There are many different types of metal used in the construction industry. Designers,architects and builders use metal in construction and manufacturing because of its durability,resistance to all forms of weather and all-round strength and resilience.
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| Different types of metals |
Various metals used for building works be broadly classified as ferrous metals and non-ferrous metals.The properties and uses of ferrous metals and some of important non-ferrous materials like aluminium and copper are explained in this chapter.
Ferrous metal
A
ferrous material is the one in which iron is a main constituent. Iron ore is
first converted into pig iron
1.
Cast iron—carbon content 1.7% to 4.5%
2.
Wrought iron—carbon content 0.05% to 0.15%
3.
Steel—carbon content 0.25% to 0.25%.
All
ferrous materials contain about 0.5 to 3% silica, less than 2% manganese, 0.15%
sulphur and
1. Cast iron: Important properties of cast iron are:
(a) Compression strength is 700 N/mm2 and tensile strength is 150 N/mm2.
(b) It is brittle and does not absorb shocks
(c) Its specific gravity is 7.5.
(d) Its structure is coarse, crystalline and
fibrous.
(e) It cannot be magnetised.
(f) It does not rust-easily.
(g) It has low melting point of about 1200°C.
Uses of Cast Iron:
1. It is used for making rain water and sanitary pipes, sanitary fittings and manhole covers.
2.
It is used for making railings and spiral stair cases.
3. Fire gratings, cover
for pumps and motors and brackets are made with cast irons.
2. Wrought Iron: It is almost pure iron. It contains less than 0.15% carbon. Attempts are made to reduce the other impurities during the process of manufacturing.
Properties of Wrought Iron:
1.
Its ultimate compressive strength is 200 N/mm2 and ultimate tensile strength is 375 N/mm2.
2.
It is ductile and brittle.
3.
Its unit weight is 77 kN/m3.
4. It melts at about 1500°C. It becomes so soft at 900°C that two pieces can be joined by hammering
5.
It can absorb shocks very well.
6.
It forms temporary magnets but it cannot be magnetised permanently.
7.
It rusts more easily.
Uses of Wrought Iron:
1.
It is used for making nails nuts and botts, wires and chains.
2. It is used for making roofing sheets, grills, fences, window gaurds etc
3. Steel: It is extensively used building material. The following three varieties of steel are extensively used:
(a) Mild steel
(b) High carbon steel and
(c) High tensile steel.
(a) Mild Steel: It contains a maximum of 0.25% carbon, 0.055% of sulphur and 0.55% of phosphorus.
Properties of Mild Steel:
(i) It is malleable and ductile
(ii) It is more elastic
(iii) It can be magnetized permanently.
(iv) Its specific gravity is 7.8.
(v) Its Young’s modulus is 2.1 × 105 N/mm2.
(vi) It can be welded easily.
(vii) It is equally strong in tension and in
compression.
Uses of Mild Steel:
(i) Round bars are extensively used as
reinforcement in R.C.C. works.
(ii) Rolled sections like I, T, L, C, plates
etc. are used to build steel columns, beams, trusses etc.
(iii) Tubular sections are used as poles and
members of trusses.
(iv) Plain and corrugated mild steel are used as
roofing materials.
(v) Mild steel sections are used in making parts of many machineries
(b) High Carbon Steel: The carbon contains in this steel is 0.7% to 1.5%.
Properties of Carbon Steel:
(i) It is more tough and elastic compared to
mild steel.
(ii) Welding is difficult.
(iii) It can be magnetized permanently.
(iv) It is stronger in compression than in
tension.
(v) It withstands shocks and vibrations better.
Uses of High Carbon Steel:
i) It is used for making tools such as drills,
files, chisels.
(ii) Many machine parts are made with high
carbon steel since it is capable of withstanding
(c) High Tensile Steel: It contains 0.8% carbon and 0.6% manganese. The strength of this steel is quite high. High tensile steel wires are used in prestressed concrete works.
Aluminium
It
is present on the surface of earth crust in most of the rooks and clay. But to
produce the metal bauxite
Properties of
Aluminium
1.
It is having silver color and bright lustre.
2.
It is very light in weight.
3.
It is good conductor of electricity.
4.
It has very good resistance to corrosion.
5.
It melts at 66°C.
6.
It is highly ductile and malleable.
7.
It has high strength to weight ratio.
Uses of Aluminium
1.
It is used to make door and window frames.
2.
Aluminium structural members are becoming popular.
3.
Aluminium wires are used as conductors of electricity.
4.
It is used as a foil.
5. Aluminium powder
serves as pigments in paints.
Copper
It is a naturally available metal in the form of ores which contain small amount of iron and sulphur After removing impurities, it is processed electrolytically to get purest metal. This metal is almost indestructible. Copper scrap can be processed to get original copper.
Properties of Copper
1.
It is having reddish brown colour.
2.
Its structure is crystalline.
3.
It is highly ductile and malleable.
4.
It resists corrosion.
5.
It can be welded easily at red heat condition.
6.
Dents on the copper can be hammered out.
7.
It has high electric and thermal conductivity.
8.
Its melting point is at 1083°C.
Uses of Copper
1.
It is used as electric wire and cable.
2.
It is used as lighting conductor.
3.
For water proofing the construction joints copper plates are used.
4.
Copper tubes are used for hot and cold water supply, gas and sanitation
connections.
5. It forms a major constituent of brass and bronze.
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