现代制造技术专业英语阅读材料169分段Word文档下载推荐.docx

1、铸铁开始用于各种工业领域。图R1-1所示汽缸座用铸铁制造。这是铁含有了太多的碳或其他等效的物质。这是不可锻造的。很明显，铸铁具有广泛的性能，因为其元素的小百分比的变化可能会引起相当大的变化。铸铁不应被认为是一个金属包含一个单独的元素，而是，作为一个具有至少六个元素组成。所有铸铁含有铁，碳，硅，锰，磷，硫。合金铸铁还有其他元素，其他元素不应该被认为是杂质，因为他们所有的物理性质有重要的影响。纯的铁，称为铁素体，很软，几乎没有用于工业生产。其它元素在铸铁铁素体调节控制所有理想的性质，如强度，硬度和可锻造性。The cast iron family includes gray, ductile （a

2、lso called nodular）, white, malleable and high-alloy irons.铸铁系列包括灰口铸铁，球墨铸铁（也被称为nodular），白口铸铁，可锻铸铁和高合金铸铁。Gray iron is itself a family of casting alloys, and is the most widely used, with an annual production several time the total for all other metals cast.灰口铸铁本身所属的种类是铸造合金，是应用最广泛的，每年生产的总量是几倍于其他铸铁的。A

3、relatively new type of cast iron is ductile iron-also called nodular iron .As its name implies, ductile iron offers more ductility than gray iron, plus higher strength.一种新型的球墨铸铁称为球墨铸铁。顾名思义，球墨铸铁具有比灰口铸铁更具延展性，加上高强度。2.Heat Treatment of Steel 2.钢的热处理Heat treatment is a method by which the heat treater ca

4、n change the physical properties of metal .There are three main operations in the heat treatment of steel: hardening, tempering, and annealing.热处理是热处理工作者用以改变金属物理性能的方法。钢热处理有三种法即淬火、回火和退火。The hardening operation consists of heating the steel above its critical range and then quenching it, that is rapid

5、ly cooling in a suitable medium such as water, brine, oil, or some other liquid. Having been hardened, the metal must be given a tempering treat-ment which consists of reheating the hardened steel to a temperature below the critical range, thus producing the required physical properties.淬火是将钢加热到临界点以

6、上然后进行急冷。急冷是指在材料合适的介质如水、盐水、油或其他液体中快速冷却。金属在淬硬后必须进行回火处理。回火是将淬硬的钢重新加热到低于临界点的温度从而获得所需的物理性能。The critical points or critical temperatures are the temperatures at which a certain change takes place in the physical condition of the steel. These points are very important because in order to properly harden a

7、piece of steel, it must be heated to a temperature above the upper critical point. Having known the critical points for a certain steel, we can easily control the heat in the furnace. Gas, oil, and electric furnaces are the most commonly used for heat treating metals.临界点或临界温度是指钢的物理性能发生某些变化的温度。这些临界点极

8、为重要因为要使钢很好地硬化就必须把钢加热到上临界温度以上。我们知道某一钢种的临界点后就能较容易得控制炉温。煤气炉、油炉和电炉是金属热处理最普遍采用的炉子。Annealing is the uniform heating of a metal above usual hardening temperatures, followed by very slow cooling. Annealing may be carried out either to soften a piece that is too hard to machine or to remachine a piece that h

9、as already been hardened. Annealing also relieves internal stresses produced by machining. 退火是将钢均匀地加热到通常的淬火温度以上然后极缓慢地冷却。若工件过硬无法机加工或是要重新机加工已经淬硬的零件这时可进行退火以使钢材软化。退火还可消除机加工时产生的内应力。Low carbon steels do not become hard when subjected to such a heat treatment because of the small amount of carbon contained

10、. If it is necessary to obtain a hard surface on a part made of such steel, surface hardening operation must be carried out. One of the methods of surface hardening is cyaniding, which is done by keeping the work in a molten bath of sodium cyanide from 5 to 30 minutes, depending on the size of the w

11、ork and the depth of penetration required. Having been subjected to such a treatment, the work is then quenched in water of oil, and a very hard case 0.01 to 0.015 inch thick is formed. This process is also called case hardening.低碳钢由于含碳量低，因此在经受这种热处理时材质不可能变硬。若欲在低碳钢制成的零件表面获得硬的表面层就须进行表面硬化处理。氰化是一种表面硬化方法

12、。氰化时将工件置入氰化钠的溶池中保温5至30分钟，保温时间取决于工件的尺寸和所需的渗透深度。工件经过这一处理后再将其淬入水或油中于是形成了一层厚度为0.01至0.015的十分硬的表面层。这类工艺过程也称为表面淬火。Nitriding is also one of the case hardening methods. This process consists of keeping the steel in hot ammonia gas for some hours. Nitrogen, formed in this condition from ammonia, penetrates into the surface of the metal , thus forming a very hard case.渗氮也是一种表面硬化法。它是将钢在热的氨气中放置数小时。在这一条件下由氨气形成的氮渗入到金属的表面从而性形成了极硬的表面层。Another method of case hardening is carburization. The work is placed into a metal box containing carburizing materials （that is , materials with high carbon content）; the box