Metals

Presented By:Presented By:

Engineer LATIF HYDER WADHOEngineer LATIF HYDER WADHO

Mehran University of Engg: & Technology Khairpur Mehran University of Engg: & Technology Khairpur

CIVIL ENGINEERING MATERIALSCIVIL ENGINEERING MATERIALS

11stst Term 1 Term 1stst Year B.E.Civil Year B.E.Civil

METALS

Arch Type Bridge

METALS:

There are hundreds of metals which are used in engineering. All the metals are extracted from quarries in the form of ores. They are made pure by some special methods in the industries.

CLASSIFICATION OF METALS

Metals are classified into two main

groups depending upon presence of iron

content.

(1) Ferrous metals:All those metals which contain iron as chief constituent are called ferrous metals.Such as:(1) Pig iron (2) Wrought iron(3) Cast iron

(2) Non-Ferrous metals:

All those metals which do not contain iron as

principal constituent are called non-ferrous metals.

Such as:– Zinc– Lead– Nickel– Chromium– Silver– Platinum– Gold and all other metals except steel and iron.

DUCTILE MATERIALS:A material which can undergo considerable deformation without rupture is called ductile material. E.g. steel.

(OR)A material that can be stretched, drawn or hammered thin without breaking. BRITTLE MATERIALS:A material which can not undergo any deformation is called brittle material. Brittle material has tendency to break into pieces easily, e.g. concrete and glass.

STEEL:Steel is an alloy (mixture of two or more than two metals) of carbon and iron. It is most important metal which is widely used in RCC construction of civil engineering.

Types of Steel:Steel is classified into three main types depending uponcarbon content.

(1) Low / Mild / Soft /Plain Carbon Steel:

In this type of steel, the carbon content is 0.15% to

0.3%.

Properties:

(1) It is ductile and malleable.

(2) It corrodes quickly.

(3) It can be easily forged, welded and riveted.

(4) It withstands shocks and sudden impacts well.

(5) It is not much affected by saline water.(6) It is equally strong in tension, compression and

in shear. Continued-------

Uses:

Mild steel round bars are extensively used

as reinforcement in R.C.C construction.

It is extensively used in the manufacturing of

various tools and equipments, machine parts,

railway tracks , transmission towers and

industrial buildings.

Mild Steel Bars

Mild Steel Plain Bars

Mild Steel Bars

(2) Medium carbon Steel:

In this type of steel, the carbon content is

0.3 to 0.8 %.

Medium steel has characteristics between

those of low –carbon and high carbon

steel.

It is widely used for boilers.

(iii) High- Carbon Steel (or) Hard Steel: In this type of steel, the carbon content is more than 0.8 to 1.5 %. Higher %age of carbon in it renders it harder and tougher.Properties:(1) Its structure is granular.(2) It is more tough and elastic than mild steel.(3) It is easier to harden and to temper.(4) It is more difficult to forge and to weld.(5) Comparatively it is stronger in compression than in tension or in shear.(6) It with stands shocks and vibrations better.

Uses of High carbon steel:(1) It is used in the pre-stressed concrete.(2) It is used for making tools such as drills, files, chisels, fine types of cutlery.(3) It is also used in the manufacturing of cutters,keys,knives,razers,etc.(4) It is used in the manufacturing of those parts of machinery that need a hard, tough, durable material capable of withstanding shocks and vibrations.

REINFORCED STEEL BARS:As plain cement concrete (PCC) is strong in compression but very weak in tension and shear. As mild steel bars are strong in tension. Therefore, mild steel bars or high carbon steel bars are embedded as reinforcement in the concrete to make good that deficiency of the plain concrete. Therefore, round, flat or square bars too can be used for that purpose.Welded wire mesh and expanded metal too are used as reinforcement in cement concrete.Commonly deformed bars or twisted bars are used in cement concrete.Therefore, RCC sections will carry compression as well as tension safely without failure.In these sections compression will be taken by concrete and tension by steel.

NON-FERROUS METALS

(1) ALUMINUM:It is more commonly used non-ferrous metal. It is widely used in every field of Engineering. Due to improved strength and durability, aluminum is a versatile material for use by Engineers.Properties and Uses:(1) Its colour is silvery white.(2) It shows bright luster on a freshly broken surface.(3) It is ductile material,(4) It is very light in weight.(5) It also resists atmospheric corrosion,(6) It is very good conductor of electricity,(7) It is used for making door and window frames,(8) It is also used in roofing, piping, etc,(9) It is also used in electric wires, cables.

(2) COPPER: It is one of the most widely used non-ferrous metals. It is not widely used in Engineering due to its high cost. Properties:(1) It is crystalline in structure,(2) Its color is reddish brown,(3) It is highly ductile,(4) It is excellent conductor of electricity,(5) When exposed to sun, its colour turns greenish,

Continued------

(6) It with stands corrosion,(7) It is soft and highly flexible,(8) It is light in weight,(9) Dents in copper can be hammered out without any damage to it.Uses:(1) It is used for winding electric motors, generators and for transmission of electricity,(2) Its sheets are used as damp proofing in buildings.

(3) LEAD:It is widely used in building construction and has draw back of being poisonous.Properties:(1) It is bluish grey metal,(2) It is soft as it can be cut with a knife, (3) It is highly ductile,(4) It is a good conductor of heat and electricity,(5) It does not corrode,(6) Its specific gravity is 11.35.Uses:(1) It is used as a base in paints,(2) Lead pipes and lead joints in sanitary fittings are extensively used. 

(4) TIN:It is one of the mostly used protective metals used in construction activities.Properties:(1) It is lustrous silvery white metal,(2) It is highly ductile,(3) It is a good conductor of heat and electricity,(4) It is soft and has good plasticity,(5) Its specific gravity is 7.3.Uses:It is used to give protective coatings to iron and steel sheets.

(5) ZINC: It is commonly used in building construction either as a base for paints or as protective coverings for metals.Properties:(1) It is bluish white crystalline metal,(2) It is brittle metal at ordinary temperature,(3) It becomes ductile between 100-1500C,(4) It is a good conductor of heat and electricity,(5) It resists corrosion.Uses:(1) It is used for galvanizing iron sheets and pipes, for batteries and printing blocks, (2) It is also used for preparing paints.

NON-FERROUS ALLOYS

(1) BRASS:Brass is an alloy of about 60-70 % copper and zinc. Hardness of this alloy depends upon the amount of zinc present in it.Properties:(1) It is very strong,(2) It is ductile alloy,(3) It resists corrosion,Uses:It is widely used for making house hold utensils, water pumps and other machine parts. 

(2) BRONZE:Bronze is an alloy of 90 % copper and 10 % tin. It can be easily machined and cast. Properties:*It resists corrosion.*It takes a fine polish.Uses:(1) It is used for manufacturing of house hold utensils.(2) Phosphorous bronze is used for making radio aerials and certain other instruments.

CORROSIONAND

METHODS OF CORROSION CONTROL

CORROSION:

Conversion of metals into various compounds by natural means or agencies is described as corrosion. Corrosion of ferrous metals appears in the form of rusting.Corrosion of metals is explained in two ways. One is by the formation of oxides. As in case of iron, reaction with oxygen, carbon dioxide and water results in the formation of bicarbonate, which in turn alters into carbonate and finally changes into hydrated oxide. Continued---

According to other explanation, the metal surface processes areas which act as cathode and anodes. The presence of water or moisture etc provides a contact between such areas which results in corrosion.

Protection against Corrosion:

Ferrous metals have tendency for corrosion. It is maximum for steel and least for cast iron. Wrought iron has a moderate tendency to rust. Therefore, all the products require a protective cover to prevent the possibility of corrosion and thereby adding to its durability. Various methods which are in commonly used include Electroplating, Galvanizing, Tin plating, Metal spraying, Painting, etc.

(1) Electroplating:This method involves the use of electric current to give a coating of chromium or nickel which is highly resistant to corrosion.(2) Galvanizing:In this method zinc is used to give a coating on the ferrous metal products.(3)Tin Plating:This method is similar to the galvanizing process. The iron products are thoroughly cleaned and washed. Then these are dipped into the hot molten tin and it will give protection against corrosion.

(4) Metal Spraying:This method involves the use of a special sprayer in which fuel gas, oxygen and air are used to make flame. The wire of metal to be sprayed like zinc, tin, or aluminium is used in these sprayers. The wire metals and a thin layer is sprayed over the ferrous metal items.(5) Painting:The iron made goods are often coated with paint. Care should be taken to first clean the iron surface thoroughly and then give a good coating of good quality paint.

THE PLEASANT END