外文翻译--材料选择与热处理.doc

Material Selection and Heat Treatment of Metal During recent years the selection of engineering materials has assumed great importance. Moreover, the process should be one of may be a decreasing availability of them. Concerns regarding environmental pollution, recycling and worker health and safety often impose new constraints. The desire for might reduction or energy savings foreign compellation, increased serviceability requirements, and customer liability actions, often the result of improper material use, has had a marked impact. In addition, the interdependence between materials and their processing has become better recognized. The development of new processes often forces reevaluation of the materials being processed. Therefore, it is imperative that design and manufacturing engineers exercise considerable care in selecting, specifying, and utilizing materials if they are to achieve satisfactory results at reasonable cost and still assure quality. The first step in the manufacture of my product is design, which usually takes place in several distinct stages: (a) conceptual; (b) functional; (c) production design. During the conceptual-design stage, the designer is concerned primarily with the function the product is to fulfill, Usually several concepts are visual Jails and considered, and a decision is made either that the idea is not practical or that the idea is sound and one or more of the conceptual designs should be developed further. Here, the only concern for materials is that materials exist that can provide the desired properties, If no such materials are available, consideration is given as to whether them is a reasonable prospect that new ones could be developed within cost and time limitations. At the functional- or engineering-design stage, a practical, workable deign is developed. Fairly complete drawings are made, and materials are selected and specified for the various components. 0ften a prototype or working model is made that can be tes