机械类专业英语阅读教程第一章部分翻译VIP专享

1. Metals and Their Use It is known that metals are very important in our life. Metals have the greatest importance for industry. All machines and other engineering constructions have metal parts; some of them consist only of metal parts. There are two large groups of metals: 1) Simple metal- more or less pure chemical elements 2) Alloys- materials consisting of a simple metal combined with some other elements. About two thirds of all elements found in the earth are metals, but not all metals may be used in industry. Those metals which are used in industry are called engineering metals. The most important engineering metal is iron, which in the form of alloys with carbon and other elements, finds greater use than any other metal. Metals consisting of iron combined with some other elements are known as ferrous metals; all the other metals are called nonferrous metals. The most important nonferrous metal are copper, aluminum, lead, zinc, tin, but all these metals are used much less than ferrous metals, because the ferrous metals are much cheaper. Engineering metals are used in industry in the form of alloys because the properties of alloys are much better than the properties of pure metals. Only aluminum may be largely used in the form of simple metal. Metals have such a great importance because of their useful properties or their strength, hardness, and their plasticity. Different metals are produced in different ways, but almost all the metal are found in the forms of metal ore (iron ore, copper ore, etcet cetra.) The ore is a mineral consistence of a metal combined with some impurities. In order to produce a metal from some metal ...