related to its melting point, operations such as annealing退火 and heat treating and hot working热加工 require a knowledge of the melting points of the materials involved.
金属的熔点对于生产过程有许多的间接效应。这是因为再结晶温度与金属的熔点有关，退火加工和热处理还有热加工时都需要金属的熔点信息。
3.Specific Heat比热 A material’s specific heat is the energy required to raise the temperature of a unit mass by one degree. Alloying element have a relatively minor effect on the specific heat of metals. The temperature rise in a workpiece工件 resulting from machining operation制造加工 is a function of the work done and of the specific heat of the workpiece material. Temperature rise升温 in a workpiece, if excessive, can decrease product quality by adversely不利的 affecting its surface roughness表面粗糙度 and dimensional accuracy空间准确性, can cause excessive tool wear工具磨损, and can result in undesirable metallurgical金相 changes in the material.
金属的比热是金属单位质量上升一度需要消耗的能量。合金元素有利于降低材料的比热。制造加工合一使工件的温度升高。如果温度升高过多的话会影响工件表面粗糙度和空间准确性，还能增加工具的磨损并且造成金相的不当改变。从而影响工件的质量。
4. Thermal Conductivity Thermal conductivity indicates the rate at which heat flows within and through a material.
Metals generally have high thermal conductivity, while ceramics and plastics have poor conductivity.
导热系数代表着温度在材料中传导速度的估计值。金属一般都有很好的导热性，而陶瓷和塑料的传导性就很差。
When heat is generated by制作 plastic deformation塑性变形 or due to friction摩擦力, the heat should be conducted引导 away at a rate比率 high enough to prevent防止 a severe剧烈 rise in temperature. The main difficulty experienced in machining titanium钛, for example, is caused by its very low thermal conductivity. Low thermal conductivity can also result in high thermal gradients and, in this way, cause inhomogeneous不同的 deformation变形 of workpieces in metalworking processes金属加工过程.
如果是由于塑性变形或者摩擦产生热量，这样的热量要迅速的被引导走，以免产生剧烈的温度起伏。例如，对于钛来说，最难的是由于它的低导热率。低导热率很容易引起高的热梯度。因此金属加工过程中会产生不均匀的变形。
5.Thermal Expansion热膨胀 The thermal expansion of materials can have several significant effects, particularly the relative expansion相对膨胀 or contraction收缩 of different materials in assemblies装配 such as moving parts in machinery that require certain clearances for proper functioning正常运行.
材料的热膨胀有几个很有意义的影响，特别是装配中的金属相对
膨胀和收缩。
Shrink fits热配合 utilize利用 thermal expansion热膨胀 and contraction收缩. For example, a part, such as a flange, is to be installed安装 over a shaft. It first is heated and then slipped over套上 a shaft which is at room temperature. When allowed to cool, the part shrinks收缩 and the assembly装配 effectively becomes an integral component.
热配合就利用了热膨胀和热收缩。例如，一部分，例如法兰会安装在轴上，首先将它加热，任何套入一个室温的轴上。等到回到室温时，就装配完成了。
6. Corrosion Resistance抗腐蚀性 Metals, ceramics, and plastics all are subject to服从 forms of corrosion. The word corrosion itself usually refers to the deterioration of metals and ceramics, while similar phenomena现象 in plastics generally are called degradation退化. Corrosion leads not only to surface deterioration恶化 of components and structures but also reduces their strength and structural integrity结构完整性.
金属，陶瓷，和塑料都有抗腐蚀性。腐蚀这个词表示了金属和陶瓷变质现象。在塑料中我们常常叫做退化。腐蚀不仅仅会使表面质量变差，还能降低材料的强度和结构完整性。
Corrosion resistance腐蚀抗性 is an important aspect方面 of material重要 selection选择 for applications应用 in the
chemical, food, and petroleum industries石油工业, as well as in manufacturing operations制作过程. In addition to除之外 various possible chemical reactions化学反应 from the elements and compounds present现在, environmental corrosion of components and structures is a major concern, particularly at elevated temperatures升温 and other transportation vehicles运输车辆.
在化学，食品，制造过程和石油工业里，抗腐蚀性是材料选择时要着重考虑的一方面。
Resistance to corrosion depends on the composition of the material and on the particular environment. Corrosive media may be chemicals (acid, alkalis, and salts), the environment (oxygen, moisture, pollution, and acid rain), and water (fresh or salt water). Nonferrous metals, stainless steels, and nonmetallic materials generally have high corrosion resistance, Steels and cast irons usually have poor resistance and must be protected by various coatings and surface treatments.
The usefulness有效性 of some level of oxidation氧化 is exhibited展出 in the corrosion resistance抗腐蚀性 of aluminum铝, titanium, and stainless steel不锈钢. Aluminum develops a thin (a few atomic layers), strong, and adherent hard-oxide film (Al2O3) that better protects the surface from further environmental corrosion. Titanium develops a film of titanium oxide (TiO2). A similar phenomenon occurs in stainless steels, which (because of the chromium present in the alloy)
develop a protective film on their surfaces. When the protective film is scratched and exposes the metal underneath, a new oxide film begins to form.
Drilling钻孔 involves producing through or blind holes in a workpiece by forcing a tool, which rotates around its axis, against the workpiece. Consequently, the range of cutting from that axis of rotation is equal to the radius of the required hole.
钻孔指在工件表面利用工具的对表面的旋转来钻通孔和盲孔。因此，所得的孔的半径的大小是由刀具的半径决定的。
Cutting Tools for Drilling Operations
In drilling operations, a cylindrical cutting tool, called a drill, is employed. The drill can have either one or more cutting edges and corresponding flutes, which can be straight or helical. The function of the flutes is to provide outlet出口 passages for the chips generated生产 during the drilling operation and also to allow lubricants润滑油 and coolants冷却剂 to reach the cutting edges and the surface being machined. Following is a survey of the commonly used drills
在钻孔操作中，一种圆柱形的叫钻的工具不断的运行。钻可以有一个或多个刃口，既可以是直的，也可以是螺旋的。平面刀具的功能是切除材料，生成碎屑，螺旋面的功能是让切下来的碎屑可以流到外界，同时让润滑油和冷却剂可以流进去到工件的加工平面。下面是一