbon roars off as carbon monoxide in a tall flame.
- 04The oxidation releases enormous heat — enough to melt the cold scrap and hold the whole bath near 1,650 °C without any fuel.
- 05The basic lime slag absorbs phosphorus and sulfur as they oxidise.
- 06After 15–20 minutes, when sampling and modern sensors show carbon at target, stop the blow, tilt, and tap the steel; hold back the slag, then add ferro-alloys to finish.
成功したとどうやって分かるか
A correct heat taps at target carbon and temperature (~1,600–1,700 °C) with low phosphorus, sulfur, and — crucially — low nitrogen, giving clean, tough steel that rolls without cracking. Modern practice reads the endpoint from the flame, the off-gas, and sub-lance sensors rather than by eye alone.
起こりうる失敗
- ⚠ Over-blowing past the endpoint — the steel over-oxidises ('burns'), iron is lost to the slag, and the metal turns brittle.
- ⚠ Acid lining instead of basic — it cannot hold a lime slag and so cannot remove phosphorus; the basic lining is what the 'basic' in the name refers to.
- ⚠ Wrong lance height or flow — too high gives a weak, slow blow; too low over-stirs and causes 'slopping,' metal and slag ejected from the mouth.
- ⚠ Too little scrap — nothing to absorb the reaction heat, so the bath overheats and attacks the lining.
この項目は完全な記述を待っています——地図製作者たちが作業中です。グラフ上の位置はすでに検証済みです。
解き放ったもの
最前線——その先はまだ記載されていません。
出典
- — Vaclav Smil, *Still the Iron Age* (2016)
- — R. F. Tylecote, *A History of Metallurgy*, 2nd ed. (1992)
- — J. K. Brimacombe et al., 'Basic Oxygen Steelmaking,' in *The Making, Shaping and Treating of Steel*, 11th ed. (1998)
このページに誤りを見つけましたか？ここに記されたすべての主張は、異議に耐えるために書かれています。 訂正を提案する →