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 时间:2011-11-29 18:49:06 贡献者:愉悦人生1100

导读:•Types of Materials 材料的类型such as aluminum or magnesium have low densities, and are used in applications that require other metallic properties but also require low weight.special properties: some ceramics are magnetic materials; some are

机械工程英语第二版叶邦彦_汉语翻译(机械工业出版社)--全本书翻译
机械工程英语第二版叶邦彦_汉语翻译(机械工业出版社)--全本书翻译

•Types of Materials 材料的类型

such as aluminum or magnesium have low densities, and are used in applications that require other metallic properties but also require low weight.

special properties: some ceramics are magnetic materials; some are piezoelectric materials; and a few special ceramics are superconductors at very low temperatures. Ceramics and glasses have one major drawback: they are brittle.

复合材料有两种:纤维加强型复合材料和微粒加强型复合材料。

properties at higher molecular weights.

The following discussion applies principally to the heat treatment of ordinary commercial steels known as plain carbon steels. With this process the rate of cooling is the controlling factor, rapid cooling from above the critical range results in hard structure, whereas very slow cooling produces the opposite effect.

remaining austenite to pearlite. The resulting structure is a mixture of primary or pro-eutectoid ferrite (ferrite that formed above the eutectoid reaction) and regions of pearlite.

workpiece to be hardened to depths) of the steel and does not affect the hardness except in unhardened or partially hardened steels.

temperature causes coalescence of the carbides with continued decrease in hardness.

steel is heated slowly to a temperature just below the critical range and held there for a prolonged period of time, this structure will be obtained.

Cyaniding

effectively resists corrosive action of water, saltwater spray, alkalies, crude oil, and natural gas.

parting line. The cope is then assembled to the drag, and the sand is poured on the cope half, covering the pattern, core and the gating system.

物来使其较快冷却。

The mold is made by making a pattern using wax or some other material that can be melted away. This wax pattern is dipped in refractory slurry, which coats the wax pattern and forms a skin. This is dried and the process of dipping in the slurry and drying is repeated until a robust thickness is achieved.

受离心力作用熔化金属被抛向型模的内壁,在那里冷却后固化。

这种铸件通常为外径处晶粒非常细小的细晶粒铸件,能耐大气腐蚀,典型的情况是管子。

内径处则有较多的杂质和内含物,但可用机加工去除。

Forging is an important hot-forming process. It is used in producing components of all shapes and sizes, from quite small items to large units weighing several tons.

making it uniform; so for heavy forgings, such as marine propeller shafts, an immensely powerful hydraulic press squeezes the metal with a force sometimes as great as 10,000 tonnes.

压模锻/精密锻:压模锻和精密锻是雏形模锻的进一步改进。

完成的零件与模膛更相似。

stress-risers in the forgings, as well as make the dies weak in service.

with adequate strength for handling during sintering, but do not produce very high strength sintered parts.

单一元素金属,或极小颗粒的预先合金粉末与润滑剂(一般是锂硬脂酸盐,重量百分比0.75%)混合,然后在金属模具中施加压力[比如600MPa (87,000lb/in.2)]挤压。

根据不同材料的化学成分,烧结的环境包括真空状态也各不相同。

例如精确的环境控制可使铁/碳材料生成特殊碳化物和机械性能。

minimal machining is required but when all things are considered this route is often very cost-effective.

•Physical properties can be controlled

如果考虑到新近的改进(例如反作用注塑成型)和采用塑料替代金属的高增长率,注塑成型在世界范围的工业重要性很可能将继续增加。

In 1956, Ankerwerk Nuremberg commercialized the modern reciprocating screw injection molding machine for thermoplastics. Today, over 50 machine manufacturers are listed in Modern Plastics Encyclopedia, offering machines to the U.S. market ranging from 2 to 6,000 tons clamping capacity.

softened by heat and of hardening on cooling, even after repeated cycling.

The latter also has an effect on processing since the life of the mold cavity is typically reduced from about 1,000,000 parts for plain resin parts to about 300,000 for glass-filled parts.

•较快注塑(到点):在填料过程中冷却较少,因此初始固化层较薄,由于剪应变稀少而粘性较低;能较好地流到角落;结晶度较小;所有这些促成表面下的方向性也较低。

主要效果是闸道将较快固化。

这样使得方向性停止产生而松弛作用开始增加。

3. 零件几乎不需要修整:例如,飞边可以最小化并且模具能被设计成自动将浇道和闸道从零件本身分离。

related operations.

parent metal.

surface and the rest passing off on the back side of the chip, Fig.7.3c.

工件材料的缺陷而产生的作用力波动。

这个要求对如铣削之类的间断切削更有用。

(1)切削工艺参数、速度、进给和切削深度

业的能量输入。

strap clamps and the like, whereas smaller workpieces are usually held by magnetic chucks.

V工件=V调节轮×cosα

磨粒越细,磨削表面越光滑。

所以,粗粒砂轮用于粗加工,而细粒砂轮则用于最后精加工。

 
 

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