6.1 Ferrous materials✅(3) Flashcards
What does ‘ferrous’ refer to?
- metals and alloys
An alloy containing iron as its main ingredient is called what
ferrous metal (and is magnetic)
What are the most common ferrous metal in aircraft structures
- Steel
- an alloy (with controlled amount of carbon and other materials)
What are the properties of pure iron?
- ductile
- soft
- easily formed
How is Iron oxide formed
- Iron reacts with oxygen
Advantage of cast iron
- low strength to weight ratio
What material is the most common man-made materials in the world
steel
What is the base material of steel
iron
How do you make steel
pig iron/cast iron is re-melted in a special furnace
what is Tensile strength?
- Ability of a metal to withstand stress in tension
What is compressive strength?
- Ability of a metal to withstand ‘pressing’ or ‘squeezing’
What is torsional strength?
- ability to resist rotational shear
What is Flexural strength?
- bending strength of a metal
What is impact strength?
- Measures ability of a metal to resist shock
What is hardness?
- ability to resist cutting, penetration, or abrasion
What is malleability?
- ability to be bent, formed, or shaped without cracking
What is brittleness?
- Materials tendency to break or shatter when exposed to stress
What is conductivity?
- Property that enables a metal to carry heat or electricity
What is thermal expansion?
- Property of a metal to expand when heated, and shrink when it is cooled
What is elasticity?
- Metals tendency to return to its original shape after normal stretching/bending
What is toughness?
- materials ability to resist tearing or breaking when bent or stretched
What is fusibility?
- ability of metal to be joined by heating and melting
What is the most common alloying element found in steel
carbon
Higher carbon content decreases the malleability and weldability of steel (T or F)
T
What is the carbon content for low carbon steel?
0.1%-0.3%
What is the carbon content for medium carbon steel?
0.3%-0.5%
What is the carbon content for high carbon steel?
0.5%-1.05%
What does sulphur cause steel to be when rolled or forged
Sulphur causes steel to be brittle
What does silicon act as when alloyed with steel
hardener
When using silicon in small quantities, what does it improve
ductility
What does nickel do when added to steel
- adds strength and hardness
- increases yield strength
What is the most widely used alloying elements used for aircraft structural steel?
molybdenum
What does chromium do when alloyed with steel
- increase strength and hardness
- improve wear and corrosion resistance
Molybdenum steels are extremely wear resistant and possesses a great deal of fatigue strength (T or F)
T
What occurs when vanadium is combined with chromium ?
- produces strong, tough, ductile steel alloy
What are most wrenches and ball bearings made out of?
Chrome-vanadium steel
Tungsten has an extremely high melting point (T or F)
T
Stainless steel can be classified into 3 groups which are?
- Austenitic
- Ferritic
- Martensitic
What are Austenitic stainless steel referred as
- referred as 200 and 300 series stainless steels
What are Ferritic stainless steel part of
- part of the 400 series of stainless alloys
Ferritic stainless steel have what as their major alloying element
-chromium
Ferritic stainless steels are magnetic (T or F)
T
What is the major alloying element with martensitic?
- Chromium (in the range of 11%-17%)
What does the first digit for classification of steel identify?
the principal alloying element
What does the last 2 digits digit for classification of steel identify?
average carbon content in %
What type of stainless steel is used for cookware/food equipment?
Austenitic
What type of stainless steel is used for kitchenware/exhaust/furnaces?
Ferritic
What type of stainless steel is used for cutlery/surgical instruments/scissors/industrial blades?
Martensitic
Steel is hardened by raising its temperature to above the upper critical temperature (T or F)?
T
What is the critical temperature?
- temperature at which a phase change occurs in a metal, during heating or cooling
What is quenching?
-rapidly cool a material after heating in water/oil
What is annealing?
- softens steel and relieves internal stresses
Why can annealed parts not be used on aircraft
due to soft and ductile nature
Explain the annealing process
Heating a steel to 10*c above upper critical limit and heat soaking it at this temperature
What is normalising?
- involves heating steel to 38*c above its upper critical limit and soaking for prescribed time
When normalising, how is the steel cooled?
at room temperature
What is tempering
- method used to decrease hardness
- increasing ductility, toughness
What is the least accurate method of estimating temperature?
- observing colour of the material being heated
What is direct hardening?
-surface heated rapidly to high temperatures
- then cooled rapidly (generally using water)
Direct hardening consists of flame or induction hardening process (T or F)?
T
How is the steel heated in induction hardening?
by an induction coil
When the steel is heated to the necessary temperature (induction hardening) what occurs next?
- current switched off
- immediately quenched by jets of water
What are the 2 methods to case harden
- Carburising
- Nitriding
When do you usually carry out normalising
- after welding
