Lesson Notes By Weeks and Term - Junior Secondary School 3

PROCESSING OF MATERIALS: ALLOYS

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TERM: FIRST TERM

SUBJECT: BASIC TECHNOLOGY

CLASS: JSS 3

REF MATERIALS

  • EVANS BASIC TECH FOR JSS BOOK 3
  • NERDC BASIC TECH FOR JSS BOOK THREE

 

WEEK FOUR

TOPIC: PROCESSING OF MATERIALS: ALLOYS

CONTENT

  1. Metal processing methods
  2. Metal alloys, examples, properties and uses.

Metals are materials used in producing some equipment used in everyday life. Metals are usually solid but a few ones are liquid or powder form. They are made raw forms called ore. 

 

METHODS OF PROCESSING METALS

Most metals do not occur in a pure state they are usually combined with other metals and earthly impuritiesto form what is called mineral ore. The ore is then mined and processedto extract the metal of interest. The methods of processing metals include:

  1. Casting 
  2. Smelting 
  3. Annealing 

 

CASTING

This is the process of melting and pouring molten metal into the mould to take the shape of the mould when it cools down or solidifies.

 

SMELTING

This is the process of extracting metals from iron ore dug from the ground.

 

ANNEALING

This is the process by which metals can be softened.

 

EVALUATION

  1. Explain the following terms: (a) casting (b) annealing (c) smelting.
  2. Briefly describe metals 

 

STAGES OF METAL PRODUCTION

There three stages in the production of metals

 

STAGE ONE: EXTRACTION STAGE: The rock containing the metal is dug from the ground with drilling and excavating. The rock and the metal mixed togetherare calledthe metal ore(the impure metal)

 

STAGE TWO: SMELTING STAGE: The metal ore is heated in a furnace( e. g blast furnace ) until the metal melts into liquid form with other impurities that have mixed with it .

 

STAGE THREE: CASTING STAGE: The hot molten (liquid) metalis poured into container of different lengths and sizes called moulds .it is left there to solidify to take up the shape of the mould, this is called casting. This is how round bars, square bar,wires and others are produced

 

EVALUATION

Briefly explain the three stages of metal production.

 

METAL ALLOYS,EXAMPLES PROPERTIES, AND USES

An alloy is a metal that is obtained by mixing two or more metals together examples are ferrous alloys and non- ferrous alloys

FERROUS ALLOYS

COMPOSITION

PROPERTIES

USES

High speed steel

Iron, carbon, vanadium and tungsten

Hard and brittle it will withstand temperatures up to 600 0C

Machine cutting tools such as drill bits.

Stainless steel 

Iron ,carbon, chromium and sometimes nickel

Hard and difficult towork,resist corrosion takes a high polish and will not rust.

Cutlery, hand cutting tools, washbasins 

and sink containers for corrosives.

High tensile steel 

Iron, carbon,nickel and chromium

Very strong and tough

Components where high strength is needed, engine parts, bolts and nuts for cars and machinery

NON FERROUS ALLOYS

ALLOYS

COMPOSITION

PROPERTIES 

USES

Brass

Copper65%, zinc 35%

Can be bent and pressed into shapes, resist corrosion very well

Plumbing industry, ammunition(bullet and  shell) Castings, wires rivets screws decorative works

Duralumin

4.5%copper, 0.5% manganese, 0.5% magnesium, and

 94.5% Aluminium

It becomes hardened with age

It is used to make aircrafts and sheets

Gilding metal


Copper 90%,  zinc 10% 

Very malleable and ductile, resist corrosion well

Decorative beaten work, cheap jewellery.

Bronze

80%copper,20% tin

Strong and tough with high tensile strength,           resist corrosion and machine well

Statues, ornaments, Bearings, springs electrical and architectural work. 



EVALUATION

  1. What is an alloy?
  2. State three examples of alloy ferrous metals and mention (2) practical uses of each.
  3. State three (3) examples of non-ferrous metal and mention (2) practical uses of each.

 

GENERAL EVALUATION

  1. Defines metals.
  2. Mention the classes of metals with examples.
  3. Differentiate between ferrous metals and non ferrous metals.
  4. Describe the processes of processing metals.

 

READING ASSIGNMENT

Read about ‘processing clay, ceramics, plastics,rubber and glass

REFERENCE BOOKS

(i) EVANS Basic Technology for JSS book 3.

(ii) NERDC Basic Technology for JSS book 3.pg.22-36.

 

WEEKEND ASSSIGNMENT

  1. The metal obtained from the processing of iron ore in blast furnace is __ (a) limestone (b) steel (c) pig iron (d) coke .
  2. The best material for making cooking pots is ___ (a) Tin  (b) steel (c) clay (d) aluminum.
  3. The process of melting and pouring molten metal into the mould to take the shape of the mould when it cools down or solidifies is called ______ (a) smelting (b) casting (c) annealing (d) furnishing.
  4. Which of the following is not a stage in the metal production? (a) extraction stage (b)fabrication stage (c)smelting stage (d)casting stage.
  5. The following are examples of alloys except(a) bass (b) bronze (c)copper (d) duralumin. 

THEORY

  1. In tabular form, mention two example of ferrous alloys and non-ferrous alloys, state their components, properties and uses
  2. Explain the process of processing metal.


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