机械英语-机械本PPT整理
延参法师语录-优美语句
Rake angle. It is the angle between the
face of the tool called the
rake face and the
normal to the machining direction. Higher the rake
angle, better is the cutting and less are the
cutting forces, increasing
the rake angle
reduces the metal backup available at the tool
rake
face.
•
前角：它是被称为前倾面的刀具面与垂直机加
工方向的夹角。前角越大，则切削越
好且切削力越小，增加前角可以减少刀具前倾面上产生的金属阻塞。
This reduces the strength of the tool tip as
well as the heat
dissipation through the tool.
Thus, there is a maximum limit to the
rake
angle and this is generally of the order of 15°for
high speed steel
tools cutting mild steel. It
is possible to have rake angles at zero or
negative.
•
但这会和减少通过刀具散发的热量一样减少刀尖
强度。因此前角有一最大限制，用
高速钢刀具切削低碳钢通常为15°。前角取零度或负值也是可能的。
The understanding of heat treatment is
embraced by the broader
study of
metallurgy[məˈtælədʒi].Metallurgy is the physics,
chemistry,
and engineering related to metals
from ore extraction to the final
product.
•
对热处理的理解包含于对冶金学较广泛的研究。冶金学是物理学、化学和涉及金属
从矿石提炼到最后产物
的工程学。
Heat treatment is the operation
of heating and cooling a metal in its
solid
state to change its physical properties
[p'rɒpətɪz]. According to
the procedure
[prəˈsi:dʒə(r)] used, steel can be hardened to
resist
cutting action and abrasion, or it can
be softened ['sɒfənd] to permit
machining.
•
热处理是将金属在固态加热和冷却以改变其物理性能的操作。按所采用的步骤，
钢
可以通过硬化来抵抗切削和磨损，也可以通过软化来允许机加工。
With the
proper heat treatment internal stresses may be
removed,
grain size reduced, toughness
increased, or a hard surface produced
on a
ductile *ˈdʌktaɪl] interior [ɪnˈtɪəriə(r)]. The
analysis of the steel
must be known because
small percentages of certain elements,
notably
carbon, greatly affect the physical properties.
• 使用合适的热处理可以去除内应力、细化晶粒、增加韧性或在柔软材料上覆盖坚硬
的表面。
因为某些元素(尤其是碳)的微小百分比极大地影响物理性能，所以必须知道
对钢的分析。
Alloy steel owe their properties to the
presence of one or more
elements other than
carbon, namely nickel, chromium, manganese,
molybdenum, tungsten, silicon, vanadium, and
copper. Because of
their improved physical
properties they are used commercially in
many
ways not possible with carbon steels.
• 合金钢的性质
取决于其所含有的除碳以外的一种或多种元素，如镍、铬、锰、钼、
钨、硅、钒和铜。由于合金钢改善的
物理性能，它们被大量使用在许多碳钢不适用
的地方。
The following discussion applies
principally to the heat treatment
ofordinary
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.
•
下列讨论主要针对被称为普通碳钢的工业
用钢而言。热处理时冷却速率是控制要素，
从高于临界温度快速冷却导致坚硬的组织结构，而缓慢冷却则
产生相反效果。
If we focus only on the materials
normally known as steels, a
simplified diagram
is often used. Those portions of the iron-carbon
diagram near the delta region and those above
2% carbon content
are of little importance to
the engineer and are deleted. A simplified
diagram, such as the one in Fig.2.1, focuses
on the eutectoid region
and is quite useful in
understanding the properties and processing of
steel.
• 如果只把注意力集中于一般所说的钢上，经常要用到简化铁碳状态图。铁碳
状态图
中靠近三角区和含碳量高于2%的那些部分对工程师而言不重要，因此将它们删除。
如图
2.1所示的简化铁碳状态图将焦点集中在共析区，这对理解钢的性能和处理是
十分有用的。
The key transition
described in this diagram is the decomposition of
single-phaseaustenite(γ) to the two-phase
ferrite plus carbide
structure as temperature
drops. Control of this reaction, which
arises
due to the drastically different carbon solubility
of austenite
and ferrite, enables a wide range
of properties to be achieved
through heat
treatment.
• 在此图中描述的关键转变是单相奥氏体(γ) 随着温度下降分解成两相铁
素体加渗碳
体组织结构。控制这一由于奥氏体和铁素体的碳溶解性完全不同而产生的反应，使
得
通过热处理能获得很大范围的特性。
Sand casting is used
to make large parts (typically iron, but also
bronze, brass, aluminum). Molten metal is
poured into a mold cavity
formed out of sand
(natural or synthetic).
•
砂型铸造用于制造大型
零件(具有代表性是铁，除此之外还有青铜、黄铜和铝)。将熔
化的金属倒入由型砂(天然的或人造的)
做成铸模腔。
The processes of sand casting are
discussed in this section, including
patterns,
sprues and runners, design considerations, and
casting
allowance
•
本节讨论砂型铸造工艺，包括型模、浇注口、浇道、设计考虑因素及铸造余量。
The
cavity in the sand is formed by using a pattern
(an approximate
duplicate of the real part),
which are typically made out of wood,
sometimes metal. The cavity is contained in an
aggregate housed in a
box called the flask.
•
砂型里的型腔是采用型模(真实零件的近似复制品)构成的，型模一般为木制，
有时也
用金属制造。型腔整个包含在一个被放入称为砂箱的箱子里的组合体内。
Core is a sand shape inserted into
the mold to produce the internal
features of
the part such as holes or internal passages. Cores
are
placed in the cavity to form holes of the
desired shapes. Core print is
the region added
to the pattern, core, or mold that is used to
locate
and support the core within the mold.
• 砂芯是插入铸模的砂型，用于生成诸如孔或内通道之类的内部特征。砂芯安放在型
腔里形成
所需形状的孔洞。砂芯座是加在型模、砂芯或铸模上的特定区域，用来在
铸模内部定位和支撑砂芯。
A riser is an extra void created in the
mold to contain excessive
molten material. The
purpose of this is to feed the molten metal to
the mold cavity as the molten metal solidifies
and shrinks, and
thereby prevents voids in the
main casting.
•
冒口是在铸模内部增加的额外空间，用于容纳
过多的熔化金属。其目的是当熔化金
属凝固和收缩时往型腔里补充熔化金属，从而防止在主铸件中产生孔
隙。
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.
•
锻造是一种重要的热成型工艺。它能用于生产各种形状和尺寸组件、从很小到重量
数吨的零件。
Forging is the process by which metal is
heated and is shaped by
plastic deformation by
suitably applying compressive y
the
compressive force is in the form of hammer blows
using a power
hammer or a press, as shown in
Fig.4.1.
• 在锻造过程中先将金属加热，然后施加合适的压力使其塑性变
形。通常压力都是以
由如图4.1所示的动力锤或压力机提供的锤击形式出现。
Hand forging tools comprise variously
shaped hammers. The base on
which the work is
supported during forging is the anvil.
•
手工锻造工具包括各种不同形状的锤子。在锻造中用于支撑工件的基础是铁砧。
Excessively [ek'sesɪvlɪ] high injection speed can
cause high surface
orientation
[,ɔːrɪən'teɪʃ(ə)] and increase susceptibility
[sə,septɪ'bɪlɪtɪ]
to stress cracking.
•
过高的注塑速度会引起较高的表面方向性及增加应力破裂的敏感性。
For
example, moldings that are to be electroplated
[ɪ'lektrə(ʊ)pleɪtid],
and will be subject to
acid ['æsɪd] solutions during plating, must be
made using very slow injection speeds to
minimize *ˈmɪnɪˌmaɪz]
surface orientation.
•
例如，要电镀的注塑件在电镀时会经受酸溶液，必须采用很低的注塑速度制造以
使
表面方向性最小化。
On the other hand, the
transverse motion component [kəm'pəʊnənt]
of
the melt front in most moldings can cause
transverse subsurface
orientation superimposed
*'sjuːpəɪm'pəʊzd] on the primary
orientation,
giving a desirable [dɪ'zaɪərəb(ə)l] biaxial
[baɪ'æksɪəl]
orientation effect.
•
另一方面，大多数注塑件的融化前部
横向运动部分能导致在主要方向性上有层理的
表面下横向方向性，产生需要的双轴方向性效应。
Orientation can be seriously
increased by obstructions [əb'strʌkʃ(ə)ns]
to
flow during filling ['fɪlɪŋ+ of the cavity. Flow
around an obstruction
causes a decrease in
melt front speed and leads to high local viscosity
[vɪ'skɒsɪtɪ] and reduced relaxation. This is
also likely to occur near the
end of the
filling phase [feɪz] if gating is inadequate
[ɪn'ædɪkwət].
• 在填充模腔时流动受到阻碍会极大地增加方向性。围绕障碍物流动使
融化前部的速
度下降并产生较高的局部粘性而减少松弛作用。如果闸道不适当，这也很可能发生
在接近填充结束阶段。