Title: BAA1312 : Engineering Material : Ferrous Metal Steel Metal Part II
1BAA1312 Engineering Material Ferrous Metal
Steel (Metal Part II)
2BAA1312 Engineering Material Ferrous Metal -
Steel
FERROUS METAL
steel
copper
iron
3BAA1312 Engineering Material Steel Defects
Rust
- Rusting is oxidation or combining of the iron
- with oxygen that occurs in the presence of
- moisture.
- Proceeds more rapidly where there is
- noticeable dampness but it occurs in any
- air with a relative humidity higher than 70.
- Rusting occurs more rapidly in salt air and
- industrial atmosphere.
- The rust is formed from the solid metal,
- reducing it size so that the members become
- weaker and loses any decorative finishes it
- might have.
- The rust penetrate deeper as time passes on.
4BAA1312 Engineering Material Steel
Protection
- Among ways to protect steel from rust are
-
- Painting
-
- Careful design
- Galvanizing
- Coating the steel with zinc
- Bituminous coatings
5BAA1312 Engineering Material Steel
Protection (contd)
- Painting
- Painting the steel prevents rust but it must be
done periodically. - Careful Design
- Prevention of rust can be done by careful design
to avoid - a) pockets / crevices that hold waterb) spots
that are inaccessible for repainting - c) sharp edges that are difficult to coat with
the required thickness of paint - Galvanizing
- Adding cooper as an alloying element into carbon
steel, make it rust resistant
6BAA1312 Engineering Material Steel
Protection (contd)
- Using zinc as steel protection
- Usage of zinc to steel protection would be able
to prolong the life of steel. - It adheres readily to the steel to form a tight
seal against the atmosphere and it corrodes
slowly that the iron/steel. - Zinc continue to protect steel even after it has
been eaten through in spots, because corrosion
will take place in the zinc in preference to the
ferrous metal. - Bituminous Coating
- Used to protect iron steel from the effects of
atmosphere, water or soil. - Appearance and odor of bitumen make them
unsuitable to be protective coatings.
7BAA1312 Engineering Material Steel Failure
- Failure can be happen because of
- Yielding of member
- Failure of connection
- Most common cause of steel building collapse
- Buckling of member
- Buckling of column rarely has resulted in
structural failure
8BAA1312 Engineering Material Steel
Connection
- Steel members must be connected to form a
structure such as bridge and building. - It can be connected by the given method
- Riveting
- Welding
- Bolting
- High Strength Bolts
9BAA1312 Engineering Material Steel
Connection (contd)
10BAA1312 Engineering Material Steel
Connection (contd)
- Revert
- One of the most common method of making
connections - Holes are punched /drilled through the members
to be connected. - A steel rivet slightly smaller than the holes is
heated to a cherry red colour and inserted
through the holes.
11BAA1312 Engineering Material Steel
Connection (contd)
- Revert
- Cooling the rivet causes the rivet to shorten,
compressing the members still further. - The disadvantage of riveting is the extra
material that is needed due to overlapping
plates.
12BAA1312 Engineering Material Steel
Connection (contd)
13BAA1312 Engineering Material Steel
Connection (contd)
- Welding
- also a popular way of fastening the connection
- the metal weld is stronger than the metal being
connected - very expensive but it gives a neat appearance
- weld metal is protected from the atmosphere
while cooling. - chemical properties of weld metal must be
matched to the - metal being welded. So, there are variety of
electrodes available.
14BAA1312 Engineering Material Steel
Connection (contd)
15BAA1312 Engineering Material Steel
Connection (contd)
- Welding
- welding consists of heating the 2 pieces to be
joined until they melt enough to use. - the heat comes from an electric arc that is
formed between a welding rod and the 2 pieces to
be welded. - a portable electric generator is connected to
the structural steel and to the welding rod and
either an alternating or a direct current is
passed through the rod and the structural members
when the rod touches or nearly touches the
members.
16BAA1312 Engineering Material Steel
Connection (contd)
- Welding
- the tip of the rod and some depth of the base
metal, called penetration are melted. - the 2 metals combine and harden upon cooling.
- the liquid metal rapidly absorbs oxygen and
nitrogen, which causes it to be brittle and lose
its resistance to corrosion unless it is
protected from the atmosphere.
17BAA1312 Engineering Material Steel
Connection (contd)
- Bolt
- Can be used instead of rivet
- Bolt is manufactured with a head at one end and
threads at the other end to which a nut can be
threaded. - When the bolt is in position to hold members
together, a tightening of the nut pulls the bolt
with a tensile force and presses inward on the
two members, causing friction between them to
resist movement. - Common bolts
- are less expensive and easier to install than
high strength bolts - suitable to be used where little strength is
required and there are no vibration, impact loads
or stress cycles. - weaker than high strength bolts because they
loosen under vibration, impact loads or cyclic
loads.
18BAA1312 Engineering Material Steel
Connection (contd)
19BAA1312 Engineering Material Steel
Connection (contd)
20BAA1312 Engineering Material Steel
Connection (contd)
21BAA1312 Engineering Material Steel
Connection (contd)
- High Strength Bolt
- High strength bolt can be installed to produce a
predetermined tension greater than that of
common bolt. - Bolts are tightened with wrenches powered by
electricity or compressed air. - High strength bolts can be divided to 2 types
a) A325 bolts of carbon steel b) A490 bolts of
alloy steel
22BAA1312 Engineering Material Aluminum
- Presentation Assignment
- Explain the process producing the aluminum.
- Advantage and disadvantage of aluminum