6.1 Flashcards
What is a ferrous metal.
Any alloy containing iron as its main ingredient
What is tensile strength
Ability to withstand stress under tension.
What is compressive strength.
Ability of a metal to withstand pressing.
What is shear strength
Ability to withstand stress acting Coplanar
What is torsional strength
Ability to resist rotational shear
What is flexural strength
Bending strength
Fatigue / Endurance strength
Ability to resist repeated loading.
Impact strength
Ability to resist shock.
What is hardness
Refers to a metal ability to resist cutting , penetrating , or abrasion
What is malleability
Can be bent , formed , or shaped without cracking or breaking.
What is ductility
Ability to be drawn into wire stock.
Resistance to failure under shock loads.
Brittleness
Tenancy to break or shatter under stress.
What is conductivity.
Cary heat and electricity.
What is toughness
Resist tearing or breakage when bent or shattered.
What is fusibility
Ability to be joined by heating + melting.
Effect of sulphur in steel
Causes steel to be brittle
Removed in the refining process
Effected of silicon in steel
Acts as a hardener
When used in small quantities, improves ductility.
In low carbon steels it can be detrimental to the surface finish.
Effect of Phosphorus in steel.
Raises yield strength.
Improves low carbon carbon steels resistance to amospheric corrosion
What effect does nickel have on steel
Adds strength + hardness
Increases yield strength
What effect does chromium have on steel?
Increase strength and hardness
Increases its wear and corrosion resistance.
What effect does molybdenum have on steel
Increases impact strength and elastic limit
Extremely wear resistant and has lots of fatigue strength
Most common type used in aircraft airframes.
What is the effect of vanadium on steel
When combined with chromium, vanadium produces a strong tough ductile steel alloy
Used in wrenches + ball bearings.
Effect of tungsten on steel
Makes a steel with a high melting point.
What is stainless steel
Used in firewalls
Contains large amounts of chromium and nickel
Divided into 3 subcategory’s based on chemical structure:
Austenitic
Martensitic
Ferretic
Austenitic stainless steel
Referred to as 200 and 300 series stainless steel.
Non-magnetic.
Ferritic stainless steel
400 series
Chromium as a major alloying element
Magnetic
Martensitic stainless steel
400 series
Magnetic
Lots of chromium- 11-17 %
Corrosion resistant .
Effect of carbon mixed with iron
Creates steel
Allows steel to be heat treated to obtain varying levels of hardness strength and toughness.
Higher content decreases malleability , weld ability
What does the first digit indicate on SAE classification of steel
The principal alloying element.
What do the last digits of SAE classification of steel indicate?
Percentage level of carbon
What is ferrite
Pure iron
Body centred cubic (BCC) crystal
Absorb up to 0.2% carbon
What is astenite?
The preferred type of steel in aviation
Face centred cubic (FCC) lattice
Absorb up to 2.0% of carbon
What is cementite?
AKA iron carbide
Very hard and brittle
Below UTC
What is pearlite
Mix of cementite and ferrite (I think)
What are the important factors in the heat treatment of steel?
Temperature
% carbon
Time taken to cool
What is martensite
Very similar structure to austenite but occurs due to rapid cooling of austenite and is very. Brittle
What type of crystal is martensite?
Body entered tetragonal
What is annealing of steel
Heating the steel around 10 degrees above its upper critical limit and holding it there (soaking)
Softens the steel and relieves internal stresses
Can’t be used on aircraft
What is normalising of steel
Heat 38 degrees above UCL and soaking it for a prescribed time.
Then allowing it to cool at room temp
Relieves internal stresses
Important for welded components
What is tempering of steel
Method used to decrease the hardness therefore increasing ductility and toughness of quenched steel and reducing its brittleness.
Accurate temperature control is needed
Examples of ways of monitoring temperature
Pyrometer
Thermocouples
Paint or crayons
Colour
What is case hardening of steel
Two types: carburising and nitriding
Hardens outer surface but keeps the inner surface tough
What is direct hardening
Flame or induction hardening
Flame hardening:
Oxy-acetylene torch
Induction hardening:
Heats entire circumference simultaneously
What type of metals are the FCC, BCC and the BCT
FCC = austenite
BCC = ferrite
BCT = martensite
What is the critical temperature
