Alloy steel

CLASSIFICATION OF MATERIALS
MATERIALS
METALS POLYMERS CERAMICS

METALS
FERROUS
Eg- steel,cast iron
NON-FERROUS
Al,Cu,Mg etc

Metals form about a quarter of the earth crust by weight.
Some of the earliest metals used include: copper, bronze and
iron
All metals except gold are generally found chemically
combined with other elements in the form of oxides and
sulphates. Commonly known as ores.
Metals are derived from ores by removing the impurities.
Those are used for engineering purpose are classified as
ferrous(iron as the major constituent) and Non-ferrous.

5
Ferrous Metals & Non-Ferrous Metals
Ferrous metals are metals that contain iron
E.g. Steel (iron and carbon)
Non-ferrous metals are metals that do not contain iron
E.g. Zinc (pure metal), Bronze (Copper and tin)
(non-ferrous may contain slight traces of iron)
Ferrous Metals Non- Ferrous Metals
Iron Aluminum
Low Carbon Steel Copper
Medium Carbon Steel Brass
High Carbon Steel Bronze
Cast Iron Zinc
Stainless Steel Lead
Tool Steels Tin
Others Others

6 Pure Metals and Alloys
• Metal that are not mixed with any other materials are known as pure
metals. Metals listed in the Periodic Table are PURE METALS
E.g. Iron (Fe), Copper (Cu) and Zinc (Zn)
• ALLOYS are mixtures of two or more metals formed together with other
elements/materials to create new metals with improved Mechanical
Properties and other properties of the base metal.
E.g. Brass (Copper and Zinc),
Steel (Iron and carbon)
Bronze(copper and tin)
Alloy = metal A + metal B + … + other elements

Ferrous Materials-STEEL
Steel is the most suitable building material among the metallic
materials.
Steel is an alloy of iron and other elements, primarily carbon.
 It is widely used in construction and other applications
because of its high tensile strength and low cost.
Classified into
Carbon Steel
Alloy Steel

In The Basis Of Carbon Content Steel Are Classified
Type of steel Carbon content
Dead mild steel < 0.15%
Mild steel 0.15-0.3%
Medium carbon steel 0.3-0.8 %
High carbon steel 0.8-1.5%
Hard steel >1%(also called as cast steel )

9 LOW CARBON STEEL
• Also known as mild steel
• Contain 0.15% -0.32% carbon
• Tough, ductile and malleable
• Easily joined and welded
• Poor resistance to corrosion
• Often used a general purpose material, Nails, screws, car
bodies,
• It is also used in the form of rolled sections ,reinforcing
bars, roof coverings etc.

Medium Carbon Steel
 Carbon content in the range of 0.3 – 0.6%.
 Can be heat treated - austenitizing, quenching and then tempering.
 Medium carbon steels have low hardenability .
 Addition of Cr, Ni, Mo improves the heat treating capacity .
 Heat treated alloys are stronger but have lower ductility .
 Typical applications – Railway wheels and tracks, gears, crankshafts.

11 High Carbon Steel
• Also known as ‘tool steel’ Contain 0.55%-1.5% carbon
• Very hard but offers Higher Strength Less ductile and less malleable.
• Hand tools (chisels, punches),Saw blades.

ALLOY STEEL
 Alloys are mixtures of two or more metals formed together with other elements/materials to
create new metals with improved Mechanical Properties and other properties of the base
metal.
 In general the properties desired in a metal to be used as building material are not present
advantage in any single metal.
 To develop specific properties a combination of metals or metallic substances is done and are
classified as alloys.
 The aim of making alloy is generally to make them less brittle, resistant to corrosion or to have
a more desirable color and luster.
 Alloy steels are broken down into two groups: low-alloy steels and high-alloy steels.
 Most commonly, the phrase "alloy steel" refers to low-alloy steels

High-Strength Low-Alloy Steels
 High-strength low-alloy (HSLA) steels, or microalloyed steels, are designed to
provide better mechanical properties and/or greater resistance to atmospheric
corrosion than conventional carbon steels.
 are designed to meet specific mechanical properties rather than a chemical
composition.
 The HSLA steels have low carbon contents (0.05-0.25% C) in order to produce
adequate formability and weldability, and they have manganese contents up to
2.0%.
 Small quantities of chromium, nickel, molybdenum, copper, nitrogen, vanadium,
niobium, titanium and zirconium are used in various combinations.

 Low-alloy Steels
 Low-alloy steels constitute a category of ferrous materials that exhibit
mechanical properties superior to plain carbon steels as the result of
additions of alloying elements such as nickel, chromium, and
molybdenum.
 Total alloy content can range from 2.07% up to levels just below that of
stainless steels, which contain a minimum of 10% Cr.
 For many low-alloy steels, the primary function of the alloying elements
is to increase hardenability in order to optimize mechanical properties
and toughness after heat treatment.
 In some cases, however, alloy additions are used to reduce
environmental degradation under certain specified service conditions.
.

USES OF ALLOYS
 Over 90% of metal use is in the form of alloys.
 Alloys are used because their chemical and physical properties are
superior for an application than that of the pure element components.
 Typical improvements include corrosion resistance, improved wear,
special electrical or magnetic properties, and heat resistance.
 Other times, alloys are used because they retain the key properties of
component metals, yet are less expensive.

Alloy steels and composition
Sl
no.
Alloy steel Composition
1 Stainless steel Chromium(10-20%)
2 Nickel steel Nickel(3.5%)
3 Invar steel Nickel (30-40%)
4 Vanadium steel Vanadium(0.1-2%)
5 Tungsten steel Tungsten(14-20%)
6 Manganese steel Manganese (12-15%)
7 Molybdenum steel Molybdenum (0.2-0.3%)

Stainless steel
 Stainless steels generally contain between 10-20% chromium as the main alloying
element.
 are valued for high corrosion resistance.
 With over 11% chromium, steel is about 200 times more resistant to corrosion than mild
steel.
 They are very hard and tough, high elastic and ultimate strength, acid and rust proof.
 These steels can be divided into three groups based on their crystalline structure:
Austenitic: Austenitic steels are non-
magnetic and non heat-treatable, and
generally contain 18% chromium, 8%
nickel and less than 0.8% carbon.
Austenitic steels form the largest
portion of the global stainless steel
market and are often used in food
processing equipment, kitchen utensils,
and piping.
Ferritic: Ferritic steels contain trace
amounts of nickel, 12-17%
chromium, less than 0.1% carbon,
along with other alloying elements,
such as molybdenum, aluminum or
titanium. These magnetic steels
cannot be hardened by heat
treatment but can be strengthened
by cold working.
Martensitic: Martensitic steels contain
11-17% chromium, less than 0.4%
nickel, and up to 1.2% carbon. These
magnetic and heat-treatable steels are
used in knives, cutting tools, as well as
dental and surgical equipment.

USES
Ball bearings Dies
Crushing machine
Kitchen utensils

Nickel steel
 Composition-(Nickel 3.5%)
 Capabilities. Nickel alloys are readily welded by either the gas or arc methods. It can be
machined, forged, cast, and easily formed.
 Properties
 More elastic
 Higher tensile strength
 Lesser brittle than mild steel
 Improved hardness and ductility
 Limitations.
 Nickel cannot withstand heat above 600° Fahrenheit. It oxidizes very slowly in
the presence of moisture or corrosive gases.
 The nickel steel alloy has more corrosion as compared to steel. The use of nickel
increases corrosion in steel

 EFFECT OF ALLOYING NICKEL TO STEEL
 Effect on Toughness ( )
When nickel is added to steel as an alloy, the nickel component increases the toughness of steel. Due to the
increase in toughness, the property of steel to resist fracture due to high impact increases. This property is
beneficial in parts made of steel subjected to shock and impact load.
 Effect on distortion ( )
The addition of nickel in steel decreases the value of distortion (distortion energy) at the time of quenching.
 Effect on Critical Temperature ( )
The critical temperature of steel decreases when nickel is added to it. Due to decrease in critical
temperature, steel becomes better for any type of heat treatment.
 Effect on Strength ( )
The strength of steel increases because of alloying nickel in the steel.
 Effect on Abrasive Resistance ( )
The abrasive resistance of steel increases when nickel is added to it as an alloy.
 Effect on Elastic Limit ( )
Nickel increases the elastic limit of steel.

Uses of Nickel Steel Alloy
 Nickel steel alloy is used for making storage cylinders for liquefied gases and for
other low temperature applications.
 Nickel steel alloy is used for heavy forgings, turbine blades, highly stressed
screws, bolts, and nuts.
 It is used for making shafts, gears, propeller shafts, and keys.
 Automobile and airplane parts.
 It is widely used in combination with chromium and molybdenum for cams,
chain pins, springs, connecting rods and their bolts, crankshafts, rolling
element, and bearings.

INVAR STEEL ALLOYS
 Composition-Nickel (30-40%)
 Invar is an iron based alloy in which iron is the base element.
 steels and cast irons are iron-carbon alloys however Invar is an iron-nickel alloy.
 Invar hardly consists of 0.01 to 0.1 percent carbon.
 In addition of iron (Fe) and nickel (Ni), invar may also contain cobalt (Co), chromium (Cr),
carbon ©, manganese (Mn), phosphorous (P), silicon (Si), sulfur (S), aluminum (Al),
magnesium (Mg), zirconium (Zr) and titanium (Ti).
 Invar alloys are widely known and utilized because they exhibit a coefficient of thermal
expansion (CTE) that is close to zero.
 The fact that Invar maintains this low CTE over room temperature has made it one of the
most effective alloys for use in precision instruments.
 USES-clocks, scientific instruments, bimetal strips in thermostats, and other materials that
require consistent monitoring systems.

VANADIUM STEEL ALLOY
 Composition-vanadium(0.1-2%)
 Properties
 High tensile and yield strength
 Resistance to softening at high temperatures.
 V-steels also provide weldability, ductility, elongation, good castability.
 Vanadium is the most widely used alloying element for strengthening steels used
in buildings and bridges.
 It is the most effective alloy for increasing the strength of reinforcing bars used
in construction.
 Vanadium-based alloys could not be used in pressurized water-cooled systems
because of excessive corrosion.
 Vanadium is widely used in various steel products, from crankshafts and
connecting rods to the chassis of many cars and trucks.

Vanadium steel pipe spanner Locomotive casting

TUNGSTEN STEEL ALLOY
 Composition-Tungsten(14-20%).
 Tungsten steel is a type of metal alloy made from a combination of tungsten and
iron.
 High cutting hardness and resistant to abrasion.
 The addition of tungsten to the alloy gives it increased hardness and resistance to
heat, allowing equipment made from tungsten steel to maintain high
performance and to resist wear at high temperatures.
 Tungsten steel is valued for its industrial uses as a tool steel and is commonly
used in industrial tools and machinery used for working other metals, such as
dies and cutting tools.

MANGANESE STEEL
 Composition-Manganese (12-15 %).
 Manganese is normally present in all commercial steels.
 It is important in the manufacture of steel because it deoxidizes the melt and facilitates
hot working of the steel by reducing the susceptibility to hot shortness.
 Manganese also combines with sulfur to form manganese sulfide stringers, which
improve the machinability of steel.
 It contributes to strength and hardness, but to a lesser degree than does carbon; the
amount of increase depends on the carbon content.
 Increasing the manganese content decreases ductility and weldability but to a lesser
extent than does an increase in carbon content.
 Manganese has a strong effect on increasing the hardenability of a steel.
 High levels of manganese produce an austenitic steel with improved wear and abrasion
resistance.
 Manganese has less of a tendency toward macrosegregation than any of the common
elements.

USES
 Points and crossings in railways.
 Rollers
 Jaws of crushers
 Heavy earth and mining equipments

MOLYBDENUM STEEL
 Molybdenum increases the hardenability of steel and is particularly
useful in maintaining the hardenability between specified limits.
 This element, especially in amounts between 0.15 and 0.30%.
 Hardened steels containing molybdenum must be tempered at a higher
temperature to achieve the same amount of softening.
 Molybdenum is unique in the extent to which it increases the high-
temperature tensile and creep strengths of steel.
 It retards the transformation of austenite to pearlite far more than it
does the transformation of austenite to bainite; thus, bainite can be
produced by continuous cooling of molybdenum-containing steels.
 Uses-gears ,axles, shafts.

 Molybdenum is used efficiently and economically in alloy steel & iron to
 Improve hardenability
 Reduce temper embrittlement
 Resist hydrogen attack & sulphide stress cracking
 Increase elevated temperature strength
 Improve weldability, especially in high strength low alloy steels (HSLA)
Gears Axle shafts

Alloy steel

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