-
Ceramics and
Glasses
陶瓷和玻璃
A
ceramic
is
often
broadly
defined
as
any
inorganic
nonmetallic
material
．
By
this
definition,
ceramic
materials
would
also
include
glasses;
however,
many
materials
scientists
add
the
stipulation
that
“
ceramic
”
must
also
be
crystalline.
< br>陶瓷通常被概括地定义为无机的非金属材料。照此定义，陶瓷材料也应包括玻璃；
然而许多材料科学家添加了“陶瓷”必须同时是晶体物组成的约定。
A
glass
is
an
inorganic
nonmetallic
material
that
does
not
have
a
crystalline
structure. Such
materials are said to be amorphous.
玻璃是没有晶体状结构的无机非金属材料。这种材料被称为非结晶质材料。
Properties of Ceramics and
Glasses
Some
of
the
useful
properties
of
ceramics
and
glasses
include
high
melting
temperature,
low
density,
high
strength,
stiffness,
hardness,
wear
resistance,
and
corrosion resistance.
陶瓷和玻璃的特性
<
/p>
高熔点、低密度、高强度、高刚度、高硬度、高耐磨性和抗腐蚀性是陶瓷和玻璃的
一些有用特性。
Many
ceramics
are
good
electrical
and
thermal
insulators.
Some
ceramics
have
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.
许多陶瓷都是电和热的良绝缘体。
某些陶瓷还具有一些特殊性能
：
有些是磁性材料，
有些是
压电材料，
还有些特殊陶瓷在极低温度下是超导体。
陶瓷和玻璃都有一个主
要的缺点：
它们
容易破碎。
Ceramics are not typically
formed from the melt. This is because most
ceramics will crack extensively (i.e.
form a powder) upon cooling from the liquid
state.
陶瓷
一般不是由熔化形成的。
因为大多数陶瓷在从液态冷却时将会完全破碎
< br>(
即形成
粉末
)
。
Hence,
all
the
simple
and
efficient
manufacturing
techniques
used
for
glass
production such as casting and blowing,
which involve the molten state, cannot be
used
for
the
production
of
crystalline
ceramics.
Instead,
“sintering”
or
“firing” is the process
typically used.
因此，
< br>所有用于玻璃生产的简单有效的—诸如浇铸和吹制这些涉及熔化的技术都不能用于由
晶体物组成的陶瓷的生产。作为替代，一般采用“烧结”或“焙烧”工艺。
In sintering, ceramic powders are
processed into compacted shapes and then heated
to
temperatures
just
below
the
melting
point.
At
such
temperatures,
the
powders
react
internally to remove porosity and fully
dense articles can be obtained.
在烧结过程中，
陶瓷粉末先挤压成型然后加热到略低于熔点温度。
在这样的温度
下，
粉末内
部起反应去除孔隙并得到十分致密的物品。
An
optical
fiber
contains
three
layers:
a
core
made
of
highly
pure
glass
with
a
high
refractive
index
for
the
light
to
travel,
a
middle
layer
of
glass
with
a
lower
refractive
index
known
as
the
cladding
which
protects
the
core
glass
from
scratches
and
other
surface
imperfections,
and
an
out
polymer
jacket
to
protect
the
fiber
from
damage.
光导纤维有三层：核心由高折射指数高纯光传输
玻璃制成，中间层为低折射指数玻
璃，
是保护核心玻璃表面不被
擦伤和完整性不被破坏的所谓覆层，
外层是聚合物护套，
用于<
/p>
保护光导纤维不受损。
In
order for the core glass to have a higher
refractive index than the cladding,
the
core glass is doped with a small, controlled
amount of an impurity, or dopant,
which
causes light to travel slower, but does not absorb
the light.
为了使核心玻璃有比覆层大的折射指数，
在其中掺入微小的、
可控数量的能减缓光速而不会
吸收光线
的杂质或搀杂剂。
Because
the
refractive
index
of
the
core
glass
is
greater
than
that
of
the
cladding,
light
traveling
in
the
core
glass
will
remain
in
the
core
glass
due
to
total
internal
reflection as long as the light strikes
the core/cladding interface at an angle
greater than the critical angle.
由于核心玻璃的折射指数比覆层大，只要在全内反射过程中光线照射核心
/
覆层分界面的角
度比临界角大，在核心玻璃中传送的光线将仍保
留在核心玻璃中。
The
total
internal
reflection
phenomenon,
as
well
as the
high purity
of
the
core
glass,
enables light to travel long distances with
little loss of intensity.
全内反射现象与核心玻璃的高
纯度一样，使光线几乎无强度损耗传递长距离成为可能。
?
Composites
复合材料
Composites
are
formed
from
two
or
more
types
of
materials.
Examples
include
polymer/ceramic
and metal/ceramic composites.
Composites are
used because
overall
properties
of
the
composites
are
superior
to
those
of
the individual
components.
复合材料由两种或更多材料构成。例子有聚合物
/
陶瓷和金
属
/
陶瓷复合材料。之所
以使用复合材
料是因为其全面性能优于组成部分单独的性能。
For
example: polymer/ceramic composites have a greater
modulus than the polymer
component, but
aren’t as brittle as ceramics.
Two
types
of
composites
are:
fiber-reinforced
composites
and
particle-reinforced composites.
例如：聚合物
/
陶瓷复合材料具有比聚合物成分更大的
模量，但又不像陶瓷那样易碎。
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。
Fiber-reinforced Composites
Reinforcing fibers can be made of metals,
ceramics, glasses, or polymers
that
have been turned into graphite and known as
carbon fibers. Fibers increase
the
modulus of the matrix material.
纤维加强型复合材料
加强纤维可以是金属、陶瓷、玻璃或是已变成石墨的被称为碳纤维的聚合物。纤维
能加强基材的模量。
The strong
covalent bonds along the fiber’s length give them
a ve
ry high modulus
in
this
direction
because
to
break
or
extend
the
fiber
the
bonds
must
also
be
broken
or moved.
沿着纤维长度有很强结合力的共价结合在这个方向上给予复合材料很高的模量，
因为要损
坏
或拉伸纤维就必须破坏或移除这种结合。
Fibers
are
difficult
to
process
into
composites, making
fiber-
reinforced
composites relatively
expensive.
把纤维放入复合材料较困难，这使得制造纤维加强型复合材料相对昂贵。
Fiber-reinforced composites are
used in some of the most advanced, and therefore
most expensive sports equipment, such
as a time-trial racing bicycle frame which
consists of carbon fibers in a
thermoset polymer matrix.
纤维加强型复合材料用于某
些最先进也是最昂贵的运动设备，
例如计时赛竞赛用自行车骨架
就是用含碳纤维的热固塑料基材制成的。
Body
parts of race cars and some automobiles are
composites made of glass fibers
(or
fiberglass) in a thermoset matrix.
竞赛用
汽车和某些机动车的车体部件是由含玻璃纤维
(
或玻璃丝
)
的热固塑料基材制成的。
Fibers have a very high modulus
along their axis, but have a low modulus
perpendicular to their axis. Fiber
composite manufacturers often rotate layers of
fibers to avoid directional variations
in the modulus.
纤维在沿着
其轴向有很高的模量，但垂直于其轴向的模量却较低。纤维复合材料的
制造者往往旋转纤
维层以防模量产生方向变化。
Particle-
reinforced composites
Particles
used
for
reinforcing
include
ceramics
and
glasses
such
as
small
mineral particles, metal particles such
as aluminum, and amorphous materials,
including polymers and carbon black.
微粒加强型复合材料
用于加强的微粒包含了陶瓷和玻璃之类的矿物微粒，铝之类的金属微粒以及包括聚
合物和碳黑的非结晶质微粒。
Particles are used to increase the modulus of the
matrix, to decrease the
permeability of
the matrix, to decrease the ductility of the
matrix. An example
of particle-
reinforced composites is an automobile tire which
has carbon black
particles in a matrix
of polyisobutylene elastomeric polymer.
微粒用于增加基材的模量、减少基材的渗透性和
延展性。微粒加强型复合材料的一
个例子是机动车胎，它就是在聚异丁烯人造橡胶聚合物
基材中加入了碳黑微粒。
?
Polymers
聚合材料
A polymer has a repeating
structure, usually based on a carbon backbone.
The repeating structure results in
large chainlike molecules. Polymers are useful
because
they
are
lightweight,
corrosion
resistant,
easy
to
process
at
low
temperatures and
generally inexpensive.
< br>聚合物具有一般是基于碳链的重复结构。这种重复结构产生链状大分子。由于重量
轻、耐腐蚀、容易在较低温度下加工并且通常较便宜，聚合物是很有用的。
Some
important
characteristics
of
polymers
include
their
size
(or
molecular
weight),
softening
and
melting
points,
crystallinity,
and
structure.
The
mechanical
properties
of
polymers
generally
include
low
strength
and
high
toughness.
Their
strength
is
often
improved
using
reinforced
composite
structures.
聚合材料具有一些重要特性，
包括尺寸
(
< br>或分子量
)
、
软化及熔化点、<
/p>
结晶度和结构。
聚合材料的机械性能一般表现为低强度和高韧性。
它们的强度通常可采用加强复合结构来改
善。
< br>
Important Characteristics of
Polymers
Size. Single polymer
molecules typically have molecular weights between
10,000 and
1,000,000g/mol
—
that can be
more than 2,000 repeating units depending
on the polymer
structure!
聚合材料的重要特性
尺寸：
单个聚合物分
子一般分子量为
10,000
到
1,0
00,000g/mol
之间，
具体取决于
聚合物的结构—这可以比
2,000
个重复单元还多。
The
mechanical
properties
of
a
polymer
are
significantly
affected
by
the
molecular
weight, with better engineering properties at
higher molecular weights.
聚合物的分子量极大地影响其
机械性能，分子量越大，工程性能也越好。
Thermal transitions.
The
softening point
(glass
transition
temperature)
and the melting point of a polymer
will determine which it will be suitable for
applications. These temperatures
usually determine the upper limit for which a
polymer can be used.
热转换性：聚合物的软化点
(
玻璃状转
化温度
)
和熔化点决定了它是否适合应用。这
< br>些温度通常决定聚合物能否使用的上限。
For
example,
many
industrially
important
polymers
have
glass
transition
temperatures
near
the
boiling
point
of
water
(100
℃
,
212
℉
),
and
they
are
most
useful
for
room
temperature
applications.
Some
specially
engineered
polymers
can
withstand
temperatures as
high as 300
℃
(572
℉
).
例如，许多工业上的重要聚合物其玻璃状转化温度接近水
的沸点
(100
℃
,
212
℉
)
，它们被广
泛用于室温下。而某些特别制造的聚合物能经受住高达
300
℃
(572
℉
)
的温度。
Crystallinity.
Polymers
can
be crystalline
or
amorphous,
but
they
usually
have a combination of crystalline and
amorphous structures (semi-crystalline).
结晶度：聚合物可以是晶体状的或非结晶质的，
但它们通常是晶体状和非结晶质结
构的结合物
(
半晶体
)
。
Interchain interactions. The
polymer chains can be free to slide past one
another (thermo-plastic) or they can be
connected to each other with crosslinks
(thermoset or elastomer). Thermo-
plastics can be reformed and recycled, while
thermosets and elastomers are not
reworkable.
原子链间的相互作用
：聚合物的原子链可以自由地彼此滑动
(
热可塑性
)
或通过交键
互相连接
(<
/p>
热固性或弹性
)
。
热可塑性材料可以重新形成和循环使用，
而热固性与弹性材料则
是不能再使用的。
Intrachain
structure. The chemical structure of the chains
also has a
tremendous
effect
on
the
properties.
Depending
on
the
structure
the
polymer
may
be
hydrophilic
or
hydrophobic
(likes or
hates
water),
stiff
or
flexible,
crystalline
or amorphous, reactive or unreactive.
链内结构：原子链的化学结构对性能也有很大影
响。根据各自的结构不同，聚合物
可以是亲水的或憎水的
(
喜欢或讨厌水
)
、
硬的或软的、
晶体状的或非结晶质的、
易起反应的
或不易起反应的。
第二单元
The understanding
of heat treatment is embraced by the broader study
of
metallurgy.
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. According to the
procedure used, steel can be
hardened
to resist cutting action and abrasion, or it can
be softened 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
interior.
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
(
< br>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
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.
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。
?
A Simplified Iron-carbon Diagram
简化铁碳状态图
If
we focus only on the materials normally known as
steels, a simplified
diagram is often
used.
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。
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.
铁碳状态图中靠近三角区和含碳量高于
2%<
/p>
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。
< br>
The
key
transition
described
in
this
diagram
is
the
decomposition
of
single-phase
austenite(
γ
) to the two-
phase ferrite plus carbide structure as
temperature
drops.
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。
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.
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。
To
begin
to
understand
these
processes,
consider
a
steel
of
the
eutectoid
composition,
0.77%
carbon,
being
slow
cooled
along
line
x-
x’
in
Fig.2.1.
At
the
upper
temperatures,
only
austenite
is
present,
the
0.77%
carbon
being
dissolved in solid
solution with the iron. When the steel cools to 72
7
℃
(1341
℉
),
several changes occur
simultaneously.
为了理解这
些过程，
考虑含碳量为
0.77%
的共
析钢，
沿着图
2.1
的
x-x
’
线慢慢冷却。
在较高
温度时，
只存在奥氏体，
0.77%
的
碳溶解在铁里形成固溶体。
当钢冷却到
727
< br>℃
(1341
℉
)
时，将同时发生若干变化。
The
iron wants
to
change
from
the FCC austenite
structure
to the BCC ferrite
structure, but the ferrite can only
contain 0.02% carbon in solid solution.
铁需要从面心立方体奥氏体结构转变为体心立方
体铁素体结构，但是铁素体只能容
纳固溶体状态的
0.02%<
/p>
的碳。
The
rejected
carbon
forms
the
carbon-
rich
cementite
intermetallic
with
composition
Fe3C. In essence, the net reaction at
the eutectoid is austenite
0.77%C
→
ferrite
0.02%C+cementite 6.67%C.
被析出
的碳与金属化合物
Fe3C
形成富碳的渗碳体。本质上，共析体
的基本反应是奥氏体
0.77%
的碳→铁素体
< br>0.02%
的碳
+
渗碳体
6.67%
的碳。
Since this chemical separation of the carbon
component occurs entirely in
the solid
state, the resulting structure is a fine
mechanical mixture of ferrite
and
cementite. Specimens prepared by polishing and
etching in a weak solution of
nitric
acid and alcohol reveal the lamellar structure of
alternating plates that
forms on slow
cooling.
由于这种碳成分的化学分离
完全发生在固态中，产生的组织结构是一种细致的铁素
体与渗碳体的机械混合物。
通过打磨并在弱硝酸酒精溶液中蚀刻制备的样本显示出由缓慢冷
却形成
的交互层状的薄片结构。
This
structure
is
composed
of
two
distinct
phases,
but
has
its
own
set
of
characteristic
properties
and
goes
by
the
name
pearlite,
because
of
its
resemblance
to mother- of-
pearl at low magnification.
这种结构由两种截然不同
的状态组成，
但它本身具有一系列特性，
且因与低倍数放大时的
珠
母层有类同之处而被称为珠光体。
Steels having less than the eutectoid amount of
carbon (less than 0.77%)
are known as
hypo-eutectoid steels. Consider now the
transformation of such a
material
represented by cooling along line y-
y’
in Fig.2.1.
含碳量少于共析体
(
低于
0.
77%)
的钢称为亚共析钢。现在来看这种材料沿着图
2.1<
/p>
中
y-y
’
线冷却的转变情况。
At high
temperatures, the material is entirely austenite,
but upon cooling enters
a
region
where
the
stable
phases
are
ferrite
and
austenite.
Tie-line
and
level-law
calculations
show
that
low-carbon
ferrite
nucleates
and
grows,
leaving
the
remaining
austenite richer
in carbon.
在较高温度时，
这种材料全部是奥氏体
，
但随着冷却就进入到铁素体和奥氏体稳定状态的区
域。由截线
及杠杆定律分析可知，低碳铁素体成核并长大，剩下含碳量高的奥氏体。
At 727
℃
(1341
℉
), the austenite is of eutectoid
composition (0.77% carbon) and
further
cooling transforms the 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.
在
727
℃
(1341
℉
)
时，奥氏体为共析组成
(
含碳量
0.77%)
，
再冷却剩余的奥氏体就转化为珠
光体。
作为结果的组织结构是初
步的共析铁素体
(
在共析反应前的铁素体
)
和部分珠光体的混
合物。
Hypereutectoid steels are
steels that contain greater than the eutectoid
amount of carbon. When such steel
cools, as shown in z-
z’ of Fig.2.1 the
process
is
similar
to
the
hypo-
eutectoid
case,
except
that
the
primary
or
pro-eutectoid
phase
is now cementite
instead of ferrite.
过
共析钢是含碳量大于共析量的钢。当这种钢冷却时，就像图
2.1
的
z-z
’线所示，
除了初步的共析
状态用渗碳体取代铁素体外，其余类似亚共析钢的情况。
As
the
carbon-rich
phase
forms,
the
remaining
austenite
decreases
in
carbon
content,
reaching the eutectoid composition at 7
27
℃
(1341
℉
< br>). As before, any remaining
austenite transforms to pearlite upon
slow cooling through this temperature.
随着富碳部分的形成，剩余奥氏体含碳量减少，在
727
℃
(1341
℉
)
时
达到共析组织。就像以
前说的一样，当缓慢冷却到这温度时所有剩余奥氏体转化为珠光体
。
It should be
remembered that the transitions that have been
described by
the phase diagrams are for
equilibrium conditions, which can be approximated
by
slow cooling. With slow heating,
these transitions occur in the reverse manner.
应该记住由状态图描述的这种转化只适合于通过
缓慢冷却的近似平衡条件。如果缓
慢加热，则以相反的方式发生这种转化。
However,
when
alloys
are
cooled
rapidly,
entirely
different
results
may
be
obtained,
because sufficient
time is not provided for the normal phase
reactions to occur,
in such cases, the
phase diagram is no longer a useful tool for
engineering
analysis.
然而，
当快速冷却合金时，
可能得到完全不同的
结果。
因为没有足够的时间让正常的状态反
应发生，在这种情况
下对工程分析而言状态图不再是有用的工具。
?
Hardening
淬火
Hardening
is
the
process
of
heating
a
piece
of
steel
to
a
temperature
within
or above its critical
range and then cooling it rapidly.
淬火就是把钢件加热到或超过它的临界温度范围，然后使其快速冷却的过程。
If the carbon content of the
steel is known, the proper temperature to which
the
steel should be heated may be
obtained by
reference to the iron-iron
carbide phase
diagram.
However,
if
the
composition
of
the
steel
is
unknown,
a
little
preliminary
experimentation
may be necessary to determine the range.
< br>如果钢的含碳量已知，
钢件合适的加热温度可参考铁碳合金状态图得到。
然而当钢的成分不
知道时，则需做一些预备试验来确定其温度范围。
A
good
procedure
to
follow
is
to
heat-quench
a
number
of
small
specimens
of
the
steel
at various
temperatures and observe the result, either by
hardness testing or by
microscopic
examination. When the correct temperature is
obtained, there will be
a marked change
in hardness and other properties.
要遵循的
合适步骤是将这种钢的一些小试件加热到不同的温度后淬火，
再通过硬度试验或显
微镜检查观测结果。一旦获得正确的温度，硬度和其它性能都将有明显的变化。
In
any
heat-treating
operation
the
rate
of
heating
is
important.
Heat
flows
from
the
exterior
to
the
interior
of
steel
at
a
definite
rate.
If
the
steel
is
heated
too
fast,
the
outside
becomes
hotter
than
the
interior
and
uniform
structure
cannot
be obtained.
在任何热处理作业中，加热的速率都是重要的。
热量以一定的速率从钢的外部传导
到内部。如果钢被加热得太快，其外部比内部热就不能
得到均匀的组织结构。
If
a
piece
is
irregular
in
shape,
a
slow
rate
is
all
the
more
essential
to
eliminate
warping and
cracking. The heavier the section, the
longer must be
the heating time
to achieve uniform results.
如果工件形状不规则，
为了消除翘曲和开裂最根本的是加热速率要缓慢。
截面越厚，
加热的
时间就要越长才能达到均匀的结果
。
Even after the correct
temperature has been reached, the piece should be
held at
that temperature for
a sufficient period of time to permit
its thickest
section to
attain a uniform temperature.
即使加热到正确的温度后，工件也应在此温度下保持足够时间以让其最厚截面达到相同温
度。
The
hardness
obtained
from
a
given
treatment
depends
on
the
quenching
rate,
the carbon content,
and the work size. In alloy steels the kind and
amount of
alloying element influences
only the hardenability (the ability of the
workpiece
to be hardened to depths) of
the steel and does not affect the hardness except
in
unhardened or partially hardened
steels.
通过给定的热处理所得到的硬
度取决于淬火速率、含碳量和工件尺寸。除了非淬硬
钢或部分淬硬钢外，合金钢中合金元
素的种类及含量仅影响钢的淬透性
(
工件被硬化到深层
的能力
)
而不影响硬度。
Steel with low carbon
content will not respond appreciably to hardening
treatment.
As
the
carbon
content
in
steel
increases
up
to
around
0.60%,
the
possible
hardness obtainable
also increases.
含碳量低
的钢对淬火处理没有明显的反应。随着钢的含碳量增加到大约
0.60%
，可
能得到的硬度也增加。
Above
this
point
the
hardness
can
be
increased
only
slightly,
because
steels
above
the
eutectoid point are
made up
entirely
of pearlite and
cementite in
the annealed
state.
Pearlite
responds
best
to
heat-treating
operations;
and
steel
composed
mostly
of pearlite can be transformed into a
hard steel.
高于此点，
由于超过共析点钢完全
由珠光体和退火状态的渗碳体组成，
硬度增加并不多。
珠
光体对热处理作业响应最好；基本由珠光体组成的钢能转化成硬质钢。
As
the
size
of
parts
to
be
hardened
increases,
the
surface
hardness
decreases somewhat even though all
other conditions have remained the same. There
is a limit to
the rate of heat flow through steel.
即使所有其它条件保持不变，随着要淬火的零件尺寸的增加其表面硬度也会有所下
降。热量在钢中的传导速率是有限的。
No
matter how cool the quenching medium may be, if
the heat inside a large piece
cannot
escape
faster
than
a
certain
critical
rate,
there
is
a
definite
limit
to
the
inside hardness.
However, brine or water quenching is capable of
rapidly bringing
the surface of the
quenched part to its own temperature and
maintaining it at or
close to this
temperature.
无论淬火介质怎么冷，
如果在大工
件中的热量不能比特定的临界速率更快散发，
那它内部硬
度就会
受到明确限制。
然而盐水或水淬火能够将被淬零件的表面迅速冷却至本身温度并将其
保持或接近此温度。
Under
these
circumstances
there
would
always
be
some
finite
depth
of
surface
hardening regardless
of size. This is not true in oil quenching, when
the surface
temperature may be high
during the critical stages of quenching.
在这种情况下不管零件尺寸如何，其表面总归有一定深度被硬化。但油淬情况就不是如此，
< br>因为油淬时在淬火临界阶段零件表面的温度可能仍然很高。
?
Tempering
回火
Steel
that
has
been
hardened
by
rapid
quenching
is
brittle
and
not
suitable
for
most
uses.
By
tempering
or
drawing,
the
hardness
and
brittleness
may
be
reduced
to the
desired point for service
conditions
．
快速淬火硬化的钢是硬而易碎的，不适合大多数场合使用。通过回火，硬度和脆性
可以降低到使用条件所需要的程度。
As
these properties are reduced there is also a
decrease in tensile strength and
an
increase
in the ductility and toughness
of
the steel. The
operation
consists of
reheating
quench-hardened
steel
to
some
temperature
below
the
critical
range
followed by any rate
of cooling.
随着这些性能的降低，
拉伸强度也
降低而钢的延展性和韧性则会提高。
回火作业包括将淬硬
钢重新
加热到低于临界范围的某一温度然后以任意速率冷却。
Although
this
process
softens
steel,
it
differs
considerably
from
annealing
in
that
the process lends itself to close
control of the physical properties and in most
cases does not soften the steel to the
extent that annealing would. The final
structure
obtained
from
tempering
a
fully
hardened
steel
is
called
tempered
martensite.
虽然这过程使钢软化，
但它与退火是大不相同的，
因为
回火适合于严格控制物理性能并在大
多数情况下不会把钢软化到退火那种程度。
回火完全淬硬钢得到的最终组织结构被称为回火
马氏体。
Tempering is possible
because of the instability of the martensite, the
principal constituent of hardened
steel. Low-temperature draws, from
300
℉
to
400
℉
(150
℃
~205
℃
), do not cause
much decrease in hardness and are used principally
to relieve internal strains.
由于马氏体这一淬硬钢主要成分的不稳定性，使
得回火成为可能。低温回火，
300
℉到
400
℉
(150
℃
~205
℃
)
，不会引起硬
度下降很多，主要用于减少内部应变。
As
the
tempering
temperatures
are
increased,
the
breakdown
of
the
martensite
takes
place at a faster rate, and at about 60
0
℉
(315
℃
) the change to a structure called
tempered
martensite
is
very
rapid.
The
tempering
operation
may
be
described
as
one
of
precipitation and agglomeration or coalescence of
cementite.
随着回火温度的提高，马氏体以较快的速率分解，并在大约<
/p>
600
℉
(315
℃
)
迅速转变为被称
为回火马氏体的
结构。回火作业可以描述为渗碳体析出和凝聚或聚结的过程。
A substantial precipitation of
cementite begins at 600
℉
(315
℃
), which produces a
decrease
in
hardness.
Increasing
the
temperature
causes
coalescence
of
the
carbides
with continued decrease in hardness.
渗碳体的大量析出开始于
600
℉
(315
℃
)
，这使硬
度下降。温度的上升会使碳化物聚结而硬
度继续降低。
In
the
process
of
tempering,
some
consideration
should
be
given
to
time
as
well as
to temperature. Although most of the softening
action occurs in the first
few minutes
after the temperature is reached, there is some
additional reduction
in hardness if the
temperature is maintained for a prolonged time.
在回火过程中，不但要考虑温度而且要考虑时间
。虽然大多数软化作用发生在达到
所需温度后的最初几分钟，但如果此温度维持一段延长
时间，仍会有些额外的硬度下降。
Usual
practice is to heat the steel to the desired
temperature and hold it there
only long
enough to have it uniformly heated.
通常的
做法是将钢加热到所需温度并且仅保温到正好使其均匀受热。
Two special processes using interrupted quenching
are a form of tempering.
In both, the
hardened steel is quenched in a salt bath held at
a selected lower
temperature before
being allowed to cool. These processes, known as
austempering
and
martempering,
result
in
products
having
certain
desirable
physical
properties.
< br>两种采用中断淬火的特殊工艺也是回火的形式。
这两种工艺中，
< br>淬硬钢在其被允许
冷却前先在一选定的较低温度盐浴淬火。这两种分别被称为奥氏
体回火和马氏体回火的工
艺，能使产品具有特定所需的物理性能。
?
Annealing
退火
The
primary purpose of annealing is to soften hard
steel so that it may be
machined or
cold worked.
退火的主要目的是使坚硬的钢软化以便机加工或冷作。
This is usually accomplished by heating
the steel too slightly above the critical
temperature,
holding
it
there until
the
temperature
of the
piece is
uniform
throughout, and
then cooling at a slowly controlled rate so that
the temperature
of the surface and that
of the center of the piece are approximately the
same.
通常是非常缓慢地将钢加热到临界温度以上，并将其在此温度下保持到工件
全部均匀受热，
然后以受控的速率慢慢地冷却，这样使得工件表面和内部的温度近似相同
。
This process is known as
full annealing because it wipes out all trace of
previous
structure,
refines
the
crystalline
structure,
and
softens
the
metal.
Annealing
also
relieves internal
stresses previously set up in the metal.
这过程被称为完全退火，
因为它去除了以前组织结构的所有痕迹、
< br>细化晶粒并软化金属。
退
火也释放了先前在金属中的内应
力。
The
temperature
to
which
a
given
steel
should
be
heated
in
annealing
depends
on its composition; for carbon steels
it can be obtained readily from the partial
iron-iron carbide equilibrium diagram.
When the annealing temperature has been
reached, the steel should be held there
until it is uniform throughout.
给定的钢其退火温度
取决于它的成分；对碳钢而言可容易地从局部的铁碳合金平衡
图得到。达到退火温度后，
钢应当保持在此温度等到全部均匀受热。
This
usually takes about 45min for each inch(25mm) of
thickness of the largest
section. For
maximum softness and ductility the cooling rate
should be very slow,
such as allowing
the parts to cool down with the furnace. The
higher the carbon
content, the slower
this rate must be.
加热时间一般以工件的最大截面厚度计每英寸
(25mm )<
/p>
大约需
45min
。为了得到最大柔软性
和延展性冷却速率应该很慢，
比如让零件与炉子一起冷下来。<
/p>
含碳量越高，
冷却的速率必须
越慢。
The heating
rate
should
be consistent with
the size and
uniformity of
sections, so
that the entire
part is brought up to temperature as uniformly as
possible.
加热的速率也应与截面的尺寸及均匀程度相协调，这样才能使整个
零件尽可能均匀地加热。
?
Normalizing and Spheroidizing
正火和球化
The
process
of
normalizing
consists
of
heating
the
steel
about
50
℉
to
100
℉
(10
< br>℃
~40
℃
) above
the upper critical range and cooling in still air
to room
temperature.
正火处理包括先将钢加热到高于上临界区
50
< br>℉到
100
℉
(10
℃
~40
℃
)
然后在静止的
空气中冷却到室温。
This
process
is
principally
used
with
low-
and
medium-carbon
steels
as
well
as
alloy
steels to make the
grain structure more uniform, to relieve internal
stresses, or
to achieve desired results
in physical properties. Most commercial steels are
normalized after being rolled or cast.
退火主要用于低碳钢、
中碳钢及合金钢，
使晶粒结构更均匀、
释放内应力或获得所需的物理
特性。大多
数商业钢材在轧制或铸造后都要退火。
Spheroidizing
is
the
process
of
producing
a
structure
in
which
the
cementite
is in a spheroidal
distribution. If 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.
球化是使渗碳体产生成类似球状分布结构的工艺。如果把钢缓慢加热到恰好低于临
界温度并且保持较长一段时间，就能得到这种组织结构。
The globular structure obtained gives
improved machinability to the steel. This
treatment is particularly useful for
hypereutectoid steels that must be machined.
所获得的球状结构改善了钢的可切削性。此处理方法对必须机加工的过共析钢特别有用。< p>
?
Surface
Hardening
表面硬化
Carburizing
The
oldest
known
method
of
producing
a
hard
surface
on
steel
is
case
hardening
or carburizing. Iron at temperatures close to and
above its critical
temperature has an
affinity for carbon.
渗碳
最早的硬化钢表面的方法是表面淬火或渗碳。铁
在靠近并高于其临界温度时对碳具
有亲合力。
The
carbon
is
absorbed
into
the
metal
to
form
a
solid
solution
with
iron
and
converts
the outer surface into high-carbon
steel. The carbon is gradually diffused to the
interior of the part. The depth of the
case depends on the time and temperature of
the treatment.
碳被吸收进金属与铁形成固溶
体使外表面转变成高碳钢。
碳逐渐扩散到零件内部。
渗碳层的<
/p>
深度取决于热处理的时间和温度。
Pack carburizing consists of placing
the
parts
to be treated in a
closed container
with some
carbonaceous material such as charcoal or coke. It
is a long process and
used to
produce fairly thick cases of from 0.03
to 0.16
in.(0.76~4.06mm) in
depth.
固体渗碳的方法是将要处理的零件与木炭或焦炭这些含碳的材料一起放入
密闭容器。
这是一
个较长的过程，用于产生深度为
0.03
到
0.16
英寸
(0.76~4.06mm)
这么厚的硬化层。
Steel for carburizing is
usually a low-carbon steel of about 0.15% carbon
that would not in itself responds
appreciably to heat treatment. In the course of
the process the outer layer is
converted into high-carbon steel with a content
ranging from 0.9% to 1.2% carbon.
用于渗碳的一般是含碳量约为
< br>0.15%
、本身不太适合热处理的低碳钢。在处理过程
中外层转化为含碳量从
0.9%
到
1.
2%
的高碳钢。
A steel with varying carbon content and,
consequently, different critical
temperatures requires a special heat
treatment.
含碳量变化的钢具有不同的临界温度，因此需要特殊的热处理。
Because there is some grain growth in
the steel during the prolonged carburizing
treatment, the work should be heated to
the critical temperature of the core and
then cooled, thus refining the core
structure. The steel should then be reheated
to a point above the transformation
range of the case and quenched to produce a
hard, fine structure.
由于在较长的
渗碳过程中钢内部会有些晶粒生长，
所以工件应该加热到核心部分的临界温度
再冷却以细化核心部分的组织结构。然后重新加热到高于外层转变温度再淬火以生成坚硬、
细致的组织结构。
The
lower heat-treating temperature of the case
results from the fact that
hypereutectoid
steels
are
normally
austenitized
for
hardening
just
above
the
lower
critical point. A third tempering
treatment may be used to reduce strains.
由于恰好高于低临界温度通常使过共析钢奥氏体
化而硬化，所以对外层采用较低的
热处理温度。第三次回火处理可用于减少应变。
Carbonitriding
Carbonitriding,
sometimes
known
as
dry
cyaniding
or
nicarbing,
is
a
case-hardening
process
in
which
the
steel
is
held
at
a
temperature
above
the
critical
range in a gaseous
atmosphere from which it absorbs carbon and
nitrogen.
碳氮共渗
碳氮共渗，有时也称为干法氰化或渗碳氮化，是一种表面硬化工艺。通过把钢放在
高于临界温度的气体中，让它吸收碳和氮。
Any carbon-rich gas with ammonia can be
used. The wear-resistant case produced
ranges
from
0.003
to
0.030
inch(0.08~
0.76mm)
in
thickness.
An
advantage
of
carbonitriding
is
that
the
hardenability
of
the
case
is
significantly
increased
when
nitrogen is added,
permitting the use of low-cost steels.
可以使用任何富碳气体加氨气，
能生成厚度从
0.003
到
0.030
英寸
(
0.08~
0.76mm)
的耐磨外
层。碳氮共渗的优点之一是加入氮后外层的淬透性极大增加，
为使用低价钢提供条件。
Cyaniding
Cyaniding, or liquid
carbonitriding as it is sometimes called, is also
a
process that combines the absorption
of carbon and nitrogen to obtain surface
hardness in low-carbon steels that do
not respond to ordinary heat treatment.
氰化
氰化，
有时称为液体碳氮共渗，
也是一种结合了吸收碳
和氮来获得表面硬度的工艺，
它主要用于不适合通常热处理的低碳钢。
< br>
The part to be case hardened is
immersed in a bath of fused sodium cyanide salts
at a temperature slightly above the Ac1
range, the duration of soaking depending
on
the
depth
of
the
case.
The
part
is
then
quenched
in
water
or
oil
to
obtain
a
hard
surface.
需表
面硬化的零件浸没在略高于
Ac1
温度熔化的氰化钠盐溶液中，
浸泡的持续时间取决于硬
化层的深度。然后将零件在水或油中淬
火。
Case depths of 0.005 to
0.015in. (0.13~0.38mm) may be readily obtained by
this
process. Cyaniding is used
principally for the treatment of small parts.
通过这样处理可以容易地获得
0.005
到
0.015
英寸
(0.13~0.38mm
)
的硬化深度。氰化主要用
于处理小零件。
Nitriding
Nitriding is somewhat similar to ordinary case
hardening, but it uses a
different
material and treatment to create the hard surface
constituents.
渗氮
渗氮有些类似普通表面硬化，
< br>但它采用不同的材料和处理方法来产生坚硬表面成分。
In
this
process
the
metal
is
heated
to
a
temperature
of
around
950
℉
(510
℃
)
and
held
there for a period of
time in contact with ammonia gas. Nitrogen from
the gas is
introduced into the steel,
forming very hard nitrides that are finely
dispersed
through the surface metal.
这种工艺中金属加热到约
950
℉
(510
℃
)
，然后与
氨气接触一段时间。氨气中的氮进入钢内，
形成细微分布于金属表面又十分坚固的氮化物
。
Nitrogen has
greater hardening ability with certain elements
than with
others, hence, special
nitriding alloy steels have been developed.
氮与某些元素的硬化能力比其它元素大，因此开
发了专用的渗氮合金钢。
Aluminum in the
range of 1% to 1.5% has proved to be especially
suitable in steel,
in that it combines
with the gas to form a very stable and hard
constituent. The
temperature of heating
ranges from 925
℉
to 1,050
℉
(495
℃
~56
5
℃
).
在钢中含铝
1%
到
1.5%
被证明特别合
适，它能与氨气结合形成很稳定坚固的成分。其加热温
度范围为
925
℉到
1,050
℉
(495
℃
~565
℃<
/p>
)
。
Liquid nitriding utilizes molten cyanide salts
and, as in gas nitriding,
the
temperature
is
held
below
the
transformation
range.
Liquid
nitriding
adds
more
nitrogen and less carbon than either
cyaniding or carburizing in cyanide baths.
液体渗氮利用熔化的氰化物盐，就像气体渗氮，
温度保持在低于转化范围内。液体
渗氮时在氰化物溶液中加入比氰化及渗碳都较多的氮和
较少的碳。
Case thickness of
0.001 to 0.012in.(0.03~0.30mm) is obtained,
whereas for gas
nitriding the case may
be as thick as 0.025 in.(0.64mm). In general the
uses of
the
two-nitriding processes are similar.
液体
渗氮可以获得厚度为
0.001
到
0.
012
英寸
(0.03~0.30mm)
的硬化层，
然而气体渗氮则能
获得厚
0.025
英寸
(0.64mm)
的
硬化层。一般而言两种渗氮方法的用途是类似的。
Nitriding
develops
extreme
hardness
in
the
surface
of
steel.
This
hardness
ranges from 900 to 1,100 Brinell, which
is considerably higher than that obtained
by ordinary case hardening.
渗氮在钢表面获得远远超出正常标准的硬度。<
/p>
其硬度范围为
900
到
< br>1,100
布氏硬度，
这远高于普通表面硬化所获得的硬
度。
Nitriding steels, by
virtue of their alloying content, are stronger
than ordinary
steels
and
respond
readily
to
heat
treatment.
It
is
recommended
that
these
steels
be
machined
and
heat-treated
before
nitriding,
because
there
is
no
scale
or
further
work necessary after this process.
由于渗氮钢的合金比例，
它们比普通钢更强，
也容易热处理。
建议对这种钢在渗氮前先机加
工和热处理，因为
渗氮后没有剥落并不需要更多的加工。
Fortunately,
the
interior
structure
and
properties
are
not
affected
appreciably
by
the nitriding treatment and, because no
quenching is necessary, there is little
tendency to warp, develop cracks, or
change condition in any way. The surface
effectively
resists
corrosive
action
of
water,
saltwater
spray,
alkalies,
crude
oil,
and natural gas.
值得庆幸的是由于渗氮处理一点都不影响内部结构和性能，
也无需淬火，
所以几乎没有任何
产生翘曲、裂缝及变化条件的趋势。这种表面能有
效地抵御水、盐雾、碱、原油和天然气的
腐蚀反应。
第三单元
Casting
is
a
manufacturing
process
in
which
molten
metal
is
poured
or
injected
and
allowed
to
solidify
in
a
suitably shaped
mold
cavity.
During
or
after cooling,
the cast
part is removed from the mold and then processed
for delivery.
铸造是一种将熔
化的金属倒入或注入合适的铸模腔并且在其中固化的制造工艺。在
冷却期间或冷却后，把
铸件从铸模中取出，然后进行交付。
Casting
processes
and
cast-material
technologies
vary
from
simple
to
highly
complex. Material and process selection
depends on the part’s complexity and
function, the product’s quality
specifications, and the projected cost
level.
铸造工
艺和铸造材料技术从简单到高度复杂变化很大。材料和工艺的选择取决于零
件的复杂性和
功能、产品的质量要求以及成本预算水平。
Castings
are
parts
that
are
made
close
to
their
final
dimensions
by
a
casting
process.
With
a
history
dating
back
6,000 years,
the
various
casting
processes
are
in
a
state
of
continuous
refinement
and
evolution
as
technological
advances
are
being
made.
< br>通过铸造加工，铸件可以做成很接近它们的最终尺寸。回溯
6,000
年历史，各种各
样的铸造工艺就如同科技进步一样处于一个不断改进和发展
的状态。
?
Sand Casting
砂型铸造
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
< br>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。
In a two-part
mold, which is typical of sand castings, the
upper half,
including
the
top
half
of
the
pattern,
flask,
and
core
is
called
cope
and the
lower
half is called drag, as shown in
Fig.3.1. The parting line or the parting surface
is line or surface that separates the
cope and drag.
在典型砂型
铸造的两箱铸模中，上半部分
(
包括型模顶半部、砂箱和砂芯<
/p>
)
称为上型
箱，下半部分称为下型箱，见
图
3.1
所示。分型线或分型面是分离上下型箱的线或面。
The drag is first filled
partially with sand, and the core print, the
cores, and
the gating system are
placed near the 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.
首先往下型箱里部分地填入型砂和砂芯座、
砂芯，
并在靠近分型
线处放置浇注系统。
然后将
上型箱与下型箱装配在一起，再把型
砂倒入上型箱盖住型模、砂芯和浇注系统。
The sand
is compacted
by vibration and
mechanical means. Next, the cope
is
removed
from the drag, and the pattern
is carefully removed. The object is to remove the
pattern without breaking the mold
cavity.
型砂通过振动和机械方法压实。
然后从下型
箱上撤掉上型箱，
小心翼翼地取出型模。
其目的
是取出型模而不破坏型腔。
This
is
facilitated
by
designing
a
draft,
a
slight
angular
offset
from
the
vertical
to
the
vertical
surfaces
of
the
pattern.
This
is
usually
a
minimum
of
1.5mm(0.060in.),
whichever is greater. The rougher the
surface of the pattern, the more the draft
to be provided.
通过设计拔模斜度—型模垂
直相交表面的微小角度偏移量—来使取出型模变得容易。
拔模斜
度最小一般为
1.5mm(0.060in.)
，只能比此大。
型模表面越粗糙，则拔模斜度应越大。
The molten material is poured into the pouring
cup, which is part of the
gating system
that supplies the molten material to the mold
cavity.
熔化的金属从浇注杯注入型
腔，浇注杯是浇注系统向型腔提供熔化金属的部分。
The
vertical part of the gating system connected to
the pouring cup is the sprue,
and
the
horizontal
portion
is
called
the
runners
and
finally
to
the
multiple
points
where it is introduced to the mold
cavity called the gates.
将浇注系统的垂直部分与浇注
杯连接的是浇注口，
浇注系统的水平部分称为浇道，
最后到多<
/p>
点把熔化金属导入型腔的称为闸道。
Additionally there are extensions to
the gating system called vents that provide
the path for the built-up gases and the
displaced air to vent to the atmosphere.
除此之外，
还有称为排放口的浇注系统延长段，
它为合成气
体和置换空气排放到大气提供通
道。
The
cavity
is
usually
made
oversize
to
allow
for
the
metal
contraction
as
it
cools
down
to
room
temperature.
This
is
achieved
by
making
the
pattern
oversize.
To
account
for
shrinking,
the
pattern
must
be
made
oversize
by
these
factors
on
the
average. These are
linear factors and apply in each direction.
型腔通常大于所需尺寸以允许在金属冷却到室温
时收缩。这通过把型模做得大于所
需尺寸来达到。
为解决收缩效
应，
一般而言型模做得比所需尺寸大，
必须考虑线性因素并作<
/p>
用于各个方向。
These
shrinkage allowances are only approximate, because
the exact allowance is
determined by
the shape and size of the casting. In addition,
different parts of
the casting might
require different shrinkage allowances.
收缩余量仅仅是近似的，
因为准确的余量是由铸件的形状和尺寸决定的。
另外，
铸件的不同
部分也可能需要不同的收缩余量
。
Sand
castings
generally
have
a
rough
surface
sometimes
with
surface
impurities,
and
surface
variations.
A
machining
(finish)
allowance
is
made
for
this
type
of
defect.
砂型铸件一般
表面粗糙，有时还带有表面杂质和表面变异。对这类缺陷采用机加工
(
< br>最后一
道工序
)
的余量。
In general, typical
stages of sand casting operation include (as shown
in
Fig.3.2):
1. Patterns are
made. These will be the shape used to form the
cavity in the sand.
一
般而言，砂型铸造作业的典型阶段包括
(
如图
< br>3.2
所示
)
：
1.
制作型模。做成用于在型砂中形成型腔的形状。
2. Cores may also be made at this time.
These cores are made of bonded sand that
will be broken out of the cast part
after it is complete.
3.
Sand
is
mulled
(mixed)
thoroughly
with additives
such
as
bentonite
to
increase
bonding and
overall strength.
2.
同时还要制作砂芯。这些砂芯用粘结砂做成，等铸件完成
后将被打碎取出。
3.
型砂与膨润土之类的添加剂充分地混合以增强连接及整体强度。
4.
Sand
is
formed
about
the
patterns,
and
gates,
runners,
risers,
vents
and
pouring
cups
are
added
as
needed.
A
compaction
stage
is
typically
used
to
ensure
good
coverage
and solid molds.
4.
型砂在型模周围成形，并根据需要安放闸道、浇道、冒口
、排放口和浇注杯等。通常要
采取压紧步骤来保证良好的覆盖和坚固的铸型。
Cores may also be added to make
concave or internal features for the cast part.
Alignment pins may also be used for
mating the molds later. Chills may be added to
cool large masses faster.
安放
砂芯来制成铸件的凹形结构或内部特征。
为了以后铸模匹配还要用到定位销。
对大质量
铸件可能需要加入冷却物来使其较快冷却。
5. The patterns are removed, and the
molds may be put through a baking stage to
increase strength.
6. Mold
halves are mated and prepared for pouring metal.
5.
取走型模，将铸模烘焙以增加强度。
6.
匹配上下铸模，做好浇铸金属的准备。
7.
Metal
is
preheated
in
a
furnace
or
crucible
until
is
above
the
liquidus
temperature
in
a
suitab
le
range
(we
don’t
want
the
metal
solidifying
before
the
pour
is
complete).
The exact
temperature may be closely controlled depending
upon the application.
7.
金属在
熔炉或坩埚中预热到高于液化温度的一个合适范围内
(
不希望金
属在浇铸完成前
凝固
)
。确切的温度要
根据应用场合严格控制。
Degassing,
and
other
treatment processes
may
be
done
at
this
time,
such
as
removal
of impurities
(i.e. slag). Some portion of this metal may be
remelted scrap from
previously cast
parts
—
10% is reasonable.
在此期间还要进行排气和其它处理步骤，
例如去除杂质
(
即熔渣
)
。
可以加入一定量原先是这
种金属铸件的废料再融化—
1
0%
是适当的。
8. The
metal is poured slowly, but continuously into the
mold until the mold is
full.
9.
As
the
molten
metal
cools
(minutes
to
days), the
metal
will
shrink
and
the
volume
will
decrease. During this time molten metal may
backflow from the molten risers
to feed
the part and maintain the same shape.
8.
将金属缓慢而连续地注满型模。
9.
随着熔化金属的冷却
(
几分钟到几天
)
，金属收缩体积减小。在此期间
熔化金属可能从冒
口回流供给零件以保持其形状不变。
10. Once the part starts to solidify
small dendrites of solid material form in the
part.
During
this
time
metal
properties
are
being
determined,
and
internal
stresses
are being
generated. If a part is allowed to cool slowly
enough at a constant rate
then the
final part will be relatively homogenous and
stress free.
10.
在零件开始凝固其内部形
成固态金属的小型树枝状结晶期间金属性能被确定，
同时也产
生
了内应力。如果零件以恒定速率冷却得足够缓慢，最终零件将相对均质并释放内应力。
11.
Once
the
part
has
completely
solidified
below
the
eutectic
point
it
may
be
removed
with
no
concern
for
final
metal
properties.
At
this
point
the
sand
is
simply
broken
up, and the part
removed. At this point the surface will have a
quantity of sand
adhering to the surface, and solid
cores inside.
11.
一旦零件在共析点以下
完全凝固，
可以不考虑金属的最后性能而将其取出。
这时可以简
单地打碎砂型并取出零件，但零件表面会有大量型砂粘附着，内部还有实心的砂芯。
12. A bulk of the remaining
sand and cores can be removed by mechanically
striking
the part. Other options are to
use a vibrating table, sand/shot blaster, hand
labor, etc.
12.
大量
的剩余型砂和砂芯要通过机械敲击零件来去除。
其它的选择还有采用振动台、
喷砂
/
喷丸机、手工作业等等。
< br>
13.
The
final
part
is
cut
off
the
runner
gate
system,
and
is
near
final
shape
using
cutters,
torches,
etc.
Grinding
operations are
used
to
remove
any
remaining
bulk.
14. The
part
is
taken down to final shape
using
machining operations. And cleaning
operations may be used to remove
oxides, etc.
13.
最后零件要用刀具、
喷枪等切掉浇道闸道系统，
这样就接近最终形状了。
再用磨削作业
去除多余的部分。
14.
通过机加工将零件切削到最终形状。可能还要用清洗作
业去除氧化物等。
?
Investment casting
熔模铸造
Investment casting is also known as the lost wax
process. This process is
one
of
the
oldest
manufacturing
processes.
The
Egyptians
used
it
in
the
time
of
the
Pharaohs to make gold
jewelry (hence the name Investment) some 5,000
years ago.
熔模铸造也称为失蜡加
工。这是最古老的制造工艺之一。大约在
5,000
年前的法老
王时代，埃及人就用它制造黄金饰品
(
因此而得名投资
)
。
Intricate shapes can
be
made with high accuracy. In addition,
metals that are hard
to machine or
fabricate are good candidates for this process.
It can be used to
make parts that
cannot be produced by normal manufacturing
techniques, such as
turbine blades that
have complex shapes, or airplane parts that have
to withstand
high temperatures.
复杂的形状能被高精度地制造。
另外较难机加工或制作的金属都能用此工艺。
它还能用于生
产一般制造技术无法生产的零件，例如有复杂形状
的涡轮叶片或必须耐得住高温的飞机零
件。
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.
<
/p>
制作铸型的型模采用石蜡或其它一些能被融化掉的材料做成。石蜡型模浸泡在耐热
浆里，
让它覆盖型模并形成外壳，然后使其变干。
重复这个浸泡、
变干的过程直至获得足够
的厚度。
After this, the entire pattern
is placed in an oven and the wax is melted away.
This leads to a mold that can be filled
with the molten metal. Because the mold is
formed around a one-piece pattern
(which does not have to be pulled out from the
mold
as in
a
traditional
sand
casting
process),
very
intricate
parts
and
undercuts
can be made.
完成后把整个型模放在烤箱里融化石蜡。
这样就做成了能填充熔化金属的
铸型。
由于这种铸
型是环绕整块型模形成的
(
无需像传统的砂型铸造工艺那样拔模
)
< br>，
能制作十分复杂的零件和
浮雕。
The
wax
pattern
itself
is
made
by
duplicating
using
a
stereo
lithography
or
similar
model
—
which has
been fabricated using a computer solid model
master.
石蜡型模本身能用立体制版或类似的模型复制—这可以采用计算机立体
模型原版制作。
The
materials used for the slurry are a mixture of
plaster, a binder and
powdered silica,
a refractory, for low temperature melts. For
higher temperature
melts,
sillimanite
or
alumina-silicate
is
used
as
a
refractory,
and
silica
is
used
as a binder.
< br>对较低熔化温度而言，用于耐热浆的材料是石膏作粘合剂和用粉末状硅石作耐温材
料的混合物。
对较高熔化温度而言，
则采用硅线石或氧化铝硅酸
盐作耐温材料、
无水硅酸作
粘合剂。
Depending
on
the
fineness
of
the
finish
desired
additional
coatings
of
sillimanite
and
ethyl
silicate
may
be
applied.
The
mold
thus
produced
can
be
used
directly
for
light
castings,
or
be
reinforced
by placing
it
in
a
larger
container
and
reinforcing
it more slurry.
根据最后所需光洁度也可采用硅线石和乙烷基硅酸盐。
这样生成
的铸模可直接用于薄壁铸件
或通过将其放在较大容器内用更多耐热浆加强。
Just before the pour, the
mold is pre-heated to about 1,000
℃
(1,832
℉
) to
remove
any
residues
of
wax,
harden
the binder.
The
pour
in
the
pre-heated
mold also
ensures that the
mold will fill completely.
在正要浇铸之前，
将型模预热到约
1,000<
/p>
℃
(1,832
℉
)
以去除剩余石蜡、
硬化粘合剂。
在
预热的型模中浇铸也能保证型模完全充满。
Pouring
can
be
done
using gravity,
pressure
or
vacuum conditions.
Attention
must
be
paid to mold permeability when using pressure, to
allow the air to escape as
the pour is
done.
浇铸可采用重力、压力或真空条件
来实现。当使用压力时必须注意渗透性，以便在
浇铸的同时让空气逸出。
Tolerances of 0.5% of
length are routinely possible, and as low as 0.15%
is
possible
for
small
dimensions.
Castings can
weigh
from
a
few
grams
to
35kg
(0.1oz
to
80lb),
although
the
normal
size
ranges
from
200g
to
about
8kg(7oz
to
15
lb).
Normal
minimum
wall
thicknesses
are
about
1mm
to
about
0.5mm(0.040~
0.020 in.)
for
alloys
that
can be cast easily.
一
般公差可能为长度的
0.5%
，小尺寸可能低到
0.15%
。虽然通常尺寸的铸件重量范
围为
200g
到约
8kg(7oz
< br>到
15lb)
，但实际可从几克到
35kg (0.1oz to 80lb)
。对容易铸造
的
合金而言，通常壁厚约为
1mm
到
0.
5mm(0.040~ 0.020 in.)
。
The
types
of
materials
that
can
be
cast are
aluminum
alloys,
bronzes,
tool
steels, stainless steels, stellite,
hastelloys, and precious metals. Parts made
with investment castings often do not
require any further machining, because of
the close tolerances that can be
achieved.
可以用于铸造的材料类型
有：铝合金、青铜、工具钢、不锈钢、钨铬钴合金、镍基
合金和贵金属。
采用熔模铸造的零件常常不需要进一步加工，
因为熔模铸造能达到精密的公
差。
?
Centrifugal Casting
离心铸造
Centrifugal
casting
(Fig.3.3)
as
a
category
includes
centrifugal
casting,
semi-centrifugal
casting
and
centrifuging.
In
centrifugal
casting,
a
permanent
mold
is
rotated about its axis at high speeds (300 to
3,000rpm) as the molten metal is
poured.
离
心铸造
(
图
3.3)
< br>作为一个种类包括了离心铸造、半离心铸造和离心法铸造。离心
铸造中，永久性的
型模在熔化金属浇铸时以较高速度
(300
到
< br>3,000rpm)
绕其轴线旋转。
The molten metal is centrifugally
thrown towards the inside mold wall, where it
solidifies after cooling. The casting
is usually a fine grain casting with a very
fine-grained
outer
diameter,
which
is
resistant
to
atmospheric
corrosion,
a
typical
situation
with
pipes.
The
inside
diameter
has
more
impurities
and
inclusions,
which
can be machined away.
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。
Only
cylindrical shapes can be produced with this
process. Size limits are
up to
3m(10feet) diameter and 15m(50 feet) length. Wall
thickness can be 2.5mm to
125mm(0.1~5.0in.).
The
tolerances
that
can
be
held
on
the
OD
can
be
as
good
as
2.5mm
(0.1in.) and on the ID
can
be 3.8mm(0.15in.). The surface finish
ranges
from 2.5mm
to 12.5mm(0.1~0.5in.) rms(root-mean-
square).
只有圆柱形才能用此工艺生
产。尺寸限制为直径大到
3m(10feet)
、长度大到
15m(50feet)
。壁厚为
2.5m
m
到
125mm(0.1~5.0in.)
。外径公差保持在
2.5mm(0.1in.)
以内，
内径公差保持在
3.8mm(0.15in.)
以内。表面粗糙度的有效值
(
均方根
)
范围为
2.5mm
到
12.5mm(0.1~0.5in.)
。
Typical materials that can be
cast with this process are iron, steel,
stainless steels,
and
alloys
of
aluminum,
copper
and
nickel.
Two
materials
can
be
cast by introducing a second material
during the process. Typical parts made by
this
process
are
pipes,
boilers,
pressure vessels,
flywheels,
cylinder
liners
and
other
parts that are axis-symmetric.
<
/p>
可用此工艺铸造的典型材料有：铁、钢、不锈钢以及铝、铜和镍的合金。通过在生
产过程中加入第二种材料能进行两种材料铸造。
采用这种工艺制造的典型
零件有：
管子、
锅
炉、压力容器、飞轮
、汽缸衬垫和其它轴对称零件。
Semi-
centrifugal casting. The molds used can be
permanent or expendable,
can be stacked
as necessary. The rotational speeds are lower than
those used in
centrifugal casting.
半离心铸造：型模可以是永久性的或是消耗性的
，可根据需要叠加。它的旋转速度
比离心铸造低。
The center axis of the part has
inclusion defects as well as porosity and thus is
suitable
only
for
parts
where
this
can
be
machined
away.
This process
is
used
for
making
wheels, nozzles and similar
parts where
the axis of the part is removed by
subsequent machining.
零件的中心轴
附近存在缺陷和孔隙，
因此仅适用于能将这些机加工去除的零件。
这种工艺被
用于制造车轮、管嘴及类似的随后可用机加工去除中心轴部分的零件。
Centrifuging.
Centrifuging
is
used
for
forcing
metal
from
a
central
axis
of
the equipment into individual mold
cavities that are placed on the circumference.
This
provides
a
means
of
increasing
the
filling
pressure
within
each
mold
and
allows
for
reproduction of intricate details. This method is
often used for the pouring
of
investment casting pattern.
离心法铸造：离心法铸造用于迫使金属从设备的中心轴进入分布在圆周上的单独型
腔。
它为每个型腔提供了一种增加填充压力方法并允许再现复杂细节。
这种方法常用于浇铸
熔模铸型。
Full-mold casting is a
technique similar to investment casting, but
instead
of
wax
as
the
expendable
material,
polystyrene
foam
is
used
as
the
pattern.
The foam pattern is coated with a
refractory material. The pattern is encased in
a one-piece sand mold. As the metal is
poured, the foam vaporizes, and the metal
takes its place.
实型铸造是与熔模铸造类似的技术，但它用做型模的消耗材料是聚苯乙烯泡沫而不
是石蜡。泡沫型模用难熔材料覆盖。型模装入整体砂模中。当金属浇入时，泡沫材料蒸发，
金属取代其位置。
This can make
complex shaped castings without any draft or
flash. However, the
pattern cost can be
high due to the expendable nature of the pattern.
Minimum wall
thicknesses
are
2.5mm,
tolerances
can
be
held
to
0.3%
on
dimensions.
Surface
finish
can be held from
2.5
μ
m to 25
μ
m(0.1
μ
in. to
1.0
μ
in.) rms(root-mean-
square).
它能制造没有拔模斜度和缝脊的复杂形状铸件。
< br>然而由于型模的消耗特性，
型模成本可能较
高。最小壁厚
为
2.5mm
，公差能保持在尺寸的
0
.3%
之内。表面粗糙度的有效值
(
均方根
)
能
保持在
2.5
μ
m
至
25
μ
m(0.1
μ
in.
至
1.0
μ
in.)
之间。
Size limits are from 400g(1lb) to
several tons. No draft allowance is required.
Typical materials that can be cast with
this process are aluminum, iron, steel,
nickel
alloys,
copper alloys.
Types
of
parts
that
can
be
made
using
these
processes
are pump housings,
manifolds, and auto brake components.
重
量限制从
400g(1lb)
到数吨。
无需留拔模余量。
这种工艺所用的典型材料有：
铝、
铁、
钢、
镍合金、铜合金。可以采用这些工艺制造
的零件类型有泵壳、复式接头和自动刹车部件。
第四单元
?
Introduction
引言
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、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 force. Usually 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。
For
the
semimechanized
forging
of
small
to
medium-sized
components,
forging
hammers powered by various means are
employed. The feature common to all of them
is that, like the hand forging hammer,
they utilize the energy of a falling weight
to develop the pressure needed for
shaping the metal.
对
小到中等尺寸零件的半机械化锻造而言，锻锤可采用多种动力。就其一般特性而
言，都象
手工锻锤一样，它们均利用落重能量来产生金属成型所需的压力。
Larger components are forged by means
of forging presses operated by steam or
compressed
air
or
by
hydraulic
or
electric
power.
Largely
automatic
forging
machines
are used for the quantity production
of engineering parts.
锻造大零件则要用到蒸汽、
压缩空气、
液力或电力驱动的锻压机。
大型的自动
化锻机用于工
程零件的批量生产。
A distinction may be made between open-die
forging, usually in the form
of
hammer
forging,
and
closed-die
forging.
In
hammer
forging,
the
component
is
shaped
by
hammer
blows
aided
by
relatively
simple
tools.
These
may
include
open
dies
i.e.,
dies that do not
completely enclose the metal to be shaped.
锤锻中常用的开式模锻与闭式模锻是有区别的。
在锤锻中零件通过锤击辅之以相对
简单的工具成型。其中包括开式锻模，就是不完全封闭
被成型金属的模具。
One
of
the
basic
operations
of
hammer
forging
is
the
elongation
of
a
piece
of
metal
by stretching with
hammer blows, causing it to become thinner and
longer. In hand
forging the
work-
piece is usually turned 90°after
each blow, in
order to forge
it thoroughly and prevent its lateral
expansion.
锤锻的基本操作之一就是通过锤击使金属伸长，
促成其变细变长。
手工锻造时一般在每次锤
击后都转
过
90
°以充分锻打工件并防止横向膨胀。
The
opposite
of
elongation
is
upsetting,
which
produces
compressive
shortening.
For
example, the diameter of a bar can be
increased by heating and hammering axially.
与伸长相反的是镦粗，
即产生压缩性缩短。
例如，<
/p>
棒料的直径可以通过加热和轴向锤击而增
大。
More
important
is
closed-die
forging,
very
widely
used
for
mass
production
in
industry,
in
which
the
metal
is
shaped
by
pressing
between
a
pair
of
forging
dies.
The
upper
die
is
usually
attached
to
the
ram
of
a
forging
press
or
a
forging
hammer,
while the lower die is stationary.
更重要的是闭式模锻，在工业上广泛用于规模生
产。闭式模锻中金属在一对锻模之
间挤压成型。顶模通常放在锻压机的撞头或锻锤上，而
底模则是固定的。
Together
they
form
a
closed
die.
Closed-die
forging
can
produce
components
of
greater
complexity and
accuracy, with a better surface finish than the
more traditional
methods not using
closed dies. The dies are made of special heat-
resistant and
wear-resistant tool
steels.
两者合在一起形成闭式锻模。
闭式模锻能生产
高度复杂和精确的零件，
而且表面光洁度要比
不用闭式锻模的更
传统方法好。闭式锻模采用特殊的耐热、耐磨工具钢制成。
A
piece
of
hot
metal
sufficient
to
slightly
overfill
the
die
shape
is
placed
in
the
bottom
die,
and
the
top
die
is
forced
against
it,
so
that
the
metal
takes
the
internal
shape of the die.
将一块大小足以充填模腔并能稍有溢出的加热金属放入底模，
并
将顶模加压合拢，
这块金属
便获得该模腔的形状。
Closed-die
forging
is
used
for
the
rapid
production
of
large
numbers
of
fairly
small
parts
and
also
for
very
large
components.
For
the
latter,
e.g.,
modern
jet-aircraft
components, giant hydraulically
operated presses are used, which can develop
forces of 50,000 tons and more.
闭式模锻用于相当小的零件大批量快速生产，
也可用于很大的零件。
对后者而言，
例如现代
喷气飞机零件，使用能产生
50,000
吨以上压力的巨型液力锻压机。
< br>
One
valuable
feature
of
forging
is
that
it
improves
the
strength
of
the
metal
by refining the
structure and 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.
锻造有价值的特性之一是它通过使金属组织均匀而改善强度，因此对诸如船舶螺旋
桨轴之类的重型锻件，要用能达
10,000
吨压力的庞大而有力的液压机来挤压金属。
Although
the hydraulic forging press is a more expensive
piece of equipment than
a drop-forge,
it has advantages beside those of giving greater
strength and more
uniform
structure
to
large
components.
On
account
of
the
high
pressure
and
squeezing
action, it operates with less noise and
vibration than a drop-forge.
虽然这种液压锻机比
落锤锻造要昂贵得多，
但它除了能给予大零件较高的强度和更均匀的组
< br>织外还有其它优点。由于较高的压力和挤压作用，它比落锤锻造噪声及振动都小得多。
As
ingots
of
steel
weighing
30
tonnes
or
more
are
forged
in
this
way,
manual
operation
is impossible and
it is essential that all the manipulation of the
ingot is done
mechanically.
由于这种情况下被锻钢坯重量大于
30
吨，人工操作是不可能的
，钢坯的所有操作都必须是
机械化的。
Forging refines the grain
structure and improves physical properties of
the metal. With proper design, the
grain flow can be oriented in the direction of
principal stresses encountered in
actual use.
铸造细化金属的晶
粒组织、改善其物理性能。通过适当的设计，可以使晶粒流动方
向与实际使用时的主应力
方向一致。
As shown in Fig.4.2,
grain flow is the direction of the pattern that
the crystals
take during plastic
deformation. Physical properties (such as
strength, ductility
and
toughness)
are
much
better
in
a
forging
than
in
the
base
metal,
which
has
crystals
randomly oriented.
如图
4.2
所示，晶粒流动的方向就是
在塑性变形期间结晶排列的方向。锻件的物理性能
(
如
强度、延展性和韧性
)
远好于基础金属，因为基
础金属的晶粒是无序排列的。
Forgings
are
consistent
from
piece
to
piece,
without
any
of
the
porosity,
voids, inclusions
and other defects. Thus, finishing operations such
as machining
do not expose voids,
because there aren’t any. Also coating operations
such as
plating or painting are
straightforward due to a good surface, which needs
very
little preparation.
锻件各部分是连贯一
致的，没有孔隙、空洞、杂质及其它缺陷。因此像机加工之类
的精加工工序不会受空洞的
影响，
因为根本就不存在。
另外由于锻件良好的表面，
像电镀或
油漆之类的涂装工序就很简单，几乎不需要做准备工作。
Forgings
yield
parts
that
have
high
strength
to
weight
ratio,
thus
are
often
used in the design of aircraft frame
members.
A forged metal can
result in the following:
锻造生产的零件具有较高的强度重量比，所以常被用在飞机结构零件的设计中。
锻造金属可以导致下列结果：
?
Increase
length, decrease cross-section, called drawing out
the metal.
?
Decrease length, increase cross-
section, called upsetting the metal.
?
Change length,
change cross-section, by squeezing
in
closed impression dies.
This results in favorable
grain flow for strong parts.
●增加长度、减小横截面，称为延伸金属。
●减小长度、增加横截面，称为镦粗金属。
●通过用封闭锻模挤压，改变长度和横截面。
这导致有利的晶粒流使零件坚固。
?
Common Forging
Processes
常用的锻造工艺
The
metal
can
be
forged
hot
(above
recrystallization
temperatures)
or
cold.
金属既
可热锻
(
高于再结晶温度
)
也可冷锻。
Open
die forgings/Hand forgings. Open die forgings or
hand forgings are
made
with
repeated
blows
in
an
open
die,
where
the
operator
manipulates
the
workpiece
in
the die. The finished product is a rough
approximation of the die. This is what
a traditional blacksmith does, and is
an old manufacturing process.
开式模锻
/
手工锻：开式模锻或手工锻就是
操作者操纵工件在开式锻模中反复击打。
完成的产品是锻模的粗糙近似物。这就是传统铁
匠干的活，是较古老的制造工艺。
Impression die forgings/Precision forgings.
Impression die forgings and
precision
forgings are further refinements of the blocker
forgings. The finished
part more
closely resembles the die impression.
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
< br>似。
Press forgings.
Press forgings use a slow squeezing action of a
press, to
transfer a great amount of
compressive force to the workpiece. Unlike an
open-die
forging
where
multiple
blows
transfer
the
compressive
energy
to
the
outside
of
the
product,
press forging transfers the force uniformly to the
bulk of the material.
压锻：压锻通过压力机缓慢的挤压动作将巨大的压力传递给工件。不像开式模锻那
样
需要多次击打把压缩能量传递到零件外表面，压锻能将力均匀地传递给材料的主体。
This results in uniform material
properties and is necessary for large weight
forgings. Parts made with this process
can be quite large as much as 125kg(260lb)
and 3m(10 feet) long.
这使材料性能
一致，对大重量锻件而言是十分必要的。采用此工艺生产的零件重量可达
125kg(2
60lb)
而长度可达
3m(10
feet)
。
Upset forgings. Upset forging increases cross-
section by compressing the
length,
this
is
used
in
making
heads
on
bolts
and
fasteners,
valves
and
other
similar
parts.
顶锻：顶锻通过压缩长度增加横截面，用于在螺
栓等紧固件、柱塞及类似零件上制
造头部。
Roll
forgings.
In
roll
forging,
a
bar
stock,
round
or
flat
is
placed
between
die
rollers
which
reduces
the
cross-section
and increases
the
length
to
form
parts
such
as axles, leaf springs etc. This is an essential
form of draw forging.
滚锻：在滚锻时，圆的或是扁平的棒料放在模辊之间缩小横截面增加长度制成诸如
轮轴
、板簧之类的零件。这是轧锻的基本形式。
Swaging. Swaging
—
a tube or
rod is forced inside a die and the
diameter is
reduced as the
cylindrical object is fed. The die hammers the
diameter and causes
the metal to flow
inward causing the outer diameter of the tube or
the rod to take
the shape of the die.
型锻：型锻—将圆管或圆棒强制压入锻模，随着
圆柱形物体的被压入其直径减小。
锻模锤击横断面使金属向内流动导致圆管或圆棒的外径
变为锻模的形状。
Net
shape/Near-net
shape
forging.
In
net
shape
or
near-net
shape
forging,
forging
results
in
wastage
of
material
in
the
form
of
material
flash
and
subsequent
machining
operations, as shown in Fig.4.3. This wastage can
be as high as 70% for
gear blanks, and
even 90% in the case of aircraft structural parts.
纯型
/
近似纯型锻
：采用纯型锻或近似纯型锻，产生材料损
耗的主要形式是飞边以
及随后的机加工，如图
4.3
所示。齿轮毛坯材料损耗为
70%
，而飞机结构
零件的材料损耗
甚至达
90%
。
Net-shape
and
near-net-shape
processes
minimize
the
waste
by
making
precision
dies,
producing
parts with
very
little
draft
angle
(less
than
1°).
These
types
of
processes often eliminate or reduce
machining.
纯型锻和近似纯型锻工艺通过制作精密模具并生产锻模斜角很
小
(
小于
1
°
)
的零件能使材
料损耗最小化。此类工
艺通常可以省去或减少机加工。
The processes
are quite expensive in terms of tooling and the
capital expenditure
required. Thus,
these processes can be only justified for current
processes that
are
very
wasteful
where
the
material
savings
will
pay
for
the
significant
increase
in tooling costs.
从模具的角度而言这些
工艺是相当昂贵的，
需要资金投入。
因此这些工艺只有对目前很
浪费
的生产过程，在材料节约足以补偿模具成本的大量增加时才是合理的。
?
Die
Design Consideration
锻模设计的考虑因素
?
Parting
surface
should
be
along
a
single
plane
if
possible,
else
following
the
contour of the part.
The parting surface should be through the center
of the part,
not near the upper or
lower edges.
?
如
果可能分模面应沿着单一平面，否则就顺着零件轮廓方向。分模面应经过零件中心，
而不
要靠近上下边缘。
If the parting line
cannot be on a single plane, then it is good
practice to use
symmetry
of
the
design
to
minimize
the
side
thrust
forces.
Any
point
on
the
parting
surface should be less
than
75°from the principal parting plane.
如果分模面不能在单一平面，
利用设计的对称性来减小侧向推力不失
为一种好方法。
分模面
上任意点与主分模面的夹角应小于
75
°。
?
As
in most forming processes, use of
undercuts should be avoided
as these will
make the
removal of the part difficult, if not impossible.
?
如同大多数成型工艺，
如果不是非用不可，
尽量避免采用凹槽，
因为凹槽
会使零件难以
取出。
?
Generous
fillets and radius should be provided to aid in
material flow during
the forging
process. Sharp corners are stress-risers in the
forgings, as well as
make the dies
weak in service.
?
Ribs should not be high or narrow; this
makes it difficult for the material
to
flow.
?
应提供尽可能大的倒
角和半径以帮助材料在锻造过程中流动。锐角会增加锻件中的应
力，同时在使用时削弱锻
模。
?
加劲肋不要过高、过窄，因为这会造成材料流动困难。
?
Tolerances
公差
?
Dimension tolerances are usually
positive and are approximately 0.3% of the
dimension, rounded off to the next
higher 0.5mm(0.020in.).
?
尺寸公差通常为正，大约取为该尺寸的
0.3%
，并圆整到较大的
0.5mm(0.020in.)
。
?
Die
wear
tolerances
are
lateral
tolerances
(parallel
to
the
parting
plane)
and
are
roughly +0.2% for copper alloys to +0.5% for
aluminum and steel.
?
锻模磨损公差为侧向公差
(
平行于分模面
)
，对铜合金大约为
+0.2%
，对铝和钢大约为
+0.5%
。
?
Die closure
tolerances are in the direction of opening and
closing, and range
from 1mm(0.040in.)
for small forgings, die projection
area
＜
150cm2(23in.2), to
6.25mm(0.25in.) for large forgings, die
projection
area
＞
6,500cm2(100in.2).
?
锻模的闭合公差处于开闭的方向上
，
范围从对较小锻件
[
其投影面积＜<
/p>
150cm2(23in.2)]
取
为<
/p>
1mm(0.040in.)
，
到
较
大
锻
件
[
其
投
影
面
积
＞
6,500cm2(1
00in.2)]
取
为
6.25mm(
0.25in.)
。
?
Die match
tolerances are to allow for shift in the upper die
with respect to
the lower die.
?
锻模的配合公差是为了允许上模能根据下模替换。
A
proper
lubricant
is
necessary
for
making
good
forgings.
The
lubricant
is
useful in preventing sticking of the
workpiece to the die, and also acts as a
thermal insulator to help reduce die
wear.
制造良好的锻件必须有合适的滑润
剂。滑润剂对防止工件粘住锻模很有用，还可以
作为绝热体帮助减少锻模磨损。
第五单元
Powder
metallurgy(Fig.5.1)
uses
sintering
process
for
making
various
parts
out
of
metal
powder.
The
metal
powder
is
compacted
by
placing
in
a
closed
metal
cavity
(the die) under
pressure.
粉末冶金
(
图
5.1)
采用烧结工艺将
金属粉末制成各种各样的零件。金属粉末放在封
闭的金属腔
(<
/p>
模具
)
中在压力下被压实。
This
compacted
material
is
placed
in
an
oven
and
sintered
in
a
controlled
atmosphere
at high
temperatures and the metal powders coalesce and
form a solid. A Second
pressing
operation, repressing, can be done prior to
sintering to improve the
compaction and
the material properties.
被压实的材料置于炉内烧结，<
/p>
在高温下炉内环境可控，
金属粉末熔合形成固体。
在烧结前可
以进行二次挤压作业
(
再挤压
)
以改善压实状态和材料性能。
Powder metallurgy is a
highly developed method of manufacturing reliable
ferrous
and
nonferrous
parts.
Made
by
mixing
elemental
or
alloy
powders
and
compacting
the
mixture
in
a
die,
the
resultant
shapes
are
then
sintered
or
heated
in a controlled
atmosphere furnace.
粉
末冶金是一种高度发达的制造可靠铁或非铁零件的方法。通过混合元素或合金粉
末并在模
具中压实混合物，再烧结或在环境可控炉内加热制成最终形状。
?
Material
材料
The
majority
of
the
structural
components
produced
by
fixed
die
pressing
are
iron-based. The powders are elemental,
pre-alloyed, or partially alloyed.
大多数用固定模压制的结构件都是铁基的。粉末可以是单一元素、预先合金或部分
合金。
Elemental
powders,
such
as
iron
and
copper,
are
easy
to
compress
to
relatively
high
densities, produce pressed compacts
with adequate strength for handling during
sintering, but do not produce very high
strength sintered parts.
诸如铁、
铜之类的单一元素粉末较容易被压得相对密度较高、
生产具备足够强度的压制物供
烧结处理，但是无法制造出很高强度的烧结零件。
Pre-alloyed powders are harder,
less compressible and hence require
higher pressing
loads
to
produce
high
density compacts.
However,
they
are
capable
of producing high strength sintered
materials.
预先合金粉末比较硬、
不容易压实，
因此需要较高的挤压力来产生高密度的压制物。<
/p>
然而它们能生成高强度烧结材料。
Pre-alloying
is
also
used
when
the
production
of
a
homogeneous
material
from
elemental
powders
requires
very
high
temperatures
and
long
sintering
times.
The
best
examples
are the stainless steels, whose chromium and
nickel contents have to be
pre-alloyed
to allow economic production by powder
metallurgy.
如果用单一元素粉末生产均匀材料需要很高温度和较长烧结时
间，
也可用预先合金。
最好的
例子是不
锈钢，因含有铬和镍成分，所以粉末冶金必须用预先合金才经济。
Partially
alloyed
powders
are
a
compromise
approach.
Elemental
powders,
e.g.
iron with 2wt.% copper,
are mixed to produce an homogeneous blend which is
then
partially sintered to attach the
copper particles to the iron particles without
producing a fully diffused powder but
retaining the powder form.
部分合金粉末是一种折衷的方法。
单一元素粉末，
例如铁与
2%
的铜
(
重量百分比
)
混
合均匀，<
/p>
经部分烧结后铜微粒粘附到铁微粒上而没有产生充分扩散的粉末却保留了粉末的形
态。
In
this
way
the
compressibilities
of
the
separate
powders
in
the
blend
are
maintained
and the blend
will not segregate during transportation and use.
用这种方法混合物中单独粉末的可压缩性得以维持，在运送和使用期间结合将不会分离。
A
similar
technique
is
to
“glue”
the
small
percentage
of
alloying
element
onto
the
iron
po
wder.
This
“glueing”
technique
is successfully
used
to
introduce
carbon
into the
blends,
a
technique
which
prevents
carbon
segregation
and
dusting,
producing
so-
called “clean” powders.
另一种类似的技术是把小百分比的合金元素“粘
合”到铁微粒上。这种“粘合”技
术已成功用于将碳引入结合物，一种防止碳分离并起尘
的技术，生产所谓的“清洁”粉末。
?
Powder
Consolidation
粉末合成
Components
or
articles
are
produced
by
forming
a
mass
of
powder
into
a
shape,
then
consolidating to form inter-particle metallurgical
bonds.
通过将大量的粉末放入模具成型
为零件或物品，
然后合成为内有微粒的冶金结合物。
An elevated temperature diffusion
process referred to as sintering, sometimes
assisted
by
external
pressure,
accomplishes
this.
The
material
is
never
fully
molten,
although
there
might
be
a
small
volume
fraction
of
liquid
present during the
sintering process. Sintering can be
regarded as welding the particles present in
the initial useful shape.
提升
温度扩散工艺被称为烧结，
有时还辅之以外界的压力来达到目的。
虽然在烧结过程中可
能会有少量液态出现，
但材料决不是全熔
化。
烧结可以被看作是把微粒焊接成初始的有用形
状。
As a general rule both
mechanical and physical properties improve with
increasing
density.
Therefore
the
method
selected
for
the
fabrication
of
a
component
by
powder
metallurgy
will
depend
on
the
level
of
performance
required
from
the
part.
Many components are adequate when
produced at 85~90% of theoretical full density
whist others require full density for
satisfactory performance.
作为普遍规律，随着密度的增加机械和物理性能均改善。因此选择何种粉末冶金方
法来制作零件取决于其所需的性能级别。许多零件只需理论全密度的
85~90%<
/p>
而其它的则需
全密度才能满足要求。
Some
components,
in
particular
bush
type
bearings
often
made
from
copper
and
its alloys, are
produced with significant and controlled levels of
porosity, the
porosity being
subsequently filled with a lubricant.
Fortunately there is a wide choice of
consolidation techniques available.
有些零件，尤其是衬套式轴承常用铜及其合金制作，控制多孔性程度的意义重大，
因为这些孔随后要填充润滑剂。
还好有多种合成技术可供选择。
Cold Uniaxial Pressing
Elemental
metal,
or
an
atomized
pre-
alloyed
powder
is
mixed
with
a
lubricant,
typically
lithium stearate(0.75 wt.%), and pressed at
pressures of say, 600MPa
(87,000lb/in.2) in metal dies.
冷单向挤压
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
< br>600MPa (87,000lb/in.2)]
挤压。
Cold
compaction
ensures
that
the
as-
compacted,
or
“green”,
component
is
dimensionally very
accurate, as it is moulded precisely to the size
and shape of
the die.
冷挤压能保证被压制或“未加工”的零件尺寸十分精确，因为它被精确地按模具的
尺寸和形状成型。
One disadvantage of this technique is the
differences in pressed density
that
can
occur
in
different
parts
of
the
component
due
to
particle/particle
and
die
wall/particle
frictional
effects.
Typical
as-pressed
densities
for
soft
iron
components would be 7.0g/cc, i. e.
about 90% of theoretical density.
这种技术的缺点之一是由于微粒
/
微粒
和模壁
/
微粒间的摩擦效应，零件不同部位的
< br>压实密度存在差异。典型的软铁零件压制密度为
7.0g/cc
< br>，即大约是理论密度的
90%
。
Compaction
pressure
rises
significantly
if
higher
as-
pressed
densities
are
required,
and
this
practice
becomes
uneconomic
due
to
higher
costs
for
the
larger
presses
and
stronger tools to
withstand the higher pressures.
如果需要较高的
压实密度则压实压力要显著提高，
因为大型压力机成本较高并且在较高压力
下模具强度要更高这样就不合算。
Cold
Isostatic Pressing
Metal
powders are contained in an enclosure e.g. a
rubber membrane or a
metallic can that
is subjected to isostatic, which is uniform in all
directions,
external pressure. As the
pressure is isostatic the as-pressed component is
of
uniform density.
冷均衡挤压
金属粉末装入均衡受压的橡胶膜或金属罐内，
其所受外压力在各个方向都
是均匀的。
由于压力是均衡的，所以压制零件密度是均匀的。
Irregularly
shaped
powder
particles
must
be
used
to
provide
adequate
green
strength
in the as-pressed
component. This will then be sintered in a
suitable atmosphere
to yield the
required product.
必须采用不规则形状粉末微粒为压制零件提供足
够的未加工强度。
然后放入合适的环境中烧
结成所需产品。
Normally this technique
is only used for semi-fabricated products such as
bars,
billets,
sheet,
and
roughly
shaped
components,
all
of
which
require
considerable secondary operations to
produce the final, accurately dimensioned
component.
通常这种技术只用于制作诸如棒料、坯段、薄板及粗糙成型零件之类的半成品，所
有
这些都需要大量进一步加工才能生产出最终尺寸精确的零件。
Again, at economical working pressures,
products are not fully dense and usually
need additional working such as hot
extrusion, hot rolling or forging to fully
density the material.
此外使用经济
工作压力的产品不是充分致密的，
一般需要增加诸如热挤压、
热
轧或锻之类的
额外工序来使材料达到全密度。
Sintering
Sintering
is
the
process
whereby
powder
compacts
are
heated
so
that
adjacent
particles
fuse
together,
thus
resulting
in
a
solid
article
with
improved
mechanical
strength compared to the powder
compact.
烧结
烧结就是通过把粉末压制物加热使邻近的微粒熔合在一起的工艺，它能生成比粉末
压制物机械强度更好的固体物。
This
“fusing” of particles results in an increase in
the density of the part and
hence
the
process
is
sometimes
called
densification.
There
are
some
processes
such
as
hot
isostatic
pressing
which
combine
the
compaction
and
sintering
processes
into
a single step.
< br>微粒的
“熔合”
导致零件密度增加，
因此该工艺有时被称为致密化。还有一些工艺如热均衡
挤压，将压实和烧结工艺合并
为单一步骤。
After
compaction the components pass through a sintering
furnace. This
typically has two heating
zones, the first removes the lubricant, and the
second
higher temperature zone allows
diffusion and bonding between powder particles.
零件压实后通过烧结炉。一般有两个加热区，第
一个去除润滑剂，第二个温度更高
的区域让粉末微粒之间扩散并结合。
< br>
A range of atmospheres, including
vacuum, are used to sinter different materials
depending
on
their
chemical
compositions.
As
an
example,
precise
atmosphere
control
allows iron/carbon
materials to be produced with specific carbon
compositions and
mechanical properties.
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。
The density of the component can also change
during sintering, depending
on the
materials and the sintering temperature. These
dimensional changes can be
controlled
by
an
understanding
and
control
of
the
pressing
and
sintering
parameters,
根据材料和烧结温度的不同，零件的密度在烧结
过程中也会改变。因为尺寸的变化
可以通过了解并调节挤压及烧结参数进行控制，
and
components
can
be
produced
with
dimensions
that
need
little
or
no
rectification
to meet the
dimensional tolerances. Note that in many cases
all of the powder used
is present in
the finished product, scrap losses will only
occur when secondary
machining
operations are necessary.
所以零件尺寸几乎无需校正就
能满足尺寸公差。
可以看到在很多情况下所有使用的粉末都包
含
在制成品中，废料损失仅产生于需要辅助机加工时。
Hot
Isostatic Pressing
Powders are
usually encapsulated in a metallic container but
sometimes in
glass.
The
container
is
evacuated,
the
powder
out-gassed
to
avoid
contamination
of
the materials by any residual gas
during the consolidation stage and sealed-off.
热均衡挤压
粉末通常封装在金属容器内有时也装在玻璃容器内。把容器抽真空，粉末抽气是为
了防止材料在合成阶段和密封时被残留气体污染。
It is then heated and subjected to
isostatic pressure sufficient to plastically
deform both the container and the
powder.
再加热并施加均衡压力足以使容器和粉末都塑性变形。
The
rate
of
densification
of
the
powder
depends
upon
the
yield
strength
of
the powder at the temperatures and
pressures chosen. At moderate temperature the
yield
strength
of
the
powder
can
still
be
high
and
require
high
pressure
to
produce
densification in an
economic time.
粉末致密率取
决于该粉末在选定温度和压力下的屈服强度。中等温度下粉末的屈服
强度仍然较高，因此
需要较高压力使其在经济时间内致密化。
Typical
values might be 1120
℃
and
100MPa for ferrous alloys. By pressing at very
much
higher
temperatures
lower
pressures
are
required
as
the
yield
strength
of
the
material is lower. Using
a glass enclosure atmospheric pressure(15psi) is
used to
consolidate bars and larger
billets.
对铁合金典型的数值为
1120
℃和
100MPa
。由于很高温度下材料的屈服强
度较低，因此只需
较低压力就能挤压。采用玻璃容器时可用大气压力
(15psi)
合成棒料和较大坯段。
The technique requires
considerable financial investment as the pressure
vessel
has
to
withstand
the
internal
gas
pressure
and
allow
the
powder
to
be
heated
to high temperatures.
因为压力容器必须经受住内气压并允许粉末加热到较高温度，所以这种技术需要相
当可观的资金投入。
As
with
cold isostatic pressing
only semi-finished
products
are produced,
either for subsequent
working to smaller sizes, or for machining to
finished
dimensions.
此工艺与采用冷均衡挤压一样只能生产半成品，可以通过后续加工至较小尺寸，也
能用机加工到最终尺寸。
Hot
Forging (Powder Forging)
Cold
pressed
and
sintered
components
have
the
great
advantage
of
being
close
to
final shape (near-net shape), but are not fully
dense. Where densification is
essential
to
provide
adequate
mechanical properties,
the
technique
of
hot
forging,
or powder forging,
can be used.
热锻
(
粉
末锻造
)
冷挤压和烧
结零件主要优点是接近最终形状
(
近似纯形
)
，但不是充分致密的。当为
了提供足够的机械性能而致密
化是必须时，可以采用热锻或粉末锻造技术。
In powder forging an as-pressed component is
usually heated to a forging
temperature
significantly
below
the
usual
sintering
temperature
of
the
material
and
then forged in a closed
die. This produces a fully dense component with
the shape
of the forging die and
appropriate mechanical properties.
在粉末锻造中，压制零件一般加热到远低于该材料通常烧结温度的锻造温度，然后
在闭模中锻造。这能生产具有锻模形状和合适机械性能的充分致密零件。
Powder
forged
parts
generally
are
not
as
close
to
final
size
or
shape
as
cold
pressed
and sintered parts. These results from the
allowances made for thermal
expansion
effects and the need for draft angles on the
forging tools. Further,
minimal
machining
is
required
but
when
all
things
are
considered
this
route
is
often
very cost-effective.
粉末锻造零件通常不像冷挤压和烧结零件那样接近最终尺寸或形状。这是由于为热
膨胀效应而设置允差以及在锻模上需要拔模斜角所致。
此外还需少量机
加工，
但全面考虑这
种方法通常还是很划算的。
Metal Injection Moulding (MIM)
Injection moulding is very
widely used to produce precisely shaped plastic
components in
complex dies. As injection pressures are low it
is possible to
manufacture
complex
components,
even
some
with
internal
screw
threads,
by
the
use
of side cores and split tools.
金属注塑成型
(MIM)
注塑成型被很广泛地用于在复杂模具中生产形状精确的塑料零件。注塑压力较低使
得制作复杂零件成为可能，通过采用侧面型芯和分离工具甚至可以带有内螺纹。
By
mixing
fine,
typically
less
than
20
μ
m
diameter,
spherical
metal
powders
with thermoplastic
binders, metal filled plastic components can be
produced with
many of the features
available in injection moulded plastics. After
injection
moulding, the plastic binder
material is removed to leave a metal skeleton
which
is then sintered at high
temperature.
将细小
(
直径一般小于
20
μ<
/p>
m)
球形金属粉末与热塑性粘合剂混合，能生产具有多数
注塑成型塑料特征的金属充满塑料零件。
注塑成型后，
< br>去除塑料粘合材料剩下金属骨架，
然
后在高温下烧结。<
/p>
Dimensional control
can be exercised on the as-sintered component as
the
injected density is sensibly
uniform so shrinkage on sintering is also uniform.
烧结零件可以实现尺寸控制，因为注塑密度明显
均匀，所以烧结收缩也是均匀的。
Shrinkage can be large, due to both the fine
particle size of the powders
and the
substantial proportion of polymer binder used.
由于所用粉末细小微粒的尺寸和聚合物粘合剂的
真实比例，收缩可以比较大。
?
Features
特征
?
For
high
tolerance
parts,
a
sintering
part
is
put
back
into
a
die
and
repressed.
In genera this
makes the part more accurate with a better surface
finish.
?
对较大公差的零
件，
烧结后可放回模具重新挤压。
一般而言这会使零件更精确同
时具有
更好的表面光洁度。
?
A
part
has
many
voids
that
can
be
impregnated.
One
method
is
to
use
an
oil
bath.
Another
method uses vacuum first, then impregnation.
?
零件有许多可供填充的空间。
一种方法是采用油浴。
另一种方法是先抽真空然后再充满。
?
A part
surface can be infiltrated with a low melting
point metal to increase
density,
strength, hardness, ductility and impact
resistance.
?
Plating, heat treating and machining
operations can also be used.
?
零件表面能被低熔点金属渗透以增
大密度、强度、硬度、延展性和抗冲击能力。
?
仍然可以进行电镀、热处理和机加工作业。
?
Advantages
优点
?
Good tolerances and surface finish
?
Highly complex
shapes made quickly
?
Can produce porous parts and hard to
manufacture materials (e.g. cemented
oxides)
?
良好的公差和表面光洁度
?
高度复杂的形状能快速制作
?
能制作多孔零件和难以加工材料<
/p>
(
如粘结氧化物
)
?
Pores in the
metal can be filled with other materials/metals
?
Surfaces can
have high wear resistance
?
Porosity can be controlled
?
Low
waste
?
Automation is easy
?
金属中的气孔可用其它材料
/
金属填充
?
表面能具有较高的耐磨性
?
孔隙率可以控制
?
较低损耗
?
容易自动化
?
Physical
properties can be controlled
?
Variation from
part to part is low
?
Hard to machine metals can be used
easily
?
No
molten metals
?
物理性能可以控制
?
零件之间的变化较小
?
难以机加工的金属能被容易使用
?
无需熔化金属
?
No need for
many/any finishing operations
?
Permits high
volume production of complex shapes
?
Allows non-
traditional alloy combinations
?
Good control of
final density
?
不
需要很多
/
任何修整作业
?
允许加工复杂形状的大体积产品
?
允许非传统合金结合
?
对最终密度能很好地控制
?
Disadvantages
缺点
?
Metal powders deteriorate quickly when
stored improperly
?
Fixed and setup costs are high
?
Part size is
limited by the press and compression of the powder
used
?
如果存放不当金属粉末质量很快降低
?
安装和调整的成本较高
?
零件尺寸受压力机和所用粉末压缩的限制
?
Sharp corners
and varying thickness can be hard to produce
?
Non-moldable
features are impossible to produce
?
锐角和变厚度较难加工
?
不适合模压的东西不可能生产
第六单元
Injection molding (Fig.6.1) is
the predominant process for fabrication of
thermoplastics
into
finished
forms,
and
is
increasingly
being
used
for
thermosetting
plastics,
fiber-filled composites, and elastomers.
注塑成型
(
图
6.1)
是将热塑性塑料制成最终形状的主要工
艺，并且越来越多地用于
热硬化性塑料、纤维填充合成物和人造橡胶。
< br>
It
is
the
process
of
choice
for
tremendous
variety
of
parts
ranging
in
weight
from
5g
to
85kg.
It
is
estimated
that
25%
of
all
thermoplastics
are
injection
molded.
它
是重量范围为
5g
到
85kg
极大一类零件可选用的工艺。估计所有热塑性塑料中有
25%
是采用注塑成型的。
If
newer
modifications,
such
as
reaction
injection
molding,
and
the
greatly
increased rate of adoption of plastics
as substitutes for metals are considered,
it is likely that the worldwide
industrial importance of injection molding will
continue to increase.
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
< br>塑成型在世界范围的工业重要性很可能将继续增加。
Currently,
probably
close
to
half
of
all
major
processing
units
is
injection
molding
machines.
In
1988,
a
dollar
sale
of
new
injection
molding
machinery
in
the
U.S.
was
approximately
65%
of
total
major
polymer
machinery
sales
volume;
this
included
4,600
injection molding units.
当前
，大概所有主要处理设备的近一半是注塑成型机。
1988
年，
美国新的注塑成型机械销
售约占全部主要聚合物机械销售量的
6
5%
，其中包括
4,600
台注塑成型
设备。
The
machines
and
their
products
are
ubiquitous
and
are
synonymous
with
plastics
for
many people.
这类机械和它们的产品普遍存在，
对许多人来说与塑料是同义的。
A
reciprocating screw injection molding machine
combines the functions of
an extruder
and a compressive molding press.
往复螺旋注射成型机把压出机和成型压力机的功能结合起来。
It takes solid granules of
thermoplastic resin, melts and pressurizes them in
the
extruder section, forces the melt
at high velocity and pressure through carefully
designed flow channels into a cooled
mold, then ejects the finished part(s), and
automatically recycles.
把热塑
性塑料树脂的固体颗粒在压出部分融化并增压，
迫使其高速融化并通过仔细设计的流
动通道进入冷却模具，喷射成最终零件，然后自动再循环。
This machine is a descendant of the
plunger type “stuffing machine” patented by
the
Hyatt
brothers
in
1872
to
mold
celluloid.
In
1878,
the
Hyatts
developed
the
first
multicavity
mold,
but
it
was
not
until
1938
that
Quillery
(France)
patented
a
machine
incorporating a
screw to plasticize the elastomer being molded.
这种机械是
1872
年
Hyatt
兄弟获得专利权的融化赛璐珞的活塞型
“填充机
”
的派生物。
1878
年
Hyatt
兄弟开发了第一个多槽模具，
但直到<
/p>
1938
年
Quillery(
法国
)
才发明了用螺旋增塑
人造橡胶并使其成型的一体化机械。
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.
1956
年，
Ankerwerk <
/p>
Nuremberg
使用于热塑性塑料的现代往复螺旋注塑成型机
商业化。
今天，
已有超过
50
家制造商列入现代塑料制品百科全书，
能为美国市场提供压制能力从
2
到
6,000
吨
的机械。
(A machine with a
10,000-ton capacity has been built to
mold
264-gallon
HDPE trash
containers.) A
host of suppliers of auxiliary equipment, molds,
instruments, and
controls service this
major segment of the polymer industry.
(
一台能力为
10,000
吨用于成型
264
加仑高密度聚乙烯垃圾箱的机械也已制成
)
。许多辅助
设备、模具、仪器和控制系统供应商在为
聚合物工业的这一主要部分服务。
Injection molding is particularly worthy of
intensive study because it
combines
many areas of interest extrusion, mold design,
rheology, sophisticated
hydraulic
and
electronic
controls,
robotic
accessories,
design
of complex
products,
and, of course, the integration of
materials science and process engineering.
注塑成型对深入研究很有价值，因为它结合了许
多重要领域，如挤压、模具设计、
流变学、完备的液压和电子控制、机器人配件、复杂产
品的设计，
当然还有材料科学与加工
工程的综合。
The
objectives
of
injection
molding
engineers
are
simple
enough:
to
obtain
minimum
cycle
time
with
minimum
scrap,
to
attain
specified
product
performance
with
assurance, to minimize production costs
due to downtime or any other reasons, and
to steadily increase in expertise and
competitiveness.
注塑成型工程师的目标很简单：
< br>在最少废料的情况下取得最小循环时间，
在有保证的情况下
获得指定产品性能，
将由停工或其它原因产生的生产成本最小化，
还有稳定地增加专门知识
和竞争力。
Profit margins for custom injection
molders are said to be generally skimpy; an
established way to improve profits is
to be selected for more demanding, higher
margin jobs that demand the highest
level of efficiency and competence.
传统的
注塑成型机利润盈余据说一般是不足的；
为了更多需求及更高盈余工作需要选择一种
改善利润的确定方法，它要求最高水平的效率和能力。
This
text
will
concentrate
on
the
reciprocating
screw
machine
for
thermoplastics, which has largely
replaced the older reciprocating plunger types
except for very small-capacity
machines.
本文将集中论述热塑性塑
料用的往复螺旋机，除了小容量机械外它已在很大程度上
取代了较老的往复活塞式机械。
?
Injection Molding Materials
注塑成型材料
It
is not possible to injection-mold all polymers.
Some polymers like PTFE
(Poly-tetra-
fluoro-ethylene), cannot be made to flow freely
enough to make them
suitable for
injection molding.
要注
塑成型所有聚合物是不可能的。像聚四氟乙烯之类的聚合物就不能自由流动得
足以适合注
塑成型。
Other polymers, such as
a mixture of resin and glass fiber in woven or
mat form,
are unsuitable
by
their
physical
nature
for
use
in
the
process.
In
general,
polymers
which are capable of being brought to a
state of fluidity can be injection-molded.
其它聚合物，
例如树脂和编织的或垫子形的玻璃纤维的混合物，
由于它们的物理性质不适合
使用此工艺。一般而言，能进入流动状态的聚合物都
可以注塑成型。
The
vast
majority
of
injection
molding
is
applied
to
thermoplastic
polymers.
This class of materials consists of
polymers which always remain capable of being
softened by heat and of hardening on
cooling, even after repeated cycling.
注塑成型的绝大多数都用于热塑性聚合物。这类材料由具有加热软化、冷却硬化甚
至可重复循环能力的聚合物组成。
This
is
because
the
long-chain
molecules
of
the
material
always
remain
as
separate
entities and do
not form chemical bonds to one another. An
analogy car, be made
to a block of ice
that can be softened (i.e. turned back to liquid),
poured into
any shape cavity, and then
cooled to become a solid again.
这是由于这类
材料的长链分子总是保持分离的实体并不相互形成化学连结。
一辆由冰块制成
的模拟汽车，可以融化
(
即转化为液态
)
，倒入任何形状的空腔，然后冷却重新变成固体。
This property differentiates
thermoplastic materials from thermosetting ones.
In
the
latter
type
of
polymer,
chemical
bonds
are
formed
between
the
separate
molecule
chains during processing. In this case
the chemical bonding referred to as cross
linking is the hardening mechanism.
这个特性将热塑性材料与热硬化性材料区分开。
后者在加工过程中分离
的分子链之间形成化
学连结。在此情况下作为交联的化学连结是硬化机制。
In
general,
most
of
the
thermoplastic
materials
offer
high
impact
strength,
corrosion
resistance,
and
easy
processing
with
good
flow
characteristics
for
molding
complex designs.
Thermoplastics are generally divided into two
classes: namely
crystalline and
amorphous.
一般而言，大多数热
塑性材料具有较高的抗冲击强度、耐腐蚀性以及良好流动性使
其容易加工而适于复杂成型
设计。热塑性塑料通常分为两类：即结晶质的和非结晶质的。
Crystalline polymers have an ordered
molecular arrangement, with a sharp melting
point. Due to the ordered arrangement
at molecules, the crystalline polymers
reflect most incidents light and
generally appear opaque.
结晶质聚合物具有规则的分子
排列及明显的熔点。
由于规则的分子排列，
结晶质聚合物能反<
/p>
射大多数特定光线并一般表现为不透明的。
They also undergo a high shrinkage or
reduction in volume during solidification.
Crystalline polymers usually are more
resistant to organic solvents and have good
fatigue and wear-resistant properties.
Crystalline polymers also generally are
denser and have better mechanical
properties than amorphous polymers.
它们
在固化过程中收缩较大或体积减少较多。
结晶质聚合物通常多能抵御有机溶剂并具有良<
/p>
好的抗疲劳和磨损特性。
结晶质聚合物通常也比非结晶质聚合物更
致密并且具有更好的机械
性能。
The main exception to this rule is
polycarbonate, which is the amorphous polymer
of choice for high quality transparent
moldings, and has excellent mechanical
properties.
其中主要例外是聚碳酸酯，
它是可选用做高质量透明注塑件的非结晶质聚合物，
并具有卓越
的机械性能。
The
mechanical
properties
of
thermoplastics,
while
substantially
lower
than
those
of
metals,
can
be
enhanced
for
some
applications
through
the
addition
of
glass
fiber
reinforcement.
This
takes
the
form
of
short-chopped
fibers,
a
few
millimeters
in length, which are
randomly mixed with the thermoplastic resin.
就本质而言，热塑性塑料的机械性能低于金属，
但可以通过加入玻璃纤维强化予以
增强来适应某些运用。常用几毫米长的短碎纤维随机地
与热塑性树脂混合。
The fibers
can
occupy up to one
third
of the material
volume to
considerably
improve
the
material
strength
and
stiffness.
The
negative
effect
of
this
reinforcement
is
usually
a
decrease
in
impact
strength
and
an
increase
in
abrasiveness.
纤维可占材料体积的三分之一以极大改善材料的
强度和硬度。这种加强的负作用通
常是抗冲击强度降低及磨损性增加。
< br>
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.
后者对加工过程也有影响，
因为模具腔的寿命从
典型的普通树脂零件大约
1,000,000
件减少
到玻璃纤维填充树脂零件的约
300,000
件。
Perhaps the main
weakness of injection-molded parts is the
relatively low
service temperatures to
which they can be subjected. Thermoplastic
components can
only rarely be operated
continuously above 250
℃
,
with an absolute upper service
temperature of about
400
℃
.
注塑成型零件的主要缺点或许是它们能承受的工作温度相对较低。热塑性塑料零件
只有很少能连续运行在
250
℃以上，其绝对最高工
作温度约为
400
℃。
The temperature
at which a
thermoplastic
can be
operated under load can
be
defined
qualitatively
by
the
heat
deflection
temperature.
This
is
the
temperature
at
which
a simply supported
beam specimen of the material, with a centrally
applied load,
reaches a predefined
deflection.
热塑性塑料带载运行温度可从质量上定义为热偏差温度。
这是中心承载的该材料简支梁达到
预定偏差的温度。
The temperature value obviously
depends upon the conditions of the test and the
allowed deflection and for this
reason, the test values
are
only really
useful
for
comparing different polymers.
其温度值明显取决于试验条件和允许偏差，
因此对比较不同的聚合物而言只有试验数
据是真
正有用的。
?
Cycle of
Operation
作业循环
The
reciprocating
screw
injection
molding
machine
is
considered
as
consisting of two halves: a fixed
injection side, and a movable clamp side.
往复螺旋注塑成型机被认为由两部分组成：一个
固定注塑端和一个活动夹具端。
The injection
side contains the extruder that receives solid
resin in pellet or
granular
form
and
converts
it
into
a
viscous
liquid
or
melt
that
can
be
forced
through
the connecting nozzle, spine, and
runners to the gates that lead into the mold
cavities.
注塑端包含压出机，它接受小球或粒状
的固体树脂，然后将其转化为粘性液体或称为融化，
再强迫其通过连接喷嘴、中心和浇道
到闸道进入模具腔。
The
mold
is
tightly
clamped
against
injection
pressure
and
is
cooled
well
below
the
melt temperature of the
thermoplastic. When the parts in the cavities have
cooled
sufficiently the mold halves are
opened at the mold parting plane and the parts
ejected by a knockout system drop into
a receiving bin below.
模具被紧紧地夹住以抵抗注塑压力
，
并在热塑性塑料的融化温度以下很好地冷却。
当模腔内
的零件充分冷却，
剖分模在模具分模面处打开，
推出系统将零件推出落入下面的接收容器内。
This
summarizes
the
overall
cycle,
but
leaves
out
much
vital
detail
that
is
necessary
for understanding the process. However,
with this introduction, it is possible to
understand the advantages and
disadvantages of the process.
这概述了整个循环，
但省略了许多对理解此工艺所必需的很重要细节。
然而通过本介
绍，
了
解这种工艺的优缺点仍是可能的。
?
Effects of
Process Variables on Orientation
加工变量对方向性的影响
In
injection
molding,
any
variation
in
processing
that
keeps
the
molding
resin
hot throughout filling
allows increased relaxation and, therefore,
decreased
orientation.
Some
of
the
steps
that
can
be
taken
to
reduce
orientation
are
as
follows.
在注塑成型时，整个填料过程始终保持成型树脂高温的任何加工变化都会增加松弛
作用而减少方向性。下面是可以用于减少方向性的若干措施。
?
Faster
injection
(up
to
a
point):
less
cooling
during
filling,
hence
a
thinner
initial frozen layer, lower viscosity
due to shear thinning; better flow to
corners; and less crystallinity all
favor lower subsurface orientation. The
primary
effect
is
that
the
gate
will
freeze
more
quickly.
At
that
point,
orientation
stops and relaxation starts.
?
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。
?
Higher melt and mold temperatures:
lower melt viscosity, easier filling, and
greater relaxation favor reduced
orientation.
?
Reduced
packing time
and pressure:
overpacking
inhibits
relaxation
processes.
?
较高的融化和成型温度：融化粘性较低，更容易填充，较大松弛作用促成方向性减少。
?
减少挤压时间和压力：过度挤压会抑制松弛过程。
?
Reduced
gate
size:
larger
gates
take
longer
to
freeze
off
and
permit
increased
orientation.
?
减小闸道尺寸：闸道越大则固化时间越长并会使方向性增加。
Excessively high injection speed
can cause high surface orientation and
increase susceptibility to stress
cracking. For example, moldings that are to be
electroplated, and will be subject to
acid solutions during plating, must be made
using very slow injection speeds to
minimize surface orientation.
<
/p>
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。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
of
the
melt
front
in
most
moldings
can
cause
transverse
subsurface
orientation
superimposed
on
the
primary
orientation,
giving a
desirable biaxial 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
to
flow
during
filling
of
the
cavity.
Flow
around
an
obstruction
causes
a
decrease
in
melt
front
speed
and
leads to high local
viscosity and reduced relaxation. This is also
likely to occur
near the end of the
filling phase if gating is inadequate.
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。
The molder must recognize the
dangers of excessive fill speed, insufficient
injection
pressure,
excessive
melt
temperature,
and
inadequate
packing.
These
dangers are weighed
against the opposing effects on orientation
discussed above.
注塑工必
须认识过快填充速度、不足注塑压力、过高融化温度和不充分挤压的危害
性。这些危害性
要与上述方向性的反向效应相权衡。
Thicker
parts
delay
cooling
and
increase
relaxation
time
and
tend
to
result
in
lower
orientation.
Thicker
parts
also
tend
to
warp
less.
Therefore,
a
minimum
wall
thickness can be established by
experience for various shapes, materials, and
process combinations.
较厚零件
会延迟冷却并且增加松弛时间，
趋向于导致较低的方向性。
较厚
零件也有助于减少
翘曲。因此，对各种形状、材料和工艺组合能通过经验来确定最小壁厚
。
Lower
molecular
weight
and
broader
molecular
weight
distribution
in
thermoplastics
favor lower orientation and reduced
internal stress in moldings.
在热塑性塑料中较小的
分子量以及较宽泛的分子量分布促成方向性减少同时降低注塑件中
的内应力。
The skin thickness ratio
is affected by
process
variables in the
same way as
one would predict for the orientation;
that is, it decreases as the melt or mold
temperatures
and
cavity
pressure
increases.
Tensile
strength
and
stiffness
increase
as skin thickness ratio increases.
Microscopic examination thus provides another
way of studying the process
efficiently.
外壳厚度比受加工
变量影响的方式与方向性预测一样；也就是它能随融化或成型温
度及模腔压力的增加而减
少。
拉伸强度和硬度随外壳厚度比增加而增加。
因而显微镜检查
提
供了有效研究该工艺的另一方法。
?
Advantages
优点
1.
High
production
rates.
For
example,
a
CD
disk
can
be
produced
with
a
10~12s
cycle in high melt
flow index PC.
1.
高生产率
：例如，一张
CD
盘在高融体流动指数生产控制中只需
10~12s
一个循环
就能生产出来。
2. Relatively low labor
content. One operator can frequently take care of
two or more machines, particularly the
moldings are unloaded automatically onto
conveyors.
2.
相对较少的工作内容：
一个操作者经常可以照看两台以上机械，
尤其是当成品能
自动卸到输送机上时。
3.
Parts
require
little
or
no
finishing.
For
example,
flash
can
be
minimized
and
molds
can
be
arranged
to
automatically
separate
runners
and
gates
from
the
part
itself.
4. Very complex shapes can be
formed. Advances in mold tooling are largely
responsible.
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。
4.
非常复杂的形状也能成型：模具的进步很大程度上是可靠的。
5.
Flexibility
of
design
(finishes,
colors, inserts,
materials).
More
than
one material can be
molded through co-injection. Foam core materials
with solid
skins
are
efficiently
produced.
Thermosetting
plastics
and
fiber-reinforced
shapes
are injection molded.
5.
设计的灵活性
(
光洁度、颜色、
插入物、材料
)
：
通过复合注塑可以成型多于一种
材料。
可以高效地生产带有固体外壳的泡沫型芯材料。
热硬化性塑料和纤维
加强形状都可以
注塑成型。
6. Minimum scrap loss. Runners, gates, and scrap
can usually be reground.
Recycled
thermoplastics can be injection molded.
6.
废料损失最小化：
浇道、
闸道和废料通常可以重新研磨。
循环热塑性塑料可以注
塑成型。
7.
Close
tolerances
are
obtainable.
Modern
microprocessor
controls,
fitted
to precision molds, and elaborate
hydraulics, facilitate tolerances in the 0.1%
range
on dimensions
and
weights
(but
not
without
a
high
level
of
operational
skills
in constant attendance).
7.
能得到接近的公差：现代微处理器控制、合适的精密模具和精心制作的液压设
备使得尺寸和重量的公差保持在
0.1%
的范围内
(
但不是没有在持续照看时的高水平操作技
能
)
。
8.
Makes
best
use
of
the
unique
attributes
of
polymers,
such
as
flow
ability,
light weight, transparency, and
corrosion resistance. This is evident from the
number and variety of molded plastic
products in everyday use.
8.
充分利用聚合物诸如流动能力、重量轻、透明和耐腐蚀等独特属性：从日常使用
< br>成型塑料产品的数量和种类就能明显看到。
?
Disadvantages
and Problems
缺点和问题
1. High investment in equipment
and tools requires high production volumes.
2. Lack of expertise and good
preventive maintenance can cause high startup
and running costs.
1.
较高的设备和模具投资需要较高生产量才合算。
2.
缺少专门技术和良好的预防性维修会导致较
高的启动和运行成本。
3. Quality
is sometimes difficult to determine immediately.
For example,
post-mold
warpage
may
render
parts
unusable
because
of
dimensional
changes
that
are
not completed for weeks or months after
molding.
3.
质量有时难以马上确
定。
例如，
成型后的翘曲会导致零件不能用，
< br>因为在成型后
几星期甚至几个月尺寸变化都不能完成。
4.
Attention
is
required
on
many
details
requiring
a
wide
variety
of
skills
and cross-disciplinary knowledge.
5. Part design sometimes is not
well suited to efficient molding.
4.
对许多需要广泛多样性技能和交叉学科知识的细节必须加以注意。
5.
零件设计有时不能很好地适应有效率的成型。
6. Lead time for mold design,
mold manufacture and debugging trials is
sometimes very long.
6.
模具设计、模具制造和调试试验这些先导工作有时要花费很长时间。
第七单元
The
importance
of
machining
processes
can
be
emphasised
by
the
fact
that
every
product we use in our daily life has
undergone this process either directly or
indirectly.
(1) In
USA, more than $$100 billions are spent annually on
machining and
related operations.
机加工过程的重要性可通过日常生活使用的每件
产品都直接或间接经历这一过程的
事实来强调。
(1)
在美国，每年花在机加工及其相关作业上的
费用都多于千亿美元。
(2) A
large majority (above 80%) of all the machine
tools used in the
manufacturing
industry have undergone metal cutting.
(3)
An
estimate
showed
that
about
10
to
15%
of
all
the
metal
produced
in
USA
was converted into
chips.
(2)
用于制造业的全部机床
中的大多数
(
多于
80%)
都经历过金属切削。
(3) <
/p>
有估计显示美国生产的所有金属中约
10
到
15%
转变成了切屑。
These facts show the importance
of metal cutting in general manufacturing.
It is therefore important to understand
the metal cutting process in order to make
the best use of it.
这些事实说明了金属切削在常规制造中的重要性。因此了解金属切削过程以充分利
用它是重要的。
A number of
attempts have been made in understanding the metal
cutting process
and
using
this
knowledge
to
help
improve
manufacturing
operations
which
involved
metal
cutting.
在了
解金属切削过程并运用这些知识帮助改善与金属切削有关的制造作业方面已经做了许
多努
力。
A
typical
cutting
tool
in
simplified
form
is
shown
in
Fig.7.1.
The
important
features to be
observed are follows.
典型切削刀具的简化形式如图
7.1
所示。要注意的重要特征
如下。
1. 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.
1.
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。
2. Clearance angle. This is
the angle between the machined surface and the
underside of the tool called the flank
face. The clearance angle is provided such
that the tool will not rub the machined
surface thus spoiling the surface and
increasing the cutting forces. A very
large clearance angle reduces the strength
of the tool tip, and hence normally an
angle of the order of 5~6°is used.
2.
后角：
这是机加
工面与被称为后侧面的刀具底面夹角。
后角使刀具不产生会损坏
机加工面的摩擦和增加切削力。
很大的后角会削弱刀尖的强度，
因此一般采用
5~6
°的后角。
The conditions which have an
important influence on metal cutting are work
material,
cutting
tool
material,
cutting
tool geometry,
cutting
speed,
feed
rate,
depth
of cut and cutting fluid used.
<
/p>
对金属切削有重要影响的条件有工件材料、刀具材料、刀具几何形状、切削速度、
进给率、切削深度和所用的切削液。
The cutting speed, v, is the speed with which the
cutting
tool
moves through
the work material. This is generally
expressed in metres per second (ms-1).
切削速度
v
指切削刀具经过工件材料的
移动速度。通常用米每秒
(ms-1)
表示。
Feed rate, f, may be defined as the small
relative movement per cycle (per
revolution or per stroke) of the
cutting tool in a direction usually normal to the
cutting speed direction.
Depth of cut, d, is the normal distance between
the unmachined surface and
the machined
surface.
进给率
f
可定义为每循环
(
每转或每行程
)
切削刀具在通常为垂直于切削速度方向的
次要相对运动。
切削深度
d
是未加工面与已加工面之间的垂直距离。
?
Chip
Formation
切屑的形成
Metal cutting process is a very complex process.
Fig.7.2 shows the basic
material
removal operation schematically.
金属切削过程是一个很复杂的过程。图
7.2
< br>用图的形式显示了基本材料去除作业。
The
metal
in
front
of
the
tool
rake
face
gets
immediately
compressed,
first
elastically and then
plastically. This zone is traditionally called
shear zone in
view
of
fact
that
the
material
in
the
final
form
would
be
removed
by
shear
from
the
parent metal.
在刀具前倾面前的金属直接受
到压缩，
首先弹性变形然后塑性变形。
考虑到最终形状中的材<
/p>
料是通过剪切从母体金属去除的，此区域传统上称为剪切区。
The
actual
separation
of
the
metal
starts
as
a
yielding
or
fracture,
depending
upon
the
cutting
conditions,
starting
from
the
cutting
tool
tip.
Then
the
deformed
metal
(called chip) flows
over the tool (rake) face.
金属的实际分离始于屈服
或断裂
(
视切削条件而定
)
，从切削刀尖开始。然后变形金属
(
称为
-
-
-
-
-
-
-
-
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