Ferous Flashcards
What is pure aluminium
Soft
Malleable and ductile
What is cast iron
When molten iron is alloyed with more than 2% carbon
Low strength to weight ratio
What is a slag
When limestone reacts with Amy impurity in the molten iron and floats to the surface to form a slag layer
What is steel
When pure iron is remelted and carbon is introduced
Has a high density 3 times more than aluminium
Susceptible to corrosion
What is steel used for
Landing gear
What is carbon used for in alloying steel
Primary hardening element
Hardness and tensile strength increase as carbon increase
What is low carbon
0.1 - 0.3 carbon
Safety wire
Secondary structures
What is medium Cardin
0.3 - 0.5 carbon
Used when machining is required
When surface hardness is required
What is high carbon
0.5 - 1.05 carbon
When extreme hardness is required
Springs files and cutting tools
Why is sulphur used in alloying steel
Decrease ductility and weld ability
Why is manganese used in alloying steel
Contributes to strength and hardness
What dose silicon do to alloying steel
De-oxidisers
Get rid of impurity
What dose phosphorus do to alloying steel
Increases strength and hardness and corrosion resistance
Decreases ductility
What does nickel do to alloying steel
Increases hardenability
Increases strength
What does chromium do to alloying steel
Increase corrosion resistance
Increase oxidation resistance
Increase hardenability and improve high temp strength
What does molybdenum do to alloying steel
Increase hardenability
What does vanadium do to alloying steel
Increase yield strength and the tensile strength
What does titanium do to alloying steel
Improves toughness
What is AISI
American iron and steel institute
What is the first 2 digit of alloying steel mean
The specific primary alloying elements
What does the last 2 digits of alloying steel mean
The percentage of carbon
What is SAE
Society of automotive engineers
What does tempering do to steel
Decrease hardness
Increasing ductility and toughness
Relives stresses
What can be tempered
High carbon steels
What is tempering dependent of
Temperature Thermos couple controlled ovens Yellow low temp Blue high temp Purplish brown medium temp
What can not be hardened
Pure iron
Wrought iron
Low carbon
What is hardening
When steel is heated above its critical temperature allowing carbon to disperse uniformly in the iron matrix
Then collect rapidly by quenching
If quenched to quickly martensite is formed
What is the slowest quenching medium
Oil
What is the fastest quenching medium
Brine
Salt water
What is martensitic
A super saturated solid solution which is too brittle
What dose annealing do
Softens steel and relives internal stresses
What is annealing
Heating 50F above the upper critical limit and soaking it at this temp
Cooled very slowly
Makes steel very soft and ductile
What is normalising
Heating 100F above its upper critical limit and soaking it
Then cooled at room temperature
What does normalising do
Gets rid of internal stresses
What is ferrite
Pure iron
BCC
What is austenite
FCC
absorbs a lot more carbon than ferrite
What is cementite
he higher the carbon content, the more cementite will be present and the harder but more brittle the alloy will be
What is pearlite
Two phased
Layered
Alpha ferrite
Cementite
What is stainless steel
Corrosion resistance steel
Strength
Toughness
Resistance to high temperature
What are the 2 types of stainless steels
Austentic
Martensitic
What type of stainless steel most commonly used in aircraft
Austenitic 300
What are austenitic steels
200 and 300 series
Chromium-nickel
Chromium-nickel-manganese
How are austenitic steel hardened
Cold-working
Heat treatment
What are austenitic steel in the annealed condition
Non magnetic unless cold worked
How are austenitic steels formed
heating the steel mixture above the critical range and holding to form a structure called austenite. A controlled period of partial cooling
followed by a rapid quench just above the critical range.
What is a ferrific
400 series
Very low carbon
Cannot be harden by heat treatment and quenching due to low carbon
What are ferritic steels used aircraft
Pipes and tubing
What are the properties of ferritic metals
Excellent corrosion resistance at high temperatures
What is a martensitic
400 series
Straight chromium alloy that’s harden intensely if they are allowed to cool rapidly from high temperatures.
What is the difference of martensitic
Can be hardened by heat treatment
What are martensitic used for in aircraft
Turbine blades applications
What are the disadvantages of stainless steel
More difficult to cut
Have a high expansion coefficient than other steels
Lose there corrosion resistance under high temps
Precipitation-hardened stainless steels
Contain very little carbon Are solution heat-treated Can he hardened to very high strengths Good crosion resistance Used for Airframe
High strength low alloy steel
Iron based alloy can be hardened to very high strength
Aircraft landing gear
Heat is hydrogen embrittlement
Occurs in various metals
Under a load the hydrogen will migrate to the grain boundaries or voids in the metal
At high temps the hydrogen reacts with the carbon to from methane which cause a build up of pressure and propagate cracks
When dose hydrogen embrittlement increase
When hardness and strength increase
Stress and concentrations
Since most steel parts are highly-stressed, localised stress concentrations are undesirable and should always be removed.
How to stop hydrogen embrittlement
Baked at 190 degreased for 3 hours
How to protect stainless steal
Cadmium plating
Zinc spraying
Chromate passivising
How to protect non-stainless steel
Cadmium plating plus a paint finish • Phosphating plus a paint finish • Aluminium spraying • Hard chromium plating • Chemical nickel plating • Silver plating (not in contact with aluminium
What is more susceptible to corrosion
Noble metals Lower number on the galvanic scale Magnesium Zinc Aluminium
What is less susceptible to corrosion
More noble Higher on galvanic scale Platinum Gold Silver
How is galvanic corrosion measured
How dissimilar metals are
What is cAse Harding
When a hard durable surface that is suitable for load bearing
Best for low carbon
Not suitable for non-ferrous
What are the 3 types of carburising
Pack
Gas
Liquid
What is carburising
Carburising produces a thin layer of high carbon steel on the surface of a low carbon steel component
What is pack carburising
heating the component up to temperatures of 1700 degrees Fahrenheit whilst it is packed into a carbon rich material such as charcoal. The carbon penetrates the surface of metal causing it to hard
What is gas carburising
is similar to pack carburising, but utilises a carbon dioxide rich atmosphere within the oven instead of a carbon rich solid
What is liquid carburising
works by heating the metal up in a bath of either sodium cyanide or barium cyanide. Either liquid will provide the necessary carbon to surface harden the metal.
What is flame hardening
When the surface layer receive an extra heat treatment compared to the core
Heating the surface and quenching it straight after
Only on steels less than 0.4
Only after the steel has been normalised
What is induction heating
The whole surface is heated simultaneously by induction coil
Then quenched with jets of water
What is nitriding
Has a better surface finish than carburising
Is hardened tempered before surface Harding
Heating in ammonia rich environment
What does tempering do
Decreases hardness increase ductility and toughness
