LOGO

43

Metals and Metallurgy

History of Materials Science and Engineering

History of Materials Science and Engineering

Materials have played an important part in our civilization. Entire eras have been named after important materials.

All sorts of materials

Material 1: It is a kind of material with obvious property of conducting heat and electricity. The most common types of the material include steel, iron, copper, aluminum and so on.Metal

Material 2: The material can conduct electricity with a bit of help in the form of added “impurities”. Your CD,DVD player, telephone and radio

semiconductor

All sorts of materials

Material 3: Scientists try to mimic nature’s designs to create materials for other uses, such as using the foam structure of bone as an inspiration for designing materials that are lightweight and strong.

Material 4: It is a kind of material with obvious property of conducting heat and electricity. Plastic, paint and rubber are all made of this material.

biomaterial

Polymer( 聚酯材料）

the advantages of metals(para.1-2)

Compared with metals, plastics are lighter and more corrosion-resistant, but why it is not widely used in industry?(Para.2)

For one thing, plastics are not strong; for another, they cannot be recycled.

Why does man use metals so much today?(Para.1)

Because it offers the required strength and other properties at minimum cost.

metals

What material is the most important for industry?(para.3)

Metals.

Are all metals used as engineering metals? Which metal finds greater use than any other metal? (para.4)

No. Iron

Translation

The most important engineering metal is iron(Fe), which in the form of alloys with carbon(c) and other elements, finds greater use than any other metal.原译：最重要的工程金属就是铁、铁跟碳和其他元素结合形成合金的那些金属，比其他金属发现有更大的用途。

Polysemy

chemical element 化学元素

cost element 成本要素

normal element 标准电池

ferrous metals

What are ferrous metals?

Metals consisting of iron combined with some other elements are known as ferrous metals.

“Ferrous” is an adjective used to indicate the presence of iron, but why ferrous metals are called as “black metals” ， are they really black?

Only three types of ferrous metals: iron, manganese （锰） and chromium （铬 ). And they are not black! Pure iron is silver; manganese is silver; chromium is gray. The surface of iron is often covered with a black layer of iron oxide.

ferrous metals

What are nonferrous metals?

All the other metals are called nonferrous metals.

Many nonferrous metals are very important, but used much less than ferrous metals, why?

Because ferrous metals are much cheaper.

alloy

Do you know what is “alloy”?

Definition:  A material that has metallic properties and is composed of two or more chemical elements of which at least one is a metal (i.e. steel is an alloy of carbon in iron; stainless steel is an alloy of carbon, chromium （铬） and sometimes nickel （镍） in iron.)

alloying

Terms

alloying 合金化

strength

toughness 韧性

resistance to wear

magnetic properties 磁性

high electrical resistance 高电阻率

corrosion-resistance 抗腐蚀性

强度

耐磨性

metallurgy

What is metallurgy?

Metallurgy is the art of working metals, the whole process of separating them from other matters in the ore, smelting （熔炼） , refining, and parting them; sometimes, in a narrower sense, only the process of extracting metals from their ores.

Materials Science & Engineering

Henan Polytechnic University

The principal methods of shaping metals

• Mechanical working

rolling, extrusion, forging• Fabrication by joining• Machining• Powder metallurgy

• Casting

CLOZE

All metals can be classified as either _______ or ____________.

ferrousnon-ferrous

Ferrous metals are ones which contain ______. They may have small amounts of other metals or other elements added, to give the required properties.

iron

Nonferrous metals are ones which do not contain any iron. They are not magnetic and are usually more resistant to corrosion than ferrous metals. Examples are _______________________________________.

copper, aluminum, lead, zinc and tin

CLOZE

An alloy is a mixture of__________________. When a material is needed which requires certain properties and there does not exist in a pure metal we _______________. Pure white aluminum is very soft and ductile. Other elements can be added to create an _______________. This can produce a metal which is stronger than mild steel( 低碳钢） and is resistant to corrosion while still remaining light in weight.

two or more metalscombine metals

aluminum alloy

A pure metal only consists of _______________. This means that it only has one type of atom in it. The common pure metals are: aluminum, copper, iron, lead, zinc, tin, silver and gold.

a single element

Non-Ferrous Metals Chooser ChartName Composition Properties Uses

____________ Pure Metal Greyish-White, soft, malleable（可塑的） , conductive to heat and electricity, It is corrosion resistant. It can be welded but this is difficult.

Aircraft, boats, window frames, saucepans, packaging

_______________ Pure metal Red, tough, ductile, high electrical conductor, corrosion resistant.

Electrical wire, cables ,conductors, and roofs.

_______________ Pure metal The heaviest common metal. Soft, malleable, bright and shiny when new but quickly oxidizes to a dull grey. Resistant to corrosion.

Protection against X-Ray machines. Paints, roof coverings

______________ Pure metal A layer of oxide protects it from corrosion, bluish-white, easily worked.

tanks, buckets, rust-proof paints

_______________ Pure metal White and soft, corrosion resistant.

tinplate( 马口铁）

aluminum

copper

lead

zinc

tin

Questions

Why are the majority of electrical wire made from copper?

Name a nonferrous metal that is used to protect dental nurses, doctors and dentists from the harmful radiation that is given off when using X-rays?

Give the name of the metal that is suitable to make jewellery from? Why is it a good choice?

Platinum, precious metal

Metallic and Nonmetallic Materials

Metallic and Nonmetallic Materials(para1.)

Brass is the term used for alloys of copper and zinc. Typically it is more than 50% copper and from 5 to 20% zinc, in comparison to bronze which is principally an alloy of copper and tin. Despite this distinction, some types of brasses are called bronzes.

Brass has a yellow color, somewhat similar to gold. It is relatively resistant to tarnishing, and is often used as decoration.

Bronze refers to a broad range of copper alloys, usually with tin as the main additive, but sometimes with other elements such as phosphorus （磷） , manganese( 锰） , aluminum, or silicon （硅） . It is strong and tough, and has myriad uses in industry.

Metallic and Nonmetallic Materials(para1.)

Translate the following sentence:

金属是具有光泽、有良好的导电性、导热性。通常人们把金属分成两大类，黑色金属和有色金属。黑色金属主要指铁、锰、铬及其合金，而黑色金属以外的金属称为有色金属。

Metals possess the properties of luster, thermal conductivity, and electrical conductivity. Usually people take them into two parts: ferrous metals and nonferrous metals. Ferrous metals are iron, manganese, chromium and their alloys; all the others are called nonferrous metals.

Metallic and Nonmetallic Materials(para.2)

“Where the required properties are available in both, total cost becomes the determining factor.

“In case the required properties are available in both, total cost becomes the determining factor.

Where there is a will, there is a way.When the air in the tube was heated, its molecules moved faster.

Terms(para.3)密度 density

熔点 melting point

导热性和导电性 thermal and electrical conductivity

热膨胀系数 coefficient of thermal expansion

比热 Specific heat

Terms

Specific heat: the heat required to raise the temperature of one gram of a substance one degree centigrade

Description of mechanical properties

1 Strength

the measure of how a material withstands a heavy load without breaking.

Description of mechanical properties

2 hardness

The resistance a material has to cutting and surface indentations( 凹陷） .

Description of mechanical properties

3 ductility

The length that a material can be stretched without breaking.

4 Elasticity

The length that a material can be stretched without breaking.

Description of mechanical properties

5 Toughness

This describes the amount of energy a material can absorb without breaking. This is the opposite to brittleness. We measure a material's ability to absorb shock.

Dictation

Plastics and other materials(para.1)

What are the advantages and disadvantages compared with metals?

Plastics tend to be_________ to inorganic acids; plastics are very__________ with a specific gravity normally between 0.9 and 1.8. and they are easily __________ while they are soft. But most plastics do not readily _________________________.

resistantlight

be shaped

conduct heat or electricity

Plastics and other materials(para.2)

It permits the large-scale production of molded articles, such as containers, at an economic unit cost, where other material require laborious and often costly processes involving cutting, shaping, machining, assembly and decoration.

塑料的塑性使之能大量地生产单位成本低的模制器件，例如各种容器等，而其它材料则需要费力往往又比较昂贵的加工步骤如切削、成型、机加工、装配和装饰。

Examples

Where there is sound, there must be sound waves.

有声音就必定有声波。

At speed faster than the speed of sound, the plane leaves the sound waves behind where they cannot cause the plane any trouble.

当飞机以高于声速的速度飞行时， 把声波抛在后边，这样声波就不会给飞机造成麻烦。

TermsInjection molding 注射模塑

vacuum forming 真空模塑

extrusion 挤压

compression molding 压塑法

blow molding 吹塑法

Assignment

Powder MetallurgyTalk about “How much do you know about Powder Metallurgy”

Powder Metallurgy

the definition for the term” “ powder metallurgy”“ The art of producing metal powders and objects shaped from individual, mixed, or alloyed metal powders, with or without the inclusion of nonmetallic constituents, by pressing or molding objects which may be simultaneously or subsequently heated to produce a coherent mass, either without fusion, or with the fusion of a low melting constituent only.”对粉末冶金所下的定义如下：粉末冶金是制造金属粉末并将单一的、混合的或合金化的粉末用成型的方法制成制品的技术。这一制造过程可添加或不添加非金属成分；可通过加压或模压成型；可在压制时同时加热或在压制后再进行加热，能使金属粉末形成一个粘结牢固的整体；加热过程中粉末可不熔化，或只有低熔点成分熔化。

Powder Metallurgy

The development of powder metallurgy(para.2)

Definition of sintering: the pressing and heating of powdered materials close to their melting point to create a solid shape. Sintering creates materials with very uniform contents.

Two unique advantages (para.3)

Advantage 1: Advantage 2:

Unique Advantages

Powder metallurgy is a basic shape-producing method for practically all metals, in direct competition with other methods. In addition, for many refractory materials, both metals and nonmetals, powder metallurgy is the only practical means of shape production. Tungsten is typical of the refractory metals; it has a melting point of 3400°C ， and no satisfactory mold or crucible ( 炉缸） material exist for using conventional casting techniques at this temperature. For some other metals, possible to melt, impurities picked up by the liquid from the containers would be undesirable, and powder metallurgy offers the most economical means of obtaining solid shapes.

Processing steps

While theoretically any crystalline material ( 晶体材料） may be fabricated by powder metallurgy, the production of suitable has presented restrictions in many cases, either because of difficulty in obtaining adequate purity or because of economic reasons.

Paraphrase the sentence.

After selection and blending of the powder and manufacture of a die for the shape to be produced, the powder is pressed to size and shape.

选择和配制好粉末并制成具有所需产品形状的模具后， 就把粉末压制成符合尺寸和形状的产品。

Processing steps of P/M

The application of heat results in crystalline growth and the production of a homogeneous body( 均质体） .

Pay attention to the frequent use of nominal structure.

Process

Notes:green compacts 生坯，未烧结的压块

undercut 底切

wrought metals 锻造金属

tooling cost 加工成本

scrap 废料

cross holes 十字孔

screw thread 螺纹

Translation

Powder metallurgy is the process of blending fine powdered materials, pressing them into a desired shape (compacting), and then heating the compressed material in a controlled atmosphere to bond the material (sintering). The powder metallurgy process generally consists of four basic steps: (1) powder manufacture, (2) powder blending,(3) compacting, (4) sintering. Compacting is generally performed at room temperature, and the elevated-temperature process of sintering is usually conducted at atmospheric pressure. Optional secondary processing often follows to obtain special properties or enhanced precision.

Exercise

Exercise优点： 1 、绝大多数难熔金属及多孔材料只能用粉末冶金方法来制造。 2 、由于粉末冶金方法能压制成最终尺寸的压坯，而不需要或很少需要随后的机械加工，故能大大节约金属，降低产品成本。 3 、由于粉末冶金工艺在材料生产过程中并不熔化材料，也就不怕混入由坩埚等带来的杂质，故有可能制取高纯度的材料。 4 、粉末冶金适宜于生产同一形状而数量多的产品，用粉末冶金法制造能大大降低生产成本。

LOGO

43