applications and processing of metals and...
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Engineering Materials
2189101
Chedtha PuncreobutrDepartment of Metallurgical Engineering
Chulalongkorn University
Applications and processing
of metals and alloys
http://pioneer.netserv.chula.ac.th/~pchedtha/
Metals and their uses
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Metals and Alloys
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IronCopper
AluminiumZincTin
Gold
Brass ( Copper & Zinc)
Steel (Iron & Carbon)
Cast Iron (Iron & Carbon)
Duralumin (Aluminium & Copper)
Bronze (Copper, Tin, Phosphorus)
(a mixture of two or more materials)
Pure Metals Alloys
Carbon and alloy steels
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Carbon steels
Classified as low, medium and high:
1. Low-carbon steel or mild steel, < 0.3%C, bolts, nuts and sheet plates.
2. Medium-carbon steel, 0.3% ~ 0.6%C, machinery, automotive and agricultural equipment.
3. High-carbon steel, > 0.60% C, springs, cutlery, cable.
Stainless steels
• Characterized by their corrosion resistance, high strength and ductility, and high chromium content.
• Stainless as a film of chromium oxide protects the metal from corrosion
Tool steels
• Designed for high strength, impact toughness, and wear resistance at a range of temperatures.
• Alloying with Mo, W, Cr
Fe-C True Equilibrium Diagram
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Graphite formation
promoted by
• Si > 1 wt%
• slow cooling
1600
1400
1200
1000
800
600
4000 1 2 3 4 90
L
g +L
+ Graphite
Liquid +
Graphite
(Fe) C, wt% C
0.6
5740°C
T(°C)
g + Graphite
100
1153°Cg
Austenite 4.2 wt% C
+ g
Steel and its uses
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Steel is the most commonly used metal and is used in everything from Sewing needles to Skyscrapers
HMS Ark Royal
The Golden Gate Bridge
Advantages:
Disadvantages:
Low Cost, High Strength & Easy to work with.
Rusts
Stainless Steel and its uses
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Stainless Steel is a mixture of Steel and Chromium
Advantages:
Disadvantages:
Does not rust
More difficult to Join tan ordinary Mild Steel
Cutlery
Gateway Arch in St Louis – 304 series SS
Surgical Instruments
Cookware
Cast iron and its uses
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Cast Iron is a mixture of Iron and 2% Carbon.
Advantages:
Disadvantages:
Low Cost, Casts well, High Strength (under compression)
Rusts, Brittle, Difficult to join, Low Strength (under tension)
Fence Engine Block Pan
Nonferrous Alloys
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NonFerrous Alloys
• Al Alloys-low r: 2.7 g/cm3
-Cu, Mg, Si, Mn, Zn additions -solid sol. or precip.
strengthened (struct. aircraft parts & packaging)
• Mg Alloys-very low r: 1.7g/cm3
-ignites easily -aircraft, missiles
• Refractory metals-high melting T’s-Nb, Mo, W, Ta• Noble metals
-Ag, Au, Pt -oxid./corr. resistant
• Ti Alloys-relatively low r: 4.5 g/cm3
vs 7.9 for steel-reactive at high T’s
-space applic.
• Cu AlloysBrass: Zn is subst. impurity(costume jewelry, coins, corrosion resistant)Bronze : Sn, Al, Si, Ni are subst. impurities (bushings, landing gear)Cu-Be: precip. hardened for strength
Aluminium and its uses
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Advantages:
Disadvantages:
Lightweight, Malleable, Ductile & Does not corrode, Low melting point (660 C)
Higher Cost than steel, Harder to Weld
• Aluminium is found primarily in bauxite ore and is
remarkable for its ability to resist corrosion (due to
the phenomenon of passivation) and its light weight.
• Structural components made from aluminium and
its alloys are vital to the aerospace industry and very
important in other areas of transportation and
building.
Copper and its uses
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Advantages:
Disadvantages:
Malleable, Ductile, Good Conductor of heat & electricity, Does not corrode to any great extent
High Cost & Rather soft
• Copper is one of the oldest metals known to man.
The discovery of alloying copper and tin to make
bronze (the first ever alloy) was a major step
forward because bronze is harder, tougher and
stronger than copper
Tin and its uses
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Advantages:
Disadvantages:
Does not corrode
Heavy & Rather soft, Expensive
• Tin is seldom used in its pure form but
is often added to other metals to form
Alloys such as bronze, bell metal,
Babbitt metal, die casting alloy, pewter,
phosphor bronze, soft solder,
Solder (Lead Tin alloy)
Zinc and its uses
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• The most common use for Zinc is galvanising,
This is the process of dipping mild steel in a
tank of molten Zinc, this provides a corrosion
resistant coating
Galvanized Steel Bucket
Zinc is also used for sacrificial anodes on the hull of steel boats
Materials Processing
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Materials processing:
a set of transformations of input elements into products
Methods chosen depend on:
(1) Properties of materials
(2) Size and shape of finished product
(3) Cost
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Metal processing overview
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Steel Making
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Forming operation
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• Forming operations (forging, rolling, drawing, extrusion) are
where the shape of metal is changed by plastic deformation
• Forming processes are commonly classified into
cold-working and hot-working operations
• Deformation must be induced by an external force or stress.
The magnitude of which must exceed the yield strength of the
material
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Cold-working
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• Temperature at which the deformation take place is “cold”
relative to the absolute meting temperature
• Cold-working (plastic deformation) of metal results in an
increase in strength or hardness and a decrease in ductility
• Close dimensional control of the finished piece
• Good quality surface finish
• When cold-working is excessive, the metal will fracture
before reaching the final shape
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Hot-working
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• Material remains relatively soft and ductile during deformation
because it does not strain harden, hence large deformations are
possible
• Hot-working processes (rolling, extrusion or forging) is typically
used in the first step of converting cast ingot into wrought product
2189101 – Engineering MaterialsChedtha Puncreobutr
• Deformation energy requirements are less than that for cold-
working
• However, most metals experience some surface oxidation,
which results in material loss and a poor final surface finish
Forming operation
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Rolling
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Rolling
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Rolling
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Plastic deformation
Rollers in compression
thick slab
thin sheet
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Hot rolling and Cold rolling
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Hot rolling and Cold rolling
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slab
bloom
billet
sheetcoil
bar rod
structural
ingot
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Forging
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• Forging is the process where metal
(Fe, Ti, Al) is heated and shaped by
plastic deformation (compressive
forces)
• The compressive force typically
comes from successive blow or
continuous pressing)
• Forged articles have outstanding
grain structures and best
combination of mechanical
properties.
• Wrenches, automotive crankshafts
and piston connecting rods
generally formed by forging
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Forging
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Die Forging
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Closed-Die Forging
Open-Die Forging
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Extrusion
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Suitable for ductile metals such as Cu and Al
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Extrusion of Tubing
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Drawing
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Casting
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• Casting is pouring liquid metal into
carefully designed mould cavity
and solidifies into a desired shape
under controlled conditions
• The first step in all manufacturing
processes involving metal
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Casting
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Sand Casting
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Investment Casting
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Investment casting - A casting process that is used for making complex
shapes or casting of precious metals, also known as the lost wax process.
• The pattern is made of low melting materials (such as plastic or wax)
which is then coated with ceramic to form a mould.
• After the wax is melted and drained, metal is poured into the mould
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Investment Casting
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Applications:
• The process is more expensive than sand casting but provide superior
surface finish and better controlled solidification conditions
• Very thin sections can be produced and the process allows for high
dimensional accuracy
complex shapes (e.g. superalloys turbine
blade and turbocharger)
Costly materials
(gold and silver
jewellery, bronze
sculpture and
titanium medical
parts)
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Die Casting
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Die casting - A casting process in which molten metal/alloys is forced
into a die (permanent mould) under pressure and is held under pressure
during solidification
Advantages:
• High production rate
• Very low unit cost
• Good smooth surface finish
• Excellent dimensional accuracy
• Limit only to relative small pieces
and to alloys of low melting
points such as Zn, Al and Mg
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Continuous Casting
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Welding
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Welding
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