1.18
鉄鋼製造
鉄鋼製造は、高炉で鉄鉱石を鋳鉄に精錬することから始まる多段階プロセスです。この最初の段階では、炉内で鉄鉱石を燃料の一種であるコークスと砕いた石灰石で層状にします。大量の空気でコークスに点火すると一酸化炭素が生成され、鉄鉱石を純鉄に還元します。
この精錬プロセスでは、石灰石がスラグを形成するという重要…
鉄鋼製造は、高炉で鉄鉱石を鋳鉄に製錬することから始まります。製錬では、鉄鉱石にコークスと呼ばれる燃料と砕いた石灰岩を炉に重ねます。
まず、コークスを空気の爆風で点火して一酸化炭素を生成し、鉱石を溶融鉄に還元します。
石灰岩はスラグを形成し、不純物を捕らえ、溶融金属の上に浮かんでいます。この溶銑は、鋼材加工のために排水されます。
溶銑には過剰な炭素と不純物が含まれています。それらを除去するために、基本的な酸素プロセスが採用されています。これは、石灰と蛍石フラックスを使用して、溶鉄とスクラップに浸された酸素ランスを含み、リンと反応することによって廃棄可能なスラグを形成します。
最後に、必要に応じて鋼の組成を変更するために、新しい金属元素を導入することができます。
鋼が炉から注入段階に達すると、インゴットに成形されるか、ストランド鋳造機で処理されます。インゴット金型は、直径が数フィート、高さが6〜8フィートの範囲である場合があります。
また、完成した鋼は、ビームブランクまたはブルームと呼ばれる厚くて粗い形状に連続的に鋳造されます。
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Q1: What happens during the smelting stage of steel manufacturing?
Smelting occurs in a blast furnace where iron ore is layered with coke fuel and crushed limestone. Coke ignition produces carbon monoxide, which reduces the ore to molten iron. Limestone forms slag that captures impurities like silica and phosphorus, floating above the molten metal for easy separation before the purified iron drains for steel processing.
Q2: How does the basic oxygen process improve molten iron quality?
A water-cooled oxygen lance is dipped into molten iron mixed with scrap metal. Lime and fluorspar flux are added, reacting with phosphorus and other impurities to form discardable slag. This refining process removes excess carbon and contaminants, producing cleaner steel suitable for composition modification with new metallic elements.
Q3: What role does limestone play in the blast furnace?
Limestone is layered with iron ore and coke in the blast furnace. During smelting, it forms slag that captures impurities such as silica, phosphorus, and alumina from the molten iron. The slag floats above the molten metal, allowing easy separation and removal of contaminants before the purified iron is drained.
Q4: What are the two main methods for shaping steel after refining?
Refined steel is shaped through ingot molding or strand casting. Ingot molds are large containers with diameters and heights spanning several feet, producing individual ingots. Alternatively, strand-casting machines continuously cast refined steel into thick, rough shapes called beam blanks or blooms, ready for further processing into various steel products.
Q5: Why is carbon monoxide essential in iron ore reduction?
Carbon monoxide is produced when coke is ignited with a blast of air in the furnace. It acts as the reducing agent, chemically converting iron ore into molten iron by removing oxygen from the ore. This reduction process is fundamental to extracting pure iron from raw ore during the smelting stage.
Q6: What impurities does slag remove during steel manufacturing?
Slag captures impurities including silica, phosphorus, and alumina from molten iron during smelting. In the blast furnace, limestone reacts with these contaminants to form slag, which floats above the molten metal. During the basic oxygen process, lime and fluorspar flux also react with phosphorus to form additional slag for removal.
Q7: How can steel composition be customized after the basic oxygen process?
After refining removes excess carbon and impurities through the basic oxygen process, new metallic elements can be introduced to modify the steel's composition. This allows engineers to tailor the steel's properties to meet specific requirements for different applications before the material is shaped into ingots or beam blanks.