6.1 Flashcards
level 1 questions
what is a ferrous material
alloy containing iron as its main ingredient and is magnetic
why can pure iron not be used in aviation
It is ductile and soft and reacts with oxygen
what else is needed to make iron from iron ore
coke and limestone with hot air
why is limestone used to make iron
to remove impurities
what is remelted to make steel
cast iron / pig iron
what needs to be removed from cast iron to make steel and how does it happen
the carbon needs to be removed and it is done by forcing oxygen through it
what percent is low carbon steel
0.1-0.3%
what percent is medium carbon steel
0.3-0.5%
what percent is high carbon steel
0.5-1.05%
what does tensile strength withstand
tension
what does compressive strength withstand
pressing/ squeezing
what does shear strength withstand
stress coplanar to cross section
what does torsional strength withstand
rotational shear
what does flexural strength withstand
bending
what does fatigue/ endurance strength withstand
repeated loading
what does impact strength withstand
shock
what does hardness resist
cutting, penetration or abrasion
what does toughness resist
tearing/ breaking when bent/ stretched
what is the most common alloying agent
carbon
what alloying agent causes steel to be brittle and must be removed when refining
sulphur
what alloying agent acts as a hardener and in small quantities improves ductility
silicon
what alloying agent raises yield strength and improves low carbon resistance to atmospheric corrosion
phosphorous
what alloying agent adds strength and hardness to steel and increases yield strength
nickel
what alloying agent increases strength and hardness and improves wear and corrosion resistance
chromium
what alloying agent is most widely used for aircraft structure and reduces grain size
molybdenum
what alloying agent is normally combined with chromium to make ball bearing
vanadium
what alloying agent has an extremely high melting point
tungsten
what is stainless steel and what are the main alloying agents
classification of corrosion resistant steel mainly made of chromium and nickel
what are the 3 types of stainless steel
austenitic, ferritic, martensitic
what is the first digit in the classification of steels
principal alloying element
what are the last 2 digits in the classification of steels
average carbon percent
what is heat treating
process of heating up and cooling down carbon steel to change physical and mechanical properties
what is an eutectoid
a metal that can exist in more than one different form at the same temperature
what is the critical temperature
temperature when a phase change happens during heating or cooling
what is quenching
rapidly cooling a metal after heating
what is annealing
heat the metal 10C above critical temperature and heat soak it at that temperature
what does annealing do
softens steel and releaves internal stress
what is normalising
heating 38C above critical temperature and heat soaking for a prescribed time then at room temperature
what does normalising do
relieves internal stresses
what does tempering do
decreases hardness and increases ductility
what does case hardening do to low carbon steels
creates a hard durable surface
what does case hardening do to high carbon steels
makes the core very brittle
what are the 2 methods of case hardening
carburising and nitriding
what is direct hardening
surface is heated very rapidly to a high temperature by flame or induction hardening and then cooled very quickly this creates a ‘case’ of martensite on the surface
what is the difference between flame and induction hardening
flame hardening only heats up a part of the surface at at time whereas induction heats the entire surface at once
what is malleability
ability to be bent, formed or shaped without cracking or breaking
what is ductility
ability of metal to be drawn into wire, extrusions or rods
what is brittleness
material’s tendency to break or shatter when exposed to stress
what are the characteristics of austenitic stainless steel
non magnetic in annealed condition but some can be slightly magnetic after cold working
what are the characteristics of ferritic stainless steel
chromium is major alloying element, magnetic and generally have good ductility
what are the characteristics of martensitic stainless steel
good combination of corrosion resistance and superior mechanical properties they are magnetic
is steel an eutectoid
yes because it can be in different forms at the same temperature
what are the 4 states that steel can be in
ferrite, austenite, cementite, pearlite
what are the characteristics of the ferrite form of steel
pure iron, is a body-centred cubic lattice
what are the characteristics of the austenite form of steel
face-centred cubic form of iron
what are the characteristics of the cementite form of steel
chemical compound made of iron and carbon, very hard also known as iron carbide
what are the characteristics of the pearlite form of steel
2 phased lamellar structure, formed when austenite is slowly cooled below 727C
what are the 3 different crystal structures that occur in steel due to heat treatment
austenite, ferrite and martensite
what type of crystal is austenite
face-centred cubic
what type of crystal is ferrite
body-centred cubic
what type of crystal is martensite
body-centred tetragonal
what can be used to measure a metal’s temperature
pyrometers, thermocouple controlled ovens or by colour of metal
