BAA1312 : Engineering Material : Ferrous Metal Steel Metal Part II

1
BAA1312 Engineering Material Ferrous Metal
Steel (Metal Part II)
2
BAA1312 Engineering Material Ferrous Metal -
Steel
FERROUS METAL
steel
copper
iron
3
BAA1312 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.

4
BAA1312 Engineering Material Steel
Protection

• Among ways to protect steel from rust are
• Painting
• Careful design
• Galvanizing
• Coating the steel with zinc
• Bituminous coatings

5
BAA1312 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

6
BAA1312 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.

7
BAA1312 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

8
BAA1312 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

9
BAA1312 Engineering Material Steel
Connection (contd)
10
BAA1312 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.

11
BAA1312 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.

12
BAA1312 Engineering Material Steel
Connection (contd)
13
BAA1312 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.

14
BAA1312 Engineering Material Steel
Connection (contd)
15
BAA1312 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.

16
BAA1312 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.

17
BAA1312 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.

18
BAA1312 Engineering Material Steel
Connection (contd)

• Bolt

19
BAA1312 Engineering Material Steel
Connection (contd)
20
BAA1312 Engineering Material Steel
Connection (contd)
21
BAA1312 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

22
BAA1312 Engineering Material Aluminum

• Presentation Assignment
• Explain the process producing the aluminum.
• Advantage and disadvantage of aluminum