Alloy Steel

Pawandeep Singh
Pratyush Srivastava

o Alloy steel is steel that is alloyed with a variety of
elements in total amounts between 1.0% and 50%
by weight to modify or improve its mechanical
properties.
o The definition of alloy steel does not include those
effects which are negative or cure of ills that the
steel might possess were the alloying element(s)
not added.
o The term "alloy steel" is the standard term
referring to steels with other alloying elements in
addition to the carbon. Common alloyants
include Mn, Ni, Cr, Mo, V, Si and B . Less
common alloyants include Al, Co, Cu, Ti, W, Sn,
Zn, Pb and Zr.

Alloy steel has some of its properties better than
carbon steel. They are as follows:-

o Tensile strength
o Hardness
o Toughness
o Wear Resistance
o Creep
o High Temperature Resistance
o To achieve some of these improved properties the
metal may require heat treating.

o low-alloy steels : increase strength and hardenability
o high-alloy steels : improves corrosion resistance and stability at
high or low temperature.
o Most commonly, the phrase "alloy steel" refers to low-
alloy steels.
o One more classification method is based upon the
composition
o Simple alloy steel is alloy steel containing one alloying
element, for example, simple nickel steel.
o Quaternary alloy steel is alloy steel that contains two
alloying elements, as, Chromium Vanadium steel.
o Complex steel is alloy steel containing more than two
alloying elements such as high speed tool steel.

It’s a complex and highly specialized process which can be
summarized as :-
 Electric Arc furnace/Mini Blast Furnace
 Ladle Furnace
 Vacuum Degassing
 Continous Casting
 Hot Rolling
 Downstream Processing(recovery and purification)

Alloy Steel may be supplied in:-
 As rolled condition
 Heat treated
 Cold finished
 Smooth turned
 Centre less Ground

Alloy steels are manufactured in the form of:
 Bars
 Wires
 Wire Rod
 Bright Bars
Sizes
 Alloy steel products are manufactured in size ranging from 5mm
to 400mm width or diameter.
Shapes: Alloy Steel products are manufactured in the following
shapes:
 Square
 Round
 Rectangle
 Hexagon
 Flat
 Customized Shapes

 Alloying elements are added to achieve certain
properties in the material.
 added in lower percentages (less than 5%) to
increase strength or hardenability
 added in larger percentages (over 5%) to
achieve special properties, such as corrosion
resistance or extreme temperature stability.
 Mn, Si, or Al are added during the steelmaking
process to remove dissolved oxygen, sulphur
and phosphorus from the melt.
 Mn, Si, Ni, and Cu are added to increase
strength by forming solid solutions in ferrite.

 Carbon:
- Fe is alloyed with carbon to make steel and has the
effect of increasing the hardness and strength by heat
treatment but the addition of carbon enables a wide
range of hardness and strength.
 Manganese
- added to steel to improve hot working properties and
increase strength, toughness and hardenability.
- It is an austenite forming element and has been used as
a substitute for nickel in the A.I.S.I 200 Series of
Austenitic stainless steels (e.g. A.I.S.I 202 as a substitute
for A.I.S.I 304)
- Used as deoxidizer.

 Nickel
- added in large amounts, over about 8%, to high
chromium stainless steel to form the most important
class of corrosion and heat resistant steels.
- the tendency of nickel to form austenite is responsible
for a great toughness and high strength at both high
and low temperatures.
- Nickel also improves resistance to oxidation and
corrosion.
 Chromium
- to increase resistance to oxidation. This resistance
increases as more chromium is added.
- When added to low alloy steels, chromium can increase
the response to heat treatment, thus improving
hardenability and strength.
- Increase strength by forming second-phase carbide.

 Molybdenum
- when added to chromium-nickel austenitic steels,
improves resistance to pitting corrosion
- When added to low alloy steels, molybdenum
improves high temperature strengths and hardness.
 Titanium
- The main use of titanium as an alloying element in
steel is for carbide stabilisation as it forms TiC in solid
phase.
- Thus tends to minimize the occurrence of inter-
granular corrosion, as with A.I.S.I 321, when adding
approximately 0.25%/0.60% titanium
 Copper
- Improves corrosion resistance

 Phosphorus
- Phosphorus is usually added with sulphur to improve
machinability in low alloy steels,
- Phosphorus, in small amounts, aids strength and corrosion
resistance.
- Phosphorus additions are known to increase the tendency to
cracking during welding.
 Sulphur and Selenium
- improves machinability.
 Silicon
- used as a deoxidizing (killing) agent.
- contributes to hardening of the ferritic phase in steels and for this
reason silicon killed steels are somewhat harder and stiffer than
aluminium killed steels.
 Cobalt
- improves strength at high temperatures and magnetic
permeability.
- But Co containing steel cannot be used in Nuclear plants as it is
radioactive.

Density (1000 kg/m3): Around 7.85

Elastic Modulus (GPa): 190-210

Poisson's Ratio:Yield Strength 366-1793
(MPa):
Thermal Expansion (10-6/K): 9.0-15

Melting Point (°C): 1371-1454

Thermal Conductivity (W/m-K): 26-48.6

Specific Heat (J/kg-K): 452-1499

Electrical Resistivity (10-9W-m): 210-1251

Tensile Strength (MPa): 758-1882

Percent Elongation (%) : 4-31

Hardness (Brinell 3000kg): 149-627

Alloy Steels are specifically produced for sophisticated engineering
applications. Alloy Steels finds its applications in various areas:
Automotive Transmission Parts, Engine Components, Steering
Components, High Tensile Fasteners, Fuel Injection
Pumps, Bearing Axles, Gears, Crankshaft,
Transmission Chains, Springs, Combustion
chamber, Axles, Wheel Hubs

Engineering Cutting Tools, Structural Steel

Industry Mining Machinery, Energy exploration machinery,
food-processing units(non-corrosive environment)
Construction Reinforcing Bars
Agriculture Tractor Parts
Home Utensils, Decorative purposes
Railways Wagon Axles, Crankshafts, Cushioning Device
Components, Steel Liners, Traction Gears
Military Ordnance, gun barrels, projectiles, missile
components

 The application of alloy steel is increasing everyday.
 Wide use in Automotive industries
 The other major consuming sectors like auto ancillary,
seamless pipes and tubes, engineering and railways
etc. have also consumed rising quantity of alloy steel.
 Forging industry is the largest consumer of alloy steel,
which in turn caters to the need of automotive and auto
ancillary sector.
 The industry has registered a growth of over 15% p.a.
for the last two years.
 CARE(Credit Analysis & Research Limited) Research
expects the domestic alloy steel demand to grow at a
CAGR of 13.6% during the period FY11 to FY16.

 Pakistan authorities have allowed import of only alloy steel
items through Wagah border, banning entry of non alloy
steel items through this route.
 South Africa’s imports of alloy steel is increasing at a high
rate.
 Mr Wang Yong chairman of Xiwang Special Steel Co. a
subsidiary of Shandong Province based China steelmaker
Xiwang Group has stated that construction work on the
company high strength alloy steel pipe project will start
early in the second half year of this year with
commissioning expected in the third quarter. The planned
annual output capacity is 2 million tonnes.
 Iran produced 307,300 tonnes of alloy steel last calendar
year which ended on March 19th 2012 showing 11.3%
increase on the previous year. It expects to increase its
production capacity by 80% in next few years.
 Iran exported 180,000 tonnes of alloy steel previous year

 According to provisional data released by Joint Plant Committee, given below are
the production, import, export and consumption figures for alloy steel for April
2012.
 (all data is in ‘000 tonnes)

 Alloy steel (including stainless steel) constitutes only
approx. 10% of the overall annual steel production in India.
 But its share is approx. 20% in terms of value since the
products are substantially value added for specific end
users.
 Alloy steels are specifically produced for use in
sophisticated engineering products for various critical
applications such as :-
- machined components
- engine parts
- steering components and bearings
- automobile industry.

Alloy Steel

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