机械工程专业英语 lesson 19翻译（Mechanical Engineering English Lesson 19 translation）.docVIP

机械工程专业英语 lesson 19翻译（Mechanical Engineering English Lesson 19 translation） Gear material The gear can be made from a variety of materials, including metals and non metals, but the use of these materials for the design, selection of a specific gear, should be the cheapest price, and can satisfy the requirements, in the material selection, the designer must be faced in the present problems in finding out the factors is the most important, if high strength is the main consideration, should choose the steel instead of cast iron, if wear resistance is the key, then choose not iron containing material is better than iron containing materials, also reduce the noise about this aspect, non metal is better than that of metal materials. However, in many practical design problems, often have such a fact, the best material is eclectic, in other words, the properties of the selected materials, can well meet the above mentioned requirements, but not, nor necessary, is the best properties in any way, above all, we will be in accordance with the general classification of gear to discuss all kinds of metal, non metal gear material characteristics. Cast iron is one of the most widely used materials for making gears. Cast iron is low cost, easy to cast, easy to manufacture, high wear resistance, and very good noise reduction performance, making the use of cast iron material as gear is an ideal and reasonable choice. The main disadvantage of cast iron gear is its low tensile strength, which makes the gear tooth bending ability very weak and needs to be made big teeth. In addition there is a kind of cast iron is ductile iron, it is an addition of iron magnesium and cerium, which makes this mixed alloy material keeps ordinary cast iron wear resistance and easy processing, has a higher tensile strength. Considering the overall cost, strength, and wear resistance, large cast-iron gears and small steel gear combinations are generally recognized as a good design. Steel is divided into plain