金属的热处理外文翻译

金属的热处理外文翻译

外文资料翻译

Heat Treatment of Metal

The generally accepted definition for heat treating metals and metal alloys is “heating and cooling a solid metal or alloy in a way so as to obtain specific conditions and I or properties.”Heating for the sole purpose of hot working(as in forging operations) is excludedfrom this definition．Likewise，the types of heat treatment that are sometimes used for productssuch as glass or plastics are also excluded from coverage by this definition．Transformation Curves.

The basis for heat treatment is the

time-temperature-transformation curves or TTT curveswhere，in a single diagram all the three parameters are plotted．Because of the shape of thecurves，they are also sometimes called C-curves or S-curves．

Material forming processes

In this section，a short description of the process examples will begiven. But assembly andjoining processes are not described here.

Forging

Forging can be characterized as: mass conserving, solid state of work material (metal), andmechanical primary basic process-plastic deformation. A wide variety of forging processes areused, and Fig.9.1(a) shows the most common of these: drop forging. The metal is heated to asuitable working temperature and placed in the lower die cavity. The upper die is then lowered sothat the metal is forced to fill the cavity.

[1]Excess material is squeezed out between the die facesat

the periphery as flash, which is removed in a later trimming process. When the term forging isused, it usually means hot forging. Cold forging has several specialized names. The material lossin forging processes is usually quite small.

Normally, forged components require some subsequent machining, since the tolerances andsurfaces obtainable are not usually satisfactory for a finished product. Forging machines includedrop hammers and forging presses with mechanical or hydraulic drives. These machines involvesimple translatory motions.

金属的热处理

普遍认同对金属及合金热处理的定义是，以一定的方式加热或冷却固态金属或合金，以达到一定的条件和/或获得某些性能。以热加工(如锻造)为目的的加热，不在此定义之列。同样地，有时用于生产诸如玻璃或塑料制品的热处理也不属于该定义的范畴。

相变曲线热处理的基础分别是时间—温度相变曲线，即TTT曲线，3 个参数都绘制在一个图中。根据曲线的形状特点，分别称为C 曲线或S 曲线。

为了绘制TTT 曲线，将特定的钢置于给定温度下，以预先确定的时间间隔检查其结构，记录发生相变的量。我们知道共析钢(C80)在平衡条件下，在723℃以上时全为奥氏体，而低于此温度，则为珠光体。为了形成珠光体，碳原子将产生扩散形成渗碳体。扩散是一种渐进过程，需要足够的时间完成奥氏体向珠光体的转变。对于不同的样品，可以记录下在任一温度时产生相变的量。然后把这些点绘制在一条以时间和温度为坐标轴的曲线上。通过这些点就可以得到共析钢的相变曲线。左边的曲线表示任一给定温度下奥氏体

材料成型工艺方法

锻造：锻造是对固态金属材料进行初步机械加工，是产生塑性成形的质量守恒的一种基本工艺方法。锻造有很多类型，最普通的锻造为金属加热到适合加工的温度，并放进下型腔里。上型腔与下型腔合

拢，迫使金属充满型腔。多余的材料被从型腔接缝处挤出，并将被后续的清理型腔接缝工艺清除。当提到锻造术语时，通常意味热锻。冷锻有几种专门的名称。锻造工艺中损失的材料通常相当少。通常，由于公差和表面粗糙度通常不能满足最终产品的需要，因此对锻造的零件要进行一些后续加工。锻造机械包

括落锤和机械或水力驱动的锻压。这些机械包括简单的平移运动。

滚轧：滚轧是对固态金属材料进行初步机械加工，使其产生塑性变形的质量守恒的一种工艺方法。滚轧广泛应用在板材、薄板和结构桁条等制造中。图9.1(b)显示了板材或薄板的滚轧。铸造生产出的铁锭加热后，经过几个阶段厚度上变薄。由于工件的宽度保持不变，工件的长度将随着厚度的变薄而变长。在热轧阶段之后，最终阶段是进行冷却，以提高表面质量、公差，并提高强度。滚轧工艺中，根据需要，轧辊的外形被设计生产成期望的几何形状。

粉末挤压：粉末挤压是对粒状材料进行机械加工，使其产生塑性变形的质量守恒的一种工艺方法。在这里仅提到了金属粉末挤压，但通常成型砂、陶瓷材料的挤压等也属于此加工工艺。金属粉末挤压时，型腔充满标称体积粉末，见图9.1(c)施加大约500 N/mm2 的压力压紧粉末。在挤压过程中，粉末颗粒充满型腔并发生塑性变形。挤压后的典型密度是固态材