Inmetallurgy,non-ferrous metals are metals oralloys that do not containiron (allotropes of iron,ferrite, and so on) in appreciable amounts.
Generally more costly thanferrous metals, non-ferrous metals are used because of desirable properties such as low weight (e.g.aluminium), higherconductivity (e.g.copper),[1] non-magnetic properties orresistance to corrosion (e.g.zinc).[2] Some non-ferrous materials are also used in the iron andsteel industries. For example,bauxite is used asflux forblast furnaces, while others such aswolframite,pyrolusite, andchromite are used in making ferrous alloys.[3]
Important non-ferrous metals include aluminium, copper,lead,tin,titanium, and zinc, and alloys such asbrass.Precious metals such asgold,silver, andplatinum and exotic or rare metals such asmercury,tungsten,beryllium,bismuth,cerium,cadmium,niobium,indium,gallium,germanium,lithium,selenium,tantalum,tellurium,vanadium, andzirconium are also non-ferrous.[4] They are usually obtained through minerals such assulfides,carbonates, andsilicates.[5] Non-ferrous metals are usually refined throughelectrolysis.[6]
Due to their extensive use, non-ferrousscrap metals are usuallyrecycled. The secondary materials in scrap are vital to the metallurgy industry, as the production of new metals often needs them.[7] Some recycling facilities re-smelt and recast non-ferrous materials; thedross is collected and stored onsite while the metal fumes are filtered and collected.[8] Non-ferrous scrap metals are sourced from industrial scrap materials, particle emissions and obsolete technology (for example,copper cables) scrap.[9]
Non-ferrous metals were the first metals used by humans for metallurgy. Gold, silver and copper existed in their nativecrystalline yet metallic form. These metals, though rare, could be found in quantities sufficient to attract the attention of humans. Less susceptible to oxygen than most other metals, they can be found even in weathered outcroppings. Copper was the first metal to be forged; it was soft enough to be fashioned into various objects bycold forging and could be melted in acrucible. Gold, silver and copper replaced some of the functions of other resources, such as wood and stone, owing to their ability to be shaped into various forms for different uses.[10] Due to their rarity, these gold, silver and copper artifacts were treated as luxury items and handled with great care.[11] The use of copper also heralded the transition from theStone Age to theCopper Age. TheBronze Age, which succeeded the Copper Age, was again heralded by the invention ofbronze, an alloy of copper with the non-ferrous metaltin.[10]
Non-ferrous metals are used in residential,commercial and industrial applications. Material selection for a mechanical or structural application requires some important considerations, including how easily the material can be shaped into a finished part and how its properties can be either intentionally or inadvertently altered in the process. Depending on the end use, metals can be simply cast into the finished part, or cast into an intermediate form, such as aningot, then worked, or wrought, by rolling,forging, extruding, or other deformation process. Although the same operations are used with ferrous as well as nonferrous metals and alloys, the reaction of nonferrous metals to these forming processes is often more severe. Consequently, properties may differ considerably between the cast and wrought forms of the same metal or alloy.[12]
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