关于冶金的文章

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Metallurgy is a domain of materials science that studies the physical and chemical behavior of metallic elements, their intermetallic compounds, and their mixtures, which are called alloys.History An illustration of furnace bellows operated by waterwheels, from the Nong Shu, by Wang Zhen, 1313 AD, during the Chinese Yuan Dynasty.The earliest recorded metal employed by humans appears to be gold. Small amounts of natural gold have been found in Spanish caves used during the late Paleolithic period, c. 40,000 BC.[1] Historical developments in ferrous metallurgy can be found in a wide variety of past cultures and civilizations. This includes the ancient and medieval kingdoms and empires of the Middle East and Near East, ancient Egypt and Anatolia (Turkey), Carthage, the Greeks and Romans of ancient Europe, medieval Europe, ancient and medieval China, ancient and medieval India, ancient and medieval Japan, etc. Of interest to note is that many applications, practices, and devices associated or involved in metallurgy were first established in ancient China long before Europeans mastered these crafts (such as the innovation of the blast furnace, cast iron, steel, hydraulic-powered trip hammers, etc.)Extractive metallurgyExtractive metallurgy is the practice of removing valuable metals from an ore and refining the extracted raw metals into a purer form. In order to convert a metal oxide or sulfide to a purer metal, the ore must be reduced either physically, chemically, or electrolytically.Extractive metallurgists are interested in three primary streams: feed, concentrate (valuable metal oxide/sulfide), and tailings (waste). After mining, large pieces of the ore feed are broken through crushing and/or grinding in order to obtain particles small enough where each particle is either mostly valuable or mostly waste. Concentrating the particles of a value in a form supporting separation enables the desired metal to be removed from waste products.Mining may not be necessary if the ore body and physical environment are conducive to leaching. Leaching dissolves minerals in an ore body and results in an enriched solution. The solution is collected and processed to extract valuable metals.Ore bodies often contain more than one valuable metal. Tailings of a previous process may be used as a feed in another process to extract a secondary product from the original ore. Additionally, a concentrate may contain more than one valuable metal. That concentrate would then be processed to separate the valuable metals into individual constituents.Metallurgy in production engineeringIn production engineering, metallurgy is concerned with the production of metallic components for use in consumer or engineering products. This involves the production of alloys, the shaping, the heat treatment and the surface treatment of the product. The task of the metallurgist is to achieve design criteria specified by the mechanical engineer, such as cost, weight, strength, toughness, hardness, corrosion and fatigue resistance, and performance in temperature extremes.Common engineering metals are aluminium, chromium, copper, iron, magnesium, nickel, titanium and zinc. These are most often used as alloys. Much effort has been placed on understanding one very important alloy system, that of purified iron, which has carbon dissolved in it, better known as steel. Normal steel is used in low cost, high strength applications where weight and corrosion are not a problem. Cast irons, including ductile iron are also part of this system.Stainless steel or galvanized steel are used where resistance to corrosion is important. Aluminium alloys and magnesium alloys are used for applications where strength and lightness are required.A nickel-based alloy such as Monel is used in highly corrosive environments and for non-magnetic applications. The nickel-based superalloy Inconel is used in high temperature applications such as turbochargers, pressure vessels, and heat exchangers.The operating environment of the product is very important; a well-designed material will resist expected failure modes such as corrosion, stress concentration, metal fatigue, creep and environmental stress fracture. Ferrous metals and some aluminium alloys in water and especially in an electrolytic solution such as seawater, corrode quickly. Metals in cold or cryogenic conditions tend to lose their toughness becoming more brittle and prone to cracking. Metals under continual cyclic loading can suffer from metal fatigue. Metals under constant stress in hot conditions can creep.Production engineering of metalsMetals are shaped by processes such as casting, forging, Flow Forming, Rolling (metalworking), extrusion, sintering, metalworking, machining and fabrication. With casting, molten metal is poured into a shaped mould. With forging, a red-hot billet is hammered into shape. With rolling, a billet is passed through successively narrower rollers to create a sheet. With extrusion, a hot and malleable metal is forced under pressure through a die, which shapes it before it cools. With sintering, a powdered metal is compressed into a die at high temperature. With machining, lathes, milling machines, and drills cut the cold metal to shape. With fabrication, sheets of metal are cut with guillotines or gas cutters and bent into shape."Cold working" processes, where the product’s shape is altered by rolling, fabrication or other processes while the product is cold, can increase the strength of the product by a process called work hardening. Work hardening creates microscopic defects in the metal, which resist further changes of shape.Various forms of casting exist in industry and academia. These include sand casting, investment casting (also called the “lost wax process”), die casting and continuous casting.Welding is a technique for joining certain ferrous metals and certain aluminium alloys. The metals in the weld and on both sides of the join are generally similar alloys. Brazing is a technique for joining ferrous or non-ferrous metals with a copper-based (generally brass or bronze) filler.Metals can be heat-treated by annealing, quenching, tempering and case hardening to alter properties of toughness, hardness or resistance to corrosion. Annealing softens the metal and makes a shaped product tougher by reducing the effects of work hardening. Quenching and case hardening make a shaped product harder. Quenching by itself makes the metal very hard and very brittle. Tempering after quenching is used to reduce the brittleness and improve overall properties.Electroplating is the main surface-treatment technique. It involves bonding a thin layer of another metal such as gold, silver, chromium or zinc to the surface of the product. It is used to reduce corrosion as well as to improve the product's aesthetic appearance.Electrical and electronic engineeringMetallurgy is also applied to electrical and electronic materials where metals such as aluminium, copper, tin and gold are used in power lines, wires, printed circuit boards and integrated circuits.Soldering is a method of joining metallic electrical conductors where high strength is not required.Metallurgical techniquesMetallurgists study the microscopic and macroscopic or sometimes known as small and large mechanisms that cause a metal or alloy, one metal bonded with an element to form a hybrid,to behave in the way that it does, i.e. the changes that occur on the atomic level that affect the metal's (or alloy's) macroscopic properties. Examples of tools used for microscopic examination of metals are optical and electron microscopes and mass spectrometers.Metallurgists study crystallography, the effects of temperature and heat treatment on the component phases of alloys, such as the eutectic and the properties of those alloy phases.The macroscopic properties of metals are tested using machines and devices that measure tensile strength, compressive strength and hardness.

公元前1274年，古埃及与古美索不达米亚之间爆发了一场战争，因为战车上使用车轴的不同，直接决定了战争的胜负。埃及人的铜轴与美索不达米亚的铁轴代表了完全不同的两种冶金能力，铁轴战胜了铜轴。 作者从这么一个战争故事，引入了对人类冶金技术的介绍。按照作者的定义，文明的出现有三个代表性的特征，分别是书写能力，城市的产生，冶金技术的大规模利用。 发明（发现）冶金技术，算不上文明的标志，就像仅仅制造出来一台样车，跟特斯拉大规模制造电动汽车是完全不同的概念。只有能够在生活上大规模使用金属器具，才代表着文明的开始。 华夏文明对于冶金技术的掌握，从年代来说比较晚，但是从对这一技术的深入程度来说，却是早期文明里面差不多最好的。 冶金技术的出现，不仅仅体现在金属的冶炼与产品的制造上，同时也出现了许多高温条件下才能够产生的“副产品”，比如玻璃、陶瓷等。而这些副产品的进一步利用，更快的推动了人类文明的发展。 《吴军科技史纲》这门课，已经学习了一小部分。读他的课程，有一个突出的感觉，总是在不知不觉间就读了一遍，仿佛没有讲什么，却看的津津有味，这很奇怪。我想，这里面一定有什么东西是自己没弄明白的。 引人入胜，应该是作者写作文章最重要的一个特点。比如这一讲，明明是对冶金技术的介绍，却用一场三千多年前的战争来开头，让我们能够了解到当时那场战争胜负的核心原因。不进学到了科技史，也捎带了解了古代史，让读者兴趣盎然，也让作者言之有物。这样的开头，很有意思，更值得借鉴。在写作一篇文章时如何谋篇布局，这就是一个很好的榜样。 对细节的介绍，是吸引人的另一个特点。比如介绍各个古代文明社会对冶金技术掌握的先后，直接使用了大量年代数字（姑且不论真假），这就很有说服力了。如果泛泛而谈谁谁谁先发明了，谁后发明了，那就会流于无聊，读者乏味。 看别人写的东西，一方面是学习里面介绍的直接知识，另一方面更要思考作者是如何把那些知识介绍给大家的，这个方法论更重要。 凭什么人家写的文章就能够在得到上开课？已有的渊博当然很重要，但是能够把脑袋里的渊博用别人喜欢接受的方式讲出来，这个讲故事的能力，是更重要的本领。 前些天读《人类简史》，这个想法也一直在冒泡。读的时候似乎没感觉到作者介绍出来什么独有的知识，但是却愿意按照作者的思路一直看下去，这本身就代表了作者所拥有的独特能力。 茶壶里煮饺子，心里有数是不行的，只有在透明的茶壶里煮饺子才能让大家看的一清二楚。这个能让别人一清二楚自己的想法，就是写作能力。