业余爱好英文关于机械的英文文章

2021年1月27日发(作者：role)
103f
第一单元

? Types of Materials



材料的类型









Materials
may
be
grouped
in
several ways. Scientists
often classify materials
by
their
state: solid, liquid, or gas. They also separate them into organic (once living) and inorganic (never
living) materials.








材料可以按多种方法分类。
科学家常根据状态将材料分为：
固体、
液体或气体。
他
们也把材料分为有机材 料
(
曾经有生命的
)
和无机材料
(
从未有生命的
)
。








For
industrial
purposes,
materials
are
divided
into
engineering
materials
or
nonengineering materials. Engineering materials are those used in manufacture and become parts
of products.








就工业效用而言，材料被 分为工程材料和非工程材料。那些用于加工制造并成为产
品组成部分的就是工程材料。

Nonengineering
materials
are
the
chemicals,
fuels,
lubricants,
and
other
materials
used
in
the
manufacturing process, which do not become part of the product.
非工程材料则是化学品、
燃料、
润滑剂 以及其它用于加工制造过程但不成为产品组成部分的
材料。









Engineering materials may be further subdivided into:
①
Metal
②
Ceramics
③
Composite
④
Polymers, etc.








工程材料还能进一步细分为：
①
金属材料②
陶瓷材料③
复合材料

④
聚合材料，
等等。

? Metals and Metal Alloys

金属和金属合金








Metals are elements that generally have good electrical and thermal conductivity. Many
metals have high strength, high stiffness, and have good ductility.








金属就是通常 具有良好导电性和导热性的元素。许多金属具有高强度、高硬度以及
良好的延展性。

Some metals, such as iron, cobalt and nickel, are magnetic. At low temperatures, some metals and
intermetallic compounds become superconductors.
某些金属能被磁化，
例如铁、
钴和镍。
在极低的温度下，
某些金属和金属化合物能转变成超
导体。








What
is
the
difference
between
an
alloy
and
a
pure
metal?
Pure
metals
are
elements
which come from a particular area of the periodic table. Examples of pure metals include copper
in electrical wires and aluminum in cooking foil and beverage cans.








合金与纯金属的区别是什么？纯金属是在元素周期表中占据特定位置的元素。例如
电 线中的铜和制造烹饪箔及饮料罐的铝。

Alloys contain more than one metallic element. Their properties can be changed by changing the
elements present in the alloy. Examples of metal alloys include stainless steel which is an alloy of
iron, nickel, and chromium; and gold jewelry which usually contains an alloy of gold and nickel.
合金包含不止一种金属元素。
合金的性质能通过改变其中存在的元素而改变。
金属合金的例子有：不锈钢是一种铁、镍、铬的合金，以及金饰品通常含有金镍合金。










Why are metals and alloys used? Many metals and alloys have high densities and are
used in applications which require a high mass-to-volume ratio.








为什么要使用金属和合金？许多金属和合金具有高密度，因此被用在需要较高质量
体积比的场合。
Some
metal
alloys,
such
as
those
based
on
aluminum,
have
low
densities
and
are
used
in
aerospace
applications
for fuel
economy.
Many
alloys
also
have
high
fracture
toughness, which
means they can withstand impact and are durable.
某些金属合金，
例如铝基合金，
其密度低，
可用于航空航 天以节约燃料。
许多合金还具有高
断裂韧性，这意味着它们能经得起冲击并且是耐用的。









What are some important properties of metals?








Density
is
defined
as
a
material’s
mass
divided
by
its
volume.
Most
metals
have
relatively high densities, especially compared to polymers.








金属有哪些重要特性？








密度定义为材料的质量与其体积之比 。大多数金属密度相对较高，尤其是和聚合物
相比较而言。

Materials with high densities often contain atoms with high atomic numbers, such as gold or lead.
However,
some
metals
such
as
aluminum
or
magnesium
have
low
densities,
and
are
used
in
applications that require other metallic properties but also require low weight.
高密度材料通 常由较大原子序数原子构成，
例如金和铅。
然而，
诸如铝和镁之类的一些金属
则具有低密度，并被用于既需要金属特性又要求重量轻的场合。









Fracture toughness can be described as a material’s ability to avoid fracture, especially
when a flaw is introduced. Metals can generally contain nicks and dents without weakening very
much, and are impact resistant. A
football player counts on this when he trusts that his facemask
won’t shatter.


103f







断裂韧性可以描述为材料防止断裂特别是出现缺陷时不断裂的能力。金 属一般能在
有缺口和凹痕的情况下不显著削弱，
并且能抵抗冲击。
橄榄球运动员据此相 信他的面罩不会
裂成碎片。









Plastic deformation is the ability of bend or deform before breaking. As engineers, we
usually design materials so that they don’t deform under normal conditions. Y
ou don’t want your
car to lean to the east after a strong west wind.








塑性变形就是在断裂前弯曲或变形的能力。作为工程师，设计时通常要使材料在正
常条件下不变 形。没有人愿意一阵强烈的西风过后自己的汽车向东倾斜。

However, sometimes we can take advantage of plastic deformation. The crumple zones in a car
absorb energy by undergoing plastic deformation before they break.
然而，
有时我们也能利用塑性变形。
汽车上压皱的区域在它 们断裂前通过经历塑性变形来吸
收能量。








The
atomic
bonding
of
metals
also
affects
their
properties.
In
metals,
the
outer
valence
electrons are shared among all atoms, and are free to travel everywhere. Since electrons conduct
heat and electricity, metals make good cooking pans and electrical wires.








金属的原子连结对它们的特性也有影响。在金属内部，原子的外层阶电子由所有原
子共享并能到处自由移动。
由于电子能导热和导电，
所以用金属可以制造好的烹饪锅和 电线。

It is impossible to see through metals, since these valence electrons absorb any photons of light
which reach the metal. No photons pass through.
因为这些阶电子吸收到达金属的光子，所以透过金属不可能看得见。没有光子能通过金属。









Alloys
are
compounds
consisting
of
more
than
one
metal.
Adding
other
metals
can
affect
the
density,
strength,
fracture
toughness,
plastic
deformation,
electrical
conductivity
and
environmental degradation.








合金是由一种以上金属组成的混合物。加一些其它金属能影 响密度、强度、断裂韧
性、塑性变形、导电性以及环境侵蚀。

For example, adding a small amount of iron to aluminum will make it stronger. Also, adding some
chromium to steel will slow the rusting process, but will make it more brittle.

例如 ，
往铝里加少量铁可使其更强。
同样，
在钢里加一些铬能减缓它的生锈过程，
但也将使
它更脆。

? 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.







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








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
(
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，
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
?
103f
傻纳
??
Ｗ魑
?
娲
??
话悴捎 谩吧战帷被颉氨荷铡惫ひ铡
?
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
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，< br>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 len
gth give them a very 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 the
103f
ir 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 partic
le- 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.







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
(
或分子量
)
、软化及熔化点、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。

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
1,000,000g/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
些温度通常决定聚合物能否使用的上限。< br>
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
(
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

103f
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(
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。< br>







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%
的那些部分对工程师而言不重要，因此将它们删
除。如图
2. 1
所示的简化铁碳状态图将焦点集中在共析区，这对理解钢的性能和处理是十分
有用的。









The
key
transition
described
in
this
diagram
is
the
decomposition
of
single-phase
austenit
e(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 wi
103f
th the iron. When the steel cools to 727
℃
(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。< br>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
℃
(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%
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
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，< br>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< br>)
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 727
℃
(1341
℉
). 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
℃
(1 341
℉
)
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
103f
, 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.

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< br>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 medi
103f
um 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，
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 600
℉
(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
600
℉
(315
℃< br>)
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 al
103f
lowed
to
cool.
These
processes,
known
as
austempering
and
martempering,
result
in
products
having certain desirable physical properties.








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，
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. < br>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、
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
)
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。
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
℃
~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
℉
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。

? 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
?
103f
⒏
哂谄淞俳缥露仁倍蕴季哂星缀狭
Α?

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
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
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