冶金Metallurgy

冶炼方法取决于金属的活动性：钾、钠、镁、铝等活泼金属用电解熔融化合物得到；锌、铁、锡、铅、铜等中等活泼金属用碳、CO、H₂ 或较活泼金属热还原；汞、银等不活泼金属加热分解其化合物即可，金、铂则以单质存在，靠物理方法或氰化浸出获得。埃林厄姆图把各种氧化物的 ΔG°–T 关系画在一起，可判断用什么还原剂、在什么温度下能还原。

The method depends on reactivity: very active metals such as K, Na, Mg and Al are won by electrolysing molten compounds; moderately active ones such as Zn, Fe, Sn, Pb and Cu are reduced thermally with carbon, CO, H₂ or a more active metal; for Hg and Ag heating the compound is enough, and Au and Pt occur native and are recovered physically or by cyanide leaching. The Ellingham diagram plots ΔG° against T for oxides and shows which reductant works at which temperature.

人类最早使用天然金和铜，约公元前 5000 年开始冶炼铜，约公元前 3000 年进入青铜时代，公元前 1200 年前后进入铁器时代。中国商周青铜器铸造技术高超，春秋战国已掌握生铁冶铸。1886 年霍尔和埃鲁独立发明电解铝，使铝从贵金属变为大宗材料。

People first used native gold and copper, began smelting copper around 5000 BCE, entered the Bronze Age around 3000 BCE and the Iron Age around 1200 BCE. Shang and Zhou China cast bronze with great skill, and pig-iron casting was mastered by the Warring States period. In 1886 Hall and Héroult independently invented aluminium electrolysis, turning aluminium from a precious metal into a bulk material.

火法冶金在高温下熔炼，如高炉炼铁、闪速炼铜；湿法冶金用溶液浸出、萃取和电积，如锌、金、铀和稀土的提取；电冶金包括熔盐电解和电解精炼。物理冶金研究合金组织、热处理与性能的关系。当代冶金关注节能、减少 CO₂ 排放（如氢冶金）和从电子废物中回收金属。

Pyrometallurgy smelts at high temperature, as in the blast furnace and flash smelting of copper; hydrometallurgy uses leaching, solvent extraction and electrowinning, as for zinc, gold, uranium and rare earths; electrometallurgy covers molten-salt electrolysis and electrorefining. Physical metallurgy relates alloy microstructure and heat treatment to properties. Current priorities are energy saving, lower CO₂ emissions such as hydrogen-based ironmaking, and recovering metals from electronic waste.