MODULE 1] ALLOYS
An alloy is a homogeneous mixture of two or more elements with metallic properties.
If one of the constituent of alloy is mercury, it is known as amalgam. Eg. Sodium amalgam
(Na-Hg) , Aluminium amalgam (Al-Hg) .
• PLAIN CARBON STEELS
The alloys of iron with other metal (s) or/and non- metal are known as ferrous alloys. The
metal iron generally forms alloys by mixing with carbon, known as “Plain Carbon Steels”.
Since these steels essentially contain iron and carbon, are known as plain carbon steels. The
percentage of carbon in steels ranges from 0.008% to 2%.
• FERROUS ALLOY
SR. PROPERTIES MILD CARBON MEDIUM CARBON HIGH CARBON STEEL
NO. STEEL STEEL
1 CARBON 0.15%-0.30% 0.30%-0.80% 0.8%-1.5%
CONTENT
2 STRUCTURE FIBROUS - GRANULAR
3 COLOUR DARK BLUISH - -
4 TOUGHNESS LESS TOUGH TOUGHER & HARDER HARDER & WEAR RESISTANT,
THAN MILD STEEL PRODUCE KEEN CUTTING EDGE
5 DUCTILITY DUCTILE LESS DUCTILITY LESS DUCTILITY
6 WELDABILITY WELDABLE BY EASILY WELDABLE NOT WELDABLE
FORGING
7 MAGNETIC PERMANENTLY MAGNETISED PERMANENTLY MAGNETISED
PROPERTY MAGNETISED
8 SHOCK GOOD SHOCK & HIGHLY RESISTANT IT CAN WITHSTAND SHOCKS &
RESISTANCE IMPACT TO SHOCK VIBRATIONS BETTER THAN MILD
RESISTANCE & MEDIUM CARBON STEEL
• LIMITATION OF PLAIN CARBON STEEL
Very rapid rate of cooling needed to produce hardening.
In large pieces it is not possible to cool the inside rapidly enough and so only the surfaces can
be hardened.
This can be improved with addition of other elements in alloy steels.
, Effects of alloying elements Ni, Co, V, Mo, W, Cr on Properties of steel
SR ELEMENTS EFFECTS ON PROPERTIES OF APPLICATIONS OF ALLOYS
NO STEEL
.
1 CARBON Increases hardness & Tensile In manufacturing of stainless steel,
strength, Decreases ductility & Ni-Cr steel
malleability
2 NICKEL It decreases toughness, strength, Used in axles, guns, shaftings,
elasticity, harden ability. It increases vessels, balance wheels, naval
resistance to heat, corrosion & fatigue applications, pendulums,
of steel. measuring tapes, compass box
instruments.
3 COBALT It gives strength & hardness to steel. To make high speed cutting tools,
Retains permanent magnetism. locomotive castings
4 VANADIUM Increases strength, toughness, It is used in axles, springs, high
Increases harden-ability, abrasion & speed tools, locomotive castings
wear resistance, shock resistance.
5 MOLYBDENU It increases abrasion resistance, It is used in high speed tools, in
M corrosion resistance , strength at automobile parts.
elevated temperature.
6 TUNGSTEN It increases hardness, toughness, It is used in manufacturing of
tensile strength, abrasion resistance, machine tools, cutting tools, chisel,
shock resistance, heat& water drills & permanent magnets.
resistance, corrosion resistance,
magnetic properties.
7 CHROMIUM It increases hardness, wear & cutting It is used in surgical instruments,
ability of steels, increases corrosion stainless steel cutlery, connecting
resistance. rods, grinding wheels & rails, etc
• HEAT RESISTING STEEL
Alloy steels suitable for making equipment's exposed to high temperatures.
For getting such steel Molybdenum is an alloying element, which gives strength and creep
resistant to steel at high temperature. Steels containing 3.5% Mo are used as heat resisting
steels.
Chromium is a universal constituent of all heat resisting steels, because it increases corrosion
resistance at high temperatures. Heat resisting steel generally contain more than 12%
chromium.
Important heat resisting steels are:
Nichrome, a steel alloyed with 60% nickel and 12% chromium can be used at 1000 to
11000C
Steels containing16 to 20 % chromium with low carbon possess oxidation resistance up
to 9000C
An alloy is a homogeneous mixture of two or more elements with metallic properties.
If one of the constituent of alloy is mercury, it is known as amalgam. Eg. Sodium amalgam
(Na-Hg) , Aluminium amalgam (Al-Hg) .
• PLAIN CARBON STEELS
The alloys of iron with other metal (s) or/and non- metal are known as ferrous alloys. The
metal iron generally forms alloys by mixing with carbon, known as “Plain Carbon Steels”.
Since these steels essentially contain iron and carbon, are known as plain carbon steels. The
percentage of carbon in steels ranges from 0.008% to 2%.
• FERROUS ALLOY
SR. PROPERTIES MILD CARBON MEDIUM CARBON HIGH CARBON STEEL
NO. STEEL STEEL
1 CARBON 0.15%-0.30% 0.30%-0.80% 0.8%-1.5%
CONTENT
2 STRUCTURE FIBROUS - GRANULAR
3 COLOUR DARK BLUISH - -
4 TOUGHNESS LESS TOUGH TOUGHER & HARDER HARDER & WEAR RESISTANT,
THAN MILD STEEL PRODUCE KEEN CUTTING EDGE
5 DUCTILITY DUCTILE LESS DUCTILITY LESS DUCTILITY
6 WELDABILITY WELDABLE BY EASILY WELDABLE NOT WELDABLE
FORGING
7 MAGNETIC PERMANENTLY MAGNETISED PERMANENTLY MAGNETISED
PROPERTY MAGNETISED
8 SHOCK GOOD SHOCK & HIGHLY RESISTANT IT CAN WITHSTAND SHOCKS &
RESISTANCE IMPACT TO SHOCK VIBRATIONS BETTER THAN MILD
RESISTANCE & MEDIUM CARBON STEEL
• LIMITATION OF PLAIN CARBON STEEL
Very rapid rate of cooling needed to produce hardening.
In large pieces it is not possible to cool the inside rapidly enough and so only the surfaces can
be hardened.
This can be improved with addition of other elements in alloy steels.
, Effects of alloying elements Ni, Co, V, Mo, W, Cr on Properties of steel
SR ELEMENTS EFFECTS ON PROPERTIES OF APPLICATIONS OF ALLOYS
NO STEEL
.
1 CARBON Increases hardness & Tensile In manufacturing of stainless steel,
strength, Decreases ductility & Ni-Cr steel
malleability
2 NICKEL It decreases toughness, strength, Used in axles, guns, shaftings,
elasticity, harden ability. It increases vessels, balance wheels, naval
resistance to heat, corrosion & fatigue applications, pendulums,
of steel. measuring tapes, compass box
instruments.
3 COBALT It gives strength & hardness to steel. To make high speed cutting tools,
Retains permanent magnetism. locomotive castings
4 VANADIUM Increases strength, toughness, It is used in axles, springs, high
Increases harden-ability, abrasion & speed tools, locomotive castings
wear resistance, shock resistance.
5 MOLYBDENU It increases abrasion resistance, It is used in high speed tools, in
M corrosion resistance , strength at automobile parts.
elevated temperature.
6 TUNGSTEN It increases hardness, toughness, It is used in manufacturing of
tensile strength, abrasion resistance, machine tools, cutting tools, chisel,
shock resistance, heat& water drills & permanent magnets.
resistance, corrosion resistance,
magnetic properties.
7 CHROMIUM It increases hardness, wear & cutting It is used in surgical instruments,
ability of steels, increases corrosion stainless steel cutlery, connecting
resistance. rods, grinding wheels & rails, etc
• HEAT RESISTING STEEL
Alloy steels suitable for making equipment's exposed to high temperatures.
For getting such steel Molybdenum is an alloying element, which gives strength and creep
resistant to steel at high temperature. Steels containing 3.5% Mo are used as heat resisting
steels.
Chromium is a universal constituent of all heat resisting steels, because it increases corrosion
resistance at high temperatures. Heat resisting steel generally contain more than 12%
chromium.
Important heat resisting steels are:
Nichrome, a steel alloyed with 60% nickel and 12% chromium can be used at 1000 to
11000C
Steels containing16 to 20 % chromium with low carbon possess oxidation resistance up
to 9000C
