CONTENTS
INTRODUCTION
IRON CARBON DIAGRAM
STEEL CLASSIFICATIONS
 LOW CARBON STEEL
 MEDIUM CARBON STEEL
 HIGH CARBON STEEL
 STAINLESS STEEL
APPLICATIONS OF STEELS
INTRODUCTION TO STEELS….
 Steel is an alloy of iron and carbon with a small percentage of other elements
such as chromium,nickel,molybdenum,cobalt,aluminium,tungsten etc.
 Steels are widely used engineering material because of;
 The abundance of iron in the earth crust
 The high melting temperature of iron(1534℃)
 The range of mechanical properties that can be obtained.
 The composition that contain upto 2.1 wt% of carbon are classified as steels
while those containing over 2.1 wt% C are classified as cast iron.
 Steel maynot be as strong as iron, but it is far more resistant and doesnot
corrode and doesnot get rusted like iron does.
IRON CARBON PHASE DIAGRAM
CLASSIFICATION OF STEELS
1. Low carbon steels
2. Medium carbon steels
3. High carbon steels
LOW CARBON STEELS(Less than 0.25% carbon)
 Also called as mild steels
 Relatively soft and weak
 Cannot be hardened appreciably by heat treatment but it can be
strengthened by cold work.
 They posses good formability and weldability.
APPLICATIONS
 Automobile sheet metal parts, structural applications- buildings,
bridges, plate steel for fabrication and other infrastructural
developments etc.
MEDIUM CARBON STEELS
 Carbon content ranges from 0.25 to 0.60%
 They have high strength and hardness properties with the absence of
ductility and toughness.
APPLICATIONS
Machinery components and engine parts such as crankshafts and
connecting rods, gears, railway wheels, rail axles etc.
HIGH CARBON STEELS(more than 0.60% carbon)
 They are least ductile (more brittle) of the carbon steels
 They have more wear resistance
 They are capable of holding a sharp cutting edge(it is the important
property of making tools)
APPLICATIONS
 Springs, cutting tools and blades, wear resistant parts, high strength
wires, dies etc.
ALLOY STEELS
Any steel other than carbon steel is called alloy steels.
Alloying elements are chromium, nickel ,molybdenum, vanadium, tungsten,
cobalt, boron, copper and others.
Alloy steels are classified into
Low alloy steels(having 3-4% alloying element)
High alloy steels(having more than 5% alloying element)
HIGH ALLOY STEELS
STAINLESS STEEL (SS)
Highly alloyed steels are designed for corrosion resistance
Principle alloying element is chromium, usually greater than 15%(It permits a thin,
protective surface layer of chromium oxide to form when the steel is exposed to oxygen)
Nickel is another alloying ingredient in certain stainless steel to increase corrosion
protection.
In addition to corrosion resistance, SS are noted for their combination of strength and
ductility.
Carbon is used to strengthen and harden SS, but high carbon content reduces corrosion
protection.
Significantly more expensive than plain carbon or low alloy steels
APPLICATONS
Medical and surgical equipments, automotive industry, architecture, building and
construction, chemical and petrochemical industry, Razor blades, swords, scissors etc
STAINLESS STEELS
FERRITIC STAINLESS STEELS
Chromium generally 11-20%
Low carbon (less than 0.10%)and nickel content
Good corrosion resistance(but less than austenitic SS)
Magnetic
High ductility
Ferritic stainless steels have a body- centered cubic structure system
Limited weldability and toughness
APPLICATIONS
Used in boiler, washing machine, automotive trim ,exhaust system, containers,
heat exchangers, mining equipment, thermal processing, water heaters,
agricultural equipment etc.
AUSTENITIC STAINLESS STEELS
These are the most common steels. Chromium content is minimum of 16%
and carbon content is maximum of 0.15%
Sufficient nickel and manganese are added to retain the austenitic structure at
all temperatures.
They are non magnetic
Austenitic stainless steels have an austenitic crystalline structure, which is a
face centered cubic crystal structure.
More than 70%stainless steels are austenitic.
APPLICATIONS
Food and beverage processing equipments, kitchen sink, chemical industries,
cookware, pharmaceutical equipment, architecture, tanks etc.
MARTENSITIC STAINLESS STEELS
Martensitic stainless steel contains chromium(12-14%),molybdenum(0.21%),nickel(less than 2%),and carbon(about 0.1-1% giving it more hardness but
making the material a bit more brittle.)
They are not as corrosion resistant as ferritic and austenitic steels but are
extremely strong and tough ,as well as highly machinable, and can be hardened
by heat treatment.
They are used where high strength and moderate corrosion resistant is required.
These steels are magnetic
It has Body centered tetragonal martensite microstructure.
APPLICATIONS
Blade, knife, pin, surgical instrument ,petrochemical industry for steam and gas
turbines blades and buckets, hydroelectric engines, pump parts etc.
PRECIPITATION HARDENING STAINLESS STEELS
 These steels can develop very high strength by adding elements such as
copper, titanium, niobium and aluminium to the steel.
With a suitable ‘aging’ heat treatment ,very fine particles form in the matrix of
the steel which imparts strength.
These steels are non magnetic
They have good corrosion resistance comparable to austenitic steels and have
high toughness and strength
Provide an optimum combination of the properties of martensitic and austenitic
grades
APPLICATIONS
Aircraft parts, high strength shafts, spindle, pump, turbine blades, moulding
dies, valves and other engine components etc.
DUPLEX STAINLESS STEELS
Duplex stainless steels are called “duplex” because they have a two phase
microstructure consisting of grains of ferritic and austenitic stainless steel.
Contains chromium(15-30%), molybdenum(up to 5%) and small amounts of
nickel.
Higher strength than either ferritic or austenitic stainless steels. They have
moderate formability.
Greater corrosion resistance
They are magnetic, but not so much as the ferritic and martensitic.
APPLICATIONS
Pressure vessels, storage tanks, structural and industrial applications etc.
APLICATIONS OF STEELS
Industrial applications
Nuclear power systems
Fast reactors
Building and Construction
Architectural uses
Interior furnishing
Kitchen appliances
Machinery components
Turbine blades
Medical and surgical equipments
Aerospace applications
Automobiles
Railroads
Cutting tools
Metal roofing
Engine parts
Gates, windows
Water supply pipes
THANK YOU...