steel

2. Iron
Iron is widely available all over the world, but only in
combination of with other elements. It is found in the form of ores as
oxides, carbonates, silicates, and sulfides.
The most important iron- bearing minerals or iron ores are the
following:
Limonite
Hematite
Magnetite

3. SINTERING
- process of application of heat that results in the conversion of
fine ore into hard and porous lumps.
PELLETIZING
- process of forming balls in the presence of moisture and additives
such as bentonite or lime.

4. BLAST FURNACES
Iron is presently produced in blast furnaces, developed in
Europe around 1400. At that time, the hot metal is tapped in the
furnace and cast in sand was designated a “pig” if the weight is less
than 112 lb. (50.7 kg).
Molten
iron (pig
iron)
Slag
Charge

5. The iron ore in the form of pellets or sinters is charged into the furnace with coke and
limestone. COKE is carbonaceous solid made from coal, petroleum, or other raw
materials by thermal decomposition, and is typically produced by heating a mixture of
coal in the absence of air, it is charged into the furnace as pieces. Limestone is added to
act as a flux that holds the silica and alumina impurities of the ore and coke.
A powerful air blast through the bottom raises the temperature sufficiently to burn
coke, melt iron, and burn off oxygen. As the charge comes to the bottom of the furnace,
the temperature increases to about 3000 F (1650 C), which is enough to melt iron.
Pig Iron

6. A non metallic product, consisting essentially of silicates and aluminosilicates of
calcium and other bases, is produced simultaneously with the molten metal. This
product, called slag ( or fluid slag), floats to the top and is also collected at the base of
the furnace.
Pig iron is not pure iron: it is metal nearly saturated with carbon (taken from the
coke). In addition, pig iron contains manganese, silicon, and other materials.
The type and constituents of pig iron depend on the composition of the ore.
How Iron was
extracted in the
19th century…

7. APPLICATIONS
Iron is the most widely used of all the metals, accounting
for 95% of worldwide metal production. Its low cost and high
strength make it indispensable in engineering applications such as
the construction of machinery and machine tools, automobiles, the
hulls of large ships, and structural components for buildings.

8. Cast Iron, Wrought Iron and Carbon Steel
Iron products come in three commercial form
 Wrought iron (.02-0.08% carbon)
 Steel/Carbon Steel (0.12-2% carbon)
 Cast Iron (2-4% carbon)

9. Steel Products
Semi- finished products come in three types
o Blooms
o Billets
o Slabs

10.  Groups according to their composition:
1. Plain carbon steels – mostly iron and carbon, with
less than 1% carbon.
2. Low-alloy steels – iron and carbon plus other
components (usually less than 5%).
3. High-alloy steels – similar in composition to the low-
alloy steels but with higher percentage of
components added to iron and carbon.

11. Structural Steels
 Structural steel shapes are rolled flanged sections having one
dimension of the cross-section equal to or greater than 3 in. ( 7.5 cm).
 These products are used as columns, beams, and bracing members in
buildings; for trusses: as bridge girders; and in prefabricated structures
and similar construction.
Shapes:
 Wide Flange (W shape)
 I-Beam (S-shape)
 Standard Channel, C
 Structural Tee
 Angles

12. Problems alliviated when using steel:
Molds on steels
Galvanic Corrosion
Pitting Corrosion
Microbial Corrosion
High Temperature Corrosion
Chloride Stress Corrosion

13. Solutions:
Applied Coatings
Reactive coatings
Anodization – is an electrolytic passivation process

14.  Structural Steel (hot-rolled structural shapes, plates,
and bars)
Carbon Steel
 A36 grades, which is called all-purpose carbon steel (or
structural carbon steel), has a 32-ksi minimum yield
points.
 A529 steel, called structural carbon steel, has a 42-ksi
minimum yield points.

15. High strength low alloy steel
 A441 steel, called high-strength low-alloy structural
steel; Grades A441 steel is discontinued from ASTM as
of 1989.
 A572 steel, called high-strength low-alloy structural
steel.
Corrosion resistant high strength low alloy steel
 A242 steel are atmospheric corrosion-resistant high-
strength low alloy structural steel.
 A588 steel are atmospheric corrosion-resistant high-
strength low alloy structural steel.

16. Quenched and tempered alloy steel
 A514 steel, quenched and tempered alloy structural
steel, is available only as plate.

18.  Types failures in steel construction may be due to
yielding of a member, failure of connections, or
buckling of a member.
 Connection failure is the most common cause of
collapse of steel buildings.
 Buckling of columns rarely has resulted in structural
failure
 Hot-rolled steel shapes used in the majority of steel
buildings are not prone to brittle failure.

20.  Double web angle shear connection (bolted to both
the beam and girder webs).

21.  A Typical column Splice

22.  Moment base connection (triangular stiffener reduces
bending in the base plate and increases the fillet weld
length for shear).

23.  Typical shear connector that causes the steel beam and
the concrete slab to act as an integral unit (composite
beam)

24.  Connection between a steel truss (using angles) and
steel column.

25.  Reinforced concrete can thus be treated as a composite
material, made from two distinctly different materials:
Steel
Concrete
 Reinforcing steel is manufactured in three forms:
Plain Bars
Deformed Bars
Plain and Deformed wire fabric

26.  Use of reinforcing steel in
a. Concrete column and beam.
b. Welded wire fabric and reinforcing bars in ground
supported slab.

27. • Deformed or plain bars are produced in four
principal (minimum) yield levels:
Grade 40 = 40ksi (300MPa)
Grade 50 = 50ksi (350MPa)
Grade 60 = 60ksi (400MPa)
Grade 75 = 75ksi (500MPa)

28.  Reinforcing steel is rolled from properly identified heats of
mold-cast or strand-cast steel, using one or more of the
three primary processes:
Open-hearth Furnace
Basic Oxygen Steelmaking (BOS)
Electric-Arc Furnace (EAF)

32.  The carbon equivalent is measure of the chemical
elements affecting the weldability of the materials and
can be calculated as:
C.E. = %C + %Mn/6 + %Cu/40 + %Ni/20 + %Cr/10 +
%Mo/50 + %V/10
Where:
C – Carbon
Mn – Maganese
Cu – Copper
Ni – Nickel
Cr – Chromium
Mo – Molybdenum
V - Vanadium

33.  Bars are supplied in bundles, secured by wires or
bands, each bundles containing bars of only one size,
length, and grade.
 The bundles are limited to weights that can be
conveniently handled by common equipment,
approximately 3000lb (1360 kg).

34.  Welded wire fabric

35.  Uses
Welded wire fabric is used as a concrete reinforcing for
cracks control in residential slabs, driveways,
sidewalks, and slabs for light construction.
o Three causes of cracking
• Drying shrinkage
• Change in temperature and moisture
• Weak sub grade or soil

38. Epoxy coated reinforcing steel is
steel (bar, fabric, wire) coated
with a fusion bonded epoxy
powder.