Alloys
combining two or more metallic elements to give a greater strength
Harder,less malleable,low melting point.
Low electrical conductivity.
Resists corrosion and action of acids.
Increases hardness of a metal,
Modify the colour of the metal,
Good casting of the metal,good
Greater strength,
Modify the chemical activity,
Low melting point,
Micro structure
presence or absense of iron.
Principal metals
alloys of Cu+Zn = brasses
alloys of Cu+Sn = bronzes
alloys of Al =duralium
ferrous alloy
non-ferrous alloy.
Alloys that are amenable mechanical deformation
Alloys that are so brittle that forming or shaping by appreciable deformation is not possible
steel
Plain carbon steel
Hypoeutectoid steel
Soft/low Carbon steel
0.08% to 0.2%
carbon
making boiler tubes, plates, sheet steel, bolts, nails, wires, screws, gear, wheels etc
Soft, ductile, weldable, Dark bluish with fibrous structure, Low tensile strength, Shock resistant
Not susceptible to heat treatment
High/Hard Carbon steel
0.5% to 0.8%
making wheels for railway bogies, cushion spring, dies, screws etc
Welded with care
Can be tailored to desired hardness
Medium Carbon Steel
0.2% to 0.5%
carbon.
machine parts, turbine motors, railway angle, wheels, gears, hydraulic fitting, connecting rods, automobile engine parts
Tougher and harder than mild steel
Good machinability and less weldability
Good strength
Can be hardened by heat treatment
Hypereutectoid steel
Very High Carbon/Hard Steel
0.8% to 2.0%
for manufacturing various types of tools such as; hammers, drills, etc;
High strength
Can be hardened, toughened and tempered easily
Possess wear resistance
Welded easily
↑ brittleness
↑ carbon content
↓ductility
no proper corrosion resistance
not deeply hardened.
Ni,Cr,Co,Mn,Mo,V
alloy steel/special steel
Steel containing specified amounts of alloying elements other than carbon is known as alloy steel
Chromium
Copper
Manganese
Nickel
Tungsten
Molybdenum
Ferrous alloy
Stainless steel
Heat treatable
stainless steel
C=1.2%
Cr=>12-16%
Magnetic, tough & can be worked in cold condition
Possess less strength at high temperature
Resistant to corrosion
1. Can be used up to 800⁰C
2. Good resistant towards weather & water
3. In making surgical instruments, scissors, blades,etc.
Non-heat treatable
stainless steel
Magnetic type
C=1.2%
Cr=>12-16%
1. Can be forged, rolled & machined
2. Resist corrosion
Used in making chemical equipments
and automobile parts.
Non--magnetic type
Cr=18-26%
Ni=8.21%
c=0.15%
total%Cr&Ni>=23%
1. Resistance to corrosion.
2. Corrosion resistance is increased by adding molybdenum
In making household utensils, sinks, dental & surgical instrument
Nichrome
Ni=60%
Cr=12%
Fe=26%
Mn=2%
1. Good resistance to oxidation & heat
2. High melting point & electrical resistance
3. Withstand heat up to 1000-1100⁰C
1. Used for making resistance coils, heating elements in stoves & electric irons
2. Used in making parts of boilers, steam lines stills, gas turbines, aero engine valves, retorts, annealing boxes.