Chapter 11 Flashcards
What are the types of cast iron?
- Gray
- Ductile
- White
- Malleable
- Compacted graphite
What are the characteristics of gray iron?
- Graphite flakes
- Weak & brittle in tension
- Stronger in compression
- Excellent vibrational dampening
- Wear resistant
What are the characteristics of ductile iron?
- Mg and/or Ce is added
- Graphite nodules
- Matrix is often pearlite which is stronger but less ductile
What are the characteristics of white iron?
- Less than 1 weight % Si
- Pearlite + cementite
- Very hard
- Very brittle
What are the characteristics of malleable iron?
- Heat-treated white iron at 800 - 900 deg C
- Graphite in rosettes
- Reasonably strong and ductile
What are the limitations of ferrous alloys?
- Relatively high densities
- Relatively low electrical conductivity
- Generally poor corrosion resistance
What are the characteristics of compacted graphite iron?
- Relatively high thermal conductivity
- Good resistance to thermal shock
- Lower oxidation at elevated temperatures
What is a ferrous alloy?
A metal alloy where iron is the primary component (steels 0 - 1.4 wt% C and cast irons 3 - 4.5 wt% C)
What is a nonferrous alloy?
A metal alloy where iron is not the primary component
What are the types of nonferrous alloys?
- Cu
- Al
- Ti
- Mg
- Noble
- Refractory
Copper alloys
- Brass (corrosion resistant)
- Bronze
- Cu-Be (hardened)
Aluminum alloys
- Low density
- Solid solution or precipitant
- Strengthened
Magnesium alloys
- Very low densities
- Ignites easily/highly flammable
Titanium alloys
- Relatively low densities
- Reactive at high temperatures
Noble metals
- Ag, Au, Pt
- Oxidization/corrosion resistant
Refractory metals
- Nb, Mo, W, Ta
- High melting temperatures
What are the types of metal fabrication methods?
- Forming (rough stock shaped)
- Casting (molten metal molded)
- Miscellaneous (powder metallurgy and welding)
What are the types of metal forming?
- Forging (hammering or stamping)
- Rolling (hot or cold)
- Drawing (pulling)
- Extrusion (pushing)
What is the difference between hot and cold working?
Hot working
- Deformation temperature high enough for recrystallization
- Large deformations
Cold working
- Deformation below recrystallization temperature
- Strain hardening occurs
- Small deformations
What are the characteristics of metal casting?
- Metal is melted in a furnace where alloying elements may be added, then cast in a mold
- Common and inexpensive
- Good production of shapes
- Weaker products, often have internal defects
- Good option for brittle materials
What are the types of metal casting?
- Sand casting (large parts)
- Investment casting (low-volume, complex shapes)
- Die casting (high volume, low melting temps)
- Continuous casting (simple shapes)
What is investment casting?
1) Plaster of paris poured and hardened around wax pattern
2) Wax melts, leaving hollow plaster mold
3) Molten metal poured in and solidified
What is powder metallurgy?
- Good for intricate/precise shapes
1) Compaction of metal powders
2) Densification heat treatment
What is welding?
A technique for joining metals in which the actual melting of the pieces to be joined occurs in the vicinity of the bond. A filler metal may be used to facilitate the process.
What is the heat-affected zone?
The region in which the microstructure has been changed by welding
What is annealing?
Heating a metal and then allowing it to slowly cool, changes the microstructure and properties of the metal
What are the types of annealing?
- Stress relief
- Spheroidize
- Full anneal
- Process anneal
- Normalize
What is the purpose of stress relief annealing?
To reduce stresses from plastic deformation, nonuniform cooling, or phase transformation
What is the purpose of spheroidizing?
To make very soft steels for machining, achieved by heating just below the eutectoid temperature and holding for 15-25 hours
What is the purpose of full annealing?
To make soft steels for forming by heating to form austenite then furnace cooling to form coarse pearlite
What is the purpose of process annealing?
To negate the effects of cold working by recovery/recrystallization
What is the purpose of normalizing?
To decrease grain size by deforming steel, heat treating to allow for recrystallization, then smaller grains form
What is quenching?
A type of heat treatment where metal is cooled rapidly by a fluid
What is tempering?
The metal being treated, using this process, is heated under its critical point temperature and then air-cooled. Increases strength and ductility
What is hardenability?
- The measure of a material’s ability to form martensite or be heat treated
- Jominy end quench test is used
How does hardness change with distance?
Hardness decreases as distance increases
Why does hardness change with distance?
The cooling rate decreases with distance from the quenched end
What are three common quenching mediums?
- Air
- Oil
- Water
Rank the severity of quench/hardness from least to greatest
- Air
- Oil
- Water
What are the effects of an increasing surface area to volume ratio?
- Interior cooling rate increases
- Interior hardness increases
What is precipitation hardening?
Hardening/strengthening due to the formation of precipitate particles
How is hardenability affected by alloy content?
Hardenability increases with increasing alloy content
