Introduction And Ferrous Materials Flashcards
What is the definition of density?
The measure of mass per unit volume
What is the definition of fatigue?
When a metal is subjected to cyclic loads, it will start to crack after sufficient repetitions
What is the definition of elasticity?
When a material returns to its original shape after the deforming force has been removed
What is the definition of Unit Stress?
The force per unit area
Name the three simple stresses
Tensile
Compressive
Shear
What is combined stress?
A combination of tensile and shear stresses
Or
A combination of compressive and shear stresses
What is tensile stress?
The stretching or lengthening effect on a material
What is compressive stress?
The compressive or shortening effect on a material
What is shear stress?
The effect caused by layers on a material to slide over each other from opposite directions
What does Poisson’s Ratio state?
That the more the material is stretched, the thinner the material gets
What is the definition of hardness?
The ability to resist penetration/wear or cutting action
What is the definition of strength?
The ability to withstand forces which tend to deform the metal in any direction
What is the definition of plasticity?
The ability for a metal to be reshaped
What is the definition of ductility?
The ability to be drawn (stretched) into thinner sections without breaking
What is the definition of malleability?
The ability of a material to be beaten, rolled or stretched into a new shapw without breaking
What is the definition of toughness?
The ability to deform without breaking
What is the definition of Brittleness?
The ability to break easily when deformed/hammered
What is the definition of conductivity?
The ability to transmit heat or energy
What is the definition of durability?
The ability for a metal to withstand forces applied over a period of time
What are metallic materials?
A substance containing metal or a metal itself
What is a non-metallic material?
A substance containing no metal
What is a ferrous material?
A substance containing iron or any alloy that also contains iron
What is a non-ferrous material?
A metal which contains very little or no iron
What are the 4 elastic properties?
Elastic limit
Yield Strength
Ultimate Tensile Strength
Breaking Point of Sample
What is the Elastic Limit?
The maximum point of stress to which a material may be subjected and still return to its original shape.
What is the Yield Strength?
The maximum stress that can be applied without permanent deformation
What is the Ultimate Tensile Strength?
The maximum value of Tensile Stress that a material can withstand without breaking
What is the Breaking Point of a Sample?
The Modulus of Elasticity : the ratio of stress to strain within the proportional limit of a material in tension or compression
What are the three lightweight materials used for aircraft?
Aluminium
Magnesium
Titanium
What is a crystal?
A rigid body in which the constituent particles are arranged in a repeating system
What is a basic building block of a crystal called?
A Unit Cell
What does BCC stand for and how many atoms does it have in its unit cell?
Body centred cubic
9 atoms on the corners of the cube and one in the centre
What does FCC stand for and how many atoms are in its unit cell?
Face centred cubic
14 atoms on the corners and the centre of each face
What does HCP stand for and how many atoms does it have in its unit cell?
Hexagonal Close Packed
17 atoms
Name some examples of FCC types
Iron if ABOVE 910 degrees Celcius Aluminium Copper Gold Nickel Silver
Name some examples of BCC types
Iron if BELOW 919 degrees Celcius
Name examples of some HCP types
Cobalt
Magnesium
Titanium
Zinc
What is an example of a ferrous material?
Steel
What is the base material for steel?
Iron
What is iron primarily alloyed with to make steel?
Carbon
What are characteristics of pure iron?
Soft
Malleable
Ductile
How is cast iron formed?
Molten iron alloyed with 2% of carbon and is poured into a mould
How is steel made?
Pure iron is melted in a blast furnace and introduced to carbon with other alloying elements to achieve desired characteristics
Why is cast iron not favourable?
It is not strong
Name some examples of alloying ingredients for steel and their alloying properties
Carbon - primary hardening agent
Sulphur - decreases ductility
Silicon - de oxidiser
Phosphorous - increases strength and hardness
Chromium - increases corrosion and oxidisation resistance
What are the carbon percentages for LCS, MCS and HCS?
LCS - 0.1 -0.3%
MCS - 0.3 - 0.5%
HCS - 0.5 - 1.05%
How are the types of steels represented?
As a 4 digit number
What do the first and last 2 number denote in the material designation?
First 2- steel and alloys used
Last 2 - the % of carbon
What are the designations based on?
The AISI numbers and SAE numbers
What does AISI mean?
American Iron and Steel Institute
What does SAE stand for?
System of Automated Engineers
What must steel have for heat treatment to happen?
Must have carbon
What type of heat treatment is used to decrease the hardness of steel?
Tempering
What is the process to harden steel?
The material is heated above critical temperature allowing carbon to dispense uniformly in the iron matrix
The alloy is then cooled rapidly by quenching it in a quenching medium
What are the three types of quenching mediums?
Water
Oil
Brine
What is the most rapid quench medium?
Brine
What is the steel known as if the quench is too quick?
Martensitic
What characteristics does a martensitic structure have?
It is the hardest alloy
Too brittle for aircraft use
What affects the hardness of steel?
The amount of carbon
If there is more carbon in steel, the steel is…
More hard
What are the different types of heat treatment?
Tempering Annealing Hardening Normalising Quenching
What is annealing?
Heating a material and allowing it to cool slowly to increase softness and toughness and relieve internal stresses
What is normalising?
When you heat steel to 100F above its upper critical unit, soak it for a given time and then cool it at room temp
What are the names of the groups that steel is divided into depending on their structure?
Ferrite
Austenite
Cementite
Pearlite
What are the three GENERAL groups that steel is divided into based on their structure ?
Ferrite
Austenite
Martensitic
What does CRES stand for?
Corrosion Resistant Steel
What process makes a substance less corrosive?
The addition of Chromium
How are CRES identified?
By 3 digit numbers
200
300
400
What are the 200 and 300 series known as?
Austenite
What are the 2 types of 400 series known as?
Ferrite
Martensitic
What type of series is commonly used in aircraft?
300 Austenite
What are the 4 disadvantages of CRES?
Difficult to cut
Greater coefficient of expansion
Experienced technicians required
Not suitable in high temperature environments
What sort of alloy is an Austenite?
Chromium-nickel and chromium-nickel-manganese alloys
What sort of properties does an Austenite have?
18% or more chromium than nickel 3.5%-22% of nickel Contains stabilising alloys 200-300 series Cold work Strain hardened Non magnetic
What properties does a 400 series Ferrite have?
Contains 15% - 30% chromium BCC 400 series Small amounts if aluminium Magnetic Annealed and relatively low strength
What properties does a Martensitic 400 series have?
400 series 12%-18% chromium High Carbon content Heat treatable Least corrosion resistant
Precipitation Hardening (steel) properties
Little carbon 15%-17% chromium 4%-7% nickel Solution heat treated Can be hardened to very high strengths Corrosion resistant
What is the base alloy of a high strength low carbon steel?
Iron
Name an advantage of High Strength Low Carbon Steels
Can be hardened to very high strengths
What type of series is used on the landing gear?
300M
What is hydrogen embrittlement and what sort of materials are mainly used for it?
The process for hydrogen to get into the grain boundaries of steel. The carbon reacts with the hydrogen in steel and increases the pressure and causes it to crack.
Mainly ferrous and titanium alloys
What are the 2 steel alloy precautions?
Stress concentrations
Hydrogen embrittlements
What are the precautions to take for stress concentrations?
The misuse of tools leading to scratches and general damage to surface finish
What is a precaution to take for hydrogen embrittlement?
Ensure all precautions are taken to prevent embrittlement
What are methods to surface protect CRES materials?
Cadmium plates
Zinc spray
Chromium
What does surface protection on CRES materials do?
Avoid galvanic corrosion of light alloys
What is galvanic corrosion potential?
The measure of how dissimilar metals will corrode when placed against each other in an assembly
The further apart the metals in the corrosive list, the…?
The stronger the ability to corrode
Which metal will corrode?
The metal higher in the list
What is steel case hardening not suitable for?
Non- ferrous material
What is case hardening?
The process of hardening the surface
How many processes are there for case hardening and what are they?
4 processes
Carburising
Flame hardening
Induction hardening
Nitriding
Which out of the two processes of case hardening is the most common?
Caruburising
What is carburising?
Carburising produces a thin layer of high carbon steel around a softer low carbon steel core by introducing the material to carbon
How many carburising methods are there and what are they called?
3 methods
Pack carburising
Gas carburising
Liquid carburising
What is the process of pack carburising?
Heats up the component to 1700F temperatures whilst it is packed into a carbon rich materials such as charcoal. The carbon from the charcoal then penetrates the surface of the metal which causes it to harden
For pack carburising, what is the quenching medium?
Quenching medium is oil
Water causes the hard case to peel
What is the process of gas carburising?
Component is placed in a basket and then into a furnace and is passed through a suitable carbon rich gas. Carbon penetrates the surface and makes it harder.
What is the process of liquid carburising?
The component is heated at a suitable temperature then immersed into a hot salt bath at 900 degrees C
What is flame hardening?
Heat treatment for uniform compositions
The surface is heated to above upper temperatures by means of oxyacetylene torches and then quenched with a water jet built into an assembly
What is induction hardening?
The whole circumference of a material is heated simultaneously by an induction coil and quenched with a water jet built into an assembly
What is nitriding and its process?
The introduction of nitrogen to a substance For an improved surface finish
It heats up the material to 1000F in an ammonia rich environment. The ammonia breaks down and nitrogen is released and penetrates the surface of the material.
The selection of materials should be a compromise between…?
The cost and quality
What are the material characteristics of iron?
It is dense, soft and malleable
What is the process used to relieve stress in high strength steel after machining?
Normalising
If hydrogen embrittlement is suspected in a material, what should you do ?
Heat it up
What does heating up the material do if you suspect hydrogen embrittlement?
Reverts the material back to its normal state
